Ceramic material and method for producing the same

Abstract

A ceramic material and its preparation method are disclosed. The ceramic material comprises magnesium oxide and a doped oxide, wherein the doped oxide comprises cobalt tetroxide, europium trioxide, or manganese dioxide, and the weight ratio of magnesium oxide to the doped oxide is from 97.0:1.0 to 85.0:12.0. Furthermore, the method for preparing the ceramic material comprises: mixing magnesium oxide powder and doped oxide powder; and sintering the mixed magnesium oxide powder and doped oxide powder at a temperature of 1300°C to 1650°C to obtain the ceramic material, wherein the doped oxide powder comprises cobalt tetroxide powder, europium trioxide powder, or manganese dioxide powder, and the weight ratio of magnesium oxide powder to doped oxide powder is from 99.9:0.1 to 92.0:8.0.

Description

Technical Field

[0001] This invention relates to ceramic materials and their preparation methods, particularly ceramic materials comprising magnesium oxide and doped oxides and their preparation methods. Background Technology

[0002] With the development of high-temperature industrial technology, the demand for refractory materials with high temperature stability and high chemical stability is increasing. Common refractory materials include magnesium oxide, alumina, quartz, silicon carbide, boron nitride, and zirconium dioxide. However, for microwave heating, one of the high-temperature industrial heating methods, some refractory materials absorb microwaves, reducing the efficiency of microwave energy transfer to the heated object.

[0003] For example, the graphitization process for carbon fibers involves high-temperature environments, reaching 1800–2000°C, and this process typically uses microwave heating. Some refractory materials absorb microwaves, reducing the efficiency of microwave energy transfer to the raw materials used in carbon fiber production. Furthermore, some refractory materials undergo mechanical degradation or redox reactions at such high temperatures, causing components in the refractory material to escape and contaminate the raw materials used in carbon fiber production, thus affecting the purity and properties of the produced carbon fibers. Therefore, developing microwave-penetrating, high-hardness, high-temperature resistant, and chemically stable refractory materials is one of the important goals of high-temperature industrial technology development. Summary of the Invention

[0004] An embodiment of the present invention provides a ceramic material comprising: magnesium oxide and a doped oxide, wherein the doped oxide comprises cobalt tetroxide (Co3O4), europium trioxide (Eu2O3) or manganese dioxide (MnO2), and the weight ratio of magnesium oxide to the doped oxide is 97:1 to 85:12.

[0005] On the other hand, one embodiment of the present invention provides a method for preparing ceramic materials, comprising: mixing magnesium oxide powder and doped oxide powder, and sintering the mixed magnesium oxide powder and doped oxide powder at a temperature of 1300°C to 1650°C to obtain ceramic materials, wherein the doped oxide powder comprises cobalt tetroxide powder, europium trioxide powder or manganese dioxide powder, and the weight ratio of magnesium oxide powder to doped oxide powder is 99.9:0.1 to 92.0:8.0. Attached Figure Description

[0006] Figures 1a to 1b The graph shows the relationship between the hardness of ceramic materials made from magnesium oxide powder and doped oxide powders in different weight ratios. Figure 1a The doped oxide powders are Co3O4, Eu2O3, or MnO2, while Figure 1bThe doped oxide powders are lanthanum oxide (La2O3), molybdenum dioxide (MoO2), nickel monoxide (NiO), or zinc oxide (ZnO);

[0007] Figure 2 The graph shows the relationship between the dielectric constant (Dk) and the ceramic materials made from magnesium oxide powder and doped oxide powders (Co3O4, Eu2O3 or MnO2) in different weight ratios.

[0008] Figure 3 The graph shows the relationship between dielectric loss (Df) and ceramic materials made from magnesium oxide powder and doped oxide powders (Co3O4, Eu2O3 or MnO2) in different weight ratios.

[0009] Figures 4a to 4f The images show SEM images of ceramic materials made from magnesium oxide powder and different weight ratios of doped oxide powder (Co3O4). Figures 4a to 4f SEM images of ceramic materials containing Co3O4 powder with magnesium oxide powder doping weight ratios of 100:0, 99:1, 98.5:1.5, 98:2, 96:4, and 92:8, respectively.

[0010] Figure 5 SEM image of a ceramic material made from magnesium oxide powder and Co3O4 powder in a weight ratio of 98:2;

[0011] Figure 6 The XRD pattern of a ceramic material made from magnesium oxide powder and Co3O4 powder in a weight ratio of 98:2.

[0012] Figure 7 SEM image of a ceramic material made from magnesium oxide powder and ZnO powder in a weight ratio of 98:2;

[0013] Figures 8a to 8c SEM and EDS images of graphitized fibers prepared using ceramic materials according to an embodiment of the present invention are shown. Figure 8a and Figure 8b The image shows a SEM image of graphitized fibers. Figure 8c for Figure 8b EDS plot of the boxed area in the image. Detailed Implementation

[0014] The ceramic material and its preparation method of the present invention are described below with reference to the accompanying drawings, but are not intended to limit the scope of the present invention.

[0015] One embodiment of the present invention provides a ceramic material comprising: magnesium oxide and a doped oxide, wherein the doped oxide comprises Co3O4, Eu2O3, or MnO2, and the weight ratio of magnesium oxide to the doped oxide is 97:1 to 85:12. In one embodiment of the present invention, the Vickers hardness of the ceramic material is 450 Hv10 to 750 Hv10 and the dielectric loss (Df) of the ceramic material is 0.0001 (1 GHz) to 0.0007 (1 GHz).

[0016] In one embodiment of the present invention, the ceramic material may further contain unavoidable impurities. Based on 100 parts by weight of the total ceramic material, the unavoidable impurities account for 2 to 3% of the total weight. Specifically, based on 100 parts by weight of the total ceramic material, in addition to a total of 97 to 98 parts by weight of magnesium oxide and doped oxides, the ceramic material may further contain 2 to 3 parts by weight of impurities. Furthermore, the impurities may include Al₂O₃, SiO₂, CaO, Fe₂O₃, or combinations thereof.

[0017] In one embodiment of the invention, when the doped oxide is cobalt tetroxide, the weight ratio of magnesium oxide to cobalt tetroxide can be from 86.4:11.13 to 96:1.5. In these embodiments, the Vickers hardness of the ceramic material is from 459.8 Hv10 to 700 Hv10, and the dielectric loss (Df) of the ceramic material is from 0.0003 (1 GHz) to 0.0007 (1 GHz).

[0018] The ceramic material of this invention achieves excellent mechanical and dielectric properties simultaneously by incorporating magnesium oxide and doped oxides. Furthermore, tubes made from the ceramic material of this invention do not contaminate the heated object when used in microwave heating. For example, tubes made from the ceramic material of this invention do not contaminate the carbon fiber when used in microwave heating of graphitized carbon fiber.

[0019] An embodiment of the present invention provides a method for preparing ceramic materials, comprising: mixing magnesium oxide powder and doped oxide powder; and sintering the mixed magnesium oxide powder and doped oxide powder at a temperature of 1300°C to 1650°C to obtain ceramic materials, wherein the doped oxide powder is Co3O4 powder, Eu2O3 powder, or MnO2 powder, and wherein the weight ratio of magnesium oxide powder to doped oxide powder is 99.9:0.1 to 92.0:8.0. In the method for preparing ceramic materials according to an embodiment of the present invention, the purity of the magnesium oxide powder can be greater than or equal to 98%.

[0020] The method for preparing ceramic materials of the present invention increases the sinterability of magnesium oxide by doping it with specific oxide powders, while simultaneously improving the hardness of the ceramic material and reducing dielectric loss.

[0021] In one embodiment of the present invention, when the doped oxide powder is Co3O4 powder, the weight ratio of magnesium oxide powder to Co3O4 powder can be 99:1 to 92:8.

[0022] In one embodiment of the present invention, when the doped oxide powder is Co3O4 powder and the weight ratio of magnesium oxide powder to Co3O4 powder is 98.5:1.5 to 98:2, precipitates are present at the grain boundaries of magnesium oxide.

[0023] In one embodiment of the present invention, when the doped oxide powder is Co3O4 powder, the weight ratio of magnesium oxide powder to Co3O4 powder is 99:1 to 92:8, the Vickers hardness of the ceramic material is 450Hv10 to 749Hv10, and the dielectric loss (Df) of the ceramic material is 0.00027 (1GHz) to 0.0007 (1GHz).

[0024] In one embodiment of the present invention, when the doped oxide powder is Eu2O3, the weight ratio of magnesium oxide powder to Eu2O3 powder is 98.5:1.5 to 92:8, the Vickers hardness of the ceramic material is 610 Hv10 to 750 Hv10, and the dielectric loss (Df) of the ceramic material is 0.00012 (1 GHz) to 0.00025 (1 GHz).

[0025] In one embodiment of the present invention, when the doped oxide powder is MnO2, the weight ratio of magnesium oxide powder to MnO2 powder is 99.5:0.5 to 95.5:4.5, the Vickers hardness of the ceramic material is 489 Hv10 to 639 Hv10, and the dielectric loss (Df) of the ceramic material is 0.00022 (1 GHz) to 0.00034 (1 GHz).

[0026] The preparation, testing, and test results of ceramic materials in several embodiments and comparative examples of the present invention are described below.

[0027] Preparation method of ceramic materials: Magnesium oxide powder and doped oxide powder are mixed according to different compositions and proportions shown in Tables 1 to 7, and then sintered at a temperature of 1650℃ to obtain ceramic materials.

[0028] The magnesium oxide powder used in the various embodiments and comparative examples of the present invention is lightly calcined magnesium oxide with a purity of 98% and a particle size of 6.9 μm to 36.3 μm. The Co3O4 powder used in Examples 1 to 4 of the present invention is Co3O4 powder with a purity of 99.5% and a particle size of 4.3 μm to 11.73 μm. The Eu2O3 powder used in Examples 5 and 6 of the present invention is Eu2O3 powder with a purity of 99.99% and a particle size of 3.7 μm to 11.7 μm. The MnO2 powder used in Examples 7 and 8 of the present invention is MnO2 powder with a purity of 98% and a particle size of 15.8 μm to 52.6 μm. The La2O3 powder used in Comparative Examples 2 to 5 of the present invention is La2O3 powder with a purity of 99.999% and a particle size of 2.09 μm to 6.7 μm. The MoO2 powder used in Comparative Examples 6 to 9 of the present invention has a purity of 99.99% and a particle size of 7.5 μm to 45.2 μm. The NiO powder used in Comparative Examples 10 to 14 of the present invention has a purity of 99.8% and a particle size of 0.67 μm to 1.88 μm. The ZnO powder used in Comparative Examples 15 to 19 of the present invention has a purity of 99% and a particle size of 0.36 μm to 4.81 μm.

[0029] The property testing method is as follows:

[0030] Hardness was measured using a touchscreen Vickers hardness tester (HVS-10F): round ingot samples with a diameter of 12 mm to 13 mm and a thickness of 1.0 mm to 2.5 mm were taken and measured using the Vickers hardness tester, with a load of 10 kgf and a loading time of 15 seconds.

[0031] Dielectric constant (Dk) and dielectric loss (Df) were measured using an HP 4291B RF impedance / material analyzer: round ingot samples with a diameter of 12 mm to 13 mm and a thickness of 1.0 mm to 2.5 mm were used for measurement using the parallel plate method, with a test frequency of 1 GHz, a temperature of 25 °C, and a humidity of 65%.

[0032] Tables 1 to 7 below and Figures 1a to 3 The raw material composition and property test results of the ceramic materials in various embodiments and comparative examples of the present invention are disclosed.

[0033] Table 1 illustrates the composition and property test results of ceramic materials made from magnesium oxide powder doped with different weight ratios of Co3O4 powder.

[0034]

[0035] Table 2 illustrates the composition and property test results of ceramic materials made from magnesium oxide powder doped with Eu2O3 powder in different weight ratios.

[0036]

[0037] Table 3 illustrates the composition and property test results of ceramic materials made from magnesium oxide powder doped with MnO2 powder in different weight ratios.

[0038]

[0039] Table 4 illustrates the composition and property test results of ceramic materials made from magnesium oxide powder doped with La2O3 powder in different weight ratios.

[0040]

[0041] Table 5 illustrates the composition and property test results of ceramic materials made from magnesium oxide powder doped with MoO2 powder in different weight ratios.

[0042]

[0043] Table 6 illustrates the composition and property test results of ceramic materials made from NiO powder doped with magnesium oxide powder at different weight ratios.

[0044]

[0045]

[0046] Table 7 illustrates the composition and property test results of ceramic materials made from ZnO powder with different weight ratios of magnesium oxide powder.

[0047]

[0048] Please refer to Tables 1 to 7 and... Figures 1a to 1b The experimental results show that the ceramic materials of the present invention (Examples 1 to 8) doped with one of Co3O4, Eu2O, and MnO2, and with a weight ratio of magnesium oxide powder to Co3O4 powder and Eu2O powder to MnO2 powder of 99.9:0.1 to 92.0:8.0, have a hardness of 450 Hv10 to 750 Hv10. This is higher than that of undoped magnesium oxide powder (Comparative Example 1), which is beneficial for maintaining structural stability and resisting thermal damage at high temperatures. Conversely, the ceramic materials doped with one of La2O3, MoO2, NiO, and ZnO (Comparative Examples 2 to 19) have lower hardness. Reduced hardness may affect the stability of the ceramic material at high temperatures, leading to thermal expansion, deformation, or cracking.

[0049] Furthermore, please refer to Tables 1 to 3. Figure 2 and Figure 3 The experimental results show that the ceramic material of the present invention (Example 1) doped with Co3O4 and having a weight ratio of magnesium oxide powder to Co3O4 powder of 99.0:1.0 has a lower dielectric constant (Dk) than magnesium oxide powder without oxide powder (Comparative Example 1). Furthermore, the experimental results show that the ceramic materials of the present invention doped with one of Co3O4 powder, Eu2O powder, and MnO2 powder, and having a weight ratio of magnesium oxide powder to Co3O4 powder, Eu2O powder, and MnO2 powder of 99.9:0.1 to 92.0:8.0, all have a dielectric loss (Df) of less than 0.0007 (1 GHz). This is beneficial for transmitting microwaves to carbon fibers during the carbon fiber graphitization process, achieving a more uniform and efficient heating process, and thus improving the quality of the carbon fibers. Furthermore, the dielectric loss (Df) of the ceramic materials in Examples 2-8 is less than 0.0006 (1 GHz), which is beneficial for transmitting microwaves to carbon fibers during the carbon fiber graphitization process, achieving a more uniform and efficient heating process, and thus improving the quality of the carbon fibers. Although the dielectric constant (Dk) of some examples is slightly higher than that of Comparative Example 1, theoretically, the ability to penetrate microwaves is mainly evaluated based on the dielectric loss (Df). Even considering the influence of the dielectric constant on the microwave penetration ability, when microwaves pass through the ceramic material of the present invention, the energy loss reduced by the low dielectric loss is far greater than the energy loss increased by the high dielectric constant. Therefore, the ceramic material of the present invention still has better microwave penetration ability, that is, the ceramic material according to the present invention can be applied to ceramic tubes in the high-temperature process of carbon fiber graphitization, improving problems such as low microwave energy transfer efficiency, mechanical property deterioration, or redox reactions in ceramic tubes.

[0050] Figures 4a to 4f The images show SEM images of ceramic materials made from magnesium oxide powder and Co3O4 powder doped in different weight ratios. Figures 4a to 4f SEM images of ceramic materials using Co3O4 powder as raw material with doping weight ratios of 100:0, 99:1, 98.5:1.5, 98:2, 96:4, and 92:8, respectively. Figure 5 This is a high-magnification SEM image of a ceramic material (Example 3) made from magnesium oxide powder and Co3O4 powder in a weight ratio of 98:2.

[0051] Please refer to Table 1. Figures 4a to 4f and Figure 5The experimental results and SEM images show that doping magnesium oxide powder with a small amount of Co3O4 powder can prevent magnesium oxide from cracking. Furthermore, with increasing dopant content, when the weight ratio of magnesium oxide powder to Co3O4 powder is between 98.5:1.5 and 98:2, precipitates are clearly visible at the grain boundaries of magnesium oxide, and these precipitates produce an adhesive-like effect, thus significantly improving hardness.

[0052] Tables 8 to 10 below reveal the composition of the ceramic materials obtained by EDS elemental analysis in Examples 1, 3, and 4 of the present invention.

[0053] Table 8. Components of Example 1 of the Invention

[0054]

[0055] Table 9. Components of Example 3 of the Invention

[0056]

[0057]

[0058] Table 10. Components of Example 4 of the Invention

[0059]

[0060] As shown in Tables 8 to 10, each sample mainly contains MgO and Co3O4, and the proportion of Co3O4 in the sample is slightly greater than the proportion of raw material doping. Al2O3, SiO2, CaO and Fe2O3 should be impurities in the raw material.

[0061] Figure 6 The image shows the XRD pattern of a ceramic material (Example 3) with a magnesium oxide powder to Co3O4 weight ratio of 98:2. Figure 6 It can be seen that the structural phase of the ceramic material with a weight ratio of magnesium oxide powder to Co3O4 powder of 98:2 (Example 3) is mainly the pure phase of magnesium oxide.

[0062] Figure 7 This is a SEM image of a ceramic material (Comparative Example 17) with a magnesium oxide powder to ZnO powder weight ratio of 98:2. From... Figure 7 It can be seen that the ceramic material with a magnesium oxide powder to ZnO powder weight ratio of 98:2 (Comparative Example 17) did not produce precipitates at the magnesium oxide grain boundaries, and therefore could not increase the hardness.

[0063] Preparation method of ceramic tube: The ceramic material of Example 2 is made into a ceramic tube by solid-state sintering.

[0064] High-temperature treatment: Heating the ceramic tube at 1400℃ or 2000℃.

[0065] Table 11 below reveals the structural parameters of the ceramic tube before and after high-temperature treatment.

[0066] Table 11 Structural parameters of ceramic tubes before and after high-temperature treatment

[0067]

[0068]

[0069] As shown in Table 11, the ceramic tubes made of the ceramic material of the present invention show little change in structural parameters after being treated at high temperatures of 1400℃ or 2000℃, proving that the ceramic material of the present invention has high heat resistance and can withstand temperatures up to 2000℃.

[0070] Figures 8a to 8c SEM and EDS images of graphitized fibers prepared using ceramic materials according to an embodiment of the present invention are shown. Figure 8a and Figure 8b The image shows a SEM image of graphitized fibers. Figure 8c for Figure 8b The EDS plot of the boxed area in the image. Figures 8a to 8c It is known that the graphitized fibers prepared using the ceramic materials of the present invention do not contain contaminants (such as magnesium) and can have better purity and properties.

[0071] In summary, the ceramic material and its preparation method provided by this invention increase the sinterability of the ceramic material by doping it with specific types and proportions of oxides, thereby improving the hardness of the ceramic material and reducing dielectric loss, thus achieving the effect of having excellent mechanical and dielectric properties without contaminating the heated object.

Claims

1. A ceramic material, characterized in that, Include: Magnesium monoxide (MgO) and a doped oxide; The doped oxide contains cobalt tetroxide (Co3O4), europium trioxide (Eu2O3), or manganese dioxide (MnO2); and The weight ratio of the magnesium oxide to the doped oxide is from 97:1.0 to 85.0:12.

0.

2. The ceramic material as described in claim 1, characterized in that, The ceramic material has a Vickers hardness of 450 Hv10 to 750 Hv10 and a dielectric loss (Df) of 0.0001 (1 GHz) to 0.0007 (1 GHz).

3. The ceramic material as described in claim 1, characterized in that, When the doped oxide is cobalt tetroxide, the weight ratio of magnesium oxide to cobalt tetroxide is from 86.4:11.13 to 96:1.

5.

4. The ceramic material as described in claim 4, characterized in that, The ceramic material has a Vickers hardness of 459.8 Hv10 to 700 Hv10 and a dielectric loss (Df) of 0.0003 (1 GHz) to 0.0007 (1 GHz).

5. A method for preparing ceramic materials, characterized in that, Include: Mixed magnesium monoxide powder and a doped oxide powder; and The magnesium oxide powder and the doped oxide powder are sintered and mixed at a temperature of 1300°C to 1650°C to obtain the ceramic material according to claim 1; The doped oxide powder includes cobalt tetroxide powder, europium trioxide powder, or manganese dioxide powder; and The weight ratio of the magnesium oxide powder to the doped oxide powder is 99.9:0.1 to 92:

8.

6. The method for preparing ceramic materials as described in claim 5, characterized in that, When the doped oxide powder is cobalt tetroxide powder, the weight ratio of the magnesium oxide powder to the cobalt tetroxide powder is 99:1 to 92:

8.

7. The method for preparing ceramic materials as described in claim 6, characterized in that, The ceramic material has a Vickers hardness of 450 Hv10 to 749 Hv10 and a dielectric loss (Df) of 0.00027 (1 GHz) to 0.0007 (1 GHz).

8. The method for preparing ceramic materials as described in claim 5, characterized in that, When the doped oxide powder is europium trioxide powder, the weight ratio of the magnesium oxide powder to the europium trioxide powder is 98.5:1.5 to 92:

8.

9. The method for preparing ceramic materials as described in claim 8, characterized in that, The ceramic material has a Vickers hardness of 610 Hv10 to 750 Hv10 and a dielectric loss (Df) of 0.00012 (1 GHz) to 0.00025 (1 GHz).

10. The method for preparing ceramic materials according to claim 5, characterized in that, When the doped oxide powder is manganese dioxide powder, the weight ratio of the magnesium oxide powder to the manganese dioxide powder is 99.5:0.5 to 95.5:4.

5.

11. The method for preparing ceramic materials according to claim 10, characterized in that, The ceramic material has a Vickers hardness of 489 Hv10 to 639 Hv10 and a dielectric loss (Df) of 0.00022 (1 GHz) to 0.00034 (1 GHz).

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