Low-temperature liquid-phase sintered silicon carbide ceramic material and preparation method thereof

Abstract

The invention relates to a low-temperature liquid-phase sintered silicon carbide ceramic material and a preparation method thereof, and belongs to the technical field of silicon carbide ceramics. The invention discloses a low-temperature liquid-phase sintered silicon carbide ceramic material, which is prepared from the following raw materials in percentage by mass: 80.0 to 95.0 percent of silicon carbide, 4.0 to 8.0 percent of yttrium oxide, 2.0 to 6.0 percent of aluminum oxide, 1.0 to 4.0 percent of magnesium oxide and 0.5 to 2.0 percent of lithium oxide. The invention also discloses a preparation method of the low-temperature liquid-phase sintered silicon carbide ceramic material, and the preparation method comprises the following steps: mixing the raw materials of the silicon carbide ceramic material with a solvent, ball-milling and pulping, drying, pulverizing, sieving, pre-pressing and forming, and carrying out spark plasma sintering to obtain the low-temperature liquid-phase sintered silicon carbide ceramic material. The nanoscale silicon carbide powder is used as a raw material, yttrium oxide, aluminum oxide, magnesium oxide and lithium oxide are used as sintering aids, the eutectic point and viscosity of a liquid phase are remarkably reduced, the mass transfer efficiency in the sintering process is effectively promoted, the densification efficiency is improved, and heat damage of a toughening phase is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon carbide ceramics, and relates to a low-temperature liquid-phase sintered silicon carbide ceramic material and a preparation method thereof. Background Art

[0002] SiC ceramics have excellent properties such as high hardness, high strength, oxidation resistance, corrosion resistance, neutron irradiation resistance, and good thermal stability, and thus are widely used in the fields of petrochemical industry, aerospace, nuclear energy, etc. However, due to the strong covalent bond characteristics of silicon carbide, even at a high temperature of 2100 °C, the self-diffusion coefficients of C and Si are only 1.5×10 -10 and 2.5×10 - 13 cm 2 ·s -1 , respectively, resulting in difficulty in sintering SiC ceramics to densification. Adding sintering aids is the key to achieving densification of SiC ceramics. Two classic atmospheric pressure sintering methods for SiC ceramics are solid-phase sintering with B and C elements as aids and liquid-phase sintering with Y2O3-Al2O3 as aids, and the required sintering temperatures are ~2150 °C and ~1900 °C, respectively. The relatively high sintering temperature means high energy consumption, which increases the manufacturing cost of SiC ceramic products. On the other hand, to improve the toughness of SiC ceramics, carbon nanotubes, whiskers, fibers, etc. are often added as toughening phases. However, too high a sintering temperature will damage the above-mentioned toughening phases and reduce the toughening effect. Therefore, realizing low-temperature liquid-phase sintering of SiC ceramics is of great significance for reducing manufacturing costs and promoting the research of high-toughness SiC ceramic matrix composites.

[0003] Compared with solid-phase sintering, liquid-phase sintering can densify SiC ceramics at a lower temperature. The main mechanism of liquid-phase sintering is that the sintering aids and the SiO2 impurities on the surface of the SiC raw materials, or the components of the sintering aids, form a liquid phase by eutectic at high temperature, and jointly achieve the densification of the material with the dissolution-precipitation mass transfer of SiC. The composition of the liquid-phase sintering aids has a significant impact on the densification temperature. For example, the Chinese patent publication text (publication number: CN104326752A) discloses a preparation method for low-temperature atmospheric pressure liquid-phase sintering of SiC ceramics, which uses Al2O3-Y2O3-CaO oxide sintering aids, is sintered in air to reduce the liquid-phase formation temperature, holds for 60 min at a sintering temperature of 1570-1600 °C, and promotes the densification of SiC ceramics. However, a forming agent needs to be added to its formula, and the preparation process also includes water bath heating, debinding, powder burying, etc., with complex steps and long time consumption.

[0004] In the prior art, the too high sintering temperature not only leads to large energy consumption, but also limits SiC f / SiC, C fDevelopment and application of composites such as / SiC. During the sintering process of composites, excessive sintering temperature will damage the fibers, thus restricting the performance of the materials and limiting the reliability of SiC ceramic matrix composites in extreme service environments. Therefore, realizing the low-temperature sintering of silicon carbide is not only beneficial to reducing the manufacturing cost and promoting the application of SiC ceramics in the fields of bulletproof armor, abrasive tools, bearing balls, etc., but also helps to promote the development of high-performance SiC ceramic matrix composites. Summary of the Invention

[0005] The object of the present invention is to address the above problems existing in the prior art and propose a low-temperature liquid-phase sintered silicon carbide ceramic material prepared by adding a quaternary sintering aid of Y2O3 - Al2O3 - MgO - Li2O, which significantly reduces the eutectic point and viscosity of the liquid phase; and the low-temperature liquid-phase sintered silicon carbide ceramic material has high density and good mechanical properties.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A low-temperature liquid-phase sintered silicon carbide ceramic material, the raw materials of the silicon carbide ceramic material, by mass percentage, include: 80.0 - 95.0 wt.% of silicon carbide, 4.0 - 8.0 wt.% of yttrium oxide, 2.0 - 6.0 wt.% of alumina, 1.0 - 4.0 wt.% of magnesia, and 0.5 - 2.0 wt.% of lithium oxide.

[0008] In the present invention, yttrium oxide, alumina, magnesia, and lithium oxide are added as sintering aids to 80.0 - 95.0 wt% of silicon carbide, and the proportion of the sintering aids is controlled to be 5.0 - 20.0 wt%, reducing the eutectic point and viscosity in the liquid-phase sintering process and accelerating the sintering mass transfer process to achieve low-temperature densification. The present invention reduces the temperature required for densifying silicon carbide ceramics while ensuring the mechanical properties of the material, reducing energy consumption and saving costs. If the silicon carbide content in the raw materials is too high (low sintering aid content), the gaps between solid particles during the sintering process cannot be filled with a sufficient amount of liquid phase, resulting in failure to sinter densely. If the silicon carbide content in the raw materials is too low (high sintering aid content), the performance of the SiC ceramic will be reduced.

[0009] Other toughening agents such as whiskers can also be added to the formula system of the low-temperature liquid-phase sintered silicon carbide ceramic material of the present invention to improve the performance of the silicon carbide ceramic; the low-temperature densification process of the present invention has little effect on the performance of the added toughening agent, promoting the development of high-performance SiC ceramic matrix composites.

[0010] Preferably, the silicon carbide is a nano-scale powder, and the median particle size D50 of the silicon carbide powder is 40 - 60 nm.

[0011] Preferably, the crystal form of the silicon carbide is β-SiC.

[0012] Preferably, the average particle size of yttrium oxide is 10 - 50 nm, the average particle size of alumina is 10 - 50 nm, the average particle size of magnesia is 40 - 70 nm, and the average particle size of lithium oxide is 600 - 900 nm.

[0013] Preferably, the raw materials of the silicon carbide ceramic material, by mass percentage, include: 86.0 - 91.0 wt.% of silicon carbide, 5.0 - 7.0 wt.% of yttrium oxide, 2.0 - 4.0 wt.% of alumina, 1.0 - 2.0 wt.% of magnesia, and 0.5 - 2.0 wt.% of lithium oxide.

[0014] Preferably, after the raw materials of the silicon carbide ceramic material are mixed with a solvent and ball - milled to form a slurry, they are dried, crushed, sieved, pressed into a shape, and subjected to spark plasma sintering to obtain a low - temperature liquid - phase sintered silicon carbide ceramic material.

[0015] More preferably, after sieving, the average particle size of the powder is 0.05 - 0.15 mm.

[0016] More preferably, in the spark plasma sintering, the sintering heating rate is 20 - 150 °C·min -1 , the sintering temperature is 1400 - 1600 °C, the sintering holding time is 0.1 - 3 h, the sintering pressure is 10 - 100 MPa, and the sintering atmosphere is an inert gas.

[0017] Preferably, the density of the low - temperature liquid - phase sintered silicon carbide ceramic material > 3 g·cm -3 , the apparent porosity < 0.7%, the Vickers hardness > 18 GPa, and the fracture toughness > 3 MPa·m 1 / 2 .

[0018] Preferably, the density of the low - temperature liquid - phase silicon carbide ceramic material reaches 3.19 g·cm -3 , the apparent porosity reaches 0.56%, the Vickers hardness reaches 22.75 ± 0.35 GPa, and the fracture toughness reaches 3.80 ± 0.27 MPa·m 1 / 2 .

[0019] A preparation method of a low - temperature liquid - phase sintered silicon carbide ceramic material, the preparation method comprising: after the raw materials of the silicon carbide ceramic material are mixed with a solvent and ball - milled to form a slurry, they are dried, crushed, sieved, pressed into a shape, and subjected to spark plasma sintering to obtain a low - temperature liquid - phase sintered silicon carbide ceramic material;

[0020] The raw materials of the silicon carbide ceramic material, by mass percentage, include 80.0 - 95.0 wt.% of silicon carbide powder, 4.0 - 8.0 wt.% of yttrium oxide, 2.0 - 6.0 wt.% of alumina, 1.0 - 4.0 wt.% of magnesia, and 0.5 - 2.0 wt.% of lithium oxide.

[0021] Preferably, the solvent includes one or more of absolute ethanol, isopropanol, and water.

[0022] Preferably, the solid-liquid mass ratio of the raw material of the silicon carbide ceramic material to the solvent is 1:(0.1 - 10).

[0023] More preferably, the solid-liquid mass ratio of the raw material of the silicon carbide ceramic material to the solvent is 1:(1 - 5).

[0024] During the ball milling process, if the solid-liquid mass ratio of the raw material of the silicon carbide ceramic material to the solvent is too small or too large, the powder raw material cannot be evenly dispersed during the ball milling process, thus affecting the uniformity of the properties of the sintered sample.

[0025] Preferably, the pressure during the pressing and forming process is 5 - 15 MPa.

[0026] Preferably, in the spark plasma sintering, the sintering heating rate is 20 - 150 °C·min -1 , the sintering temperature is 1400 - 1600 °C, the sintering holding time is 0.1 - 3 h, the sintering pressure is 10 - 100 MPa, and the sintering atmosphere is an inert gas.

[0027] Preferably, the preparation method of the low-temperature liquid-phase sintered silicon carbide ceramic material includes: mixing the raw material of the silicon carbide ceramic material and absolute ethanol according to a mass ratio of 1:(1 - 5), ball milling to make a slurry, then vacuum drying, crushing, and sieving the slurry through a 50 - 200 mesh sieve, pressing and forming at 5 - 15 MPa, and performing spark plasma sintering in an inert gas. The sintering heating rate of the spark plasma sintering is 20 - 50 °C·min -1 , the sintering temperature is 1500 - 1600 °C, the sintering holding time is 0.1 - 1 h, the sintering pressure is 20 - 50 MPa, and the sintering atmosphere is argon or nitrogen; the low-temperature liquid-phase sintered silicon carbide ceramic material is obtained.

[0028] More preferably, the sintering temperature is 1510 - 1580 °C, the sintering holding time is 0.2 - 0.8 h, and the sintering pressure is 20 - 50 MPa.

[0029] Even more preferably, the sintering temperature is 1550 °C, the sintering holding time is 0.5 h, and the sintering pressure is 30 MPa.

[0030] Preferably, the density of the low-temperature liquid-phase sintered silicon carbide ceramic material > 3 g·cm -3 , the apparent porosity < 0.7%, the Vickers hardness > 18 GPa, and the fracture toughness > 3 MPa·m 1 / 2 .

[0031] Further preferably, the density of the low temperature liquid phase silicon carbide ceramic material is 3.19 g·cm -3 , apparent porosity reaches 0.56%, Vickers hardness reaches 22.75±0.35GPa, fracture toughness reaches 3.80±0.27MPa·m 1 / 2 .

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses nano-scale silicon carbide powder as raw material and yttrium oxide, aluminum oxide, magnesium oxide and lithium oxide as sintering aids, wherein lithium oxide can achieve low melting point with SiO2 impurities inherent in the nano-SiC raw material and other oxide auxiliary components, significantly reducing the low melting point and viscosity of the liquid phase, effectively promoting the mass transfer efficiency during the sintering process, improving the densification efficiency, thereby reducing the production cost, and reducing the thermal damage of the toughening phase during the preparation of the silicon carbide ceramic-based composite material.

[0034] 2. The sintering aid used in the present invention is a four-component Y2O3-Al2O3-MgO-Li2O, which work together to reduce the reaction temperature; Li2O in the four-component sintering aid is eutectic with Y2O3, Al2O3, and MgO at 1650°C, 1347°C, and 1689°C, respectively, and has a lower eutectic temperature than the Y2O3-Al2O3-MgO ternary aid (eutectic at 1750°C); and Li2O can be eutectic with SiO2 on the SiC surface at 1261.8°C, which is also lower than the eutectic temperature of MgO and SiO2 of 1543°C.

[0035] 3. The amount of lithium oxide added to the raw material system of the present invention is 0.5-2.0wt%. Too little addition will result in the inability of lithium oxide to form a sufficient low-melting liquid phase with other components; too much addition will result in a large amount of lithium oxide volatilizing during the sintering process, resulting in intergranular closed pores; both are not conducive to the densification process of SiC ceramics.

[0036] 4. The preparation process of the present invention does not require the addition of other additives such as binders and catalysts. Only silicon carbide and sintering aids are needed to achieve the preparation of low-temperature liquid-phase sintered silicon carbide ceramic materials.

[0037] 5. In the preparation process of the low-temperature liquid phase sintered silicon carbide ceramic material of the present invention, the heating rate is fast and the insulation time is short, which has the advantages of high efficiency and energy saving and significantly reduces the production cost.

[0038] 6. The low-temperature liquid phase sintered silicon carbide ceramic material of the present invention has high density, Vickers hardness and fracture toughness, and has broad application prospects as an ideal candidate material for bulletproof armor, sealing rings and sliding bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic process flow diagram for preparing low-temperature liquid-phase sintered silicon carbide ceramic materials according to the present invention.

[0040] Figure 2 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Example 1 of the present invention.

[0041] Figure 3 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Example 2 of the present invention.

[0042] Figure 4 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Example 3 of the present invention.

[0043] Figure 5 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Comparative Example 1 of the present invention.

[0044] Figure 6 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Comparative Example 2 of the present invention.

[0045] Figure 7 Microscopic diagram of the low-temperature liquid-phase sintered silicon carbide ceramic material obtained in Comparative Example 3 of the present invention. Detailed implementation manners

[0046] The following are specific examples of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these examples.

[0047] Unless otherwise specified, the materials used in the present invention are commercially available products, and the methods used are conventional technical means.

[0048] The schematic process flow diagram for preparing silicon carbide ceramics according to the present invention is as Figure 1 shown.

[0049] Example 1

[0050] Weigh the raw materials, by mass percentage, including: 88.8 wt% of nano-β-SiC powder, 6.2 wt% of Y2O3, 2.6 wt% of Al2O3, 1.8 wt% of MgO, 0.6 wt% of Li2O; mix the above raw materials with anhydrous ethanol solvent, the solid-liquid mass ratio is 1:3, and make a slurry by ball milling for 4 h in a drum. Then place the slurry in a rotary evaporator and dry it under vacuum at 60 °C for 1 h. Take it out, crush it, pass through a 100-mesh sieve, and carry out pressure molding with a pressure of 8 MPa; then carry out spark plasma sintering under an Ar atmosphere, with a heating rate of 30 °C·min -1 , the sintering temperature is 1600 °C, the holding time is 0.5 h, and the pressure is 30 MPa.

[0051] The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as shown in Figure 2 ; its density is 3.16 g·cm -3 , and the open porosity is 0.41%.

[0052] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0053] Example 2

[0054] Weigh the raw materials. By mass percentage, it includes: 88.8 wt% of nano-β-SiC powder, 6.2 wt% of Y2O3, 2.6 wt% of Al2O3, 1.8 wt% of MgO, 0.6 wt% of Li2O; then mix the above raw materials with anhydrous ethanol solvent, and the solid-liquid mass ratio is 1:3, and make a slurry by ball milling for 4 h in a roller mill. Subsequently, place the slurry in a rotary evaporator and dry it under vacuum at 60 °C for 1 h. Take it out, crush it, pass through a 100-mesh sieve, and carry out pressure molding with a pressure of 8 MPa; then carry out spark plasma sintering under an Ar atmosphere, with a heating rate of 30 °C·min -1 , the sintering temperature is 1550 °C, the holding time is 0.5 h, and the pressure is 30 MPa.

[0055] The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as shown in Figure 3 ; its density is 3.19 g·cm -3 , and the open porosity is 0.56%.

[0056] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0057] Example 3

[0058] Weigh the raw materials. By mass percentage, it includes: 88.8 wt% of nano-β-SiC powder, 6.2 wt% of Y2O3, 2.6 wt% of Al2O3, 1.8 wt% of MgO, 0.6 wt% of Li2O; then mix the above raw materials with anhydrous ethanol solvent, and the solid-liquid mass ratio is 1:3, and make a slurry by ball milling for 4 h in a roller mill. Subsequently, place the slurry in a rotary evaporator and dry it under vacuum at 60 °C for 1 h. Take it out, crush it, pass through a 100-mesh sieve, and carry out pressure molding with a pressure of 8 MPa; then carry out spark plasma sintering under an Ar atmosphere, with a heating rate of 30 °C·min -1 , the sintering temperature is 1500 °C, the holding time is 0.5 h, and the pressure is 30 MPa.

[0059] The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as shown in Figure 4 ; its density is 2.91 g·cm -3 , and the open porosity is 7.66%.

[0060] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0061] Comparative Example 1

[0062] Compared with Example 1, the difference lies in the raw materials, which include, by mass percentage: 88.2 wt% of nano-β-SiC powder, 6.9 wt% of Y2O3, 2.9 wt% of Al2O3, and 2.0 wt% of MgO.

[0063] The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as Figure 5 shown; its density is 3.21 g·cm -3 , and the open porosity is 0.55%.

[0064] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0065] Comparative Example 2

[0066] Compared with Example 2, the difference lies in the raw materials, which include, by mass percentage: 88.2 wt% of nano-β-SiC powder, 6.9 wt% of Y2O3, 2.9 wt% of Al2O3, and 2.0 wt% of MgO. The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as Figure 6 shown; its density is 3.03 g·cm -3 , and the open porosity is 5.08%.

[0067] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0068] Comparative Example 3

[0069] Compared with Example 3, the difference lies in the raw materials, which include, by mass percentage: 88.2 wt% of nano-β-SiC powder, 6.9 wt% of Y2O3, 2.9 wt% of Al2O3, and 2.0 wt% of MgO. The microstructure of the prepared low-temperature liquid-phase sintered silicon carbide ceramic material is as Figure 7 shown; its density is 2.84 g·cm -3 , and the open porosity is 11.84%.

[0070] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0071] Comparative Example 4

[0072] Compared with Example 2, the difference lies in the raw materials, which include, by mass percentage: 89.0 wt% of nano-β-SiC powder, 6.9 wt% of Y2O3, 2.9 wt% of Al2O3, and 1.2 wt% of Li2O.

[0073] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0074] Comparative Example 5

[0075] Compared with Example 2, the difference lies in the raw materials, which include, by mass percentage: 88.6 wt% of nano-β-SiC powder, 9.8 wt% of Y2O3, and 1.6 wt% of Li2O.

[0076] The properties of the prepared silicon carbide ceramic material are shown in Table 1.

[0077] Table 1 Performance Table of Silicon Carbide Ceramic Material

[0078]

[0079] Examples 1 - 3 demonstrate the properties of samples sintered at different temperatures with Y2O3 - Al2O3 - MgO - Li2O as sintering aids, and Comparative Examples 1 - 3 demonstrate the properties of samples sintered at corresponding different temperatures with Y2O3 - Al2O3 - MgO ternary components as sintering aids.

[0080] Comparing Example 2 and Comparative Example 2, when the sintering temperature is the same at 1550 °C, due to the effect of the sintering aid component Li2O, the density of the sample in Example 2 is higher than that of the sample in Comparative Example 2. As can be seen from Table 1, the open porosity (0.56%) of the sample in Example 2 is lower than that of the sample in Comparative Example 2 (5.08%). Figure 3 and Figure 6 The comparison clearly shows the difference in porosity between the two groups of samples; the Vickers hardness (22.74 ± 0.35 GPa) of the sample in Example 2 is higher than that of the sample in Comparative Example 2 (21.82 ± 0.71 GPa), and the fracture toughness of the sample in Example 2 is slightly higher than that of the sample in Comparative Example 2.

[0081] Similarly, comparing Example 3 and Comparative Example 3, when the sintering temperature is the same at 1500 °C, the density of the sample in Example 3 is higher than that of the sample in Comparative Example 3. As can be seen from Table 1, the open porosity (7.66%) of the sample in Example 3 is lower than that of the sample in Comparative Example 3 (11.84%). Figure 4 and Figure 7 The comparison clearly shows the difference in porosity between the two groups of samples; the Vickers hardness (19.61 ± 0.50 GPa) of the sample in Example 3 is higher than that of the sample in Comparative Example 3 (18.56 ± 0.97 GPa), and the fracture toughness of the sample in Example 3 is slightly higher than that of the sample in Comparative Example 3.

[0082] Comparing Example 1 and Comparative Example 1, when the sintering temperature of both is 1600 °C, due to the effect of the sintering aid component Li2O in Example 1, the open porosity is slightly lower than that of the sample in Comparative Example 1, and the fracture toughness is slightly higher than that of the sample in Comparative Example 1. This is because Li2O volatilizes rapidly at 1600 °C and hardly participates in the densification process, and the improvement of the sintered density is not obvious.

[0083] Comparing Example 2 and Comparative Example 3, it can be found that for the samples containing the Li2O aid compared with the samples without the Li2O aid, under the condition that the highest sintering temperature is 50 °C lower than that of the latter, silicon carbide ceramics with high density and good hardness can still be obtained.

[0084] In Comparative Examples 4 and 5, the formula systems without adding MgO and without adding Al2O3 and MgO respectively have poor densification of the products sintered at 1550 °C, that is, the effects achieved when Y2O3 - Al2O3 - MgO - Li2O is used as the sintering aid in the present invention cannot be realized.

[0085] It can be seen that by using the raw material formula system of the low-temperature liquid-phase sintered silicon carbide ceramic material of the present invention, within a certain sintering temperature range, the density of the silicon carbide ceramic material first increases and then decreases. At 1550 °C, a highly dense silicon carbide ceramic material can be obtained, and the fracture toughness is excellent.

[0086] Moreover, when the four components in the four-component sintering aid Y2O3 - Al2O3 - MgO - Li2O are adjusted within the proportion range of the low-temperature liquid-phase sintered silicon carbide ceramic material raw materials described in the present invention, low-temperature liquid-phase sintering can be achieved at 1500 - 1600 °C, and the densification of the silicon carbide ceramic material can be realized.

[0087] In summary, the present invention uses nano-scale silicon carbide powder as the raw material and yttrium oxide, aluminum oxide, magnesium oxide, and lithium oxide as the sintering aids, significantly reducing the eutectic point and viscosity of the liquid phase, effectively promoting the mass transfer efficiency during the sintering process; combined with the preparation method of pressurization, short time, and low-temperature sintering, it improves the densification of silicon carbide ceramics, reduces the thermal damage of the toughening phase, and reduces the production cost.

[0088] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described specific embodiments or use similar ways to substitute, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A low temperature liquid phase sintered silicon carbide ceramic material, characterized in that: The raw materials of the silicon carbide ceramic material include, by mass percentage, 80.0-95.0wt.% of silicon carbide, 4.0-8.0wt.% of yttrium oxide, 2.0-6.0wt.% of aluminum oxide, 1.0-4.0wt.% of magnesium oxide, and 0.5-2.0wt.% of lithium oxide.

2. The low temperature liquid phase sintered silicon carbide ceramic material according to claim 1, characterized in that: The silicon carbide is nanometer-scale powder, and the median particle size D50 of the silicon carbide powder is 40-60nm; the crystal form of the silicon carbide powder is β-SiC.

3. The low temperature liquid phase sintered silicon carbide ceramic material according to claim 1, characterized in that: The average particle size of the yttrium oxide is 10-50 nm, the average particle size of the aluminum oxide is 10-50 nm, the average particle size of the magnesium oxide is 40-70 nm, and the average particle size of the lithium oxide is 600-900 nm.

4. The low temperature liquid phase sintered silicon carbide ceramic material according to claim 1, characterized in that: The raw materials of silicon carbide ceramic material are mixed with solvent and ball-milled to prepare slurry, and then dried, crushed, screened, pressed and sintered by spark plasma to obtain low-temperature liquid phase sintered silicon carbide ceramic material.

5. The low temperature liquid phase sintered silicon carbide ceramic material according to claim 1, characterized in that: The density of the low temperature liquid phase sintered silicon carbide ceramic material is greater than 3 g·cm -3 , apparent porosity <0.7%, Vickers hardness >18GPa, fracture toughness >3MPa·m 1 / 2 .

6. A method for preparing a low-temperature liquid phase sintered silicon carbide ceramic material, characterized in that: The preparation method comprises: mixing the raw material of silicon carbide ceramic material with a solvent, ball-milling the mixture to make a slurry, drying, crushing, screening, pressing and forming, and spark plasma sintering to obtain a low-temperature liquid phase sintered silicon carbide ceramic material; The raw materials of the silicon carbide ceramic material include, by mass percentage, 80.0-95.0wt.% of silicon carbide powder, 4.0-8.0wt.% of yttrium oxide, 2.0-6.0wt.% of aluminum oxide, 1.0-4.0wt.% of magnesium oxide, and 0.5-2.0wt.% of lithium oxide.

7. The method for preparing low temperature liquid phase sintered silicon carbide ceramic material according to claim 6, characterized in that: The solvent includes one or more of anhydrous ethanol, isopropanol, and water.

8. The method for preparing low temperature liquid phase sintered silicon carbide ceramic material according to claim 6, characterized in that: The pressure during the compression molding process is 5 to 15 MPa.

9. The method for preparing low temperature liquid phase sintered silicon carbide ceramic material according to claim 6, characterized in that: The solid-liquid mass ratio of the raw material and the solvent of the silicon carbide ceramic material is 1:(0.1-10).

10. The method for preparing low temperature liquid phase sintered silicon carbide ceramic material according to claim 6, characterized in that: The sintering heating rate in the spark plasma sintering is 20 to 150° C. min -1 The sintering temperature is 1400-1600°C, the sintering holding time is 0.1-3h, the sintering pressure is 10-100MPa, and the sintering atmosphere is inert gas.

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