A method for metallization of the surface of a homogeneous oxide ceramic

Abstract

The present invention provides a method for metallizing the surface of a homogeneous oxide ceramic, belonging to the technical field of ceramic metallization; the metallization method includes pretreatment, primary deposition, preparation of a metallization paste, coating and sintering; for the primary deposition, the pretreated ceramic is placed in a modified titanium dioxide sol, dried and then calcined to obtain the ceramic after primary deposition; the preparation method of the modified titanium dioxide sol is as follows: tetrabutyl titanate is added to absolute ethanol, and then aldehyde-functionalized alumina fibers are added to obtain reaction solution A; deionized water and glacial acetic acid are added to absolute ethanol to obtain reaction solution B; reaction solution A is added to reaction solution B, the temperature is raised to 44-48 °C, and 4-vinyl aniline is added, and the mixture is kept warm and stirred to obtain titanium dioxide sol; by using the metallization method of the present invention, the uniformity is good, the bonding strength between the ceramic and the metal coating is strong, the shear strength under compression is high, and the performance of resistance to high and low temperature cycling is excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic metallization, and particularly relates to a method for metallizing the surface of a homogeneous oxide ceramic. Background Art

[0002] With the development of technology, the applications of shielding materials and antennas are becoming more and more extensive, and at the same time, the requirements for shielding materials and antennas are getting higher and higher; with the development of electronic devices towards miniaturization, light weight and high performance, traditional metal shielding exposes more drawbacks. It is prone to corrosion in complex environments, affecting the shielding performance and also shortening the service life of the device; as a key component in a wireless communication system, an antenna is required to have high stability and performance in harsh environments.

[0003] Ceramics have excellent properties such as high hardness, high strength, good insulation, high temperature resistance and corrosion resistance, and play an important role in the fields of electrical and electronics, aerospace, mechanical manufacturing, medical treatment and construction; however, ceramics are insulators themselves, having the defect of not being conductive, and it is difficult to directly connect with metal components, which limits their further expansion in application scenarios such as electrical connection, heat conduction and structural integration.

[0004] Metallization is a ceramic surface treatment technology, which refers to forming a dense, uniform and strongly bonded metal layer on the ceramic surface, thereby endowing the ceramic material with metal properties that it originally does not have. Through metallization treatment, the metallized layer can be used as an intermediate layer to achieve reliable connection between the ceramic and the metal; it can also endow the ceramic surface with electrical conductivity, thermal conductivity, and improve the wear resistance and corrosion resistance of the ceramic surface, etc., and extend the service life of the ceramic;

[0005] The ceramic after metallization treatment can meet the usage requirements of shielding materials, antennas, etc. under complex working conditions, and metallization is of great significance for broadening the application range of ceramics.

[0006] At present, the main methods for metallizing the ceramic surface are sintered metal powder method, thin film method and electroless plating method;

[0007] Among them, in the sintered metal powder method, metal powder and binder are mixed and then coated on the ceramic surface, and then the metal powder is made to form a metal layer on the ceramic surface by high-temperature sintering. However, this method has the defect of poor bonding strength between the metal layer and the ceramic matrix, and the metal layer is prone to peeling off during use, thus shortening the service life. Moreover, high-temperature sintering will reduce the mechanical properties of the ceramic, etc., narrowing the usage range of the ceramic product;

[0008] The thin film method is to deposit a thin metal layer on the ceramic surface by methods such as chemical vapor deposition or physical vapor deposition. It can obtain a uniform and dense metallized layer, but its equipment cost is high and its process is relatively complex.

[0009] The electroless plating method uses redox reactions to deposit a metal layer on the surface of ceramics. This method has a relatively low cost, but the bonding strength of the metallized layer is weak, and the electroless plated metal layer is prone to oxidation at high temperatures, affecting its applicability at high temperatures.

[0010] With the development of technology, some existing technologies also metallize ceramics through the sol-gel method. However, for the metallized ceramics obtained, there are defects such as poor bonding strength between the ceramic matrix and the metallized layer, low shear strength under compression, and poor resistance to high and low temperature cycling. Summary of the Invention

[0011] In order to solve the technical problems existing in the prior art, the present invention provides a method for metallizing the surface of homogeneous oxide ceramics, which has good uniformity, strong bonding strength between the ceramic matrix and the metal coating, high shear strength under compression, excellent resistance to high and low temperature cycling, and strong applicability in complex environments.

[0012] A method for metallizing the surface of homogeneous oxide ceramics includes the steps of pretreatment, primary deposition, preparation of metallizing slurry, coating, and sintering, which are specifically as follows:

[0013] The oxide ceramic is one of alumina ceramics, quartz ceramics, and zirconia ceramics;

[0014] 1. Pretreatment

[0015] Place the ceramics in acetone with a mass 6 - 10 times that of the ceramics, raise the temperature to 53 - 60 °C, perform ultrasonic treatment, with an ultrasonic time of 12 - 18 min, an ultrasonic power of 132 - 146 W, and an ultrasonic frequency of 27 - 35 kHz. After the ultrasonic treatment is completed, filter out, and then put it into a sodium hydroxide solution with a mass 6 - 10 times that of the ceramics, and continue ultrasonic treatment while keeping the ultrasonic power and frequency unchanged. Control the ultrasonic time to be 22 - 28 min. After the ultrasonic treatment is completed, filter out, and then wash with deionized water until the washing liquid is neutral. After drying, obtain the pretreated ceramics;

[0016] The mass concentration of the sodium hydroxide solution is 8 - 12%.

[0017] 2. Primary deposition

[0018] Place the pretreated ceramic in the modified titanium dioxide sol, with the modified titanium dioxide sol completely submerging the pretreated ceramic. Control the lifting speed at 2.5 - 3.5 cm / min to obtain a titanium dioxide sol film on the surface of the pretreated ceramic. Then dry it at 62 - 67 °C for 11.5 - 12.5 h, and then put it into a calcination furnace. Heat it at a rate of 2.6 - 3.3 °C / min to 345 - 355 °C, hold for 12 - 18 min, and then heat it at a rate of 1.2 - 1.7 °C / min to 516 - 523 °C, hold for 1.4 - 1.6 h to obtain the ceramic after the first deposition;

[0019] The preparation method of the modified titanium dioxide sol is as follows: Add tetrabutyl titanate to absolute ethanol, and then add aldehyde-functionalized alumina fibers, and stir evenly to obtain reaction solution A; Add deionized water and glacial acetic acid to absolute ethanol, and stir evenly to obtain reaction solution B; Slowly add reaction solution A to reaction solution B, control the addition rate at 0.4 - 0.6 g / min. After the addition is completed, continue to stir for 27 - 34 min. After the stirring ends, heat it at a rate of 0.7 - 1.2 °C / min to 44 - 48 °C, add 2.0 - 2.4 g of 4-vinyl aniline, hold and stir for 32 - 38 min. After the stirring ends, obtain the titanium dioxide sol;

[0020] In the reaction solution A, the mass ratio of the absolute ethanol, tetrabutyl titanate, and aldehyde-functionalized alumina fibers is 67.4 - 68.5:32.2 - 32.7:5.3 - 5.8;

[0021] In the reaction solution B, the mass ratio of the absolute ethanol, deionized water, and glacial acetic acid is 106 - 112:10.0 - 10.4:10.3 - 10.8;

[0022] The mass ratio of the reaction solution B, reaction solution A, and 4-vinyl aniline is 126.3 - 133.2:104.9 - 106.7:2.0 - 2.4;

[0023] The preparation method of the aldehyde-functionalized alumina fibers is as follows: Place the alumina fibers in a sodium hydroxide solution, soak them at 70 - 74 °C for 1.8 - 2.2 h, filter and dry to obtain the soaked alumina fibers; Place the soaked alumina fibers in an ethanol solution, stir evenly, add a cinnamaldehyde solution, stir and react at 43 - 47 °C for 1.8 - 2.2 h, then add sodium borohydride, and stir and react at 3.5 - 4.6 °C for 2.7 - 3.4 h. After the reaction ends, filter, wash, and dry to obtain the aldehyde-functionalized alumina fibers;

[0024] The diameter of the alumina fibers is 3.2 - 3.6 μm, and the length is 13 - 16 μm;

[0025] The mass ratio of the alumina fiber to the sodium hydroxide solution is 9.5 - 10.4:78.6 - 83.5;

[0026] The mass concentration of the sodium hydroxide solution is 13 - 16%;

[0027] The mass ratio of the alumina fiber after soaking, the ethanol solution, the cinnamaldehyde solution, and sodium borohydride is 4.7 - 5.2:56 - 63:21.7 - 23.2:1.7 - 2.2;

[0028] The mass concentration of the ethanol solution is 16 - 20%;

[0029] The cinnamaldehyde solution is a mixture of cinnamaldehyde and a 10 - 13 wt% ethanol solution, and the mass ratio of cinnamaldehyde to the 10 - 13 wt% ethanol solution is 1.2:8.2 - 8.8.

[0030] 3. Preparation of metallization paste

[0031] Mix molybdenum powder, manganese powder, alumina powder, barium carbonate powder, calcium oxide powder, zirconium oxide powder, and boron oxide powder, then add absolute ethanol for ball milling. The ball milling time is 7.6 - 8.2 h, the ball milling speed is 77 - 85 rpm, and the ball - to - material ratio is 2 - 4:1. After ball milling, add silane coupling agent A - 186 and continue ball milling for 3.8 - 4.2 h, with a ball milling speed of 115 - 127 rpm. After ball milling, filter, wash, and dry to obtain a pretreated composite powder; mix ethyl cellulose, terpineol, glycerol, and glyceryl monostearate, and then perform water - bath heating until completely dissolved to obtain an additive; mix the pretreated composite powder with the additive, and then perform ultrasonic treatment. The ultrasonic time is 27 - 34 min, the ultrasonic frequency is 32 - 37 kHz, and the ultrasonic power is 156 - 165 W. After ultrasonic treatment, obtain the metallization paste;

[0032] The mass ratio of the molybdenum powder, manganese powder, alumina powder, barium carbonate powder, calcium oxide powder, zirconium oxide powder, boron oxide powder, absolute ethanol, and silane coupling agent A - 186 is 62.6 - 63.2:20.5 - 21.4:7.3 - 7.8:0.6 - 1.0:2.2 - 2.7:0.3 - 0.5:1.6 - 2.0:196 - 206:7.2 - 7.8;

[0033] The mass ratio of the ethyl cellulose, terpineol, glycerol, and glyceryl monostearate is 1.0 - 1.4:17.0 - 17.5:1.8 - 2.2:0.7 - 1.0;

[0034] The mass ratio of the pretreated composite powder to the additive is 96.6 - 97.4:20.8 - 21.5.

[0035] 4. Coating and Sintering

[0036] The metallization paste is screen-printed onto the ceramic surface after the first deposition. The coating thickness is controlled to be 28 - 32 μm. After coating, it is dried at 108 - 113 °C. After naturally cooling to room temperature, it is heated to 610 - 630 °C at a rate of 9.5 - 10.5 °C / min in a nitrogen atmosphere, held for 17 - 25 min, then heated to 1080 - 1130 °C at a rate of 4.2 - 5.5 °C / min, held for 13 - 20 min, then heated to 1400 - 1420 °C at a rate of 2.0 - 2.8 °C / min, held for 55 - 65 min, then cooled to 720 - 740 °C at a rate of 5.8 - 6.2 °C / min, held for 35 - 45 min, and finally cooled to 380 - 410 °C at a rate of 1.8 - 2.2 °C / min, and cooled in the furnace to room temperature to complete the metallization step, obtaining metallized ceramics.

[0037] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0038] 1. The present invention metallizes the ceramic surface by a specific method. First, the substrate is pretreated to remove organic and inorganic pollutants on the ceramic surface and activate the ceramic surface to enhance the adhesion of the subsequent coating. Then, a modified titanium dioxide sol is used for primary deposition to form a uniform and dense titanium dioxide coating on the ceramic surface, which is beneficial to the adhesion and combination of the subsequent metallization paste. The modified titanium dioxide sol includes aldehyde-functionalized alumina fibers. Specifically, the alumina fibers are first treated with alkali to make their surface contain more hydroxyl groups, and then aldehyde groups are introduced to carry out a condensation reaction with the hydroxyl groups, so that the aldehyde groups are introduced onto the surface of the alumina fibers. Sodium borohydride further reduces and stabilizes the reaction system, so that the aldehyde groups are stably connected to the surface of the alumina fibers. 4-Vinylaniline is also introduced into the modified titanium dioxide sol. The aldehyde groups of the aldehyde-functionalized alumina fibers can carry out a Schiff base reaction with 4-vinyl aniline, so that a stable three-dimensional structure is formed in the titanium dioxide sol, thereby improving the stability of the modified titanium dioxide sol. Moreover, the aldehyde-functionalized alumina fibers can be embedded in the micro-porous structure of the ceramic surface, increasing physical anchoring points and greatly improving the bonding force between the modified titanium dioxide sol and the ceramic substrate. Finally, during the subsequent sintering process, the strength of the coating is increased and the high and low temperature cycle resistance performance of the coating is ensured. In the step of preparing the metallization paste, the powder is first pretreated with an epoxy-based silane coupling agent, so that the surface of the pretreated composite powder contains more epoxy groups. Thus, when it is coated on the ceramic after primary deposition, it can react with the amino groups of the modified titanium dioxide sol, thereby enhancing the bonding force between the metallization paste and the ceramic. Combined with the addition of additives, the homogeneity of the coating is ensured, the reflectivity is improved, and finally the stability of the coating is good, the bonding force with the ceramic is high, and the applicability in complex environments such as high and low temperature cycles is excellent.

[0039] 2. The metallized ceramic obtained by metallizing a 99 alumina ceramic substrate using the metallization method of the present invention has a bonding strength of 51.2 - 53.6 MPa, a shear strength of 24.4 - 27.2 MPa, and a visible light reflectivity in the range of 380 - 780 nm of 70 - 75%.

[0040] 3. The metallized ceramic obtained by metallizing a 99 alumina ceramic substrate using the metallization method of the present invention is heated to 1500 °C at a rate of 30 °C / min, held for 1.0 h, and then cooled to 20 °C at a rate of 50 °C / min and held for 1.0 h. The above operations are taken as one cycle. After 20 cycles, the mass change rate is 0.14 - 0.19%, the bonding strength is 47.6 - 50.5 MPa, and the shear strength is 13.6 - 16.3 MPa. Detailed implementation mode

[0041] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described.

[0042] The oxide ceramic is one of alumina ceramics, quartz ceramics, and zirconia ceramics.

[0043] Example 1

[0044] 1. Pretreatment

[0045] The ceramic is placed in acetone with a mass six times that of the ceramic, the temperature is raised to 53°C, ultrasonic treatment is carried out, the ultrasonic time is 12 min, the ultrasonic power is 132 W, and the ultrasonic frequency is 27 kHz. After the ultrasonic treatment is completed, it is filtered out and then put into a sodium hydroxide solution with a mass eight times that of the ceramic, and ultrasonic treatment is continued while keeping the ultrasonic power and frequency unchanged. The ultrasonic time is controlled to be 22 min. After the ultrasonic treatment is completed, it is filtered out and then washed with deionized water until the washing liquid is neutral. After drying, the pretreated ceramic is obtained.

[0046] 2. First deposition

[0047] The pretreated ceramic is placed in the modified titanium dioxide sol, and the modified titanium dioxide sol completely submerges the pretreated ceramic. The pulling speed is controlled to be 2.5 cm / min, and a titanium dioxide sol film is obtained on the surface of the pretreated ceramic. Then it is dried at 62°C for 12.5 h, and then put into a calcination furnace, heated to 345°C at a rate of 2.6°C / min, held for 18 min, and then heated to 516°C at a rate of 1.7°C / min and held for 1.6 h to obtain the ceramic after the first deposition;

[0048] The preparation method of the modified titanium dioxide sol is as follows: 32.2 g of tetrabutyl titanate is added to 67.4 g of absolute ethanol, and then 5.3 g of aldehyde-functionalized alumina fibers are added and stirred evenly to obtain reaction solution A; 10.0 g of deionized water and 10.3 g of glacial acetic acid are added to 106 g of absolute ethanol and stirred evenly to obtain reaction solution B; 104.9 g of reaction solution A is slowly added to 126.3 g of reaction solution B, and the addition rate is controlled to be 0.4 g / min. After the addition is completed, stirring is continued for 27 min. After the stirring is completed, the temperature is raised to 44°C at a rate of 0.7°C / min, and 2.0 g of 4-vinyl aniline is added, and the mixture is stirred and held for 32 min. After the stirring is completed, the titanium dioxide sol is obtained;

[0049] The preparation method of the aldehyde-functionalized alumina fiber is as follows: Place 9.5 g of alumina fiber in 78.6 g of 13 wt% sodium hydroxide solution, soak it at 70 °C for 2.2 h, filter it out and dry it to obtain the soaked alumina fiber; Place 4.7 g of the soaked alumina fiber in 56 g of 16 wt% ethanol solution, stir evenly, add 21.7 g of cinnamaldehyde solution, stir and react at 43 °C for 2.2 h, then add 1.7 g of sodium borohydride, stir and react at 3.5 °C for 3.4 h. After the reaction is completed, filter, wash and dry to obtain the aldehyde-functionalized alumina fiber;

[0050] The diameter of the alumina fiber is 3.2 μm and the length is 13 μm;

[0051] The cinnamaldehyde solution is a mixture of cinnamaldehyde and 10 wt% ethanol solution, and the mass ratio of cinnamaldehyde to 10 wt% ethanol solution is 1.2:8.2;

[0052] 3. Preparation of metallized slurry

[0053] Mix 62.6 g of molybdenum powder, 20.5 g of manganese powder, 7.3 g of alumina powder, 0.6 g of barium carbonate powder, 2.2 g of calcium oxide powder, 0.3 g of zirconium oxide powder, and 1.6 g of boron oxide powder, then add 196 g of absolute ethanol for ball milling. The ball milling time is 7.6 h, the ball milling speed is 85 rpm, and the ball-to-material ratio is 2:1. After the ball milling is completed, add 7.2 g of silane coupling agent A-186 and continue ball milling for 3.8 h. The ball milling speed is 127 rpm. After the ball milling is completed, filter, wash and dry to obtain the pretreated composite powder; Mix 1.0 g of ethyl cellulose, 17.0 g of terpineol, 1.8 g of glycerol, and 0.7 g of glycerol monostearate, and then perform water bath heating until completely dissolved to obtain the added auxiliary agent;

[0054] Mix 96.6 g of the pretreated composite powder with 20.8 g of the added auxiliary agent, and then perform ultrasonic treatment. The ultrasonic time is 27 min, the ultrasonic frequency is 32 kHz, and the ultrasonic power is 156 W. After the ultrasonic treatment is completed, obtain the metallized slurry.

[0055] 4. Coating and sintering

[0056] The metallization paste is screen-printed onto the ceramic surface after the first deposition, and the coating thickness is controlled to be 28 μm. After the coating is completed, it is dried at 108 °C. After naturally cooling to room temperature, it is heated to 610 °C at a rate of 9.5 °C / min in a nitrogen atmosphere, held for 25 min, then heated to 1080 °C at a rate of 4.2 °C / min, held for 20 min, then heated to 1400 °C at a rate of 2.8 °C / min, held for 65 min, then cooled to 720 °C at a rate of 6.2 °C / min, held for 45 min, and finally cooled to 410 °C at a rate of 1.8 °C / min and cooled in the furnace to room temperature to complete the metallization step and obtain metallized ceramics.

[0057] Example 2

[0058] 1. Pretreatment

[0059] The ceramic substrate is placed in acetone with a mass 8 times that of the substrate, the temperature is raised to 56 °C, and ultrasonic treatment is carried out. The ultrasonic treatment time is 15 min, the ultrasonic power is 140 W, and the ultrasonic frequency is 31 kHz. After the ultrasonic treatment is completed, it is filtered out and then put into a 10 wt% sodium hydroxide solution with a mass 8 times that of the substrate, and ultrasonic treatment is continued while keeping the ultrasonic power and frequency unchanged. The ultrasonic treatment time is controlled to be 25 min. After the ultrasonic treatment is completed, it is filtered out and then washed with deionized water until the washing liquid is neutral. After drying, the pretreated ceramic is obtained.

[0060] 2. First deposition

[0061] The pretreated ceramic is placed in the modified titanium dioxide sol, and the modified titanium dioxide sol completely submerges the pretreated ceramic. The pulling speed is controlled to be 3.0 cm / min, and a titanium dioxide sol film is obtained on the surface of the pretreated ceramic. Then it is dried at 65 °C for 12.0 h, and then put into a calcining furnace and heated to 350 °C at a rate of 3.0 °C / min, held for 15 min, and then heated to 520 °C at a rate of 1.5 °C / min, held for 1.5 h to obtain the ceramic after the first deposition;

[0062] The preparation method of the modified titanium dioxide sol is as follows: 32.5 g of tetrabutyl titanate is added to 68.0 g of absolute ethanol, and then 5.6 g of aldehyde-functionalized alumina fibers are added and stirred evenly to obtain reaction solution A; 10.2 g of deionized water and 10.5 g of glacial acetic acid are added to 110 g of absolute ethanol and stirred evenly to obtain reaction solution B; 106.1 g of reaction solution A is slowly added to 130.7 g of reaction solution B, and the addition rate is controlled to be 0.5 g / min. After the addition is completed, stirring is continued for 30 min. After the stirring is completed, the temperature is raised to 46 °C at a rate of 1.0 °C / min, 2.2 g of 4-vinyl aniline is added, and stirring is carried out at a constant temperature for 35 min. After the stirring is completed, the titanium dioxide sol is obtained;

[0063] The preparation method of the aldehyde-functionalized alumina fiber is as follows: Place 10.0 g of alumina fiber in 80.0 g of 15 wt% sodium hydroxide solution, soak it at 72 °C for 2.0 h, filter it out and dry it to obtain the soaked alumina fiber; Place 5.0 g of the soaked alumina fiber in 60 g of 18 wt% ethanol solution, stir evenly, add 22.5 g of cinnamaldehyde solution, stir and react at 45 °C for 2.0 h, then add 2.0 g of sodium borohydride, stir and react at 4.0 °C for 3.0 h. After the reaction is completed, filter, wash and dry to obtain the aldehyde-functionalized alumina fiber;

[0064] The diameter of the alumina fiber is 3.5 μm and the length is 15 μm;

[0065] The cinnamaldehyde solution is a mixture of cinnamaldehyde and 12 wt% ethanol solution, and the mass ratio of cinnamaldehyde to 12 wt% ethanol solution is 1.2:8.5.

[0066] 3. Preparation of metallized paste

[0067] Mix 63.0 g of molybdenum powder, 21.0 g of manganese powder, 7.6 g of alumina powder, 0.8 g of barium carbonate powder, 2.5 g of calcium oxide powder, 0.4 g of zirconium oxide powder, and 1.8 g of boron oxide powder, then add 200 g of anhydrous ethanol for ball milling. The ball milling time is 8.0 h, the ball milling speed is 80 rpm, and the ball-to-material ratio is 3:1. After the ball milling is completed, add 7.6 g of silane coupling agent A-186 and continue ball milling for 4.0 h. The ball milling speed is 120 rpm. After the ball milling is completed, filter, wash and dry to obtain the pretreated composite powder; Mix 1.2 g of ethyl cellulose, 17.2 g of terpineol, 2.0 g of glycerol, and 0.8 g of glycerol monostearate, and then perform water bath heating until completely dissolved to obtain the added auxiliary agent;

[0068] Mix 97.1 g of the pretreated composite powder with 21.2 g of the added auxiliary agent, and then perform ultrasonic treatment. The ultrasonic time is 30 min, the ultrasonic frequency is 35 kHz, and the ultrasonic power is 160 W. After the ultrasonic treatment is completed, obtain the metallized paste.

[0069] 4. Coating and sintering

[0070] The metallization paste is screen-printed onto the ceramic surface after the first deposition, and the coating thickness is controlled to be 30 μm. After coating, it is dried at 110 °C. After naturally cooling to room temperature, it is heated to 620 °C at a rate of 10.0 °C / min in a nitrogen atmosphere, held for 20 min, then heated to 1100 °C at a rate of 5.0 °C / min, held for 15 min, then heated to 1410 °C at a rate of 2.5 °C / min, held for 60 min, then cooled to 730 °C at a rate of 6.0 °C / min, held for 40 min, and finally cooled to 400 °C at a rate of 2.0 °C / min and cooled to room temperature in the furnace to complete the metallization step and obtain metallized ceramics.

[0071] Example 3

[0072] 1. Pretreatment

[0073] The ceramic is placed in acetone with a mass 10 times that of the ceramic, the temperature is raised to 60 °C, and ultrasonic treatment is carried out. The ultrasonic time is 18 min, the ultrasonic power is 146 W, and the ultrasonic frequency is 35 kHz. After the ultrasonic treatment, it is filtered out, and then put into a 12 wt% sodium hydroxide solution with a mass 10 times that of the ceramic, and ultrasonic treatment is continued while keeping the ultrasonic power and frequency unchanged. The ultrasonic time is controlled to be 28 min. After the ultrasonic treatment, it is filtered out, and then washed with deionized water until the washing liquid is neutral. After drying, the pretreated ceramic is obtained.

[0074] 2. First deposition

[0075] The pretreated ceramic is placed in the modified titanium dioxide sol, and the modified titanium dioxide sol completely submerges the pretreated ceramic. The pulling speed is controlled to be 3.5 cm / min, and a titanium dioxide sol film is obtained on the surface of the pretreated ceramic. Then it is dried at 67 °C for 11.5 h, and then put into a calcination furnace and heated to 355 °C at a rate of 3.3 °C / min, held for 12 min, and then heated to 523 °C at a rate of 1.2 °C / min and held for 1.4 h to obtain the ceramic after the first deposition;

[0076] The preparation method of the modified titanium dioxide sol is as follows: 32.7 g of tetrabutyl titanate is added to 68.5 g of absolute ethanol, and then 5.8 g of aldehyde-functionalized alumina fibers are added and stirred evenly to obtain reaction solution A; 10.4 g of deionized water and 10.8 g of glacial acetic acid are added to 112 g of absolute ethanol and stirred evenly to obtain reaction solution B; 106.7 g of reaction solution A is slowly added to 133.2 g of reaction solution B, and the addition rate is controlled to be 0.6 g / min. After the addition is completed, stirring is continued for 34 min. After the stirring is completed, the temperature is raised to 48 °C at a rate of 1.2 °C / min, 2.4 g of 4-vinyl aniline is added, and stirring is carried out for 38 min while keeping the temperature. After the stirring is completed, the titanium dioxide sol is obtained;

[0077] The preparation method of the aldehyde-functionalized alumina fiber is as follows: 10.4 g of alumina fiber is placed in 83.5 g of 16 wt% sodium hydroxide solution and soaked at 74 °C for 1.8 h. After filtration and drying, the soaked alumina fiber is obtained; 5.2 g of the soaked alumina fiber is placed in 63 g of 20 wt% ethanol solution. After stirring evenly, 23.2 g of cinnamaldehyde solution is added, and the mixture is stirred and reacted at 47 °C for 1.8 h. Then, 2.2 g of sodium borohydride is added, and the mixture is stirred and reacted at 4.6 °C for 2.7 h. After the reaction is completed, the aldehyde-functionalized alumina fiber is obtained through filtration, washing, and drying.

[0078] The diameter of the alumina fiber is 3.6 μm, and the length is 16 μm.

[0079] The cinnamaldehyde solution is a mixture of cinnamaldehyde and 13 wt% ethanol solution, and the mass ratio of cinnamaldehyde to 13 wt% ethanol solution is 1.2:8.8.

[0080] 3. Preparation of metallization paste

[0081] 63.2 g of molybdenum powder, 21.4 g of manganese powder, 7.8 g of alumina powder, 1.0 g of barium carbonate powder, 2.7 g of calcium oxide powder, 0.5 g of zirconium oxide powder, and 2.0 g of boron oxide powder are mixed, and then 206 g of anhydrous ethanol is added for ball milling. The ball milling time is 8.2 h, the ball milling speed is 77 rpm, and the ball-to-material ratio is 4:1. After the ball milling is completed, 7.8 g of silane coupling agent A-186 is added, and ball milling is continued for 4.2 h. The ball milling speed is 115 rpm. After the ball milling is completed, the pretreated composite powder is obtained through filtration, washing, and drying; 1.4 g of ethyl cellulose, 17.5 g of terpineol, 2.2 g of glycerol, and 1.0 g of glycerol monostearate are mixed, and then heated in a water bath until completely dissolved to obtain the added auxiliary agent.

[0082] 97.4 g of the pretreated composite powder and 21.5 g of the added auxiliary agent are mixed, and then ultrasonic treatment is carried out. The ultrasonic time is 34 min, the ultrasonic frequency is 37 kHz, and the ultrasonic power is 165 W. After the ultrasonic treatment is completed, the metallization paste is obtained.

[0083] 4. Coating and sintering

[0084] The metallization paste is screen-printed onto the ceramic surface after the first deposition, and the coating thickness is controlled to be 2 μm. After coating, it is dried at 113 °C. After naturally cooling to room temperature, it is heated to 630 °C at a rate of 10.5 °C / min in a nitrogen atmosphere, held for 17 min, then heated to 1130 °C at a rate of 5.5 °C / min, held for 13 min, then heated to 1420 °C at a rate of 2.0 °C / min, held for 55 min, then cooled to 740 °C at a rate of 5.8 °C / min, held for 35 min, and finally cooled to 380 °C at a rate of 2.2 °C / min and cooled in the furnace to room temperature to complete the metallization step and obtain the metallized ceramic.

[0085] Comparative Example 1

[0086] Based on Example 2, the difference is that

[0087] In the first deposition step, the modified titanium dioxide sol is replaced with titanium dioxide sol in equal amounts;

[0088] The preparation method of the titanium dioxide sol is as follows: 32.5 g of tetrabutyl titanate is added to 68.0 g of absolute ethanol and stirred evenly to obtain reaction solution A; 10.2 g of deionized water and 10.5 g of glacial acetic acid are added to 110 g of absolute ethanol and stirred evenly to obtain reaction solution B; 106.1 g of reaction solution A is slowly added to 130.7 g of reaction solution B, and the addition rate is controlled at 0.5 g / min. After the addition is completed, stirring is continued for 30 min. After the stirring ends, the titanium dioxide sol is obtained;

[0089] The remaining operations are the same.

[0090] Comparative Example 2

[0091] Based on Example 2, the difference is that

[0092] (1) In the first deposition step

[0093] In the preparation method of the modified titanium dioxide sol, the aldehyde-functionalized alumina fiber is replaced with the untreated alumina fiber in equal amounts. The diameter of the alumina fiber is 3.5 μm and the length is 15 μm;

[0094] (2) In the step of preparing the metallization paste

[0095] In the preparation method of the pretreated powder, the silane coupling agent A-186 is replaced with absolute ethanol in equal amounts;

[0096] The remaining operations are the same.

[0097] Experimental performance

[0098] Select 99 alumina ceramics as the metallization substrate, and then metallize the metallization substrate by the methods of Examples 1-3 and Comparative Examples 1-2 respectively to obtain the samples to be tested;

[0099] 1. Test the bonding strength, compression-shear strength, visible light reflectivity in the range of 380-780 nm, and high temperature resistance of the samples to be tested. The results are as follows:

[0100]

[0101] 2. Heat the above samples to be tested at a rate of 30 °C / min to 1500 °C, hold for 1.0 h, then cool down to 20 °C at a rate of 50 °C / min, and hold for 1.0 h. The above operations are taken as a cycle period. After 20 cycle periods, test the bonding strength and compression-shear strength again. The results are as follows:

[0102]

[0103] The present invention metallizes the ceramic surface by a specific method. First, the substrate is pretreated to remove organic and inorganic pollutants on the ceramic surface and activate the ceramic surface to enhance the adhesion of the subsequent coating. Then, a modified titanium dioxide sol is used for primary deposition to form a uniform and dense titanium dioxide coating on the ceramic surface, which is beneficial to the adhesion and combination of the subsequent metallization paste. The modified titanium dioxide sol includes aldehyde-functionalized alumina fibers. Specifically, the alumina fibers are first treated with alkali to make their surface contain more hydroxyl groups, and then aldehyde groups are introduced to carry out a condensation reaction with the hydroxyl groups, so that the aldehyde groups are introduced onto the surface of the alumina fibers. Sodium borohydride further reduces and stabilizes the reaction system, so that the aldehyde groups are stably connected to the surface of the alumina fibers; 4-vinyl aniline is also introduced into the modified titanium dioxide sol. The aldehyde groups of the aldehyde-functionalized alumina fibers can carry out a Schiff base reaction with 4-vinyl aniline, so that a stable three-dimensional structure is formed in the titanium dioxide sol, thereby improving the stability of the modified titanium dioxide sol. Moreover, the aldehyde-functionalized alumina fibers can be embedded in the micro-porous structure of the ceramic surface to increase physical anchoring points, greatly improving the bonding force between the modified titanium dioxide sol and the ceramic matrix. Finally, during the subsequent sintering process, the strength of the coating is improved, and the high and low temperature cycle resistance of the coating is ensured; in the step of preparing the metallization paste, the powder is first pretreated with an epoxy-based silane coupling agent, so that the surface of the pretreated composite powder contains more epoxy groups, so that when it is coated on the ceramic after primary deposition, it can react with the amino groups of the modified titanium dioxide sol, thereby enhancing the bonding force between the metallization paste and the ceramic. Combining with the addition of additives, the homogeneity of the coating is ensured, the reflectivity is improved, and finally the stability of the coating is good, the bonding force with the ceramic is high, and the applicability in complex environments such as high and low temperature cycles is excellent.

[0104] On the basis of Example 2, Comparative Example 1 replaced the modified titanium dioxide sol with a conventional titanium dioxide sol in equal amounts, omitted the aldehyde-functionalized alumina component and the 4-vinyl aniline component. The titanium dioxide sol could not form a stable three-dimensional structure, thereby making the performance of the titanium dioxide sol unstable. Moreover, the aldehyde-functionalized alumina fiber was omitted, and it could not be embedded in the ceramic surface to enhance the strength of the coating. Eventually, the bonding force between the metal and the ceramic was low, and after multiple high and low temperature cycles, the strength performance decreased significantly, shortening the service life of the metallized ceramic.

[0105] In Comparative Example 2, only alumina fibers without any treatment were added to the modified titanium dioxide sol. Although it could increase the bonding force with the ceramic to a certain extent, the aggregation force of the alumina fibers was strong, and their dispersibility in the titanium dioxide sol was poor. They could not crosslink with 4-vinyl aniline to form a stable network structure, thus making the modified titanium dioxide sol unstable. In the preparation method of the pretreated powder in Comparative Example 2, the treatment with the silane coupling agent A-186 was omitted, which would cause the metallized slurry and the ceramic after the first deposition to not bind strongly, ultimately reducing the bonding force between the metal and the ceramic, weakening the compression-shear strength, and having poor high and low temperature cycle resistance.

[0106] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0107] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for metallizing the surface of a homogeneous oxide ceramic, characterized in that, It includes a pre-treatment step, a primary deposition step, a preparation step of a metallization paste, a coating step, and a sintering step. In the primary deposition step, the pre-treated ceramic is placed in a modified titanium dioxide sol, dried and then calcined to obtain the ceramic after primary deposition. The preparation method of the modified titanium dioxide sol is as follows: tetrabutyl titanate is added to absolute ethanol, and then aldehyde-functionalized alumina fibers are added, and they are stirred evenly to obtain reaction liquid A; deionized water and glacial acetic acid are added to absolute ethanol, and they are stirred evenly to obtain reaction liquid B; reaction liquid A is slowly added to reaction liquid B, stirred evenly, heated to 44 - 48 °C, 4-vinyl aniline is added, and it is kept stirring to obtain the titanium dioxide sol. The pre-treated composite powder is mixed with an additive, and then ultrasonic treatment is carried out to obtain a metallization paste; the preparation method of the pre-treated composite powder is as follows: molybdenum powder, manganese powder, alumina powder, barium carbonate powder, calcium oxide powder, zirconium oxide powder, and boron oxide powder are mixed, then absolute ethanol is added for a first ball milling treatment, and then silane coupling agent A-186 is added for a second ball milling treatment to obtain the pre-treated composite powder.

2. A method for metallizing the surface of a homogeneous oxide ceramic according to claim 1, wherein In the pre-treatment step, the ceramic is placed in acetone with a mass 6 - 10 times that of the ceramic, the temperature is raised to 53 - 60 °C, ultrasonic treatment is carried out, the ultrasonic time is 12 - 18 min, the ultrasonic power is 132 - 146 W, the ultrasonic frequency is 27 - 35 kHz. After the ultrasonic treatment is completed, it is filtered out, and then put into a sodium hydroxide solution with a mass 6 - 10 times that of the ceramic, and ultrasonic treatment is continued while keeping the ultrasonic power and frequency unchanged. The ultrasonic time is controlled to be 22 - 28 min. After the ultrasonic treatment is completed, it is filtered out, and then washed with deionized water until the washing liquid is neutral, and dried to obtain the pre-treated ceramic. The mass concentration of the sodium hydroxide solution is 8 - 12%.

3. A method for metallizing the surface of a homogeneous oxide ceramic according to claim 1, wherein In the primary deposition step, the pre-treated ceramic is placed in the modified titanium dioxide sol, and the modified titanium dioxide sol completely immerses the pre-treated ceramic. The pulling speed is controlled to be 2.5 - 3.5 cm / min, and a titanium dioxide sol film is obtained on the surface of the pre-treated ceramic. Then it is dried at 62 - 67 °C for 11.5 - 12.5 h, and then put into a calcining furnace, heated at a rate of 2.6 - 3.3 °C / min to 345 - 355 °C, held for 12 - 18 min, and then heated at a rate of 1.2 - 1.7 °C / min to 516 - 523 °C, held for 1.4 - 1.6 h to obtain the ceramic after primary deposition.

4. A method for metallizing the surface of a homogeneous oxide ceramic according to claim 1, wherein In the preparation method of the modified titanium dioxide sol, in reaction liquid A, the mass ratio of absolute ethanol, tetrabutyl titanate, and aldehyde-functionalized alumina fibers is 67.4 - 68.5:32.2 - 32.7:5.3 - 5.

8. In the reaction solution B, the mass ratio of the absolute ethanol, deionized water, and glacial acetic acid is 106-112:10.0-10.4:10.3-10.8; The mass ratio of the reaction solution B, reaction solution A, and 4-vinyl aniline is 126.3-133.2:104.9-106.7:2.0-2.

4.

5. The method for metallization of a homogeneous oxide ceramic surface according to claim 1, wherein The preparation method of the aldehyde-group modified alumina fiber is as follows: place the alumina fiber in a sodium hydroxide solution, soak it at 70-74 °C for 1.8-2.2 h, filter and dry it to obtain the soaked alumina fiber; place the soaked alumina fiber in an ethanol solution, stir evenly, add a cinnamaldehyde solution, stir and react at 43-47 °C for 1.8-2.2 h, then add sodium borohydride, stir and react at 3.5-4.6 °C for 2.7-3.4 h. After the reaction is completed, filter, wash, and dry to obtain the aldehyde-group modified alumina fiber.

6. The method for metallization of a homogeneous oxide ceramic surface according to claim 5, wherein The diameter of the alumina fiber is 3.2-3.6 μm, and the length is 13-16 μm; The mass ratio of the alumina fiber to the sodium hydroxide solution is 9.5-10.4:78.6-83.5; The mass concentration of the sodium hydroxide solution is 13-16%; The mass ratio of the soaked alumina fiber, ethanol solution, cinnamaldehyde solution, and sodium borohydride is 4.7-5.2:56-63:21.7-23.2:1.7-2.2; The mass concentration of the ethanol solution is 16-20%; The cinnamaldehyde solution is a mixture of cinnamaldehyde and a 10-13 wt% ethanol solution, and the mass ratio of cinnamaldehyde to the 10-13 wt% ethanol solution is 1.2:8.2-8.

8.

7. The method for metallization of a homogeneous oxide ceramic surface according to claim 1, wherein In the preparation method of the metallization paste, the mass ratio of the pretreated composite powder to the additive is 96.6-97.4:20.8-21.

5.

8. The method for metallization of a homogeneous oxide ceramic surface according to claim 1, wherein In the preparation method of the pretreated composite powder, for the first ball milling treatment, the ball milling time is 7.6-8.2 h, the ball milling speed is 77-85 rpm, and the ball-to-material ratio is 2-4:1; For the second ball milling treatment, the ball milling time is 3.8-4.2 h, and the ball milling speed is 115-127 rpm; The mass ratio of the molybdenum powder, manganese powder, alumina powder, barium carbonate powder, calcium oxide powder, zirconium oxide powder, boron oxide powder, absolute ethanol, and silane coupling agent A-186 is 62.6-63.2:20.5-21.4:7.3-7.8:0.6-1.0:2.2-2.7:0.3-0.5:1.6-2.0:196-206:7.2-7.

8.

9. The method for metallization of a homogeneous oxide ceramic surface according to claim 1, wherein In the preparation method of the metallization paste, the preparation method of the additive is to mix ethyl cellulose, terpineol, glycerol and glycerol monostearate, and then carry out water bath heating until completely dissolved to obtain the additive; The mass ratio of the ethyl cellulose, terpineol, glycerol and glycerol monostearate is 1.0 - 1.4:17.0 - 17.5:1.8 - 2.2:0.7 - 1.

0.

10. According to the method for metallizing the surface of a homogeneous oxide ceramic according to claim 1, characterized in that, The coating and sintering steps are as follows: screen-print the metallization paste onto the surface of the ceramic after the first deposition, control the coating thickness to be 28 - 32 μm. After coating, dry at 108 - 113 °C. After naturally cooling to room temperature, in a nitrogen atmosphere, heat up at a rate of 9.5 - 10.5 °C / min to 610 - 630 °C, keep warm for 17 - 25 min, then heat up at a rate of 4.2 - 5.5 °C / min to 1080 - 1130 °C, keep warm for 13 - 20 min, then heat up at a rate of 2.0 - 2.8 °C / min to 1400 - 1420 °C, keep warm for 55 - 65 min, then reduce the temperature at a rate of 5.8 - 6.2 °C / min to 720 - 740 °C, keep warm for 35 - 45 min, and finally reduce the temperature at a rate of 1.8 - 2.2 °C / min to 380 - 410 °C, and cool with the furnace to room temperature to complete the metallization step and obtain the metallized ceramic.

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