Block aerogel composite material and preparation method thereof

A composite material and aerogel technology, applied in the field of bulk aerogel composite materials and their preparation, can solve the problems of breaking or separating from fibers, falling off of aerogel fragments, and high hardness of the composite, so as to improve mechanical properties. , The effect of reducing preparation cost and high specific surface area

Inactive Publication Date: 2012-12-05

GRADUATE SCHOOL OF THE CHINESE ACAD OF SCI GSCAS

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AI-Extracted Technical Summary

Problems solved by technology

However, the resulting composite is relatively hard, and the particles will be broken or separated ...

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Method used

As can be seen from the results of the foregoing examples, the airgel composite material of the present invention is formed by reticulating the cellulose nanofiber skeleton and the sol, significantly improving the mechanical properties of the airgel composite material, and obtaining low heat Conductivity, low density, high specific surface area airgel composites. Compared with airgel that is not composited with cellulose and can only be prepared as powder by freeze-drying, the composite cellulose airgel material prepared by this method can be freeze-dried to obtain a large-sized block material, which is a huge The advantages pave the way for the practical application of airgel materials in more fields.

Organic airgel has resorcinol-formaldehyde (RF), melamine-formaldehyde (MF), phenolic resin paint-formaldehyde (PF), mixed cresol-formaldehyde (JF), polyisocyanate (PUR), homogeneous Pyrogallol-formaldehyde (P-F), etc. Compared with inorganic aerogels (such as silica aerogel), organic aerogels have strong infrared absorption, which makes organic aerogels have lower radiation thermal conductivity.

[0127] Each get tetraethyl orthosilicate 6L, deionized water 2L, ethanol 9.2L mix uniformly and add 0.16L 1% hydrochloric acid, stir 1h and then add 0.55L 0.1M ammonia water to obtain silica sol. The previously prepared cellulose airgel is immersed in the sol system, and the cellulose block is taken out after shrinking and swelling back to...

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Abstract

The invention discloses a block aerogel composite material and a preparation method thereof. The block aerogel composite material consists of reticular cellulose nano fiber skeletons and sol in a combining way, wherein the porosity of the aerogel composite material is 80-99.5 percent, the density is 0.015-0.680g/cm<3>, the BET specific surface area is 150-1200m<2>/g, the coefficient of heat conductivity is 0.015-0.045Wm<-1>k<-1> and the modulus of elasticity is 0.5-150MPa. The block aerogel composite material provided by the embodiment of the invention has the advantages that since the material consists of the reticular cellulose nano fiber skeletons and the sol in the combining way, the mechanical property of the block aerogel composite material can be obviously improved, the heat conductivity is low, the density is small and the specific surface area is large; and besides, the equipment cost can be decreased by adopting a relatively low and safe freeze-drying method to replace the traditional supercritical drying method.

Technology Topic

Supercritical dryingElastic modulus +6

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Examples

Experimental program(6)
Comparison scheme(1)

Example Embodiment

[0087] In the preparation of the organosol, those skilled in the art can select or adjust the ratio of each component according to the actual situation, so as to obtain the desired organosol.

[0088] According to an embodiment of the present invention, the organic sol precursor used is resorcinol and formaldehyde, the alkaline catalyst is sodium carbonate, and the molar ratio of resorcinol:formaldehyde:water:sodium carbonate may be 1:1.5 ~2.5: 50 to 1500: 0.001 to 0.1, preferably 1: 1.8 to 2.2: 50 to 1000: 0.002 to 0.1, preferably 1: 1.8 to 2.0: 150 to 500: 0.005 to 0.05.

[0089] When the sol is a metal oxide sol, the specific operation steps may include: uniformly mixing the precursor of the metal oxide sol with alcohol and water, then adding an acid catalyst and stirring to obtain the metal oxide sol.

[0090] It should be understood that the materials used in the preparation process of the metal oxide sol are not particularly limited. The organic sol precursors include butyl titanate, titanium chloride, iron chloride, iron nitrate, zirconium chloride, and zirconium nitrate. , Tin chloride, tin nitrate, aluminum chloride, aluminum n-butoxide, aluminum isopropoxide, aluminum nitrate, preferably butyl titanate, the alcohol includes ethanol, methanol, propanol, isopropanol, preferably ethanol, so The acid catalyst includes acetic acid, hydrochloric acid, nitric acid, sulfuric acid, and preferably acetic acid.

[0091] According to an embodiment of the present invention, the metal oxide sol precursor used is butyl titanate, the alcohol is ethanol, and the acid catalyst is acetic acid. The molar ratio of butyl titanate:ethanol:water:acetic acid is 1:1-20:1-16:0.8-5.5, preferably 1:8-18:2-8:1.3-2.5, and more preferably 1:1: 5~15: 3~5: 1.5~2.0.

[0092] According to the method for preparing a bulk aerogel composite material of the present invention, step c) is to react the reticulated cellulose nanofiber skeleton provided above with the sol to obtain a composite. Specifically, step c) may include:

[0093] c-1) Immerse the cellulose nanofiber skeleton in the sol, and take it out after the cellulose nanofiber skeleton is contracted and swelled back to its original volume;

[0094] c-2) Put the taken-out cellulose nanofiber skeleton in an alcohol atmosphere to gel and age to obtain a composite of cellulose nanofiber skeleton and sol.

[0095] There are no special restrictions on the materials and reaction conditions involved in step c). The alcohol used in step c-2) can be methanol, ethanol, propanol or butanol. According to an embodiment of the present invention, the alcohol is preferably ethanol.

[0096] The aging described in step c-2) is continued for a period of time at a certain temperature. According to an embodiment of the present invention, the aging temperature may be 20 to 80°C, preferably 30 to 60°C, more preferably 40 to 50°C. The aging time can be 1-24h, preferably 2-18h, more preferably 5-15h.

[0097] According to the method for preparing a bulk aerogel composite material of the present invention, step d) is finally performed to freeze-dry the composite, thereby obtaining the aerogel composite material of the present invention. This step includes two steps of solvent replacement and freeze drying.

[0098] In the solvent replacement, according to an embodiment of the present invention, tert-butanol or a mixed solution of tert-butanol and deionized water is used. There is no special restriction on the volume ratio of the tert-butanol and the deionized water. Preferably, the volume ratio of the deionized water to the tert-butanol is (0-3):1.

[0099] Regarding the freeze-drying method, it should be understood that there are no special restrictions on the equipment used in the freeze-drying process. For example, it can be a conventional freezing or heating equipment, as long as it can reach the temperature required for the reaction.

[0100] Specifically, according to an embodiment of the present invention, the operation of step d) may specifically include:

[0101] The compound obtained in step c) is placed in a mixed solution of tert-butanol and deionized water preheated to 50-100°C for solvent replacement reaction. After reacting for 2 to 72 hours, the reacted compound is heated to 0-50 Freeze-drying at ℃ to obtain the aerogel composite material, such as figure 2 Shown.

[0102] In addition, in order to further improve the mechanical properties of the aerogel composite material, according to an embodiment of the present invention, the freeze-dried aerogel composite material can also be carbonized in an inert gas atmosphere to obtain a carbonized aerogel Composite materials.

[0103] The selection of the inert gas is not particularly limited. Preferably, the inert gas may be nitrogen.

[0104] Therefore, according to an embodiment of the present invention, the method for preparing a bulk aerogel composite material of the present invention may further include the following steps:

[0105] e) Carbonizing the aerogel composite material in an inert gas atmosphere to obtain a carbonized aerogel composite material.

[0106] According to the method for preparing a bulk aerogel composite material of the present invention, a bulk aerogel block can be obtained. It should be understood that the size of the aerogel material prepared by the method is not particularly limited, as long as there is a corresponding mold and reaction vessel, a composite aerogel of any shape and size can be prepared.

[0107] According to the method for preparing a bulk aerogel composite material of the present invention, the size range of the finally obtained aerogel composite material can reach 2000*1000*80mm. In one embodiment, the size of the aerogel composite material obtained by the method of the present invention is 1500*800*50 mm. In another embodiment, the size of the aerogel composite material obtained by the method of the present invention is 1000*600*40 mm. In another embodiment, the size of the aerogel composite material obtained by the method of the present invention is 600*500*30 mm. In another embodiment, the size of the aerogel composite material obtained by the method of the present invention is 500*400*20 mm.

[0108] The method for preparing aerogel composite material of the present invention uses a relatively cheap and safe drying method to replace the traditional supercritical drying method, reduces the preparation cost of aerogel composite material, obtains large-size bulk materials, and further expands the aerogel Application of glue composite materials.

[0109] The aerogel composite material of the present invention can be used for thermal insulation materials, optical materials, electrode materials, semiconductor materials, magnetic materials, etc., in aviation, energy, information, environmental protection, medicine, pesticides, metallurgy, construction, fire and flame retardant and scientific experiments And other fields have great application potential. In particular, the aerogel composite material of the present invention is suitable for use as a thermal insulation material in the construction field, including its application to the thermal insulation layer of building materials.

Example Embodiment

[0112] Example 1

[0113] The pre-cultured seed culture of Acetobacter xylinum was inoculated into 12L of Acetobacter xylinum fermentation culture at an inoculum of 10%, shaken sufficiently, and placed in a constant temperature of 30℃ for 15 days to obtain a cellulose hydrogel. . The fermentation broth of Acetobacter xylinum contains 2% glucose, 0.5% peptone, 0.5% yeast powder, 0.27% disodium hydrogen phosphate pentahydrate, 0.115% citric acid-water compound, pH 6.0, and high temperature sterilization for 20 minutes.

[0114] The cellulose hydrogel fermented by microorganisms was placed in a 5% NaOH aqueous solution at 90°C for 10 hours, and then placed in deionized water at 85°C for 15 hours. During this period, the deionized water was replaced 3 times, and the volume ratio was 1: The mixture of 1 tert-butanol and deionized water is solvent replaced at 60°C for 10 hours, during which the mixture is replaced twice, and the sample is freeze-dried until the sample is completely dry to obtain the reticulated microbial cellulose skeleton (cellulose aerogel).

[0115] Add 1.1kg resorcinol, 0.6kg formaldehyde and 50g NaCO to 20L deionized water 3 After stirring uniformly, the prepared cellulose network skeleton is placed in the organosol, and the cellulose block is taken out after shrinking and swelling back to its original volume. After the resorcinol and formaldehyde gel are placed in an oven at 50°C for aging for 4 hours, then put into a 1:1 mixture of tert-butanol and deionized water for solvent replacement at 50°C for 15 hours, during which time the mixture is replaced 4 times. The solvent-replaced gel is placed in a refrigerator at -20°C for 14 hours, and then freeze-dried until the sample is completely dry, to obtain a complete organic (RF) composite aerogel material with significantly enhanced strength and flexibility. Its main parameters are shown in Table 1.

[0116] Table 1 The main parameters of the composite aerogel prepared according to Example 1

[0117]

Example Embodiment

[0118] Example 2

[0119] The pre-cultured seed culture of Acetobacter xylinum was inoculated into 10L of the fermentation culture of Acetobacter xylinum at an inoculum of 12%, shaken sufficiently, and placed in a constant temperature of 30℃ for 20 days to obtain a cellulose hydrogel. . The fermentation broth of Acetobacter xylinum contains glucose 4%, peptone 0.8%, yeast powder 0.5%, disodium hydrogen phosphate pentahydrate 0.35%, citric acid-water compound 0.115%, pH 6.2, and high temperature sterilization for 20 minutes.

[0120] The cellulose hydrogel fermented by microorganisms was placed in a 6% NaOH aqueous solution at 90°C for 8 hours, and then placed in deionized water at 85°C for 15 hours. The deionized water was replaced 3 times during the period, and the volume ratio was 1: The mixture of 1 tert-butanol and deionized water is subjected to solvent replacement at 58°C for 10 hours, during which the mixture is replaced twice, and the sample is freeze-dried until the sample is completely dry to obtain a reticulated microbial cellulose skeleton (cellulose aerogel).

[0121] Add 3L of butyl titanate, 1L of deionized water, and 0.816L of acetic acid to 5.5L of ethanol, stir and mix to obtain TiO 2 Sol. Place the prepared cellulose network skeleton on the TiO 2 In the sol, take out the cellulose block after shrinking and swelling back to its original volume. To be TiO 2 The gel was then placed in an oven at 50°C for aging for 4 hours, and then put in a 1:1 mixture of tert-butanol and deionized water at 60°C for solvent replacement for 20 hours, during which the mixture was replaced 4 times. The solvent-replaced gel is placed in a refrigerator at -20°C for 10 hours, and then freeze-dried until the sample is completely dry, to obtain a complete and flexible titanium dioxide composite aerogel material. Its main parameters are shown in Table 2.

[0122] Table 2 The main parameters of the composite aerogel prepared according to Example 2

[0123]

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PUM

Property	Measurement	Unit
Size	50.0 ~ 1500.0	mm
Size	40.0 ~ 1000.0	mm
tensile		MPa
Particle size		Pa
strength	10

Description & Claims & Application Information

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Block aerogel composite material and preparation method thereof

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

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Examples

Example Embodiment

Example Embodiment

Example Embodiment

PUM

Description & Claims & Application Information

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