The Standard Molar Enthalpies of Formation of Nano-ZnO Particles with Different Morphologies

Abstract

The thermodynamic properties of nano-ZnO particles with different morphologies were studied. First, based on the measurements of XRD and SEM, the morphologies of the five nano-ZnO products were determined as sheet, block, sieve, column, and rod, and their particle size was about 40 nm. Then, based on a designed thermodynamic cycle, the standard molar enthalpies of formationΔfHmӨof the nano-ZnO particles were determined by the RD496-2000 microcalorimeter, and they areΔfHmӨ(sheet) =(-337.43 ± 0.47) kJ·mol−1,ΔfHmӨ(block) =(-336.57 ± 0.43) kJ·mol−1,ΔfHmӨ(sieve) =(-337.04 ± 0.57) kJ·mol−1,ΔfHmӨ(column) =(-343.56 ± 0.39) kJ·mol−1, andΔfHmӨ(rod) =(-341.43 ± 0.41) kJ·mol−1. The results show that the bigger difference of the morphologies of nano-ZnO, the bigger difference of the standard molar enthalpies of formation.