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The rock-salt ordered A2CuWO6 (A = Sr, Ba) with I4/m space group and disordered SrCu0.5M0.5O3−δ (M = Ta, Nb) with Pm3m space group perovskites were successfully obtained via a solid-state reaction route. Heat treatment of Ba2CuWO6 over 900 °C in air leads to phase decomposition to the barium tungstate and copper oxide. Thermogravimetric measurements reveal the strong stoichiometric oxygen content and specific oxygen capacity (ΔWo) exceeding 2.5% for Ba2CuWO6. At the same time, oxygen content reveals Cu3+ content in SrCu0.5Ta0.5O3−δ. Under the following reoxidation of Ba2CuWO6, step-like behavior in weight changes was observed, corresponding to possible Cu+ ion formation at 900 °C; in contrast, no similar effect was detected for M5+ cations. The yellow color of Ba2CuWO6 enables to measure the band gap 2.59 eV. SrCu0.5Ta0.5O3−δ due to high oxygen valance concentration has a low thermal conductivity 1.28 W·m−1·K−1 in the temperature range 25–400 °C. [ABSTRACT FROM AUTHOR]

Nanotubular titanium oxide is widely known as a prospective semiconductor photocatalyst for the process of water splitting. Its photoelectrochemical (PEC) efficiency can be improved by doping with 3d metal. In this work, the synthesis of nanotubular titanium oxide (NTO) was carried out by anodizing titanium substrates using two doping techniques. First, Ni-doped TiO2 was obtained by immersion in Ni salt solution; second, an ethylene glycol-based fluoride electrolyte containing Ni2+ ions solution was used. The obtained samples were analyzed using SEM, XRD, and photoelectrochemical methods. The produced Ni-doped NTO exhibited photocatalytic activity twice as high as that of nondoped NTO. Additionally, it was found that the immersion technique initiated a shift of the incident photon to converted electron (IPCE) spectra to the visible part of the spectrum. [ABSTRACT FROM AUTHOR]

The microstructure of Basalt matrix composite materials produced by pressureless aluminum melt infiltration at 950 °C was investigated. It is established that uniform elements distribution is observed within the whole sample depth. Interestingly, aluminum content variation considerably matches the hardness of the sample profile that is connected with alumina phase presence. Sample color changes during temperature treatment due to phase transitions were observed. The appearance of the hematite (Fe2O3) phase makes the initial preform red. After infiltration by molten aluminum, oxygen-deficient alumosilicate phases turn the color black. The infiltration process decreases the porosity insufficiently due to a partial reduction of alumosilicates by molten Al and the hardness of infiltrated samples was only 2.2 GPa. Nevertheless, a huge thermal conductivity rise from 1.45 to 4.53 W/(m·K), along with a fracture toughness increase, makes the produced composite a prospective wear-resistant material. Moreover, the developed low-temperature production technology allows for obtaining a very cost-effective material. [ABSTRACT FROM AUTHOR]