Preparation method of high-porosity ceramic with controllable aperture and structure

Abstract

The invention relates to a preparation method of high-porosity ceramic with controllable pore diameter and structure. The preparation method comprises the following steps: taking the following raw materials in percentage by mass: 85-95% of alpha-powder, 0.5-5% of carbon black, 3-6% of camphor, 0.5-2% of powder and 1-3% of MgO powder; mixing and pretreatment: spheroidizing the raw materials by taking absolute ethyl alcohol as a medium to obtain slurry, and drying and sieving the slurry to obtain composite ceramic powder; molding: performing dry pressing molding on the composite ceramic powder to obtain a green body; and rubber discharging and sintering are conducted, specifically, the green body is placed in a high-temperature sintering furnace, heat treatment is conducted under the air atmosphere, and the heat treatment is divided into four steps including the stepped rubber discharging stage, the pre-sintering stage, the final sintering stage and the cooling stage.

Description

Technical Field

[0001] This invention belongs to the field of ceramics, and particularly relates to a method for preparing high porosity ceramics with controllable pore size and structure. Background Technology

[0002] High porosity Ceramics are widely used in high-temperature filtration, catalyst supports, and lightweight structural materials due to their excellent chemical stability, high specific surface area, and good mechanical strength. Achieving high porosity, controllable pore structure, and excellent mechanical properties is the core objective in their preparation.

[0003] Currently, common methods for preparing porous ceramics include the addition of pore-forming agents, foaming, and impregnation with organic precursors. However, these methods generally suffer from the following technical bottlenecks: 1. The contradiction between porosity and strength: Traditional methods often severely sacrifice the mechanical strength of the material when achieving high porosity (>70%), limiting its application in pressure environments. 2. Poor controllability of pore structure: Wide pore size distribution, irregular shape, and uncontrollable connectivity make it difficult to meet the specific requirements of applications with precise separation, fluid dynamics, or cell growth. 3. Environmental friendliness and safety of the process: Some pore-forming agents (such as certain polymers) produce harmful fumes during thermal decomposition, or require complex atmosphere protection, increasing process costs and environmental burden. 4. Poor structural uniformity: Foaming methods easily produce closed pores and uneven pore structure, while processes such as slip casting are difficult to prepare components with complex shapes.

[0004] Therefore, developing a method for preparing porous ceramics that can simultaneously achieve high porosity, high strength, excellent controllability of pore structure, simple process and environmental friendliness has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high porosity ceramics with controllable pore size and structure.

[0006] A method for preparing high-porosity ceramics with controllable pore size and structure.

[0007] (1) Raw materials: including the following mass percentage of raw materials: 85~95wt% of α- Powder, 0.5~5 wt% carbon black, 3~6 wt% camphor, 0.5~2 wt% Powder, 1~3wt% MgO powder;

[0008] (2) Mixing and pretreatment: The raw materials in step (1) are mixed with anhydrous ethanol to obtain a slurry. The slurry is dried and sieved to obtain composite ceramic powder.

[0009] (3) Molding: The composite ceramic powder is dry-pressed to obtain a green body;

[0010] (4) Debinding and sintering: The green body is placed in a high-temperature sintering furnace and heat-treated in an air atmosphere. The heat treatment is divided into four steps: step debinding stage, pre-sintering stage, final sintering stage, and cooling stage.

[0011] Furthermore, the α- The powder has a particle size of 0.5~1.5μm, the carbon black has a particle size of 100~400nm, and the camphor has a particle size of 1~2μm. The particle size of the powder is ≤1.0μm, and the particle size of the MgO powder is ≤1.0μm.

[0012] Furthermore, the ball milling speed is 200~300 rpm, and the ball milling time is 6~12 hours; the temperature during slurry drying is 70~90℃, and the slurry is sieved through an 80~100 mesh sieve.

[0013] Furthermore, the dry pressing is carried out under a pressure of 50~100MPa and held for 1~3 minutes.

[0014] Furthermore, during the debinding and sintering process, the debinding stage involves a stepped debinding phase: heating from room temperature to 400-500℃ at a rate of 1-3℃ / min and holding for 60-120 minutes; a pre-sintering phase: continuing to heat at a rate of 3-5℃ / min to 1000-1150℃ and holding for 30-60 minutes; a final sintering phase: heating at a slow rate of 1-2℃ / min to the final sintering temperature of 1300-1400℃ and holding for 120-180 minutes; and a cooling phase: cooling to room temperature in the furnace to obtain the finished product. The stepped debinding process effectively removes camphor and carbon black, resulting in different pore sizes during this stage; the pre-sintering phase involves MgO and... Magnesium aluminum spinel begins to form ( ) first phase, Start solid solution The crystal lattice initially strengthens the green body; the slow heating process during the final sintering stage is crucial for controlling grain growth and pore structure stability, ultimately forming a structure composed of magnesium aluminum spinel and dissolved titanium. It is a high-strength porous network for bonding phases.

[0015] The beneficial effects of this invention are:

[0016] 1. In this invention, carbon black serves to form micron-sized main channels, regulate macroscopic pore size, and provide high specific surface area and nucleation sites. Camphor is a crystallizing additive; during the molding process, it not only acts as a temporary binder, but more importantly, its crystallinity guides the directional alignment of ceramic particles, forming a unique pore wall structure and significantly improving the strength of the green body. It is a sintering aid used to lower the sintering temperature, promote liquid-phase sintering, and densify the pore walls. MgO is a strength-enhancing additive that improves mechanical properties.

[0017] 2. This invention achieves controllable pore structure by combining carbon black (nanoscale) and camphor (micronscale) to design a dual-scale composite pore structure at the low-temperature decomposition stage. Micron-scale channels ensure high permeability, while nanoscale pores provide a high specific surface area. By adjusting the ratio and particle size of the two pore-forming agents, the pore size distribution and porosity of the material can be precisely controlled (adjustable within the range of 50%-85%). Therefore, through the synergistic pore-forming effect of carbon black and camphor, nano-carbon black provides numerous nucleation sites, ensuring the formation of fine, uniform micropores; camphor leaves pores with specific morphologies during sublimation, and its crystallization properties help improve the strength of the green body. The combination of these two elements achieves a multi-level pore structure design from the nanoscale to the microscale.

[0018] 3. In this invention, MgO and synergy, Traditionally used as a sintering aid to suppress Excessive grain growth results in a small amount of aluminum titanate, which acts as a self-healing material to repair cracks. Adding MgO to alumina leads to a reduction in grain size, thereby increasing strength. Spinel is formed through interfacial diffusion, and the spinel phase improves crack healing behavior. MgO and... It forms a spinel solid solution, which, together with magnesium aluminum spinel, constitutes a strong and tough ceramic bonding phase, greatly enhancing the mechanical properties of the pores. Therefore, MgO and... The synergistic effect enables ceramics to possess both high porosity and excellent mechanical properties.

[0019] 4. The present invention employs a stepwise sintering process: In the low-temperature stage, organic matter and pore-forming agents are removed to form a preliminary porous structure. In the medium- and high-temperature stages, grain growth and sintering densification are achieved, and the balance between porosity and strength is optimized by controlling the heating rate. The multi-stage sintering process, especially the slow heating in the final sintering stage, allows the pores to fully round under surface tension and release residual stress, while simultaneously suppressing the collapse and coarsening of the pore structure at high temperatures, resulting in a unique structure with high porosity and excellent strength. The porous ceramics prepared by the method of this invention can maintain a high porosity of 50-85% and controllable pore size and structure, while also exhibiting significantly higher compressive strength than traditional porous ceramics with similar porosity. ceramics. Attached Figure Description

[0020] Figure 1 This is a SEM image of the porous ceramic prepared in Example 1 of this invention;

[0021] Figure 2 This is a SEM image of the porous ceramic prepared in Example 2 of this invention;

[0022] Figure 3 This is a SEM image of the porous ceramic prepared in Example 3 of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments. The following description of the embodiments is only for the purpose of helping to understand the present invention.

[0024] Example 1: A method for preparing high-porosity ceramics with controllable pore size and structure.

[0025] (1) Raw materials: including the following mass percentage of raw materials: 855 wt% of α- Powder, 5 wt% carbon black, 6 wt% camphor, 2 wt% Powder, 2wt% MgO powder; α- The particle size of the powder is 0.5~1.5μm, the particle size of the carbon black is 100~400nm, and the particle size of the camphor is 1~2μm. The particle size of the powder is ≤1.0μm, and the particle size of the MgO powder is ≤1.0μm;

[0026] (2) Mixing and pretreatment: The raw materials in step (1) are ball-milled with anhydrous ethanol as the medium to obtain a slurry. The slurry is dried and sieved to obtain composite ceramic powder. The ball milling speed is 200 rpm and the ball milling time is 6 hours. The temperature of the slurry drying is 70℃ and it is sieved through an 80-mesh sieve.

[0027] (3) Molding: The composite ceramic powder is dry-pressed to obtain a green body; the dry pressing is carried out under a pressure of 50MPa and held for 1 minute.

[0028] (4) Debinding and sintering: The green body is placed in a high-temperature sintering furnace and heat-treated in an air atmosphere. The heat treatment is divided into four steps: step debinding stage, pre-sintering stage, final sintering stage, and cooling stage. During debinding and sintering, the step debinding stage is as follows: the temperature is increased from room temperature to 400℃ at a rate of 1℃ / min and held for 60 minutes; the pre-sintering stage is as follows: the temperature is increased to 1000℃ at a rate of 3℃ / min and held for 30 minutes; the final sintering stage is as follows: the temperature is increased to the final sintering temperature of 1300℃ at a slow rate of 1℃ / min and held for 120 minutes; the cooling stage is as follows: the body is cooled to room temperature in the furnace to obtain the finished product.

[0029] Example 2: A method for preparing high-porosity ceramics with controllable pore size and structure.

[0030] (1) Raw materials: including the following mass percentage of raw materials: 95wt% of α- Powder, 0.5 wt% carbon black, 3 wt% camphor, 0.5 wt% Powder, 1wt% MgO powder; α- The powder has a particle size of 0.5~1.5μm, the carbon black has a particle size of 100~400nm, and the camphor has a particle size of 1~2μm. The particle size of the powder is ≤1.0μm, and the particle size of the MgO powder is ≤1.0μm;

[0031] (2) Mixing and pretreatment: The raw materials in step (1) are ball-milled with anhydrous ethanol as the medium to obtain a slurry. The slurry is dried and sieved to obtain composite ceramic powder. The ball milling speed is 250 rpm and the ball milling time is 9 hours. The temperature of the slurry drying is 80℃ and it is sieved through a 90-mesh sieve.

[0032] (3) Molding: The composite ceramic powder is dry-pressed to obtain a green body; the dry pressing is carried out under a pressure of 70MPa and held for 2 minutes.

[0033] (4) Debinding and sintering: The green body is placed in a high-temperature sintering furnace and heat-treated in an air atmosphere. The heat treatment is divided into four steps: step debinding stage, pre-sintering stage, final sintering stage, and cooling stage. During debinding and sintering, the step debinding stage is as follows: the temperature is increased from room temperature to 450℃ at a rate of 2℃ / min and held for 90 minutes; the pre-sintering stage is as follows: the temperature is increased to 1100℃ at a rate of 4℃ / min and held for 40 minutes; the final sintering stage is as follows: the temperature is increased to the final sintering temperature of 1350℃ at a slow rate of 1.5℃ / min and held for 150 minutes; the cooling stage is as follows: the green body is cooled to room temperature in the furnace to obtain the finished product.

[0034] Example 3: A method for preparing high-porosity ceramics with controllable pore size and structure.

[0035] (1) Raw materials: including the following mass percentages of raw materials: 89 wt% of α- Powder, 3 wt% carbon black, 4 wt% camphor, 1 wt% Powder, 3wt% MgO powder; α- The powder has a particle size of 0.5~1.5μm, the carbon black has a particle size of 100~400nm, and the camphor has a particle size of 1~2μm. The particle size of the powder is ≤1.0μm, and the particle size of the MgO powder is ≤1.0μm;

[0036] (2) Mixing and pretreatment: The raw materials in step (1) are ball-milled with anhydrous ethanol as the medium to obtain a slurry. The slurry is dried and sieved to obtain composite ceramic powder. The ball milling speed is 300 rpm and the ball milling time is 12 hours. The temperature of the slurry drying is 90℃ and it is sieved through a 100-mesh sieve.

[0037] (3) Molding: The composite ceramic powder is dry-pressed to obtain a green body; the dry pressing is carried out under a pressure of 100MPa and held for 3 minutes.

[0038] (4) Debinding and sintering: The green body is placed in a high-temperature sintering furnace and heat-treated in an air atmosphere. The heat treatment is divided into four steps: step debinding stage, pre-sintering stage, final sintering stage, and cooling stage. During debinding and sintering, the step debinding stage is as follows: the temperature is increased from room temperature to 500℃ at a rate of 3℃ / min and held for 120 minutes; the pre-sintering stage is as follows: the temperature is increased to 1150℃ at a rate of 5℃ / min and held for 60 minutes; the final sintering stage is as follows: the temperature is increased to the final sintering temperature of 1400℃ at a slow rate of 2℃ / min and held for 180 minutes; the cooling stage is as follows: the green body is cooled to room temperature in the furnace to obtain the finished product.

[0039] It should be noted that those skilled in the art can make various modifications to this invention without departing from its principles, and these modifications and improvements also fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing high-porosity ceramics with controllable pore size and structure, characterized in that, (1) Obtaining raw materials: Raw materials including the following mass percentages: 85~95wt% α- Powder, 0.5~5 wt% carbon black, 3~6 wt% camphor, 0.5~2 wt% Powder, 1~3wt% MgO powder; (2) Mixing and pretreatment: The raw materials in step (1) are mixed with anhydrous ethanol to obtain a slurry. The slurry is dried and sieved to obtain composite ceramic powder. (3) Molding: The composite ceramic powder is dry-pressed to obtain a green body; (4) Debinding and sintering: The green body is placed in a high-temperature sintering furnace and heat-treated in an air atmosphere. The heat treatment is divided into four steps: step debinding stage, pre-sintering stage, final sintering stage, and cooling stage.

2. The method for preparing high-porosity ceramics with controllable pore size and structure according to claim 1, characterized in that, The α- The particle size of the powder is 0.5~1.5μm, the particle size of the carbon black is 100~400nm, the particle size of the camphor is 1~2μm, the particle size of the TiO2 powder is ≤1.0μm, and the particle size of the MgO powder is ≤1.0μm.

3. The method for preparing high-porosity ceramics with controllable pore size and structure according to claim 1, characterized in that, The ball milling speed is 200~300 rpm, and the ball milling time is 6~12 hours; the temperature for drying the slurry is 70~90℃, and the slurry is sieved through an 80~100 mesh sieve.

4. The method for preparing high-porosity ceramics with controllable pore size and structure according to claim 1, characterized in that, The dry pressing process is carried out under a pressure of 50~100MPa and held for 1~3 minutes.

5. The method for preparing high-porosity ceramics with controllable pore size and structure according to claim 1, characterized in that, During the debinding and sintering process, the debinding stage involves a stepped debinding stage: heating from room temperature to 400-500℃ at a rate of 1-3℃ / min and holding for 60-120 minutes; the pre-sintering stage involves continuing to heat at a rate of 3-5℃ / min to 1000-1150℃ and holding for 30-60 minutes; the final sintering stage involves heating at a slow rate of 1-2℃ / min to the final sintering temperature of 1300-1400℃ and holding for 120-180 minutes; and the cooling stage involves cooling the product to room temperature in the furnace to obtain the finished product.

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