Porous ceramic matrix as well as preparation method and application thereof

Abstract

The invention provides a porous ceramic matrix and a preparation method and application thereof.The preparation method comprises the following steps that 1, talcum powder, an aluminum source, washed kaolin, calcined kaolin and fused quartz powder are subjected to first mixing to obtain mixed inorganic powder, the mixed inorganic powder, a pore forming agent and a binder are subjected to second mixing to obtain a mixed precursor material, and the mixed precursor material is subjected to second mixing; kneading the mixed precursor material to obtain a pug; and (2) carrying out molding treatment on the pug to obtain a biscuit, carrying out hole plugging treatment on the biscuit, and carrying out sintering treatment to obtain the porous ceramic matrix. According to the method, the porous ceramic matrix meeting the porosity and the median aperture required by the gasoline engine particulate filter can be prepared, and the porous ceramic matrix is high in structural stability and small in dimensional tolerance, has high strength and cannot be damaged in the packaging and vehicle running process.

Description

Technical Field

[0001] The invention belongs to the technical field of gasoline engine tail gas emission control, and relates to a porous ceramic matrix and a preparation method and application thereof. Background Art

[0002] Gasoline engines have always only used a three-way catalyst (TWC) for exhaust after-treatment to meet emission standards for the three major types of harmful gases they emit: carbon monoxide, hydrocarbons, and nitrogen oxides. However, when emission regulations reached National VI B, even small amounts of solid particulate matter (PM) emitted by gasoline engines exceeded regulatory limits. This necessitated the installation of a wall-flow honeycomb ceramic filter, also known as a gasoline particulate filter (GPF), in the after-treatment system to filter PM from the exhaust. When PM accumulates to a certain level in the carrier and affects engine power, the GPF needs to be regenerated to restore the filter to its original state.

[0003] Unlike the DPF in the diesel engine after-treatment system, due to the limited installation space left for the after-treatment system in passenger cars, the GPF must be coated with a three-way catalyst in addition to the catalyst required for regeneration. Therefore, the porosity of the GPF product is required to be 60%-65%, and the median pore size is required to be 18μm-25μm.

[0004] CN119430997A discloses a gasoline engine particulate filter with low back pressure increase and narrow pore size distribution and a preparation method thereof. The preparation process of the gasoline engine particulate filter comprises the following steps: mixing an inorganic raw material, a pore-forming agent, a binder and water to prepare a mud material; kneading the mud, extruding, microwave drying and high-temperature firing to obtain a ceramic matrix; and plugging the pores of the ceramic matrix and coating it with a catalyst to obtain the gasoline engine particulate filter.

[0005] CN108358652A discloses a method for preparing a ceramic filter element for a gasoline engine particulate filter with a pore gradient structure. The pore gradient fiber porous ceramic filter element is prepared by mixing ceramic fibers of varying aspect ratios with a high-temperature binder solution. The fibers are then batch-formed in descending order of aspect ratio using a vacuum filtration method that involves sedimentation and accumulation, followed by single-stage drainage. The pore gradient fiber porous ceramic filter element is then microwave-dried and heat-treated to obtain the filter element, which is then loaded with a catalyst for low-temperature regeneration.

[0006] The gasoline engine particulate filter or porous ceramic filter described in the above solution has poor structural stability and low strength, which makes it easy to be damaged during packaging or vehicle operation. Summary of the Invention

[0007] The purpose of the present invention is to provide a porous ceramic substrate, a preparation method and application thereof. The method of the present invention can produce a porous ceramic substrate that meets the porosity and median pore size required by a gasoline engine particulate filter. The porous ceramic substrate has high structural stability, small dimensional tolerance, high strength, and will not be damaged during packaging and vehicle operation.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a porous ceramic substrate, the method comprising the following steps:

[0010] (1) talc, aluminum source, washed kaolin, calcined kaolin and fused quartz powder are first mixed to obtain a mixed inorganic powder, the mixed inorganic powder, a pore-forming agent and a binder are second mixed to obtain a mixed precursor material, and the mixed precursor material is kneaded to obtain a mud material;

[0011] (2) The clay material is molded to obtain a green body, the green body is pore-blocked, and then fired to obtain the porous ceramic matrix.

[0012] The present invention pre-mixes the inorganic powders thoroughly before adding the pore-forming agent and binder for mixing, ensuring uniform powder mixing and preventing the problem of powder temperature rise. The talc powder of the present invention is used as the crystal nucleus raw material for synthesizing cordierite. The oriented arrangement of its plate-like structure guides the C-axis of the cordierite crystals synthesized during the firing process to align in the direction of product extrusion, thereby ensuring that the thermal expansion coefficient of the porous ceramic matrix obtained by firing is less than 0.8×10 -6 / °C. Fine-particle aluminum hydroxide is introduced into the aluminum source to enhance the reactivity of alumina and increase the content of cordierite synthesized during the firing process, thereby ensuring the product's thermal shock resistance temperature exceeds 650°C. Alumina also has high refractoriness, and any residual alumina in the product enhances its refractoriness. Washed kaolin is plastic. During the firing process, after temperatures reach 200°C, the organic binder in the green body is completely burned away, no longer providing strength. At this point, the porous structure's strength relies entirely on the plasticity of the washed kaolin, preventing collapse due to its own weight. Meanwhile, unreacted kaolin synthesizes mullite, enhancing the overall strength of the porous ceramic. Fused quartz powder undergoes frequent transformations during the firing process, effectively regulating the product's firing shrinkage. This shrinkage is inversely proportional to the amount of fused quartz powder used. Therefore, adjusting the proportion of fused quartz powder in the formulation can reduce firing shrinkage, thereby reducing the risk of dimensional deviations. The method of the present invention can produce a porous ceramic matrix with small dimensional tolerance, high strength and high thermal shock resistance temperature through the synergistic effect of various materials under appropriate conditions.

[0013] Preferably, the median particle size D50 of the talc powder in step (1) is 25 μm to 35 μm, for example, 25 μm, 28 μm, 30 μm, 32 μm or 35 μm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0014] Controlling the median particle size of the talc powder of the present invention within the above range can increase the pore size of the porous ceramic matrix.

[0015] Preferably, the talc powder in step (1) contains iron oxide and titanium oxide.

[0016] In order to ensure the strength of products with high porosity and large pore size, the talc powder, washed kaolin and / or calcined kaolin used in the present invention must contain iron oxide and titanium oxide.

[0017] Preferably, based on the mass of the talc powder being 100%, the mass fraction of the iron oxide is 1% to 2.5%, for example, 1%, 1.5%, 1.8%, 2% or 2.5%, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0018] Preferably, based on the mass of the talc powder being 100%, the mass fraction of the titanium oxide is 1.5% to 3.5%, for example, 1.5%, 2%, 2.5%, 3% or 3.5%, etc., and is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0019] Preferably, the aluminum source in step (1) includes calcined aluminum oxide and aluminum hydroxide.

[0020] The invention dopes aluminum hydroxide into the calcined aluminum oxide to improve the reaction activity of the calcined aluminum oxide during the calcining process.

[0021] Preferably, the mass ratio of the calcined alumina to aluminum hydroxide is (0.5-2):1, for example: 0.5:1, 0.8:1, 1:1, 1.5:1 or 2:1, etc., and is not limited to the listed values. Other unlisted values within this numerical range are also applicable.

[0022] Preferably, the median particle size D50 of the calcined alumina is 15 μm to 25 μm, for example, 15 μm, 18 μm, 20 μm, 22 μm or 25 μm, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0023] Preferably, the median particle size D50 of the aluminum hydroxide is 0.5 μm to 1.5 μm, for example, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm or 1.5 μm, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0024] Preferably, the median particle size D50 of the washed kaolin in step (1) is 1.5 μm to 2.5 μm, for example, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm or 2.5 μm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0025] Preferably, the median particle size D50 of the calcined kaolin in step (1) is 0.5 μm to 1.5 μm, for example, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm or 1.5 μm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0026] Preferably, the washed kaolin and / or calcined kaolin in step (1) contains iron oxide and titanium oxide.

[0027] Preferably, based on the mass of the washed kaolin and / or calcined kaolin being 100%, the mass fraction of the iron oxide is 0.5% to 1.5%, for example, 0.5%, 0.8%, 1%, 1.2% or 1.5%, etc., and is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0028] Preferably, based on the mass of the washed kaolin and / or calcined kaolin being 100%, the mass fraction of the titanium oxide is 0.8% to 2%, for example: 0.8%, 1%, 1.2%, 1.5% or 2%, etc., and is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0029] The washed kaolin and / or calcined kaolin of the present invention contains iron oxide and titanium oxide, i.e., at least one of the washed kaolin and the calcined kaolin contains iron oxide and titanium oxide. For example, the washed kaolin may contain iron oxide and titanium oxide, the calcined kaolin may contain iron oxide and titanium oxide, or both may contain iron oxide and titanium oxide. The mass proportions of the iron oxide and titanium oxide are the independent mass proportions in the washed kaolin and / or calcined kaolin. For example, the washed kaolin may contain 1% iron oxide and 5% titanium oxide, while the calcined kaolin does not contain iron oxide and titanium oxide.

[0030] Preferably, the median particle size D50 of the fused quartz powder in step (1) is 4 μm to 6 μm, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0031] Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the talc powder is 37% to 40%, for example, 37%, 37.5%, 38%, 39% or 40%, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0032] Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the aluminum source is 30% to 35%, for example: 30%, 31%, 32%, 34% or 35%, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0033] Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the washed kaolin is 8% to 20%, for example, 8%, 10%, 12%, 15% or 20%, etc., and is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0034] Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the calcined kaolin is 1% to 23%, for example, 1%, 5%, 10%, 15% or 23%, etc., and is not limited to the listed values, and other values not listed within this numerical range are also applicable.

[0035] Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the fused quartz powder is 12% to 20%, for example, 12%, 15%, 16%, 18% or 20%, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0036] In the present invention, controlling the mass proportion of the fused quartz powder in the mixed inorganic powder within the above range can reduce the shrinkage rate of the product during firing, ensuring that the dimensional tolerance of the one-piece molded product meets ±0.5 mm.

[0037] Preferably, the first mixing method in step (1) includes crushing and weightless mixing.

[0038] Preferably, the first mixing time in step (1) is 2 min to 5 min, for example, 2 min, 2.5 min, 3 min, 4 min or 5 min, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0039] Preferably, the speed of the blades of the first mixing in step (1) is 40 rpm to 60 rpm, for example, 40 rpm, 45 rpm, 50 rpm, 55 rpm or 60 rpm, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0040] Preferably, in step (1), the rotation speed of the first mixing crushing rod is 2000rpm to 3000rpm, for example, 2000rpm, 2200rpm, 2500rpm, 2800rpm or 3000rpm, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0041] The crushing and weightless mixing of the present invention is mixing using a weightless mixer with a crushing rod.

[0042] Preferably, the pore-forming agent in step (1) comprises any one or a combination of at least two of starch, polymethyl methacrylate powder or acrylic resin foam beads. Typical but non-limiting combinations include a combination of starch and polymethyl methacrylate powder, a combination of polymethyl methacrylate powder and acrylic resin foam beads, or a combination of starch and acrylic resin foam beads.

[0043] Preferably, the median particle size D50 of the pore-forming agent in step (1) is 25 μm to 35 μm, for example, 25 μm, 28 μm, 30 μm, 32 μm or 35 μm, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0044] Preferably, the volume ratio of the pore-forming agent to the mixed inorganic powder in step (1) is (0.4-0.6):1, for example: 0.4:1, 0.45:1, 0.5:1, 0.55:1 or 0.6:1, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0045] Preferably, the binder in step (1) comprises hydroxypropyl methylcellulose.

[0046] Preferably, the viscosity of the hydroxypropyl methylcellulose is 4000 mPa·s to 20000 mPa·s, for example, 4000 mPa·s, 5000 mPa·s, 10000 mPa·s, 15000 mPa·s or 20000 mPa·s, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0047] Preferably, the mass ratio of the binder to the mixed inorganic powder in step (1) is (0.05-0.08):1, for example: 0.05:1, 0.055:1, 0.06:1, 0.07:1 or 0.08:1, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0048] Preferably, a dispersant and a water-soluble liquid lubricant are added during the kneading process in step (1).

[0049] Preferably, the dispersant comprises water.

[0050] Preferably, the mass ratio of the mixed precursor material to the dispersant is 1:(0.25-0.3), for example: 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29 or 1:0.3, etc., and is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0051] Preferably, the water-soluble liquid lubricant includes any one or a combination of at least two of potassium laurate, polyvinyl alcohol or polyethylene glycol. Typical but non-limiting combinations include a combination of potassium laurate and polyvinyl alcohol, a combination of polyvinyl alcohol and polyethylene glycol, or a combination of potassium laurate and polyethylene glycol.

[0052] Preferably, the mass ratio of the mixed precursor material to the water-soluble liquid lubricant is 1:(0.01-0.03), for example: 1:0.01, 1:0.015, 1:0.02, 1:0.025 or 1:0.03, etc., and is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0053] Preferably, the median particle size D50 of the particles in the mud material in step (1) is 5nm to 50nm, for example: 5nm, 8nm, 10nm, 20nm or 50nm, etc., not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0054] Preferably, the clay material is screened before the molding process in step (2).

[0055] Preferably, the filter net used in the screen processing includes a bottom net and a screen net arranged on the bottom net.

[0056] Preferably, the mesh number of the bottom net is 10-30 meshes, for example, 10 meshes, 20 meshes or 30 meshes, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0057] Preferably, the mesh size of the sieve is 100-120 meshes, for example, 100 meshes, 110 meshes or 120 meshes, etc., and is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0058] Preferably, the extrusion pressure of the screen treatment is ≥7 MPa.

[0059] Preferably, the number of times of the network processing is 3 to 5 times, for example: 3 times, 4 times or 5 times.

[0060] The interval time between each screen treatment of the present invention is greater than 12 hours, and the mud material is sealed and stored in a closed environment with a humidity of 70% to 90% and a temperature of 30° C. to 40° C. during the screen interval.

[0061] The meshing method of the present invention can improve the arrangement of the flaky kaolin and plate-shaped talc particles in the mud material into as many fixed shapes as possible.

[0062] Preferably, after the molding process in step (2), a water-retaining agent is applied to the surface of the blank and then dried.

[0063] The molding process described in this invention utilizes die plastic extrusion. To further align the flaky kaolin and talc particles in the extrusion direction, a porous plate with a diameter of 5 to 8 mm is installed 300 to 500 mm from the front end of the die. This plate is topped with a layer of 100-mesh screen and a layer of 20-mesh screen. To enhance product strength, the outer skin thickness is controlled, ranging from 1.5 to 3 times the lattice wall thickness.

[0064] Preferably, the water retaining agent comprises any one of diesel, gasoline or white oil or a combination of at least two thereof. Typical but non-limiting combinations include a combination of diesel and white oil, a combination of gasoline and white oil, or a combination of diesel and gasoline.

[0065] The water-retaining agent of the present invention can ensure that the outer skin of the green body will not wrinkle or crack during the drying process.

[0066] Preferably, the drying method comprises microwave drying.

[0067] Preferably, after the drying process, the moisture content of the green body is 1% to 2%, for example, 1%, 1.2%, 1.5%, 1.8% or 2%, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0068] Preferably, the blank is cut before the hole plugging process in step (2).

[0069] The green blank before plugging the hole is cut on both sides according to the height of the firing shrinkage ruler.

[0070] Preferably, the pore plugging treatment in step (2) includes sequentially performing laser drilling and printing-type scraping of mud material.

[0071] The blank after plugging the holes of the present invention is fired in a kiln. The blank needs to be placed on a kiln tool and a 10mm-15mm gasket cut from a product of the same specification is added.

[0072] Preferably, the temperature of the calcination treatment in step (2) is 1425°C to 1440°C, for example: 1425°C, 1428°C, 1430°C, 1435°C or 1440°C, etc., and is not limited to the listed values. Other values not listed within this numerical range are also applicable.

[0073] Preferably, the calcination treatment time in step (2) is 8 h to 12 h, for example, 8 h, 9 h, 10 h, 11 h or 12 h, etc., and is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0074] In a second aspect, the present invention provides a porous ceramic substrate, which is prepared by the preparation method described in the first aspect.

[0075] In a third aspect, the present invention provides a gasoline engine particulate filter, which comprises the porous ceramic substrate as described in the second aspect.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) The method of the present invention can produce a porous ceramic substrate that meets the porosity and median pore size required for a gasoline engine particulate filter. The porous ceramic substrate has high structural stability, small dimensional tolerance, high strength, and will not be damaged during packaging and vehicle operation.

[0078] (2) The method of the present invention controls the addition amount of each raw material and the preparation conditions to obtain a porous ceramic matrix with a thermal expansion coefficient of 0.3×10 -6 / ℃~0.6×10 -6 / ℃, the thermal shock temperature can reach above 750℃, the median pore diameter is within 20μm~24μm, the porosity is within 62%~64%, and while meeting the requirements of gasoline engine particulate filter, the isostatic strength can reach above 3.4MPa, and the dimensional tolerance is controlled within ±0.42mm. DETAILED DESCRIPTION

[0079] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0080] The brands and models of raw materials used in the examples and comparative examples of the present invention are as follows:

[0081] Talc powder (Mengdu M45), calcined alumina (China Aluminum Corporation HA-20), aluminum hydroxide (Shandong Aluminum Corporation FM-01), washed kaolin (Yingceramics LL), calcined kaolin (Datong Jinyuan JY-105) and fused quartz powder (Lianrui New Materials GG-152).

[0082] Example 1

[0083] This embodiment provides a porous ceramic substrate, and the preparation method of the porous ceramic substrate is as follows:

[0084] (1) Talc powder with a median particle size D50 of 30 μm (containing 1.5% by mass of iron oxide and 2.5% by mass of titanium oxide), an aluminum source (including calcined alumina with a median particle size D50 of 20 μm and aluminum hydroxide with a median particle size D50 of 1 μm, the mass ratio of calcined alumina to aluminum hydroxide being 1:1), washed kaolin with a median particle size D50 of 2 μm (containing 1% by mass of iron oxide and 1.5% by mass of titanium oxide), calcined kaolin with a median particle size D50 of 1 μm and fused silica powder with a median particle size D50 of 5 μm were mixed in a mass ratio of 38:32:10:8:12 to obtain a mixture. The invention relates to a method for preparing a slurry of inorganic powder, mixing the mixed inorganic powder, starch having a median particle size D50 of 30 μm and hydroxypropyl methylcellulose having a viscosity of 10,000 mPa·s to obtain a mixed precursor material, kneading the mixed precursor material, adding water and potassium laurate during the kneading process to obtain a slurry of particles having a median particle size D50 of 20 nm, wherein the volume ratio of starch to the mixed inorganic powder is 0.5:1, the mass ratio of hydroxypropyl methylcellulose to the mixed inorganic powder is 0.06:1, the mass ratio of the mixed precursor material to water is 1:0.27, and the mass ratio of the mixed precursor material to potassium laurate is 1:0.02;

[0085] (2) The clay material is screened using a filter consisting of a 120-mesh screen and a 20-mesh bottom screen. The extrusion pressure is 8 MPa, and the clay material is screened four times with an interval of 15 hours between each screen. During the interval between screens, the clay material must be sealed and stored in a closed environment with a humidity of 80% and a temperature of 35°C. After the screen treatment, the clay material is plastically extruded using a mold. After obtaining the blank, diesel is evenly sprayed on its surface. After microwave drying, the blank with a moisture content of 1.25% is obtained. Double-sided cutting is performed according to the height of the firing shrinkage ruler. The cut blank is plugged by laser drilling + printing and scraping the clay material. After plugging, the blank is placed on the kiln furniture and a 12 mm gasket cut from the same specification product is added. The blank is fired at 1430°C for 10 hours to obtain the porous ceramic matrix.

[0086] Example 2

[0087] This embodiment provides a porous ceramic substrate, and the preparation method of the porous ceramic substrate is as follows:

[0088] (1) Talc powder with a median particle size D50 of 25 μm (containing 2.5% by mass of iron oxide and 1.5% by mass of titanium oxide), an aluminum source (including calcined alumina with a median particle size D50 of 15 μm and aluminum hydroxide with a median particle size D50 of 0.5 μm, the mass ratio of calcined alumina to aluminum hydroxide being 1:0.5), washed kaolin with a median particle size D50 of 1.5 μm, calcined kaolin with a median particle size D50 of 0.5 μm (containing 1.5% by mass of iron oxide and 0.8% by mass of titanium oxide) and fused silica powder with a median particle size D50 of 6 μm were mixed in a mass ratio of 40:32:10:4:1. 4. Mixing to obtain a mixed inorganic powder, mixing the mixed inorganic powder, starch having a median particle size D50 of 35 μm and hydroxypropyl methylcellulose having a viscosity of 4000 mPa·s to obtain a mixed precursor material, kneading the mixed precursor material, adding water and potassium laurate during the kneading process to obtain a slurry having a median particle size D50 of 50 nm, wherein the volume ratio of starch to the mixed inorganic powder is 0.6:1, the mass ratio of hydroxypropyl methylcellulose to the mixed inorganic powder is 0.08:1, the mass ratio of the mixed precursor material to water is 1:0.3, and the mass ratio of the mixed precursor material to potassium laurate is 1:0.03;

[0089] (2) The clay material is screened using a filter consisting of a 100-mesh screen and a 20-mesh bottom screen. The extrusion pressure is 8 MPa, and the clay material is screened 4 times with an interval of 15 hours between each screen. During the interval between screens, the clay material must be sealed and stored in a closed environment with a humidity of 80% and a temperature of 35°C. After the screen treatment, the clay material is plastically extruded using a mold. After obtaining the blank, diesel is evenly sprayed on its surface. After microwave drying, the blank with a moisture content of 1.18% is obtained. Double-sided cutting is performed according to the height of the firing shrinkage ruler. The cut blank is plugged by laser drilling + printing and scraping the clay material. After plugging, the blank is placed on the kiln and a 12 mm gasket cut from the same specification product is added. The blank is fired at 1440°C for 8 hours to obtain the porous ceramic matrix.

[0090] Example 3

[0091] This embodiment provides a porous ceramic substrate, and the preparation method of the porous ceramic substrate is as follows:

[0092] (1) Talc powder with a median particle size D50 of 35 μm (containing 1% by mass of iron oxide and 3.5% by mass of titanium oxide), an aluminum source (comprising calcined alumina with a median particle size D50 of 25 μm and aluminum hydroxide with a median particle size D50 of 1.5 μm, with the mass ratio of calcined alumina to aluminum hydroxide being 0.5:1), washed kaolin with a median particle size D50 of 2.5 μm, calcined kaolin with a median particle size D50 of 1.5 μm (containing 0.5% by mass of iron oxide and 2% by mass of titanium oxide), and fused silica powder with a median particle size D50 of 4 μm were mixed in a mass ratio of 38:35:8:6:13. A mixed inorganic powder is obtained, the mixed inorganic powder, starch having a median particle size D50 of 25 μm, and hydroxypropyl methylcellulose having a viscosity of 20,000 mPa·s are mixed to obtain a mixed precursor material, the mixed precursor material is kneaded, water and potassium laurate are added during the kneading process, and a slurry having a median particle size D50 of 5 nm is obtained, wherein the volume ratio of starch to the mixed inorganic powder is 0.4:1, the mass ratio of hydroxypropyl methylcellulose to the mixed inorganic powder is 0.05:1, the mass ratio of the mixed precursor material to water is 1:0.25, and the mass ratio of the mixed precursor material to potassium laurate is 1:0.01;

[0093] (2) The clay material is screened using a filter consisting of a 100-mesh screen and a 20-mesh bottom screen. The extrusion pressure is 8 MPa, and the clay material is screened 4 times with an interval of 15 hours between each screen. During the interval between screens, the clay material must be sealed and stored in a closed environment with a humidity of 80% and a temperature of 35°C. After the screen treatment, the clay material is plastically extruded using a mold. After obtaining the blank, diesel is evenly sprayed on its surface. After microwave drying, the blank with a moisture content of 1.1% is obtained. Double-sided cutting is performed according to the height of the firing shrinkage ruler. The cut blank is plugged by laser drilling + printing and scraping the clay material. After plugging, the blank is placed on the kiln furniture and a 12 mm gasket cut from the same specification product is added. The blank is fired at 1425°C for 12 hours to obtain the porous ceramic matrix.

[0094] Example 4

[0095] The only difference between this embodiment and embodiment 1 is that the talc does not contain iron oxide and titanium oxide. Other conditions and parameters are exactly the same as those in embodiment 1.

[0096] Example 5

[0097] The only difference between this embodiment and embodiment 1 is that the washed kaolin does not contain iron oxide and titanium oxide. Other conditions and parameters are exactly the same as those in embodiment 1.

[0098] Example 6

[0099] The only difference between this embodiment and embodiment 1 is that the mass fraction of the fused quartz powder in the mixed inorganic powder is 10% (the missing portion is replaced with talc powder of equal mass), and the other conditions and parameters are exactly the same as those in embodiment 1.

[0100] Example 7

[0101] The only difference between this embodiment and embodiment 1 is that the mass fraction of the fused quartz powder in the mixed inorganic powder is 25% (the amount of talc added is reduced to maintain mass balance), and the other conditions and parameters are exactly the same as those in embodiment 1.

[0102] Example 8

[0103] The only difference between this embodiment and embodiment 1 is that the median particle size D50 of the talc powder is 20 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0104] Example 9

[0105] The only difference between this embodiment and embodiment 1 is that the median particle size D50 of the talc powder is 40 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0106] Example 10

[0107] The only difference between this embodiment and embodiment 1 is that the median particle size D50 of the calcined alumina is 10 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0108] Example 11

[0109] The only difference between this embodiment and embodiment 1 is that the median particle size D50 of the calcined alumina is 30 μm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0110] Comparative Example 1

[0111] The only difference between this comparative example and Example 1 is that no washed kaolin is added (the missing part is replaced with calcined kaolin of equal mass), and other conditions and parameters are exactly the same as those in Example 1.

[0112] Comparative Example 2

[0113] The only difference between this comparative example and Example 1 is that calcined kaolin is not added (the missing part is replaced with washed kaolin of equal mass), and other conditions and parameters are exactly the same as those in Example 1.

[0114] Comparative Example 3

[0115] The only difference between this comparative example and Example 1 is that no fused quartz powder is added (the missing part is replaced with calcined kaolin of equal mass), and other conditions and parameters are exactly the same as those in Example 1.

[0116] Performance testing:

[0117] The porous ceramic substrates obtained in the examples and comparative examples were tested:

[0118] Thermal expansion coefficient: Xiangtan Xiangyi PCY-G high-precision thermal expansion instrument; thermal shock resistance temperature: Luoyang Hengli HLX-12 muffle furnace; median pore diameter and porosity: Quantachrome PoreMaster 33 fully automatic mercury intrusion instrument; isostatic strength: Suzhou Qiantong Instrument QT-5100S isostatic press. The test results are shown in Table 1:

[0119] Table 1

[0120]

[0121]

[0122] As can be seen from Table 1, from Examples 1-3, the method of the present invention can control the addition amount of each raw material and the preparation conditions to obtain a porous ceramic matrix with a thermal expansion coefficient of

[0123] 0.3×10 -6 / ℃~0.6×10 -6 / ℃, the thermal shock temperature can reach above 750℃, the median pore diameter is within 20μm~24μm, the porosity is within 62%~64%, and while meeting the requirements of gasoline engine particulate filter, the isostatic strength can reach above 3.4MPa, and the dimensional tolerance is controlled within ±0.42mm.

[0124] From the comparison between Example 1 and Examples 4-5, it can be seen that the present invention uses talc powder composed of iron oxide and titanium oxide and washed kaolin and / or calcined kaolin to obtain a large-pore, high-strength ceramic material while ensuring the high porosity of the ceramic material. If iron oxide and titanium oxide are not contained, the strength of the material will be greatly reduced.

[0125] By comparing Example 1 with Examples 6-7, it can be seen that in the preparation process of the inorganic ceramic material described in the present invention, the amount of fused quartz powder added to the mixed inorganic powder will affect its performance. When the mass fraction of the fused quartz powder in the mixed inorganic powder is controlled at 12% to 20%, the performance of the inorganic ceramic material obtained is better. If the mass fraction of the fused quartz powder in the mixed inorganic powder is too low, the porous ceramic matrix obtained will shrink too much during firing, resulting in a significant increase in the dimensional tolerance. If the mass fraction of the fused quartz powder in the mixed inorganic powder is too high, the thermal expansion coefficient of the porous ceramic matrix obtained will be significantly increased due to the high amount of residual silicon dioxide after the reaction, and the thermal shock resistance temperature will also be significantly decreased.

[0126] By comparing Example 1 with Examples 8-9, it can be seen that during the preparation process of the inorganic ceramic material described in the present invention, the median particle size D50 of the talc powder will affect its performance. When the median particle size D50 of the talc powder is controlled within 25μm to 35μm, the performance of the inorganic ceramic material obtained is better. If the median particle size D50 of the mixed talc powder is too small, the expansion coefficient of the obtained porous ceramic matrix increases and the thermal shock resistance temperature decreases due to the decrease in the directional arrangement ratio of the talc; if the median particle size D50 of the talc powder is too large, the talc powder particles cannot be peeled into a plate-like structure, and the expansion coefficient of the obtained porous ceramic matrix increases and the thermal shock resistance temperature decreases due to the decrease in the directional arrangement ratio of the talc.

[0127] By comparing Example 1 and Examples 10-11, it can be seen that during the preparation process of the inorganic ceramic material described in the present invention, the median particle size D50 of the calcined alumina will affect its performance. When the median particle size D50 of the calcined alumina is controlled within 25μm to 35μm, the performance of the inorganic ceramic material obtained is better. If the median particle size D50 of the calcined alumina is too small, the reaction activity will be improved, and the thermal expansion coefficient and thermal shock resistance temperature of the product will be improved, but the median pore size of the product will be significantly reduced; if the median particle size D50 of the calcined alumina is too large, the thermal expansion coefficient and thermal shock resistance temperature of the product will be significantly deteriorated, and the median pore size of the product will also be significantly increased, exceeding the upper limit of the specification.

[0128] From the comparison between Example 1 and Comparative Example 1, it can be seen that washed kaolin is added during the preparation of the inorganic ceramic material of the present invention. The washed kaolin has plasticity and can obtain a honeycomb structure after kneading. Once the washed kaolin is not in the formula, the porous green body will lose strength after the organic binder is fired, and collapse due to its own weight will occur.

[0129] A comparison between Example 1 and Comparative Example 2 demonstrates that the addition of calcined kaolin during the preparation of the inorganic ceramic material of the present invention can partially replace the function of washed kaolin, thereby reducing the amount of washed kaolin required. However, when using only washed kaolin, the product can experience severe firing cracking, resulting in significantly larger dimensional tolerances.

[0130] A comparison between Example 1 and Comparative Example 3 demonstrates that the addition of fused quartz powder during the preparation of the inorganic ceramic material of the present invention reduces the product's firing shrinkage due to crystal phase transformation during firing. Without fused quartz in the formulation, the product's firing shrinkage is significantly increased, significantly increasing the product's dimensional tolerances.

[0131] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection 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 those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a porous ceramic substrate, characterized in that: The preparation method comprises the following steps: (1) talc, aluminum source, washed kaolin, calcined kaolin and fused quartz powder are first mixed to obtain a mixed inorganic powder, the mixed inorganic powder, a pore-forming agent and a binder are second mixed to obtain a mixed precursor material, and the mixed precursor material is kneaded to obtain a mud material; (2) The clay material is molded to obtain a green body, the green body is pore-blocked, and then fired to obtain the porous ceramic matrix.

2. The preparation method according to claim 1, wherein The median particle size D50 of the talc powder in step (1) is 25 μm to 35 μm; Preferably, the talc powder in step (1) contains iron oxide and titanium oxide; Preferably, based on the mass of the talc powder being 100%, the mass fraction of the iron oxide is 1% to 2.5%; Preferably, based on the mass of the talc powder being 100%, the mass fraction of the titanium oxide is 1.5% to 3.5%; Preferably, the aluminum source in step (1) comprises calcined aluminum oxide and aluminum hydroxide; Preferably, the mass ratio of the calcined alumina to aluminum hydroxide is (0.5-2):1; Preferably, the median particle size D50 of the calcined alumina is 15 μm to 25 μm; Preferably, the median particle size D50 of the aluminum hydroxide is 0.5 μm to 1.5 μm; Preferably, the median particle size D50 of the washed kaolin in step (1) is 1.5 μm to 2.5 μm; Preferably, the median particle size D50 of the calcined kaolin in step (1) is 0.5 μm to 1.5 μm; Preferably, the washed kaolin and / or calcined kaolin in step (1) contains iron oxide and titanium oxide; Preferably, based on the mass of the washed kaolin and / or calcined kaolin being 100%, the mass fraction of the iron oxide is 0.5% to 1.5%; Preferably, based on the mass of the washed kaolin and / or calcined kaolin being 100%, the mass fraction of the titanium oxide is 0.8% to 2%; Preferably, the median particle size D50 of the fused quartz powder in step (1) is 4 μm to 6 μm.

3. The preparation method according to claim 1 or 2, wherein Based on the mass of the mixed inorganic powder being 100%, the mass fraction of the talc powder is 37% to 40%; Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the aluminum source is 30% to 35%; Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the washed kaolin is 8% to 20%; Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the calcined kaolin is 1% to 23%; Preferably, based on the mass of the mixed inorganic powder being 100%, the mass fraction of the fused quartz powder is 12% to 20%; Preferably, the first mixing method in step (1) includes crushing and weightless mixing; Preferably, the first mixing time in step (1) is 2 min to 5 min; Preferably, the speed of the first mixing blade in step (1) is 40 rpm to 60 rpm; Preferably, the rotation speed of the crushing rod of the first mixing in step (1) is 2000 rpm to 3000 rpm.

4. The preparation method according to any one of claims 1 to 3, wherein The pore-forming agent in step (1) comprises any one of starch, polymethyl methacrylate powder or acrylic resin foam beads, or a combination of at least two thereof; Preferably, the median particle size D50 of the pore-forming agent in step (1) is 25 μm to 35 μm; Preferably, the volume ratio of the pore-forming agent to the mixed inorganic powder in step (1) is (0.4-0.6):1; Preferably, the binder in step (1) comprises hydroxypropyl methylcellulose; Preferably, the viscosity of the hydroxypropyl methylcellulose is 4000 mPa·s to 20000 mPa·s; Preferably, the mass ratio of the binder to the mixed inorganic powder in step (1) is (0.05-0.08):

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that During the kneading process of step (1), a dispersant and a water-soluble liquid lubricant are added; Preferably, the dispersant comprises water; Preferably, the mass ratio of the mixed precursor material to the dispersant is 1:(0.25-0.3); Preferably, the water-soluble liquid lubricant comprises any one or a combination of at least two of potassium laurate, polyvinyl alcohol or polyethylene glycol; Preferably, the mass ratio of the mixed precursor material to the water-soluble liquid lubricant is 1:(0.01-0.03).

6. The preparation method according to any one of claims 1 to 5, characterized in that Before the molding process in step (2), the clay material is passed through a mesh; Preferably, the filter net used in the screen processing includes a bottom net and a screen provided on the bottom net; Preferably, the mesh number of the bottom net is 10 to 30 meshes; Preferably, the mesh size of the sieve is 100-120 mesh; Preferably, the extrusion pressure of the screen treatment is ≥7 MPa; Preferably, the number of times of the network processing is 3 to 5 times.

7. The preparation method according to any one of claims 1 to 6, characterized in that After the molding process in step (2), a water-retaining agent is applied to the surface of the blank and the blank is dried; Preferably, the water retaining agent comprises any one of diesel, gasoline or white oil or a combination of at least two thereof; Preferably, the drying method comprises microwave drying; Preferably, after the drying process, the moisture content of the green body is 1% to 2%; Preferably, the blank is cut before the hole plugging process in step (2); Preferably, the pore plugging treatment in step (2) includes sequentially performing laser drilling and printing-type scraping of mud material.

8. The preparation method according to any one of claims 1 to 7, wherein The temperature of the sintering treatment in step (2) is 1425° C. to 1440° C.; Preferably, the calcination treatment time in step (2) is 8 hours to 12 hours.

9. A porous ceramic substrate, characterized in that The porous ceramic substrate is prepared by the preparation method according to any one of claims 1 to 8.

10. A gasoline engine particulate filter, characterized in that: The gasoline engine particulate filter comprises the porous ceramic substrate according to claim 9.

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