Abstract: A hydrophobic aerogel is fabricated by reacting a polymer having a skeleton structure of (SiO.sub.2).sub.n with a hydrophobic agent having hydrophobic groups as well as functional groups reactive to silanol groups to obtain a denatured polymer, forming a gel consisting of two phase of a dispersing medium and the denatured polymer which was performed a hydrophobic treatment, and then, supercritically drying the gel at temperature and pressure above a critical point of the dispersing medium. The hydrophobic aerogel has improved characteristics free from deterioration in light transmissivity as well as lowered thermal resistance and also free from a dimensional variation such as shrinkage which would otherwise occur by contact with moisture, so that it can maintain the excellent characteristics for long time periods. Particularly, the aerogel is useful as a material having excellent light transmissivity and thermal resistance.

Abstract: An optical fiber comprises a core 1 extending in a longitudinal direction and a cladding 3 of silica aerogel preferably having a hydrophobic property to provide a high optical transmission efficiency. The silica aerogel of the cladding is prepared by polymerizing a hydrolyzed alkoxysilane before a supercritical drying treatment and is subjected to a hydrophobic treatment before or during the supercritical drying.

Abstract: A hydrophobic aerogel having excellent transparency is formed by the following process of the present invention. That is, a first gel having a SiO.sub.2 skeleton structure is prepared by hydrolysis and condensation of an alkoxysilane compound in the presence of a solvent. The solvent contained in the first gel is replaced at least partially with a medium to form a second gel. The second gel is reacted with a hydrophobic agent having hydrophobic groups as well as functional groups reactive with silanol groups under a supercritical condition of the medium to form a hydrophobic gel. The medium contained in the hydrophobic aerogel is removed by a supercritical drying method, so that the hydrophobic aerogel having improved transparency and an extremely fine porous structure is obtained.

Abstract: A method of preparing an inorganic porous member causes a layered inorganic compound in swelled state with a solvent contained therein to be dried in a super critical state, so as to have holes held between respective layers of the inorganic compound, whereby the layered compound can be excellently maintained with less agglomeration caused upon removal of the solvent and the hole volume in the entire inorganic porous member can be remarkably increased.

Abstract: A method for manufacturing a fine porous member provides that vacant space within the porous member is sufficiently finely small such that the thermal conductivity of the member is lower than that of stationary air. In the method, a fine particle powder together with an ultrafine particle powder preliminarily subjected to a surface treatment for prevention of cohesiveness and employed at least as a part of the fine particle powder, are molded into the fine porous member, whereby the vacant space between the respective particles are made finely small to a remarkable extent and the porous member is provided as highly adapted to be used as a heat insulator.