Thermal diffusivity of binary mixture of n-tricosane and n-tetracosane by Fourier transform temperature wave analysis

The phase transitions of binary mixtures of n-tricosane (C23H48)/n-tetracosane (C24H50) are investigated by Fourier transform temperature wave analysis (FT-TWA) and differential scanning calorimetry (DSC). The phase diagram determined by both methods gives a good agreement. Thermal diffusivity shows an odd-even effect at the solid state, and the temperature dependence of thermal diffusivity of the mixture is classified into two types, odd-like type and even-like type, depending on the mixing ratio. The increase of thermal diffusivity in the rotator phase RI (orthorhombic rotator phase) prior to the phase transition to α-RII (rhombohedral rotator phase with hexagonal subcell) is found for odd number n-tricosane (C23H48). A detailed study of the rotator phase transition is shown by the measurement of thermal diffusivity.