Sintering aid for reducing sintering temperature of 95% alumina ceramic and preparation method thereof

Abstract

The invention discloses a sintering aid for reducing the sintering temperature of 95% aluminum oxide ceramic and a preparation method thereof, and the method comprises the following steps: 1, pouring H3BO3, ZnO and SiO2 into a ball milling tank, carrying out wet ball milling, drying, and screening out mixed powder with the required particle size; 2, transferring the mixed powder into a glass melting furnace preheated to 1200-1300 DEG C, preserving heat, then raising the temperature of the glass melting furnace to 1450 DEG C at the heating rate of 3-5 DEG C / min, and preserving heat to obtain a high-temperature molten substance ZBS; 3, rapidly pouring the high-temperature molten substance ZBS into a liquid quenching medium, continuously stirring to quench and cool the high-temperature molten substance ZBS, collecting irregular glass particles, and drying the irregular glass particles to obtain glass particles with irregular shapes; and step 4, firstly carrying out ultrasonic cleaning on the glass particles with irregular shapes, then transferring the glass particles into a mortar, and grinding to obtain ZnO-B2O3-SiO2 glass powder, namely the sintering aid. The sintering aid prepared by the invention can obviously reduce the sintering temperature of 95% of alumina ceramic, densifies the structure of the alumina ceramic, and is beneficial to improving the electric field intensity.

Description

Technical Field

[0001] The invention relates to a sintering aid for ceramic materials, in particular to a sintering aid for reducing the sintering temperature of 95% alumina ceramics and a preparation method thereof. Background Art

[0002] 95% alumina ceramics (ceramics in which Al2O3 accounts for 95% of the total mass) are widely used in new energy vehicles, aerospace, and chemical industries due to their high breakdown resistance and excellent mechanical properties. They can be made into devices such as high-voltage circuit housings and ceramic circuit substrates. However, the higher sintering temperature during the preparation process of 95% alumina ceramics runs counter to the current concept of "improving energy utilization and developing green new energy". The higher sintering temperature not only increases the production cost of the enterprise, but also causes more defects on the surface of 95% alumina ceramics, significantly reducing performance.

[0003] Given that high sintering temperature significantly limits the industrial development of 95% alumina ceramics, developing a suitable sintering aid to reduce the sintering temperature without affecting the performance of 95% alumina ceramics is of great significance to the industrialization process of 95% alumina ceramics. Summary of the Invention

[0004] The purpose of the present invention is to provide a sintering aid for reducing the sintering temperature of 95% alumina ceramics and a preparation method thereof, which can significantly reduce the sintering temperature of 95% alumina ceramics, densify their structure, and improve the electric field strength.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics comprises the following steps:

[0007] Step 1: Pour 30% to 75% H3BO3, 10% to 50% ZnO, and 15% to 25% SiO2 into a ball mill according to mass percentage, perform wet ball milling, dry, and then use a sieve to sieve out the mixed powder of the desired particle size;

[0008] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace that has been preheated to 1200-1300°C, keep the temperature for the first time, then raise the temperature of the glass melting furnace to 1450°C at a heating rate of 3-5°C / min, and keep the temperature again to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0009] Step 3: quickly pour the high-temperature molten material ZBS into the liquid quenching medium, stir it continuously, quench it and cool it, collect the irregular glass particles and dry them to obtain irregularly shaped glass particles ZBS-glass;

[0010] Step 4: First, the irregularly shaped glass particles ZBS-glass are ultrasonically cleaned, and then transferred to a mortar and fully ground to obtain ZnO-B2O3-SiO2 glass powder, i.e., a sintering aid.

[0011] Furthermore, the liquid medium for wet ball milling in step 1 is distilled water, and the mass ratio of raw materials, distilled water and ball stone is 1:5:1.5.

[0012] Furthermore, the initial insulation time in step 2 is 5 to 10 minutes.

[0013] Furthermore, the time for the second insulation in step 2 is 1 to 2 hours.

[0014] Furthermore, the liquid quenching medium in step 3 is distilled water with a temperature of 25 to 35°C.

[0015] Furthermore, in step 3, the irregular glass particles are collected using a dust-free cloth.

[0016] Furthermore, step 4 also includes: pouring the ground glass powder into a ball mill, performing wet ball milling, drying, and then using a sieve to sieve out ZnO-B2O3-SiO2 glass powder of a desired particle size.

[0017] Furthermore, the liquid medium for wet ball milling in step 4 is distilled water, and the mass ratio of the raw material, distilled water and balls is 1:5:3, and the diameter of the balls is less than 3 mm.

[0018] Furthermore, the sieves used in step 1 and step 4 are both 150 mesh.

[0019] A sintering aid for reducing the sintering temperature of 95% alumina ceramics.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] 1) The present invention adopts a simple process to prepare a ternary glass system composed of ZnO, B2O3 and SiO2 using low-cost raw materials. As a sintering aid, it has a positive effect on reducing the sintering temperature of 95% alumina ceramics. The reasons are: first, B2O3, as a strong flux raw material, forms a low-melting-point glass with ZnO and SiO2, which is beneficial to the sintering process; second, the ZnO-B2O3-SiO2 ternary glass has the function of promoting mass transfer and dissolving Al2O3, and can form a more complex boron-containing aluminum silicate melt, which is beneficial to improving the sintering activation energy of 95% alumina ceramics; third, the liquid phase formed by the ZnO-B2O3-SiO2 ternary glass at high temperature is beneficial to reducing the diffusion activation energy and accelerating material migration, and ZnO forms a multi-element low-melting-point glass with BO and SiO, which can further reduce the temperature of liquid phase generation; fourth, Zn 2 + Partially substituted Al 3 +Forming a solid solution, introducing lattice distortion and vacancy defects, is beneficial to enhancing the diffusion rate; therefore, compared with existing sintering aids, the ZnO-B2O3-SiO2 ternary glass prepared by the present invention can significantly reduce the sintering temperature of alumina ceramics by 95% through the coordinated design of liquid-phase sintering and interfacial chemical reaction.

[0022] 2) The liquid phase formed by the ZnO-B2O3-SiO2 ternary glass prepared in the present invention has the function of filling pores and promoting grain boundary migration, which is beneficial to the densification of the sintering process of 95% alumina ceramics, thereby improving the mechanical strength and wear resistance of the prepared device.

[0023] 3) The present invention improves the mechanical properties and electric field strength of alumina ceramics by 95% by leveraging the crystalline phase precipitated during the sintering process of ZnO-B2O3-SiO2 ternary glass and the coordinated optimization of the glass network structure, making it more suitable for high-frequency electronic devices, large-size ceramic components and other fields that are sensitive to temperature and have high reliability requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The wettability of different types of oxides used in the present invention on the surface of 95% alumina ceramic green body;

[0025] Figure 2 XRD patterns of ZnO-B2O3-SiO2 ternary glasses prepared in Examples 1 to 5 of the present invention;

[0026] Figure 3 The results of the infiltration of the ZnO-B2O3-SiO2 ternary glass prepared in Examples 1 to 5 of the present invention on the surface of a 95% alumina ceramic green body;

[0027] Figure 4The improvement of the sintering temperature of 95% alumina ceramics by the ZnO-B2O3-SiO2 ternary glass prepared by the present invention;

[0028] Figure 5 The improvement of the electric field strength of 95% alumina ceramics by the ZnO-B2O3-SiO2 ternary glass prepared by the present invention;

[0029] Figure 6 These are the SEM images of 95% alumina ceramics prepared without adding ZnO-B2O3-SiO2 ternary glass and the SEM images of 95% alumina ceramics prepared with adding ZnO-B2O3-SiO2 ternary glass. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0031] Example 1

[0032] Step 1: Pour 30% H3BO3, 50% ZnO and 20% SiO2 into a ball mill according to mass percentage, use distilled water as the liquid medium, and wet ball mill according to the mass ratio of raw materials, distilled water and ball stone of 1:5:1.5. After drying, use a 150-mesh sieve to sieve out the mixed powder of the required particle size;

[0033] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace preheated to 1200°C and keep it warm for 9 minutes. Then, increase the temperature of the glass melting furnace to 1450°C at a heating rate of 3°C / min and keep it warm for 1 hour to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0034] Step 3: Pour the high-temperature molten ZBS into 25°C distilled water quickly, stirring continuously to prevent the glass particles from sticking together, quenching and cooling the glass particles, and collecting the irregular glass particles with a dust-free cloth and drying them to obtain irregularly shaped glass particles ZBS-glass;

[0035] Step 4: First, ultrasonically clean the irregularly shaped glass particles ZBS-glass, then transfer them to a mortar and grind them thoroughly with a uniform force by rotating the grinding rod clockwise to obtain glass powder ZBS-glass-A.

[0036] Step 5: Pour the glass powder ZBS-glass-A into a ball mill, select balls with a diameter of less than 3 mm, use distilled water as the liquid medium, and perform wet ball milling in a mass ratio of raw materials, distilled water and balls of 1:5:3. After drying, use a 150-mesh sieve to sieve out the ZnO-B2O3-SiO2 glass powder of the required particle size, i.e., the sintering aid.

[0037] Example 2

[0038] Step 1: Pour 35% H3BO3, 40% ZnO and 25% SiO2 into a ball mill according to mass percentage, use distilled water as the liquid medium, and wet ball mill according to the mass ratio of raw materials, distilled water and ball stone of 1:5:1.5. After drying, use a 150-mesh sieve to sieve out the mixed powder of the required particle size;

[0039] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace preheated to 1250°C and keep it warm for 6 minutes. Then, increase the temperature of the glass melting furnace to 1450°C at a heating rate of 4°C / min and keep it warm for 2 hours to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0040] Step 3: Pour the high-temperature molten ZBS into 35°C distilled water quickly, stirring continuously to prevent the glass particles from sticking together, quenching and cooling the glass particles, and collect the irregular glass particles with a dust-free cloth and dry them to obtain irregularly shaped glass particles ZBS-glass;

[0041] Step 4: First, ultrasonically clean the irregularly shaped glass particles ZBS-glass, then transfer them to a mortar and grind them thoroughly with a uniform force by rotating the grinding rod clockwise to obtain glass powder ZBS-glass-A.

[0042] Step 5: Pour the glass powder ZBS-glass-A into a ball mill, select balls with a diameter of less than 3 mm, use distilled water as the liquid medium, and perform wet ball milling in a mass ratio of raw materials, distilled water and balls of 1:5:3. After drying, use a 150-mesh sieve to sieve out the ZnO-B2O3-SiO2 glass powder of the required particle size, i.e., the sintering aid.

[0043] Example 3

[0044] Step 1: Pour 50% H3BO3, 30% ZnO and 20% SiO2 into a ball mill according to mass percentage, use distilled water as the liquid medium, and wet ball mill according to the mass ratio of raw materials, distilled water and ball stone of 1:5:1.5. After drying, use a 150-mesh sieve to sieve out the mixed powder of the required particle size;

[0045] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace preheated to 1300°C and keep it warm for 8 minutes. Then, increase the temperature of the glass melting furnace to 1450°C at a heating rate of 5°C / min and keep it warm for 1.5 hours to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0046] Step 3: Pour the high-temperature molten ZBS into 30°C distilled water quickly, stirring continuously to prevent the glass particles from sticking together, quenching and cooling the glass particles, and collecting the irregular glass particles with a dust-free cloth and drying them to obtain irregularly shaped glass particles ZBS-glass;

[0047] Step 4: First, ultrasonically clean the irregularly shaped glass particles ZBS-glass, then transfer them to a mortar and grind them thoroughly with a uniform force by rotating the grinding rod clockwise to obtain glass powder ZBS-glass-A.

[0048] Step 5: Pour the glass powder ZBS-glass-A into a ball mill, select balls with a diameter of less than 3 mm, use distilled water as the liquid medium, and perform wet ball milling in a mass ratio of raw materials, distilled water and balls of 1:5:3. After drying, use a 150-mesh sieve to sieve out the ZnO-B2O3-SiO2 glass powder of the required particle size, i.e., the sintering aid.

[0049] Example 4

[0050] Step 1: Pour 60% H3BO3, 20% ZnO and 20% SiO2 into a ball mill according to mass percentage, use distilled water as the liquid medium, and wet ball mill according to the mass ratio of raw materials, distilled water and ball stone of 1:5:1.5. After drying, use a 150-mesh sieve to sieve out the mixed powder of the required particle size;

[0051] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace preheated to 1200°C and keep it warm for 10 minutes. Then, increase the temperature of the glass melting furnace to 1450°C at a heating rate of 5°C / min and keep it warm for 1 hour to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0052] Step 3: Pour the high-temperature molten ZBS into 35°C distilled water quickly, stirring continuously to prevent the glass particles from sticking together, quenching and cooling the glass particles, and collect the irregular glass particles with a dust-free cloth and dry them to obtain irregularly shaped glass particles ZBS-glass;

[0053] Step 4: First, ultrasonically clean the irregularly shaped glass particles ZBS-glass, then transfer them to a mortar and grind them thoroughly with a uniform force by rotating the grinding rod clockwise to obtain glass powder ZBS-glass-A.

[0054] Step 5: Pour the glass powder ZBS-glass-A into a ball mill, select balls with a diameter of less than 3 mm, use distilled water as the liquid medium, and perform wet ball milling in a mass ratio of raw materials, distilled water and balls of 1:5:3. After drying, use a 150-mesh sieve to sieve out the ZnO-B2O3-SiO2 glass powder of the required particle size, i.e., the sintering aid.

[0055] Example 5

[0056] Step 1: Pour 75% H3BO3, 10% ZnO and 15% SiO2 into a ball mill according to mass percentage, use distilled water as the liquid medium, and wet ball mill according to the mass ratio of raw materials, distilled water and ball stone of 1:5:1.5. After drying, use a 150-mesh sieve to sieve out the mixed powder of the required particle size;

[0057] Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace preheated to 1300°C and keep it warm for 5 minutes. Then, increase the temperature of the glass melting furnace to 1450°C at a heating rate of 3°C / min and keep it warm for 2 hours to fully melt the mixed powder to obtain a high-temperature molten material ZBS;

[0058] Step 3: Pour the high-temperature molten ZBS into 25°C distilled water quickly, stirring continuously to prevent the glass particles from sticking together, quenching and cooling the glass particles, and collecting the irregular glass particles with a dust-free cloth and drying them to obtain irregularly shaped glass particles ZBS-glass;

[0059] Step 4: First, ultrasonically clean the irregularly shaped glass particles ZBS-glass, then transfer them to a mortar and grind them thoroughly with a uniform force by rotating the grinding rod clockwise to obtain glass powder ZBS-glass-A.

[0060] Step 5: Pour the glass powder ZBS-glass-A into a ball mill, select balls with a diameter of less than 3 mm, use distilled water as the liquid medium, and perform wet ball milling in a mass ratio of raw materials, distilled water and balls of 1:5:3. After drying, use a 150-mesh sieve to sieve out the ZnO-B2O3-SiO2 glass powder of the required particle size, i.e., the sintering aid.

[0061] Figure 1The wetting conditions of nine oxides on the surface of 95% alumina ceramic green body after sintering are shown. The analysis shows that: B2O3, ZnO and SiO2 have obvious wetting phenomenon on 95% alumina ceramic green body; SnO2 also has a slight wetting effect; MgO, ZrO2 and Y2O3 have residues on the surface of 95% alumina ceramic green body, indicating that the wetting effect is poor; La2O3 causes impurities to appear on the surface of 95% alumina ceramic green body, which is not conducive to being used as a sintering aid; Bi2O3 evaporates and pits appear on the surface of 95% alumina ceramic green body, which is not conducive to the sintering of 95% alumina ceramic green body; by comparing the wetting phenomena of different oxides, it can be seen that B2O3, ZnO and SiO2 are the most feasible raw materials for ternary glass sintering aids.

[0062] Figure 2 The XRD patterns of the ZnO-B2O3-SiO2 ternary glasses prepared in Examples 1 to 5 are shown. It can be seen that each sample has a typical amorphous characteristic peak of glass. As the ZnO content increases and the B2O3 content decreases, it can be seen that the peak at 25-40° gradually becomes obvious, indicating that the amorphous glass structure can be adjusted by regulating the ratio of ZnO to B2O3, which plays an important role in reducing the sintering temperature of 95% alumina ceramics and promoting their densification. The reasons are: first, the borosilicate glass phase is formed by B2O3 and SiO2, which has excellent First, the glass phase forms a low-viscosity liquid phase at high temperature, which fills the gaps between particles through capillary action, promoting particle rearrangement and dissolution-precipitation mass transfer, thereby significantly reducing the sintering temperature of alumina ceramics. Third, the ternary glass formed by ZnO, B2O3 and SiO2 can promote the densification of 95% alumina ceramics at a lower temperature. Therefore, regulating and optimizing the ratio of ZnO to B2O3 in the glass sintering aid plays an important role in reducing the sintering temperature of 95% alumina ceramics and promoting densification.

[0063] Figure 3 The wetting results of ZnO-B2O3-SiO2 ternary glass prepared in Examples 1 to 5 on the surface of 95% alumina ceramic green body are shown. It can be seen that the five samples have good wetting effect on the 95% alumina ceramic green body. The good wetting ability between the sintering aid and the ceramic green body is the main sign of it as an excellent sintering aid, indicating that ZnO-B2O3-SiO2 ternary glass has a good sintering aid effect on 95% alumina ceramic.

[0064] Figure 4The improvement of the sintering temperature of the ZnO-B2O3-SiO2 ternary glass prepared in Example 1 is demonstrated. It can be seen that after adding the glass sintering aid, the sintering temperature of 95% alumina ceramics can be reduced by about 100°C, which has a positive effect on improving energy utilization and reducing material production costs for enterprises.

[0065] Figure 5 The improvement of the electric field strength of 95% alumina ceramics by the ZnO-B2O3-SiO2 ternary glass prepared in Example 1 is demonstrated. It can be seen that adding different amounts of ZnO-B2O3-SiO2 ternary glass sintering aid has different effects on the electric field strength of 95% alumina ceramics. The reason is that an appropriate amount of glass phase can optimize the grain boundary structure of alumina ceramics, form a uniform interface layer, and reduce the interface polarization between grain boundaries and grains. Moreover, the glass liquid phase formed by the ZnO-B2O3-SiO2 ternary glass also has the function of filling pores and defects, which is also conducive to the improvement of the electric field strength.

[0066] Figure 6 SEM images of 95% alumina ceramics prepared without adding the ZnO-B2O3-SiO2 ternary glass prepared in Example 1 and SEM images of 95% alumina ceramics prepared with the addition of 0.4% ZnO-B2O3-SiO2 ternary glass are shown. It can be seen that after adding the ZnO-B2O3-SiO2 ternary glass, the pores inside the 95% alumina ceramics are reduced, the grain size is reduced, and the ceramics are more dense. This is because the ZnO-B2O3-SiO2 ternary glass forms a liquid phase during the sintering process, which reduces the sintering temperature of the ceramics and promotes the mass transfer and dissolution of Al2O3 inside the ceramics, thereby accelerating the densification process of the 95% alumina ceramics and reducing the grain size of the 95% alumina ceramics. The smaller grains inside the ceramics and their higher density are conducive to improving their electric field strength.

Claims

1. A method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics, characterized in that: The steps include: Step 1: Pour 30% to 75% H3BO3, 10% to 50% ZnO, and 15% to 25% SiO2 into a ball mill according to mass percentage, perform wet ball milling, dry, and then use a sieve to sieve out the mixed powder of the desired particle size; Step 2: Transfer the mixed powder to a quartz crucible inside a glass melting furnace that has been preheated to 1200-1300°C, keep the temperature for the first time, then raise the temperature of the glass melting furnace to 1450°C at a heating rate of 3-5°C / min, and keep the temperature again to fully melt the mixed powder to obtain a high-temperature molten material ZBS; Step 3: quickly pour the high-temperature molten material ZBS into the liquid quenching medium, stir it continuously, quench it and cool it, collect the irregular glass particles and dry them to obtain irregularly shaped glass particles ZBS-glass; Step 4: First, the irregularly shaped glass particles ZBS-glass are ultrasonically cleaned, and then transferred to a mortar and fully ground to obtain ZnO-B2O3-SiO2 glass powder, i.e., a sintering aid.

2. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: The liquid medium for wet ball milling in step 1 is distilled water, and the mass ratio of raw materials, distilled water and ball stone is 1:5:1.

5.

3. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: The initial insulation time of step 2 is 5 to 10 minutes.

4. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: The time for the second heat preservation in step 2 is 1 to 2 hours.

5. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: The liquid quenching medium in step 3 is distilled water with a temperature of 25 to 35°C.

6. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: In step 3, the irregular glass particles are collected using a dust-free cloth.

7. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 1, characterized in that: The step 4 further comprises: pouring the ground glass powder into a ball mill, performing wet ball milling, drying, and then using a sieve to sieve out ZnO-B2O3-SiO2 glass powder of a desired particle size.

8. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 7, characterized in that: The liquid medium for wet ball milling in step 4 is distilled water, and the mass ratio of raw materials, distilled water and balls is 1:5:3, and the diameter of the balls is less than 3 mm.

9. The method for preparing a sintering aid for reducing the sintering temperature of 95% alumina ceramics according to claim 7, characterized in that: The sieves in step 1 and step 4 are both 150 mesh.

10. A sintering aid prepared by the method according to any one of claims 1 to 9 for reducing the sintering temperature of 95% alumina ceramics.

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