尖晶石型纳米CoAl2O4色料水热合成工艺研究

分别以钴、铝的氯化物、硝酸盐和硫酸盐为起始原料,NaOH为沉淀剂,用水热法合成了纳米尖晶石型钴蓝色料。分别研究了填充度、pH值、nCo/nAl、起始原料种类以及浓度等对合成色料物相组成、颗粒大小与形貌和呈色的影响。用XRD、TEM和色度分析对样品进行了表征。结果表明:以浓度分别为0.15 mol/L和0.3 mol/L的CoCl2.6H2O和AlCl3为起始原料,在填充度为70%、pH值为13、nCo/nAl为1/2的条件下,245℃水热培育20 h制得呈色良好的尖晶石型钴蓝色料,颗粒为八面体型,晶型完整,粒径多为100 nm以下。相同条件下,以钴、铝的硫酸盐为起始原料,产物中除CoAl2O4外,还有Co-Al LDHs、γ-AlO(OH)和β-Al(OH)3;以钴、铝的硝酸盐为起始原料,样品呈绿色,颗粒为八面体型CoAl2O4,粒径多为100 nm以上。

Study on Hydrothermal Synthesis Technique of Spinel CoAl2O4 Nanocolorants

Spinel CoAl2O4 nanocolorants were synthesized by hydrothermal method using chloride,nitrate and sulfate salts of cobalt and aluminum as raw materials,NaOH as precipitating agent.The influence of filling factors,pH values,nCo/nAl ratios and the species of starting materials and their concentration on the phase composition,particle size and morphology and coloration of the pigments was systematically examined.X-ray diffraction,transmission electron microscope and colorimetric analysis were employed to characterize the as-prepared samples.Results indicate that spinel type cobalt blue pigments were achieved by hydrothermal treatment at 245 ℃ for 20 h,using CoCl2·6H2O and AlCl3 with concentration of 0.15 mol/L and 0.3 mol/L,filling factor of 70%,pH value of 13 and nCo/nAl of 1/2,respectively.The crystals are of octahedral shape with high perfection and most of the sizes are below 100 nm.Under the same processing conditions,besides CoAl2O4,there are also Co-Al LDHs,γ-AlO(OH) and β-Al(OH)3 phases present in the resulting pigments prepared when the starting materials is sulfate salts of cobalt and aluminum.However,the as-prepared samples appear a green color when using nitrate salts as starting materials.The pigment particles are of octahedral shaped CoAl2O4 and most of the sizes are above 100 nm.