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91.
92.
Y. Nakamura Ichiro Tanaka N. Takeuchi S. Koshiba H. Sakaki 《Journal of Electronic Materials》1998,27(11):1240-1243
We studied morphology of GaAs surfaces and the transport properties of two-dimensional electron gas (2DEG) on vicinal (111)B
planes. Multi-atomic steps (MASs) are found on the vicinal (111)B facet grown by molecular beam epitaxy, which will affect
electron transport on the facet. We also studied how the morphology of GaAs epilayers on vicinal (111)B substrates depends
on growth conditions, especially on the As4 flux. The uniformity of MASs on the substrates have been improved and smooth surfaces were obtained when the GaAs was grown
with high As4 flux, providing step periodicity of 20 nm. The channel resistance of the 2DEG perpendicular to the MASs is reduced drastically
with this smooth morphology. These findings are valuable not only for fabricating quantum devices on the (111)B facets but
also those on the vicinal (111)B substrates. 相似文献
93.
It is demonstrated that glassy carbon powder can be thermochemically activated. During activation, a film with open pores is created on the glassy carbon particles. This film has a large internal surface area, which is accessible to liquids and gases. A simple model for the evolution of the internal surface area in glassy carbon powder during thermochemical gas-phase oxidation is also presented and compared with experimental data. Experimental results are in qualitative agreement with the model. We found that a sharp particle size distribution is desirable with regard to potential technical applications. 相似文献
94.
95.
高水固结尾砂充填采矿充填体合理配比的研究 总被引:7,自引:4,他引:3
高水固结尾砂充填采矿是一种新型充填采矿法。试验测定了高水固结尾矿充填体的强度和变形特征;研究分析了影响充填体强度的主要因素、高水充填工艺的特殊要求,以及上向,下向进路开采对充填体强度和稳定性的要求,提出了满足支护强度,工艺及经济需求的充填材料的合理配比范围。 相似文献
96.
In the absence of a bulk diffusion effect, it is shown for the first time that the impedance spectra for the chlorine evolution reaction on a rotating thin ring electrode comprise three consecutive semicircles in the capacitive half of the complex plane. The first (highest frequency) semicircle is due to the charge-transfer resistance for chloride discharge and the simultaneous chlorine adsorption coupled to the double-layer capacitance. The second semicircle (around 5 Hz) is due to the adsorption and desorption of a chlorine intermediate. The third (lowest frequency, around 0.5 Hz) semicircle is due to the relaxation of surface oxygen species. The impedance data allow the steps of the overall reaction to be examined individually. On a Pt surface the rate of chloride discharge and simultaneous chlorine adsorption (the admittance of the first semicircle) is first order with respect to chloride concentration and has a potential-dependence close to 58 mV/decade. The rate of the adsorption and desorption process (the admittance of the second semicircle) is second order with respect to chloride concentration, and has a potential dependence close to 30 mV/decade. The time constant for the adsorption/desorption processes is ca 20 ms, independent of electrode potential in the range studied. These features are consistent with a mechanism in which a faster discharge reaction (Cl− Clad + e) is followed by a slower surface combination reaction (2Clad → Cl2), but inconsistent with mechanisms in which ion + atom desorption is predominant, the initial chloride discharge is slow, or a unipositively charged chlorine species is involved. 相似文献
97.
98.
航空齿轮表面硬化层断裂性能研究 总被引:1,自引:0,他引:1
按照航空齿轮的具体工艺过程,对材料12Cr2Ni4A的拉伸试样和断裂试样进行设计和加工,通过三点弯曲实验,重点研究了齿轮材料硬化层的硬度分布,硬化试样拉伸力学性能参数和断裂性能参数,实验结果表明,所采用试样的加工工艺方案是可行的,所获得的Kc基本反映我国航空硬化齿轮材料的断裂性能特征,为定量预测航空硬化齿轮疲劳寿命提供实验和理论分析的依据。 相似文献
99.
优化SMC模压工艺控制制品收缩率和表面粗糙度 总被引:1,自引:0,他引:1
优化SMC模压工艺参数:模压压力分为二阶段,选定最佳压力释放时机和压力;适宜降低模压温度。可显著降低SMC制品的固化收缩率,提高其表观质量、试验表明,同时采用的线收缩率和表面粗糙度两种检测和村定方法具有很好的同一性。 相似文献
100.
Titipong Issariyakul Mangesh G. KulkarniAjay K. Dalai Narendra N. Bakhshi 《Fuel Processing Technology》2007
Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester. To untangle this problem, two-stage (acid and alkali catalyzed) method was used for biodiesel synthesis. More than 90% ester was obtained when two-stage method was used compared to ∼ 50% ester in single stage alkaline catalyst. In the case of mixed alcohol, a relatively smaller amount of ethyl esters was formed along with methyl esters. Acid value, viscosity, and cetane number of all the esters prepared from WFG were within the range of the ASTM standard. Esters obtained from WFG showed good performance as a lubricity additive. 相似文献