Specific heat capacity of nanoporous Al₂O₃

¹ School of Electric Power Engineering, China University of Mining and Technology - Xuzhou 221116, PRC
² School of Mechanical Engineering, University of Science and Technology Beijing - 30 Xueyuan Road, Haidian District, 100083 Beijing, PRC
³ School of Materials Science and Engineering, University of Science and Technology Beijing - 30 Xueyuan Road, Haidian District, 100083 Beijing, PRC

^(a) yhfeng@me.ustb.edu.cn

Received: 24 April 2013
Accepted: 4 September 2013

Abstract

Based on Lindemann's criterion, a specific heat capacity model for nanoporous material was proposed by defining the surface-atom layer, to take the surface atoms and the volume atoms separately into account. The height of the surface-atom layer was determined from the experiment, and results show that only the first layer atoms on the surface should be separately considered for nanoporous Al₂O₃. The shape factor of the pore was also introduced in the model with values between 2 (for cylindrical pore) and 3 (for spherical pore) to characterize the morphology of the pore. It turns out experimentally that the specific heat capacity of the analyzed nanoporous Al₂O₃ is much larger than that of the bulk, which can be interpreted as due to the fact that the surface atom plays a more important role than the volume one. And the smaller the radius and/or the larger the porosity, which lead to a larger surface-volume ratio, the larger the specific heat capacity becomes. The nanoporous material could be a better heat storage medium than the corresponding bulk with a much lighter weight, smaller volume but higher heat storage capacity.