Hydrothermal synthesis of large sized Cr2O3 polyhedrons under free surfactant

•2–39 μm Cr2O3 polyhedrons were obtained via surfactant-free process.•It is the most simple hydrothermal process.•Mechanism of the process was discussed.

2–39 µm Cr2O3 particles were prepared via a simple hydrothermal process under surfactant-free. K2Cr2O7 and HCHO were used as raw materials. The sizes and morphologies of products were adjusted by the quantity of added HCHO and the concentration of reactants. The mechanism for big-sized Cr2O3's formation has been disscussed. Compositions of precursor and products were analyzed by X-ray techniques, and sizes, microstructures and morphologies were investigated by field emission scanning electron microscope (SEM).

Graphical abstract5–200 µm approximately round Cr2O3 can be applied as spraying materials for its outstanding properties such as high temperature resistance, corrosion resistance, wear resistance, but few investigations focus on the synthesis of large sized Cr2O3 particles.We ever successfully prepared 9–18 µm Cr2O3 polyhedrons under the assistance of citric acid in hydrothermal system and 38–72 µm Cr2O3 particles under the assistance of CTAB via hydrothermal process. These results have been published in 2 papers of Materials Letters.Through further investigation, we found that large sized Cr2O3 could also be prepared under fit reaction conditions though there was no surfactant in the system. No literature has reported free surfactant process to synthesize large sized Cr2O3 in hydrothermal system.In this paper, 7–38 µm Cr2O3 particles were prepared via a simple hydrothermal process under free surfactant, the cause for big sized Cr2O3's formation is to find fit kinetic parameters of crystal growth.Figure optionsDownload full-size imageDownload as PowerPoint slide