Fiber-reinforced Al2O3 aerogel and preparation method thereof

Abstract

The invention relates to fiber-reinforced Al2O3 aerogel and a preparation method thereof, and belongs to the technical field of ceramic aerogel materials. The method is used for solving the problems that existing aerogel preparation conditions are harsh, the process is complex and the cost is high. The fiber-reinforced Al2O3 aerogel is prepared from the following raw materials: dry glue powder, a gel injection molding system raw material, a pore forming agent and a fiber reinforcement body. The fiber-reinforced Al2O3 aerogel has the advantages of complete structure, low thermal conductivity coefficient, high porosity, heat insulation function, simple preparation method, low cost and low energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic aerogels, and in particular to a fiber-reinforced Al2O3-based aerogel and a preparation method thereof. Background Art

[0002] Ceramic aerogel is a material with a three-dimensional porous structure. It has the characteristics of low density, high porosity and low thermal conductivity. Due to its unique properties, it has attracted much attention in materials science. Ceramic aerogel has been widely used in fields such as thermal insulation and environmental protection.

[0003] The preparation of ceramic aerogels usually involves the sol-gel method and drying technology. Most of the current aerogel preparation methods are sol-gel methods. The raw materials used in the sol-gel method are usually expensive, and under ordinary drying, capillary forces cause the nanopores in the matrix to collapse, resulting in excessive shrinkage of the matrix, making it difficult to prepare aerogels by ordinary drying. Therefore, the drying conditions for aerogels are generally supercritical, freeze-drying and atmospheric pressure drying, but this results in harsh preparation conditions and complex processes. Summary of the invention

[0004] In view of the above analysis, the present invention aims to provide a fiber-reinforced Al2O3-based aerogel and a preparation method thereof, so as to solve at least one of the following technical problems: (1) the existing aerogel preparation conditions are harsh, the process is complex and the cost is high; (2) the existing aerogel is difficult to prepare under ordinary drying; (3) most of the existing ceramic aerogels are prepared at high temperatures.

[0005] The purpose of the present invention is mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a fiber-reinforced Al2O3 aerogel, wherein the raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore formers and fiber reinforcements.

[0007] Furthermore, the raw materials of the gel casting system include monomers, crosslinking agents, initiators and catalysts.

[0008] Furthermore, the pore-forming agent includes one or more of agar powder, microcrystalline cellulose and melamine.

[0009] Furthermore, the fiber reinforcement includes one or more of silica nanotubes, mullite fibers and sepiolite fibers.

[0010] Furthermore, the mass ratios of dry rubber powder, monomer, crosslinking agent, pore-forming agent, fiber reinforcement, initiator and catalyst to the total mass of raw materials are 50% to 75%, 6% to 10%, 0.5% to 1%, 10% to 25%, 1% to 8%, 0.5% to 1.8% and 0.1% to 0.5% respectively.

[0011] The present invention also provides a method for preparing the above-mentioned fiber-reinforced Al2O3-based aerogel, comprising:

[0012] Step 1, acidification preparation: add water and dry rubber powder into the mold, put it into a water bath and stir, add pore-forming agent and nitric acid and stir, then seal and place at room temperature for precipitation;

[0013] Step 2, preparing slurry: removing the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0014] Step 3, preparing a green body: adding a gel casting system raw material and a fiber reinforcement into a uniformly stirred mixture, wherein the gel casting system raw material includes a monomer, a cross-linking agent, an initiator and a catalyst, stirring evenly and removing bubbles in time to obtain a green body;

[0015] Step 4, green body drying and demoulding: the green body is left to stand at room temperature until the edges shrink, and then put into an oven for drying. After the green body is dried and demoulded, it is taken out from the mold;

[0016] Step 5: Sintering: Sintering the dried green body to obtain fiber-reinforced Al2O3 aerogel.

[0017] Furthermore, in step 1, the precipitation is controlled to be placed for 2 to 5 days.

[0018] Furthermore, in step 4, the oven is controlled to be in a non-blowing state.

[0019] Furthermore, in step 4, the drying temperature is controlled to be 30-60°C.

[0020] Furthermore, in step 5, the sintering temperature is controlled to be 500-700° C. and kept warm for 1-3 hours.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] The fiber-reinforced Al2O3 aerogel of the present invention adopts a porous dry gel powder as a raw material, into which a gel injection molding system raw material, a pore-forming agent and a fiber reinforcement are added. The porous structure of the powder can compensate for the collapse of the pores inside the green body during ordinary drying. At the same time, the fiber reinforcement is added to inhibit shrinkage. The fiber-reinforced Al2O3 aerogel is prepared by low-temperature sintering to increase the porosity of the ceramic aerogel, reduce process complexity, and obtain a fiber-reinforced Al2O3 aerogel with both low thermal conductivity and good thermal insulation performance.

[0023] In the preparation method of the Al2O3 aerogel of the present invention, due to the synergistic effect between the raw materials, the porous structure can compensate for the collapse of the pores inside the structure of the green body during ordinary drying, and the fiber reinforcement is added to inhibit shrinkage. Therefore, the green body can be left standing at room temperature and then transferred to an oven for drying. There is no need to use supercritical, freeze-drying and normal pressure drying, and the process is simple. In addition, the sintering temperature in the method of the present invention is low, which greatly reduces energy loss and can reduce production costs.

[0024] In the preparation method of the Al2O3 aerogel of the present invention, during the sintering process, the temperature and time are precisely controlled to prevent the aerogel from cracking, and finally the Al2O3 aerogel with a complete structure is obtained.

[0025] The Al2O3 aerogel of the present invention has a porosity of 83.94% to 92.16%, a thermal conductivity of 0.051 to 0.083 W / m·K, a shrinkage of 1.9% to 5.2%, and a volume density of 0.351 to 0.436 / cm 3 The aerogel produced has low thermal conductivity, high porosity, and also has the function of heat insulation.

[0026] The preparation method of the present invention utilizes dry rubber powder with a porous structure as raw material. The porous structure of the powder compensates for the collapse of pores inside the green body during ordinary drying. At the same time, fiber reinforcement is added to inhibit shrinkage, and a fiber-reinforced Al2O3 aerogel is prepared at low temperature, which solves the barriers of thermal insulation, low thermal conductivity and low cost coexisting in ceramic aerogel.

[0027] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents pointed out in the embodiments of the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0029] Figure 1 This is an optical image of the fiber-reinforced Al2O3 aerogel after drying and before sintering in Example 1;

[0030] Figure 2 This is an optical image of the fiber-reinforced Al2O3 aerogel after drying and sintering in Example 1;

[0031] Figure 3 This is a scanning electron microscope image of the matrix of the fiber-reinforced Al2O3 aerogel of Example 2;

[0032] Figure 4 This is a thermal insulation diagram of the fiber-reinforced Al2O3-based aerogel of Example 1;

[0033] Figure 5 It is a schematic diagram of the crushing and slagging of Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0035] The invention provides a fiber-reinforced Al2O3 aerogel. The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement.

[0036] Specifically, the dry glue powder used may be commercial dry glue powder available on the market, and the main component of the dry glue powder is pseudo-boehmite.

[0037] Specifically, the raw materials of the gel casting system include monomers, crosslinking agents, initiators and catalysts.

[0038] Specifically, the above-mentioned monomer can be acrylamide and / or N-isopropylacrylamide.

[0039] Specifically, the cross-linking agent may be N,N'-methylenebisacrylamide or N-hydroxymethylacrylamide.

[0040] Specifically, the initiator may be one or more of ammonium persulfate, potassium persulfate and hydrogen peroxide.

[0041] Specifically, the catalyst may be N,N,N',N'-tetramethylethylenediamine or N,N-dimethylaniline.

[0042] Specifically, the pore-forming agent includes one or more of agar powder, microcrystalline cellulose, and melamine.

[0043] Specifically, the fiber reinforcement includes one or more of silica nanotubes, sepiolite fibers or mullite fibers.

[0044] Specifically, considering that too little amount of crosslinking agent and initiator will prolong the gelation process, affecting the efficiency of the green body and its mechanical properties; on the contrary, if the crosslinking agent and initiator are used in excess, the gelation speed will be too fast, resulting in uneven structure, making it difficult to effectively control the entire process. Therefore, the mass ratio of the crosslinking agent and initiator to the total mass of the raw materials is controlled to be 0.5% to 1% and 0.5% to 1.8% respectively.

[0045] Specifically, considering that insufficient amount of pore former will result in less pores in the green body, while excessive amount of pore former will result in too many pores, resulting in too low strength of the ceramic, the mass of the pore former is controlled to be 10% to 25% of the total mass of the raw materials.

[0046] Specifically, considering that the fiber reinforcement content is insufficient, its reinforcing effect will not be fully demonstrated, resulting in poor mechanical properties of the aerogel; on the contrary, excessive fiber reinforcement may weaken the overall performance of the material due to entanglement and uneven distribution between fibers, and intensify solid heat conduction between fibers, which has an adverse effect on thermal insulation performance. Therefore, the mass proportion of fiber reinforcement is controlled to be 1% to 8%.

[0047] Specifically, taking into account comprehensively, the mass ratio of dry rubber powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst to the total mass of raw materials is controlled to be 50% to 75%, 6% to 10%, 0.5% to 1%, 10% to 25%, 1% to 8%, 0.5% to 1.8%, 0.1% to 0.5%. For example, the mass ratio of dry rubber powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst to the total mass of raw materials is controlled to be 58% to 73%, 6.5% to 9.5%, 0.55% to 0.95%, 13% to 25%, 1.2% to 7.3%, 0.6% to 1.5%, 0.1% to 0.45%.

[0048] The present invention also provides a method for preparing the above-mentioned fiber-reinforced Al2O3-based aerogel, comprising:

[0049] Step 1, acidification preparation: add water and dry rubber powder into the mold, stir at 60-80°C, then add pore-forming agent and nitric acid, stir, then seal and place at room temperature for precipitation;

[0050] Step 2, preparing slurry: removing (e.g., sucking out) the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0051] Step 3, preparing a green body: adding a gel casting system raw material and a fiber reinforcement into a uniformly stirred mixture, wherein the gel casting system raw material includes a monomer, a cross-linking agent, an initiator and a catalyst, stirring evenly and removing bubbles in time to obtain a green body;

[0052] Step 4, green body drying and demoulding: the green body is left to stand at room temperature until the edges shrink, and then put into an oven for drying. After the green body is dried and demoulded, it is taken out from the mold;

[0053] Step 5: Sintering: Sintering the dried green body to obtain fiber-reinforced Al2O3 aerogel.

[0054] Specifically, in the above step 1, considering that too high temperature and too long stirring time will cause the water in the system to evaporate too quickly, affecting the slurry concentration and process control, too low temperature and too short stirring time will cause poor powder processing effect. Therefore, the mold can be placed in a water bath at 60-80°C (e.g., 63°C, 65°C, 67°C, 70°C, 73°C, 75°C, 77°C) and stirred for 1-2h (e.g., 1.2h, 1.3h, 1.5h, 1.7h, 1.9h).

[0055] Specifically, in the above step 1, water is added to disperse the dry glue powder. If too little water is added, the dry glue powder will gather together and cannot be dispersed. If too much water is added, the subsequent precipitation time will be increased. Therefore, the mass ratio of water to dry glue powder is controlled to be 8 to 10:1, for example 8:1, 9:1, 10:1.

[0056] Specifically, in the above step 1, the acidification concentration of nitric acid is 0.02-0.08 mol / L.

[0057] Specifically, in the above step 1, if the stirring time is too long after adding the pore-forming agent and nitric acid, the water in the system will evaporate too quickly and the slurry will be too viscous, while if the stirring time is too short, the treatment effect will be poor. Therefore, the stirring time is controlled to be 0.5 to 1 hour (for example, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours).

[0058] Specifically, in the above step 1, water and dry rubber powder are first added and stirred, and then the pore-forming agent and nitric acid are added and stirred. If they are added together, the dry rubber powder will be unevenly dispersed and easily agglomerated with the pore-forming agent, affecting the subsequent gelation.

[0059] Specifically, in the above step 1, if the precipitation is placed for too long, it will increase the preparation time and cost, and if it is too short, it will be difficult to fully react and the structure will be uneven. Therefore, the room temperature is controlled to seal and place the precipitation for 2 to 5 days, for example, 2.5 days, 3 days, 3.5 days, 4 days, and 4.5 days.

[0060] Specifically, in the above step 3, considering that some oxygen will be dissolved in the slurry and bubbles will be generated during the mixing of the slurry, it may cause obvious holes on the surface or inside of the green body after drying and forming, which will reduce its mechanical strength and may cause cracking of the sample during room temperature drying or sintering. Therefore, vacuum degassing, vibration degassing, centrifugal degassing and other methods can be used for degassing.

[0061] Specifically, in the above step 4, the principle for judging edge shrinkage is that the edge of the green body is substantially separated from the mold when the mold is slightly shaken.

[0062] Specifically, in the above step 4, considering that the free water inside the green body evaporates rapidly in the oven blast state, many tiny pores may be formed inside the green body, resulting in uneven shrinkage, and excessive capillary force may cause the green body to crack or deform. Therefore, the oven is controlled to be in a non-blast state.

[0063] Specifically, in the above step 4, it is considered that too high a drying temperature will increase the shrinkage and may cause the product to crack; however, too low a drying temperature will extend the drying cycle and increase production costs. Therefore, the drying temperature is controlled to be 30-60°C, and the drying time is 2-5 days (days), such as 2.5 days, 3 days, 3.5 days, 4 days, and 4.5 days. For example, the drying temperature is 35°C, 40°C, 45°C, 50°C, and 55°C.

[0064] Specifically, in the above step 5, it is considered that a sintering temperature that is too high will weaken the thermomechanical stability of the material, increase the thermal conductivity, and thus reduce its thermal insulation effect; and when the sintering temperature is too low, the migration of powder particles and the movement of grain boundaries are limited, which may weaken the strength of the material and its stability under temperature changes. Therefore, the sintering temperature is controlled to be 500-700°C, and the holding time is 1-3h. For example, the sintering temperature is 530°C, 550°C, 570°C, 600°C, 630°C, 650°C, and 670°C.

[0065] Specifically, the above preparation method uses dry rubber powder with a porous structure as raw material. The porous structure can compensate for the collapse of pores inside the structure of the green body during ordinary drying. At the same time, fiber reinforcement is added to inhibit shrinkage, and fiber-reinforced Al2O3 aerogel is prepared by low-temperature sintering to increase the porosity of the ceramic aerogel, reduce process complexity, reduce costs, etc., to obtain fiber-reinforced Al2O3 aerogel with both low thermal conductivity and good thermal insulation performance.

[0066] Specifically, the fiber-reinforced Al2O3 aerogel of the present invention has a complete structure, a porosity of 83.94% to 92.16%, a thermal conductivity of 0.051 to 0.083 W / m·K, a shrinkage of 1.9% to 5.2%, and a volume density of 0.351 to 0.436 / cm 3 .

[0067] Compared with the prior art, the fiber-reinforced Al2O3 aerogel of the present invention adopts a porous dry gel powder as a raw material, to which a gel injection molding system raw material, a pore-forming agent and a fiber reinforcement are added, and the porous structure can compensate for the pore collapse inside the structure of the green body during ordinary drying. At the same time, the fiber reinforcement is added to inhibit shrinkage, and the fiber-reinforced Al2O3 aerogel is prepared by low-temperature sintering to increase the porosity of the ceramic aerogel, reduce the process complexity, and obtain a fiber-reinforced Al2O3 aerogel with both low thermal conductivity and good thermal insulation performance.

[0068] In the preparation method of the Al2O3 aerogel of the present invention, due to the synergistic effect between the raw materials, the porous structure of the powder can compensate for the collapse of the pores inside the green body during ordinary drying, and the fiber reinforcement is added to inhibit shrinkage. Therefore, the green body can be left standing at room temperature and then transferred to an oven for drying. There is no need to use supercritical, freeze-drying and normal pressure drying, and the process is simple; and the sintering temperature is low, which greatly reduces energy loss and can reduce production costs.

[0069] In the preparation method of the Al2O3 aerogel of the present invention, during the sintering process, the temperature and time are precisely controlled to prevent the aerogel from cracking, and finally the Al2O3 aerogel with a complete structure is obtained.

[0070] The Al2O3 aerogel of the present invention has a porosity of 83.94% to 92.16%, a thermal conductivity of 0.051 to 0.083 W / m·K, a shrinkage of 1.9% to 5.2%, and a volume density of 0.351 to 0.436 / cm 3 The aerogel produced has low thermal conductivity, high porosity, and also has the function of heat insulation.

[0071] The preparation method of the present invention utilizes dry rubber powder with a porous structure as a raw material. The porous structure compensates for the pore collapse inside the matrix caused by capillary force during ordinary drying. At the same time, fiber reinforcement is added to inhibit shrinkage, and a fiber-reinforced Al2O3 aerogel is prepared at low temperature, which solves the barriers of thermal insulation, low thermal conductivity and low cost coexisting in ceramic aerogels.

[0072] Example 1

[0073] The present embodiment provides a fiber-reinforced Al2O3 aerogel and a preparation method thereof. The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement. The main component of the dry glue powder is pseudo-boehmite. The raw materials of the gel injection molding system include monomers, cross-linking agents, initiators and catalysts. The monomer is acrylamide, the cross-linking agent is N,N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the catalyst is N,N,N',N'-tetramethylethylenediamine. Agar powder is a pore-forming agent, and silicon oxide nanotubes are fiber reinforcements; the mass proportions of dry glue powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst are 65.4%, 6.54%, 0.65%, 24.6%, 1.38%, 1.3% and 0.13% respectively.

[0074] The preparation method comprises the following steps:

[0075] Step 1, acidification preparation: add water and dry glue powder into the mold, stir at 60°C for 1 hour, then add agar powder and nitric acid with an acidification concentration of 0.04 mol / L and stir for 0.5 hour, then seal and place at room temperature for precipitation for 3 days; the mass ratio of water to dry glue powder is 9:1;

[0076] Step 2, preparing slurry: sucking out the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0077] Step 3, preparing a green body: adding the raw materials of the gel casting system and the silicon oxide nanotubes to the uniformly stirred mixture, stirring evenly and removing bubbles in time to obtain a green body;

[0078] Step 4, green body drying and demoulding: the green body of step 3 is placed at room temperature until the edges shrink, and then placed in a 40°C oven for drying. After the green body is dried, it is demoulded and taken out of the mold;

[0079] Step 5, sintering: sinter the dried green body at 600°C to obtain fibrous Al2O3 aerogel.

[0080] Figure 1 This is an optical image of the fiber-reinforced Al2O3 aerogel after drying and before sintering in Example 1; Figure 2 This is an optical image of the fiber-reinforced Al2O3 aerogel after drying and sintering in Example 1; Figure 4 This is the thermal insulation diagram of the fiber-reinforced Al2O3 aerogel of Example 1.

[0081] The fiber-reinforced Al2O3 aerogel of this embodiment has a complete structure, a porosity of 89.58% to 91.23%, a thermal conductivity of 0.058 to 0.067 W / m·K, a shrinkage of 2.1% to 3.2%, and a volume density of 0.365 to 0.376 g / cm 3 .

[0082] Example 2

[0083] The present embodiment provides a fiber-reinforced Al2O3 aerogel and a preparation method thereof. The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement. The main component of the dry glue powder is pseudo-boehmite. The raw materials of the gel injection molding system include monomers, cross-linking agents, initiators and catalysts. The monomers are N-isopropylacrylamide and acrylamide with a mass ratio of 1:1. The cross-linking agent is N,N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the catalyst is N,N-dimethylaniline. Melamine is a pore-forming agent, and silicon oxide nanotubes are fiber reinforcements. The mass proportions of dry glue powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst are 72.15%, 7.22%, 0.72%, 14.28%, 4.04%, 1.45% and 0.14% respectively.

[0084] The preparation method comprises the following steps:

[0085] Step 1, acidification preparation: add water and dry glue powder into the mold, stir at 60°C for 1.5h, then add melamine and 0.04mol / L nitric acid and stir for 0.6h, then seal and place at room temperature for precipitation for 3.5d; the mass ratio of water to dry glue powder is 8:1;

[0086] Step 2, preparing slurry: sucking out the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0087] Step 3, preparing a green body: adding the raw materials of the gel casting system and the silicon oxide nanotubes to the uniformly stirred mixture, stirring evenly and removing bubbles in time to obtain a green body;

[0088] Step 4, green body drying and demoulding: the green body of step 3 is placed at room temperature until the edges shrink, and then placed in a 50°C oven for drying. The green body is removed from the mold after being dried and demoulded;

[0089] Step 5, sintering: sinter the dried green body at 650° C. to obtain fiber-reinforced Al2O3 aerogel.

[0090] Figure 3 This is a scanning electron microscope image of the matrix of the fiber-reinforced Al2O3 aerogel of Example 2.

[0091] The Al2O3 aerogel prepared in this embodiment has a complete structure, a porosity of 86.94% to 87.35%, a thermal conductivity of 0.071 to 0.077 W / m·K, a shrinkage of 3.0% to 4.6%, and a volume density of 0.377 to 0.396 g / cm 3 .

[0092] Example 3

[0093] The present embodiment provides a fiber-reinforced Al2O3 aerogel and a preparation method thereof. The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement. The dry glue powder is pseudo-boehmite. The gel injection molding system raw materials include monomers, cross-linking agents, initiators, promoters and catalysts. The monomer is acrylamide, the cross-linking agent is N,N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the catalyst is N,N,N',N'-tetramethylethylenediamine. Microcrystalline cellulose is a pore-forming agent, and sepiolite fiber is a fiber reinforcement; the mass proportions of dry glue powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst are 65.4%, 6.54%, 0.65%, 24.59%, 1.37%, 1.32% and 0.13% respectively.

[0094] The preparation method comprises the following steps:

[0095] Step 1, acidification preparation: add water and dry glue powder into the mold, stir at 70°C for 1.2h, then add microcrystalline cellulose and nitric acid with an acidification concentration of 0.04mol / L and stir for 0.8h, then seal and place at room temperature for precipitation for 2d; the mass ratio of water to dry glue powder is 9:1;

[0096] Step 2, preparing slurry: sucking out the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0097] Step 3, preparing a green body: adding the raw materials of the gel casting system and the sepiolite fiber to the uniformly stirred mixture, stirring evenly and removing bubbles in time to obtain a green body;

[0098] Step 4, green body drying and demoulding: the green body of step 3 is placed at room temperature until the edges shrink, and then placed in a 45°C oven for drying. After the green body is dried and demoulded, it is taken out from the mold;

[0099] Step 5, sintering: sinter the dried green body at 600° C. to obtain fiber-reinforced Al2O3 aerogel.

[0100] The Al2O3 aerogel prepared in this embodiment has a complete structure, a porosity of 88.67% to 91.04%, a thermal conductivity of 0.074 to 0.079 W / m·K, a shrinkage of 2.8% to 4.1%, and a volume density of 0.375 to 0.397 g / cm 3 .

[0101] Example 4

[0102] The present embodiment provides a fiber-reinforced Al2O3 aerogel and a preparation method thereof. The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement. The dry glue powder is pseudo-boehmite. The gel injection molding system raw materials include monomers, cross-linking agents, initiators, promoters and catalysts. The monomer is acrylamide, the cross-linking agent is N,N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the catalyst is N,N,N',N'-tetramethylethylenediamine. Microcrystalline cellulose is a pore-forming agent, and sepiolite fiber is a fiber reinforcement; the mass proportions of dry glue powder, monomer, cross-linking agent, pore-forming agent, fiber reinforcement, initiator and catalyst are 58.2%, 9.50%, 0.90%, 23.16%, 7.21%, 0.6% and 0.43% respectively.

[0103] The preparation method comprises the following steps:

[0104] Step 1, acidification preparation: add water and dry glue powder into the mold, stir at 65°C for 1.2h, then add microcrystalline cellulose and nitric acid with an acidification concentration of 0.04mol / L and stir for 0.8h, then seal and place at room temperature for precipitation for 2.5d; the mass ratio of water to dry glue powder is 9:1;

[0105] Step 2, preparing slurry: sucking out the upper suspension after precipitation, and stirring the remaining mixture evenly;

[0106] Step 3, preparing a green body: adding the raw materials of the gel casting system and the sepiolite fiber to the uniformly stirred mixture, stirring evenly and removing bubbles in time to obtain a green body;

[0107] Step 4, green body drying and demoulding: the green body of step 3 is placed at room temperature until the edges shrink, and then placed in a 45°C oven for drying. After the green body is dried and demoulded, it is taken out from the mold;

[0108] Step 5: Sintering: Sinter the dried green body at 600° C. to obtain fiber-reinforced Al2O3 aerogel.

[0109] The Al2O3 aerogel prepared in this embodiment has a complete structure, a porosity of 83.94% to 86.16%, a thermal conductivity of 0.076 to 0.082 W / m·K, a shrinkage of 4.4% to 5.2%, and a volume density of 0.417 to 0.436 g / cm 3 .

[0110] Comparative Example 1

[0111] Comparative Example 1 discloses a fiber-reinforced Al2O3-based aerogel prepared by the same method as in Example 1, except that:

[0112] The pore-forming agent used in step 1 and the fiber reinforcement in step 3 are not added; the oven temperature in step 4 is 60°C.

[0113] Comparative Example 2

[0114] Comparative Example 2 discloses a fiber-reinforced Al2O3-based aerogel prepared by the same method as in Example 1, except that:

[0115] The pore-forming agent used in step 1 is melamine, and the mass proportion of melamine is 15%; in step 3, no fiber reinforcement is added; and in step 4, the oven temperature is 50°C.

[0116] Comparative Example 3

[0117] Comparative Example 3 discloses a fiber-reinforced Al2O3-based aerogel prepared by the same method as in Example 2, except that:

[0118] The concentration of nitric acid used in the acidification in step 1 is 0.03 mol / L, the pore-forming agent used is glucose, and the mass proportion of glucose is 10%, and the fiber reinforcement used in step 3 is mullite fiber, and the mass proportion of glucose is 10%.

[0119] Comparative Example 4

[0120] Comparative Example 4 discloses a fiber-reinforced Al2O3-based aerogel prepared by the same method as in Example 3, except that:

[0121] The concentration of nitric acid used for acidification in step 1 is 0.02 mol / L, and the pore-forming agent used is hydroxypropyl starch, which accounts for 15% by mass; the fiber reinforcement used in step 3 is mullite fiber; the oven temperature in step 4 is 100°C; and the sintering temperature in step 5 is 800°C.

[0122] Figure 5 This is a schematic diagram of the crushing and slagging of Comparative Example 4.

[0123] The relevant performance parameters of the fiber-reinforced Al2O3 aerogels of the embodiments and comparative examples are shown in Table 1. It can be seen that the fiber-reinforced Al2O3 aerogels of the present invention have a complete structure, low thermal conductivity, high porosity and good thermal insulation performance.

[0124] Table 1 Relevant performance parameters of the embodiments and comparative examples

[0125]

[0126] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A fiber-reinforced Al2O3 aerogel, characterized in that: The raw materials of the fiber-reinforced Al2O3 aerogel include dry glue powder, gel injection molding system raw materials, pore-forming agent and fiber reinforcement.

2. The fiber-reinforced Al2O3-based aerogel according to claim 1, characterized in that: The raw materials of the gel casting system include monomers, crosslinking agents, initiators and catalysts.

3. The fiber-reinforced Al2O3-based aerogel according to claim 2, characterized in that: The pore-forming agent includes one or more of agar powder, microcrystalline cellulose and melamine.

4. The fiber-reinforced Al2O3-based aerogel according to claim 2, characterized in that: The fiber reinforcement includes one or more of silica nanotubes, mullite fibers and sepiolite fibers.

5. The fiber-reinforced Al2O3-based aerogel according to any one of claims 2 to 4, characterized in that: The mass ratios of dry rubber powder, monomer, crosslinking agent, pore-forming agent, fiber reinforcement, initiator and catalyst to the total mass of raw materials are 50% to 75%, 6% to 10%, 0.5% to 1%, 10% to 25%, 1% to 8%, 0.5% to 1.8% and 0.1% to 0.5% respectively.

6. A method for preparing the fiber-reinforced Al2O3-based aerogel according to any one of claims 1 to 5, characterized in that: include: Step 1, acidification preparation: add water and dry rubber powder into the mold, put it into a water bath and stir, add pore-forming agent and nitric acid and stir, then seal and place at room temperature for precipitation; Step 2, preparing slurry: removing the upper suspension after precipitation, and stirring the remaining mixture evenly; Step 3, preparing a green body: adding a gel casting system raw material and a fiber reinforcement into a uniformly stirred mixture, wherein the gel casting system raw material includes a monomer, a cross-linking agent, an initiator and a catalyst, stirring evenly and removing bubbles in time to obtain a green body; Step 4, green body drying and demoulding: the green body is left to stand at room temperature until the edges shrink, and then put into an oven for drying. After the green body is dried and demoulded, it is taken out from the mold; Step 5: Sintering: Sintering the dried green body to obtain fiber-reinforced Al2O3 aerogel.

7. The preparation method according to claim 6, characterized in that: In the step 1, the precipitation is controlled to be placed for 2 to 5 days.

8. The preparation method according to claim 6, characterized in that: In step 4, the oven is controlled to be in a non-blowing state.

9. The preparation method according to claim 6, characterized in that: In step 4, the drying temperature is controlled to be 30-60°C.

10. The preparation method according to any one of claims 6 to 9, characterized in that: In the step 5, the sintering temperature is controlled to be 500-700° C. and kept warm for 1-3 hours.

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