【作者】 韩财飞；

【导师】 顾嫒娟；

【作者基本信息】 苏州大学 ， 材料学， 2010， 硕士

【摘要】 高介电常数(高K值)聚合物基电介质复合材料在电子和电机等行业中有着极为重要的运用,因此提高电介质材料的介电常数非常有意义。碳纳米管(CNTs)具有较大的长径比和较高的电导率,使其成为比较合适的高介电复合材料的填料。尽管在过去的一段时间,人们对CNTs填充复合材料的介电行为和渗流现象进行了一定的研究,然而对于CNTs在交变电场下的极化规律,CNTs与基体树脂不同的界面、更高的频率(GHz)以及变化温度的条件下复合材料介电性能和渗流现象的机理研究仍然不清楚。本文主要研究了多壁碳纳米管(MWCNTs)/氰酸酯(CE)高介电纳米复合材料的制备方法及其性能。为了提高MWCNTs与CE的相容性,改善MWCNTs与CE的界面性能,采用Fenton试剂对MWCNTs进行表面改性,利用红外光谱、拉曼光谱等对改性后的碳纳米管(MWCNTs-OH)进行表征,结果表明MWCNTs表面接枝了大量的羟基,然后采用原位聚合法分别制备出MWCNTs/CE和MWCNTs-OH/CE高介电纳米复合材料。对MWCNTs/CE和MWCNTs-OH/CE复合材料的热性能进行研究,结果表明1wt%MWCNTs加入CE树脂中,降低了树脂的Tg和耐热性能,而加入1wt%MWCNTs -OH后,材料的Tg保持不变,并显著地提高了材料的热稳定性。对MWCNTs/CE和MWCNTs-OH/CE复合材料的介电性能进行研究,结果表明两种MWCNTs复合材料的渗流阈值大致相等,大约都为0.62wt%。复合材料达到渗流阈值时,复合材料的介电常数迅速增大。1KHz下MWCNTs/CE复合材料最大介电常数为114,而MWCNTs-OH/CE复合材料最大介电常数为165,填料与基体不同的界面性能对复合材料的介电常数影响显著。复合材料发生渗流效应时,不但介电常数迅速增大,介电损耗也呈非线性的迅速增大。10-3.25×109Hz、MWCNTs含量低于渗流阈值时,复合材料的介电常数和介电损耗随频率的变化很小,然而当MWCNTs含量超过渗流阈值时,介电常数和介电损耗随频率的增大迅速降低。1KHz、-50-200℃范围内,MWCNTs含量低于渗流阈值时,复合材料的介电常数与介电损耗几乎不随温度的变化而变化,当MWCNTs含量超过渗流阈值时,复合材料的介电常数随着温度的升高而下降,介电损耗随着温度升高而升高。更多还原

【Abstract】 High dielectric constant (high K)polymer matrx composites have a significant future in electron and electric industry, so it is important to enhance the dielectric constant. Carbon nanotubes (CNTs) with large aspect ration and high electric conducitivity have been pursued with the hope of delivering CNTs properties to a processable and synergistic host. In the past years, dielectric performance and percolation effect were studied, but the law of polarization under the alternating current field, the mechanism of dielectric performance and percolation effect under the different interface of CNTs and CE matrix, higher frequency (GHz), changed temperature conditions remains unclear.In this thesis, the preparation and properties of multi-walled carbon nanotubes/ cyanate ester (MWCNTs/CE) nanocomposites were studied. In order to enhance the compatibility and improve the property of interface between the filler and the matrix resin, MWCNTs were modified by Fenton reagent, the corresponding modified MWCNTs coded as MWCNTs-OH. MWCNTs-OH were characterized by Fourier transform infrared spectrum(FTIR), Raman spectrum(RM), etc. The results indicated that a large number of hydroxyl were grafted on the surface of MWCNTs. And then, MWCNTs/CE and MWCNTs-OH/CE nanocomposites were prepared by in-situ polymerization.The thermal properties of MWCNTs/CE and MWCNTs-OH/CE composites were studied. The results showed that the addition of 1wt% MWCNTs into CE decreased the glass transition temperature (Tg) and thermal stability, while the incorporation of 1wt% MWCNTs-OH did not decline Tg and significantly improved the thermal stability of CE. The dielectric properties of MWCNTs/CE and MWCNTs-OH/CE composites were studied. The results showed that the percolation thresholds of the two kinds of composites were approximately equal, about 0.62wt%. The dielectric constants increased remarkably after the percolation threshold. However, the largest dielectric constant of the two kinds of composites was different. 1 KHz, the largest dielectric constant of MWCNTs/CE composites was 114 with 1wt% MWCNTs, while it reached 165 for MWCNTs-OH/CE composites with about 1.5wt% MWCNTs-OH. The different interface of fillers and matrix made great influence on the dielectric constants of composites. The dielectric loss of both kinds of composites increased non-linear as the dielectric constant when the percolation occurred. 101-3.25×109Hz, when the content of MWCNTs was lower than the percolation threshold, the dielectric constants and dielectric loss of both kinds of composites changed little with the increase of the test frequency, however, when the content of MWCNTs was more than the percolation threshold, the dielectric constants and dielectric loss of both kinds of composite decreased quickly with the increase of the test frequency. 1KHz, -50-200℃, the content of CNTs was lower than the percolation threshold, the dielectric constants and dielectric loss were independence on temperature; The content of CNTs was more than the percolation threshold, the dielectric constants decreased with increasing temperature while the dielectric loss increased with increasing temperature.更多还原