A heat insulating material includes an aerogel that has macro-pores and meso-pores. A method for manufacturing a heat insulating material, including: a sol preparation step of adding a gelling agent into sodium silicate such that a molar ratio of the gelling agent relative to NaO.sub.2 is 0.1 to 0.75, and adjusting a sol into which macro-pores are introduced by leaving unreacted Na and non-cross-linked oxygen in a siloxane skeleton; an impregnating and gelling step of impregnating a nonwoven fabric fiber structure with the sol to form a composite of hydrogel-nonwoven fabric fiber; a hydrophobizating step of mixing the formed composite of hydrogel-nonwoven fabric fiber with a silylating agent to modify a surface thereof; and a drying step of removing a liquid contained in the surface modified composite of hydrogel-nonwoven fabric fiber by drying under a temperature and pressure lower than respective critical values.

A heat insulating material includes an aerogel that has macro-pores and meso-pores. A method for manufacturing a heat insulating material, including: a sol preparation step of adding a gelling agent into sodium silicate such that a molar ratio of the gelling agent relative to NaO.sub.2 is 0.1 to 0.75, and adjusting a sol into which macro-pores are introduced by leaving unreacted Na and non-cross-linked oxygen in a siloxane skeleton; an impregnating and gelling step of impregnating a nonwoven fabric fiber structure with the sol to form a composite of hydrogel-nonwoven fabric fiber; a hydrophobizating step of mixing the formed composite of hydrogel-nonwoven fabric fiber with a silylating agent to modify a surface thereof; and a drying step of removing a liquid contained in the surface modified composite of hydrogel-nonwoven fabric fiber by drying under a temperature and pressure lower than respective critical values.

An inorganic fiber molded body includes an alumina fiber, an inorganic porous filler, and a colloidal silica, in which a ratio of crystalline minerals in the alumina fiber is 30% by mass or more and 80% by mass or less, the inorganic porous filler contains CaO.Math.6Al.sub.2O.sub.3 in which a particle diameter D95, which has a cumulative value of 95% in a volume frequency particle size distribution, is 300 μm or less, and in 100% by mass of the inorganic fiber molded body, a content of the alumina fiber is 15% by mass or more and 70% by mass or less, a content of the inorganic porous filler is 20% by mass or more and 79% by mass or less, and a content of the colloidal silica is 2% by mass or more and 8% by mass or less.

An inorganic fiber molded body includes an alumina fiber, an inorganic porous filler, and a colloidal silica, in which a ratio of crystalline minerals in the alumina fiber is 30% by mass or more and 80% by mass or less, the inorganic porous filler contains CaO.Math.6Al.sub.2O.sub.3 in which a particle diameter D95, which has a cumulative value of 95% in a volume frequency particle size distribution, is 300 μm or less, and in 100% by mass of the inorganic fiber molded body, a content of the alumina fiber is 15% by mass or more and 70% by mass or less, a content of the inorganic porous filler is 20% by mass or more and 79% by mass or less, and a content of the colloidal silica is 2% by mass or more and 8% by mass or less.

A method for preparing a silane coupling agent/silica/plant fiber composite includes the following steps: S1: pretreating plant fiber; S2: preparing hydrolysate of a silane coupling agent; S3: preparing a silane coupling agent/plant fiber composite; S4: preparing a silica nanoparticle dispersion; and S5: preparing a silane coupling agent/silica nanoparticle/plant fiber composite. Through the covalent interaction among a silanol group (Si—OH) formed by hydrolysis of the silane coupling agent, Si—OH of the silica, and a hydroxyl group (—OH) on the surface of the plant fiber, the present invention enables silica nanoparticles to be grafted on the surface of the plant fiber. Using a hydrophobic film formed by the silane coupling agent, harmful ions are prevented from invading, and the volume stability of the fiber is improved. Using the pozzolanic activity of the silica nanoparticles, the alkalinity and calcium hydroxide content around the fiber are reduced.

A method for preparing a silane coupling agent/silica/plant fiber composite includes the following steps: S1: pretreating plant fiber; S2: preparing hydrolysate of a silane coupling agent; S3: preparing a silane coupling agent/plant fiber composite; S4: preparing a silica nanoparticle dispersion; and S5: preparing a silane coupling agent/silica nanoparticle/plant fiber composite. Through the covalent interaction among a silanol group (Si—OH) formed by hydrolysis of the silane coupling agent, Si—OH of the silica, and a hydroxyl group (—OH) on the surface of the plant fiber, the present invention enables silica nanoparticles to be grafted on the surface of the plant fiber. Using a hydrophobic film formed by the silane coupling agent, harmful ions are prevented from invading, and the volume stability of the fiber is improved. Using the pozzolanic activity of the silica nanoparticles, the alkalinity and calcium hydroxide content around the fiber are reduced.

A structure for manufacturing castings, containing an inorganic fiber, a layered clay mineral, and an inorganic particle other than the layered clay mineral and having an organic content of 5 mass % or lower or having a mass loss of 5 mass % or lower when heated at 1000° C. for 30 minutes. The inorganic particle preferably contains one or more selected from obsidian, graphite, and mullite. The inorganic fiber preferably contains carbon fiber. The inorganic fiber preferably has an average length of 0.5 to 15 mm. The layered clay mineral preferably contains one or more selected from bentonite and montmorillonite.

A structure for manufacturing castings, containing an inorganic fiber, a layered clay mineral, and an inorganic particle other than the layered clay mineral and having an organic content of 5 mass % or lower or having a mass loss of 5 mass % or lower when heated at 1000° C. for 30 minutes. The inorganic particle preferably contains one or more selected from obsidian, graphite, and mullite. The inorganic fiber preferably contains carbon fiber. The inorganic fiber preferably has an average length of 0.5 to 15 mm. The layered clay mineral preferably contains one or more selected from bentonite and montmorillonite.

The present invention describes various methods for manufacturing gel composite sheets using segmented fiber or foam reinforcements and gel precursors. Additionally, rigid panels manufactured from the resulting gel composites are also described. The gel composites are relatively flexible enough to be wound and when unwound, can be stretched flat and made into rigid panels using adhesives.

The present invention describes various methods for manufacturing gel composite sheets using segmented fiber or foam reinforcements and gel precursors. Additionally, rigid panels manufactured from the resulting gel composites are also described. The gel composites are relatively flexible enough to be wound and when unwound, can be stretched flat and made into rigid panels using adhesives.