纳米粒子在SiC／PTFE复合材料中分散三维仿真与分形表征

3D simulation and fractal characterization of nano particles dispersion in SiC/PTFE composites

为了从理论上探讨纳米粒子在基体材料中的分布规律,以纳米SiC质量分数为3%、5%、7%、9%的SiC/PTFE(聚四氟乙烯)复合材料为例,根据纳米SiC的半径(25nm)、密度(3.2g/cm3)、质量分数和基体材料的密度(2.2g/cm3),以10-12 g为质量单位、25nm∶1像素为比例尺,建立了纳米粒子在基体中均匀/偏聚分布的三维仿真模型,基于其盒维数定量表征了不同团聚/偏聚程度的纳米粒子的分散度,并进行了力学实验验证。结果表明:均匀分布下随着纳米SiC粒子半径的不断增加,或体积分数的不断减小,其盒维数也逐渐减小;当SiC粒子半径超过100nm时,不再具有分形特性。偏聚分布下随着纳米SiC粒子(半径为50nm)间距的不断加大,或体积分数的不断减小,或层状、线状、团状分布的依次改变,其盒维数也逐渐减小;相同体积分数下偏聚分布的盒维数低于均匀分布;当粒子间距超过450nm时,不再具有分形特性。均匀分布下纳米SiC/PTFE复合材料的力学性能测试结果与其三维仿真模型的盒维数线性相关(|R|>0.9)。盒维数可定量表征纳米粒子的分散度,并可用于预测纳米复合材料的宏观性能。

To study the distribution regularity of nano particles in matrix material theoretically, SiC/PTFE（Poly Tetra Fluoro Ethylene） composites with SiC mass fraction of 3%, 5%, 7% and 9% were used as examples. According to the radius （25 nm）, the density （3.2 g/cm3）, mass fraction of SiC particles and the density of PTFE matrix material（2.2 g/cm3 ）, 3D simulation models of uniform/deviation distributed nano particles in matrix material were established with 10^-12 g for quality unit and to 25 nm ： 1 pixel for the scale. Based on box dimensions, dispersions of various cluster/deviation nano particles were characterized quantitatively and verified by mechanical experiment. Experimental results indicate that the box dimension of SiC particles decreases gradually in uniform distribution with the continuous increment of their radius, or the decrement of their volume fractions, and fractal characteristics doesn＇t exist in the case of their radius above 100 nm. In another hand, the box dimension of SiC particles （50 nm for radius） decreases gradually in deviation distribution with the continuous increment of their span, or the decrement of their volume fractions, or varying of their distribution from layer and line to reunion, which is less than that in uniform distribution with the same volume fraction, and fractal characteristics doesn＇t exist in the case of their span beyond 450 nm. Linear correlations （IRIS0.9） are observed between test results of mechanical properties of SiC/PTFE composites and box dimensions of their 3D simulation models in uniform distribution. Dispersions of nano particles can be characterized quantitatively using box dimension, which can be used to predict macroscopic properties of composites.