Alumina-zirconia composite powder, its preparation method and application

Abstract

The application discloses an alumina-zirconia composite powder and a preparation method and application thereof. The composite powder comprises the following components in percentage by mass: 60-70% of alumina, 20-35% of zirconia and 1.5-5% of additives, wherein the additives comprise magnesium oxide, calcium oxide and silicon dioxide. The preparation of the composite powder comprises the following steps: (1) wet grinding micron-sized alumina and a first additive in the presence of water to obtain a first slurry; wet grinding micron-sized zirconia and a second additive in the presence of water to obtain a second slurry; (2) uniformly mixing the first slurry and the second slurry, and drying to obtain the composite powder. The composite powder prepared by the preparation method has good uniformity, and the composite ceramic material prepared from the composite powder has advantages of high hardness, high strength and high toughness, and has a good application prospect in the fields of medical devices, electronic equipment and the like.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to an alumina-zirconia composite powder, its preparation method, and its application. Background Technology

[0002] Ceramic materials, due to their excellent properties such as high hardness, high wear resistance, high temperature resistance, and corrosion resistance, have been widely used in machinery, electronics, chemical industry, aerospace, and other fields. Alumina ceramics and zirconia ceramics are two common ceramic materials, each with its own unique performance advantages. Alumina ceramics have advantages such as high hardness, high strength, high wear resistance, high temperature resistance, and corrosion resistance, but its toughness is relatively low. Zirconia ceramics have advantages such as high toughness, high strength, high temperature resistance, and corrosion resistance, but its hardness is relatively low. With the increasing demand for ceramics with both high toughness and high hardness in fields such as medical devices, electronic equipment, automobile manufacturing, aerospace, tool manufacturing, and industrial machinery, researchers are intentionally combining alumina and zirconia to leverage the performance advantages of both alumina and zirconia ceramics to obtain ceramics with both high toughness and high hardness.

[0003] Currently, the alumina-zirconia composite powders required for preparing alumina-zirconia composite ceramics are typically obtained by adding additives or other components to pre-treated alumina powder and then performing secondary grinding and mixing. However, due to the significant differences in particle size and dispersion ability among the different powders, the resulting powder has poor uniformity. Especially for larger agglomerated particles, this can lead to localized eutectic melting during ceramic sintering, causing localized stress, defects, and decreased mechanical properties, resulting in low yield. Therefore, there is an urgent need for a method to prepare alumina-zirconia composite powders with uniform size and good homogeneity to improve the performance of the alumina-zirconia composite ceramics prepared from it. Summary of the Invention

[0004] This invention provides an alumina-zirconia composite powder, its preparation method, and its application. By introducing specific additives and improving the preparation process, this invention obtains an alumina-zirconia composite powder with uniform size and good powder uniformity. The alumina-zirconia composite ceramic prepared from this alumina-zirconia composite powder has high strength, high toughness, and good high temperature resistance, and its hardness is higher than that of pure alumina ceramic.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] The first aspect of the present invention provides an alumina-zirconia composite powder comprising the following components by mass percentage: 60wt%-70wt% alumina, 20wt%-35wt% zirconia and 1.5wt%-5wt% additives, wherein the additives comprise magnesium oxide, calcium oxide and silicon dioxide.

[0007] A second aspect of this invention provides a method for preparing the alumina-zirconia composite powder described in the first aspect, comprising the following steps:

[0008] (1) Micron-sized alumina and micron-sized first additive are subjected to a first wet grinding process in the presence of water to obtain a first slurry; the micron-sized first additive includes micron-sized magnesium oxide and micron-sized silicon dioxide; the D50 of the particles in the first slurry is less than 300nm;

[0009] Micron-sized zirconium oxide and a micron-sized second additive are subjected to a second wet milling process in the presence of water to obtain a second slurry; the micron-sized second additive includes micron-sized magnesium oxide and micron-sized calcium oxide; the D50 of the particles in the second slurry is less than 500 nm.

[0010] (2) The first slurry and the second slurry are stirred and mixed evenly, and then dried to obtain the alumina-zirconia composite powder.

[0011] Further, in step (1), before wet grinding, each raw material is first crushed and ground to achieve a particle size of micron, so as to better disperse and obtain a more uniformly mixed powder; preferably, the particle size of the micron-sized alumina is preferably 0.2-0.5μm; the particle size of the micron-sized magnesium oxide is preferably 1-2μm; the particle size of the micron-sized silicon dioxide is preferably 2-5μm; the particle size of the micron-sized zirconium oxide is preferably 0.4-0.6μm; and the particle size of the micron-sized calcium oxide is preferably 1-2μm.

[0012] Further, in step (1), the mass ratio of micron-sized magnesium oxide to micron-sized silicon dioxide in the first micron-sized additive is preferably 3:2; and the mass ratio of micron-sized magnesium oxide to micron-sized calcium oxide in the second micron-sized additive is preferably 2:1.

[0013] Further, in step (1), micron-sized alumina is first dispersed in water to obtain an alumina dispersion, and then a micron-sized first additive is added for a first wet grinding; preferably, the solid content of the alumina dispersion is 30%-50%, and the mass ratio of the micron-sized first additive to the micron-sized alumina is (0.02-0.05):1.

[0014] Further, in step (1), micron-sized zirconia is first dispersed in water to obtain a zirconia dispersion, and then a second micron-sized additive is added for a second wet grinding process; preferably, the solid content of the zirconia dispersion is 20%-40%; the mass ratio of the second micron-sized additive to the micron-sized zirconia is (0.01-0.03):1.

[0015] Further, in step (1), in the first wet grinding step: the grinding medium is 0.2-0.5mm zirconia grinding beads, the ball-to-material ratio is (4-6):1, grinding is performed for 4-6 hours, and the grinding speed is 1600-2200rpm; preferably, the grinding speed is set to increase gradually during the first wet grinding process. In some preferred embodiments, the ball-to-material ratio is 5:1, and the first wet grinding process is performed according to grinding at 1600rpm for 1 hour, 1800rpm for 1 hour, 2000rpm for 1 hour, and 2200rpm for 2 hours.

[0016] Further, in step (2), in the second wet grinding step: the grinding medium is 0.2-0.5mm zirconia grinding beads, the ball-to-material ratio is (4-6):1, grinding is performed for 5-7 hours, and the grinding speed is 1800-2400rpm; preferably, the grinding speed is set to increase gradually during the second wet grinding process. In some preferred embodiments, the ball-to-material ratio is 5:1, and the second wet grinding process is performed according to grinding at 1800rpm for 1 hour, grinding at 2000rpm for 1 hour, grinding at 2200rpm for 2 hours, and grinding at 2000rpm for 2 hours.

[0017] Furthermore, in step (2), the stirring time is preferably 1-3 hours, such as 1 hour, 2 hours, 3 hours, etc.

[0018] Furthermore, in step (2), the drying temperature is preferably 100-110℃.

[0019] The third aspect of the present invention provides an alumina-zirconia composite ceramic, which is prepared from the alumina-zirconia composite powder described in the first aspect or the alumina-zirconia composite powder described in the second aspect.

[0020] Further, the alumina-zirconia composite powder is subjected to molding treatment, and then sintered under an inert atmosphere to obtain the alumina-zirconia composite ceramic. The molding treatment includes dry pressing, isostatic pressing, injection molding, etc. In the dry pressing step, the pressure is 80-120MPa and the holding time is 5-10min. The sintering temperature is 1300-1400℃ and the sintering time is 3-6h, for example, sintering at 1350℃ for 4h.

[0021] Furthermore, the hardness of the alumina-zirconia composite powder is greater than 1500 HV.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention provides an alumina-zirconia composite powder and its preparation method. Alumina and zirconia are treated separately by wet grinding. Magnesium oxide and silicon dioxide are introduced during the wet grinding of alumina, and magnesium oxide and calcium oxide are introduced during the wet grinding of zirconia. In the presence of these specific additives and combined with the above grinding process, an alumina-zirconia composite powder with uniform size and good powder homogeneity is obtained. The above preparation method is simple to operate and has good process controllability, making it suitable for mass production of alumina-zirconia composite powder.

[0024] 2. The alumina-zirconia composite ceramic prepared from the alumina-zirconia composite powder of this invention exhibits extremely high hardness, significantly improved compared to traditional single alumina ceramics or zirconia ceramics. Vickers hardness testing shows that, under a loading force of 50 N and a loading time of 15 s, the hardness of the alumina-zirconia composite ceramic material of this invention reaches 1800 HV, far exceeding the hardness of pure alumina ceramics (hardness 1500 HV) and pure zirconia ceramics (hardness 1200 HV) under the same testing conditions. Furthermore, the alumina-zirconia composite ceramic prepared by this invention also possesses excellent strength properties (flexural strength up to 800 MPa), toughness (fracture toughness up to 8 MPa·m^(1 / 2)), and high-temperature resistance. It is not easily broken or damaged under external forces, effectively absorbing impact and ensuring the reliability of the material during use. It can be used for extended periods at 1500℃ without significant performance degradation, making it suitable for applications under high-temperature working conditions. Attached Figure Description

[0025] Figure 1 The image shows the alumina-zirconia composite powder prepared in Example 1. Detailed Implementation

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. "Comprising" or "containing" as used herein means that it may include or contain other components in addition to the stated components. "Comprising" or "containing" as used herein may also be replaced with the closed form "is" or "consisting of".

[0027] The present invention will be further described below with reference to specific embodiments and accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0028] Example 1

[0029] This embodiment relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The alumina-zirconia composite powder comprises 70% alumina, 25% zirconia, 3.1% magnesium oxide, 0.5% calcium oxide, and 1.4% silicon dioxide, as detailed below:

[0030] Preparation of alumina-zirconia composite powder:

[0031] (1) A certain amount of additives such as magnesium oxide, calcium oxide, and silicon dioxide are placed in a planetary ball mill in batches for grinding and pulverization. The grinding beads are zirconia beads with particle sizes of 5 mm, 3 mm, and 1 mm, and the mass ratio of the grinding beads is 1:2:2. The rotation speed is 400 rpm. The ball milling time is adjusted according to the required particle size after refinement. The particle size requirements of the additives after grinding are as follows: magnesium oxide D50 is 1 μm and 1.5 μm, calcium oxide D50 is 1 μm, and silicon dioxide D50 is 2 μm.

[0032] (2) Alumina powder was mixed with water to prepare an alumina slurry with a solid content of 40%. Additives were then added, consisting of magnesium oxide (1.5 μm) and silicon dioxide (2 μm) in a mass ratio of 3:2. The amount of additives added was 3.5% of the alumina powder, with magnesium oxide at 2.1% and silicon dioxide at 1.4%. The mixture was then fed into a horizontal sand mill for wet grinding. The ball-to-particle ratio was 5:1, and the zirconium oxide grinding beads had a particle size of 0.2-0.5 mm. The milling speed was gradually adjusted at 1600 rpm for 1 hour, 1800 rpm for 1 hour, 2000 rpm for 1 hour, and 2200 rpm for 2 hours, grinding for 5 hours to ensure the alumina D50 reached below 300 nm. The resulting wet-ground slurry was slurry 1.

[0033] (3) Zirconia powder was mixed with water to prepare an alumina slurry with a solid content of 30%. Additives were then added, consisting of magnesium oxide (1 μm) and calcium oxide (1 μm) in a 2:1 mass ratio. The amount of additives added was 1.5% of the alumina powder, with magnesium oxide at 1% and silicon dioxide at 0.5%. The mixture was then fed into a horizontal sand mill for wet grinding. The ball-to-particle ratio was 5:1, and the zirconia grinding beads had a particle size of 0.2-0.5 mm. The milling speed was gradually adjusted to 1800 rpm for 1 hour, 2000 rpm for 1 hour, 2200 rpm for 2 hours, and 2400 rpm for 2 hours, grinding for 6 hours to ensure the alumina D50 reached below 500 nm. The resulting wet-ground slurry was slurry 2.

[0034] (4) Add slurry 1 and slurry 2 at a certain mass ratio of 2:1 into a constant temperature stirrer and stir for 1 hour. Then dry in an oven at 100-110℃ for 4 hours to obtain alumina-zirconia composite powder, such as... Figure 1 As shown.

[0035] Preparation of alumina-zirconia composite ceramics:

[0036] The above-mentioned alumina-zirconia composite powder was loaded into a mold and dry-pressed at a pressure of 100 MPa for 10 minutes. The molded blank was then placed in a sintering furnace and sintered at 1350°C for 4 hours in a nitrogen atmosphere to obtain alumina-zirconia composite ceramic.

[0037] Example 2

[0038] This embodiment relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The only difference from Example 1 is that the alumina-zirconia composite powder contains 65% alumina, 30% zirconia, 3.1% magnesium oxide, 0.5% calcium oxide and 1.4% silicon dioxide. All other operations are the same, and the corresponding alumina-zirconia composite powder and alumina-zirconia composite ceramic are prepared.

[0039] Example 3

[0040] This embodiment relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The only difference from Example 1 is that the alumina-zirconia composite powder contains 60% alumina, 35% zirconia, 3.1% magnesium oxide, 0.5% calcium oxide and 1.4% silicon dioxide. All other operations are the same, and the corresponding alumina-zirconia composite powder and alumina-zirconia composite ceramic are prepared.

[0041] Comparative Example 1

[0042] This comparative example relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The only difference from Example 1 is that the alumina-zirconia composite powder contains 70% alumina, 25% zirconia, and 5% magnesium oxide. In this example, an equal amount of magnesium oxide is used to replace silicon dioxide and calcium oxide. All other operations are the same, and the corresponding alumina-zirconia composite powder and alumina-zirconia composite ceramic are prepared.

[0043] Comparative Example 2

[0044] This comparative example relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The only difference from Example 1 is that the order of adding silicon dioxide and calcium oxide is reversed. All other operations are the same, and the corresponding alumina-zirconia composite powder and alumina-zirconia composite ceramic are prepared.

[0045] Comparative Example 3

[0046] This comparative example relates to the preparation of an alumina-zirconia composite powder and an alumina-zirconia composite ceramic. The difference from Example 1 lies only in that all materials are mixed once and then wet-milled. The ball-to-particle ratio in the milling is 5:1, and the zirconia grinding beads have a particle size of 0.2-0.5 mm. The milling speed is gradually adjusted at 1800 rpm for 1 hour, 2000 rpm for 1 hour, 2200 rpm for 2 hours, and 2400 rpm for 2 hours, for a total of 6 hours to obtain a mixed slurry. This slurry is then dried in an oven at 100-110℃ for 4 hours to obtain the alumina-zirconia composite powder.

[0047] Preparation of alumina-zirconia composite ceramics:

[0048] The above-mentioned alumina-zirconia composite powder was loaded into a mold and dry-pressed at a pressure of 100 MPa for 10 minutes. The molded blank was then placed in a sintering furnace and sintered at 1350°C for 4 hours in a nitrogen atmosphere to obtain alumina-zirconia composite ceramic.

[0049] Comparative Example 4

[0050] This comparative example relates to the preparation of a pure alumina ceramic. The only difference from Example 1 is that the pure alumina ceramic powder contains 95% alumina, 3.1% magnesium oxide, 0.5% calcium oxide and 1.4% silicon dioxide. All other operations are the same, and the corresponding pure alumina ceramic is prepared.

[0051] Comparative Example 5

[0052] This comparative example relates to the preparation of a pure zirconia ceramic. The only difference from Example 1 is that the pure alumina ceramic powder contains 95% zirconia, 3.1% magnesium oxide, 0.5% calcium oxide and 1.4% silicon dioxide. All other operations are the same, and the corresponding pure zirconia ceramic is prepared.

[0053] Performance testing

[0054] The hardness, three-point bending strength, fracture toughness, and high-temperature resistance of the alumina-zirconia composite ceramics prepared in Examples 1-3 and Comparative Examples 1-3, the pure alumina ceramic prepared in Comparative Example 4, and the pure zirconia ceramic prepared in Comparative Example 5 were tested. The test methods are as follows:

[0055] Hardness test: Using a diamond indenter with a cone angle of 120 degrees and a spherical radius of 0.2 mm at the tip, the indenter is pressed into the material surface with the rated test force (50 N) for the rated time (15 s), and then the test force is removed. The hardness value is obtained based on the depth of the indentation.

[0056] Three-point bending strength test: Using a measuring instrument with an accuracy of 0.01 mm, such as a vernier caliper or micrometer, measure the length, width, and thickness of the specimen and record the measurement values ​​for each specimen. Place the specimen horizontally on the two supporting cylinders of the three-point bending fixture, ensuring that the long axis of the specimen is perpendicular to the loading direction and the center of the specimen is located at the midpoint of the two supporting cylinders. Based on the test requirements and the characteristics of the ceramic material, set the loading speed and data acquisition frequency of the testing machine to accurately record the load and displacement data during the test. Start the testing machine, causing the loading cylinder to move downwards at the set speed, applying a vertical load to the specimen. During the test, closely observe the deformation of the specimen until it breaks. The testing machine automatically records the maximum load and corresponding displacement data at the time of specimen breakage. Record the breaking load value for each specimen. The three-point bending strength (σ) of ceramics is calculated using the formula σ = 3FL / 2bh2, with units of megapascals (MPa). Where F is the maximum load (N) at which the specimen breaks, L is the span between the centers of the two supporting cylinders (mm), b is the width of the specimen (mm), and h is the thickness of the specimen (mm).

[0057] Fracture toughness test: A certain load is applied to a smooth ceramic surface using an indenter until obvious cracks appear at the four corners of the indentation. The size of the indentation and the length of the resulting cracks are measured using an optical or scanning electron microscope. The fracture toughness value of the material is calculated by combining the load, material hardness and elastic modulus, and calibration constant.

[0058] High-temperature resistance test: The ceramic sample is placed directly into a high-temperature furnace and heated at different set temperatures. At each temperature stage, the appearance changes of the ceramic sample are observed, such as color changes, whether cracks or deformation appear, etc. At the same time, measuring tools (such as calipers) can be used to measure the dimensional changes of the sample to determine its dimensional stability and thus determine its high-temperature resistance temperature.

[0059] The test results are shown in Table 1 below:

[0060] Table 1

[0061]

[0062] As shown in Table 1, compared with pure alumina ceramics (Comparative Example 4) and pure zirconia ceramics (Comparative Example 5), the alumina-zirconia composite ceramics prepared in Examples 1-3 have higher hardness, strength, toughness, and superior high-temperature resistance. Specifically, the alumina-zirconia composite ceramic prepared in Example 1 has a hardness as high as 1800 HV (superior to pure alumina ceramics), a flexural strength as high as 800 MPa, and a fracture toughness far superior to pure zirconia ceramics, reaching 8 MPa·m^(1 / 2). Furthermore, it exhibits superior stability below 1550℃.

[0063] As shown in Example 1 and Comparative Examples 1 and 2, the introduction and order of addition of silicon dioxide and calcium oxide affect the hardness, strength, and toughness of the composite ceramic. Furthermore, Comparative Example 3 directly mixes all materials once and prepares the composite powder through wet sand milling. The composite ceramic prepared from this powder has a significantly lower hardness, less than that of pure alumina ceramic, and other properties are also significantly lower than those of Example 1. Therefore, this invention, through improvements to the powder composition and preparation process, can effectively improve the uniformity of the components in the powder and the mechanical properties of the sintered ceramic.

[0064] The embodiments described above are merely preferred examples to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing an alumina-zirconia composite powder, characterized in that, The alumina-zirconia composite powder is composed of the following components by mass percentage: 60wt%-70wt% alumina, 20wt%-35wt% zirconia and 1.5wt%-5wt% additives, the sum of the mass percentages of the above components is 100%, and the additives are magnesium oxide, calcium oxide and silicon dioxide. The preparation method includes the following steps: (1) Micron-sized alumina and micron-sized first additive are subjected to a first wet grinding process in the presence of water to obtain a first slurry; the micron-sized first additive is micron-sized magnesium oxide and micron-sized silicon dioxide; the D50 of the particles in the first slurry is less than 300 nm. Micron-sized zirconium oxide and a micron-sized second additive are subjected to a second wet milling process in the presence of water to obtain a second slurry; the micron-sized second additive is micron-sized magnesium oxide and micron-sized calcium oxide; the D50 of the particles in the second slurry is less than 500 nm. (2) The first slurry and the second slurry are stirred and mixed evenly, and then dried to obtain the alumina-zirconia composite powder.

2. The preparation method according to claim 1, characterized in that, In step (1), the particle size of the micron-sized alumina is 0.2-0.5 μm; The micron-sized magnesium oxide has a particle size of 1-2 μm; The particle size of the micron-sized silica is 2-5 μm; The micron-sized zirconium oxide has a particle size of 0.4-0.6 μm; The micron-sized calcium oxide has a particle size of 1-2 μm.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of micron-sized magnesium oxide to micron-sized silicon dioxide in the micron-sized first additive is 3:2; The mass ratio of micron-sized magnesium oxide to micron-sized calcium oxide in the micron-sized second additive is 2:

1.

4. The preparation method according to claim 1, characterized in that, In step (1), micron-sized alumina is first dispersed in water to obtain an alumina dispersion, and then micron-sized first additive is added for first wet grinding. The solid content of the alumina dispersion is 30%-50%; The mass ratio of the micron-sized first additive to the micron-sized alumina is (0.02-0.05):

1.

5. The preparation method according to claim 1, characterized in that, In step (1), micron-sized zirconia is first dispersed in water to obtain a zirconia dispersion, and then a second micron-sized additive is added for a second wet grinding process. The solid content of the zirconium oxide dispersion is 20%-40%; The mass ratio of the micron-sized second additive to the micron-sized zirconium oxide is (0.01-0.03):

1.

6. The preparation method according to claim 1, characterized in that, In step (1), the first wet grinding step is as follows: the grinding medium is 0.2-0.5 mm zirconia grinding beads, the ball-to-material ratio is (4-6):1, grinding is performed for 4-6 hours, and the grinding speed is 1600-2200 rpm; In the second wet grinding step: the grinding media is 0.2-0.5 mm zirconia grinding beads, the ball-to-material ratio is (4-6):1, grinding is performed for 5-7 hours, and the grinding speed is 1800-2400 rpm.

7. The preparation method according to claim 6, characterized in that, The grinding speed is set to increase incrementally during the first wet grinding process.

8. The preparation method according to claim 6, characterized in that, The grinding speed is set to increase incrementally during the second wet grinding process.

9. The preparation method according to claim 1, characterized in that, In step (2), the stirring time is 1-3 hours; The drying temperature is 100-110 ℃.

10. An alumina-zirconia composite ceramic, characterized in that, The alumina-zirconia composite powder is prepared by the preparation method according to any one of claims 1-9.

11. The alumina-zirconia composite ceramic according to claim 10, characterized in that, The alumina-zirconia composite powder is shaped and then sintered under an inert atmosphere to obtain the alumina-zirconia composite ceramic. The molding process includes dry pressing, wherein the pressure is 80-120 MPa and the holding time is 5-10 min. The sintering temperature is 1300-1400 ℃, and the sintering time is 3-6 h.

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