Preparation method of columnar mullite reinforced silicon carbide composite ceramic membrane support and product prepared by preparation method

Abstract

The invention discloses a preparation method of a columnar mullite-reinforced silicon carbide composite ceramic membrane support and a product prepared by the preparation method, silicon carbide powder and aluminum oxide are used as main raw materials, and a sintering aid and a pore forming agent are combined to obtain the silicon carbide composite ceramic membrane support in which columnar mullite crystals are generated in situ at the necks of silicon carbide particles. The preparation method is simple and low in cost, the silicon carbide ceramic membrane support with high porosity, good mechanical strength and water flux and excellent corrosion resistance can be prepared through normal-temperature and normal-pressure sintering, and application and development of a ceramic membrane separation technology are promoted.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic membrane separation, and in particular to a method for preparing a silicon carbide ceramic membrane support and a product obtained therefrom. Background Art

[0002] In recent years, global water shortage and water pollution have become increasingly prominent, posing a serious threat to human health and ecosystems. Traditional water treatment technologies face many challenges in dealing with complex water quality and increasing environmental standards, such as low efficiency, high energy consumption, and secondary pollution. Therefore, it is urgent to explore and develop new water treatment technologies that are efficient, low energy, and environmentally friendly. The importance and advantages of membrane technology in the field of filtration are mainly reflected in improving filtration efficiency, reducing resource consumption, reducing environmental pollution, and promoting sustainable development. Membrane technology plays an increasingly important role in water treatment, food industry, chemical manufacturing, energy industry, environmental remediation and other fields, and has become an important technical means to promote green development and sustainable development. Among them, silicon carbide ceramic membrane, as a new high-performance material, has the potential to replace traditional materials. Compared with other inorganic membrane materials, such as alumina and zirconium oxide, silicon carbide supports have significant advantages in high temperature resistance, high hardness and wear resistance, chemical stability and mechanical strength.

[0003] The reaction sintering method for preparing silicon carbide ceramic membrane supports has significant advantages such as low sintering temperature, simple process, low cost, adjustable pore structure, wide applicability and good environmental protection. These advantages make the reaction sintering method an efficient, economical and environmentally friendly method for preparing silicon carbide ceramic membrane supports. However, in actual preparation, silicon carbide will oxidize during the sintering process, which affects the mechanical strength and chemical stability of the silicon carbide ceramic membrane. How to effectively improve and enhance the comprehensive performance of the silicon carbide ceramic membrane support during the preparation process has a positive role in promoting the application and development of silicon carbide ceramic membranes. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support body, using silicon carbide powder and alumina as the main raw materials, combined with a sintering aid and a pore-forming agent, by in-situ generation of columnar mullite crystals at the neck of silicon carbide particles, thereby enhancing neck bonding, improving the mechanical strength of the support body, and effectively improving comprehensive properties such as water flux and corrosion resistance. Another purpose of the present invention is to provide a product obtained by using the above-mentioned method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support body.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support, comprising the following steps:

[0007] (1) Silicon carbide powder, aluminum oxide, and a sintering aid are used as basic raw materials, and a pore former is used as an auxiliary raw material. The mixture is ball-milled, aged, and dried to obtain a mixed powder; the mass ratio of the silicon carbide powder: aluminum oxide: sintering aid is 78-82: 8-14: 8-12, and the sintering aid is molybdenum trioxide or tungsten trioxide; the amount of the pore former is 8-12wt% of the basic raw material;

[0008] (2) granulating and dry-pressing the mixed powder to obtain a silicon carbide membrane support green body after drying;

[0009] (3) The silicon carbide ceramic membrane support body green body is sintered, and the sintering process is as follows: heating from room temperature to 600-800°C at 2°C / min, keeping the temperature for 90-120min, then heating to 1250-1350°C at 5°C / min, keeping the temperature for 110-140min, and then naturally cooling to room temperature in the furnace to obtain a silicon carbide composite ceramic membrane support body.

[0010] Furthermore, the particle size of the silicon carbide powder of the present invention is D50=25-40 μm; the pore-forming agent is walnut shell powder, and its particle size is D50=30-80 μm.

[0011] Furthermore, the ball milling treatment in step (1) of the present invention is to ball mill for 50 to 70 minutes according to the ratio of material: ball: water = 1: 1 to 2: 1, and then add a polyethylene aqueous solution with a concentration of 1 to 5wt% and ball mill for 20 to 40 minutes, wherein the amount of the polyethylene aqueous solution is 2 to 5wt% of the mixed material; the aging time is 12 to 36 hours. The drying temperature in step (1) and step (2) is 60 to 110°C, and the drying time is 4 to 24 hours.

[0012] The product obtained by the preparation method of the columnar mullite reinforced silicon carbide composite ceramic membrane support body is a product whose physical phases are silicon carbide, silicon dioxide and mullite crystal phases; the ceramic membrane support body uses silicon carbide particles as the skeleton, columnar mullite crystals are formed at the neck bonding part between the silicon carbide particles, and there are slender needle-shaped mullite whiskers on the surface of the silicon carbide particles. The flexural strength of the silicon carbide composite ceramic membrane support body is 32.59-40.51MPa, the porosity is 31.91-39.77%, the average pore size is 1.707-3.521μm, and the water flux is 26140.17-42359.31L·m -2 ·h -1 bar -1 .

[0013] The present invention has the following beneficial effects:

[0014] (1) The present invention uses silicon carbide powder and aluminum oxide as main raw materials, combined with sintering aids and pore-forming agents, to prepare a silicon carbide composite ceramic membrane support body, with silicon carbide particles as the skeleton, and uses aluminum oxide as the aluminum source, silicon dioxide generated by silicon carbide under oxidizing conditions as the silicon source, and molybdenum trioxide or tungsten trioxide as the sintering aid. Under the action of, mullite crystals are formed at high temperature, not only slender needle-shaped mullite whiskers are formed on the surface of the silicon carbide particles, but also columnar mullite crystals are formed on the neck of the silicon carbide particles, interspersed in the middle of the neck, and improve the overall mechanical strength of the support body like a bridge. At the same time, mullite itself also has good chemical stability, so the silicon carbide ceramic membrane support body prepared by the present invention has good corrosion resistance.

[0015] (2) The preparation method of the present invention is simple and low-cost. A silicon carbide composite ceramic membrane support having high porosity, good mechanical strength and water flux, and excellent corrosion resistance can be prepared by sintering at room temperature and pressure, which is conducive to promoting the application and development of ceramic membrane separation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings:

[0017] Figure 1 is the XRD spectrum of the silicon carbide ceramic membrane support prepared in the embodiment of the present invention;

[0018] Figure 2 The SEM images of the silicon carbide ceramic membrane support bodies prepared in Example 1 and Example 2 of the present invention (a: Example 1; b: Example 2);

[0019] Figure 3 Graph showing the pore size distribution of the silicon carbide ceramic membrane support prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] Embodiment 1:

[0021] This embodiment provides a method for preparing a columnar mullite reinforced silicon carbide ceramic membrane support, and the steps are as follows:

[0022] (1) Silicon carbide powder, alumina, and molybdenum trioxide as a sintering aid are used as basic raw materials, and walnut shell powder as a pore-forming agent is used as an auxiliary raw material. The mass ratio of silicon carbide powder: alumina: sintering aid is 78:14:8, and the amount of the pore-forming agent is 8wt% of the basic raw material. The mixture is ball-milled at a speed of 516 r / min for 50 minutes according to the ratio of material: ball: water = 1:1:1, and then a 5% polyethylene aqueous solution (the amount is 2wt% of the mixture) is added, and the ball milling is continued for 40 minutes. The obtained mixed slurry is aged for 12 hours and then dried at 80°C for 12 hours to obtain a mixed powder;

[0023] (2) granulating the mixed powder, dry pressing the mixed powder under a pressure of 12 MPa, and drying the mixed powder at 60° C. for 10 h to obtain a green body of a silicon carbide membrane support having a certain strength;

[0024] (3) The green body of the silicon carbide ceramic membrane support is sintered. The sintering process is as follows: heating from room temperature to 800°C at 2°C / min, keeping the temperature for 90 min, then heating to 1250°C at 5°C / min, keeping the temperature for 140 min, and then naturally cooling to room temperature in the furnace to obtain a silicon carbide composite ceramic membrane support.

[0025] Embodiment 2:

[0026] This embodiment provides a method for preparing a columnar mullite reinforced silicon carbide ceramic membrane support, and the steps are as follows:

[0027] (1) Silicon carbide powder, alumina, and tungsten trioxide as a sintering aid are used as the basic raw materials, and walnut shell powder as a pore-forming agent is used as the auxiliary raw material. The mass ratio of silicon carbide powder: alumina: sintering aid is 80:10:10, and the amount of the pore-forming agent is 10wt% of the basic raw material. The obtained mixture is ball-milled at a speed of 516 r / min for 60 minutes according to the ratio of material: ball: water = 1:1.5:1, and then a 1% polyethylene aqueous solution (the amount is 5wt% of the mixture) is added and the ball milling is continued for 30 minutes. The obtained mixed slurry is aged for 24 hours and then dried at 60°C for 24 hours to obtain a mixed powder;

[0028] (2) granulating the mixed powder, dry pressing the mixed powder under a pressure of 12 MPa, and drying the mixed powder at 80° C. for 8 h to obtain a green body of a silicon carbide membrane support having a certain strength;

[0029] (3) The green body of the silicon carbide ceramic membrane support is sintered. The sintering process is as follows: heating from room temperature to 600°C at 2°C / min, keeping the temperature for 120 min, then heating to 1350°C at 5°C / min, keeping the temperature for 110 min, and then naturally cooling to room temperature in the furnace to obtain a silicon carbide composite ceramic membrane support.

[0030] Embodiment three:

[0031] This embodiment provides a method for preparing a columnar mullite reinforced silicon carbide ceramic membrane support, and the steps are as follows:

[0032] (1) Silicon carbide powder, alumina, and tungsten trioxide as a sintering aid are used as the basic raw materials, and walnut shell powder as a pore-forming agent is used as the auxiliary raw material. The mass ratio of silicon carbide powder: alumina: sintering aid is 82:8:12, and the amount of the pore-forming agent is 12wt% of the basic raw material. The mixed material is ball-milled at a speed of 516 r / min for 70 minutes according to the mass ratio of material: ball: water = 1:2:1, and then a 3% polyethylene aqueous solution (the amount is 3wt% of the mixed material) is added and the ball milling is continued for 20 minutes. The obtained mixed slurry is aged for 36 hours and then dried at 110°C for 4 hours to obtain a mixed powder;

[0033] (2) granulating the mixed powder, dry pressing the mixed powder under a pressure of 12 MPa, and drying the mixed powder at 110° C. for 4 h to obtain a green body of a silicon carbide membrane support having a certain strength;

[0034] (3) The green body of the silicon carbide ceramic membrane support is sintered. The sintering process is as follows: heating from room temperature to 700°C at 2°C / min, keeping the temperature for 100 min, then heating to 1300°C at 5°C / min, keeping the temperature for 130 min, and then naturally cooling to room temperature in the furnace to obtain a silicon carbide composite ceramic membrane support.

[0035] The comparative example is that no sintering aid is added in Example 1 and other conditions are the same as those in Example 1. The performance indicators of the silicon carbide composite ceramic membrane support prepared in the example of the present invention and the ceramic membrane support prepared in the comparative example are shown in Table 1.

[0036] Table 1 Performance indicators of the silicon carbide composite ceramic membrane support prepared in the embodiment of the present invention

[0037]

[0038] *Acid solution corrosion: Test the flexural strength of the material after corrosion in 20% sulfuric acid solution at 90℃ for 1h.

[0039] *Alkaline solution corrosion: Test the flexural strength of the material after corrosion in 1% sodium hydroxide solution at 90℃ for 1h.

[0040] The silicon carbide composite ceramic membrane support prepared in the embodiment of the present invention is as follows Figure 1 As shown in FIG. 1 , the support body has three crystal phases: silicon carbide, silicon dioxide and mullite. Figure 2As shown, silicon carbide is the matrix of the support body, and silicon dioxide is the oxidation product of silicon carbide. On the basis of this product, it reacts with alumina and sintering aids to generate columnar mullite crystals at the neck bonding between silicon carbide particles, and mullite whiskers are formed on the surface of silicon carbide particles; the average pore size of the ceramic membrane support body is 2.417μm (see Figure 3 ). Compared with the comparative example, at the same sintering temperature, the effective connection of the mullite crystals at the neck of the silicon carbide particles in Example 1 improves the mechanical properties of the support body by about 3 times.

Claims

1. A method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support, characterized in that The following steps are involved: (1) Silicon carbide powder, aluminum oxide, and a sintering aid are used as basic raw materials, and a pore former is used as an auxiliary raw material. The mixture is ball-milled, aged, and dried to obtain a mixed powder; the mass ratio of the silicon carbide powder: aluminum oxide: sintering aid is 78-82: 8-14: 8-12, and the sintering aid is molybdenum trioxide or tungsten trioxide; the amount of the pore former is 8-12wt% of the basic raw material; (2) granulating and dry-pressing the mixed powder to obtain a silicon carbide membrane support green body after drying; (3) The silicon carbide ceramic membrane support body green body is sintered, and the sintering process is as follows: heating from room temperature to 600-800°C at 2°C / min, keeping the temperature for 90-120min, then heating to 1250-1350°C at 5°C / min, keeping the temperature for 110-140min, and then naturally cooling to room temperature in the furnace to obtain a silicon carbide composite ceramic membrane support body.

2. The method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support according to claim 1, characterized in that: The particle size of the silicon carbide powder is D50=25-40 μm; the pore-forming agent is walnut shell powder, and its particle size is D50=30-80 μm.

3. The method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support according to claim 1, characterized in that: The ball milling treatment in the step (1) is to perform ball milling for 50 to 70 minutes according to the ratio of material: ball: water = 1: 1 to 2: 1, and then add a polyethylene aqueous solution with a concentration of 1 to 5 wt% and mix for 20 to 40 minutes. The amount of the polyethylene aqueous solution is 2 to 5 wt% of the mixed material; the aging time is 12 to 36 hours.

4. The method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support according to claim 1, characterized in that: In the steps (1) and (2), the drying temperature is 60 to 110° C. and the drying time is 4 to 24 hours.

5. A product obtained by the method for preparing a columnar mullite reinforced silicon carbide composite ceramic membrane support according to any one of claims 1 to 4, characterized in that: The physical phases of the silicon carbide composite ceramic membrane support are silicon carbide, silicon dioxide and mullite crystal phases; the ceramic membrane support uses silicon carbide particles as a skeleton, columnar mullite crystals are located at the neck bonding points between the silicon carbide particles, and there are slender needle-shaped mullite whiskers on the surface of the silicon carbide particles.

6. The product according to claim 5, characterized in that: The silicon carbide composite ceramic membrane support has a flexural strength of 32.59-40.51 MPa, a porosity of 31.91-39.77%, an average pore size of 1.707-3.521 μm, and a water flux of 26140.17-42359.31 L·m -2 ·h -1 bar -1 .

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