An approach of molten salt treatment to the preparation of high-crystallinity Ni ultrafine particles for applications of film electrodes

A B S T R A C T Ni ultrafine particles synthesized via aqueous solution method have advantages such as narrow particle size distribution and low cost. However, the particle crystallinity is usually poor, which may lead to severe shrinkage during the sintering process for the preparation of film electrodes. In this study, Ni ultrafine particles with a size of about 180 nm are synthesized via an aqueous solution method, then heat treated in a bath of binary chloride salts (AlCl 3 -NaCl) at different temperatures, and finally made into a paste, printed onto a ceramic substrate and sintered into a conductive film. The results show that the crystallinity, oxidation resistance and thermal shrinkage resistance of the samples after molten salt treatment are significantly improved. The sintered film electrode prepared from Ni sample without molten salt treatment exhibits severe shrinkage and large disconnected areas, whereas the integrity and continuity of the films with molten salt treatment are notably improved. Lower resistivities are observed for film samples with molten salt treatment. The results show that molten salt treatment is an effective way to increase the crystallinity of Ni ultrafine particles, and thus reduce the thermal shrinkage and improve the integrity of Ni film electrodes.