Composite superhard materials containing boron carbide

The possibility is shown to produce composite superhard materials containing boron carbide and having enhanced thermostability as well as high elastic characteristics, hardness, and fracture toughness. The sufficiently high fracture toughness of the composite is due to the structure with an enhanced strength of phase boundaries, which forms at high p, T parameters of sintering.     

Electronic-voltage transformers for distributive mains

Requirements for electromagnetic, capacitance, and electronic voltage measuring transformers in 10- to 110-kV mains are clarified. The urgency of developing electronic-voltage transformers that will meet the requirements of upcoming international standards and have the function of standard analog output signals for actual substations is shown. Results of modeling are given that confirming that it is possible to use this innovation, which eliminates ferroresonance phenomena and PSP rearrangement and facilitates effects on equipment. Designs and specifications of 110-kV electronic transformers are given.     

Gasification of wood chips

The gasification of wood chips in a steam-air blast is considered. The expected gas properties are calculated when using a steam-oxygen blast. The yield and composition of generator gas, the degree of steam decomposition, and the efficiency of gasification are determined. Applications are identified for the gas produced.     

Sulfuric acid decomposition on the Pt/n-SiC catalyst for SI cycle to produce hydrogen

The sulfuric acid decomposition should be performed in the wide temperature ranges from 550 °C to 950 °C to absorb the sensible heat of He in SI process. Therefore, the catalysts for the reaction should be stable even in the very corrosive reaction condition of 650 °C. Here, the Pt/n-SiC catalyst was prepared for the purpose and compared with the Pt/SiC catalyst. The both catalysts showed the high stability in the temperature ranges from 650 to 850 °C. The n-SiC with the surface area of 187.1 m²/g was prepared using nano-sized SiO₂, which resulted in amorphous SiC phase. The SiC support with the surface area of 19.2 m²/g for the comparison showed the well crystalline structure. In spite of the large surface area differences between the n-SiC and SiC support, the Pt particle sizes of the Pt/n-SiC (average Pt size: 26.4 nm) catalyst were not so much different from those of the Pt/SiC (average Pt size: 26.1 nm) catalyst after the calcination at 1000 °C for 3 h. However, the catalytic activity of the Pt/n-SiC was much higher than that of the Pt/SiC. XRD analysis indicated that the Pt particles on the Pt/n-SiC was more stable than those of the Pt/SiC in the sulfuric acid decomposition and XPS analysis showed that the Pt valence state on the Pt/n-SiC was higher than that on the Pt/SiC. The surface analysis showed that the surface of the n-SiC particles was covered by SiO₂ and Si₄C_4−xO₄. These experimental results indicate that the Pt metal particles on n-SiC were stabilized on the oxidized Si surface. Therefore, it is suggested that the Pt particles stabilized on the oxidized Si surface can be a reason for the higher activity of the Pt/n-SiC catalyst as compared with the Pt/SiC catalyst.     

Silicon carbide fiber-reinforced composite membrane for high-temperature and low-humidity polymer exchange membrane fuel cells

Currently, efforts are being made to commercialize a fuel cell system through research on fuel cell material enhancements. In particular, improvements in the membrane-electrode assembly, a key component of polymer electrolyte membrane (PEM) fuel cells, are essential to increase the performance of a fuel cell, in addition to accelerating its commercialization. Therefore, in this study, we used silicon carbide (SiC) fibers (web type) by electrospinning, which possess superior material, thermal, and chemical properties, as a structural material for the composite electrolyte membrane in the membrane-electrode assembly by impregnating it with the polymer electrolyte ionomer of short-side chain (SSC). In addition, we enhanced the ion-exchange capability of functionalized SiC fibers by introducing the hydroxyl (OH) group and phosphoric acid. The resulting functionalized composite electrolyte membrane exhibited a 70% better ion-exchange capability than the conventional cast electrolyte membrane and SiC webs composite electrolyte membranes was observed to excellent mechanical strength. We characterized and illustrative modeled the functionalized silicon carbide fibers, on the basis of which we further developed composite membrane. We then fabricated a unit cell of PEMFC based on this composite electrolyte membrane, and evaluated its single-cell performance, electrochemical properties, and accelerated voltage life-time durability test of operating 35 h according to the electro- and physic-chemical characteristics of the MEA under high-temperature and low humidity (120 °C/RH 40%).     

Properties of Cu,Ni, and V doped-LaCrO <Subscript>3</Subscript> interconnect materials prepared by pechini,ultrasonic spray pyrolysis and glycine nitrate processes for SOFC

The ceramic interconnect,La_0.8Sr_0.05Ca_0.15(Cr_{1 −x} , B_x)O₃ (B = Cu, Ni, V, x = 0.02, 0.1, 0.5) (LSCCB) powders were prepared by Pechini method, Ultrasonic Spray Pyrolysis (USP) and Glycine Nitrate Process (GNP). Nano sized powders were synthesized by GNP and their chemical compositions were confirmed by ICP analysis. The electrical conductivities of LSCCCu, LSCCNi, and LSCCV samples were 34 S/cm, 48 S/cm, and 22 S/cm at 800^∘C in air, respectively. Among the LSCCB powders, the LSCCNi sample shows highest relative density and electrical conductivity. In a low oxygen partial pressure, however, LSCCV sample was more stable. The perovskite phase of the composition LSCCV sample is of large practical interest for interconnects in SOFC because of the stability in low oxygen partial pressure.