Abstract
Coral sand (coral fossil sand), the main ingredient of which is calcium carbonate, is a kind of naturally found materials in the bottom of the sea near the coral islands like Okinawa. While marbles derived from coral sand as a metamorphic rock are produced in Taiwan. Producing marbles artificially by sintering has been very difficult, because calcium carbonate decomposes at high temperatures and changes to calcium oxide, generating gaseous carbon dioxide. The only method which can consolidate calcium carbonate powder has been the encapsulation HIP method in which a green powder body is encapsulated in a metal can and subjected to a high pressure and high temperature condition. This method, however, is not practical to be utilized for commercial production, because the encapsulation technology requires a lot of skill, expensive materials and equipment. In this study, the possibility of full densification of calcium carbonate powder by capsule-free HIP'ing without capsule was investigated by using a coral sand powder as a sample material. And further the mechanical properties of the obtained dense sintered compact were evaluated for the application to tiles.
