Method for manufacturing fine porous member

A method for forming a fine porous insulating member having low thermal conductivity, comprising the steps of:

• obtaining a quantity of ultrafine particle powder through a dry process carried out at a temperature above about 1,600.degree. C.;
• maintaining said quantity of ultrafine particle powder thus obtained at a temperature above about 150.degree. C.;
• treating said quantity of ultrafine particle powder maintained at said temperature of above about 150.degree. C. with a surface treatment agent through a gas phase reaction to substantially remove surface cohesiveness, said ultrafine particle powder having a particle size of from about 1 nm to about 20 nm;
• combining the treated ultrafine particle powder with a quantity of fine particle powder, thereby forming a mixture, the amount of fine particle powder in the mixture being less than 75 wt.%, said fine particle powder having a particle size of from about 20 to about 10,000 nm;
• and
• molding the mixture into a fine porous insulating member, the surface treatment agent rendering vacant spaces within the insulating member sufficiently small whereby the thermal conductivity of the insulating member is less than that of air.