Preparation of Cr₂O₃ nanoparticles via surfactants-modified precipitation method and their catalytic effect on nitridation of silicon powders

Abstract

Cr₂O₃ nanoparticles (NPs) were successfully prepared by a facile surfactant-modified precipitation method, and their phase composition and microstructure were characterized by X-ray diffraction, field emission-scanning electron microscopy and transmission electron microscopy. The effects of various processing parameters including surfactants type and amount, pH value and firing temperature on the synthesis of Cr₂O₃ NPs were investigated. Highly dispersed Cr₂O₃ NPs with an average crystalline size of 17 nm were obtained under the following optimal conditions: [Cr(NO₃)₃·9H₂O] = 0.0316 mol/L, PEG/Cr₂O₃ = 5 wt %, pH = 5.2, calcination temperature = 500°C and holding time = 2 h. Cr₂O₃ NPs showed a significant accelerating effect on the nitridation of Si powder, the conversion rate of Si to Si₃N₄ after 2 h at 1300°C reached 100 wt % upon using 3 wt % Cr₂O₃ NPs as catalysts, but only 40 wt % in the case without using any catalysts.