A kind of unburned oxide aerogel and preparation method thereof

Abstract

The present invention relates to an unburned oxide aerogel and a preparation method thereof. The technical scheme is as follows: the unburned oxide aerogel raw materials and their contents: basic magnesium sulfate whiskers are 3-10wt%; 80-90wt% in deionized water; magnesium oxide is 0.3-1.5wt%; ρ-Al2O3 is 1-3wt%; and aluminum sol is 0.5-10wt%. According to the unburned oxide aerogel raw materials and their contents: basic magnesium sulfate whiskers are placed in the deionized water, ultrasonically dispersed to obtain a mixed solution I; magnesium oxide and ρ-Al2O3 are added to the mixed solution I, ultrasonically dispersed to obtain a mixed solution II; aluminum sol is added to the mixed solution II, mixed to obtain a wet gel I; the wet gel I is cured in a constant temperature and humidity chamber to obtain a wet gel II; the wet gel II is dried in an oven to obtain the unburned oxide aerogel. The present invention has the characteristics of simple preparation process, low cost, low energy consumption, easy molding and high safety, and the manufactured products do not require calcination and have good thermal insulation performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of unburned oxide aerogels, and specifically relates to an unburned oxide aerogel and a preparation method thereof. Background Art

[0002] Aerogel has the advantages of low thermal conductivity, high porosity, large specific surface area and low density. It is widely used in aerospace, petrochemical, environmental protection, industrial kilns and other fields. Compared with existing thermal insulation materials, aerogel has attracted much attention due to its low thermal conductivity and excellent high temperature resistance. At present, the research on thermal insulation aerogel is mainly focused on two types: non-oxide aerogel and oxide aerogel. Non-oxide aerogels such as nitride aerogel and carbide aerogel have good thermal insulation properties under vacuum and inert atmosphere, but are easily oxidized and ablated in oxygen-containing environments, causing structural collapse. At present, the high-temperature service of aerogel is mainly carried out in an air atmosphere, so the development of efficient oxide aerogel is the focus of current scientific researchers.

[0003] Aerogel drying can be achieved through three methods: supercritical drying, freeze drying, and atmospheric pressure drying. Supercritical drying equipment is expensive and complex to operate. Freeze drying is limited by equipment and is difficult to prepare large samples. Atmospheric pressure drying offers the advantages of simplicity and low cost, but producing aerogels requires overcoming the problem of gel skeleton destruction and collapse caused by capillary pressure.

[0004] The patented technology of "Preparation Method of High-Temperature and Low-Temperature Resistant Blocky Spinel Aerogel Material" (Publication No.: CN106478134A) synthesizes magnesium-aluminum spinel aerogel through supercritical drying. However, during the supercritical drying process, the supercritical drying medium is carbon dioxide or ethanol, and the pressure in the high-pressure reactor can reach up to 17MP during supercritical drying of ethanol; when carbon dioxide is supercritically dried, the pressure in the high-pressure reactor can reach up to 12MPa. This method requires multiple solution replacements during the aerogel preparation process, the preparation is too complicated, and there are safety hazards in the high-pressure environment, making it difficult to achieve industrial production.

[0005] Ji Q, Zhang L, et al. AlphaAl2O3 Nanosheet-Based Biphasic Aerogels with High-Temperature Resistance up to 1600°C [J]. ACS applied materials & interfaces, 2023. DOI: 10.1021 / acsami.2c20272. from Shandong University prepared α-Al2O3 nanosheet aerogels. The aerogels prepared have good thermal insulation properties. However, the preparation process is complicated. α-Al2O3 nanosheets need to be prepared first, then calcined at 1200°C and assembled into aerogels. In addition, due to equipment limitations, freeze drying cannot produce large-scale aerogels, making large-scale production difficult. The raw materials required for the experiment are complex and costly, and multiple high-temperature calcinations are required during the preparation process, which consumes a lot of energy.

[0006] Wu Xiaodong et al. (Wu X, Shao G, Shen X, et al. The low-temperature fabrication of nanocrystalline MgAl2O4 spinel aerogel by anon-alkoxide sol-gel route [J]. Materials Letters, 2017, 207 (nov. 15): 137-140.) from Nanjing University of Science and Technology prepared nanorod magnesium aluminum spinel aerogel. However, the propylene oxide used is a flammable and explosive chemical, and is toxic, posing a significant safety hazard. The magnesium aluminum spinel aerogel prepared by this method needs to be calcined, and as the calcination temperature increases, its specific surface area decreases significantly, indicating a significant decrease in porosity and poor high-temperature resistance and thermal insulation properties. Furthermore, although the prepared magnesium aluminum spinel aerogel can be prepared into bulk samples, its molding ability is poor.

[0007] The defects of the existing technology are: complex process, high cost, low safety, high energy consumption and poor molding ability. The preparation of oxide aerogel requires high temperature calcination and poor thermal insulation performance. Summary of the Invention

[0008] The present invention aims to overcome the defects of the prior art and aims to provide a method for preparing unburned oxide aerogels with simple preparation process, low cost, low energy consumption, easy forming and high safety. The unburned oxide aerogels prepared by this method do not require calcination and have good thermal insulation performance.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is:

[0010] The unburned oxide aerogel raw materials and their content:

[0011] Basic magnesium sulfate whiskers are 3 to 10 wt%;

[0012] 80-90 wt% in deionized water;

[0013] 0.3-1.5 wt% of magnesium oxide;

[0014] ρ-Al2O3 is 1 to 3 wt%;

[0015] The aluminum sol is 0.5 to 10 wt%.

[0016] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0017] The wet gel I is cured in a constant temperature and humidity chamber for 12 to 48 hours to obtain a wet gel II.

[0018] The wet gel II is dried in an oven for 12 to 48 hours to obtain a calcined oxide aerogel.

[0019] The purity of MgSO4.5Mg(OH)2.3H2O in the basic magnesium sulfate whisker is ≥90%; the aspect ratio of the basic magnesium sulfate whisker is ≥5.

[0020] The content of AlOOH in the aluminum sol is 10-60 wt %; and the particle size of AlOOH in the aluminum sol is ≤20 nm.

[0021] The temperature of the constant temperature and humidity box is 30-70° C.; the humidity of the constant temperature and humidity box is 35-95% RH.

[0022] The temperature of the oven is 50-80°C.

[0023] The particle size of the magnesium oxide is ≤30 μm; and the purity of the magnesium oxide is ≥90%.

[0024] The particle size of the ρ-Al2O3 is ≤30 μm; the purity of the ρ-Al2O3 is ≥90%.

[0025] Due to the adoption of the above technical solution, the present invention has the following positive effects and outstanding features compared with the prior art:

[0026] 1. The present invention uses basic magnesium sulfate whiskers, magnesium oxide, ρ-Al2O3 and aluminum sol as raw materials, which are low in price, low in production cost and non-toxic.

[0027] 2. The present invention uses basic magnesium sulfate whiskers, magnesium oxide, ρ-Al2O3 and aluminum sol as raw materials. By controlling the raw material ratio, mixing them evenly and then drying them, the preparation method is simple and safe to operate.

[0028] 3. The present invention adopts a constant temperature and humidity combined with atmospheric pressure drying method to prepare the unburned oxide aerogel, without the need for calcination or other heat treatment. Therefore, the present invention has the advantages of simple operation and low energy consumption.

[0029] 4. This invention utilizes a constant temperature and humidity combined with atmospheric pressure drying to prepare unfired oxide aerogels, reducing the surface tension of the wet gel and achieving a more balanced gas-liquid interface. The resulting unfired oxide aerogels overcome the poor formability of existing aerogels, offering the advantages of easy molding and resistance to cracking.

[0030] 5. The present invention adopts a normal pressure drying method to prepare the unburned oxide aerogel, which overcomes the equipment limitation, can prepare large-sized aerogel, and can realize large-scale production.

[0031] 6. The present invention can maintain the stability of the aerogel skeleton structure and retain the pore structure during the drying process. Therefore, the prepared unburned oxide aerogel has the advantages of low bulk density and high porosity, and has excellent thermal insulation properties. It can be widely used in industrial kilns, aerospace, environmental protection and other fields.

[0032] The unburned oxide aerogel prepared by the present invention is tested to have a volume density of 0.28 to 0.33 g / cm 3 ; Porosity is 90.7-92.2%; Thermal conductivity is 0.063-0.086 W·m -1 ·K -1 .

[0033] Therefore, the present invention has the characteristics of simple preparation process, low cost, low energy consumption, easy forming and high safety. The prepared unburned oxide aerogel does not require calcination and has good thermal insulation performance. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments, which does not limit the scope of protection thereof.

[0035] A non-burning oxide aerogel and its preparation method. The preparation method described in this specific embodiment is:

[0036] The unburned oxide aerogel raw materials and their content:

[0037] Basic magnesium sulfate whiskers are 3 to 10 wt%;

[0038] 80-90 wt% in deionized water;

[0039] 0.3-1.5 wt% of magnesium oxide;

[0040] ρ-Al2O3 is 1 to 3 wt%;

[0041] The aluminum sol is 0.5 to 10 wt%.

[0042] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0043] The wet gel I is cured in a constant temperature and humidity chamber for 12 to 48 hours to obtain a wet gel II.

[0044] The wet gel II is dried in an oven for 12 to 48 hours to obtain a calcined oxide aerogel.

[0045] The content of AlOOH in the aluminum sol is 10-60 wt%.

[0046] The temperature of the constant temperature and humidity box is 30-70° C.; the humidity of the constant temperature and humidity box is 35-95% RH.

[0047] The temperature of the oven is 50-80°C.

[0048] in:

[0049] The purity of MgSO4·5Mg(OH)2·3H2O in the basic magnesium sulfate whiskers is ≥90%; the aspect ratio of the basic magnesium sulfate whiskers is ≥5;

[0050] The particle size of AlOOH in the aluminum sol is ≤20nm;

[0051] The particle size of the magnesium oxide is ≤30 μm; the purity of the magnesium oxide is ≥90%;

[0052] The particle size of the ρ-Al2O3 is ≤30 μm; the purity of the ρ-Al2O3 is ≥90%.

[0053] The details will not be described in detail in the embodiments.

[0054] Example 1

[0055] A non-burning oxide aerogel and its preparation method. The preparation method described in this embodiment is:

[0056] The unburned oxide aerogel raw materials and their content:

[0057] Basic magnesium sulfate whiskers are 3wt%;

[0058] 90wt% in deionized water;

[0059] 0.3 wt% magnesium oxide;

[0060] ρ-Al2O3 is 2wt%;

[0061] The aluminum sol is 4.7 wt%.

[0062] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0063] The wet gel I was cured in a constant temperature and humidity chamber for 48 hours to obtain a wet gel II.

[0064] The wet gel II was dried in an oven for 24 hours to obtain a non-fired oxide aerogel.

[0065] The content of AlOOH in the aluminum sol is 60 wt %.

[0066] The temperature of the constant temperature and humidity box is 30° C.; the humidity of the constant temperature and humidity box is 35% RH.

[0067] The temperature of the oven is 80°C.

[0068] The unburned oxide aerogel prepared in this embodiment was tested and found to have a volume density of 0.33 g / cm 3 ; Porosity is 90.7%; Thermal conductivity is 0.086W·m -1 ·K -1 .

[0069] Example 2

[0070] A non-burning oxide aerogel and its preparation method. The preparation method described in this embodiment is:

[0071] The unburned oxide aerogel raw materials and their content:

[0072] Basic magnesium sulfate whiskers are 10wt%;

[0073] 80wt% in deionized water;

[0074] 1.5 wt% magnesium oxide;

[0075] ρ-Al2O3 is 3wt%;

[0076] The aluminum sol is 5.5 wt%.

[0077] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0078] The wet gel I was cured in a constant temperature and humidity chamber for 24 hours to obtain a wet gel II.

[0079] The wet gel II was dried in an oven for 12 hours to obtain an unburned oxide aerogel.

[0080] The content of AlOOH in the aluminum sol is 45 wt %.

[0081] The temperature of the constant temperature and humidity box is 70° C.; the humidity of the constant temperature and humidity box is 95% RH.

[0082] The temperature of the oven is 60°C.

[0083] The unburned oxide aerogel prepared in this example was tested and found to have a volume density of 0.32 g / cm 3 ; Porosity is 90.8%; Thermal conductivity is 0.082W·m -1 ·K -1 .

[0084] Example 3

[0085] A non-burning oxide aerogel and its preparation method. The preparation method described in this embodiment is:

[0086] The unburned oxide aerogel raw materials and their content:

[0087] Basic magnesium sulfate whiskers are 8wt%;

[0088] 88.5wt% in deionized water;

[0089] 0.5 wt% magnesium oxide;

[0090] ρ-Al2O3 is 2.5wt%;

[0091] The aluminum sol is 0.5 wt%.

[0092] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0093] The wet gel I was cured in a constant temperature and humidity chamber for 12 hours to obtain a wet gel II.

[0094] The wet gel II was dried in an oven for 48 hours to obtain a non-fired oxide aerogel.

[0095] The content of AlOOH in the aluminum sol is 30 wt %.

[0096] The temperature of the constant temperature and humidity box is 40° C.; the humidity of the constant temperature and humidity box is 80% RH.

[0097] The temperature of the oven is 70°C.

[0098] The unburned oxide aerogel prepared in this example was tested and found to have a volume density of 0.28 g / cm 3 ; Porosity is 92.2%; Thermal conductivity is 0.063W·m -1 ·K -1 .

[0099] Example 4

[0100] A non-burning oxide aerogel and its preparation method. The preparation method described in this embodiment is:

[0101] The unburned oxide aerogel raw materials and their content:

[0102] Basic magnesium sulfate whiskers are 5wt%;

[0103] 83 wt% in deionized water;

[0104] 1 wt% magnesium oxide;

[0105] ρ-Al2O3 is 1wt%;

[0106] The aluminum sol is 10 wt%.

[0107] According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I.

[0108] The wet gel I was cured in a constant temperature and humidity chamber for 36 hours to obtain a wet gel II.

[0109] The wet gel II was dried in an oven for 36 hours to obtain a non-fired oxide aerogel.

[0110] The content of AlOOH in the aluminum sol is 10 wt %.

[0111] The temperature of the constant temperature and humidity box is 50° C.; the humidity of the constant temperature and humidity box is 50% RH.

[0112] The temperature of the oven is 50°C.

[0113] The unburned oxide aerogel prepared in this example was tested and found to have a volume density of 0.31 g / cm 3 ; Porosity is 91.1%; Thermal conductivity is 0.073W·m -1 ·K -1 .

[0114] Compared with the prior art, this embodiment has the following positive effects and outstanding features:

[0115] 1. This specific embodiment uses basic magnesium sulfate whiskers, magnesium oxide, ρ-Al2O3 and aluminum sol as raw materials, which are low in price, low in production cost and non-toxic.

[0116] 2. This specific embodiment uses basic magnesium sulfate whiskers, magnesium oxide, ρ-Al2O3 and aluminum sol as raw materials. By controlling the raw material ratio, mixing them evenly and then drying them, the preparation method is simple and safe to operate.

[0117] 3. This embodiment adopts a constant temperature and humidity combined with atmospheric pressure drying method to prepare the unburned oxide aerogel, without the need for calcination or other heat treatment. Therefore, this embodiment has the advantages of simple operation and low energy consumption.

[0118] 4. This specific embodiment utilizes a constant temperature and humidity combined with atmospheric pressure drying to prepare unfired oxide aerogels, reducing the surface tension of the wet gel and achieving a more balanced gas-liquid interface. The resulting unfired oxide aerogels overcome the poor formability of existing aerogels, offering advantages such as ease of molding and resistance to cracking.

[0119] 5. This specific embodiment adopts a normal pressure drying method to prepare the unburned oxide aerogel, which overcomes the equipment limitation, can prepare large-sized aerogels, and can achieve large-scale production.

[0120] 6. This specific embodiment can maintain the stability of the aerogel skeleton structure and retain the pore structure during the drying process. Therefore, the prepared unburned oxide aerogel has the advantages of low bulk density and high porosity, and has excellent thermal insulation properties. It can be widely used in industrial kilns, aerospace, environmental protection and other fields.

[0121] The unburned oxide aerogel prepared in this embodiment is tested to have a volume density of 0.28 to 0.33 g / cm 3 ; Porosity is 90.7-92.2%; Thermal conductivity is 0.063-0.086 W·m -1 ·K -1 .

[0122] Therefore, this specific embodiment has the characteristics of simple preparation process, low cost, low energy consumption, easy forming and high safety. The prepared unburned oxide aerogel does not require calcination and has good thermal insulation performance.

Claims

1. A method for preparing a non-burning oxide aerogel, characterized in that The preparation method is: The unburned oxide aerogel raw materials and their content: Basic magnesium sulfate whiskers are 3~10wt%, Deionized water is 80~90wt%, Magnesium oxide is 0.3~1.5wt%, ρ-Al2O3 is 1~3wt%, Aluminum sol is 0.5~10wt%; According to the raw materials of the unburned oxide aerogel and their content: the basic magnesium sulfate whiskers are placed in the deionized water and ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I and ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II and mixed to obtain a wet gel I; Curing the wet gel I in a constant temperature and humidity chamber for 12 to 48 hours to obtain wet gel II; The wet gel II is dried in an oven for 12 to 48 hours to obtain a non-fired oxide aerogel.

2. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The purity of MgSO4.5Mg(OH)2.3H2O in the basic magnesium sulfate whiskers is ≥90%; the aspect ratio of the basic magnesium sulfate whiskers is ≥5.

3. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The content of AlOOH in the aluminum sol is 10-60 wt %; and the particle size of AlOOH in the aluminum sol is ≤20 nm.

4. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The temperature of the constant temperature and humidity chamber is 30-70° C.; the humidity of the constant temperature and humidity chamber is 35-95% RH.

5. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The temperature of the oven is 50-80°C.

6. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The particle size of the magnesium oxide is ≤30 μm; and the purity of the magnesium oxide is ≥90%.

7. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: The particle size of the ρ-Al2O3 is ≤30 μm; the purity of the ρ-Al2O3 is ≥90%.

8. A fire-free oxide aerogel, characterized in that The unburned oxide aerogel is an unburned oxide aerogel prepared by the method for preparing the unburned oxide aerogel according to any one of claims 1 to 7.