Preparation method of phase-separation and crystallization cordierite microcrystalline glass combined with aluminum silicate ceramic material and product thereof

Abstract

This invention discloses a method for preparing a phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material and its product, which is prepared from a base material and a binder; the raw material composition of the base material is 10-25 wt% cordierite-based microcrystalline glass powder, 10-30 wt% mullite aggregate, 30-60 wt% corundum aggregate, and 10-20 wt% clay powder, wherein the raw material composition of the cordierite-based microcrystalline glass powder is 23-25 ​​wt% MgO, 17-19 wt% Al2O3, and 57-59 wt% SiO2. This invention uses phase-separated crystalline cordierite microcrystalline glass as a sintering aid. By introducing cordierite crystals into the aluminosilicate ceramic matrix through in-situ synthesis of microcrystalline glass, it not only provides a low-temperature sintering aid but also effectively improves the performance of aluminosilicate ceramic materials. This is of great significance for overcoming the problems existing in the application of microcrystalline glass in the prior art and improving the cost-effectiveness of aluminosilicate ceramic materials. Therefore, it has broad market prospects and is conducive to the promotion and application of the technology and the advancement and development of the industry.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a method for preparing a phase-separated crystalline cordierite microcrystalline glass-in-glass combined with aluminosilicate ceramic material and its products. Background Technology

[0002] Cordierite glass-ceramics are high-performance adhesives with advantages such as low thermal expansion, high hardness, and good dielectric properties, and are widely used as electronic packaging materials and ceramic adhesives. These excellent properties of cordierite glass-ceramics mainly originate from the cordierite crystals precipitated within the glass. To improve the crystallinity (crystal count) of cordierite glass-ceramics, transition metal oxides such as TiO2 and Fe2O3 are often added as nucleating agents. However, adding these nucleating agents obviously reduces the refractoriness of the glass, limiting its application in high-temperature structures. Therefore, how to improve the crystallinity of glass-ceramics without adding external nucleating agents has been a persistent problem for researchers. Solving this problem will help promote the application of cordierite glass-ceramics as high-temperature adhesives.

[0003] Besides adding nucleating agents to promote crystallization, phase separation is another method. Magnesium ions have a high ionic potential and are strong ions that promote phase separation. If phase separation crystallization can be utilized, it is hoped that the crystallinity of glass can be improved without adding nucleating agents.

[0004] Besides the issues mentioned above, the volume expansion of glass during crystallization is also a significant limitation to its use as a binder. Crystallization expansion loosens the bonded particles, easily leading to a looser structure. However, glass only acquires the properties required by the user after crystallization. Therefore, overcoming the contradiction between crystallization and bonding is a problem that has troubled researchers. Correspondingly, adding phase separation to promote crystallization further enhances the anti-densification behavior.

[0005] Cordierite microcrystalline glass, as a low-temperature sintering aid, can compensate for the high sintering temperature of aluminosilicate ceramics. Furthermore, its low coefficient of thermal expansion reduces the thermal expansion coefficient of aluminosilicate ceramics, thus improving their resistance to rapid heating and cooling. However, the crystallization expansion of the glass can cause de-densification, reducing its sinterability. Moreover, to improve its refractoriness, other nucleating agents are often not added; therefore, improving the crystallinity of the glass between particles is also crucial. Thus, effectively addressing these two issues is of great significance for improving the quality of aluminosilicate ceramic materials and reducing product costs. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing aluminosilicate ceramic material with phase-separated crystalline cordierite microcrystalline glass. This method uses phase-separated crystalline cordierite microcrystalline glass as a sintering aid for aluminosilicate ceramics, introduces cordierite through phase separation and in-situ synthesis, and achieves a high-density aluminosilicate ceramic with superior thermal shock resistance through complementary sintering properties between the glass and the ceramic matrix. Another objective of this invention is to provide products obtained using the above-described method for preparing aluminosilicate ceramic material with phase-separated crystalline cordierite microcrystalline glass.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a method for preparing a phase-separated crystalline cordierite microcrystalline glass-in-the-lime ceramic material bonded with aluminosilicate. The ceramic material is prepared from a base material and a binder. The base material comprises 10-25 wt% cordierite-based microcrystalline glass powder, 10-30 wt% mullite aggregate, 30-60 wt% corundum aggregate, and 10-20 wt% clay powder. The cordierite-based microcrystalline glass powder comprises 23-25 ​​wt% MgO, 17-19 wt% Al₂O₃, and 57-59 wt% SiO₂. The binder is used at 8-12 wt% of the base material. The preparation method includes the following steps:

[0009] (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the raw material composition ratio, the mixture is melted into a glass liquid, and then the glass liquid is poured into water for quenching to obtain a frit. After ball milling, cordierite-based microcrystalline glass powder is obtained.

[0010] (2) After mixing the base material according to the raw material composition ratio, add the binder and mix evenly, then press and dry to obtain a green body;

[0011] (3) The green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 900-1000℃ for a holding time of ≥10h, and then the temperature is raised to 1200-1300℃ for a second stage of high-temperature sintering for a holding time of 4-6h; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

[0012] Furthermore, the cordierite microcrystalline glass powder of this invention has a particle size of 10–75 μm, the mullite aggregate has a particle size of 40–325 mesh, the corundum aggregate has a particle size of 40–500 mesh, and the clay powder has a particle size of 25–75 μm. The binder is a 5 wt% PVA solution. The clay is two or more of kaolin, spherical clay, and bauxite.

[0013] In the above scheme, the melting temperature in step (1) of the present invention is 1500-1600℃, and the melting time is 2-3 hours. The moisture content of the dried green body in step (2) is <1%.

[0014] The product obtained by the above-described method for preparing phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material has a water absorption rate ≤8.6% and a coefficient of thermal expansion ≤4.27×10⁻⁶. -6 ·℃ -1 Glass crystallinity ≥ 85% and flexural strength > 60 MPa.

[0015] The present invention has the following beneficial effects:

[0016] (1) This invention uses cordierite microcrystalline glass, which can generate viscous flow at low temperatures, as a sintering aid. Low-temperature sintering and phase separation are carried out simultaneously. This invention designs a glass composition with high MgO content and a system of long-term low-temperature holding. On the one hand, the high MgO content enhances the low-temperature viscous flow of the glass melt (the higher the MgO content, the better the flowability). Long-term low-temperature holding extends the flow time, allowing the glass to encapsulate various aggregates and powders, promoting the elimination of pores inside the ceramic body, improving the density of the product, and achieving the purpose of reducing the sintering temperature of aluminosilicate ceramics. On the other hand, the high MgO content and long-term low-temperature holding promote phase separation inside the glass melt. The local component deviation caused by phase separation and the phase separation interface, combined with the surface defects of the melt powder, jointly promote crystallization behavior and increase the number of crystals.

[0017] (2) This invention designs a sintering system in which the sintering properties of microcrystalline glass and ceramic body are complementary. Natural clay will expel structural water at low temperatures and form pores, which is an anti-densification behavior. Therefore, clay is often pre-calcined in production. At this time, the low-temperature viscous flow of glass near its transformation temperature point is used to counteract the pore-forming behavior. When crystallization occurs at high temperature, the structure becomes loose due to the crystallization expansion effect. The fine clay powder generates liquid phase flow to promote shrinkage and counteract this expansion effect, thereby avoiding the high-temperature (>1400℃) firing process and saving more energy.

[0018] (3) By maintaining the temperature at a low temperature for a long time, the present invention avoids the crystallization temperature point of the glass, avoids crystallization and reduces the amount of viscous flow, and solves the problem that high sintering temperature leads to crystallization and weakens the sinterability of the glass, resulting in poor sintering effect.

[0019] (4) This invention enhances the viscous flow of glass by designing a high MgO content, which allows the glass to wet the ceramic body well and enhances the ion migration ability of the glass. However, this results in a lack of Al2O3 and SiO2. At this time, combined with the high activity of clay and a small amount of impurities, the glass absorbs some clay powder and corundum powder during the high-temperature crystallization process, which replenishes the missing Al2O3 and SiO2 in the glass, making its composition closer to the chemical composition of cordierite (2MgO 2Al2O3 5SiO2), thereby improving the crystallization ability of the glass.

[0020] (5) The process of this invention is simple and the firing temperature is low. It is of great significance for improving the quality of aluminosilicate ceramic materials and overcoming various problems in the application of microcrystalline glass. Therefore, it has a broad market prospect and is conducive to the promotion and application and the progress and development of industry technology. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0022] Figure 1 This is the XRD pattern of the phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material obtained in the embodiments of the present invention;

[0023] Figure 2 This is a microstructure image of the phase separation and crystallization of the microcrystalline glass portion of the ceramic material of the present invention after acid etching (secondary electron image obtained by scanning electron microscopy after HF acid etching for 60s). Detailed Implementation

[0024] Example 1:

[0025] This embodiment describes a method for preparing a phase-separated crystalline cordierite microcrystalline glass bonded to aluminosilicate ceramic material, obtained from a base material and a binder. The base material consists of 25wt% cordierite-based microcrystalline glass powder (75μm particle size), 30wt% mullite aggregate (of which 15wt% is 40 mesh, 5wt% is 80 mesh, and 10wt% is 325 mesh), 30wt% corundum aggregate (of which 15wt% is 40 mesh, 5wt% is 120 mesh, and 10wt% is 400 mesh), and 15wt% clay powder (25μm particle size) (of which 7.5wt% is kaolin and 7.5wt% is bauxite). The cordierite-based microcrystalline glass powder consists of 23wt% MgO, 19wt% Al2O3, and 58wt% SiO2. wt%; the binder is a 5 wt% PVA solution, and its amount is 12 wt% of the base material; the preparation method includes the following steps:

[0026] (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the above proportion, the mixture is placed in an electric furnace and kept at 1600℃ for 2 hours to melt into a glass liquid. Then the glass liquid is poured into water and quenched to obtain a frit. After ball milling, cordierite-based microcrystalline glass powder is obtained.

[0027] (2) After mixing the above base materials according to the raw material composition ratio, add the binder and mix evenly, then press and mold, and dry at 110°C to obtain a green body with a moisture content of <1%;

[0028] (3) The above green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 900℃ for 11 hours, and then the temperature is raised to 1200℃ for a second stage of high-temperature sintering for 4 hours; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

[0029] Example 2:

[0030] This embodiment describes a method for preparing a phase-separated crystalline cordierite microcrystalline glass bonded to aluminosilicate ceramic material, which is obtained from a base material and a binder. The raw material composition of the base material is 10wt% cordierite-based microcrystalline glass powder (10μm particle size), 20wt% mullite aggregate (of which 10wt% is 40 mesh and 10wt% is 80 mesh), 50wt% corundum aggregate (of which 30wt% is 40 mesh, 10wt% is 250 mesh and 10wt% is 500 mesh), and 20wt% clay powder (50μm particle size) (of which 10wt% is spherical clay and 10wt% is bauxite). The raw material composition of the cordierite-based microcrystalline glass powder is 24wt% MgO, 17wt% Al2O3, and 59wt% SiO2. The binder is a 5wt% PVA solution, which is used in an amount of 8wt% of the base material. The preparation method includes the following steps:

[0031] (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the above proportion, the mixture is placed in an electric furnace and kept at 1500℃ for 3 hours to melt into glass liquid. Then the glass liquid is poured into water and quenched to obtain frit. After ball milling, cordierite-based microcrystalline glass powder is obtained.

[0032] (2) After mixing the above base materials according to the raw material composition ratio, add the binder and mix evenly, then press and mold, and dry at 100°C to obtain a green body with a moisture content of <1%;

[0033] (3) The above green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 950℃ for 11 hours, and then the temperature is raised to 1250℃ for a second stage of high-temperature sintering for 5 hours; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

[0034] Example 3:

[0035] This embodiment describes a method for preparing a phase-separated crystalline cordierite microcrystalline glass bonded to aluminosilicate ceramic material, which is obtained from a base material and a binder. The raw material composition of the base material is 15wt% cordierite-based microcrystalline glass powder (35μm particle size), 10wt% mullite aggregate (80 mesh particle size), 60wt% corundum aggregate (of which 30wt% is 40 mesh, 10wt% is 325 mesh, and 20wt% is 500 mesh), and 15wt% clay powder (68μm particle size) (of which 5wt% is kaolin, 5wt% is bauxite, and 5wt% is spherical clay). The raw material composition of the cordierite-based microcrystalline glass powder is 25wt% MgO, 18wt% Al2O3, and 57wt% SiO2. The binder is a 5wt% PVA solution, which is used in an amount of 10wt% of the base material. The preparation method includes the following steps:

[0036] (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the above proportion, the mixture is placed in an electric furnace and kept at 1550℃ for 2.5h to melt it into glass liquid. Then the glass liquid is poured into water and quenched to obtain a molten block. After ball milling, cordierite-based microcrystalline glass powder is obtained.

[0037] (2) After mixing the above base materials according to the raw material composition ratio, add the binder and mix evenly, then press and mold, and dry at 110°C to obtain a green body with a moisture content of <1%;

[0038] (3) The above green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 1000℃ for 10 hours, and then the temperature is raised to 1300℃ for a second stage of high-temperature sintering for 6 hours; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

[0039] Example 4:

[0040] This embodiment describes a method for preparing a phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material, which is obtained from a base material and a binder. The raw material composition of the base material is 20wt% cordierite-based microcrystalline glass powder (35μm particle size), 30wt% mullite aggregate (80 mesh particle size), 40wt% corundum aggregate (of which 30wt% is 40 mesh and 10wt% is 325 mesh), and 10wt% clay powder (75μm particle size) (of which 5wt% is kaolin and 5wt% is bauxite). The raw material composition of the cordierite-based microcrystalline glass powder is 24wt% MgO, 18wt% Al2O3, and 58wt% SiO2. The binder is a 5wt% PVA solution, which is used in an amount of 11wt% of the base material. The preparation method includes the following steps:

[0041] (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the above proportion, the mixture is placed in an electric furnace and kept at 1575℃ for 3 hours to melt into glass liquid. Then the glass liquid is poured into water and quenched to obtain frit. After ball milling, cordierite-based microcrystalline glass powder is obtained.

[0042] (2) After mixing the above base materials according to the raw material composition ratio, add the binder and mix evenly, then press and mold, and dry at 110°C to obtain a green body with a moisture content of <1%;

[0043] (3) The above green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 975℃ for 12 hours, and then the temperature is raised to 1300℃ for a second stage of high-temperature sintering for 5 hours; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

[0044] Comparative Examples 1, 2, and 3 were respectively defined as follows: no clay powder was added (i.e., mullite of the same particle size was used to replace clay), no long-term low-temperature holding (i.e., the holding time of the first stage of low-temperature sintering was 3 hours), and no long-term high-temperature holding (i.e., the holding time of the second stage of high-temperature sintering was 3 hours). (Other conditions were the same as in Example 1.)

[0045] Comparative Example 4 was conducted without the introduction of clay powder and without prolonged low-temperature heat preservation (i.e., replacing clay with mullite of the same particle size and holding for 3 hours during a single low-temperature sintering period). All other conditions were the same as in Example 2.

[0046] Comparative Example 5 was conducted without the introduction of clay powder and without prolonged low-temperature and high-temperature sintering (i.e., replacing clay with mullite of the same particle size, with a first-stage low-temperature sintering holding time of 3 hours and a second-stage high-temperature sintering holding time of 3 hours). All other conditions were the same as in Example 2.

[0047] The properties and glass crystallinity of the ceramic materials obtained by the embodiments and comparative examples of the present invention are shown in Table 1.

[0048] Table 1. Properties and glass crystallinity of ceramic materials prepared in the embodiments and comparative examples of the present invention.

[0049]

[0050] The glass crystallinity was determined using the internal standard method (with corundum as a reference), combined with the calculation of the amount of cordierite in the green body using MDI Jade 6.5 software, and then divided by the amount of glass added.

[0051] As can be seen from Table 1, the cordierite microcrystalline glass combined with aluminosilicate ceramic materials prepared in the embodiments of the present invention all have low water absorption, low coefficient of thermal expansion, high crystallinity and high strength.

[0052] Comparing the data of Example 1 and Comparative Example 1, it can be seen that without adding clay as part of the ceramic body, the water absorption rate of the product increases, the coefficient of thermal expansion increases, and the crystallinity decreases. This is because the high-temperature firing aid effect of clay is missing, which means that the effect of glass crystallization expansion is not offset. At the same time, the lack of highly active clay incorporated into the glass reduces the crystallinity of the microcrystalline glass, which also increases the coefficient of thermal expansion.

[0053] Comparing the data of Example 1 and Comparative Example 2, it can be seen that without long-term low-temperature heat preservation, the water absorption rate of the product increases, the coefficient of thermal expansion increases, and the crystallinity decreases. This is because, on the one hand, the lack of low-temperature viscous flow of glass increases the number of pores, and on the other hand, the lack of long-term low-temperature heat preservation results in fewer phase separations. The lack of glass phase separations and interfaces is not conducive to crystallization.

[0054] Comparing the data from Example 1 and Comparative Example 3, it can be seen that without prolonged high-temperature insulation, the product has a higher water absorption rate, an increased coefficient of thermal expansion, and a decreased crystallinity. This is because high-temperature insulation promotes the precipitation of clay into a liquid phase, which facilitates densification. At the same time, the highly active clay dissolves into the glass, replenishing the lack of SiO2 and Al2O3 in the glass, making the glass composition closer to the chemical composition of cordierite, which is beneficial to increasing the crystal content.

[0055] Comparing the data of Example 2 and Comparative Example 4, it can be seen that without the simultaneous introduction of clay and long-term low-temperature insulation, the water absorption rate and coefficient of thermal expansion of the product are higher, and the crystallinity is further reduced. This is because the lack of highly active clay dissolved in the glass and the lack of sintering complementary design reduce the density, reduce the amount of phase separation and crystallization, reduce the crystallinity of the glass-ceramic, and also increase the coefficient of thermal expansion.

[0056] Comparing the data of Example 2 and Comparative Example 5, it can be seen that if clay is not introduced simultaneously and long-term low-temperature and high-temperature insulation is not performed, the various properties of the product will drop significantly. This is because the design of complementary sintering properties is lacking, and the behavior of high-temperature absorption of clay to promote crystallization is also lacking.

[0057] The phase-separated crystalline cordierite microcrystalline glass-in-glass combined with aluminosilicate ceramic material prepared in the embodiments of the present invention, such as... Figure 1 As shown, it contains crystal phases of corundum, mullite, and cordierite; such as Figure 2 As shown, after HF acid etching, the protrusions are phases that are not easily etched and separated, while crystals mainly grow over a large area at the interface or edge of the phase separation, which illustrates the importance of phase separation for crystallization.

Claims

1. A method for preparing a phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material, characterized in that: The ceramic material is prepared from a base material and a binder; the raw material composition of the base material is 10-25 wt% cordierite-based microcrystalline glass powder, 10-30 wt% mullite aggregate, 30-60 wt% corundum aggregate, and 10-20 wt% clay powder, wherein the raw material composition of the cordierite-based microcrystalline glass powder is 23-25 ​​wt% MgO, 17-19 wt% Al2O3, and 57-59 wt% SiO2; the amount of binder used is 8-12 wt% of the base material; the preparation method includes the following steps: (1) After mixing the raw materials of the cordierite-based microcrystalline glass powder according to the raw material composition ratio, the mixture is melted into a glass liquid, and then the glass liquid is poured into water for quenching to obtain a frit. After ball milling, cordierite-based microcrystalline glass powder is obtained. (2) After mixing the base material according to the raw material composition ratio, add the binder and mix evenly, then press and dry to obtain a green body; (3) The green body is sintered in two stages, namely, a first stage of low-temperature sintering is carried out at 900-1000℃ for a holding time of ≥10h, and then the temperature is raised to 1200-1300℃ for a second stage of high-temperature sintering for a holding time of 4-6h; then it is naturally cooled to room temperature to obtain cordierite microcrystalline glass combined with aluminosilicate ceramic material.

2. The preparation method of the phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material according to claim 1, characterized in that: The cordierite microcrystalline glass powder has a particle size of 10–75 μm, the mullite aggregate has a particle size of 40–325 mesh, the corundum aggregate has a particle size of 40–500 mesh, and the clay powder has a particle size of 25–75 μm.

3. The preparation method of the phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material according to claim 1, characterized in that: The binder is a 5 wt% PVA solution.

4. The method for preparing the phase-separated crystalline cordierite microcrystalline glass-in-glass bonded aluminosilicate ceramic material according to claim 1, characterized in that: The clay is a combination of two or more of the following: kaolin, spherical clay, and bauxite.

5. The method for preparing the phase-separated crystalline cordierite microcrystalline glass-in-glass bonded aluminosilicate ceramic material according to claim 1, characterized in that: In step (1), the melting temperature is 1500-1600℃ and the melting time is 2-3h.

6. The method for preparing the phase-separated crystalline cordierite microcrystalline glass-in-glass bonded aluminosilicate ceramic material according to claim 1, characterized in that: The moisture content of the dried green body in step (2) is <1%.

7. The product obtained by the preparation method of the phase-separated crystalline cordierite microcrystalline glass combined with aluminosilicate ceramic material as described in any one of claims 1-6.

8. The article of claim 7, characterized in that: The cordierite microcrystalline glass combined with aluminosilicate ceramic material has a water absorption rate of ≤8.6% and a coefficient of thermal expansion of ≤4.27×10⁻⁶. -6 ·℃ -1 Glass crystallinity ≥ 85% and flexural strength > 60 MPa.

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