Roles of interaction between components in CZZA/HZSM-5 catalyst for dimethyl ether synthesis via CO2 hydrogenation

The roles of interaction between two catalyst components in CuO–ZnO–ZrO₂–Al₂O₃ (CZZA)/HZSM-5 bifunctional catalyst for dimethyl ether (DME) synthesis via carbon dioxide hydrogenation were investigated. It was found that CZZA catalyst showed excellent stability during methanol (MeOH) synthesis for 100 h, while there was a severe loss of catalytic activity in the bifunctional catalyst for DME synthesis. Hence, the effects of different degrees of intimacy of two catalyst components were studied for DME synthesis, including mixed and separated modes. For the mixed mode, the particle size of catalysts and the amount of reaction intermediates were proven to influence the catalyst deactivation. For the separated mode, the catalysts showed rapid deactivation within a short time. Various characterizations indicated that the remarkable deactivation of separated mode was mainly caused by the decrease of copper active centers (e.g., sintering and oxidation) and blockage of acid sites via increased coke deposition on HZSM-5.     

Defect formation and its effect on the thermodynamic properties of Pu2Zr2O7 pyrochlore: a first-principles study

In the past decades, pyrochlores, such as Gd₂Zr₂O₇, have demonstrated great potential to immobilize nuclear wastes such as Pu, which results in the production of Pu₂Zr₂O₇. Due to the high radioactivity of Pu, it is difficult to investigate the radiation response behavior of Pu₂Zr₂O₇ and its physical properties of the damaged state experimentally. Consequently, few related data have been reported in the literature thus far. In this study, first-principles calculations have been carried out to investigate the defect formation and its effect on the thermodynamic properties of Pu₂Zr₂O₇. It reveals that Pu_Zr antisite and O_8a interstitial defects are very easy to form in Pu₂Zr₂O₇. In particular, the O_8a interstitial defect can be formed spontaneously, while it is mechanically unstable. When vacancy, interstitial or antisite defects are formed in Pu₂Zr₂O₇, and the elastic moduli and Debye temperature are decreased. Besides, better ductility is resulted. As compared with other zirconate pyrochlores, such as Gd₂Zr₂O₇, the Pu₂Zr₂O₇ is suggested to be less resistant to radiation-induced amorphization. This study demonstrates that the created defects due to self-radiation from actinide decay have remarkable influences on the thermophysical properties of Pu₂Zr₂O₇.     

High extinction-ratio microstructure fiber based on chalcogenide glasses

Extinction ratio (ER) is one of the important parameters to characterize the polarization-maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled-off extrusion method. The core and cladding material of the fiber are Ge₉As₂₃Se₆₈ and Ge₁₀As₂₂Se₆₈. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid-infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18-cm-long PM fiber for the first time.     

Preparation and study of stable fluorine-free superhydrophobicity of cotton fibers

This paper proposes a method of directly modifying the surface of cotton fiber to achieve super-hydrophobic properties. The process was directly utilized the long-chain alkyl siloxane and the nano-SiO₂ modified cotton cloth, which was simple to operate, low in cost and environmentally friendly. This study discussed the influence of solvent ratio, reactant content and ammonia content on hydrophobicity. The solvent ratio had the greatest influence, and the maximum water contact angle (CA) changes were70° ± 1°. The maximum water CA of the superhydrophobic cotton fabric prepared after process selection was 162 ± 1.5°; it had good acid, alkali and salt resistance. After 24 h in a solution with a pH of 1–14, CA remained almost unchanged; After 144 h in a 3.5% salt solution, CA stabilized above 132°; it had self-cleaning properties; it had good selective adsorption performance, which can quickly separate oil and water; it had good mechanical stability. After 300 times abrasion of sandpaper, which still shows hydrophobic properties.     

Effect of nano fillers on the properties of polytetrafluoroethylene composites: Experimental and theoretical simulations

Polytetrafluoroethylene (PTFE) has excellent corrosion resistance and a low coefficient of friction; however, its high wear rate and low hardness severely limit its use. In the work, nano particles were used as fillers for PTFE. The composites were prepared by the homogeneous mixing of PTFE and other fillers and sintered at high temperatures. The work aimed to investigate the effect of various nano fillers (nanocarbon powders, graphene, fullerene, nano graphite powders, and nano copper powders) on the mechanical, thermal, and frictional properties of composites. The results of the experiments showed that the addition of graphene could improve the stress and strain values of the composites, and all the nano fillers could improve the thermal conductivity of the PTFE composites. The friction experiments showed that fullerenes could significantly improve the wear resistance of PTFE composites. In the theoretical simulation, the thermal conductivity of PTFE composites was predicted using ANSYS software, with the changes in the temperature and friction force in the friction process. The theoretical simulation results matched with the experimental values, which proved the accuracy of the theoretical simulations.     

高性能特种弹性体的拓展（一） ——三元乙丙橡胶、丙烯基弹性体和乙丁橡胶

综述近年来在非轮胎橡胶制品领域拓展应用的一些具有特殊性能和特种用途、能在苛刻条件下使用的高性能特种弹性体。本综述第1部分包含新型三元乙丙橡胶(EPDM)——5-乙烯基-2-降冰片烯型EPDM、超高相对分子质量EPDM、超低门尼粘度EPDM、生物基EPDM和EPDM合金以及丙烯基弹性体和乙丁橡胶,介绍这些弹性体的品种、牌号和特性,列举其在汽车部件、胶管、胶带和密封件等橡胶制品中应用的胶料配方以及分析其胶料性能。     

高性能特种弹性体的拓展（三） ——硅橡胶（续完）

综述近年来在非轮胎橡胶制品领域拓展应用的一些具有特殊性能和特种用途、能在苛刻条件下使用的高性能特种弹性体。本综述第3部分报道近年来高性能硅橡胶领域的一些研究和应用进展。添加新型热稳定剂（气相法二氧化钛）和耐热增效剂（3价金属-有机硅络合物）可以显著提高硅橡胶的耐高温性能。低苯基硅橡胶是比目前通用的甲基乙烯基硅橡胶耐高低温性能更优异的硅橡胶,可在－70～250 ℃热空气环境中长期使用,也可在300 ℃下短期使用。采用集中交联技术可获得高撕裂强度甲基乙烯基硅橡胶。概述陶瓷化硅橡胶的组成和陶瓷化过程,简述国内在瓷化体系（成瓷填料和助溶剂）以及阻燃陶瓷化硅橡胶方面的研究状况。介绍加成型液体硅橡胶的基本组成、功能性添加剂和交联反应原理及其在输配电用复合绝缘子中的应用。     

适用于非整数次幂的高精度混合基FFT谐波测量算法

快速傅里叶变换(FFT)是目前谐波分析中常用的分析算法,加窗插值FFT算法能够改善频谱泄漏和栅栏效应,但是FFT对采样数据序列有一定的长度要求.以基2为例,针对非2整数次幂数据序列无法采用快速傅里叶变换的问题,在分析研究常规混合基FFT算法频谱分布的基础上,提出一种适用于非整数次幂的高精度混合基FFT谐波测量算法.该算法采用四根谱线对混合基结果进行插值校正计算,该文详细分析推导了该算法的原理和修正过程.仿真及试验结果表明,在非2整数次幂条件下,与常规混合基FFT算法、补零FFT算法相比,该算法具有更高的谐波分析准确度,并且参数设置更加灵活.     

高功率密度SiC静止无功补偿器强迫风冷散热综合建模及优化设计方法

为了提高大功率高功率密度电力电子装置热设计的准确性和设计效率,该文综合热传导、对流换热与流体力学理论,针对电力电子装置的典型强迫风冷散热系统,提出基于截面积二次方根为无量纲特征长度的综合热模型,并提出一种强迫风冷散热系统体积最优的优化设计方法.以380V/50kvar高功率密度静止无功补偿器(SVG)为例,比较所提出的综合热模型与温升实验的热阻,综合热模型平均热阻误差在7％以内,即在SVG满载运行时,散热器平均表面温升的绝对误差ΔTe在1.3℃以内.该文提出的综合热模型相对于传统热模型精度提升62％,证明了综合热模型的准确性.基于所提出的优化方法设计的散热系统体积4.03L,对比传统方法设计的体积5.7L,体积缩小30％,从而证明了该文提出优化设计方法的可行性.     

考虑生物质供给价格弹性的工业园区综合能源系统规划

针对以生物质联供机组为核心的综合能源系统(integrated energy system,IES)在实际运行过程中存在的生物质燃料收集困难、供应不稳定等问题,文章提出了一种考虑生物质供给价格弹性的综合能源系统规划方法。首先,基于生物质收购价格弹性理论建立了秸秆收集成本模型,并将其引入工业园区综合能源系统双层规划中。其次,上层模型以设备规划容量及秸秆收购价格为优化变量,以年化综合费用最小为优化目标;下层模型以设备逐时出力及秸秆消耗量为优化变量,以考虑价格弹性的秸秆收集成本在内的年运行成本最小为优化目标,并采用粒子群算法和CPLEX工具箱进行联合求解。最后,以吉林省某典型工业园区为算例验证了所提规划方法更贴合工程实际情况,具有更加优越的经济性。