CN114031376B - A kind of preparation method of high hardness, fine grain ZTA system composite phase ceramic material - Google Patents

Abstract

The invention discloses a preparation method of a high-hardness, fine-grained ZTA system multiphase ceramic material. After the steps of material preparation, raw material treatment, mixing ball milling, powder drying, sieving and debinding, and molding, the preparation method is finally carried out in a discharge plasma sintering furnace. The green body is sintered in a specific sintering process, and the green body is quickly sintered under a specific temperature and pressure environment to obtain a high-hardness, fine-grained ZTA system multi-phase ceramic material. The high-hardness, fine-grain ZTA system composite ceramic material particles prepared by the preparation method of the present invention are closely arranged, the grain distribution is uniform and fine, there is no obvious defect, the average particle size is at least 0.4 μm, and it has good hardness and fracture toughness. and bending strength, it can be used in high-precision fields such as ceramic choppers, and the production process is simple, easy to achieve mass production, and has broad application prospects.

Description

A kind of preparation method of high hardness, fine grain ZTA system composite phase ceramic material

technical field

The invention belongs to the technical field of preparation of composite ceramic materials, and in particular relates to a preparation method of a high-hardness, fine-grain ZTA system composite ceramic material.

Background technique

In the semiconductor packaging industry, most low-cost mid-range packaging and memory chip stacking and other packaging processes are inseparable from ceramic rivets. Ceramic rivets are the most important consumable tools in the packaging process. The working environment is usually heated, Pressurization and application of ultrasonic vibrations place extremely high demands on the material properties of the riving knife. At present, alumina ceramics are considered to be excellent materials for making riving knives because of a series of advantages such as high hardness, high specific gravity, fine grains, high surface finish, and high dimensional accuracy.

However, from the perspective of the properties of the alumina ceramic material itself, the melting point of alumina is relatively high, and the ionic bond is strong, resulting in a decrease in the particle diffusion coefficient. The mechanical properties are reduced and the air tightness is deteriorated. At present, copper wires with a hardness harder than gold wires are gradually used in the IC packaging process. Copper wires are more economical than gold wires. However, when copper is used as a welding wire, greater ultrasonic energy is required during welding, which will cause cracks during welding. The end face of the knife will be subjected to a large shear stress, and the crystal particles are easy to fall off, which puts forward higher requirements for the mechanical properties of the ceramic such as bending strength, wear resistance and hardness.

The current preparation process of ZTA ceramics is to add ZrO ₂ powder to Al ₂ O ₃ powder, mix mechanically, granulate and shape, then fire at high temperature and post-process. Although this preparation method is simple in process and low in cost, it always has the problem of uneven dispersion and agglomeration of ZrO ₂ powder in the Al ₂ O ₃ matrix, uneven distribution of the second phase in the matrix after firing, and some main crystal phase particles Problems such as abnormal growth will reduce the performance of ZTA composite ceramics. Excessive sintering temperature and long holding time will lead to coarse grains and affect the performance of ceramics. The invention patent of the patent application number 201811435382.5 sinters the green body under normal pressure at 1400°C-1500°C, and then hot isostatic pressing sintering at 1300°C-1400°C in an atmosphere of protective gas to obtain alumina ceramics, which adopts two-step sintering If the sintering process is carried out for a long time, the time required for sintering the sample will increase. The invention patent with the patent application number 201810622814.7 uses hot isostatic pressing to prepare ceramics and can achieve certain performance, but the sintering time is as long as several hours, which is too long and consumes a lot of energy.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a high-hardness, fine-grain ZTA system composite ceramic material with short sintering time, high fracture toughness, good wear resistance, high hardness and flexural strength .

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) The alumina powder and the yttria-stabilized zirconia (3Y-ZrO ₂ ) powder are respectively immersed in water, centrifuged and dried to complete the raw material pretreatment;

2) adding a dispersant to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1), and then ball milling, vacuum drying, sieving, debinding, and shaping to obtain an embryo body;

3) Place the green body obtained in step 2) into a spark plasma sintering furnace for sintering. The sintering is divided into early sintering, mid-sintering and late sintering. The specific sintering process is:

Early stage of sintering: the temperature is raised from room temperature to 600-800°C, the heating rate is 50-150°C/min, and the sintering pressure is 0MPa;

Middle stage of sintering: The temperature continues to rise to 1170-1200°C on the basis of the temperature in the early stage of sintering, and the heating rate is 100-200°C/min. During this heating process, the sintering pressure gradually rises to 20-40MPa, and the temperature is kept for 3-5 minutes after the temperature rise is completed. , while keeping warm, pressurize gradually until the sintering pressure reaches 45-60MPa;

Late sintering stage: after the heat preservation in the middle stage of sintering is completed, the temperature is raised to 1300-1400°C based on the temperature in the middle stage of sintering. Medium-term pressure consistent;

After the heat preservation in the later stage of sintering is completed, the sintering is completed, the heating and pressure are stopped, and the furnace is lowered to room temperature, and the high-hardness, fine-grain ZTA system composite ceramic material is obtained.

According to the above scheme, in the step 1), the mass ratio of the alumina powder to the yttria-stabilized zirconia powder is (60-90): (10-40).

According to the above scheme, in the step 1), the purity of the alumina powder is above 99.99%, and the particle size is 30-80nm; the purity of the yttria-stabilized zirconia powder is above 99.99%, and the particle size is 30-80nm.

According to the above scheme, in the step 1), the three steps of water immersion, centrifugation and vacuum drying pretreatment are repeated 2 to 3 times in sequence.

According to the above scheme, in the described step 1), the pretreatment process is:

Water immersion: add deionized water 3 to 5 times its own mass to alumina powder or yttria stabilized zirconia powder, and stir for 40 to 80 minutes under magnetic stirring at 300 to 800 r/min to complete water immersion;

Centrifugation: Centrifuge the alumina powder or yttria-stabilized zirconia powder after water immersion, the centrifugal rate is 5000-7000r/min, the centrifugation time is 20-60min, and the centrifugation is completed;

Vacuum drying: Dry the centrifuged alumina powder or yttria-stabilized zirconia powder at a temperature of 100-120°C for 12-24 hours to complete the vacuum drying to obtain the pretreated raw material alumina powder or yttria-stabilized zirconia powder Zirconium powder.

According to the above scheme, in the step 2), the amount of the dispersant added is 0.01-0.2% of the total mass of the raw alumina powder and the yttria-stabilized zirconia powder.

According to the above scheme, in the step 2), the dispersant is Isobam104 (copolymer of isobutylene and maleic anhydride).

According to the above scheme, in the step 2),

Ball milling: The ball milling time is 12-24 hours, the ball milling rate is 150-300r/min, and uniform powder is obtained;

Vacuum drying: The drying time is 12-24 hours, and the drying temperature is 60-100°C;

Screening and debinding: 150-mesh sieve is used, the degumming environment is a vacuum environment, the degumming temperature is 400-500°C, and the degumming time is 2-4 hours.

According to the above scheme, the step 2) also includes adding chromium oxide powder in the ball milling process, that is, after adding dispersant and chromium oxide powder to the pretreated alumina powder and yttria-stabilized zirconia powder. ball milling.

Preferably, the purity of the chromium oxide powder is above 99.99%, and the particle size is 30-50 nm.

Preferably, the added amount of the chromium oxide powder is 1-20% of the total mass of the raw alumina powder and the yttria-stabilized zirconia powder; preferably 1-10%.

The invention provides a method for preparing a ZTA system multi-phase ceramic material, adopting spark plasma sintering technology for sintering, and designing a three-stage sintering process in the early stage, middle stage and late stage of sintering, and designing different temperatures and pressures for different stages of sintering; wherein:

On the one hand, spark plasma sintering (SPS) has higher thermal efficiency and can realize rapid heating and cooling of samples, so it can effectively inhibit the growth of grains during the heating process, and at the same time, it can assist the sintering process by applying external axial pressure, which can realize The rapid densification of materials reduces the possible volatilization of components and inhibits the occurrence of undesirable phase transitions. When sintering the non-conductive ZTA raw material SPS, although there is no strong experimental evidence for discharge and plasma in the sintering process, the design of the sintering process can also achieve the purpose of rapid sintering, which can be obtained in a time much lower than other sintering methods. A sintered body with the same or even higher performance than other sintering methods.

On the other hand, design different pressures and temperatures in different sintering stages: control the lower temperature, heating rate and axial pressure in the early stage of sintering to ensure that the residual water and organic matter inside the powder are discharged as much as possible, which is conducive to improving the density of the sintered body ;In the mid-sintering stage, the temperature is raised rapidly to the expected temperature first, and the volume of the sintered body shrinks significantly. At the same time, increasing the pressure helps to hinder the movement of the grain boundary so as to achieve the purpose of controlling the grain size; Increase the pressure to the required maximum value to make the phase transformation in zirconia more sufficient and maintain a certain internal stress in the sintered body; reduce the heating rate in the later stage of sintering, continue to increase the temperature to the expected maximum value and keep it warm, and control the sintered body. The uniform temperature of the part ensures that there is no large difference in the grain size between the center and the edge of the sintered body, which is conducive to the improvement of the overall performance. At the same time, the pressure is kept consistent with the maximum pressure in the middle stage of sintering, which can effectively control the grain size in the later stage of sintering.

The present invention has the following beneficial effects:

1. The present invention provides a method for preparing a ZTA system multiphase ceramic material, using alumina powder and yttria-stabilized zirconia powder as the main raw materials, ball milling the raw materials after pretreatment, vacuum drying, sieving, debinding, and shaping , the obtained green body is sintered by spark plasma sintering technology, and a three-stage sintering process is designed in the early stage, middle stage and late stage of sintering, and different stages are matched with different temperatures and pressures, so that the temperature and pressure can be increased in stages, which is more conducive to the sintering process; the present invention By designing a reasonable sintering process, the ZTA system composite ceramic material is prepared with zirconia toughened alumina (ZTA) as the matrix, the particles are closely arranged, the grain distribution is uniform and fine, there is no obvious defect, and the average particle size is at least 0.4μm , has good hardness, fracture toughness and bending strength, and can be used in high-precision fields such as ceramic choppers, and the production process is simple, the sintering temperature is low, and it is easy to realize mass production, with broad application prospects.

2. The sintering time of the present invention is short, and the entire sintering process can be completed within half an hour. At the same time, the sintering temperature is low, and a high-quality ceramic body can be obtained at a maximum of 1350°C, which can effectively improve efficiency and reduce energy consumption and cost.

3. Further, chromium oxide is added in the ball milling process, and the chromium oxide is mixed with the raw materials in advance to assist sintering, so that the ZTA structure is more uniform and refined, and Cr ₂ O ₃ and Al ₂ O ₃ are both corundum structures, which can form a replacement solid solution. The lattice distortion caused by the replacement of Al ³⁺ ions by large Cr ³⁺ ions leads to local compressive stress that hinders the penetration of cracks through grain boundaries. At the same time, this compressive stress will also hinder grain growth, grain refinement, and material strengthening. Performance has been further improved.

Description of drawings

Fig. 1 is the microstructure view of the products prepared in Comparative Example 2 and Example 3 of the present invention, wherein (a) corresponds to the product prepared in Comparative Example 2, and (b) corresponds to the product prepared in Example 3.

Fig. 2 is the temperature-pressure curve of the sintering process adopted by the embodiment of the present invention and the comparative example, wherein (a) corresponds to the temperature-pressure curve of the sintering process 1, (b) corresponds to the temperature-pressure curve of the sintering process 2, and (c) corresponds to The temperature and pressure curve of sintering process 3.

Fig. 3 is the XRD spectrum of the product prepared in Example 3 of the present invention.

FIG. 4 is an enlarged view of diffraction peaks corresponding to crystal planes corresponding to products prepared in Examples 1-5 of the present invention with different doping amounts of Cr ₂ O ₃ at different concentrations.

Fig. 5 is a microstructural diagram of different concentrations of Cr ₂ O ₃ doping corresponding to products prepared in Examples 1-5 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings.

In the following examples, the additive is chromium oxide powder, the dispersant is Isobam104 (copolymer of isobutylene and maleic anhydride), the purity of the alumina powder is 99.99%, and the particle size is 30-80nm; the yttrium oxide is stably oxidized The purity of the zirconium (3Y-ZrO ₂ ) powder is above 99.99%, and the particle size is 30-80nm; the purity of the chromium oxide powder is above 99.99%, and the particle size is 30-50nm.

Example 1

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) Raw material pretreatment

Weigh the alumina powder and yttria-stabilized zirconia (3Y-ZrO ₂ ) powder according to the mass ratio of 4:1, respectively immerse the alumina powder and yttria-stabilized zirconia powder in water, centrifuge and dry to obtain The processed raw material aluminum powder and raw material zirconium powder; complete the processing of the main raw materials, wherein:

Water immersion step: Put alumina powder and yttria stabilized zirconia powder into different beakers, add deionized water with a mass ratio of 4 times each, and stir for 60 minutes under 500r/min magnetic stirring to complete water immersion The water immersion step mainly cleans the alumina powder and the yttria-stabilized zirconia powder.

Centrifugation: The alumina powder and yttria-stabilized zirconia powder after water immersion are centrifuged separately, the centrifugal speed is 6000r/min, the centrifugation time is 30min, and the centrifugation is completed; the water in the raw materials after water immersion is completely removed.

Vacuum drying: Put the centrifuged alumina powder and yttria-stabilized zirconia powder into a vacuum drying oven respectively, and dry them for 24 hours at a temperature of 105°C to complete the vacuum drying to obtain raw aluminum powder and raw zirconium powder ; The dried powder can meet the needs of subsequent practical use.

The above three steps of water immersion, centrifugation and vacuum drying are repeated twice in sequence, and repeated twice to make the raw material free from other impurities and make the raw material more pure.

2) Mixed ball mill

Mixed ball milling: add dispersant to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttria-stabilized zirconia powder 0.2% of the total mass of the powder, and then put the mixed powder into a ball mill jar, add zirconia ball milling balls 3 times the mass of the mixed powder, and carry out ball milling. The ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving, debinding and shaping

Powder drying: put the uniform powder after ball milling in step 2) into a dryer, and the drying environment is vacuum. Specifically, the dryer adopts a vacuum dryer with a drying time of 24 hours and a drying temperature of 80°C to obtain a dry powder .

Screening and debinding: sieve the dry powder, use a 150-mesh sieve, put the sieved dry powder into a crucible and send it to a debinding furnace for debinding. The debinding environment is a vacuum environment, and the debinding temperature is 475°C, the debinding time is 3h.

Shaping: Inject the degummed dry powder into a graphite mold for shaping, and obtain a green body shaped in the graphite mould.

4) Sintering

Place the green body obtained in step 3) into a discharge plasma sintering furnace, seal the discharge plasma sintering furnace and vacuumize it. At this time, the temperature in the discharge plasma sintering furnace is room temperature and the environment is vacuum, and sintering begins. The sintering process is divided into sintering The sintering process is named as sintering process 3 in the early stage, mid-sintering stage and post-sintering stage, specifically:

Early stage of sintering: heat the spark plasma sintering furnace, raise the temperature of the spark plasma sintering furnace from room temperature to 700°C, and the heating rate is 100°C/min. During this process, the sintering pressure is 0Mpa.

From room temperature to 700°C, the heating rate should not be too fast (100°C/min). The water and organic matter remaining in the green body in the early stage of sintering will be discharged in the form of gas. If the sintering heating rate is too fast, it will cause water and The organic matter cannot be vaporized or decomposed well. As the temperature continues to rise, these gases will remain in the matrix, resulting in a decrease in the compactness of the sintered body, which will eventually lead to a significant decline in mechanical properties. At the same time, a low axial pressure should be maintained in the early stage of sintering. The gas in the green body can be continuously discharged under the action of vacuum, and the gas inside the powder can also be discharged in the early stage of sintering by maintaining a low axial pressure. If a large pressure is applied in the early stage of sintering, the powder The gas generated in the center will not be able to escape well due to the blockage of the capillary channel caused by the axial pressure.

Mid-sintering stage: raise the temperature of the spark plasma sintering furnace from 700°C to 1170°C at a heating rate of 150°C/min. During the heating process, the sintering pressure gradually rises to 37.5MPa. Increase the pressure gradually until the sintering pressure reaches 50MPa.

Raise the temperature from 700°C to 1170°C and hold at 1170°C for 3 minutes. 1170°C is the phase transition temperature from monoclinic phase (m-ZrO ₂ ) to tetragonal phase (t-ZrO ₂ ) in 3Y-ZrO ₂ , at this temperature The lower sintered body has obvious volume shrinkage. At this time, the sintering rate is increased to (150°C/min) and the temperature is raised to 1170°C and then kept for 3 minutes. The graphite mold heats up the green body. Because of its fast heating rate, it is very important to keep the temperature uniform in the sintering area. At the same time, as the temperature rises, the grains in the green body begin to grow. At this time, the pressure rises from 0 MPa at 700°C to 37.5MPa (1.2T), at this pressure helps to hinder the movement of the grain boundary to achieve the purpose of controlling the grain size, the pressure rises from 37.5MPa (1.2T) to the sintering pressure of 50MPa (1.6T) when the temperature is kept at 1170°C for 3 minutes , the heat preservation and pressurization at this time will make the phase transformation in the zirconia more sufficient, and keep a certain internal stress in the sintered body.

Later stage of sintering: After the medium temperature holding, the temperature of the spark plasma sintering furnace was raised from 1170°C to 1350°C at a heating rate of 60°C/min, and the high temperature was held for 3 minutes. During this process, the sintering pressure was kept at 50MPa.

Heat from 1170°C to 1350°C and keep warm for 3 minutes. At this time, the heating rate is slowed down (60°C/min). The purpose of slowing down the heating rate and keeping warm is to control the temperature uniformity of each part of the sintered body. As a result, there is a large difference in the grain size between the center and the edge of the sintered body, and the performance of different regions of the sintered body is also different, which eventually reduces the overall performance of the composite ceramics. The grains continue to grow as the temperature rises, reaching The sintering pressure is 50MPa (1.6T), and the sintering pressure is maintained at the same time during the subsequent heating and holding processes to effectively control the grain size in the later stage of sintering.

After the sintering is completed and the high-temperature insulation is completed, stop the heating of the discharge plasma sintering furnace and stop the pressure at the same time. After the furnace temperature of the discharge plasma sintering furnace cools down to room temperature, the finished product is taken out to obtain the high-hardness, fine-grained ZTA system Composite ceramic materials.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area Structural analysis, the specific results are shown in Table 1.

It can be seen from Table 1 that the obtained high-hardness, fine-grained ZTA system composite ceramic material has a porosity of 1.53%, a sample density of 4.24g/cm ³ , a Vickers hardness of 18.27GPa, and a fracture toughness of 5.32MPa.m ^1/2 , the flexural strength is 629.01MPa, the average grain size of alumina is distributed in the range of 0.64±0.1μm, and the average grain size of zirconia is distributed in the range of 0.30±0.1μm, the X-ray diffraction of ZTA composite ceramic material samples According to the test, it can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Example 2

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, and the added mass of the additive chromia powder is 1% of the total mass of the alumina powder and yttria-stabilized zirconia powder, then put the mixed powder into a ball mill jar, and add the mixed powder Three times the mass of zirconia ball milling balls were used for ball milling, the ball milling time was 12 hours, and the ball milling rate was 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) sintering: the specific operation is the same as in Example 1.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the porosity of the high-hardness, fine-grained ZTA system composite ceramic material is 1.17%, the sample density is 4.26g/cm ³ , the Vickers hardness is 18.30GPa, and the fracture toughness is 5.64MPa.m ^1/2 , the flexural strength is 801.01MPa, the average grain size of alumina is distributed within the range of 0.85±0.1μm, and the average grain size of zirconia is distributed within the range of 0.28±0.1μm. For ZTA composite ceramic material samples The X-ray diffraction test is carried out, and it can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Example 3

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, the mass of the additive added is 5% of the total mass of the alumina powder and yttria stabilized zirconia powder, then the mixed powder is put into a ball mill jar, and 3 times the mass of the mixed powder is added Zirconia ball milling balls are used for ball milling, the ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) sintering: the specific operation is the same as in Example 1.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the obtained high-hardness, fine-grained ZTA system composite ceramic material has a porosity of 0.48%, a sample density of 4.25g/cm ³ , a Vickers hardness of 20.18GPa, and a fracture toughness of 6.37MPa.m ^1/2 , the flexural strength is 666.60MPa, the average grain size of alumina is distributed in the range of 0.4±0.1μm, and the average grain size of zirconia is distributed in the range of 0.20±0.1μm. For ZTA composite ceramic material samples Carrying out X-ray diffraction test, it can be seen from the XRD diffraction peaks that the zirconia in the sample is basically a tetragonal phase, and the XRD pattern of the product prepared in this embodiment is shown in Figure 3 .

Example 4

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, the mass of the additive added is 10% of the total mass of the alumina powder and yttria stabilized zirconia powder, then the mixed powder is put into a ball mill jar, and 3 times the mass of the mixed powder is added Zirconia ball milling balls are used for ball milling, the ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) sintering: the specific operation is the same as in Example 1.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the obtained high-hardness, fine-grained ZTA system composite ceramic material has a porosity of 0.74%, a sample density of 4.28g/cm ³ , a Vickers hardness of 19.02GPa, and a fracture toughness of 5.54MPa.m ^1/2 , the flexural strength is 795.84MPa, the average grain size of alumina is distributed within the range of 0.58±0.1μm, and the average grain size of zirconia is distributed within the range of 0.24±0.1μm. For ZTA composite ceramic material samples The X-ray diffraction test is carried out, and it can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Example 5

A method for preparing a high-hardness, fine-grained ZTA system composite ceramic material is provided, comprising the following steps:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, the mass of the additive added is 20% of the total mass of the alumina powder and yttria stabilized zirconia powder, then the mixed powder is put into a ball mill jar, and 3 times the mass of the mixed powder is added Zirconia ball milling balls are used for ball milling, the ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) sintering: the specific operation is the same as in Example 1.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the obtained high-hardness, fine-grained ZTA system composite ceramic material has a porosity of 0.50%, a sample density of 4.29g/cm ³ , a Vickers hardness of 18.53GPa, and a fracture toughness of 4.79MPa.m ^1/2 , and the flexural strength is 537.69MPa. The X-ray diffraction test is carried out on the ZTA composite ceramic material sample. It can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Comparative example 1

A preparation method of a ZTA system composite ceramic material is provided, comprising the steps of:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia (3Y-ZrO ₂ ) powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, the mass of the additive added is 5% of the total mass of the alumina powder and yttria stabilized zirconia powder, then the mixed powder is put into a ball mill jar, and 3 times the mass of the mixed powder is added Zirconia ball milling balls are used for ball milling, the ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) Sintering: Place the green body obtained in step 3) into a discharge plasma sintering furnace, seal the discharge plasma sintering furnace and vacuumize it. At this time, the temperature in the discharge plasma sintering furnace is room temperature and the environment is vacuum, and sintering starts. The process is named sintering process 1.

Specifically: heat the spark plasma sintering furnace, raise the temperature of the spark plasma sintering furnace from room temperature to 700°C, the heating rate is 100°C/min, and then raise the temperature to 1350°C, the heating rate is 130°C/min, the pressure is accompanied by The heating process increases linearly. When the temperature rises to 1350°C, pressurize to a sintering pressure of 30MPa, and finally hold the heat for 3 minutes.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the porosity of the obtained high-hardness, fine-grained ZTA system composite ceramic material is 1.17%, the sample density is 4.20g/cm ³ , the Vickers hardness is 20.04GPa, and the fracture toughness is 5.93MPa.m ^1/2 , the flexural strength is 473.91MPa, the average grain size of alumina is distributed in the range of 0.82±0.1μm, and the average grain size of zirconia is distributed in the range of 0.37±0.1μm. For ZTA composite ceramic material samples The X-ray diffraction test is carried out, and it can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Comparative example 2

A preparation method of a ZTA system composite ceramic material is provided, comprising the steps of:

1) Raw material pretreatment: weigh alumina powder and yttria-stabilized zirconia powder according to the mass ratio of 4:1, and the specific operation of pretreatment is the same as that in Example 1.

2) Mixing ball milling: add dispersant and additives to the pretreated alumina powder and yttria-stabilized zirconia powder in step 1) to form a mixed powder, wherein the added mass of dispersant is the raw material alumina powder and yttrium oxide 0.2% of the total mass of the stabilized zirconia powder, the mass of the additive added is 5% of the total mass of the alumina powder and yttria stabilized zirconia powder, then the mixed powder is put into a ball mill jar, and 3 times the mass of the mixed powder is added Zirconia ball milling balls are used for ball milling, the ball milling time is 12 hours, and the ball milling rate is 300r/min. Obtain a uniform powder.

3) Drying, sieving and debinding and shaping: the specific operation is the same as in Example 1.

4) Sintering: Place the green body obtained in step 3) into a discharge plasma sintering furnace, seal the discharge plasma sintering furnace and vacuumize it. At this time, the temperature in the discharge plasma sintering furnace is room temperature and the environment is vacuum, and sintering starts. The process is named sintering process 2.

Specifically: heat the spark plasma sintering furnace, raise the temperature of the spark plasma sintering furnace from room temperature to 700°C, the heating rate is 100°C/min, and then raise the temperature to 1350°C, the heating rate is 130°C/min, the pressure is accompanied by The heating process increases linearly. When the temperature rises to 1350 ° C, the pressure is increased to 50 MPa for sintering pressure, and finally the heat preservation and pressure holding are carried out for 3 minutes.

Clean and polish the surface of the obtained high-hardness, fine-grained ZTA system composite ceramic material for hardness testing, and cut and obtain rectangular samples for flexural strength testing, XRD phase analysis, and field emission scanning electron microscopy for the area From the structural analysis, it can be seen from Table 1 that the porosity of the high-hardness, fine-grained ZTA system composite ceramic material is 1.07%, the sample density is 4.25g/cm ³ , the Vickers hardness is 18.32GPa, and the fracture toughness is 4.73MPa.m ^1/2 , the flexural strength is 542.72MPa, the average grain size of alumina is distributed in the range of 0.49±0.1μm, and the average grain size of zirconia is distributed in the range of 0.23±0.1μm. For ZTA composite ceramic material samples The X-ray diffraction test is carried out, and it can be seen from the XRD diffraction peak that the zirconia in the sample is basically a tetragonal phase.

Table 1. The performance test data of embodiment 1-5 and comparative example 1-2

The design of sintering rate and sintering pressure in the early stage of sintering is the key to improving the compactness of multiphase ceramics. It can be clearly compared in Figure 1 that the microstructure of sintering process 2 and sintering process 3 under the composition of ZTA-5Cr The structure is relatively obvious. It can be seen that the pores on the surface of the composite ceramics sintered by sintering process 3 are significantly reduced. It can be seen from Figure 2 that the temperature and pressure curves of sintering process 1, sintering process 2 and sintering process 3 change. After optimizing the sintering process, the pores in the sintered body are significantly reduced. The reasonable sintering process reduces the grain size of the composite ceramics, making the sintered sample particles tightly arranged, improving the bending strength and fracture toughness of the sample, and the sample also has higher hardness.

From Examples 1-5, it can be seen that adding an appropriate amount of chromium oxide is beneficial to refine the grain size, improve hardness, fracture toughness and flexural strength, wherein a small amount of chromium oxide (1%) can significantly improve the flexural strength, However, as the chromium oxide continues to increase, the flexural strength first decreases, then increases, and then decreases; while the hardness, fracture toughness and grain size all increase first and then decrease with the increase of chromium oxide. By comparing the data in Table 1, it can be clearly seen that when the sintering pressure increases, the grain size of the sample decreases to a certain extent. The diffraction peaks corresponding to the crystal planes corresponding to the doping amount of Cr ₂ O ₃ in different concentrations of the products prepared in Examples 1-5 are shown in Figure 4, and the addition of Cr ₂ O ₃ will form a solid solution with Al ₂ O ₃ . Figure 5 shows the microstructure diagrams of the Cr ₂ O ₃ doping amounts prepared in Examples 1-5 at different concentrations.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (8)

1. A preparation method of a high-hardness and fine-grain ZTA complex-phase ceramic material is characterized by comprising the following steps of:

1) Respectively carrying out water leaching, centrifugation and drying on the alumina powder and the yttria-stabilized zirconia powder to complete raw material pretreatment;

2) Adding a dispersing agent and chromium oxide powder into the pretreated aluminum oxide powder and yttrium oxide stabilized zirconia powder in the step 1), ball-milling, vacuum drying, sieving, removing glue, and shaping to obtain a blank; wherein the addition amount of the chromic oxide powder is 1-10% of the total mass of the raw materials of the aluminum oxide powder and the yttrium oxide stabilized zirconia powder, and the grain diameter of the chromic oxide powder is 30-50nm;

3) Placing the green body obtained in the step 2) into a spark plasma sintering furnace for sintering, wherein the sintering comprises a sintering early stage, a sintering middle stage and a sintering late stage, and the specific sintering process comprises the following steps:

and (3) sintering earlier stage: the temperature is increased from room temperature to 600-800 ℃, the heating rate is 50-150 ℃/min, and the sintering pressure is 0MPa;

in the middle stage of sintering: the temperature is continuously increased to 1170-1200 ℃ on the basis of the temperature at the early stage of sintering, the temperature increase rate is 100-200 ℃/min, the sintering pressure is gradually increased to 20-40 MPa in the temperature increase process, the temperature is kept for 3-5 min after the temperature increase is finished, and the pressure is gradually increased while the temperature is kept until the sintering pressure reaches 45-60 MPa;

and (3) at the later stage of sintering: after the heat preservation in the middle sintering stage is finished, the temperature is heated to 1300-1400 ℃ on the basis of the temperature in the middle sintering stage, the heating rate is 50-100 ℃/min, the heat preservation is carried out for 3-5 min, and in the process, the pressure is continuously maintained to be consistent with the pressure in the middle sintering stage;

and after the heat preservation in the later sintering stage is finished, stopping heating and pressurizing, and cooling to room temperature along with the furnace to obtain the high-hardness fine-grain ZTA system complex-phase ceramic material.

2. The preparation method according to claim 1, wherein in the step 1), the mass ratio of the alumina powder to the yttria-stabilized zirconia powder is (60-90): (10 to 40).

3. The preparation method according to claim 1, wherein in the step 1), the purity of the alumina powder is more than 99.99%, and the particle size is 30-80 nm; the purity of the yttria-stabilized zirconia powder is more than 99.99 percent, and the particle size is 30-80 nm.

4. The preparation method according to claim 1, wherein in the step 1), the three steps of water immersion, centrifugation and vacuum drying pretreatment are sequentially repeated for 2 to 3 times.

5. The preparation method according to claim 1, wherein in the step 1), the pretreatment process is:

water leaching: adding deionized water with the mass of 3-5 times that of the alumina powder or yttria-stabilized zirconia powder into the alumina powder or yttria-stabilized zirconia powder, and stirring the mixture for 40-80 min under the magnetic stirring of 300-800 r/min to complete water leaching;

centrifuging: centrifuging the alumina powder or yttria-stabilized zirconia powder subjected to water leaching at the centrifugation rate of 5000-7000 r/min for 20-60 min to finish the centrifugation;

and (3) vacuum drying: drying the centrifuged alumina powder or yttria-stabilized zirconia powder at the temperature of 100-120 ℃ for 12-24 hours to complete vacuum drying, thereby obtaining the pretreated raw material alumina powder or yttria-stabilized zirconia powder.

6. The preparation method according to claim 1, wherein in the step 2), the amount of the dispersant added is 0.01 to 0.2% of the total mass of the raw materials of the alumina powder and the yttria-stabilized zirconia powder.

7. The method according to claim 1, wherein in the step 2),

ball milling: the ball milling time is 12-24 h, the ball milling speed is 150-300 r/min, and uniform powder is obtained;

and (3) vacuum drying: the drying time is 12-24 h, and the drying temperature is 60-100 ℃;

sieving and removing glue: adopting a 150-mesh sieve, wherein the glue discharging environment is a vacuum environment, the glue discharging temperature is 400-500 ℃, and the glue discharging time is 2-4 h.

8. The method according to claim 1, wherein the purity of the chromium oxide powder is 99.99% or more.

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