High-temperature-resistant and low-pressure-drop-resistant ceramic filtering material as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant and low-pressure-drop-resistant ceramic filtering material as well as a preparation method and application thereof, and belongs to the field of preparation of ceramic filtering materials. According to the scheme, ultra-light silicon nitride nanowire foam serves as a base body, silicon carbide is deposited in situ through CVI, on one hand, the nanowire foam can be strengthened through bonding nodes formed between nanowires, on the other hand, hole diameters distributed in a gradient mode can be formed inside and outside the foam, and in other words, the hole diameter sizes are gradually reduced from the core portion of the foam to the outer surface of the foam; secondly, the ultralight silicon nitride nanowire foam subjected to chemical vapor infiltration strengthening treatment is cut in the thickness direction, the thickness of a sample can be effectively reduced, and finally the porous ceramic material with high strength, high porosity and low pressure drop characteristics is prepared. The bottleneck that porosity and strength of traditional honeycomb ceramics are difficult to synergistically improve is broken through, and the honeycomb ceramic has good application prospects in the fields of high-temperature tail gas filtration, diesel engine carbon particle filter materials, metal liquid impurity filtration and the like.

Description

Technical Field

[0001] This invention belongs to the field of ceramic filter material preparation technology, specifically relating to a high-temperature resistant, low-pressure-drop ceramic filter material, its preparation method, and its application. Background Technology

[0002] Existing high-temperature filtration materials mainly include honeycomb ceramics, ceramic fiber felts, metal wire mesh, and ceramic foams. While they can meet basic dust removal and purification needs to a certain extent, they still have many shortcomings. For example, their temperature resistance is poor, and they are generally unable to operate stably for extended periods above 1000 ℃. Some glass fiber and low-end ceramic materials are prone to strength reduction or structural deformation at high temperatures. Meanwhile, traditional honeycomb ceramics and dense fiber felts often generate high pressure drops while maintaining filtration efficiency, increasing fan energy consumption and system operating costs. Most ceramic matrices are relatively heavy, leading to increased equipment weight and maintenance inconvenience. Furthermore, once a honeycomb or woven structure is formed, its pore size distribution is difficult to adjust, lacking flexible geometric design methods. In high-value-added applications such as molten metal purification or high-temperature metal powder filtration, currently common alumina ceramic foams and silicon carbide filter sheets are prone to breakage or clogging under metal corrosion and thermal shock, affecting product quality and continuous production.

[0003] Therefore, with the urgent needs of industries such as metallurgy, chemical industry, aerospace, automotive exhaust purification, and metal additive manufacturing for energy conservation and emission reduction, high temperature stability, lightweighting, and flexible design, existing ceramic filter materials are no longer able to meet the comprehensive performance indicators of long-term high temperature resistance, low pressure drop, high porosity, and high strength. Therefore, a new type of filter material is urgently needed to solve these problems. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-temperature resistant and low-pressure-drop ceramic filter material and its preparation method, so as to solve the technical problem that existing ceramic filter materials cannot simultaneously possess the properties of long-term high temperature resistance, low pressure drop, high porosity, and high strength.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material, comprising the following steps: 1) Using ultralight silicon nitride nanowire foam as a matrix, silicon carbide is deposited on the nanowire surface of ultralight silicon nitride nanowire foam by chemical vapor infiltration. 2) Cut the ultralight silicon nitride nanowire foam along the thickness direction after chemical vapor infiltration strengthening treatment; 3) Grind, clean, and dry the cut products to obtain samples; 4) The sample was subjected to high-temperature heat preservation treatment and then cooled to obtain a high-temperature resistant and low-pressure-drop ceramic filter material.

[0006] Preferably, the ultralight silicon nitride nanowire foam is composed of silicon nitride nanowires with a diameter of 30-150 nm, or a porous three-dimensional network structure composed of several silicon nitride nanowires with a diameter of 30-150 nm, and the density of the ultralight silicon nitride nanowire foam is 1-5 mg / cm³. 3 .

[0007] Preferably, in step 1), the precursor used for chemical vapor infiltration deposition of silicon carbide is methyltrichlorosilane, the deposition pressure is 800-4000 Pa, the deposition temperature is 900-1200 ℃, and the deposition time is 3-20 h.

[0008] Preferably, in step 2), mechanical cutting is used to cut the pore size of the ultralight silicon nitride nanowire foam from a gradient distribution of "small-large-small" along the thickness direction to a gradient distribution of "large-small" or "small-large".

[0009] Preferably, in step 3), the polishing involves polishing the cut product sequentially with 800-grit, 1000-grit, and 2000-grit sandpaper; the cleaning is performed using ultrasonic cleaning, with 2-5 cleaning cycles, each lasting 10 minutes; and the drying is carried out at 80-100 ℃ for 1-6 hours.

[0010] Preferably, in step 4), the sample is subjected to high-temperature heat treatment at 1000-1200 ℃ for 0.5-4 h. After the heat treatment is completed, the temperature is reduced to 500 ℃ or below to obtain the target product.

[0011] This invention also discloses a high-temperature resistant, low-pressure-drop ceramic filter material prepared using the above-described method, wherein the bulk density of the high-temperature resistant, low-pressure-drop ceramic filter material is 50-900 mg / cm³. 3 The porosity is 72%-93%, and the average pore size is 5-25 μm.

[0012] Preferably, the compressive strength of the high-temperature resistant, low-pressure-drop ceramic filter material is 2-30 MPa, and the maximum stable operating temperature is 1000°C. o C, pressure drop below 5 kPa.

[0013] Preferably, the high-temperature resistant and low-pressure-drop ceramic filter material is suitable for use at 950°C. o It does not fracture after 500 thermal shocks at temperature C.

[0014] This invention also discloses the application of the above-mentioned high-temperature and low-pressure-drop ceramic filter material in high-temperature exhaust gas filtration, diesel engine carbon particle filtration, and metal liquid impurity filtration.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The method for preparing high-temperature resistant and low-pressure-drop ceramic filter material disclosed in this invention involves first depositing silicon carbide (SiC) in situ using ultralight silicon nitride nanowire foam as a matrix via chemical vapor infiltration (CVI). CVI can strengthen the nanowire foam by forming bonding nodes between the nanowires and can also create a gradient distribution of pore sizes inside and outside the foam, i.e., the pore size gradually decreases from the foam core to the outer surface. Secondly, the ultralight silicon nitride nanowire foam after chemical vapor infiltration strengthening is cut along the thickness direction, which can effectively reduce the thickness of the sample, and finally prepare a porous ceramic material with high strength, high porosity and low pressure drop characteristics.

[0016] Preferably, the silicon nitride nanowire foam matrix reinforced by chemical vapor infiltration (CVI) silicon carbide deposition is mechanically cut, considering that the original pore size of the matrix exhibits a symmetrical gradient distribution of "small-large-small" along the thickness direction. Mechanical cutting removes the small-pore segments on one side of the matrix through physical trimming, retaining only the asymmetrical structure of the large-pore-small pore segment, thereby adjusting the original symmetrical gradient of "small-large-small" to a unidirectional gradient distribution of "large-small" or "small-large". This unidirectional gradient change allows the fluid to pass through only one dense layer with small pores, significantly shortening the resistance path. From an application perspective, the "large-small" gradient can be used for forward filtration from coarse to fine filtration, where the large-pore end first traps large particles of impurities, and the small-pore end achieves fine filtration; while the "small-large" gradient can be used in backflushing regeneration scenarios, where the backflushing airflow enters from the small-pore end and diffuses rapidly at the large-pore end, making it easier to remove trapped impurities.

[0017] The high-temperature resistant and low-pressure-drop ceramic filter material prepared by the above method of the present invention also has low density (50-1000 mg / cm³). 3 High porosity (72%-90%), high mechanical strength (compressive strength 2-30 MPa), low pressure drop (below 5 kPa), excellent temperature resistance and thermal shock resistance (950 kPa). o (It can withstand 500 thermal shocks without cracking), breaking through the bottleneck of traditional honeycomb ceramics where porosity and strength are difficult to improve in a coordinated manner. It has good application prospects in high-temperature exhaust gas filtration, diesel engine carbon particle filtration materials, and metal liquid impurity filtration. Attached Figure Description

[0018] Figure 1 SEM images of ultralight silicon nitride nanowire foam; where (a) represents 1 mg / cm³. 3 (b) has a density of 5 mg / cm³. 3 ; Figure 2 Density 200 mg / cm³ 3SEM images of the gradient structure of the high-temperature and low-pressure-drop ceramic filter material; where (a) is the surface and (b) is the core. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. 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 should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings: Example 1 In this embodiment, a sample with a density of 100 mg / cm³ was prepared. 3 The specific steps for using low-pressure-drop ceramic filter materials are as follows: The material prepared using the method disclosed in Chinese Invention Patent No. CN109553395B has a density of 1 mg / cm³. 3 Silicon nitride nanowire foam is used as a raw material; see [link / reference]. Figure 1In step (a), the sample was placed in a CVI deposition furnace, and hydrogen and argon were introduced into the furnace at a temperature of 1000 °C. The hydrogen gas flow rate was 6 L / min, and the argon gas flow rate was 6 L / min. The flow rate of methyltrichlorosilane was maintained at 0.8 L / min, the deposition pressure was controlled at approximately 900 Pa, and the deposition time was 3 h. After deposition and cooling to room temperature, the sample was removed and cut along the thickness direction using a diamond wire cutter to thin the sample. Then, it was successively polished with 800-grit, 1000-grit, and 2000-grit sandpaper, and then ultrasonically cleaned three times in an ultrasonic vibrator, each time for 10 minutes. After cleaning, it was dried in a 100 °C oven for 1 hour. Finally, the sample was placed in a 1000 °C muffle furnace for high-temperature holding for 0.5 hours, and removed when the temperature dropped to 500 °C or below. The density of the sample was measured to be 100 mg / cm³. 3 The surface layer has an average pore size of 20 μm, the core has an average pore size of 22 μm, a porosity of 92%, and a compressive strength of 2 MPa. The microstructure of its surface and core is as follows: Figure 2 As shown, the nanowires on the surface are thicker than those in the core, exhibiting a gradient structure with decreasing wire diameter and increasing pore size from the surface inwards.

[0022] Example 2 In this embodiment, a sample with a density of 300 mg / cm³ was prepared. 3 The specific steps for using low-pressure-drop ceramic filter materials are as follows: The material prepared using the method disclosed in Chinese Invention Patent No. CN109553395B has a density of 2 mg / cm³. 3 Silicon nitride nanowire foam is used as a raw material; see [link / reference]. Figure 1In step (b), the sample was placed in a CVI deposition furnace, and hydrogen and argon were introduced into the furnace at a temperature of 1000 °C. The hydrogen gas flow rate was 4 L / min, and the argon gas flow rate was 4 L / min. The flow rate of methyltrichlorosilane was maintained at 1 L / min, the deposition pressure was controlled at approximately 2200 Pa, and the deposition time was 2 h. After deposition was completed and cooled to room temperature, the sample was removed and cut along the thickness direction using a diamond wire cutter to thin the sample. Then, it was polished sequentially with 800-grit, 1000-grit, and 2000-grit sandpaper, and then ultrasonically cleaned three times in an ultrasonic vibrator for 10 minutes each time. After cleaning, it was dried in a 100 °C oven for 3 hours. Finally, the sample was placed in a muffle furnace at 1100 °C for high-temperature holding for 4 hours. The sample was removed when the temperature dropped to 500 °C or below. The sample was tested and found to have a density of 300 mg / cm3, an average surface pore size of 18 μm, an average core pore size of 22 μm, a porosity of 89%, and a compressive strength of 5.8 MPa.

[0023] Example 3 In this embodiment, a sample with a density of 500 mg / cm³ was prepared. 3 The specific steps for using low-pressure-drop ceramic filter materials are as follows: The material prepared using the method disclosed in Chinese Invention Patent No. CN109553395B has a density of 5 mg / cm³. 3 Silicon nitride nanowire foam is used as a raw material; see [link / reference]. Figure 1 In step (b), the sample was placed in a CVI deposition furnace, and hydrogen and argon were introduced into the furnace at a temperature of 1000 °C. The hydrogen gas flow rate was 6 L / min, and the argon gas flow rate was 6 L / min. The flow rate of methyltrichlorosilane was maintained at 1 L / min, the deposition pressure was controlled at approximately 2000 Pa, and the deposition time was 3 h. After deposition and cooling to room temperature, the sample was removed and cut along the thickness direction using a diamond wire cutter to thin the sample. Then, it was polished sequentially with 800-grit, 1000-grit, and 2000-grit sandpaper, and then ultrasonically cleaned three times in an ultrasonic vibrator, each time for 10 minutes. After cleaning, it was dried in a 100 °C oven for 3 hours. Finally, the sample was placed in a muffle furnace at 1100 °C for high-temperature holding for 4 hours. The sample was removed when the temperature dropped to 500 °C or below. The density of the sample was measured to be 500 mg / cm³. 3 The surface average pore size is 12 μm, the core average pore size is 16 μm, the porosity is 85%, and the compressive strength is 12 MPa.

[0024] Example 4 In this embodiment, a sample with a density of 750 mg / cm³ was prepared. 3 The specific steps for using low-pressure-drop ceramic filter materials are as follows: The material prepared using the method disclosed in Chinese Invention Patent No. CN109553395B has a density of 4 mg / cm³. 3 Silicon nitride nanowire foam is used as a raw material; see [link / reference]. Figure 1 In step (b), the sample was placed in a CVI deposition furnace, and hydrogen and argon were introduced into the furnace at a temperature of 1100 °C. The hydrogen gas flow rate was 6 L / min, and the argon gas flow rate was 6 L / min. The flow rate of methyltrichlorosilane was maintained at 2 L / min, the deposition pressure was controlled at approximately 1500 Pa, and the deposition time was 9 h. After deposition and cooling to room temperature, the sample was removed and cut along the thickness direction using a diamond wire cutter to thin it. Then, it was polished with 800-grit, 1000-grit, and 2000-grit sandpaper in sequence, followed by ultrasonic cleaning four times in an ultrasonic vibrator, each time for 10 minutes. After cleaning, it was dried in a 100 °C oven for 3 hours. Finally, the sample was placed in a muffle furnace at 1200 °C for high-temperature holding for 2 hours. The sample was removed when the temperature dropped to 500 °C or below. The density of the sample was measured to be 750 mg / cm³. 3 The surface average pore size is 8 μm, the core average pore size is 16 μm, the porosity is 77%, and the compressive strength is 22 MPa.

[0025] Example 5 In this embodiment, a sample with a density of 900 mg / cm³ was prepared. 3 The specific steps for using low-pressure-drop ceramic filter materials are as follows: Using silicon nitride nanowire foam prepared by the method disclosed in Chinese Invention Patent No. CN109553395B as raw material, the foam was placed in a CVD deposition furnace. Hydrogen and argon were introduced into the furnace at a temperature of 1000 °C, with a hydrogen flow rate of 6 L / min and an argon flow rate of 6 L / min. The flow rate of methyltrichlorosilane was maintained at 0.5 L / min, and the deposition pressure was controlled at approximately 4000 Pa for 20 h. After deposition and cooling to room temperature, the sample was removed and cut along its thickness direction using diamond wire cutting to thin it. Then, it was successively polished with 800-grit, 1000-grit, and 2000-grit sandpaper, followed by ultrasonic cleaning three times in an ultrasonic vibrator, each cleaning lasting 10 minutes. After cleaning, it was dried in a 100 °C oven for 6 hours. Finally, the sample was placed in a muffle furnace at 1200℃ for 4 hours and held at that temperature until the temperature dropped to 500℃ or below before being removed. The density of the sample was measured to be 900 mg / cm³. 3 The surface average pore size is 6 μm, the core average pore size is 11 μm, the porosity is 72%, and the compressive strength is 30 MPa.

[0026] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a high-temperature, low-pressure-drop ceramic filter material, characterized in that, Includes the following steps: 1) Using ultralight silicon nitride nanowire foam as a matrix, silicon carbide is deposited on the nanowire surface of ultralight silicon nitride nanowire foam by chemical vapor infiltration. 2) Cut the ultralight silicon nitride nanowire foam along the thickness direction after chemical vapor infiltration strengthening treatment; 3) Grind, clean, and dry the cut products to obtain samples; 4) The sample was subjected to high-temperature heat preservation treatment and then cooled to obtain a low-pressure-drop ceramic filter material.

2. The method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to claim 1, characterized in that, The ultralight silicon nitride nanowire foam consists of silicon nitride nanowires with a diameter of 30-150 nm, or a porous three-dimensional network structure composed of several silicon nitride nanowires with a diameter of 30-150 nm. The density of the ultralight silicon nitride nanowire foam is 1-5 mg / cm³. 3 .

3. The method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to claim 1, characterized in that, In step 1), the precursor used for chemical vapor infiltration deposition of silicon carbide is methyltrichlorosilane, the deposition pressure is 800-4000 Pa, the deposition temperature is 900-1200 ℃, and the deposition time is 3-20 h.

4. The method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to claim 1, characterized in that, In step 2), mechanical cutting is used to cut the pore size of the low-pressure-drop porous ceramic from a gradient distribution of "small-large-small" to a gradient distribution of "large-small" or "small-large" along the thickness direction.

5. The method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to claim 1, characterized in that, In step 3), the polishing process involves polishing the cut product sequentially with 800-grit, 1000-grit, and 2000-grit sandpaper; the cleaning process uses ultrasonic cleaning, which is performed 2-5 times for 10 minutes each time; and the drying process is carried out at 80-100 ℃ for 1-6 hours.

6. The method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to claim 1, characterized in that, In step 4), the sample is subjected to high-temperature heat treatment at 1000-1200 ℃ for 0.5-4 h. After the heat treatment is completed, the temperature is reduced to 500 ℃ or below to obtain the target product.

7. A high-temperature resistant, low-pressure-drop ceramic filter material prepared by the method for preparing a high-temperature resistant, low-pressure-drop ceramic filter material according to any one of claims 1-6, characterized in that, The bulk density of this low-pressure-drop ceramic filter material is 50-900 mg / cm³. 3 The porosity is 72%-93%, and the average pore size is 5-25 μm.

8. The high-temperature resistant, low-pressure-drop ceramic filter material according to claim 7, characterized in that, This high-temperature, low-pressure-drop ceramic filter material has a compressive strength of 2-30 MPa and a maximum stable operating temperature of 1000°C. o C, pressure drop below 5 kPa.

9. The high-temperature resistant, low-pressure-drop ceramic filter material according to claim 7, characterized in that, This high-temperature resistant, low-pressure-drop ceramic filter material is at 950°C. o It does not fracture after 500 thermal shocks at temperature C.

10. The application of the high-temperature resistant, low-pressure-drop ceramic filter material according to any one of claims 7-9 in high-temperature exhaust gas filtration, diesel engine carbon particle filtration, and metal liquid impurity filtration.

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