金属纳米粒子在聚合物中的磁致排列──实验及分子动力学模拟

Magnetic-field-induced Alignment of Metal Nanoparticles in Polymer──Experiments and Molecular Dynamics Simulation

用磁场控制碳包镍纳米颗粒在环氧树脂中的排列, 制备了具有优异电学性能的一维有序的纳米复合材料. 在添加质量分数为3%～10%的镍纳米颗粒时, 导电率提高了3个数量级, 介电常数增大了2～3倍. 对纳米颗粒的磁致排列进行了分子模拟, 结果表明, 偶极强相互作用是导致纳米粒子排列的主要原因, 排列过程经历了聚合、成链和粗化等阶段, 成链的时间尺度在秒数量级. 模拟结构与实验观察结果基本一致.

A one-dimensional ordered nanocomposite was fabricated by utilizing magnetic field to control the alignment of carbon-coated nickel（ Ni@ C） nanoparticles in epoxy resin. It exhibits an excellent improvement in electrical conductance and dielectric constant. With the loading mass fraction of 3%-10%, the resistivity of resulting composite decreases by 3 orders of magnitude with respect to unaligned composite. A molecular dynamics model was designed to simulate the structure evolution of nanoparticles in resin curing. The simulated results show that the alignment of nanoparticles arises from the dominant magnetic dipolar interaction, and experiences a shift from aggregation to chaining then to chain thickening; the time scale for chain growth is the order of seconds, there is nearly not dynamics barrier for the alignment of Ni@ C nanoparticles in epoxy resin; the simulated structure agrees basically with those observed in experiments.