Plasma-surface interaction study, suitable surface materials and surface processing are some of the most important issues in the tokamak fusion program. This article starts with an outline of the major problems in plasma-surface interaction study, and then describes coating of wall with low-Z materials, discharge cleaning and long-term maintenance of cleaned surfaces giving typical examples of recent surface materials and processing development. Some topics on sputtering and techniques for surface analysis of the wall are also presented.

View full abstract

The principles and methods of high resolution solid-state NMR spectroscopy are explained briefly, followed by a review of recent reports especially on surface science studied by the technique. Two methods are used to obtain high resdution spectra, depending on the magnitude of homonuclear dipolar broadening. In the rare spin system, e.g., ¹³C, ²⁹Si, and ¹⁵N, the line broadening is mostly due to heteronuclear dipolar coupling and chemical shift anisotropy, The techniques of magic angle spinning of the sample, dipolar decoupling, and cross polarization are effective to obtain high resolution spectra. As for abundant spins such as ¹H, homonuclear dipolar broadening is usually dominant, which is suppressed by the multiple pulse technique. Structures and dynamics of surface species have been investigated by measuring high resolution spectra of ¹³C, ²⁹Si, ¹H, ³¹P, and ¹⁹F nuclei; usefulness of the technique is discussed.

View full abstract

This paper describes the surface structure and hydrogenation activity of plate-type Raney iron catalysts. When molten aluminum was sprayed onto surface of iron plate and the plate was heated, an alloy layer was formed at the boundary. Raney iron catalyst was prepared by leaching aluminum from the alloy with an aqueous sodium hydroxide. The characteristics of the alloy phase and the surface of the catalyst were determined by means of an electron probe microanalyzer and X-ray diffractometer. The alloy phase was FeAl₃ and Fe₂Al₅. Catalyst based on alloy from SUS 304 (stainless steel containing 8% Ni and 18% Cr) substrate exhibted greater activity in hydrogenation of acetone than a similar catalyst based on SUS 430 (Stainless steel containing 16% Cr).

View full abstract

Thin films of amorphous Si₃N₄ were prepared by rf-sputtering method and the effects of titanium, oxygen and chlorine on crystallization were examined. When the Ti-doped amorphous Si₃N₄ was heat-treated in N₂ gas, TiN precipitated in the amorphous matrix above 1100°C. Above 1500°C the TiN precipitates enhanced the direct conversion of amorphous Si₃N₄ to β-Si₃N₄. The conversion rate is proportional to the area of the precipitated TiN surfaces. High resolution electron microscopy revealed that epitaxial growth of β-Si₃N₄ took place on the TiN surface. Chlorine atoms added to amorphous Si₃N₄ led to preferential conversion of amorphous Si₃N₄ to α-Si₃N₄. Oxygen atoms incorporated in amorphous Si₃N₄ influenced the crystallization temperature of the amorphous Si₃N₄.

View full abstract

When SUS 304 is heated in vacuum the surface is covered with a monolayer of sulfur. In case of SUS 321, however, TiC precipitates on the surface. In this report, the effect of these surface compositions of stainless steels on the adherence of TiC coating films was investigated in order to improve the adherence. TiC was deposited on SUS 304, SUS 321 and preheated SUS 321 by means of an activated reactive evaporation. Adherence of TiC on these steels was evaluated by thermal cycling test. The crack growth behavior in the coated layer showed that TiC films adhered best to preheated SUS 321 and secondly best to SUS 321 and worst to SUS 304. The depth profile showed that adherence depended on the depth of intermediate layer between TiC films and stainless steels. This intermediate layer was the thickest between TiC films and preheated SUS 321. The relaxation mechanism of thermal stress was explained with the thickness of the intermediate layer.

View full abstract

C₁ chemistry involves several new technologies for utilization of natural gas, coal etc. as raw materials for the chemical industry. The discussion includes commercial processes such as the Eastman acetic anhydride process, the Monsanto acetic acid process, the Ube dialkyl oxalate process, the Mitsubishi Chemical dialkyl malonate process as well as several C₁ processes that are currently under development.

View full abstract

The principle and characteristics of AES (Auger Electron Spectroscopy) for surface analysis are described. Next, the fundamentals and techniques of AES analysis are discussed with various examples of practical problems and their solutions. Important points for applications of AES are listed up in the tables.

View full abstract