Silicon carbide porous ceramics and methods of making the same
By using β-silicon carbide powder gradation and a specific sintering process, the problem of uncontrollable pore size in silicon carbide porous ceramics was solved, enabling the preparation of high-quality and low-cost silicon carbide porous ceramics with excellent mechanical properties and porosity.
Patent Information
- Application Number
- CN202410372418.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-29
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2044-03-29
AI Technical Summary
In existing technologies, the uneven particle size distribution of α-SiC powder leads to uncontrollable pore size of silicon carbide porous ceramics, and high-temperature firing is required, which affects their quality and cost.
Using β-silicon carbide powder as raw material, through particle size distribution design and the addition of dispersants and binders, combined with a specific sintering process, porous silicon carbide ceramics with controllable pore size were prepared, thereby reducing the sintering temperature.
It achieves uniform pore size distribution (3~6μm), high porosity (>45%), and excellent mechanical properties (flexural strength >57.6MPa), while reducing sintering temperature and cost.
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Figure CN118344153B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of inorganic non-metallic materials, and particularly relates to a silicon carbide porous ceramic and a preparation method thereof. BACKGROUND
[0002] At present, the large-scale production of ceramic membranes is concentrated on oxide ceramics, such as alumina and zirconia ceramics. Compared with traditional alumina, zirconia, silica and other oxide porous ceramics, silicon carbide porous ceramics have better hydrophilicity, higher permeability, better chemical stability and higher mechanical strength, so that they have a broader application prospect in the field of wastewater treatment. At present, silicon carbide porous ceramics are mostly prepared by using α-SiC as raw material. However, since the α-SiC powder is prepared by high-temperature smelting, the particle size distribution of the raw material powder is wide, and the sphericity cannot meet the requirements, so that the silicon carbide porous ceramic has a wide pore size distribution and the pore size is uncontrollable; and high temperature is needed to sinter the silicon carbide porous ceramic. SUMMARY
[0003] The present application aims at the above-mentioned deficiencies in the prior art, and provides a silicon carbide porous ceramic prepared by using β-silicon carbide powder as raw material and a preparation method thereof. The silicon carbide porous ceramic substrate has excellent mechanical properties (bending strength > 57.6 MPa), high porosity (porosity > 45%), controllable pore size (average pore size is 3-6 μm), and uniform pore size distribution, which effectively ensures the quality and quantity.
[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:
[0005] The first object of the present application is to provide a preparation method of a silicon carbide porous ceramic. The silicon carbide porous ceramic is prepared from the following raw materials by weight parts: 80-95 parts of coarse β-silicon carbide powder, 5-20 parts of fine β-silicon carbide powder, 2-8 parts of silicon powder, 2-6 parts of dispersant, and 2-8 parts of binder. The particle size of the coarse β-silicon carbide powder is 10-40 μm, the particle size of the fine β-silicon carbide powder is 0.5-2.5 μm, and the particle size of the silicon powder is 3-8 μm. The preparation method comprises the following steps:
[0006] Step S1, the β-SiC powders with different particle sizes are proportionally weighed and graded, and a certain amount of silicon powder, dispersant, binder and 10-30% ethanol aqueous solution are added, mixed in a ceramic ball mill jar to obtain raw material;
[0007] Step S2, the raw material is placed in a drying oven to obtain a mixed material for tabletting;
[0008] Step S3, a certain amount of the mixture is weighed in a tablet machine die, and is formed under a certain pressure condition; the formed silicon carbide porous ceramic body is degassed at a certain temperature in a nitrogen atmosphere;
[0009] Step S4, the degassed silicon carbide porous ceramic body is wrapped with graphite paper, and is sintered in a hot-pressing sintering furnace in an inert atmosphere; and the silicon carbide porous ceramic is obtained after annealing.
[0010] Further, in step S1, the gradation of the coarse beta-silicon carbide powder and the fine beta-silicon carbide powder is (8:2)~(9.5:0.5).
[0011] Further, in step S1, the dispersing agent is polyacrylic acid, and the binder is polyvinylpyrrolidone.
[0012] Further, in step S1, the solid-liquid ratio of the raw material is 5:1~8:1.
[0013] Further, in step S2, the drying process is as follows: after rotary evaporation drying at 85~95℃ for 2~4h to form a fluid, the fluid is placed in a forced air drying oven at 60~75℃ for 2~4h.
[0014] Further, in step S3, the degassing system of the silicon carbide porous ceramic body is as follows: under an argon atmosphere, the temperature is raised to 550~850℃ at a rate of 5~10℃ / min, and the temperature is maintained at this temperature for 40~60min.
[0015] Further, in step S4, the sintering system of the silicon carbide porous ceramic body is as follows: under a high-purity argon atmosphere, the temperature is raised to 1300~1500℃ at a rate of 5~10℃ / min, and the temperature is maintained for 60~100min; then the temperature is raised to 1900~2200℃ at a rate of 5~10℃ / min, and the temperature is maintained for 60~100min.
[0016] Further, in step S3, the tabletting process is as follows: under a pressure of 3~5MPa, the pressure is maintained for 2min.
[0017] The second object of the present application is to provide a silicon carbide porous ceramic obtained by the above preparation method.
[0018] Further, the average pore size of the silicon carbide porous ceramic is 3~6μm.
[0019] Compared with the prior art, the present application has the following beneficial effects:
[0020] (1) The present application provides a kind of porous silicon carbide ceramic and its preparation method, and by β-SiC powder grading, pore size controllable is realized, the prepared porous silicon carbide ceramic substrate not only has relatively excellent mechanical properties (bending strength > 57.6MPa), high porosity (porosity > 45%), pore size controllable (average pore size is 3-6 μm), and pore size distribution is uniform, effectively ensure its quality and quality.
[0021] (2) The present application utilizes β-SiC powder grading of different particle sizes to realize the preparation of porous silicon carbide ceramic with controllable pore size, optimizes the process flow, reduces the sintering temperature, realizes the pore size controllable of porous silicon carbide material, reduces the sintering temperature of porous silicon carbide ceramic, and finally reduces the cost of porous silicon carbide ceramic. BRIEF DESCRIPTION OF DRAWINGS
[0022] Figure 1 XRD diagram of porous silicon carbide ceramic before and after sintering;
[0023] Figure 2 XRD comparison diagram of porous silicon carbide ceramic prepared at different sintering temperatures;
[0024] Figure 3 SEM images of different porous silicon carbide ceramic samples under 20 μm scale, wherein (a) is the sample prepared in Example 1, (b) is the sample prepared in Example 2, (c) is the sample prepared in Example 3, and (d) is the sample prepared in Comparative Example 3;
[0025] Figure 4 SEM images of different porous silicon carbide ceramic samples under 5 μm scale, wherein (a) is the sample prepared in Example 1, (b) is the sample prepared in Example 2, (c) is the sample prepared in Example 3, and (d) is the sample prepared in Comparative Example 3;
[0026] Figure 5a Pore size distribution diagram of the sample prepared in Example 1;
[0027] Figure 5b Pore size distribution diagram of the sample prepared in Example 2;
[0028] Figure 6 Bending strength analysis diagram of samples with different silicon contents. DETAILED DESCRIPTION
[0029] To make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application are described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, only for explaining the present application, and cannot be understood as limiting the present application.
[0030] The reagent materials used in the present application are commercially available.
[0031] Example 1
[0032] The present embodiment provides a preparation method of β-silicon carbide porous ceramics.
[0033] The following raw materials are used in parts by weight: 95 parts of coarse β-silicon carbide powder, 5 parts of fine β-silicon carbide powder, 4 parts of silicon powder, 3 parts of polyacrylic acid, and 3 parts of polyvinylpyrrolidone, wherein the particle size of the coarse β-silicon carbide powder is 28 μm, the particle size of the fine β-silicon carbide powder is 2.5 μm, the particle size of the silicon powder is 3 μm, the polyacrylic acid is a dispersant, and the polyvinylpyrrolidone is a binder.
[0034] The specific process is as follows:
[0035] In step S1, the coarse and fine β-SiC powders with different particle sizes are weighed according to the above proportions for gradation design, and a certain amount of silicon powder, dispersant, binder, and 20 wt.% ethanol aqueous solution are added. The solid-liquid ratio is 5:1, and the mixture is placed in a ceramic ball mill jar for 20 h to obtain green materials. The frequency of the ceramic ball mill jar is 20-30 Hz.
[0036] In step S2, the green materials are dried in a rotary evaporator at 80℃ for 3 h and then placed in a forced air drying oven at 60℃ for 5 h to obtain mixed materials for tabletting.
[0037] In step S3, 3 g of the mixed materials are weighed and placed in a tablet press die. Under the condition of 5 MPa pressure, the materials are shaped for 2 min, and the shaped silicon carbide porous ceramic body is degassed in a nitrogen atmosphere at 650℃.
[0038] In step S4, the degassed silicon carbide porous ceramic body is wrapped with graphite paper and placed in a hot-pressing sintering furnace. Sintering is carried out in an argon atmosphere. The temperature is raised to 1300℃ at a rate of 10℃ / min and maintained for 100 min. Then the temperature is raised to 2100℃ at a rate of 5℃ / min and sintered for another 2 h. After sintering, the silicon carbide porous ceramic body is naturally cooled to room temperature, taken out, and the surface is cleaned. The final product is the silicon carbide porous ceramic.
[0039] The silicon carbide porous ceramic prepared in this embodiment has uniform pore size and a porosity of 55%. It has good mechanical properties, with a bending strength of 57.6 MPa.
[0040] Example 2
[0041] The present embodiment provides a preparation method of β-silicon carbide porous ceramics.
[0042] The following raw materials are used by weight parts: 90 parts of coarse β-silicon carbide powder, 10 parts of fine β-silicon carbide powder, 4 parts of silicon powder, 3 parts of polyacrylic acid, and 3 parts of polyvinylpyrrolidone, wherein the particle size of the coarse β-silicon carbide powder is 28 μm, the particle size of the fine β-silicon carbide powder is 1 μm, the particle size of the silicon powder is 3 μm, the polyacrylic acid is a dispersant, and the polyvinylpyrrolidone is a binder.
[0043] The specific process is as follows:
[0044] In step S1, the coarse and fine β-SiC powders with different particle sizes are weighed according to the above proportions for gradation design, and a certain amount of silicon powder, dispersant, binder, and 10 wt.% ethanol aqueous solution are added. The solid-liquid ratio is 6:1, and the mixture is placed in a ceramic ball mill jar for 20 h to obtain a raw material. The frequency of the ceramic ball mill jar is 20-30 Hz.
[0045] In step S2, the raw material is dried in a rotary evaporator at 80℃ for 3 h and then placed in a forced air drying oven at 60℃ for 5 h to obtain a mixed material for tabletting.
[0046] In step S3, 3 g of the mixed material is weighed and placed in a tablet press die. Under the condition of 5 MPa pressure, it is shaped for 2 min. The shaped silicon carbide porous ceramic body is degassed in a nitrogen atmosphere at 650℃.
[0047] In step S4, the degassed silicon carbide porous ceramic body is wrapped with graphite paper and placed in a hot-pressing sintering furnace. Sintering is carried out in an argon atmosphere. The temperature is raised to 1300℃ at a rate of 10℃ / min and held for 100 min. Then the temperature is raised to 2100℃ at a rate of 5℃ / min and sintered for 2 h. After sintering, the silicon carbide porous ceramic body is naturally cooled to room temperature, taken out, and the surface is cleaned. The final product is a silicon carbide porous ceramic product.
[0048] The silicon carbide porous ceramic prepared in this example has a porosity of 51% and a bending strength of 48.7 MPa.
[0049] Example 3
[0050] The present example provides a preparation method of β-silicon carbide porous ceramic.
[0051] The following raw materials are used by weight parts: 80 parts of coarse β-silicon carbide powder, 20 parts of fine β-silicon carbide powder, 4 parts of silicon powder, 3 parts of polyacrylic acid, and 3 parts of polyvinylpyrrolidone, wherein the particle size of the coarse β-silicon carbide powder is 28 μm, the particle size of the fine β-silicon carbide powder is 0.5 μm, the particle size of the silicon powder is 3 μm, the polyacrylic acid is a dispersant, and the polyvinylpyrrolidone is a binder.
[0052] The specific process is as follows:
[0053] Step S1, the different particle size of the coarse and fine β-SiC powder is weighed according to the above ratio, and a certain amount of silicon powder, dispersant, binder and 30wt.% ethanol aqueous solution are added, the solid-liquid ratio is 7:1, and the mixture is placed in a ceramic ball mill jar for 20h to obtain a raw material;
[0054] Step S2, the raw material is placed in a rotary evaporator and dried at 80℃ for 3h, and then placed in a forced air drying oven and dried at 60℃ for 5h to obtain a mixed material for tabletting; the frequency of the ceramic ball mill jar is 20-30Hz;
[0055] Step S3, 3g of the mixed material is weighed and placed in a tablet press die, and is shaped under the condition of 5MPa pressure for 2min, and the shaped silicon carbide porous ceramic body is degassed at 650℃ in a nitrogen atmosphere;
[0056] Step S4, the degassed silicon carbide porous ceramic body is wrapped with graphite paper and placed in a hot-pressing sintering furnace, and sintered in an argon atmosphere, heated to 1300℃ at a rate of 10℃ / min and kept for 100min, and then heated to 2100℃ at a rate of 5℃ / min and sintered for 2h, after sintering, the silicon carbide porous ceramic body is naturally cooled to room temperature, taken out and the surface is cleaned, and the final product is a silicon carbide porous ceramic product.
[0057] The silicon carbide porous ceramic prepared in this example has a porosity of 49%; and a bending strength of 46.2MPa.
[0058] Comparative Example 1
[0059] This comparative example provides a preparation method of silicon carbide porous ceramic.
[0060] The specific process is basically the same as that of Example 1, except that in step S4, the degassed silicon carbide porous ceramic body is directly placed in a hot-pressing sintering furnace without wrapping with graphite paper. The silicon carbide porous ceramic prepared has a porosity of 40%; and a bending strength of 30.2MPa.
[0061] Comparative Example 2
[0062] This comparative example provides a preparation method of silicon carbide porous ceramic.
[0063] The specific process is basically the same as that of Example 1, except that the particle size of the fine β-silicon carbide powder is 1μm. The silicon carbide porous ceramic prepared has a porosity of 45%; and a bending strength of 45.1MPa.
[0064] Comparative Example 3
[0065] This comparative example provides a preparation method of silicon carbide porous ceramic.
[0066] The specific process is basically the same as that of Example 1, except that the particle size of the coarse β-silicon carbide powder is 40 μm. The prepared silicon carbide porous ceramic has a porosity of 45% and a bending strength of 30.8 MPa.
[0067] Comparative Example 4
[0068] The present comparative example provides a method for preparing a silicon carbide porous ceramic.
[0069] The specific process is basically the same as that of Example 3, except that the silicon carbide powder is α-silicon carbide. The prepared silicon carbide porous ceramic has a porosity of 44% and a bending strength of 24.2 MPa.
[0070] Reference Figure 1 The XRD patterns of the silicon carbide porous ceramic before and after sintering are shown in FIG. 2. As can be seen from the figure, the β-silicon carbide in the raw material is converted into α-silicon carbide.
[0071] Reference Figure 2 The XRD comparison chart of the silicon carbide porous ceramic prepared at different sintering temperatures is shown in FIG. 3. As can be seen from the figure, as the temperature increases, the degree of conversion of β phase into α phase also increases.
[0072] Reference Figure 3 FIG. 4 shows the SEM images of different silicon carbide porous ceramic samples under a 20 μm scale, wherein (a) is the sample prepared in Example 1, (b) is the sample prepared in Example 2, (c) is the sample prepared in Example 3, and (d) is the sample prepared in Comparative Example 3. It can be seen that the particle size of the coarse particles is consistent, the larger the particle size of the fine particles, the more uniform the pore size distribution, and when the particle size of the fine particles is the same, the increase of the coarse particles leads to relatively poor inter-particle bonding.
[0073] Reference Figure 4 FIG. 5 shows the SEM images of different silicon carbide porous ceramic samples under a 5 μm scale, wherein (a) is the sample prepared in Example 1, (b) is the sample prepared in Example 2, (c) is the sample prepared in Example 3, and (d) is the sample prepared in Comparative Example 3. It can be seen that the small particles are connected to the large particles by sintering necks to increase the strength of the sample.
[0074] Reference Figure 5a FIG. 6 shows the pore size distribution of the sample prepared in Example 1. It can be seen that the pore size distribution of the prepared sample is narrow and unimodal, indicating that the pore size distribution is uniform, the average pore size is 3-6 μm, the pore size ratio is high, and the concentrated pore size is 5.2 μm-6.2 μm.
[0075] Reference Figure 5b FIG. 7 shows the pore size distribution of the sample prepared in Example 2. It can be seen that the pore size distribution of the prepared sample is narrow and unimodal, indicating that the pore size distribution is uniform, the average pore size is 3-6 μm, the pore size ratio is high, and the concentrated pore size is 4.5 μm-5.3 μm.
[0076] Shuang LA et al. prepared recrystallized silicon carbide porous ceramics with an average pore size of 1 pm and a porosity of about 30% using two different particle sizes of silicon carbide powder (coarse powder (D50=5 pm): fine powder (D50=5 pm)=5:1), and the maximum bending strength was 45 MPa; Liang P et al. prepared recrystallized silicon carbide porous ceramics with a large pore size (9 pm-22 pm) and a porosity of 30%-35% using two different particle sizes of silicon carbide powder (fine powder (D50=2.5 pm): coarse powder (D50=100 pm)=30%-70%), and the bending strength was 24.7 MPa-45.1 MPa; Baitalik S et al. prepared recrystallized silicon carbide porous ceramics with a porosity of 36% and a maximum bending strength of 38 MPa using three different particle sizes of silicon carbide powder with average particle sizes of 22.4 pm, 51.7 pm and 99.2 pm. The silicon carbide porous ceramics prepared by the present application have good mechanical properties (bending strength >57.6 MPa), a relatively uniform pore size (average pore size: 3-6 pm) and a high porosity (>45%), as shown in Comparative Examples 1-3, with the change of the ratio of coarse and fine powder, the average pore size and the bending strength of the silicon carbide porous ceramics are positively correlated, and as shown in the figure, with the increase of the content of silicon powder, the average pore size and the bending strength of the silicon carbide porous ceramics first increase to a certain peak value and then decrease, and the peak value is when the silicon content is 4 parts. Therefore, under a certain process, the pore size control of silicon carbide porous ceramics by raw material grading can effectively ensure its quality and quantity. Therefore, the silicon carbide porous ceramics produced by the present application have a broader market prospect and are more suitable for promotion. Figure 6
[0077] The above not involved, applicable to the prior art.
[0078] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, but will not deviate from the direction of the present application or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made according to the technical essence of the present application to the above embodiments shall be included in the protection scope of the present application.
Claims
1. A method for producing a porous silicon carbide ceramic, characterized by, The silicon carbide porous ceramic is prepared from the following raw materials by weight parts: 80-95 parts of coarse β-silicon carbide powder, 5-20 parts of fine β-silicon carbide powder, 2-8 parts of silicon powder, 2-6 parts of dispersant, 2-8 parts of binder, the particle size of the coarse β-silicon carbide powder is 10-40 μm, the particle size of the fine β-silicon carbide powder is 0.5-2.5 μm, and the particle size of the silicon powder is 3-8 μm, and the preparation method comprises the following steps: S1, the coarse and fine β-SiC powder with different particle sizes is proportionally weighed and graded, and a certain amount of silicon powder, dispersant, binder and 10-30 wt.% ethanol aqueous solution are added, mixed in a ceramic ball mill tank to obtain raw materials; the grading of the coarse β-silicon carbide powder and the fine β-silicon carbide powder is (8:2) to (9.5:0.5); the dispersant is polyacrylic acid, and the binder is polyvinylpyrrolidone; S2, the raw material is dried to obtain a mixture for tabletting; S3, a certain amount of the mixture is weighed in the tablet press mold, and is formed under certain pressure conditions; the formed silicon carbide porous ceramic body is degassed in a certain temperature and nitrogen atmosphere; the degassing system of the silicon carbide porous ceramic body is heated to 550-850℃ at 5-10℃ / min under nitrogen atmosphere, and is treated at this temperature for 40-60 min; S4, the degassed silicon carbide porous ceramic body is wrapped with graphite paper and placed in a hot-pressing sintering furnace for sintering in an inert atmosphere, and the silicon carbide porous ceramic is obtained after annealing; the sintering system of the silicon carbide porous ceramic body is heated to 1300-1500℃ at 5-10℃ / min under high-purity argon atmosphere and is kept for 60-100 min, and then is heated to 1900-2200℃ at 5-10℃ / min and is kept for 60-100 min.
2. The production method according to claim 1, wherein In step S2, the drying process is rotary evaporation drying at 85-95℃ for 2-4h, and then drying in a blast drying oven at 60-75℃ for 2-4h.
3. The production method according to claim 2, wherein In step S3, the tabletting process is constant pressure for 2 min under a pressure of 3-5 MPa.
4. A silicon carbide porous ceramic prepared by the preparation method of any one of claims 1-3.
5. The porous silicon carbide ceramic of claim 4, wherein, The average pore size of the silicon carbide porous ceramic is 3-6 μm.