Papers by Author: Shuji Sakaguchi

Abstract: ISO/TC206 'Fine ceramics' is one of a technical committee (TC) in the International Organization for Standardization (ISO), established in 1992. The first plenary meeting for this TC was held in 1994, and the latest meeting was held in August 2015, in Jeju, Republic of Korea. The scope of this TC covers very wide field concerning the ceramic materials for industrial applications, in forms of powders, monoliths, coatings and composites, and in functions of mechanical, thermal, chemical, electrical, magnetic, optical and their combinations. This TC consists of 18 participating member (P-member) countries and 13 observing member (O-member) countries. We already have 81 published standards from this TC. About 30 new work items are under discussion, about 15 items are waiting for starting the discussion, and about 10 items are in the process for revision of the published standards. In this TC, we have 12 working groups. More than twenty years have passed since starting this TC, generally speaking, the categories of the discussed items tends to shift, from some testing methods for fundamental properties (strength, density, thermal properties etc.), to some properties for specified applications, such as ceramic bearing materials, photocatalytic materials and electrical applications.

Abstract: Temperature dependence of internal friction on silicon nitride ceramics with yttria and alumina sintering aids was discussed using 4-elements visco-elastic model. It is known that the internal friction of this ceramic material shows a characteristic peak at around 1040 oC and an exponential increase over 1200 oC. This temperature dependence of internal friction was well approximated with using parallel Maxwell model. The parameters for this model and the relaxation time on this model were obtained. The relaxation time was very short, compared to the transient creep deformation of this ceramics. The analyzed results on internal friction could not be related with the creep deformation.