Rare earth doped silicon carbide particle trap and preparation method and application thereof

Abstract

The invention provides a rare earth doped silicon carbide particle trap as well as a preparation method and application thereof. The silicon carbide particle trap is prepared from the following raw materials: silicon carbide powder, a composite sintering aid, a pore forming agent and a binder, the composite sintering aid comprises boride, yttrium-zirconium powder and lanthanum-yttrium composite oxide. By optimizing the formula composition of the silicon carbide particle trap, the thermal conductivity, compressive strength and oxidation resistance of the product are remarkably improved, the thermal expansion coefficient of the product is reduced, and the service life of the product is further prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon carbide ceramics, and relates to a rare earth-doped silicon carbide particulate filter and its preparation method and application. Background Art

[0002] With the global emphasis on environmental protection, countries have gradually implemented strict exhaust emission standards. Since 2023, China has fully implemented the National VI a standard and plans to upgrade to the more stringent National VI b and National VII standards. Particulate matter in diesel vehicle exhaust needs to be removed through high-temperature catalytic combustion. However, traditional cordierite materials cannot meet the requirements of high temperature and high thermal shock due to their low softening temperature and insufficient thermal shock resistance. Silicon carbide, with its high melting point (about 2700°C), excellent thermal conductivity and chemical stability, has become a substitute material.

[0003] The material formulations of existing silicon carbide particulate filters mostly use boron carbide (B4C), boron nitride (BN) or yttrium zirconium powder (Y-ZrO2) as high-temperature sintering aids, which have the following problems: First, the prepared silicon carbide particulate filter has a relatively high thermal expansion coefficient, resulting in concentrated high-temperature thermal stress and easy cracking; second, the antioxidant property of the particulate filter is insufficient, and grain boundary oxidation accelerates under long-term high-temperature environments, affecting the service life; third, the thermal conductivity of the particulate filter is limited, resulting in uneven temperature distribution during the regeneration process and a high risk of local overheating.

[0004] In summary, it has become an urgent problem for those skilled in the art to prepare a silicon carbide particulate filter with low thermal expansion coefficient, high thermal conductivity and excellent antioxidant property. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a rare earth-doped silicon carbide particulate filter and its preparation method and application. By optimizing the formulation composition of the silicon carbide particulate filter, the thermal conductivity, compressive strength and antioxidant property of the product are significantly improved, and the thermal expansion coefficient of the product is reduced, thereby extending the service life of the product.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a rare earth-doped silicon carbide particulate filter, and the preparation raw materials of the silicon carbide particulate filter include silicon carbide powder, composite sintering aid, pore former and binder;

[0008] The composite sintering aid includes boride, yttrium zirconium powder and lanthanum yttrium composite oxide.

[0009] The silicon carbide particulate filter provided by the present invention improves the composition of the composite sintering aid formula. By doping a certain amount of rare earth elements (lanthanum element and yttrium element), combining with the traditional boron element and yttrium zirconium powder, a quaternary synergistic sintering aid is formed, which can effectively improve the oxidation resistance and density of the silicon carbide particulate filter, and significantly reduce the thermal expansion coefficient.

[0010] It should be noted that La 3+ ions and Y 3+ ions inhibit abnormal grain growth by occupying the silicon carbide grain boundary sites, reduce the grain boundary energy and the thermal expansion coefficient. Secondly, the lanthanum element generates a La-Si-O glass phase at high temperature to fill the microcracks and improve the oxidation resistance. Moreover, the yttrium element and the boron element synergistically promote liquid phase sintering, shorten the sintering time and improve the density.

[0011] As a preferred technical solution of the present invention, the silicon carbide powder includes first silicon carbide, second silicon carbide and third silicon carbide.

[0012] Preferably, the average particle size of the first silicon carbide is 20 - 50 μm.

[0013] Preferably, the average particle size of the second silicon carbide is 0.1 - 0.5 μm.

[0014] Preferably, the average particle size of the third silicon carbide is 30 - 50 nm.

[0015] As a preferred technical solution of the present invention, the boride includes boron nitride and / or boron carbide.

[0016] Preferably, the yttrium zirconium powder is zirconium oxide powder doped with yttrium oxide.

[0017] Preferably, based on the total mass of the yttrium zirconium powder being 100%, the content of yttrium oxide is 3% - 5%.

[0018] Preferably, the lanthanum-yttrium composite oxide includes lanthanum oxide and yttrium oxide.

[0019] Preferably, the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum-yttrium composite oxide is 1:(0.5 - 2).

[0020] As a preferred technical solution of the present invention, the pore former includes polystyrene microspheres and / or corn starch.

[0021] Preferably, the binder includes any one or a combination of at least two of polyvinyl alcohol, sodium polyacrylate, methyl cellulose or hydroxyethyl cellulose.

[0022] As a preferred technical solution of the present invention, based on the total mass of the silicon carbide powder and the composite sintering aid being 100%, the content of the first silicon carbide is 60%-80%, the content of the second silicon carbide is 10%-25%, the content of the third silicon carbide is 5%-10%, the content of the boride is 1%-3%, the content of the yttrium zirconium powder is 2%-4%, and the content of the lanthanum yttrium composite oxide is 1%-3%.

[0023] Preferably, the content of the pore-forming agent is 15%-20% of the total mass of the silicon carbide powder and the composite sintering aid.

[0024] Preferably, the content of the binder is 1%-5% of the total mass of the silicon carbide powder and the composite sintering aid.

[0025] As a preferred technical solution of the present invention, the thermal expansion coefficient of the silicon carbide particulate filter is 3.2×10 -6 -3.8×10 -6 / °C.

[0026] Preferably, the thermal conductivity of the silicon carbide particulate filter is 25-35 W / (m·K).

[0027] In a second aspect, the present invention provides a method for preparing a silicon carbide particulate filter as described in the first aspect. The preparation method includes the following steps:

[0028] (1) Pretreat the silicon carbide powder, and then mix the composite sintering aid, the pore-forming agent, the binder, and the pretreated silicon carbide powder to obtain a mud;

[0029] (2) Extrusion-mold and sinter the mud obtained in step (1) in sequence to obtain the silicon carbide particulate filter.

[0030] The preparation method provided by the present invention can remove surface oxides and metal impurities by pretreating the silicon carbide powder, improve the oxidation resistance of silicon carbide, and extend its service life; the overall preparation method is simple, easy to operate, and suitable for large-scale production.

[0031] As a preferred technical solution of the present invention, the pretreatment in step (1) is: impregnating the first silicon carbide, the second silicon carbide, and the third silicon carbide in an acid solution.

[0032] Preferably, the acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:(1-5).

[0033] Preferably, the mass concentration of the hydrofluoric acid is 40%-55%.

[0034] Preferably, the mass concentration of the nitric acid is 50%-70%.

[0035] Preferably, after the pretreatment in step (1), solid-liquid separation and drying are successively carried out.

[0036] As a preferred technical solution of the present invention, the pressure for extrusion molding in step (2) is 5-10 Mpa.

[0037] Preferably, the sintering in step (2) is carried out under a protective gas.

[0038] Preferably, the charging rate of the protective gas is 50-200 mL / min.

[0039] Preferably, the heating rate of the sintering in step (2) is 3-15 °C / min.

[0040] Preferably, the heating end point of the sintering in step (2) is 1900-2500 °C.

[0041] Preferably, the heat preservation time of the sintering in step (2) is 2-8 h.

[0042] Preferably, post-treatment is carried out after the sintering in step (2).

[0043] Preferably, the post-treatment includes polishing and machining carried out successively.

[0044] In a third aspect, the present invention provides an application of the silicon carbide particulate filter as described in the first aspect in diesel vehicle exhaust.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) For the silicon carbide particulate filter provided by the present invention, the composition of the composite co-firing agent formula is improved. By doping a certain amount of rare earth elements (lanthanum element and yttrium element), combining the traditional boron element with yttrium zirconium powder to form a quaternary synergistic co-firing agent, the oxidation resistance and density of the silicon carbide particulate filter can be effectively improved, and the coefficient of thermal expansion can be significantly reduced;

[0047] (2) For the silicon carbide particulate filter provided by the present invention, by optimizing the composition of the silicon carbide powder formula and adopting a nano-scale silicon carbide powder grading ratio scheme, the nano silicon carbide particles are filled in the gaps between the coarse powder and the fine powder, reducing the sintering porosity and increasing the thermal conductivity, thereby improving the problem of uneven temperature distribution during the regeneration process and reducing the risk of local overheating, which is beneficial to enhancing the quality stability of the silicon carbide particulate filter and further extending the service life of the silicon carbide particulate filter;

[0048] (3) The silicon carbide particulate filter provided by the present invention has excellent thermal conductivity and compressive strength, and reduces the coefficient of thermal expansion. Among them, the coefficient of thermal expansion is as low as 3.2×10 -6 / °C, with a thermal conductivity as high as 34.9 W / (m·K) and a compressive strength as high as 23.6 MPa;

[0049] (4) The preparation method provided by the present invention can remove surface oxides and metal impurities by pre-treating the silicon carbide powder, improve the oxidation resistance of the silicon carbide particulate filter, and extend its service life; the overall preparation method is simple, easy to operate, and suitable for large-scale production. Specific Embodiments

[0050] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0051] The specific embodiments of the present invention provide a rare earth-doped silicon carbide particulate filter, and the raw materials for preparing the silicon carbide particulate filter include silicon carbide powder, a composite sintering aid, a pore-forming agent, and a binder;

[0052] The composite sintering aid includes boride, yttrium zirconium powder, and lanthanum yttrium composite oxide.

[0053] In some embodiments of the present invention, the silicon carbide powder includes first silicon carbide, second silicon carbide, and third silicon carbide.

[0054] In some embodiments of the present invention, the average particle size of the first silicon carbide is 20 - 50 μm, for example, it can be 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, or 48 μm, etc.

[0055] In some embodiments of the present invention, the average particle size of the second silicon carbide is 0.1 - 0.5 μm, for example, it can be 0.45 μm, 0.4 μm, 0.35 μm, 0.3 μm, 0.25 μm, 0.2 μm, 0.15 μm, or 0.1 μm, etc.

[0056] In some embodiments of the present invention, the average particle size of the third silicon carbide is 30 - 50 nm, for example, it can be 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 46 nm, or 48 nm, etc.

[0057] It should be noted that by optimizing the formulation composition of the silicon carbide powder and adopting a nano-scale silicon carbide powder grading ratio scheme, the nano silicon carbide particles are filled in the gaps between the coarse powder and the fine powder, reducing the sintering porosity, improving the thermal conductivity, further improving the problem of uneven temperature distribution during the regeneration process, reducing the risk of local overheating, and thus being beneficial to enhancing the quality stability of the silicon carbide particulate filter and further extending the service life of the silicon carbide particulate filter.

[0058] In some embodiments of the present invention, the boride includes boron nitride and / or boron carbide.

[0059] In some embodiments of the present invention, the yttrium zirconium powder is zirconium oxide powder doped with yttrium oxide.

[0060] Preferably, based on the total mass of the yttrium zirconium powder being 100%, the content of yttrium oxide is 3% - 5%, for example, it can be 3.2%, 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.5%, 4.6% or 4.8%, etc.

[0061] In some embodiments of the present invention, the lanthanum yttrium composite oxide includes lanthanum oxide and yttrium oxide.

[0062] In some embodiments of the present invention, the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum yttrium composite oxide is 1:(0.5 - 2), for example, it can be 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.4, 1:1.5, 1:1.6 or 1:1.8, etc.

[0063] It should be noted that by regulating the ratio of lanthanum oxide to yttrium oxide in the lanthanum yttrium composite oxide, if the mass ratio of lanthanum oxide to yttrium oxide is too low, due to too little lanthanum element, the La - Si - O glass phase formed at high temperature is reduced, resulting in a decrease in oxidation resistance; if the mass ratio of lanthanum oxide to yttrium oxide is too high, due to too little yttrium element, the synergistic effect of promoting liquid phase sintering with boron element is reduced, resulting in a decrease in density.

[0064] In some embodiments of the present invention, the pore former includes polystyrene microspheres and / or corn starch.

[0065] In some embodiments of the present invention, the binder includes any one or a combination of at least two of polyvinyl alcohol, sodium polyacrylate, methyl cellulose or hydroxyethyl cellulose.

[0066] In some embodiments of the present invention, based on the total mass of the silicon carbide powder and the composite sintering aid being 100%, the content of the first silicon carbide is 60% - 80%, for example, it can be 62%, 65%, 66%, 68%, 70%, 72%, 75%, 76% or 78%, etc.; the content of the second silicon carbide is 10% - 25%, for example, it can be 12%, 15%, 16%, 18%, 20%, 22% or 24%, etc.; the content of the third silicon carbide is 5% - 10%, for example, it can be 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9% or 9.5%, etc.; the content of the boride is 1% - 3%, for example, it can be 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.5%, 2.6% or 2.8%, etc.; the content of the yttrium zirconium powder is 2% - 4%, for example, it can be 2.2%, 2.5%, 2.6%, 2.8%, 3%, 3.2%, 3.5%, 3.6% or 3.8%, etc.; the content of the lanthanum yttrium composite oxide is 1% - 3%, for example, it can be 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.5%, 2.6% or 2.8%, etc.

[0067] It should be noted that by adjusting the ratio of each component in the silicon carbide powder and the composite sintering aid, the silicon carbide particulate filter can have excellent oxidation resistance and density, while reducing the thermal expansion coefficient, thereby extending its service life.

[0068] In some embodiments of the present invention, the content of the pore former is 15% - 20% of the total mass of the silicon carbide powder and the composite sintering aid, for example, it can be 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19% or 19.5%, etc.

[0069] Preferably, the content of the binder is 1% - 5% of the total mass of the silicon carbide powder and the composite sintering aid, for example, it can be 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, etc.

[0070] In some embodiments of the present invention, the thermal expansion coefficient of the silicon carbide particulate filter is 3.2×10 -6 -3.8×10 -6 / °C, for example, it can be 3.3×10 -6 / °C, 3.4×10 -6 / °C, 3.5×10 -6 / °C, 3.6×10 -6 / °C or 3.7×10 -6 / °C, etc.

[0071] In some embodiments of the present invention, the thermal conductivity of the silicon carbide particulate filter is 25-35 W / (m·K), and for example, it can be 26 W / (m·K), 28 W / (m·K), 30 W / (m·K), 32 W / (m·K), or 34 W / (m·K), etc.

[0072] In the present invention, the silicon carbide particulate filter has a low coefficient of thermal expansion and a high thermal conductivity.

[0073] The specific embodiments of the present invention further provide a preparation method of the silicon carbide particulate filter as described above, and the preparation method includes the following steps:

[0074] (1) Pretreat the silicon carbide powder, and then mix the composite sintering aid, pore former, binder, and the pretreated silicon carbide powder to obtain a mud;

[0075] (2) Extrusion-mold and sinter the mud described in step (1) in sequence to obtain the silicon carbide particulate filter.

[0076] In some embodiments of the present invention, the pretreatment in step (1) is: impregnating the first silicon carbide, the second silicon carbide, and the third silicon carbide in an acid solution.

[0077] In some embodiments of the present invention, the acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:(1-5), and for example, it can be 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or 1:4.5, etc.

[0078] In some embodiments of the present invention, the mass concentration of the hydrofluoric acid is 40%-55%, and for example, it can be 42%, 45%, 46%, 48%, 50%, 52%, or 54%, etc.

[0079] In some embodiments of the present invention, the mass concentration of the nitric acid is 50%-70%, and for example, it can be 52%, 55%, 56%, 58%, 60%, 62%, 65%, 66%, or 68%, etc.

[0080] Preferably, solid-liquid separation and drying are sequentially carried out after the pretreatment in step (1).

[0081] In some embodiments of the present invention, the pressure of the extrusion molding in step (2) is 5-10 Mpa, and for example, it can be 5.5 Mpa, 6 Mpa, 6.5 Mpa, 7 Mpa, 7.5 Mpa, 8 Mpa, 8.5 Mpa, 9 Mpa, or 9.5 Mpa, etc.

[0082] In some embodiments of the present invention, the sintering in step (2) is carried out under a protective gas.

[0083] In the present invention, the protective gas includes argon.

[0084] In some embodiments of the present invention, the charging rate of the protective gas is 50 - 200 mL / min, for example, it can be 60 mL / min, 80 mL / min, 100 mL / min, 120 mL / min, 150 mL / min, 160 mL / min, 180 mL / min, etc.

[0085] In some embodiments of the present invention, the heating rate of the sintering in step (2) is 3 - 15 °C / min, for example, it can be 5 °C / min, 6 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 14 °C / min, etc.

[0086] In some embodiments of the present invention, the heating end point of the sintering in step (2) is 1900 - 2500 °C, for example, it can be 1950 °C, 2000 °C, 2050 °C, 2100 °C, 2150 °C, 2200 °C, 2250 °C, 2300 °C, 2350 °C, 2400 °C, 2450 °C, etc.

[0087] In some embodiments of the present invention, the heat preservation time of the sintering in step (2) is 2 - 8 h, for example, it can be 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, etc.

[0088] In some embodiments of the present invention, post - treatment is also carried out after the sintering in step (2).

[0089] In some embodiments of the present invention, the post - treatment includes polishing and machining carried out in sequence.

[0090] The specific embodiments of the present invention also provide an application of the silicon carbide particulate filter as described above in diesel vehicle exhaust.

[0091] The numerical ranges described in the present invention not only include the above - listed point values, but also include any point values between the above - mentioned numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention.

[0092] Unless otherwise defined, the technical terms used in the following examples and comparative examples have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The materials used in the following examples and comparative examples can all be obtained through commercial purchase or prepared by conventional methods in the prior art.

[0093] Example 1

[0094] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. The raw materials for preparing the silicon carbide particulate filter include silicon carbide powder, a composite sintering aid, a pore-forming agent, and a binder;

[0095] The composite sintering aid includes a boride, yttrium zirconium powder, and a lanthanum yttrium composite oxide; the boride is boron carbide; the yttrium zirconium powder is zirconia powder doped with yttrium oxide. Based on the total mass of the yttrium zirconium powder being 100%, the content of yttrium oxide is 5%; the lanthanum yttrium composite oxide is lanthanum oxide and yttrium oxide with a mass ratio of 1:1;

[0096] The silicon carbide powder includes first silicon carbide, second silicon carbide, and third silicon carbide; the average particle size of the first silicon carbide is 30 μm; the average particle size of the second silicon carbide is 0.4 μm; the average particle size of the third silicon carbide is 40 nm;

[0097] Based on the total mass of the silicon carbide powder and the composite sintering aid being 100%, the content of the first silicon carbide is 70%, the content of the second silicon carbide is 15%, the content of the third silicon carbide is 5%, the content of the boride is 2%, the content of the yttrium zirconium powder is 3%, and the content of the lanthanum yttrium composite oxide is 2%;

[0098] The pore-forming agent is polystyrene microspheres; the content of the pore-forming agent is 18% of the total mass of the silicon carbide powder and the composite sintering aid;

[0099] The binder is polyvinyl alcohol; the content of the binder is 5% of the total mass of the silicon carbide powder and the composite sintering aid.

[0100] The preparation method includes the following steps:

[0101] (1) Immerse the first silicon carbide, second silicon carbide, and third silicon carbide in an acid solution, then filter and dry them in sequence to obtain pretreated silicon carbide powder. Then, mix the composite sintering aid, pore-forming agent, binder, and pretreated silicon carbide powder according to the above ratio to obtain a mud;

[0102] The acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:3; the mass concentration of hydrofluoric acid is 40%; the mass concentration of nitric acid is 68%;

[0103] (2) Extrude the mud obtained in step (1) at a pressure of 6 MPa, then sinter it in argon at a heating rate of 10 °C / min to 2200 °C and hold for 2 h. Then, after grinding and size processing, obtain the silicon carbide particulate filter;

[0104] The charging rate of the argon is 100 mL / min.

[0105] Example 2

[0106] This example provides a rare earth - doped silicon carbide particulate filter and a preparation method thereof. The raw materials for preparing the silicon carbide particulate filter include silicon carbide powder, a composite sintering aid, a pore - forming agent, and a binder;

[0107] The composite sintering aid includes boride, yttrium - zirconium powder, and lanthanum - yttrium composite oxide; the boride is boron carbide; the yttrium - zirconium powder is zirconia powder doped with yttrium oxide. Taking the total mass of the yttrium - zirconium powder as 100%, the content of yttrium oxide is 3%; the lanthanum - yttrium composite oxide is lanthanum oxide and yttrium oxide with a mass ratio of 1:2;

[0108] The silicon carbide powder includes first silicon carbide, second silicon carbide, and third silicon carbide; the average particle size of the first silicon carbide is 25μm; the average particle size of the second silicon carbide is 0.2μm; the average particle size of the third silicon carbide is 30nm;

[0109] Taking the total mass of the silicon carbide powder and the composite sintering aid as 100%, the content of the first silicon carbide is 60%, the content of the second silicon carbide is 22%, the content of the third silicon carbide is 8%, the content of the boride is 3%, the content of the yttrium - zirconium powder is 4%, and the content of the lanthanum - yttrium composite oxide is 3%;

[0110] The pore - forming agent is polystyrene microbeads; the content of the pore - forming agent is 20% of the total mass of the silicon carbide powder and the composite sintering aid;

[0111] The binder is polyvinyl alcohol; the content of the binder is 5% of the total mass of the silicon carbide powder and the composite sintering aid.

[0112] The preparation method includes the following steps:

[0113] (1) Immerse the first silicon carbide, second silicon carbide, and third silicon carbide in an acid solution, then filter and dry them in sequence to obtain pretreated silicon carbide powder. Then, mix the composite sintering aid, pore - forming agent, binder, and pretreated silicon carbide powder according to the above ratio to obtain a mud;

[0114] The acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:5; the mass concentration of hydrofluoric acid is 40%; the mass concentration of nitric acid is 68%;

[0115] (2) Extrude the mud obtained in step (1) at a pressure of 10 MPa, then sinter it in argon at a heating rate of 8℃ / min to 1900℃ and hold for 5 h, and then obtain the silicon carbide particulate filter after grinding and sizing;

[0116] The charging rate of the argon gas is 100 mL / min.

[0117] Example 3

[0118] This example provides a rare earth doped silicon carbide particulate filter and a preparation method thereof. The raw materials for preparing the silicon carbide particulate filter include silicon carbide powder, a composite sintering aid, a pore former, and a binder;

[0119] The composite sintering aid includes a boride, yttrium zirconium powder, and a lanthanum yttrium composite oxide; the boride is boron carbide; the yttrium zirconium powder is zirconia powder doped with yttrium oxide. Based on the total mass of the yttrium zirconium powder being 100%, the content of yttrium oxide is 5%; the lanthanum yttrium composite oxide is lanthanum oxide and yttrium oxide with a mass ratio of 1:0.5;

[0120] The silicon carbide powder includes first silicon carbide, second silicon carbide, and third silicon carbide; the average particle size of the first silicon carbide is 50 μm; the average particle size of the second silicon carbide is 0.5 μm; the average particle size of the third silicon carbide is 50 nm;

[0121] Based on the total mass of the silicon carbide powder and the composite sintering aid being 100%, the content of the first silicon carbide is 80%, the content of the second silicon carbide is 10%, the content of the third silicon carbide is 5%, the content of the boride is 1%, the content of the yttrium zirconium powder is 2%, and the content of the lanthanum yttrium composite oxide is 2%;

[0122] The pore former is polystyrene microspheres; the content of the pore former is 15% of the total mass of the silicon carbide powder and the composite sintering aid;

[0123] The binder is polyvinyl alcohol; the content of the binder is 3% of the total mass of the silicon carbide powder and the composite sintering aid.

[0124] The preparation method includes the following steps:

[0125] (1) Immerse the first silicon carbide, second silicon carbide, and third silicon carbide in an acid solution, and then successively filter and dry to obtain pretreated silicon carbide powder. Then, mix the composite sintering aid, pore former, binder, and pretreated silicon carbide powder according to the above ratio to obtain a mud;

[0126] The acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:1; the mass concentration of the hydrofluoric acid is 40%; the mass concentration of the nitric acid is 68%;

[0127] (2) Extrude the mud material described in step (1) under a pressure of 5 MPa, then heat it to 2500 °C at a rate of 12 °C / min under argon and hold for 2 h, and then obtain the silicon carbide particulate trap after grinding and size processing;

[0128] The charging rate of the argon is 100 mL / min.

[0129] Example 4

[0130] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the content of the third silicon carbide is adjusted to 2%, and the contents of the first silicon carbide and the second silicon carbide are increased equally in proportion, other conditions are the same as those in Example 1.

[0131] Example 5

[0132] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the content of the third silicon carbide is adjusted to 7%, and the contents of the first silicon carbide and the second silicon carbide are decreased equally in proportion, other conditions are the same as those in Example 1.

[0133] Example 6

[0134] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the content of the third silicon carbide is adjusted to 10%, and the contents of the first silicon carbide and the second silicon carbide are decreased equally in proportion, other conditions are the same as those in Example 1.

[0135] Example 7

[0136] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the content of the third silicon carbide is adjusted to 15%, and the contents of the first silicon carbide and the second silicon carbide are decreased equally in proportion, other conditions are the same as those in Example 1.

[0137] Example 8

[0138] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the average particle size of the third silicon carbide is 10 nm, other conditions are the same as those in Example 1.

[0139] Example 9

[0140] This example provides a rare earth-doped silicon carbide particulate trap and a preparation method thereof. Except that the average particle size of the third silicon carbide is 100 nm, other conditions are the same as those in Example 1.

[0141] Example 10

[0142] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum-yttrium composite oxide is 1:0.2, other conditions are the same as those in Embodiment 1.

[0143] Embodiment 11

[0144] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum-yttrium composite oxide is 1:0.5, other conditions are the same as those in Embodiment 1.

[0145] Embodiment 12

[0146] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum-yttrium composite oxide is 1:2, other conditions are the same as those in Embodiment 1.

[0147] Embodiment 13

[0148] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum-yttrium composite oxide is 1:3, other conditions are the same as those in Embodiment 1.

[0149] Embodiment 14

[0150] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the content of the lanthanum-yttrium composite oxide is adjusted to 0.5%, and the contents of the boride and the yttrium zirconium powder are increased in equal proportion and in equal amount, other conditions are the same as those in Embodiment 1.

[0151] Embodiment 15

[0152] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the content of the lanthanum-yttrium composite oxide is adjusted to 5%, and the contents of the boride and the yttrium zirconium powder are reduced in equal proportion and in equal amount, other conditions are the same as those in Embodiment 1.

[0153] Embodiment 16

[0154] This embodiment provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the silicon carbide powder is not pretreated in step (1), other conditions are the same as those in Embodiment 1.

[0155] Comparative Example 1

[0156] This comparative example provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the third silicon carbide is not added, and the contents of the first silicon carbide and the second silicon carbide are increased in equal proportion and in equal amount, other conditions are the same as those in Embodiment 1.

[0157] Comparative Example 2

[0158] This comparative example provides a silicon carbide particulate filter and a preparation method thereof. Except that no lanthanum-yttrium composite oxide is added and the contents of boride and yttrium zirconium powder are increased in equal proportions and equal amounts, other conditions are the same as those in Example 1.

[0159] Comparative Example 3

[0160] This comparative example provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the lanthanum-yttrium composite oxide is replaced with lanthanum oxide, other conditions are the same as those in Example 1.

[0161] Comparative Example 4

[0162] This comparative example provides a rare earth-doped silicon carbide particulate filter and a preparation method thereof. Except that the lanthanum-yttrium composite oxide is replaced with yttrium oxide, other conditions are the same as those in Example 1.

[0163] The silicon carbide particulate filters prepared in the above examples and comparative examples were tested for thermal expansion coefficient, thermal conductivity, compressive strength, and porosity. Among them, the thermal expansion coefficient was tested using a thermomechanical analyzer in the range of 35°C - 180°C, the thermal conductivity was tested using a thermal conductivity tester according to the ASTM D5470 method, the compressive strength was tested according to GB / T 25994-2010, and the porosity was tested using the mercury intrusion method. The above test results are shown in Table 1.

[0164] Table 1

[0165]

[0166]

[0167] As can be seen from Table 1:

[0168] (1) The silicon carbide particulate filters and the preparation methods thereof provided in Examples 1 - 3 of the present invention, by adding a lanthanum-yttrium composite oxide containing a certain proportion of lanthanum element and yttrium element to the silicon carbide particulate filter and combining with the addition of third silicon carbide (nano-silicon carbide powder), the prepared silicon carbide particulate filter has excellent thermal conductivity and compressive strength, reduces the thermal expansion coefficient, improves the mass stability, and further extends the service life; among them, the thermal expansion coefficient is as low as 3.2×10 -6 / °C, the thermal conductivity is as high as 34.9 W / (m·K), the compressive strength is as high as 23.6 MPa, and the porosity is as low as 47.3%;

[0169] (2) By comparing Example 1 with Examples 4 - 7 and Comparative Example 1, it can be seen that by adding the third silicon carbide and controlling its addition amount range, the nano - silicon carbide particles are filled in the gaps between the coarse powder and the fine powder, which can improve the thermal conductivity and compressive strength of the silicon carbide particle trap, and the porosity of the sintered silicon carbide particle trap decreases, indicating that the density of the silicon carbide particle trap has increased;

[0170] (3) By comparing Example 1 with Examples 8 - 9, it can be seen that by controlling the average particle size range of the third silicon carbide, it is beneficial to improve the thermal conductivity and compressive strength of the silicon carbide particle trap. When the average particle size of the third silicon carbide is too small, at the same mass ratio, the number of particles of the third silicon carbide increases, and the third silicon carbide sublimes at high temperature, acting as a pore - forming agent. The existence of too much third silicon carbide leads to an increase in porosity; when the average particle size of the third silicon carbide is too large, large pores are generated during sublimation at high temperature, increasing the porosity and reducing the compressive strength and density;

[0171] (4) By comparing Example 1 with Examples 10 - 13, it can be seen that by controlling the mass ratio range of lanthanum oxide and yttrium oxide, combining traditional boride and yttrium - zirconium powder to form a quaternary synergistic sintering aid. La 3+ and Y 3+ ions occupy the silicon carbide grain boundary sites, inhibit abnormal grain growth, reduce the grain boundary energy, and reduce the thermal expansion coefficient; yttrium element and boride synergistically promote liquid - phase sintering, improve the density, and thus increase the compressive strength; when the mass ratio of lanthanum oxide to yttrium oxide is too low, due to too little lanthanum element, the La - Si - O glass phase formed at high temperature is reduced, resulting in a decrease in oxidation resistance; when the mass ratio of lanthanum oxide to yttrium oxide is too high, due to too little yttrium element, the synergistic effect of promoting liquid - phase sintering with boron element is reduced, resulting in a decrease in density;

[0172] (5) By comparing Example 1 with Examples 14 - 15 and Comparative Example 2, it can be seen that when the addition amount of the lanthanum - yttrium composite oxide is too low or the lanthanum - yttrium composite oxide is not added, due to the lack of La 3+ and Y 3+ , the thermal expansion coefficient increases; when the addition amount of the lanthanum - yttrium composite oxide is too high, the corresponding content of boride and yttrium - zirconium powder decreases, and the quaternary synergistic effect decreases, resulting in a decrease in compressive strength and an increase in porosity, indicating a decrease in density;

[0173] (6) By comparing Example 1 with Example 16, it can be seen that if the silicon carbide powder is not pretreated, due to the existence of oxides and metal impurities on the surface of the silicon carbide powder, the oxidation resistance of the silicon carbide particle trap cannot be improved, and its service life is shortened;

[0174] (7) From the comparison between Comprehensive Example 1 and Comparative Examples 3-4, it can be seen that when only lanthanum oxide is added, not only can the thermal expansion coefficient not be reduced, but also the synergistic effect with boron cannot be fully exerted, thus the density cannot be improved, resulting in a decrease in the compressive strength of the silicon carbide particulate filter; when only yttrium oxide is added, not only can the thermal expansion coefficient not be reduced, but also the oxidation resistance of the silicon carbide particulate filter cannot be improved, thereby shortening its service life.

[0175] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A rare earth-doped silicon carbide particulate filter, characterized in that, The raw materials for preparing the silicon carbide particulate filter include silicon carbide powder, a composite sintering aid, a pore former, and a binder; The composite sintering aid includes a boride, yttrium zirconium powder, and a lanthanum yttrium composite oxide.

2. The silicon carbide particulate trap according to claim 1, characterized in that, The silicon carbide powder includes first silicon carbide, second silicon carbide, and third silicon carbide; Preferably, the average particle size of the first silicon carbide is 20 - 50 μm; Preferably, the average particle size of the second silicon carbide is 0.1 - 0.5 μm; Preferably, the average particle size of the third silicon carbide is 30 - 50 nm.

3. The silicon carbide particulate trap according to claim 1 or 2, wherein The boride includes boron nitride and / or boron carbide; Preferably, the yttrium zirconium powder is zirconia powder doped with yttrium oxide; Preferably, based on the total mass of the yttrium zirconium powder being 100%, the content of yttrium oxide is 3% - 5%; Preferably, the lanthanum yttrium composite oxide includes lanthanum oxide and yttrium oxide; Preferably, the mass ratio of lanthanum oxide to yttrium oxide in the lanthanum yttrium composite oxide is 1:(0.5 - 2).

4. The silicon carbide particulate filter according to any one of claims 1-3, characterized in that, The pore former includes polystyrene microspheres and / or corn starch; Preferably, the binder includes any one or a combination of at least two of polyvinyl alcohol, sodium polyacrylate, methyl cellulose, or hydroxyethyl cellulose.

5. The silicon carbide particulate filter according to any one of claims 1-4, characterized in that, Based on the total mass of the silicon carbide powder and the composite sintering aid being 100%, the content of the first silicon carbide is 60% - 80%, the content of the second silicon carbide is 10% - 25%, the content of the third silicon carbide is 5% - 10%, the content of the boride is 1% - 3%, the content of the yttrium zirconium powder is 2% - 4%, and the content of the lanthanum yttrium composite oxide is 1% - 3%; Preferably, the content of the pore former is 15% - 20% of the total mass of the silicon carbide powder and the composite sintering aid; Preferably, the content of the binder is 1% - 5% of the total mass of the silicon carbide powder and the composite sintering aid.

6. The silicon carbide particulate trap according to any one of claims 1-5, characterized in that, The thermal expansion coefficient of the silicon carbide particulate filter is 3.2×10 -6 -3.8×10 -6 / °C; Preferably, the thermal conductivity of the silicon carbide particulate filter is 25 - 35 W / (m·K).

7. A method for preparing a silicon carbide particulate filter according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Pretreat the silicon carbide powder, and then mix the composite sintering aid, the pore former, the binder, and the pretreated silicon carbide powder to obtain a mud; (2) Extrusion-mold and sinter the mud obtained in step (1) in sequence to obtain the silicon carbide particulate filter.

8. The preparation method according to claim 7, wherein The pretreatment in step (1) is: Immerse the first silicon carbide, the second silicon carbide, and the third silicon carbide in an acid solution; Preferably, the acid solution includes a mixed solution of hydrofluoric acid and nitric acid with a volume ratio of 1:(1 - 5); Preferably, the mass concentration of the hydrofluoric acid is 40% - 55%; Preferably, the mass concentration of the nitric acid is 50% - 70%; Preferably, after the pretreatment in step (1), solid-liquid separation and drying are carried out in sequence.

9. The preparation method according to claim 7 or 8, characterized in that, The pressure for the extrusion molding in step (2) is 5 - 10 Mpa; Preferably, the sintering in step (2) is carried out under a protective gas; Preferably, the charging rate of the protective gas is 50 - 200 mL / min; Preferably, the heating rate for the sintering in step (2) is 3 - 15 °C / min; Preferably, the heating end point for the sintering in step (2) is 1900 - 2500 °C; Preferably, the heat preservation time of the sintering in step (2) is 2 - 8 h; Preferably, post - treatment is also carried out after the sintering in step (2); Preferably, the post - treatment includes grinding and machining carried out in sequence.

10. Application of a silicon carbide particulate trap as described in any one of claims 1 - 6 in diesel vehicle exhaust.

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