新型纳米复合材料Cu/SiO_2的热特性及相变特性的分子动力学研究

Thermal properties and phase transition properties of Cu/SiO_2 nanocomposites

使用相变材料可有效地实现能量的高效和合理利用,从而有助于解决能源与环境问题。提出一种纳米结构复合相变材料,由填充纳米颗粒和纳米孔基材组装而成。主要采用分子动力学模拟,研究纳米金属颗粒、纳米孔基材和复合材料的相变行为及相变热特性,讨论不同尺寸或工况下它们的热特性变化,并进行比较。研究表明,铜纳米颗粒的熔点随尺寸的变大而逐渐升高,且熔点比块材低,比热容比块材高;SiO_2基材不存在固定熔点,而有一个跨度较大的熔化区,各工况下比热容比块料值明显偏小,比热容随其尺寸大小和温度升高而增大。研究表明,Cu/SiO_2复合相变材料的熔点高于Cu颗粒和纳米孔基材,Cu/SiO_2体系增强了结构稳定性。同时,填充Cu纳米颗粒能有效地改善纳米孔基材的储热特性。

Phase-change materials can be used to effectively realize the high efficiency and reasonable utilization of energy. We present a nanocomposite phase-change material,which is assembled mainly with filled nanoparticles and nanoporous substrates. Molecular dynamics method was used to simulate the phase-change behavior and thermal properties of metallic nanoparticles,nanoporous substrate,and composite. Thermal properties of metallic nanoparticles and nanoporous substrate were discussed under different sizes and conditions and compared with the thermal properties of composite materials. The research shows that the melting point of copper nanoparticlesincreases gradually with size and it is lower than that of bulk copper. Meanwhile,the heat capacity of copper nanoparticles is higher than that of bulk copper. Nanoporous SiO2 substrate has no fixed melting point but has a large span of the melting zone,and its heat capacity increases with size or temperature and is significantly smaller than that of bulk SiO2. The results show that the melting points of Cu/SiO2 composites are higher than those of Cu nanoparticles and substrate,which means that composites enhance the structural stability. Meanwhile,the filled Cu nanoparticles effectively improve the heat storage characteristics of the nanoporous substrate.