Specific Heat of Aerogels

The physical property specific heat is the measure of the amount of heat Q required to increase the temperature of a unit mass m of a substance by 1 K. One differentiates between specific heat under constant pressure, Cp, and at constant volume c. The following applies for specific heat under constant pressure  

The specific heat not only describes the capacity to store heat, but also influences the dynamics of heat transfer within aerogels according to the equation of heat transfer (23.1) and (23.4). The higher the specific heat, the slower the heat propagation within a material, if the density and the effective thermal conductivity remain constant. In the late eighties and early nineties several authors investigated the specific heat of silica aerogels in detail [9,51, 52, 54, 64-67]. The focus of their research work was the study of the density of vibrational states g(a ) correlated to the specific heat and the solid thermal conductivity by phonons  

Data for the specific heat of carbon aerogels in the temperature range from 300 to 1,800 K are provided by Wiener et al. [44]. The specific heat values are described by an empirical analytical equation  

For the determination of the thermal diffusivity the Laserflash method is applied [40]. 

Kistler, S.S., The Relation between Heat Conductivity and Stractuie in Silica Aerogel. J. Phys. Chem., 1935.39 

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Abstract This chapter provides an insight into the different aspects of heat transfer in aerogels and their thermal properties. In this context, the principal heat transfer mechanisms are discussed and illustrated by exemplary experimental results. Typical thermal conductivity values and radiative properties as well as their dependency on external conditions such as temperature or atmosphere are discussed for different classes of aerogels. The chapter concludes with a brief discussion about the specific heat of aerogels. 

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