微波加热制备SiC/Mullite球体的工艺和性能

以粉煤灰微珠和炭黑为原料，通过微波加热碳热还原法原位合成了SiC/Mullite球体。利用X射线衍射(XRD)，场发射扫描电子显微镜(FESEM)对产物进行了物相和结构表征。研究表明：在1100 ~1300 ℃之间，微珠表面的SiO2通过固(SiO2)–固(C)反应机理而形成SiC，而内部Mullite依然维持微珠球形骨架，从而形成SiC/Mullite球体。温度高于1300 ℃时，SiC通过固–液–气机理定向生长为晶须且Mullite亦参与反应，从而使粉煤灰微珠失去其球形形貌。本试验的最佳工艺条件为n(C): n(SiO2)=4.2，温度1200 ℃下恒温1 h

Synthesis and Characterization of SiC/Mullite Spheres by Microwave Heating

Fly ash microspheres and carbon black were taken as raw materials to prepare SiC/Mullite microspheres by microwave heating carbon thermal reduction. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were applied to characterize the phase composition and microstructure of SiC/Mullite spheres.The phase composition and the structure were characterized by XRD and FESEM. The results show that the reaction mechanism mainly associates with solid-solid reaction between C(s) and SiO2(s) on the surface of fly ash microspheres with its spherical shape unchanging when the temperature is between 1100-1300 oC. When the temperature is higher than 1300 oC, SiC has easier orientation growth into whisker through VLS mechanism for the presence of liquid phase. Mullite is involved in the reaction; therefore, fly ash microspheres cannot maintain its spherical shape. The optimum conditions of our experiments are n(C):n(SiO2)=4.2, 1200 oC and 1 h