Unfired oxide aerogel and preparation method thereof

Abstract

The invention relates to an unfired oxide aerogel and a preparation method thereof. The technical scheme is as follows: the unfired oxide aerogel comprises the following raw materials in percentage by weight: 3-10wt% of basic magnesium sulfate whisker; the content of the deionized water is 80-90 wt%; the magnesium oxide accounts for 0.3 to 1.5 wt%; the content of rho-Al2O3 is 1 to 3 weight percent; and the content of the aluminum sol is 0.5-10 wt%. The preparation method comprises the following steps: putting basic magnesium sulfate whiskers into deionized water according to the raw materials and the content of the unfired oxide aerogel, and carrying out ultrasonic dispersion to obtain a mixed solution I; adding magnesium oxide and rho-Al2O3 into the mixed solution I, and performing ultrasonic dispersion to obtain a mixed solution II; adding aluminum sol into the mixed solution II, and mixing to obtain wet gel I; maintaining the wet gel I in a constant-temperature and constant-humidity box to obtain wet gel II; and drying the wet gel II in a drying oven to prepare the unfired oxide aerogel. The preparation method has the characteristics of simple preparation process, low cost, low energy consumption, easiness in forming and high safety, and the prepared product does not need to be calcined and has 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 divided into three methods: supercritical drying, freeze drying, and atmospheric pressure drying. Supercritical drying equipment is expensive and complicated to operate. Freeze drying is limited by equipment and is difficult to prepare large-sized samples. Atmospheric pressure drying has the advantages of simple operation and low cost, but atmospheric pressure drying to prepare 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 synthetic block spinel aerogel material" (publication number: CN106478134A) synthesizes magnesium aluminum spinel aerogel through supercritical drying. However, in 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 when ethanol is supercritically dried; 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 preparation of aerogels, 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℃[J]. ACSapplied materials&interfaces, 2023. DOI: 10.1021 / acsami.2c20272. from Shandong University prepared α-Al2O3 nanosheet aerogels. The prepared aerogels have good thermal insulation properties. However, the preparation process is complicated. It is necessary to prepare α-Al2O3 nanosheets first, and then calcine them at 1200℃ to assemble them into aerogels. And due to equipment limitations, freeze drying cannot prepare large-size aerogels, and it is difficult to achieve large-scale production. The raw materials required for the experiment are complex and costly. Multiple high-temperature calcinations are required during the preparation process, which consumes a lot of energy.

[0006] Wu Xiaodong et al. of Nanjing University of Technology (WuX, Shao G, ShenX, et al. The lowtemperature fabrication of nanocrystalline MgAl2O4 spinel aerogel by anon-alkoxide sol-gel route [J]. Materials Letters, 2017, 207 (nov. 15): 137-140.) prepared nanorod magnesium aluminum spinel aerogel, but the propylene oxide used is a flammable and explosive chemical, and is toxic, and there is a great 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 that the porosity is significantly reduced, and the high temperature resistance and thermal insulation performance are poor. And although the prepared magnesium aluminum spinel aerogel can prepare block 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 object, the technical solution adopted by the present invention is:

[0010] The unburned oxide aerogel raw material and its content:

[0011] Basic magnesium sulfate whisker is 3 to 10 wt%;

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

[0013] Magnesium oxide is 0.3-1.5wt%;

[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 non-fired 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 10-60wt%; the particle size of AlOOH in the aluminum sol is ≤20nm.

[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; 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 whisker, 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, controls the raw material ratio, mixes them evenly and then dries them. The preparation method is simple and safe to operate.

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

[0029] 4. The present invention adopts constant temperature and humidity combined with normal pressure drying to prepare the unburned oxide aerogel, which reduces the surface tension of the wet gel and makes the gas-liquid interface more balanced. The prepared unburned oxide aerogel overcomes the problem of poor forming ability of existing aerogels and has the advantages of easy forming and not easy to crack.

[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 volume density and high porosity, and has excellent thermal insulation performance, and 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: 90.7-92.2%; Thermal conductivity: 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 is further described below in conjunction with specific implementation modes, but is not intended to limit the protection scope thereof.

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

[0036] The unburned oxide aerogel raw material and its content:

[0037] Basic magnesium sulfate whisker is 3 to 10 wt%;

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

[0039] Magnesium oxide is 0.3-1.5wt%;

[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 non-fired oxide aerogel.

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

[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 whisker is ≥90%; the aspect ratio of the basic magnesium sulfate whisker 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] This will not be described in detail in the embodiments.

[0054] Example 1

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

[0056] The unburned oxide aerogel raw material and its content:

[0057] Basic magnesium sulfate whisker is 3wt%;

[0058] 90wt% in deionized water;

[0059] Magnesium oxide: 0.3wt%;

[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 an unburned oxide aerogel.

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

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

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

[0068] The unburned oxide aerogel prepared in this example was tested: the volume density was 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 a preparation method thereof. The preparation method described in this embodiment is:

[0071] The unburned oxide aerogel raw material and its content:

[0072] Basic magnesium sulfate whisker is 10wt%;

[0073] 80wt% in deionized water;

[0074] Magnesium oxide is 1.5wt%;

[0075] ρ-Al2O3 is 3wt%;

[0076] The aluminum sol is 5.5wt%.

[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 is 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 chamber is 70° C.; the humidity of the constant temperature and humidity chamber is 95% RH.

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

[0083] The unburned oxide aerogel prepared in this example was tested: the volume density was 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 a preparation method thereof. The preparation method described in this embodiment is:

[0086] The unburned oxide aerogel raw material and its content:

[0087] Basic magnesium sulfate whisker is 8wt%;

[0088] 88.5wt% in deionized water;

[0089] Magnesium oxide: 0.5wt%;

[0090] ρ-Al2O3 is 2.5wt%;

[0091] The aluminum sol is 0.5wt%.

[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 an unburned oxide aerogel.

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

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

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

[0098] The unburned oxide aerogel prepared in this example was tested: the volume density was 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 a preparation method thereof. The preparation method described in this embodiment is:

[0101] The unburned oxide aerogel raw material and its content:

[0102] Basic magnesium sulfate whisker is 5wt%;

[0103] 83wt% in deionized water;

[0104] Magnesium oxide is 1wt%;

[0105] ρ-Al2O3 is 1wt%;

[0106] The aluminum sol is 10wt%.

[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 an unburned oxide aerogel.

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

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

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

[0113] The unburned oxide aerogel prepared in this example was tested: the volume density was 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 specific implementation has the following positive effects and outstanding features:

[0115] 1. This specific implementation method uses basic magnesium sulfate whiskers, magnesium oxide, ρ-Al2O3 and aluminum sol as raw materials, which are cheap, have low production costs and are non-toxic.

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

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

[0118] 4. This specific embodiment adopts constant temperature and humidity combined with normal pressure drying to prepare the unburned oxide aerogel, which reduces the surface tension of the wet gel and makes the gas-liquid interface more balanced. The prepared unburned oxide aerogel overcomes the problem of poor forming ability of existing aerogels and has the advantages of easy forming and not easy to crack.

[0119] 5. This specific embodiment adopts the 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.

[0120] 6. This specific implementation method 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 volume density and high porosity, and has excellent thermal insulation performance, and can be widely used in industrial kilns, aerospace, environmental protection and other fields.

[0121] The unburned oxide aerogel prepared in this specific embodiment is tested: the volume density is 0.28-0.33 g / cm 3 ; Porosity: 90.7-92.2%; Thermal conductivity: 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 need to be calcined 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 material and its content: Basic magnesium sulfate whisker is 3-10wt%, 80-90wt% in deionized water, 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 whisker is placed in the deionized water, ultrasonically dispersed to obtain a mixed solution I; the magnesium oxide and the ρ-Al2O3 are added to the mixed solution I, ultrasonically dispersed to obtain a mixed solution II; the aluminum sol is added to the mixed solution II, 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 whisker is ≥90%; the aspect ratio of the basic magnesium sulfate whisker 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 10-60wt%; the particle size of AlOOH in the aluminum sol is ≤20nm.

4. The method for preparing the unburned oxide aerogel according to claim 1, characterized in that: 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.

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; 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 non-burning 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.