CN1654324A

CN1654324A - Method for preparing SiO2 aerogel with nanometer apertures under normal pressure

Info

Publication number: CN1654324A
Application number: CNA2005100111448A
Authority: CN
Inventors: 倪文; 张大陆; 肖晋宜; 刘凤梅
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2005-01-07
Filing date: 2005-01-07
Publication date: 2005-08-17

Abstract

The normal pressure process of preparing SiO2 aerogel with nanometer pores belongs to the field of inorganic non-metal material preparation. The present invention features the cheap water glass as silicon source, the surfactant to alter the surface property of SiO2 aerogel hydrophobicity, the ion exchange resin to eliminate great amount of sodium ions and to lower the effect of the sodium ions on the heat conductivity of SiO2 aerogel, and template agent to control narrow pore size distribution and pore size for realize nanometer level super heat insulating material structure. The normal pressure process has greatly reduced preparation time, and the produced SiO2 aerogel has both hydrophobicity and heat stability and performance similar to SiO2 aerogel produced through supercritical process.

Description

A kind of normal pressure prepares nanoporous SiO 2The method of aerogel

Technical field

The invention belongs to field of inorganic nonmetallic material, particularly a kind of normal pressure prepares nanoporous SiO ₂The aerogel method.

Background technology

SiO ₂Aerogel is a kind of mano-porous material, has many potential to use.Aspect adiabatic, because SiO ₂The aerogel yardstick is the porous material less than 50 nanometers, and the diameter in hole is the mean free path less than molecule, makes SiO ₂Aerogel is during as thermal insulation material, between the molecule of gas do not bump or probability very little, the thermal conduction of gas significantly reduces, thermal conductivity is also lower than air, thermal conductivity at normal temperatures is 0.03～0.05W/mK.SiO ₂Aerogel 90%～98%, gas, density 0.05～0.2g/cm ³, the specific surface area height makes it will be widely used aspect absorbent and the support of the catalyst.SiO ₂The specific inductivity of aerogel is low, and aspect optical property, reflection coefficient has only 1.01.In addition, will be widely used at aspects such as sound insulation, medicament slow release, pharmaceutical carriers.

Before more than 60 year, Kristler just begins to prepare SiO for the silicon source with postcritical method with water glass ₂Aerogel.Hajime Tamon tetramethoxysilance prepares silica aerogel for the silicon source, and the aerogel product of gained is transparent, do not introduce new ion, and available this product is made adiabatic transparent material.

R.Deshpande at first synthesized SiO with water glass in condition of normal pressure in 1996 ₂Aerogel.

China's application number is " modified nanometer heat insulating material and the production technique thereof " that 97106652.3 patent has been introduced inventions such as Wang Jue, this patent is the silicon source with methyl silicate, water glass, silicon sol etc., with methyl alcohol, acetone, ethyl ester etc. is solvent, and in colloidal sol-gelation process, mix titania powder as infrared light screening agent, mix glass fibre, kaolin, polynite, attapulgite as inorganic strengthening agent, carry out supercritical drying with methyl alcohol, ethanol, carbonic acid gas as drying medium, can obtain complete flawless lightweight silica aerogel heat preserving and insulating material.

In sum, above SiO ₂The preparation method of aerogel mainly contains: be the silicon source with the tetraethoxy and be the silicon source with water glass, silicon sol, adopt supercritical drying and constant pressure and dry to prepare.But, when adopting tetraethoxy to be the silicon source,, cost an arm and a leg because starting material are difficult for obtaining by the data record.When adopting water glass to be the silicon source, sodium ion has most of remaining, has influenced the reduction of product thermal conductivity.The investment that the supercritical drying that adopts needs is big, cost height, high-tension apparatus operational hazards.And the atmosphere pressure desiccation that adopts is longer cycle time, and possess hydrophilic property, does not reach supercritical drying and prepares SiO ₂The performance of aerogel.The SiO that makes simultaneously ₂The aerogel aperture distributes bigger, can not guarantee SiO fully ₂The hole of aerogel all or the overwhelming majority becomes the nano level hole, so the heat-insulating property of material does not reach the ideal performance requirement of super insulating material.

Summary of the invention

The present invention is the silicon source with cheap water glass, and purpose is to find out the method that adopts the normal pressure means to solve the remaining problem of sodium ion.

A kind of normal pressure prepares nanoporous SiO ₂The method of aerogel is characterized in that the present invention is the silicon source with cheap water glass, adds tensio-active agent and changes SiO ₂The surface properties of aerogel makes it hydrophobic.Select a large amount of removal sodium ion of ion exchange resin, reduce sodium ion SiO ₂The influence of aerogel thermal conductivity.And adopting template to control pore size distribution and size, the size in hole can be controlled in the narrow scope, realizes the structural requirement of real nano-porous super thermal insulation material.

1) raw material is prepared

Water glass water sulfuric acid methane amide storng-acid cation exchange resin (732 type) template (n-Butyl Amine 99) ethanol normal hexane trimethylchlorosilane

2) material produce

Water glass (concentration is 21%～41%, and modulus is 3.0～3.3) is added storng-acid cation exchange resin (732 type) and template (n-Butyl Amine 99), with the deionized water dilution,

Make catalyzer with sulfuric acid or methane amide, the Na of last whole solution ₂SiO ₃Concentration be 8%.The limit adds the sulfuric acid limit, and to be stirred to PH be 8～10, obtains colloidal sol, adds Photoresist and fortifying fibre simultaneously, and leave standstill and make it gel, transparent nattier blue gel.The gel of gained is aging in plastic beaker, with the water in the ethanol exchange wet gel.With the normal hexane exchange, the mixing solutions with normal hexane and trimethylchlorosilane soaks then.Dry at 150 ℃ of removal organism.

3) product properties

SiO by above-mentioned prepared ₂The nano-porous super thermal insulation material The performance test results

600 ℃ of thermal conductivities	≤0.09W/(m·K)
600 ℃ of thermal conductivities	≤0.09W/(m·K)		Specific surface area	600～1600m ²/g	Generally be 600～1000
Porosity	95％	Be up to 99%	Specific surface area	600～1600m ²/g	Generally be 600～1000
Porosity	95％	Be up to 99%	Specific refractory power	1.0～1.05	To solid material is low-down
Thermostability	≥600℃	Fusing point is 1200 ℃	Specific refractory power	1.0～1.05	To solid material is low-down
Thermostability	≥600℃	Fusing point is 1200 ℃	Compressive strength	＞0.2Mpa
Insulation resistance	＞200Ω		Compressive strength	＞0.2Mpa
Insulation resistance	＞200Ω		Na ²⁺Remove	More than 99%

4) excellent results of the present invention

This method can be good at a SiO ₂Aerogel is controlled at nano level, and a smaller scope.And a large amount of removals sodium ion, solved because of SiO ₂The pore size distribution of aerogel is uneven and because of the water that exists of sodium ion does not wash clean influence to its thermal conductivity, and has solved the problem of its hydrophobicity and thermostability, and the normal pressure preparation time shortens greatly, and performance is not less than the SiO of overcritical production ₂Aerogel

The SiO that adopts this method to prepare ₂The product aperture of aerogel is accounting for more than 95% between 20～30nm, and safety, cost are low, hydrophobic good, put into water, waft on the water, still do not sink at 30 days.Can reduce SiO greatly by present method ₂The thermal conductivity of aerogel, and the constant pressure and dry time shortened to 3 days.Favourable present method can reduce SiO greatly ₂The thermal conductivity of aerogel, and the constant pressure and dry time shortened to 3 days.Help large-scale continuous and produce block SiO ₂Aerogel.This method also can be used for preparing nanometer SiO simultaneously ₂Powder.

Description of drawings

Fig. 1 is technological process of production figure of the present invention

Fig. 2 is the sem photograph of product of the present invention

Embodiment

1. the order of pressing water glass, sulfuric acid, water, glycerine, n-Butyl Amine 99 adds.Water glass/sulfuric acid=0.7～1 (mol ratio), fixedly pH value is about 8 to become glue, digestion time was generally 4～8 hours.Above-mentioned colloid is worn out a couple of days, wash with water, wash repeatedly with ethanol, wash with normal hexane then, wash with normal hexane and TMCS at last, filter, put into the loft drier freeze-day with constant temperature then, organism is removed in calcining, obtains nano-pore structure SiO ₂Aerogel.

2. the order of pressing water glass, methane amide, acetate, water, ethylene glycol, n-Butyl Amine 99 adds water glass/methane amide=0.6～1 (mol ratio).Wherein water has comprised the water in the water glass.Addition sequence is to add the methane amide that dilutes after water glass adds entry, adds acetate and template again and stirs several minutes.Drying at room temperature is put into the loft drier freeze-day with constant temperature then, and organism is removed in calcining, obtains nano-pore structure SiO ₂Aerogel.

Claims

1. a normal pressure prepares nanoporous SiO ₂The method of aerogel is characterized in that the present invention is the silicon source with cheap water glass, adds tensio-active agent and changes SiO ₂The surface properties of aerogel; Select a large amount of removal sodium ion of ion exchange resin, reduce sodium ion SiO ₂The influence of aerogel thermal conductivity; Adopt template to control pore size distribution and size.

2. normal pressure prepares nanoporous SiO according to claim 1 ₂The method of super insulating material is characterized in that concentration of sodium silicate is 21%～41%, modulus is 3.0～3.3; Tensio-active agent is a trimethylchlorosilane; Ion exchange resin is 732 type storng-acid cation exchange resins; Template is a n-Butyl Amine 99.

3. normal pressure prepares nanoporous SiO as claimed in claim 1 or 2 ₂The method of aerogel is characterized in that SiO ₂The aerogel production stage is:

With concentration is 21%～41%, and modulus is that 3.0～3.3 water glass add 732 type storng-acid cation exchange resins and n-Butyl Amine 99 template, dilutes with deionized water;

Make catalyzer with sulfuric acid or methane amide, the Na of last whole solution ₂SiO ₃Concentration be 8%, the limit adds the sulfuric acid limit, and to be stirred to PH be 8-10, obtains colloidal sol, adds Photoresist and fortifying fibre simultaneously, and leave standstill and make it gel, transparent nattier blue gel; The gel of gained is aging in plastic beaker, with the water in the ethanol exchange wet gel; With the normal hexane exchange, the mixing solutions with normal hexane and trimethylchlorosilane soaks then; Dry at 150 ℃ of removal organism, can obtain nanoporous SiO ₂Aerogel.