LOW TEMPERATURE HEAT CAPACITY AND THERMAL STABILITY OF NANOCRYSTALLINE IRON

The sample of nanocrystalline iron with the average grain size of 87nm was prepared by thermal plasma technique, and characterized by XRD and SEM. Measurement of low temperature heat capacity of the nano-Fe has been performed in the temperature range of 79-371K with an automated adiabatic calorimeter. Enhanced heat capacities varying from 8% to 14% were observed. The differential scanning calorimetric measurement showed one broad exothermic regime from 400K to 700K corresponding to the enthalpy releasing. due to the contribution of nonequibrium lattice defects. An endothermic peak at 850K due to a γ→α+γ phase transition of nc-Fe was observed.