Substitution and recycling of critical raw materials in optoelectronic, magnetic and energy devices III

Resume : Our modern society relies heavily on electronic and optoelectronic devices to sustain communication networks and industrial systems. The devices and systems at the core of digital transformation and the energy transition are based on hardware requiring an intensive use of Critical Raw Materials (CRM) . In 2016, the EIT RawMaterials (EITRM) started its operations to address innovation and education, also with emphasis to CMRs. Initiated and funded by the EIT (European Institute of Innovation and Technology), a body of the European Union, the EITRM is the largest consortium in the raw materials sector worldwide. Its vision is to develop raw materials into a major strength for Europe. Its mission is to enable sustainable competitiveness of the European minerals, metals and materials sector along the value chain by driving innovation, education and entrepreneurship. Substitution of critical and toxic raw materials is one of the core thematic areas covered by the community: as of 2020, 25 active projects are covering the substitution of CRMs. In these projects partners collaborate on finding new, innovative solutions to secure the supplies and sustain the raw materials sector in Europe. The talk will briefly explain the opportunities available within the EITRM’s programmes, starting with an overview of the challenges posed by the transition to the use of renewable energies and to electric vehicles and what impact this will have on the demand of specific metals and minerals. An overview of the project portfolio that the EIT RawMaterials is deploying to tackle these challenges will be given. We will also show some specific examples of projects addressing substitution and recycling of CRMs. Finally, the opportunities offered by the recently-established European Raw Materials Alliance (ERMA) will be presented.

Resume : Energy storage devices (e.g. fuel cells and electrolysers) utilise Platinum Group Metals (PGMs) as catalysts for their effective operation and exhibit an increasing utilisation trend being environmentally friendly energy production means. Europe is the world’s largest consumer of PGMs with a share of ca. 20% of the global demand. In 2019, the EU demand of PGMs was ~71.5 t Pd, 78.7 t Pt and 4 t Rh, with ~90%, 54% and 80% respectively channelled to the production of catalysts. PGMs are very expensive materials that are currently experiencing a risk of supply as they were in deficit in 2019, and the production of PGMs in the EU is insignificant; ~84% of the supply comes from South Africa and Russia, countries with suboptimal geopolitical stability. Recycling of PGMs from end-of-life products and their partial substitution in the production of new ones, are solutions to minimize the supply/demand gap. The innovation business planning needed to market the recovered/saved PGMs includes marketing tools and financial indicators utilised from an innovative perspective. SWOT analysis of a prospective start-up is formed together with a Business Model Canvas centred by the value proposition offered to determine commercialisation parameters. Further, a Business Plan is set illustrating the production capacities and the determination of its financial sustainability by calculating the Net Present Value (NPV), Initial Rate of Return (IRR) and the break-even point for the investment made.

Resume : Platinum Group Metals (PGMs) are key critical metals for Europe, that is dependent on export from the main producing countries, i.e. South Africa and Russia, which together are responsible for 75 to 80% of the PGM world mine supply. On the demand side, the EU legislation on pollution emission standards has pushed the use of automotive catalytic converters (ACCs) in vehicles, making that the manufacturing of ACCs represents by far the largest PGMs (Pt, Pd & Rh) consuming application. The concentrations of PGMs in ACC urban mines is much higher (>2000 ppm) than conventional mines in South Africa and Russia (2-10 ppm) and therefore recycling of ACCs present an important source of PGMs for sustainably supply and reduced environmental footprint. Hydrometallurgical recovery methods are seen as sustainable alternatives to well established and industrially applicable pyrometallurgical techniques. However, research efforts have not yet led to industrialization. A better understanding of complex ACC material in terms of morphology, liberation, metallurgical associations, metal speciation and metal liberation should improve the process performances. Recycling oriented characterization of different types of ACCs available on the market was performed using SEM-EDS. These included cordierite based diesel oxidation (DOC) and three-way catalysts (C-TWC), silicon carbide based diesel particle filter (DPF), and metallic based three way catalyst (M-TWC). Structural design differences were noticed between different catalyst types and all ACCs contained complex compositional complexity. Washcoat distribution in DPF was found to be different than other ACCs. Catalysts were found to contain secondary deposition layers of poisons with varying degree of contamination of Zn, Ca, P, K, S, Pb etc. PGM particles were found to be uniformly distributed in the washcoat. They were also trapped in the poisoning layer, attached to or contained within the washcoat components such as ceria and alumina. PGM and washcoat components were heavily sintered and grown in size. Sintering had blocked the active surfaces/PGM liberation by loss of surface area which also results in reduction of porosity. SEM-EDS proved to be a powerful tool to analyze several phenomena that have happened to ACCs over the operational lifetime. The information obtained at nanoscale provided for better understanding of ACCs and variance within ACC urban deposit useful for subsequent pretreatment or hydrometallurgical PGM recovery routes.

Resume : Volatile organic compounds (VOCs) are a large group of organic substances with high vapour pressure, which are considered as atmospheric pollutants of a particular concern, because of their global warming and smog generation potential, and the adverse effects on the human health. Emitters of VOCs are a number of organic industries, as well as the extraction, storage and combustion of organic fuels and fuels from wastes for energy production, and the automotive engines. The most reliable method to eliminate VOCs is their thermal catalytic oxidation, which, however, requires expensive catalysts of critical materials, such as platinum-group metals (PGMs), mostly Pt and Pd. Recently, transition metal oxides are being studied as alternatives, such as CuO, Co3O4, MnO2 and Cr2O3. Each catalytic system consists of a carrier with developed specific surface area on which the active catalytic centers are distributed uniformly, and thus, ceramic materials and zeolites are commonly used as substrates. In our previous studies was observed that the coal fly ash zeolites (CFAZ) derived by utilization of coal fly ash from Thermal Power Plants possess high catalytic activity toward the total oxidation of VOCs obeyed by the particular surface, textural and compositional characteristics of these materials, namely high surface values, mixed micro-mesoporosity and uniformly spread metal oxides (Fe2O3, Fe3O4, MgO, MnO, TiO2) and metal traces (W, V, Co, Cu) transferred from the raw coal ash that act as active oxidation cites. The obtained results showed a decrease in the temperature of the oxidation of toluene with 200 °C as compared to the catalytic destruction over Pt and Rh. In this study, micro wave plasma surface modification of CFAZ is performed to enhance their catalytic activity. CHF3 and SF6 were used as plasma agents at two different times of treatments – 30 s and 60 s. The obtained hierarchal CFAZ were characterized by XRD, SEM and N2-physisorption to clarify the effect of plasma treatment on the surface properties, morphology and structure of the modified samples. The catalytic performance of the modified CFAZ was investigated in a flow system toward toluene oxidation in the temperature range of 50-800 °C. It has been observed that CHF3 treatment favors the catalytic activity of CFAZ at shorter treatment duration, while SF6 plasma treatment inhibits their catalytic properties. The development of efficient low-cost catalyst by utilization of coal fly ash will contribute on the one hand to the saving of critical raw materials such as PGMs, and on the other to the utilization of the enormous resource of coal ash instead of its landfilling in accordance to the modern trends for development of circular economy and smart waste management. Acknowledgements: This work was financially supported by the National Science Fund, Ministry of Education and Science of R. Bulgaria under the contract DN 17/18 and was performed in the frame of COST CA15102 CIG ITHACA11.

Resume : A new list of critical raw materials published in 2020 contains materials with a high demand in many applications from cutting tools to electronics and aerospace. Coatings, in general, are employed in various fields of human activity for decades and centuries and are under a constant and intensive development. However, new challenges are rising as well. This research brings a review of a recent progress in PVD coatings considering the aspect of their effectiveres in a mitigation of critical raw materials problem and the most important applications. Own achievements in protective coatings development will be presented.

Resume : Climate change related to greenhouse gas emissions can be battled on many fronts. Ensuring stable availability of renewable electricity is second to none. The contribution of transport to CO2 emissions is of great importance too. Electrification of (light) transport like person vehicles, motorcycles etc. with certainty can lead to a reduction of CO2 emissions, especially when charging with renewable electricity sources such as solar, wind or hydropower. Also, deployment of (intermittent) renewable energy sources will benefit from the introduction of low-cost stationary batteries. However, today’s lithium ion batteries that provide the energy storage for these applications, depend heavily on elements of limited abundance and large toxicity such as Co, and even Li supplies themselves are being questioned. This motivates a great interest into Co-free cathode materials for lithium ion batteries on the one hand, besides Na-ion batteries on the other hand. Here, an overview will be given of our recent research into Co-free materials for lithium ion batteries based on manganese, as well as novel materials for Na-ion batteries (cathodes, electrolytes). These materials are synthesized by means of wet chemical routes, either using citrate based metal ion solutions, via precursor gel intermediates and final calcination / combustion, either involving hydrolysis – condensation processes. The developed synthesis methods allow controlled particle size and morphology as well as crystallographic surface plane orientation, as will be demonstrated for LNMO, besides surface modification to form core-shell particles e.g. TiO2 and lithium titanate coated LNMO, affecting capacity retention. (Extra-ordinary) sodium titanate phases (Na2Ti3O7:Zr; Na2+xTi4O9/C) were found and showed improved properties such as prolonged cycle life. Materials properties including crystal phase, particle size and morphology, porosity, besides electrochemical properties such as discharge capacity, capacity retention, Coulombic efficiency, ion conductivity etc. will be discussed for each of the cases mentioned here. In conclusion, though current applications are dominated by lithium ion batteries, which are highly dependent on Co-containing cathode materials, many alternatives can be envisioned. As the current presentation demonstrated, in-depth research provides a profound basis for improvements to a level where new materials become competitive with the established technologies. References: F. Ulu Okudur et al. RSC Advances 8 (2018) 7287, D. De Sloovere et al. Chem. Mater. 30 (2018) 8521, A. Paulus et al. Dalton Trans. 49 (2020) 10486 The following projects are acknowledged for financial support: Research Foundation Flanders (G040116N, G053519N, SBO XL-Lion), and Horizon 2020 LCBAT-5 COBRA project 875568.

Resume : Energy storage systems are increasingly important in the development of modern society, where lithium-ion batteries (LIBs) show a predominant role. The global warming, the exhaustion of combustible fossils and the growth in the demand critical raw materials (CRMs) in the battery field makes imperative the establishment of a widespread strategy for sustainability that includes the fabrication of batteries based on renewable resources. Cellulose and its derivatives offer an opportunity to shift from the use of petroleum-derived materials and CRMs to greener solutions while extending the electrochemical performance. Here we prove the suitability of cellulose-derived materials to develop different battery components with controllable structure, suitable for LIBs, sodium-ion batteries (NIBs) and aqueous zinc batteries (AZBs). The strategies here shown could support a transition to a circular economy as they create harmless secondary products, thus merging efficient resource utilization and value creation. To evaluate the potential of cellulose as an alternative to traditional polyolefin-based LIB separators, we prepared mesoporous cellulose nanocrystal membranes composed of loosely packed CNCs with a specific surface area of 172 m2•g−1. Low contact angle values against conventional organic electrolyte and biocompatible ionic liquids was obtained, reaching ionic conductivities up to 2.7 mS•cm−1. A specific capacity of 122 mAh•g−1 at C/2 in Li/LiFePO4 cells was delivered, outperforming the performance of glass microfiber separators. We further replaced the environmental harmful organic electrolyte by a biocompatible ionic liquid, [C2 mim][NTf2], obtaining a capacity of ~82 mAh•g−1 at C/8, indicating that mesopores provide efficient paths for Li ion migration through the membrane. We also applied cellulose to pattern mesoporous materials which can be used as LIB anodes. Highly porous black TiO2−X free-standing films with a unique combination of chirality and crystalline TiO2 core/disordered amorphous TiO2−X shell provides an enhanced Li diffusion. As a result, increased capacity retention was achieved form black titania in comparison to white titania. The physical framework provided by the mesoporous carbon network enhances the electrolyte penetration and Li diffusion through the enlarged pores while accommodating the volume changes during Li insertion/extraction into the black TiO2−X-based nanostructure. We here provide novel avenues for the replacement and upgrade of traditional energy storage systems upon the use of renewable, low-cost and easy to fabricate cellulose. Interestingly, prepared materials display custom-made structures, outperforming traditional polymers based on petroleum. To sum up, we prove the potential of natural biopolymers to be a frontrunner in the uptake of circular economy concepts within the energy storage field.

Resume : The impact of our “modern” civilizations on the available resources, the environment, the biodiversity and the climate, induces serious threats for future generations. This suddenly changes the paradigm in terms of priority for humanity. One of the proposed solutions consisted in making our linear society model (extraction of raw materials, product manufacturing, use and landfill) more circular which consists in reusing the products, then the components and finally the residual materials while always maintaining them at their maximum value level. The principle of Circular Economy that was born and here after we introduce its evolution. In 1987 the United Nations defined the Sustainable Development as a model of sustainable growth for humanity. It considers that in long term the society must be stable on 3 pillars: the economic growth, the environmental preservation and societal well-being. Starting from a simple systemic model of recirculating loop for the manufacturing sector, the Circular Economy has evolved into a global and sustainable model incorporating these three pillars of the Sustainable Development. The European Green Deal, which defines our new civilization development strategy, also comprises it through the “New Circular Economy Action Plan”. According to it, the success of the transition to the Circular Economy relies in a large extent on digital technologies and ... innovation. The innovation for the Circular Economy maximizes the Global Impact on the 3 pillars and more precisely in terms of climate neutrality in 2050, health preservation plus environmental regeneration and business competitiveness improvement. Maximizing the Global Impact during the innovation process defines the Eco-innovation. The Eco-innovation is the way to innovate in and for the Circular Economy and is our next innovation method. The current innovation method is reversed: now it starts from the finality. That means thinking in terms of Global Impact, to deduce the necessary and sufficient technologies, not necessarily high-tech, neither low-tech but right-tech. The pending question is how to consider economy, the environment and the society? The most mature methodology is concerning the environmental issues thanks to the Eco-design approach. This is a well-known method for designing products and processes while minimizing the consumed resources and the effects on the environment at each stage of their life cycle. Ecodesign makes it possible to improve, redesign or even imagine completely new concepts thanks to reflections carried out early in the design process by involving all stakeholders. The Ecodesign method can rely on Life Cycle Analysis (or LCA), a standardized method, which can quantify the environmental impacts of a product at each stage of its life cycle from the extraction of raw material to end-of-life treatments, including manufacture, transport and use. LCA is carried out with software and environmental databases. LCA makes it possible to identify which stage of the life cycle presents the most impact, which environmental aspect is preponderant or which substance is an issue. LCA can therefore help the Ecodesign process by identifying possibilities for the product improvement without degrading other aspects. Eco-innovation opens new avenues for research and technological developments!

Resume : The production costs of hydrogen storage materials is one of the major barriers hindering their application in mobile and/or stationary application. Magnesium and magnesium-based compounds have been studied as potential hydrogen storage materials for several decades because of their relatively high hydrogen storage capacity, and fast sorption kinetics (when doped with suitable additives). The possibility of recycling magnesium-based wastes to produce magnesium-based compounds might significantly contribute to the cost reduction of these materials. This research aims at studying the possibility to use waste magnesium alloys to produce high-quality hydrogen storage materials.

Resume : Critical Raw Materials (CRMs) combine raw materials of high importance to the EU economy and of high risk associated with their supply. In this regard the renewed industrial EU strategy is focused on stimulation of the production of CRMs by enhancing new mining and recycling activities in the EU, as well as on fostering efficient use and reuse of critical raw materials, a priority area in the EU circular economy action plan. On the other hand mechanochemical treatment of waste materials is a powerful tool for pollution remediation and waste management. Mechanochemistry is defined to describe the chemical and physicochemical transformations of materials as a result of the mechanical energy input. In this paper the investigated materials were series of Fe–based CRM-containing amorphous alloys applied in practice as transformer magnetic cores. The ribbon samples were treated in a high-energy planetary ball mill at different experimental conditions. The aim of the investigation is to explore the appropriate conditions of mechanochemical processing of studied materials in order to obtain only their partial crystallisation and formation of nanocrystals in their amorphous structure. The changes of the bulk and the surface of the initial and mechanochemically treated samples will be reported using the results from following characterization methods: powder X-ray diffraction, Scanning Electron Microscopy, RT and LNT Mössbauer spectroscopy, as well as conversion electron Mössbauer spectroscopy. Acknowledgements: The authors gratefully acknowledge the financial support of the Bulgarian National Science Fund at the Ministry of Education and Science - Project № КП-06-КОСТ/18/ 2019. This article is based on the project activities of COST Action CA 18112 “Mechanochemistry for Sustainable Industry” (Mech@SustInd), supported by COST (European Cooperation in Science and Technology).

Resume : Rare earth elements (REEs) are critical raw materials with a wide range of industrial applications, whose demand has been steadily increasing in the last decades driven by the ever-expanding market of electronic devices. The recovery of REEs from waste electronic devices is considered a strategic solution to secure REEs supply, while minimizing waste generation and implementing sustainable and environmentally friendly manufacturing policies (Tunsu et al. 2015, Diaz et al. 2016). Well-established hydrometallurgical routes rely on a combination of acidic and oxidative treatments to extract metal ions from solid wastes into aqueous solutions (Resende and Morais 2015). Adsorption emerged as a simple, cost-effective and non-toxic approach to concentrate, purify and recover REEs from the REE leaching solutions. Lately, polymers, natural fibres, clays, carbon-based materials, metal-organic frameworks and metal oxide particles have been considered as sorbent materials. Nanocomposites consisting porous polymeric membranes and ultrathin nanoparticles are deemed to have a great potential in the separation and pre-concentration of REEs from aqueous streams (Chen et al. 2018). Due to the broad range of applications (catalysis, fuel cells, polishing, biomedicine), cerium oxide is one of the most engineered oxides at nano-/micro-scale. In this work, cerium oxide nanoparticles with very small size (≈ 3 nm) and high specific surface area (>200 m2/g) were synthesized by alkaline precipitation and hydrothermal condensation of cerium inorganic precursors (Prieur et al. 2020). Then, the nanoparticles were incorporated into porous polymeric (e.g. poly(vinyl alcohol)) membranes consisting of electrospun nanofibers to facilitate physical confinement, sorbent regeneration and mechanical stability. The composite membranes were tested for the adsorption of REEs (Eu3 , Gd3 , Yb3 ) from aqueous solutions in batch and continuous-flow sorption conditions. The maximum adsorption capacities (qM) in static conditions, as determined via the Langmuir adsorption model, ranged between 15 and 320 mgREE/gCeO2, with the larger value relative to the sorption of Yb3 . The electrospun membranes proved to adsorb Eu3 in repeated adsorption cycles with a minimal loss of adsorptive material. Regeneration of the adsorbent with a mild acidic solution was demonstrated, with a residual recovery of 30% in Eu3 mass after five desorption steps. This work shows that ceria nanoparticles embedded in polymeric nanofibrous membranes are promising adsorbents for the removal of REE ions from aqueous solutions. References Tunsu C, et al. (2015). Hydrometallurgy, 156, 239-258. Diaz L. et al. (2016). Journal of cleaner production, 125, 236-244. Resende LV, Morais CA (2015). Minerals Engineering, 70, 217-221. Chen L, et al. (2018). Separation and Purification Technology, 197, 70-85. Prieur D, et al. (2020). Inorganic Chemistry, 59(8), 5760-7.

Resume : The printed circuit board assemblies (PCBAs) are an essential component of any Waste Electrical and Electronic Equipment (WEEE), and concentrate some of the CRMs, notably in integrated circuits and light emitting diodes (LEDs), tantalum in capacitors, palladium in multi-layer ceramic capacitors and to a lesser extent neodymium in permanent magnets and integrated circuits.

Resume : Concentrated Solar Power (CSP) systems are identified among the most promising technology to contribute to the energy mix and achieve the European renewables energy target set at 32% by 2030. However, though CSP have demonstrated to be a mature technology, a number of innovative CSP concepts are reported for suffering from problems such as high costs, complexity and poor reliability because of the lack of reliable materials capable of withstanding the high temperatures and harsh environment needed to enhance CSP performances. The NEXTOWER project aimed at introducing a set of innovative materials to boost the performance of atmospheric air-based concentrated solar power (CSP) systems to make them more efficient and economically viable. Tower systems with open volumetric receivers are appealing for the use of ambient air as heat transfer fluid, with clear advantages in terms of environmental compatibility, and show potential for efficient (electrical and thermal) power generation. Yet, their industrial exploitation has been so far hindered by limitations in the materials used both for the receiver - the core component - and for thermal storage. This study aims at identifying the potential environmental impacts and economic performance associated with the development of a on innovative CSP system developed within the framework of the NEXTOWER project. The results of the analysis, per unit of electricity produced, will be compared to other renewable technologies with the same level of dispatchability to better evaluate strengths and limitations of the system under exam. Special focus will be dedicated to the raw materials which are identified as the most innovative potential for this technology. A streamlined environmental evaluation will be performed following an LCA eco-design approach. This will enable the identification of the hot-spots and trade-offs among the relevant environmental categories, and, ultimately, help fine-tune the development of the NEXTOWER system in order to limit its environmental impacts. While the economic performances will be evaluated by estimating the potential Levelised Cost of Electricity (LCoE) of the power produced to identify the relative contribution of the NEXTOWER sub-systems and explore ways for reducing the overall NEXTOWER LCoE.

Resume : Among the most critical aspects of relevance to biomedical applications of nanoscale crystals is their size-mediated functionality in the cellular environment [1]. Here, we combine nanochemistry, detailed characterization and Monte Carlo simulations to explore the relation of size and shape on nanoscale surfaces and interfaces emerging in core-shell iron-oxide nanocrystals, while we also discuss those imperfections that assist magnetic properties relevant to nanobiotechnology [2]. Connecting compositional complexity and nanomagnetism allows us to gain insights on how controlled cation vacancy-induced disorder tailors physical properties, including exploitable thermal energy transfer for small-size magnetic nanocarriers. Synchrotron X-ray total scattering experiments corroborate our idea that size-dependent evolution of the metal-cation valence state, produces pinning defects which promote favorable magnetic exchange interactions at subcritical sizes (< 10 nm), and importantly beyond the limitations of finite-size effects alone. We offer a description of the atomic interactions and provide some knowledge on the different length-scale mechanisms required to facilitate the performance of single-crystal nanoscale particles as functional nanoheaters. [1] D. Yoo et al., Acc. Chem. Res. 44, 863, (2011). [2] A. Lappas et al., Phys. Rev. X 9, 041044 (2019).

Resume : As known, the permanent magnets are one of the strategic metal-based products in the world industry due to a wide range of their applications: from micro-electromechanical and nano-electromechanical systems to high-power electricity generators using many tons of magnetic materials containing critical rare-earth metals. Such the non-renewable elements are the main factor that constrains or increases the cost of fabrication of magnetic products. The new tailored metallic phases do not containing critical elements (non-renewable on the Earth) may act as an alternative to the permendur and rare-earth permanent magnets. The martensitic α″-Fe16N2-type phase, — an object of our study, — with unique and promising magnetic properties stands as an alternative to the rare-earth intermetallics or permendur on the world market of the production of permanent magnets. Currently, there is a lack of full understanding of how we can change the external thermodynamic parameters (temperature, pressure or deformation) and regulate the structure, thereby the properties of magnetic α″-Fe16N2-type martensite. To overcome such a theoretical gap, we are motivated in the development of the microscopic model of a “hybrid” solid solution, where the interstitial non-metal (N) atoms from octahedral interstices can partially move to the sites of b.c.c. (or tetragonal) lattice of metal (Fe) with vacancies. We constructed the model and adapted it for the non-stoichiometric phase of Fe–N martensite maximally ordered by analogy with α″-Fe16N2, where N atoms are in the interstices and at the sites of b.c.t.-Fe above the Curie point. We stress an importance of adequate data on the available (in the literature) temperature- and concentration-dependent microscopic energy parameters of the interactions of atoms and vacancies. The features of varying (viz. non-monotonic decreasing with increasing temperature) the relative concentration of N atoms in the octahedral interstices of b.c.t.-Fe, and therefore, the degree of its tetragonality (correlating with this concentration) are elucidated. Within the wide range of varying the total content of introduced N atoms, the ratio of the equilibrium concentration of residual site vacancies to the concentration of thermally activated vacancies in a pure b.c.c.-Fe is demonstrated at a fixed temperature.

Resume : In spintronics, antiferromagnetic layers have been used to pin a magnetisation of its neighbouring ferromagnetic layer via the exchange coupling in a spin-valve-type read sensor in a hard disk drive and in a magnetic random access memory. The magnetic memories can be used in extreme conditions, such as near the engine of an automobile and motor bicycles at high temperature, which is advantageous over the conventional semiconductor-based memories. The most commonly used antiferromagnet is an IrMn alloy because of its corrosion resistance and high Néel temperature [1]. However Iridium is a critical raw material as a platinum group metal, which requires the development of an alternative material [2]. We have been developing alternative Heusler alloys with the form of X2YZ consisting of common elements, X, Y and Z, to replace the IrMn alloy [3]. We reported a completely disordered phase with X-Y-Z mixing can still exhibit antiferromagnetic behaviour for Mn-based Heusler alloys [4]. We investigated D019 Mn3Ga and Mn3Ge films with and without doping of ferromagnetic elements. These films were found to be in a single-phase polycrystalline phase with perpendicular anisotropy. By attaching a ferromagnetic Co0.6Fe0.4 and [Co/Pt]3 layer, both in-plane and perpendicular exchange bias fields were measured to be 446 Oe at 120 K for a Mn1.99Fe0.49Ga film and 163 Oe for Mn1.96Fe0.67Ga film at 120 K, respectively. Median blocking temperature of Mn2FeGa films were estimated to be 235 and 185 K for in-plane and perpendicular cases, respectively. These results are compatible with the current memory fabrication process and very useful to develop antiferromagnetic materials and implement them into a spintronic device. This work has partially been supported by EU-COST (Ithaca), UK-EPSRC (EP/M02458X/1 and EP/V007211/1) and JST CREST (JPMJCR17J5). [1] A. Hirohata and K. Takanashi, J. Phys. D: Appl. Phys. 47, 193001 (2014). [2] A. Hirohata et al., J. Phys. D: Appl. Phys. 50, 443001 (2017). [3] C. Felser and A. Hirohata, Heusler Alloys (Springer, Berlin, 2015). [4] T. Ogasawara et al., J. Magn. Magn. Mater. 473, 7 (2019).

Resume : Additive manufacturing attracts much interest in technological sectors as it allows for designing and fabricating complex objects with tuned properties [1]. In the permanent magnet (PM) sector the challenge is to develop magnets with high filling factor (FF), while avoiding the deterioration of their PM properties. Improved ferrites and MnAl alloys are promising rare earth-free candidates for plugging the gap between conventional ferrites and NdFeB, provided a successful development of their PM properties [2]. Composites (PM particles/polymer) made of gas-atomized τ-phase MnAlC (industrial collaboration with Höganäs AB, Sweden), Sr-ferrite, NdFeB, and hybrid (Sr-ferrite/NdFeB) powders (mean particle size: 5-50 μm) have been used for extruding magnetic filaments [3]. The combination of materials and particle sizes allowed for obtaining PM filaments with a coercivity ranging between 1.5-10 kOe. Particle size was a key parameter for obtaining flexible filament: fine particles (< 20 μm) and an optimized fine-to-coarse particles ratio lead to filaments with a high FF (> 80%) and non-deteriorated PM properties. Optimized and highly loaded MnAlC-based filament was used for 3D-printing objects as a proof-of-concept. The magnetic measurements carried out on the printed objects have proved that alternative PM materials can be efficiently synthesized and processed for developing novel PMs by additive manufacturing under controlled processing temperature, which might be used for sensing applications [3]. Acknowledgements Authors acknowledge fruitful collaboration and discussions with B. Skårman, H. Vidarsson and P.-O. Larsson from Höganäs AB (Sweden), and A. Nieto and R. Altimira from IMA S.L.U. (Spain). Authors additionally acknowledge financial support from EU M-ERA.NET and MINECO through the projects "NEXMAG" (M-ERA.NET Project Success Case, Ref. PCIN-2015-126) and "3D-MAGNETOH" (Ref. MAT2017-89960-R); Regional Government of Madrid through "NANOMAGCOST" project (Ref. P2018/NMT-4321); and Höganäs AB through the industrial contract "GAMMA". References [1] L.E. Murr, J. Mater. Sci. Technol. 32, 987 (2016). [2] A. Bollero et al., ACS Sustainable Chem. Eng. 5, 3243 (2017); J. Rial et al., Acta Mater. 157, 42 (2018). [3] E.M. Palmero et al., Sci. Technol. Adv. Mater. 19, 465 (2018); IEEE Trans. Magn. 55, 2101004 (2019); Addit. Manuf. 33, 101179 (2020).

Resume : Nowadays the use of permanent magnets (PM) is increasing in different applications such as energy and transport. In order to obtain a high magnetic performance currently the most extended choice are PMs containing critical raw elements (rare-earths (REs)). Alternatives are investigated to fill the gap between ferrites and NdFeB magnets. MnAl alloy has become a RE-free PM candidate as long as development of the ferromagnetic τ-phase [1]. The theoretical high maximum energy product (BH)max of MnAl is 12 MGOe, with an advantageous lower density compared to NdFeB (5.2 vs. 7.6 g/cm3) [2]. Increasing coercivity has been achieved recently by microstructural modification and controlled phase transformation through the flash-milling process [3,4]. In this study, MnAlC bulk magnets were obtained by hot-pressing starting from gas-atomized and flash-milled (60 s) powder [5]. A novel result is the demonstration that MnAlC magnets can be prepared by hot-pressing taking ε-phase powder as a precursor and managing, in a single step, both the ε to τ-MnAlC phase transformation and the powder compaction to result in a high-density (93%) MnAlC magnet. The hot-pressed magnet showed an enhancement of the coercivity of up to 25 % and a slightly superior magnetization at remanence by comparison with the annealed loose powder. The large coercivity obtained for the magnet may be explained based on a reduced mean crystallite size (27 nm), the induced strain during compaction and the formation of both β-Mn and Mn3AlC phases [5]. On this basis, we have demonstrated that coercivity of the compacted magnet can be further increased in about 15% by starting from flash-milled gas-atomized powder, due to an enhanced content of β-Mn and Mn3AlC phases. In order to validate our single step approach, we have also applied hot-pressing to gas-atomized τ-phase MnAlC powder (previously transformed from ε-phase through annealing, i.e. implying an additional processing step). Remanence and coercivity values are comparable, which proves that the single step method used in this study presents a new route in comparison to a two-steps method. These results open the path to new possibilities towards the industrial fabrication of MnAlC as a RE-free PM alternative. Acknowledgments IMDEA acknowledges financial support from EU M-ERA.NET and MINECO through the projects "NEXMAG" (Project Success Case at H2020 M-era.Net Programme, Ref. PCIN-2015-126) and "3D-MAGNETOH" (Ref. MAT2017-89960-R); Regional Government of Madrid through "NANOMAGCOST" project (Ref. P2018/NMT-4321); and Höganäs AB through the industrial collaboration "ECNanoManga". [1] H. Kono, J. Phys. Soc. Japan 13, 1444 (1958). [2] J.H. Park et al., J. Appl. Phys. 107, 09A731 (2010). [3] J. Rial et al., Acta Mater. 157, 42 (2018). [4] J. Rial et al., Engineering. 6 (2), 173 (2020). [5] C. Muñoz-Rodríguez et al., J. Alloys Compd. 847, 156361 (2020)

Resume : Earth-abundant materials for electrochemical water splitting typically show a lower efficiency than noble and rare metal electrocatalysts. Nanostructuring and appropriate material design can largely improve the performances of low-cost electrocatalysts, opening the route towards profitable mass production. Here, we report on a quantitative investigation of the oxygen evolution reaction (OER) on Ni-based nanowall (NW) electrodes. The NiO and Ni(OH)2 NW films (200 or 400 nm thick) are produced by chemical bath deposition followed by calcination at 350 °C. The morphology and the chemical arrangement of the NW were studied, before and after the OER, by scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The OER electrocatalytic activity was investigated by electrochemical measurements under alkaline conditions (1 M KOH), demonstrating a stable overpotential of 345 mV at 10 mA cm−2, a Tafel slope of 48 mV dec−1 and an O2 turnover conversion frequency (TOF) of up to 0.18 s−1. The quantitative measurement of active electrocatalysts, through cross-correlation of the experimental data, shows nearly 100% material utilization in the 200 nm NiO NW. In thicker NiO or Ni(OH)2 NW films this fraction decreases below 60%, probably due to the decrease in the electric potential along the nanostructure, as revealed by numerical simulation. These data and discussion support the use of low-cost Ni-based nanostructures for high-efficiency and sustainable electrocatalysts.

Resume : Platinum group metal-free electrocatalysts have shown promising features for catalyzing oxygen reduction reaction (ORR) at the cathode of different types of fuel cells [1-3]. However, high costs for synthesis, stability and activity issues under operating conditions, still limit their applicability. We propose a facile synthesis strategy to obtain Fe-N-C ORR catalysts consisting on a nitrogen and iron wet impregnation of carbon black followed by pyrolysis steps. Three different nitrogen sources (dopamine, imidazole and benzimidazole), and two different pyrolysis atmospheres (Ar and NH3) were investigated. The obtained materials were characterized in terms of structure, morphology, surface chemistry, thermal and electrochemical properties. Tailoring the synthesis parameters allowed obtaining electrodes with a high porosity and accessible active sites, as indicated by Raman and X-ray photoelectron spectroscopies, and cyclic voltammetry with rotating ring disk electrode. We found that the pyrolysis step under ammonia atmosphere led to high electrochemical active surface area (ECSA) and the use of imidazole as nitrogen-rich organic precursor improved ORR activity in alkaline pH. This can be ascribed to the modification of surface chemistry of the electrocatalysts triggered by the N-rich organic precursor and pyrolysis atmosphere. The catalyst obtained by using imidazole and pyrolyzed in NH3 had a variety of iron-, oxygen- and nitrogen-functional groups, nitrogen being mainly distributed in imine-, pyridinic- and pyrrolic-N. In addition, durability tests showed a stable ECSA and ORR activity after cycling of the prepared electrocatalysts outperforming durability of Pt-based materials in alkaline environment and indicating applicability in anion exchange membrane fuel cells. References 1. Thompson et al. Nat Catal, 2019, 2, 558. 2. Mecheri et al, Appl Catal B-Environ, 2018, 237, 699. 3. Artyushkova et al. ACS Appl. Energy Mater. 2019, 2, 5406.

Resume : In recent years, with the increasingly prominent problem of environmental pollution, photocatalytic materials based on perovskite or perovskite-derived structures have become the focus of research and attention due to their excellent performance for degradation of persistent organic pollutants. Photocatalysis is a promising option for the remediation of low concentrations of organic pollutants in waste-water because of its high oxidation potential without utilizing any chemicals reagents. In practical applications the perovskite structure as photocatalyst has limitation such as the problem of easily composited photo-generated electrons and holes that may reduce catalytic efficiency. In order to improve the photocatalytic performance and efficiency of electron- hole separation, graphene has been introduced in the perovskite - type oxides structure. This work presents the elaboration and testing the photocatalytic perovskite- graphene LaMnO3-rGO (LMO-rGO) and SrTiO3-rGO(STO-rGO) nanocomposites system by novel eco-friendly chemical solution deposition processes. In order to determine the thermal decomposition behavior, the precursor powder obtained by drying the precursor solution was investigated by thermogravimetry coupled with quadrupole mass spectrometry (TG-QMS), and differential thermal (DTA) analysis. The kinetics of the thermal decomposition of the precursor powder was studied under oxygen and humid oxygen atmosphere from ambient temperature up to 1000 oC. The fabrication of the LMO-rGO and STO-rGO films consists in the deposition of the precursor solution on glass substrates by dip-coating, followed by pyrolysis and crystallization in a control atmosphere. The films have been structurally and morphologically characterized by XRD, AFM and TEM, respectively, and the photocatalytic properties have been determined. Acknowledgements This work was supported by UEFISCDI through PN-III-P1-1.1-TE-2016-2017, SMARTWIN research grant No. 132/10.10.2018

Resume : One of the major challenges in the field of hydrogen generation from water splitting is the development of earth-abundant, efficient and stable electrocatalysts alternative to the noble metal catalysts whose large-scale application is limited by high cost and scarcity. Transition metal compounds have recently sparked considerable attention owing to their low cost, availability and theoretically high catalytic activity. Particularly, Ni-based metal alloy phosphides have been proved to show enhanced catalytic performance for the oxygen evolution reaction (OER) involved in the water electrolysis. Herein, we report a feasible and efficient chemical method for the fabrication of nickel phosphide (Ni-P) electrocatalysts via electroless deposition on nickel substrates. The physico-chemical characterizations show the formation of the desired phase. The effect of the structural and morphological properties of the deposited material on the electrocatalytic performance is discussed. The electrochemical investigations show that the Ni-P alloy exhibits a remarkable oxygen evolution reaction activity in alkaline media, delivering a current density of 10 mA cm−2 at the overpotential of only 292 mV with a long-term stability. These findings suggest that nanostructured Ni–P on nickel foam is a potential candidate for boosting H2 production through water splitting. Finally, the present electroless method provides a facile design for the synthesis of efficient non-noble metal electrocatalysts.

Resume : We discuss the effects of annealing on the physical properties of radio-frequency sputtered indium tin oxide (ITO) thin films, grown onto optical glass substrates. Two types of thermal treatments were performed denoted here in-situ and ex-situ. The in-situ one consisted of intentionally heating the samples’ substrate during the deposition process, while the ex-situ annealing was made using an oven at 200°C, 300°C, and 400°C, respectively. The structural, optical, morphological, and electrical properties of fabricated samples were discussed in terms of pristine ones. Both in-situ and ex-situ thermal treatments improved the crystalline arrangement of ITO thin films, although no significant changes were observed in their optical properties. By evaluating the Skewness parameter was determine that the annealing affects the planarity of samples. The electrical behavior was analyzed by Van der Pauw measurements in the ranges of 300 K – 10 K and it showed that by the ex-situ thermal treatment the electrical resistivity values were increased, most likely due to the increase of the density of oxygen vacancies. Keywords: indium thin oxide, radio-frequency magnetron sputtering, thermal treatment, annealing Acknowledgments: This work was financially supported by The Romanian National Authority for Scientific Research, UEFISCDI, under the project 25TE/2020 and project 115TE/2020.

Resume : Random networks of 1D nanoelements, such as nanotubes, graphene nanoribbons, and metal nanowires, have attracted significant research interest recently for next-generation transparent conductors as a substitute for indium tin oxide. At high optical transmittance values required for transparent conductors, the conductivity of nanowire networks is governed by percolation transport. It is generally assumed that the nanowire-nanowire junction resistance is much larger than the nanowire resistance itself. Although this is the case for nanotube networks, recent experiments have shown that, for metal nanowire networks, the junction resistance can be significantly lowered by post-deposition treatments. In this work, we present comprehensive Monte Carlo simulations to study the effect of the junction-to-nanowire resistance ratio on the conductivity and percolation critical exponents of nanowire networks. We vary the resistance ratio over six orders of magnitude, ranging from a junction- to a nanowire-dominated network. We study the effect of the resistance ratio as a function of nanowire density, nanowire length, device size, nanowire alignment, and nanowire curviness. We find that the resistance ratio plays a crucial role in determining both the conductivity and the percolation critical exponents of nanowire networks. Monte Carlo simulations are an essential predictive tool for investigating and optimizing the electronic properties of transparent, conductive nanowire networks as a potential substitute for critical raw materials.

Resume : Photovoltaics (PVs) fabricated by printing at low temperature onto flexible substrates are attractive for a broad range of applications in buildings and transportation, where flexibility, colour-tuneability, light-weight and low cost are essential requirements. Two emerging PV technologies that have strong potential to meet these requirements are organic PVs and perovskite PVs. However, it is widely recognised that these classes of PV can only fulfil their full cost advantage and functional advantages over conventional thin film PVs if a suitable transparent, flexible electrode is forthcoming.[1] Indium-tin oxide (ITO) is currently the dominant transparent conductor used in opto-electronics, including PVs. However, its fragile ceramic nature makes it poorly compatible with flexible substrates and indium has been identified as a ‘critical raw material’ for the European economic area, due to the high risk of supply shortage expected in the next 10 years.[2] Consequently there is a need to develop a viable alternative to ITO, particularly for utility in emerging PVs large for which quantities will be needed in the coming decades to help address the threat posed by global warming. Grids and fused nanowire networks of the most electrically conductive metals; silver and copper, can perform as well as ITO as a transparent electrode in PVs [3]. Conventional methods for fabricating these types of electrodes involve printing or spraying costly solutions of metal nanoparticles or nanowires, or selective removal of metal by etching thin films of these metals using harmful chemicals, or by electrochemical deposition - an inherently chemical intensive and slow solution based process. This talk will present a new approach to the fabrication of high performance transparent electrodes based on both grids [4,5] and fused nanowire networks [6] of these metals, and demonstrate utility in organic PVs. These electrodes offer a far-field transparency > 80% and sheet resistance ≤ 5 ohms per square on flexible plastic substrates, performance that exceeds that of ITO coated plastic. The new approach described is based on the finding that silver and copper vapour do not condense onto certain organofluorine compounds, so these metals can be selectively deposited by thermal evaporation without a mask. The beauty of this approach lies in its simplicity and versatility, since vacuum evaporation of metals is a well-established and widely available metal deposition method, and the shape and size of the metal features deposited is limited only by the dimensions of the organofluorine free domains. This new approach avoids the use of harmful chemical etchants and critical raw materials, and leaves the metal surface uncontaminated. References [1] Lu, H., Ren, X., Ouyang D., Choy, W.C.H., Small, 14, 2018,1703140. [2] https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:52020DC0474 [3] Lee, H. B, et al. J. Mater. Chem. C, 7, 2019, 1087. [4] Varagnolo, S., Lee, J., Amari, H., Hatton, R. A., Materials Horizons, 7, 2019,143. [5] Varagnolo, S, Park, K-W., Lee, J-K., R. A. Hatton, J. Mater. Chem. C, 8, 2020, 13453. [6] Lee, J., Varagnolo, S., Walker, M., Hatton R. A., Adv. Funct. Mater., 30, 2020, 2005959.

Resume : Nowadays, research in new materials is instrumental to reach a sustainable, energy saving and eco-friendly development. Materials free of “Critical” Raw elements are very attractive and the research in this direction is strongly increased, looking for available alternatives and the most promising materials are new organic materials. Polymers can guarantee very high versatility in terms of structural and optical response with high potential in several applications. We studied the properties of a novel organic compound (2,4-diamino-6-phenyl-1,3,5-triazine), thermally treated (400°), for the synthesis of gold nanopores controlling the degree of screw dislocation. Thanks to their properties the obtained structures are suitable for photocatalytic, biosensing and imaging applications.

Resume : BPO4 crystal has one of the shortest absorption edges of 134 nm and it is perspective as a media for blue lasers. The use of low temperature gradients in the process of single crystal growth is necessary to reduce the temperature stresses of the growing crystal and to improve the crystal quality. The material obtained under these conditions has significant advantages such as increased optical homogeneity and high structural perfection. The TSSG method was used for BPO4 crystals growth [1]. Samples weighing up to 1.5 g were obtained. The growth was carried out under conditions of a low axial temperature gradient of ~ 1K/cm. The seed was oriented in [010] direction. The critical influence of temperature fluctuations that led to the growth of plate crystals was determined. The influence of chemical purity both raw materials and grown crystals analyzed by ICP-MS on absorption spectra, optical homogeneity, point defects and thermal conductivity in 10-310 K temperature range was studied. The research was supported by Russian Science Foundation by the grant 19-79-10003. [1] S. Zhao, G. Zhang, K. Feng, J. Lu, Y. Wu. Crystal Research and Technology, 2012, 391–396.

Resume : The design of highly emissive lanthanide-based compounds especially in NIR-region (800-1600 nm) is still a challenge, justifying the intense research activity of the scientific community in this field. А series of novel intensive NIR-emitting neodymium(III) complexes with pyrazolic 1,3-diketones bearing linear CnF2n 1 group (where n = 1,3,6) were synthesized. The symmetry of ligand environment was established by analysis of Stark splitting of emission lines in photoluminescence spectra and single crystal X-ray diffraction data, and was additionally investigated in terms of Judd–Ofelt theory. The most intensive luminescence of the complexes was observed for the (4)F(3/2) → (4)I(11/2) transition commonly used for lasing. However, the (4)F(3/2) → (4)I(9/2) transition unexpectedly makes the major integral contribution to the luminescence of the compounds. Based on the electroluminescence studies, we revealed the potential of complexes for fabrication of NIR-emitting OLEDs. Pure NIR-emission at 880 and in some cases around 1060 nm was observed for simple solution-processed OLED structures. New complexes due to their high solubility (up to 6 % by weight) in acrylic monomers such MMA were successfully used for preparation of hybrid materials optically transparent under visible light but emitting characteristic for Nd3 ion lines in NIR-region when exposed to mild UV-light (365 nm). We are grateful to Russian Science Foundation (project № 19-13-00272) for the financial support of this research.

Resume : Fluoride compounds and solid solutions in PbF2-REF3 (RE= rare earth element) systems with the general formula Pb1-xRxF2 x, fluorite structure and a wide homogeneity region are of interest for investigation as photonics materials, phosphors, including anti-Stokes ones. We synthesized solid solutions both by the solid-phase method and by co-precipitation from aqueous solutions. The crystallization region of single-phase powders in PbF2-ErF3 system was 12-42 mol.% ErF3 at co-precipitation techniques. The most intense bands on the Er3 luminescent spectra are those in the blue and green parts of the spectrum. In samples obtained by solid-phase synthesis, effective anti-Stokes caused by up-conversion was observed. Samples obtained by co-precipitation of anti-Stokes luminescence did not appear. The cubic single-phase region in PbF2-EuF3 system was 0-46 mol.% EuF3 at solid-phase synthesis and 7-53 mol.% EuF3 at co-precipitation techniques. Eu3 luminescent centers in solid solutions obtained by solid-phase synthesis had a greater symmetry than those obtained by co-precipitation. This research was financially supported by the Russian Science Foundation by the grant No 19-79-10003.

Resume : Critical raw materials (CRMs) are key elements for the operation of many lighting devices. Nevertheless, in the last few years, a lot of effort has been made in order to develop CRM-free technology which can effectively reduce the use of toxic heavy metals. Fluorescent carbon-based nanoparticles known as Carbon Dots (CDs) represent a potential powerful system to achieve the production of more environmental-friendly lighting tools e.g. LEDs and lasers. CD tunable photoluminescence emission across the visible range, along with their facile and cost-effective synthesis routes, makes them highly desirable for this application. Our research focuses on understanding the deeply connection between structure and photoluminescence to properly adapt CD properties to lighting use. CDs obtained by hydrothermal synthesis of citrazinic acid and urea have been fully characterized underlying the role of molecular state on the emissive contribution.

Resume : Thermoelectric (TE) materials are prospective candidates for the energy applications by converting the waste heat into electricity. CoSb3 is a simple binary compound which can be used as a potential TE material for a wide range of temperature. Pristine CoSb3 has n-type character at room temperature, which changes to p-type at ~450K. Some of the research groups have observed p-type [1, 2] while some obtained n-type [3-5] conduction in CoSb3 by similar processing routes. This kind of bipolar nature of the CoSb3 could be useful to tune it as a p-type or n-type TE material. There are some studies which show that the excess of Sb in CoSb3, i.e. CoSb3 x eliminates the bipolar conduction in CoSb3 and leads to p-type conduction [6]. This work presents the effect of stoichiometric ratio on the thermoelectric performance of the CoSb3 based Skutterudites materials. We have synthesized a series of CoSb3 based samples with different stoichiometry by changing the Sb and Co ratio and studied the effect on the TE properties of the alloy. The fast and cost-effective route of arc melting and spark plasma sintering was utilized for the sample preparations. The temperature-dependent electrical and thermal transport properties were measured and the figure-of-merit (ZT) has been calculated. The experimental results indicate that all of the synthesized samples exhibit a semiconducting behavior and yield a high Seebeck Coefficient (n-type conduction) from room temperature to ~550 K. Thereafter, it shows the p-type conduction. Further, an enhanced figure-of-merit (ZT) ~ 0.06 at 430 K was realized for the particular composition Co0.97Sb3.03. The TE performance of these alloys can be improved by employing the doping approach. References [1] T.H. Nakagawa H, Kasama A, Anno H and Matsubara K, Proc. 16th Int. Conf. on Thermoelectrics (Dresden, Germany) (Piscataway: IEEE) (1997) 351. [2] Z. Zhou, C. Uher, A. Jewell, T. Caillat, Influence of point-defect scattering on the lattice thermal conductivity of solid solution Co (Sb 1− x As x) 3, Physical Review B, 71 (2005) 235209. [3] Y. Kawaharada, K. Kurosaki, M. Uno, S. Yamanaka, Thermoelectric properties of CoSb 3, Journal of alloys and compounds, 315 (2001) 193-197. [4] K. Wojciechowski, J. Toboła, J. Leszczyński, Thermoelectric properties and electronic structure of CoSb3 doped with Se and Te, Journal of alloys and compounds, 361 (2003) 19-27. [5] V. Kuznetsov, L. Kuznetsova, D. Rowe, Effect of partial void filling on the transport properties of NdxCo4Sb12 skutterudites, Journal of Physics: Condensed Matter, 15 (2003) 5035. [6] W.-S. Liu, B.-P. Zhang, J.-F. Li, L.-D. Zhao, Effects of Sb compensation on microstructure, thermoelectric properties and point defect of CoSb3 compound, Journal of Physics D: Applied Physics, 40 (2007) 6784.

Resume : Non-ITO transparent and conductive oxide films are materials of growing importance in application fields like thin film solar cells, photocatalysis, environment purification, gas sensors or photo-electro-chromic devices and other emerging technologies. In this work, TiO2 and Nb-doped TiO2 thin films prepared by RF sputtering in different atmospheres (Ar, Ar-O2 and Ar-H2) were deposited. The electrical and optical properties of the Nb-doped TiO2 thin films, in the as-grown state and after vacuum annealing, were studied in relation with the chemical properties, structural defects and crystallinity of the films grown in the different sputtering gas mixtures. Strong correlations were evidenced between the nature, the morphology and the environment of the defects and the electrical parameters characterizing the doped films.

Resume : Currently, electric motors and generators use high energy permanent magnets based on RE2Fe14B phases (RE: rare earth) with high amounts of RE often including heavy-RE metals (Dy, Tb), the most critical group of the raw materials. REFe12 alloys are seen as potential alternatives to RE ₂ Fe ₁₄ B since they have a significantly lower amount of RE-metals with similar or better values of remnant magnetization (MR) and high magnetocrystalline anisotropy (MCA), which can give rise to a large energy product (BH) _max. However, these 1:12 alloys need other elements (i.e. Ti, Si, Mo) replacing Fe in order to stabilize the ThMn ₁₂ tetragonal structure that gives rise to the high values of MCA. In this work, we have studied the SmFe ₁₂ system with small substitutions of Mo in order to stabilize the 1:12 tetragonal structure and determine its effect on the MCA and the resulting coercivity in nanostructured magnets. Alloys with nominal compositions SmFe _12-x Mo _x (x = 0.5, 1) were produced by arc-melting and then annealed at 1050 ºC for 48 h (intrinsic properties of the 1:12 phase on field-oriented powders). Extrinsic properties were studied in melt spun ribbons: wheel speeds of 15 and 35 m/s (resulting into amorphous or highly disordered ribbons), which were heat-treated, in vacuum, at different temperatures ranging from 650 ºC to 950 ºC for different times in order to obtain nanostructured ribbons that crystallized in the ThMn12 tetragonal structure. Structural and magnetic characterization showed that small Mo substitutions (x = 0.5) can stabilize the uniaxial 1:12 structure keeping high MCA (anisotropy field H _a >10 T), developing coercivities of 0.36T after optimal heat treatments. This coercive field is still low regarding to H _a . This may be due to the crystallization of bcc-Fe phase during processing of samples as a consequence of the Sm evaporation.

Resume : The structural, elastic, electronic, and magnetic properties of quaternary OsCrMnSb and IrCrMnSb Heusler alloys are performed employing ab initio electronic structure calculations. It has been identified that the YI type is the most stable structure among the three configurations for both OsCrMnSb and IrCrMnSb alloys in the magnetic state. The calculated cubic elastic constants show that these alloys fulfill the mechanical stability criteria. The band structures and density of state calculations reveal the half-metallic (HM) behavior of these alloys with a direct gap, and the half metallicity is rather originated from the Cr-d states. Results on magnetic properties suggest that OsCrMnSb and IrCrMnSb are half-metallic anti-ferromagnets. However, the inclusion of spin-orbit coupling affects strongly the IrCrMnSb alloy, losing its HM nature.

Resume : In recent years, graphene has attracted great interest in different research fields while its electronic and optical properties have been intensively studied in view of several applications, in particular as transparent conductive electrode (TCE). Graphene can be readily grown on copper foils by CVD and the extremely high room-temperature carrier mobility (≈20 000 cm2V−1s−1) makes it a promising candidate to replace the conventional semiconductor and conductor materials in specific electronic devices. Handling these 2D, atomic thickness films has proved an arduous task requiring the development of novel technologies. In this framework, it is extremely useful to be capable to fabricate and handle membranes composed of single or multi-layer graphene completed with metallic contacts of arbitrary geometry. This gives the possibility to transfer in a single step the contacted graphene on the target substrate using the cyclododecane supported technique invented by the authors. The main advantage of the technique is the possibility to obtain a novel TCE/metal-grid integrated structure, especially applicable in the photovoltaic field, which allows to avoid any further substrate process after the transfer of graphene. To test this concept, in the present work we have realized Graphene/Gold-grid membranes of different area and transferred them on c-Si substrates in order to obtain Graphene/silicon Schottky barrier solar cells. The devices have been completely electrically characterized. An encouraging 7.1% power conversion efficiency (PCE) has been obtained by current-voltage characteristics under 1 Sun illumination for a device with 4 cm2 active area. The experiment can be extended to Graphene membranes with grids made of other metals, such as Aluminium.

Resume : The most widely used transparent conductor electrode (TCE) in organic devices is Indium Tin Oxide (ITO) due to its high optical transparency, metallic conductivity and high work function favoring an efficient injection of holes into many organic semiconductors. Because indium is a critical raw material, expensive, short supply, toxic and difficult to use on flexible substrates, it is necessary to identify new alternative for TCE from cheaper materials showing high transmission and low resistivity for small thickness of the electrodes. This paper presents some investigations on the optical and electrical properties of the heterostructures realized with arylenevinylene oligomer: perylene diimide mixed active layer and 3 layers, oxide/metal/oxide TCE (e.g. ZnO/Ag/ZnO; ZnO/Au/ZnO, AZO/Ag/AZO, AZO/Au/AZO). The 3 layers electrode was deposited by sputtering on glass and optically and electrically characterized in correlation with the morphological and structural particularities evidenced by SEM, AFM and XRD measurements. The heterostructures were characterized by spectroscopic (UV-VIS, Photoluminescence) and microscopic (SEM, AFM) methods and the properties of heterostructures with different types of 3 layers TCE will be compared with those of the same heterostructures realized with ITO electrode. The effect of a supplementary layer of PEDOT-PSS intercalated between the TCE and organic layer on the properties of the heterostructures has been also investigated.

Resume : Nowadays, recycling waste aluminium materials are of great importance in reducing environmental pollution and growing economic proficiency. Herein the aluminium (Al) powder prepared from waste Al cans with high energy-grinding cum ball milling method. The different sizes (200 μm, 500 μm, 500 μm, 750 μm) of aluminium can powder achieved with different ball milling time (30 min., 1 hr, 2 hr, 3 hr) reaction. The prepared waste Al cans powder and their composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET). The hydrogen generation of aluminium and activated aluminium powders were systematically investigated in the tap water. The results exhibited that powder size, ball milling time, pH concentration, acidic-basic media and reaction temperature affected the hydrolysis rate and hydrogen yield significantly.; 0.5 gm (200 μm) of Al cans powder with grinding time of 1 hour generated 515 mL hydrogen within 10 minutes in the optimal reaction conditions. On the other hand, activated aluminium composites have shown enhanced hydrogen generation. From the observation, it is found that the milling process formed many grain boundaries and dislocations on the particle surface and the different metals support to Al surfaces formed micro-galvanic cells during the hydrolysis reaction which is responsible for the acceleration of hydrogen reaction. However, the synergistic effect in activated Al composites was also observed. Additionally, the activated Al composites exhibited good recyclability after subsequent runs of hydrolytic response, making it a robust catalyst for hydrogen generation. The hydrolysis mechanism was also predicted based on the experimental results and kinetic study. The production of hydrogen from hydrolysis of waste Al cans powder is a promising way to reduce environmental pollution and instrument corrosion and could be considered as a potential catalyst for portable hydrogen fuel systems.

Resume : Alkaline membrane fuel cells (AEMFCs) have been seen as strong technological candidates in the transition to a sustainable economy, since these devices can generate electrical energy at low or zero pollutant emissions. However, oxygen reduction reaction (ORR) at the cathode side of these cells still hamper their applicability due to the use of scarcely available and expensive materials such as Platinum Group Metals (PGMs). In this context, PGM-Free catalysts appear as a suitable alternative. Despite the promising results reported in the literature, high costs for synthesis, stability and activity issues under operating conditions still limits their applicability in AEMFCs [1-3]. Metal organic frameworks (MOFs) represents a promise and scalable alternative to obtain atomically dispersed M-N-C active sites in PGM-Free catalysts. These materials consist of metal-centered joined by organic linkers to form large networks of crystalline nature [4]. High surface area, structured nano and microscale cavities, availability of in-pore functionality and outer-surface modification, and diversity of metal center ions and N-containing ligands are among the properties that render MOFs attractive alternative as M-N-C precursors [5]. In this scenario, we propose the synthesis of Fe-N-C and Co-N-C catalysts derived from Zeolitic Imidazolate Frameworks (ZIFs), synthesized by solvothermal method at room temperature. In our approach, functionalized Black Pearls were used as carbon support and zinc-based ZIFs as template to incorporate iron (II) ions onto the ZIF, for Fe-N-C catalysts, or directly used as a single source of metal and nitrogen (Co-N-C), by a wet impregnation and pyrolysis steps in argon atmosphere. The effect of pyrolysis temperature over graphitization of the zinc-based ZIF and removal of the zinc (II) ions from the Fe-N-C catalyst precursor and the effect of Co-based ZIF percentage in the Co-N-C materials were investigated. Synthesis of ZIFs were confirmed by FTIR, XRD and TGA analysis and electrochemical characterization by static and hydrodynamic cyclic voltammetry shown that, the increase of pyrolysis temperature led to high ORR activity of the Fe-N-C catalysts and the high content of Co-based ZIF also enhance the catalytic performance. Both Fe- and Co-N-C exhibited a competitive ORR activity compared to Pt- and PGM-Free based catalysts reported in literature [6,7]. References 1. Firouzjaie et al. ACS Catal. 2020, 10 (1), 225–234. 2. Mustain et al. Energy Environ. Sci. 2020, 13 (9), 2805. 3. Mecheri et al, Appl Catal B-Environ, 2018, 237, 699. 4. Barkholtz et al. Materials Horizons, 2017, 4, 1, 20. 5. Ren et al. Nano Today, 2013, 8, 6, 577. 6. Martinaiou et al. J. Power Sources, 2018, 375, 222. 7. Santori et al. J. Electrochem. Soc. 2019, 166 (7), F3311.

Resume : CVD graphene has been synthesized and transferred onto different substrates and onto unfinished silicon heterojunction solar cells (Si-HJSCs) to be characterized and tested as innovative front transparent conductive electrode. The devices have area up to 4 cm2 and have been realized on n-type c-Si wafers with three different p-type emitters facing the dry-transferred graphene stack: amorphous silicon (a-Si:H), nanocrystalline silicon (nc-Si:H), and nanocrystalline silicon oxide (nc-SiOx:H). The material characterization has shown that the devised layer-by-layer transfer method provides good quality material with twisted multilayer structure. As for electrical and optical properties, with five layers a sheet resistance of 100 Ω/square has been achieved while maintaining a relatively high transmittance (higher than 85% over the whole visible range). Si-HJSCs cells using n-type Si wafers have been fabricated and completed by transferring graphene on the front side of different p-type doped Si- and SiOx-based emitters. While the graphene integration with p-a-Si:H emitter is found deleterious (S-shaped current-voltage characteristic), the results are encouraging when using graphene onto p-nc-Si:H and p-ncSi-Ox emitter. The best devices with graphene, complemented with optimized front DARC, show a short circuit current density increment of 1.4 mA/cm2 with respect to our reference devices using AZO as TCE, which provides also antireflection effects. Voc and FF are presently lower than the values of the reference cell, likely suffering from a still not optimized contact between graphene and underlying emitter material. Regardless of the presently achieved performance, the observed, not so obvious, compatibility of Si-HJSCs with the proposed graphene implementation and transfer prove the high quality of transferred CVD-graphene over relevant area (up to 4 cm2) and validate the feasibility of the graphene-over-device fabrication sequence, paving the way to graphene-integrated Si-HJSCs, free from conventional plasma-based TCEs and their deleterious effects due to plasma luminescence and ion bombardment. The planned refinement of the graphene fabrication, transfer and handling procedures are all advancements that can also be applied to heterostructures based on other emerging two-dimensional materials.

Resume : The synthesis of novel electrode materials based on earth-abundant and low-cost precursors is of great interest for implementing electrochemical technologies for a more sustainable future. Electrochemical reactions important for generation of low-carbon hydrogen and fuel cell technologies currently require the use of electrocatalysts based on precious metals. In this report we discuss the synthesis of low-cost carbon-based porous cathodes and the study of their activity as electrocatalysts for the hydrogen evolution (HER) and the oxygen reduction reactions (ORR). Low temperature hydrothermal carbonization, followed by reactive thermal treatments, of a resorcinol-based resin containing N-rich and Fe-rich precursors was used for the synthesis of functional carbon electrodes. The resin was blended with a sacrificial polymer and a conductive nanocarbon to enhance porosity and conductivity, respectively. Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) were used to characterize the morphology and metal-content, respectively, while X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) provided information on material composition. The materials were tested in the form of powders as ORR and HER electrocatalysts in alkaline solution and acid solutions, respectively, indicating good activity based on determinations of onset potentials and electron numbers involved. The role of the conductive nanocarbon scaffold is discussed as part of this report. 1. Karthik, M.; Faik, A.; Doppiu, S.; Roddatis, V.; D’Aguanno, B., A simple approach for fabrication of interconnected graphitized macroporous carbon foam with uniform mesopore walls by using hydrothermal method. Carbon 2015, 87, 434-443. 2. Marzorati, S.; Vasconcelos, J. M.; Ding, J.; Longhi, M.; Colavita, P. E., Template-free ultraspray pyrolysis synthesis of N/Fe-doped carbon microspheres for oxygen reduction electrocatalysis. Journal of Materials Chemistry A 2015, 3 (37), 18920-18927.

Resume : The Mn4+-activated crystalline host compounds have been paid increasing attention as the cheap and eco-friendly red-emitting phosphors owing to simple synthetic processes and abundant starting materials. The magnesium and zinc titatanates look very attractive as host matrix since the raw materials used for their synthesis are safe for human health and widely used in pharmaceutical, cosmetic and food industries. In this contribution, we report on optical and structural studies of Mn4+ activated (ZnxMg1-x)2TiO4 red phosphors using X-ray diffraction, photoluminescence (PL) and electron paramagnetic resonance methods. The phosphors were synthesized at 1100°C and 1200°C via solid state reaction. As the Zn content was increased from x=0.1 to 0.75, two phenomena affecting the opposite way on the PL intensity were found: (i) a rise of Mn4+ center concentration, and (ii) an enhancement of Mn4+ PL thermal quenching. It is shown that intense thermal quenching is the main cause of low PL intensity in Zn2TiO4 and (Zn0.75Mg0.25)2TiO4, while the phosphors with x=0.1 and 0.25 demonstrate thermal stability of Mn4+ red PL comparable to Mg2TiO4. An up to 2 times increased Mn4+ red PL in Mn-doped (Zn0.25Mg0.75)2TiO4 sintered at 1100°C as compared to similar Mn4+ activated Mg2TiO4 phosphor was revealed. A decrease of the PL intensity in the phosphors sintered at 1200°C is ascribed to the increase of Mn2+ defect concentration.

Resume : Renewable energies sources are becoming an important reality in combination to energy storage in smart grid and a very relevant application of lithium-ion batteries (LIBs). The increasing use of LIBs is expected to pose problems in lithium supply due to geopolitical constraints and the reduction of lithium resources. [J. Song et al., Journal of Cleaner Production 2019, 215, 570e581] In contrast to lithium, sodium is abundant and more evenly distributed in the Earth’s crust (0.01% lithium vs 2.83% sodium), but sodium has higher molecular weight and less theoretical capacity. For these reasons, in smart-grid integrated energy storage, were gravimetric energy density is not so important like for electric vehicles or for portable devices, sodium ion batteries (NIBs) can be an excellent alternative to LIB's. [F li et al. J. Mater. Chem. A, 2019, 7, 9406] The majority of high performance sodium cathodes reviewed in literature contain toxic and expensive elements like cobalt, vanadium or nichel. [A. Mauger et al., Materials 2020, 13, 3453; H. Li et al., Adv. Funct. Mater. 2020, 30, 2000473] Na0.44MnO2 (NMO) is instead a well-investigated cathode material for NIBs based on earth's abundant and non-toxic elements. Unfortunately NMO presents performance problems in long cycling tests due to Mn3+ dissolution in the liquid electrolyte. [M. S. Chae, Adv. Energy Mater. 2020, 10, 2000564] Many studies have already been pursued to tackle this problem while maintaining the goal of optimizing the work potential of this material. In particular, the role of crystal morphology or the partial substitution of manganese with other transition elements are strategies currently under intense investigation. [X. Zhou et al., Electrochemistry Communications 122 (2021) 106897] In this work, we have investigated the structural, morphological, defect and electrochemical properties of NMO by using a combination of experimental and computational techniques. In particular, the effects of a partial substitution of Cu for Mn in the NMO structure is investigated on the Na0.44Mn0.9Cu0.1O2 composition. Atomistic modelling was used to probe the energetic of dopant incorporation in the tunnel structure; molecular dynamics was used to investigate the Na-ion diffusion in pure and doped systems, highlighting the effect of temperature and doping on the transport properties of this material, particularly with reference to the mechanism of Na intercalation in the different channels of this peculiar crystal structure. From the experimental point of view, the effect of morphology and the structural changes due to Cu-doping was studied by means of SEM-EDS and XRPD analysis. Improved electrochemical performances of the Na0.44Mn0.9Cu0.1O2 compared to the undoped system were demonstrated with a long cycling GCPL test at C/2 rate.

Resume : The production of WEEE, waste of electrical and electronic equipment, is continuously increasing due to the rapid technological development which has been witnessing in the last decades. WEEE represents the fastest growing category of waste globally. This inevitably leads to the problem of disposing this waste as it is not biodegradable and contains substances that are toxic to the environment. This work arises from the need to move from simple disposal in landfills or incineration, to the valorization of such waste through two paths: recovery and recycling. This research focuses on a single type of WEEE, liquid crystal displays (LCD), which is only now entering its end of life phase. The recovery concept is linked to the Critical Raw Material contained in the LCDs, in particular with reference to Indium, for which a method of extraction from LCDs has already been patented. Sadly the recovery of Indium from LCDs cannot be considered economically sustainable and therefore does not allow us to talk about circular economy. Therefore it is also necessary to focus on recycling the material remaining after Indium recovery, for which the construction sector seems to be very promising fate. The work aims to use LCD waste scraps after the extraction of Indium, in a sustainable way both economically and environmentally, making mortars with these waste as ingredients in substitution of binders, additives and aggregates.

Resume : Group III-nitrides have acquired an important role in science and technology of compound semiconductors for fabricating the novel electronic and optical devices. AlN, InN, GaN and to a lesser extent BN and their alloys InGaN, AlGaN, and AlInN are of great interest for the high temperature electronics and optoelectronics applications. InGaN/GaN and AlGaN/GaN heterostructures have been thoroughly studied compared to AlInN/GaN heterostructure due to difficulties of their growth. However, the recent growh technologies leading to high quality films renewed interest especially when the ternary Al1 − xInxN alloy presents a band gap that covers the widest energy range (0.69–6.25 eV) compared to other nitride compounds. This material provides a unique range of composition coverage making it an ideal candidate to fabricate electronic and optoelectronic devices such as high-power high-frequency field-effect transistors, blue and ultraviolet light-emitting and laser diodes, resonant- cavity light-emitting diodes, surface-emitting lasers, and solar blind ultraviolet photodetectors. In the present study, we conducted an ab-initio Density Functional Theory (DFT) analysis of the lattice mismatch and thermal strain effects on the optical and elastic properties of the zincblende phase of the Al1-x Inx N/GaN ternary/binary heterostructure. Optical parameters such as absorption coefficient, reflectivity coefficient, refraction index, extinction index, and high frequency dielectric constant are computed for the Al1-xInxN ternary over the entire range of indium composition x. Furthermore, the elastic parameters such elastic constants C11, C12, C44, shear modulus G ,Young’s modulus E, Poisson ratio ν and ductility factor of the zincblende structure AlN, InN semiconductors and their ternary alloys, Al1-x Inx N were derived. Results are presented and compared with available data for the wurtzite phase, yielding a useful database for the optical device modelling.

Resume : Thermoelectric (TE) is the promising technology for waste heat recovery and the performance of TE devices is given by figure-of-merit, ZT=(S^2 σT)⁄κ, where, S, σ, T & κ stands for Seebeck coefficient, electrical conductivity, absolute temperature & total thermal conductivity, respectively. The combined term S^2 σ describes the power factor (α) which represents the electronic part in TE performance. Half-Heusler (HH) alloys lead the promising class of materials for several applications such as thermoelectrics, magnetism, spintronic. Among HHs, ZrNiSn is widely studied for its thermoelectric properties. Bodak et al.1 show the low-temperature electronic transport and magnetic properties of Mn-doped ZrNiSn. Here, we have investigated the effect of Mn-doping on the electronic transport properties of ZrNiSn for high temperatures (room temperature to ~873 K). The ZrNi1-xMnxSn (x=0-0.04) samples were prepared via Arc Melting and then consolidated by using Spark Plasma Sintering. The desired half-Heusler phase for all the synthesized samples was confirmed by the X-ray diffraction technique. Further, the samples were characterized for thermoelectric properties. The electrical conductivity increases with temperature which is corresponding to the semiconducting behavior. At high temperature ~873 K, electrical conductivity was realized to be decreased in Mn-doped ZrNiSn, and Seebeck coefficient shows marginal variation compared to pristine ZrNiSn. The power factor of 3.53 mW-1K-2 at ~873 K was realized in pristine ZrNiSn HH which was found to be decreased in Mn-doped ZrNiSn HHs. References: 1. Bodak, O.; Padlyak, B.; Stadnyk, Y. V.; Pierre, J.; Tkachuk, A.; Romaka, L.; Gorelenko, Y. K., Synthesis, crystal structure and physical properties of ZrNiSn semiconductor doped with Mn. Journal of alloys and compounds 2001, 317, 357-362.

Resume : Due to the small amounts of indium available, indium oxide-based solar cells using ITO have a high cost. One alternative is to use another transparent conducting electrode for this purpose. Thin films deposited with fluorine-doped tin oxide (FTO) involve low costs compared to the use of indium and also high morphological, structural, optical and electrical qualities. This paper is a study of the quality of films deposited on glass substrates by the method of spray pyrolysis. To improve the thin films, the most important deposition parameters were researched: the substrate temperature, deposition time and the influence of the diameter of the spray nozzle. The results show that increasing the temperature of the substrate, increases the surface roughness obtaining dense films. Increasing the deposition time changes the morphology producing very porous film. Equally, the droplet size of the spray solution influences the morphology, transparency and strength. Two nozzles with different diameters were used. The thickness and porosity of the films increases as the nozzle diameter increases. Increasing the temperature improves the optical and electrical properties of the deposited films. This work shows the optimal parameters for obtaining FTO layers with promising potential in photovoltaic applications.

Resume : In currently commercially available solar cells, the electrodes (playing an important role in the charge carrier photogeneration) are based on Indium Tin Oxide (ITO) films, which are very interesting materials because of their electrical and optical properties. The main disadvantage of this powerful material (ITO) is related to the poor global Indium resources and expensive production and extraction. The present paper describes alternatives for this well-known transparent conductive oxide electrode. For its replacement, a new architecture was established and studied: oxide/metal/oxide (NiO, TiO2, TiO2-Nb as oxides and silver as metal), to highlight their properties similar with those of ITO. To emphasize the optical properties of these promising alternative thin films, ellipsometric and spectrophotometric techniques have been used, giving comparative information about optical band gap, refractive index, and extinction coefficient and transmittance values.

Resume : Hybrid halide perovskites are a new class of solution-processed semiconductors that combine low-temperature (<100 °C) synthesis and high performances. The past few years, hybrid halide perovskites such as CH3NH3PbI3 have shown promising results for the detection of high-energy ionizing radiation (X- and Gamma-rays). Their success can be attributed to perovskites strong absorption of ionizing radiation owing to the presence of heavy atoms such as Pb, I, Br; together with high charge carrier mobilities, long exciton diffusion and long charge carrier lifetime.[1] Their large-scale commercialization is however hindered by their poor stability, owing to the volatility of the small organic cation CH3NH3+. 2D layered hybrid halide perovskites (R-NH3)2PbX4 (R = organic chain, X = Cl-, Br-, I-) have recently shown an increasing interest in the fields of solar cells and LEDs. This sub-class of perovskite crystallizes in a natural, self-assembled quantum well structure and possess several interesting features, among which a much better stability than their 3D counterparts.[2,3] We will present in this work the first solid-state ionizing radiation detector based on a 2D layered hybrid perovskite. This material can be deposited from solution in the form of micro-crystalline thin films that display a single crystalline orientation. We will expose the direct integration of this material onto a pre-patterned flexible substrate and demonstrate the effective detection of X-Rays with sensitivity values as high as 757 uC.Gy-1.cm-2 and a Limit of Detection (LoD) of 8 nGy.s-1, which is among the lowest reported value for solid-state detectors. 2D perovskites offers the prospects of flexible solid-state detectors capable of working at low radiation flux, and opens the way for a viable alternative to silicon for real-time X-Ray dosimetry. 1 L. Basiricò, S. P. Senanayak, A. Ciavatti, M. Abdi-Jalebi, B. Fraboni and H. Sirringhaus, Adv. Funct. Mater., 2019, 9. 2 D. B. Mitzi, Journal of the Chemical Society, Dalton Transactions, 2001, 0, 1–12. 3 J. V. Passarelli, D. J. Fairfield, N. A. Sather, M. P. Hendricks, H. Sai, C. L. Stern and S. I. Stupp, J. Am. Chem. Soc., 2018, 140, 7313–7323.

Resume : Energy savings and environmental considerations have led the European Union to ban inefficient lighting, such as incandescent and halogen bulbs, resulting in a massive adoption of Light-Emitting Diode (LED) technology. This shift from conventional lighting to LED lighting observed on a great diversity of application (automotive lighting, television, mobile phones, display panels, etc.) goes hand-in-hand with a more complex design and the need of valuable metals such as Au, Ag, and Cu and critical raw materials (CRM) among which are gallium, indium, and rare earth elements (REEs). That expansion of LED-based products will eventually contribute to a significant amount of specific e-waste that will soon require proper collection strategies and suitable and economic recycling routes yet to be developed. To this end, a detailed and process-oriented characterisation is essential.

Resume : The lighting sector is living a soft but drastic revolution both in concept design and, hence emitting devices. The global market share of alternatives lighting sources as Light Emitting Devices (LEDs) and Compact Fluorescence Lights (CFLs), will raise from few percentage of the global market share in 2010 to almost 90% in the 2020, increasing from the current value of about US$26 billion (2017) to more than US$72 billion in 2020. In this framework, Critical Raw Materials (CRM), mainly Rare Earths elements assume a fundamental role and do not have alternatives in the current LED technology and as phosphors in general. The development of new emitting elements that are cost effective with improved quantum efficiency and color quality is of highest priority for the next future European market of fluorescent devices. In this talk we will analyze the technical and physical requirements of the phosphors in LED and CFL, and strategies to obtain efficient emitting materials free and/or with reduced contents of CRM. We will discuss new classes of organic phosphors with high stability at high temperature based on Carbon Nitride structures and the achievement of hybrids materials with improved and tunability performance. Hybrid organic/inorganic structures with external inorganic and protective shell, as well reverse structures, with the organic part acting as antenna element for inorganic emitting elements will be showed and discussed.

Resume : Metal halide perovskites is a class of crystalline compounds which have garnered great interest in the recent years. Thanks to their intrinsic properties: high absorption coefficients, high photoluminescence quantum yield, high charge-carrier mobilities, band gap tunability, narrow-band emission, they show great prospective in different applications such as lasers, photodetectors, light emitting diodes. However, most of the recent studies are dedicated to increase their stability and lifetime in real operation conditions. Phase transitions among different polymorphs have been observed depending on temperature, light flux and/or atmospheric stresses (oxygen, moisture and heat). The high temperature phase is a cubic perovskite, with high efficiency and narrow emission line. Unfortunately, for all the members of the group of caesium lead trihalides perovskites, the cubic phase is metastable at room temperature and spontaneously converts to an orthorhombic phase, characterized by a wide band gap and weak and broad emission. In order to stabilize the cubic phase in CsPbI3, we studied the synthesis' conditions of Cs4PbI6 and its role in stabilizing caesium lead iodide perovskite at room temperature.

Resume : The molecular model is one of the most appealing to explain the peculiar optical properties of Carbon nanodots (CNDs) and was proven to be successful for the bottom up synthesis, where a few molecules were recognized. Among the others, citrazinic acid is relevant for the synthesis of citric acid-based CNDs. The formation of citrazinic acid single monomer and oligomers is expected to affect the optical properties of the CNDs. By combining DFT calculations with experimental characterization, we discussed the formation of different ionic species of citrazinic acid in water solutions and the formation of some molecular aggregates, mainly dimers, trimers and some selected tetramers. Calculated optical absorption spectra, vibrational features and NMR properties are compared to the experimental data and discussed in view of their contribution to those properties of CNDs, confirm that the presence of citrazinic acid, including its ionic and aggregated forms, should be considered in the interpretation of the spectroscopic features of citric acid related CNDs.

Resume : In the last few years, a big effort has been made to develop more environmental-friendly lighting technology. Fluorescent carbon-based nanoparticles known as Carbon Dots (CDs) represent a promising green and low-cost substitute of critical raw materials currently used in optical devices. CD tunable photoluminescence emission across the visible range, along with their high quantum yield especially in the blue-green region, makes them highly desirable for this application. CD production generally involves the pyrolysis or carbonization of small organic molecules, which represent an efficient route to obtain CDs in a cheaper way on large scale, but makes difficult to achieve homogenous samples in size and distribution. The use of mesoporous silica not only allows the homogeneity of the sample and a suitable solid-state matrix, but also provides a tool to deepen the multiple emissive contributions due to the complex CD structure, which is currently not fully understood. Using as precursors citric acid and urea, we synthesized CDs via calcination directly in two types of mesoporous silica matrices with different morphologies and pore sizes. Optical and structural properties have been measured and compared to the ones of CDs dispersed in water in order to explore potential solid-state lighting solutions.

Resume : Carbon dots (CDs) are potentially a valid alternative to semiconductor quantum dots or luminescent rare-earth doped materials. In particular, CDs with emissions in the blue/green range are almost competitive with the most common semiconductor nanocrystals and are proposed as low-cost and non-toxic alternatives in many fields of optical technologies. However, many issues still need to be addressed, including the reproducibility of synthesis, low quantum yield at large wavelengths (red emission) and their incorporation into solid matrices without efficiency losses. In this work, we will talk about these problems and the methodological perspectives for overcoming them by engineering new hybrid heterostructures.

Resume : Bio-phosphors are emerging as an alternative to rare-earth down-converting filters applied to LEDs. They can be produced either with biogenic emitters, basically Fluorescent Proteins (FPs), embedded in polymer matrices [1–3], or with artificial emitters dispersed in biogenic matrices, such as, DNA [4], proteins [5], etc. The first Bio-HLED based on FP phosphors featured a loss <10% of the emission intensity after 100 h [1]. This performance was recently enhanced by long-living devices featuring a zero-thermal quenching with a FP green phosphor, reaching >150 days of stability [6]. However, up to date there is a limited number of deep red emitting FPs meeting high photostabilities and photoluminescent quantum yields (QY) – tipically QY <10%. Therefore, red emitting FPs designed for lighting applications are strongly desired. Here, we report the design and characterization of an innovative protein-based phosphor using Lactococcal multidrug resistance Regulator (LmrR) hosting a highly emissive squaraine dye – SQR1 and we disclose its application as bio-phosphor in white Bio-HLEDs. The remarkable stability of the complex in solid polymer matrix with QY ~ 30% led to a Bio-HLEDs with power efficiencies of around 50 lm/W and remarkable photo-stabilities > 300 h. Thus, we provided two main advantages: i) a new route towards red bio-phosphors using emitters otherwise soluble in toxic solvents, ii) highly stable and efficient bio-hybrid LEDs. Overall, we strongly believe that this work opens the way to the use of ad hoc designed proteins in solid-state lighting applications. 1. Weber, M. D. et al. Bioinspired Hybrid White Light-Emitting Diodes. Adv. Mater. 27, 5493–5498 (2015). 2. Fernández‐Luna, V. et al. Deciphering Limitations to Meet Highly Stable Bio‐Hybrid Light‐Emitting Diodes. Adv. Funct. Mater. 29, 1904356 (2019). 3. Aguino, C. F. et al. Single-Component Biohybrid Light-Emitting Diodes Using a White-Emitting Fused Protein. ACS Omega 3, 15829–15836 (2018). 4. Reddy, M. S. P. & Park, C. Bright luminescence from pure DNA-curcumin-based phosphors for bio hybrid light-emitting diodes. Sci. Rep. 6, 1–7 (2016). 5. Benson, K., Ghimire, A., Pattammattel, A. & Kumar, C. V. Protein Biophosphors: Biodegradable, Multifunctional, Protein-Based Hydrogel for White Emission, Sensing, and pH Detection. Adv. Funct. Mater. 27, 1702955 (2017). 6. Espasa, A. et al. Long-living and highly efficient bio-hybrid light-emitting diodes with zero-thermal-quenching biophosphors. Nat. Commun. 11, 1–10 (2020).

Resume : Abstract One of the main challenges in the materials research is the development of new materials for the production and the efficiently use of energy capable to make possible the development of the durable society. In this context, the electrochromic windows have gained considerable interest because they reversibly change its transparency color when a voltage is applied, as a consequence of the redox reactions with a counter electrode. In the electrochromic smart windows, WO3 is the key element where it is responsible for the coloring and bleaching of the device. The commercially available electrochromic windows are based on WO3 and NiO films deposited by physical methods. In this work, the chemical solution deposition method is used for producing electrochromic oxides films (NiO/WO3) with high performances, but with lower costs, deposited onto indium tin oxide coated glass substrates by spin-coating technique. The morphological, structural, optical and electrochromic properties of the thin films were characterized by using scanning electron microscopy, X-ray diffraction, ultraviolet-visible spectrophotometer and cyclic voltammetry, respectively. In order to establish the growth process of the film, the precursor chemistry, as well as the correlation between the synthesis methods and the structural, morphological and electrochromic properties are also investigated. [1] C.G. Granqvist, M.A, Arvizu, H.Y. Qu, R.T. Wen, G.A. Niklasson, Advances in electrochromic device technology: Multiple roads towards superior durability, 357 (2019) 619-625 [2] C.G. Granqvist, M.A, Arvizu, I.B. Pehlivan, H.Y. Qu, R.T. Wen, G.A. Niklasson, Electrochromic materials and devices for energy efficiency and human comfort in buildings; A critical review, Electrochimica Acta 59 (2018) 1170-1182 Acknowledgement This work was supported by UEFISCDI through PN-III-P1-1.1-TE-2016-2017, SMARTWIN research grant No. 132/10.10.2018

Resume : Cost effective electrically conductive materials with good luminescent properties are very attractive for manifold electronic applications such as light-emitting diodes, solar cells, sensors, etc. Polymer based composite materials where polymer is a matrix and organic or inorganic materials is nanofiller with their positive qualities and bottlenecks are often used. Graphene nanoplatelets can serve as nanofiller for polymers for strong increase of the electrical conductivity. The main problem in such composites is a strong luminescent quenching typically observed in electrically conducting materials partially in nanocarbon containing materials. However, we have found luminescent composites with low luminescence quenching only, and conducting luminescent materials have been obtained. In this talk our best achievements and literature data on the creation approaches and physical properties of electrically conducting and luminescent nanocomposites based on polymer filled with graphene nanoplatelets covered by inorganic or organic Eu complexes are presented and analyzed. The prospects of our future studies and possible applications of such composites are discussed. It is shown how they can be used for 3D printing technology.

Resume : Germanium (Ge) is considered as one of the potential strategic and critical metals due to its unique properties to the function of numerous commercial and industrial applications such as solar cells, fiber optics, radiation detectors, infrared optics, metallurgy, chemotherapy, and polymerization catalysis. Germanium ore deposits are rare in nature because Ge is mainly associated with minerals of other metals. Refinery production of Ge is mainly recovered from zinc (Zn) concentrates, coal deposits, coal fly ashes, and recycled materials like from fiber optic scrap. Recent estimate suggests that the supply potential of Ge from Zn is five times that of current Ge production, and that supply potential from coal is double than that of Ge from Zn. Several processes have been used for the recovery of Ge from its sources. Atmosphere leaching of feed materials with sulfuric acid followed by separation and purification of Ge by solvent extraction are the potential hydro-metallurgical process options to produce high purity Ge strip solution for Ge recovery. In the hydro-metallurgical process, one can recover > 80% Ge. As first part of this work, we give an overview of this process method and its subsequent process steps to produce higher grade GeO2 (germanium dioxide). Ge separation from other methods is compared and their extraction efficiency will be discussed. A high yielding reduction of this intermediate product GeO2 into Ge metal by using hydrogen (H2) is presented as 2nd half of this paper. There is only limited optimized process readily accessible and available, particularly for realizing a very high-yield reduction due to very high material-cost. The reduction process was carried out in a newly commissioned equipment, which can be operated at high temperatures under H2 atmosphere. This equipment is controlled by programmable logic controller and has a closed fused silica (quartz) tube. This quartz tube is extremely resistant to thermal shocks compared to alumina tubes. Hence one can speed up the heating and cooling procedures. The two step experiment process details and the optimized process parameters will be reported. As a result, we have successfully completed the reduction of 10s of kg with an average yield of 99.85% using the established process. Subsequently, the metallic Ge could be purified to intrinsic purity (6N) by zone-refining with an overall yield of 99.05% for semiconductor materials device use. Special attention was given to avoid any losses during the whole process and the remaining residue is subjected to further recycling.

Resume : Niobium and Tantalum are two strategic metals that are included in the 2020 list of critical raw materials for the European Union [1]. This is due to their importance for high-tech products and emerging innovations, along with a high risk for their secure supply. For this reason, it is important to find new sources of these metals in Europe, as well as kept the materials and products manufactured with them in the life cycle as long as possible. In this work, the oxides of two of these strategic materials, Niobium and Tantalum, are recovered from tailings of the Penouta Sn–Ta–Nb deposit (located in Galicia, North Spain) via hydrometallurgical route [2,3]. The recovered oxides are in the form of powders. These powders have been used to obtain microrods by a thermal treatment. The structures have been characterized by means of X-ray diffraction, scanning electron microscopy, luminescence and Raman spectroscopy. The possibility of using these microrods for optical, sensing and energy storage applications will be discussed and related to the crystal structure of the oxides obtained [4,5]. [1] https://rmis.jrc.ec.europa.eu/uploads/CRM_2020_Report_Final.pdf [2] F. A. López, et al. (2018) Minerals 8, 20. [3] O. Rodríguez et al. (2020) RSC Adv., 10, 21406-21412 [4] C. Nico, et al. (2016) Progress in Materials Science 80, 1-37. [5] S. Xia, et al. (2018) Nano Energy 45, 407-412.

Resume : The platinum group metals (PGMs) are a family of six structurally and chemically similar elements (Pt, Pd, Rh, Os , Ir, Ru) that are most valued for their wide range of industrial, medical, and electronic applications. PGMs are good automotive emission control catalysts because they are useful in catalysing NO to nitrogen and to oxidise carbon monoxide (CO) and hydrocarbons (HC) to carbon dioxide CO2. In terms of the extent to which they are used, there are generally around 3 to 7 grams of PGMs in a standard catalytic converter. However, the amount varies depending on the size of the catalytic device and the application (light/heavy duty vehicles). Another rapidly developing energy conversion technology is Fuel Cell and electrolyzers applications, offering higher efficiencies than conventional technologies since, unlike batteries, they never "run out". Fuel cells are electrochemical devices that convert the energy of a chemical reaction directly into electricity, with heat and water as by-products. Platinum and ruthenium on the electrodes play a large role in this technology. Because they have so many uses, the PGMs are in high demand and mining alone does not produce enough supply. Pyrometallurgical processes are favored for the recycling of PGM-bearing materials such as catalytic converters because of the high recovery rates. However, hydrometallurgical process, under certain conditions, could be proved green and sustainable technology, with high PGMs recovery rates. MONOLITHOS has demonstrated a hydrometallurgical single step, low acidity (3.5M HCl), short in time (t 3hrs), with high S/L ratio 70% , without pretreatment, method for extracting Pt, Pd and Rh from spent Three Way Catalysts obtaining recovery rates of 100%, 95% and 61%, respectively. Heavy duty DOC catalysts and DPF filters have also been subjected to this process exhibiting Pt recovery rates of 95% and 75%, respectively. The efficiency of this innovative hydrometallurgical method will be examined on membrane electrode assemblies of both fuel cells and electrolyzers. Leaching solutions, containing precious metals, will be further purified and used for synthesis of new catalytic systems.

Resume : It is a matter of strategic independence for Europe to urgently find processes taking account of environmental and economic issues, when mining and recycling rare earth elements (REE). Separation and recycling of rare earths from electronic waste is important for the success of present and future carbon-free technologies. Hydrometallurgical separation based on nanoscience is one of the first technologies allowing the take-off of circular economy. Liquid-liquid extraction is a promising method for retrieving rare earths from electronic waste. However, an optimized process on an industrial scale has not been established. One major reason is the lack of fundamental knowledge, therefore designing a cost-efficient, adaptive and predictive formulation is still out of scope of possibilities. Emulsification and demulsification processes in extraction devices are only efficient when the coexisting phases are located between binodal tie-lines in the Winsor II regime. Most of extraction processes are based on the combination of an extractant with a diluent. The main disadvantage of these processes is the formation of viscous emulsions known as third phase accident. This occurs when processes are intensified by increasing solute and extractant concentration. Our objective is to develop the fundamental understanding involved in the process’ complex fluids (experimental and theoretical) concerning liquid-liquid extraction of REE and furthermore to use it to design new, cost effective and environment-friendly recycling processes. A new and promising approach has been recently proposed using Ultra Flexible MicroEmulsions (UFME) which are characterized by an Ornstein-Zernike scattering often observed for weak extractants. These surfactant-free self-assembly is based on the usage of hydrotropic co-solvents instead of the classical extractant/diluent couple. Co-solvents as well as hydrotropes quench the formation of third phases. A systematic comparison of the extracting power of a given formulation by the classical solvent-based, modifier enhanced co-solvent based and the new possible UFME route is now necessary. This requires measuring with enough precision the free energy of transfer of ions along the lines in quaternary phase diagram. This is only achievable by using a newly developed liquid-liquid extraction microfluidic device coupled to X-ray fluorescence microanalysis. Our contribution towards a more complete understanding in this matter is the analysis and comparison of the phase behavior, extracting efficiency and selectivity of such systems as well as the correlation of these findings with the “ienaics” approach by identifying the molecular driving forces favouring or quenching the transfer. We will propose in this talk a comparison of extraction power of a popular extractant: HDEHP used with a branched alkane as a classical solvent and a co-solvent approach using a hydrotrope.

Resume : A large European city as Brussels produces tons of sewage sludge from wastewater treatment that need to be discarded, generating important economical and environmental impacts. A thorough analysis of the metals concentrations in sludges have revealed high quantities of precious metals in these materials with a potential annual production of 9 kg of gold if all Brussels sludge would be mined.1) The demand for gold as well as its production and price, have been increasing nearly exponentially since the beginning of the 20th century.2) There is thus a general interest in developing an efficient, integrated, green and low-cost methodology to harvest the substantial quantities of the precious metals present in urban wastewater treatment plant residues. In this framework we present advances in the selective extraction of gold (III) in leachates (Athos process) of the North wastewater (wastewater) treatment plant in Brussels using calix[4]arene tetra-acid as collecting ligand: i) as reducing and precipitating agent and ii) as iron oxide nanoparticle (IONPs) functionalization ligand in order to develop a selective magnetic separation process. In a first step, we have compared the efficiency of the calix[4]arene tetra-acid-tetra-ammonium in collecting gold with that of commercial reducing agents such as sodium citrate and the 2-(4-aminophenoxy)acetic acid. By UV-vis titrations we confirmed a selective interaction of gold (III) with the calixarene and 2-(4-aminophenoxy)acetic acid respectively at pH’s of 2-3.7 and 10. We also confirmed the reduction of Au(III) by observing the formation of a localized surface plasmon resonance band around 520 nm, typical of NPs with a size inferior than 20 nm, at pH 2-8 for the calix[4]arene and 8-10 for 2-(4-aminophenoxy)acetic acid. We monitored the formation of gold NPs as a function of time by UV-vis and DLS, showing that the fastest reduction occurred in less than 60 minutes at pH 8 for both reducing agents. In a second step, IONPs were synthesized and functionalized with the calix[4]arene tetra-acid in two steps. First, 13 nm IONPs were prepared by the co-precipitation of iron chlorides in basic medium and then fully oxidised to Fe (III) by an acid treatment with HNO3. Next, IONPs were functionalized at pH 8 with the calix[4]arene tetra-acid-tetra-diazonium by mechanical shaking in basic conditions. We confirmed the excellent particle stability in water by comparing the average hydrodynamic size (DHDS) and Z-potential of IONPs and IONPs@calix as a function of pH. Finally, we monitored the ability to collect Au(III) using these particles in different pH conditions. The most efficient and selective extraction conditions are found at pH 8. 1) Vriens B, et. al. (2017) Quantification of Element Fluxes in Wastewaters: A Nationwide Survey in Switzerland. Environ. Sci. Technol. 51: 10943−10953 2) Sverdrup H and Ragnarsdottir KV, (2014) Natural Resources in a Planetary Perspective, Geochemical Perspectives 3(2), 228p

Resume : During recent years it has been reported that using mixed rare earth oxides (REOs) as dopant may strongly improve the functional properties of zirconia ceramics such as increasing thermal shock resistance of zirconia-based thermal barrier coatings (TBCs) and improving ionic conductivity of solid oxide fuel cells (SOFCs), the reasons for this behaviour being a surface segregation mechanism reducing the grain growth activation energy of zirconia nanostructured coatings and improving bulk and grain boundary conductions in sintered zirconia ceramics. Here we present some original results to demonstrate the potential use of mixed REOs obtained from monazite concentrates with natural occurring composition as dopant in the design of high temperature oxide coatings and sintered zirconia-based oxide materials, with high impact in reducing the actually reagents consumption and costs by eliminating the whole cycle of individual REO extraction and efficient use of raw materials by reduction/ substitution of critical elements in materials for high temperature applications. The evolution of microstructure, thermal and impedance properties vs. REOs concentration in doping zirconia ceramics is discussed.

Resume : Perovskites solar cells have irrupted in the photovoltaic field with no precedent. Rising the power conversion efficiencies (PCE) from ~4% to more than 25% can be considered as one possible replacement to silicon solar cells. However, long-term stability together with the lack of a fully understanding of the intrinsic processes limit its up scaling to industry. To overcome those issues, different strategies such as compositional engineering of perovskite material as well as new synthesized hole transport materials (HTMs) were accomplished. As a layered structure, in order to reduce internal losses, an optimized interface between the different layers of the perovskite device is paramount. In this regard, an optimized surface passivation layer is seen as an ideal approach to protect the surface from extrinsic factors, without altering the electro-optical properties. In this work, we present how the utilization of a passivation layer protects the perovskite layer from atmospheric degradation as well as compensate the possible iodine segregation on the perovskite layer. As result, an improved PCE (20%) was also obtained as the passivation layer lessen trap-states towards the HTM layers, reducing interfaces recombination processes and therefore improving the open circuit voltage.

Resume : Since the 50's different materials and technologies were tested for solar cells manufacturing. Today 90 % of solar cells commercial panels are based on Silicon. However, even if silica is one of the most abundant compound on Earth, due it intensively use, silicon is since 2017 one of 27 critical raw materials for the EU. In order to reduce fabrication cost and increase the energy conversion efficacy, many strategies were considered, such as: new active materials, multi-junction cells (multiple semiconductors stacked cells, intermediate band semiconductors solar cell, up and down converters. Perovskite solar cells based on CH3NH3PbI3 by achieving in less than five years, efficiencies comparable to silicon solar cells, show the potential of these new materials to replace Silicon. In this paper structural, morphological optical and electronical properties of CH3NH3PbI3 thin films deposited by spin coating, with different spin speeds on glass and conductive patterned substrates were investigated in order to achieve a deeper understanding of physical properties of this class of materials. The XRD investigations indicate the formation generally of the cubic phase, or a mixture between cubic and tetragonal phase. The variation of the electrical conductivity at exposure to light in function of time and light intensity and the variation of the electrical conductivity in function of temperature were investigated and interpreted.

Resume : At the end of 2017, roughly 1.8% of the worldwide electricity came from solar photovoltaics (PV), which is foreseen to have a crucial role in all significant future energy scenarios with an installed capacity around 5 TW by 2050. Although silicon solar cells currently rule the PV market, the extremely versatile thin film-based devices (mainly Cu(In,Ga)Se2 and CdTe ones) have almost matched them in performance, and they present room for improvement. The low availability of some elements in the present commercially available PV technologies and the recent sharp fall of silicon module price below 1 $/Wp focused the scientific community's attention on cheap earth-abundant materials. In this framework, thin-film solar cells based on Cu2ZnSnS4 (CZTS) and the related sulphur selenium alloy Cu2ZnSn(S,Se)4 (CZTSSe) were actively investigated in the last ten years. More recently, chalcogenide PV absorbers potentially face TW range applications better than CZTS and CZTSSe due to the higher abundance of their constituting elements getting considerable attention. They are based on both MY2 (where M = Fe, Cu, Sn and Y = S and/or Se) and Cu2XSnY4 (where X = Fe, Mn, Ni, Ba, Co, Cd and Y = S and/or Se) chalcogenides.1 An extensive review of emerging earth-abundant thin-film solar cells based on both MY2 and Cu2XSnY4 species will be given, with particular attention to iron-based photovoltaics and solution processing. 2-3 (1) Le Donne, A.; Trifiletti, V.; Binetti, S. New Earth-Abundant Thin Film Solar Cells Based on Chalcogenides. Frontiers in Chemistry 2019, 7 (297). (2) Tseberlidis, G.; Trifiletti, V.; Le Donne, A.; Frioni, L.; Acciarri, M.; Binetti, S. Kesterite solar-cells by drop-casting of inorganic sol–gel inks. Solar Energy 2020, 208, 532-538. (3) Trifiletti, V.; Mostoni, S.; Butrichi, F.; Acciarri, M.; Binetti, S.; Scotti., R. Study of Precursor-Inks Designed for High-Quality Cu2ZnSnS4 Films for Low-Cost PV Application. ChemistrySelect 2019, 4 (17).

Resume : Over the last decades, significant progress has been made in inorganic materials to enable them as next generation photovoltaic materials that can fulfil the green energy requirements. Cu2ZnSn(S,Se)4 stands out as a p-type absorber material due to exemption from scarce and strategic elements and its similarities with Cu2InGaSe4. In parallel, organic materials such as fullerenes and its derivatives have emerge as effective n-type semiconductors with electron transport properties. We report the usage of n-type fullerenes materials with different kesterite-based absorbers in a thin film polycrystalline solar cell, which allows a partial replacement of the CdS buffer layer with C60 or C70 fullerenes. An optimization of the layer stack and post-heating treatment, result in an increased open circuit voltage and thus device performance. Impedance measurements reveals that using C60 as an interlayer increases built-in potential, suggesting reduction in the interfacial recombination in CZTS based solar cells.

Resume : Silver nanowire (AgNW) networks have significant potential in devices using transparent electrodes (TE) such as solar cells, flexible light-emitting devices, touch screens or transparent heaters. Research over the last decade has demonstrated that AgNW networks are promising alternatives to indium tin oxide regarding their cost and their superior mechanical properties [Sannicolo et al., Small, 2016, 12, 6052]. This work aimed to optimize the physical properties and improve the stability of AgNW networks to allow their successful integration into devices. During this study, we compared two post-deposition treatments to optimize the physical properties of AgNW network, e.g. using in situ resistance measurements. Thermal annealing is commonly used post-deposition to reduce electrical resistance in AgNW network faced with thermal ramps [Lagrange et al., Nanoscale, 2015, 7, 17410]. Capillary-force-induced cold welding is also a simple and effective post-treatment technique, whereby moisture is applied to the AgNW network at low temperature. To improve the stability of AgNW network, we used Atmospheric Pressure Spatial Atomic Layer Deposition [Nguyen et al., Nanoscale 2019, 11, 314; Muñoz-Rojas et al., Mater. Horizons, 2014, 1, 314] to coat nanowires with a thin conformal oxide layer. The thermal annealing treatment required the heating temperature and duration to be strictly controlled to prevent degradation of the AgNW network, this method is also limiting for heat-sensitive substrates. When applying the cold-welding treatment, the presence of sub-micronic water meniscus induced a strong capillary force between nanowires and also between AgNWs and the substrate, causing welding of the nanowire junctions. Following this post-deposition treatment, the electrical resistance of the AgNW network decreases by at least 30%, and AgNW adhesion to the substrate was simultaneously improved. Furthermore, the roughness of the AgNW network decreased, potentially helping to prevent short-circuits in devices relying on thin active layers, such as solar cells. Finally, coating AgNWs with oxides like ZnO or SnO2 improved network stability. Our approach simply and efficiently optimized the properties of AgNW networks and enhanced their stability, in addition it is compatible with high-throughput roll-to-roll fabrication for industrial applications.

Resume : Hard-soft coupled magnetic nanoparticles have gained a tremendous amount of interest during the last decade for short-term development of advanced applications related to spintronics.1 Indeed, they are a potential alternative to produce permanent magnets in order to circumvent supply storages caused by the critical need for rare earth elements in communications and mobility applications. With this purpose, the main goal is to overcome superparamagnetism, which results from size reduction to the nanoscale.3 A very attractive approach is the design of core-shell nanoparticles that display exchange coupling between interfacial spins of hard and soft magnetic phases which result in the significant enhancement of the magnetic anisotropy energy. Ferrites (MFe2O4, with M: Co, Mn, Ni), which exist in several chemical compositions, allow the fine modulation of hardness and softness of the magnetic phases. Nevertheless, core@shell nanoparticles which combine two different ferrites remain superparamagnetic at room temperature. Here, we report on an original strategy to synthesize onion-type nanoparticles that are ferrimagnetic at room temperature and mainly consist of iron oxide with a mean size that does not exceed 16 nm. The significant enhancement of the magnetic properties at room temperature is ascribed to a double interfacial exchange coupling resulting from the Fe3-dO4@CoFe2O4@Fe3-dO4 structure. More details in : Pichon, B. P. et al. J. Am. Chem. Soc. 2019, 141, 9783-9787 1. López-Ortega, A. et al. Phys. Rep. 2015, 553, 1?32. 2. Gutfleisch, O. et al. Adv. Mater. 2011, 23 (7), 821. 3. Nogués, J. et al. Phys. Rep. 2005, 422 (3), 65?117.

Resume : La1-xDyxMn1-yZnyO3 system belongs to the family of perovskites-ABO3- and contains two well-defined magnetic sublattices. In this work, we study the influence of non-magnetic dilution on the magnetic properties at temperatures ranging from 10 K to 300 K. For the diluted samples, the Magnetization vs. Temperature shows a transition from paramagnetic to ferromagnetic (FM) phase at Tc. FM spin clusters are observed at the paramagnetic regime. This FM coupling was described by a Heisenberg Hamiltonian which reproduces a non-linear behavior of the \chi^-1 (T). The effective moment of the clusters is obtained from the high-temperature DC susceptibility. The effective exchange constants are estimated using an open-source program for high-temperature expansion (HTE) of the uniform susceptibility for the Heisenberg model.

Resume : Solid-state refrigeration is considered as a promising alternative to the less efficient conventional gas-compression-expansion refrigeration. Particularly, magnetocaloric (MC) cooling is the most elaborated today method of solid state refrigeration and development of the suitable MC materials is in the core of this field of research. The aim of the present work was to investigate MC materials based on the Heusler type NiCoMnSn metamagnetic shape memory alloys (MetaMSMAs) and explore their potential application for the solid state cooling on macro- and microscales. The alloy composition, facilitating the martensitic transformation near room temperature with low thermal hysteresis, was elaborated. The actual alloy was fabricated by the induction method and casting. The ingot was solution treated at 900C for two hours. Part of the ingot was used to prepare melt-spun ribbons which, in turn, served for easy manufacturing a powder by grinding. The material on each stage was heat treated and characterized magnetically and structurally. MC effect was measured by the magnetic field induced adiabatic temperature change (dT _ad ). The powder of MetaMSMA was used for room temperature additive manufacturing. As a result, a printable ink exhibiting inverse MC effect (dT _ad about 2K in the field of 2T) was created for the first time. The technology now can be used for 2D printing of cooling microdevices for flexible electronics.

Resume : Nanocrystals of magnetic materials can show interesting behaviors stemming from the combination of chemistry and magnetic performance, which also determines or directs their final purpose. Different examples of magnetic nanocrystals of transition metal oxides, synthesized and manipulated by wet-chemistry methods, will be detailed describing the magnetic behavior and the possible diversity of the ultimate functionalities (magneto-optical activity, exchange bias, spin dynamics, etc. or heat delivery and magnetic guidance of self-propelled swimmers).

Resume : We report the facile and low-cost preparation as well as detailed characterization of dense arrays of passivated ferromagnetic nickel (Ni) nanotubes (NTs) vertically-supported onto solid Au-coated Si substrates. The proposed fabrication method relies on electrochemical synthesis within the nanopores of a supported anodic aluminum oxide (AAO) template and allows for fine tuning of the NTs ferromagnetic walls just by changing the cathodic reduction potential during the nanostructures’ electrochemical growth. Subsequently, the experimental platform allowed further passivation of the Ni NTs with the formation of ultra-thin antiferromagnetic layers of nickel oxide (NiO). Using adequately adapted magnetic measurements, we afterwards demonstrated that the thickness of the NT walls and of the thin antiferromagnetic NiO layer, strongly influences the magnetic behavior of the dense array of exchange-coupled Ni/NiO NTs. The specific magnetic properties of these hybrid ferromagnetic/antiferromagnetic nanosystems were then correlated with the morpho-structural and geometrical parameters of the NTs, as well as ultimately strengthened by additionally-implemented micromagnetic simulations. The effect of the unidirectional anisotropy strongly amplified by the cylindrical geometry of the ferromagnetic/antiferromagnetic interfaces has been investigated with the magnetic field applied both parallel and perpendicular to the NTs axis. Keywords: dense arrays of vertically-aligned heterostructured nickel/nickel oxide (Ni/NiO) nanotubes (NTs); supported anodic aluminum oxide (AAO) nanoporous media; template-assisted electrochemical synthesis; unidirectional anisotropy in quasi one-dimensional (1D) nanostructures; exchange bias field and coercivity of cylindrical ferromagnetic/antiferromagnetic Ni/NiO interfaces; micromagnetic simulations. Acknowledgements: This research was funded by the “Executive Unit for Financing Higher Education, Research, Development and Innovation” - UEFISCDI (Romania) through the grants: PN-III-P1-1.1-TE-2019-0868 (TE 115/2020), PN-III-P1-1.1-PD-2019-1141 (PD 163/2020), 7PCCF/2018, 47PCCDI/2018 and POC P_37_697 REBMAT (28/01.09.2016), as well as by the “Fonds de la Recherche Scientifique” - FNRS (Belgium).

Resume : Rubber vulcanization, combined with the addition of reinforcing fillers as silica nanoparticles (NPs), is the main industrial process to provide highly performant rubber-based materials. Rate and efficiency are industrially catalyzed by accelerators, activators and co-activators, whose typical examples are sulfenamides, zinc oxide and fatty acids, respectively. Micro-crystalline ZnO is a worldwide employed activator, as it impacts on the kinetics of the process and promotes highly cross-linked materials [1]. However, its high hydrophilic character and low distribution into the rubber matrix leads to a high-required zinc content, connected to non-negligible potential environmental risks due to zinc release from rubber products, especially during tyre lifecycle [2]. Pushed by this issue, a novel activator was developed, based on the introduction of highly dispersed and active metal sites in the vulcanization process, aiming at the complete substitution of ZnO, by keeping high curing efficiencies. The activator was rationally designed in order to increase the metal availability and reactivity towards the other curing agents. Thus, Zn(II) single sites were anchored on the surface of SiO2 NPs, a common reinforcing filler, through the coordination with functionalizing silane groups, to obtain a novel double function filler with both activating and reinforcing properties. The material was first synthesized by using a two-steps procedure. Silica was pre-functionalized with a silane-grafting agent, by the hydrolysis and condensation of the silane molecules on the silica surface. The functionalization was confirmed by surface and structural techniques (as Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA)), showing the formation of a silane monolayer (~5 molecules nm-2). Then, the functionalized silica was reacted with a zinc precursor. The characterization highlighted isolated metal centers coordinated with two silane groups bonded to silica, where the metal amount is tunable by varying the silica functionalization degree. The new activator was used to prepare silica/isoprene nanocomposites (IR NCs) by blending and compression molding, vulcanized (170°C, 5 minutes) without using micro-crystalline ZnO. Compared to ZnO, it exhibited higher efficiency as activator in the vulcanization process IR NCs, leading to a considerable kinetic impact, high cross-linking degrees and improved dynamic-mechanical properties, thanks to the higher metal reactivity as single sites. Finally, the structural stability of metal single sites during the curing reactions and in the final materials may represent a turning point towards the elimination of zinc leaching phenomena. The results highlighted that this material is a promising candidate to substitute ZnO in the industrial rubber vulcanization. [1] Susanna A. et al., European Polymer Journal, 2017, 93, 63-74. [2] Mostoni S. et al., Catalysts, 2019, 9, 664

Resume : Beside nuclear and medical applications, isotopes are used to investigate climate change. Evaluation of hydrogen isotopes in aquous solution gives important data about the geology of the region, especially in underwater environments. Large earthquakes and volcanic eruptions cause changes in the hydrogeological properties of natural springs and submerged fumarols show the makeup of the magma underneath. In this study, we propose a sensitive material to evaluate deuterium concentration in aqueous samples based on palladium-functionalized CNTs. The sensing behavior was investigated in a series of deuterium-enriched solutions ranging from 25 to 10.000 ppm. We performed cyclic voltammtery and impedance spectroscopy studies on the samples. The analytical response of the composite to deuterium is given by the linear regression equation Ipc = 0.0042[D] 38.7614, with R2 = 0.9237. We established a good correspondance between the intensity of the oxidation peaks and the concentration of deuterium in water samples. Keywords: hydrogen isotope detection, CNT functionalization, Palladium, cyclic voltammetry, impedance spectroscopy. Acknowledgements: 87PD/2020, 393PED/2020, 18/N/2019, 19PFE/17.10.2018

Resume : The discovery of ferroelectricity in doped hafnium oxide thin films has turned it into one of the leading CMOS-compatible lead-free materials used to replace PZT. Ferroelectric hafnium oxide can open the way to the design of new devices in multiple fields like ferroelectric memories, negative capacitance field effect transistors (FET), pyroelectric sensors or microsystems. Doping is key to stabilize the ferroelectric phase. In this work, hafnium zirconium oxide thin films have been obtained by plasma RF sputtering of Hf0.5Zr0.5O2 (HZO) monotarget, unlike the majority of published reports that use co-sputtering. In addition, different deposition conditions have been investigated (e.g. addition of O2 plasma, RF power w or w/o capping electrode) as well as various post-deposition annealing. Thickness ranges from 13 nm to 32 nm, lightly thicker than those reported in the literature. We studied the physical, structural and electrical properties of HZO films incorporated in metal-insulator-metal stacks. All HZO films showed ferroelectric behavior even those of highest thickness as evidenced by 1) the apparition of an orthorhombic phase in XRD analysis, 2) the butterfly shape of capacitance voltage curve and 3) the P-E (polarization-electric field) hysteresis loop

Resume : In recent years, there has been a rise in exposure to electromagnetic radiation resulting from the evolution of technologies such as communication and data transfer technologies. 5G is the new generation of radio-frequency electromagnetic fields that will support the new era of mobile internet and differs from the older technologies by the increased number of base-stations needed and their higher frequencies (up to the millimeter -wave band that can go as high as 300 GHz). There are some uncertainties about the risks associated with the exposure to these radiations, and as so, there are enough evidences concerning the public health to start a demand for innovative solutions for this problem. In this context, a solution based on electromagnetic interference (EMI) shielding is needed, namely solutions that allow having flexible, transparent and light-weight shields usable for blocking high-frequency regions such as the ones used by 5G wireless internet or radar applications. In this work, a numerical simulation of the Shielding Effectiveness (SE) of a metallic mesh was carried out through the use of the Finite Element Method (FEM) with COMSOL Multiphysics software. The influence of the thickness of the mesh pattern and the dimensions of the perforated component on the SE were investigated while the height and material type (silver ink) were maintained throughout the study. The EMI shielding performance evaluation of the different patterns was carried out though the use of simulated rectangular wave guides. Additionally, the simulation was accompanied by an experimental verification. The experimental method used for producing the geometries constituted by silver ink was screen printing. The SE of the geometries was measured by a rectangular wave guide transmission line technique from 5.85 GHz to 18 GHz. The experimental results agreed with the simulated data, for the same studied designs. Additionally, the results revealed the possibility of having interesting SE values while reducing the material’s quantity usage such as reducing 26% of the covered area and having SE ~ 37 dB. This property is helpful for using design geometries in order to reduce the use of typical EMI shielding materials such as metals like nickel, aluminium, silver or copper. It was also revealed the possibility of creating shields more flexible, light-weight, breathable with see-through properties that can be applied in a wide range of applications such as flexible EMI shielding clothing, transparent EMI shielding windows, device protection or wearable electronics. Acknowledgments. Funded by FEDER through COMPETE 2020 under the project RFProTex - POCI-01-0247-FEDER-039833. AS thanks FEDER through COMPETE 2020 for PhD scholarship. CP thanks FCT for the FCT Investigator contract IF/01080/2015.