Controlled synthesis of large-sized Cr2O3 via hydrothermal reduction

Abstract In this paper, large sized polyhedron-like and plate-like Cr2O3 were firstly obtained via hydrothermal synthesis under the assistance of the surfactant citric acid. The raw materials were K2Cr2O7 and HCHO. With the increase of citric acid from 0.02, 0.05, 0.1, 0.12 to 0.16 g in sequence, morphologies of products changed accordingly. When it was 0.12 g and reaction temperature was 180 °C, polyhedrons with the size of 9–18 μm formed. With the increase of reaction temperature and keeping other reaction conditions the same, morphologies of products also changed obviously. When it was 240 °C, products were different sized plates from 5 μm to 106 μm made up of tiny particles. Influences of spatial effects and viscosity from amount of the added surfactant and reaction temperatures on the nucleation and diffusion rate lead to differences of stacking manners of precursor particles, and then lead to different morphologies of the products. Microstructures of materials were observed by a field emission scanning electron microscope and composition of products was investigated by X-ray techniques.