High-strength light-weight environment-friendly ceramic and preparation method thereof

Abstract

The application relates to the technical field of ceramic materials, and discloses a high-strength light-weight environment-friendly ceramic and a preparation method thereof, the method comprises raw material pretreatment, slurry preparation, gel injection molding, vacuum freeze drying and segmented sintering, through adoption of industrial solid waste as a main raw material and acid pickling pretreatment, the purification and activity improvement of the raw material are ensured, meanwhile, through the action of a dispersing agent and a foaming agent in slurry preparation, uniform and stable ceramic slurry is formed, resource utilization of waste is realized, environmental influence is reduced, and the uniformity of a product is improved; through crosslinking agent and ultraviolet radiation auxiliary formation of a three-dimensional network structure, and in combination with pre-freezing gradient regulation, directional pores can be formed in the body in real time, the controllability of a pore structure is ensured, and in the drying process, structural deformation is avoided, the light weight and heat insulation performance of the ceramic are improved.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly ceramic materials technology, specifically to a high-strength, lightweight, environmentally friendly ceramic and its preparation method. Background Technology

[0002] Ceramic materials have outstanding characteristics such as high temperature resistance, corrosion resistance, high strength, and high hardness. In many fields such as chemical engineering, aerospace, biology, energy, and environmental protection, there is often a need for lightweight ceramic materials with ultra-low density, uniform internal microstructure, and high strength.

[0003] Currently, in the field of ceramic material preparation, traditional methods often use high-purity natural raw materials, resulting in high production costs and resource consumption. At the same time, it is difficult to achieve both lightweight and high-strength properties of the material. In the pursuit of lightweighting, porosity is often increased, but this can easily lead to a decrease in the strength of the ceramic body, poor structural uniformity, and uncontrollable internal pore size distribution, affecting the stability of thermal insulation performance. In addition, existing processes have low utilization rates of industrial solid waste. Solid wastes such as waste ceramics and fly ash cannot be efficiently utilized. During sintering, impurities or improper process control can easily lead to incomplete crystal phase development and insufficient densification, thus affecting the mechanical properties and durability of the final product.

[0004] Therefore, a high-strength, lightweight, and environmentally friendly ceramic and its preparation method are proposed to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength, lightweight, and environmentally friendly ceramic and its preparation method, solving the problems mentioned in the background technology of difficulty in simultaneously achieving the lightweight and high-strength characteristics of materials, the stability of thermal insulation performance, and incomplete crystal phase development and insufficient densification.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-strength, lightweight, and environmentally friendly ceramics, comprising the following steps:

[0007] Step 1: Raw material pretreatment. Select industrial solid waste fly ash, waste ceramic crushed material and kaolin as the main raw materials. The weight ratio is 40-60 parts fly ash, 20-30 parts waste ceramic crushed material and 10-15 parts kaolin. Crush and screen until the particle size is ≤50μm, and then put them into a mixer to dry mix evenly.

[0008] Step 2: Slurry preparation. Add the pretreated raw materials to a water-based solvent, and add 0.5-1.5 parts of dispersant, 3-5 parts of binder, and 2-4 parts of foaming agent. Ball mill and mix at a stirring rate of 400-800 r / min for 2-4 hours to form a uniform and stable ceramic slurry.

[0009] Step 3: Gel injection molding. The slurry is injected into the mold and allowed to stand for gelation for 1-2 hours at a temperature of 60-80℃ and a relative humidity of 50%-70% to form a preform with a three-dimensional network structure.

[0010] Step 4: Vacuum freeze drying. Place the green body in a vacuum freeze drying equipment and pre-freeze it at -30℃ to -50℃ for 4-6 hours. Then, sublime dry it under a vacuum of ≤10Pa for 12-24 hours to obtain a porous ceramic preform.

[0011] Step 5: Segmented sintering. The preform is placed in a high-temperature sintering furnace. First, the temperature is raised to 600-800℃ at 3-5℃ / min and held for 1 hour for debinding. Then, the temperature is raised to 1250-1350℃ at 5-8℃ / min and held for 2-3 hours for densification sintering. After cooling in the furnace, a high-strength, lightweight, and environmentally friendly ceramic product is obtained.

[0012] Preferably, in step one, the fly ash needs to be acid-washed first:

[0013] Fly ash is soaked in a 10%-15% hydrochloric acid solution with a liquid-to-solid ratio of 3:1, stirred and reacted at 60-80℃ for 2-3 hours, filtered, washed with water until neutral, dried, crushed and sieved.

[0014] The waste ceramic crushed material is building ceramic or daily-use ceramic waste, which is coarsely crushed by a jaw crusher and then finely crushed by a planetary ball mill to a particle size ≤30μm.

[0015] Preferably, in step two:

[0016] The water-based solvent is deionized water, and the amount added is 80%-120% of the total weight of the raw materials;

[0017] The dispersant is at least one of sodium polyacrylate or sodium hexametaphosphate;

[0018] The adhesive is polyvinyl alcohol or hydroxypropyl methylcellulose;

[0019] The foaming agent is either ammonium bicarbonate or hydrogen peroxide.

[0020] Preferably, in step three, 0.1-0.3 parts of a crosslinking agent are added during gel casting. The crosslinking agent is either N,N'-methylenebisacrylamide or glutaraldehyde. Crosslinking is assisted by ultraviolet radiation during gelation, with a radiation intensity of 10-30 mW / cm². 2 Time: 10-30 minutes.

[0021] Preferably, in step four, the pre-freezing gradient of the green body needs to be controlled before vacuum freeze-drying:

[0022] First, the temperature is lowered to -10℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is lowered to below -30℃ at a rate of 2℃ / min, allowing ice crystals to grow uniformly and form directional channels.

[0023] Preferably, in step five, the sintering process needs to be carried out under an inert atmosphere, with the inert gas being nitrogen or argon, and the gas flow rate being 0.5-2 L / min;

[0024] Microwave-assisted sintering is used in the later stage of sintering, with a microwave power of 5-10kW, a frequency of 2.45GHz, and an assisted sintering time of 20-40min.

[0025] Preferably, 1-3 parts of reinforcing fiber are added during the preparation of the slurry in step two. The reinforcing fiber is at least one of carbon fiber, alumina fiber or calcium silicate fiber, with a fiber length of 50-200 μm and an aspect ratio of ≥20.

[0026] Preferably, the reinforcing fiber needs to undergo surface modification treatment first: the fiber is immersed in a silane coupling agent KH-550 and an ethanol solution with a concentration of 2%-5%, ultrasonically treated at 60°C for 30-60 minutes, and then dried before use.

[0027] A high-strength, lightweight, and environmentally friendly ceramic has a three-dimensional interconnected macroporous structure inside the ceramic body, with a pore size distribution range of 50-300μm and a porosity controlled between 55% and 65%.

[0028] The ceramic matrix is ​​composed of mullite crystalline phase, glassy phase and residual quartz phase, wherein the content of mullite crystalline phase is not less than 45 vol%, and the grain size is 0.5-2 μm;

[0029] The bulk density of ceramics is 1.0-1.5 g / cm³. 3 After polishing, the surface roughness Ra is less than 0.8μm.

[0030] Preferably, the ceramic surface is coated with an alumina wear-resistant coating by a sol-gel method, and the coating thickness is 10-30 μm;

[0031] The coating consists of a γ-alumina transition layer and an α-alumina surface layer, wherein the grain size of the surface layer is 100-500 nm.

[0032] The coating preparation method includes immersing sintered ceramic in a sol containing aluminum nitrate and aluminum isopropoxide, pulling it into a film at a speed of 2-5 mm / s, drying it at 80-100℃, and then heat-treating it at 600-800℃ for 0.5-1 hour to form a dense coating.

[0033] Compared with the prior art, the present invention provides a high-strength, lightweight, and environmentally friendly ceramic and its preparation method, which has the following beneficial effects:

[0034] 1. In this invention, when preparing high-strength, lightweight, and environmentally friendly ceramics, industrial solid waste is used as the main raw material and subjected to acid washing pretreatment to ensure the purification and activity enhancement of the raw materials. At the same time, through the action of dispersants and foaming agents in slurry preparation, a uniform and stable ceramic slurry is formed, realizing the resource utilization of waste materials, reducing environmental impact, and improving the uniformity of products.

[0035] 2. In this invention, during the gel casting and vacuum freeze-drying process, a three-dimensional network structure is formed with the assistance of crosslinking agents and ultraviolet radiation, and combined with pre-freezing gradient control, so that directional channels can be formed in real time inside the green body, ensuring the controllability of the pore structure, and avoiding structural deformation during the drying process, thereby improving the lightweight and heat insulation performance of the ceramic.

[0036] 3. In this invention, during segmented sintering and the addition of reinforcing fibers, microwave-assisted sintering and fiber surface modification treatment are used to promote the densification process of the ceramic matrix. The sintering process is optimized according to the formation of the mullite crystal phase, so that the product has high strength and low water absorption, reduces the risk of performance fluctuation, and improves the durability and stability of the ceramic. Attached Figure Description

[0037] Figure 1 This is a flowchart of a method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: A method for preparing a high-strength, lightweight, and environmentally friendly ceramic, comprising the following steps:

[0040] Step 1: Raw material pretreatment. Industrial solid waste fly ash, waste ceramic crushed material and kaolin are selected as the main raw materials. The weight ratio is 40 parts fly ash, 20 parts waste ceramic crushed material and 10 parts kaolin. The raw materials are crushed and screened to a particle size ≤50μm, and then placed in a mixer to dry mix evenly.

[0041] Step 2: Slurry preparation. The pretreated raw materials are added to a water-based solvent, along with 0.5 parts of dispersant, 3 parts of binder, and 2 parts of foaming agent. The mixture is ball-milled at a stirring rate of 400 r / min for 2 hours to form a uniform and stable ceramic slurry.

[0042] Step 3: Gel injection molding. The slurry is injected into the mold and allowed to stand for 1 hour at a temperature of 60℃ and a relative humidity of 50% to gel, forming a preform with a three-dimensional network structure.

[0043] Step 4: Vacuum freeze drying. Place the green body in a vacuum freeze drying equipment and pre-freeze it at -30℃ for 4 hours. Then, sublime dry it under a vacuum degree ≤10Pa for 12 hours to obtain a porous ceramic preform.

[0044] Step 5: Segmented sintering. The preform is placed in a high-temperature sintering furnace. First, the temperature is increased to 600℃ at 3℃ / min and held for 1 hour for debinding. Then, the temperature is increased to 1250℃ at 5℃ / min and held for 2 hours for densification sintering. After cooling in the furnace, a high-strength, lightweight, and environmentally friendly ceramic product is obtained.

[0045] In step one, the fly ash needs to be acid-washed first:

[0046] Fly ash was soaked in a 10% hydrochloric acid solution with a liquid-to-solid ratio of 3:1, stirred and reacted at 60°C for 2 hours, filtered, washed with water until neutral, dried, crushed and sieved.

[0047] Waste ceramic crushing material is building ceramics or daily-use ceramic waste. After being coarsely crushed by a jaw crusher, it is finely crushed by a planetary ball mill to a particle size of ≤30μm.

[0048] In step two:

[0049] The water-based solvent is deionized water, and the amount added is 80% of the total weight of the raw materials;

[0050] The dispersant is at least one of sodium polyacrylate or sodium hexametaphosphate;

[0051] The binder is polyvinyl alcohol or hydroxypropyl methylcellulose;

[0052] The foaming agent is either ammonium bicarbonate or hydrogen peroxide.

[0053] In step three, 0.1 parts of a crosslinking agent need to be added during gel casting. The crosslinking agent is either N,N'-methylenebisacrylamide or glutaraldehyde. Crosslinking is assisted by ultraviolet radiation during gelation, with a radiation intensity of 10 mW / cm². 2 Time: 10 minutes.

[0054] In step four, the pre-freezing gradient of the green body needs to be controlled before vacuum freeze-drying:

[0055] First, the temperature is lowered to -10℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is lowered to below -30℃ at a rate of 2℃ / min, allowing ice crystals to grow uniformly and form directional channels.

[0056] In step five, the sintering process must be carried out under an inert atmosphere, with the inert gas being nitrogen or argon, and the gas flow rate being 0.5 L / min.

[0057] Microwave-assisted sintering was used in the later stage of sintering, with a microwave power of 5kW, a frequency of 2.45GHz, and an assisted sintering time of 20min.

[0058] In step two, during the preparation of the slurry, one part of reinforcing fiber is added. The reinforcing fiber is at least one of carbon fiber, alumina fiber or calcium silicate fiber, with a fiber length of 50 μm and an aspect ratio of ≥20.

[0059] The reinforcing fibers need to undergo surface modification treatment first: the fibers are immersed in a 2% ethanol solution of silane coupling agent KH-550, ultrasonically treated at 60℃ for 30 minutes, and then dried before use.

[0060] A high-strength, lightweight, and environmentally friendly ceramic has a three-dimensional interconnected macroporous structure inside the ceramic body, with a pore size distribution range of 50 μm and a porosity controlled at 55%.

[0061] The ceramic matrix is ​​composed of mullite crystalline phase, glassy phase and residual quartz phase, wherein the content of mullite crystalline phase is not less than 45 vol%, and the grain size is 0.5 μm;

[0062] The bulk density of ceramics is 1.0 g / cm³. 3 After polishing, the surface roughness Ra is less than 0.8μm.

[0063] An alumina wear-resistant coating was prepared on the ceramic surface by the sol-gel method, and the coating thickness was 10 μm.

[0064] The coating consists of a γ-alumina transition layer and an α-alumina surface layer, wherein the grain size of the surface layer is 100 nm.

[0065] The coating preparation method includes immersing the sintered ceramic in a sol containing aluminum nitrate and aluminum isopropoxide, pulling it into a film at a speed of 2 mm / s, drying it at 80°C, and then heat-treating it at 600°C for 0.5 hours to form a dense coating.

[0066] Example 2: A method for preparing a high-strength, lightweight, and environmentally friendly ceramic, comprising the following steps:

[0067] Step 1: Raw material pretreatment. Industrial solid waste fly ash, waste ceramic crushed material and kaolin are selected as the main raw materials. The weight ratio is 50 parts fly ash, 25 parts waste ceramic crushed material and 13 parts kaolin. The materials are crushed and screened to a particle size ≤50μm, and then placed in a mixer to dry mix evenly.

[0068] Step 2: Slurry preparation. The pretreated raw materials are added to a water-based solvent, along with 1.0 part of dispersant, 4 parts of binder, and 3 parts of foaming agent. The mixture is ball-milled at a stirring rate of 600 r / min for 3 hours to form a uniform and stable ceramic slurry.

[0069] Step 3: Gel injection molding. The slurry is injected into the mold and allowed to gel at 70°C and 60% relative humidity for 1.5 hours to form a preform with a three-dimensional network structure.

[0070] Step 4: Vacuum freeze drying. Place the green body in a vacuum freeze drying equipment and pre-freeze it at -40℃ for 5 hours. Then, sublime dry it under a vacuum degree ≤10Pa for 18 hours to obtain a porous ceramic preform.

[0071] Step 5: Segmented sintering. The preform is placed in a high-temperature sintering furnace. First, the temperature is increased to 700℃ at 4℃ / min and held for 1 hour for debinding. Then, the temperature is increased to 1300℃ at 6.5℃ / min and held for 2.5 hours for densification sintering. After cooling in the furnace, a high-strength, lightweight, and environmentally friendly ceramic product is obtained.

[0072] In step one, the fly ash needs to be acid-washed first:

[0073] Fly ash was soaked in a 13% hydrochloric acid solution with a liquid-to-solid ratio of 3:1 and stirred at 70°C for 2.5 hours. After filtration, it was washed with water until neutral, dried, crushed, and sieved.

[0074] Waste ceramic crushing material is building ceramics or daily-use ceramic waste. After being coarsely crushed by a jaw crusher, it is finely crushed by a planetary ball mill to a particle size of ≤30μm.

[0075] In step two:

[0076] The water-based solvent is deionized water, and the amount added is 100% of the total weight of the raw materials;

[0077] The dispersant is at least one of sodium polyacrylate or sodium hexametaphosphate;

[0078] The binder is polyvinyl alcohol or hydroxypropyl methylcellulose;

[0079] The foaming agent is either ammonium bicarbonate or hydrogen peroxide.

[0080] In step three, 0.2 parts of a crosslinking agent need to be added during gel casting. The crosslinking agent is either N,N'-methylenebisacrylamide or glutaraldehyde. Crosslinking is assisted by ultraviolet radiation during gelation, with a radiation intensity of 20 mW / cm². 2 Time: 20 minutes.

[0081] In step four, the pre-freezing gradient of the green body needs to be controlled before vacuum freeze-drying:

[0082] First, the temperature is lowered to -10℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is lowered to below -30℃ at a rate of 2℃ / min, allowing ice crystals to grow uniformly and form directional channels.

[0083] In step five, the sintering process must be carried out under an inert atmosphere, with the inert gas being nitrogen or argon, and the gas flow rate being 1.25 L / min.

[0084] Microwave-assisted sintering was used in the later stage of sintering, with a microwave power of 8kW, a frequency of 2.45GHz, and an assisted sintering time of 30min.

[0085] In step two, two parts of reinforcing fiber are added during slurry preparation. The reinforcing fiber is at least one of carbon fiber, alumina fiber or calcium silicate fiber, with a fiber length of 125 μm and an aspect ratio of ≥20.

[0086] The reinforcing fibers need to undergo surface modification treatment first: the fibers are immersed in a silane coupling agent KH-550 and a 3.5% ethanol solution, ultrasonically treated at 60℃ for 45 minutes, and then dried before use.

[0087] A high-strength, lightweight, and environmentally friendly ceramic has a three-dimensional interconnected macroporous structure inside the ceramic body, with a pore size distribution range of 175μm and a porosity controlled at 60%.

[0088] The ceramic matrix is ​​composed of mullite crystalline phase, glassy phase and residual quartz phase, wherein the content of mullite crystalline phase is not less than 45 vol%, and the grain size is 1.25 μm;

[0089] The bulk density of ceramics is 1.25 g / cm³. 3 After polishing, the surface roughness Ra is less than 0.8μm.

[0090] An alumina wear-resistant coating was prepared on the ceramic surface by the sol-gel method, and the coating thickness was 20 μm.

[0091] The coating consists of a γ-alumina transition layer and an α-alumina surface layer, wherein the grain size of the surface layer is 300 nm.

[0092] The coating preparation method includes immersing sintered ceramic in a sol containing aluminum nitrate and aluminum isopropoxide, pulling it into a film at a speed of 3.5 mm / s, drying it at 90°C, and then heat-treating it at 700°C for 0.75 hours to form a dense coating.

[0093] Example 3: A method for preparing a high-strength, lightweight, and environmentally friendly ceramic, comprising the following steps:

[0094] Step 1: Raw material pretreatment. Industrial solid waste fly ash, waste ceramic crushed material and kaolin are selected as the main raw materials. The weight ratio is 60 parts fly ash, 30 parts waste ceramic crushed material and 15 parts kaolin. The materials are crushed and screened to a particle size ≤50μm, and then placed in a mixer to dry mix evenly.

[0095] Step 2: Slurry preparation. The pretreated raw materials are added to a water-based solvent, along with 1.5 parts of dispersant, 5 parts of binder, and 4 parts of foaming agent. The mixture is ball-milled at a stirring rate of 800 r / min for 4 hours to form a uniform and stable ceramic slurry.

[0096] Step 3: Gel injection molding. The slurry is injected into the mold and allowed to stand for 2 hours at a temperature of 80℃ and a relative humidity of 70% to gel, forming a preform with a three-dimensional network structure.

[0097] Step 4: Vacuum freeze drying. Place the green body in a vacuum freeze drying equipment and pre-freeze it at -50℃ for 6 hours. Then, sublime dry it under a vacuum degree ≤10Pa for 24 hours to obtain a porous ceramic preform.

[0098] Step 5: Segmented sintering. The preform is placed in a high-temperature sintering furnace. First, the temperature is increased to 800℃ at 5℃ / min and held for 1 hour for debinding. Then, the temperature is increased to 1350℃ at 8℃ / min and held for 3 hours for densification sintering. After cooling in the furnace, a high-strength, lightweight, and environmentally friendly ceramic product is obtained.

[0099] In step one, the fly ash needs to be acid-washed first:

[0100] Fly ash was soaked in a 15% hydrochloric acid solution with a liquid-to-solid ratio of 3:1, stirred and reacted at 80℃ for 3 hours, filtered, washed with water until neutral, dried, crushed and sieved.

[0101] Waste ceramic crushing material is building ceramics or daily-use ceramic waste. After being coarsely crushed by a jaw crusher, it is finely crushed by a planetary ball mill to a particle size of ≤30μm.

[0102] In step two:

[0103] The water-based solvent is deionized water, and the amount added is 120% of the total weight of the raw materials.

[0104] The dispersant is at least one of sodium polyacrylate or sodium hexametaphosphate;

[0105] The binder is polyvinyl alcohol or hydroxypropyl methylcellulose;

[0106] The foaming agent is either ammonium bicarbonate or hydrogen peroxide.

[0107] In step three, 0.3 parts of a crosslinking agent need to be added during gel casting. The crosslinking agent is either N,N'-methylenebisacrylamide or glutaraldehyde. Crosslinking is assisted by ultraviolet radiation during gelation, with a radiation intensity of 30 mW / cm². 2 Time: 30 minutes.

[0108] In step four, the pre-freezing gradient of the green body needs to be controlled before vacuum freeze-drying:

[0109] First, the temperature is lowered to -10℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is lowered to below -30℃ at a rate of 2℃ / min, allowing ice crystals to grow uniformly and form directional channels.

[0110] In step five, the sintering process must be carried out under an inert atmosphere, with the inert gas being nitrogen or argon, and the gas flow rate being 2L / min.

[0111] Microwave-assisted sintering was used in the later stage of sintering, with a microwave power of 10kW, a frequency of 2.45GHz, and an assisted sintering time of 40min.

[0112] In step two, during the preparation of the slurry, three parts of reinforcing fiber are added. The reinforcing fiber is at least one of carbon fiber, alumina fiber or calcium silicate fiber, with a fiber length of 200 μm and an aspect ratio of ≥20.

[0113] The reinforcing fibers need to undergo surface modification treatment first: the fibers are immersed in a silane coupling agent KH-550 and a 5% ethanol solution, ultrasonically treated at 60℃ for 60 minutes, and then dried before use.

[0114] A high-strength, lightweight, and environmentally friendly ceramic has a three-dimensional interconnected macroporous structure inside the ceramic body, with a pore size distribution range of 300 μm and a porosity controlled at 65%.

[0115] The ceramic matrix is ​​composed of mullite crystalline phase, glassy phase and residual quartz phase, wherein the content of mullite crystalline phase is not less than 45 vol%, and the grain size is 2 μm;

[0116] The bulk density of ceramics is 1.5 g / cm³. 3 After polishing, the surface roughness Ra is less than 0.8μm.

[0117] An alumina wear-resistant coating was prepared on the ceramic surface by the sol-gel method, and the coating thickness was 30 μm.

[0118] The coating consists of a γ-alumina transition layer and an α-alumina surface layer, wherein the grain size of the surface layer is 500 nm.

[0119] The coating preparation method includes immersing the sintered ceramic in a sol containing aluminum nitrate and aluminum isopropoxide, pulling it into a film at a speed of 5 mm / s, drying it at 100°C, and then heat-treating it at 800°C for 1 hour to form a dense coating.

[0120] Comparative Example 1: The difference between this comparative example and Example 1 is that no foaming agent was added when preparing the slurry in this comparative example.

[0121] Comparative Example 2 differs from Example 1 in that no reinforcing fibers were added during the preparation of the slurry in this comparative example.

[0122] Comparative Example 3 differs from Example 1 in that the fly ash in this comparative example was not acid-washed.

[0123] Comparative Example 4 differs from Example 1 in that microwave-assisted sintering was not used in this comparative example.

[0124] The high-strength, lightweight, and environmentally friendly ceramics prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and methods are as follows:

[0125] The bulk density was determined using Archimedes' method of displacement.

[0126] The compressive strength test was conducted using a universal testing machine with a cubic specimen measuring 20mm × 20mm × 20mm and a loading rate of 0.5mm / min.

[0127] Thermal conductivity was measured using a Hot Disk thermal constant analyzer at 25°C using a TPS 2500S probe.

[0128] For the water absorption test, the sample was dried to constant weight at 110℃ and then soaked in deionized water for 24 hours. After removing and wiping off the surface moisture, the sample was weighed and the percentage increase in mass was calculated.

[0129] The test data of the high-strength, lightweight, and environmentally friendly ceramics prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below:

[0130]

[0131] By comparing and analyzing the data in the table, it can be seen that the high-strength, lightweight, and environmentally friendly ceramics prepared using the processes in Examples 1-3 exhibit significantly superior performance compared to the ceramic materials prepared using the processes in Comparative Examples 1-4. This indicates that by using industrial solid waste as the main raw material and performing acid washing pretreatment, the purification and activity enhancement of the raw materials are ensured. Simultaneously, the dispersant and foaming agent in the slurry preparation process form a uniform and stable ceramic slurry, realizing the resource utilization of waste materials, reducing environmental impact, and improving product uniformity. During gel casting and vacuum freeze-drying, a three-dimensional network structure is formed with the assistance of crosslinking agents and ultraviolet radiation, combined with pre-freezing gradient control, enabling the real-time formation of directional channels within the green body. This ensures the controllability of the pore structure and avoids structural deformation during drying, improving the lightweight and heat insulation properties of the ceramic. During segmented sintering and the addition of reinforcing fibers, microwave-assisted sintering and fiber surface modification treatment promote the densification process of the ceramic matrix. The sintering process is optimized based on the formation of the mullite crystal phase, resulting in products with high strength and low water absorption, reducing the risk of performance fluctuations, and improving the durability and stability of the ceramic.

[0132] By comparing and analyzing the relevant data in the table, it can be seen that the high-strength, lightweight, and environmentally friendly ceramic prepared by the process of this invention has low bulk density, high compressive strength, excellent thermal insulation performance, and low water absorption. This indicates that the high-strength, lightweight, and environmentally friendly ceramic and its preparation method provided by this invention have a broader market prospect and are more suitable for widespread application.

[0133] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0134] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-strength, lightweight, and environmentally friendly ceramics, characterized in that: Includes the following steps: Step 1: Raw material pretreatment. Select industrial solid waste fly ash, waste ceramic crushed material and kaolin as the main raw materials. The weight ratio is 40-60 parts fly ash, 20-30 parts waste ceramic crushed material and 10-15 parts kaolin. Crush and screen until the particle size is ≤50μm, and then put them into a mixer to dry mix evenly. In step one, the fly ash needs to be acid-washed first: Fly ash is soaked in a 10%-15% hydrochloric acid solution with a liquid-to-solid ratio of 3:1, stirred and reacted at 60-80℃ for 2-3 hours, filtered, washed with water until neutral, dried, crushed and sieved. Step 2: Slurry preparation. Add the pretreated raw materials to a water-based solvent, and add 0.5-1.5 parts of dispersant, 3-5 parts of binder, and 2-4 parts of foaming agent. Ball mill and mix at a stirring rate of 400-800 r / min for 2-4 hours to form a uniform and stable ceramic slurry. In step two, 1-3 parts of reinforcing fiber are added during slurry preparation. The reinforcing fiber needs to undergo surface modification treatment first. The fiber is soaked in a 2%-5% ethanol solution containing silane coupling agent KH-550, ultrasonically treated at 60℃ for 30-60 minutes, and then dried before use. Step 3: Gel injection molding. The slurry is injected into the mold and allowed to stand for gelation for 1-2 hours at a temperature of 60-80℃ and a relative humidity of 50%-70% to form a preform with a three-dimensional network structure. Step 4: Vacuum freeze drying. Place the green body in a vacuum freeze drying equipment and pre-freeze it at -30℃ to -50℃ for 4-6 hours. Then, sublime dry it under a vacuum of ≤10Pa for 12-24 hours to obtain a porous ceramic preform. Step 5: Segmented sintering. The preform is placed in a high-temperature sintering furnace. First, the temperature is raised to 600-800℃ at 3-5℃ / min and held for 1 hour for debinding. Then, the temperature is raised to 1250-1350℃ at 5-8℃ / min and held for 2-3 hours for densification sintering. After cooling in the furnace, a high-strength, lightweight, and environmentally friendly ceramic product is obtained. Microwave-assisted sintering is used in the later stage of sintering, with a microwave power of 5-10kW, a frequency of 2.45GHz, and an assisted sintering time of 20-40min.

2. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: The waste ceramic crushed material is building ceramic or daily-use ceramic waste, which is coarsely crushed by a jaw crusher and then finely crushed by a planetary ball mill to a particle size ≤30μm.

3. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: In step two: The water-based solvent is deionized water, and the amount added is 80%-120% of the total weight of the raw materials; The dispersant is at least one of sodium polyacrylate or sodium hexametaphosphate; The adhesive is polyvinyl alcohol or hydroxypropyl methylcellulose; The foaming agent is either ammonium bicarbonate or hydrogen peroxide.

4. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: In step three, 0.1-0.3 parts of a crosslinking agent need to be added during gel injection molding. The crosslinking agent is one of N,N'-methylenebisacrylamide or glutaraldehyde. During the gelation process, crosslinking is assisted by ultraviolet radiation with an intensity of 10-30 mW / cm² and a time of 10-30 min.

5. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: In step four, the pre-freezing gradient of the green body needs to be controlled before vacuum freeze-drying: First, the temperature is lowered to -10℃ at a rate of 1℃ / min and held for 30 minutes. Then, the temperature is lowered to below -30℃ at a rate of 2℃ / min, allowing ice crystals to grow uniformly and form directional channels.

6. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: In step five, the sintering process must be carried out under an inert atmosphere, with the inert gas being nitrogen or argon, and the gas flow rate being 0.5-2 L / min.

7. The method for preparing a high-strength, lightweight, and environmentally friendly ceramic according to claim 1, characterized in that: The reinforcing fiber is at least one of carbon fiber, alumina fiber or calcium silicate fiber, with a fiber length of 50-200 μm and an aspect ratio of ≥20.

8. A high-strength, lightweight, and environmentally friendly ceramic, prepared using the method described in any one of claims 1-7, characterized in that: The ceramic body has a three-dimensional interconnected macroscopic pore structure with a pore size distribution range of 50-300μm and a porosity controlled between 55% and 65%. The ceramic matrix is ​​composed of mullite crystalline phase, glassy phase and residual quartz phase, wherein the content of mullite crystalline phase is not less than 45 vol%, and the grain size is 0.5-2 μm; The ceramic has a bulk density of 1.0-1.5 g / cm³, and its surface roughness Ra is less than 0.8 μm after polishing.

9. A high-strength, lightweight, and environmentally friendly ceramic according to claim 8, characterized in that: The ceramic surface is coated with an alumina wear-resistant coating by a sol-gel method, and the coating thickness is 10-30 μm. The coating consists of a γ-alumina transition layer and an α-alumina surface layer, wherein the grain size of the surface layer is 100-500 nm. The coating preparation method includes immersing sintered ceramic in a sol containing aluminum nitrate and aluminum isopropoxide, pulling it into a film at a speed of 2-5 mm / s, drying it at 80-100℃, and then heat-treating it at 600-800℃ for 0.5-1 hour to form a dense coating.

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