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In the present study, the boron carbide ceramics reinforced with silicon carbide fibers (B 4 C-SiC f) were fabricated by incorporating various contents of SiC f ranging from 2.5 to 10 wt%. The B 4 C-SiC f powder mixtures were sintered using the Field Assisted Sintering Technique (FAST), also known as Spark Plasma Sintering (SPS), at temperatures of 1800 °C and 2000 °C for 5 min by applying a pressure of 70 MPa in argon atmosphere, while heating and cooling rates were maintained at 100 °C/min and 50 °C/min, respectively. The influence of the initial powder ratio on the sintering behavior, relative density, microstructural development, and mechanical properties of the obtained B 4 C-SiC f composites was investigated. The results indicated that the sintered ceramic materials contained only the initial compounds, i.e. B 4 C and SiC phases. Scanning Electron Microscopy (SEM) showed that the sintered composites consisted of densely compacted B 4 C grains. The highest relative density (>99 %) was achieved for the sample with 95 wt%B 4 C and 5 wt%SiC f , sintered at 2000 °C. Depending on the constituent content and the densification temperature the obtained composites demonstrated hardness values ranging from 29 to 43 GPa. The maximal hardness was attained in the composite with 95 wt%B 4 C sintered at 2000 °C. To assess the performance of the composites under extreme conditions, the ablation resistance was evaluated using a flowing oxyacetylene torch test. The material containing 5 wt%SiC f exhibited superior ablation resistance when compared to the other compositions. The attained results of this study showed that the SPS technique is a highly effective method for the densification of additive-free B 4 C-SiC f ceramic composites, showcasing promising properties for applications in extreme environments. [ABSTRACT FROM AUTHOR]

Hydroxyapatite was used as the inert matrix for in-situ immobilization of strontium (Sr) radioactive isotopes at room temperature. A nano-emulsification method was applied to synthesize Sr-substituted calcium hydroxyapatite (Ca 1−x Sr x ) 10 (PO 4 ) 6 (OH) 2 . The concentration of incorporated Sr was in the range of 0 ≤ x ≤ 1. Immobilization of Sr was evaluated using a stable isotope instead of radioactive isotope. The effect of strontium concentration on the crystal structure was studied and the results have showed that in the whole concentration range, Sr forms solid solutions with the host hydroxyapatite crystal structure. Powders comprised of nanometre sized particles were obtained and their properties, such as crystallite and particle size, changes in lattice parameters as function of dopant content and thermal stability, were further examined. It was found that the crystal structure of obtained powders is thermally stable at high temperatures. No secondary phases were formed in as-prepared powders or during calcination. The results in this study showed that nano-emulsion strategy provides a simple pathway for synthesis of a single-phase Sr-substituted hydroxyapatite, which can be used for immobilization of Sr radioactive isotopes. [ABSTRACT FROM AUTHOR]

• MoO 2 and MoO 3 were prepared by electrodeposition and thermal treatment in air. • The prepared catalysts enhanced the rate of plasma degradation and mineralization of organic dye. • The catalytic mechanism was reveled. • MoO 2 and MoO 3 enhanced production of plasma-generated ⋅OH which oxidizes the dye. • The catalysts kept most of their activity after 5 consecutive uses. MoO 2 and MoO 3 were applied as catalysts for plasma degradation of organic compound. They were prepared by electrodeposition (MoO 2) and electrodeposition followed by thermal treatment (MoO 3), and then characterized by the cyclic voltammetry, SEM, EDX, XRD, and FTIR. The RB 19 was degraded by self-made non-thermal atmospheric pressure pulsating plasma corona reactor. Decolourization mechanism, parameters, kinetics, and influence of the catalysts were examined. Mo-oxides enhanced degradation reactions rate constants by 45% – 50%, increased decolourization rate at all the tested pHs, discharged current densities, and decreased energy consumption. Degradation followed the pseudo-first kinetics order and proceeded via plasma-generated ⋅OH radical, which attacked dye molecule; MoO 2 and MoO 3 , excited by plasma-generated UV radiation and high-energy chemical species bombardment, enhanced decomposition of plasma-generated H 2 O 2 into ⋅OH radicals, thus enhancing production of degradation agent. Higher percentage of mineralization was attained in the presence of catalysts, which maintained their degradation activity after 5 uses. [ABSTRACT FROM AUTHOR]