Method for preparing tubular silicon carbide film through co-sintering

Abstract

The invention discloses a co-firing preparation method of a middle layer and a film layer of a tubular multilayer silicon carbide ceramic film. The method comprises the following steps: firstly, coating the surface of a silicon carbide support body with a small-particle-size silicon carbide intermediate layer, and then coating the intermediate layer with a silicon carbide film layer with a smaller particle size and a core-shell structure, so as to prepare the tubular silicon carbide ceramic film. Compared with a two-step sintering process, a section of heating and heat preservation process is omitted, and the energy consumption and the time cost in the preparation process are remarkably reduced. Meanwhile, by utilizing the characteristic of strong oxidation resistance of the core-shell structure of the film layer, the matching of the film layer and the middle layer on sintering temperature is realized, and the problem of film layer densification in the co-firing process is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of porous ceramic material preparation technology, and relates to a method for co-sintering to prepare tubular silicon carbide films. Background Technology

[0002] SiC membranes are a novel inorganic membrane material with excellent mechanical strength, chemical stability, thermal shock resistance, and hydrophilicity, attracting increasing attention from academia and industry in recent years. Compared to polymers (such as PVDF) and inorganic materials (such as Al2O3 and ZrO2), SiC membranes exhibit higher efficiency in oil-water emulsion separation. However, most commercially available SiC ceramic membranes are prepared through high-temperature (>2000 °C) recrystallization processes in an inert atmosphere, hindering their widespread application due to high manufacturing costs. Therefore, reducing sintering energy consumption and preparation costs has become a key issue in the current ceramic membrane field.

[0003] Co-sintering is a promising technology for cost reduction, as it can lower preparation costs and shorten the preparation cycle. However, there is a mismatch in sintering temperatures between silicon carbide powders of different particle sizes. To achieve co-sintering of the support and membrane layers, and the intermediate layer and membrane layers, common methods include adjusting the formulation and changing the sintering procedure. For example, Chinese invention patent CN108911706A reports a method for co-sintering a fly ash ceramic microfiltration membrane. By doping rigid fibers into the fly ash support, the mismatch problem between the support and membrane layers during sintering is alleviated, and a microfiltration membrane with a pore size of about 100 nm and a thickness of 40-50 µm is prepared by holding at 1050 °C for 2 h. Chinese invention patent CN118255592A reports a two-step co-firing method for preparing a silicon carbide ceramic support and membrane layer. By optimizing the sintering process and segmenting the heat preservation process, the shrinkage of the membrane layer is reduced while meeting the strength requirements of the support. Microfiltration membranes with a pore size of approximately 220 nm and a thickness of 21 µm are prepared by heat preservation at 1050 °C and 900 °C for 1 h respectively. This method reduces the impact of excessively high sintering temperatures on the membrane layer by sacrificing the heat preservation time of the support. However, this inevitably affects the mechanical properties of the silicon carbide membrane and does not completely solve the problem of temperature mismatch between the intermediate layer and the membrane layer.

[0004] This invention achieves the co-sintering of silicon carbide intermediate layer and film layer by coating the surface of film particles with a layer of aluminum oxide to delay the oxidation of the film layer, thereby matching the sintering temperature between the intermediate layer and the film layer. Summary of the Invention

[0005] This invention utilizes the strong oxidation resistance of core-shell structured powder to match the sintering temperatures of the silicon carbide intermediate layer and the film layer, thereby achieving the co-sintering preparation of the silicon carbide intermediate layer and the film layer.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: (1) Weigh out silicon carbide powder and methylcellulose separately and disperse them in deionized water, wherein silicon carbide powder accounts for 5-20% of the total mass and methylcellulose accounts for 0.1-1.5% of the total mass; (2) After the solution in step (1) is thoroughly stirred, add defoamer TL-56NQ and stir at low speed for 30 min to prevent excessive bubbles in the solution from causing defects in the film layer; (3) The coating liquid obtained in step (2) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry; (4) Weigh out silicon carbide powder and aluminum sol respectively, wherein the silicon carbide powder accounts for 70-100% of the total mass of the two and the aluminum sol accounts for 0-30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven at 80-120 °C. (5) Disperse the core-shell powder obtained in step (4) together with methylcellulose in deionized water, wherein the core-shell powder accounts for 5-20% of the total mass and the methylcellulose accounts for 0.1-1.5% of the total mass; (6) After the solution in step (5) has been thoroughly stirred, add defoamer TL-56NQ and stir at low speed for 30 min to prevent excessive bubbles in the solution from causing defects in the film layer. (7) The coating liquid obtained in step (6) is applied to the inner surface of the tubular silicon carbide film obtained in step (3) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (8) Place the dried silicon carbide film from step (7) into a muffle furnace for sintering. Hold at 700~1000 °C for 2 h, and finally cool to room temperature with the furnace. The heating rate is controlled at 1~2 °C / min, and the sintering atmosphere is air.

[0007] The preferred silicon carbide powder used in step (1) has a particle size of 300~800 nm.

[0008] The tubular silicon carbide used in step (3) preferably has an average pore size of 0.7 to 5 μm.

[0009] The preferred silicon carbide powder used in step (4) has a particle size of 50~150 nm.

[0010] In step (4), the pH is adjusted to 7-12 with ammonia.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention prevents the infiltration of film particles into a silicon carbide film by constructing a gradient pore structure of support-intermediate layer-film layer, thus preparing a silicon carbide film with narrow pore size.

[0012] 2. This invention delays the oxidation of silicon carbide particles in the film layer through a core-shell structure, and achieves the co-sintering preparation of the film layer and the intermediate layer. This preparation method greatly reduces the preparation process and sintering energy consumption, and provides a new way for the low-cost preparation of inorganic ceramic films such as silicon carbide. Attached Figure Description

[0013] Figure 1 A macroscopic photograph of the silicon carbide film prepared in Example 1.

[0014] Figure 2 The image shows an electron microscope (EM) image of the silicon carbide ceramic film prepared in Example 1.

[0015] Figure 3 This is a cross-sectional electron microscope image of the silicon carbide ceramic film prepared in Example 1.

[0016] Figure 4 The image shows an electron microscope (EM) image of the silicon carbide ceramic film prepared in Example 5. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Example 1

[0018] A method for co-sintering to prepare tubular silicon carbide films, the specific steps of which are as follows: (1) Weigh out silicon carbide powder with a particle size of 500 nm and methylcellulose and disperse them in deionized water, wherein the silicon carbide powder accounts for 5% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ and stir at low speed for 30 min.

[0019] (2) The coating liquid obtained in step (1) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry.

[0020] (3) Weigh out silicon carbide powder and aluminum sol with a particle size of 100 nm respectively, wherein the silicon carbide powder accounts for 70% of the total mass of the two and the aluminum sol accounts for 30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven.

[0021] (4) Disperse the core-shell powder obtained in step (3) together with methylcellulose into deionized water, wherein the core-shell powder accounts for 5% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After thorough stirring, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0022] (5) The coating liquid obtained in step (4) is applied to the inner surface of the tubular silicon carbide film obtained in step (2) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (6) In an air atmosphere, the temperature is increased to 900 °C at 2 °C / min and held for 2 h, and finally cooled to room temperature with the furnace.

[0023] The prepared tubular silicon carbide film, such as Figure 1 As shown, it has a length of 12 cm, an inner diameter of 8 mm, and an outer diameter of 12 mm. Its surface microstructure was observed using a scanning electron microscope. Figure 2 The medium-strength silicon carbide surface is defect-free and exhibits a porous structure. The film layer does not show signs of over-sintering, and there are obvious sintering necks between the particles. Figure 3 The image shows a cross-sectional electron microscope image of the prepared silicon carbide film. The thickness of the intermediate layer is approximately 33.2 μm, and the thickness of the film layer is approximately 5.5 μm. Example 2

[0024] A method for co-sintering to prepare tubular silicon carbide films, the specific steps of which are as follows: (1) Weigh out silicon carbide powder with a particle size of 500 nm and methylcellulose and disperse them in deionized water, wherein the silicon carbide powder accounts for 10% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ and stir at low speed for 30 min.

[0025] (2) The coating liquid obtained in step (1) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry.

[0026] (3) Weigh out silicon carbide powder and aluminum sol with a particle size of 100 nm respectively, wherein the silicon carbide powder accounts for 70% of the total mass of the two and the aluminum sol accounts for 30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven.

[0027] (4) Disperse the core-shell powder obtained in step (3) together with methylcellulose into deionized water, wherein the core-shell powder accounts for 10% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After thorough stirring, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0028] (5) The coating liquid obtained in step (4) is applied to the inner surface of the tubular silicon carbide film obtained in step (2) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (6) In an air atmosphere, the temperature is increased to 900 °C at 2 °C / min and held for 2 h, and finally cooled to room temperature with the furnace.

[0029] The thickness of the intermediate layer was measured to be approximately 89.3 μm and the thickness of the film layer was approximately 13.3 μm using scanning electron microscopy. Example 3

[0030] A method for co-sintering to prepare tubular silicon carbide films, the specific steps of which are as follows: (1) Weigh out silicon carbide powder with a particle size of 800 nm and methylcellulose and disperse them in deionized water, wherein the silicon carbide powder accounts for 15% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0031] (2) The coating liquid obtained in step (1) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry.

[0032] (3) Weigh out silicon carbide powder and aluminum sol with a particle size of 100 nm respectively, wherein the silicon carbide powder accounts for 70% of the total mass of the two and the aluminum sol accounts for 30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven.

[0033] (4) Disperse the core-shell powder obtained in step (3) together with methylcellulose into deionized water, wherein the core-shell powder accounts for 15% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After thorough stirring, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0034] (5) The coating liquid obtained in step (4) is applied to the inner surface of the tubular silicon carbide film obtained in step (2) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (6) In an air atmosphere, the temperature is increased to 900 °C at 2 °C / min and held for 2 h, and finally cooled to room temperature with the furnace.

[0035] The thickness of the intermediate layer was measured to be approximately 135.6 μm and the thickness of the film layer was approximately 17.2 μm using scanning electron microscopy. Example 4

[0036] A method for co-sintering to prepare tubular silicon carbide films, the specific steps of which are as follows: (1) Weigh out silicon carbide powder with a particle size of 360 nm and methylcellulose and disperse them in deionized water, wherein the silicon carbide powder accounts for 20% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0037] (2) The coating liquid obtained in step (1) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry.

[0038] (3) Weigh out silicon carbide powder and aluminum sol with a particle size of 50 nm respectively, wherein the silicon carbide powder accounts for 70% of the total mass of the two and the aluminum sol accounts for 30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven.

[0039] (4) Disperse the core-shell powder obtained in step (3) together with methylcellulose into deionized water, wherein the core-shell powder accounts for 15% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After thorough stirring, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0040] (5) The coating liquid obtained in step (4) is applied to the inner surface of the tubular silicon carbide film obtained in step (2) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (6) In an air atmosphere, the temperature is increased to 900 °C at 2 °C / min and held for 2 h, and finally cooled to room temperature with the furnace.

[0041] The thickness of the intermediate layer was measured to be approximately 159.1 μm and the thickness of the film layer was approximately 16.3 μm using scanning electron microscopy. Example 5

[0042] A method for co-sintering to prepare tubular silicon carbide films, the specific steps of which are as follows: (1) Weigh out silicon carbide powder with a particle size of 500 nm and methylcellulose and disperse them in deionized water, wherein the silicon carbide powder accounts for 5% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ and stir at low speed for 30 min.

[0043] (2) The coating liquid obtained in step (1) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry.

[0044] (3) Weigh out silicon carbide powder with a particle size of 100 nm and methylcellulose and disperse them together in deionized water, wherein the silicon carbide powder accounts for 5% of the total mass and the methylcellulose accounts for 0.3% of the total mass. After stirring thoroughly, add defoamer TL-56NQ dropwise and stir at low speed for 30 min.

[0045] (4) The coating liquid obtained in step (3) is applied to the inner surface of the tubular silicon carbide film obtained in step (2) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (5) In an air atmosphere, the temperature is increased to 900 °C at 2 °C / min and held for 2 h, and finally cooled to room temperature with the furnace.

[0046] Its surface microstructure was observed using a scanning electron microscope. Figure 4 The surface of the silicon carbide film exhibits agglomeration after excessive sintering. The thickness of the intermediate layer is measured to be approximately 28.7 μm, and the film thickness is approximately 7.2 μm.

Claims

1. A method for co-sintering to prepare tubular silicon carbide films, characterized in that, The specific steps are as follows: (1) Weigh out silicon carbide powder and methylcellulose separately and disperse them in deionized water, wherein silicon carbide powder accounts for 5-20% of the total mass and methylcellulose accounts for 0.1-1.5% of the total mass; (2) After the solution in step (1) is thoroughly stirred, add defoamer TL-56NQ and stir at low speed for 30 min to prevent excessive bubbles in the solution from causing defects in the film layer; (3) The coating liquid obtained in step (2) is coated onto the inner surface of the tubular silicon carbide by dip-coating, and the prepared silicon carbide film is placed in an oven to dry; (4) Weigh out silicon carbide powder and aluminum sol respectively, wherein the silicon carbide powder accounts for 70-100% of the total mass of the two and the aluminum sol accounts for 0-30% of the total mass of the two. Then add the two substances to anhydrous ethanol solution, adjust to alkaline conditions with ammonia water, stir magnetically for 12 h, then centrifuge, and then dry completely in an oven at 80-120 °C. (5) Disperse the core-shell powder obtained in step (4) together with methylcellulose in deionized water, wherein the core-shell powder accounts for 5-20% of the total mass and the methylcellulose accounts for 0.1-1.5% of the total mass; (6) After the solution in step (5) has been thoroughly stirred, add defoamer TL-56NQ and stir at low speed for 30 min to prevent excessive bubbles in the solution from causing defects in the film layer. (7) The coating liquid obtained in step (6) is applied to the inner surface of the tubular silicon carbide film obtained in step (3) by dip-coating. The prepared silicon carbide film is placed in an oven to dry. (8) Place the dried silicon carbide film from step (7) into a muffle furnace for sintering. Hold at 700~1000 °C for 2 hours, and finally cool to room temperature with the furnace. The heating rate is controlled at 1~2 °C / min, and the sintering atmosphere is air.

2. The method for co-sintering to prepare tubular silicon carbide films according to claim 1, characterized in that, The silicon carbide powder added in step (1) has a particle size of 300~800 nm.

3. The method for co-sintering to prepare tubular silicon carbide films according to claim 1, characterized in that, The average pore size of the tubular silicon carbide used in step (3) is 0.7~5 μm.

4. The method for co-sintering to prepare tubular silicon carbide films according to claim 1, characterized in that, The silicon carbide powder added in step (4) has a particle size of 50~150 nm.

5. The method for co-sintering to prepare tubular silicon carbide films according to claim 1, characterized in that, In step (4), ammonia is added to adjust the pH to 7-12.

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