Alumina ceramic and preparation method thereof

Abstract

The present invention belongs to the technical field of alumina ceramics, and specifically relates to an alumina ceramic and a preparation method thereof. The present invention provides an alumina ceramic, and the preparation raw materials include the following components in mass fractions: 90 to 110 parts of alumina, 1 to 5 parts of rare earth materials, and 5 to 10 parts of fibers. In the present invention, by introducing rare earth elements, the grain boundaries and microstructures can be optimized, which complement the mechanical support network formed by the fibers; at the same time, the addition of rare earth elements can enhance the bonding force between the fibers and the matrix, thereby enhancing the reinforcement effect. Through the synergistic effect of rare earth elements and fibers, the present invention not only has a significant effect on improving the flexural strength and fracture toughness, but also improves the wear resistance, corrosion resistance and high temperature resistance of the material, so that the final alumina ceramic has a wider range of engineering application potential.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina ceramics, and in particular relates to an alumina ceramic and a preparation method thereof. Background Art

[0002] Alumina ceramics are an important engineering ceramic material, which are widely used in various engineering fields due to their excellent wear resistance, corrosion resistance and high temperature stability. However, the flexural strength and fracture toughness of alumina ceramics are relatively low, which limits their application in certain high-strength and high-durability fields. To solve this problem, researchers have conducted a lot of research, trying to improve the flexural strength and fracture toughness of alumina ceramics by changing the preparation method of alumina ceramics or adding other materials.

[0003] The existing solutions are mainly to change the preparation method of alumina ceramics, such as adding different sintering aids, or changing the sintering conditions, to improve the microstructure and mechanical properties of alumina ceramics. In addition, some studies have improved the bending strength and fracture toughness of alumina ceramics by adding other ceramic materials, such as carbon nanotubes and wollastonite.

[0004] Although the existing technology has improved the bending strength and fracture toughness of alumina ceramics to a certain extent, there are still some problems and disadvantages. First, the existing preparation methods often require special equipment or complicated operation processes, which increases the production cost. Secondly, the existing preparation methods can only improve the compressive strength and fracture toughness of alumina ceramics to a certain extent, and cannot meet the application requirements of some high-strength and high-durability fields. Summary of the invention

[0005] The object of the present invention is to provide an alumina ceramic and a preparation method thereof. The alumina ceramic provided by the present invention has higher bending strength and fracture toughness.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an alumina ceramic, the preparation raw materials of which include the following components in parts by mass:

[0008] 90-110 parts of alumina, 1-5 parts of rare earth material, and 5-10 parts of fiber.

[0009] Preferably, the rare earth material includes one or more of yttrium oxide, neodymium oxide and samarium oxide.

[0010] Preferably, the fiber comprises one of silicon carbide fiber, lead titanate fiber and mullite fiber; the aspect ratio of the fiber is 15 to 50, and the diameter is 2 to 8 μm.

[0011] Preferably, the raw materials for preparation further include 3 to 4 parts by weight of a binder;

[0012] The binder includes one or more of paraffin, stearic acid, polyethylene and polypropylene.

[0013] The present invention also provides a method for preparing the alumina ceramics described in the above technical solution, comprising the following steps:

[0014] Alumina, rare earth materials and fibers are mixed and magnetized to obtain a magnetized material;

[0015] The magnetized material is pressed and sintered in sequence to obtain the alumina ceramic.

[0016] Preferably, the mixing method is wet ball milling; the rotation speed of the wet ball milling is 20 to 100 rpm, and the time is 0.5 to 2 hours.

[0017] Preferably, the magnetization conditions include: a magnetic field strength of 10 to 15 T, a gravity field of 1 to 2 G, and a time of 15 to 25 min.

[0018] Preferably, after the magnetization, the obtained slurry is dried at a temperature of 80° C. for 12 hours.

[0019] Preferably, the compression molding pressure is 4-6 MPa, the temperature is 150-180° C., and the molding time is 5-10 s.

[0020] Preferably, the sintering temperature is 1200-1500° C., and the holding time is 2-4 hours.

[0021] The present invention provides an alumina ceramic, and the raw materials for preparing the ceramic include the following components in mass fractions: 90 to 110 parts of alumina, 1 to 5 parts of rare earth materials, and 5 to 10 parts of fibers. In the present invention, by introducing rare earth elements, the grain boundaries and microstructures can be optimized, which complement the mechanical support network formed by the fibers; at the same time, the addition of rare earth elements can enhance the bonding force between the fibers and the matrix, thereby enhancing the reinforcement effect. Through the synergistic effect of rare earth elements and fibers, the present invention not only has a significant effect on improving the bending strength and fracture toughness, but also improves the wear resistance, corrosion resistance and high temperature resistance of the material, so that the final alumina ceramic has a wider range of engineering application potential. DETAILED DESCRIPTION

[0022] The present invention provides an alumina ceramic, the preparation raw materials of which include the following components in parts by mass:

[0023] 90-110 parts of alumina, 1-5 parts of rare earth material, and 5-10 parts of fiber.

[0024] The raw material for preparing the alumina ceramic provided by the present invention comprises 90 to 110 parts by mass of alumina, preferably 95 to 105 parts by mass, and more preferably 100 parts by mass. In the present invention, the purity of the alumina is preferably 99.9%. In the present invention, the particle size of the alumina is preferably 0.5 μm.

[0025] The raw materials for preparing the alumina ceramics provided by the present invention include 1 to 5 parts by mass of rare earth materials, more preferably 2 to 4 parts, and more preferably 3 parts. In the present invention, the rare earth material preferably includes one or more of yttrium oxide, neodymium oxide and samarium oxide. In the present invention, when the rare earth material is two or more of the above-mentioned options, the present invention has no special limitation on the ratio between the raw materials, and any ratio can be used. In the present invention, the purity of the rare earth material is preferably 99.9%.

[0026] In the present invention, by introducing rare earth elements into alumina ceramics, the following advantages are mainly achieved: (1) Crystal structure regulation and enhancement effect: Rare earth elements usually have a small ionic radius and a complex electronic structure. Their introduction can introduce defects or distortions into the alumina crystal structure, thereby improving the stability of the grain boundaries and the control of crystal growth. This regulatory effect helps to form a more dense and uniform crystal structure in the ceramic material, thereby improving the bending strength and fracture toughness. (2) Enhanced grain boundary bonding: The addition of rare earth elements can promote the bonding force of the grain boundaries and reduce the unevenness of the size and distribution of the grains. This is crucial for inhibiting grain boundary sliding and hindering the progress of crack extension to the entire ceramic material, thus helping to improve the bending strength and fracture toughness. (3) Crystal growth control: The addition of rare earth elements can affect the sintering process of alumina ceramics, allowing the crystals to grow more uniformly and form a dense structure during the sintering process. This uniform crystal growth can improve the mechanical properties of the material, including strength and toughness. (4) Modification of particle interfaces: Rare earth elements can introduce chemical modifications on the surface of powder particles to improve the contact and bonding properties between particles. This modification helps to reduce the porosity of the material during hot pressing and sintering, thereby improving the density and mechanical properties of the final ceramic material.

[0027] The raw material for preparing the alumina ceramic provided by the present invention comprises 5 to 10 parts by mass of fiber, more preferably 6 to 9 parts, and more preferably 7 to 8 parts. In the present invention, the fiber preferably comprises one of silicon carbide fiber, lead titanate fiber and mullite fiber; the aspect ratio of the fiber is preferably 15 to 50, and the diameter is preferably 2 to 8 μm.

[0028] In the present invention, the advantages of adding fibers are: (1) Enhanced mechanical support: The main function of fibers is to form a strong mechanical support network in ceramic materials. This network can effectively resist external loads, prevent crack expansion, and slow down the formation and propagation of cracks. In particular, when ceramic materials are subjected to stress, fibers can bear part of the load, thereby reducing stress concentration and improving the bending strength of the material. (2) Increased fracture toughness: The presence of fibers can significantly improve the fracture toughness of ceramic materials, and can keep the material at a high strength even when cracks appear. This is because the distribution of fibers in the material can effectively bridge cracks and prevent them from expanding. Therefore, fibers can delay the fracture process of the material, making it more durable and reliable. (3) Improved thermomechanical properties: The addition of fibers also helps to improve the thermomechanical properties of alumina ceramic materials. Fibers can reduce material damage caused by thermal stress and improve their stability and service life in high temperature environments. (4) As a reinforcing agent, fibers can significantly improve the bending strength and fracture toughness of the material through their strengthening effect and crack blocking effect in the preparation of the above-mentioned alumina ceramic powder, so that the final ceramic material can meet the engineering requirements of high strength and high durability.

[0029] In the present invention, the raw materials for preparation preferably further include 3 to 4 parts by weight of a binder; the binder preferably includes one or more of paraffin, stearic acid, polyethylene and polypropylene.

[0030] The present invention also provides a method for preparing the alumina ceramics described in the above technical solution, comprising the following steps:

[0031] Alumina, rare earth materials and fibers are mixed and magnetized to obtain a magnetized material;

[0032] The magnetized material is pressed and sintered in sequence to obtain the alumina ceramic.

[0033] The invention mixes aluminum oxide, rare earth material and fiber, and obtains magnetized material after magnetization.

[0034] In the present invention, the mixing method is preferably wet ball milling; the medium of the wet ball milling is preferably deionized water. The present invention has no special limitation on the amount of deionized water added, and it can be used as known to those skilled in the art. In the present invention, the rotation speed of the wet ball milling is preferably 20 to 100 rpm, and the time is preferably 0.5 to 2. In the present invention, ball milling can make the fibers evenly dispersed in the slurry, ensuring its uniformity in the entire material.

[0035] In the present invention, when the raw materials for preparation further include a binder, it is preferably added during the mixing process.

[0036] In the present invention, the magnetization conditions include: the magnetic field intensity is preferably 10-15T, more preferably 11-14T, and more preferably 12-13T; the gravity field is preferably 1-2G; the time is preferably 15-25min, and more preferably 18-20min. In the present invention, the magnetization is preferably carried out in a magnetic field generator. In the present invention, magnetization can make the fibers arranged more orderly, further enhancing their effect in the material, and obtaining a composite material with anisotropy in mechanical, thermal and other properties; the magnetic field can indirectly affect the distribution of rare earth materials and the interaction with the fibers, thereby optimizing the comprehensive performance of the material. At the same time, the magnetic field helps to improve the bonding strength between the fibers and the ceramic matrix, which can enhance the bending strength by promoting the fiber bridging effect of the material.

[0037] After the magnetization, the present invention also preferably includes drying the obtained slurry, and the drying temperature is preferably 80° C. and the drying time is preferably 12 hours.

[0038] After obtaining the magnetized material, the present invention sequentially performs compression molding and sintering on the magnetized material to obtain the alumina ceramic.

[0039] In the present invention, the pressing method is preferably hot pressing. In the present invention, the pressing pressure is preferably 4-6 MPa, the temperature is preferably 150-180° C., and the molding time is preferably 5-10 s.

[0040] In the present invention, the sintering temperature is preferably 1200-1500° C., more preferably 1300-1400° C.; the holding time is preferably 2-4 hours.

[0041] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0042] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] Preparation:

[0045] 100 parts of alumina ceramics, with a purity of 99.9% and an average particle size of 0.5 μm;

[0046] 8 parts of silicon carbide fiber, with a diameter of 5 μm and an aspect ratio of 15 to 35;

[0047] 3 parts of yttrium oxide, purity 99.9%;

[0048] Alumina ceramics, fibers and yttrium oxide were placed in a ball mill, and 30 parts of deionized water were added as a medium for wet ball milling for 2 hours at a speed of 50 rpm to ensure the uniformity of the mixture. The mixed slurry was poured into a magnetic field generator, and a magnetic field with a magnetic field strength of 12 T and a gravity field of 1 G was applied for magnetization for 20 minutes. The magnetized slurry was dried in an oven at 80°C for 12 hours to obtain a magnetized material.

[0049] The magnetized material was placed in a mold and pressed for 8 seconds at a pressure of 5 MPa and a temperature of 160°C to obtain a molded sample. The molded sample was placed in a sintering furnace and sintered at a temperature of 1300°C for 3 hours to obtain an alumina ceramic sample.

[0050] Example 2

[0051] Alumina ceramics were prepared in the same manner as in Example 1, except that 3 parts of stearic acid were added during the wet ball milling process.

[0052] Example 3

[0053] Alumina ceramics were prepared in the manner of Example 1, except that 3 parts of yttrium oxide were replaced by 1 part of yttrium oxide, 1 part of neodymium oxide and 1 part of samarium oxide.

[0054] Example 4

[0055] Alumina ceramics were prepared in the same manner as in Example 1, except that 3 parts of yttrium oxide were replaced by 3 parts of neodymium oxide.

[0056] Example 5

[0057] Alumina ceramics were prepared in the same manner as in Example 1, except that 3 parts of yttrium oxide were replaced by 3 parts of samarium oxide.

[0058] Example 6

[0059] Alumina ceramics were prepared in the manner of Example 1, except that the silicon carbide fiber was replaced by mullite fiber, wherein the diameter of the mullite fiber was 5 μm and the aspect ratio was 15-50.

[0060] Example 7

[0061] Alumina ceramics were prepared in the manner of Example 1, except that silicon carbide fibers were replaced with lead titanate fibers, wherein the lead titanate fibers had a diameter of 3 μm and an aspect ratio of 20-30.

[0062] Comparative Example 1

[0063] Alumina ceramics were prepared in the same manner as in Example 1, except that yttrium oxide was not added.

[0064] Comparative Example 2

[0065] Alumina ceramics were prepared in the same manner as in Example 1, except that no fibers were added.

[0066] Comparative Example 3

[0067] Alumina ceramics were prepared in the same manner as in Example 1, except that magnetization was not performed.

[0068] Performance Testing

[0069] The flexural strength of the alumina ceramics of the embodiments and comparative examples was tested according to GB / T 6569-2006 “Standard for Testing Methods of Bending Strength of Fine Ceramics”.

[0070] According to GB / T23806-2009 “Fine Ceramics Fracture Toughness Test Method Single Edge Precracked Beam (SEPB) Method”, the fracture toughness values ​​of the alumina ceramics of the embodiments and comparative examples were tested.

[0071] The test results are shown in Table 1.

[0072] Table 1 Properties of alumina ceramics obtained in Examples and Comparative Examples

[0073] Bending strength(Mpa) <![CDATA[Fracture toughness (Mpa.m 1 / 2 )]]> <![CDATA[Density after sintering g / cm 3 > Example 1 1386 9.8 3.950 Example 2 1388 9.8 3.912 Example 3 1392 9.9 3.946 Example 4 1332 9.7 3.942 Example 5 1365 9.6 3.956 Example 6 1365 9.8 3.946 Example 7 1389 9.7 3.952 Comparative Example 1 986 7.5 3.922 Comparative Example 2 1012 7.5 3.943 Comparative Example 3 1030 7.6 3.938

[0074] It can be seen from Table 1 that, without reducing other properties of alumina ceramics, such as the density of alumina ceramics obtained by sintering, the compressive strength and fracture toughness of alumina ceramics can be improved by introducing a magnetic field.

[0075] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An alumina ceramic, characterized in that: The raw materials for preparation are composed of the following components in parts by weight: 90-110 parts of alumina, 1-5 parts of rare earth material, 5-10 parts of fiber; The rare earth material is one or more of yttrium oxide, neodymium oxide and samarium oxide; The fiber comprises one of lead titanate fiber and mullite fiber; the aspect ratio of the fiber is 15-50, and the diameter is 2-8 μm; The preparation method of the alumina ceramic comprises the following steps: Alumina, rare earth materials and fibers are mixed and magnetized to obtain magnetized material; the mixing method is wet ball milling; The magnetized material is pressed and sintered in sequence to obtain the alumina ceramic; The wet ball milling has a rotation speed of 20-100 rpm and a time of 0.5-2 h; The magnetization conditions include: a magnetic field strength of 10-15 T, a gravity field of 1-2 G, and a time of 15-25 min.

2. The alumina ceramic according to claim 1, characterized in that: The preparation raw materials also include 3 to 4 parts by weight of a binder; The binder includes one or more of paraffin, stearic acid, polyethylene and polypropylene.

3. The method for preparing the alumina ceramic according to claim 1 or 2, characterized in that: The following steps are involved: Alumina, rare earth materials and fibers are mixed and magnetized to obtain magnetized material; the mixing method is wet ball milling; The magnetized material is pressed and sintered in sequence to obtain the alumina ceramic.

4. The preparation method according to claim 3, characterized in that: After the magnetization, the obtained slurry is dried at a temperature of 80° C. for 12 hours.

5. The preparation method according to claim 3, characterized in that: The compression molding process has a pressure of 4-6 MPa, a temperature of 150-180° C., and a molding time of 5-10 s.

6. The preparation method according to claim 3, characterized in that: The sintering temperature is 1200-1500° C., and the heat preservation time is 2-4 hours.