Analysis of the lumped τ2 effect in relaxation calorimetry

Abstract

In thermal relaxation calorimetry, the heat capacity can be calculated from the time constant τ1=Cp/Kb of the exponential decay of the cooling curve. If the thermal bond between the sample and sample holder is poor, the cooling curve is described by T-T 0=A1 exp(-t/τ1)+A2 exp(-t/τ2). Analysis shows that the heat capacity of the sample plus addenda is Cp=Kb (A1τ 1+A2τ2)/(A1+A2). For most cases, a good approximation is given by Cp=Kb (A 1τ1/ΔT), which does not require the measurement of A2 or τ2. An expression is presented for calculating the conductance of the thermal bond of the sample to the substrate.