Advanced Materials Research Vols. 156-157

Abstract: Submerged Entry nozzle is one of the key functional refractories for continuous casting and the safe and efficiency of the continuous casting is directly influenced by the properties of ZrO2-C materials located at the slag line of the submerged entry nozzle. In general, a little anti-oxidants such as SiC, Si or B4C will be introudced into ZrO2-C materials and anti-oxidants also influence the corrosion resistance of ZrO2-C materials. So this paper researched the properties especially the corrosion resistance of ZrO2-C materials with SiC, Si or B4C additions. The results show that the properties of ZrO2-C materials are relate to the composition of ZrO2-C materials and the corrosion resistance of ZrO2-C materials have no obvious relationship with other properties such as apparent porosity, bulk density, et al. The addition of anti-oxidants will all decrease the corrosion resistance of ZrO2-C material. The decreasing degree of corrosion resistance by Si is the most and the decreasing degree of corrosion resistance by SiC is the least. The corrosion resistance of ZrO2-C material with B4C addition is relate to the kind of the mold slag. To obtain the ZrO2-C material with excellent corrosion resistance antioxidants should not be added into ZrO2-C materials.

Abstract: A kinematic analysis is apply to gear trains of the main reducer of helicopter , and established the mathematical model of the system structure and layout of the gear trains use the graph theory representation to caculate the mechanical efficiency of it base on the kinematics, moment balance theory, power conservation principle and so on. The paper also introduced the constrained optimization function to carried on the gear train to increase the efficiency of the gear trains and improve the layout of the system structure, which to provide the basis of system structural analysis and design of the reducer.

Abstract: Quantitative analysis of tetragonal phase in barium titanate powders and fundament of standard curve was discussed from the result of X-ray diffraction (XRD) experiment via testing the standard series prepared powder samples. Some different conclusions compared with the past researches were drawn by analyzing the XRD data including the integrated intensity of a certain diffraction peak, difference in 2θ between peak (002) and (200) △2θ and d (interplanar spacing) value. Thus a useful method was provided for quantitative analysis tetragonal phase in barium titanate powders by synthesized by hydrothermal method.

Abstract: Pure MnNb2O6 powders was successfully prepared by hydrothermal method using Nb2O5•nH2O and Mn(NO3)2 as precursors and HCl, HF, NaOH, NH4OH solutions as mineralization agent. The phase composition and morphology of the prepared powder were characterized by X-ray diffraction and scanning electron microscopy. The effect of mineralizers on phase formation was investigated. The results show that the MnNb2O6 powders with crystallite size of ~24nm can be obtained with Mn(NO3)2 and Nb2O5•nH2O as precursors in neutral and alkaline solution at 200 for 168h. The particle size of the MnNb2O6 powder was ~300nm after heat treatment at a temperature of 600 . The SEM photographs show that the morphology of the MnNb2O6 powder are rod-like particles and the MnNb2O6 powders are highly dispersed.

Abstract: To use dimethyl ether as fuel for compression ignition engine to partially replace fossil oil, this study developed a city bus operating on DME blended with diesel oil. Considering fuel lubricity, viscosity, and calorific value, the optimized mixing ratio for blend fuel was chosen as 20 wt% DME in diesel oil (D20). Vapor pressure experiments carried out using a highly accurate thermophysical property measurement system showed that the backpressure for blended fuels must not be lower than 0.6Mpa to avoid vapor block in the engine fuel supply system. Moreover, because DME attacks conventional polymer sealants in the fuel system, new sealants made of nitrile rubber (NBR) were used to replace those original one. Experiments demonstrated that these were resistant to swelling by DME. For engine performance, it was found that fueled with D20, the rated engine power output can be comparable to that of diesel engine after increasing the supplied fuel amount per cycle, while the overall fuel economy was improved simultaneously. Moreover, for load characteristics at 1800r/min, over 70% reduction in smoke and 20% reduction in nitrogen oxides (NOx) emission were achieved, indicating that using DME blends as fuel can significantly improve the engine emissions.

Abstract: Effect of a furniture interior air purifying device on reducing concentrations of formaldehyde in air

Abstract: The performance of Ni/SiO2 Catalysts modified by La2O3, ZrO2 and CeO2 were tested in a BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) membrane reactor by catalytic partial oxidation of coke oven gas (COG) under atmospheric pressure. The results show that the oxygen permeation flux increased dramatically with Ni/RxOy/SiO2 (R = La, Zr or Ce) catalysts by adding the element of rare earth especially the La during the reforming reaction. At optimized reaction conditions, the dense oxygen permeable membrane had an oxygen permeation flux around 16.4 ml/cm2•min and a CH4 conversion of 99.2% have been achieved at 900 oC.

Abstract: In view of the characteristics of the low-noise and high-strength of auto gears, this paper proposes a new method of optimization of fine-pitch tooth profile. Based on the constant gear-pair parameter values of transmission ratio, modulus, pressure angle, the method takes the optimal contact ratio as design object, sets up the constraint conditions such as noise limit index, non-interference, non-undercutting, and non-sharpened in the tip, and optimizes the addendum coefficient and coefficient so as to increase the contact ratio. In addition, this paper makes a finite element strength analysis on the design result, and the result shows that the new method can not only reduces noise but also improves gear strength of fine-pitch gear.

Abstract: A low-cost process for removing boron from metallurgical grade silicon was developed by Si-Al alloying, and the separation procedure of silicon grains from Si-Al melt by solidification was investigated in this paper. The microstructure and purity of silicon were characterized and detected by metallographic analysis, energy dispersive X-ray spectrometers analysis and inductive coupled plasma atomic emission spectroscopy analysis. The results showed that the content of boron in the purified silicon decreased from 128.00 ppmw to 27.62 ppmw. In addition, the process of purification with Si-Al alloying combined with the treatment of hydrofluoric acid could remove boron to a low content of 13.81 ppmw, the removal rate of which is 89.21 %. The results indicated that the removal of boron from metallurgical grade silicon by Si-Al alloying is an efficient and prospective method.

Abstract: Extruded insulation is a major kind of insulation used in power cable. It is significant to evaluate extruded insulation lifetime suffered from electrical aging, which can improve the reliability of power cable. In this paper, a step-stress test method is used in accelerated life tests and Weibull model is used to statistic analysis for the mean lifetime of several samples under the same voltage value, and then the least square method is used to calculate the parameter of Weibull distribution. This paper uses inverse power function to fit test data and calculate voltage endurance coefficients. Constant-stress test data is also used as the counterpart of that measured by the step-stress test. It is indicated that the test voltages of step-stress test are more easily selected than that of constant tests and the data of the former is less scattered and the result is more reliable.