微波法制备纳米铁酸锌及其晶粒生长动力学

纳米铁酸锌广泛应用于催化和材料领域,为了避免传统焙烧法高耗能的缺点,本实验选用高效微波法制备纳米铁酸锌,并与常规焙烧进行对比,研究了铁酸锌晶粒生长动力学。采用FTIR、XRD和SEM对样品进行表征。结果表明,相同焙烧温度和焙烧时间下,微波法制备的铁酸锌比常规制备的样品结晶度高,颗粒大小更均匀。通过谢乐公式计算不同温度下铁酸锌粒径得出,焙烧温度低于500℃时,焙烧方式对铁酸锌粒径影响较大;纳米铁酸锌晶粒生长动力学研究显示,微波焙烧时晶粒的平均生长指数为9.66,低于常规焙烧生长指数(10.6),表明微波焙烧时晶粒的平均生长速率较高,有利于晶粒生长;同时,微波晶粒生长平均活化能为122.1kJ/mol,远低于常规焙烧平均活化能(179.4kJ/mol),说明微波可以降低晶粒生长活化能,且微波的“非热效应”影响晶粒的生长。

Microwave sintering of nano-grained zinc ferrite and its grain growth kinetics

The nano-grained zinc ferrite was prepared by high-efficiency microwave sintering,which eliminated the drawback of high energy consumption in traditional sintering. The grain growth kinetics of zinc ferrite by both microwave and traditional sintering were studied. The Fourier transforms infrared spectra,X-ray diffraction and scanning electron microscope were used to characterize the microstructure of the zinc ferrite. Our results showed that zinc ferrite samples obtained by microwave sintering were of better-crystallized phase and more homogeneous grain size distribution than those by the traditional sintering. The particle size of zinc ferrite was calculated by the Scherrer equation. Calcinations method has a significant impact on the grain size when the calcinations temperature is lower than 500℃. The kinetic studies of grain growth showed that the average exponent value of grain growth was 9.66 for the nano-grained zinc ferrite sintered by microwave,lower than that of the traditional sintered samples. It indicates that microwave can accelerate the reaction distinctively. The average activation energy of microwave and traditional sintered zinc ferrite are 122.1kJ/mol and 179.4 kJ/mol,respectively. It reveals that microwave can reduce activation energy of the grain growth and the non-thermal effect of microwave has an effect on the grain growth.