An ink composition for additive manufacture of silica aerogel objects essentially consists of a gellable silica sol containing an admixture of 30 to 70 vol. % of a mesoporous silica powder in a base solvent. The mesoporous silica powder has a particle size range of 0.001 to 1 mm and a tap density of 30 to 200 kg/m3 and comprises at least 10% by weight of silica aerogel powder. The composition has a yield stress in the range of 30 to 3000 Pa and a viscosity of 5 to 150 Pa.Math.s at a shear rate of 50 s-1. Furthermore, the composition has shear thinning properties defined as a reduction in viscosity by a factor between 10 and 103 for an increase in shear rate by a factor of 104 to 105. A method of additive manufacturing of a three-dimensional silica aerogel object by direct ink writing comprises providing such ink composition, forcing the same through a convergent nozzle, thereby forming a jet of the ink composition which is directed in such manner as to form a three-dimensional object by additive manufacturing. After initiating and carrying out gelation of the gellable silica sol constituting said object, a drying step yields the desired three-dimensional silica aerogel object.

A thermal insulation sheet is used that includes a fiber, a silica aerogel contained in the fiber, and a fibrous cavity. A method for manufacturing a thermal insulation sheet is used that includes: an impregnation step of impregnating a silica aerosol in a nonwoven fabric substrate containing a fiber that is insoluble in an acidic solution, and a fiber that is soluble in the acidic solution; a gelling step of gelling the silica aerosol; a hydrophobizing step of hydrophobizing the gel; and a drying step of drying the gel. The fiber that is soluble in the acidic solution is dissolved in the hydrophobizing step.

A thermal insulation sheet is used that includes a fiber, a silica aerogel contained in the fiber, and a fibrous cavity. A method for manufacturing a thermal insulation sheet is used that includes: an impregnation step of impregnating a silica aerosol in a nonwoven fabric substrate containing a fiber that is insoluble in an acidic solution, and a fiber that is soluble in the acidic solution; a gelling step of gelling the silica aerosol; a hydrophobizing step of hydrophobizing the gel; and a drying step of drying the gel. The fiber that is soluble in the acidic solution is dissolved in the hydrophobizing step.

The present invention relates to a method for producing a silica aerogel and a silica aerogel produced thereby. More specifically, a first water glass solution is used to form a first silica wet gel, and then a second water glass solution is additionally added to form a second silica wet gel organically bonded to the first silica wet gel which serves as a basic skeleton, so that a silica aerogel with enhanced physical properties is formed to increase the resistance to shrinkage in ambient drying, and the concentration of silicon dioxide in each of the first and second water glass solutions is controlled, thereby providing a method for producing a silica aerogel by which a silica aerogel having a specific tap density and controllable density can be produced, and also providing a silicon aerogel produced by the method.

A porous SiO2 xerogel is produced using temporary pore fillers or solid skeletal supports, which are removed by thermal oxidation at the end of the production process (e.g. carbon or organic), by means of a sol-gel-process by subcritical drying of the gel. The SiO.sub.2 xerogel includes pores having a pore size from more than 50 nm to less than 1000 nm. The SiO.sub.2 xerogel has a density of less than 400 kg/m.sup.3, a carbon content of less than 10%, a thermal conductivity at 800 C. below 0.060 W/m*K, a thermal conductivity at 400 C. below 0.040 W/m*K, and a thermal conductivity at 200 C. below 0.030 W/m*K.

A porous SiO2 xerogel is produced using temporary pore fillers or solid skeletal supports, which are removed by thermal oxidation at the end of the production process (e.g. carbon or organic), by means of a sol-gel-process by subcritical drying of the gel. The SiO.sub.2 xerogel includes pores having a pore size from more than 50 nm to less than 1000 nm. The SiO.sub.2 xerogel has a density of less than 400 kg/m.sup.3, a carbon content of less than 10%, a thermal conductivity at 800 C. below 0.060 W/m*K, a thermal conductivity at 400 C. below 0.040 W/m*K, and a thermal conductivity at 200 C. below 0.030 W/m*K.

A low-density gel product of the present disclosure has a coating layer on a surface thereof, the coating layer being composed of a polymer of a gas-phase polymerizable monomer. The low-density gel product of the present disclosure has an improved mechanical strength. The low-density gel product is, for example, an aerogel or xerogel. The low-density gel product can be, for example, in the form of a monolithic body such as a sheet or in the form of particles. The gas-phase polymerizable monomer is, for example, at least one selected from an olefin, styrene, a styrene derivative, (meth)acrylic acid, a (meth)acrylic acid ester, para-xylylene, and a para-xylylene derivative.

The invention relates to a continuous sol-gel method for producing quartz glass, comprising the following steps: (a) continuously metering a silicon alkoxide into a first reactor (R1) and carrying out an at least partial hydrolysis process by adding an aqueous mineral acid, thereby obtaining a first product flow (A); (b) continuously producing an aqueous silicic acid dispersion by continuously mixing water and silicic acid in a second reactor, thereby obtaining a second product flow (B); (c) continuously mixing the product flows (A) and (B) in a third reactor (R3) in order to produce a pre-sol, thereby obtaining a third product flow (C); (d) continuously adding an aqueous base to the product flow (C), thereby obtaining a sol; (e) continuously filling the exiting sol into moulds, thereby obtaining an aquagel; (f) drying the aquagel, thereby obtaining xerogels; and (g) sintering the xerogels, thereby obtaining quartz glass, with the proviso that at least one of the steps (a) to (e) additionally includes a degassing process of at least one feed material used in the step.

The invention relates to a continuous sol-gel method for producing quartz glass, comprising the following steps: (a) continuously metering a silicon alkoxide into a first reactor (R1) and carrying out an at least partial hydrolysis process by adding an aqueous mineral acid, thereby obtaining a first product flow (A); (b) continuously producing an aqueous silicic acid dispersion by continuously mixing water and silicic acid in a second reactor, thereby obtaining a second product flow (B); (c) continuously mixing the product flows (A) and (B) in a third reactor (R3) in order to produce a pre-sol, thereby obtaining a third product flow (C); (d) continuously adding an aqueous base to the product flow (C), thereby obtaining a sol; (e) continuously filling the exiting sol into moulds, thereby obtaining an aquagel; (f) drying the aquagel, thereby obtaining xerogels; and (g) sintering the xerogels, thereby obtaining quartz glass, with the proviso that at least one of the steps (a) to (e) additionally includes a degassing process of at least one feed material used in the step.

Xerogels and compositions comprising xerogels comprising a transition metal oxide and silicon oxide xerogel matrix. The xerogels and compositions can be made from mixtures of transition metal alkoxide(s) and tetraalkoxysilane(s) and, optionally, alkyltrialkoxysilane(s), aminoalkyl-, alkylaminoalkyl-, dialkylaminoalkyltrialkoxysilane(s), or a combination thereof. The xerogels and compositions can be used as antifouling coatings on, for example; boats.