| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve a reaction rate for forming a coating membrane and to reduce the remaining amount of an unreacted impurity by performing a heating treatment of a powder-dispersed solution at a specific time when dispersing the powder in a metal alkoxide solution and thereafter hydrating the metal alkoxide to form a metal oxide membrane on the powder. SOLUTION: A powder-dispersed solution before, during or after a reaction is preferably heat treated at 50-380 deg.C. That is, the powder covered with a metal oxide membrane is produced by preferably heating a metal alkoxide solution (e.g. an ethanol solution of silicon ethoxide) dispersing powder (e.g. powdered carbonyl iron) at 50-200 deg.C and thereafter performing a hydration reaction, or by washing the powder after the hydration reaction with a polar solvent (e.g. ethanol), redispersing the powder and performing the heating treatment preferably at 50-200 deg.C in the method for producing the powder covered with the metal oxide membrane. Thereby, unreacted material in the membrane can be reduced. Further, the powder is heat treated preferably at 80-380 deg.C under a high pressure (in a sealed autoclave) to improve the crystallinity in the membrane.</p> |
