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Wurtzite based materials have the advantages of being cheap, no-toxic and offering excellent opto-electrical, piezoelectric and pyroelectric properties. The nanocrystalline wurtzite ZnS, being a room temperature stable material unlike its bulk counterpart, is interesting because of its potential in piezoelectric and pyroelectric energy harvesting. In this work we aimed to tailor a simple synthesis method for nanocrystalline wurtzite production, which would be easy to scale up. We used the well-known reaction of zinc chloride with thiourea or sodium sulfide dissolved in ethyl glycol at a carefully controlled molar ratio in medium temperature conditions (140-150°C) to produce pure, nanocrystalline ZnS in the hexagonal (wurtzite) phase, via a series of consecutive experiments. The amount of solvent was kept the same (60 ml of ethyl glycol) by re-using what remained of the solvent from the previous reaction and topping up the quantity lost. The productivity yield increased over 6 successive reactions from 156 mg to 446 mg per batch at a constant mMZn/mMS = 1 ratio. The obtained nanopowder has been characterized using TG, BET, FTIR, TEM and SEM techniques. Our plan is to build an in-house pilot plant that should produce substantial amounts of wurtzite ZnS nano-powder in an environmentally friendly and cost effective way. Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 797951.

Pyroelectric materials can harvest energy from naturally occurring ambient temperature change, as well as from artificial temperature change, notably from industrial activity. At a time of climate emergency, pyroelectric energy harvesting is a highly promising technology that should ultimately lead to the development of autonomous and self-powered electronic devices and which has the potential to harvest enormous amount of wasted heat. One interesting but rarely studied class of pyroelectric materials are non-ferroelectric pyroelectrics; these include semiconductor materials with a wurtzite crystalline structure such as CdS, ZnO or ZnS. We studied ZnS, and explored a simple, co-precipitation synthesis for nanocrystalline wurtzite ZnS production. The structural, morphological and dielectric properties of two selected samples were investigated to examine the effects of different molar concentrations of precursor Zn and S ions (mMZn/mMS = 0.47 and 1.22) in the reactive solution. Alongside these results, we present our recently built in-house semi-pilot plant that is able to produce substantial amounts of wurtzite ZnS nanopowder in an environmentally friendly and cost effective way. The obtained ZnS nanopowder is intended both as a precursor for pyroelectric ceramics and as a filler for ferroelectric polymer-based composite thin films (PVDF co-polymers). Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 797951. This project was also partially supported by the Piano triennale di realizzazione 2019-2021 della ricerca di sistema elettrico nazionale – Progetto 1.3 Materiali di frontiera per usi energetici (C.U.P. code: I34I19005780001). ; This project was also partially supported by the Piano triennale di realizzazione 2019-2021 della ricerca di sistema elettrico nazionale – Progetto 1.3 Materiali di frontiera per usi energetici (C.U.P. code: I34I19005780001).

Pyrolectric materials are able to harvest energy both from naturally and artificially occurring temperature changes. These materials could be the right way to recover some of the enormous amount of energy wasted as heat and help to develop new devices for harvesting thermal ambient energy. In this work it was investigated the development of bulk, dense pyroelectric ceramics, ideally with a highly developed texture and small grain size, using a micron-sized powder of the ZnS wurtzite phase as precursor material. The Two-Step Sintering (TSS) process is a useful method to obtain high sintered density and to limit the grain growth associated with the final stage of the sintering process. One of the main advantages of this method is the lowering of the sintering temperature. The microstructural, morphological and electrical properties of TSS-ZnS were determined and compared to ZnS produced by the conventional sintering process, performed at 1250°C. TSS-ZnS showed comparable density and a finer microstructure than conventional ZnS (five times lower grain size). It was demonstrated that the TSS process is a pressureless, simple and cost‐effective sintering method to obtain high density materials with controlled grain growth, without using a dopant or binder. The TSS produced ZnS ceramic was tested for pyroelectric energy harvesting. It is expected that the efficiency of the ceramic in harvested energy could be further improved by decreasing the grain size down to the nanoscale. Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 797951.

Two types of photocatalysts, 1%Pt/Cd1−x Znx S/g-C3 N4 (x = 0.2–0.3) and Cd1−x Znx S/1% Pt/g-C3 N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3 N4. The characterization of photo-catalysts showed that, for 1%Pt/Cd1−x Znx S/g-C3 N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−x Znx S/1%Pt/g-C3 N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−x Znx S photocat-alysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3 N4 surface, Cd1−x Znx S/1%Pt/g-C3 N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−x Znx S and g-C3 N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8 Zn0.2 S/1% Pt/g-C3 N4. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ; Funding: This work was supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental order for Boreskov Institute of Catalysis (project AAAA-A21-121011390009-1) and was also funded by the Russian Foundation for Basic Research (project No. 20-33-70086). A.S.V. and I.A.W. thank Minobrnauki research project FEUZ-2020-0059 for financial support.

Ce travail traite d'un problème de pollution liée à la présence de métaux de base dans des passifs environnementaux issus d'un traitement métallurgique des minerais sulfureux cuivre – zinc provenant de la mine de Kipushi en République Démocratique du Congo. L'objectif principal de ce travail a été d'arriver à proposer des scénarios de gestion durable au passif environnemental de la filière présentant les risques environnementaux les plus élevés. Pour cela, on a d'abord procédé à une identification des différents problèmes environnementaux tout au long de la filière de traitement sur les quatre sites d'exploitation. Ensuite on a prélevé des échantillons puis procéder par des tests de disponibilité à la lixiviation à l'eau déminéralisée pour évaluer les fractions solubles des métaux de base présents et aussi par des tests de conformité de mise en décharge afin de classer ces rejets conformément à la directive européenne 2003-33-CE. Ainsi, les rejets Ex – UZK ont été identifiés comme les plus dangereux de la filière au regard de cette directive, car les quantités lixiviées de cuivre et de zinc dans ces rejets ont dépassé largement les limites fournies par la directive, et donc ils ne peuvent même pas être mis en décharge de classe I sans traitement métallurgique préalable pouvant permettre leur dépollution. Par contre, les autres rejets de la filière, en l'occurrence les rejets de flottation de Kipushi et les scories de fusion pour matte de cuivre, peuvent eux être acceptés en décharge de classe I, sans traitement préalable au regard des limites fournies par la même directive. Les procédés de lixiviation acide chaude et de digestion ont été proposés et retenus comme scénarios de gestion durable à appliquer à ces rejets Ex – UZK, car ils se réalisent tous deux en milieu acide sulfurique d'une part et d'autre part leur application et surtout leur faisabilité en République Démocratique du Congo reste possible ;en outre ils aboutissent à des nouveaux rejets contenant le fer sous forme d'hématite, pouvant être stocké ...

Copyright (2011) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. ; We perform Raman-scattering measurements at high hydrostatic pressures on c-face and a-face InN layers to investigate the high-pressure behavior of the zone-center optical phonons of wurtzite InN. Linear pressure coefficients and mode Grneisen parameters are obtained, and the experimental results are compared with theoretical values obtained from ab initio lattice-dynamical calculations. Good agreement is found between the experimental and calculated results. © 2011 American Institute of Physics. ; Work supported by the Spanish MICINN (Projects MAT2010-16116, MAT2008-06873-C02-02, MAT2010-21270-C04-04, and CSD2007-00045), the Catalan Government (BE-DG 2009), and the Spanish Council for Research (PIE2009-CSIC). ; Ibanez, J.; Manjón Herrera, FJ.; Segura, A.; Oliva, R.; Cusco, R.; Vilaplana Cerda, RI.; Yamaguchi, T. (2011). High-pressure Raman scattering in wurtzite indium nitride. Applied Physics Letters. 99:119081-119083. https://doi.org/10.1063/1.3609327 ; S ; 119081 ; 119083 ; 99 ; Veal, T., McConville, C., & Schaff, W. (Eds.). (2009). Indium Nitride and Related Alloys. doi:10.1201/9781420078107 ; Gallinat, C. S., Koblmüller, G., Brown, J. S., Bernardis, S., Speck, J. S., Chern, G. D., … Wraback, M. (2006). In-polar InN grown by plasma-assisted molecular beam epitaxy. Applied Physics Letters, 89(3), 032109. doi:10.1063/1.2234274 ; Li, S. X., Wu, J., Haller, E. E., Walukiewicz, W., Shan, W., Lu, H., & Schaff, W. J. (2003). Hydrostatic pressure dependence of the fundamental bandgap of InN and In-rich group III nitride alloys. Applied Physics Letters, 83(24), 4963-4965. doi:10.1063/1.1633681 ; Gorczyca, I., Plesiewicz, J., Dmowski, L., Suski, T., Christensen, N. E., Svane, A., … Speck, J. S. (2008). Electronic structure and effective masses of InN under pressure. Journal of Applied Physics, 104(1), 013704. ...