| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat insulating ceramic layer using nepheline as an aggregate, having a thermal expansion coefficient equivalent to that of the ferrous base material, excellent in bonding strength to the base material or bonding layer and high in heat resistance and strength. SOLUTION: This heat insulating ceramic layer is formed on the surface of the base material directly or through a bonding layer. In this case, a nepheline grain is used as the aggregate, and a binder consisting of silica grain and metalloxane polymer is filled or interposed between the aggregates while leaving a void to chemically bond the aggregates or the aggregate to the base material or bonding layer. When the insulating layer forming slurry is prepared, the nepheline grain as the aggregate and the binder are mixed in a sufficiently acidic or alkaline soln. so that the surface potential of the grain dispersed in the slurry does not pass the isoelectric point due to an increase in slurry pH by the alkali metal ion eluted from the grain, or the mixing is conducted after the grain surface is coated with a film preventing the elution of the alkali metal ion. |
