Effect of nanoparticle size on the thermal decomposition thermodynamics in theory and experiment

Abstract

Thermal decomposition reactions of nanoparticles are often concerned in the processes of preparation and application of nanomaterials. However, it is the nanoparticle size that leads to great difference in thermal decomposition thermodynamics between nanoparticles and corresponding bulk substances. In this paper, the decomposition model of a nanoparticle was established to investigate the theoretical size-dependent thermodynamics in nanoscale decomposition system, and the theoretical relations of the thermodynamic properties with particle size were, respectively, derived. In experiment, the decomposition thermodynamics of nanosized zinc carbonate particles was studied, and the influence regularities of particle size on thermodynamic quantities were obtained. The experimental results are in accordance with the corresponding theoretical thermodynamic relations. These results show that there is a striking effect of particle size on the decomposition thermodynamics. The thermodynamic properties decrease with the decrease of particle size, whereas the equilibrium constant and the molar heat capacity of reaction at constant volume increase; logarithm of the equilibrium constant, the heat capacity of reaction and the thermodynamic properties are linearly related to reciprocal of the particle diameter, respectively. In addition, the temperature coefficient of the heat capacity of reaction also has strong size dependence; that is, the temperature coefficient becomes smaller with the particle size decreasing.