溶胶-凝胶法制备氧化铝纤维的组织结构与晶化动力学

Microstructure and crystallization kinetics of alumina fibers prepared by sol-gel method

以异丙醇铝和九水硝酸铝为铝源,去离子水为溶剂,聚合物A为纺丝助剂,采用溶胶-凝胶法制备氧化铝长纤维,利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和傅里叶红外光谱仪(FR-IR)等,对纤维的形貌和组织结构进行观察与分析,并结合kissinger-akahira-sunose(KAS)法、flynn-wall-ozawa(FWO)法和Starink法研究纤维的结晶动力学。结果表明:凝胶纤维的直径约为4~7μm,纤维形貌良好,无明显开裂;当纤维以10℃/min的速率从室温加热至1 200℃时,纤维在800~900℃间由非晶相转变为γ-Al_2O_3,在1 100℃以上温度下γ-Al_2O_3转变为α-Al_2O_3;通过KAS法计算得到氧化铝纤维由非晶相转变成γ-Al_2O_3的激活能为412.1 kJ/mol,由γ-Al_2O_3向α-Al_2O_3转变的激活能为422.3 kJ/mol,与Starink法和FWO法的计算结果吻合良好,验证了KAS法计算结果的精确有效性。

In this paper, continuous alumina gel fibers were prepared by sol-gel method using aluminum nitrate （AN） and aluminum isopropylate （AIP） as raw materials, deionized water as solvent and polymer-A as spinning additives. The morphology and microstructure of alumina fibers were characterized by X-ray diffractometer （XRD）, scanning electron microscopy （SEM）, transmission electron microscope （TEM） and Fourier transformation infrared spectrometer （FT-IR）. Furthermore, the crystallization kinetics of fibers were analyzed by kissinger-akahira-sunose （KAS） method, flyrm- wall-ozawa （FWO） method and Starink method. The results show that, alumina fibers exhibit consistent diameter distribution of 4-7μm, the morphologies of fibers are good and no obvious cracks have been found both before and after thermal treatment. When thermal treatment is conducted from room temperature to 1 200℃ at the heating rate of 10 ℃/min, total phase transformation process are divided into two steps： fibers are amorphous at 800 ℃, then they turn to y-Al2O3 at 800-900 ℃ and y-A1203 tums to α-Al2O3 at over 1 100 ℃. The activation energy of phase transition of amorphism to γ-Al2O3 in alumina fibers is 412.1 kJ/mol and that of γ-A1203 to α-Al2O3 is 422.3 kJ/mol calculated by KAS methods. Those results are consistent with the values calculated by FWO and Starink methods, which identifies that values of energy are reasonable and accurate.