不同盐类原料对水热合成CoAl2O4尖晶石纳米色料的影响

Effect of Different Salts on the Hydrothermal Synthesis of Nano CoAl2O4 Spinel Pigments

分别采用钴和铝的硝酸盐、硫酸盐和氯化物作为原料,在245℃温度下水热处理24 h,制备纳米尖晶石型CoAl2O4蓝色料。通过3 M NaOH溶液调节Co-Al前驱体溶液的pH值。采用X射线衍射分析（XRD）、透射电镜（TEM）、差示扫描量热法-热重分析（DSC-TG）,傅里叶红外光谱（FTIR）以及色度计对所得合成产物进行了表征分析。结果表明,钴、铝的硝酸盐为原料所得水热产物在三类原料中呈色最差;以硫酸钴和硫酸铝为原料、pH=11时所得产物的蓝度值最佳（b＊=-28.92）,随着pH值的变化,对产物的色度产生显著影响;钴、铝的氯化物为原料合成的产物为蓝色或者蓝绿色,能在9～11的较宽pH值范围内得到呈色稳定的蓝色料。水热产物呈现出绿色调的主要原因是部分Co^3＋取代了Al^3＋填充的CoAl2O4晶体中的八面体空隙,为六配位结构。

Cobalt nitrate and aluminum nitrate, aluminum chloride and cobalt chloride, cobalt sulfate and aluminum sulfate were used as raw materials to prepare cobalt aluminate （CoAl2O4） spinel blue pigment at 245 ℃ for 24 h by hydrothermal method, respectively. The pH values of Co-AI mixed precursor solutions were adjusted by 3M NaOH solution. The as-synthesized pigments were characterized by X-ray powder diffraction（XRD）, transmission electron microscopy（TEM）, differential scanning calorimetry ＆ thermogravimetry analysis（DSC-TG）, Fourier transform infrared spectroscopy（FTIR） and chromometer. The results show that CoAl2O4 blue pigment with b^＊ value of -28.92 better than others was obtained at pH value of 11 when using cobalt sulfate and aluminum sulfate as raw materials. And their color changed with the variation of pH values. The pigments synthesized with cobalt chloride and aluminum chloride as raw materials were generally blue or cyan. The obtained pigments fabricated by cobalt sulfate and aluminum sulfate had no regular of coloration change. Analysis results indicate that the products presenting green is due to Co^2＋ ions replace the Al^3＋ filled octahedral sites of the original CoAl2O4 spinel structure, and the Co^2＋ are located in the tetrahedral sites as well as in the octahedral sites in the CoAl2O4 nanocrystals.