Katsumi Mabuchi

Growth process of protective oxides formed on type 304 and 430 stainless steels at 1273 k

Abstract Oxidation of Type 304 and 430 stainless steels for up to 1 h was studied at 1273 K and the composition and structure of the oxide were determined by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In the initial several tens of seconds, only iron-rich corundum-type oxide was formed, whereas the final oxide was composed of an inner chromium-rich corundum-type oxide layer and an outer mixed layer of corundum-type and spinel-type oxides. An iron-rich metallic α phase was observed on Type 304 stainless steel. This suggests a growth mechanism where corundum-type oxide on Type 304 stainless steel repeats cycles of breakage and curing of the oxide, resulting in the formation of metallic α phase in the oxide layer. A similar reaction is postulated to take place in the oxidation of Type 430 stainless steel.

The effect of the oxidation atmosphere on the initial oxidation of type 430 stainless steel at 1273 K

“Division of Material Science and Engineering, Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8 Sapporo, 060 Japan bHitachi Works, Hitachi Ltd, Saiwai 3, Hitachi, 319-12 Japan ‘Hitachi Research Laboratory, Hitachi Ltd, l-l, Omika 7, Hitachi, 319-12 Japan dHitachi Kyowa Engineering Ltd, Benten 3, Hitachi, 319-12 Japan Abstract-Type 430 stainless steel with 0.9 wt% manganese was oxidized in 02/H20/N2 atmospheres at 1273 K. Iron-rich corundum-type oxide formed in the very initial oxidation stage changed to a chromium-rich oxide with time in all atmospheres. The chromium content in a spinel-type oxide, which appeared after formation of the the corundum-type oxide, increased with increasing oxygen partial pressure. It is considered that the spinel-type oxide forms through a two-step reaction: first, reduction of Mn,O, to MnO; second, solid-state reaction of MnO with corundum oxide. The rate-determining step appears to be the first reaction. 0 1998 Elsevier Science Ltd. All rights reserved Keywords: A. stainless steel, B. SEM, B. XPS, B. X-ray diffraction, C. oxidation.

Newly Developed Abrasive-free Copper CMP Slurry Based on Electrochemical Analysis

In order to reduce microscratches and obtain minimized dishing and erosion, we have developed new abrasive-free Cu CMP slurries. During the development of these slurries, some electrochemical examination was performed. The most effective knowledge was obtained through the analysis using rotary Cu disk electrode under pressure. On the basis of these studies, new abrasive-free Cu CMP slurries with a high removal rate and excellent planarity were designed and developed. The mechanism of reducing dishing and erosion was also discussed.

Development of a New Nanoscale Electrochemical Method Using Scanning Tunneling Microscopy

A new in-situ measurement technique for analyzing corrosion of the submicron level area in liquids was developed. In this technique, after topography is measured with a scanning tunneling microscope (STM), the measurement mode is switched and electrochemical measurements such as cyclic voltammetry are conducted by using the STM probe as a working electrode. The distance between the probe and the material is separated up to the distance where the tunneling current does not flow. The valency, concentration, and species of dissolution ions from metal can be inferred according to potential and the current density of the reduction peak of a cyclic voltammogram. We report the corrosion behavior of copper minuteness wiring using the new technique.