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通过分子动力学模拟对聚乙烯/银纳米颗粒复合物的结构、极化率和红外光谱、热力学性质、力学特性进行计算,分析其随模拟温度和银颗粒尺寸的变化规律.模拟结果表明:聚乙烯/银纳米颗粒复合物为各向同性的无定形结构,温度升高可提高银纳米颗粒的分散均匀性;银纳米颗粒表面多个原子层呈现无定形状态,并在银颗粒和聚乙烯基体的界面形成电极化层,界面区域随颗粒尺寸和温度的增加分别减小和增加;与聚乙烯体系相比,聚乙烯/银纳米颗粒复合物的极化率高很多,且随温度的升高和银颗粒尺寸的减小而增大;银颗粒尺寸直接影响界面电偶极矩的强度和振动频率,红外光谱峰强度和峰位随颗粒尺寸发生变化;聚乙烯/银纳米颗粒复合物具有比聚乙烯体系更高的等容热容和与聚乙烯体系相反的负值热压力系数,热容随颗粒尺寸的变化较小,但随温度的升高而明显减小,具有显著的温度效应;热压力系数随温度的变化较小,但随颗粒尺寸的增加而减小,具有明显的尺度效应,温度稳定性更好;聚乙烯/银纳米颗粒复合物的力学特性表现出各向同性材料的弹性常数张量,具有比聚乙烯体系更高的杨氏模量和泊松比,并且都随温度的升高和银颗粒尺寸的增大而减小,加入银纳米颗粒可有效改善聚乙烯的力学性质.
The structure, polarizability and infrared spectra, thermodynamic properties and mechanical properties of the polyethylene / silver nanoparticle composites were calculated by molecular dynamics simulation, and their variations with simulated temperature and silver particle size were analyzed. The simulation results showed that the poly Ethylene / silver nanoparticle composites are isotropic amorphous structure, the temperature increase can improve the dispersion uniformity of silver nanoparticles; silver nanoparticles on the surface of multiple atomic layers appear in an amorphous state, and silver particles and polyethylene matrix The interface area decreases and increases with the increase of particle size and temperature, respectively. Compared with the polyethylene system, the polarizability of polyethylene / silver nanoparticle composites is much higher, and with the increase of temperature And the silver particle size decreases. The silver particle size directly affects the strength and vibrational frequency of the dipole moment in the interface. The peak intensity and the peak position of the infrared spectrum change with the particle size. The polyethylene / silver nanoparticle composite has the ratio The higher isocannatic heat capacity of polyethylene system and the negative heat pressure coefficient opposite to that of polyethylene system, the smaller the heat capacity changes with the particle size, but obviously decreases with the increase of temperature Small, with a significant temperature effect; thermal pressure coefficient with temperature changes smaller, but with the increase of particle size decreases, with obvious scale effect, better temperature stability; polyethylene / silver nanoparticle complex mechanics Properties exhibit elastic constant tensors of isotropic materials with higher Young’s modulus and poisson’s ratio than polyethylene systems, and both decrease with increasing temperature and silver particle size, adding silver nano Particles can effectively improve the mechanical properties of polyethylene.