Sintering aids for the production of SiC ceramics and a method for their production

Abstract

The application discloses a sintering aid for preparing SiC ceramics and a preparation method thereof, wherein the sintering aid is composed of lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; the mass ratio of each component is given; the lanthanum oxide La2O3 and the silicon dioxide SiO2 are used as main components of the sintering aid, other components are used as auxiliary components, and distilled water is used as a ball milling solvent to prepare the sintering aid. The technical scheme of the application solves the problems that the existing sintering aid for preparing SiC ceramics cannot simultaneously consider high-quality SiC ceramic products and low sintering temperature, and the existing preparation method of the sintering aid brings certain danger to equipment and personnel and is low in economy.

Description

TECHNICAL FIELD

[0001] The present application relates to, but not limited to, the technical field of inorganic non-metallic materials, and particularly to a sintering aid for preparing SiC ceramics and a preparation method thereof. BACKGROUND

[0002] SiC has strong covalent bonds, and its ceramic preparation mechanism is evaporation-condensation, and the sintering temperature is 2200 DEG C, and the sintering condition is harsh. At present, the commonly used preparation method of SiC ceramics is to add a sintering aid to prepare SiC ceramics, and the sintering temperature can be greatly reduced.

[0003] At present, the commonly used sintering aids are: 1) microsilica powder, Suzhou soil, etc.; 2) Al2O3, MgO, etc.; 3) B, C, etc.; 4) Al2O3-Y2O3, etc. The SiC ceramics prepared by using microsilica powder, Suzhou soil, Al2O3, MgO and other sintering aids have low bending strength, high porosity and large pore size, and excessive intergranular phase content. Although B and C can be used as sintering aids for pressureless sintering, the sintering temperature is high; and the Al2O3-Y2O3 sintering aid will produce gas phase substances with SiC at high temperature, which will adversely affect the density and structure. The conventional method for preparing the sintering aid is to use anhydrous ethanol as a grinding agent, and in industrial mass production, the use of anhydrous ethanol has high safety hazards, and is dangerous to equipment and personnel, and has low economic efficiency.

[0004] The SiC ceramics prepared by using the above-mentioned commonly used sintering aids cannot simultaneously achieve high-quality SiC ceramic products and low sintering temperature, and the method for preparing the sintering aid will bring certain danger to the equipment and personnel, and has low economic efficiency. SUMMARY

[0005] The purpose of the present application is to solve the above technical problems, and the embodiments of the present application provide a sintering aid for preparing SiC ceramics and a preparation method thereof, so as to solve the problems that the existing sintering aid for preparing SiC ceramics cannot simultaneously achieve high-quality SiC ceramic products and low sintering temperature, and the existing method for preparing the sintering aid will bring certain danger to the equipment and personnel, and has low economic efficiency.

[0006] The technical scheme of the present application: in a first aspect, the embodiments of the present application provide a sintering aid for preparing SiC ceramics, which comprises: the composition of the sintering aid comprises lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; the mass ratio of each component is:

[0007] lanthanum oxide La2O3, 45% ± 5%;

[0008] Silicon dioxide SiO2, 40% ± 5%;

[0009] Magnesium oxide MgO, 2% ± 0.5%;

[0010] Sodium carbonate Na2CO3, 2.5% ± 0.5%;

[0011] Calcium oxide CaO, 2% ± 0.5%;

[0012] Strontium carbonate SrCO3, 6% ± 0.5%;

[0013] Yttrium oxide Y2O3, 2.5% ± 0.5%;

[0014] The sum of the mass ratio of all components is 100%.

[0015] Optionally, in the sintering aid for preparing SiC ceramic as described above,

[0016] The sintering aid is prepared by taking lanthanum oxide La2O3 and silicon dioxide SiO2 as the main components, taking other components as the auxiliary components, and taking distilled water as the ball milling solvent.

[0017] Optionally, in the sintering aid for preparing SiC ceramic as described above, the sintering aid is prepared by taking lanthanum oxide La2O3 and silicon dioxide SiO2 as the main components, taking other components as the auxiliary components, and taking distilled water as the ball milling solvent.

[0018] SiO2 is used to form a molten phase for reducing the temperature of ceramic phase to generate ceramic; and the generated molten phase is used to increase the migration rate between ceramic grains, so as to facilitate the sintering densification of ceramic;

[0019] CaO is used to prevent the martensitic transformation of ceramic phase at low temperature, so as to reduce the compressive stress caused by volume expansion;

[0020] MgO is used to improve the bending strength of ceramic phase, and to reduce the pores of the prepared SiC ceramic;

[0021] Yttrium oxide Y2O3 and lanthanum oxide La2O3 are used to generate ceramic phase with few pores and fine grains;

[0022] MgO-Y2O3-La2O3 is used as the sintering aid, and the grain size of the ceramic reaches a sub-micron level.

[0023] In a second aspect, the embodiment of the present application further provides a preparation method of a sintering aid for preparing SiC ceramic, comprising:

[0024] According to the composition of the sintering aid for preparing SiC ceramics and the mass ratio of each component, raw materials are prepared, and the raw materials are subjected to mixing, sintering, ball milling, screening and drying processes to prepare a high-temperature-resistant and corrosion-resistant composite oxide sintering aid; the prepared composite oxide sintering aid is used to prepare SiC ceramics with high density.

[0025] Optionally, in the preparation method of the sintering aid for preparing SiC ceramics, the preparation method comprises the following steps:

[0026] Step 1: preparing raw materials, comprising: according to the total mass of the sintering aid to be prepared, raw materials are weighed according to the composition of the sintering aid for preparing SiC ceramics and the mass ratio of each component;

[0027] Step 2: sintering the raw materials, comprising: the raw materials are loaded into a corundum crucible, the corundum crucible is placed in a heating furnace, the temperature is raised to 1100-1300℃, and then the temperature is maintained for a preset time before natural cooling;

[0028] Step 3: ball milling the mixed block after sintering, comprising: the corundum crucible is taken out, the mixed block is separated, foreign matter and impurities in the mixed block are removed, the mixed block is loaded into a ball mill tank, porcelain balls and distilled water are added for ball milling for 2-8 hours; wherein the mass ratio of the powder for ball milling: porcelain ball: distilled water is 1:1:2;

[0029] Step 4: screening, the slurry after ball milling is screened;

[0030] Step 5: drying, the screened slurry is dried at 40-200℃ for 12-15 hours to form a sintering aid block.

[0031] Optionally, in the preparation method of the sintering aid for preparing SiC ceramics, for raw materials less than 200 mesh, before the step 2, the method further comprises:

[0032] Step 1a: the raw materials weighed in step 1 are placed in a corundum ball mill tank, and the raw materials: porcelain balls are ball milled at a mass ratio of 1:1 for 2-8 hours to form a mixed powder;

[0033] Step 1b: the mixed powder after ball milling in step 1a is screened through an 80-mesh screen.

[0034] Optionally, in the preparation method of the sintering aid for preparing SiC ceramics,

[0035] The sintering aid block prepared in the step 5 is used to ball mill and screen together with SiC raw materials when preparing SiC ceramics to prepare SiC ceramics.

[0036] Optionally, in the method for preparing the sintering aid for SiC ceramics as described above, after step 5, the method further comprises:

[0037] Step 6, crushing, crushing the dried sintering aid block;

[0038] Step 7, sieving the crushed sintering aid block into a sieve with a preset mesh size, and crushing and sieving the larger blocks until all are sieved.

[0039] Optionally, in the method for preparing the sintering aid for SiC ceramics as described above,

[0040] The preset mesh size of the sieve is 160 mesh or more.

[0041] The method for preparing the sintering aid for SiC ceramics and the sintering aid provided by the embodiments of the present application have the following beneficial effects:

[0042] 1) The raw materials are safe and non-toxic, and can be used in large quantities;

[0043] 2) The sintering temperature of SiC can be greatly reduced. Compared with the sintering temperature of 2200℃ in the prior art, the sintering temperature of the sintering aid prepared by the method provided by the present application can be as low as 1100℃, which has good processability, improves safety, and reduces energy consumption;

[0044] 3) The ball milling process of the material uses distilled water, which is economical and safe;

[0045] 4) The prepared SiC ceramic has excellent salt mist corrosion resistance;

[0046] 5) The prepared SiC ceramic has high density and a porosity of less than 1%;

[0047] 6) The SiC ceramic has small deformation, small internal stress, high strength and good thermal shock resistance during sintering;

[0048] 7) The SiC ceramic has small phase grain size, high ceramic strength and good corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used to explain the technical solutions of the present application together with the embodiments of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0050] Figure 1 The process flow chart of the preparation method of the sintering aid for preparing SiC ceramic provided in the embodiments of the present application is shown. DETAILED DESCRIPTION

[0051] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other at will.

[0052] As described above in the background, the commonly used method for preparing SiC ceramic is to add a sintering aid for sintering, and the sintering temperature can be greatly reduced. However, the existing sintering aid for preparing SiC ceramic cannot simultaneously consider the problems of high-quality SiC ceramic product and low sintering temperature, and the existing method for preparing the sintering aid brings certain danger to the equipment and personnel, and has low economy and the like.

[0053] In view of the above problems, the embodiments of the present application provide a sintering aid for preparing SiC ceramic and a preparation method thereof. A composite oxide sintering aid with high temperature resistance and corrosion resistance is prepared by taking SiO2, La2O3 and other oxides and rare earth oxides as raw materials, and mixing, drying, crushing, sintering and ball milling according to a certain ratio, and high-density SiC ceramic can be prepared.

[0054] The following specific embodiments provided by the present application can be combined with each other, and the same or similar concepts or processes can not be described again in some embodiments.

[0055] The sintering aid for preparing SiC ceramics provided by the embodiment of the present application comprises: lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3.

[0056] Lanthanum oxide La2O3, 45%±5%;

[0057] Silicon dioxide SiO2, 40%±5%;

[0058] Magnesium oxide MgO, 2%±0.5%;

[0059] Sodium carbonate Na2CO3, 2.5%±0.5%;

[0060] Calcium oxide CaO, 2%±0.5%;

[0061] Strontium carbonate SrCO3, 6%±0.5%;

[0062] Yttrium oxide Y2O3, 2.5%±0.5%;

[0063] In addition, the sum of the mass proportions of all the components is 100%.

[0064] It should be noted that in the sintering aid for preparing SiC ceramics provided by the embodiment of the present application, lanthanum oxide La2O3 and silicon dioxide SiO2 are used as the main components of the sintering aid, other components are used as auxiliary components, and distilled water is used as the ball milling solvent to prepare the sintering aid, and the sintering aid for SiC ceramics is prepared through ball milling, sintering, drying, crushing and sieving.

[0065] In a specific embodiment of the embodiment of the present application, the proportions of the components of the sintering aid for preparing SiC ceramics are shown in the following Table 1:

[0066] Table 1 Proportion table of sintering aid

[0067] Serial number Name Chemical formula Mass proportion (wt. %) 1 Lanthanum oxide La2O3 45 2 Silicon dioxide SiO2 40 3 Magnesium oxide MgO 2 4 Sodium carbonate Na2CO3 2.5 5 Calcium oxide CaO 2 6 Strontium carbonate SrCO3 6 7 Yttrium oxide [Y2O3] 2.5

[0068] The sintering aid for preparing SiC ceramics provided by the embodiment of the present application has the following advantages compared with other types of sintering aids:

[0069] (1) SiO2 is used to form a molten phase, which can greatly reduce the temperature of ceramic phase to generate ceramics, and the molten phase generated is used to increase the migration rate between ceramic grains, which is beneficial to the densification of ceramic sintering;

[0070] (2) CaO is used to prevent the martensitic transformation of ceramic phase at low temperature, so as to reduce the compressive stress caused by volume expansion;

[0071] (3) The use of MgO can improve the bending strength of the ceramic phase and reduce the porosity of the prepared SiC ceramic;

[0072] (4) The use of Y2O3 and La2O3 can produce a ceramic phase with less porosity and fine grain size, and can prepare a ceramic with good oxidation resistance;

[0073] (5) The use of MgO-Y2O3-La2O3 as a sintering aid can achieve a submicron grain size of the ceramic; the closed porosity is less than 1%;

[0074] (6) The traditional ball milling solvent for sintering aid is an organic solvent (such as anhydrous ethanol), which has a large safety hazard and high cost. In the embodiment of the present application, distilled water is used instead of organic solvent for mixing and ball milling, which has no safety hazard, is economical, and reduces the solvent evaporation during ball milling.

[0075] Based on the sintering aid for preparing SiC ceramic provided by the embodiment of the present application, the embodiment of the present application also provides a preparation method for preparing the sintering aid for preparing SiC ceramic; as shown in Figure 1 The process flow chart of the preparation method for preparing the sintering aid for preparing SiC ceramic provided by the embodiment of the present application is shown.

[0076] The preparation method provided by the embodiment of the present application uses the composition and mass ratio of each component of the sintering aid for preparing SiC ceramic provided by any of the above embodiments to prepare raw materials, and the raw materials are prepared through mixing, sintering, ball milling, screening and drying processes to prepare a high-temperature-resistant and corrosion-resistant composite oxide sintering aid. The prepared composite oxide sintering aid is used to prepare SiC ceramic with high density.

[0077] The preparation method provided by the embodiment of the present application specifically includes the following steps:

[0078] Step 1, preparing raw materials, including: according to the total mass of the sintering aid to be prepared, the raw materials are weighed according to the composition and mass ratio of each component of the sintering aid for preparing SiC ceramic provided by any of the above embodiments;

[0079] Step 2, sintering the raw materials, including: loading the raw materials into a corundum crucible, placing the corundum crucible in a heating furnace, heating to 1100-1300℃, and naturally cooling after maintaining the temperature for a predetermined time;

[0080] Step 3, ball milling the mixed block after sintering, including: taking out the corundum crucible, separating the mixed block, removing foreign matter and impurities in the mixed block, loading the mixed block into a ball mill tank, adding porcelain balls and distilled water for ball milling for 2-8h.

[0081] The step, wherein the powder for ball milling: porcelain ball: distilled water (mass ratio) = 1:1:2. It should be noted that in the process of sintering the material powder to form the material block, the raw material will be adhered to the crucible, and the foreign matter impurities may be the product adhered to the crucible wall when the material block is separated from the crucible; or because the material block is tightly adhered to the crucible, it is difficult to separate, and the crucible block may be mixed; or in the sintering process, due to uneven mixing, the local material powder may form a product that does not match the expected product.

[0082] Step 4, screening, screening the slurry after ball milling;

[0083] Step 5, drying, drying the screened slurry at 40-200°C for 12-15h to form a sintering aid material block.

[0084] In an implementation manner of the embodiment of the present application, for raw materials less than 200 mesh, before the step 2, further comprising:

[0085] Step 1a, placing the raw materials weighed in step 1 into a corundum ball mill tank, and ball milling for 2-8h to form a mixed powder according to the raw material: porcelain ball (mass ratio) = 1:1;

[0086] Step 1b, screening the mixed powder after ball milling in step 1a through an 80 mesh screen.

[0087] In an implementation manner of the embodiment of the present application, the sintering aid material block prepared in the above step 5 is used for ball milling with SiC raw materials to prepare SiC ceramics.

[0088] In an implementation manner of the embodiment of the present application, after the above step 5, further comprising the following steps:

[0089] Step 6, crushing, crushing the dried sintering aid material block;

[0090] Step 7, screening the crushed sintering aid material block into a screen with a predetermined mesh size (for example, 160 mesh or more), and continuing to crush and screen the larger material block until all is screened.

[0091] The embodiment of the present application provides a sintering aid for preparing SiC ceramics and a preparation method thereof, and the composition of the sintering aid comprises lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; wherein, the lanthanum oxide La2O3 and the silicon dioxide SiO2 are used as main components of the sintering aid, and other components are used as auxiliary components, and distilled water is used as a ball milling solvent to prepare the sintering aid, and the sintering aid for SiC ceramics is prepared through ball milling, sintering, drying, crushing and sieving. In the above components, the SiO2 forms a molten phase, which can greatly reduce the temperature of ceramic phase to generate ceramics; and the molten phase is used to increase the migration rate between ceramic grains, which is beneficial to the sintering densification of ceramics; the CaO can prevent the martensitic transformation of the ceramic phase at low temperature, so as to reduce the compressive stress caused by volume expansion; the MgO can improve the bending strength of the ceramic phase, and reduce the pores of the prepared SiC ceramics; the yttrium oxide Y2O3 and the lanthanum oxide La2O3 can generate a ceramic phase with less porosity and small grain size, and can prepare a ceramic with good oxidation resistance; the grain size of the sintering aid ceramic reaches a submicron level; the closed porosity is less than 1%; in addition, the traditional ball milling solvent of the sintering aid is an organic solvent (such as anhydrous ethanol), which has great safety hazards and high cost. In the embodiment of the present application, distilled water is used instead of the organic solvent for mixing and ball milling, which has no safety hazards, is high in economy, and reduces the solvent volatilization in the ball milling process. The technical scheme provided by the present application has the following beneficial effects:

[0092] 1) The raw materials are safe and non-toxic, and can be used in large quantities;

[0093] 2) The sintering temperature of the SiC can be greatly reduced, and compared with the sintering temperature of 2200 DEG C in the prior art, the sintering temperature of the sintering aid prepared by the preparation method of the present application can be as low as 1100 DEG C, which has good processability, can improve safety and reduce energy consumption;

[0094] 3) The ball milling process of the material uses distilled water, which is high in economy and safety;

[0095] 4) The prepared SiC ceramics have excellent salt mist corrosion resistance;

[0096] 5) The prepared SiC ceramics have high density and porosity less than 1%;

[0097] 6) The SiC ceramics have small deformation, small internal stress, high strength and good thermal shock resistance in the sintering process;

[0098] 7) The SiC ceramic phase has small grain size, high ceramic strength and good corrosion resistance.

[0099] The sintering aid for preparing SiC ceramic and the preparation method thereof provided by the embodiment of the present application are described in detail below through some specific embodiments.

[0100] Embodiment 1

[0101] The embodiment 1 provides a preparation method of a sintering aid for preparing SiC ceramic, referring to the figure, the preparation of the sintering aid in the embodiment 1 is carried out in the following steps: Figure 1

[0102] 1. Preparation of raw materials

[0103] The total mass of the prepared sintering aid is 200g. Wear acid and alkali latex gloves, and weigh the materials according to the proportioning table in turn with a balance.

[0104] For the preparation of sintering aid with a total mass of 200g, the required mass of raw materials is as follows: lanthanum oxide (La2O3) 90g; silicon dioxide (SiO2) 80g; magnesium oxide (MgO) 4g; sodium carbonate (Na2CO3) 5g; calcium oxide (CaO) 4g; strontium carbonate (SrCO3) 12g; yttrium oxide (Y2O3) 5g.

[0105] 2. Ball milling

[0106] Put the weighed materials into a corundum ball mill tank, and mill for 4h at a material: 95 ceramic ball (mass ratio) = 1:1.

[0107] 3. Sieving

[0108] Pass the mixed material powder after ball milling through an 80-mesh sieve.

[0109] 4. Sintering

[0110] Put the sieved material powder into a corundum crucible, and place the corundum crucible in an electric furnace, and heat the furnace to 1100-1300℃, keep the temperature for a certain time, turn off the power and cool naturally.

[0111] 5. Ball milling

[0112] Take out the corundum crucible, manually separate the material blocks, remove foreign matter and impurities, put the material blocks into a ball mill tank, add ceramic balls and distilled water, and mill for 5h at a material: ceramic ball: distilled water (mass ratio) = 1:1:2. Crush the material blocks with a stainless steel shovel.

[0113] Sieving

[0114] Pass the slurry after ball milling through a sieve and put it into a enamel or stainless steel plate.

[0115] Drying

[0116] Dry the slurry in the enamel plate at 120±5℃ for 12-15h.

[0117] Crushing​

[0118] The dried sintering aid lumps are crushed using a stainless steel spatula.

[0119] Screening

[0120] The crushed sintering aid lumps are placed in a sieve of a certain mesh size (160 or more) and are manually sieved. Larger lumps are crushed using a stainless steel spatula until all are sieved. The larger the mesh size, the finer the size

[0121] 10. Storage

[0122] The sieved powder is placed in a jar and is labeled for classification.

[0123] Example 2

[0124] This example 2 provides a method for preparing a sintering aid for preparing SiC ceramics, referring to FIG. 1, the sintering aid is prepared in this example 2 according to the following steps: Figure 1

[0125] 1. Preparation of ingredients

[0126] A total of 200 g of sintering aid is prepared. Wear acid and alkali latex gloves, and use a balance to weigh the materials according to the ratio table.

[0127] For a total of 200 g of sintering aid to be prepared, the required raw materials have the following masses: lanthanum oxide (La2O3) 100 g; silicon dioxide (SiO2) 75 g; magnesium oxide (MgO) 5 g; sodium carbonate (Na2CO3) 4 g; calcium oxide (CaO) 5 g; strontium carbonate (SrCO3) 11 g; yttrium oxide (Y2O3) 5 g.

[0128] 2. Ball milling

[0129] The weighed materials are placed in a corundum ball mill jar, and the material: 95 ceramic balls (mass ratio) = 1:1, and ball milling is performed for 8 h.

[0130] 3. Sieving

[0131] The mixed material powder after ball milling is sieved through a 160 mesh sieve.

[0132] 4. Sintering

[0133] The sieved powder is placed in a corundum crucible, which is placed in an electric furnace. The furnace is heated to 1300°C ± 10°C, and the power is turned off after a certain period of time for natural cooling.

[0134] 5. Ball milling

[0135] ​Take out the corundum crucible, separate the blocks by hand, remove the foreign matter and impurities, put the blocks into the ball mill tank, add porcelain balls and distilled water, and mill for 5 h. Use a stainless steel shovel to crush the blocks.

[0136] 6. Sieving

[0137] The milled slurry is sieved and put into a enamel or stainless steel tray.

[0138] 7. Drying

[0139] The slurry in the enamel tray is dried at 120±5°C for 12 h.

[0140] 8. Storage

[0141] The dried powder is put into a wide-mouth bottle and classified and labeled.

[0142] Although the embodiments of the present application are as described above, the content is only the embodiments adopted for the purpose of facilitating the understanding of the present application, and is not intended to limit the present application. Any person skilled in the art of the present application can make any modification and change in the form and details without departing from the spirit and scope of the present application disclosed, but the patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A sintering aid for the production of SiC ceramics, characterized in that The composition of the sintering aid includes lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3, and the mass ratio of each component is respectively: Lanthanum oxide La2O3, 45%±5%; Silicon dioxide SiO2, 40%±5%; Magnesium oxide MgO, 2%±0.5%; Sodium carbonate Na2CO3, 2.5%±0.5%; Calcium oxide CaO, 2%±0.5%; Strontium carbonate SrCO3, 6%±0.5%; Yttrium oxide Y2O3, 2.5%±0.5%; The sum of the mass ratios of all components is 100%.

2. The sintering aid for preparing SiC ceramics according to claim 1, wherein, Lanthanum oxide La2O3 and silicon dioxide SiO2 are used as the main components of the sintering aid, other components are used as auxiliary components, and distilled water is used as the ball milling solvent to prepare the sintering aid.

3. The sintering aid for the production of SiC ceramics according to claim 2, characterized in that In each component of the sintering aid, SiO2 is used to form a molten phase to reduce the temperature of ceramic phase to generate ceramics, and the generated molten phase is used to increase the migration rate between ceramic grains to facilitate the sintering densification of ceramics; CaO is used to prevent the martensitic transformation of ceramic phase at low temperature to reduce the compressive stress caused by volume expansion; MgO is used to improve the bending strength of ceramic phase and reduce the pores of the prepared SiC ceramics; Y2O3 and La2O3 are used to generate ceramic phase with few pores and small grains; MgO-Y2O3-La2O3 is used as the sintering aid, and the grain size of the prepared ceramic reaches submicron level.

4. A method for producing a sintering aid for SiC ceramics, characterized in that It comprises: The composition of the sintering aid for preparing SiC ceramics according to any one of claims 1-3 and the mass ratio of each component are used to prepare raw materials, and the prepared high-temperature-resistant and corrosion-resistant composite oxide sintering aid is prepared by mixing, sintering, ball milling, screening and drying processes; the prepared composite oxide sintering aid is used to prepare high-density SiC ceramics.

5. The method for producing a sintering aid for SiC ceramics according to claim 4, characterized in that, It comprises: Step 1, preparing raw materials, including: according to the total mass of the sintering aid to be prepared, the composition of the sintering aid for preparing SiC ceramics according to any one of claims 1-3 and the mass ratio of each component are weighed; Step 2, sintering process of raw materials, including: loading the raw materials into a corundum crucible, placing the corundum crucible in a heating furnace, heating to 1100-1300℃, and naturally cooling after keeping the temperature for a preset time; Step 3, ball milling process of the sintered mixture, including: taking out the corundum crucible, separating the mixture, removing impurities in the mixture, loading the mixture into a ball mill tank, adding porcelain balls and distilled water for ball milling for 2-8h; wherein the mass ratio of powder, porcelain ball and distilled water for ball milling is 1:1:2; Step 4, screening, screening the ball-milled slurry; Step 5, drying, drying the screened slurry at 40-200℃ for 12-15h to form a sintering aid block.

6. The method for producing a sintering aid for SiC ceramics according to claim 5, characterized in that, For raw materials less than 200 mesh, before the step 2, further comprising: Step 1a, put the raw materials weighed in step 1 into a corundum ball mill jar, with the mass ratio of raw materials: porcelain balls = 1:1, ball mill for 2h~8h to form a mixed powder; Step 1b, pass the mixed powder after step 1a ball milling through an 80 mesh screen.

7. The method for preparing the sintering aid for SiC ceramics according to claim 5, wherein the sintering aid block prepared in step 5 is used for ball milling and screening together with SiC raw materials to prepare SiC ceramics. The sintering aid block prepared in step 5 is used for ball milling and screening together with SiC raw materials to prepare SiC ceramics.

8. The method for producing a sintering aid for SiC ceramics according to claim 5, characterized by, After step 5, further comprising: Step 6, crushing, crush the dried sintering aid block; Step 7, put the crushed sintering aid block into a screen with a preset mesh size, and continue to crush and screen the larger blocks until all are screened.

9. The method for preparing the sintering aid for SiC ceramics according to claim 8, wherein the preset mesh size of the screen is 160 mesh or more. ​

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