MoO₂-Mo系热力学性质的气态平衡法研究

来源期刊：中南大学学报(自然科学版)1982年第4期

论文作者：方正 陈新民

文章页码：1 - 10

关键词：热力学性质； 平衡法； 平衡常数； 氧化物； 热力学稳定性； 热力学稳定相； 热扩散； 混合气体； 平衡数据； 平衡实验

摘    要：本文使用自行设计的热重装置对MoO₂-Mo系中间氧化物热力学稳定性及金属-氧化物平衡作了H₂O/H₂气氛下气态平衡法的研究。在P_H2O/P_H2从0.123到0.507,温度由625至912℃范围内直接测定了反应1/2MoO₂+H₂=1/2Mo+H₂O（g）的平衡常数。平衡常数K_p与绝对温度T之间的关系可表达为方程:lgK_p=1.612（2257.7/T）。实验表明,Mo₃O,MoO和Mo₂O₃等中间氧化物在本研究的温度和氧压范围内不能作为热力学稳定相存在。

Abstract:

A study of thermodynamic stability for the intermediate oxides and theequilibria between metal-oxide in the system MoO₂-Mo was made with H₂O/H₂gas equilibration method using specially designed thermogravimetrical appa-ratus.

The equilibrium constants of the reaction

（1/2）MoO₂+ H₂=（1/2）Mo + H₂O （g）

were measured at the P_H2O/P_H2 ratios between 0.123 and 0.507 and in the tem- perature range from 625 to 912℃ The results may be summarized by thefollowing equation

lgk_p= 1.612-（2257.7/T）

The standard enthalpy of formation and absolute entropy of MoO₂ at298.15k were calculated as follows:

^f△H_298.15⁰ = - 141.86±0.3 kcal./mole

S_298.15⁰= 11.18±0.2 cal./k.mole

The standard molar free energy of formation of MoO₂ is given by^f△G_T⁰= - 142740 + 53.644T - 1.08TlnT - 1.825×10^-3T² + 0.595×10⁵T^-1（cal./mole） between 298 and 2000k.

This study indicates that the controversial Mo₃O, MoO and Mo₂O₃ report-ed cannot exist as stable phases in the range of the present experimentalemperatures and partial pressures of oxygen.