In order to widen the application of iron oxide yellow pigments (α‐FeOOH) in high temperature industry, α‐FeOOH coated with calcium phosphate (α‐FeOOH/Ca) were modified with stearic acid (Sa) through dry process. Scanning electron microscope (SEM), transmission electron microscope (TEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), and thermogravimetry (TG) were employed to characterize the effect of surface modification. The effects of Sa dosage on the thermal resistance of α‐FeOOH/Ca after modification were also discussed. The crystal structure of α‐FeOOH/Ca does not change after modification with Sa, but the ratio of length to diameter about α‐FeOOH/Ca is smaller. Sa can react with α‐FeOOH/Ca in the form of –COOCa and HPO₄²⁻ based on FT‐IR and XPS analyses. TG‐DTG results suggest that calcium phosphate and Sa improve the thermal stability of α‐FeOOH. The value of color difference of modified α‐FeOOH/Ca first decrease and then increase with increasing of Sa dosage, which is studied by CIE ΔL, Δa, and Δb colorimetric analyses. The amount of Sa affects the thermal resistance and dispersion performance of α‐FeOOH/Ca simultaneously; also the relationship between thermal resistance and dispersion is inversely proportional. Experimental characterizations reveal that introduction of the phosphates and Sa not only prevents the loss of water on the surface of α‐FeOOH but improve its activation index and dispersibility in organic solvents.

中文翻译：

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硬脂酸改性的表面分析，以改善磷酸钙涂覆的氧化铁黄颜料的耐热性

为了拓宽氧化铁黄颜料（α-FeO​​OH）在高温行业中的应用，对磷酸钙（α-FeO​​OH/ Ca）包覆的α-FeO​​OH进行了干法硬脂酸（Sa）改性。使用扫描电子显微镜（SEM），透射电子显微镜（TEM），X射线衍射（XRD），傅里叶变换红外光谱（FT-IR），X射线光电子能谱（XPS）和热重分析（TG）进行表征表面改性的效果。还讨论了Sa用量对改性后α-FeO​​OH/ Ca热阻的影响。用Sa改性后，α-FeO​​OH/ Ca的晶体结构不会改变，但大约α-FeO​​OH/ Ca的长径比较小。Sa可以–COOCa和HPO ₄ ^2-的形式与α-FeO​​OH/ Ca反应基于FT-IR和XPS分析。TG‐DTG结果表明，磷酸钙和Sa改善了α‐FeOOH的热稳定性。改性α-FeO​​OH/ Ca的色差值随Sa剂量的增加先降低后增加，这通过CIEΔL，Δa和Δb比色分析研究。Sa的含量同时影响α-FeO​​OH/ Ca的耐热性和分散性能；热阻和分散之间的关系也成反比。实验特性表明，引入磷酸盐和Sa不仅可以防止水在α-FeO​​OH表面的流失，而且可以提高其活化指数和在有机溶剂中的分散性。