A MODEL FOR EXPLORING PARTICLE-SIZE AND TEMPERATURE-DEPENDENCE OF EXCESS HEAT-CAPACITIES OF NANOCRYSTALLINE SUBSTANCES

Einstein and Debye vibration modes are considered to be different in s urface atoms and in interior atoms of fine solid particles. A model is constructed to predict particle size and temperature dependence of ex cess heat capacities of nanocrystalline substances. Tt is shown that e xcess heat capacity is not proportional to specific surface area. Howe ver, when specific surface area is far less than a characteristic area of a sample, the specific excess heat capacity can be viewed as indep endent of particle size. Several types of temperature dependence of ex cess heat capacity are predicted, including monotonous increase with i ncrease in temperature, one-peak and two-peaks excess heat capacity vs , temperature curves. The proposed model has been used to fit experime ntal data of nanostructured silver anal rutile. (C) 1998 Acta Metallur gica Inc.