A method for preparing an ultra-high strength rigid ceramic insulating tile

Abstract

The application provides a preparation method of an ultrahigh-strength rigid ceramic heat insulation tile and belongs to the technical field of heat protection materials. A phenolic resin precursor is dissolved in anhydrous ethanol and urotropin is added, a sintering aid powder is added into the phenolic resin precursor solution to prepare a mixed solution; the mixed solution is uniformly sprayed onto the surface of ceramic fibers and dried to obtain pretreated fibers A; the pretreated fibers A are added into water and transferred into a beater for beating, after the beating, filtration and drying, pretreated fibers B are obtained; the pretreated fibers B are uniformly and thickly laid into the mold cavity of a mold pressing mold, the mold is heated and kept warm, then cooled and demolded to obtain a heat insulation tile dry blank; the heat insulation tile dry blank is transferred into a muffle furnace and two-stage temperature rising sintering is performed to obtain the ultrahigh-strength rigid ceramic heat insulation tile. The application solves the problems of uneven strength and insufficient out-of-plane mechanical strength of the ultrahigh-strength rigid ceramic heat insulation tile prepared by using the existing method.

Description

Technical Field

[0001] This invention relates to a method for preparing ultra-high strength rigid ceramic heat insulation tiles, belonging to the field of thermal protection materials technology. Background Technology

[0002] Rigid ceramic heat insulation tiles are a traditional aerospace thermal protection material. Current preparation methods generally include mixing ceramic fibers and sintering aids into a pulp, filtering and forming, drying, and sintering. The ceramic fibers are typically quartz fibers, alumina fibers, aluminosilicate fibers, and mullite fibers. The sintering aids are mostly boron compound powders such as boron nitride powder and boron carbide powder, with a density generally around 0.15 g / cm³. 3 ~0.50g / cm 3 Within the specified range. Under existing preparation methods, sintering aids are generally mixed directly with ceramic fibers in powder form to form a slurry. This results in significant and uncontrollable loss of sintering aid powder during filtration. Furthermore, due to the differences in morphology and density between the aid powder and ceramic fibers, their suspension states and settling rates in the slurry are inconsistent. This leads to uneven distribution of the sintering aid powder within the wet fiber blank during filtration, resulting in gradient differences in the thickness direction and further contributing to uneven strength of the insulation tile.

[0003] Ultra-high strength rigid ceramic heat insulation tiles generally refer to those with a density of 0.6 g / cm³. 3 These are heat-insulating tiles with a compressive strength of over 10 MPa and a tensile strength of over 3 MPa. Due to their high density, current manufacturing methods generally involve using materials with a density of 0.15 g / cm³. 3 ~0.50g / cm 3 Based on the existing heat-insulating tiles, the density is forcibly compressed to 0.6 g / cm³ by repeatedly pressurizing the wet blank during the filter forming stage. 3 The above points highlight the drawbacks of this method. Firstly, during repeated pressurization, the slurry in the wet blank is squeezed out, along with the sintering aid powder, making the amount and distribution of the sintering aid powder more uncontrollable. Secondly, as the density of the wet blank increases, the saturated liquid slurry within the fiber gaps is difficult to drain, and continued forced pressurization can easily cause the wet blank to burst, leak slurry, and crack. Thirdly, wet filtration and repeated pressurization cause excessive fiber orientation along the planar direction, reducing the number of fibers oriented along the thickness direction. This significantly reduces the out-of-plane compressive strength and out-of-plane tensile strength of the insulation tile, typically below 5 MPa for compressive strength and below 1 MPa for tensile strength. To address these problems in the existing technology, a new method for preparing ultra-high strength rigid ceramic insulation tiles is urgently needed. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of uneven strength and insufficient out-of-plane mechanical strength in the preparation of ultra-high strength rigid ceramic heat insulation tiles using existing methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing ultra-high strength rigid ceramic heat insulation tiles includes the following steps:

[0007] 1) Weigh out ceramic fiber, sintering aid powder and phenolic resin precursor according to a mass ratio of 100:(1~15):(5~20);

[0008] 2) Dissolve the phenolic resin precursor weighed in step 1) in anhydrous ethanol and add hexamethylenetetramine. Stir until completely dissolved. Then add the weighed sintering aid powder to the phenolic resin precursor solution and stir evenly to obtain a mixed solution.

[0009] 3) The mixed solution obtained in step 2) is evenly sprayed onto the surface of the ceramic fiber weighed in step 1) and dried to obtain pretreated fiber A.

[0010] 4) Add the pretreated fiber A obtained in step 3) to water and transfer it to a pulper for pulping. After pulping, filter and dry to obtain pretreated fiber B.

[0011] 5) The pretreated fiber B obtained in step 4) is spread evenly into the mold cavity of the molding die. After molding to the thickness corresponding to the preset density, the mold is heated and kept warm, then cooled and demolded to obtain the dry blank of the heat insulation tile.

[0012] 6) Transfer the dry blank of the heat insulation tile obtained in step 5) to a muffle furnace, first heat it to 600-800℃ and keep it at that temperature for 2-5 hours, then heat it to 1000-1400℃ and keep it at that temperature for 1-5 hours, then cool it to room temperature and take it out to obtain ultra-high strength rigid ceramic heat insulation tile.

[0013] Further, the ceramic fiber mentioned in step 1) includes one or two of fiber X and fiber Y, wherein fiber X is quartz fiber, and fiber Y is one or a combination of alumina fiber, aluminosilicate fiber, zirconium fiber, and mullite fiber, and the mass ratio of fiber X to fiber Y is 100:(0-50).

[0014] Further, the sintering aid powder mentioned in step 1) is one or a combination of boron nitride powder, boron carbide powder, silicon boride powder, and silicon powder.

[0015] Further, the weight of hexamethylenetetramine in step 2) is 5% to 15% of the weight of the phenolic resin precursor.

[0016] Furthermore, the amount of anhydrous ethanol added in step 2) is 0.5 to 2 times the weight of the phenolic resin precursor.

[0017] Further, in step 4), the mass ratio of water to pretreated fiber is 100:(1-10).

[0018] Further, in step 4), pulping is performed until at least 70% of the fiber length is distributed in the range of 0.5 to 2 mm.

[0019] Furthermore, the preset density range mentioned in step 5) is 0.6–1.0 g / cm³. 3 .

[0020] Further, in step 5), the mold is heated to 90-120°C and kept at that temperature for 10-50 hours.

[0021] Furthermore, in step 6), the temperature is first increased to 600-800℃ at a heating rate of 5-10℃ / min, and then increased to 1000-1400℃ at a heating rate of 1-5℃ / min.

[0022] The beneficial effects achieved by this invention are as follows:

[0023] 1) By mixing the sintering aid powder with the binder in step 2) and fixing the sintering aid powder to the surface of the ceramic fiber with the binder in step 3), the problem that the powdered sintering aid is difficult to adhere to the surface of the ceramic fiber under the impact of water flow and is lost with the water when the powdered sintering aid and the ceramic fiber are filtered together under the existing technology is solved.

[0024] 2) Step 4) aims to process the ceramic fibers to a specified length range and loosen any ceramic fibers that may have adhered in step 3). Step 5) allows the ceramic fibers to be dry-molded to a specified length of 0.6–1.0 g / cm³. 3The dry molding process eliminates the need for liquid slurry, thus solving the problems of cracking, slurry bursting, and bursting inherent in wet molding. This is because wet molding involves a large amount of moisture in the wet blank. As the density of the wet blank increases, the moisture within the fiber gaps is difficult to expel due to fiber blockage. Since liquids are not compressible, forced pressure can easily cause the wet blank to burst, burst, and crack. Simultaneously, it also solves the problem of fiber layer-by-layer deposition on the filter screen during wet molding, where the fiber distribution is parallel to the screen (two-dimensional orientation) with few fibers perpendicular to the screen. The pre-treated fibers used in this invention have a better three-dimensional orientation, and the dry lamination process avoids the layer-by-layer deposition caused by wet filtration. Therefore, the overall three-dimensional distribution of the fibers is better, significantly improving the fiber distribution problem inherent in wet molding. After molding, heating the mold allows the phenolic resin precursor to melt and solidify, firmly bonding the ceramic fibers together to obtain a stable dry blank for the heat-insulating tile.

[0025] 3) Through step 6), the dry blank of the heat insulation tile can be sintered. The purpose of holding it at 600-800℃ for 2-5 hours is to remove the organic phenolic resin coating on the fiber surface and expose the sintering aid in situ. At the same time, the sintering aid oxidizes and flows at this temperature. Holding it at 1000-1400℃ for 1-5 hours can achieve effective bonding of the sintering aid to the ceramic fiber through the glass transition reaction, resulting in ultra-high strength rigid ceramic heat insulation tile. Detailed Implementation

[0026] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, detailed descriptions are provided below in conjunction with embodiments.

[0027] Example 1:

[0028] A method for preparing ultra-high strength rigid ceramic heat insulation tiles includes the following steps:

[0029] 1) Weigh out ceramic fiber, sintering aid powder, and bonding agent according to a mass ratio of 100:15:20.

[0030] The ceramic fiber comprises two components, fiber X and fiber Y, wherein fiber X is quartz fiber and fiber Y is alumina fiber, and the mass ratio of the two components X and Y is 100:50.

[0031] The sintering aid powder is boron nitride powder;

[0032] The adhesive additive is a phenolic resin precursor;

[0033] 2) Dissolve the phenolic resin precursor weighed in step 1) in anhydrous ethanol and add hexamethylenetetramine. Stir until completely dissolved. Then add the weighed sintering aid powder to the phenolic resin precursor solution and stir evenly to obtain a mixed solution.

[0034] The weight of the hexamethylenetetramine is 15% of the weight of the phenolic resin precursor.

[0035] The amount of anhydrous ethanol added is twice the weight of the phenolic resin precursor.

[0036] 3) The mixed solution obtained in step 2) is evenly sprayed onto the surface of the ceramic fiber weighed in step 1) and dried to obtain pretreated fiber A.

[0037] 4) Add the pretreated fiber obtained in step 3) to water and transfer it to a pulper for pulping until 70% of the fiber length is distributed in the range of 0.5 to 2 mm. After pulping, filter and dry to obtain pretreated fiber B.

[0038] The mass ratio of water to pretreated fiber is 100:10;

[0039] 5) The pretreated fiber B obtained in step 4) is spread evenly into the mold cavity of the molding die. After molding to the thickness corresponding to the specified density, the mold is heated to 120°C and kept at that temperature for 10 hours. After cooling and demolding, the dry blank of the heat insulation tile is obtained.

[0040] The specified density range is 1.0 g / cm³. 3 ;

[0041] 6) Transfer the dry blank of the heat insulation tile obtained in step 5) to a muffle furnace, raise the temperature to 800°C at a heating rate of 10°C / min, hold for 2 hours, then raise the temperature to 1400°C at a heating rate of 5°C / min, hold for 1 hour, and then cool to room temperature to obtain ultra-high strength rigid ceramic heat insulation tile.

[0042] The prepared ultra-high strength rigid ceramic heat insulation tile is dimensionally complete, internally intact, and free from cracks or bursts. It has a uniform density distribution, an out-of-plane compressive strength of 15 MPa at room temperature, an out-of-plane tensile strength of 3.5 MPa at room temperature, and a temperature resistance of 1500℃.

[0043] Example 2:

[0044] A method for preparing ultra-high strength rigid ceramic heat insulation tiles includes the following steps:

[0045] 1) Weigh out ceramic fiber, sintering aid powder, and bonding agent according to a mass ratio of 100:1:5.

[0046] The ceramic fiber is quartz fiber;

[0047] The sintering aid powder is boron nitride powder;

[0048] The adhesive additive is a phenolic resin precursor;

[0049] 2) Dissolve the phenolic resin precursor weighed in step 1) in anhydrous ethanol and add hexamethylenetetramine. Stir until completely dissolved. Then add the weighed sintering aid powder to the phenolic resin precursor solution and stir evenly to obtain a mixed solution.

[0050] The weight of the hexamethylenetetramine is 5% of the weight of the phenolic resin precursor.

[0051] The amount of anhydrous ethanol added is 0.5 times the weight of the phenolic resin precursor.

[0052] 3) The mixed solution obtained in step 2) is evenly sprayed onto the surface of the ceramic fiber weighed in step 1) and dried to obtain pretreated fiber A.

[0053] 4) Add the pretreated fiber obtained in step 3) to water and transfer it to a pulper for pulping until 70% of the fiber length is distributed in the range of 0.5 to 2 mm. After pulping, filter and dry to obtain pretreated fiber B.

[0054] The mass ratio of water to pretreated fiber is 100:1;

[0055] 5) The pretreated fiber B obtained in step 4) is spread evenly into the mold cavity of the molding die. After molding to the thickness corresponding to the specified density, the mold is heated to 90°C and kept at that temperature for 50 hours. After cooling and demolding, the dry blank of the heat insulation tile is obtained.

[0056] The specified density range is 0.6 / cm³. 3 ;

[0057] 6) Transfer the dry blank of the heat insulation tile obtained in step 5) to a muffle furnace, raise the temperature to 600°C at a heating rate of 5°C / min, hold for 5 hours, then raise the temperature to 1000°C at a heating rate of 1°C / min, hold for 5 hours, and then cool to room temperature to obtain an ultra-high strength rigid ceramic heat insulation tile.

[0058] The prepared ultra-high strength rigid ceramic heat insulation tile is dimensionally complete, has good internal quality, no cracks or bursts on the surface, has uniform density distribution, has an out-of-plane compressive strength of 8 MPa at room temperature, an out-of-plane tensile strength of 2 MPa at room temperature, and can withstand temperatures up to 1100℃.

[0059] Example 3:

[0060] A method for preparing ultra-high strength rigid ceramic heat insulation tiles includes the following steps:

[0061] 1) Weigh out ceramic fiber, sintering aid powder, and bonding agent according to a mass ratio of 100:8:10.

[0062] The ceramic fiber comprises two components, fiber X and fiber Y, wherein fiber X is quartz fiber and fiber Y is alumina fiber, and the mass ratio of the two components X and Y is 100:25.

[0063] The sintering aid powder is boron carbide powder;

[0064] The adhesive additive is a phenolic resin precursor;

[0065] 2) Dissolve the phenolic resin precursor weighed in step 1) in anhydrous ethanol and add hexamethylenetetramine. Stir until completely dissolved. Then add the weighed sintering aid powder to the phenolic resin precursor solution and stir evenly to obtain a mixed solution.

[0066] The weight of the hexamethylenetetramine is 10% of the weight of the phenolic resin precursor.

[0067] The amount of anhydrous ethanol added is 1 times the weight of the phenolic resin precursor.

[0068] 3) The mixed solution obtained in step 2) is evenly sprayed onto the surface of the ceramic fiber weighed in step 1) and dried to obtain pretreated fiber A.

[0069] 4) Add the pretreated fiber obtained in step 3) to water and transfer it to a pulper for pulping until 70% of the fiber length is distributed in the range of 0.5 to 2 mm. After pulping, filter and dry to obtain pretreated fiber B.

[0070] The mass ratio of water to pretreated fiber is 100:5;

[0071] 5) The pretreated fiber B obtained in step 4) is spread evenly into the mold cavity of the molding die. After molding to the thickness corresponding to the specified density, the mold is heated to 100°C and kept at that temperature for 30 hours. After cooling and demolding, the dry blank of the heat insulation tile is obtained.

[0072] The specified density range is 0.8 g / cm³. 3 ;

[0073] 6) Transfer the dry blank of the heat insulation tile obtained in step 5) to a muffle furnace, raise the temperature to 700°C at a heating rate of 8°C / min, hold for 4 hours, then raise the temperature to 1300°C at a heating rate of 3°C / min, hold for 3 hours, and then cool to room temperature to obtain ultra-high strength rigid ceramic heat insulation tile.

[0074] The prepared ultra-high strength rigid ceramic heat insulation tile is dimensionally complete, internally intact, and free from cracks or bursts. It has a uniform density distribution, an out-of-plane compressive strength of 12 MPa at room temperature, an out-of-plane tensile strength of 2.5 MPa at room temperature, and a temperature resistance of 1300℃.

[0075] Comparative example:

[0076] Compared with Example 3, the existing preparation method includes the following steps:

[0077] 1) Weigh out ceramic fiber, sintering aid powder, and bonding agent according to a mass ratio of 100:8:10.

[0078] The ceramic fiber comprises two components, X and Y, wherein component X is quartz fiber and component Y is alumina fiber, and the mass ratio of components X to Y is 100:25; the sintering aid powder is boron carbide powder; and the bonding aid is starch.

[0079] 2) The weighed ceramic fibers, sintering aid powder, and adhesive additive are mixed and dispersed in water to prepare a mixed slurry;

[0080] 3) Filter the prepared mixed slurry to obtain a wet blank;

[0081] 4) Transfer the prepared wet blank to a press platform and press it until the density reaches 0.8 g / cm³. 3 Stop after the corresponding thickness;

[0082] 5) Place the pressed wet blank in an oven for drying. After drying, transfer it to a muffle furnace and heat it to 700°C at a rate of 8°C / min. Hold it at this temperature for 4 hours. Then heat it to 1300°C at a rate of 3°C / min. Hold it at this temperature for 3 hours. Then cool it to room temperature and remove it to obtain the rigid ceramic heat insulation tile prepared by the prior art.

[0083] Rigid ceramic heat insulation tiles prepared using existing technology have internal cracking defects, external cracks, and edge breakage caused by slurry bursting during molding. They also have uneven density distribution, room temperature out-of-plane compressive strength of 5 MPa, room temperature out-of-plane tensile strength of 0.8 MPa, and temperature resistance of 1250℃.

[0084] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. A method for preparing ultra-high strength rigid ceramic heat insulation tiles, characterized in that, Includes the following steps: 1) Weigh out ceramic fiber, sintering aid powder and phenolic resin precursor according to a mass ratio of 100:(1~15):(5~20); 2) Dissolve the phenolic resin precursor weighed in step 1) in anhydrous ethanol and add hexamethylenetetramine, wherein the weight of hexamethylenetetramine is 5% to 15% of the weight of the phenolic resin precursor. Stir until completely dissolved, and then add the weighed sintering aid powder to the phenolic resin precursor solution and stir evenly to obtain a mixed solution. 3) The mixed solution obtained in step 2) is evenly sprayed onto the surface of the ceramic fiber weighed in step 1) and dried to obtain pretreated fiber A. 4) Add the pretreated fiber A obtained in step 3) to water and transfer it to a pulper for pulping. Pulping is carried out until at least 70% of the fiber length is distributed in the range of 0.5 to 2 mm. After pulping, filter and dry to obtain pretreated fiber B. 5) The pretreated fiber B obtained in step 4) is spread evenly into the mold cavity of the molding die. After molding to the thickness corresponding to the preset density, the mold is heated to 90-120℃ and kept at that temperature for 10-50 hours. Then it is cooled and demolded to obtain the dry blank of the heat insulation tile. 6) Transfer the dry blank of the heat insulation tile obtained in step 5) to a muffle furnace, first heat it to 600-800℃ and keep it at that temperature for 2-5 hours, then heat it to 1000-1400℃ and keep it at that temperature for 1-5 hours, then cool it to room temperature and take it out to obtain ultra-high strength rigid ceramic heat insulation tile.

2. The method as described in claim 1, characterized in that, The ceramic fiber mentioned in step 1) includes one or two of fiber X and fiber Y, wherein fiber X is quartz fiber, and fiber Y is one or a combination of alumina fiber, aluminosilicate fiber, zirconia fiber, and mullite fiber, and the mass ratio of fiber X to fiber Y is 100:(0-50).

3. The method as described in claim 1, characterized in that, The sintering aid powder mentioned in step 1) is one or a combination of boron nitride powder, boron carbide powder, silicon boride powder, and silicon powder.

4. The method as described in claim 1, characterized in that, The amount of anhydrous ethanol added in step 2) is 0.5 to 2 times the weight of the phenolic resin precursor.

5. The method as described in claim 1, characterized in that, The mass ratio of water to pretreated fiber in step 4) is 100:(1-10).

6. The method as described in claim 1, characterized in that, The preset density range mentioned in step 5) is 0.6–1.0 g / cm³. 3 .

7. The method as described in claim 1, characterized in that, In step 6), the temperature is first increased to 600-800℃ at a rate of 5-10℃ / min, and then increased to 1000-1400℃ at a rate of 1-5℃ / min.