摘要
用热重法测定了不同气氛下锌蒸气的氧化动力学曲线 ,用扫描电镜跟踪观察分析了产物的结晶形貌 ,结果表明 ,氧化动力学遵守直线规律时 ,产物是无定形、颗粒状和单针状的 Zn O;氧化动力学为抛物线规律时 ,产物是四针状或多针状的 Zn O.动力学转变规律的原因是锌蒸气中气态锌原子与凝聚生成的锌液滴之间存在动态平衡 ,气态锌原子的氧化过程遵守直线规律 ;而锌液滴的氧化过程分为两个阶段 ,分别受收缩球状界面反应模型 R3和三维扩散模型 D4 动力学控制 ,表观活化能分别为 1 0 6.3～ 1 0 8.2和 1 1 4.2～ 1 1 7.3 k J/mol;扩散过程实际上是锌原子通过氧化膜层由里向外扩散 ,扩散系数 D=2 .46～ 9.70× 1 0 - 5cm2
The kinetics of oxidizing zinc vapor in different atmospheres at an elevated temperature was determined by thermogravimetric analysis and the morphologies of products were examined by scanning electron microscopy. The results showed that the product morphologies were of amorphous, granular, needle-like ZnO when the kinetics progressed linearly and the morphologies of tetrapod and/or multipod-like ZnO appeared as the kinetics proceeded parabolically. The cause of the kinetics change was the coexistence of atomized zinc and tiny zinc droplets formed in zinc vapor under proper conditions. The kinetics advanced linearly as the atomized zinc was oxidized while the kinetics followed the interface reaction R_3 and Ginstling-Brounstein D_4 model with apparent activation energy of 106.3_108.2 kJ/mol and 114.2_117.3 kJ/mol respectively in the early and later stages of the zinc droplets oxidation. The oxidation process of the tiny zinc droplets is controlled by the outward diffusion of Zn through the oxidation scale and the diffusion coefficient D=2.46×10 -5_9.70×10 -5 cm2/s.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2005年第2期213-217,共5页
Chemical Journal of Chinese Universities
基金
国家自然科学基金 (批准号 :5 0 2 3 40 10 )资助
关键词
锌蒸气
锌液滴
氧化行为
氧化锌结晶形貌
Zinc vapor
Zinc droplets
Oxidation behavior
ZnO crystalline morphologies
