Gy. Sun et al., ADIABATIC CALORIMETRIC STUDY ON SHAPE-MEMORY ALLOYS - HEAT-CAPACITIESAND MARTENSITIC PHASE-TRANSFORMATION OF NI47TI44NB9 AND NB80TI14NI6 ALLOYS, Thermochimica acta, 266, 1995, pp. 231-238
A low-temperature precision adiabatic calorimeter for heat capacity me
asurements has been constructed, The heat capacities of a shape memory
alloy (Ni47Ti44Nb9) and a normal reference alloy (Nb80Ti14Ni6) have b
een measured in the temperature range from 60 to 350 K with this calor
imeter, The heat capacity curve of the normal alloy is smooth and cont
inuous over the whole temperature range, An anomaly, indicating the ma
rtensitic phase transformation, in the heat capacity curve of the shap
e memory alloy was observed at T = 234.0 +/- 0.5 K with a maximum, whe
re C-p,C-m = 34.86 +/- 0.21 J K-1 mol(-1). The molar enthalpy and mola
r entropy associated with the martensitic transformation were determin
ed as Delta(trs)H(m) degrees = 411.9 +/- 2.5 J mol(-1)and Delta(trs)S(
m) degrees = 1.76 +/- 0.01 J K-1 mol(-1), respectively.