A toughened ceramic and a method of making the same

Abstract

The application relates to the technical field of ceramics, and specifically discloses a toughened ceramic and a preparation method thereof. The toughened ceramic comprises a ceramic body and a glaze layer, and the ceramic body comprises the following raw materials in parts by weight: ceramic clay, 1-3 parts of wollastonite, 5-10 parts of porcelain powder, 13-17 parts of feldspar, 10-15 parts of ball clay, 5-8 parts of dolomite, 100-120 parts of Zhangcun clay, 50-60 parts of silicon micro powder loaded with silicon carbide whiskers, and 150-200 parts of water. The preparation method comprises the following steps: firstly, the ceramic clay, the silicon micro powder loaded with silicon carbide whiskers and the water are uniformly mixed after being ball milled, then sodium nitride is added and uniformly mixed to obtain a slurry; secondly, the slurry is injected into a gypsum mold to obtain a ceramic green body through slurry injection forming; and finally, the ceramic green body is subjected to high-temperature sintering, glazing and re-firing to obtain the toughened ceramic. The toughened ceramic disclosed by the application can be used for ceramic production, and the toughened ceramic has the effect of improving the toughening effect of the toughened ceramic.

Description

Technical Field

[0001] This application relates to the technical field of ceramics, and more specifically, to a toughened ceramic and a method for preparing the same. Background Technology

[0002] Ceramics are often used as structural materials, characterized by high melting point, high hardness, and high wear resistance. However, ceramics are also brittle, which can lead to cracking during the firing process. Strengthening and toughening ceramics can reduce cracking and improve their brittleness.

[0003] Currently, existing methods for strengthening and toughening ceramics involve using physical and chemical methods such as phase transformation, fiber or whisker reinforcement, and the use of ultrafine powders and dispersed reinforcing particles to significantly improve the mechanical properties of ceramic materials, thereby obtaining ceramics with uniform structure and strong performance.

[0004] Regarding the aforementioned technologies, the inventors believe that the method of toughening ceramics by adding whiskers to ceramic clay has the problem that whiskers are prone to agglomeration, resulting in uneven distribution in the ceramic clay and thus poor toughening effect. Summary of the Invention

[0005] To improve the toughening effect of toughened ceramics, this application provides a toughened ceramic and its preparation method.

[0006] In a first aspect, this application provides a toughened ceramic, which adopts the following technical solution: A toughened ceramic includes a ceramic body and a glaze layer, wherein the ceramic body comprises the following raw materials in parts by weight: Ceramic clay: 1-3 parts wollastonite, 5-10 parts porcelain powder, 13-17 parts feldspar, 10-15 parts ball clay, 5-8 parts dolomite, and 100-120 parts Zhangcun clay. 50-60 parts of silicon carbide whiskers supported on silicon micropowder 150-200 parts water.

[0007] By adopting the above technical solution, silicon micropowder-loaded silicon carbide whiskers are added to the ceramic body as a toughening component to improve the toughness of the ceramic body. The silicon content in silicon carbide is relatively high, and during the firing process of the ceramic system, it can generate a glass phase with certain fluidity, continuity and density to fill and bond cracks, thereby reducing the occurrence of cracking in the ceramic. Silica powder has good adsorption properties, which is beneficial for loading silicon carbide whiskers onto it. On the one hand, it can reduce the problem of silicon carbide whiskers entangled and agglomerated, so that the silicon carbide whiskers can be evenly dispersed in the ceramic clay. On the other hand, during the high-temperature firing process, the presence of silica powder can reduce the damage to silicon carbide whiskers caused by firing and enhance the interfacial bonding between silicon carbide whiskers and ceramic matrix.

[0008] Preferably, the silicon micropowder-supported silicon carbide whiskers comprises the following preparation steps: A1. The silicon micro powder is first immersed in a 2-4 mol / L hydrochloric acid solution for 1-2 hours, wherein the weight ratio of the silicon micro powder to the hydrochloric acid solution is 1:(1-2); A2. Add silicon carbide whiskers and ultrasonically disperse for 10-15 minutes. The mass ratio of silicon carbide whiskers to silicon micro powder is (1-1.5):1, to obtain silicon micro powder-supported silicon carbide whiskers.

[0009] By adopting the above technical solution, the specific surface area of ​​silicon micropowder can be increased after acid treatment with hydrochloric acid, thereby enhancing the adsorption capacity of silicon micropowder for silicon carbide whiskers and enabling silicon carbide whiskers to be stably loaded on the silicon micropowder.

[0010] Preferably, the particle size of the silicon micropowder-supported silicon carbide whiskers is 10-30 micrometers.

[0011] By adopting the above technical solution, when the particle size of silicon micropowder loaded with silicon carbide whiskers is in the range of 10-30 micrometers, it can be better dispersed in ceramic clay, and can give full play to the toughening effect during the firing process, reducing the occurrence of cracks in ceramics.

[0012] Preferably, the raw material also contains 2-5 parts of a surfactant, wherein the surfactant is sodium ethoxylated alkyl sulfate.

[0013] By adopting the above technical solution, sodium ethoxylated alkyl sulfate, as a surfactant, is easily soluble in water, which can reduce the friction between ceramic clay particles, give the ceramic clay particles good fluidity, and enhance the dispersion effect of toughening components.

[0014] Preferably, 30-50 parts of sodium nitride are also added to the raw materials of the ceramic body.

[0015] By adopting the above technical solution, sodium nitride is mixed into the ceramic slurry. When sodium nitride mixes with water in the ceramic slurry, it releases a large amount of heat. The heat generated by the reaction of sodium nitride and water helps to improve the bonding between silicon micropowder-loaded silicon carbide whiskers and ceramic clay. Furthermore, the reaction of sodium nitride and water produces sodium hydroxide. Sodium hydroxide does not have a toughening effect, but it can promote the toughening effect of toughening substances. This is because when sodium hydroxide and silicon micropowder are fired together, the silicon-oxygen bonds in the silicon micropowder are broken, thereby releasing silicon dioxide, increasing the viscosity of the glass phase in the ceramic system, and thus improving the creep resistance of silicon carbide whiskers, further improving the toughening effect of ceramics.

[0016] In addition, after the surface of the silicon micro powder is treated with hydrochloric acid, the hydrochloric acid remaining on the surface of the silicon micro powder can react with some of the sodium nitride to produce sodium chloride during the preparation of ceramic slurry. Sodium chloride, as an electrolyte, can increase the viscosity of the ethoxylated alkyl sulfate solution, so that the ceramic slurry can be formed quickly during the molding process and is less likely to experience a decrease in slurry viscosity due to temperature rise, resulting in poor molding effect.

[0017] Preferably, 20-30 parts of phosphorus tailings are also added to the ceramic clay.

[0018] By adopting the above technical solution, the phosphorus tailings contain high levels of silicon dioxide and calcium oxide. The sodium hydroxide generated by the reaction of sodium nitride with water provides an alkaline environment, which can also promote the release of silicon dioxide from the phosphorus tailings. During the high-temperature firing process, the phosphorus tailings react with calcium oxide and other oxides in the ceramic clay to form a glass phase, which further increases the viscosity of the glass phase, improves the high-temperature creep resistance of silicon carbide whiskers, and thus enhances its toughening effect.

[0019] Secondly, this application provides a method for preparing toughened ceramics, employing the following technical solution: A method for preparing toughened ceramics includes the following steps: S1. Ceramic clay, silicon carbide whiskers supported on silicon micro powder, surfactant and water are ball-milled and mixed to obtain a slurry; S2. Pour the slurry into a plaster mold and obtain a ceramic green body through slip casting. S3. The ceramic green body is sintered to obtain a ceramic blank. The ceramic blank is then glazed and fired again to obtain toughened ceramic.

[0020] By adopting the above technical solution, silicon micropowder loaded with silicon carbide whiskers is added to the ceramic clay as a toughening component, which can reduce the problem of poor dispersion and agglomeration of silicon carbide whiskers. In addition, the presence of silicon micropowder can protect the silicon carbide whiskers from damage during the firing process, thereby improving the toughening effect.

[0021] Preferably, when sodium nitride is added to the raw materials of the ceramic body, the preparation method includes the following steps: S1, the ceramic clay, silicon micro powder loaded with silicon carbide whiskers, surfactant and water are ball-milled and mixed, and then sodium nitride is added and mixed to obtain a slurry; S2. Pour the slurry into a plaster mold and obtain a ceramic green body through slip casting. S3. After drying, glazing, and firing the ceramic green body, toughened ceramic is obtained.

[0022] By adopting the above technical solution, sodium nitride is mixed evenly before slurry casting. A portion of the sodium nitride reacts with water to generate a large amount of heat, so that the ceramic clay does not need to be heated additionally during the slurry casting process and can have a certain molding temperature, which helps to shorten the molding time. In addition, the generation of heat also provides reaction conditions for the reaction of another portion of sodium nitride with hydrochloric acid. Sodium nitride reacts with the hydrochloric acid remaining on the silica powder to generate sodium chloride. Sodium chloride can increase the viscosity of the surfactant, which is beneficial to the molding of ceramics and makes the ceramics less prone to cracking during the slurry casting process.

[0023] In summary, this application has the following beneficial effects: 1. Since this application uses silicon micropowder to support silicon carbide whiskers, on the one hand, it can reduce the problem of silicon carbide whiskers entangled and agglomerated, so that silicon carbide whiskers can be uniformly dispersed in ceramic clay; on the other hand, during the high-temperature firing process, the presence of silicon micropowder can reduce the damage to silicon carbide whiskers caused by firing and enhance the interfacial bonding between silicon carbide whiskers and ceramic matrix.

[0024] 2. Sodium nitride is preferred in this application. When sodium nitride is mixed into ceramic slurry, it reacts with water to produce sodium hydroxide. Sodium hydroxide does not have a toughening effect, but it can promote the toughening effect of the toughening material. This is because when sodium hydroxide is fired together with silicon micropowder, it can break the silicon-oxygen bonds in the silicon micropowder, thereby releasing silicon dioxide, increasing the viscosity of the glass phase in the ceramic system, and thus improving the creep resistance of silicon carbide whiskers, further improving the toughening effect of the ceramic.

[0025] 3. The method of this application involves first mixing ceramic clay, silicon micropowder-loaded silicon carbide whiskers, surfactant, and water through ball milling, then adding sodium nitride and mixing again to obtain a slurry; then injecting the slurry into a plaster mold to obtain a ceramic green body through slip casting; finally, after high-temperature sintering, glazing, and firing again, a toughened ceramic is obtained, which is beneficial to the forming of the ceramic and makes it less prone to cracking during the slip casting process. Detailed Implementation

[0026] Raw material source: The raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0027] The chemical composition of phosphate tailings is shown in the table below: The chemical composition of ceramic clay and glaze raw materials is as follows: Example

[0028] Examples 1A-1C A toughened ceramic includes a ceramic body and a glaze layer, wherein the ceramic body comprises the following raw materials: Ceramic clay: 1-3 kg wollastonite, 5-10 kg porcelain powder, 13-17 kg feldspar, 10-15 kg ball clay, 5-8 kg dolomite, 100-120 kg Zhangcun clay; 50-60 kg of silicon carbide whiskers were supported on silicon micropowder with a particle size of 20 micrometers. 150-200 kg of water.

[0029] The preparation method of silicon micropowder-supported silicon carbide whiskers includes the following steps: A1. First, immerse the silicon micro powder in a 3 mol / L hydrochloric acid solution for 1.5 h. The weight ratio of silicon micro powder to hydrochloric acid solution is 1:1.5. A2. Add silicon carbide whiskers and ultrasonically disperse for 15 minutes. The mass ratio of silicon carbide whiskers to silicon micro powder is 1:1 to obtain silicon micro powder loaded silicon carbide whiskers. A method for preparing toughened ceramics includes the following steps: S1. Ceramic clay, silicon micro powder loaded with silicon carbide whiskers, surfactant and water are ball-milled for 12 hours and then mixed to obtain a slurry. S2. Pour the slurry into a plaster mold and obtain a ceramic green body through slip casting. S3. Dry the ceramic green body for 12 hours, then apply glaze with a glaze thickness of 3 mm. After glazing, fire at 1300℃ for 18 hours to obtain toughened ceramic.

[0030] The ceramic glaze is prepared by mixing 22 kg of solvent powder, 22 kg of feldspar, 7 kg of wollastonite, 8 kg of calcite, 3 kg of dolomite, 3 kg of calcined zinc oxide, 2 kg of calcined alumina, 1 kg of frit, and 35 kg of water.

[0031] The amounts of raw materials used in the ceramic body of Examples 1A-1C are shown in Table 1.

[0032] Table 1. Raw material consumption for ceramic green bodies in Examples 1A-1C (unit: kg) Examples 2A-2D A toughened ceramic, which differs from Example 1B in that the silicon micropowder supports silicon carbide whiskers with a different particle size.

[0033] The silicon micropowder-supported silicon carbide whiskers in Example 2A have a particle size of 10 micrometers; The silicon micropowder-supported silicon carbide whiskers in Example 2B have a particle size of 30 micrometers; The silicon micropowder-supported silicon carbide whiskers in Example 2C have a particle size of 5 micrometers; The silicon micropowder-supported silicon carbide whiskers in Example 2D have a particle size of 50 micrometers; Examples 3A-3C A toughened ceramic, which differs from Example 1B in that 2-5 kg ​​of surfactant is added to the raw material of the ceramic body, and the surfactant is sodium ethoxylated alkyl sulfate. In Example 3A, the amount of surfactant used was 2 kg; In Example 3B, the amount of surfactant used was 3.5 kg; The amount of surfactant used in Example 3C was 5 kg.

[0034] Examples 4A-4C A toughened ceramic, differing from Example 3A, in that 30-50 kg of sodium nitride is added to the raw materials of the ceramic body. When sodium nitride is added to the raw materials, its preparation method includes the following steps: S1. Ceramic clay, silicon carbide whiskers supported on silicon micro powder, surfactant and water are ball-milled and mixed, and then sodium nitride is added and mixed to obtain slurry. S2. Pour the slurry into a plaster mold and obtain a ceramic green body through slip casting. S3. Dry the ceramic green body for 12 hours, then apply glaze with a glaze thickness of 3 mm. After glazing, fire at 1300℃ for 18 hours to obtain toughened ceramic.

[0035] In Example 4A, the amount of sodium nitride used was 30 kg; In Example 4B, the amount of sodium nitride used was 40 kg; In Example 4C, the amount of sodium nitride used was 50 kg.

[0036] Examples 5A-5C A toughened ceramic, which differs from Example 4A in that 20-30 kg of phosphorus tailings are added to the ceramic clay.

[0037] In Example 5A, the amount of phosphorus tailings used was 20 kg; The amount of phosphorus tailings used in Example 5B was 25 kg; The amount of phosphorus tailings used in Example 5C is 30 kg.

[0038] Example 6 A toughened ceramic, which differs from Example 4B in that an equal amount of aluminum nitride is used instead of sodium nitride.

[0039] Example 7 A toughened ceramic, which differs from Example 4B in that sodium nitride is directly added to the ceramic clay for mixing.

[0040] Comparative Example Comparative Example 1 A toughened ceramic, which differs from Example 1B in that the amount of silicon micropowder-supported silicon carbide whiskers is 0 kg.

[0041] Comparative Example 2 A toughened ceramic, which differs from Example 1B in that silicon micropowder-supported silicon carbide whiskers are replaced with an equal amount of silicon carbide whiskers.

[0042] Performance testing The tests include: 1. Bending strength test The test shall be conducted in accordance with the method specified in GB / T 4741-1999 "Test Method for Bending Strength of Ceramic Materials".

[0043] The test results are shown in Table 2. Table 2 Test results of Examples 1-7 and Comparative Examples 1-2 As can be seen from Examples 1A-1C and Comparative Examples 1-2, and Table 2, the toughened ceramics of Examples 1A-1C have better flexural strength. This indicates that by loading silicon carbide whiskers onto silicon micropowder, this application can, on the one hand, reduce the problem of silicon carbide whiskers entangled and agglomerated, allowing the silicon carbide whiskers to be uniformly dispersed in the ceramic clay; on the other hand, during the high-temperature firing process, the presence of silicon micropowder can reduce the damage to silicon carbide whiskers caused by firing and enhance the interfacial bonding between silicon carbide whiskers and the ceramic matrix.

[0044] As can be seen from Examples 1B and 2A-2D and Table 2, the flexural strength of Examples 1B and 2A-2B is better than that of Examples 2C-2D. This indicates that when the particle size of the silicon micropowder-supported silicon carbide whiskers in this application is in the range of 10-30 micrometers, it can be better dispersed in the ceramic clay and can give full play to the toughening effect during the firing process, reducing the occurrence of cracks in the ceramic.

[0045] Combining Examples 3A-3C and Example 1B with Table 2, it can be seen that Examples 3A-3C are all superior to Example 1B, indicating that the addition of sodium ethoxylated alkyl sulfate as a surfactant in this application can reduce the friction between ceramic clay materials, give the ceramic clay particles good fluidity, and enhance the dispersion effect of the toughening components.

[0046] Combining Examples 3A, 4A-4C, and 6 with Table 2, it can be seen that Examples 4A-4C are superior to Example 3A. This indicates that when sodium nitride is mixed into the ceramic slurry, it releases a large amount of heat when mixed with water in the slurry. The heat generated by the reaction of sodium nitride with water helps to improve the bonding between silicon micropowder-loaded silicon carbide whiskers and ceramic slurry. Furthermore, the reaction of sodium nitride with water produces sodium hydroxide. Sodium hydroxide does not have a toughening effect, but it can promote the toughening effect of the toughening material. This is because when sodium hydroxide is fired together with silicon micropowder, it can break the silicon-oxygen bonds in the silicon micropowder, thereby releasing silicon dioxide, increasing the viscosity of the glass phase in the ceramic system, and thus improving the creep resistance of silicon carbide whiskers, further improving the toughening effect of the ceramic.

[0047] In addition, after the surface of the silicon micro powder is treated with hydrochloric acid, the hydrochloric acid remaining on the surface of the silicon micro powder can react with some of the sodium nitride to produce sodium chloride during the preparation of ceramic slurry. Sodium chloride, as an electrolyte, can increase the viscosity of the ethoxylated alkyl sulfate solution, so that the ceramic slurry can be formed quickly during the molding process and is less likely to experience a decrease in slurry viscosity due to temperature rise, resulting in poor molding effect.

[0048] Combining Examples 4A and 5A-5C with Table 2, it can be seen that Examples 5A-5C are all superior to Example 4A, indicating that the phosphorus tailings added in this application contain higher levels of silicon dioxide and calcium oxide. The sodium hydroxide generated by the reaction of sodium nitride with water provides an alkaline environment, which can also promote the release of silicon dioxide from the phosphorus tailings. During the high-temperature firing process, the phosphorus tailings react with calcium oxide and other oxides in the ceramic clay to form a glassy phase, which further increases the viscosity of the glassy phase, improves the high-temperature creep resistance of silicon carbide whiskers, and thus enhances its toughening effect.

[0049] Combining Examples 4B and 7 with Table 2, it can be seen that Example 4B is superior to Example 7. This indicates that the sodium nitride in this application is mixed in separately before slip casting, so that a portion of the sodium nitride reacts with water to generate a large amount of heat. This allows the ceramic clay to have a certain molding temperature without additional heating during the slip casting process, which helps to shorten the molding time. Furthermore, the heat generation also provides reaction conditions for the reaction of another portion of sodium nitride with hydrochloric acid. The sodium nitride reacts with the hydrochloric acid remaining on the silica powder to generate sodium chloride. Sodium chloride can increase the viscosity of the surfactant, which is beneficial to the molding of ceramics and makes the ceramics less prone to cracking during the slip casting process.

[0050] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A toughened ceramic, characterized in that, It includes a ceramic body and a glaze layer, wherein the ceramic body comprises the following raw materials in parts by weight: Ceramic clay: 1-3 parts wollastonite, 5-10 parts porcelain powder, 13-17 parts feldspar, 10-15 parts ball clay, 5-8 parts dolomite, and 100-120 parts Zhangcun clay. 50-60 parts of silicon carbide whiskers supported on silicon micropowder 150-200 parts water; The silicon micropowder-supported silicon carbide whiskers include the following preparation steps: A1. The silicon micro powder is first immersed in a 2-4 mol / L hydrochloric acid solution for 1-2 hours, wherein the weight ratio of the silicon micro powder to the hydrochloric acid solution is 1:(1-2). A2. Add silicon carbide whiskers and ultrasonically disperse for 10-15 minutes. The mass ratio of silicon carbide whiskers to silicon micro powder is (1-1.5):1, to obtain silicon micro powder-supported silicon carbide whiskers. The raw materials for the ceramic body also contain 30-50 parts of sodium nitride and 2-5 parts of surfactant, wherein the surfactant is sodium ethoxylated alkyl sulfate. The method for preparing ceramics includes the following steps: S1. Ceramic clay, silicon carbide whiskers supported on silicon micro powder, surfactant and water are ball-milled and mixed, and then sodium nitride is added and mixed to obtain slurry. S2. Pour the slurry into a plaster mold and obtain a ceramic green body through slip casting. S3. After drying, glazing and firing the ceramic green body, toughened ceramic is obtained.

2. The toughened ceramic according to claim 1, characterized in that: The silicon micropowder-supported silicon carbide whiskers have a particle size of 10-30 micrometers.

3. The toughened ceramic according to claim 1, characterized in that: The ceramic clay also contains 20-30 parts of phosphorus tailings.

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