Advanced Materials Research Vols. 557-559

Abstract: Electrode pastes are used in solar cells for the formation of electrodes at both ends of the semiconductor substrate. The physical, chemical, and electrochemical properties of electrode pastes have important influences on the conversion efficiency and stability of the solar cells. Generally speaking, the constituents of electrode paste include organic binder, solvent, metallic conductive powders, glass frit, and some minor additives, all specially formulated to attain the properties of good electrical conductivity, wide sintering temperature, low warp, low pollution, and low cost.

Abstract: Microporous carbons (MCs) for supercapacitors were prepared from coal tar pitch (CTP) with potassium hydroxide (KOH) as activating agent at different KOH/CTP mass ratio by different heating modes. The results show that the specific surface area (S_BET), micropore surface area (S_mic), total pore volume (V_t) and micropore volume ((V_mic) of MCs made by microwave heating at 30 min heating time increases with the KOH/CTP mass ratio, respectively. At 14/7 of the KOH/CTP mass ratio, the SBET of MCs made by microwave heating at 30 min heating time reaches 1786 m²/g while that of MCs made by conventional heating at 180 min heating time is 1769 m²/g. The specific capacitance and energy density of the former reaches 269 F/g and 9.2 Wh/kg in 6 M KOH aqueous electrolyte while that of the latter is up to 307 F/g and 10.5 Wh/kg, respectively. And yet, the former brings bigger MC yield and bigger retention of energy density. The effects of the pore size distribution and pore volume on the specific capacitance and energy density of MC samples with the similar SBET by different heating modes are addressed in this paper.

Abstract: A new tubular cathode support for Direct Ethanol Fuel Cell (DEFC) was prepared by the gelcasting process using mesocarbon microbead(MCMB) and graphite as the main raw materials. Through the tubular cathode electrical property test, the advantages and disadvantages of cathode tube performance are studied at different graphite proportion. The results showed that when the graphite is more than 30 percent, the charge transmission ability has become extremely close. When the graphite ratio is 40 and 50 percent, the electrical performance is the best. With the graphite doping ratio of 40 percent, the electrode electrochemical reaction will have been reinforced when the temperature is high. When the air flow is 100 ml/min, the electricity capacity is better.

Abstract: Li₄Ti₅O₁₂ nanoparticles were synthesized through hydrothermal method. The structure and morphology characteristics of the composite were investigated by XRD, SEM. Meanwhile, electrochemical properties were analyzed through charging-discharging test. The prepared Li₄Ti₅O₁₂ nanoparticles had good rate performance and cycling performance. It exhibited discharging capacity of 136.0 mAh/g at a high rate of 10 C. It also had good performance when it charging at low rate and discharging at high rate.

Abstract: Nitrogen-doped carbon supported Co catalysts (CoNC) were synthesized via condensation reaction of pre-polymer of melamine formaldehyde resin with addition of cobalt nitrate salt, followed by carbonization in nitrogen. Rotating disk electrode technique (RDE) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) were used to identify the structure and oxygen reduction reaction (ORR) kinetics of the catalysts. The results show that the catalysts with 3.77 wt% Co loading yield the best ORR catalytic activity. Koutecky-Levich plots indicate ORR mechanism is governed by mixed mechanisms and the measured electron number varies between 2 and 4. SEM image shows an irregular lamellar structure of CoNC catalyst formed at high temperature, and different Co loadings in CoNC catalyst do not change its surface morphology.

Abstract: A novel series of ceramic samples La₂Mo_2-xTi_xO_9-δ (x = 0, 0.025, 0.05, 0.075) were prepared by solid-state reaction method. Their structures and phase transitions were studied by XRD, DSC and CTE. Their Electrical conductivities and oxygen ion transport numbers were measured by AC impedance spectroscopy at 773~1073 K and EMF at 673~1073 K, respectively. Results showed that even when x=0.075, the sample was almost pure oxygen ion conductor under the oxygen partial pressure gradient of 1.0 atm/0.21 atm, and though all the Ti-doped samples still underwent α/β structure transition, no abrupt change in the electrical conductivity was observed accompanying with the transition. They exhibited considerably higher electrical conductivity than La₂Mo₂O₉, especially at 773~873 K and the conductivity increased with increasing x value. The value of conductivity for La₂Mo_1.925Ti_0.075O_9-δ reached 8.5×10^-3 S•cm^-1 at 773 K and 0.08 S•cm^-1 at 1,073 K.

Abstract: Magnesium is potential biodegradable implant materials due to its attractive biological property, degradability and possesses mechanical properties similar to bone. But cast magnesium has an unsatisfactory mechanical property. Microstructure, mechanical properties, and degradation properties of the extruded pure Mg have been investigated by use of optical microscope, tensile testing, and Hank's solution that simulates bodily fluids. Microstructure observation has shown that the extrusion significantly refined the grain size of the cast magnesium, which mainly contributes to the high tensile strength and good elongation. The degradation rate is shown to be significantly reduced by grain refinement produced by extrusion. The results of the present study showed that pure magnesium by extrusion treatment is a simple and promising way of enhancing the mechanical properties and corrosion resistance of pure Mg in Hanks' solution.

Abstract: In the process of die-casting die design, the die castings should be usually left in the moving die in order to design ejecting mechanism conveniently when open mould. For the special structure of die castings, when lateral side core-pulling mechanism and larger wrapping force on the fixed-die core than on the moving-die core are required, the time-lapse core-pulling mechanism with side slide block can be adopted, which can make die castings left in the moving-die after open mould, and assure die castings production to do successfully. Time-lapse core-pulling mechanism with side slide block is ingenious and simple, and doesn’t increase the production cost of die casting die, and has certain reference value to the design of it.

Abstract: The cemented carbide tool and high speed steel tool are used as experimental cutting tools. The cutting properties of composite were studied by cutting lathe, tool microscope and light-section method microscope. The results show that carbide and high speed steel tool flank wear rate increase with the increasing of SiC particles size as well as the content of SiC particles. When the particles size of SiC is 40μm, composite cutting surface roughness increases with increasing of the content of SiC particles. While the particles size of SiC is 20μm, composite cutting surface roughness decreases with increasing of the content of SiC particles. In the same cutting conditions, the Carbide tolls have longer life than high-speed steel tools.

Abstract: Numerical simulation of the die for cylinder upsetting is done by Marc AutoForge software on base of elastic-plastic theoretical mechanical model to analyze transient temperature field, equivalent total strain field and thermal strain field. Then qualitative and quantitative relationship is found between these Factors and die-damage. A new method-Heat Exchange Balance Method is put forward to solve the cooling problems of hot -forging die by combinating with production practice , research practice and using basic theory of finite element and thermal.