Cordierite powder raw material, cordierite honeycomb ceramic and preparation method thereof

Abstract

The application relates to a cordierite powder raw material, a cordierite honeycomb ceramic and a preparation method thereof. The cordierite powder raw material comprises a cordierite forming raw material, the cordierite forming raw material comprises flaky talc, and the cordierite powder raw material satisfies the following relationship formula: F=D 50 / (T*Delta theta), 0.022 mu m / degree <= F <= 0.09 mu m / degree; wherein, D 50 is the median particle size of the cordierite forming raw material, the unit is mu m, T is the average ratio of diameter to thickness of the flaky talc, Delta theta is the difference between the angle of repose of the cordierite powder raw material and the angle of fall of the cordierite powder raw material, the unit is degree, 5 degrees <= Delta theta <= 22 degrees, thus, the cracking rate of the honeycomb ceramic green body can be reduced, and the mold abrasion is reduced.

Description

Technical Field

[0001] This application relates to the field of ceramic materials technology, and in particular to cordierite powder raw materials, cordierite honeycomb ceramics and their preparation methods. Background Technology

[0002] Cordierite honeycomb ceramics, due to their excellent thermal stability and low coefficient of thermal expansion, are widely used as carrier materials for automotive three-way catalytic converters (TWC) and selective catalytic reduction filters (SCR). Their preparation typically employs an extrusion molding process, where cordierite powder is uniformly mixed with binders, water, etc., and then extruded through a die to obtain a green body, which is then dried and sintered to produce the finished product. However, green bodies made from traditional cordierite powder have uneven density, are prone to longitudinal cracks, and experience increased die wear, affecting the yield and product consistency of cordierite honeycomb ceramics. Summary of the Invention

[0003] This application provides a cordierite powder raw material, cordierite honeycomb ceramics and a method for preparing the same, with the aim of reducing the cracking rate of the honeycomb ceramic green body and reducing mold wear.

[0004] A first aspect of this application provides a cordierite powder raw material, comprising cordierite forming raw materials, wherein the cordierite forming raw materials include flaky talc, and the cordierite powder raw material satisfies the following relationship: F=D 50 / (T×Δθ), 0.022μm / °≤F≤0.09μm / °;

[0005] Among them, D 50 The median particle size of the cordierite forming raw material is in μm; T is the average diameter-to-thickness ratio of the flaky talc; Δθ is the difference between the angle of repose and the angle of collapse of the cordierite powder raw material, in °, where 5°≤Δθ≤22°.

[0006] In some embodiments, 5μm≤D 50 ≤10μm.

[0007] In some embodiments, 2 ≤ T ≤ 15.

[0008] In some embodiments, 5°≤Δθ≤22°.

[0009] In some embodiments, the angle of repose of the cordierite powder raw material is 30°~50°.

[0010] In some embodiments, the collapse angle of the cordierite powder raw material is 18°~30°.

[0011] In some embodiments, the average diameter of the flaky talc is 10 μm to 25 μm.

[0012] In some embodiments, the average thickness of the flaky talc is 0.5 μm to 1.5 μm.

[0013] In some embodiments, the cordierite forming raw materials further include at least one of alumina and aluminum hydroxide and kaolin.

[0014] In some embodiments, the cordierite forming raw material further includes silicon dioxide.

[0015] In some embodiments, the cordierite forming raw material comprises the following components by mass percentage: 35%~43% flaky talc, 8%~34% alumina, 3%~16% aluminum hydroxide, 10%~45% kaolin and 2%~19% silica.

[0016] In some embodiments, the median particle size of the flaky talc is 5 μm to 16 μm.

[0017] In some embodiments, the median particle size of the alumina is 1 μm to 7 μm.

[0018] In some embodiments, the median particle size of the aluminum hydroxide is 2 μm to 8.5 μm.

[0019] In some embodiments, the median particle size of the kaolin is 4 μm to 9 μm.

[0020] In some embodiments, the median particle size of the silica is 1.5 μm to 9 μm.

[0021] In some embodiments, the cordierite powder raw material further includes at least one of a flow aid and a pore-forming agent.

[0022] In some embodiments, the flow aid includes one or more of stearic acid, polyvinyl alcohol, ammonium polyacrylate, and carboxymethyl cellulose.

[0023] In some embodiments, the mass percentage of the flow aid relative to the mass of the cordierite forming raw material is 0.1% to 5%.

[0024] A second aspect of this application provides a method for preparing cordierite honeycomb ceramics, comprising the following steps:

[0025] The preparation of honeycomb ceramic green body includes mixing cordierite powder raw material, lubricant, binder and water as described in the first aspect of this application, and then successively kneading and extruding the mixture.

[0026] The preparation of the cordierite honeycomb ceramic includes drying the honeycomb ceramic green body and then sintering it.

[0027] In some embodiments, the sintering temperature is 1350℃~1450℃, and the sintering time is 6h~10h.

[0028] In some embodiments, the sintering atmosphere includes an oxygen-containing atmosphere; optionally, the volume fraction of oxygen in the oxygen-containing atmosphere is 6% to 15%.

[0029] In some embodiments, the longitudinal crack rate of the honeycomb ceramic green body is less than or equal to 1%.

[0030] In some embodiments, the extrusion pressure fluctuation of the extrusion molding is less than or equal to 1 MPa.

[0031] In some embodiments, the wear of the die used in the extrusion molding is less than or equal to 1 μm per 5000 meters extruded.

[0032] In some embodiments, the mixing time is 10 min to 60 min.

[0033] In some embodiments, the lubricant is a block polyether with a mass fraction of 10% to 30%.

[0034] In some embodiments, the mass percentage of the lubricant relative to the mass of the cordierite powder raw material is 1% to 5%.

[0035] In some embodiments, the adhesive includes one or more of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and methyl cellulose.

[0036] In some embodiments, the mass percentage of the binder relative to the mass of the cordierite powder raw material is 5% to 10%.

[0037] A third aspect of this application provides a cordierite honeycomb ceramic, which is obtained by the preparation method of cordierite honeycomb ceramic described in the second aspect of this application.

[0038] In some embodiments, the porosity of the honeycomb ceramic is 14% to 36%.

[0039] In some embodiments, the coefficient of thermal expansion of the honeycomb ceramic at 800°C is 0.2 × 10⁻⁶. -6 ℃ -1 ~0.6×10 -6 ℃ -1 .

[0040] Compared with traditional technologies, the above-mentioned cordierite powder raw materials have at least the following advantages:

[0041] By controlling the median particle size D of the cordierite raw material 50The average aspect ratio of flaky talc and the difference Δθ between the angle of repose and the angle of collapse of cordierite powder raw material satisfy F=D 50 / (T×Δθ), and 0.022μm / °≤F≤0.09μm / °, can determine the composition of the cordierite raw material (i.e., D). 50 The key flaky talc raw material (i.e., average diameter-to-thickness ratio) and the macroscopic flowability index (i.e., Δθ) of cordierite forming raw material are correlated, allowing for more precise control and improvement of the flowability of cordierite powder raw material. This enhances the density uniformity and extrusion molding stability of honeycomb ceramic green bodies, thereby reducing the green body cracking rate and extrusion molding die wear of honeycomb ceramics. Detailed Implementation

[0042] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0043] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," and "third" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0044] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0045] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0047] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise expressly specified.

[0048] The system of cordierite powder raw materials is complex, with significant differences in the morphology of each component. For example, talc and kaolin are usually in the form of flakes, while silica and alumina are mostly in the form of granules or polygons. The particle size distribution and particle shape of different raw materials are intertwined, which makes the flow behavior of cordierite powder raw materials nonlinear. Simply controlling the particle size of a single raw material or adding additives makes it difficult to ensure the density uniformity and extrusion molding stability of the green body made from cordierite powder raw materials. As a result, cordierite honeycomb ceramics have long faced technical bottlenecks such as high green body cracking rate and large mold wear.

[0049] Based on this, the first aspect of this application provides a cordierite powder raw material, comprising cordierite forming raw materials, wherein the cordierite forming raw materials include flaky talc, and the cordierite powder raw material satisfies the following relationship: F=D 50 / (T×Δθ), 0.022μm / °≤F≤0.09μm / °;

[0050] Among them, D 50 The median particle size of the cordierite raw material is expressed in μm. T is the average diameter-to-thickness ratio of the flaky talc. Δθ is the difference between the angle of repose and the angle of collapse of the cordierite powder raw material, expressed in °, where 5°≤Δθ≤22°.

[0051] In this application, cordierite forming raw material refers to the raw material composition used to form cordierite, which includes a magnesium source, an aluminum source and a silicon source to meet the chemical formula requirements of cordierite.

[0052] In this application, the median particle size D of the cordierite forming raw material is... 50 This refers to the particle size corresponding to a cumulative particle size distribution percentage of 50% for the raw materials; D 50 The larger the value, the better the flowability of the cordierite powder.

[0053] In this application, the diameter-to-thickness ratio of the flaky talc is the ratio of the average maximum diameter of the flaky talc to the average thickness. The larger the diameter-to-thickness ratio of the flaky talc, the easier it is to form an overlapping structure when stationary. The contact area of ​​the flaky talc increases, its adhesion is enhanced, it is easy to agglomerate, and its fluidity is reduced.

[0054] In this application, the angle of repose refers to the maximum angle formed between the inclined plane and the horizontal plane when the cordierite powder raw material is naturally piled up. The larger the angle of repose, the greater the internal friction of the cordierite powder and the worse its fluidity. Conversely, the smaller the angle of repose, the better the fluidity of the cordierite powder.

[0055] In this application, the angle of collapse refers to the angle between the newly stable side of the remaining cone-shaped material and the horizontal plane after the angle of repose of cordierite powder raw material is measured and an external force is applied to the accumulated material to cause its surface to collapse. The angle of collapse can reflect the ability of the cordierite powder raw material's accumulated structure to resist local instability and collapse. The smaller the angle of collapse, the easier it is for the powder to collapse and flow after being disturbed. The larger the angle of collapse, the more stable the accumulation is, but the more difficult the flow is.

[0056] The larger the difference between the angle of repose and the angle of collapse, Δθ, the more sensitive the cordierite powder is to external disturbances and the better its fluidity; the smaller the difference between Δθ and Δθ, the more stable the powder's packing structure is, the easier it is to form arches, and the worse its fluidity.

[0057] F=D 50 / (T×Δθ) represents the ratio of the particle size contribution of each component in the cordierite powder forming raw material to the shape-packing resistance. This is achieved by controlling the median particle size D of the cordierite forming raw material. 50 The average aspect ratio of flaky talc and the difference Δθ between the angle of repose and the angle of collapse of cordierite powder raw material satisfy the above relationship, and 0.022μm / °≤F≤0.09μm / ° and 5°≤Δθ≤22°, which can determine the composition of cordierite raw material (i.e., D). 50 The key flaky talc raw material (i.e., average diameter-to-thickness ratio) and the macroscopic flowability index (i.e., Δθ) of cordierite forming raw material are correlated, allowing for more precise control and improvement of the flowability of cordierite powder raw material. This enhances the density uniformity and extrusion molding stability of honeycomb ceramic green bodies, thereby reducing the green body cracking rate and extrusion molding die wear of honeycomb ceramics.

[0058] As a non-limiting example, F may be 0.022μm / °, 0.024μm / °, 0.026μm / °, 0.028μm / °, 0.03μm / °, 0.032μm / °, 0.034μm / °, 0.036μm / ° , 0.038μm / °, 0.04μm / °, 0.042μm / °, 0.044μm / °, 0.046μm / °, 0.048μm / °, 0.05μm / °, 0.052μm / °, 0.054μm / °, 0.0 56 μm / °, 0.058 μm / °, 0.06 μm / °, 0.062 μm / °, 0.064 μm / °, 0.066 μm / °, 0.068 μm / °, 0.07 μm / °, 0.072 μm / °, 0.074 μm / °, 0.076 μm / °, 0.078 μm / °, 0.08 μm / °, 0.082 μm / °, 0.084 μm / °, 0.086 μm / °, 0.088 μm / °, 0.09 μm / °, or any range between the two mentioned above.

[0059] As a non-limiting example, Δθ can be 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22° or a range between any two of the foregoing.

[0060] In some embodiments, 5μm≤D 50 ≤10μm. Controlling the median particle size D of the cordierite formation raw material. 50 Within the aforementioned range, it is beneficial to balance powder flowability, extrusion molding stability, and sintering activity. Specifically, it can reduce the longitudinal crack rate of green body, reduce extrusion pressure fluctuations, reduce die wear, and at the same time reduce the increase in thermal expansion coefficient caused by excessively large particle size or the agglomeration and deterioration of flowability caused by excessively small particle size.

[0061] As a non-restrictive example, D 50 The value can be 5μm, 5.2μm, 5.4μm, 5.6μm, 5.8μm, 6μm, 6.2μm, 6.4μm, 6.6μm, 6.8μm, 7μm, 7.2μm, 7.4μm, 7.6μm, 7.8μm, 8μm, 8.2μm, 8.4μm, 8.6μm, 8.8μm, 9μm, 10μm, or any range between the two aforementioned values.

[0062] Non-limitingly, the median particle size D of the cordierite-forming raw material can be controlled by methods such as airflow classification, adjusting the grinding process, and secondary dispersion after mixing. 50 The size ranges from 5μm to 9μm.

[0063] In some embodiments, the particle size of the cordierite forming material is 5 μm to 10 μm. For example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any range between the two mentioned above.

[0064] In some embodiments, 2 ≤ T ≤ 15. Controlling the average diameter-to-thickness ratio T of the flake talc within the above range is beneficial for improving the fluidity of the cordierite forming raw material, enhancing the density uniformity of the honeycomb ceramic green body, and reducing the green body cracking rate and thermal expansion coefficient of the cordierite honeycomb ceramic. When T is too large, the fluidity of the cordierite forming raw material is poor, making it prone to green body cracks; when T is too small, the thermal expansion coefficient of the cordierite honeycomb ceramic increases. As a non-limiting example, T can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, or any range between the foregoing.

[0065] In a non-limiting manner, the average diameter and average thickness of flaky talc can be controlled by selecting talc from different origins, talc with different processing techniques, and by using methods such as wet grinding and peeling, centrifugation, or sedimentation grading, thereby controlling the average diameter-to-thickness ratio T of flaky talc to be 2 to 15.

[0066] In some embodiments, 5°≤Δθ≤22°. Controlling the difference Δθ between the angle of repose and the angle of collapse of the cordierite powder raw material within the above range is beneficial for uniformly mixing the cordierite powder raw material, reducing component segregation or local agglomeration, and preventing easy stratification during transportation. This improves the component uniformity of the honeycomb ceramic green body, thereby reducing the coefficient of thermal expansion of the cordierite honeycomb ceramic, and further reducing the green body cracking rate and die wear during extrusion molding.

[0067] In some embodiments, the angle of repose of the cordierite powder raw material is 30° to 50°. As a non-limiting example, the angle of repose of the cordierite powder raw material can be 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49°, 50° or a range between any two of the foregoing.

[0068] In some embodiments, the collapse angle of the cordierite powder raw material is 18° to 30°. As a non-limiting example, the collapse angle of the cordierite powder raw material can be 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, 26°, 27°, 28°, 29°, 30° or any range between the foregoing.

[0069] Controlling at least one of the angle of repose and angle of collapse of cordierite powder raw material within the above range is beneficial to uniformly mix the cordierite powder raw material, reduce the problems of component segregation or local agglomeration and easy stratification during transportation, improve the component uniformity of honeycomb ceramic green body, and further reduce the green body cracking rate of cordierite honeycomb ceramic and the die wear of extrusion molding.

[0070] Non-limitingly, the angle of repose and angle of collapse of the cordierite powder raw material can be controlled by introducing a flow aid into the cordierite powder raw material or by changing at least one of the types and contents of the components in the cordierite forming raw material, thereby controlling the difference Δθ between the angle of repose and the angle of collapse of the cordierite powder raw material to be 5°~22°.

[0071] In some embodiments, the average flake diameter of the flaky talc is 10 μm to 25 μm. As a non-limiting example, the average flake diameter of the flaky talc can be 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 25 μm or any range between the foregoing.

[0072] In some embodiments, the average thickness of the flake talc is 0.5 μm to 1.5 μm. As a non-limiting example, the average thickness of the flake talc can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or any range between the foregoing.

[0073] Controlling at least one of the average flake diameter and average thickness of the flaky talc within the above-mentioned range is beneficial to further improve the flowability of cordierite powder raw materials.

[0074] In some embodiments, the cordierite forming raw materials also include at least one of alumina and aluminum hydroxide and kaolin.

[0075] In some embodiments, the raw materials for forming cordierite also include silicon dioxide.

[0076] In some embodiments, the cordierite forming raw material comprises the following components in the indicated mass percentages: 35%–43% flaky talc, 8%–34% alumina, 3%–16% aluminum hydroxide, 10%–45% kaolin, and 2%–19% silica. Controlling the composition of the cordierite forming raw material within the above range is beneficial for further improving the flowability of the cordierite powder raw material.

[0077] As a non-limiting example, the mass percentage of flaky talc in the cordierite forming raw material may be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, or any range between the foregoing.

[0078] As a non-limiting example, the mass percentage of alumina in the cordierite forming raw material may be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or any range between the foregoing.

[0079] As a non-limiting example, in the cordierite forming raw material, the mass percentage of aluminum hydroxide may be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or any range between the foregoing.

[0080] As a non-limiting example, the mass percentage of kaolin in the cordierite forming raw material may be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 45%, or any range between the foregoing.

[0081] As a non-limiting example, the mass percentage of silica in the cordierite forming raw material may be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or any range between the foregoing.

[0082] In some embodiments, the median grain size of the flaky talc is 5 μm to 16 μm. As a non-limiting example, the median grain size of the flaky talc can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm or any range between the foregoing.

[0083] In some embodiments, the median particle size of alumina is 1 μm to 7 μm. As a non-limiting example, the median particle size of alumina can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or any range between the foregoing.

[0084] In some embodiments, the median particle size of aluminum hydroxide is 2 μm to 8.5 μm. As a non-limiting example, the median particle size of aluminum hydroxide can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or any range between the foregoing.

[0085] In some embodiments, the median particle size of kaolin is 4 μm to 9 μm. As a non-limiting example, the median particle size of kaolin can be 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, or any range between the foregoing.

[0086] In some embodiments, the median particle size of the silica is 1.5 μm to 9 μm. As a non-limiting example, the median particle size of the silica can be 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, or any range between the foregoing.

[0087] In some embodiments, the cordierite powder raw material further includes at least one of a flow aid and a pore-forming agent. The flow aid in the cordierite powder raw material helps to improve its flowability, and the pore-forming agent is used to form the porous structure of the honeycomb ceramic.

[0088] In some embodiments, the flow aid includes one or more of stearic acid, polyvinyl alcohol, ammonium polyacrylate, and carboxymethyl cellulose.

[0089] In some embodiments, the mass percentage of the flow aid relative to the mass of the cordierite forming raw material is 0.1% to 5%.

[0090] A second aspect of this application provides a method for preparing cordierite honeycomb ceramics, comprising the following steps:

[0091] The preparation of honeycomb ceramic green body includes mixing cordierite powder raw material, lubricant, binder and water according to the first aspect of this application, and then successively kneading and extruding the mixture.

[0092] The preparation of cordierite honeycomb ceramics includes drying the honeycomb ceramic green body and then sintering it.

[0093] Using the above-mentioned cordierite powder raw material to make cordierite honeycomb ceramics can reduce the cracking rate of honeycomb ceramic green bodies and reduce the wear of molds used in extrusion molding.

[0094] In some embodiments, the sintering temperature is 1350°C to 1450°C, and the sintering time is 6 hours to 10 hours. As a non-limiting example, the sintering temperature can be 1350°C, 1360°C, 1370°C, 1380°C, 1390°C, 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, or any two of the foregoing, and the sintering time can be 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or any two of the foregoing.

[0095] In some embodiments, the sintering atmosphere includes an oxygen-containing atmosphere. Further, the volume fraction of oxygen in the oxygen-containing atmosphere is 6% to 15%. As a non-limiting example, the above volume fraction can be 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any range between the foregoing.

[0096] In some embodiments, the longitudinal crack rate of the honeycomb ceramic green body is less than or equal to 1%. This results in a relatively low longitudinal crack rate, improving product yield and consistency. As a non-limiting example, the longitudinal crack rate of the honeycomb ceramic green body can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any range between the foregoing.

[0097] In some embodiments, the extrusion pressure fluctuation during extrusion molding is less than or equal to 1 MPa. This results in a relatively stable extrusion pressure, which is beneficial for further reducing the green body cracking rate of cordierite honeycomb ceramics. As a non-limiting example, the extrusion pressure fluctuation during extrusion molding can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, or a range between any two of the foregoing.

[0098] In some embodiments, the wear amount of the die used in extrusion molding is less than or equal to 1 μm per 5000 meters extruded. Therefore, the wear amount of the die used in extrusion molding is controlled within a low range, which can extend the die's service life and reduce production costs. As a non-limiting example, the aforementioned wear amount can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, or a range between any two of the foregoing.

[0099] In some embodiments, the mixing time is 10 min to 60 min. This facilitates the uniform mixing of the cordierite powder raw material, lubricant, binder, and water. As a non-limiting example, the mixing time can be 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or any range between the foregoing.

[0100] In some embodiments, the lubricant comprises 10% to 30% by mass of block polyether. As a non-limiting example, the mass fraction of block polyether may be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, or any range between the foregoing.

[0101] In some embodiments, the mass percentage of the lubricant relative to the mass of the cordierite powder raw material is 1% to 5%. As a non-limiting example, the above percentage can be 1%, 2%, 3%, 4%, 5%, or any range between the foregoing.

[0102] In some embodiments, the binder includes one or more of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and methyl cellulose.

[0103] In some embodiments, the mass of the binder is 5% to 10% of the mass of the cordierite powder raw material. As a non-limiting example, the above percentage can be 5%, 6%, 7%, 8%, 9%, 10%, or any range between the foregoing.

[0104] A third aspect of this application provides a cordierite honeycomb ceramic, which is obtained by the preparation method of cordierite honeycomb ceramic provided in the second aspect of this application.

[0105] In some embodiments, the porosity of the honeycomb ceramic is 14% to 36%. As a non-limiting example, the porosity of the honeycomb ceramic can be 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, or any range between the foregoing.

[0106] In some embodiments, the coefficient of thermal expansion of the honeycomb ceramic at 800°C is 0.2 × 10⁻⁶. -6 ℃ -1 ~0.6×10 -6 ℃ -1 Therefore, the coefficient of thermal expansion of the honeycomb ceramic at 800℃ is controlled within a low range. As a non-limiting example, the coefficient of thermal expansion of the honeycomb ceramic at 800℃ can be 0.2 × 10⁻⁶. -6 ℃ -1 0.3×10 -6 ℃ -1 0.4×10 -6 ℃ -1 0.5×10 -6 ℃ -1 0.6×10 -6 ℃ -1 Or the range between any two of the aforementioned.

[0107] To further illustrate this application, the technical solution of this application is described in detail below with reference to specific embodiments. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0108] The test methods for each embodiment and comparative example are as follows:

[0109] (1) Median particle size test of cordierite raw materials

[0110] The median particle size of flaky talc and kaolin was determined using a laser particle size analyzer (wet or dry method) with a non-spherical model, and the median particle size of alumina, aluminum hydroxide, and silica was determined using a spherical model. The median particle size of flaky talc, alumina, aluminum hydroxide, kaolin, and silica is denoted as D. A50 D B50 D C50 D D50 D E50 The mass percentages of platy talc, alumina, aluminum hydroxide, kaolin, and silica in the raw materials for cordierite formation are denoted as W. A W B W C W D W E ;

[0111] Median grain size D of cordierite raw materials 50 Calculate using the following method:

[0112] D 50 =exp(W A ×lnD A50 +W B ×lnD B50 +W C ×lnD C50 +W D ×lnD D50 +W E ×lnD E50 ).

[0113] (2) Average diameter-to-thickness ratio test of flaky talc

[0114] At least 50 complete flaky talc pieces were measured using a scanning electron microscope (SEM); the maximum diameter of the flaky talc pieces was determined, and the average value was calculated to obtain the average diameter of the flaky talc pieces; the thickness of the flaky talc pieces was determined, and the average value was calculated to obtain the average thickness of the flaky talc pieces; the average diameter-to-thickness ratio of the flaky talc pieces = the average diameter of the flaky talc pieces / the average thickness of the flaky talc pieces.

[0115] (3) Angle of repose and angle of collapse test of powder raw materials

[0116] Fix the funnel above a horizontal base plate, allowing the powder raw material to fall naturally from the funnel outlet and accumulate into a cone. Measure the height H1 and the base diameter D1 of this cone, and then use the formula θ... r=arctan(2H1 / D1), calculate the angle of repose θr of the powder raw material;

[0117] Then, lift the bottom plate vertically by 1cm to 2cm and release it to allow it to freely impact the horizontal platform. Repeat this 3 to 5 times, measure the height H2 of the material pile after vibration and the diameter D2 of the bottom surface, and calculate the collapse angle of the powder raw material using the formula θc=arctan(2H2 / D2).

[0118] (4) Longitudinal crack rate test of honeycomb ceramic green body

[0119] The cracking of the honeycomb ceramic green body products was observed under light. The number of longitudinal cracks in 1000 products was counted, and the longitudinal crack rate was calculated according to the following formula: Longitudinal crack rate = (number of longitudinal cracks in the product / 1000) × 100%.

[0120] (5) Wear test of the die used in extrusion molding

[0121] The wear amount is calculated by analyzing the groove width before and after use of the mold, combined with the total length of the produced products; Wear amount = (groove width before use - groove width after use) / total length of produced products.

[0122] (6) Porosity test of honeycomb ceramics

[0123] Prepare a sample block with dimensions of 25mm×25mm×25mm±0.5mm and weigh the dry weight of the sample block. After vacuuming for 10 minutes using a vacuum pump, boil the sample block in a microwave oven. After cooling to room temperature, blow away excess moisture from the sample block with an air gun, weigh the sample block, and calculate the water absorption rate and porosity.

[0124] (7) Test of thermal expansion coefficient of honeycomb ceramic at 800℃

[0125] After the honeycomb ceramics were sintered, they were disassembled and several sample blocks were taken out, each measuring 25mm × 5mm × 5mm. The samples were then tested according to the test methods in GB / T 16535-2008.

[0126] Example 1

[0127] The preparation method of cordierite honeycomb ceramics includes the following steps:

[0128] A mixture of platy talc with a median particle size of 14.9 μm, alumina with a median particle size of 4.3 μm, aluminum hydroxide with a median particle size of 2.1 μm, kaolin with a median particle size of 8.2 μm, and silica with a median particle size of 3.3 μm was prepared in the following percentages: platy talc 36.0%, alumina 33.0%, aluminum hydroxide 12.0%, kaolin 12.0%, and silica 7.0%, to obtain the cordierite forming raw material; the median particle size D of the cordierite forming raw material was... 50The thickness of the flaky talc is 6.55 μm, the average diameter of the flaky talc is 18.2 μm, the average thickness is 1.5 μm, and the average aspect ratio T is 12.1.

[0129] The angle of repose and angle of collapse of the cordierite raw material were measured. If the difference between the two (angle of repose - angle of collapse) was less than 5°, carboxymethyl cellulose, a flow aid, was added to the mixed powder and mixing continued until the difference between the angle of repose and angle of collapse of the obtained cordierite powder raw material was ≥5°. The angle of repose of the cordierite powder raw material was 40.1°, the angle of collapse was 24.2°, and the difference between the angle of repose and angle of collapse, Δθ, was 15.9°.

[0130] Cordierite powder raw material, 20% by mass of block polyether (lubricant), hydroxymethyl cellulose (binder) and water are mixed and then subjected to kneading, extrusion molding and microwave drying to obtain a honeycomb ceramic green body. The mass percentage of block polyether relative to the mass of cordierite powder raw material is 3%, the mass percentage of hydroxymethyl cellulose relative to the mass of cordierite powder raw material is 7%, the molecular weight of block polyether is 20 kDa, the polyether includes a first structural unit derived from ethylene oxide and a second structural unit derived from ethylene oxide, the first structural unit accounts for 80% of the molar proportion of the polyether, and the block combination is multi-block.

[0131] Cordierite honeycomb ceramic was obtained by sintering the green body of the honeycomb ceramic in air at 1430℃ for 10 h; the porosity of the cordierite honeycomb ceramic was 35.4%, and the coefficient of thermal expansion at 800℃ was 0.5×10⁻⁶. -6 ℃ -1 .

[0132] Examples 2-10

[0133] The preparation method of cordierite honeycomb ceramics is basically the same as in Example 1, except that at least one of the following is changed: the median particle size and mass percentage of each component in the cordierite forming raw material, the mass percentage of the flow aid in the cordierite powder raw material, the angle of repose and the angle of collapse of the cordierite powder raw material, and the average diameter-to-thickness ratio of the flaky talc, as shown in Tables 1 and 2, thereby changing the F value.

[0134] Comparative Examples 1-7

[0135] The preparation method of cordierite honeycomb ceramics is basically the same as in Example 1, except that at least one of the following is changed: the median particle size and mass percentage of each component in the cordierite forming raw material, the mass percentage of the flow aid in the cordierite powder raw material, the angle of repose and the angle of collapse of the cordierite powder raw material, and the average diameter-to-thickness ratio of the flaky talc, as shown in Tables 1 and 2, thereby changing the F value.

[0136] The test results of each embodiment and comparative example are shown in Tables 1 to 3.

[0137] Table 1

[0138]

[0139] Table 2

[0140]

[0141] The mass percentages in Table 2 refer to the mass percentages of each component in the cordierite raw material.

[0142] Table 3

[0143]

[0144] As shown in Tables 1 to 3, the extrusion pressure fluctuations in Examples 1 to 10 were at a low level. Furthermore, compared to Comparative Examples 1 to 7, the longitudinal crack rate of the honeycomb ceramic green bodies in Examples 1 to 10 and the wear of the extrusion die per 5000 meters were relatively low, indicating that the median particle size D of the cordierite forming raw material was controlled. 50 The average diameter-to-thickness ratio of flaky talc and the difference Δθ between the angle of repose and the angle of collapse of cordierite powder raw material satisfy F=D 50 / (T×Δθ), 0.022μm / °≤F≤0.09μm / ° and 5°≤Δθ≤22° can reduce the cracking rate of honeycomb ceramic green bodies and reduce mold wear.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A cordierite powder raw material, characterized in that, The raw materials include cordierite, which comprises flaky talc, and the cordierite powder raw materials satisfy the following relationship: F=D 50 / (T×Δθ), 0.022μm / °≤F≤0.09μm / °; Among them, D 50 The median particle size of the cordierite forming raw material is in μm; T is the average diameter-to-thickness ratio of the flaky talc; Δθ is the difference between the angle of repose and the angle of collapse of the cordierite powder raw material, in °, where 5°≤Δθ≤22°.

2. The cordierite powder raw material according to claim 1, characterized in that, The cordierite powder raw material has one or more of the following characteristics: (1)5μm≤D 50 ≤10μm; (2)2≤T≤15； (3) 5°≤Δθ≤22°; (4) The angle of repose of the cordierite powder raw material is 30°~50°; (5) The collapse angle of the cordierite powder raw material is 18°~30°; (6) The average diameter of the flaky talc is 10 μm to 25 μm; (7) The average thickness of the flaky talc is 0.5μm~1.5μm.

3. The cordierite powder raw material according to claim 1 or 2, characterized in that, The cordierite forming raw material further includes at least one of alumina and aluminum hydroxide and kaolin; optionally, the cordierite forming raw material further includes silicon dioxide.

4. The cordierite powder raw material according to claim 3, characterized in that, The cordierite powder raw material has one or more of the following characteristics: (1) The cordierite forming raw material comprises the following components in the following mass percentages: 35%~43% flaky talc, 8%~34% alumina, 3%~16% aluminum hydroxide, 10%~45% kaolin and 2%~19% silicon dioxide; (2) The median particle size of the flaky talc is 5 μm to 16 μm; (3) The median particle size of the alumina is 1 μm to 7 μm; (4) The median particle size of the aluminum hydroxide is 2 μm to 8.5 μm; (5) The median particle size of the kaolin is 4μm~9μm; (6) The median particle size of the silica is 1.5 μm to 9 μm.

5. The cordierite powder raw material according to claim 1 or 2, characterized in that, The cordierite powder raw material also includes at least one of a flow aid and a pore-forming agent.

6. The cordierite powder raw material according to claim 5, characterized in that, The cordierite powder raw material has one or more of the following characteristics: (1) The flow aid includes one or more of stearic acid, polyvinyl alcohol, ammonium polyacrylate and carboxymethyl cellulose; (2) The mass of the flow aid is 0.1% to 5% of the mass of the cordierite forming raw material.

7. A method for preparing cordierite honeycomb ceramics, characterized in that, Includes the following steps: The preparation of honeycomb ceramic green body includes mixing cordierite powder raw material as described in any one of claims 1 to 6, lubricant, binder and water, and then successively kneading and extruding the mixture. The preparation of the cordierite honeycomb ceramic includes drying the honeycomb ceramic green body and then sintering it.

8. The preparation method according to claim 7, characterized in that, The preparation method satisfies one or more of the following conditions: (1) The sintering temperature is 1350℃~1450℃, and the sintering time is 6h~10h; (2) The sintering atmosphere includes an oxygen-containing atmosphere; optionally, the volume fraction of oxygen in the oxygen-containing atmosphere is 6% to 15%; (3) The longitudinal crack rate of the honeycomb ceramic green body is less than or equal to 1%; (4) The extrusion pressure fluctuation of the extrusion molding is less than or equal to 1 MPa; (5) The wear of the die used in the extrusion molding is less than or equal to 1 μm for every 5000 meters extruded; (6) The mixing time is 10 min to 60 min; (7) The lubricant comprises 10% to 30% by mass of block polyether; (8) The mass percentage of the lubricant relative to the mass of the cordierite powder raw material is 1% to 5%; (9) The adhesive includes one or more of carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinyl alcohol, and methyl cellulose; (10) The mass of the binder is 5% to 10% of the mass of the cordierite powder raw material.

9. A cordierite honeycomb ceramic, characterized in that, The cordierite honeycomb ceramic was prepared using the method described in any one of claims 7 to 8.

10. The cordierite honeycomb ceramic according to claim 9, characterized in that, The cordierite honeycomb ceramic has one or more of the following characteristics: (1) The porosity of the honeycomb ceramic is 14%~36%; (2) The coefficient of thermal expansion of the honeycomb ceramic at 800℃ is 0.2×10⁻⁶. -6 ℃ -1 ~0.6×10 -6 ℃ -1 .

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