热分解含氨草酸钴复盐制备纤维状多孔钴粉

摘要

以氨为配位剂,通过配位沉淀法制备纤维状钴粉复杂前驱体,并采用XRD,IR,SEM和TGA/DTA研究前驱体粉末的物相、成分与形貌,系统考察前驱体粉末热分解过程中热分解条件如热分解气氛、热分解温度、热分解时间和升温速率对金属钻粉形貌、粒度和比表面积的影响.研究结果表明:在Co(Ⅱ)-C2042——NH3-NH4+-H2O反应体系中得到的前驱体为含氨草酸钴复盐,形貌为纤维状,氨与钴离子配合并生成含氨草酸钴复盐是纤维状形貌形成的内在机制,它是通过含NH3基配合物以链状结构连接[(NH3)M-OX-M(NH3)]2+生长基元以轴向取向连生形成一维形貌;在弱还原性气氛、热分解时间为30～60 min、升温速率为15～20 K/min、热分解温度为623～723 K条件下,热分解含氨草酸钴复盐粉末可以制备比表面积为10.44 m2·g-1的纤维状多孔金属钴粉,其孔结构为两端开放的管状毛细孔且多为中孔.%A novel precursor of fibrous cobalt powders was synthesized by coordination-precipitation process using ammonia as complex agent. The phase, composition and morphology of the novel precursor were characterized by XRD,IR, DTA/TGA and SEM analysis. The influences of various conditions in pyrolysis, such as decomposition atmosphere,decomposition temperature, decomposition time and heating rate, on the morphology, average size and specific surface area of the cobalt powders were investigated. The results show that the precursors obtained in reaction system Co(Ⅱ )-C2O42--NH3-NH4+-H2O is ammoniacal complex of cobalt oxalate and the morphology is fibrous. The formation of the complex of oxalate cobalt with ammonia precipitated by coordination of ammonia and cobalt reacting with oxalate is quite essential to form fibrous morphology for the precursor, which may be formed through [(NH3)M-OX-M(NH3)] 2+growth units along the axial direction. The fibrous cobalt powders with 10.44 m2·g-1 for specific surface area are produced in weak reducing atmosphere, 623-723 K for decomposition temperature, 30-60 min for decomposition time, 15-20 K/min of heating rate. The structure of pores in cobalt powders is capillary tube with open ports and the majority is mesoporous.