Sintering aid for preparing SiC ceramic and preparation method of sintering aid

Abstract

The invention discloses a sintering aid for preparing SiC ceramic and a preparation method of the sintering aid, and the sintering aid comprises the following components: 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, and in the components of the sintering aid, lanthanum oxide La2O3 and 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. According to the technical scheme, the problems that a high-quality SiC ceramic product and the low sintering temperature cannot be considered at the same time when an existing sintering aid is used for preparing SiC ceramic, and the problems that an existing mode for preparing the sintering aid brings certain danger to equipment and personnel, and the economical efficiency is low are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, but is not limited thereto, and in particular to a sintering aid for preparing SiC ceramics and a preparation method thereof. Background Art

[0002] SiC has strong covalent bonds, and its ceramic preparation mechanism is evaporation-condensation, with a sintering temperature of 2200°C and harsh sintering conditions. Currently, the commonly used method for preparing SiC ceramics is to add sintering aids for sintering preparation, and the sintering temperature can be greatly reduced.

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

[0004] The use of the above-mentioned commonly used sintering aids to prepare SiC ceramics cannot take into account both high-quality SiC ceramic products and low sintering temperatures. In addition, the method of preparing the sintering aids will bring certain risks to equipment and personnel, and has low economic efficiency. Summary of the invention

[0005] Purpose of the present invention: In order to solve the above-mentioned technical problems, the embodiments of the present invention provide a sintering aid for preparing SiC ceramics and a preparation method thereof, so as to solve the problem that the existing sintering aid for preparing SiC ceramics cannot take into account both high-quality SiC ceramic products and lower sintering temperatures, and the existing method for preparing sintering aids will bring certain risks to equipment and personnel and low economic efficiency.

[0006] Technical solution of the present invention: In the first aspect, the embodiment of the present invention provides a sintering aid for preparing SiC ceramics, comprising: the components of the sintering aid include: lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; the mass proportions of the components are respectively;

[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 proportions of all components is 100%.

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

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

[0017] Optionally, in the sintering aid for preparing SiC ceramics as described above, among the components of the sintering aid,

[0018] SiO2 is used to form a molten phase to reduce the temperature of the ceramic phase to generate ceramics; and the generated molten phase is used to increase the migration rate between ceramic grains to facilitate the sintering and densification of the ceramics;

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

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

[0021] Yttrium oxide Y2O3 and lanthanum oxide La2O3 are used to produce ceramic phases with less pores and fine grains;

[0022] The grain size of the ceramic using MgO-Y2O3-La2O3 as sintering aid reaches submicron level.

[0023] In a second aspect, an embodiment of the present invention further provides a method for preparing a sintering aid for preparing SiC ceramics, comprising:

[0024] According to the composition of the sintering aid for preparing SiC ceramics as described in any one of claims 1 to 3 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 high-density SiC ceramics.

[0025] Optionally, the method for preparing a sintering aid for preparing SiC ceramics as described above comprises:

[0026] Step 1, preparing raw materials, comprising: weighing raw materials according to the total mass of the sintering aid to be prepared, and the components and mass ratios of the components of the sintering aid for preparing SiC ceramics according to any one of claims 1 to 3;

[0027] Step 2, sintering the raw materials, including: loading the raw materials into a corundum crucible, placing the corundum crucible in a heating furnace, heating it to 1100° C. to 1300° C., keeping it warm for a preset time, and then cooling it naturally;

[0028] Step 3, ball milling the sintered mixed material block, including: taking out the corundum crucible, separating the mixed material block, removing foreign matter and impurities in the mixed material block, putting the mixed material block into a ball mill, adding porcelain balls and distilled water for ball milling for 2h to 8h; wherein the powder used for ball milling: porcelain balls: distilled water (mass ratio) = 1:1:2;

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

[0030] Step 5, drying, drying the screened slurry at 40°C to 200°C for 12h-15h to form sintering aid blocks.

[0031] Optionally, in the method for preparing a sintering aid for preparing SiC ceramics as described above, for a raw material with a mesh size less than 200, before step 2, the method further comprises:

[0032] Step 1a, placing the raw materials weighed in step 1 in a corundum ball mill, and milling for 2h to 8h to form a mixed powder according to the ratio of raw materials to porcelain balls (mass ratio) = 1:1;

[0033] Step 1b, passing the mixed powder after ball milling in step 1a through an 80-mesh sieve.

[0034] Optionally, in the method for preparing a sintering aid for preparing SiC ceramics as described above,

[0035] The sintering aid material block prepared in step 5 is used for ball milling and sieving together with SiC raw materials when preparing SiC ceramics to prepare SiC ceramics.

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

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

[0038] Step 7: Place the crushed sintering aid material blocks into a sieve with a preset mesh size for screening, and continue to crush and screen the larger material blocks until all of them are screened.

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

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

[0041] Beneficial effects of the present invention: An embodiment of the present invention provides a sintering aid for preparing SiC ceramics and a preparation method thereof, wherein the components of the sintering aid include: lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; wherein lanthanum oxide La2O3 and silicon dioxide SiO2 are used as the 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 screening. Among the various components mentioned above, SiO2 forms a molten phase, which can greatly reduce the temperature of ceramic phase generation; and the generated molten phase is used to increase the migration rate between ceramic grains, which is beneficial to the sintering and densification of ceramics; CaO can prevent the ceramic phase from undergoing martensitic transformation at low temperatures to reduce the compressive stress caused by volume expansion; MgO can improve the bending strength of the ceramic phase and reduce the pores of the prepared SiC ceramic; yttrium oxide Y2O3 and lanthanum oxide La2O3 can produce ceramic phases with fewer pores and fine grains, and can prepare ceramics with good antioxidant ability; the grain size of MgO-Y2O3-La2O3 as a sintering aid ceramic reaches the submicron level; the closed porosity is less than 1%; in addition, the traditional ball milling solvent of the sintering aid is an organic solvent (for example, anhydrous ethanol), which has great safety hazards and high costs. In the embodiment of the present invention, distilled water is used instead of an organic solvent for mixed ball milling, which has no safety hazards, high economy, and reduces the solvent volatilization during the ball milling process. The technical solution provided by the present invention has 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°C in the prior art, the sintering temperature of the preparation method of the sintering aid provided by the present invention can be as low as 1100°C, which has good processability, can improve safety and reduce energy consumption;

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

[0045] 4) The prepared SiC ceramics have excellent salt spray corrosion resistance;

[0046] 5) The prepared SiC ceramics have high density and porosity less than 1%;

[0047] 6) During the sintering process, SiC ceramics have small deformation, small internal stress, high strength and good thermal shock resistance;

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

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

[0050] Figure 1 A process flow chart of a method for preparing a sintering aid for preparing SiC ceramics provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present invention more clear, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0052] As described in the above background technology, the commonly used method for preparing SiC ceramics is to add sintering aids for sintering preparation, and the sintering temperature can be greatly reduced. However, the existing sintering aids for preparing SiC ceramics cannot take into account the problems of high-quality SiC ceramic products and low sintering temperatures, and the existing methods for preparing sintering aids will bring certain risks to equipment and personnel, and have low economic efficiency.

[0053] In response to the above problems, an embodiment of the present invention provides a sintering aid for preparing SiC ceramics and a preparation method thereof, which uses various oxides such as SiO2, La2O3 and rare earth oxides as raw materials, and is mixed, dried, crushed, sintered, ball milled, etc. in a certain ratio to prepare a high-temperature resistant and corrosion-resistant composite oxide sintering aid, and can prepare high-density SiC ceramics.

[0054] The present invention provides the following specific embodiments which can be combined with each other. The same or similar concepts or processes may not be described in detail in some embodiments.

[0055] An embodiment of the present invention provides a sintering aid for preparing SiC ceramics, wherein the components of the sintering aid include: 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 components is 100%.

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

[0065] In a specific implementation of the embodiment of the present invention, the composition ratio of the sintering aid for preparing SiC ceramics is shown in Table 1 below:

[0066] Table 1 Sintering aid ratio table

[0067] Serial number name Chemical formula Mass ratio (wt.%) 1 Lanthanum Oxide <![CDATA[La2O3]]> 45 2 Silicon dioxide <![CDATA[SiO2]]> 40 3 Magnesium Oxide MgO 2 4 Sodium carbonate <![CDATA[Na2CO3]]> 2.5 5 Calcium Oxide CaO 2 6 Strontium carbonate <![CDATA[SrCO3]]> 6 7 Yttrium Oxide <![CDATA[Y2O3]]> 2.5

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

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

[0070] (2) The use of CaO can prevent the martensitic transformation of the ceramic phase at low temperatures, thereby reducing the compressive stress caused by volume expansion;

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

[0072] (4) The use of yttrium oxide Y2O3 and lanthanum oxide La2O3 can produce ceramic phases with fewer pores and fine grains, and can prepare ceramics with better oxidation resistance;

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

[0074] (6) Sintering aids Conventional ball milling solvents are organic solvents (such as anhydrous ethanol), which have great safety hazards and high costs. In the embodiment of the present invention, distilled water is used instead of organic solvents for mixed ball milling, which has no safety hazards, high economic efficiency, and reduces solvent volatilization during the ball milling process.

[0075] Based on the sintering aid for preparing SiC ceramics provided in the embodiment of the present invention, the embodiment of the present invention also provides a preparation method of the sintering aid for preparing SiC ceramics; Figure 1 , which is a process flow chart of a method for preparing a sintering aid for preparing SiC ceramics provided in an embodiment of the present invention.

[0076] The preparation method provided in an embodiment of the present invention adopts the components of the sintering aid for preparing SiC ceramics provided in any of the above embodiments and the mass ratio of each component to prepare raw materials, 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 high-density SiC ceramics.

[0077] The preparation method provided in the embodiment of the present invention specifically comprises the following steps:

[0078] Step 1, preparing raw materials, including: weighing raw materials according to the total mass of the sintering aid to be prepared, and according to the components and mass ratios of the sintering aid for preparing SiC ceramics provided in 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 it to 1100° C. to 1300° C., keeping it warm for a preset time, and then cooling it naturally;

[0080] Step 3, ball milling the sintered mixed material block, including: taking out the corundum crucible, separating the mixed material block, removing foreign matter and impurities in the mixed material block, putting the mixed material block into a ball mill jar, adding porcelain balls and distilled water for ball milling for 2h to 8h.

[0081] In this step, the powder used for ball milling: porcelain ball: distilled water (mass ratio) = 1:1:2. It should be noted that during the process of sintering the powder to form a material block, the raw material will adhere to the crucible, and the foreign matter impurities may be the crucible wall products that stick to the material block when separating the material block from the crucible; or because the material block is tightly adhered to the crucible and difficult to separate, the can needs to be broken for separation, at this time, the crucible block may be mixed in; or during the sintering process, due to uneven mixing, the powder may locally form products that do not meet expectations.

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

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

[0084] In one implementation of the embodiment of the present invention, for raw materials with a mesh size less than 200, before step 2, the following steps are further included:

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

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

[0087] In one implementation of the embodiment of the present invention, the sintering aid material block prepared in the above step 5 is used for ball milling and sieving together with SiC raw materials when preparing SiC ceramics to prepare SiC ceramics.

[0088] In an implementation of the embodiment of the present invention, after the above step 5, the following steps may also be included:

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

[0090] Step 7: Put the crushed sintering aid material blocks into a sieve with a preset mesh size (for example, 160 mesh or more) for screening, and continue to crush and screen the larger material blocks until all of them are screened.

[0091] The embodiments of the present invention provide a sintering aid for preparing SiC ceramics and a preparation method thereof. The components of the sintering aid include: lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; wherein lanthanum oxide La2O3 and silicon dioxide SiO2 are used as the 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. After ball milling, sintering, drying, crushing and screening, a sintering aid for SiC ceramics is prepared. Among the various components mentioned above, SiO2 forms a molten phase, which can greatly reduce the temperature of ceramic phase generation; and the generated molten phase is used to increase the migration rate between ceramic grains, which is beneficial to the sintering and densification of ceramics; CaO can prevent the ceramic phase from undergoing martensitic transformation at low temperatures to reduce the compressive stress caused by volume expansion; MgO can improve the bending strength of the ceramic phase and reduce the pores of the prepared SiC ceramic; yttrium oxide Y2O3 and lanthanum oxide La2O3 can produce ceramic phases with fewer pores and fine grains, and can prepare ceramics with good antioxidant ability; the grain size of MgO-Y2O3-La2O3 as a sintering aid ceramic reaches the submicron level; the closed porosity is less than 1%; in addition, the traditional ball milling solvent of the sintering aid is an organic solvent (for example, anhydrous ethanol), which has great safety hazards and high costs. In the embodiment of the present invention, distilled water is used instead of an organic solvent for mixed ball milling, which has no safety hazards, high economy, and reduces the solvent volatilization during the ball milling process. The technical solution provided by the present invention 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 SiC can be greatly reduced. Compared with the sintering temperature of 2200°C in the prior art, the sintering temperature of the preparation method of the sintering aid provided by the present invention can be as low as 1100°C, which has good processability, can improve safety and reduce energy consumption;

[0094] 3) The ball milling process uses distilled water, which is highly economical and safe;

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

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

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

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

[0099] The sintering aid for preparing SiC ceramics and the preparation method thereof provided in the embodiments of the present invention are described in detail through some specific examples as follows.

[0100] Example 1

[0101] This embodiment 1 provides a method for preparing a sintering aid for preparing SiC ceramics, referring to Figure 1 As shown, in this embodiment 1, the sintering aid is prepared according to the following steps:

[0102] 1. Ingredients

[0103] Prepare a total mass of 200g of sintering aid. Wear acid and alkali resistant latex gloves and weigh the materials in order according to the ratio table using a balance.

[0104] The total mass of the sintering aid required is 200g. The masses of the raw materials required are: 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] Place the weighed material in a corundum ball mill, at a material:95 porcelain ball (mass ratio) = 1:1, and ball mill for 4 hours.

[0107] 3. Screening

[0108] The ball-milled mixture was sieved through an 80-mesh sieve.

[0109] 4. Sintering

[0110] Put the sieved powder into a corundum crucible, place the corundum crucible in an electric furnace, heat it up to 1100℃~1300℃, keep it warm for a certain period of time, turn off the power and cool it naturally.

[0111] 5. Ball milling

[0112] Take out the corundum crucible, separate the material blocks manually, remove foreign matter and impurities, put the material blocks into the ball mill, add porcelain balls and distilled water, material: porcelain balls: distilled water (mass ratio) = 1:1:2, ball mill for 5 hours. Use a stainless steel shovel to crush the material blocks.

[0113] Sieve

[0114] The ball-milled slurry is sieved and placed in an enamel pan or a stainless steel pan.

[0115] drying

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

[0117] broken

[0118] The dried sintering aid blocks are scooped up with a stainless steel shovel and then crushed.

[0119] Sieve

[0120] Put the crushed sintering aid blocks into a sieve with a certain mesh number (above 160), screen them manually, and continue to crush the larger blocks with a stainless steel shovel until all of them are screened. The larger the mesh number, the finer the

[0121] 10. Save

[0122] Put the sifted powder into wide-mouth bottles and label them according to categories.

[0123] Example 2

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

[0125] 1. Ingredients

[0126] Prepare a total mass of 200g of sintering aid. Wear acid and alkali resistant latex gloves and weigh the materials in order according to the ratio table using a balance.

[0127] The total mass of the sintering aid required is 200g. The masses of the raw materials required are: 100g of lanthanum oxide (La2O3); 75g of silicon dioxide (SiO2); 5g of magnesium oxide (MgO); 4g of sodium carbonate (Na2CO3); 5g of calcium oxide (CaO); 11g of strontium carbonate (SrCO3); and 5g of yttrium oxide (Y2O3).

[0128] 2. Ball milling

[0129] The weighed material was placed in a corundum ball mill, with the material:95 porcelain ball (mass ratio) = 1:1, and ball milled for 8 hours.

[0130] 3. Screening

[0131] The ball-milled mixture was sieved through a 160-mesh sieve.

[0132] 4. Sintering

[0133] Put the sieved powder into a corundum crucible, place the corundum crucible in an electric furnace, heat it up to 1300℃±10℃, keep it warm for a certain period of time, turn off the power and cool it naturally.

[0134] 5. Ball milling

[0135] Take out the corundum crucible, separate the material blocks manually, remove foreign matter and impurities, put the material blocks into the ball mill, add porcelain balls and distilled water, material: porcelain balls: distilled water (mass ratio) = 1:1:2, ball mill for 5 hours. Use a stainless steel shovel to crush the material blocks.

[0136] 6. Sieve

[0137] The ball-milled slurry is sieved and placed in an enamel pan or a stainless steel pan.

[0138] 7. Drying

[0139] Dry the slurry in the enamel tray at 120±5℃ for 12h.

[0140] 8. Save

[0141] Put the dried powder into wide-mouth bottles and label them according to categories.

[0142] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A sintering aid for preparing SiC ceramics, characterized in that: The components of the sintering aid include: lanthanum oxide La2O3, silicon dioxide SiO2, magnesium oxide MgO, sodium carbonate Na2CO3, calcium oxide CaO, strontium carbonate SrCO3 and yttrium oxide Y2O3; the mass proportions of the components are 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 proportions of all components is 100%.

2. The sintering aid for preparing SiC ceramics according to claim 1, characterized in that: The sintering aid is prepared by using lanthanum oxide La2O3 and silicon dioxide SiO2 as main components of the sintering aid, using other components as auxiliary components, and using distilled water as ball milling solvent.

3. The sintering aid for preparing SiC ceramics according to claim 2, characterized in that: Among the components of the sintering aid, SiO2 is used to form a molten phase to reduce the temperature of the ceramic phase to generate ceramics; and the generated molten phase is used to increase the migration rate between ceramic grains to facilitate the sintering and densification of the ceramics; CaO is used to prevent the martensitic transformation of the ceramic phase at low temperatures to reduce the compressive stress caused by volume expansion; MgO is used to improve the bending strength of the ceramic phase and reduce the pores of the prepared SiC ceramics; Yttrium oxide Y2O3 and lanthanum oxide La2O3 are used to produce ceramic phases with less pores and fine grains; The grain size of the ceramic using MgO-Y2O3-La2O3 as sintering aid reaches submicron level.

4. A method for preparing a sintering aid for preparing SiC ceramics, characterized in that: include: According to the composition of the sintering aid for preparing SiC ceramics as described in any one of claims 1 to 3 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 high-density SiC ceramics.

5. The method for preparing a sintering aid for preparing SiC ceramics according to claim 4, characterized in that: include: Step 1, preparing raw materials, comprising: weighing raw materials according to the total mass of the sintering aid to be prepared, and the components and mass ratios of the components of the sintering aid for preparing SiC ceramics according to any one of claims 1 to 3; Step 2, sintering the raw materials, including: loading the raw materials into a corundum crucible, placing the corundum crucible in a heating furnace, heating it to 1100° C. to 1300° C., keeping it warm for a preset time, and then cooling it naturally; Step 3, ball milling the sintered mixed material block, including: taking out the corundum crucible, separating the mixed material block, removing foreign matter and impurities in the mixed material block, putting the mixed material block into a ball mill, adding porcelain balls and distilled water for ball milling for 2h to 8h; wherein the powder used for ball milling: porcelain balls: distilled water (mass ratio) = 1:1:2; Step 4, screening, screening the slurry after ball milling; Step 5, drying, drying the screened slurry at 40°C to 200°C for 12h-15h to form sintering aid blocks.

6. The method for preparing a sintering aid for preparing SiC ceramics according to claim 5, characterized in that: For raw materials with a mesh size less than 200, before step 2, the method further comprises: Step 1a, placing the raw materials weighed in step 1 in a corundum ball mill, and milling for 2h to 8h to form a mixed powder according to the ratio of raw materials to porcelain balls (mass ratio) = 1:1; Step 1b, passing the mixed powder after ball milling in step 1a through an 80-mesh sieve.

7. The method for preparing a sintering aid for preparing SiC ceramics according to claim 5, characterized in that: The sintering aid material block prepared in step 5 is used for ball milling and sieving together with SiC raw materials when preparing SiC ceramics to prepare SiC ceramics.

8. The method for preparing a sintering aid for preparing SiC ceramics according to claim 5, characterized in that: After step 5, the method further includes: Step 6, crushing, crushing the dried sintering aid material blocks; Step 7: Place the crushed sintering aid material blocks into a sieve with a preset mesh size for screening, and continue to crush and screen the larger material blocks until all of them are screened.

9. The method for preparing a sintering aid for preparing SiC ceramics according to claim 8, characterized in that: The preset mesh number of the sieve is 160 mesh or more.

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