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61.
Hexagonal boron nitride (BN) platelets, also known as white graphite, are often used to improve the thermal conductivities of polymeric matrices. Due to the poor interfacial compatibility between BN platelets and polymeric matrices, in this study, polyrhodanine (PRd) was used to modify BN platelets and prepared functionalized BN-PRd platelets, thereby enhancing the interfacial interaction between the thermal conductive filler and polymeric matrix. Then, BN-PRd platelets were dispersed into the nitrile butadiene rubber (NBR) matrix to yield high thermally conductive composites. The presence of N? C═S groups in PRd allowed the combination of PRd and NBR chains containing stable covalent bonds via vulcanization reaction. The thermal conductivity of the as-prepared 30 vol% BN-PRd/NBR composite reached 0.40 W/mK, representing an increment of 135% over pure NBR (0.17 W/mK). In addition, the largest tensile strength of NBR composite containing 30 vol% BN-PRd platelets was 880% times of pure NBR. The 30 vol% BN-PRd/NBR composite also displayed a relatively high dielectric constant (9.35 at 100 Hz) and a low dielectric loss tangent value (0.07 at 100 Hz), indicating their usefulness as dielectric flexible materials of microelectronics. In sum, the simplicity and good efficiency of formation of covalent bonds between boron nitride and rubber chains look very promising for large-scale industrial production of high thermally conductive composites. 相似文献
62.
63.
Yuning Yang Qingzhi Yang Liqun Qi 《Journal of Optimization Theory and Applications》2014,163(3):841-858
This paper presents new approximation bounds for trilinear and biquadratic optimization problems over nonconvex constraints. We first consider the partial semidefinite relaxation of the original problem, and show that there is a bounded approximation solution to it. This will be achieved by determining the diameters of certain convex bodies. We then show that there is also a bounded approximation solution to the original problem via extracting the approximation solution of its semidefinite relaxation. Under some conditions, the approximation bounds obtained in this paper improve those in the literature. 相似文献
64.
65.
CHEN Liqun 《力学与实践》2019,41(2):196
为对美国静力学教材有较为全面的理解,以便于在教学和教材建设中参考借鉴,本文研究这些教材的历史发展与现状。概述美国静力学教材的起源与演变。选择有代表性的7本仍在使用的教材,考察这些教材的主要内容及其教学处理,分析这些教材的教学理念和特点。 相似文献
66.
Yazhen Wang Rifang Li Hongge Jia Guoxing Yang Yutao Di Chenxi Xu Liqun Ma Hui Zhang Yongli Zhou Yu Zang Shuangping Xu Zhaoyang Sun Liwu Zu Chenge Yue Tianyu Lan 《Chemical Papers》2018,72(11):2871-2877
A novel peroxy group-containing silane coupling agent was synthesized and anchored on the surface of titanium dioxide nanoparticles (nano-TiO2) to form an immobilized-initiator-modified nano-TiO2 species. In this study, the kinetic parameters of the peroxy group-containing silane were tested and assessed using DSC. The pre-exponential factor (Ad) was 8.973?×?108 and the activation energy (Ea) was 80.736 kJ mol?1. Moreover, the empirical Arrhenius equation was determined to be ln Kd?=???80.736/RT?+?ln(8.973?×?108). To obtain continuous polymers, acrylonitrile (AN) and methyl methacrylate (MMA) were polymerized using the novel peroxy group-containing silane and FeSO4 as an initiator system. The number average molecular weights (Mn of PAN?=?3×104 and Mn of PMMA?=?1.4?×?105) and polydispersity indexes (PDI of PAN?=?2.76 and PDI of PMMA?=?1.65) were determined by GPC. It was suggested that the redox initiation system can generate highly reactive species on the surfaces of inorganic nanoparticles. The nano-TiO2-grafted polymers were successfully obtained. 相似文献
67.
Qian Sun Xueying Song Li Gao Wei Chen Yamin Li Liqun Mao Jing-He Yang 《Chemical Papers》2018,72(9):2203-2214
The series of graphene materials and N-doped graphene materials were successfully synthesized and improved by high-temperature treatment with trace iron oxide. XRD, Raman, FT-IR, TEM and XPS were employed for these catalysts. The catalytic performance of these catalysts was investigated in the selective oxidation of ethylbenzene with tert-butyl hydroperoxide as oxidant. The impacts of temperature, mass of catalysts, reaction time and oxidants on the selective oxidation of ethylbenzene were also investigated. The N-doped graphene materials exhibit greatly remarkable catalytic performance than others. The conversion of ethylbenzene is more than 90% and the selectivity of acetophenone is more than 95% at 353 K. Graphene can be used as catalyst owing to its unique structures and chemical properties. The characterization tests show that the doping of N atoms can create more defects and more active sites in the N-doped graphene materials which could greatly improve the catalytic performance. Furthermore, such cost-effective graphene-based catalysts possess good stability and could be reused at least five times without remarkable loss of the catalytic activity. 相似文献
68.
Two-dimensional vibrational spectroscopy is applied to investigate the dilution process of 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim][BF4]) in water. With increasing water content in ionic liquid (IL)/water mixtures, the C-H stretching vibration of the imidazolium cation showed systematic blue-shifts, which reflect the weakening of the cohesion between the cation and anion of ILs. The two-dimensional IR results reveal that the ILs sense quite different environments during the whole dilution process. First, the three-dimensional network structure of pure ILs was destroyed gradually into ionic clusters, then the clusters were further dissociated into ionic pairs surrounded by water molecules, and finally the latter became the dominant form in bulk water. Within the concentration range we investigated (0.02相似文献
69.
In this work, the in vivo degradation and tissue compatibility of a novel class of inherently fluorescent copolyanhydrides, P(dCPS:SA), were investigated. It was found that the degradation of the copolyanhydrides increased with the increase of SA content in the copolymers. The in vivo degradation rate of the copolymers was slower than that studied in vitro. A surface erosion characteristic of the copolyanhydrides was revealed by SEM and fluorescent microscopy. Mild inflammatory reactions were observed on days 6 and 10 after implantation for all the studied copolymers. By the end of 30 d, there were almost no inflammation reactions taking place. 相似文献
70.
The stochastic nonlinear complementarity problem has been recently reformulated as an expected residual minimization problem which minimizes an expected residual function defined by an NCP function. In this work, we show that the expected residual function defined by the Fischer–Burmeister function is an function. 相似文献