Alumina porous ceramics with multi-level pore structure and preparation method thereof

Abstract

The invention discloses an alumina porous ceramic with a multi-level pore structure and a preparation method thereof. The method comprises the following steps: mixing ρ-Al2O3 powder, a sintering aid, a catalyst, a pore-forming agent and a solvent, stirring until uniform, and obtaining a ceramic slurry, wherein, in parts by mass, the ratio of the ρ-Al2O3 powder to the catalyst is (7-9):(1-3), the mass of the pore-forming agent is 10-30wt% of the mass of the ρ-Al2O3 powder, the mass of the sintering aid is 1-3wt% of the mass of the ρ-Al2O3 powder, and the mass sum of the crystal water contained in the solvent and the catalyst is the same as the mass sum of the ρ-Al2O3 powder and the catalyst; injecting the ceramic slurry into a mold for solidification, drying, demoulding, and baking to obtain a green body, and sintering the green body at 1000-1300°C for 1-2h to obtain the alumina porous ceramic with a multi-level pore structure. The present invention uses a frame constructed of alumina wafers as a matrix, and silica-based hollow glass microspheres as pore-forming agents uniformly distributed in the alumina matrix to form alumina porous ceramics with a multi-level pore structure, which has good high-temperature resistance, excellent mechanical properties and high porosity.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous ceramics, and in particular relates to an alumina porous ceramic with a multi-level pore structure and a preparation method thereof. Background Art

[0002] Porous ceramic materials have good high temperature resistance, chemical corrosion resistance and mechanical properties. Porous ceramics with through-hole structures can be used in fields such as catalyst loading and fluid filtration due to their high porosity, low density and high specific surface area. Corundum-phase alumina porous ceramics are a commonly used porous ceramic material. Among them, the porous ceramics composed of corundum-phase alumina hexagonal wafers grown and interlocked through a gas phase reaction process have good through-hole structure and stress buffering capacity, but their compressive strength still needs to be improved. The improvement of the compressive strength of porous ceramic materials is often accompanied by a decrease in porosity, which in turn affects the application value of the material in catalyst loading and fluid filtration. Therefore, the improvement of the compressive strength of alumina porous ceramic materials with wafer interlocking structure under the premise of maintaining a high porosity is conducive to improving the application potential of the material. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an alumina porous ceramic with a multi-level pore structure, which has good physical and chemical stability, high porosity, and excellent mechanical properties, and can be used as a catalyst loading material and fluid filtration material.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned alumina porous ceramics with a multi-level pore structure. The preparation method uses alumina porous ceramics with a chip interlocking structure as a matrix, and assists in forming a multi-level pore structure inside the matrix by adding a pore-forming agent, thereby obtaining a higher porosity of the alumina porous ceramics while improving its mechanical properties.

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

[0006] A method for preparing a porous alumina ceramic having a multi-level pore structure comprises the following steps:

[0007] Step 1: mixing ρ-Al2O3 powder, a sintering aid, a catalyst, a pore-forming agent, and a solvent, and stirring until uniform to obtain a ceramic slurry, wherein, by weight, the ratio of the ρ-Al2O3 powder to the catalyst is (7-9):(1-3), the mass of the pore-forming agent is 10-30wt% of the mass of the ρ-Al2O3 powder, the mass of the sintering aid is 1-3wt% of the mass of the ρ-Al2O3 powder, and the mass of the crystallization water contained in the solvent and the catalyst is the same as the mass of the ρ-Al2O3 powder and the catalyst;

[0008] In step 1, the sintering aid is cerium oxide.

[0009] In step 1, the catalyst is aluminum fluoride (AlF3·3H2O).

[0010] In step 1, the pore-forming agent is silica-based hollow glass microspheres.

[0011] In step 1, the solvent is water.

[0012] In step 1, the ρ-Al2O3 powder, sintering aid and catalyst are ball-milled and sieved separately before mixing.

[0013] In step 1, the sieving mesh number is 80 to 100 meshes.

[0014] In step 1, the ball milling is dry ball milling, the rotation speed of the ball milling is 250-260 r / min, and the ball milling time is 13-17 h.

[0015] In step 1, the stirring speed is 470-520 r / min, and the stirring time is 4-6 min.

[0016] Step 2: injecting the ceramic slurry into a mold for solidification, drying, demoulding, and baking to obtain a green body, and sintering the green body at 1000-1300° C. for 1-2 hours to obtain an alumina porous ceramic with a multi-level pore structure.

[0017] In step 2, the drying temperature is 27-35° C., and the drying time is 20-24 hours.

[0018] In step 2, the drying temperature is 40-50° C., and the drying time is 4-6 hours.

[0019] In step 2, the heating rate to 1000-1300° C. is 1-3° C. / min.

[0020] The alumina porous ceramics with a multi-level pore structure obtained by the above preparation method have a porosity of 75-80% and a compressive strength of 12-20 MPa.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses a frame constructed of flaky interlocking alumina wafers as a matrix, and silica-based hollow glass microspheres as pore-forming agents uniformly distributed in the alumina matrix to form an alumina porous ceramic with a multi-level pore structure. The ceramic has good high-temperature resistance, excellent mechanical properties and high porosity, and can be used as a catalyst loading material or fluid filtration material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the microstructure of the porous alumina ceramic prepared in Example 1, where 1 is the alumina wafer and 2 is the pore formed by the pore-forming agent;

[0024] Figure 2 This is a scanning electron microscope morphology image of the alumina porous ceramic prepared in Example 2;

[0025] Figure 3 The XRD patterns of the alumina porous ceramics prepared in Example 1 and Example 2 are shown;

[0026] Figure 4 This is a scanning electron microscope micromorphology image of the alumina porous ceramic prepared in Example 4;

[0027] Figure 5 This is a compression deformation curve of the alumina porous ceramic prepared in Example 3;

[0028] Figure 6 This is a scanning electron microscope microscopic morphology of the alumina porous ceramics prepared in Example 3. DETAILED DESCRIPTION

[0029] ρ-Al2O3 powder was purchased from Chinalco Shandong Aluminum Company, Zibo, Shandong;

[0030] Aluminum fluoride was purchased from Aladdin;

[0031] Silica-based hollow glass microspheres were purchased from 3M Company, USA, model number k46;

[0032] Cerium oxide was purchased from Shandong Desheng New Materials Co., Ltd.;

[0033] The model of the XRD test instrument is: ARL Equinox 3000, France;

[0034] The model of the SEM testing instrument is: FEI Verios 460L, Germany;

[0035] The model of the compressive strength testing instrument is: electronic universal testing machine.

[0036] In the following examples, water is deionized water.

[0037] The preparation method of the present invention adopts a water-based gel injection molding method and adds a pore-forming agent (silica-based hollow glass microspheres are used as the pore-forming agent). ρ-Al2O3 powder, a sintering aid, a catalyst, a solvent and the pore-forming agent are uniformly mixed by magnetic stirring to obtain a ceramic slurry. The obtained ceramic slurry is injection molded, cured and dried to obtain a green body. The green body is calcined at a high temperature to finally form an alumina porous ceramic with a multi-level pore structure.

[0038] The technical solution of the present invention is further described below with reference to specific embodiments.

[0039] Example 1

[0040] A method for preparing a porous alumina ceramic having a multi-level pore structure comprises the following steps:

[0041] Step 1, the ρ-Al2O3 powder, sintering aid and catalyst are respectively ball-milled (dry ball milling) at a speed of 260r / min for 15h, sieved, the mesh size is 80 mesh, the sieved ρ-Al2O3 powder, sintering aid and catalyst are mixed with a pore-forming agent and a solvent, and magnetically stirred at a speed of 500r / min for 5min until uniform to obtain a ceramic slurry, wherein, by mass, the ratio of ρ-Al2O3 powder to catalyst is 7:3, the mass of the pore-forming agent is 10wt% of the mass of the ρ-Al2O3 powder, the sintering aid is 3wt% of the mass of the ρ-Al2O3 powder, the sum of the mass of the crystallization water contained in the solvent and the catalyst is equal to the sum of the mass of the ρ-Al2O3 powder and the catalyst, wherein the sintering aid is cerium oxide, the catalyst is aluminum fluoride (AlF3·3H2O), the pore-forming agent is silica-based hollow glass microspheres, and the solvent is water;

[0042] Step 2: Use gel injection molding to inject the ceramic slurry into the mold and let it stand for 20 minutes to solidify, then dry it at 28°C for 24 hours, demold it, and dry it at 40°C for 5 hours to obtain a green body. The green body is placed in a high-temperature furnace and heated to 1300°C at a heating rate of 2°C / min and sintered at 1300°C for 2 hours to obtain alumina porous ceramics.

[0043] The X-ray diffraction pattern of the alumina porous ceramic with a multi-level pore structure prepared in Example 1 is as follows: Figure 3 As shown, the corundum aluminum oxide phase can be detected from the X-ray diffraction pattern. Figure 1 This is a scanning electron microscope image of the microstructure of the alumina porous ceramic with a multi-level pore structure prepared in Example 1. Figure 1 In the figure, 1 is an alumina wafer, and 2 is a hole formed by a pore-forming agent. The internal pore structure of the porous alumina ceramic includes pores formed by the interlocking alumina wafers and pores formed by the pore-forming agent.

[0044] The test results show that the alumina porous ceramics with a multi-level pore structure prepared in Example 1 have a porosity of 77.35%, a compressive strength of 12.1 MPa, and a density of 0.75 g / cm 3 , the average pore diameter is 911nm.

[0045] Example 2

[0046] A method for preparing alumina porous ceramics with a multi-level pore structure is basically the same as the "method for preparing alumina porous ceramics with a multi-level pore structure" in Example 1. The only difference is that the mass of the pore-forming agent in this embodiment is 20wt% of the mass of the ρ-Al2O3 powder.

[0047] Figure 2 The scanning electron microscope morphology of the microstructure of the alumina porous ceramic with a multi-level pore structure prepared in Example 2 is shown in FIG. Figure 2 It can be seen that the alumina porous ceramics with a multi-level pore structure are composed of alumina wafers. At the same time, the pores formed by the pore-forming agent can be clearly seen.

[0048] The X-ray diffraction pattern of the alumina porous ceramic prepared in Example 2 is as follows: Figure 3 As shown, the corundum aluminum oxide phase can be detected from the X-ray diffraction pattern.

[0049] The test results show that the alumina porous ceramics with a multi-level pore structure prepared in Example 2 have a porosity of 76.1%, a compressive strength of 19.8 MPa, and a density of 0.85 g / cm 3 , the average pore diameter is 1003nm.

[0050] Example 3

[0051] A method for preparing alumina porous ceramics with a multi-level pore structure is basically the same as the "method for preparing alumina porous ceramics with a multi-level pore structure" in Example 2. The only difference is that the sintering temperature in step 2 of this example is 1100°C.

[0052] Figure 6 This is a scanning electron microscope microscopic morphology image of the alumina porous ceramic with a multi-level pore structure prepared in Example 3. Figure 5 This is the compression deformation curve of the alumina porous ceramic with a multi-level pore structure prepared in Example 3. The curve can be divided into an elastic part and a compaction part. The inflection point of the curve is the compressive strength of the alumina porous ceramic prepared in Example 3.

[0053] The test results show that the alumina porous ceramics with a multi-level pore structure prepared in Example 3 have a porosity of 79.1%, a compressive strength of 14.3 MPa, and a density of 0.58 g / cm 3, the average pore diameter is 903nm.

[0054] Example 4

[0055] A method for preparing alumina porous ceramics with a multi-level pore structure is basically the same as the "method for preparing alumina porous ceramics with a multi-level pore structure" in Example 3. The only difference is that the mass of the pore-forming agent in this embodiment is 30wt% of the mass of the ρ-Al2O3 powder.

[0056] Figure 4 This is a scanning electron microscope microscopic morphology image of the alumina porous ceramic with a multi-level pore structure prepared in Example 4.

[0057] The test results show that the alumina porous ceramics with a multi-level pore structure prepared in Example 4 have a porosity of 78.3%, a compressive strength of 14.7 MPa, and a density of 0.62 g / cm 3 , the average pore diameter is 927nm.

[0058] Comparative Example 1

[0059] A method for preparing a conventional alumina porous ceramic is essentially the same as the method for preparing a porous alumina ceramic with a hierarchical pore structure in Example 1, with the only difference being that no sintering aid or pore-forming agent is added in Comparative Example 1. Tests show that the conventional alumina porous ceramic prepared in Comparative Example 1 has a porosity of 74.9%, a compressive strength of 0.32 MPa, and a density of 0.88 g / cm 3 .

[0060] Comparative Example 2

[0061] A method for preparing a conventional alumina porous ceramic is basically the same as the "method for preparing a conventional alumina porous ceramic" in Comparative Example 1, with the only difference being that the ratio of ρ-Al2O3 powder and catalyst in Comparative Example 2 is 8:2 by mass.

[0062] After testing, the conventional alumina porous ceramics prepared in Comparative Example 2 had a porosity of 71.3%, a compressive strength of 0.27 MPa, and a density of 0.95 g / cm 3 .

[0063] Comparative Example 3

[0064] A method for preparing a conventional alumina porous ceramic is basically the same as the "method for preparing an alumina porous ceramic with a multi-level pore structure" in Example 1, with the only difference being that no pore-forming agent is added in Comparative Example 3.

[0065] The test results show that the porosity of the conventional alumina porous ceramic prepared in Comparative Example 3 is 77.9%, the compressive strength is 1.3 MPa, and the density is 0.87 g / cm 3 .

[0066] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A method for preparing alumina porous ceramics with a multi-level pore structure, characterized in that: The alumina porous ceramic with a hierarchical pore structure uses a framework constructed of flaky interlocking alumina wafers as a matrix, and silica-based hollow glass microspheres are evenly distributed in the matrix as pore-forming agents. The alumina porous ceramic with a hierarchical pore structure has a porosity of 75-80% and a compressive strength of 12-20 MPa. The preparation method of the alumina porous ceramic with a hierarchical pore structure includes the following steps: Step 1: Mixing ρ-Al2O3 powder, a sintering aid, a catalyst, a pore-forming agent and a solvent, and stirring until uniform to obtain a ceramic slurry, wherein, by weight, the ratio of the ρ-Al2O3 powder to the catalyst is (7-9):(1-3), the mass of the pore-forming agent is 10-30wt% of the mass of the ρ-Al2O3 powder, the mass of the sintering aid is 1-3wt% of the mass of the ρ-Al2O3 powder, and the mass of the crystal water contained in the solvent and the catalyst is the same as the mass of the ρ-Al2O3 powder and the catalyst; wherein the sintering aid is cerium oxide, the pore-forming agent is silica-based hollow glass microspheres, the catalyst is aluminum fluoride, and the solvent is water; Step 2: injecting the ceramic slurry into a mold for solidification, drying, demoulding, and baking to obtain a green body, and sintering the green body at 1000-1300° C. for 1-2 hours to obtain an alumina porous ceramic with a multi-level pore structure.

2. The preparation method according to claim 1, characterized in that In step 1, the ρ-Al2O3 powder, sintering aid and catalyst are respectively ball-milled and sieved before mixing, and the sieve mesh number is 80-100 meshes.

3. The preparation method according to claim 2, characterized in that In step 1, the ball milling is dry ball milling, the rotation speed of the ball milling is 250-260 r / min, and the ball milling time is 13-17 h.

4. The preparation method according to claim 1, characterized in that In step 1, the stirring speed is 470-520 r / min, and the stirring time is 4-6 min.

5. The preparation method according to claim 1, characterized in that In step 2, the drying temperature is 27-35° C., and the drying time is 20-24 hours.

6. The preparation method according to claim 1, characterized in that In step 2, the drying temperature is 40-50° C., and the drying time is 4-6 hours.

7. The preparation method according to claim 1, characterized in that In step 2, the heating rate to 1000-1300° C. is 1-3° C. / min.

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