Abstract
Hard chromium plating has been used to improve hardness, resistance to corrosion, friction and heat in various fields. However, alternative technology of hard chromium plating is desired because of toxicity of raw materials. Thus, we developed a novel method to fabricate a hard film by using Cr nanoparticles. Although this method is easy and environmentally friendly, Cr nanoparticles are expensive at present because Cr nanoparticles are synthesized by vapor deposition. In this study, we tried to synthesize Cr nanoparticles in solvent by ultrasonic decomposition of Cr(CO)_6. Cr(CO)_6 was fully decomposed by ultrasonic irradiation in decanol at 50 ℃ for 30 min. The product had a low crystallinity and particles sizes were about 5 nm. In TG-DTA, products exhibited weight loss (33 %) around 1000 ℃ in Ar by decomposition of organics. In XRD, Cr and Cr_2O_3 were observed after heating at 1000 ℃ in Ar. It is considered that surfaces of Cr nanoparticles were formed oxide shells of Cr_2O_3 as passive layers. When the atmosphere was changed from Ar to air in 1000 ℃, products exhibited weight gain due to oxidation of Cr.
