纳米粒子的熔点与粒径的关系

推导纳米粒子的熔点与其粒径的定量关系，并从热力学的角度阐明纳米粒子烧结过程的实质及烧结温度与粒径的关系．利用热力学及表面化学的有关理论，虚拟固相和液相之间的相变过程，根据相平衡条件，将纳米粒子的熔点与粒径联系起来，并以金属铅(Pb)为例进行计算．结果表明，纳米粒子粒径越小，比表面自由能越高，其化学势则比相同条件下的块状固体高很多，导致其熔点和烧结温度大大低于同样材质的块状固体．以金属Pb为例，通过熔点和粒径之间的定量关系计算的结果与实验结果吻合．因此纳米粒子的熔点和烧结温度与其粒径有关，即粒子越小，熔点和烧结温度越低、

Nanoparticle Size and Melting Point Relationship

To deduce the quantitative relationship between the melting point of nanoparticles and their radius, and set forth the sintering processes of nano-systems and the qualitative relation between the sintering temperature and the radius of nanoparticles from a thermodynamics angle, the phase transition process between solid and liquid states has been proposed, and thermodynamics and surface chemistry theories and phase equilibrium conditions were used. The relationship was applicable to lead (Pb). The results show that owing to its small size and high special surface free energy, the chemical potential of a material in the form of nanoparticles was much higher than that of the bulk. As a result, the melting point of nanoparticles was depressed in comparison to that of the bulk crystals. The calculated results for metal lead were coincident with the experimental ones. So there is a relationship between the melting point and the sintering temperature of a nanoparticle and its radius. The smaller the nanoparticle radius, the lower the melting point and sintering temperature.