The corrosion rates of AISI 316L and AISI 321H austenitic stainless steel, immersed in a stagnant isothermal mixture of 60% NaNO 3 and 40% KNO 3 molten salt at 550°C in atmospheric air are 8.6 and 9.0 µm/yr, respectively. The corrosion mechanism was proposed by recording the weight changes of the steel coupons at different time intervals up to 3000 h, and by the characterization of multilayer oxide scales formed on the steel surface. Multilayers made of different oxides, mainly Fe 2 O 3 and Fe 3 O 4 , are the principal scale products. At 3000 h, the thickness of the scale layer formed on AISI 321H (7.5 ± 2.9 µm) is slightly higher than the one formed at the AISI 316L (6.9 ± 2.1 µm). This small difference might reflect the partial spallation of the corrosion layer on AISI 321H, which is seen for times longer than 1000 h. A minimal change of the composition of the molten nitrate salt is observed in time and is predominantly due to the appearance of soluble chromate products and nitrite compounds (0.004 wt% and 1.4 wt% at 3000 h, respectively). The observed corrosion behaviour of these alloys shows that they are good candidate for usage as containers of molten nitrate salts in the thermal energy storage (TES) system for a CSP plant.

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One of the areas of research on materials for thin-film solar cells focuses on replacing In and Ga with more earth-abundant elements. In that respect, chalcostibite (CuSbS2) is being considered as a promising environmentally friendly and cost-effective photovoltaic absorber material. In the present work, single CuSbS2 phase was synthesized directly by a short-duration (2 h) mechanochemical-synthesis step starting from mixtures of elemental powders. X-ray diffraction analysis of the synthesized CuSbS2 powders revealed a good agreement with the orthorhombic chalcostibite phase, space group Pnma, and a crystallite size of 26 nm. Particle-size characterization revealed a multimodal distribution with a median diameter ranging from of 2.93 μm to 3.10 μm. The thermal stability of the synthesized CuSbS2 powders was evaluated by thermogravimetry and differential thermal analysis. No phase change was observed by heat-treating the mechanochemically synthesized powders at 350 °C for 24 h. By UV-VIS-NIR spectroscopy the optical band gap was determined to be 1.41 eV, suggesting that the mechanochemically synthesized CuSbS2 can be considered suitable to be used as absorber materials. Overall, the results show that the mechanochemical process is a viable route for the synthesis of materials for photovoltaic applications.

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