Low-temperature open-pore porous ceramic and preparation method thereof

Abstract

The invention discloses a preparation method of low-temperature open-pore porous ceramic. The method comprises the following steps: taking one of tailings, metallurgical slag or natural clay minerals as a framework material, taking water-soluble chlorine salt powder as a pore forming agent, and taking waste glass powder as a structural stabilizer; mixing the three components according to a set proportion, carrying out compression molding, and sintering at a temperature lower than 1000 DEG C to obtain a compact ceramic body; and immersing the porous ceramic into water to dissolve out chlorine salt, and drying to obtain the open-pore porous ceramic. According to the preparation method, the solution from which the chlorine salt is dissolved out is evaporated and crystallized, so that the pore-forming agent can be recycled, and recycling is realized. The porous ceramic with a stable structure is prepared at a low temperature, the process is simple, energy is saved, consumption is reduced, the pore-forming agent can be recycled, and the method has the advantages of being environmentally friendly and low in cost.

Description

Technical Field

[0001] This invention relates to the field of ceramic material preparation technology, and in particular to a low-temperature open-pore porous ceramic and its preparation method. Background Technology

[0002] Porous ceramics, with their tunable pore structure (including porosity, pore size distribution, and pore morphology) and excellent physicochemical properties, are widely used in filtration and separation, catalyst supports, thermal insulation materials, biomedical materials, sound absorption and damping materials, sensitive components, and energy fields. The performance of porous ceramics is highly dependent on their microstructure, which is determined by the preparation technique. Among the various preparation methods, the pore-forming agent method is considered one of the most widely used and fundamental methods for preparing porous ceramics.

[0003] Among the many methods for preparing porous ceramics, the method of adding pore-forming agents is widely used because of its simple process and good controllability of pore structure. However, the existing pore-forming agent technology has the following prominent defects: (1) High sintering temperature: In order to achieve the densification of ceramic particles, the sintering temperature of traditional porous ceramics is generally above 1200℃, which consumes a lot of energy and has high cost; (2) Pore-forming agents are not recyclable: Whether it is organic pore-forming agents removed by combustion or inorganic pore-forming agents removed by thermal decomposition, organic pore-forming agents disappear after combustion and are consumed in the process, which cannot be recycled and causes waste of resources; (3) The decomposition of pore-forming agents during sintering may cause cracking of the green body or collapse of the pore wall, affecting the mechanical properties and pore uniformity of the final product. In addition, some studies using inorganic salts (such as NaCl) as pore-forming agents still have the process of removing the pore-forming agent first and then sintering at high temperature (>1000℃), which causes the pre-formed pores to close or deform in the subsequent high-temperature process, making it difficult to obtain an ideal open pore structure. Therefore, developing a method for preparing porous ceramics that involves low-temperature sintering, recyclable pore-forming agents, and a reasonable process sequence has significant industrial application value and environmental significance. Summary of the Invention

[0004] This application provides a low-temperature open-pore porous ceramic and its preparation method. The method uses waste glass powder as a low-temperature structural stabilizer and innovatively implements the process of "first low-temperature sintering for densification, and then water leaching to dissolve the pore-forming agent". It successfully achieves low-temperature sintering below 1000℃ and achieves the full recovery and recycling of chloride pore-forming agent. It solves the problems of high energy consumption, high cost and difficulty in controlling pore structure in traditional methods.

[0005] This application provides a method for preparing low-temperature open-pore porous ceramics, characterized by the following steps:

[0006] Step 1: Preparation of raw materials

[0007] Prepare a framework material, a pore-forming agent, and a structural stabilizer, wherein the framework material is one of tailings, metallurgical slag, or natural clay minerals, the pore-forming agent is a water-soluble chloride salt, and the structural stabilizer is waste glass powder.

[0008] Step 2: Preparation of porous ceramics

[0009] The skeleton material, pore-forming agent and structural stabilizer are mixed evenly in a set ratio and pressed into a ceramic body. The ceramic body is then sintered at a temperature below 1000°C and cooled to obtain a dense ceramic body containing chloride salts. The dense ceramic body is immersed in water and left to stand. After drying, a porous ceramic with an open-pore structure can be obtained.

[0010] The chloride salt solution obtained from dissolution can be recovered by evaporation and crystallization to obtain chloride salt pore-forming agent with sufficient purity.

[0011] Preferably, the mass ratio of the skeleton material, the pore-forming agent, and the structural stabilizer is 75~65:25~30:5.

[0012] Preferably, the sintering temperature in step two is 850℃~980℃, and the sintering time is 1.5~2h.

[0013] Preferably, the tailings are selected from iron tailings or copper tailings; the metallurgical slag is selected from steel slag, blast furnace slag or red mud; and the natural clay minerals are selected from bentonite, kaolin or diatomite.

[0014] Preferably, the chloride salt is NaCl or KCl.

[0015] Preferably, the chloride salt is NaCl.

[0016] Preferably, the skeleton material and the pore-forming agent both need to pass through a 200-mesh sieve, and the structural stabilizer needs to pass through a 300-mesh sieve.

[0017] The present invention also provides a porous ceramic prepared by any of the above preparation methods, wherein the porous ceramic has an apparent porosity of 45% to 70% and a compressive strength of 10 MPa to 60 MPa.

[0018] One technical solution provided in this application embodiment has at least the following technical effects:

[0019] 1. This invention introduces waste glass powder as a low-temperature structural stabilizer, which can form a liquid phase at temperatures below 1000℃ to promote the rearrangement and densification of ceramic particles, significantly reducing the sintering temperature, saving energy costs, and effectively reducing energy consumption.

[0020] 2. This invention uses water-soluble chloride salt as a pore-forming agent. After sintering, it is completely dissolved by water immersion. The solution can be recycled to high-purity chloride salt after evaporation and crystallization, realizing the multiple recycling of the pore-forming agent and reducing raw material costs and environmental burden.

[0021] 3. The present invention first sintersects to form a dense green body, and then impregnates it with water to create pores. This avoids the structural damage caused by the decomposition of the pore-forming agent in the traditional process, and finally obtains open-pore ceramics with uniform pore distribution, intact pore walls and good mechanical properties.

[0022] 4. The preparation method of the present invention is applicable to a variety of inexpensive mineral raw materials such as tailings, metallurgical slag or natural clay minerals. The process is simple, easy to scale up, and has high economic efficiency and promotion value. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the preparation process and principle of an embodiment of this application. Detailed Implementation

[0024] The overall concept of this invention is to introduce waste glass powder as a low-temperature structural stabilizer, utilizing its formation of a water-insoluble silicate liquid phase during sintering to achieve effective densification of the ceramic framework at low temperatures (<1000℃). Based on this, water-soluble inorganic salts are used as pore-forming agents, employing a process sequence of "first sintering for densification, then water leaching for dissolution." This ensures the structural strength of the green body during the sintering stage while allowing for complete removal of the pore-forming agent during subsequent water treatment, forming interconnected open pores and enabling the recycling and reuse of the pore-forming agent. This invention integrates the advantages of low-temperature sintering, pore-forming agent recycling, and structural control, providing a new approach for low-cost, green, and sustainable porous ceramic preparation.

[0025] To better understand the above technical solution, the specific implementation methods will be described in detail below.

[0026] The following examples are intended to illustrate specific implementations of the present invention, but should not be construed as limiting the scope of protection of the present invention. The skeleton material, chloride salt type, and process parameters described in this invention can all be adjusted according to actual needs, and the properties of the resulting porous ceramics fluctuate within a certain range.

[0027] Example 1

[0028] (1) Preparation of raw materials

[0029] Iron tailings powder is used as the skeleton material, serving as the matrix for porous ceramics; NaCl powder is used as a pore-forming agent; and waste glass powder is used as a structural stabilizer to promote the low-temperature sintering and densification process of the porous ceramics. The skeleton materials, iron tailings powder and NaCl powder, must pass through a 200-mesh sieve, while the waste glass powder must pass through a 300-mesh sieve.

[0030] (2) Preparation of porous ceramics

[0031] The iron tailings powder, NaCl powder and waste glass powder from step (1) are mixed evenly in a mixer at a mass ratio of 70:25:5 to obtain a mixture. The mixture is loaded into a mold and pressed into a green body under a pressure of 20 MPa. The green body is placed in a muffle furnace and heated to 950℃ at a rate of 5℃ / min, held for 2 h, and cooled with the furnace to obtain a dense ceramic green body containing NaCl. The sintered green body is immersed in deionized water and left to stand for 24 h to allow the NaCl to dissolve completely. The sample is taken out and dried in an oven at 80℃ for 12 h to obtain a porous ceramic with open pores.

[0032] In this embodiment, the iron tailings-based open-pore porous ceramic is cylindrical. The performance of the iron tailings-based open-pore porous ceramic was tested, and the test results are shown in Table 1 and Table 2.

[0033] Example 2

[0034] (1) Preparation of raw materials

[0035] Bentonite powder was used as the skeleton material, serving as the matrix for porous ceramics; NaCl powder was used as a pore-forming agent; and waste glass powder was used as a structural stabilizer to promote the low-temperature sintering and densification process of the porous ceramics. The skeleton materials, bentonite powder and NaCl powder, both needed to pass through a 200-mesh sieve, while the waste glass powder needed to pass through a 300-mesh sieve.

[0036] (2) Preparation of porous ceramics

[0037] The bentonite powder, NaCl powder and waste glass powder from step (1) are mixed evenly in a mixer at a mass ratio of 65:30:5 to obtain a mixture. The mixture is loaded into a mold and pressed into a green body under a pressure of 20 MPa. The green body is placed in a muffle furnace and heated to 980℃ at a rate of 5℃ / min, held for 2 h, and cooled with the furnace to obtain a dense ceramic green body containing NaCl. The sintered green body is immersed in deionized water and left to stand for 24 h to allow the NaCl to dissolve completely. The sample is taken out and dried in an oven at 80℃ for 12 h to obtain a porous ceramic with open pores.

[0038] In this embodiment, the bentonite-based open-pore porous ceramic is cylindrical. The performance of the bentonite-based open-pore porous ceramic was tested, and the test results are shown in Table 1 and Table 2.

[0039] Example 3

[0040] (1) Preparation of raw materials

[0041] Kaolin powder was used as the framework material, serving as the matrix for porous ceramics; NaCl powder was used as a pore-forming agent; and waste glass powder was used as a structural stabilizer to promote the low-temperature sintering and densification process of the porous ceramics. The kaolin powder and NaCl powder, both framework materials, needed to pass through a 200-mesh sieve, while the waste glass powder needed to pass through a 300-mesh sieve.

[0042] (2) Preparation of porous ceramics

[0043] The kaolin powder, NaCl powder and waste glass powder from step (1) are mixed evenly in a mixer at a mass ratio of 70:25:5 to obtain a mixture. The mixture is loaded into a mold and pressed into a green body under a pressure of 20 MPa. The green body is placed in a muffle furnace and heated to 960℃ at a rate of 5℃ / min, held for 2 h, and cooled with the furnace to obtain a dense ceramic green body containing NaCl. The sintered green body is immersed in deionized water and left to stand for 24 h to allow the NaCl to dissolve completely. The sample is taken out and dried in an oven at 80℃ for 12 h to obtain a porous ceramic with open pores.

[0044] In this embodiment, the kaolin-based open-pore porous ceramic is cylindrical. The performance of the kaolin-based open-pore porous ceramic was tested, and the test results are shown in Table 1 and Table 2.

[0045] Table 1. Apparent porosity of samples from Examples 1-3

[0046] Material Sample 1 / % Sample 2 / % Iron tailings 53.75 55 Bentonite 61.97 52.94 Kaolin 59.03 52.17

[0047] Table 2 Compressive strength of samples from Examples 1-3

[0048] raw material Compressive strength / MPa Iron tailings 27 Bentonite 44 Kaolin 16

[0049] In Examples 1-3, the solution after leaching NaCl in water can be used to recover NaCl powder after evaporation, crystallization, and drying. Its purity meets the requirements for reuse as a pore-forming agent, thus realizing the recycling of the pore-forming agent.

[0050] In Examples 1-3, NaCl can be replaced with other water-soluble chloride salts such as KCl.

[0051] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing low-temperature open-pore porous ceramics, characterized in that, Includes the following steps: Step 1: Preparation of raw materials Prepare a framework material, a pore-forming agent, and a structural stabilizer, wherein the framework material is one of tailings, metallurgical slag, or natural clay minerals, the pore-forming agent is a water-soluble chloride salt, and the structural stabilizer is waste glass powder. Step 2: Preparation of porous ceramics The skeleton material, pore-forming agent and structural stabilizer are mixed evenly in a set ratio and pressed into a ceramic body. The ceramic body is then sintered at a temperature below 1000°C and cooled to obtain a dense ceramic body containing chloride salts. The dense ceramic body is immersed in water and left to stand. After drying, a porous ceramic with an open-pore structure can be obtained. The chloride salt solution obtained from dissolution can be recovered by evaporation and crystallization to obtain chloride salt pore-forming agent with sufficient purity.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the skeleton material, the pore-forming agent, and the structural stabilizer is 75~65:25~30:

5.

3. The preparation method according to claim 1, characterized in that, The sintering temperature in step two is 850℃~980℃, and the sintering time is 1.5~2h.

4. The preparation method according to claim 1, characterized in that, The tailings are selected from iron tailings or copper tailings; the metallurgical slag is selected from steel slag, blast furnace slag or red mud; the natural clay minerals are selected from bentonite, kaolin or diatomite.

5. The preparation method according to claim 1, characterized in that, The chloride salt is NaCl or KCl.

6. The preparation method according to claim 5, characterized in that, The chloride salt is NaCl.

7. The preparation method according to claim 1, characterized in that, The skeleton material and the pore-forming agent must pass through a 200-mesh sieve, and the structural stabilizer must pass through a 300-mesh sieve.

8. A low-temperature open-pore porous ceramic, prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The porous ceramic has a porosity of 45% to 70% and a compressive strength of 10 MPa to 60 MPa.

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