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11.
Analysis of the intragranular microstructure in ceramic nanocomposites and their effect on the mechanical properties 下载免费PDF全文
Junting Luo Shuyi Luo Chunxiang Zhang Yahong Xue Guoqing Chen 《Journal of the American Ceramic Society》2018,101(11):5151-5156
The formation of intragranular microstructure in Al2O3/ZrO2 and Si2N2O/Si3N4 nanocomposites was analyzed, and the effect of intragranular microstructure on the mechanical properties of nanocomposites was investigated. Results suggest 3 requisite conditions for the formation of intragranular microstructure and the role of intracrystalline glass phase and scar microstructure. In case of Al2O3/ZrO2, the intragranular microstructure leads to the formation of transgranular fracture, which in turn improves the mechanical properties via strengthening and toughening. On the other hand, in case of Si3N4/Si2N2O nanocomposites, intragranular microstructure reduces the possibility of bridging, pulling out, and crack deflection, thereby leading to the deterioration of strength and toughness. Based on these results, we can conclude that the formation of intragranular microstructure does not necessarily improve the mechanical properties in all kinds of materials. Rather, the effect of intragranular microstructure on the mechanical properties of nanocomposites is related to the strengthening and toughing mechanism of matrix materials. 相似文献
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Fabrication of supported Pd–Ir/Al2O3 bimetallic catalysts for 2‐ethylanthraquinone hydrogenation 下载免费PDF全文
Runrun Hong Yufei He Junting Feng Dianqing Li 《American Institute of Chemical Engineers》2017,63(9):3955-3965
A series of χ wt % Pd‐(1‐χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ‐Al2O3 have been prepared by co‐impregnation and calcination‐reduction, and subsequently employed in the hydrogenation of 2‐ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al2O3 catalyst afforded the highest yield of H2O2, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2‐ethyl‐5,6,7,8‐tetrahydroanthraquinone (H4eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017 相似文献
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采用成核/晶化隔离法制备出一系列Ni2+-Co2+-Fe2+-Fe3+-SO42--LDHs层状前驱体,焙烧后得到尖晶石型铁氧体Ni1-xCoxFe2O4。对样品的晶体结构及元素组成进行分析,结果表明,制得的尖晶石型铁氧体Ni1-xCoxFe2O4 晶体结构优良, 元素组成可控性强。分别将Ni1-xCoxFe2O4、NiFe2O4和CoFe2O4的磁学性能参数的理论混合值和机械混合值随x[x=nCo)∶n(Ni)]的变化情况进行比较,发现Ni1-xCoxFe2O4的磁学性能并不是简单的NiFe2O4和CoFe2O4磁学性能的加合,Co和Ni原子之间存在着一定的协同效应,且当x为0.2时,Ni1-xCoxFe2O4的磁学性能最佳。 相似文献
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Junting Xu Linxian Feng Zhengxi Liu Linshen Chen Yi Deng Chunming Cui Wei Chen 《应用聚合物科学杂志》1999,71(6):897-901
Syndiotactic polypropylene (s‐PP) was prepared by metallocene catalyst and was fractionated with the temperature rising elution fractionation (TREF) technique. The nonisothermal behavior of the obtained fractions was investigated. Fractions was first cooled at different rates and then heated at a constant rate. The parameters such as the peak crystallization temperature (Tc), the onset crystallization temperature (Ton), the difference between Ton and Tc (ΔT1 = Ton − Tc), the crystallization enthalpy (ΔH), the peak melting temperatures (Tm1, Tm2), and the difference between the Tm1 and Tm2 (ΔT2 = Tm2 − Tm1) were obtained. The dependence of these parameters on cooling rate, syndiotacticity, and molecular weight was discussed. It is found that Tc, Ton, ΔH, Tm1, and Tm2 systematically increase with increasing syndiotacticity and are depressed on increasing the cooling rate. Cooling rate, syndiotacticity, and molecular weight show different influences on ΔT1. In the melting process of s‐PP, double peaks were observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 897–901, 1999 相似文献
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本文通过丙稀酸与环氧酚醛树脂开环反应,制备出能紫外光固化的酚醛树脂结合剂,研究了制备该树脂的合适工艺条件为:催化剂N,N-二甲基苯胺的用量为体系总质量的1%,反应温度为80±5℃,反应时间为5~7h;用这种可紫外光固化的酚醛树脂制作的涂附磨具试样,不仅固化速度快,仅需4~5m in即可固化完全,而且磨削比是常规热固化试样的3倍多,使用性能大大提高。 相似文献
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TC4钛合金高温本构关系的研究 总被引:1,自引:0,他引:1
在Gleeble-1500热模拟机上对TC4钛合金进行高温热压缩试验,热模拟压缩试验变形条件:温度800~1030℃,应变速率0.001~10 s-1;变形程度60%.结果表明:TC4钛合金在变形开始阶段,流动应力随应变的增加迅速增加,当应变超过一定值后,流动应力开始下降并逐渐趋于稳定,出现稳态流动特征;变形温度、应变速率的减小使TC4钛合金高温变形时的峰值应力显著降低.并通过对数据的回归处理,确定了合金在(α+β)相区地热变形激活能是565.96 kJ/mol,β相区是402.879 kJ/mol.研究发现峰值应力σp、稳态应力σres、峰值应变εp、稳态应变εres等与Z参数之间呈线性关系. 相似文献
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综述了反胶束萃取氨基酸的研究进展,包括反胶束萃取氨基酸机理及应用.其机理为:氨基酸以带电离子状态进入反胶束的"水池" 内或微胶团球粒的界面分子膜层内而被分离,氨基酸离子与形成反胶团的表面活性剂离子间的静电作用越强,氨基酸的萃取率越高,水溶液中盐浓度越大,氨基酸萃取率越低.由2-乙基己基琥珀酸酯磺酸钠(AOT)阴离子表面活性剂和三辛基甲基氯化铵(TOMAC)季铵盐阳离子表面活性剂形成的反胶束适用于低盐浓度的氨基酸料液,如从发酵液中萃取分离苯丙氨酸,二 (2-乙基己基)磷酸铵表面活性剂形成的反胶束可用于从高盐浓度的胱氨酸母液中萃取分离出精氨酸.介绍了反应条件对反胶束萃取氨基酸的影响. 相似文献
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介绍六自由度微动平台的原理、结构;对旋转自由度的实现进行了设计;同时对旋转自由度的调整精度进行了分析。这种形式的六自由度微动平台具有系统简单,可操作性强,实时监控调节,性价比高等优势。 相似文献