纳米氧化锌的低温热容和热力学性质

用扫描电子显微镜(SEM)测定了纳米氧化锌试样的粒径, SEM结果表明ZnO试样平均粒径为30 nm. 在83～350 K温区, 用精密低温绝热量热计测定了ZnO的等压摩尔热容, 拟合出其等压摩尔热容与热力学温度的函数关系式: C_p＝－3.249＋0.2400T－3.413×10^－4T ²＋4.485×10^－7T ³.根据热容与热力学函数关系, 计算了以298.15 K为基准的纳米ZnO的热力学函数, 并与粗晶ZnO和18 nm ZnO热容文献报导值进行了比较, 从能量角度分析了不同粒径ZnO热容曲线差别产生的原因.

Low-temperature Heat Capacity and Thermodynamic Functions of Nano ZnO

The size of nano ZnO powders was determined to be 30 nm in diameter by SEM. The isobaric molar heat capacity C_p of the nano ZnO was measured with high precision adiabatic low-temperature calorimeter in temperature range from 83 K to 350 K. The relationship of C_p with temperature T was established as:C_p＝－3.249＋0.2400T－3.413×10^－4T ²＋4.485×10^－7T ³.The thermodynamic functions of the nano ZnO, relative to the standard temperature of 298.15 K, were derived based on the heat capacity data through thermodynamic relationship. The measured C_p values were compared with those of coarse crystal and 18 nm ZnO powders cited from literature and the difference between the C_p curves was analyzed.