Abstract: Through hydrogen reduction of alkali metal chromates, chromic oxide green can be prepared by the thermal decomposition of chromium oxyhydroxide (CrOOH). It was reported that the crystal structures of CrOOH have a significant effect on the color of the chromic oxide green obtained. However, the mechanisms remain unclear and need to be systematically studied. In this work, two kinds of CrOOH with different crystal structures were prepared by aqueous hydrogen reduction of sodium chromate. The chemical composition, phase structure, and morphologies of the prepared CrOOH were characterized by chemical titration, FT-IR, XRD, and SEM. The thermal decomposition processes were discussed according to the TG-DSC results. Subsequently, CrOOH with different crystal structures were used as the raw materials to prepare chromic oxide green with different color performance. The structure and morphologies of the chromic oxide green obtained were characterized by XRD and SEM. The color performance data of chromic oxide green was reported by a Datacolor 110 colorimeter using the CIE L*a*b* (1976) colorimetric system according to the International Commission on Illumination. The results showed that the CrOOH samples prepared were of base center orthorhombic structure and trigonal structure, respectively. The morphology of the CrOOH samples was flaky and hexagonal sheet shape, respectively. Their compositions could be expressed as Cr2O3?1.49H2O and Cr2O3?1.12H2O, respectively. Compared with the chromic oxide green sample obtained by the thermal decomposition of trigonal CrOOH, the chromic oxide green sample obtained by the thermal decomposition of CrOOH with base center orthorhombic structure yielded a smaller particle size, more uniform particle size distribution, and a brighter yellower color. Finally, chromic oxide green pigments with different color performances, such as bright yellow-green, blue-green, and dark green, were obtained using different ratios of CrOOH raw materials with base center orthorhombic and trigonal structures.

Key words: Chromium oxyhydroxide, Thermal decomposition, Chromic oxide green, Crystal structure, Color performance.

摘要： 羟基氧化铬(CrOOH)热分解制备氧化铬绿颜料是铬酸盐氢还原法制备氧化铬绿清洁工艺的单元之一。研究表明，CrOOH的结构对其热分解所得氧化铬绿的色度有显著影响，但CrOOH晶体结构对所得氧化铬绿色度的影响尚未有系统研究报道。本工作通过铬酸钠溶液氢还原制备得到了两种晶型的CrOOH并借助化学滴定、傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)和热重-差示扫描量热分析(TG-DSC)对其组成、结构、形貌和热分解过程进行了研究。以两种不同晶型的CrOOH为原料调控制备得到了不同色度的氧化铬绿颜料，借助XRD和SEM对其物相和形貌进行了表征，并使用Datacolor110色度仪测定了其色度参数。结果表明，两种CrOOH的晶体结构分别为底心正交和三方，其形貌分别呈现片状和六方片状，组成可分别写作Cr2O3?1.49H2O和Cr2O3?1.12H2O。与三方CrOOH相比，底心正交的CrOOH热分解得到的氧化铬绿颗粒尺寸更小、大小更均匀、颜色更亮更黄。最终，以不同比例的底心正交和三方CrOOH为原料，调控制备得到了多种色调的氧化铬绿颜料。

关键词: 羟基氧化铬, 热分解, 氧化铬绿, 晶型, 色度