Size Dependence Of Melting Point Research Articles

Melting and thermodynamic properties of nanoscale binary chloride salt as high-temperature energy storage material

Phase change heat transfer in nanoporous shape-stabilised phase change materials (ss-PCMs) is of great importance for the efficient utilization of novel energy storage materials. However, the lack of thermodynamic properties hinders the study on phase change heat transfer. In this paper, we selected the binary chloride salts (NaCl–KCl), the promising high-temperature energy storage materials for concentrating solar power, and computed their melting point using the molecular dynamics method. This study not only provides the most fundamental thermal information for the study on phase change heat transfer but reveals the mechanism of the size dependence of melting point from the aspect of the atoms. It is found that the ions in small nanoclusters vibrate more intensely and the crystal structure is easier to be destroyed, leading to lower melting point. The ion self-diffusion coefficient is also computed and analysed from the local microstructure; and it is found that the coefficient is not affected remarkably by the component and the size of nanoclusters.

Molecular dynamics studies of the size and temperature dependence of the kinetics of freezing of Fe nanoparticles

Molecular dynamics (MD) computer simulations have been carried out and a novel modified technique of Voronoi polyhedra has been performed to identify solid-like particles in a molten nanoparticle. This technique works quite well in analyzing the effects of particle size on nucleation rates of iron nanoparticles in the temperature range of 750–1160 K. Nanoparticles with 1436 and 2133 Fe atoms have been examined and the results are compared with those obtained earlier with Fe331 nanoparticles. Nucleation rates for freezing obtained from MD simulations for Fe2133 vary from 8.8×1034 m3/s to 4.1×1035 m3/s at over a temperature range from 1160 K to 900 K, Rates for. Fe1436 and Fe331 are somewhat higher. Nucleation rates increase as supercooling deepens until the viscosity of the liquid increases sharply enough to slow down the rate. Bt applying classical nucleation theory, the interfacial free energy between solid and liquid cab be estimated From this and other thermodynamic information can be derived a theoretical expression for the size-dependence of the heat of fusion of nanoparticles. Results agreed quite well with those observed in our MD observations. An earlier expression in the literature for this size-dependence was shown to be incorrect. The size dependence of melting point is discussed.

Size dependence and phase transition during melting of fcc-Fe nanoparticles: A molecular dynamics simulation

Continuous melting and cooling of isolated fcc-Fe nanoparticles with 59–9577 atoms are studied by Molecular Dynamics (MD) simulation with Sutton–Chen potential. An energy minimization process was employed to obtain the stable solid structure for simulation of melting. The energy-minimized nanoparticles show lower potential energy and radius compared with the counterparts without energy minimizing. The size dependence of melting point shows perfect linear variation with N−1/3 for particles above a limit of 113 atoms. The bulk melting temperature of 1833.3K, which is close to the experimental data (1811K for bcc and 1800.8K for fcc), has been predicted by a linear relationship. Two different inner structures, including five-fold twinning and lamellar structures, have been found to be the initial stable configurations prior to melting, and both surface premelting and internal defects were verified as the origins for melting behavior.

Size dependence of melting point in small particles

Size dependence of melting point in small particles

Size dependence of melting point in small particles

Size dependence of melting point in small particles