CN113816770B - Preparation method for improving surface activity of aluminum oxide-zirconium oxide composite ceramic - Google Patents

Abstract

A method for improving the surface activity of alumina-zirconia composite ceramics. The laser cladding method is used to synthesize hydroxyapatite on the surface of alumina-zirconia composite ceramics in situ, and the obtained coating has a uniform thickness and improves alumina-zirconia. The surface activity of zirconia composite ceramics; realize the metallurgical bond between the coating and the substrate, so that there is no crack and gap between the two, and the bond is firm. Compared with the sol-gel method, the electrochemical method and the electrophoretic deposition method, the invention has no lengthy chemical reaction cycle in the whole process, thereby shortening the preparation time, simplifying the processing procedure and saving the experiment cost.

Description

Preparation method for improving the surface activity of alumina-zirconia composite ceramics

technical field

The invention relates to the field of biomedical materials, in particular to a preparation method for improving the surface activity of alumina-zirconia composite ceramics.

Background technique

Bioceramics have been widely used in biomedical fields, such as bone fillers, hip joint repair, due to their excellent physical and chemical stability, good biocompatibility and mechanical compatibility, special bioaffinity and sterilization. body and dentures. Among them, zirconia ceramics have been regarded as the first choice for denture restorations, and can be used clinically as dental crowns, fixed partial dentures and implants. This is mainly because in addition to its excellent mechanical properties and biocompatibility, it also has aesthetic properties comparable to natural teeth. However, under the influence of humid environment in vivo, zirconia ceramics will spontaneously undergo crystal transformation, a phenomenon called aging. Aging will reduce the mechanical properties of zirconia ceramics and affect its clinical service life. At present, the development of zirconia-alumina composite ceramics is one of the methods to improve the anti-aging ability. The addition of alumina can greatly increase the threshold of phase transition of zirconia ceramics, thereby inhibiting the occurrence of phase transition.

However, both alumina and zirconia are biologically inert ceramics with poor osseointegration and osteoinduction behaviors. After implantation in the human body, it cannot form a close chemical bond with natural bone, nor can it induce the formation of new bone. Usually, a fibrous capsule with no bonding effect is formed at the interface between the implant and the natural bone, which leads to the loosening of the implant and affects the long-term use effect. Therefore, surface modification of alumina-zirconia ceramics is an urgent problem to be solved at present. Hydroxyapatite has a chemical composition similar to that of human teeth and bone tissue, so it is often used as a coating material for inert implants. Among the preparation methods of coatings, spraying is one of the most common methods. Literature [K.Kulpetchdara,A.Limpichaipanit,G.Rujijanagul,et al.HA/β-TCP plasma sprayed coatings on Ti substrate forbiomedical application[J].Ceramics International 44(2018)1328–1333.] using plasma spraying method in A hydroxyapatite/calcium phosphate composite coating was prepared on the surface of the titanium substrate. Literature [A.Jemat,M.J.Ghazalia,M.Razali,et al.Influence of the nano hydroxyapatite powder onthermally sprayed HA coatings onto stainless steel[J].Surface&CoatingsTechnology 306(2016)181–186.] using thermal spraying method on stainless steel substrate A hydroxyapatite coating was successfully prepared on the surface. From the current public sources, the methods for surface modification of ceramic substrates mainly focus on wet spraying method, coating method and biomimetic method. Literature [K.Pardun,L.Treccani,E.Volkmann,et al.Mixed zirconiacalciumphosphate coatings for dental implants:Tailoring coating stability and bioactivity potential[J].Materials Science and Engineering C 48(2015)337–346.] using wet method The active coating of calcium zirconium phosphate was successfully prepared on the surface of zirconia implant by spraying method. Although the coatings prepared by the above methods all showed biological activity, there were cracks and gaps between the coatings and the substrate, and the bonding was not strong.

J.Pou,M.Boutinguiza,et al.Main characteristics of calcium phosphatecoatings obtained by laser cladding[J].Applied Surface Science 247(2005)486–492.]通过同步送粉的方式将羟基磷灰石熔覆在钛合金表面，成功对钛合金进行了表面改性。然而羟基磷灰石粉末价格昂贵，直接使用其作为原始涂层粉末会增加生产成本，因此可使用CaHPO₄·2H₂O和CaCO₃混合粉末来替代羟基磷灰石作为原始涂层粉末。在高能激光束的作用下，CaHPO₄·2H₂O和CaCO₃能够原位反应生成羟基磷灰石等活性材料。文献[邓迟,张亚平,高家诚.激光熔覆生物陶瓷涂层和界面的研究[J].应用激光,26(1)(2006)21-28.]以CaHPO₄·2H₂O和CaCO₃混合粉末为原始涂层粉末，采用CO₂激光在钛合金表面原位合成具有良好生物活性的涂层，改善了钛合金的表面性能。文献[M.Zheng,D.Fan,X.K.Li,etal.Microstructure and osteoblast response of gradient bioceramic coating ontitanium alloy fabricated by laser cladding[J].Applied Surface Science 255(2008)426–428.]以CaHPO₄·2H₂O和CaCO₃混合粉末为原始涂层粉末，采用CO₂激光在Ti合金表面原位合成梯度活性涂层，并通过添加稀土元素进一步细化组织和提高涂层的生物活性。In recent years, the laser cladding method has attracted extensive attention due to its simple and flexible processing, and its ability to achieve metallurgical bonding of substrates and coatings. It uses a high-energy laser beam as a heating source, and clads the required material on the surface of the substrate by pre-powder or synchronous powder feeding, which is a promising coating preparation process. Literature [F.

J.Pou,M.Boutinguiza,et al.Main characteristics of calcium phosphatecoatings obtained by laser cladding[J].Applied Surface Science 247(2005)486–492.] The hydroxyapatite cladding on the The surface of titanium alloy was successfully modified. However, hydroxyapatite powder is expensive, and using it directly as the original coating powder will increase the production cost, so the mixed powder of CaHPO ₄ ·2H ₂ O and CaCO ₃ can be used instead of hydroxyapatite as the original coating powder. Under the action of high-energy laser beam, CaHPO ₄ ·2H ₂ O and CaCO ₃ can react in situ to generate active materials such as hydroxyapatite. Literature [Deng Chi, Zhang Yaping, Gao Jiacheng. Study on Laser Cladding Bioceramic Coatings and Interfaces [J]. Applied Laser, 26(1)(2006) 21-28.] Mixing CaHPO ₄ ·2H ₂ O and CaCO ₃ The powder is the original coating powder, and a coating with good biological activity was synthesized in situ on the surface of titanium alloy by _CO2 laser, which improved the surface properties of titanium alloy. Literature [M.Zheng,D.Fan,XKLi,etal.Microstructure and osteoblast response of gradient bioceramic coating ontitanium alloy fabricated by laser cladding[J].Applied Surface Science 255(2008)426–428.] with CaHPO ₄ 2H _{2 The} mixed powder of O and CaCO3 is the original coating powder, and the gradient active coating was synthesized in situ on the surface of Ti alloy by _CO2 laser, and the structure was further refined and the biological activity of the coating was improved by adding rare earth elements.

In order to further improve the molding quality of the laser cladding coating, it is necessary to reasonably control the thickness and uniformity of the preset coating. To this end, the literature [RRBehera,A.Hasan,MRSankar,et al.Laser cladding with HA and functionally graded TiO ₂ -HA precursors on Ti–6Al–4V alloy for enhancingbioactivity and cyto-compatibility[J].Surface&Coatings Technology 352(2018) 420-436.] The original coating powder is made into slurry and spread on the surface of the substrate, followed by laser cladding, which can well ensure the uniformity of the pre-coating. However, the preparation of the slurry and the drying treatment after coating will undoubtedly make the experimental link more lengthy and waste manpower and material resources. In addition, compared with the metal substrate, the high melting point and brittleness of the ceramic substrate increase the difficulty of preparing the coating. Due to the high melting point of the ceramic substrate, the required input laser energy density during cladding is high. However, it is brittle and prone to cracking and deformation of the substrate under great thermal shock. Therefore, the literature [O.Carvalho,F.Sousa,S.Madeira,et al.HAp-functionalized zirconia surfaces via hybrid laser processfor dental applications[J].Optics and Laser Technology 106(2018)157–167.]by laser sintering The hydroxyapatite coating was prepared on the surface of zirconia ceramics by the method. Compared with the laser cladding method, the laser sintering method uses a lower laser energy density and does not cause a large thermal shock to the ceramic substrate, which can avoid the problem of cracking and deformation of the ceramic substrate, but it will cause the coating to be combined with the substrate. Unstable problem.

SUMMARY OF THE INVENTION

In order to overcome the problems of poor bonding between the coating and the substrate and poor fluidity of the original coating powder in the prior art, the present invention provides a method for improving the surface activity of the alumina-zirconia composite ceramic.

The concrete process of the present invention is:

Step 1, prepare spherical powder:

When preparing spherical powder, a mixed powder of CaHPO ₄ ·2H ₂ O and CaCO ₃ is prepared; a solution is added to the mixed powder, and a mixed slurry is obtained after ball milling. The mass percentage of CaHPO ₄ ·2H ₂ O is 78-82%, and the mass percentage of CaCO ₃ is 18-22%

The resulting mixed slurry was dried to obtain the original coating powder. The mass of the original coating powder is 200-250g;

Distilled water is added to the obtained original coating powder, and the mixture is uniformly stirred to obtain a mixed slurry. The mass percentage of the original coating powder and distilled water is 40-50:60-50.

A spherical powder with a particle size distribution range of 21.9-122.5 μm was obtained by a centrifugal spray granulator.

During spray granulation, the inlet air temperature and the outlet air temperature of the centrifugal spray granulator are respectively 350-400°C and 140-160°C. The rotation speed of the feed pump is 10-15r/min.

Step 2, apply the spherical powder layer:

The obtained spherical powder is spread on the surface of the alumina-zirconia composite ceramic substrate to obtain a uniformly spread spherical powder layer; the thickness of the spherical powder layer is 200-250 μm.

In the alumina-zirconia composite ceramic substrate, alumina is 55-70%, zirconia is 30-45%, and the percentages are mole percentages.

Step 3, prepare alumina-zirconia composite ceramics:

Through the laser cladding method, the spherical powder coated on the surface of the alumina-zirconia composite ceramic substrate is melted and solidified, and an active coating is obtained on the surface of the substrate. The specific process is as follows:

The first step is to preheat the substrate.

The alumina-zirconia composite ceramic substrate covered with spherical powder is placed on a heating table for preheating, and the heating temperature is 150-300°C.

The second step is to set the processing parameters.

Move the laser nozzle to the axis of symmetry in the width direction of the alumina-zirconia composite ceramic substrate, and make the laser nozzle 10 mm away from the starting end of the substrate. The vertical distance between the laser nozzle and the substrate is 15mm. Set the laser scanning power to be 600-800W, the scanning speed to be 650-750mm/min, the scanning path to be single-track linear scanning, and the scanning distance to be 30-60mm.

In the third step, a fused active coating is obtained on the surface of the alumina-zirconia composite ceramic substrate by using a laser cladding method.

Turn on the laser, and laser clad the spherical powder coated on the surface of the alumina-zirconia composite ceramic substrate; the spherical powder absorbs laser energy to melt, and forms a fused active coating on the surface of the alumina-zirconia composite ceramic substrate . Natural cooling to obtain surface-modified alumina-zirconia composite ceramics.

In the laser cladding, the water content in the glove box is maintained at 0.5 ppm, the oxygen content is 34-39 ppm, and the box pressure is 2-3 mbar. The shielding gas for laser cladding is pure argon.

The invention utilizes the laser cladding method to synthesize hydroxyapatite on the surface of the alumina-zirconia composite ceramic in situ, improves the surface activity of the alumina-zirconia composite ceramic, realizes the metallurgical bonding between the coating and the substrate, and simplifies the The experimental technology and the experimental cost are saved.

Compared with the prior art, the present invention has the following outstanding features:

1. Compared with the traditional slurry coating method, the present invention uses spherical powder composed of CaHPO ₄ ·2H ₂ O and CaCO ₃ during coating, as shown in FIG. 1 . The traditional slurry coating method is to mix CaHPO ₄ 2H ₂ O and CaCO ₃ powder with a binder in a certain proportion, make a slurry and then spread it on the surface of the substrate, then dry the slurry, and pre-set the slurry. The layer is laser clad. In the present invention, the CaHPO ₄ ·2H ₂ O and CaCO ₃ powders are made into slurry, granulated to turn them into spherical powders, and then spread on the surface of the substrate to perform laser cladding on the spherical powders. In contrast, the coating of spherical powder can avoid the problems of cracking and peeling of the preset layer caused by drying after coating the slurry, and improve the molding quality of the coating after cladding. At the same time, since the laser cladding is carried out in a closed glove box, for the traditional slurry laying method, if multiple layings are required, the substrate needs to be taken out of the glove box every time, and the substrate is re-laid. After the slurry is coated and dried, it is put into the glove box again for laser cladding; and the spherical powder coating used in the present invention can directly complete the process of multiple coating and cladding in the glove box.

2. The present invention utilizes a high-energy laser beam to melt spherical powder composed of CaHPO ₄ ·2H ₂ O and CaCO ₃ , and directly in situ reacts on the surface of an alumina-zirconia composite ceramic substrate to synthesize hydroxyapatite (hydroxyapatite) that is similar to human bone components. Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ) and other calcium phosphate active materials, as shown in FIG. 2 . From the phase analysis results of the coating surface, it can be seen that the coating contains a large number of calcium phosphate active phases, which are Ca ₁₀ with crystal plane indices (-234), (144), (006) and (106) respectively. (PO ₄ ) ₆ (OH) ₂ phase 1, Ca ₄ P ₂ O ₉ phase 2 with crystal plane indices (-222), (105), (220), (342), (526) Ca ₃ (PO ₄ ) ₂ phase 3, crystal face index of (132), (121), (541), (-622), (242) Ca ₂ P ₂ O ₇ phase 4, crystal face index of (112) , (032), (-241) Ca(PO ₃ ) ₂ phase 5, crystal face index is (033), (-236) CaP ₄ O ₁₁ phase 6, these calcium phosphate salts will cause PO in human body fluids ₄ ^3- and Ca ²⁺ were adsorbed on the surface of the coating, thereby inducing the formation of bone-like phosphates on the surface of the coating. Therefore, it can be determined that the coating prepared by the laser cladding method of the present invention has biological activity, and the surface activity of the alumina-zirconia composite ceramic is improved.

3. The process is simple and the molding speed is fast. Compared with the sol-gel method, electrochemical method and electrophoretic deposition method, the whole process does not have a lengthy chemical reaction cycle, thereby shortening the preparation time and simplifying the processing procedure.

4. The interface between the coating and the substrate is firmly bonded. Under the action of the laser beam, both the coating and the upper surface of the substrate are melted, and local mutual diffusion occurs in the molten state, resulting in a chemical metallurgical bond between the coating and the substrate. Similar to the literature [O.Carvalho,F.Sousa,S.Madeira,et al.HAp-functionalized zirconia surfaces viahybrid laser process for dental applications[J].Optics and Laser Technology106(2018)157–167.] using laser sintering method in Hydroxyapatite coatings prepared on the surface of zirconia substrates and literatures [A.Jemat,M.J.Ghazalia,M.Razali,et al.Influence of the nano hydroxyapatitepowder on thermally sprayed HA coatings onto stainless steel[J].Surface&Coatings Technology 306 (2016) 181–186.] Compared with the hydroxyapatite coating prepared on the stainless steel substrate by the thermal spraying method, there is no crack and gap between the coating prepared by the present invention and the substrate, and the combination is firm, as shown in Figure 3 Show.

Description of drawings

Fig. 1 is the topography of the powder after granulation of the present invention.

Fig. 2 is the phase analysis spectrum of the surface of the active coating prepared by the present invention.

3 is a microstructure diagram at the interface between the active coating prepared by the present invention and the substrate, and a microstructure diagram at the interface between the active coating prepared by the laser sintering method and the thermal spraying method and the substrate.

In the figure: 1. Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ phase with crystal plane indices of (-234), (144), (006), (106); 2. Crystal plane indices of (-222), (105) Ca ₄ P ₂ O ₉ phase; 3. The crystal plane index is (220), (342), (526) Ca ₃ (PO ₄ ) ₂ phase; 4. The crystal plane index is (132), (121 ), (541), (-622), (242) Ca ₂ P ₂ O ₇ phases; 5. Ca(PO ₃ ) ₂ phases with crystal plane indices (112), (032), (-241); 6. The CaP ₄ O ₁₁ phase with crystal plane indices of (033) and (-236); 7. The bonding interface between the coating prepared by the present invention and the substrate. Above the dotted line is the coating area, and below the dotted line is the substrate area. 8. The bonding interface between the coating prepared by the laser sintering method and the substrate. 9. The bonding interface between the coating prepared by thermal spraying and the substrate.

Figure 4 is a flow chart of the present invention. .

Detailed ways

The present invention is a method for improving the surface activity of an alumina-zirconia composite ceramic substrate, and its process will be specifically described through five embodiments.

The concrete process of the present invention is:

Step 1, prepare spherical powder.

The first step is to formulate the original coating powder.

Take 80% CaHPO ₄ ·2H ₂ O and 20% CaCO ₃ , and the percentages are mass percentages. 200 g of mixed powder was prepared.

20 ml of polyvinyl alcohol solution and 100 ml of absolute ethanol were added to the mixed powder, and the mixed slurry was obtained after ball milling at a speed of 550 r/min for 4 hours.

The obtained mixed slurry was dried at room temperature for 24 h to obtain the original coating powder.

The second step is to prepare the slurry.

Distilled water is added to the original coating powder obtained in step 1, and the mixture is uniformly stirred to obtain a mixed slurry. The mass percentage of the original coating powder and distilled water is 40-50:60-50.

The third step is spray granulation.

Turn on the centrifugal spray granulator, and set the inlet air temperature and outlet air temperature of the centrifugal spray granulator to 350°C and 140°C, respectively. Turn on the centrifuge, air heater, turn on the motor and feed pump in sequence. The resulting slurry is fed into a centrifugal nozzle. The rotational speed of the feed pump is 10-15 r/min. After the slurry is all conveyed, turn off the heater and centrifugal fan, and collect spherical powder from the powder collector at the bottom of the spray dryer. The particle size distribution of the spherical powder ranges from 21.9 μm to 122.5 μm.

Step 2, laying a spherical powder layer on the surface of the alumina-zirconia composite ceramic substrate.

The spherical powder obtained in step 1 was spread on the surface of the alumina-zirconia composite ceramic substrate by using a doctor blade to obtain a uniformly spread spherical powder layer; the thickness of the spherical powder layer was 200 μm.

The alumina-zirconia composite ceramic substrate is composed of alumina and zirconia, wherein the alumina is 55% and the zirconia is 45%, and the percentages are mole percentages.

The size of the substrate is 70mm×12mm×4mm.

Step 3, laser cladding the spherical powder on the surface of the alumina-zirconia composite ceramic substrate.

Through the laser cladding method, the spherical powder coated in step 2 is further melted and solidified to obtain an active coating on the surface of the substrate. The specific preparation process is as follows:

The first step is to preheat the substrate.

The alumina-zirconia composite ceramic substrate covered with spherical powder was placed on a heating table for preheating, and the heating temperature was 150°C.

The second step is to set the processing parameters.

Move the laser nozzle to the axis of symmetry in the width direction of the alumina-zirconia composite ceramic substrate, and make the laser nozzle 10 mm away from the starting end of the substrate. Adjust the vertical distance between the laser nozzle and the substrate to be 15mm. Set the laser scanning power to be 600-800W, the scanning speed to be 650-750mm/min, the scanning path to be single-track linear scanning, and the scanning distance to be 30mm.

The path of the laser nozzle during scanning is set to take the current position of the laser nozzle as the starting point, and scan in a straight line parallel to the length of the substrate.

In the third step, a fused active coating is obtained on the surface of the alumina-zirconia composite ceramic substrate by using a laser cladding method.

Turn on the laser, and clad the spherical powder coated on the surface of the alumina-zirconia composite ceramic substrate by laser cladding.

During the laser cladding, a laser beam is outputted by a laser nozzle and irradiated on the surface of the spherical powder covered; the spherical powder absorbs laser energy and melts to form a molten pool. The laser nozzle moves according to the set path and stops at a distance of 30mm from the starting position.

During the scanning process, with the movement of the laser nozzle, the spherical powder coated on the surface of the alumina-zirconia composite ceramic substrate is continuously melted. When the laser beam leaves, a fused active coating is formed on the surface of the alumina-zirconia composite ceramic substrate.

During the laser cladding process, the moving speed of the laser nozzle is the set scanning speed.

The laser cladding process is completed in a glove box with pure argon as a protective atmosphere. The water content in the glove box is maintained at 0.5 ppm, the oxygen content is 34-39 ppm, and the box pressure is 2-3 mbar. The laser is a CO ₂ laser, the model is Rofin DC-015.

When the laser scanning is completed, the laser is turned off, the heating furnace is turned off, the substrate and the fused active coating are cooled naturally together, and the surface-modified alumina-zirconia composite ceramic is obtained.

The present invention describes its specific process in detail through five implementation cases. The coating components and preparation process of each embodiment are the same, and the difference lies in the process parameters of each embodiment.

The process parameters of each embodiment of table 1

Note: The contents of CaHPO ₄ ·2H ₂ O and CaCO ₃ in Table 1 are all mass percentages; the contents of original coating powder and distilled water are all mass percentages, and the contents of zirconia and alumina are all molar percentages.

By adjusting the process parameters in the whole process, the invention ensures that the spherical powder on the surface of the substrate is completely melted and part of the upper surface layer of the substrate is melted to obtain an active coating without cracks and gaps between the coating and the substrate.

Claims (4)

1. A preparation method for improving the surface activity of alumina-zirconia composite ceramic is characterized by comprising the following specific steps:

step 1, preparing spherical powder:

in the preparation of spherical powder, caHPO is prepared ₄ · 2H ₂ O and CaCO ₃ The mixed powder of (1); adding the solution into the mixed powder, and performing ball milling to obtain mixed slurry; drying the obtained mixed slurry to obtain original coating powder;

adding distilled water into the obtained original coating powder, and uniformly stirring to obtain mixed slurry;

preparing spherical powder with the particle size distribution range of 21.9-122.5 mu m by a centrifugal spray granulator;

the mass of the original coating powder is 200-250 g; the CaHPO ₄ · 2H ₂ 78-82% of O and CaCO ₃ The mass percentage of the component (A) is 18-22%;

step 2, paving a spherical powder layer:

spreading the obtained spherical powder on the surface of an alumina-zirconia composite ceramic substrate to obtain a uniformly spread spherical powder layer; the thickness of the spherical powder layer is 200-250 mu m;

step 3, preparing the alumina-zirconia composite ceramic:

the method comprises the following steps of melting and solidifying spherical powder paved on the surface of an alumina-zirconia composite ceramic substrate by a laser cladding method, and obtaining an active coating on the surface of the substrate, wherein the specific process comprises the following steps:

firstly, preheating a substrate;

placing the alumina-zirconia composite ceramic substrate coated with the spherical powder on a heating table for preheating, wherein the heating temperature is 150-300 ℃;

in the alumina-zirconia composite ceramic substrate, 55-70% of alumina and 30-45% of zirconia are contained, and the percentages are mole percentages;

secondly, setting processing parameters;

moving a laser nozzle to the symmetrical axis of the aluminum oxide-zirconium oxide composite ceramic substrate in the width direction, and enabling the laser nozzle to be 10mm away from the starting end of the substrate; the vertical distance between the laser nozzle and the substrate is 15mm; setting the laser scanning power to be 600-800W, the scanning speed to be 650-750 mm/min, the scanning path to be single-path linear scanning, and the scanning distance to be 30-60 mm;

thirdly, obtaining a fused active coating on the surface of the alumina-zirconia composite ceramic substrate by using a laser cladding method;

starting a laser, and carrying out laser cladding on the spherical powder paved on the surface of the alumina-zirconia composite ceramic substrate; the spherical powder absorbs laser energy to melt, and a fused active coating is formed on the surface of the alumina-zirconia composite ceramic substrate; and naturally cooling to obtain the surface modified alumina-zirconia composite ceramic.

2. The preparation method for improving the surface activity of the alumina-zirconia composite ceramic according to claim 1, wherein when the mixed slurry is prepared in the step 1, the mass percentage of the original coating powder to the distilled water is 40 to 50:60 to 50.

3. The preparation method for improving the surface activity of the alumina-zirconia composite ceramic according to claim 1, wherein in the step 1, during spray granulation, the air inlet temperature and the air outlet temperature of the centrifugal spray granulator are 350-400 ℃ and 140-160 ℃ respectively; the rotational speed of the feeding pump is 10-15 r/min.

4. The preparation method for improving the surface activity of the alumina-zirconia composite ceramic according to claim 1, wherein in the laser cladding, the water content in a glove box is maintained at 0.5ppm, the oxygen content is 34-39 ppm, and the box pressure is 2-3 mbar; the protective gas for laser cladding is pure argon.

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