A study on low-Z coatings for nuclear fusion reactor first wall

Various low-Z coating materials are produced by means of chemical vapor deposition, ion plating, activation reaction evaporation, magnetron sputtering, solid-phase reaction bonding, and vacuum arc deposition. Ion plating is carried out to produce a SiC-Al2O3 composite coating material. Substrate temperature control is performed to provide TiC coating material which has an interface consisting of a layer with an oxygen concentration gradient, or which contains a tungsten intermediate layer. For magnetron sputtering, parameters such as the composition, substrate bias voltage and sputtering gas pressure are optimized to produce TiC coatings with high thermal stability. In the case of solid-phase reaction bonding, graphite-metal bonding material is produced by using an ion-plated metal intermediate layer. An ion-gun type vacuum arc deposition source is developed which is suited for in-situ coating of the first wall. The relations between the production conditions and major characteristics, including thermal stability and mechanical properties, of the coating materials are investigated. Then, by using the results of the investigation, various low-Z coating materials with good thermal properties are produced, and useful coating techniques are developed. (N.K.)