| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high density sintered compact useful as a pearl nucleus by adding a specified amt. of an alkali metal or alkaline earth metal oxide as a sintering aid to calcium carbonate powder having a specified average particle diameter and a specified BET specific surface area and sintering them by a discharge plasma sintering method. SOLUTION: One or more kinds of alkali metal or alkaline earth metal oxides are added as a sintering aid by 1-20wt.% to calcium carbonate powder having 0.5-4μm average particle diameter and >=5m<2> /g BET specific surface area and they are sintered by a discharge plasma sintering method to obtain the objective sintered compact having >=2.6g/cm<3> density. The sintering aid is added as an aq. soln. by means of a kneader in the case of water-soluble oxides such as NaOH and it is dry-mixed by means of a ball mill, etc., in the case of slightly soluble oxides such as Mg(OH)2 . The sintering is carried out at 400-600 deg.C for about 5-10min in an inert gaseous atmosphere under 200kg/cm<2> pressure or under reduced pressure. When the sintered compact is used as a pearl nucleus, the size is regulated to 3-10mm. |
