Shoichi Nakashima

Surface modification of structural materials by dynamic ion mixing process

Abstract TiN films were formed on a silicon substrate by a dynamic mixing process and cross-sections of this specimen, as well as a specimen with only nitrogen-ion-implanted silicon, were observed by transmission electron microscopy (TEM). In the TEM images, intermediate layers were observed between the substrate and the TiN film. The intermediate layers were considered to be nitrogen-ion-implanted silicon and an intermixed layer of vaporized titanium, sputtered-out substrate (silicon) atoms and implanted nitrogen ions. Field testing of the tools was done, where TiN films were formed on the WCCo alloy tool material by the dynamic mixing process. The TiN coated tools were twice as good as uncoated tools.

ZrO2 and Cu functionally gradient materials prepared by a dynamic ion mixing process

Abstract ZrO2-Cu films have been prepared as functionally gradient materials (FGM) which change continuously from Cu to ZrO2. Partially stabilized ZrO2 (PSZ) and the PSZ-Cu FGM films were prepared on a Cu substrate by a dynamic ion mixing process. Oxygen ion irradiation was essential for the FGM formation of the PSZ-Cu films, because films deposited without oxygen ion irradiation were easily peeled from the substrate during the deposition steps. The electron beam deposition rates of Cu and ZrO2 were individually controlled. The FGM structures were analysed by X-ray photoelectron spectroscopy and transmission electron microscopy. Cu and PSZ crystal grains were finely mixed in the FGM layers. The thermal resistance of the FGMs was examined by a heat test in which the film surface was heated by an Ar + H2 plasma jet. No cracks were observed on the PSZ-Cu FGM surfaces after the test. However, for PSZ film (without the FGM layer) on the Cu substrate, cracks were seen.