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Cavitation erosion, corrosion and synergism behaviors of HVOF sprayed WC-25WB-10Co-5NiCr and MoB-25NiCr coatings were investigated in this study. Conventional WC-10Co-4Cr and Cr 3 C 2 -25NiCr coatings were also characterized for comparison purposes. The cavitation erosion and cavitation-corrosion experiments were carried out in deionized water and 3.5 wt% NaCl solution respectively. The average mass loss rate was defined to assess the destruction of the coating surface. The cavitation erosion resistance and the cavitation-corrosion resistance were adopted to quantitatively analyze the difference of cavitation erosion and cavitation-corrosion performance of the coatings. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were employed to evaluate the corrosion resistance of all the coatings. In addition, the equivalent circuit models were designed to fit the EIS. The cumulative mass loss of all the coatings was measured under the conditions of pure cavitation erosion, pure corrosion and cavitation-corrosion. The total mass loss rate, pure cavitation rate, pure corrosion rate as well as synergistic mass loss rate were calculated to discuss their relative contributions responsible for the material removal. The cavitation-corrosion mechanisms were also discussed by analyzing the eroded surface for all the coatings. [ABSTRACT FROM AUTHOR]

The development of Ti 3 C 2 T x -based high performance electrode materials has been proposed to meet the practical requirements of supercapacitors. In this study, transition metal complexes decorated MXene Ti 3 C 2 T x hybrid electrode nanocomposites are fabricated by a facile polyvinylpyrrolidone (PVP)-assisted liquid impregnation strategy (abbreviated as PVP-M/akTi 3 C 2 T x (M = Mn or Ni)). The intercalated Ti 3 C 2 T x is observed to possess a distinct layered structure wrapped by cloud-like Mn/Ni complexes, which form a heterojunction to help the charge transfer of PVP-M/akTi 3 C 2 T x in aqueous electrolytes such as KOH, LiOH, Li 2 SO 4 and Na 2 SO 4. The electrochemical performance of pristine and modified MXene in the above electrolytes changes greatly, mainly due to the difference of electrolytes' ionic radius and conductivity. Typically, the PVP-Mn/akTi 3 C 2 T x and PVP-Ni/akTi 3 C 2 T x nanocomposites exhibit superior specific capacitances of 154.6 F g−1 and 167.65 F g−1 at 0.3 A g−1 current density in 1 M KOH electrolyte, respectively. Moreover, due to the complete progressive activation process of the electrode materials, the specific capacitance further increased by 25% and 56% after thousands of cycles, and finally kept at 95.70% and 96.21% of the maximum value respectively, indicating the superstability of these electrode materials. This study provides a new perspective to tailor the microstructures of Ti 3 C 2 T x electrode materials for energy applications. [ABSTRACT FROM AUTHOR]

Abstract: Cubic boron nitride (cBN) powder was coated with Ni nanoparticle and SiO2 nanolayer (abbreviated as cBN/Ni and cBN/SiO2, respectively) by rotary chemical vapor deposition (RCVD), and compacted with SiO2 powder by spark plasma sintering at 1473–1973K for 0.6ks. The effects of Ni and SiO2 coatings on the densification, phase transformation of cBN and hardness of SiO2–cBN composites were compared. The phase transformation of cBN to hBN was identified at 1973K in SiO2–cBN/SiO2 composites, 300K higher than that in SiO2–cBN/Ni composites, indicating that SiO2 retarded the transformation of cBN. The relative density of SiO2–cBN/SiO2 with 50vol% cBN sintered at 1873K was 99% with a hardness of 14.5GPa. [Copyright &y& Elsevier]

Abstract: Transparent SiO2 bodies were prepared by pressureless sintering (PLS) and spark plasma sintering (SPS). The effects of sintering and annealing temperature on the transmittance of the SiO2 bodies were investigated. The SiO2 bodies sintered by SPS and PLS at 1073–1573K were amorphous. With increasing the sintering temperature to 1673K, the SiO2 bodies sintered by PLS were crystallized while those sintered by SPS were still amorphous. The relative density of the SiO2 bodies sintered by SPS was 98.5% at 1373K and 100% at 1573K, whereas that sintered by PLS was 92.6% at 1373K and 98.9% at 1573K. The transmittance was 91.0% and 81.5% at a wavelength (λ) of 2μm for the SiO2 sintered bodies by SPS and PLS, respectively. In the ultraviolet range, the transmittance of the SiO2 bodies sintered by SPS at 1573K was about 40% at λ =200nm and increased to 75% after annealing at 1073K for 1h, which was about three times of the transmittance of the SiO2 bodies sintered by PLS (24.8%). [Copyright &y& Elsevier]

Abstract: SiO2–cBN composites were consolidated by spark plasma sintering at 1473–1973K. The effects of cBN content and sintering temperature on the relative density, phase transformation, microstructure and mechanical properties of the SiO2–cBN composites were investigated. The relative density of the SiO2–cBN composites increased with increasing SiO2 content. The phase transformation of cBN to hBN in SiO2–cBN composites was identified at 1973K, showing the highest transformation temperature in cBN-containing composites. The SiO2–20vol% cBN composites sintered at 1673K showed the highest hardness and fracture toughness of 12.5GPa and 1.5MPam1/2, respectively. [Copyright &y& Elsevier]

Abstract Core-shell structural composites are promising to quench the desire for low-cost, lightweight and multifunctional magnetic materials, but the fabrication of highly pure shell nanoparticles with a desired morphology on a heterogeneous nuclear is still a big challenge. This study gives a successful illustration by in-situ synthesizing BaFe 12 O 19 nanoparticles as a shell on Al 2 O 3 core powders using BaCl 2 and FeCl 3 as precursors, instead of commonly used Ba(NO 3) 2 and Fe(NO 3) 3 , by a modified heterogeneous precipitation process followed by calcination for crystallization. After calcination of the precipitants from the raw precursor mixture of BaCl 2 :FeCl 3 for 1:10 at 800 °C, and for 1:8.5 at 900 °C, respectively, pure BaFe 12 O 19 formed on pristine Al 2 O 3 , mostly with a hexagonal plane, about 100–200 nm in basal diameter and 20–100 nm in thickness. The highest saturation magnetization and coercivity of the coated Al 2 O 3 @ BaFe 12 O 19 powders was 23.3 emu/g and 5149 Oe, quite higher than that of the direct-mixed Al 2 O 3 -BaFe 12 O 19 composite powder, and BaFe 12 O 19 -containing composites reported in literature, which could be attributed to the hexagonal shape of BaFe 12 O 19 and uniform shell dispersion on Al 2 O 3 core. The formation mechanism for the Al 2 O 3 @BaFe 12 O 19 powders was discussed in detail. [ABSTRACT FROM AUTHOR]

The sliding wear properties of high-velocity oxygen-fuel (HVOF) sprayed nanostructured WC-CoCr cermet coatings against Al 2 O 3 under dry friction at different temperatures were investigated using a pin-on-disk high-temperature tribometer. The microhardness data of the coatings were also statistically analyzed by using the Weibull distribution. The results showed that nanostructured coatings exhibited a mono-modal distribution under indentation load of 100 g, and a bimodal distribution under indentation load of 300 g. With increasing test temperature, the coatings showed an increase in wear rate. The evolution of the sliding wear mechanism of the coatings with the increase of the temperature was extrusion deformation at room temperature, carbide particle pull-out, oxidation wear and adhesive wear at 200 °C, and a combination of binder extrusion and fatigue delamination coupled with oxidation wear at 500 °C. [ABSTRACT FROM AUTHOR]