粒径对Ni/硅橡胶复合材料压敏性及介电性质的影响

采用不同粒径的Ni粉与硅橡胶(110型)按质量比2.4∶1.0制成Ni/硅橡胶复合材料, 分别测量了其压敏导电性及介电性质, 并结合扫描电镜照片对其微观导电机制进行了分析。结果表明随着填料Ni粉粒径的减小, Ni/硅橡胶复合材料的直流电阻率对外加压强更加敏感: 在低压强下, 粒径为74、48和18 μm的样品的电阻率随压强的变化率分别为1.73×104、2.59×104和3.71×10 4 Ω·m/kPa。样品直流电阻率陡降的区域随粒径的减小向压强较小的方向移动, 显示出复合材料的渗流阈值与填充粒子的粒径有关: 粒径越小, 渗流阈值也越小。Ni/硅橡胶复合材料的交流电导率、介电常数、介电损耗均随填料Ni粉粒径的减小而变大: Ni粉粒径为18 μm的Ni/硅橡胶复合材料的电导率约为10-2 S·m-1, 比74 μm粒径样品的电导率(约10-7 S·m-1)提高了5个数量级; 对应的介电常数由约102提高到约103。改变填料Ni粉粒径可以有效地调节复合材料的弹性和压敏、电输运特性。 

Influence of Ni particle size on the piezoresistivity and dielectric properties of Ni/silicone rubber composite

Ni/silicone rubber composites with nickel powders of different particle sizes were prepared at a filler/ silicone rubber mass ratio of 2.4∶1.0. The piezoresistivity and the dielectric properties of the composite samples at room temperature were measured. The mechanism of electric conduction is discussed together with the SEM images of the samples. The results show that piezoresistivity of Ni/silicone rubber composite is enhanced by reducing the filler particle size: at low pressures, the pressure derivative of resistivity, of samples prepared with Ni powders of particle size 74, 48 and 18 μm is 1.73×104、2.59×104 and 3.71×10 4 Ω·m/kPa respectively. The sharp drop in resistivity shifts to the low pressure end as the filler particle size decreases, suggesting that the percolation threshold of Ni/silicone rubber composites decreases with reduced filler particle size. AC conductivity, dielectric constant and dielectric loss of Ni/silicone rubber composites all increase with the decrease of particle size: the conductivity of the sample with filler particle diameter 18 μm reaches about 10-2 S·m-1, which is five orders of magnitude greater than that of the sample with filler particle diameter 74 μm(about 10-7 S·m-1), and the corresponding dielectric constant is also increased from about 102 to about 103. Elasticity, piezoresistivity, and electronic transport properties of the composite can be adjusted by changing the filler particle size.