Madan Singh

Effects of size and shape on the specific heat, melting entropy and enthalpy of nanomaterials

Abstract A simple theory is proposed to study the size- and shape-dependent specific heat, melting entropy and enthalpy of nanomaterials. The particle size and shape are demonstrated to affect the specific heat, melting entropy and enthalpy of nanomaterials. The model is applied to Ag, Cu, In, Se, Au and Al nanomaterials in spherical, nanowire and nanofilms shapes. The specific heat is observed to increase with the decrease in particle size, whereas the melting entropy and enthalpy decrease as the particle size decreases. Our theoretical predictions agree well with available experimental and computer simulation results, thereby supporting the validity of formulation developed.

Grain-size effects on the thermal conductivity of nanosolids

Abstract A theoretical model has been developed for the calculation of the thermal conductivity of nanomaterials with different shapes, such as spherical nanosolids, nanowires and nanofilms, based on size-dependent atomic cohesive energy. Thermal conductivity of nanosolids with different shapes decreased as the grain size decreased. The obtained results are compared with the available experimental data. A close agreement between theory and experiment confirmed the validity of the discussed method.

Modeling shape and size dependence of thermal expansion and Debye temperature of nanocrystals

A simple theoretical model is developed to explore the size and shape dependence of thermal expansion and Debye temperature of nanomaterials. The model theory is based on cohesive energy and surface area change of the nanocrystals compared to the bulk crystals. It is found that the Debye temperature decreases with the decrease in particle size whereas, the thermal expansion increases as the particle size decreases. The present modelling results and predictions are very consistent with the available experiment results, implying that the model could be expected to be a general approach to understand the thermodynamic properties of nanomaterials. Copyright