Alumina ceramic composite material and preparation method thereof

Abstract

The invention discloses an aluminum oxide ceramic composite material and a preparation method thereof, and belongs to the technical field of ceramic materials. The ceramic material is prepared from the following raw materials in parts by weight: 25-40 parts of nano aluminum oxide, 30-45 parts of micron aluminum oxide, 15-20 parts of silicon carbide whiskers, 1.5-3 parts of graphene and 5-7 parts of a sintering aid. The nano aluminum oxide can fill particle gaps of the micron aluminum oxide and improve compactness and hardness, the silicon carbide whiskers are added to improve the toughness of the ceramic material, microwave sintering and hot pressing sintering are combined for application, energy consumption is greatly reduced, grains are refined, the ceramic material has wide application prospects in practice, the preparation method is simple, and the preparation method is suitable for industrial production. And large-scale industrial production can be carried out.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and particularly relates to an alumina ceramic composite material and a preparation method thereof. Background Art

[0002] As a typical structural ceramic material, alumina ceramics have been widely used in the fields of mechanical seals, cutting tools, wear-resistant components, etc. due to their high hardness, high temperature resistance, corrosion resistance and other characteristics. However, the fracture toughness of traditional alumina ceramics is relatively low (usually <4 MPa·m1 / 2), with high brittleness and poor thermal shock resistance, which limits their service life under complex working conditions. Especially in high-load or impact environments, the material is prone to fracture failure due to crack propagation. In addition, the sintering temperature of pure alumina ceramics usually needs to reach above 1600 °C, resulting in high energy consumption and grain coarsening (average size >5 μm), further weakening its mechanical properties.

[0003] In order to improve the comprehensive properties of alumina ceramics, existing technologies mostly adopt strategies such as adding reinforcing phases (such as silicon carbide whiskers, nanoparticles, etc.) or optimizing the sintering process. However, nano-reinforcing phases are prone to agglomeration due to their large specific surface area, resulting in uneven dispersion; although micron-sized reinforcing phases can alleviate the agglomeration problem, the improvement of toughness is limited. At the same time, conventional sintering processes (such as atmospheric pressure sintering, single hot pressing sintering) are difficult to achieve grain refinement and directional arrangement of reinforcing phases while reducing energy consumption, resulting in difficulty in synergistically improving the density and strength-toughness of the material. Therefore, developing a preparation method that can achieve efficient dispersion of multi-scale reinforcing phases, high density and low energy consumption has become an urgent technical problem to be solved in the field of alumina-based composites. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an alumina ceramic composite material with good density, high flexural strength and good fracture toughness; another technical problem to be solved by the present invention is to provide a preparation method for an alumina ceramic composite material, which uses the combined application of microwave sintering and hot pressing sintering, greatly reduces energy consumption and refines grains, and the preparation method is simple, environmentally friendly and suitable for large-scale production.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] An alumina ceramic composite material is made from the following raw materials in parts by weight: 25-40 parts of nano-alumina, 30-45 parts of micro-alumina, 15-20 parts of silicon carbide whiskers, 1.5-3 parts of graphene, and 5-7 parts of sintering aids.

[0007] Further, the particle size of the nano-alumina is 50-80 nm, the particle size of the micro-alumina is 1-3 μm, and the particle size of the silicon carbide whiskers is 0.2-0.5 μm.

[0008] Further, the sintering aid is a Y2O3-MgO-SiO2 composite additive.

[0009] Further, the molar ratio of Y2O3, MgO and SiO2 in the Y2O3-MgO-SiO2 composite additive is 1:1:2.

[0010] Further, the preparation method of the Y2O3-MgO-SiO2 composite additive comprises the following steps:

[0011] (1) Dissolve yttrium nitrate hexahydrate and magnesium nitrate hexahydrate in ethanol, stir until completely dissolved; add TEOS, and dropwise add ammonia water to adjust the pH to 3-4;

[0012] (2) Add citric acid, and stir at a constant temperature of 60 °C for 2-4 h to form a transparent sol;

[0013] (3) Age the sol at 80 °C for 24 h to form a wet gel; then dry it in an oven at 120 °C for 12 h to obtain a dry gel; grind the dry gel into a powder;

[0014] (4) Calcinate the powder in a muffle furnace to obtain the Y2O3-MgO-SiO2 composite additive.

[0015] Further, the preparation method of the alumina ceramic composite material comprises the following steps:

[0016] (1) Place nano-alumina, micro-alumina, silicon carbide whiskers, graphene and a sintering aid in ethanol, ball mill and then spray granulate;

[0017] (2) Compress the granulated material by cold isostatic pressing to obtain a green body;

[0018] (3) First, microwave sinter the green body, then hot press sinter it, and finally air cool it to room temperature to obtain the product.

[0019] Further, in the step (1), the ball milling medium is zirconia ceramic balls, the ball milling speed is 300 rpm, and the ball milling time is 8-12 h; during spray granulation, the inlet temperature of the spray tower is 200 °C and the outlet temperature is 80 °C.

[0020] Further, in the step (2), the cold isostatic pressure is 200-300 MPa.

[0021] Further, in the step (3), the microwave sintering temperature is 1200-1300 °C, the heating rate is 30 °C / min, and the holding time is 30 min.

[0022] Further, in the step 3), the hot pressing sintering temperature is 1400 - 1600 °C, the pressure is 30 - 45 MPa, the heat preservation time is 1 - 2 h, and the vacuum degree ≤ 10 -2 Pa.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The present invention uses nano-aluminum oxide and micro-aluminum oxide to overcome the brittle defect of traditional aluminum oxide. Moreover, the nano-aluminum oxide can fill the particle gaps of the micro-aluminum oxide to improve the densification and hardness. Adding silicon carbide whiskers can improve the toughness of the ceramic material. Adding graphene can utilize its two-dimensional sheet structure to disperse stress and inhibit crack propagation, and can further improve the fracture toughness of the material.

[0025] (2) The present invention combines microwave sintering and hot pressing sintering, which greatly reduces energy consumption and refines grains. In the microwave sintering stage, the rapid heating characteristic is utilized to activate the surface of nano-particles to achieve densification; in the hot pressing sintering stage, residual pores can be eliminated, energy consumption can be reduced, and the vacuum environment can effectively inhibit abnormal grain growth and avoid coarsening.

[0026] (3) The preparation method of the present invention is simple, low in cost, environmentally friendly and suitable for large-scale production. Specific Embodiments

[0027] The following specific embodiments are used to further clarify the present invention. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0028] Unless otherwise specified, the materials used in the following embodiments are all commercially available products.

[0029] In the following embodiments, the particle size of nano-aluminum oxide is 50 - 80 nm, the particle size of micro-aluminum oxide is 1 - 3 μm, and the particle size of silicon carbide whiskers is 0.2 - 0.5 μm.

[0030] Example 1

[0031] The preparation method of Y2O3-MgO-SiO2 composite additive includes the following steps:

[0032] (1) Dissolve 40.9 g of yttrium nitrate hexahydrate and 7.3 g of magnesium nitrate hexahydrate in 200 mL of ethanol, stir until completely dissolved; add 21.8 g of TEOS, and dropwise add ammonia water to adjust the pH to 3 - 4.

[0033] (2) Add 10.5 g of citric acid, stir at a constant temperature of 60 °C for 3 h to form a transparent sol;

[0034] (3) The sol is aged at 80 °C for 24 h to form a wet gel; then it is dried in an oven at 120 °C for 12 h to obtain a dry gel; the dry gel is ground into a powder;

[0035] (4) The powder is calcined in a muffle furnace at 800 °C for 3 h to obtain the Y2O3-MgO-SiO2 composite additive.

[0036] Example 2

[0037] A preparation method of an alumina ceramic composite material, comprising the following steps:

[0038] (1) 35 parts of nano-alumina, 30 parts of micro-alumina, 20 parts of silicon carbide whiskers, 3 parts of graphene and 7 parts of Y2O3-MgO-SiO2 are placed in a ball mill, and 500 mL of ethanol is taken. 475 parts of zirconia ceramic balls are added to the ball mill and ball milled at a rotation speed of 300 rpm for 12 h; spray granulation is carried out, the inlet air temperature of the spray granulation tower is set at 200 °C, and the outlet temperature is set at 80 °C. The particle size of the spray granulation material is 80 - 150 μm;

[0039] (2) The granulated material is cold isostatically pressed into a green body under a pressure of 250 MPa.

[0040] (3) The green body is first microwave sintered, heated to 1250 °C at a heating rate of 30 °C / min in a nitrogen atmosphere and held for 30 min; then hot press sintered, under vacuum conditions (≤10 -2 Pa), heated to 1450 °C at a pressure of 45 MPa at a heating rate of 10 °C / min and held for 1.5 h, and finally air-cooled to room temperature to obtain the alumina ceramic composite material.

[0041] Example 3

[0042] A preparation method of an alumina ceramic composite material, comprising the following steps:

[0043] (1) 40 parts of nano-alumina, 35 parts of micro-alumina, 15 parts of silicon carbide whiskers, 3 parts of graphene and 7 parts of Y2O3-MgO-SiO2 are placed in a ball mill, and 500 mL of ethanol is taken. 500 parts of zirconia ceramic balls are added to the ball mill and ball milled at a rotation speed of 300 rpm for 8 h; spray granulation is carried out, the inlet air temperature of the spray granulation tower is set at 200 °C, and the outlet temperature is set at 80 °C. The particle size of the spray granulation material is 80 - 150 μm;

[0044] (2) The granulated material is cold isostatically pressed into a green body under a pressure of 250 MPa.

[0045] (3) First, microwave sinter the green body. Under a nitrogen atmosphere, heat it to 1250 °C at a heating rate of 30 °C / min and hold for 40 min. Then, perform hot-press sintering. Under vacuum conditions (≤10 -2 Pa), heat it to 1450 °C at a pressure of 40 MPa and a heating rate of 10 °C / min, hold for 1.5 h, and finally air-cool to room temperature to obtain the alumina ceramic composite.

[0046] Example 4

[0047] A method for preparing an alumina ceramic composite, comprising the following steps:

[0048] (1) Place 25 parts of nano-alumina, 45 parts of micro-alumina, 15 parts of silicon carbide whiskers, 1.5 parts of graphene, and 7 parts of Y2O3-MgO-SiO2 in a ball mill. Take 500 mL of ethanol, 467.5 parts of zirconia ceramic balls, add them to the ball mill, and ball mill for 10 h at a rotation speed of 300 rpm; perform spray granulation. Set the inlet temperature of the spray granulation tower to 200 °C and the outlet temperature to 80 °C. The particle size of the spray granulation material is 80 - 150 μm;

[0049] (2) Perform cold isostatic pressing on the granulated material at a pressure of 250 MPa to obtain a green body;

[0050] (3) First, microwave sinter the green body. Under a nitrogen atmosphere, heat it to 1280 °C at a heating rate of 30 °C / min and hold for 30 min. Then, perform hot-press sintering. Under vacuum conditions (≤10 -2 Pa), heat it to 1450 °C at a pressure of 40 MPa and a heating rate of 10 °C / min, hold for 1.5 h, and finally air-cool to room temperature to obtain the alumina ceramic composite.

[0051] Example 5

[0052] A method for preparing an alumina ceramic composite, comprising the following steps:

[0053] (1) Place 42 parts of nano-alumina, 37 parts of micro-alumina, 15 parts of silicon carbide whiskers, 3 parts of graphene, and 5 parts of Y2O3-MgO-SiO2 in a ball mill. Take 500 mL of ethanol, 510 parts of zirconia ceramic balls, add them to the ball mill, and ball mill for 12 h at a rotation speed of 300 rpm; perform spray granulation. Set the inlet temperature of the spray granulation tower to 200 °C and the outlet temperature to 80 °C. The particle size of the spray granulation material is 80 - 150 μm;

[0054] (2) Perform cold isostatic pressing on the granulated material at a pressure of 250 MPa to obtain a green body;

[0055] (3) First, microwave sinter the green body. Under a nitrogen atmosphere, heat it at a heating rate of 30 °C / min to 1250 °C and hold for 30 min. Then, perform hot pressing sintering. Under vacuum conditions (≤10 -2 Pa), heat it at a pressure of 40 MPa and a heating rate of 10 °C / min to 1480 °C, hold for 1.5 h, and finally air cool to room temperature to obtain the alumina ceramic composite material.

[0056] Example 6

[0057] A preparation method of an alumina ceramic composite material includes the following steps:

[0058] (1) Place 40 parts of nano-alumina, 35 parts of micro-alumina, 15 parts of silicon carbide whiskers, 3 parts of graphene, and 7 parts of Y2O3-MgO-SiO2 in a ball mill. Take 500 mL of ethanol, 500 parts of zirconia ceramic balls, add them to the ball mill, and ball mill at a rotation speed of 300 rpm for 10 h. Perform spray granulation. Set the inlet air temperature of the spray granulation tower to 200 °C and the outlet temperature to 80 °C. The particle diameter of the spray granulation material is 80 - 150 μm;

[0059] (2) Cold isostatically press the granulated material at a pressure of 250 MPa to obtain a green body;

[0060] (3) First, microwave sinter the green body. Under a nitrogen atmosphere, heat it at a heating rate of 30 °C / min to 1250 °C and hold for 30 min. Then, perform hot pressing sintering. Under vacuum conditions (≤10 -2 Pa), heat it at a pressure of 30 MPa and a heating rate of 10 °C / min to 1450 °C, hold for 2 h, and finally air cool to room temperature to obtain the alumina ceramic composite material.

[0061] Comparative Example 1

[0062] A preparation method of an alumina ceramic composite material includes the following steps:

[0063] (1) Place 40 parts of nano-alumina, 35 parts of micro-alumina, 15 parts of silicon carbide whiskers, and 7 parts of Y2O3-MgO-SiO2 in a ball mill. Take 500 mL of ethanol, 485 parts of zirconia ceramic balls, add them to the ball mill, and ball mill at a rotation speed of 300 rpm for 10 h. Perform spray granulation. Set the inlet air temperature of the spray granulation tower to 200 °C and the outlet temperature to 80 °C. The particle diameter of the spray granulation material is 80 - 150 μm;

[0064] (2) Cold isostatically press the granulated material at a pressure of 250 MPa to obtain a green body;

[0065] (3) First, microwave sinter the green body. Heat it to 1250 °C at a heating rate of 30 °C / min in a nitrogen atmosphere and hold for 40 min. Then, perform hot pressing sintering. Under vacuum conditions (≤10 -2 Pa), heat it to 1450 °C at a pressure of 40 MPa and a heating rate of 10 °C / min, hold for 1.5 h, and finally air cool to room temperature to obtain the alumina ceramic composite material.

[0066] Comparative Example 2

[0067] A preparation method of an alumina ceramic composite material includes the following steps:

[0068] (1) Place 40 parts of nano-alumina, 35 parts of micro-alumina, 15 parts of silicon carbide whiskers, 3 parts of graphene, and 7 parts of Y2O3-MgO-SiO2 in a ball mill. Take 500 mL of ethanol, 500 parts of zirconia ceramic balls, add them to the ball mill, and ball mill for 10 h at a rotation speed of 300 rpm. Perform spray granulation. Set the inlet air temperature of the spray granulation tower to 200 °C and the outlet temperature to 80 °C. The particle size of the spray granulation material is 80 - 150 μm;

[0069] (2) Cold isostatically press the granulated material. The pressure of cold isostatic pressing is 250 MPa to obtain a green body;

[0070] (3) Hot press sinter the green body. Heat it to 1600 °C at a heating rate of 5 °C / min, hold for 2 h, and finally air cool to room temperature to obtain the alumina ceramic composite material.

[0071] Perform performance tests on Examples 2 - 6 and Comparative Examples 1 - 2. The test results are shown in Table 1 below.

[0072] Table 1 Results of various performance parameters of the alumina ceramic composite materials prepared in Examples 2 - 6 and Comparative Examples 1 - 2

[0073]

[0074] As can be seen from Table 1, the main application properties of the alumina ceramic composite materials prepared in Examples 2 - 6 of this application, namely flexural strength, fracture toughness, density, and Vickers hardness, are all superior to those of Comparative Examples 1 - 2, indicating that the alumina ceramic composite material has good flexural strength, fracture toughness, density, and Vickers hardness.

[0075] Comparing Example 3 with Comparative Example 1, it can be seen that after adding graphene, the density and fracture toughness of the ceramic composite material increase, indicating that graphene has a stress dispersion effect; comparing Example 3 with Comparative Example 2, the combined application of microwave sintering and hot press sintering can reduce energy consumption and refine grains, avoiding grain coarsening and pore residue.

[0076] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An alumina ceramic composite material, characterized in that: It is made from the following raw materials in parts by weight: 25-40 parts of nano-aluminum oxide, 30-45 parts of micro-aluminum oxide, 15-20 parts of silicon carbide whiskers, 1.5-3 parts of graphene, and 5-7 parts of sintering aid.

2. The alumina ceramic composite material according to claim 1, characterized in that: The particle size of the nano-aluminum oxide is 50-80 nm, the particle size of the micro-aluminum oxide is 1-3 μm, and the particle size of the silicon carbide whiskers is 0.2-0.5 μm.

3. The alumina ceramic composite material according to claim 1, characterized in that: The sintering aid is a Y2O3-MgO-SiO2 composite additive.

4. The alumina ceramic composite material according to claim 3, characterized in that: In the Y2O3-MgO-SiO2 composite additive, the molar ratio of Y2O3, MgO to SiO2 is 1:1:

2.

5. The alumina ceramic composite material according to claim 3, characterized in that: The preparation method of the Y2O3-MgO-SiO2 composite additive includes the following steps: (1) Dissolve yttrium nitrate hexahydrate and magnesium nitrate hexahydrate in ethanol, stir until completely dissolved; add TEOS, and dropwise add ammonia water to adjust the pH to 3-4; (2) Add citric acid, stir at a constant temperature of 60 °C for 2-4 h to form a transparent sol; (3) Age the sol at 80 °C for 24 h to form a wet gel; then dry it in an oven at 120 °C for 12 h to obtain a dry gel; grind the dry gel into a powder; (4) Place the powder in a muffle furnace for calcination to obtain the Y2O3-MgO-SiO2 composite additive.

6. The preparation method of the alumina ceramic composite material according to any one of claims 1 to 5, characterized in that: It includes the following steps: (1) Place nano-aluminum oxide, micro-aluminum oxide, silicon carbide whiskers, graphene and sintering aid in ethanol, ball mill and then spray granulate; (2) Compress the granulated material by cold isostatic pressing to obtain a green body; (3) First perform microwave sintering on the green body, then perform hot pressing sintering, and finally air-cool to room temperature to obtain the product.

7. The preparation method of the alumina ceramic composite material according to claim 6, characterized in that: In step (1), the ball milling medium is zirconia ceramic balls, the ball milling speed is 300 rpm, and the ball milling time is 8-12 h; during spray granulation, the inlet temperature of the spray tower is 200 °C and the outlet temperature is 80 °C.

8. The preparation method of the alumina ceramic composite material according to claim 6, characterized in that: In step (2), the cold isostatic pressure is 200-300 MPa.

9. The preparation method of the alumina ceramic composite material according to claim 6, characterized in that: In step (3), the microwave sintering temperature is 1200-1300 °C, the heating rate is 30 °C / min, and the holding time is 30 min.

10. The preparation method of the alumina ceramic composite material according to claim 6, wherein: In step 3), the hot pressing sintering temperature is 1400 - 1600 °C, the pressure is 30 - 45 MPa, the heat preservation time is 1 - 2 h, and the vacuum degree ≤ 10 -2 Pa.

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