Method for preparing zirconium oxide toughened aluminum oxide ceramic by utilizing nano zirconium dioxide powder produced by high-temperature plasma combustion method

Abstract

The invention discloses a method for preparing zirconium oxide toughened aluminum oxide ceramic by utilizing nano zirconium dioxide powder produced by a high-temperature plasma combustion method, and belongs to the technical field of ceramic material preparation. Nano zirconium dioxide powder produced by a high-temperature plasma combustion method is used as a raw material, the nano zirconium dioxide powder, aluminum oxide nano powder, a proper amount of binder and a proper amount of sintering aid are uniformly mixed, and then the zirconium oxide toughened aluminum oxide ZTA ceramic is obtained through compression molding and high-temperature sintering in sequence. The superfine zirconia powder produced by a high-temperature plasma combustion method is applied to preparation of the ZTA toughened ceramic, so that the grain size of the ZTA ceramic can be reduced, the sintering activity of the zirconia powder can be improved, the sintering temperature of the ZTA ceramic can be reduced, the dosage proportion of the zirconia powder raw material can be reduced, and the mechanical property of the ZTA ceramic can be enhanced; the comprehensive performance of the ZTA toughened ceramic is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic material preparation, and in particular relates to a method for preparing zirconia-toughened alumina ceramics using nano zirconium dioxide powder produced by a high-temperature plasma combustion method. Background Art

[0002] With the rapid development of modern industry and technology, the demand for high-performance ceramic materials is growing. Traditional single-phase ceramic materials have certain performance limitations. For example, alumina ceramics have high hardness but insufficient toughness, which restricts their application in areas requiring high impact resistance. While zirconia ceramics offer good toughness, other properties, such as hardness, need to be improved in certain applications.

[0003] To overcome the shortcomings of single ceramic materials, the concept of composite ceramics emerged. By combining ceramic materials with different properties, the advantages of each can be combined. Zirconia-toughened alumina (ZTA) ceramics were developed in this context. They combine the advantages of alumina (high hardness, high melting point, and chemical stability) with the high toughness of zirconia.

[0004] In the aerospace field, materials must be able to withstand extreme temperature fluctuations and high-stress environments while also being lightweight and highly reliable. In machining, tool materials must possess high hardness, high wear resistance, and sufficient toughness to cope with complex cutting conditions. In the biomedical field, implant materials must possess excellent biocompatibility and mechanical properties. ZTA ceramics are gaining attention in response to these application requirements.

[0005] Zirconia, a key core material in ZTA ceramics, has a material whose raw powder properties, including phase, particle size, dispersibility, and surface activity, directly influence the characteristics and performance of ZTA ceramics sintered with alumina through solid-state reaction. The addition of zirconia powder inhibits alumina grain growth, reducing the grain size of the ZTA ceramic. Smaller grains increase the number of grain boundaries, requiring more energy for crack propagation, thereby increasing the strength and toughness of the ceramic and significantly enhancing its mechanical properties. Furthermore, zirconia powder can fill the alumina grain boundaries, strengthening them. These strengthened grain boundaries inhibit rapid crack propagation and improve the fracture toughness of the ceramic. Stable zirconia powder in ZTA ceramics undergoes a phase transformation from tetragonal to monoclinic under stress. This phase transformation produces volume expansion, generating compressive stress at the crack tip, hindering further crack propagation and thus achieving a toughening effect.

[0006] To further optimize the performance of ZTA ceramics, it is necessary to control and improve the particle size, dispersibility, surface activity, and sintering activity of the zirconia raw material powder. First, reducing the particle size of the zirconia raw material powder can lower the sintering temperature. Ultrafine zirconia powder can, to a certain extent, promote the sintering of ZTA ceramics and reduce the sintering temperature. This is because zirconia powder has high activity and can interact with alumina to form a sintering neck at a lower temperature, accelerating the sintering process. Lowering the sintering temperature not only saves energy but also reduces the adverse effects of high temperatures on ceramic properties, such as excessive grain growth and phase structure changes. Second, improving the dispersibility of the zirconia raw material powder. Well-dispersed zirconia powder can fill the pores between alumina particles, reducing porosity and increasing the sintered density of the ZTA ceramic. High-density ZTA ceramics exhibit improved mechanical properties, corrosion resistance, and insulation properties. Third, enhancing the surface activity of the zirconium dioxide raw material powder can lower the sintering temperature of ZTA ceramics, increase the sintering density, and reduce the proportion of zirconium dioxide raw material powder, thereby obtaining ZTA ceramics with excellent mechanical properties, reducing production costs, and improving economic benefits. However, existing processes for preparing nano-zirconium dioxide powders are difficult to meet these optimization and improvement needs.

[0007] Previous studies have shown that the continuous, large-scale production of nano-zirconium dioxide powders using high-temperature plasma combustion methods can control the morphology, dispersibility, and surface activity of the resulting nano-zirconium dioxide powders, thereby improving their performance. Due to the high temperature, high speed, and high energy density of this method, the resulting nano-zirconium dioxide powders have small particle size, good dispersibility, and abundant surface active sites. The present invention utilizes this method as a raw material for preparing ZTA ceramics, significantly improving their grain size, density, and sintering activity in sintered ZTA ceramics, enhancing the mechanical properties of the ZTA ceramics, and reducing the proportion of the raw zirconium dioxide powder used, resulting in excellent economic benefits. Summary of the Invention

[0008] In order to solve the above-mentioned shortcomings of the existing preparation process of zirconia-toughened alumina ceramics, the present invention aims to propose a method for preparing zirconia-toughened alumina ceramics using nano-zirconia powder produced by high-temperature plasma combustion. The ultrafine zirconia powder produced by high-temperature plasma combustion is applied to the preparation of ZTA toughened ceramics, which can reduce the grain size of ZTA ceramics, improve the sintering activity of zirconia powder, lower the sintering temperature of ZTA ceramics, reduce the usage ratio of zirconia powder raw materials, enhance the mechanical properties of ZTA ceramics, and thus improve the comprehensive performance of ZTA toughened ceramics.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing zirconia-toughened alumina ceramics using nano-zirconia powder produced by a high-temperature plasma combustion method. The preparation raw materials consist of 80 parts of zirconium dioxide nano-powder produced by a high-temperature plasma combustion method, 20 parts of alumina nano-powder, 1-5 parts of a binder, and 0.5-1 part of a sintering aid. The binder is prepared as an aqueous solution and added. The nano-zirconia powder is uniformly mixed with the alumina nano-powder, the binder, and the sintering aid. The mixture is then pressed and sintered at 1600°C to obtain the zirconia-toughened alumina ZTA ceramics.

[0011] As a preferred technical solution of the present invention, the nano-zirconium dioxide powder is prepared by first ultrafinely grinding zirconium hydroxide using a disc jet mill and then using a high-temperature plasma combustion method. The high-temperature plasma combustion method has a flame temperature of 2500°C and a reaction time of less than 1 second. The prepared nano-zirconium dioxide powder has an average particle size of 20 nm and a purity of over 99.9%. The nano-aluminum oxide powder has an average particle size of 500 nm and a purity of 99.5%. The binder is polyvinyl alcohol (PVA), and the sintering aid is magnesium carbonate.

[0012] As a preferred technical solution of the present invention, the preparation method involves mixing zirconium dioxide nanopowder with alumina nanopowder, a binder solution, and a sintering aid to form a uniform ceramic-aid mixed slurry. The mixed slurry is then dry-pressed to remove some of the water. The slurry is then placed in a mold and pressure is applied to form it, ensuring uniform filling within the mold. Appropriate pressure is applied to obtain a dense ceramic green body. After forming, the green body is sintered in a sintering furnace at a controlled heating rate of 10°C / min and a sintering hold time of 2 hours to ensure the densification and mechanical properties of the sintered product, the zirconium oxide-toughened alumina (ZTA) ceramic.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. High-temperature plasma combustion method is a method that uses the high temperature and high activity environment generated by plasma to make the raw materials undergo chemical reactions and rapidly nucleate and grow, thereby synthesizing zirconium dioxide nanopowder. Compared with traditional liquid phase method, solid phase method, etc., it has the following advantages:

[0015] ①Reaction conditions:

[0016] Traditional methods: For example, the precipitation method usually requires reactions at relatively low temperatures and a long reaction time, generally requiring several hours or even dozens of hours to complete the reaction and aging process; the sol-gel method also requires multiple steps of reaction and long drying, calcination and other treatments.

[0017] High-temperature plasma combustion method: The reaction is carried out in a high-temperature, high-energy plasma environment, which can reach extremely high temperatures instantly, allowing the reaction to be completed in a very short time, usually only a few seconds to tens of seconds, greatly improving production efficiency.

[0018] ②Product purity:

[0019] Traditional methods: In the precipitation method, the addition of precipitants may introduce impurity ions, requiring multiple washing, filtration and other complex post-processing steps to improve product purity. The organic reagents used in the sol-gel method may also remain, affecting product purity.

[0020] High-temperature plasma combustion method: No precipitant or other substances that may introduce impurities are required during the reaction process, and the high temperature environment is conducive to the volatilization and removal of impurities. Therefore, high-purity zirconium dioxide nanopowders can be synthesized. The purity of the powder can reach over 99.9%, improving the performance stability of the powder.

[0021] ③Particle size and distribution:

[0022] Traditional methods: Liquid phase method and solid phase method are difficult to accurately control the growth and agglomeration of particles, which easily leads to a wide particle size distribution and poor product consistency.

[0023] High-Temperature Plasma Combustion: The high temperature and activity of the plasma allow the raw materials to react rapidly and evenly, allowing for better control of the nucleation and growth processes. This results in the synthesis of small, uniformly distributed zirconium dioxide nanopowders, which improves product performance and application effectiveness. Precisely controlling the reaction parameters during the reaction allows the zirconium dioxide vapor to condense in a uniform environment, resulting in a narrow powder size distribution, which improves the dispersion and consistency of the powder in subsequent applications.

[0024] ④Crystal structure:

[0025] Traditional method: During the preparation process, the formation and transformation of the crystal phase are difficult to control, and parameters such as temperature and time often need to be strictly controlled. In addition, the crystal phase structure of different batches of products may vary to a certain extent.

[0026] High-temperature plasma combustion method: By adjusting the parameters of the plasma, the reaction temperature and atmosphere can be more accurately controlled, which is conducive to the formation of zirconium dioxide nanopowders with specific crystal phase structures, such as stable cubic phase or tetragonal phase, to meet the crystal phase requirements of different application fields.

[0027] ⑤Technological process:

[0028] Traditional methods generally include multiple complex steps, such as solution preparation, reaction, aging, drying, calcination, etc. Each step requires strict control of conditions and is cumbersome to operate. In addition, a large amount of wastewater, waste gas and other pollutants will be generated during the production process, which puts a certain amount of pressure on the environment.

[0029] High-temperature plasma combustion method: The process flow is relatively simple, does not require complex pre-treatment and post-treatment processes, reduces production links and pollutant emissions, and has good environmental benefits.

[0030] 2. The present invention applies ultrafine zirconia powder produced by high-temperature plasma combustion method to ZTA ceramics, which can improve the densification and mechanical properties of ZTA ceramics, mainly manifested in:

[0031] ① Significantly improved fracture toughness: The maximum flexural strength of the ZTA ceramics prepared by the present invention can be increased to 680-700 MPa, which is more than 15% higher than that of traditional ZTA ceramics (flexural strength of about 600 MPa), effectively improving the brittleness of alumina ceramics and broadening their application range.

[0032] ② Enhanced hardness and wear resistance: Due to the uniform distribution of zirconia powder and good toughening effect, the hardness and wear resistance of the ZTA ceramics prepared by the present invention are also significantly improved. In the wear test, the wear rate is reduced by 10% to 15%, and it can be used in more severe wear environments.

[0033] ③ Reduced production costs: The preparation method of the present invention is relatively simple, and the raw materials are widely available and low-cost. By improving the performance and production efficiency of ZTA ceramics, the production cost of ZTA ceramics is indirectly reduced, thereby improving the market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Actual digital photos of zirconia-toughened alumina ZTA ceramic specimens prepared in Examples 1, 2, and 3.

[0035] Figure 2 The mechanical properties test diagram of zirconia-toughened alumina ZTA ceramics prepared in Examples 1, 2, and 3 (curves 1, 2, and 3 correspond to the samples prepared in Examples 1, 2, and 3, respectively).

[0036] Figure 3 These are the fracture morphology characterization images of the zirconia-toughened alumina ZTA ceramics prepared in Example 3 (a and b represent high and low magnifications, respectively). DETAILED DESCRIPTION

[0037] An embodiment of the present invention proposes a method for preparing zirconia-toughened alumina ceramics using nano-zirconium dioxide powder produced by a high-temperature plasma combustion method. The nano-zirconium dioxide powder produced by a high-temperature plasma combustion method is used as a raw material, and is uniformly mixed with alumina nano-powder and an appropriate amount of a binder (for example, a polyvinyl alcohol solution) and a sintering aid (for example, magnesium carbonate). The zirconia-toughened alumina ZTA ceramics are then obtained by sequentially pressing and high-temperature sintering.

[0038] Example 1: Preparation of Zirconia Toughened Alumina ZTA Ceramic Sample Bar 1

[0039] Raw material composition:

[0040] Nano-sized Al2O3, 8 g, average particle size 500 nm, purity 99.5%.

[0041] Micron-sized ZrO2, 2 g, average particle size 1 μm, purity 99.5%.

[0042] Binder (polyvinyl alcohol solution), 0.3 g, was prepared into a solution using hot water, and the concentration was controlled to be 5 wt%.

[0043] Sintering aid (magnesium carbonate), 0.1 g.

[0044] Preparation method:

[0045] Nano-sized Al₂O₃, micro-sized ZrO₂, a binder (polyvinyl alcohol solution), and a sintering aid (magnesium carbonate) were mixed for 3 hours to form a uniform ceramic-aid slurry. The slurry was then dry-pressed to remove some of the water. The mixture was then placed in a mold and pressed to form a compact ceramic body, ensuring uniform filling within the mold. Appropriate pressure was applied to obtain a dense ceramic body. The formed body was then sintered in a furnace at a controlled heating rate of 10°C / min, a sintering temperature of 1600°C, and a sintering time of 2 hours to produce zirconia-toughened alumina (ZTA) ceramic bar 1.

[0046] Example 2: Preparation of Zirconia Toughened Alumina ZTA Ceramic Sample Bar 2

[0047] Raw material composition:

[0048] Nano-sized Al2O3, 8 g, average particle size 500 nm, purity 99.5%.

[0049] The commercial ball milling method produces 2 g of nano-ZrO2 with an average particle size of 200 nm and a purity of 99.5%.

[0050] Binder (polyvinyl alcohol solution), 0.3 g, was prepared into a solution using hot water, and the concentration was controlled to be 5 wt%.

[0051] Sintering aid (magnesium carbonate), 0.1 g.

[0052] Preparation method:

[0053] Nano-sized Al₂O₃, commercially produced nano-sized ZrO₂, a binder (polyvinyl alcohol solution), and a sintering aid (magnesium carbonate) were mixed for 3 hours to form a uniform ceramic-aid slurry. The slurry was then dry-pressed to remove some moisture. The mixture was then placed in a mold and pressed to form a compact ceramic body, ensuring uniform filling within the mold. Appropriate pressure was applied to obtain a dense ceramic body. The formed body was then sintered in a sintering furnace at a controlled heating rate of 10°C / min, a sintering temperature of 1600°C, and a sintering time of 2 hours to produce zirconia-toughened alumina (ZTA) ceramic bar 2.

[0054] Example 3: Preparation of Zirconia Toughened Alumina ZTA Ceramic Sample Bar 3

[0055] Raw material composition:

[0056] Nano-sized Al2O3, 8 g, average particle size 500 nm, purity 99.5%.

[0057] Nano-sized ZrO2 (2 g) was produced by high-temperature plasma combustion method with an average particle size of 20 nm and a purity exceeding 99.9% (refer to Chinese invention patent application CN 112408473A for the preparation method).

[0058] Binder (polyvinyl alcohol solution), 0.3 g, was prepared into a solution using hot water, and the concentration was controlled to be 5 wt%.

[0059] Sintering aid (magnesium carbonate), 0.1 g.

[0060] Preparation method:

[0061] Nano-sized Al₂O₃, nano-sized ZrO₂ produced by high-temperature plasma combustion, a binder (polyvinyl alcohol solution), and a sintering aid (magnesium carbonate) were mixed for 3 hours to form a uniform ceramic-aid slurry. The slurry was then dry-pressed to remove some moisture. The mixture was then placed in a mold and pressed to form a compact ceramic body, ensuring uniform filling within the mold. Appropriate pressure was applied to obtain a dense ceramic body. The formed body was then sintered in a sintering furnace at a controlled heating rate of 10°C / min, a sintering temperature of 1600°C, and a sintering time of 2 hours to produce zirconia-toughened alumina (ZTA) ceramic bar 3.

[0062] The zirconia toughened alumina ZTA ceramic sample strips prepared in Examples 1, 2, and 3 are as follows: Figure 1 As shown, the specimen strips are approximately 40 mm long, 5 mm wide, and 4 mm thick. The surface of the ZTA ceramic specimens requires fine grinding and polishing to ensure surface flatness. The surface roughness should be controlled below Ra 0.8 μm to minimize the impact of surface defects on test results. Furthermore, the specimen strips should be free of obvious defects such as cracks and pores, as these defects can act as stress concentration points and reduce the specimen's mechanical properties.

[0063] Accurately place the ZTA ceramic specimen strip on the two fulcrums of the three-point bending test fixture. Ensure that the length of the specimen is perpendicular to the line connecting the fulcrums, and that the center of the specimen is exactly in the middle of the two fulcrums. During placement, be gentle to avoid causing additional damage to the specimen. Before applying any load, the testing machine needs to be zeroed. This includes zeroing the load and displacement sensors to eliminate the equipment's own errors and the influence of the specimen's own weight. Start the testing machine and slowly and steadily apply a vertical downward load at a pre-set loading rate. During the test, the testing machine system automatically records the load-displacement curve and displays the changes in load and displacement in real time. Observe the deformation of the specimen during loading until the specimen breaks.

[0064] See also Figure 2 By comparison, it can be found that the maximum bending strengths of the zirconia-toughened alumina ZTA ceramic specimens prepared in Examples 1, 2, and 3 are 614 MPa, 660 MPa, and 695 MPa, respectively. It can be seen that the present invention uses nano-zirconium dioxide powder produced by high-temperature plasma combustion as a raw material to sinter and prepare ZTA toughened ceramics. Since the prepared zirconium dioxide nanopowder has high activity and good dispersibility, when preparing ZTA ceramics, problems such as abnormal growth of ceramic grains caused by high-temperature sintering can be reduced, which is conducive to obtaining ZTA ceramics with excellent performance.

[0065] See also Figure 3 It was found that the zirconium dioxide nanopowder prepared by the high-temperature plasma combustion method has good dispersibility and activity, making it easier for the zirconium dioxide nanopowder to fill pores during sintering, promoting densification of the ceramic, thereby improving the density of the ZTA ceramic. As a toughening phase in ZTA ceramics, the zirconium dioxide nanopowder's fine, uniform particle size and good dispersibility can more effectively hinder crack propagation, thereby improving the fracture toughness of the ceramic.

[0066] In summary, the zirconium dioxide nanopowder product produced by the high-temperature plasma combustion method of the present invention has good dispersibility, rich surface state and high activity due to the action of high-temperature plasma. This is beneficial for the zirconium dioxide nanopowder to be used as sintered ZTA ceramics. The interface bonding force between the highly active zirconium dioxide nanoparticles and the alumina matrix is stronger, and a more stable interface structure can be formed, thereby enhancing the mechanical properties of the ceramics and improving their wear resistance, corrosion resistance and other properties. In addition, the sintering temperature of the ZTA ceramics can be reduced, the usage ratio of the zirconium dioxide powder raw material can be reduced, and the comprehensive performance and economic benefits of the ZTA toughened ceramics can be improved.

Claims

1. A method for preparing zirconia-toughened alumina ceramics using nano-zirconia powder produced by high-temperature plasma combustion, characterized in that: The preparation raw materials consist of 80 parts of zirconium dioxide nanopowder produced by high-temperature plasma combustion method, 20 parts of alumina nanopowder, 1-5 parts of binder and 0.5-1 parts of sintering aid. The binder is prepared into an aqueous solution and added. The nano-zirconium dioxide powder is evenly mixed with the alumina nanopowder, binder and sintering aid, and then the zirconia-toughened alumina ZTA ceramics are obtained by pressing and sintering at 1600 °C.

2. The method according to claim 1, wherein The nano zirconium dioxide powder is prepared by first ultrafinely grinding zirconium hydroxide using a disc jet mill and then using a high-temperature plasma combustion method; the flame flow temperature of the high-temperature plasma combustion method is 2500°C and the reaction time is less than 1 second; the average particle size of the prepared nano zirconium dioxide powder is 20nm and the purity reaches above 99.9%.

3. The method according to claim 1, wherein The average particle size of the aluminum oxide nanopowder is 500 nm and the purity is 99.5%.

4. The method according to claim 1, wherein The binder is polyvinyl alcohol (PVA), and the sintering aid is magnesium carbonate.

5. The method according to claim 1, wherein Zirconium dioxide nanopowder is mixed with alumina nanopowder, a binder solution and a sintering aid to form a uniform ceramic-aid mixed slurry. Then, the dry pressing method is adopted to dry the mixed slurry to remove some moisture, put it into a mold and apply pressure to shape it, ensuring uniform filling in the mold and applying appropriate pressure to obtain a dense ceramic body.

6. The method according to claim 5, wherein The formed ceramic body was placed in a sintering furnace for sintering. The heating rate was controlled at 10 ℃ / min and the sintering time was kept at 2 h to ensure the densification and mechanical properties of the sintered product, i.e., zirconia-toughened alumina ZTA ceramics.

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