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21.
Polystyrene (PS) was compounded with graphite that possesses high thermal conductivity and layer structures, and the PS/graphite thermal conductive nano‐composites were prepared. Thermal conductivity of PS improved remarkably in the presence of the graphite, and a much higher thermal conductivity of 1.95 W/m K can be achieved for the composite with 34 vol% of colloidal graphite. The Maxwell‐Eucken model and the Agari model were used to evaluate the thermal conductivity of the composites. For the purpose of improving the interfacial compatibility of PS/graphite, realizing the exfoliation and nano‐dispersion of graphite in the PS matrix, three intercalation methods, including rolling intercalation, solvent intercalation, and pan milling intercalation, were applied to prepare the composites, and the morphologies, thermal conductivities, and mechanical properties of the composites were investigated. It should be noted that the one prepared by pan milling intercalation not only had excellent thermal conductivity but also much higher mechanical properties, resulting from a high degree of layer exfoliation of the graphite, the formation of the chain structure agglomerates of the graphite, and the creation of more conductive paths under the strong shear stress of pan milling. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
22.
Chenxi Jia Wei Qi Zhimin He Haoming Yang Bin Qiao 《Central European Journal of Chemistry》2006,4(2):285-298
Two heptapeptides have been prepared by Fmoc methodology using Wang resin as solid support. For attachment of the first amino
acid, several coupling systems were evaluated, and DIC/DMAP system could give yields of >99% and low levels of racemization.
The selection of scavenger combination to deprotect side chains revealed that H2O/p-cresol was good at scavenging trityl and 1,2-ethanedithiol was highly efficient for scavenging t-butyl. Through shortening
the preactivation time to 5 min, the racemization which occurred during formation of amide bonds coupled by HBTU was minimized.
The crude peptides were characterized by RP-HPLC and MS, and sequenced by MS/MS to acquire reliable amino acid sequence information. 相似文献
23.
Photocatalytic C−C Bond Cleavage and Amination of Cycloalkanols by Cerium(III) Chloride Complex
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Dr. Jing‐Jing Guo Dr. Anhua Hu Yilin Chen Jianfeng Sun Haoming Tang Prof. Dr. Zhiwei Zuo 《Angewandte Chemie (International ed. in English)》2016,55(49):15319-15322
A general strategy for the cleavage and amination of C?C bonds of cycloalkanols has been achieved through visible‐light‐induced photoredox catalysis utilizing a cerium(III) chloride complex. This operationally simple methodology has been successfully applied to a wide array of unstrained cyclic alcohols, and represents the first example of catalytic C?C bond cleavage and functionalization of unstrained secondary cycloalkanols. 相似文献
24.
用扫描热显微镜测量微小区域热导性质的探讨 总被引:3,自引:1,他引:2
随着高新技术的迅速发展,许多研究对象已进入亚微米和纳米范畴。在对这些对象的热性能和热可靠性的研究中,亚微米尺度的热物性测量已成为关键技术之一。例如:在微电子、微电子机械系统(MEMS)领域中,已使用纳米量级厚度的材质和做出纳米尺度线宽的器件。在材料科学、生物学、医学和化学等许多领域,高空间分辨率下的热物性测量也具有重要意义。本文经过实验;初步用扫描热显微镜判定了微小区域材料热导性质的差别,并从理论上探讨了用该仪器测量微小区域热导性质的方法原理。 相似文献
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We report herein the kinetic studies on hydrolysis of three cyanopyridines in high‐temperature water. 3‐Cyanopyridine, 4‐cyanopyridine and 2‐cyanopyridine underwent consecutive hydrolysis to the corresponding pyridinecarboxamides and picolinic acids. Further decarboxylation to pyridine was observed for 2‐cyanopyridine hydrolysis. Experiments at different initial reactant concentrations revealed that these compounds exhibited the first‐order kinetics. Experiments at different temperatures showed that the first‐order rate constants displayed an Arrhenius behavior with activation energies of 74.3, 40.3, and 83.7 kJ mol?1 for 3‐cyanopyridine, 4‐cyanopyridine, 2‐cyanopyridine, respectively. The activation energies obtained for 3‐pyridinecarboxamide, 4‐pyridinecarboxamide and 2‐pyridinecarboxamide hydrolysis are 80.1, 32.7, and 70.5 kJ mol?1, respectively. The effect of substituent position on activation energies for cyanopyridine and pyridinecarboxamide hydrolysis is ortho ≈ meta > para. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 641–648, 2012 相似文献
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Huaifang Zhang Yanbo Li Chuanqi Cheng Jin Zhou Dr. Pengfei Yin Haoming Wu Prof. Zhiqin Liang Prof. Jiangwei Zhang Qinbai Yun Prof. An-Liang Wang Prof. Lijie Zhu Prof. Bin Zhang Prof. Wenbin Cao Prof. Xiangmin Meng Prof. Jing Xia Prof. Yifu Yu Prof. Qipeng Lu 《Angewandte Chemie (International ed. in English)》2023,62(4):e202213351
The direct electrochemical nitric oxide reduction reaction (NORR) is an attractive technique for converting NO into NH3 with low power consumption under ambient conditions. Optimizing the electronic structure of the active sites can greatly improve the performance of electrocatalysts. Herein, we prepare body-centered cubic RuGa intermetallic compounds (i.e., bcc RuGa IMCs) via a substrate-anchored thermal annealing method. The electrocatalyst exhibits a remarkable NH4+ yield rate of 320.6 μmol h−1 mg−1Ru with the corresponding Faradaic efficiency of 72.3 % at very low potential of −0.2 V vs. reversible hydrogen electrode (RHE) in neutral media. Theoretical calculations reveal that the electron-rich Ru atoms in bcc RuGa IMCs facilitate the adsorption and activation of *HNO intermediate. Hence, the energy barrier of the potential-determining step in NORR could be greatly reduced. 相似文献
28.
在流体粒子概率密度函数输运方程中考虑颗粒对流体的反作用力,发展了考虑双向耦合效应的LB气固两相流模型,引入Smagorinsky亚格子模型模拟高雷诺数气相流场.对经典后台阶气固两相流动进行模拟,气相和颗粒相速度分布与实验结果进行比较,发现考虑双向耦合效应的LB气固两相流模型结果明显优于单向耦合结果.进一步研究不同惯性颗粒在流场中的弥散特性,小颗粒(St~O(0.1))对流体的跟随性较好,在流场中分布较为均匀;而St~O(1)的颗粒难被流场涡卷吸进入涡内,呈现倾向性弥散现象;大颗粒(St~O(10))由于自身惯性进入流场涡,在流场中分布较为均匀. 相似文献
29.
多孔媒质是充满连通管道的物质。在研究多孔媒质中液体的流动现象时发现,当流体相对于固-液界面处的带电表面运动时,由于液流和电磁场的耦合就出现了电声耦合(电动)现象。电动法同地震法结合,有可能成为油藏探测的潜在方法。 相似文献
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Considering the problems of high costs, low catalytic activity and selectivity in the metal-based catalysts for CO2 electroreduction, we apply boron-containing metal-free B2S sheet as an alternative to the traditional metal-based catalysts. Reaction energy calculations identify the preferred “Formate” pathway for CO2 conversion to CH3OH on B2S, in which the thermodynamic energy barrier obtained by using the Computational Hydrogen Electrode model is 0.57 eV, and the kinetic energy barrier obtained by searching the transition states is 1.18 eV. Another possible reaction pathway, “RWGS+CO-hydro”, is suppressed and the hydrogen evolution reaction (HER) side reaction is nonspontaneous. Compared to Cu(211) with the highest catalytic activity among all transition metals, B2S sheet exhibits a better catalytic activity with a lower overpotential for CO2 reduction and a better selectivity that suppresses the non-target reaction. 相似文献