Fabrication of Permittivity graded materials applied for electric power apparatus

本研究取得的主要成果如下：1.采用离心法制备了大规模功能梯度材料，并以氧化铝/环氧树脂混合物为原料制备了氧化铝梯度环氧树脂。2.研究发现，球形填料比不规则填料具有更好的性能，因为球形填料增加了功能梯度材料的最大堆积分数，从而获得了较大的介电常数变化范围。3.在不同的离心时间和速度、氧化铝性质、混合物比例等条件下进行了制备。在此基础上，得到了制备条件与梯度之间的关系。4.测量了氧化铝填充环氧树脂的热扩散系数与氧化铝填充分数的函数关系。利用该关系计算了功能梯度材料的热电阻率。基于数值计算结果，得到了梯度…分布之间的关系利用自行研制的功能梯度材料柱对未来全固态变电站接头处将出现的固/固界面进行了模拟，并在不同界面条件下(如界面粗糙度、功能梯度材料界面的组合和均匀界面)对界面抗雷电冲击电压的特性进行了实验研究。根据实验结果发现，在这种界面表面引入功能梯度材料会导致耐电电压的增加。然而，表面的粗糙度对这种表面的电学性质有很大的影响。6.开发了一种新的模拟程序，可以模拟颗粒在离心过程中的运动。在该程序中，精确地模拟了颗粒直径的累积分布，并准确地考虑了阻力与堆积分数的关系。实验结果与数值计算结果的比较表明，对堆积分数梯度分布的估计具有较高的精度。最后，验证了该仿真程序的有效性。较少

Major results obtained from the present research project are as follows :1.An centrifugal method was employed to fabricate large-scaled functionally graded materials (FGMs), and alumina-graded epoxy resin was fabricated from alumina/epoxy mixtures.2.It is found that spherical fillers are preferable than irregular fillers, since the spherical fillers increase the maximum packing fraction attainable in FGMs, and accordingly, attain large range of the variation of dielectric constant.3.The fabrication was conducted under various conditions of centrifugal time and velocity, alumina properties, ratio of the mixture, and so on. Based on results, relationship between the fabrication conditions and the gradient is obtained.4.A coefficient of thermal diffusion of alumina filled epoxy resin was measured as a function of the alumina packing fraction. This relationship was used to calculate the thermal resistivity of FGM. Based on the numerical results, relationship between the profiles of gradien … More t and the thermal resistivity of FGM is quantitatively obtained.5.Solid/solid interface, which will appear in the joints of future all solid substation, was modeled by using the FGM columns fabricated by the authors, and properties of the interface against the lightning impulse voltage was experimentally examined under various interface conditions such as the roughness of the interface, combination of the FGM interface and the uniform interface. Based on the experimental results, it is found that the introduction of FGM on the surface of such interface causes increase of the electrical withstand voltage. However, the roughness of the surface has significant influence on the electrical properties of such surface.6.A novel simulation code, which can simulate movement of particles during the centrifugal process, was developed. In this code, the cumulative distribution of the particle diameters was precisely simulated and the dependency of the drag force on the packing fraction was exactly considered. Comparison between the experimental and numerical results shows that the estimation of profiles of gradient in the packing fraction was conducted with reasonable precision. In the end, the effectiveness of the present simulation code is verified. Less