有机凝胶-热分解法制备MgO,Al_2O_3,MgAl_2O_4微细纤维

Preparation of Fine MgO,α-Al_2O_3,Spinel MgAl_2O_4 Fibres by the Organic Gel-Thermal Decomposition Method

以柠檬酸、乳酸及金属盐为原料,采用有机凝胶-热分解法制备了微细氧化镁、α-氧化铝和尖晶石结构铝酸镁纤维。所得纤维结构致密、晶粒细小,直径可小于1μm,长径比大。通过FTIR,XRD,DSC及SEM对纤维前驱体凝胶的结构、热分解过程及热处理产物的形貌进行了表征。凝胶的可纺性与组成凝胶的羧酸盐分子结构、羧酸和金属离子的摩尔比等因素有关。柠檬酸和乳酸中的羧基分别以单齿配位于Mg2+和Al3+可能形成线性分子[(C6H6O7)2Mg3],[(C3H5O3)3Al]和[(C6H6O7)4MgAl2],由这些线性分子组成的凝胶显示出了良好的可纺性。

Fine magnesia, α-alumina, spinel magnesium aluminate fibres were successfully prepared by the organic gel-thermal decomposition method from the raw materials of citric acid or lactic acid and their metal salts. The fibres synthesized were featured with diameters of approximate 1 μm with high aspect ratios （length/diameter） and small crystalline grains. The structure, thermal decomposition process and morphologies of gel precursors and the fibres derived from thermal- decomposition of the gel precursors were characterized by FTIR, XRD, DSC and SEM. It is found that the spinnability of the gel precursors is related with the molecular structures of metal-carboxylates, molar ratios of carboxylic acids and metal ions. These linear-type structural molecules showed a good spinnability, such as （C6H6O7）2Mg3 for magnesium citrate gel, （C3H5O3）3Al for aluminum lactate gel, and （C6H6O7）4MgAl2 for magnesium and aluminum citrate gel, formed during gel formations complexing reactions by the mono-dentate approach between carboxylate and metal ions.