CN112592150A - Preparation method of alumina-silica aerogel heat-insulation composite material - Google Patents
Preparation method of alumina-silica aerogel heat-insulation composite material Download PDFInfo
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Abstract
The invention belongs to the technical field of heat insulation materials, and discloses a preparation method of an alumina-silica aerogel heat insulation composite material. The preparation method of the material adopts raw materials without organic aluminum/inorganic aluminum/organic silicon compounds, organic solvent replacement is avoided in the preparation process, flammable and explosive ethanol solvent is not used as a drying medium, the raw materials and the preparation process are green, environment-friendly and safe, the manufacturing cost is low, and batch production and large-scale application are easy.
Description
Technical Field
The invention relates to the technical field of heat insulation materials, in particular to a preparation method of an alumina-silica aerogel heat insulation composite material.
Background
The nano aerogel heat insulation composite material has the advantages of light weight, high temperature resistance and low heat conductivity, and is a research hotspot in the field of high-performance heat insulation and preservation at present (Zhao S, et al. Additive manufacturing of silica aerogels, Nature, 2020(584): 387-392.). For example, the silica aerogel thermal insulation composite material is the most studied aerogel thermal insulation composite material which is used on a large scale at present, the high-temperature thermal conductivity of the silica aerogel thermal insulation composite material is extremely low, and the thermal conductivity at 800 ℃ is only 0.038W/m.K (Von Jian, et al. aerogel high-efficiency thermal insulation material, scientific publishing Co., Ltd., 2016.11.), and the silica aerogel thermal insulation composite material is widely applied to the high-temperature thermal insulation fields of aerospace, industrial pipelines, petrochemical industry and the like. However, silica aerogels have increased porosity, increased particle size, and increased thermal conductivity when heated at 800 ℃ and thus have a maximum use temperature of no more than 800 ℃ (Jean P, et al. Comparison between sintered and compressed aerogels. Optical Materials, 2004(26): 167-.
Pure alumina aerogels have higher service temperatures than silica aerogels, but generally do not exceed 1000 ℃ (Poco J, et al, Synthesis of high porosity, Journal of Non-Crystalline Solids, 2001(285): 57-63). In order to further increase the use temperature, researchers have introduced the heterogeneous element Si (Horiuchi T, et al, Maintenance of large surface area of aluminum grown at an electrically heated temperature above 1300 ℃ by prepared silica-containing boehmite aerogel, Journal of Non-Crystalline sol, 2001(291): 187-198.) into alumina aerogel, and the use temperature of the prepared alumina-silica aerogel can reach 1200-1300 ℃. However, the preparation of the alumina-silica aerogel requires an organic aluminum compound (aluminum isopropoxide) as an aluminum source of the aerogel and an organic silicon compound (tetraethoxysilane) as a silicon source of the aerogel, and the aerogel is subjected to four steps of sol-gel, aging, solvent replacement and supercritical drying, wherein a large amount of flammable and explosive organic solvent, namely ethanol, is required in the solvent replacement, and the generated waste solvent requires an additional post-treatment process; ethanol is also used as a drying medium in the drying process, and the ethanol is prepared by a supercritical drying process, and due to the flammable and explosive characteristics of the ethanol, the explosion-proof requirement of a supercritical drying equipment system is high, and the drying process has large potential safety hazard and is complicatedThe process flow and the dangerous supercritical drying process ensure that the existing alumina-silica aerogel heat-insulation composite material has higher manufacturing cost and limit the large-scale application of the composite material in the field of heat insulation and heat preservation. Although there are also aluminum sources obtained by using inorganic aluminum compounds (Wu X, et Al. Novel Al)2O3–SiO2(iii) composite aerogels with high moisture surface area at evolved temporal methods with differential alumina/silica molar ratios, RSC Advances, 2016(6): 5611) or organic solvent-free replacement process (Yang J, et. factor one-step predictor-to-organic solvent Synthesis of silica-polypalemia aerogels with high spectral surface area at evolved temporal methods, Journal of Materials, 2017 (889): 897) or non-super-drying process (III, synthetic X. Synthesis of aluminum2O3-SiO2The research reports on the preparation of alumina-silica aerogel by using Reinforcement and molecular compression drying, Journal of Non-Crystalline Solids, 2017(471): 160-.
Therefore, how to prepare the alumina-silica aerogel heat-insulating composite material with high temperature resistance, low thermal conductivity and high strength by using a green, environment-friendly and safe process method by using a non-organic aluminum/inorganic aluminum/organic silicon compound as a raw material and non-ethanol as a solvent of sol, and a non-organic solvent replacement process and a non-ethanol as a drying medium in the preparation process is a target which is constantly pursued by researchers.
Disclosure of Invention
The invention aims to provide an alumina-silica aerogel heat insulation composite material with the highest use temperature of 1500 ℃, high temperature resistance, low thermal conductivity and high strength, and a preparation method of the material.
In order to realize the aim, the invention provides a preparation method of a high-temperature-resistant alumina-silica aerogel heat-insulation composite material, which comprises the following steps:
step 1, preparing a fiber prefabricated part by taking inorganic ceramic fibers as raw materials;
step 2, mixing and stirring the water-based alumina sol and the water-based silica sol to obtain mixed sol, adding ammonia water into the mixed sol, and continuously stirring to obtain alumina-silica sol;
step 3, putting the fiber prefabricated member obtained in the step 1 into a vacuum impregnation tank, and vacuumizing to-0.1 MPa; then injecting the alumina-silica sol obtained in the step 2 into a fiber prefabricated part in a vacuum impregnation tank, and maintaining the pressure for 0.5-1 hour to obtain a fiber/sol mixture;
step 4, placing the fiber/sol mixture obtained in the step 3 into a water bath kettle at the temperature of 15-75 ℃ for standing until the sol is gelled, and continuing to age for 2-3 days to obtain the fiber/sol mixture after the gel is aged;
step 5, putting the fiber/gel mixture obtained in the step 4 after gel aging into a hydrothermal kettle, and carrying out hydrothermal auxiliary drying treatment to obtain an alumina-silica aerogel heat-insulation composite material blank;
step 6, drying the alumina-silica aerogel heat insulation composite material blank obtained in the step 5 to obtain an alumina-silica aerogel heat insulation composite material;
wherein, the water-heat auxiliary drying treatment in the step 5 comprises the following specific processes: and (3) putting the fiber/gel mixture obtained after the gel aging in the step (4) into a hydrothermal kettle, pre-filling 3MPa of industrial nitrogen or argon into the hydrothermal kettle, controlling the temperature rise rate of the hydrothermal kettle to be 0.5-1 ℃/min, raising the temperature in the hydrothermal kettle to 180-300 ℃, controlling the drying pressure in the hydrothermal kettle to be 6-15 MPa, drying and keeping the temperature for 0-2 hours, slowly releasing the water gas in the kettle, controlling the pressure release speed to be 1-2 MPa/hour, and taking out the fiber/gel mixture when the temperature in the kettle is reduced to below 50 ℃ after the pressure is reduced to normal pressure, thereby obtaining an alumina-silica aerogel heat-insulating composite material blank. In this step, the drying and holding time of 0 hour means: controlling the heating rate of the hydrothermal kettle to be 0.5-1 ℃/min, raising the temperature in the hydrothermal kettle to 180-300 ℃, directly carrying out subsequent operations of releasing water vapor in the kettle, relieving pressure and cooling and taking out a product after the drying pressure in the hydrothermal kettle reaches 6-15 MPa.
Further, in step 1, the inorganic ceramic fiber is at least one of mullite fiber, alumina and zirconia fiber.
Further, in the step 1, the apparent density of the inorganic ceramic fiber is 0.15-0.30g/cm3。
Further, in the step 2, the solid contents of the water-based alumina sol and the silica sol are both 15-30%.
Further, in the step 2, the volume ratio of the water-based alumina sol to the water-based silica sol to ammonia water is 5:1: 0.1-0.7.
Further, in the step 6, the temperature in the drying treatment process is 110-140 ℃, and the heat preservation time is 12-24 hours.
Compared with the prior art, the invention has the following advantages:
(1) the preparation method of the alumina-silica aerogel heat-insulation composite material provided by the invention is simple
The preparation process of the high-temperature-resistant alumina-silica aerogel heat-insulation composite material comprises 6 process steps of preparing a fiber prefabricated member, preparing alumina-silica sol, vacuum impregnation, gel aging, hydrothermal auxiliary drying and drying, wherein the alumina-silica sol is obtained by simply mixing commercially available water-based alumina and water-based silica sol which are green and environment-friendly and take water as a solvent, an organic solvent replacement process is not used in the preparation process, a flammable and explosive ethanol solvent is not used as a drying medium, and the raw materials and the preparation process are green, environment-friendly and safe, are low in manufacturing cost and are suitable for large-scale production.
(2) The alumina-silica aerogel heat-insulating composite material prepared by the method has high temperature resistance
The high-temperature-resistant alumina-silica aerogel heat-insulation composite material prepared by the method has high temperature resistance, consists of high-temperature-resistant inorganic ceramic fibers and alumina-silica aerogel, is placed in a muffle furnace for 1500 ℃ heat treatment for 1800s, has the thickness shrinkage of less than 1.50 percent, and is kept intact.
(3) The alumina-silica aerogel heat-insulating composite material prepared by the invention has low thermal conductivity
The high-temperature-resistant alumina-silica aerogel heat-insulation composite material prepared by the method has the thermal conductivity of only 0.076W/m.K at 1000 ℃ and is greatly lower than the high-temperature thermal conductivity (0.17W/m ∙ K, http:// www.zircarceramics.com/pages/flex/specs/almat. htm) of alumina fibers produced by Zircar ceramics at 980 ℃, which is because the alumina-silica aerogel particles filled in micron-sized holes of a fiber prefabricated member are fused to a certain degree under the hydrothermal action in the hydrothermal auxiliary drying process of the invention, so that the structural strength of the nanometer collapsed framework of the gel is obviously improved, the gel nanometer framework is ensured not to be generated due to overhigh specific surface tension of water in the pressure relief process of releasing water vapor, and the alumina-silica aerogel is changed into alumina-silica aerogel along with the release of the water in the gel, the aerogel with the nano-porous structure can effectively inhibit gas heat transfer in the material. Meanwhile, in order to avoid the problem that the solid heat transfer among aerogel particles is increased due to too high fusion degree of the alumina-silica gel particles, the invention can effectively regulate and control the fusion degree among the gel particles by controlling the drying temperature, pressure and heat preservation time in the hydrothermal auxiliary drying process, thereby controlling the solid heat transfer of an aerogel network structure, so that the nano porous alumina-silica aerogel formed in the hydrothermal auxiliary drying process can fill the holes of the fiber prefabricated member, and keep low solid heat transfer, and finally endow the material with very low high-temperature heat conductivity.
(4) The alumina-silica aerogel heat-insulating composite material prepared by the method has high strength
The alumina-silica aerogel heat-insulation composite material prepared by the invention adopts inorganic ceramic fibers as a mechanical reinforcing phase of the material, and simultaneously, in the hydrothermal auxiliary drying process, alumina-silica aerogel with higher skeleton strength is formed in micron-sized holes among the fibers, the periphery of the fibers is wrapped by the aerogel, so that the material has good mechanical property, and the compressive strength of the material is up to more than 0.12MPa (3% strain).
(5) The alumina-silica aerogel heat-insulation composite material prepared by the invention has the advantages of high temperature resistance, low thermal conductivity, high strength and the like, and is particularly suitable for the fields of high-temperature heat insulation and preservation with extremely high temperature resistance requirements, such as aviation, aerospace, industrial kilns and the like. In addition, the preparation method and the preparation process are simple, green and environment-friendly, have short preparation period, can form the complex special-shaped heat-insulating component, and are suitable for engineering and large-scale production.
In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a general flow chart of the production process of the present invention;
FIG. 2 is a scanning electron microscope microscopic morphology image of the composite material prepared in example 1 of the present invention;
FIG. 3 is a partial enlarged view of the aerogel part in FIG. 2, specifically a scanning electron microscope microscopic morphology view of the nanoporous alumina-silica aerogel in the composite material prepared by the present invention.
Detailed Description
Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.
The high-temperature-resistant alumina-silica aerogel heat-insulation composite material provided by the invention is prepared from an inorganic ceramic fiber prefabricated member and nano porous alumina-oxygenSilica aerogel matrix. The inner pores of the inorganic ceramic fiber prefabricated member are filled with the nano porous alumina-silica aerogel, and the surface of the inorganic ceramic fiber is coated with the nano porous alumina-silica aerogel. The apparent density of the inorganic ceramic fiber prefabricated part is 0.15-0.30g/cm3(inclusive of endpoints). The sol of nanoporous alumina-silica aerogel is a water-based (with water as the solvent) alumina-silica sol. The mass fraction of the alumina-silica aerogel in the whole composite material is 50-70%, and the mass fraction of the inorganic ceramic fiber in the whole composite material is 30-50%.
As shown in figure 1, the preparation method of the alumina-silica aerogel heat-insulation composite material provided by the invention comprises 6 steps of preparing a fiber prefabricated member, preparing alumina-silica sol, carrying out vacuum impregnation, carrying out gel aging, carrying out hydrothermal auxiliary drying and drying. The method specifically comprises the following steps:
in a first step, a fiber preform is prepared by:
clamping and fixing inorganic ceramic fibers with certain mass by using a forming die (the volume of the die is selected according to the volume of the alumina-silica aerogel heat-insulation composite material to be prepared, and the volume of the alumina-silica aerogel heat-insulation composite material is equal to that of the fiber prefabricated member, so that the volume of the die can just accommodate the fiber prefabricated member) to form the fiber prefabricated member, wherein the apparent density of the inorganic ceramic fibers is 0.15-0.30g/cm before clamping3(calculating the fiber mass according to the fiber mass = volume × density, weighing the inorganic ceramic fiber by a balance with the precision of 0.1g, wherein the volume is the volume of the fiber preform), and making the arrangement direction of the inorganic ceramic fiber perpendicular to the heat flow direction during heat insulation use to obtain the fiber preform.
The inorganic ceramic fiber may be at least one of mullite fiber, alumina, zirconia fiber.
The second step is that: the method for preparing the alumina-silica sol comprises the following steps:
the catalyst is prepared by respectively taking commercially available water-based alumina sol and water-based silica sol as aluminum source and silicon source raw materials and ammonia water (the molar concentration is 0.5 mol/L) as a catalyst. The method comprises the following specific steps: firstly, mixing and stirring alumina sol and silica sol for 10min, then adding ammonia water into the mixed sol, and continuously stirring for 30min to obtain alumina-silica sol. Wherein the volume ratio of the alumina sol to the silica sol to the ammonia water is 5:1 (0.1-0.7).
The solid content of the water-based alumina sol and the silica sol is 15-30%.
The third step: vacuum impregnation is carried out by the following steps:
firstly, putting the fiber prefabricated member obtained in the first step into a vacuum impregnation tank, and vacuumizing to-0.1 MPa; and then injecting the alumina-silica sol obtained in the second step into a fiber prefabricated member in a vacuum impregnation tank, wherein the function of a vacuumizing mode is to enable the sol to be fully permeated into the fiber prefabricated member, the fiber prefabricated member is required to be immersed by the sol to ensure the impregnation sufficiency, then maintaining the pressure for 0.5-1 hour, and introducing air into the vacuum impregnation tank to eliminate vacuum to obtain a fiber/sol mixture.
The fourth step: aging the gel by the following steps:
and (3) placing the fiber/sol mixture obtained in the third step into a water bath kettle at 15-75 ℃ for standing until the sol is gelled, and continuing to stand and age in the water bath kettle for 2-3 days to obtain the fiber/sol mixture after the gel is aged.
Fifthly, hydrothermal auxiliary drying, which comprises the following steps:
and (3) putting the fiber/gel mixture obtained after the gel aging in the fourth step into a hydrothermal kettle, pre-filling 3MPa of industrial nitrogen or argon (the purity is more than or equal to 99.5%) into the hydrothermal kettle, controlling the temperature rise rate of the hydrothermal kettle to be 0.5-1 ℃/min, raising the temperature in the hydrothermal kettle to 180-300 ℃, controlling the drying pressure in the hydrothermal kettle to be 6-15 MPa, drying and preserving the temperature for 0-2 hours, slowly releasing the water gas in the kettle, controlling the pressure release speed to be 1-2 MPa/hour, taking out the fiber/gel mixture after the temperature in the kettle is reduced to below 50 ℃ after the pressure is reduced to normal pressure, and obtaining an alumina-silica aerogel heat-insulating composite material blank.
Sixthly, drying treatment, which comprises the following steps:
and (3) putting the alumina-silica aerogel heat insulation composite material blank obtained in the fifth step into a common oven, drying, controlling the temperature of the oven to be 110-140 ℃, keeping the temperature for 12-24 hours, and removing a small amount of residual moisture in the blank to obtain the final alumina-silica aerogel heat insulation composite material.
The preparation method adopts alumina and silica sol which take water as a solvent, takes inorganic ceramic fiber as a reinforcing phase, and prepares the alumina-silica aerogel heat-insulating composite material with high temperature resistance, low thermal conductivity and high strength by 6 process steps of simple preparation of a fiber prefabricated member, preparation of the alumina-silica sol, vacuum impregnation, gel aging, hydrothermal auxiliary drying, drying and the like. The aluminum oxide-silicon oxide sol is obtained by simply mixing commercially available water-based aluminum oxide and water-based silicon oxide sol which are green and environment-friendly and take water as a solvent, an organic solvent replacement process is not needed in the preparation process, a flammable and explosive ethanol solvent is not used as a drying medium, and the raw materials and the preparation process are green, environment-friendly, safe, low in manufacturing cost and suitable for large-scale production.
The invention is explained and illustrated below with reference to specific examples.
Example 1:
a preparation method of an alumina-silica aerogel heat insulation composite material comprises the following steps:
(1) production of fiber preforms
Clamping and fixing mullite fiber with a certain mass by using a mold to form a fiber prefabricated part, wherein the apparent density of the mullite fiber is 0.15g/cm before clamping3And the arrangement direction of the mullite fiber is vertical to the heat flow direction during heat insulation, so that the mullite fiber prefabricated part is obtained.
(2) Preparing alumina-silica sol
Firstly, mixing and stirring a commercially available water-based alumina sol (with the solid content of 15 percent, Zibojinqi chemical technology Co., Ltd.) and a commercially available water-based silica sol (with the solid content of 15 percent, Hangzhou Wanjing New Material Co., Ltd.) for 10min, then adding ammonia water into the mixed sol, and continuously stirring for 30min to obtain an alumina-silica sol with the solid content of 15 percent, wherein the volume ratio of the water-based alumina sol to the water-based silica sol to the ammonia water is 5:1: 0.5.
(3) Vacuum impregnation
Firstly, putting the fiber prefabricated member obtained in the first step into a vacuum impregnation tank, and vacuumizing to-0.1 MPa; and then injecting the alumina-silica sol obtained in the second step into a fiber prefabricated member placed in a vacuum impregnation tank through a pipeline, fully permeating the sol into the fiber prefabricated member by adopting a vacuumizing mode, immersing the fiber prefabricated member in the sol, maintaining the pressure for 0.5 hour, and introducing air into the vacuum impregnation tank to eliminate vacuum to obtain a fiber/sol mixture.
(4) Aging of the gel
And (3) placing the fiber/sol mixture obtained in the third step into a water bath kettle at 45 ℃ for standing until the sol is gelled, and continuing to stand and age in the water bath kettle for 2 days to obtain the fiber/sol mixture.
(5) Hydrothermal assisted drying
And (3) putting the fiber/gel mixture obtained in the fourth step into a hydrothermal kettle, pre-filling 3MPa of industrial nitrogen (the purity is more than or equal to 99.5%) into the hydrothermal kettle, controlling the temperature rise rate of the hydrothermal kettle to be 1 ℃/min, raising the temperature in the hydrothermal kettle to 180 ℃, controlling the drying pressure in the hydrothermal kettle to be 6MPa, drying and keeping the temperature for 0 hour, slowly releasing the moisture in the kettle, controlling the pressure release rate to be 2 MPa/hour, and taking out the fiber/gel mixture when the temperature in the kettle is reduced to below 50 ℃ after the pressure is reduced to the normal pressure to obtain an alumina-silica aerogel heat-insulation composite material blank.
(6) Drying process
And (3) putting the alumina-silica aerogel heat insulation composite material blank obtained in the fifth step into a common oven, drying, controlling the temperature of the oven at 130 ℃, keeping the temperature for 24 hours, and removing a small amount of residual moisture in the blank to obtain the final alumina-silica aerogel heat insulation composite material.
The alumina-silica aerogel thermal insulation composite prepared in example 1 had a density of 0.30g/cm3The thermal conductivity at 1000 ℃ is 0.088W/m ∙ K (by adopting YB/T4130-1.50%, and a compressive strength at 3% deformation of 0.12 MPa.
FIG. 2 is a scanning electron microscope microscopic morphology image of the composite material prepared in the present example; FIG. 3 is a partial enlarged view of the aerogel part in FIG. 2, specifically a scanning electron microscope microscopic morphology view of the nanoporous alumina-silica aerogel in the composite material prepared by the present invention. As can be seen from fig. 2 and 3, the composite material is composed of mullite fiber and nanoporous alumina-silica aerogel, and the aerogel is filled in the pores of the inorganic ceramic fiber, so that the material has very low high-temperature thermal conductivity; meanwhile, the aerogel is tightly wrapped around the fibers and has good interface combination with the fibers, and the mullite fibers have strong supporting effect on the aerogel and are used as main bearing bodies of the composite material, so that the composite material has high mechanical property and the compressive stress is up to more than 0.12MPa (3% strain).
Examples 2 to 11
In the first step of the preparation method, the fiber type basically has no influence on the high-temperature thermal conductivity and the mechanical property of the composite material, but the apparent density of the fiber has important influence on the high-temperature thermal conductivity and the mechanical property of the composite material, the apparent density of the fiber is properly increased, the high-temperature thermal conductivity of the material can be further reduced, the mechanical property of the material can be improved, but the fiber type and the apparent density have little influence on the temperature resistance of the material (the heat treatment is carried out at 1500 ℃ for 1800s, and the thickness shrinkage is less than 1.5%). In the second step of preparing alumina-silica sol, the catalyst is added in order to control the time of sol gelation and basically has no influence on the final performance of the material; the solid content of the sol is increased, so that the density, the strength and the high-temperature thermal conductivity of the material are increased. In the third step of vacuum impregnation, the sol can be ensured to be uniformly permeated into the fiber prefabricated member within the range of vacuum degree and pressure maintaining time used by the method, and the final performance of the material is not influenced; the standing aging time has no influence on the material performance. And step four, gel aging, water bath temperature and aging time have no influence on the performance of the material basically. And in the fifth step, hydrothermal auxiliary drying is carried out, the used heating speed, pressure relief speed and the like have no obvious influence on the performance of the material, but the temperature, drying pressure and pressure holding time in the kettle all have important influences on the performance of the material. The aim of the sixth step of drying is mainly to remove a small amount of moisture remained in the material, so that the drying temperature and the heat preservation time have no influence on the performance of the material.
Therefore, the process parameters affecting the performance of the composite material of the present invention mainly include 5 parameters, such as fiber surface density, sol solid content, and temperature in the kettle, drying pressure and dwell time in the hydrothermal-assisted drying, and therefore, in examples 2 to 11, the 5 process parameters are mainly changed to further explain the present invention. The process parameters used in examples 2-11 are shown in Table 1, except that the process parameters are as written in the Table, the process parameters are the same as in example 1.
TABLE 1 preparation of alumina-silica aerogel thermal insulation composite Material Process parameters and Material Properties
As can be seen from table 1, as the apparent fiber density, sol solid content, temperature in the kettle, pressure in the kettle, and drying time increased, the material density, high temperature thermal conductivity, and strength increased, and the thickness shrinkage decreased. Further experimental research results show that when the apparent density of the fibers and the solid content of the sol are further increased on the basis of the invention, although the strength of the material is further improved, the density of the prepared composite material is also increased, so that the solid heat transfer of the material is increased, and the high-temperature thermal conductivity of the material is increased; when the temperature in the kettle, the pressure in the kettle and the drying time are too high, the degree of the 'fusion' of the gel particles is too high, and the high-temperature thermal conductivity of the material is increased although the strength of the material is increased.
In conclusion, the alumina-silica aerogel heat-insulation composite material prepared by the invention has the advantages of high temperature resistance, low thermal conductivity, high strength and the like, and is particularly suitable for the fields of high-temperature heat insulation and preservation with extremely high requirements on temperature resistance, such as aviation, aerospace, industrial kilns and the like. In addition, the preparation method and the preparation process are simple, green and environment-friendly, have short preparation period, can form the complex special-shaped heat-insulating component, and are suitable for engineering and large-scale production.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The preparation method of the alumina-silica aerogel heat insulation composite material is characterized by comprising the following steps of:
step 1, preparing a fiber prefabricated part by taking inorganic ceramic fibers as raw materials;
step 2, mixing the water-based alumina sol and the water-based silica sol to obtain mixed sol, and adding ammonia water into the mixed sol to obtain alumina-silica sol;
step 3, putting the fiber prefabricated member obtained in the step 1 into a vacuum impregnation tank, and vacuumizing to-0.1 MPa; then injecting the alumina-silica sol obtained in the step 2 into a fiber prefabricated part in a vacuum impregnation tank, and maintaining the pressure for 0.5-1 hour to obtain a fiber/sol mixture;
step 4, placing the fiber/sol mixture obtained in the step 3 into a water bath kettle at the temperature of 15-75 ℃ for standing, and continuing to age for 2-3 days after the sol is gelled to obtain a fiber/gel mixture after the gel is aged;
step 5, putting the fiber/gel mixture obtained in the step 4 after gel aging into a hydrothermal kettle, and carrying out hydrothermal auxiliary drying treatment to obtain an alumina-silica aerogel heat-insulation composite material blank;
step 6, drying the alumina-silica aerogel heat insulation composite material blank obtained in the step 5 to obtain an alumina-silica aerogel heat insulation composite material;
wherein, the water-heat auxiliary drying treatment in the step 5 comprises the following specific processes: and (4) putting the fiber/gel mixture obtained after the gel aging in the step (4) into a hydrothermal kettle, then pre-filling 3MPa of nitrogen or argon into the hydrothermal kettle, controlling the temperature rise rate of the hydrothermal kettle to be 0.5-1 ℃/min, raising the temperature in the hydrothermal kettle to 180-300 ℃, controlling the pressure to be 6-15 MPa, drying and keeping the temperature for 0-2 hours, then controlling the pressure release speed to be 1-2 MPa/hour, reducing the pressure in the kettle to the normal pressure, and reducing the temperature in the kettle to be below 50 ℃.
2. The method of claim 1, wherein in step 1, the inorganic ceramic fibers are at least one of mullite fibers, alumina fibers, and zirconia fibers.
3. The method for preparing the alumina-silica aerogel thermal insulation composite material according to claim 1, wherein in the step 1, the apparent density of the inorganic ceramic fiber is 0.15-0.30g/cm3。
4. The preparation method of the alumina-silica aerogel thermal insulation composite material as claimed in claim 1, wherein in the step 2, the solid content of the water-based alumina sol and the solid content of the water-based silica sol are both 15-30%.
5. The preparation method of the alumina-silica aerogel heat-insulation composite material according to claim 1, wherein in the step 2, the volume ratio of the water-based alumina sol to the water-based silica sol to ammonia water is 5:1: 0.1-0.7.
6. The preparation method of the alumina-silica aerogel heat insulation composite material as claimed in claim 1, wherein in the step 6, the temperature in the drying process is 110-140 ℃, and the heat preservation time is 12-24 hours.
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