A special ceramic material and its preparation method

Abstract

This application relates to the technical field of special ceramics, and specifically discloses a special ceramic material and a preparation method thereof. The special ceramic material comprises raw materials in the following weight parts: 50 - 60 parts of alumina powder, 5 - 10 parts of wollastonite powder, 3 - 5 parts of boron nitride powder, 10 - 20 parts of water, and 25 - 30 parts of a reinforcing solution. The reinforcing solution comprises 20 - 30 parts of epoxy resin, 3 - 8 parts of an epoxy resin curing agent, and 2 - 5 parts of carbon nanotubes. Its preparation method comprises steps such as batching, shaping, and sintering. The special ceramic material of this application can be used in ceramic production, and has the advantages of improving the strength and forming rate of the ceramic material.

Description

Technical Field

[0001] This application relates to the technical field of special ceramics. More specifically, it relates to a special ceramic material and a preparation method thereof. Background Art

[0002] Special ceramics are mainly ceramic materials made of oxides, carbides, nitrides, silicides, etc. as the main raw materials, and can also be compounded with metals. They are widely used in high-temperature environments, machinery, electronics, aerospace, medical engineering, etc.

[0003] Currently, the existing preparation methods of special ceramics include two methods: dry forming and wet forming. Dry forming includes methods such as dry pressing, isostatic pressing, ultra-high pressure pressing, and powder electromagnetic forming. Wet forming generally includes plastic forming and colloidal casting forming.

[0004] In view of the above related technologies, the method of pressure forming has the problem that the forming density of the blank is uneven, resulting in the ceramic material after firing being prone to cracking, deformation, and low strength. Summary of the Invention

[0005] In order to improve the firing strength of ceramics and reduce the deformation of ceramics, this application provides a special ceramic material and a preparation method thereof.

[0006] A special ceramic material provided by this application adopts the following technical solution:

[0007] In a first aspect, this application provides a special ceramic material, adopting the following technical solution:

[0008] A special ceramic material includes the following raw materials in parts by weight:

[0009] 50 - 60 parts of alumina powder,

[0010] 5 - 10 parts of wollastonite powder,

[0011] 3 - 5 parts of boron nitride powder,

[0012] 10 - 20 parts of water,

[0013] 25 - 30 parts of reinforcing solution,

[0014] The reinforcing solution includes 20 - 30 parts of epoxy resin, 3 - 8 parts of epoxy resin curing agent, and 2 - 5 parts of carbon nanotubes.

[0015] By adopting the above technical solutions, the ceramic products made of alumina powder have the advantages of high mechanical strength and high hardness. Wollastonite can improve the sintering density and strength, and boron nitride further improves the mechanical properties and insulation properties of the ceramic material; the addition of the reinforcing solution further improves the crack resistance of the ceramic, which is beneficial to the improvement of the strength of the ceramic material. The epoxy resin and the epoxy resin curing agent can make the carbon nanotubes evenly distributed in the ceramic clay, thereby reducing the agglomeration between the ceramic clay particles, which is beneficial to improving the strength and forming rate of the ceramic material.

[0016] The combined action of the epoxy resin and the epoxy resin curing agent can reduce the deformation of the ceramic green body during the early forming process, thereby ensuring the forming rate and firing strength of the ceramic during the firing process, and the firing between the ceramic clay particles is closer.

[0017] Preferably, the diameter of the carbon nanotubes is 6 - 10 nm and the length is 20 - 30 μm.

[0018] By adopting the above technical solutions, the carbon nanotubes have excellent mechanical properties and high tensile strength. Applying the carbon nanotubes to special ceramic materials can enhance the mechanical properties of the ceramic materials. And under the extrusion of the ceramic clay and in the environment of an external electric field, a polarization effect will occur, enabling the carbon nanotubes to be arranged neatly and directionally, thereby ensuring more uniform firing density, high firing strength and low deformation rate of the ceramic materials.

[0019] Preferably, it further includes 20 - 30 parts of a mixed solution, and the mixed solution includes 2 - 5 parts of cellulose diacetate and 10 - 20 parts of acetone.

[0020] By adopting the above technical solutions, cellulose diacetate has a flexible linear molecular chain. When the environmental temperature reaches its glass transition temperature, it will enter the high elastic state. And under the external force of pressure, the molecular chain of the polymer changes from a coiled state to an extended state, and cellulose diacetate can penetrate into the carbon nanotubes; the carbon nanotubes provide a channel for the entry of cellulose diacetate, and the cellulose diacetate chain segment contains hydroxyl groups, which can combine with cellulose diacetate through the hydroxyl groups, enabling cellulose diacetate to remain in the carbon nanotubes;

[0021] During the heating process of the ceramic firing, the linear molecular chain of cellulose diacetate shrinks, providing a shrinkage force for the green ceramic body, making the combination between the ceramic clay particles closer, with uniform shrinkage density, thereby improving the strength of the special ceramic, and at the same time reducing the deformation caused by uneven shrinkage.

[0022] Preferably, the mixed solution further includes 20 - 30 parts of spodumene powder.

[0023] By adopting the above technical solution, the spodumene powder has a relatively low melting point. During the ceramic firing process, the organic substances in the mixed solution and the reinforcing solution are gradually carbonized, leaving pores. The spodumene powder melts and fills the pores. Moreover, due to the shrinkage of the linear molecular chains of cellulose diacetate during the initial heating, it provides power for the molten spodumene powder to enter the pores of the carbon nanotubes, which is conducive to the molten spodumene filling the pores, thereby improving the firing density and strength.

[0024] Preferably, the particle size of the spodumene powder is 10 - 15 nm.

[0025] By adopting the above technical solution, the spodumene powder is embedded at the orifices of the carbon nanotubes and the gaps of the ceramic mud during the pressing process, improving the density and wear resistance of the ceramic surface. When the spodumene melts during firing, it can also fully and rapidly enter the pores of the ceramic body, reducing the uneven shrinkage density and large shrinkage stress during pressing caused by the hard texture and difficult deformation of the ceramic mud itself during the ceramic firing process, and avoiding cracking. The molten spodumene can relieve the occurrence of cracks inside the ceramic body during the firing process, thereby improving the firing strength of the ceramic material and reducing the deformation effect.

[0026] Preferably, the epoxy resin curing agent is m-phenylenediamine.

[0027] By adopting the above technical solution, the epoxy resin and m-phenylenediamine are cured when reaching the curing temperature, which is conducive to reducing the deformation of the ceramic body during the forming process, improving the firing density and strength, and reducing the deformation rate.

[0028] In a second aspect, the present application provides a preparation method of a special ceramic material, adopting the following technical solution:

[0029] A preparation method of a special ceramic material includes the following preparation steps:

[0030] S1. Batching: Weigh the raw materials of the ceramic material according to the above weight parts and mix them evenly;

[0031] S2. Forming: Inject the above raw materials into a mold, heat up to 40 - 50 °C and keep warm for 5 - 8 min, and at the same time apply voltage. After static pressure forming, a green body is obtained. The green body is left to dry at a temperature of 70 - 80 °C for 2 - 3 hours, and then the mixed solution is poured in to obtain a green compact; S3. Sintering: Put the green compact into a kiln for hot pressing and firing to obtain the special ceramic material.

[0032] By adopting the above technical solution, voltage is applied during the forming process of the ceramic body, so that the carbon nanotubes are arranged neatly. Then the mixed solution is evenly poured in, and the cellulose diacetate is pressed into the carbon nanotubes, which can achieve the effect of uniform shrinkage. The spodumene powder melts and fills the pores, improving the firing density and strength of the ceramic material and reducing deformation.

[0033] Preferably, the voltage in S2 is 5.5 - 5.8V.

[0034] By adopting the above technical solution, due to the strong dielectric properties of carbon nanotubes, after being treated by an external electric field with a voltage of 5.5 - 5.8V, the bonding ability between carbon nanotubes and epoxy resin can be improved, and they can be arranged orderly on the surface of the ceramic green body, improving the mechanical properties of the ceramic material.

[0035] In summary, the present application has the following beneficial effects:

[0036] 1. Since the present application adopts an enhancing solution, epoxy resin and carbon nanotubes act synergistically, enabling the carbon nanotubes to be evenly dispersed in the ceramic mud, increasing the mechanical properties of the ceramic material and making it less likely to crack and deform.

[0037] 2. In the present application, a mixed solution is preferably used. The cellulose diacetate has flexible linear molecular chains that can penetrate into the carbon nanotubes for filling. Moreover, the linear molecular chains of cellulose diacetate will contract in a high-temperature environment, giving a more compact contraction force to the combination of the ceramic mud. And the cellulose diacetate enters the uniformly distributed carbon nanotubes, achieving a uniform contraction effect, enhancing the strength of the ceramic material and reducing the deformation of the ceramic.

[0038] 3. The preparation method of the present application, through processes such as batching, forming, and sintering, the obtained special ceramic material has strong mechanical properties, a high forming rate, and is not prone to deformation. Specific Embodiments

[0039] Source of Raw Materials:

[0040] All raw materials of the examples and comparative examples in the present application are commercially available.

[0041] Aluminum oxide powder, with a particle size not greater than 2.5μm;

[0042] Wollastonite powder, with a particle size of 325 mesh;

[0043] Boron nitride powder, with a particle size of 325 mesh;

[0044] m-Phenylenediamine, CAS No.: 108 - 45 - 2, molecular weight 108.14;

[0045] Carbon nanotubes, CAS: 308068 - 56 - 6;

[0046] Bisphenol A epoxy resin, CAS No.: 25085 - 99 - 8, molecular weight 340.41;

[0047] Cellulose diacetate, CAS No.: 9035 - 69 - 2, molecular weight 378.47.

[0048] Example

[0049] Examples 1.1 - 1.3

[0050] A special ceramic material, comprising raw materials with the following weights:

[0051] 50 - 60 kg of alumina powder,

[0052] 5 - 10 kg of wollastonite powder,

[0053] 3 - 5 kg of boron nitride powder,

[0054] 10 - 20 kg of water,

[0055] 25 - 30 kg of strengthening solution,

[0056] The strengthening solution comprises 20 kg of epoxy resin, 3 kg of epoxy resin curing agent and 2 kg of carbon nanotubes;

[0057] Among them, the epoxy resin curing agent is m - phenylenediamine, and the epoxy resin is bisphenol A epoxy resin; the diameter of the carbon nanotubes is 7 nm and the length is 25 μm;

[0058] The raw material dosages of Examples 1.1 - 1.3 are shown in Table 1.

[0059] Table 1 Raw material dosages of Examples 1.1 - 1.3

[0060]

[0061] It includes the following preparation steps:

[0062] S1. Batching: Weigh the raw materials of the ceramic material according to the above weight parts and mix them evenly;

[0063] S2. Molding: Inject the above raw materials into a mold, heat up to 40 °C and keep warm for 5 min, and at the same time apply an alternating current voltage of 5.5 V with frequencies of 0 Hz, 10 kHz, 0.1 MHz, 0.5 MHz, and 3 MHz. After static pressure molding, a green body is obtained. The green body is left to stand and dry at 70 °C for 2 hours and then poured with a mixed solution to obtain a green blank;

[0064] S3. Sintering: Put the green blank into a tunnel kiln furnace for step - by - step heating, and obtain the special ceramic material through hot - press firing. The firing pressure is 30 Mpa, the firing temperature is 1350 °C, and the firing cycle is 6 hours.

[0065] Among them, the mixed solution is 2 kg of cellulose diacetate and 10 kg of acetone.

[0066] Example 2

[0067] A special ceramic material, which is different from that of Example 1.2 in that the raw materials of the reinforcing solution are 30 kg of epoxy resin, 8 kg of epoxy resin curing agent and 5 kg of carbon nanotubes.

[0068] Example 3

[0069] A special ceramic material, which is different from that of Example 1.2 in that the raw materials of the reinforcing solution are 25 kg of epoxy resin, 5 kg of epoxy resin curing agent and 3 kg of carbon nanotubes.

[0070] Example 4

[0071] A special ceramic material, which is different from that of Example 1.2 in that the diacetate cellulose in the mixed solution is replaced with an equal amount of hydroxymethyl cellulose.

[0072] Examples 5.1 - 5.3

[0073] A special ceramic material, based on Example 1.2, is different in that 20 - 30 kg of spodumene powder is further added to the mixed solution; the particle size of the spodumene powder is 10 nm.

[0074] 20 kg of spodumene powder is further added to the mixed solution of Example 5.1;

[0075] 25 kg of spodumene powder is further added to the mixed solution of Example 5.2;

[0076] 30 kg of spodumene powder is further added to the mixed solution of Example 5.3.

[0077] Example 6

[0078] A special ceramic material, based on Example 5.1, is different in that the particle size of the spodumene powder is 13 nm.

[0079] Example 7

[0080] A special ceramic material, based on Example 5.1, is different in that the particle size of the spodumene powder is 15 nm.

[0081] Example 8

[0082] A special ceramic material, based on Example 5.1, is different in that the particle size of the spodumene powder is 5 nm.

[0083] Example 9

[0084] A special ceramic material, based on Example 5.1, is different in that the particle size of the spodumene powder is 20 nm.

[0085] Example 10

[0086] A special ceramic material, based on Example 5.1, is different in that spodumene powder is replaced with an equal amount of anorthoclase powder.

[0087] Comparative example

[0088] Comparative example 1

[0089] A special ceramic material, different from Example 1.1, is that the dosage of the reinforcing solution is 0 kg.

[0090] Comparative example 2

[0091] A special ceramic material, different from Example 1.1, is that the dosage of carbon nanotubes is 0 kg.

[0092] Comparative example 3

[0093] A special ceramic material, different from Example 1.1, is that the dosages of epoxy resin and epoxy resin curing agent are both 0 kg.

[0094] Comparative example 4

[0095] A special ceramic material, different from Example 1.1, is that the dosage of the mixed solution is 0 kg.

[0096] Comparative example 5

[0097] A special ceramic material, different from Example 1.1, is that no voltage is applied in the forming step of S2.

[0098] Performance detection test

[0099] The tests include:

[0100] 1. Special ceramic strength test

[0101] Use a universal material testing machine to test the flexural strength of the special ceramic.

[0102] 2. Ceramic deformation rate test

[0103] Determine the deformation rate of the ceramic according to the method specified in GB / T 3300-2008. Test 50 ceramic samples respectively, and take the average value of the height difference of the mouth edge of the tested ceramic as the reference value. Represent the deformation degree of the ceramic by the multiple of the reference value. The higher the multiple, the greater the deformation degree.

[0104] Carry out strength tests and deformation rate tests on the special ceramic materials of Examples 1-10 and Comparative Examples 1-5. The test results are shown in Table 2.

[0105] Table 2 Test results of Examples 1-10 and Comparative Examples 1-5

[0106]

[0107]

[0108] Combining Examples 1.1 - 1.3 and Comparative Examples 1 - 3 and considering the flexural strength and deformation rate test results in Table 2, it can be seen that Examples 1.1 - 1.3 are all superior to Comparative Examples 1 - 3, indicating that the addition of the strengthening solution further improves the crack resistance of the ceramic, is beneficial to enhancing the strength of the ceramic material. The epoxy resin and epoxy resin curing agent can make the carbon nanotubes evenly distributed in the ceramic mud, thereby reducing the agglomeration between the ceramic mud particles, which is beneficial to improving the strength and forming rate of the ceramic material; the combined action of the epoxy resin and epoxy resin curing agent can reduce the deformation of the ceramic green body during the initial forming process, thus ensuring the forming rate and firing strength of the ceramic during the firing process, and making the firing between the ceramic mud particles more compact.

[0109] Combining Example 1.2 and Examples 2 - 3 and considering Table 2, it can be seen that the flexural strength and deformation rate test results of Example 1.2 and Examples 2 - 3 are similar, indicating that the special ceramic material produced by the strengthening solution and other ceramic muds under the ratio of this application has good mechanical properties and a low deformation rate.

[0110] Combining Example 1.2 and Example 4, Comparative Example 4 and considering Table 2, it can be seen that Example 1.2 is superior to Example 4 and Comparative Example 4, indicating that the linear molecular chain of diacetate cellulose added in this application can enter the carbon nanotubes. As the temperature rises, the molecular weight of diacetate cellulose shrinks, giving a force for the ceramic mud to approach each other, making the density of the fired ceramic more compact and the strength increased. And because the carbon nanotubes are evenly distributed in the ceramic mud, the shrinkage of diacetate cellulose can also be carried out evenly when it shrinks, making the ceramic density uniform and the formed shape more stable.

[0111] Combining Example 1.2 and Examples 5.1 - 5.3 and considering Table 2, it can be seen that Examples 5.1 - 5.3 are all superior to Example 1.2, indicating that when lithium feldspar powder is added in this application, during the firing process of the ceramic, the organic substances in the mixed solution and the strengthening solution are gradually carbonized, leaving pores, and the lithium feldspar powder melts and fills the pores. And because the linear molecular chain of diacetate cellulose shrinks during the initial temperature rise, it provides power for the molten lithium feldspar powder to enter the pores of the carbon nanotubes, which is beneficial to the molten lithium feldspar filling the pores, and thus improves the firing density and strength.

[0112] Combined with Example 5.1 and Examples 6-9 and in combination with Table 2, it can be seen that Example 5.1 and Examples 6-7 are all superior to Examples 8-9, indicating that the feldspar powder within the particle size range of this application is embedded at the orifice of the carbon nanotubes and the gaps of the ceramic mud during the pressurization process, improving the density and wear resistance of the ceramic surface. When the feldspar melts during firing, it can also fully and rapidly enter the pores of the ceramic body, reducing the uneven shrinkage density and large shrinkage stress during pressurization caused by the hard texture and difficult deformation of the ceramic mud itself, which may lead to cracking. The molten feldspar can relieve the occurrence of cracks inside the ceramic body during the firing process, thereby improving the firing strength of the ceramic material and reducing the deformation rate.

[0113] Combined with Example 5.1 and Example 10 and in combination with Table 2, it can be seen that Example 5.1 is superior to Example 10, indicating that the feldspar has a lower melting point and a lower thermal expansion coefficient, which will not have an adverse impact on the ceramic firing. At the same time, it can fill the gaps between the ceramics, making the firing density of the ceramics uniform and the strength high.

[0114] Combined with Example 1.1 and Comparative Example 5 and in combination with Table 2, it can be seen that Example 1.1 is superior to Comparative Example 5, indicating that in the process of forming the ceramic body of this application, voltage is applied to make the carbon nanotubes arranged neatly, and then the mixed solution is evenly poured in, which is convenient for cellulose diacetate to be pressed into the carbon nanotubes, and can achieve the effect of uniform shrinkage. The feldspar powder melts and fills the pores, improving the firing density and strength of the ceramic material and reducing deformation.

[0115] This specific embodiment is only an interpretation of this application and is not a limitation to this application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A method for preparing a special ceramic material, characterized in that, It includes the following preparation steps: S1. Batching: Weigh the raw materials of the ceramic material according to the weight parts of 50-60 parts of alumina powder, 5-10 parts of wollastonite powder, 3-5 parts of boron nitride powder, 10-20 parts of water and 25-30 parts of reinforcing solution, and mix them evenly. The reinforcing solution includes 20-30 weight parts of epoxy resin, 3-8 weight parts of epoxy resin curing agent and 2-5 weight parts of carbon nanotubes; S2. Molding: Inject the above raw materials into a mold, heat up to 40-50 °C and keep warm for 5-8 min, and at the same time apply voltage. After static pressure molding, a green body is obtained. The green body is left to dry statically at a temperature of 70-80 °C for 2-3 hours, and then 20-30 weight parts of a mixed solution are poured in to obtain a green compact. The mixed solution includes 2-5 weight parts of diacetate cellulose, 10-20 weight parts of acetone and 20-30 weight parts of spodumene powder; S3. Sintering: Put the green compact into a kiln for hot pressing and sintering to obtain a special ceramic material.

2. The preparation method of a special ceramic material according to claim 1, characterized in that: The diameter of the carbon nanotubes is 6-10 nm and the length is 20-30 μm.

3. The preparation method of a special ceramic material according to claim 1, characterized in that: The particle size of the spodumene powder is 10-15 nm.

4. The preparation method of a special ceramic material according to claim 1, characterized in that: The epoxy resin curing agent is m-phenylenediamine.

5. The preparation method of a special ceramic material according to claim 1, wherein: The voltage in S2 is 5.5-5.8 V.

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