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《Composite Interfaces》2013,20(5-7):407-422
The addition of carbon nanofibers to a polymeric matrix is known to affect its mechanical and electrical properties, although the mechanisms responsible for the changes are not sufficiently understood. Particularly, there are currently no adequate predictive methods that allow the creation of knowledge-based structures tailored for specific electrical response. We have developed a method for predicting the electric and dielectric properties of nanofiber-reinforced polymer matrices based on the application of the graph theory and circuit laws. We consider the individual properties of the polymeric matrix and the complex nanofiber network (including fiber orientation, concentration, and size), under an applied external electric field, and from the analysis we obtain information such as perlocative pathways, breakdown voltage, and impedance of the overall system. Simulations for two-phase systems consisting of a dielectric matrix and randomly oriented nanofibers have shown that the concentration and the length of the fibers affect the properties. Increased concentrations or longer fibers both result in networks for which it is easier to establish conducting paths through breakdown mechanisms. 相似文献
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《Composite Interfaces》2013,20(8):633-644
The poor hydrolytic stability of silane interphase greatly limits the use of fiber reinforced composites (FRC) in demanding applications in which the FRC part is permanently exposed to a moist environment such as in prosthetic dentistry and orthodontics. To improve hydrolytic stability of the interphase between the matrix composed of a blend of triethyleneglycol dimethacrylate (TEGMA) and bisphenol A glycidylmethacrylate (Bis–GMA) monomers and glass or alumina oxide fibers, a two-step hydrosilylation procedure was employed. The process consisted of creating hydride intermediate on the fiber surface followed by hydrosilylation reaction attaching the unsaturated organic monomer (Bis–GMA) forming stable –Si–C bonds. Infrared spectroscopy (FTIR) confirmed formation of the hydride intermediate on the surface and then, attachment of the appropriate organic compound in the second step. The amount of deposited interphase and its stability was significantly enhanced compared to standard silanization treatment. Fracture surfaces were observed by scanning electron microscopy (SEM) before and after environmental exposure proving that the most stable interfacial bond was obtained with the two-step treated fibers. It was concluded that hydrosilylation provides a viable alternative to silanization for both glass and ceramic fibers in composites intended for applications requiring enhanced hydrolytic stability of the composite parts. 相似文献
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电动势法对LiCl-Li~2SO~4-H~2O体系25℃热力学性质研究 总被引:4,自引:0,他引:4
用自制的锂离子选择电极和经典Ag-AgCl电极,测定25℃时LiCl-Li~2SO~4-H~2O三元体系中离子强度0.01~6.0mol.kg^-1的LiCl平均活度系数.,由实验数据,用多元线性回归法求取Pitzer方程、Harned方程的离子作用参数和系数,并用上述方程计算LiCl在混合溶液中的平均活度系数,分别以Inγ~±LiCl和logγ~±LiCl的形式与实验值进行比较,标准偏差均小于0.008.本工作测得的LiCl平均活度系数的自然对数与等压法测定的渗透系数拟合的Pitzer方程参数计算值比较,标准偏差为0.0097.同时计算了Li~2SO~4在该体系中的平均活度系数和混合溶液的渗透系数以及混合超额自由能. 相似文献
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本文用分光光度法测定了离子强度为 0.2 至4.2 范围内的离子对CuSO: 和配阴离子Fe(Tiron)- 在各种支持电解质中的稳定性. 在各种支持电解质中, 两个配合物体系的稳定性随离子强度变化的趋势基本一致, 但稳定性的极小值位置则大相同. 稳定性数据表明,B体系在离子强度小于2.0 时适用; 对Fe(Tiron) -体系则完全不能应用. 本文简单地讨论了造成上述情况的原因. 测得CuSo4 和Fe(Tiron)- 在25°C 时的热力学稳定常数logK. 分别为2.17和19.50. 相似文献
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通过分子设计技术合成了两种侧链种类和长度可能控制的接枝乙烯基酯树脂(VER),并用它们与聚氨酯(PU)形成了同步互穿网络(SIN)。通过DSC,SEM,TEM,FTIR等考察了接枝VER的共聚单体对VERSIN的形态结构与力学性能的影响。研究结果表明,用甲基丙烯酸甲酯(MMA)为共聚单体的接枝VER网络中的MMA链段与PU网络中的硬段有较好的相容性,导致这类PU/接枝VERSIN中两个网络间的相容性和互穿程度好于由苯乙烯为共聚单体时合成4SIN。因此,在这两类共聚单体合成的SIN中,由MMA形成的接枝VER网络增强PU网络的效果更为显著。 相似文献