Substitution of critical raw materials: synthesis, characterization and processing of new advanced materials in optoelectronic and magnetic devices

Resume : In this talk I shall review our work on the development of a range of new light emitting materials, from inorganic silicates to (crystalline and amorphous) organic-inorganic hybrids, and organic materials. While much work has been dedicated to lanthanide (Ln3+) silicates, the properties of Ln3+ ions embedded (diluted) in transition metal silicate matrices also deserved attention. These phosphors are very robust to temperature and chemical agents and combine nanoporosity and light emission being particularly suited for sensing devices. Even if some of the crystalline hybrids (Metal Organic Frameworks) developed may also be used in the latter devices, they are particularly amenable to optical centres engineering: transition metals, Ln3+ ions, organic linkers and guest residing in the nanopores may all be active centres. Moreover, their frameworks may be modified post-synthesis via conventional organic chemistry methods, in order to fine-tune light emission. Amorphous hybrids (such as monoamidosils) are best suited for certain applications since, e.g., they are easily processed as films and may exhibit intriguing light emission properties (based on order-disorder phenomena). Finally, we have started developing novel organic dyes exhibiting aggregation-induced emission enhancement (contrasting with most dyes that are non-emissive in concentrated solutions or in the solid state) and wish to report some intriguing findings.

Resume : In the field of catalysis and optoelectronics researchers make extensive use of metallic elements that are considered critical materials. In order to create the conditions for the gradual replacement of the mentioned elements, we propose an approach based on the use of hybrid organic-inorganic. In this work we plan to characterize some hybrids utilizing carbon nitride compounds as organic part. The latters are easily tunable in their properties as a function of the temperature. In this work we show how the use of materials CN can be of great impact for the replacement of critical materials or to improve the performance of existing ones.

Resume : Luminescent compounds become the interesting topics of white light-emitting diodes due to their great performances to convert the monochromatic light from LEDs to produce a broad white light spectrum. One common approach to generate the white light emission with LEDs is the combination of a 450 nm blue LEDs with rare-earth phosphors such as commercially Ce-doped lanthanide aluminates embedded into a polymer matrix. However, the availability of rare earth materials, the low color rendering index and the too-cold color temperature of the white light LEDs system have been presented as the drawbacks to penetrate into the general LED lighting markets. In this research, we present the development of rare-earth-free luminescent composites combined with a 450 nm InGaN blue LED chip in order to provide a suitable white light. The rare-earth-free luminescent compounds were synthesized by the encapsulation of selected fluorescent organic dyes into inorganic matrices. Then the luminescent composites were prepared by dispersing these rare-earth-free luminescent compounds into a polymer matrix. The optical performance and the photometric parameters of the combination of luminescent composites with a blue LED will be discussed.

Resume : Light-emitting electrochemical cells (LECs) are single-layer solid-state devices composed of an organic semiconductor material containing mobile ions sandwiched between two electrodes. LECs possess advantages over the more developed organic light-emitting diodes such as fault-tolerant processability from solution, low driving voltage or the use of air-stable electrodes. The best-performing LECs use ionic transition-metal complexes (iTMCs) as triplet emitters. It has been realized, however, that the limited availability and high price of metals such as iridium and ruthenium hinders the development of LECs for large-area and low-cost lighting applications. Recently, non-ionic small molecules, charged organic thermally activated delayed fluorescence emitters and cyanine dyes have been presented as alternatives to iTMCs. Cyanines are charged semiconducting and luminescent molecules that are cheap and commercially available and that can be coated from environmentally benign solvents. Here, we present an analysis of the operation mechanism and (still limited) stability of cyanine LECs. We introduce a generic experimental method to determine the center of the intrinsic region (where light emission occurs) that is based on spectral photocurrent response measurements on semi-transparent devices combined with optical modelling. Together with transient capacitance measurements, this yields a detailed picture of the evolution of the p-i-n region in this promising class of LECs.

Resume : With the development of green energies, the need for high-performance hard magnets is growing every day. Hard magnets are key components of the electrical motors and generators of electrical and hybrid cars, and the generators of gearless wind turbines. They are being used as well in micro-sized systems, e.g. for capturing or sorting biological species. Today high performance magnets almost exclusively belong to the R-Fe-B family (R = rare-earth). Better magnets are needed, in particular for high temperature applications. Owing to the unsuccessful search for new hard magnetic materials, over the last 30 years, it is essential to improve the properties of existing materials. Material optimization relies on the introduction of minor additional elements. Based on the change in anisotropy and exchange expected to result from atom substitutions, a software has been developed predicting their impact on the material’s intrinsic magnetic properties. Coercivity represents the resistance to magnetization reversal, hard magnetic materials may offer to an applied magnetic field. Coercivity is specific to anisotropic materials, but controlled as well by defects at the nanometer scale. The preparation of model materials, the experimental analysis of magnetization processes and numerical modeling, have transformed our understanding of coercivity. This guides the search for optimized materials with improved coercivity and has opened the road towards new coercivity concepts.

Resume : European countries are almost entirely dependent on the import of key and strategic raw materials that are the core of hi-tech/hi-value products, such as rechargeable batteries, laser technology, permanent magnets, steels and high value alloys, conductive layers, or LEDs. Unfortunately, these elements cannot usually be replaced by another material, and its availability of supply is highly significant for the European Union’s economy, being also strongly dependent on international political economic circumstances. Such raw materials are called Critical Raw Materials (CRMs). The case of permanent magnets (PMs) is of crucial and strategic importance, since it is a key industrial product used in major sectors like the production of clean energy (wind power), transportation (electric vehicles), information and technology (hard drives), or medicine (nuclear magnetic resonance). Unfortunately PMs combine both the problem of dependence on CRMs produced in a major percentage by a single country, with the fact that its full production value chain is dominated technologically by the same country that controls the raw material. Indeed PMs, depending on the approach, use significant quantities of Nd, Co or/and Rare Earths. All of them are classified by the EU Commission as critical, since they are produced by China and imported in percentages greater than 85%. Moreover China controls within the RE Magnets value chain more than 97% of the global production of RE ore, concentrate, and oxide; > 95% of the metal production; and now manufactures about 80% of all rare earth magnets, (Japan makes about 17%, and about 3% are made in Europe)[1]. The EU efforts and the importance of this problematic for the EU industry will be discussed. Present roadmaps in the context of the European Innovation Partnership on Raw Materials and other EU platforms will be presented [2]. Aiming to find new rare-earth free/lean materials for PM which meet the high standards of the existing magnets a multi-scale simulation approach plus materials synthesis and experimental verification will be used to identify possible candidates. In this regard, we are planning to boost and host an international cooperation [3] for an open-source materials database arising from massive DFT screening, and incorporating the results of other international projects. Big Data analytics are being implemented and the template and technical approach of other previous materials data bases will be used. References [1] Adapted from a presentation by Jeff Green of J.A. Green and Co., (Green & Zolnowski, 2011) [2] http://ec.europa.eu/eip/raw-materials/en/content/european-innovation-partnership-eip-raw-materials [3] NOVAMAG: NOVel, critical materials free, high Anisotropy phases for permanent MAGnets, by design. H2020-NMP-2015-two-stage. 686056-2


Resume : Permanent magnets have lastly become essential to daily life products, this huge market being mostly trusted by rare earth-based magnets. The fear of a supply limitation has recently motivated numerous efforts on rare-earth free permanent magnets. We demonstrate the feasibility to elaborate rare-earth free permanent magnets based on cobalt nanorods assemblies with energy product (BH)max exceeding 150 kJ.m-3. The cobalt rods were prepared by the polyol process and assembled from wet suspensions under a magnetic field. The almost perfect M(H) loop squareness together with electron microscopy and small angle neutron scattering demonstrate the excellent alignment of the rods within the assemblies. The magnetic volume fraction was carefully measured by coupling magnetic and thermogravimetric analysis and found to be in the range 45 to 55% depending on the rod diameter and the alignment procedure. This allowed a quantitative assessment of the (BH)max. The highest (BH)max of 165 kJ.m-3 was obtained for a sample combining a high magnetic volume fraction and a very large M(H) loop squareness. Therefore, such bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama. Our present goal consists in increasing the magnetic volume fraction by avoiding the rod oxidation and decreasing the ligand amount. Thus, rare earth free permanent magnets of 250 kJ.m-3, competing with bounded SmCo and NdFeB, is a reasonable short-term target.

Resume : We present preparative methods towards a three-dimensional magnetic data storage medium based on arrays of parallel, cylindrical metallic nanowires structured along their length. The preparation utilizes porous anodic alumina as an inert template that defines the geometry (cylinder length, diameter and pitch), combined with galvanic deposition of the functional materials inside the pores. We demonstrate that the composition of nickel-cobalt alloys can be tuned systematically at one constant deposition potential, whereby the magnetocrystalline anisotropy can be minimized. The wires then display maximal shape anisotropy. The definition of bits along the 'vertical' direction of each wire is performed either by the introduction of non-magnetic segments or by modulation of the pore diameter. The former strategy is made possible by pulsed electrodeposition from a ternary electrolyte. The latter structure is achieved by combining several anodization steps. We demonstrate the presence of magnetic domain boundaries at such designed pinning points using bulk magnetometry and single-wire imaging techniques. As future read/write elements we introduce ultrathin oxide layers by atomic layer deposition and demonstrate a magnetoresistance of these layers.

Resume : Antiferromagnetic alloy Iridium Manganese (IrMn) is currently used in all spin electronic devices such as the read head element in hard disk drives and will be required in all devices for spin electronic technology based on the giant magnetoresistive and tunnelling magnetoresistive effects [1]. This material will also be required in all magnetic sensors based on these effects. The reason that IrMn is at present the alloy of choice is because it has a very high thermal stability of the antiferromagnetic orientation and can be deposited in thin form easily without the need for any phase transformation. Additionally, because of the properties of Iridium, which is one of the most stable materials in the universe, the alloy has high corrosion resistance even in thin film form down below 10 nm. In this study, we aim to replace the rare metal Ir with one of the many Heusler alloys which are known to form AF phases where the crystal structure and particularly the lattice spacings are closely controlled. The Heusler alloys consist of either an XYZ or an X2YZ structure where X and Y are usually the common transition metals and Z is either a semiconductor or a non-magnetic metal [2]. All these elements are plentiful and relatively inexpensive compared with Iridium, which is already very expensive. We grew a series of antiferromagnetic Heusler alloys, such as Ni2MnAl and Mn2VSi, using sputtering. Structural and magnetic properties of these alloys were studied. Exchange bias was observed in epitaxial alloys at low temperatures (< 100K) and the corresponding interfacial atomic structures were observed using cross-sectional transmission electron microscopy (TEM). The correlations between the magnetic properties and crystalline structures are discussed. This work has partially been supported by EU-FP7 (NMP3-SL-2013-604398), EPSRC (EP/I000933/1, EP/K03278X/1 and EP/M02458X/1). [1] A. Hirohata and K. Takanashi, J. Phys. D: Appl. Phys. 47, 193001 (2014). [2] C. Felser and A. Hirohata, Heusler Alloys (Springer, Berlin, 2015).

Resume : Magnetic materials are important in the production, transmission and use of electrical energy. Advanced permanent magnets (PMs) contain rare earth (RE) elements and are used in a multitude of applications [1] that play important roles in energy-efficient, low-carbon technologies. Recent severe price fluctuations for REs have prompted the search for alternative types of magnets to functionalize specific applications. Among these alternatives, high-performance ferrites and tau-phase Mn-Al are promising choices due to the abundance of the constituent elements and potential for good magnetic properties [2,3]. Of equal importance to the search for alternative magnets is the necessity of considering environmental issues and factory production efficiency by finding energy- and cost-efficient recycling methods. This presentation will cover aspects related to the synthesis, processing and industrial recycling of RE-free PMs. In particular the following topics will be addressed: - Tuning microstructure of ferrites for the production of high-coercive isotropic powders. - Rapid-milling as a fast processing technique developing the magnetic performance of MnAl powders. - Recycling of ferrites in manufacturing line. Optimization of an ultrafast-milling technique has allowed us successful preparation of highly-coercive isotropic ferrites powders: Sr-ferrite (SrFe12O19)-based nanocomposites and single-phase Co-ferrite (CoFe2O4). This technique has resulted in a 3-fold increase in coercivity (1.5 kOe to 4.7 kOe) of co-precipitated Co-ferrite powders after only 3 min of milling [4]. This large increase is attributed to a combination of a fine microstructure and stress anisotropy imparted during milling. Sr-ferrite-based powders with coercivity > 6 kOe have been also obtained using this technique, which provides some of the largest coercivity values reported for isotropic Sr-ferrite powders. Rapid milling for only 3 min of Mn-Al particles obtained by the gas atomization technique, followed by heat treatment, has resulted in an increase in coercivity from 2.0 to 4.9 kOe, standing as the highest coercivity value reported for Mn-Al binary alloys to date. This improvement is attributed to microstructural changes in combination with an increased content of tau-phase generated during processing [5]. Processing of permanent magnet powders into bulk magnets has been successfully achieved through sintering and polymerization, with further proof of their workability by implementation and testing in technological devices. The presentation will conclude with demonstration of a novel recycling procedure for ferrites from wastes generated in production line that has been successfully demonstrated in an industrial environment. The procedure is cost-efficient allowing to the company the reuse of ferrites from their resulting residues, i.e. improving the production efficiency, and with no need of an extra-cost for removal of this waste by an external company. Acknowledgements: Research supported by Spanish MINECO (Spanish Ministry of Science and Innovation): ENMA-National Project (MAT2014-56955-R) and Northeastern University, MINECO through M-era.Net Programme: NEXMAG Project (PCIN-2015-126), EU-FP7 NANOPYME Project (No. 310516), Regional Government (Comunidad de Madrid): NANOFRONTMAG (Ref. S2013/MIT-2850), MINECO (project MAT2013-45165-P) and the PAI of the Regional Government of Andalucía. References: [1] L.H. Lewis et al., Metall. Mater. Trans. A 44, 2-20 (2013). [2] NANOPYME website: www.nanopyme-project.eu [3] F. Jiménez-Villacorta et al., Metals 4, 8 (2014). [4] F.J. Pedrosa et al., Submitted. [5] J.Y. Law et al., Submitted.

Resume : The quest for novel materials that can replace currently used Rare Earth (RE) compounds in a wide part of the spectrum of industrial necessities where the high performance of RE permanent magnets are not strictly required, has recently emerged as a hot research topic. In this context, the reduction to the nanoscale of traditional magnetic materials such as spinel ferrites, can be a promising approach. In this contribution we present a deep investigation on the magnetic properties of a series of cobalt ferrite nanoparticles, (NPs), with different composition, size in a broad range (4 to 60 nm), narrow size distribution and controlled shape. The study of the evolution of the magnetic properties with the Co content, particles size and shape, allowed us to identify the parameters which optimize the properties determining the best performance as permanent magnet. We also investigated the possibility of further enhancing the properties of the material by exploiting exchange anisotropy. We found that using highly exchange-coupled antiferromagnetic-ferrimagnetic Co0.3Fe0.7O|Co0.6Fe2.4O4 core/shell NPs a large increase of the (BH)max product can be obtained after a field cool process. This result arises from the high exchange bias due to the crystalline quality of the boundary and the lack of cation intermixing between the two phases. Overall, the collected data gave us the opportunity to discuss the feasibility of the use of this material for the realization of permanent magnet.

Resume : In the last years, a global concern about the substitution of critical raw materials and the development of new efficient magnetic devices free from critical raw materials has emerged. Today’s technological applications require a strong demand of permanent magnets, largely driven by wind turbines and electric vehicles markets. Nd2Fe14B magnets are now manufactured in quantities of the order of 100 000 tonnes per year, being the largest contribution of the annual 7 billion dollars permanent magnet market. This increased demand combined with the strategically geographical situation of rare earth materials has contributed to the search of new efficient alternatives of permanent magnets free from critical rare earth materials. [1,2] Two promising candidates have gained large attention. On one hand, hexagonal ferrites have raised an interest that grows exponentially today in terms of their high performance-to-cost ratio, becoming massively important from the commercial and technological point of view. Hexaferrites have applications as permanent magnets, as well as in magnetic recording and data storage and as components in electrical devices, particularly those operating at microwave/GHz frequencies. In particular, the M-type strontium ferrite (SrFe12O19, SrF in short) is one of the most promising hexagonal ferrites for its high uniaxial magnetocrystalline anisotropy constant, excellent chemical stability and good wear resistance. [3,4] On the other hand, Mn-based permanent magnets, such as MnAl emerge as a promising choice in terms of the abundance of the constituent elements and potential intrinsic magnetic properties. Jointly with good machinability and excellent corrosion resistance, MnAl owns even larger uniaxial magnetocrystalline anisotropy (K∼107 erg/cm3) and a theoretical energy product over 12 MGOe.[5,6] However, practical implementation of these magnets requires first, a proper understanding and optimization of the magnetic properties with morphology and microstructure. To this regard, thin films with controlled properties in terms of the deposition parameters can be used as model systems to optimize the bulk permanent magnets performance. Thorough investigations including both experiments and micromagnetic simulations can further improve the basic magneto-structural understanding. Despite the large number of publications dealing with SrF, including nanocrystalline powders, platelets, nanoribbons or self-assembled nanodots, there is no complete understanding of the coercivity behaviour of in the submicron range. Segregation of grains was believed to account for larger coercivity and more isotropic behaviour of SrF grains prepared at 0% of O2. On the other hand, variations in the magnetic anisotropy directions or the coexistence of amorphous and crystalline SrF phases have been also predicted for the experimental increased in coercivity in SrF. Very recently, a decrease in coercivity of SrF films deposited by pulsed laser deposition has been attributed to surface crystalline defects using experiments and micromagnetic modelling.[4,7,8] Regarding MnAl, many fundamental questions still remain unclear. Experimental energy product values well below the theoretical ones have been reported. Although recent studies of (001) oriented thin films deposited on GaAs or Cr show large magnetization and anisotropy, it appears not easy to develop coercivity in this material. Decomposition of the ferromagnetic τ-phase into the stable but non-magnetic γ (Al8Mn5) and β (Mn) phases that usually occurs when annealing above 900 K or coexistence of other different MnAlx phases can further complicate this image.[5,9,10] A combined study based on experiments and micromagnetic simulations of thin films has been performed here to get further insight of the magnetic behaviour of M-type SrF system. Independently of the preparation conditions, strong uniaxial magnetocrystalline anisotropy close to the theoretical one is evidenced. Nonetheless, small changes in the oxygen ratio and in-situ heating lead to different SrF grains characteristics, which determine the strong variations of the magnetization curves, ranging from quasi-isotropic to highly anisotropic ones, and their different coercive fields.[11] Regarding MnAl, further understanding of the τ-phase formation process from the onset of the growth becomes of particular interest regarding the reported difficulty in literature in obtaining MnAl films with a maximized amount of τ-phase. Investigations of MnAl films prepared by means of different techniques, such as MBE or sputtering, including Mn/Al bilayers with varying thickness of both layers (to modify MnAlx composition) and different substrate and annealing temperatures are presented. Our results from model SrF and MnAl systems can aid to stablish magneto-structural correlations for further improvement of the corresponding bulk permanent magnets for practical applications. Acknowledgements: Research supported by MINECO (Spanish Ministry of Science and Innovation): ENMA-National project (MAT2014-56955-R), MINECO through M-era.Net Programme: NEXMAG project (PCIN-2015-126), FPDI-2013 (JdC, MINECO), EU-FP7 NANOPYME Project (No. 310516) and Regional Government (Comunidad de Madrid): NANOFRONTMAG (Ref. S2013/MIT-2850). References 1. EU FP7 NANOPYME Project: www.nanopyme-project.eu 2. J.M.D. Coey, Phys.: Condens. Matter 26, 064211 (2014) 3. J. Lee, Y.-K. Hong, W. Lee, G. S. Abo, J. Park, W.-M. Seong, and W.-K. Ahn, J. Appl. Phys. 113, 073909 (2013) 4. R. C. Pullar, Prog. Mater. Sci. 57, 1191 (2012) 5. F. Jiménez-Villacorta, J.L. Marion, J.T. Oldham, M. Daniil, M.A. Willard and L.H. Lewis, Metals 4, 8 (2014) 6. Q. Zeng, I. Baker, J.B. Cui, and Z.C. Yan, J. Magn. Magn. Mat. 308, 214 (2007) 7. B. R. Acharya, S. Prasad, N. Venkataramani, A karra and T. Suzuki, IEEE Trans. Mag. 33 3640-3642 (1997) 8. Y.-M. Kang, J. Lee, Y. J. Kang, J.-B. Park, S. I. Kim, S. M. Lee, and K. Ahn, Appl. Phys. Lett. 103, 122407 (2013) 9. S. H. Nie, L. J. Zhu, J. Lu, D. Pan, H. L. Wang, X. Z. Yu, J. X. Xiao, and J. H. Zhao, Appl. Phys. Lett. 102, 152405 (2013) 10. M. Hosoda, M. Oogane, M. Kubota,T. Kubota, H. Saruyama, S. Iihama, H. Naganuma and Y. Ando, J. Appl. Phys. 111, 07A324 (2013) 11. E. Céspedes, G. Rodríguez-Rodríguez, C. Navío, R. Guerrero, M. Rodríguez, F. J. Pedrosa, F. Mompeán, M. García Hernández, A. Quesada, J. Camarero and A. Bollero, submitted (2016)

Resume : To design new permanent magnets without critical elements such as Dy, it is of importance to understand the mechanism of high coercivity of existing permanent magnets from the viewpoint of electron theory. Recent experiments demonstrated the doping of Cu is effective to improve the coercivity of Nd-Fe-B permanent magnets [1,2]. Although the decrease of the melting temperature of Nd metals by forming Nd-Cu alloys improves the quality of microstructures, the possibility of direct improvements of local magnetic anisotropy at the microstructure interfaces has not been examined. In this study, we simulated Cu-doped Nd2Fe14B/NdOx interfaces, which have been observed around triple junctions in Nd-Fe-B magnets [1,3]. We performed first-principles calculations on the basis of density functional theory by the OpenMX code [4]. After examining the stability of Cu atoms at interfaces, the magnetic anisotropy of Nd was studied based on crystal-field analysis, whereas that of Fe was calculated using a formalism using perturbation theory [5]. We have found that Cu can improve local magnetic anisotropy. [1] H. Sepehri-Amin, et al., Acta Mater. 61, 6622 (2013); ibid. 61, 1982 (2013); ibid. 60, 819 (2012). [2] A. Yasui, et al., J. Appl. Phys. 117, 17B313 (2015). [3] T. Fukagawa et al., J. Magn. Magn. Mater. 322, 3346 (2010). [4] T. Ozaki, Phys. Rev. B 67, 155108 (2003); http://www.openmx-square.org/ [5] Z. Torbatian, T. Ozaki, S. Tsuneyuki, and Y. Gohda, Appl. Phys. Lett. 104, 242403 (2014).

Resume : Nowadays, precious materials are widely used in heterogeneous catalysis for the production of specific products or electricity generation. In particular, platinum (Pt) still can be considered the best catalysts for electrochemical systems such as electrolytic cells or fuel cells. In both cases, Pt has largely been used to catalyze H2 production, but overall to accelerate the Oxygen Reduction Reaction (ORR), which is the most critical point in determining the whole yield of these devices. However, the relative high cost, along with the “supply risk”, make Pt among the Critical Row Materials list. So, exploring catalysts included in the not–Pt group metals is becoming mandatory. Owing to their lower cost and availability, transition metal based catalysts can be suggested as a promising alternative. This work considered Ni oxide and Ni/Al mixed metal oxide based materials as cathodes for ORR: different nickel oxide electrodes were synthesized and characterized by electrochemical techniques. Moreover, the photoactivity of the samples was also studied, in view of their use in the field of dye sensitized solar cells, for the environmentally friendly energy production.

Resume : Recently, nanostructured materials such as nanoparticles, wires, and tubes have attracted much attention due to their unique potential applications for solar cells, water splitting, and environmental remediation. The electrocatalytic splitting of water, hydrogen or oxygen evolution reaction (HER or OER), by nanostructured materials has been considered a promising candidate and useful procedure, especially. The metal oxides (Ru, Co, Ir, Ni and Fe) and metal-free carbon materials (CNT and Graphene) have been made great efforts to study for non-precious metal catalysts as substitutes for Pt-catalysts. Among different OER catalysts, metal oxide nanostructures would be desirable to develop electrocatalysts based on considerably cheaper metals such as Ni and Fe. Furthermore, developing mesoporous catalysts materials on high-surface-area is very useful strategy in order to achieve high-efficiency hydrogen and oxygen gas evolution. The monodispersed and mesoporous NiFe2O4/NiO concave hollow nanocubes were successfully fabricated via Ni2[Fe(CN)6] nanocube precursors and calcination process. We report the synthesis and characterization of mesoporous NiFe2O4/NiO concave hollow nanocubes under controlled several experiment condition. Also, the mesoporous NiFe2O4/NiO concave hollow nanocubes electrode shows significantly enhanced OER performance compared to NiFe2O4 particles by solid state reaction.

Resume : Water electrolysis is considered as the ?cleanest? way to produce hydrogen, when the required electricity is derived from renewable energy sources such as solar or wind. In order to improve the yield of hydrogen and to reduce the overpotential of electrolysis, electrocatalysts for hydrogen and oxygen evolution reactions (HER & OER) are usually indispensable. Presently, platinum and noble metal oxides (e.g., RuO2 and IrO2) are the state-of-the-art catalysts for HER and OER, respectively. These noble metals are not only expensive but also have limited availability in the crust. To overcome the prohibitive cost barrier to market penetration and to enable widespread deployment of water electrolyzers, it is of paramount importance to develop efficient, cheap, and durable electrocatalysts to expedite HER and OER. Notwithstanding remarkable progress in bifunctional electrocatalysts, there are few materials that can simultaneously catalyze HER and OER in the same medium. In this presentation, we report a self-supported three-dimensional porous foam electrode composed of micro/nano-hybrid structures of nickel phosphide ? an emerging non-precious electrocatalysts [1, 2]. The electrode is fabricated by a simple, cost-effective, and readily-scalable method, and can be directly used as either cathode or anode in an alkaline electrolyzer. Overall electrochemical water splitting has been realized using an electrolyzer constructed by two identical as-fabricated electrodes, and a high energy efficiency of 91% is achieved at 10 mA cm-2. Substitution of noble metal electrocatalysts with our bifunctional porous nickel phosphide foam electrodes would significantly simplify the fabrication procedure of water electrolyzers and substantially lower the production costs, which will promote the widespread deployment of electrolyzers in the future. References: [1] X. G. Wang, Y. V. Kolen?ko, X. Q. Bao, K. Kovnir, L. F. Liu, Angew. Chem. Int. Ed. 2015, 54, 8188 [2] X. G. Wang, W. Li, D. H. Xiong, L. F. Liu, J. Mater. Chem. A. under revision

Resume : White LEDs are the future of lighting sources, but the manufacturing process of the main phosphor used for blue light conversion still raises a lot of problems. YAG:Ce,Eu or cerium, europium (co)doped yttrium aluminum garnet nanopowders were prepared by a (co)precipitation method using like raw materials: the nitrates as sources of cations, ammonium hydrogen carbonate as precipitant agent and polyvinylpyrrolidone as reaction medium. The spectroscopy has been used to study the chemical configuration and luminescent properties and shows an optimal sinterability time and temperature in order to obtain an YAG:Ce,Eu phosphor with corresponding properties for developing of the optoelectronic devices with white light emission. FT-IR and FT-Raman spectroscopy were used to study phase evolution of the product from precipitate to the finished powder obtained after heat treatment at 1400 °C. The vibrational spectrometry is used for structural characterization in terms of optimizing time and sintering temperature. The EDX spectra show the molar ratio of samples and the sample purity. Photoluminescence spectra of YAG:Ce,Eu phosphor were studied as a function of time and temperature sintering. Luminescence properties show high photoluminescence quantum yield (QY). The experimental results shows the method to be suitable to synthesize YAG:Ce,Eu phosphor.

Resume : The phenomenon of luminescence enhancement was studied in organic-metal oxides hybrids. Nanoscaled oxides were synthesized by hydrothermal method. The crystal phase was monitored by X-ray diffraction patterns and Raman scattering. Steady-state photoluminescence measurements show a significant increase of rare earth luminescence at the realization of the hybrid. The detailed analysis of time decay profile of Lanthanide luminescence indicate an important variation of radiative recombination processes in the presence of organic functionalization proving a correlation with surface defects and non-radiative recombination.

Resume : The recovery from industrial process residues of toxic metals belonging to the class of critical elements meets at the same time the goal to obviate to the shortage of the metal itself and to fulfill EU environmental regulations.Adsorption results to be the best strategy to remove metals from aqueous media. We have chosen Co to test detonation nanodiamonds (DND) , characterized by grain size <10nm , as solid phase adsorbent. After the purification the DND samples are treated following a specific two-step protocol: oxidation by H2SO4/H2O2 mixtures and functionalization with amine groups. Three different amidated DND samples have been prepared using ethylenediamine (NH2CH2CH2NH2), 1,3-diaminopropane (NH2(CH2)3NH2) and 1,6-diaminohexane (NH2(CH2)6NH2) , respectively. For each experiment 3 mg of amidated DND were dispersed in 30 ml of standard 100 ppm solution of Co, incubated for 18 h and centrifugated . The amounts of adsorbed Co , evaluated measuring the residual Co concentration in the supernatant , reach very high values, up to 60% .Co is easily recovered from the solid phase and the DND adsorbent can be re-activated by acidification , giving rise to an efficient recycling chain .The high adsorption and the good regeneration capabilities make DND an ideal candidate for Co removal from aqueous solutions , meeting at the same time the issue of critical metals re-use and also that of wastewater purifications.

Resume : We have investigated the influence of chromium (Cr) doping on the magneto-electrical properties of polycrystalline samples La0.80Sr0.20Mn1-xCrxO3 (x=0.00 and 0.1) , prepared by sol-gel method. This materiels has attracted much attention due to their extraordinary magnetic and electronic properties as well as their promise for the potential technological applications.Comparison of experimental data with the theoretical models shows that in the metal-ferromagnetic region, the electrical behavior of three samples is quite well described by a theory based on electron-electron, electron-phonon and electron-magnon scattering and Kondo-like spin dependent scattering. For the high temperature paramagnetic insulating regime, the adiabatic small polaron hopping (SPH) model is found to fit well the experimental curves.

Resume : Hybrid nanocomposite materials are important to improve electrical and optoelectronic properties of, e.g., light emitting devices, solar cells, biosensors. In this work we coupled polyaniline (PANI), a p-type conductive polymer, and n-type porous Si (PSi) to form a bulk heterojunction [1], already reported as a rectifying p-n junction [2]. PANI/PSi structures were obtained by three electrochemical (EC) steps: a) functionalization of PSi by EC reduction of 4-nitrobenzenediazonium salts (NBD); b) EC reduction of nitro groups to amino groups; c) polymerization of aniline by cyclic voltammetry. Depending on the redox state [3], different PANI forms are obtained, e.g. emeraldine salt (protonated form) and emeraldine base (deprotonated form). To evaluate the reversibility of PANI redox states, PANI/PSi junctions have been dipped first in a basic solution (pH=9) and then in an acid solution (pH=4), starting from a p-type PANI protonated form. Our results demonstrate, in addition to an increased photocurrent in the visible range with respect to pristine PSi, the possibility to modify the PANI/PSi photocurrent efficiency by a doping/de-doping process controlled by the pH. This can be used, for instance, to build a photovoltaic pH sensor. REFERENCES [1] G. Mula et al., Nanoscale Res. Lett.7, (2012), 377 [2] P. Kumar et al., Synthetic Metals 160, (2010), 1507?1512 [3] A. Baba et al., J. Electroan. Chem. 562, (2004), 95?103

Resume : The La0.8Ba0.1Ca0.1Mn0.85Co0.15O3 sample has been prepared by polymerization complex sol-gel method. The structural, magnetocaloric and electrical properties have been studied. The sample crystallizes in the orthorhombic structure with Pbnm space group. Furthermore the experimental study, a theoretical approaches were adopted to investigate the magnetocaloric and electrical behavior of this sample. The important parameters such as maximum entropy change , full width at half maximum and relative cooling power (RCP) have been explained qualitatively. The analysis of electrical resistivity data show the semiconductor behavior in all whole temperature, which can be explain by Small polaron hopping (SPH) and Mott's variable range hopping (VRH) models.

Resume : Solid state lightings are now rapidly replacing their traditional counter parts that is incandescent and fluorescent light sources. These solid state lightings also knowns as phosphor converted light emitting diodes (pc-LEDs) possess a number of advantages coinciding with the prevalent notion of energy conservation and non-hazardous to our planet. Other numerous advantages associated with these lights include brighter glow, longer lift times, tenability of color temperatures and color rendering index. The matured and common version of these pc-LEDs combine a blue LED with a yellow emitting phosphor to observe white light. Although YAG:Ce3+ is a commercially available and widely used yellow phosphor, but the quest for new materials is also in process to overcome and add to the limitations (like CRI, CCT, thermal stability, etc) of this phosphor. Divalent europium doped orthosilicates are another intensively investigated class of phosphors. These possess a wide excitation band extending from UV to blue region making them potential for their applications in pc-LEDs. To add to this they have been reported for tenability of their emission color ranging from Blue to deep red region. Thermal stability characteristics of these class of phosphors are also very interesting, with the end compositions (like Ba2SiO4, Sr2SiO4 and Ca2SiO4) exhibiting lower thermal stability than the intermediate compositions (like SrBaSiO4). Here we report a novel high intensity, yellow emitting intermediate composition of Sr1.44Ba0.46SiO4:0.1Eu2+ as a potential candidate for the application in pc-LEDs. The phosphor synthesized emission intensities higher than commercial YAG:Ce3+, sphere like morphology and the quantum efficiencies were calculated to be higher than 85%. The phosphors were synthesized thorough liquid phase precursor process (LPP); a process developed by our group. Interestingly further experiments revealed that the size of the particles can be tuned by exploiting the non-stoichiometric precursor amounts of WSS, with higher amounts resulting in comparatively smaller size distribution. On the other hand non-stoichiometric lower amounts resulted in larger sized particle size distribution of the synthesized phosphors.

Resume : Quantum dot (QD) light-emitting diodes (QLEDs) emerge as a next generation flat-panel display due to their unique display qualities, such advantages as narrow emission spectrum (high color purity), chemical stability, low cost solution process, etc. Since the first demonstration of efficient QLEDs, intensive researches have been carried out to improve the device performances such as luminous efficiency, driving voltage and lifetime. However, some of efficient QLEDs using metal oxides as the electron transport layer suffer from charge imbalance due to their different intrinsic properties compared to organic hole transport materials. Thus, the potential application of QLEDs requires the fine control of electron?hole charge balance. To improve the charge balance in QLEDs, in this work, we introduce red-emitting QLEDs adopting a green phosphorescent organic dye (Ir(ppy)2(acac)) near the QD layer, with an inverted structure of ITO/ZnO/QD/CBP/MoO3/Al. Here, the green phosphorescent organic dye was blended with QD solution or vacuum-deposited between QD and hole transport layers, resulting in electron?hole charge balance of QLEDs. Both the electroluminescence characteristics and the analysis on charge balance with a green phosphorescent dye will be presented.

Resume : In recent years, increasing interest has been given to the synthesis of metal-oxide semiconductor nanomaterials such as nanotubes, nanowires, nanoparticles, and hollow nanostructures. Especially, metal-oxide semiconductor nanomaterials are attractive candidates as active elements for advanced nanoscale devices due to their unique electronic and optical properties, low effective density, high specific surface area, and shell permeability that are important in many technology applications such as catalysis, photonics, sensors, solar energy conversion, and electrochemical energy storage. Among the various semiconductor materials, gallium oxide (Ga2O3) with ?-, ?-, ?-, ?-, and ?-crystal structures, and which has a wide band-gap of 4.9 eV at room temperature, is a promising candidate material for transparent conducting oxide, electroluminescent devices, photocatalysis, and gas sensors. Especially, controlled morphology and size of ?-Ga2O3 have gained interest in photocatalytic materials due to extraordinary ability to photodegrade of organic pollutants such as RhB, methylene blue and Orange 7 under exposure to ultraviolet light irradiation. The monodispersed and mesoporous Ga2O3 microspheres were successfully fabricated via glucose assisted hydrothermal and calcination process. We report the synthesis and characterization of mesoporous Ga2O3 microspheres under controlled several experiment condition. Also, as prepared samples show an activity for the photocatalytic degradation of methylene blue (MB) under UV light radiation.

Resume : The field of photocatalyst using the energy from sunlight has been expanded and developed with regard to energy and environment. Especially the two most important application of photocatalyst are solar water splitting and purification of water by removing organic pollutants. To achieve this improved efficiency, various semiconductor materials have been studied as photocatalyst due to their advanced light absorption ability and transfer of the photo-generated charge carriers to the conduction band. These photocatalytic efficiency have been affected by morphological features because semiconductor consisted of porous and nanoscale three-dimensional structure has the considerable surface area and the number of available reaction site. In this study, we synthesized the monodispersed mesoporous ZnGa2O4 microsphere through solvothermal method and calcination process. And the crystallinity, morphology, and porosity of the monodispersed mesoporous ZnGa2O4 microsphere were characterized by XRD, SEM and TEM. Also we present the photocatalytic activity of the degradation of methylene blue & rhodamine B to demonstrate the effect of the monodispersed and mesoporous special structure.

Resume : OLEDs are promising next-generation display devices. The use of OLED ranges from mobile displays to flexible, bendable and transparent devices. Substrates for flexible devices require more difficult conditions. Deposition also plays a critical role in fabricating OLEDs. We investigated the effect of various doping concentration by non-uniform deposition process and parameter extraction methods. Reference device consists of all uniformly doped organic layers. Experimental group has non-uniformly doped organic layers, HTL, EML, and ETL. Current-Voltage(I-V) and Capacitance-Voltage(C-V) characteristics are analyzed. We extracted device parameters of threshold voltage and ideal factors andcompared depending on the device structures. The peak capacitance voltage and threshold voltage increased in non-uniformly doped HTL devices with the reduction of the ideality factor, representing the efficient OLED devices.

Resume : TiO2 is a n-type oxide semiconductor widely used in many fields of chemical engineering and materials engineering including either traditional catalysis, or photocatalysis, dye-sensitized solar cells, lithiuminsertion-based devices, integrated circuits, gas sensors and in the paint industry. A number of methods have been employed to prepare TiO2 films, including e-beam evaporation, sputtering, chemical vapor deposition and sol-gel process. In this work structural and electrical properties of titanium oxide thin film obtained by e-beam evaporation and annealed at different temperatures were studied using different characterization techniques, in order to evaluate its use as emitter layer or back contact in silicon based heterojunction solar cells. According to XRD analyses the obtained TiO2 films showed mainly the presence of anatase crystal structure once annealed at T> 400 °C. Electrical and optical characterization of the annealed samples shows the best results for the films annealed at T> 400 °C with a resistivity of ca.10-2 ohm cm, a mobility of 3 cm2/Vs and carrier concentration of 1019/cm3. From capacitance-voltage characteristics of TiO2 /p-c-Si the built?in potential will be evaluated in order to evaluate the band alignment. Therefore, the observed results indicate formation of good quality titanium oxide films by using e-beam evaporation deposition technique followed by thermal annealing, with physical and electrical properties desirable for our applications.

Resume : Transparent and conductive oxide (TCO) materials are fundamental for a number of opto-electrical applications. One of the most widely used TCOs is Indium Tin Oxide (ITO), but Indium has recently been listed among the critical raw materials by the European Commission. It is therefore important to develop alternatives to Indium Tin Oxide (ITO) thin films transparent electrodes. NiO is an attractive material for its potential applications as a p-type transparent and conductive layer, both in conventional solar cells applications and in the new emerging branch named invisible electronics, including transparent lighting and fully transparent displays. NiO is composed by non-expensive, non-toxic and abundant elements, can be grown by several methods and it can reach conductivities of 10-2 Ohm cm. We have grown thin non stoichiometric NiO films (NiOx) by RF sputtering at room temperature. The material shows a degenerate p-type behavior, resistivity down to about 10-2 Ohm cm and transparency around 50%. To test the material potential for heterojunction fabrication, we have deposited NiOx films on both n- and p-type Silicon. On n-type Si the I-V characteristics show a typical rectifying behavior, and the CV measurements give a high Vbi value. On p-type Si the electrical characterization suggest the formation of a p -p junction where the NiO plays the role of the p material. We conclude that NiOx is a degenerate semiconductor with valence band deeply under the Si one, and it is thus a good candidate for junction and contact formation in c-Si solar cells.

Resume : Optically transparent conductive films (TCF) have attracted much of attention in recent years due to their application in various devices, such as touch screens, panel displays, organic light emitting diodes and solar cells. Chemical stability and mechanical robustness of the TCFs are crucial conditions when the long-term perspective is considered. In this regard, conductive boron doped diamond thin films offer superior mechanical durability and chemical inertness along with high optical transparency, thus they are able to advantageously substitute commonly used Indium Tin Oxide (ITO) electrodes which are expensive due to scarce indium and tend to fracture over time. The major drawback of transparent and conductive boron-doped nanocrystalline diamond (B-NCD) films is their high sheet resistance (~1 kΩ/sq) compared to ITO electrodes (~100 Ω/sq) at equivalent transparency, which is mainly attributed to polycrystalline nature of the diamond film and boron inclusions. To fully realize the potential of diamond films as the TCF material, the optimal “tradeoff” between optical transparency and sheet resistance of boron-doped nanocrystalline diamond films should be found. [1] In this work we studied electrical and optical properties of boron-doped nanocrystalline diamond films with variable boron concentration and thickness obtained by microwave plasma enhanced chemical vapor deposition (MW-PE-CVD). Boron concentration and thickness have been determined for layers with highest optical transparency and least sheet resistance. B-NCD films with sheet resistance values comparable to that of ITO layers (~100 Ω/sq) has on average 60% less transparency. Transparent and conductive electrodes with sheet resistance below 50 Ω/sq and high optical transparency have been obtained by the integration of a thin and nanostructured Ti-grid, sandwiched between the glass substrate and B-NCD film. [1] A. Kovalenko, P. Ashcheulov, A. Guerrero, P. Heinrichová, L. Fekete, M. Vala, M. Weiter, I. Kratochvílová, G.G. Belmonte. Sol. Energ. Mat. Sol. C. 134 (2015) 73 - 79.

Resume : A new promising inert matrix as host of luminescent ions is proposed. Al2SiO5 samples, doped with rare earths (Ce, Tb single doped and co-doped) are proposed as good prospect for the development of new UV-visible converter with reduced content of rare earths elements. Structural characterization by Raman, XRD spectroscopy and TEM imaging reveals the sillimanite phase and nanosized dimension of the investigated powders. Optical characterization by steady time and time resolved emission spectroscopy for the single doped and co-doped samples allows to identify an efficient energy transfer from Ce to Tb ions under near UV excitation wavelength. The intense green emission observed in the Ce:Tb co-doped Al2SiO5 system suggests its potential application as efficient blue pumped green emitter phosphor to be exploited for white LED: to this purpose we tested the compound in combination with a red emitting doping ion recording for Ce:Tb:Cr:ASO system a correlated color temperature of 6720K.

Resume : Novel fluorescent nanoarchitectures are investigated to engineer organic-inorganic hybrids for applications in photonics, in particular as white LED. The selected fluorescent compounds are Carbon-dots (CDs) whose emission properties can be tuned by quantum confinement and surface functionalization. To achieve photonic applications the fluorescent compounds will be embedded in suitable matrices, such ordered mesoporous silica. The fluorescent quantum yields of C-dots in the blue/green range is almost competitive to those of CdSe/ZnS, and the efficiency in the red/IR range could be increased by proper functionalization of the CDs surface and by exploiting the interaction with silica surface. The chosen host matrix is ordered mesoporous silica because its huge specific surface area allows hosting large concentrations of fluorescent CDs. The analysis of the interaction of CDs with the matrix, in terms of physical and chemical confinement of emitting compounds, is a strategic issue to fill the current knowledge gap about CDs in embedded systems. The reference benchmark are the emission properties in water suspension, aiming to transfer at the solid state the spectroscopic features gathered at the liquid one.

Resume : Atomic layer deposition (ALD) is a self-limited growth method which relies on sequential reactions of gas phase precursor molecules with a solid surface to deposit oxides, metals and other materials in an atomic layer-by-layer fashion. The unique surface-controlled chemistry of ALD enables the conformal coating of high surface area nanoporous materials and provides atomic-level control over the coating thickness. These key advantages offer ALD the ability to precisely tune the pore size and chemical surface composition of nanoporous materials, and therefore render ALD an enabling technology for the controlled atomic-scale design of supported catalysts. In addition, the nucleation controlled growth mode observed for noble metal ALD processes can be used advantageously to conformally deposit metal nanoparticles. In this presentation, an experimental study is presented that demonstrates the ability of ALD for conformal deposition in nanometer-sized mesopores [Dendooven et al., Nanoscale, 2014, 6, 14991]. Secondly, case studies will be presented where ALD is used to incorporate acid sites in zeolites [Verheyen et al., Chem. Commun., 2014, 50, 4610], introduce photoactive TiO2 in mesoporous silica [Sree et al., Nanoscale, 2013, 5, 5001] and embed Pt nanoparticles in metal organic frameworks [Leus et al., Nanomaterials, 2016].

Resume : We researched pore characteristics of porous Nickel and Cobalt particles by ultrasonic spray pyrolysis process. Spray pyrolysis is a powerful method for preparing metal and metal oxide particles, because of the easy control of target composition, particle structures. A composition of spray solution, amount of polystyrene (PS) beads as a pore former, reaction temperature, and carrier gas flow rate were investigated to make various structures of porous nickel oxide and cobalt oxide particles. The prepared porous nickel oxide and cobalt oxide particles from the spray pyrolysis were heat-treated at H2 atmospheres as a reduction-reaction for making Ni and Co porous particles. The structures of porous particles were characterized by SEM, TEM, and EDS, also the specific surface area and phase changes of porous particles were analyzed by BET and XRD, respectively. The Ni and Co porous particles showed a spherical micro-structure distributed the nano-pore on entire particles. The results showed that the composition of spray solution, precursor-to-PS beads ratio, reaction temperature and residence time play crucial roles in the preparation of porous particles from the spray pyrolysis process. The porous metal particles with high surface area showed a higher catalytic activity than nonporous metal particles, hence, the porous metal particles can be considered as potential candidates for raw materials of active catalysts.

Resume : In the past decades, interest for new catalysts and new catalytic reactions increases greatly due to their large applications. New catalysts were described for an increasing number of organics reactions. Nevertheless, most of the homogenous catalysts are difficult to adapt to industrial process due to separation and regeneration problems. Moreover, though highly efficient, most of the catalysts are containing noble and/or toxic metals and so new protocols more economically and environmentally friendly need to be developed. Recently, more attention has been paid to the use of nanomaterials as support. In fact, due to their unique properties and their enhanced surface volume ratio putting them at the frontier between heterogeneous and homogeneous catalysis,[1] nanomaterials are quickly becoming the support of choice for catalysis applications. Among them, magnetic nanoparticles appear as an ultimate nano-support due to their easiness of recovery owing to their magnetic properties.[2] In this context, ongoing with previous works on nanocatalysis[3-4], we will present a new simple Pd supported magnetic nanocatalyst which turns out to be extremely efficient for C-C coupling reactions that played a very important role in a wide range of industrial and pharmaceutical applications. This green nano-catalyst prepared with cheap reactant and working under eco-friendly conditions (aqueous media and under aerobic conditions) with Pd quantity down to 100 ppm appears to be one of the most efficient up to date for Suzuki-Miyaura cross coupling.[5] This very stable catalyst (> 12 months in water under aerobic conditions) is moreover reusable up to 7 times with total conversion and small amount of palladium leaching. Finally preliminary results on its exemplification on other C-C coupling and reduction reactions will be presented. References [1] S. Shylesh, V. Schünemann, W. R. Thiel, Angew. Chem. Int. Ed., 2011, 49, 3428. [2] M. B. Gawande, P. S. Branco, R. S. Varma, Chem. Soc. Rev., 2013, 42, 3371. [3] P. Demay Drouhard, E. Nehlig, J. Hardouin, L. Motte, E. Guénin, Chem. Eur. J., 2013, 19, 8388-8392. [4] E .Nehlig, L. Motte, E. Guénin, Catal. Today,2013 90. [5] E. Nehlig, L.Motte, E. Guenin, RSC Adv. 2015, 5, 104688. [6] E. Nehlig, B. Waggeh, N. Millot, Y. Lalatonne, L. Motte, E Guénin, Dalton Trans., 2015, 44, 2, 501.

Resume : Magnesium hydride is a very promising material for solid-state hydrogen storage. However, metallic catalysts are widely used to increase their overall efficiency. Atomic scale modeling is able to enlight the role of the catalyst and to provide a quantitative description of their effect. This is useful to assess a comparative description between different catalysts in order to propose an optimized use of them. Thus an accurate numerical model of MgH2 - Mg interface has been developed to study the mechanism of action of several catalysts and how they interact with the interface in which H atoms diffuse.

Resume : Magnetic materials are well spread for day life applications such as sensors or magnetic recording. Nevertheless most of these applications require raw materials such as rare earth (permanent magnets NdFeB or SmCo) or platinium group metals (FePt in forthcoming heat magnetic recording devices) which have been classified as critical by the European Commission due to the high risk of supply shortage expected in the next 10 years.1 Therefore, the development of new nanotechnological devices with a reduced or completely eliminated critical content is strongly desired. In this way, the design of materials at the nanoscale is a very efficient research field to produce high performance technological devices. The magnetic properties can be modulated significantly as a function of size and shape, and also by controlling the collective properties of nanoparticle arrays. We focus here on the fundamental understanding of core-shell nanoparticles combining exchange ?coupled magnetic materials. The aim is to produce nanoparticles with high magnetic anisotropy which is mandatory for further development of new CRM free magnetic devices. An abundant and low cost material, Fe3O4, is combined to an antiferromagnetic CoO shell in order to enhance the magnetic stability of Fe3O4 nanoparticles against temperature resulting from size reduction. These nanoparticles are discussed as maters of synthesis2 and assembling3 which structures control the intrinsic and collective properties, respectively. Advantages and limitations of these systems will be presented as well as, briefly, perspectives. References 1. European Commission, 2011. Tackling the Challenges in Commodity Markets and Raw Materials. COM (2011) 25 final, Brussels. 2. a) W. Baaziz et al., J. Phys. Chem. C, 2013, 117, 11436. b) X. Liu et al, Chem. Mater., 2015, 27, 4073 4. Dolci et al. submitted

Resume : Exchange coupling is a promising method for optimization of the properties of magnetic materials. Exchange coupling between ferromagnetic (FM) and antiferromagnetic (AFM) materials may lead to the well-known exchange bias, which may manifest itself as a shift of the hysteresis loop and/or an increase in coercivity. These systems are potential candidates for new hard magnetic materials. However, this requires a detailed understanding and control of the magnetic properties. For this purpose, we have prepared nano-composite FM-AFM model systems by embedding FM nanoparticles into AFM thin films using the inert gas condensation (IGC) technique. Using this method, a large variety of FM-AFM material combinations may be investigated. Parameters like the fraction of FM in the composite, the FM particle size and mean FM inter-particle distance have been varied, and their influence on the magnetic properties is reported. Based on our results, and referring to earlier work in this field done over the past 50 years, we discuss the requirements for optimization of these materials for possible applications as novel hard magnets.

Resume : The FePt-based hard magnetic nanocomposites of exchange spring type were prepared by isothermal annealing of melt-spun Fe52Pt28Nb2B18 (% at) ribbons. The relationship between microstructure and magnetic properties was investigated by qualitative and quantitative structural analysis based on the X-ray diffraction, transmission electron microscopy and 57Fe Mössbauer spectrometry on one hand and the SQUID magnetometry on the other hand. The microstructure consists of L10-FePt hard magnetic grains (15-45 nm in diameter) dispersed in a soft magnetic medium composed by A1 FePt, Fe2B and boron-rich (FeB)PtNb remainder phase. The ribbon annealed at 700°C for 1h exhibits promising hard magnetic properties at room temperature: Mr/Ms=0.69; Hc=820kA/m and (BH)max = 70kJ/m3. Indeed, the strong exchange coupling between hard and soft magnetic phases was demonstrated by a smooth demagnetizing curve and positive ?M-peak in Henkel plot. In addition, the hard magnetic characteristics remain rather stable up to 400K indicating a good prospect for the utilization of these permanent magnets in a wide temperature range.

Resume : The magnetic and structural properties of ordered arrays of Co/Py bilayers antidots arrays has been investigated and correlated by means Magneto-Optic Kerr Effect (MOKE), Vibrating Sample Magnetometer (VSM) and X-ray Absorption Spectroscopy (XAS). Nanoscale patterned magnetic films are employed for technological purposes profiting of the possibility of tuning the magnetic properties in a controlled way. Antidots arrays have been commonly prepared by nanolithography techniques. An alternative route based in electrochemical processes and physical deposition is proposed in this work. Spring magnets are composed of hard and soft magnetic phases that interact by exchange coupling. These systems are expected to exhibit enhanced magnetic energy product compared to single-phase material. The study has been carry out on a system with constant Co thickness of 28 nm and variable Py thickness from 10 to 43 nm. Structural characterization suggests the presence of CoO at the internal antidot walls with increasing antidot diameter, while no significant change in the Co oxidation is found with increasing the Py layer. The magnetic characterization reveals a modification of the strength of the magnetic coupling between magnetic layers by the presence of the antidots. That modification depends on the relative thickness of Py layer. The magnetic properties of Co/Py spring magnet system can be managed by the geometrical properties of antidots arrays.

Resume : Multiferroic alloys have considerable interest nowadays in view of their wide spread applications as magnetic sensors, transducers, and energy materials. These alloys execute a reversible magnetostructural transition from a high temperature austenite phase to a low temperature martensite phase on cooling and heating cycles. In this investigation, we explore a partial Cr ? Mn substitution to demonstrate how it helps an alloy formation in the alloys Ni50Mn37-y CrySn13 (y ? 2.0) with tailored structural, magnetic and thermal properties. The various alloys were prepared by arc melting the metal mixtures in a water cooled copper crucible in argon atmosphere. X-ray diffraction patterns confirm the martensite phase at room temperature. Its structure changes from a tetragonal structure to an orthorhombic as y ? 2.0, with lattice parameters a = 0.7802 nm and b = 0.5122 nm at y = 0, and a = 0.7632 nm, b = 0.7083 nm and c = 0.4869 nm on y ? 2.0 respectively. It reveals a NM ?7M structural change with c/a varied from 0.656 to 0.638. The crystallite size is increased from 13 to 19 nm and the lattice strain is decreased from 2.50 to 2.10 % with the Cr addition. The substitution of manganese (0.130 nm atomic radius) by chromium (of smaller atomic radius 0.125 nm) results in consistently lower lattice volume, 0.3118 nm3 at y = 0, to 0.2632 nm3 on y ? 2. The values of Young modulus and hardness (determined through a nano-indentation technique) are varied from 6.5801 to 51.480 GPa and 3.237 to 4.270 GPa respectively on y-value is raised over 0.5. An implication is that the chromium effectively tunes the valence electron density from 8.110 to 8.090 electrons per atom and a large change in the entropy ?SM?A = 13.8321 to 3.695 J/kg-K (?SM?A = 20.0605 to 4.428 J/kg-K in the recycle) in the martensite ? austenite transition as it is useful for the magnetic refrigeration and other cooling devices.

Resume : Aluminum-doped zinc oxide (AZO) is a transparent conductive oxide (TCO) that can be used in thin film form as a transparent electrode of electro-optical devices and is regarded as one of the best alternatives to indium tin oxide (ITO). Nevertheless, most real applications require a large conductivity of TCO on large surface areas. Moreover, the rapid growth of transparent electronics and electro-optical devices on flexible supports calls for the development of methods to synthesize transparent conducting films without thermal assistance while keeping high electrical and optical performances. Magnetron sputtering has emerged as a reference method for the synthesis of AZO films. It is particularly interesting due to its scalability to industrial scale. Unfortunately, AZO films usually produced without thermal assistance using magnetron sputtering tend to exhibit a strong inhomogeneity of the electrical properties with a large sensitivity to the process parameters (composition of the gas phase, geometry of the experiment) [1,3]. It has been shown that the properties of AZO films can be improved using high power Impulse Magnetron Sputtering (HiPIMS) [2]. This method uses short pulses of high electrical power density that produce a highly ionized vapor. This presentation highlights the interest of HiPIMS to synthesize AZO films of high electronic conductivity on large surface areas. By carefully controlling the process parameters, resistivity values as low as 4.10-4  cm and showing very small variation with the sample position have been obtained. Using electronic structure, electrical, optical and structure analysis combined to a simple model for reactive HIPIMS, it is shown how the process offers improved control over the electrical resistivity compared to conventional direct current reactive sputtering. References [1] D. Horwat, A. Billard, Thin Solid Films 515 (2007) 5444 [2] F. Ruske, A. Pflug, V. Sittingera, W. Werner, B. Szyszka, D.J. Christie, Thin Solid Films 516 (2008) 4472 [3] M. Jullien, D. Horwat, F. Manzeh, R. Escobar Galindo, Ph. Bauer, J.F. Pierson, J.L. Endrino, Sol. Energ. Mat. Sol. C. 95 (2011) 2341

Resume : Very good quality transparent conducting thin films structures (?=2·10-5?·cm, T ? 90%) were prepared by sputtering, reactive sputtering and pulsed laser deposition on plastic substrates. The morphological, optical and electrical properties of ZnO:Al, ZnO/Ag/ZnO, ZnO/Au/ZnO and ZnO/Ag/Au/ZnO deposited both on glass and PET substrates were analysed and compared. The Haake figures of merit for ?=550nm are comprised between 4·10-3?-1 and 29 ·10-3?-1 in function of the nature of the metallic interlayer Ag, Au or Ag/Au. The electrical properties stability with the temperature of oxide/metal/oxide structures is remarkable in comparison with the usual behaviour of single oxide films. These films are very promising for third generation flexible organic solar cells. Concerning the replacement of ITO with ZnO, from the figure of merit point of view results are comparable, however an inconvenient could rise from the fact that the roughness of zinc oxides films deposited on PET is more important than that of ITO films. Nevertheless, the roughness of indium tin oxide and zinc oxide films deposited on glass substrates are similar. In the same time, even in the case of ITO multilayer structures ITO/Au/ITO, the main advantages of three layer structure consist in the reduction of the films thickness from about 150-800nm to about 40-50nm and in a much better stability of the electrical resistivity to the temperature variations.

Resume : Oxide-based films and nanostructures have emerged as important materials for a wide range of applications such as photovoltaics, optoelectronics, gas sensing and electronics. To develop an appropriate understanding of the properties of these oxides, it is necessary to address the material preparation methods and defect probing issues. This work reports on TiO2 and Nb-doped TiO2 thin films synthesis processes, their stoichiometry control and defect identifying, in relation with their electrical and optical properties. Thin films of TiO2:Nb with different Nb concentrations (0-10 at.%) were grown by RF sputtering on glass, silicon and polymer substrates at room temperature. The effect of post-deposition annealing conditions (temperature and atmospheres (vacuum, Ar and Ar-H2 gas)) on the film properties was investigated. Optical emission spectroscopy for plasma diagnostics was employed while the nature of the structural defects in the as-grown films and after annealing and the optical properties of the prepared films were characterized using X-ray diffraction, X-ray photoelectron and Auger electron spectroscopies and UV-visible-NIR spectrophotometry respectively. The lowest resistivity obtained for the film deposited on glass at room temperature and annealed at 350 °C was 7×10-4 Ohm.cm (sheet resistance ∼106 Ohm /sq.) while that measured on flexible substrate was 1.3×10-3 Ω.cm (sheet resistance ∼162 Ohm /sq.). The lowest resistivity obtained in our work is only 3-fold higher than for epitaxially grown TiO2:Nb films on single crystalline LaAlO3 and SrTiO3 substrates at 600 °C (2-3×10-4 Ω.cm). The most conductive Nb:TiO2 films had an average visible transmittance > 78% (for a 85±5 nm thickness) and an optical band gap of 3.45 eV.

Resume : Doped ZnO is potentially a cheap replacement for ITO for use in the many applications for transparent conducting oxides, and silicon doped ZnO (SiZO) in particular has had plenty of recent attention. In this study we investigated how vacuum annealing influences the properties and microstructure of SiZO films prepared by RF sputtering onto MgO substrates using advanced microscopy techniques such as high resolution transmission electron microscopy (HRTEM) and transmission Kikuchi diffraction (TKD). Vacuum annealing greatly improved both the carrier concentrations and electron mobility of the films, and the annealed films also had higher Zn/O ratios and better out-of-plane crystal alignment. However, arrays of nano-pores were found by Fresnel imaging on the grain boundaries of the annealed films, and appear to form from the top surface of the films. For the first time, we have also clearly demonstrated that dopant segregation occurs in these annealed SiZO films. The combination of nano-pores and Si segregation are probably the two major factors that limit the achieved electrical properties, and this presentation will describe progress with modifying the processing parameters to limit these damaging features.

Resume : ZnO and GaN are wide band gap semiconductor compounds with unique properties favourable for the development of short-wavelength light emitting devices and high-power electronics. From the point of view of applications, over the last decades gallium nitride proved to be more successful. In particular, GaN played a major role in the development of modern solid-state lighting industry, success that resulted in the Nobel Prize for Physics being awarded to Shuji Nakamura, Isamu Akasaki and Hiroshi Amano, in 2014. Note that recently an electrically pumped inversionless polariton lasing at room temperature from a bulk GaN-based microcavity diode has been demonstrated [1,2]. Actually GaN is considered the second most important semiconductor material after Si, especially taking into account its utility for the development of high-frequency, high-power electronics. On the other hand, growing attention is paid nowadays to zinc oxide which exhibits direct band gap (Eg = 3.37 eV) close to that of GaN. The growing interest to ZnO is caused not only by the abundance of Zn element in Earth?s crust, but also by the fascinating properties of crystalline material. For example, the binding energy of excitons in ZnO (60 meV) is considerably higher than in GaN (25 meV) which discloses the perspectives of zinc oxide for the development of cost-effective UV light-emitting devices. In this paper, we carry out a comparative analysis of the technologies for the growth of ZnO and GaN, properties and applications in different fields, including optoelectronics, photonics and biomedicine. Besides, we review the recent development of various hybrid structures [3,4] for multifunctional applications. [1] P. Battacharya et al., Phys. Rev. Lett. 112, 236802 (2014); [2] M. Z. Baten et al., Sci. Rep. 5, 11915 (2015); [3] A. Schuchardt et al., Sci. Rep. 5, 8839 (2015); O. Lupan et al., Sensors & Actuators B ? Chemical 221, 544 (2015).

Resume : One of most intriguing challenges of modern nanotechnologies is the development of optical and/or electrical devices free from raw materials. To this purpose, Zinc Oxide (ZnO) is a material of choice: its optical characteristics, a direct bandgap (Eg 3.4eV) and a large exciton-binding energy (60 meV), are indeed favorable for a wide variety of practical applications such as light emission, photocatalysis, photovoltaics. Much effort is, therefore, paid to optimize synthesis processes successful to produce high purity ZnO nanoparticles with controlled physical/chemical properties. In this work, we used the pulsed Nd:YAG (1064 nm) laser ablation in water, a green and versatile method, by which the ZnO results from the oxidation of Zn nanoparticles; photoluminescence properties were investigated by time-resolved spectra acquired under a tunable laser excitation. The emission consists of two bands that are excited by band-to-band transition above Eg: the first, peaked at 3.3 eV and decaying in a sub-ns timescale, is due to the excitonic recombination; the second, centered at 2.3 eV and decaying in ms, is associated with oxygen vacancies and strongly depends on the oxidation process during the ablation. These results are promising in view to the realization of bight ZnO based nanosystems thus increasing their application in lighting technologies.

Resume : Green Light Emitting Diodes (LEDs) are typically made of AlGaInP or InGaN. Both of these heterostructures include Indium, that is a rare, precious and expensive material.[1] Here, we demonstrate that hybrid organic/inorganic bromide Perovskite LEDs (PLEDs) are a promising alternative to the currently used green LEDs, resulting in durable and stable performances with the added value of drastic reduction of costs with respect to the conventional LEDs; in facts, PLEDs are solution processable and do not require high temperature and high vacuum procedures. PLEDs were fabricated using, for the first time, a mesoscopic structure, usually adopted in Perovskite solar cells. This turned out to be a winning choice, since the devices, tested in ambient conditions and without encapsulation, showed a lifetime of over 50 minutes, overwhelming the previous record of 2 minutes obtained with PLEDs based on a planar heterojunction structure.[2] Moreover, our PLEDs showed a remarkably narrow full width half maximum(FWHM) of 20.8nm, registered in full operative conditions, comparable and even lower respect the one typically shown by classical green LEDs.[3] Finally, a dynamic analysis has shown a 670?s rise time and 750?s fall time, demonstrating the possibility to adopt PLEDs for display applications. 1 Schwarz-Schampera, U. et al.,Indium: Geology, mineralogy, and economics. Springer 2013 2 Jaramillo-Quintero O. A. et al.,J. Phys. Chem. Lett. 6, 1883 (2015) 3 Jiang, Y. et al.,Sci. Rep. 5,10883 (2015)

Resume : The recent success of metal halide perovskites as light-harvesting materials stems from a peculiar blend of optoelectronic properties, particularly remarkable carrier mobilities, diffusion lengths comparable to those of inorganic semiconductors and band gap tuneability. So far, only limited research effort has been devoted to leveraging such properties for light emission, and many related processes remain unclear. Here, we investigate the dynamics of light emission from metal halide perovskites by transient photoluminescence spectroscopy. On the grounds of our findings, we identify the challenges ahead on the way to engineering perovskite-based lasers. Upon impulsive excitation (150 fs), we observe the onset of amplified spontaneous emission (ASE) at injected carrier densities of 10^18 per cc. We observe ASE with 4-ns pulses but not upon 300-ns-long excitation, the latter being a closer approximation to the continuous-wave operation (CW) of laser devices. Through time-resolved optical thermometry, we show an increase in plasma temperature over the duration of excitation. We identify a runaway heating mechanism as limiting factor on the duration of light amplification. We link its source to the morphology of the sample, carrier lifetime at ASE threshold, Auger recombination coefficient and thermal resistance of both the sample and the substrate. We draw an instructive parallel with similar warming issues in early nitride-based lasers and we present our strategy towards CW lasing.

Resume : This study is focused on developing a transparent electrode (TE) as the metamaterial with tunable work functions, which aim to improve the compatibility problem between the interface of organic light-emitting diode (OLED) devices and the transparent electrodes in order to reach the highest efficiency of integrated devices, eventually. The ?m-scaled square metal grid TE was developed to replace the commercial ITO anode. Two kinds of physical features including the width of the metal line (A) and the dimension of the square opening (B) were investigated on ?m-scaled metal grid TE. We found that the transmittance and sheet resistance of the metal grid can be tuned by altering the A/B ratio. The optical transmittance of 84 %, sheet resistance of 8.5 ohm/square, and work function of 4.9 eV of our designed metal grid with a metal coverage percentage (MCP) of 9.9% can be achieved. For application of our metal grid in a green OLED device on glass, the external quantum efficiency (EQE), power efficacy and turn-on voltage can be reached to 21.3 % (at 100 cd m-2), 80.8 lm W-1 (at 100 cd m-2) and 2.5 V (at 0.1 cd m-2), respectively. Furthermore, we will demonstrate the results of the bending test of the flexible metal grid-based TE on PET substrate and the performance of the flexible green OLED device.

Resume : Scintillator materials are playing a major role in many applications where ionizing radiation detection is needed. Several excellent crystalline scintillators, in parallel with novel nano-scintillators and nano-composite systems, are being engineered. The intense research activity in this field is triggered by the needs of modern medical imaging and radiotherapy techniques, as well as by high energy physics, homeland security, and environmental applications. Most of these applications require high density scintillators with an intense and fast optical response in the nanosecond time scale. Such requirements are often pursued by employing rare-earth ions (RE) both as constituents of the host matrix and as luminescent activators. Single crystals and optical ceramics based on lutetium, yttrium, gadolinium mixed oxides doped with cerium or praseodymium are deeply investigated and in many cases they are already present in the market. These systems all display intense and fast scintillation responses thanks to the allowed 5d-4f transition of Ce or Pr featuring a decay time of few tens of ns. The substitution of RE in scintillators can be planned by taking in careful consideration application requirements. Some examples of on-going research are proposed. In such cases high density is pursued by involving RE-free hosts like hafnates and tungstates; fast and efficient scintillation responses due to intrinsic, defect related, or ns2 ions related optical transitions are considered.

Resume : Lithium fluoride is a phosphor, which is highly sensitive for ionizing radiation, especially when it is doped with a proper activator. This material can host an electronic defect known as color center, which is characterized as anionic vacancy in the crystal structure. The color centers are interesting because of their potential application. We report on excitation of the photoluminescence of rare earth doped lithium fluoride by means of the surface plasmon resonance of Al layer. The advantage of this method is high efficiency of the excitation, which is applicable to ultra-thin films. The p-polarized UV diode laser light is coupled to surface plasmon resonance using a fused silica prism in a Kretschman configuration. The angular dependence of reflected intensity is measured using a theta?2theta goniometer. The surface plasmon at resonance condition induces the luminescence in the adjacent doped fluoride layer. The luminescence is collected using a fiber optics and detected by a spectrophotometer. For the experiment, we used pure LiF films and LiF doped by Eu or Pr. The fluoride layer was deposited on Al-coated fused silica substrate by electron beam evaporation. For the experiment, we prepared several samples with thickness ranging from 20 nm to 70 nm. We studied effect of photoluminescence enhancement in doped fluoride structure by the surface plasmon resonance effect. The results shows that the induced color center photoluminescence is significantly enhanced by rare earth doping. Strong quenching effect was observed in the thinnest fluoride layers at the vicinity of the Al surface. The influence of the x-ray irradiation on the photoluminescence was studied. Significant reduction of F2 aggregated color center is observed upon the x-ray irradiation. Optical constants and thickness of the prepared fluoride film were evaluated by spectroscopic ellipsometry in the ultraviolet, visible, near infrared and infrared spectral range. The results were analytically compared with the theoretical simulation of angular dependence of p-polarized reflectivity and electric field intensity induced in the fluoride films.

Resume : Fluorides exhibit unique optical features, such as low phonon energy and high transparency in UV region. Fluoride doped by rare-earth (RE) makes them excellent for optoelectronics and photonics applications. Nano-structured materials, where the metallic nano-particles (NPs) are distributed in a dielectric matrix, represent new type of material with unique optical properties such as local surface plasmon resonance LSPR. Most of the plasmonic research has so far focused on “classical” materials Ag and Au. However, other less used metals could bring significantly new functionalities. For example Al NPs yield an LSPR within the deep UV optical range and by tuning the size of NPs the resonance could be shifted up visible spectral range. Despite potential and low cost of Al, the exploitation of its plasmonics is very recent and still facing both scientific and technical challenges probably due to degradation caused by rapid oxidation. This problem could be solved by using fluorides matrices, which will embed the Al NPs. In our work we demonstrated successfully fabrication of “classical” Ag and Al NPs embedded by CaF2 and Pr3+:CaF2 films fabricated by Pulsed Laser Deposition techniques (NPs) with auxiliary Electron Beam Evaporation (fluoride) at UHV conditions. The prepared layers were analysed by spectral ellipsometer in the spectral range from 145 nm to 1000 nm. The analysis of the measured date revealed an absorption band at about 450 nm and 200 nm, which corresponds to LSPR of incorporated Ag and Al NPs, respectively. Results were compared and discussed with the results of analysis structural properties performed by SEM, TEM, AFM and XRD. The effect of NPs on the fluorescence spectra of Pr3+ ion were studied as a function of structural properties.

Resume : Solid state reaction (SSR) method has been usually used as a basic synthesis technique to obtain the ceramic materials, including phosphor materials, multilayer ceramic capacitors (MLCC), positive temperature coefficient of resistance (PTCR) thermistor and electro-optic devices and dynamic random-access ferroelectric memories (DRAMs), because it’s very simply and easy. However, ceramic materials were synthesized at very high temperatures in solid state reaction method. Because ionic diffusion in ionic crystal is very slow at room temperature, therefore elevated temperature is essential for solid state reaction method. The high temperature synthesis leads to increase in the processing cost and irregular particle morphology. In contrast, we recently proposed the low temperature synthesis thechnique that is water assisted solid state reaction (WASSR) method, to synthesize the single phase ceramic materials low temperature, and we successfully synthesized a number of ceramic materials including phosphors. In WASSR, water addition is the key point to initiate and propagate the reaction between the raw materials and water act as reaction accelerator. The addition of water forms an unstable intermediate phase at the contact points between raw materials particles. The unstable phase plays a key role in reaction promotes the reaction between raw materials. Furthermore, the water present on the surfaces of the raw materials powder effectively suppresses the loss of reaction heat produced at the contact points and the stored reaction heat contribute to promote the reaction. In this study, we present the practicability of our original novel solid state reaction method on an industrial application in the ceramic oxide materials synthesis processing.

Resume : NiOx (oxygen poor) /NiOy (oxygen rich) bilayer homojunctions is presented as an alternative approach to obtain a reliable and uniform multilevel cell (MLC) characteristics in NiO based resistive switching (RS) cells. By fabricating bilayer structure with varying the oxygen partial pressure during deposition process, improved resistance and switching voltage distribution including high ON/OFF ratio and good endurance characteristics was achieved as compare to single layer cell (NiOx). Resistance controllability between the different non-volatile and stable resistance levels of Cu/NiOy/NiOx/Pt memory cell were observed by varying compliance current which was attributed to compliance current dependent variation in size of conducting filaments. Temperature dependent variation of resistances of high and low resistance states of the bilayer and single layer cells was investigated to elucidate current conduction and resistive switching mechanisms. Based on the gained insights through experimental observations, a comparison between the possible sketches for RS phenomena of bilayer and single layer memory cells are also discussed. The observed reproducible and nonvolatile multilevel resistive switching, good memory window, good/acceptable endurance and long retention properties were favourable for the purpose of practical RRAM applications using the NiOy/NiOx bilayer memory cell.

Resume : Modern society hinges upon information as much as it does on electric power consumption, with an ever increasing variety of electronic devices used both in industry and at home, in power systems, portable devices, batteries, etc. Overall, energy consumption has increased globally by 600% in the last 5 decades, basing their main source on fossil fuels (oil, gas, coal) with over 87% contribution and with the pollution problems that this entails. For this reason the scientific community has joined efforts to develop new renewable and sustainable energy based on engineering materials such as hydrogen storage, batteries, thermoelectrics, etc. Here is where magnetic materials play an important role in improving the efficiency and performance of devices for generation and conversion of electrical power and transportation. Permanent magnets are essential components in motors of electric and hybrid cars, wind generators, turbines, etc. The current high-energy permanent magnets commercially available use considerably large amounts of critical raw materials, such as Dy and Nd, to obtain high values of coercivity and increase their thermal stability. Considering the above we have focused on the development of high coercivity rare-earth-lean and Dy-free Nd-Fe-B permanent magnets by grain boundary engineering. In this work, we present recent results about the influence on microstructure of the Nb and Cu addition and on the infiltration process of the Nd content. Our experiments were carried out on melt-spun ribbons using the low melting point Pr3(Co-Cu) eutectic alloy as infiltration material. The coercivity was enhanced in all samples after infiltration, obtaining the best enhancement in samples with a high content of α-Fe phase, reaching values of Hc ≈ 25 kOe. In the low α-Fe stoichiometric composition the highest coercivity obtained was Hc ≈ 11 kOe. These results give us insight on the influence of the α-Fe phase on the infiltration process.

Resume : A progress in modern technologies requires new materials with specific properties for different kind of applications. In the field of magnetism very promising are Fe-Nb-B type of nanocrystalline alloys which exhibit unique and mostly superior magnetic properties. In this field high-coercive magnets have a special meaning in application for which increased resistance to high magnetic fields is needed. From practical point of view, interesting are bulk alloys with dimensions in order of several mm. Recently, we have reported properties of (Fe< sub>80< /sub>Nb< sub>y< /sub>B< sub>14< /sub>)< sub>1-x< /sub>Tb< sub>x< /sub> bulk nanocrystalline alloys, in the form of 1.5mm rods, that are characterized by magnetic coercivity exceeding 7 T at room temperature [1]. In this work we present structure and magnetic properties of the (Fe< sub>80< /sub>Nb< sub>6< /sub>B< sub>14< /sub>)< sub>1-x< /sub>Dy< sub>x< /sub> (x=0.08-0.16) bulk nanocrystalline alloys prepared by the suction casting technique with, additionally, different cooling rate controlled by the sample diameter (0.5?1.5mm). The investigation were carried out using SQUID magnetometer as well as MFM, XRD and SEM techniques. It was shown that the observed magnetic hardening effect depends on the applied cooling rate and is related to a formation of dendritic Dy< sub>2< /sub>Fe< sub>14< /sub>B grain microstructure. [1] A.Chrobak, G.Zió?kowski, N.Randrianantoandro, J.Klimontko, D.Chrobak, K.Prusik, J.Rak, Acta Mater., vol.98, pp.318?326, 2015

Resume : Abundance and relatively low cost of Ce provide a great incentive for its use in rare-earth permanent magnets. It has been recently reported [1] that the tetragonal Ce(Fe,Co,Ti)12 compounds may exhibit application-worthy intrinsic magnetic properties. In this work, an attempt has been made to convert these intrinsic properties into the functional properties of a permanent magnet. Ce1-xSmxFe9Co2Ti alloys based on the ThMn12-type crystal structure have been synthesized via melt-spinning of prefabricated alloys and via mechanochemical processing of CeO2 - Sm2O3 - Fe2O3 - TiO2 - Co - Ca - CaO powder mixtures. Coercive fields up to 0.8 kOe and 2.1 kOe were obtained in annealed melt-spun alloys with x = 0 and x = 0.5, respectively. Submicron, partially anisotropic particles collected after the mechanochemical synthesis for x = 0.5 and x = 1 exhibited coercivity (energy product) of 1.8 kOe (5.4 MGOe) and 5.8 kOe (9.8 MGOe), respectively. The low magnetic anisotropy field of CeFe9Co2Ti alloy makes at least a partial Sm-substitution for Ce necessary for developing a reasonably high coercivity. [1] D. Goll, R. Loeffler, R. Stein, U. Pflanz, S. Goeb, R. Karimi, G. Schneider, Phys. Status Solidi RRL 8, 862 (2014)

Resume : The magnetocaloric effect (MCE) is a topic of increasing scientific interest due to the enhanced energy efficiency of magnetic refrigerators when compared to those based on the compression/expansion of gasses. The MCE consists in the reversible changes in temperature (∆Tad) or in entropy (∆S) that occur in magnetic materials subjected, respectively to adiabatic or isothermal magnetic field change. Although the characterization of ∆S and ∆Tad can be directly or indirectly obtained [1,2], and the agreement between both measurements well accepted [3], a general expression for the indirect determination of ∆Tad from ∆S , valid for materials undergoing first-(FOPT) or second-order phase transitions (SOPT), and the comparison to its direct determination is still remains to be done. We provide magnetization, latent heat and specific heat data which allow us to indirectly obtain ∆Tad in Ni-Mn-Sn and Ni-Mn-In Heusler alloys at different magnetic field values up to μ0H = 3 T, in the temperature range where FOPT and SOPT take place. From the observed results, large discrepancies in the indirect measurement of ∆Tad arise depending on whether the latent heat is taken or not into account. The observed key role of the latent heat in materials undergoing first-order phase transitions is discussed References: [1] J.-H. Chen, et al. Acta Materialia 105 (2016) 176e181. [2] A. Planes, et al J. Phys.: Condens. Matter 21 (2009) 233201. [3] E. Palacios, et al , J. Phys.: Conf. Ser. 200 (2010) 092011

Resume : About two thirds of known world tungsten deposits are in the form of scheelite (CaWO4) mineral. China accounts for more than 80 % of world tungsten mine production and Chinese domestic demand has increased rapidly in the past years. As a consequence, European Union has classified tungsten as the critical raw material (CRM) with the largest economic importance. More than 60 % of the world consumption of tungsten is in the form of tungsten carbide and, therefore, cemented carbides (hardmetals) are the main driving force behind tungsten demand. In addition, hardmetals with ultrafine grain size (≤ 200 nm) are attracting a growing interest in the world tungsten carbide market. The creation of a supply source of WC for hardmetal manufacturing small and medium enterprises (SMEs) is becoming a serious issue, which could be addressed by finding enriched mineral in the international market in such quantities as to assure their production needs. Moreover, processes which could allow producing WC powders by reducing the use of chemicals and the amount of industrial waste, as well as by decreasing the number of high-temperature processing steps and their temperatures, are particularly appealing from an environmental point of view. For these reasons, there is a renewed interest in the carbothermic reduction of scheelite. The comprehensive study performed at the University of Rome Tor Vergata has demonstrated that quantitative transformation of scheelite into nanostructured WC is possible by using mixtures of CaWO4 and carbon subjected to ball milling and annealed at 1100-1200 °C. In addition, for the first time we show that the use of selected additives allows both reducing the reaction temperature and/or the milling intensity, and tailoring the particle size of WC.

Resume : The SUPERMAT virtual centre developed by 7 Research Centres from France, Spain, Italy, Sweden, UK and Romania with recognised expertise in advanced materials and processing technologies will foster the progress in these fields. The principal activities of this virtual centre can be listed as: (1) improving existing modelling and simulation tools for ab-initio design of novel multifunctional materials for extreme environments; (2) select case studied materials with high application potential; (3) propose best available technologies for selected materials; (4) elaborate characterisation methods to be certified for future standardisation, (5) propose the European curricula for PhD students in the field of materials for extreme conditions and (6) proposing joint collaborative research projects for H2020 calls as well as contributing to the strategy of EIT Nanofutures and Critical Raw Materials. Applications presented include: molecular dynamics modelling of smart doped materials to replace CRMs, integration of soft chemical procedures for synhtesis and deposition of doped ZnO and TiO2 for transparent conductive layers and spintronics, smart processes for high temperature sensors, batteries for extreme conditions, special processes for field assisted sintering nanocomposite materials with reduced rare earth elements. Acknowledgment: This project has received funding from the European Union?s Horizon 2020 research and innovation programme under grant agreement No 692216.?

Resume : Triphenylamine (TPA) derivatives have attracted considerable attention because of their electroactive properties and potential applications as hole transporters, light emitters and photoconductors. TPA derivatives are electroactive conducting materials with an easily oxidizable electroactive center and excellent hole transport capacity. Therefore, a study of the electrochemical process of TPA-based materials is a very important category. Aromatic polyimides (PIs) have excellent thermal stability, dimensional stability, and mechanical properties. Commonly, PIs are prepared using dianhydride and diamine monomers in a polar aprotic solvent to synthesize poly(amic acid), which is a precursor of PI. The PAA precursor obtained is then converted to PI by thermal imidization or chemical imidization. In this study, PAAs were prepared using different TPA derivatives with various TPA moiety, with a dianhydride monomer in NMP. The PIs were then synthesized by the chemical imidization of PAAs solutions. The chemical structures and thermal properties of the synthesized PIs were determined using spectroscopic methods including 1H NMR and Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. In addition, the electrical properties and spectroelectrochemical behavior was investigated in terms of the chemical structure of the TPA derivatives.

Resume : Low dark current (off-current) and high photo current are both essential for a solution processed organic photodetector (OPD) to achieve high photo-responsivity. Currently, most OPDs utilize a bulk heterojunction (BHJ) photo-active layer that is prepared by the one-step deposition of a polymer:fullerene blend solution. However, the BHJ structure is the main cause of the high dark current in solution processed OPDs. It is revealed that the detectivity and spectral responsivity of the OPD can be improved by utilizing a photo-active layer consisting of an interdiffused polymer/fullerene bilayer (ID-BL). This ID-BL is prepared by the sequential solution deposition (SqD) of poly(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) solutions. The ID-BL OPD is found to prevent undesirable electron injection from the holecollecting electrode to the ID-BL photo-active layer resulting in a reduced dark current in the ID-BL OPD. Based on dark current and external quantum efficiency (EQE) analysis, the detectivity of the ID-BL OPD is determined to be 7.60 × 1011 Jones at 620 nm. This value is 3.4 times higher than that of BHJ OPDs. Furthermore, compared to BHJ OPDs, the ID-BL OPD exhibited a more consistent spectral response in the range of 400 ? 660 nm.

Resume : Bulk heterojunction (BHJ) solar cells are designed to reduce the recombination caused by the short diffusion length of exitons, commonly, the polymer and fullerene are blended in one solution and active layer was accomplished within one step. Recently, the sequential deposition for organic photovoltaic (SqD-OPV) devices give an alternative way to study the organic solar cells, which is comparable to the conventional BHJ OPVs. In the SqD-OPVs, the inter-diffused heterojunction is completed by the swelling of PCBM solution into the pre-located polymer bottom layer. In this article, we have developed SqD-OPVs with high performance by incorporating a processing additive of 1-chloronaphthalene (1-CN) without thermal annealing treatment. We found that the SqD OPVs give more ordered face-on polymer molecular packing without the disturbance of PCBM compared with OPVs processed with blending method. In absence of PCBM, the polymer processed with 1vol% 1-CN generated a dense and well-connected fibrous polymer network, as confirmed by AFM. The nano fibrils with width around 30-50nm are is optimal for the device performance. The space charge limited current results revealed that the nano fibrils with a face on orientation were effective in enhancing the hole carrier mobility and reducing the charge recombination, which lead to a power conversion efficiency of 4.5% under AM 1.5G illumination.

Resume : A new A-D-A (Acceptor- Donor-Acceptor) type small molecules based on thiazole-borane complex (?-spacer) and 2,5-bis(alkyl)-3,6-di(thiophen-2-yl) pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) derivatives were designed and synthesized employing Pd-catalyzed Stille and Suzuki cross-coupling reaction as a key step. The synthesized boron based complex exhibited high electron affinity, which indicates deep HOMO energy levels and good visible absorption led to their use as donors in BHJ (bulk heterojunction) solar cells. Inverted devices were fabricated, reaching efficiencies as high as 3.07%.(The photovoltaic device based on SDB and PC71BM exhibits a potential power conversion efficiency of 3.07%, a moderate open-circuit voltage of 0.88eV and a relatively high short-circuit current density of 7.00 mAm-2). To probe structure-property relationship and search for design principle, we have synthesized thiazole-boron based electron donating small molecules. In this study, we report a new synthetic approach, molecular structure, charge carrier mobility and morphology of blended film and their correlation with the photovoltaic J-V characteristics in details.

Resume : Dried gel with uniform composition has many different final shapes like film, fiber, nano-particles and composite, as sol-gel process occurs in liquid state. Dried silica gel absorbs infrared ray well, possesses superb insulating qualities and does not become yellow. Smart window is a controllable window of which transparent and opaque states can be switched by an electric field. It is expected to be a solution for buildings and transportation vehicles to reduce heating and cooling energy. It can be used not only for saving energy solution, but also for displays and tunable optical modulators. In this study, a sol-gel method was adapted to synthesize gel-glass dispersed liquid crystals (GDLC) as a smart window. [1] Difference of refractive indexes between xerogel matrix and liquid crystal causes the high light-scattering to be opaque state. In a new method, so-gel solution is made of two alkoxides to stabilize sol state, and blue dye was added to absorb visible light in opaque state. Using a filter paper, gel floaters produced by direct injection of the nitric acid was filtered. Nematic liquid crystal was added to the solution of sol, which was coated on an indium-tin-oxide (ITO) coated glass. After drying, liquid crystal was coated additionally on the sol-gel film to fill empty holes, which enhanced the optical properties. We changed concentration of nitric acid and nematic liquid crystals and drying environment and various optical properties were measured such as transmittance and response time.

Resume : Exchange-coupled hard/soft magnetic phases are promising candidates for permanent magnets with enhanced energy densities. Rare-earth/transition-metal alloys like NdCo5 arise as suitable hard phases in those magnets. Besides, NdCo5 exhibits a temperature driven spin reorientation transition (SRT), in which the magnetization easy direction rotates from the hexagonal c-axis to the basal plane. In this work, a NdCo5/Fe bilayer was prepared by pulsed laser deposition on a MgO(110) substrate and investigated by vibrating sample magnetometry and ferromagnetic resonance (FMR). The SRT typical of NdCo5 was observed also in the bilayer. Regarding the magnetization dynamics, the interlayer magnetic coupling is weak, thus allowing the identification of the FMR signals in the sample as originating mainly from individual responses of the Fe and NdCo5 layers. In the NdCo5 layer, the effective coupling field is negligible compared to the internal anisotropy, and the magnetization precession similar to the one found in a single NdCo5 layer. In the magnetically soft Fe, however, the precession occurs in the exchange field stemming from the dynamically fixed NdCo5 layer, giving rise to a partial transfer of magnetic anisotropy from the latter and enabling us to follow the SRT of NdCo5 by measuring the Fe FMR peak field position. Controlling the anisotropy direction in the soft layer by using the SRT in the hard layer can find applications in future magnetic devices. The work has been supported by FCT of Portugal through the projects and grants BI/UI96/7195/2015, UID/CTM/50025/2013, RECI/FIS-NAN/0183/2012 (FCOMP-01-0124-FEDER-027494) and through the bursary PD/BD/113944/2015, as well as by NUST ?MISiS? through grant no. K3-2015-003.

Resume : A single-phase tris(8-hydroxyquinoline) aluminum, gallium and indium (Mq3) crystalline samples were synthesized under controlled temperature and 8-hydroxyquinoline (8-Hq) partial pressure (P8-Hq). The influence of P8-Hq on structural and luminescent characteristics of Mq3 crystalline samples was examined. It was found out that the P8-Hq increase resulted in the changes of photoluminescent spectra maximum, decay kinetic and structural characteristics. The multilayers OLED devices were produced by vacuum thermal evaporation techniques using Mq3 single-phase samples, synthesized under the different P8-Hq,.as an emission material. The characteristics of the fabricated OLED structures were examined. Within the solid state chemistry framework the observed differences in the results for the synthesized under various conditions samples can be explained by the formation of the thermodynamically equilibrium crystal structure with a certain number of defects. These defects results from a change of the number M (M = Al, Ga, In) atoms at a constant amount of 8-Hq ligands under different P8-Hq. In inorganic chemistry this phenomenon is called non-stoichiometry of the crystalline samples. For this class of metal-organic complexes non-stoichiometry phenomenon has not been described yet. The control of non-stoichiometry of Mq3 and similar metal complexes could solve the problem of the production of organic semiconductor materials with controlled properties for OLED technology improvement.

Resume : There is a general paradox in present research and application of chalcogenide solar materials. On one side, CIGS (CuIn1-xGaxSe2) thin film solar cells attracted a big attention owing to their high power conversion efficiency and good stability. On the other side, these materials represent the potential environmental problem due to Se toxicity and moreover, In and Ga are rare elements and are therefore expensive. Quaternary semiconductor nanocrystals provide promising alternatives to conventional photovoltaic materials because of their environmental acceptance (application of S instead of toxic Se), cheapness and availability (application of earth-abundant Fe, Zn and Sn instead of scarce In and Ga). For example kesterite (CZTS) and stannite (CITS) combine many advantageous characteristics for photovoltaic applications, namely that they are composed of the abundant and non-toxic elements, suitable band gap, high absorption coefficient and high radiation stability. Stannite Cu2FeSnS4 has been recently prepared by several techniques such as solution-based, hot injection and microwave irradiation. However, these techniques are complex, time-consuming, need high temperature and toxic organic solvents. In this study we demonstrate the use of precursors in the form of elements (Cu, Fe, Sn, S) to obtain CITS by solid-state one-pot mechanochemical synthesis. In this processing route, the unique nanostructures and properties are developed (1). We report the kinetics of the mechanochemical synthesis. Methods of XRD, SEM, EDS, HRTEM, Raman, UV-Vis, magnetic and specific surface area measurements were applied. CITS polymorphs were obtained with the tetragonally body-centered structure and crystallite sizes 17-19 nm. New magnetic properties were also documented. The obtained results confirm the excellent structural properties of synthesized Cu2FeSnS4 nanocrystals. 1.BalហPeter: Mechanochemistry in Nanoscience and Minerals Engineering, Springer, Berlin Heidelberg 2008

Resume : In this study, we present a comparative investigation of refractive index for single-layer TiO2 and multilayer TiO2?SiO2 Optical Coatings. Samples are grown on SiO2, glass, SiO2/Si and Al2O3 from aqueous colloidal suspensions of titania at room temperature. The refractive index dispersion has been evaluated from optical waveguiding using the prism coupling [1]. We have correlated the microstructure with the refractive index of the material. We have characterized the optical properties (index, anisotropy, loss) of the deposited layers at different wavelengths (from 454nm to 1539nm). The ordinary (no) and extraordinary (ne) refractive indices are respectively, 2.2069 and 2.2135 at 632.8 nm, and waveguide loss experiments have been demonstrated. In addition, we have qualified the film properties between the substrate to layer interface, directly from the measured optical data.

Resume : In 2014, the European Union identified 20 raw materials critical for economic importance and high supply risk. Indium, largely used for the innovative technologies production, is included in this list. Currently, the largest producer of this metal is China, where it is mined as a by-product of zinc production. The worldwide indium consumption is mainly due to the production of an indium-tin-oxide (ITO) film, necessary for the liquid crystal display (LCD) operation. The fast evolution of LCD technologies caused the growth of indium demand and the increase of waste electrical and electronic equipment (WEEE). Considering the metal concentration in the end-of-life LCD (about 150 ppm), comparable with that in minerals (1-100ppm), the aim of this study is to make the scrap a secondary indium resource. With this purpose, a recovery process was developed carrying out an acidic leaching, followed by a zinc cementation. The first step allowed a complete indium extraction using 2M sulfuric acid at 80°C for 10 min. In order to increase the process sustainability, we used a cross-current configuration that allowed an increase of metal concentration and a decrease of reagents consumption. The consecutive cementation step allowed an indium recovery higher than 90%, using 5 g/L of zinc powder at pH 3 and 55°C for 10 min. Considering the European target to reduce the primary raw material demand, the high efficiency combined with a simple configuration, makes the process extremely promising.

Resume : GaN and related alloys such as AlGaN have attracted a great deal of attention due to their potential for wide-band gap optoelectronic applications. In the present work, AlGaN/GaN epitaxial films have been grown on SiN surface-treated sapphire substrate by metal organic vapor phase epitaxy (MOVPE) under atmospheric-pressure. The Al content in the studied samples is varied between 3% and 15% though the change of the flow rate of trimethylaluminum (TMA) from 12 µmol/min to 32 µmol/min. The optical properties and carrier dynamics of the AlGaN/GaN epitaxial films are investigated by means of time-resolved Photoluminescence (TR-PL). Low temperature measurements show that the PL emission peak broadens and shifts to higher energies when the TMA flow rate is increased. Simultaneously, the PL decay time increases with increasing Al contents in the studied films. These observations can be attributed to the carrier localization effects in band tail states due to compositional fluctuations in the AlGaN layers. Remarkably, the PL spectrum of the epitaxial film with a relatively high Al content of 15 % reveals several peaks. In order to find out about the origin of these features, temperature-dependent PL measurements are performed in the range from 25 K to 300 K. Keywords: AlGaN, Metal organic vapor phase epitaxy, Photoluminescence, time-resolved photoluminescence.

Resume : The dependence of carrier effective mass of GaNxAs1-x, InNxP1-x, InNxAs1-x, and InNxSb1-x alloys on nitrogen content is theoretically investigated using a 10-band k.p model. The electron effective mass m*e at the bottom of conduction band in GaNxAs1-x and InNxP1-x exhibits a gradual increase as a function of N concentration in the range 0-1% and a decrease for x between 1 and 5 %. However, the behavior of m*e in InNxAs1-x and InNxSb1-x shows a strongly decrease in all studied x-range. Our theoretical results are compared with the available data reported in the literature. On the other hand, contrary to heavy-hole effective mass m*hh, the light-hole effective mass m*lh in all studied alloys is significantly affected by nitrogen states which modify the non-parabolicity of the LH band. The modification of the carrier effective mass affects the transport and mobility properties of the III-N-V alloys. Keywords: Diluted III-N-V alloys; 10-band k.p model; carrier effective mass. * Corresponding author: ahmed.rebey@fsm.rnu.tn

Resume : InAsBi layers were elaborated on semi-insulating (100) GaAs substrates misoriented10° by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE) reactor. Spectral reflectance in the range of 200 to 1100 nm was employed to in situ monitor epitaxy. For determining the optical constants of InAsBi films, an optical model incorporating time-dependent surface roughness and time-dependent growth rate was used to simulate the in situ reflectance. A theoretical motivation for the introduction of these two parameters instead of a standard single rms roughness and growth rate is provided Several InAsBi samples grown at different growth temperatures were used to illustrate ways in which the parameters introduced can be evaluated. Reflectivity analysis was ex situ correlated by atomic force microscopy. Keywords: InAsBi, In situ spectral reflectance, optical model, refractive index Corresponding authors: ahmed.rebey@fsm.rnu.tn, hedi.fitouri@fsm.rnu.tn

Resume : Large amounts of liquid crystal displays (LCDs) are entering their end-of-life stage.So, for the WEEE European directives, efforts must be undertaken to reuse or securely dispose LCD waste. Plenty of ideas on how to recycle were suggested, but no practical process was reported yet, although it is possible to recover many reusable materials, such as glass, plastic and precious metals, in particular Indium. Indium is one of the element included by the European Commission in the list of 20 raw materials critical for economic importance and high supply risk. The present work aims to valorize LCD scraps after Indium recovery in a simple manner, with low cost both economically and environmentally speaking. This application was explored by many researchers, although most focused only on the use of glass powder waste LCD to design concrete. The present work deals the possible use of LCD scraps as it is after cross-current leaching of Indium with H2SO4. The experimental work consists of scraps characterization, washing procedure optimization to remove any residual acid, mortar production and performance testing, Life Cycle Analysis. The results show that LCD scraps exhibit little or no pozzolanic activity.This delay on reactivity can be ascribed to organic residues that prevent the pozzolanic reaction and/or to a lower fineness than that typical of binders or fillers. For this reason the actual investigation focuses to exploit the waste as partial replacement of traditional aggregates

Resume : The present work is dedicated to the complex study of soft magnetic nanostructured Fe-TiB(2) films with high saturation inductance . The Fe-xTi-yB (x=0-14, y=0-29) films were deposited onto the glass and metal substrates by direct current magnetron sputtering of Fe target covered with different amounts of ceramic TiB(2) segments (1.9 - 37cm^2). The sputtering was performed in Ar atmosphere. The films were annealed in a vacuum (10^-4 Pa) at temperatures 200÷500^0C for modification of their structure. The structure and magnetic properties of the as-deposited and annealed films were studied by means of XRD, TEM, GDOES, SEM, EDS and VSM. Mechanical properties were measured by nanoindentation at loads of 1-5 mN. The single-phase nanocrystalline structure consisting of bcc solid solution based on α-Fe is formed in the films. The formation of the solid solution is testified by the fact that the lattice parameter of the bcc phase (from 2.879 Å - 2.934 Å) is higher than that of pure α Fe (2.866 Å). The grain size of the bcc phase is in range of 7-30 nm depending on (Ti B) concentration in films. The annealing of the films leads to a decrease in the bcc phase lattice parameter and the appearance of the Fe(3)B phase. The bcc phase grain size is not changed at annealing. It was shown that annealed at 300-500^0C films are strong ferromagnetic with high saturation inductance (up to 2.1 T). Films demonstrated extremely high hardness (more higher than that for Fe).

Resume : The optical properties and specifies of free-volume nanostructure (using positron annihilation method) of Chalcogenide glasses (ChG) belonging to the series (80GeS2–20Ga2S3)100−x(CsCl)x with x = 0; 5; 10; 15 were investigated. As shown in Fig. 1, the addition of CsCl induces a white shift of the visible transmission. By adding up to 15% mol. of the alkali halide in the glassy matrix, the band-gap evolves from 2.64 eV to 2.91 eV. From a structural point of view, the addition of less than 15 % of CsCl in GeS2–Ga2S3 glasses is characterized by the formation of GaS4−xClx tetrahedral that are dispersed in the glass network. In other words, the average number of Ga–S bonds is decreased for the benefit of the average number of Ga–Cl bonds. The evolution of the free volume when CsCl is added in the base glass has been discussed following changes of positron annihilation parameters. Atomic densification caused by CsCl additives depresses positron annihilation trapping rate leading to their significant inhibition, while the geometric sizes of the free-volume positron trapping nanovoids grow. Thus, the results testify in a favor of rather unchanged nature of corresponding free-volume nanovoids responsible for positron trapping in the studied glasses, when mainly concentration of these traps is a subject to most significant changes with composition.

Resume : Transparent conductive oxides (TCOs) [1] are one of the applicable coatings that can be used in opto-electronic industry and electronic devices. These years, different methods are applied to perform such transparent conductive layers. Between the different methods, the researchers try to find low-cost and simple processed methods [2] that can be scaled-up in large amount with high conductivity and transparency properties. In this paper, we tried to fabricate aluminium doped zinc oxide (AZO) as TCO with the optimized condition of transparency and conductivity. AZO thin films are deposited using direct oxidation of these coated substrates. To provide AZO thin films with this method, different metallic coatings are sputtered on soda glass substrate. Zinc (Zn), Aluminium (Al), and Zn-Al alloy are used as metal targets in sputtering process. A thin layer of these metallic coating with different thickness was sputtered on the glass substrates in argon gas atmosphere. The electrical properties of the samples are analysed with 4-point probe where they show high conductivity in the ranges of 1 to 100 kOhm/square for the samples with thickness less than 100 nm. Structural and morphological characteristics are also analysed with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The SEM images show uniform thin films with the grain sizes about 50 nm and the XRD patterns confirms the formation of wurzite structure. The optical properties are also investigated with UV-spectroscopy and ellipsometry which indicate the high transparency of the fabricated samples. The samples could be good candidates as TCO material for photovoltaic application and light emitting device. [1] P.P. Edwards et. al. Dalton Transactions 19 (2004) 2995–3002. [2] S.H. Mousavi, T.S. Müller, P.W. de Oliveira, J. Mater. Sci. 24 (2013) 3338-3343.

Resume : Fluorescent micro and nanoparticles (NPs) find applications in a wide range of fields, from biomedicine, as probes for tagging and labeling, in particular for super-resolution fluorescence microscopy, to photonics, as active medium for nanolasing. The fluorescence properties of colloidal sealed Rhodamine 6G doped mesostructured silica nanoparticles prepared by a one-pot templated base-catalyzed sol–gel self-assembly method are reported. The hybrid organic-inorganic nanoparticles is tested against water and alcohols dye leaching showing larger resilience to leaching in water, and efficient super fluorescence 100 times larger than the fluorescence of CdSe/ZnS quantum dots. These outstanding features are achieved by exploiting the presence of the surfactant applied for the formation of the mesostructure in a twofold role, that is, both as dye splitting element and as sealing agent against leaching effect. The resilience to dye leaching in water, a basic requirement for bio-imaging applications, is further increased by long aging in water suspension, yielding the formation of a silica-silica core-shell architecture.

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