A high-strength LTCC composite ceramic material and its preparation method

Abstract

This invention relates to the field of low-temperature co-fired ceramic materials and their preparation, specifically to a high-strength LTCC composite ceramic material and its preparation method. A method for preparing a high-strength LTCC composite ceramic material includes: preparing nano-alumina-modified hydroxyapatite whiskers; preparing composite nanowires and hafnium carbide nanowires; preparing europium-doped ceramic powder; and preparing the LTCC composite ceramic material. This invention involves hydroxylating hydroxyapatite whiskers, adding them to alumina sol, subjecting them to ultrasonic treatment and static aging, followed by heat treatment to produce nano-alumina-modified hydroxyapatite whiskers. These whiskers, along with nano-SiC whiskers and CMBS glass powder, form an LTCC composite ceramic material. The two components complement each other, serving as the main load-bearing unit, absorbing most of the load. Furthermore, the nano-alumina particles introduced onto the surface of the hydroxyapatite whiskers can pin grain boundaries, thereby significantly improving the flexural strength of the LTCC composite ceramic material.

Description

Technical Field

[0001] This invention relates to the field of low-temperature co-fired ceramic materials and their preparation, specifically to a high-strength LTCC composite ceramic material and its preparation method. Background Technology

[0002] Low-temperature co-fired ceramic technology is a modern, advanced ceramic process for multi-chip modules. It leverages multi-layered wiring substrate design to achieve high-density circuit integration, enabling the direct integration of passive components such as resistors, capacitors, inductors, and filters within the ceramic substrate. This enhances the functional integration of electronic devices and is widely used in high-frequency, high-reliability electronic equipment such as microwave devices, multi-chip modules, and spacecraft and satellite payloads. This technology requires densification of the ceramic at relatively low sintering temperatures (typically below 900°C) to allow for co-firing with low-resistivity, low-melting-point internal conductor materials (such as Ag and Au), avoiding electrode oxidation or melting, thereby reducing conductor losses and meeting the demands of high-frequency applications.

[0003] Based on the method of introducing the glass phase, LTCC substrate materials can be divided into microcrystalline glass materials and glass / ceramic composite materials. Although microcrystalline glass materials have a lower sintering temperature, they have poor mechanical strength and low bending strength. Moreover, it is usually difficult to reduce the dielectric constant and dielectric loss at the same time. Traditional glass / ceramic composite materials usually have a higher sintering temperature, making it difficult to meet the requirements of low-temperature sintering. In order to lower the sintering temperature, a large amount of glass phase is often added, which leads to a decrease in mechanical strength. The bending strength is usually less than 200MPa. The low mechanical strength makes LTCC substrates prone to cracking or breaking under harsh environments such as impact and vibration, resulting in decreased reliability. It also limits the further development of packaging substrates towards thinner and smaller sizes.

[0004] Therefore, it is necessary to propose a high-strength LTCC composite ceramic material and its preparation method to extend its service life. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength LTCC composite ceramic material and its preparation method.

[0006] This invention provides a method for preparing a high-strength LTCC composite ceramic material, comprising the following steps: S1: Preparation of nano-alumina modified hydroxyapatite whiskers S1.1: Add hydroxyapatite whiskers to 0.1mol / L nitric acid solution at a ratio of 1g:(10-20)mL, disperse by ultrasonication for 20-30min, activate, and then obtain activated whiskers by centrifugation, washing with water until neutral and vacuum drying; S1.2: Disperse the above activated whiskers in deionized water at a ratio of 1g:(6-8)mL, add 25% ammonia water, and sonicate for 20-30min to perform hydroxylation. After centrifugation, washing and drying, hydroxylated whiskers are obtained. The amount of ammonia water added is 10% of the volume of deionized water. S1.3: Dissolve aluminum nitrate in anhydrous ethanol at a ratio of 1g:(40-50)mL, stir thoroughly to obtain an aluminum nitrate solution, and dissolve citric acid in deionized water at a ratio of 1g:(20-30)mL, then add it to the aluminum nitrate solution. Stir for 20-30 minutes, then add ammonia to adjust the pH to 3.5-4 to obtain an alumina sol. S1.4: Add the above hydroxylated whiskers to the above alumina sol, sonicate for 40-50 min, let stand and age for 20-24 h, and then filter, wash and vacuum dry to obtain composite powder; S1.5: The above composite powder is placed in a muffle furnace and heated to 450-550℃ at 5℃ / min, held for 3-4 hours, and then cooled to room temperature with the furnace to obtain nano-alumina modified hydroxyapatite whiskers. S2: Preparation of composite nanowires and hafnium carbide nanowires Composite nanowires were prepared using silicon powder as raw material, and hafnium carbide nanowires were prepared using hafnium tetrachloride powder as raw material. S3: Preparation of europium-doped ceramic powder After pretreatment, fly ash is wet-milled and mixed with talc, alumina, magnesium oxide and europium oxide. After pressing and sintering, europium-doped ceramic powder is obtained. S4: Preparation of LTCC composite ceramic materials First, CMBS glass powder is prepared using CaO, MgO, B2O3 and SiO2 as raw materials. Then, it is mixed with the above-mentioned nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, the above-mentioned composite nanowires, the above-mentioned hafnium carbide nanowires and the above-mentioned europium doped ceramic powder to form a slurry. After casting and molding, it is then heat-treated and sintered to obtain LTCC composite ceramic material.

[0007] Furthermore, S2 specifically includes the following steps: S2.1: Mix silicon powder and aluminum powder and place them in a tube furnace. Introduce a mixture of nitrogen and hydrogen gas and heat the mixture to 1200-1300℃ at 10℃ / min. Hold the mixture at this temperature for 1-2 hours and then cool it down to 500-600℃ at 10℃ / min. Finally, cool the mixture in the furnace to room temperature to obtain composite nanowires. S2.2: After cleaning the graphite substrate, place it in a nickel nitrate solution and soak for 1-2 hours. After removing it, dry it at 60-80℃ and then suspend it in the high-temperature zone of a vertical resistance furnace. Then, place hafnium tetrachloride powder in the low-temperature zone of the vertical resistance furnace, evacuate to 2 kPa, introduce hydrogen and argon, and heat to 1000-1400℃ at 5-15℃ / min. Then, introduce methane and deposit for 2-4 hours. After that, cool naturally to room temperature under hydrogen protection to obtain hafnium carbide nanowires.

[0008] Furthermore, S3 specifically includes the following steps: S3.1: Add fly ash to the mixed dispersion at a ratio of 1g:(1.3-1.5)mL, ball mill at 450-500r / min for 1-2h, then add dilute hydrochloric acid with a mass concentration of 180-200g / L, stir at 75-85℃ for 2-3h, and dry to obtain pretreated fly ash; S3.2: Add talc, alumina, magnesium oxide and europium oxide to the pretreated fly ash, wet grind at 400-500 r / min for 40-50 min, and then dry at 70-80℃ to obtain mixed raw powder; S3.3: The above mixed raw powder is placed in a tablet press and pressed into a green body at a pressure of 15-25 MPa. Then, it is cold isostatically pressed at a pressure of 200-300 MPa for 20-30 seconds. After sintering at 1100-1200℃ for 2-3 hours, it is cooled to room temperature in the furnace and ground to obtain europium-doped ceramic powder.

[0009] Furthermore, S4 specifically includes the following steps: S4.1: Mix CaO, MgO, B2O3 and SiO2 evenly and ball mill for 2-3 hours. Then place it in a high-temperature furnace and heat it to 1250℃ at 10℃ / min. Hold it for 1-2 hours. Then pour it into deionized water and quench it to form a glass block. After drying and grinding, CMBS glass powder is obtained. S4.2: The above CMBS glass powder, the nano-alumina modified hydroxyapatite whiskers obtained in step S1.5, the nano-SiC whiskers, the composite nanowires obtained in step S2.1, the hafnium carbide nanowires obtained in step S2.2, and the europium-doped ceramic powder obtained in step S3.3 are added to a mixed organic solvent and ball-milled to obtain a mixed slurry. S4.3: After vacuum degassing the above mixed slurry, it is cast into a film, dried, cut and stacked, and then heat-treated in a muffle furnace at 500-600℃ for 40-50 minutes, and then heated to 850-900℃ for sintering for 1-2 hours to obtain LTCC composite ceramic material.

[0010] Furthermore, the mass ratio of aluminum nitrate to citric acid is (1.4-1.6):1, and the mass ratio of hydroxylated whiskers to aluminum nitrate is (8.3-8.5):1.

[0011] Furthermore, the amount of aluminum powder used is 1-3% of the mass of silicon powder, and the volume ratio of nitrogen to hydrogen in the mixed gas is (19-20):1.

[0012] Furthermore, the nickel nitrate solution is a 1-2 mol / L aqueous solution of nickel nitrate, and the volume ratio of hydrogen to argon is (3-5):1.

[0013] Furthermore, the molar ratio of magnesium oxide, aluminum oxide and silicon dioxide in the mixed raw powder is 2:2:5, and the amount of europium oxide added is 0.5-1.5% of the total mass of pretreated fly ash, talc, aluminum oxide and magnesium oxide.

[0014] Furthermore, the composition of CMBS glass powder is: 26-30wt% CaO, 18.8-21.2wt% MgO, 38-40wt% B2O3, with the balance being SiO2, and the mass ratio of CMBS glass powder, nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, composite nanowires, hafnium carbide nanowires and europium doped ceramic powder is (12-16):(1.8-2.6):(1-2):1:(0.6-0.8):(6-8).

[0015] A high-strength LTCC composite ceramic material, which is prepared by the preparation method of a high-strength LTCC composite ceramic material described in any one of the above claims.

[0016] The present invention has the following advantages: 1. In this invention, hydroxyapatite whiskers are hydroxylated and added to alumina sol. After ultrasonic treatment and static aging, they are then heat-treated to produce nano-alumina-modified hydroxyapatite whiskers. These whiskers are then mixed with nano-SiC whiskers and CMBS glass powder to form LTCC composite ceramic materials. Since the nano-SiC whiskers are more rigid and provide the main support, while the nano-alumina-modified hydroxyapatite whiskers provide additional load-bearing points, the two complement each other and serve as the main load-bearing units, bearing most of the load. Furthermore, the nano-alumina particles introduced on the surface of the hydroxyapatite whiskers can pin grain boundaries, hindering the growth of ceramic matrix grains and dislocation movement, and inhibiting crack propagation, thereby producing a dispersion strengthening effect. This significantly improves the flexural strength of the LTCC composite ceramic material.

[0017] 2. In this invention, after pretreatment of fly ash, it is ball-milled and mixed with talc, alumina, magnesium oxide, and europium oxide, followed by pressing and sintering to produce europium-doped ceramic powder. This powder is then mixed with CMBS glass powder to form LTCC composite ceramic material. The europium-doped ceramic powder itself has a low dielectric constant and dielectric loss, which directly reduces the dielectric constant of CMBS glass. Furthermore, the rare earth europium in the europium-doped ceramic powder segregates at grain boundaries, pinning them, inhibiting abnormal grain growth, refining ceramic grains, and increasing the number of grain boundaries per unit volume. This reduces the overall electronic and ionic polarization intensity, thereby lowering the dielectric constant of the composite ceramic material. Furthermore, after europium-doped ceramic powder is combined with the CMBS glass phase, the molten glass phase will surround the high resistivity europium-doped ceramic powder grains, blocking the continuous ion migration channels in the glass phase and reducing the dielectric loss of the CMBS glass. At the same time, europium will form local positively charged enrichment in the lattice, binding the surrounding oxygen ions through Coulomb force, reducing the migration ability of oxygen vacancies, reducing the loss caused by ionic conductivity, and thus reducing the dielectric loss of the composite ceramic material.

[0018] 3. In this invention, by mixing composite nanowires and hafnium carbide nanowires with CMBS glass powder to prepare LTCC composite ceramic materials, on the one hand, due to the good chemical compatibility between the composite nanowires and the CMBS glass matrix, when a crack encounters the composite nanowires, it will be deflected due to the high toughness of the silicon nitride core, and when it encounters the hafnium carbide nanowires, it will be forced to branch due to rigid obstruction, increasing the length of the propagation path and significantly improving the energy consumption for crack propagation. On the other hand, when the crack passes through the matrix, the nanowires spanning both sides of the crack will form a "mechanical bridge". The composite nanowires can form a strong interfacial bond, which is conducive to stress transmission and ensures the effective activation of the bridging mechanism. The hafnium carbide nanowires provide extremely high bridging strength and stiffness, thereby achieving the effect of synergistically improving the fracture toughness of the LTCC composite ceramic material. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation method of the high-strength LTCC composite ceramic material used in an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0021] Example 1: A method for preparing a high-strength LTCC composite ceramic material, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of nano-alumina modified hydroxyapatite whiskers S1.1: Hydroxyapatite whiskers were added to 0.1 mol / L nitric acid solution at a ratio of 1 g: 10 mL, ultrasonically dispersed for 20 min, activated, and then centrifuged, washed with water until neutral, and vacuum dried to obtain activated whiskers; S1.2: The activated whiskers were dispersed in deionized water at a ratio of 1g:6mL, 25% ammonia solution was added, and the mixture was sonicated for 20min to perform hydroxylation. After centrifugation, washing, and drying, hydroxylated whiskers were obtained. The amount of ammonia solution added was 10% of the volume of deionized water. S1.3: Dissolve aluminum nitrate in anhydrous ethanol at a ratio of 1g:40mL, stir thoroughly to obtain an aluminum nitrate solution, dissolve citric acid in deionized water at a ratio of 1g:20mL, add it to the aluminum nitrate solution, stir for 20min, then add ammonia to adjust the pH to 3.5 to obtain an alumina sol, wherein the mass ratio of aluminum nitrate to citric acid is 1.4:1; S1.4: The above hydroxylated whiskers are added to the above alumina sol, ultrasonically treated for 40 min, and then allowed to stand for aging for 20 h. After filtration, washing and vacuum drying, composite powder is obtained, wherein the mass ratio of hydroxylated whiskers to aluminum nitrate is 8.3:1. S1.5: The above composite powder is placed in a muffle furnace and heated to 450°C at 5°C / min, held for 3 hours, and then cooled to room temperature with the furnace to obtain nano-alumina modified hydroxyapatite whiskers. S2: Preparation of composite nanowires and hafnium carbide nanowires S2.1: Silicon powder and aluminum powder are mixed and placed in a tube furnace. A mixture of nitrogen and hydrogen is introduced and the temperature is raised to 1200℃ at 10℃ / min. After holding the temperature for 1 hour, the temperature is lowered to 500℃ at 10℃ / min and then cooled to room temperature with the furnace to obtain composite nanowires. The amount of aluminum powder is 1% of the mass of silicon powder, and the volume ratio of nitrogen to hydrogen in the mixed gas is 19:1. S2.2: After cleaning the graphite substrate, it was placed in a nickel nitrate solution and soaked for 1 hour. After removal, it was dried at 60°C and then suspended in the high-temperature zone of a vertical resistance furnace. Then, hafnium tetrachloride powder was placed in the low-temperature zone of the vertical resistance furnace, and the vacuum was evacuated to 2 kPa. Hydrogen and argon were introduced, and the temperature was increased to 1000°C at 5°C / min. Methane was then introduced, and after deposition for 2 hours, it was naturally cooled to room temperature under hydrogen protection to obtain hafnium carbide nanowires. The nickel nitrate solution was a 1 mol / L aqueous solution of nickel nitrate, and the volume ratio of hydrogen to argon was 3:1. S3: Preparation of europium-doped ceramic powder S3.1: Add fly ash to the mixed dispersion at a ratio of 1g:1.3mL, ball mill at 450r / min for 1h, then add dilute hydrochloric acid with a mass concentration of 180g / L, stir at 75℃ for 2h, and dry to obtain pretreated fly ash, wherein the composition of fly ash is: 0.75%MgO, 5.98%CaO, 1.64%TiO2, 5.57%Fe2O3, 31.56%Al2O3, and the balance is SiO2; S3.2: Add talc, alumina, magnesium oxide and europium oxide to the above pretreated fly ash, wet grind at 400 r / min for 40 min, and then dry at 70℃ to obtain mixed raw powder. The molar ratio of magnesium oxide, alumina and silica in the mixed raw powder is 2:2:5, and the amount of europium oxide added is 0.5% of the total mass of pretreated fly ash, talc, alumina and magnesium oxide. The composition of talc is: 31.4% MgO, 0.68% CaO, 0.07% TiO2, 0.71% Fe2O3, 0.49% Al2O3, and the balance is SiO2. S3.3: The above mixed raw powder is placed in a tablet press and pressed into a green body at a pressure of 15 MPa. Then, it is cold isostatically pressed at a pressure of 200 MPa for 20 seconds. After sintering at 1100℃ for 2 hours, it is cooled to room temperature in the furnace and ground to obtain europium-doped ceramic powder. S4: Preparation of LTCC composite ceramic materials S4.1: CaO, MgO, B2O3 and SiO2 are uniformly mixed and ball-milled for 2 hours. Then, the mixture is placed in a high-temperature furnace and heated to 1250℃ at a rate of 10℃ / min. The temperature is maintained for 1 hour. The mixture is then poured into deionized water and quenched to form a glass block. After drying and grinding, CMBS glass powder is obtained. The composition of CMBS glass powder is: 26wt% CaO, 18.8wt% MgO, 38wt% B2O3, and the balance is SiO2. S4.2: The above-mentioned CMBS glass powder, the nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers obtained in step S1.5, the composite nanowires obtained in step S2.1, the hafnium carbide nanowires obtained in step S2.2, and the europium-doped ceramic powder obtained in step S3.3 are added to a mixed organic solvent and ball-milled to obtain a mixed slurry. The mass ratio of CMBS glass powder, nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, composite nanowires, hafnium carbide nanowires, and europium-doped ceramic powder is 12:1.8:1:1:0.6:6. S4.3: After vacuum degassing the above mixed slurry, it is cast into a film, dried, cut and stacked, and then heat-treated at 500℃ for 40 minutes in a muffle furnace, and then heated to 850℃ for sintering for 1 hour to obtain LTCC composite ceramic material.

[0022] Example 2, a method for preparing a high-strength LTCC composite ceramic material, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of nano-alumina modified hydroxyapatite whiskers S1.1: Hydroxyapatite whiskers were added to 0.1 mol / L nitric acid solution at a ratio of 1 g: 15 mL, ultrasonically dispersed for 25 min, activated, and then centrifuged, washed with water until neutral, and vacuum dried to obtain activated whiskers; S1.2: The activated whiskers were dispersed in deionized water at a ratio of 1g:7mL, 25% ammonia solution was added, and the mixture was sonicated for 25min to induce hydroxylation. After centrifugation, washing, and drying, hydroxylated whiskers were obtained. The amount of ammonia solution added was 10% of the volume of deionized water. S1.3: Dissolve aluminum nitrate in anhydrous ethanol at a ratio of 1g:45mL, stir thoroughly to obtain an aluminum nitrate solution, dissolve citric acid in deionized water at a ratio of 1g:25mL, add it to the aluminum nitrate solution, stir for 25min, then add ammonia to adjust the pH to 3.7 to obtain an alumina sol, wherein the mass ratio of aluminum nitrate to citric acid is 1.5:1; S1.4: The above hydroxylated whiskers are added to the above alumina sol, ultrasonically treated for 45 min, and then allowed to stand for aging for 22 h. After filtration, washing and vacuum drying, composite powder is obtained, wherein the mass ratio of hydroxylated whiskers to aluminum nitrate is 8.4:1. S1.5: The above composite powder was placed in a muffle furnace and heated to 500°C at a rate of 5°C / min. The temperature was maintained for 3.5 hours and then cooled to room temperature with the furnace to obtain nano-alumina modified hydroxyapatite whiskers. S2: Preparation of composite nanowires and hafnium carbide nanowires S2.1: Silicon powder and aluminum powder are mixed and placed in a tube furnace. A mixture of nitrogen and hydrogen is introduced and the temperature is raised to 1250℃ at 10℃ / min. After holding the temperature for 1.5h, the temperature is lowered to 550℃ at 10℃ / min and then cooled to room temperature with the furnace to obtain composite nanowires. The amount of aluminum powder is 2% of the mass of silicon powder, and the volume ratio of nitrogen to hydrogen in the mixed gas is 19.5:1. S2.2: After cleaning the graphite substrate, it was placed in a nickel nitrate solution and soaked for 1.5 hours. After removal, it was dried at 70°C and then suspended in the high-temperature zone of a vertical resistance furnace. Hafnium tetrachloride powder was then placed in the low-temperature zone of the vertical resistance furnace, and the vacuum was evacuated to 2 kPa. Hydrogen and argon were introduced, and the temperature was increased to 1200°C at 10°C / min. Methane was then introduced, and after deposition for 3 hours, it was naturally cooled to room temperature under hydrogen protection to obtain hafnium carbide nanowires. The nickel nitrate solution was a 1.5 mol / L aqueous solution of nickel nitrate, and the volume ratio of hydrogen to argon was 4:1. S3: Preparation of europium-doped ceramic powder S3.1: Add fly ash to the mixed dispersion at a ratio of 1g:1.4mL, ball mill at 475r / min for 1.5h, then add dilute hydrochloric acid with a mass concentration of 190g / L, stir at 80℃ for 2.5h, and dry to obtain pretreated fly ash, wherein the composition of fly ash is: 0.75%MgO, 5.98%CaO, 1.64%TiO2, 5.57%Fe2O3, 31.56%Al2O3, and the balance is SiO2; S3.2: Add talc, alumina, magnesium oxide and europium oxide to the above pretreated fly ash, wet grind at 450 r / min for 45 min, and then dry at 75℃ to obtain mixed raw powder. The molar ratio of magnesium oxide, alumina and silica in the mixed raw powder is 2:2:5, and the amount of europium oxide added is 1% of the total mass of the pretreated fly ash, talc, alumina and magnesium oxide. The composition of talc is: 31.4% MgO, 0.68% CaO, 0.07% TiO2, 0.71% Fe2O3, 0.49% Al2O3, and the balance is SiO2. S3.3: The above mixed raw powder is placed in a tablet press and pressed into a green body at a pressure of 20 MPa. Then, it is cold isostatically pressed at a pressure of 250 MPa for 25 seconds. After sintering at 1150℃ for 2.5 hours, it is cooled to room temperature in the furnace and ground to obtain europium-doped ceramic powder. S4: Preparation of LTCC composite ceramic materials S4.1: CaO, MgO, B2O3 and SiO2 are uniformly mixed and ball-milled for 2.5 hours. Then, the mixture is placed in a high-temperature furnace and heated to 1250℃ at a rate of 10℃ / min. The temperature is maintained for 1.5 hours. The mixture is then poured into deionized water and quenched to form a glass block. After drying and grinding, CMBS glass powder is obtained. The composition of CMBS glass powder is: 28wt% CaO, 20wt% MgO, 39wt% B2O3, and the balance is SiO2. S4.2: The above-mentioned CMBS glass powder, the nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers obtained in step S1.5, the composite nanowires obtained in step S2.1, the hafnium carbide nanowires obtained in step S2.2, and the europium-doped ceramic powder obtained in step S3.3 are added to a mixed organic solvent and ball-milled to obtain a mixed slurry. The mass ratio of CMBS glass powder, nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, composite nanowires, hafnium carbide nanowires, and europium-doped ceramic powder is 14:2.2:(1-2):1:0.7:7. S4.3: After vacuum degassing the above mixed slurry, it is cast into a film, dried, cut and stacked, and then heat-treated at 550℃ for 45 minutes in a muffle furnace, and then heated to 875℃ for sintering for 1.5 hours to obtain LTCC composite ceramic material.

[0023] Example 3: A method for preparing a high-strength LTCC composite ceramic material, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of nano-alumina modified hydroxyapatite whiskers S1.1: Hydroxyapatite whiskers were added to 0.1 mol / L nitric acid solution at a ratio of 1 g: 20 mL, ultrasonically dispersed for 30 min, activated, and then centrifuged, washed with water until neutral, and vacuum dried to obtain activated whiskers; S1.2: The activated whiskers were dispersed in deionized water at a ratio of 1g:8mL, 25% ammonia solution was added, and the mixture was sonicated for 30min to perform hydroxylation. After centrifugation, washing, and drying, hydroxylated whiskers were obtained. The amount of ammonia solution added was 10% of the volume of deionized water. S1.3: Dissolve aluminum nitrate in anhydrous ethanol at a ratio of 1g:50mL, stir thoroughly to obtain an aluminum nitrate solution, dissolve citric acid in deionized water at a ratio of 1g:30mL, add it to the aluminum nitrate solution, stir for 30min, then add ammonia to adjust the pH to 4 to obtain an alumina sol, wherein the mass ratio of aluminum nitrate to citric acid is 1.6:1; S1.4: Add the above hydroxylated whiskers to the above alumina sol, sonicate for 50 min, then let stand and age for 24 h, and then filter, wash and vacuum dry to obtain composite powder, wherein the mass ratio of hydroxylated whiskers to aluminum nitrate is 8.5:1. S1.5: The above composite powder is placed in a muffle furnace and heated to 550°C at 5°C / min, held for 4 hours, and then cooled to room temperature with the furnace to obtain nano-alumina modified hydroxyapatite whiskers. S2: Preparation of composite nanowires and hafnium carbide nanowires S2.1: Silicon powder and aluminum powder are mixed and placed in a tube furnace. A mixture of nitrogen and hydrogen is introduced and the temperature is raised to 1300℃ at 10℃ / min. After holding the temperature for 2 hours, the temperature is lowered to 600℃ at 10℃ / min and then cooled to room temperature with the furnace to obtain composite nanowires. The amount of aluminum powder is 3% of the mass of silicon powder, and the volume ratio of nitrogen to hydrogen in the mixed gas is 20:1. S2.2: After cleaning the graphite substrate, it was placed in a nickel nitrate solution and soaked for 2 hours. After removal, it was dried at 80°C and then suspended in the high-temperature zone of a vertical resistance furnace. Then, hafnium tetrachloride powder was placed in the low-temperature zone of the vertical resistance furnace, and the vacuum was drawn to 2 kPa. Hydrogen and argon were introduced, and the temperature was raised to 1400°C at 15°C / min. Methane was then introduced, and after deposition for 4 hours, it was naturally cooled to room temperature under hydrogen protection to obtain hafnium carbide nanowires. The nickel nitrate solution was a 2 mol / L nickel nitrate aqueous solution, and the volume ratio of hydrogen to argon was 5:1. S3: Preparation of europium-doped ceramic powder S3.1: Add fly ash to the mixed dispersion at a ratio of 1g:1.5mL, ball mill at 500r / min for 2h, then add dilute hydrochloric acid with a mass concentration of 200g / L, stir at 85℃ for 3h, and dry to obtain pretreated fly ash, wherein the composition of fly ash is: 0.75%MgO, 5.98%CaO, 1.64%TiO2, 5.57%Fe2O3, 31.56%Al2O3, and the balance is SiO2; S3.2: Add talc, alumina, magnesium oxide and europium oxide to the above pretreated fly ash, wet grind at 500 r / min for 50 min, and then dry at 80℃ to obtain mixed raw powder. The molar ratio of magnesium oxide, alumina and silica in the mixed raw powder is 2:2:5, and the amount of europium oxide added is 1.5% of the total mass of the pretreated fly ash, talc, alumina and magnesium oxide. The composition of talc is: 31.4% MgO, 0.68% CaO, 0.07% TiO2, 0.71% Fe2O3, 0.49% Al2O3, and the balance is SiO2. S3.3: The above mixed raw powder is placed in a tablet press and pressed into a green body at a pressure of 25 MPa. Then, it is cold isostatically pressed at a pressure of 300 MPa for 30 seconds. After sintering at 1200℃ for 3 hours, it is cooled to room temperature in the furnace and ground to obtain europium-doped ceramic powder. S4: Preparation of LTCC composite ceramic materials S4.1: CaO, MgO, B2O3 and SiO2 are uniformly mixed and ball-milled for 3 hours. Then, the mixture is placed in a high-temperature furnace and heated to 1250℃ at a rate of 10℃ / min. The temperature is maintained for 2 hours. The mixture is then poured into deionized water and quenched to form a glass block. After drying and grinding, CMBS glass powder is obtained. The composition of CMBS glass powder is: 30wt% CaO, 21.2wt% MgO, 40wt% B2O3, and the balance is SiO2. S4.2: The above-mentioned CMBS glass powder, the nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers obtained in step S1.5, the composite nanowires obtained in step S2.1, the hafnium carbide nanowires obtained in step S2.2, and the europium-doped ceramic powder obtained in step S3.3 are added to a mixed organic solvent and ball-milled to obtain a mixed slurry. The mass ratio of CMBS glass powder, nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, composite nanowires, hafnium carbide nanowires, and europium-doped ceramic powder is 16:2.6:2:1:0.8:8. S4.3: After vacuum degassing the above mixed slurry, it is cast into a film, dried, cut and stacked, and then heat-treated at 600℃ for 50 minutes in a muffle furnace, and then heated to 900℃ for 2 hours to obtain LTCC composite ceramic material.

[0024] Comparative Example 1 differs from Example 1 in that the nano SiC whiskers in step S4.2 are replaced with an equal amount of nano alumina-modified hydroxyapatite whiskers.

[0025] Comparative Example 2 differs from Example 1 in that the nano-alumina modified hydroxyapatite whiskers in step S4.2 are replaced with an equal amount of nano-SiC whiskers.

[0026] Comparative Example 3 differs from Example 1 in that the europium-doped ceramic powder in step S4.2 is removed.

[0027] Comparative Example 4 differs from Example 1 in that the composite nanowires in step S4.2 are replaced with an equal amount of hafnium carbide nanowires.

[0028] Comparative Example 5 differs from Example 1 in that the hafnium carbide nanowires in step S4.2 are replaced with an equal amount of composite nanowires.

[0029] Test example: Test 1: The flexural strength of the LTCC composite ceramic materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested respectively. The tests were repeated three times and the average value was taken. The results are shown in Table 1.

[0030] Table 1: Flexural Strength Test Results of LTCC Composite Ceramic Materials Example 1 432.2 Example 2 434.7 Example 3 435.9 Comparative Example 1 335.8 Comparative Example 2 356.1 As shown in Table 1 above, when only one of nano-alumina modified hydroxyapatite whiskers or nano-SiC whiskers was used in Comparative Examples 1 and 2, the flexural strength of the LTCC composite ceramic materials was lower than that in Example 1. This indicates that by hydroxylating the hydroxyapatite whiskers, adding them to alumina sol, and then subjecting them to ultrasonic treatment and static aging followed by heat treatment to produce nano-alumina modified hydroxyapatite whiskers, and then mixing them with nano-SiC whiskers and CMBS glass powder to produce LTCC composite ceramic materials, the combination of the two can significantly improve the flexural strength of the LTCC composite ceramic materials.

[0031] Test 2: The dielectric properties of the LTCC composite ceramic materials prepared in Examples 1-3 and Comparative Example 3 were tested respectively. The tests were repeated three times and the average value was taken. The results are shown in Table 2.

[0032] Table 2: Test Results of Dielectric Properties of LTCC Composite Ceramic Materials Example 1 4.5 0.64 Example 2 4.3 0.57 Example 3 4.3 0.55 Comparative Example 3 5.5 1.4 As shown in Table 2 above, when europium-doped ceramic powder was not added in Comparative Example 2, the dielectric constant and dielectric loss of the LTCC composite ceramic material were higher than those in Example 1. This shows that by pretreating fly ash, ball milling and mixing it with talc, alumina, magnesium oxide and europium oxide, and then pressing and sintering it to prepare europium-doped ceramic powder, and then mixing it with CMBS glass powder to prepare LTCC composite ceramic material, the dielectric constant and dielectric loss of the composite ceramic material can be reduced simultaneously.

[0033] Test 3: The fracture toughness of the LTCC composite ceramic materials prepared in Examples 1-3 and Comparative Examples 4-5 were tested respectively. The tests were repeated three times and the average value was taken. The results are shown in Table 3.

[0034] Table 3: Fracture toughness test results of LTCC composite ceramic materials Example 1 4.8 Example 2 5.0 Example 3 5.1 Comparative Example 4 3.5 Comparative Example 5 3.9 As shown in Table 3 above, when only one of hafnium carbide nanowires or composite nanowires was used in Comparative Examples 4 and 5, the fracture toughness of the LTCC composite ceramic materials was lower than that in Example 1. This shows that by mixing composite nanowires and hafnium carbide nanowires with CMBS glass powder to prepare LTCC composite ceramic materials, the two can synergistically improve the fracture toughness of LTCC composite ceramic materials.

[0035] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing a high-strength LTCC composite ceramic material, characterized in that, Includes the following steps: S1: Preparation of nano-alumina modified hydroxyapatite whiskers S1.1: Hydroxyapatite whiskers were added to a 0.1 mol / L nitric acid solution, ultrasonically dispersed, activated, and then centrifuged, washed with water until neutral, and vacuum dried to obtain activated whiskers; S1.2: The above activated whiskers are dispersed in deionized water, 25% ammonia solution is added, and ultrasonic treatment is performed to hydroxylate the whiskers. After centrifugation, washing and drying, hydroxylated whiskers are obtained. The amount of ammonia solution added is 10% of the volume of deionized water. S1.3: Dissolve aluminum nitrate in anhydrous ethanol and stir thoroughly to obtain an aluminum nitrate solution. Dissolve citric acid in deionized water and add it to the aluminum nitrate solution. After stirring and mixing, add ammonia to adjust the pH to 3.5-4 to obtain an alumina sol. S1.4: The above hydroxylated whiskers are added to the above alumina sol, ultrasonically treated, then allowed to stand for aging, and then filtered, washed and vacuum dried to obtain composite powder; S1.5: The above composite powder is placed in a muffle furnace and heated to 450-550℃ at 5℃ / min, held for 3-4 hours, and then cooled to room temperature with the furnace to obtain nano-alumina modified hydroxyapatite whiskers. S2: Preparation of composite nanowires and hafnium carbide nanowires Composite nanowires were prepared using silicon powder as raw material, and hafnium carbide nanowires were prepared using hafnium tetrachloride powder as raw material. S3: Preparation of europium-doped ceramic powder After pretreatment, fly ash is wet-milled and mixed with talc, alumina, magnesium oxide and europium oxide. After pressing and sintering, europium-doped ceramic powder is obtained. S4: Preparation of LTCC composite ceramic materials First, CMBS glass powder is prepared using CaO, MgO, B2O3 and SiO2 as raw materials. Then, it is mixed with the above-mentioned nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, the above-mentioned composite nanowires, the above-mentioned hafnium carbide nanowires and the above-mentioned europium-doped ceramic powder to form a slurry. The mass ratio of CMBS glass powder, nano-alumina modified hydroxyapatite whiskers, nano-SiC whiskers, composite nanowires, hafnium carbide nanowires and europium-doped ceramic powder is (12-16):(1.8-2.6):(1-2):1:(0.6-0.8):(6-8). After tape casting, heat treatment and sintering are performed to obtain LTCC composite ceramic material. S2 specifically includes the following steps: S2.1: Mix silicon powder and aluminum powder and place them in a tube furnace. Introduce a mixture of nitrogen and hydrogen gas and heat the mixture to 1200-1300℃ at 10℃ / min. Hold the mixture at this temperature for 1-2 hours and then cool it down to 500-600℃ at 10℃ / min. Finally, cool the mixture in the furnace to room temperature to obtain composite nanowires. S2.2: After cleaning the graphite substrate, place it in a nickel nitrate solution and soak for 1-2 hours. After removing it, dry it at 60-80℃ and then suspend it in the high-temperature zone of a vertical resistance furnace. Then, place hafnium tetrachloride powder in the low-temperature zone of the vertical resistance furnace, evacuate to 2 kPa, introduce hydrogen and argon, and heat to 1000-1400℃ at 5-15℃ / min. Then, introduce methane and deposit for 2-4 hours. After that, cool naturally to room temperature under hydrogen protection to obtain hafnium carbide nanowires.

2. The method for preparing a high-strength LTCC composite ceramic material according to claim 1, characterized in that, S3 specifically includes the following steps: S3.1: Add fly ash to the mixed dispersion at a ratio of 1g:(1.3-1.5)mL, ball mill at 450-500r / min for 1-2h, then add dilute hydrochloric acid with a mass concentration of 180-200g / L, stir at 75-85℃ for 2-3h, and dry to obtain pretreated fly ash; S3.2: Add talc, alumina, magnesium oxide and europium oxide to the pretreated fly ash, wet grind at 400-500 r / min for 40-50 min, and then dry at 70-80℃ to obtain mixed raw powder; S3.3: The above mixed raw powder is placed in a tablet press and pressed into a green body at a pressure of 15-25 MPa. Then, it is cold isostatically pressed at a pressure of 200-300 MPa for 20-30 seconds. After sintering at 1100-1200℃ for 2-3 hours, it is cooled to room temperature in the furnace and ground to obtain europium-doped ceramic powder.

3. The method for preparing a high-strength LTCC composite ceramic material according to claim 2, characterized in that, S4 specifically includes the following steps: S4.1: Mix CaO, MgO, B2O3 and SiO2 evenly and ball mill for 2-3 hours. Then place it in a high-temperature furnace and heat it to 1250℃ at 10℃ / min. Hold it for 1-2 hours. Then pour it into deionized water and quench it to form a glass block. After drying and grinding, CMBS glass powder is obtained. S4.2: The above CMBS glass powder, the nano-alumina modified hydroxyapatite whiskers obtained in step S1.5, the nano-SiC whiskers, the composite nanowires obtained in step S2.1, the hafnium carbide nanowires obtained in step S2.2, and the europium-doped ceramic powder obtained in step S3.3 are added to a mixed organic solvent and ball-milled to obtain a mixed slurry. S4.3: After vacuum degassing the above mixed slurry, it is cast into a film, dried, cut and stacked, and then heat-treated in a muffle furnace at 500-600℃ for 40-50 minutes, and then heated to 850-900℃ for sintering for 1-2 hours to obtain LTCC composite ceramic material.

4. The method for preparing a high-strength LTCC composite ceramic material according to claim 1, characterized in that, The mass ratio of aluminum nitrate to citric acid is (1.4-1.6):1, and the mass ratio of hydroxylated whiskers to aluminum nitrate is (8.3-8.5):

1.

5. The method for preparing a high-strength LTCC composite ceramic material according to claim 1, characterized in that, The amount of aluminum powder used is 1-3% of the mass of silicon powder, and the volume ratio of nitrogen to hydrogen in the mixed gas is (19-20):

1.

6. The method for preparing a high-strength LTCC composite ceramic material according to claim 1, characterized in that, The nickel nitrate solution is a 1-2 mol / L aqueous solution of nickel nitrate, and the volume ratio of hydrogen to argon is (3-5):

1.

7. The method for preparing a high-strength LTCC composite ceramic material according to claim 2, characterized in that, The molar ratio of magnesium oxide, aluminum oxide and silicon dioxide in the mixed raw powder is 2:2:5, and the amount of europium oxide added is 0.5-1.5% of the total mass of pretreated fly ash, talc, aluminum oxide and magnesium oxide.

8. The method for preparing a high-strength LTCC composite ceramic material according to claim 3, characterized in that, The composition of CMBS glass powder is: 26-30wt% CaO, 18.8-21.2wt% MgO, 38-40wt% B2O3, with the balance being SiO2.

9. A high-strength LTCC composite ceramic material, characterized in that, It is prepared by the preparation method of a high-strength LTCC composite ceramic material according to any one of claims 1-8.

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