炭黑/聚合物复合材料的研究进展

综述了炭黑/聚合物复合材料的研究进展。该类复合材料主要是通过共混、接枝、沉积、聚合制备的。讨论了聚合物结构、分子量及表面张力对炭黑填充的聚合物及共混物的导电性和物理性质的影响,以及用不同聚合方法制备炭黑/聚合物复合材料。着重讨论了如何获得低渗流阈的炭黑填充的导电复合材料及制备聚合物为壳,炭黑为核的核壳材料。

双交联体系互穿聚合物网络对石墨烯/乙烯-醋酸乙烯酯共聚物/高密度聚乙烯复合材料抗静电性能的影响

以高密度聚乙烯(HDPE)、乙烯-醋酸乙烯酯共聚物(EVA)为基体材料,石墨烯为导电填料,2,5-二甲基-2,5-双(叔丁基过氧基)己烷(DBPH)、三烯丙基异氰脲酸酯(TAIC)为交联剂,通过物理-化学方法在2种交联剂的协同作用下制备了具有互穿聚合物网络(IPN)结构的石墨烯/EVA/HDPE复合材料。实验结果表明,所用2种交联剂的协同作用能使复合材料的交联度达到54.3%。扫描电镜图中可以观察到EVA和HDPE形成的IPN结构可以促使石墨烯在复合材料基体中形成较完善的网络结构。实验结果还表明网络结构能在复合材料达到抗静电性能标准的情况下,很大程度上减少了石墨烯在EVA/HDPE基体中的添加量。当复合材料的交联度为40%~50%时,会出现类渗流阈现象,石墨烯的质量分数为2%时,复合材料的拉伸强度达到28.1 MPa,体积电阻率达到10~8Ω·cm。

Effective thermal and electrical conductivity of graphite nanoplatelet composites

The relationship between the thermal/electrical conductivity enhancement in graphite nanoplatelets （GNPs） composites and the properties of filling graphite nanoplatelets is studied. The effective thermal and electrical conductivity enhancements of GNP-oil nanofluids and GNP-polyimide composites are measured. By taking into account the particle shape, the volume fraction, the thermal conductivity of filling particles and the base fluids, the thermal and electrical conductivity enhancements of GNP nanofluids are theoretically predicted by the generalized effective medium theory. Both the nonlinear dependence of effective thermal conductivity on the GNP volume fraction in nanofhiids and the very low percolation threshold for GNP-polyimide composites are well predicted. The theoretical predications are found to be in reasonably good agreement with the experimental data. The generalized effective medium theory can be used for predicting the thermal and electrical properties of GNP composites and it is still available for most of the thermal/electrical modifications in two-phase composites.

Enhanced dielectric permittivity of graphite oxide/polyimide composite films

Graphite oxide(GO) was prepared by the pressurized oxidation method and incorporated into polyimide(PI) matrix to fabricate high-k composite films by in-situ polymerization and subsequent thermal treatment. The results show that the as-prepared GO had good dispersion and compatibility in PI matrix due to the introduction of abundant oxygen-containing functional groups during the oxidation. The residual graphitic domains and the thermal treatment induced reduction of GO further enhanced the dielectric permittivity of the resulting GO–PI composites. The dielectric permittivity of the GO–PI composites exhibited a typical percolation behavior with a percolation threshold of 0.0347 of volume ratio and a critical exponent of 0.837. Near the percolation threshold, the dielectric permittivity of the GO–PI composite increased to 108 at 10~2 Hz and was 26 times that of the pure PI.

磁性纳米薄膜的霍尔效应研究

霍尔效应是磁性纳米薄膜特有的性能,本文主要探究了其产生机理,分析了近年来该领域的研究进展和应用前景,并对研发应用中存在的问题做了总结。

Shift in the percolation threshold of compressed composites—A 3D Monte Carlo simulation

The shift in the percolation threshold of compressed composites was studied by a 3D continuum percolation model. A Monte Carlo (MC) method was employed in the simulations. The percolation threshold was found to rise with the compression strain, which captures the basic trend in compression-induced conductivity variation from the experiments. Both fiber bending and texture formation contribute to the percolation threshold. The results suggest that fillers with a high aspect ratio are more desirable for sensor and electrical switch applications.

EPIDEMICS ON SMALL WORLDS OF TREE-BASED WIRELESS SENSOR NETWORKS

Due to link additions, small world phenomena exist in tree-based wireless sensor networks. Epidemics on small worlds of tree-based networks are studied, and the epidemic threshold at which the outbreak of the epideIrlic occurs is calculated. Epidemiological processes are analyzed when the infection probability is larger than the percolation threshold. Although different epidemiological processes occur on the underlying tree topology, the number of infected nodes increases exponentially as the infection spreads. The uniform immunization procedure is conducted in the homogeneous small-world network. The infection still extends exponentially Mthough the immunization effectively reduces the prevalence speed.