第三介质作用下坡道对轮轨黏着特性影响

利用JD-1轮轨模拟试验机,通过设计坡道试验夹具实现了不同坡道接触条件的轮轨模拟试验,研究了第三介质条件下坡度对轮轨界面黏着特性的影响规律.结果表明:在干态、水介质和防冻液介质条件下,上下坡道工况的轮轨黏着系数均低于平直轨道工况;随坡道坡度的增加,黏着系数呈下降趋势且下坡道的黏着系数下降更为明显;与水介质相比较,轮轨界面存在防冻液时更容易引起低黏着现象;上坡道工况下,随速度和轴重的增加轮轨界面黏着系数呈略微下降的趋势.     

A Study on the Effects of Carrier Gases on the Structure and Morphology of Carbon Nanotubes Prepared by Pyrolysis of Ferrocene and C2H2 Mixture

Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.     

CO removal by two-stage methanation for polymer electrolyte fuel cell

In order to remove CO to achieve lower CO content of below 10 ppm in the CO removal step of reformer for polymer electrolyte fuel cell （PEFC） co-generation systems, CO preferential methanation under various conditions were studied in this paper. Results showed that, with a single kind of catalyst, it was difficult to reach both CO removal depth and CO2 conversion ratio of below 5%. Thus, a two-stage methanation process applying two kinds of catalysts is proposed in this study, that is, one kind of catalyst with relatively low activity and high selectivity for the first stage at higher temperature, and another kind of catalyst with relatively high activity and high selectivity for the second stage at lower temperature. Experimental results showed that at the first stage CO content was decreased from 1% to below 0.1% at 250-300 ℃, and at the second stage to below 10 ppm at 150-185 ℃. CO2 conversion was kept less than 5%, At the same time, influence of inlet CO content and GHSV on CO removal depth was also discussed in this paper.     

单原子催化材料在电化学氢循环应用中的研究进展

单原子催化剂(SACs)是一类仅含有孤立的单个金属原子作为催化活性中心的催化材料. 由于其具有100%的原子利用率、 独特的化学结构及优异的催化活性等优点, 近年来在电化学催化和电能转换设备领域备受关注. 本文综合评述了单原子催化材料的设计理念、 合成方法和表征方法, 同时对其在氢电化学循环 (电解水制氢和氢燃料电池领域)的实际应用进行了系统介绍, 并对单原子催化材料的研究和应用前景进行了展望.     

气体雾化复相RE(NiAlCu)x微晶贮氢电极合金

采用气体雾化法制备了新型ＲＥ（ＮｉＡｌＣｕ）ｘ微晶贮氢合金粉末,并进行了微观这及电化学性能研究。合金颗粒呈较为规则的球形,ｘ＝４．５时,微观结构由基体ＡＢ５相及沿相界２的Ａ３与Ａ昌相复合结构组成;ｘ＝４．９时,微观结构帛基体ＡＢ５相及少量叶不连续网状分布的ＡＢ相复合结构组成;ｘ＝５．６时,微观结构由基体,ＡＢ５相及沿相界分布的ＡＢ５与Ｎｉ３Ａｌ共晶相复合结构组成。合金的电化学容量为２１０￣３００ｍ     

Finite-time prescribed performance control of MEMS gyroscopes

This paper addresses the finite-time prescribed performance control of MEMS gyroscopes. From the perspective of practical engineering, this paper arranges the desirable transient and steady-state performances according to the engineering requirements in the controller design procedure. For the tracking performance, prescribed performance control is studied to limited the steady-state error and the maximum overshoot. For the prescribed settling time, super-twisting sliding mode control and nonsingular terminal sliding mode control are employed to achieve finite-time convergence, respectively. The system stability is verified via Lyapunov approach. Through simulation tests, it is demonstrated that prescribed performance and finite-time convergence can be obtained under the proposed control scheme.

     

Hydrogen production through diesel steam reforming over rare-earth promoted Ni/γ-Al_2O_3 catalysts

Rare-earth (La, Ce, Yb) promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal’s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.     

Enantioseparation Using Chitosan Tris(3-chlorophenylcarbamate) as a Chiral Stationary Phase for HPLC

A novel chiral stationary phase (CSP) consisting of a silica-based chitosan tris(3-chlorophenylcarbamate) derivative was used for the enantioseparation of nine racemic compounds in the normal phase mode by high-performance liquid chromatography (LC). The influence of the type and percentage of modifier in the mobile phase on the optimization of the resolution was investigated. The resolution of epoxiconazole using this system was compared with those achieved using commercially available Chiralcel^® OD-H and Chiralpak^® AD-H columns. Among the tested racemates, seven racemic compounds were separated most quickly on the CSP of chitosan tris(3-chlorophenylcarbamate). Baseline or near-baseline separation was achieved for benzoin, penconazole, hexaconazole, and epoxiconazole, while the others were partially separated. The enantioseparation results for epoxiconazole were not inferior to those of commercially available Chiralcel^® OD-H and Chiralpak^® AD-H columns.     

蒽醌法生产过氧化氢用新型氢化催化剂的制备

 采用水合肼液相还原法制备了负载型镍催化剂，对其催化蒽醌加氢反应的活性进行了考察，采用电感耦合等离子发射光谱、X射线衍射以及H2化学吸附等手段对催化剂进行了表征，并与用氢气还原法制备的催化剂进行了对比．结果表明，用水合肼还原制备的催化剂的Ni粒子较大，Ni分散度及H2吸附量较低，但其催化蒽醌氢化反应的活性高得多．