Composite ceramic materials, articles, and methods of manufacture

Abstract

This application relates to composite ceramic materials, articles, and manufacturing methods. The composite ceramic materials disclosed herein comprise two or more crystalline phases, wherein a first crystalline phase comprises a first refractory material having a first melting point, and a second crystalline phase comprises a second refractory material having a second melting point lower than the first melting point, and the second crystalline phase comprises the second refractory material with a large domain size. Articles comprising such composite ceramic materials, such as honeycomb structures, catalytic substrates, and particulate filters, and methods for manufacturing them are also disclosed herein.

Description

[0001] This application claims priority to U.S. Provisional Application No. 62 / 420403, filed November 10, 2016, pursuant to 35 USC § 119, the entire contents of which are incorporated herein by reference. Background Technology Technical Field

[0003] This specification generally relates to composite ceramic materials and articles and their manufacture, and more specifically, to composite ceramic materials and articles having a large ceramic phase. Technical Background

[0005] Ceramic products made of refractory ceramic materials (e.g., cordierite, silicon carbide, and aluminum titanate) can be used to manufacture catalytic substrates and particulate filters. Summary of the Invention

[0006] The composite ceramic materials disclosed herein comprise two or more crystalline phases, wherein a first crystalline phase comprises a first refractory material having a first melting point, and a second crystalline phase comprises a second refractory material having a second melting point lower than the first melting point, and the second crystalline phase comprises the second refractory material with a large domain size. This document also discloses articles comprising such composite ceramic materials, such as honeycomb structures, catalytic substrates, and particulate filters, as well as methods for manufacturing them.

[0007] In the first aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material having a first melting point; and a second crystalline phase comprising a second refractory material having a second melting point lower than the first melting point, wherein the second crystalline phase comprises a particle size greater than 5000 µm. 2The domain size is determined by electron backscatter diffraction (EBSD). Domain size refers to a continuous or semi-continuous region of cordierite grains whose crystallographic orientation is closely related. Crystals within a domain have approximately the same orientation, while adjacent domains have significantly different orientations, exceeding 20 degrees of mis-orientation. The crystallographic orientation of the cordierite grains is determined by electron backscatter diffraction (EBSD), and the domain is determined by image analysis of EBSD plots of grains with similar c-axis orientations. In some embodiments, the first crystalline phase constitutes at least 50 vol% of the material. In some embodiments, the second crystalline phase constitutes less than 50 vol% of the material. In some embodiments, the first crystalline phase constitutes at least 50 vol% of the material, and the second crystalline phase constitutes less than 50 vol% of the material. In some embodiments, the first crystalline phase constitutes at least 50 wt% of the material. In some embodiments, the second crystalline phase constitutes less than 35 wt% of the material. In some embodiments, the first crystalline phase constitutes at least 55% by weight of the material, and the second crystalline phase constitutes less than 35% by weight of the material. In some embodiments, the first crystalline phase constitutes at least 60% by weight of the material, and the second crystalline phase constitutes less than 30% by weight of the material. In some embodiments, the melting point of the first crystalline phase is greater than 1500°C. In some embodiments, the melting point of the second crystalline phase is less than 1500°C. In some embodiments, the melting point of the second crystalline phase is 1450°C or less; in some of these embodiments, the melting point of the second crystalline phase is between 1300°C and 1450°C; in some of these embodiments, the melting point of the second crystalline phase is between 1425°C and 1450°C. In some embodiments, the melting point of the first crystalline phase is greater than 1500°C, and the melting point of the second crystalline phase is less than 1500°C.

[0008] In the second aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material, the first crystalline phase having a first melting point; and a second crystalline phase comprising a second refractory material, the second crystalline phase having a second melting point lower than the first melting point, wherein the second crystalline phase has a particle size greater than 2500 µm. 2 The average domain size was measured by electron backscatter diffraction (EBSD). In some embodiments, the second crystalline phase has a size greater than 3000 µm. 2 The average domain size, measured by electron backscatter diffraction (EBSD), is greater than 5000 µm in some embodiments. 2 In some implementations, greater than 10000 µm 2 In some implementations, greater than 15000 µm 2 In some implementations, greater than 20000 µm 2 .

[0009] In the third aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material, the first crystalline phase having a first melting point; and a second crystalline phase comprising a second refractory material, the second crystalline phase having a second melting point lower than the first melting point, wherein the second crystalline phase comprises a particle size greater than 4,000 µm. 2 The domain size is greater than 2500 µm. 2 The average domain size was determined by electron backscatter diffraction (EBSD). In some embodiments, the first crystalline phase comprises tialite. In some embodiments, the first crystalline phase further comprises MgTi2O5. In some embodiments, the second crystalline phase comprises cordierite. In some embodiments, the ceramic material further comprises a third crystalline phase containing andalusite.

[0010] In a fourth aspect, the composite ceramic material disclosed herein comprises: a first crystalline phase comprising aluminosilicate, the first crystalline phase having a first melting point and a first maximum domain size in a selected cross-sectional plane; and a second crystalline phase comprising cordierite, the second crystalline phase having a second melting point lower than the first melting point and having a second maximum domain size in the selected cross-sectional plane, wherein the ratio of the second maximum domain size to the first maximum domain size is 6.0 or greater. In some embodiments, the ratio of the second maximum domain size to the first maximum domain size is 7.0 or greater; in some embodiments, it is 8.0 or greater; in some embodiments, it is 10.0 or greater; in some embodiments, it is 15 or greater; and in some embodiments, it is 20 or greater.

[0011] In a fifth aspect, this document discloses a method for manufacturing an article comprising a composite ceramic material, the method comprising: heating a body comprising a starting mixture, the starting mixture comprising a first refractory material or a precursor thereof (or both) and a second refractory material or a precursor thereof (or both), wherein, if a first refractory material precursor is present, the heating is sufficient to cause at least some of the precursor to reactively form the first refractory material, and if a second refractory material precursor is present, the heating is sufficient to cause at least some of the precursor to reactively form the second refractory material, and the heating is sufficient to cause at least some of the first refractory material to melt and to come into contact with at least some of the second refractory material without causing the second refractory material to melt during the heating process; and then cooling the body to form a composite ceramic material comprising a first crystalline phase comprising the first refractory material and a second crystalline phase comprising the second refractory material, wherein the second crystalline phase comprises a particle size greater than 5000 µm. 2 The domain size was measured by electron backscatter diffraction (EBSD).

[0012] Additional features and advantages are set forth in the following detailed description, some of which will be apparent to those skilled in the art from the description made, or will be recognized by practicing the embodiments described herein, including the following detailed description, the claims and the accompanying drawings.

[0013] It should be understood that the foregoing general description and the following detailed description describe various embodiments of the methods and apparatus for forming ceramic materials, and are intended to provide a general overview or framework for understanding the nature and characteristics of the claimed subject matter. The included drawings provide further understanding of the various embodiments and are incorporated in and form a part of this specification. The drawings illustrate the various embodiments described herein and, together with the description, serve to explain the principles and operation of the claimed subject matter. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing the relationship between lattice expansion and temperature for aluminum titanate and cordierite.

[0015] Figure 2 This is a schematic diagram of the orthorhombic structure of cordierite crystals, and the corresponding expansion on each axis.

[0016] Figure 3 The diagram illustrates the orthorhombic structure of cordierite crystals.

[0017] Figure 4 This displays regions / areas with similar cordierite orientations corresponding to image analysis of EBSD data from an exemplary implementation.

[0018] Figure 5 This displays regions / areas with similar cordierite orientations corresponding to image analysis of EBSD data from an exemplary implementation.

[0019] Figure 6 Showing regions / areas with similar cordierite orientations from image analysis of EBSD data corresponding to comparative examples.

[0020] Figure 7 Showing regions / areas with similar cordierite orientations from image analysis of EBSD data corresponding to comparative examples.

[0021] Figure 8 Showing regions / areas with similar cordierite orientations from image analysis of EBSD data corresponding to comparative examples.

[0022] Figure 9 Showing regions / areas with similar cordierite orientations from image analysis of EBSD data corresponding to comparative examples. Detailed Implementation

[0023] The following will provide detailed reference to various embodiments of the method for producing ceramic products (including the extraction of at least some organic material prior to firing), examples of which are shown in the accompanying drawings. Wherever possible, the same reference numerals are used in all the drawings to denote the same or similar parts.

[0024] Unless otherwise stated, it is not intended to be construed as requiring the steps of any method described herein to be performed in a specific order, nor is it intended to be construed as requiring any specific orientation of the device. Therefore, when a method claim does not actually state that its steps follow a certain order, or any device claim does not actually specifically state the order or orientation of individual components, or does not in the claims or description otherwise specifically indicate that the steps are limited to a specific order, or does not state a specific order or orientation of the device components, it is not intended to imply any order or orientation in any way. This also applies to any possible unexpressed basis for interpretation, including: the logic regarding the setup steps, operational flow, component order, or component orientation; the general meaning obtained from grammatical structure or punctuation; and the number or type of embodiments described in the specification.

[0025] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein include plural references. Thus, for example, a “one” component may include aspects having two or more such components, unless otherwise explicitly stated in the text.

[0026] Unless otherwise specifically stated to the contrary, the “% by weight,” “percentage by weight,” or “weight percentage” of the inorganic or organic components in batch mixtures as used herein are based on the total weight of the inorganic matter containing that component. The organic components listed herein are added on a basis of 100% inorganic components used.

[0027] The specific and preferred values ​​disclosed herein for components, ingredients, additives, reactants, constants, and scaling factors are merely illustrative. They do not exclude other limiting values ​​or other values ​​within a defined range. The compositions, apparatus, and methods disclosed herein include any value or combination of the numerical values, specific numerical values, or ranges thereof described herein. Any range of numerical values ​​described herein contemplates all values ​​within that range and is to be understood as supporting any subrange of claims that describes terminals having actual numerical values ​​within a suspected specific range.

[0028] The raw materials used to form ceramics include inorganic materials. For example, the raw materials for forming ceramics can be: raw materials for forming cordierite, raw materials for forming aluminum titanate, raw materials for forming silicon carbide, raw materials for forming alumina, alumina, silicon oxide, magnesium oxide, titanium oxide, aluminum-containing components, silicon-containing components, and titanium-containing components, etc. As used herein, aluminosilicate is aluminum titanate (Al₂TiO₅), or a solid solution of aluminum titanate (Al₂TiO₅) and magnesium titanate (MgTi₂O₅).

[0029] The raw materials for forming cordierite may include, for example, at least one magnesium source, at least one alumina source, and at least one silicon dioxide source. The raw materials for forming cordierite may also include one or more of clay and titanium dioxide, as well as alkaline earth metals and oxides.

[0030] In the embodiments described herein, the magnesium source includes, but is not limited to, magnesium oxide or other materials with low water solubility that convert to MgO upon calcination, such as Mg(OH)₂, MgCO₃, and combinations thereof. For example, the magnesium source may be talc (Mg₃Si₄O₂). 10 (OH)2), including calcined and / or uncalcined talc, as well as coarse talc and / or fine talc.

[0031] Alumina sources include, but are not limited to, powders that, when heated to sufficiently high temperatures without the presence of other raw materials, produce substantially pure aluminum oxides. Examples of suitable alumina sources may include: α-alumina, transition alumina such as γ-alumina or p-alumina, hydrated alumina or aluminum trihydrate, gibbsite, corundum (Al₂O₃), boehmite (AlO(OH)), pseudoboehmite, aluminum hydroxide (Al(OH)₃), aluminum hydroxyaluminate, and mixtures thereof.

[0032] Silica can exist in its pure chemical state, such as α-quartz or fused silica. Silica sources can include, but are not limited to, amorphous silica, such as fused silica or sol-gel silica, silicone resins, low-alumina zeolites that are essentially non-alkaline, diatomaceous earth silica, kaolin, and crystalline silica, such as quartz or cristobalite. Furthermore, silica sources can also include, but are not limited to, sources that form silica, comprising compounds that form free silica upon heating. For example, silicic acid or organometallic silicon compounds can form free silica upon heating.

[0033] The hydrated clay used as raw material for forming cordierite may include, for example, but not limited to, kaolinite (Al2(Si2O5)(OH)4), hydrous kaolinite (Al2(Si2O5)(OH)4), etc. H2O), pyrophyllite (Al2(Si2O5)(OH)2), and combinations thereof or mixtures thereof.

[0034] The raw materials for forming aluminum titanate may include, for example, an alumina source, a magnesium oxide source, and a titanium oxide source. In one aspect, the titanium oxide source may be a titanium dioxide composition, such as rutile titanium oxide, anatase titanium oxide, or a combination thereof. The alumina source and magnesium oxide source may be selected from the alumina source and magnesium oxide source described above. Exemplary non-limiting inorganic batch component mixtures suitable for forming aluminum titanate include those disclosed in U.S. Patents Nos. 4,483,944, 4,855,265, 5,290,739, 6,620,751, 6,942,713, 6,849,181, 7,001,861, and 7,294,164, which are incorporated herein by reference.

[0035] The raw materials for forming silicon carbide may include, for example, finely powdered silicon metal, carbon precursors, and powdered silicon-containing fillers. The carbon precursor may be, for example, a water-soluble crosslinked thermosetting resin with a viscosity of less than about 1000 centipoise (cp). The thermosetting resin used may be a high-carbon-yield resin, in an amount such that the carbon-to-silicon ratio in the resulting batch mixture is about 12:28 (by weight), which is the Si-C stoichiometric ratio required for the formation of silicon carbide. Suitable silicon-containing fillers include silicon carbide, silicon nitride, andalusite, or other refractory materials. Exemplary non-limiting inorganic batch component mixtures suitable for forming silicon carbide include those disclosed in U.S. Patents 6,555,031 and 6,699,429, which are incorporated herein by reference.

[0036] The raw materials that form alumina may include Al2O3 and / or components that form alumina.

[0037] In addition to the inorganic raw materials for forming ceramics, the ceramic batch mixture 101 may contain organic materials, including lubricants, surfactants, binders, and / or one or more pore-forming materials. As used herein, the term "organic material" excludes the amount of solvents (e.g., water) contained in the various batch compositions. The organic materials are used to form a flowable dispersion with a high ceramic material loading. The lubricants and surfactants are chemically compatible with the inorganic components and provide sufficient strength and stiffness to allow handling of the green body. In embodiments, the organic material in the ceramic batch mixture 101 may be from about 1% to about 60% or even from about 2% to about 20% by weight of the inorganic components, based on super-addition. In some embodiments, the organic material in the ceramic batch mixture 101 may be from about 5% to about 15%, from about 7% to about 12%, or even from about 9% to about 10% by weight of the inorganic components, based on super-addition. In some embodiments, the organic material in the ceramic batch mixture 101 may be about 5% to about 11% or about 7%, based on the weight percentage of the inorganic component and the super-addition.

[0038] In some embodiments, the organic material may include a binder and may include one or more pore-forming materials. For example, the amount of organic binder present as an additive in the batch mixture may be from about 0.1% to 10.0% by weight of the inorganic ceramic batch component. The binder may include, but is not limited to, cellulose-containing components such as methylcellulose, ethyl hydroxyethyl cellulose, hydroxybutyl methylcellulose, hydroxymethylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, hydroxybutyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium carboxymethyl cellulose, and mixtures thereof. Methylcellulose and / or methylcellulose derivatives, such as hydroxypropyl methylcellulose, are particularly suitable as organic binders.

[0039] The pore-forming agent is preferably a short-lived particulate material that evaporates due to combustion during the drying and / or heating of the green body, leaving a larger porosity than when obtained using other methods. Pore-forming materials can include, for example: carbon (e.g., graphite, activated carbon, petroleum coke, and carbon black), starch (e.g., corn, barley, beans, potatoes, rice, cassava, peas, sago palm, wheat, canna lily, and walnut shell powder), polymers (e.g., polybutene, polymethylpentene, polyethylene, polypropylene, polystyrene, polyamide (nylon), epoxy resins, ABS, acrylics, and polyester (PET)), hydrogen peroxide, and / or resins (e.g., phenolic resins). One or more pore-forming materials can be used. For example, a combination of polymers and starch can be used for pore formation. In some embodiments, the ceramic batch mixture may contain about 10% by weight to about 60% by weight of an organic pore-forming agent. The median particle size d of the organic pore-forming agent... 50 It can be less than or equal to 20 micrometers. In some embodiments, the median particle size d of the organic pore-forming agent... 50 Particle size less than or equal to 15 micrometers or even median d 50 Less than or equal to 10 micrometers.

[0040] Lubricants can provide flowability to ceramic precursor batch compositions and can facilitate the shaping of batch mixtures into green bodies by allowing the batch to maintain sufficient stiffness during the forming (i.e., extrusion) process. Lubricants may include, for example, mineral oils distilled from petroleum, synthetic and semi-synthetic base oils (including Group II and III waxy base oils), polyalphaolefins, and alpha-olefins. In various embodiments, the amount of lubricant present, on an over-addition basis, is at least 3% by weight of the inorganic component.

[0041] Organic surfactants can be provided to adsorb onto inorganic particles, keeping them in suspension and preventing their clustering. These organic surfactants may include, for example, C8-C... 22Fatty acids and / or their esters or alcohol derivatives, such as stearic acid, lauric acid, linoleic acid, oleic acid, myristic acid, palmitic acid and palmitoleic acid, soybean lecithin, and mixtures thereof. For example, the amount of organic surfactant present, when added in excess, is at least 0.3% by weight of the inorganic component.

[0042] In various embodiments, a solvent may be added to the batch mixture to produce a ceramic paste (precursor, etc.), thereby forming a green body. In embodiments, the solvent may include an aqueous-based solvent, such as water or a solvent miscible with water. In some embodiments, the solvent is water. The amount of aqueous solvent present in the ceramic precursor batch is from about 20% to about 50% by weight.

[0043] Organic materials can be added to at least one inorganic component and mixed to form ceramics or batch mixtures for forming ceramics. For example, inorganic components can be combined as powder materials and thoroughly mixed to form substantially homogeneous batches.

[0044] The batch mixture can be shaped or formed into a green body structure using forming methods such as molding, pressing, casting, and extrusion. For example, the batch mixture can be extruded using an extruder to form a green body. Depending on the specific implementation, the extruder can be a hydraulic plunger extruder, a two-stage vacuum single-screw extruder, or a twin-screw mixer with a die assembly connected to the extruder outlet. The batch mixture can be extruded at a predetermined temperature and speed.

[0045] Preferably, the batch mixture is formed into a honeycomb structure. The honeycomb structure preferably includes a mesh structure defining a plurality of channels separated by channel walls. However, the green body can be in any form other than a honeycomb structure.

[0046] After at least some organic material evaporates and is removed from the green body, the green body is subsequently transferred to a kiln, where it is fired at a selected temperature in a suitable atmosphere for a duration depending on the composition, size, and geometry of the green body, thereby obtaining a fired porous ceramic product, such as a porous ceramic honeycomb structure. The kiln can be, for example, but not limited to, a tunnel kiln, a periodic kiln, a fuel-fired or direct-fired kiln, an electric kiln, or a microwave-assisted kiln.

[0047] Firing time and temperature depend on factors such as the composition and quantity of materials in the green body, and the type of equipment used to fire the green body. During firing, the temperature in the firing atmosphere can be increased at a rate greater than 50°C / hour.

[0048] The heating rate can be greater than or equal to about 50°C per hour (°C / hour). For example, in some embodiments, the heating rate can be about 50°C / hour to about 200°C / hour, about 60°C / hour to about 130°C / hour, or about 75°C / hour to about 125°C / hour. In various embodiments, the heating rate can be less than or equal to about 200°C / hour, less than or equal to about 130°C / hour, less than or equal to about 125°C / hour, or even less than or equal to about 80°C / hour. In some embodiments, the heating rate can be about 75°C / hour, about 100°C / hour, or even about 125°C / hour. In some embodiments, the heating rate can be limited to 200°C / hour or less. In embodiments, the specific heating rate used can depend at least in part on the size of the green body, the composition of the ceramic batch mixture used to form the green body, and the shape of the green body.

[0049] In the first aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material having a first melting point; and a second crystalline phase comprising a second refractory material having a second melting point lower than the first melting point, wherein the second crystalline phase comprises a particle size greater than 5000 µm. 2 The domain size is determined by electron backscatter diffraction (EBSD). In some embodiments, the first crystalline phase constitutes at least 50% by volume of the material. In some embodiments, the second crystalline phase constitutes less than 50% by volume of the material. In some embodiments, the first crystalline phase constitutes at least 50% by volume of the material, and the second crystalline phase constitutes less than 50% by volume of the material. In some embodiments, the first crystalline phase constitutes at least 50% by weight of the material. In some embodiments, the second crystalline phase constitutes less than 35% by weight of the material. In some embodiments, the first crystalline phase constitutes at least 55% by weight of the material, and the second crystalline phase constitutes less than 35% by weight of the material. In some embodiments, the first crystalline phase constitutes at least 60% by weight of the material, and the second crystalline phase constitutes less than 30% by weight of the material. In some embodiments, the melting point of the first crystalline phase is greater than 1500°C. In some embodiments, the melting point of the second crystalline phase is less than 1500°C. In some embodiments, the melting point of the second crystalline phase is 1400°C or less; in some of these embodiments, the melting point of the second crystalline phase is 1300°C to 1450°C; in some of these embodiments, the melting point of the second crystalline phase is 1425°C to 1450°C. In some embodiments, the melting point of the first crystalline phase is greater than 1500°C, and the melting point of the second crystalline phase is less than 1500°C.

[0050] In some embodiments, the second crystalline phase comprises a particle size greater than 10,000 µm. 2The domain size, measured by electron backscatter diffraction (EBSD), is greater than 15000 µm in some embodiments. 2 In some implementations, greater than 20000 µm 2 In some implementations, greater than 25000 µm 2 This was measured by electron backscatter diffraction (EBSD), and in some embodiments, greater than 30,000 µm. 2 This was measured using electron backscatter diffraction (EBSD).

[0051] In some embodiments, the second crystal phase has a diameter greater than 3000 µm. 2 The average domain size, measured by electron backscatter diffraction (EBSD), is greater than 4000 µm in some embodiments. 2 In some implementations, greater than 5000µm 2 In some implementations, greater than 6000 µm 2 In some implementations, greater than 7000 µm 2 In some implementations, greater than 10000 µm 2 In some implementations, greater than 15000 µm 2 In some implementations, greater than 20000 µm 2 This was measured using electron backscatter diffraction (EBSD).

[0052] In some embodiments, the first crystalline phase comprises tialite. In some embodiments, the first crystalline phase primarily comprises tialite. In some embodiments, the first crystalline phase comprises various refractory materials in solid solution with each other. In some embodiments, the first crystalline phase comprises MgTi2O5 in solid solution with tialite. In some embodiments, the first crystalline phase comprises andalusite.

[0053] In some embodiments, the ceramic material further includes a third crystalline phase. In some embodiments, the first crystalline phase includes andalusite and the second crystalline phase includes cordierite. In some embodiments, the first crystalline phase includes andalusite, the second crystalline phase includes cordierite, and the third crystalline phase includes aluminous pseudobrookite. In some embodiments, the first crystalline phase includes andalusite, the second crystalline phase includes cordierite, and the third crystalline phase includes aluminous pseudobrookite and MgTi2O5. In some embodiments, the third crystalline phase includes andalusite. In some embodiments, the first crystalline phase includes aluminous pseudobrookite and the second crystalline phase includes cordierite. In some embodiments, the first crystalline phase includes aluminous pseudobrookite, the second crystalline phase includes cordierite, and the third crystalline phase includes andalusite. In some embodiments, the first crystalline phase includes aluminous pseudobrookite and MgTi2O5; in some of these embodiments, the first crystalline phase includes aluminous pseudobrookite and MgTi2O5 in a solid solution.

[0054] In some embodiments, the second crystalline phase includes cordierite. In some embodiments, the second crystalline phase mainly includes cordierite. In some embodiments, the second crystalline phase is essentially composed of cordierite. In some embodiments, the second crystalline phase is cordierite.

[0055] In some embodiments, the first crystalline phase comprises a structure primarily consisting of argillaceous diatomite crystals.

[0056] In some embodiments, at least a majority of the first crystalline phase provides a multi-branched solid network, and at least some of the second crystalline phases are positioned directly adjacent to one or more branches of the solid network.

[0057] In some embodiments, the ratio of the maximum domain size of the second crystal phase to the maximum domain size of the first crystal phase is 6.0 or greater, in some embodiments it is 7.0 or greater, in some embodiments it is 8.0 or greater, in some embodiments it is 10.0 or greater, in some embodiments it is 15 or greater, and in some embodiments it is 20 or greater.

[0058] In some embodiments, the second crystal phase has a size greater than 10,000 µm. 2 The domain is in direct contact with the grains of the first crystalline phase. In some embodiments, the size of the second crystalline phase is greater than 10,000 µm. 2 The domain at least partially surrounds the grains of the first crystalline phase.

[0059] In some embodiments, the first crystalline phase further includes one or more rare earth oxides.

[0060] In some embodiments, the ceramic material comprises a bulk porosity of more than 40%, which is measured by the mercury porosity method.

[0061] In some embodiments, the material includes a plurality of pores, wherein the pore size distribution d10 of the plurality of pores is 10 µm or greater.

[0062] In some embodiments, the material includes a plurality of pores, the pore size distribution of which has a d50 of 15 µm or greater.

[0063] In some embodiments, the material includes a plurality of pores, the pore size distribution of which has a d50 of 15 to 20 µm.

[0064] In some embodiments, the ceramic structure disclosed herein comprises the ceramic material described above. In some embodiments, at least one wall of the ceramic structure disclosed herein comprises the ceramic material described above. In some embodiments, the ceramic honeycomb structure disclosed herein comprises a cross-wall matrix comprising the ceramic material described above; in some of these embodiments, a catalytic cleaning material is disposed on at least one wall of the honeycomb structure. In some embodiments, the filter disclosed herein comprises a honeycomb structure comprising the ceramic material described above; in some of these embodiments, the filter further comprises a plurality of plugs disposed in a plurality of channels of the honeycomb structure.

[0065] In the second aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material, the first crystalline phase having a first melting point; and a second crystalline phase comprising a second refractory material, the second crystalline phase having a second melting point lower than the first melting point, wherein the second crystalline phase has a particle size greater than 2500 µm. 2 The average domain size was measured by electron backscatter diffraction (EBSD). In some embodiments, the second crystalline phase has a size greater than 3000 µm. 2 The average domain size, measured by electron backscatter diffraction (EBSD), is greater than 5000 µm in some embodiments. 2 In some implementations, greater than 10000 µm 2 In some implementations, greater than 15000 µm 2 In some implementations, greater than 20000 µm 2 .

[0066] In some embodiments, the first crystalline phase comprises tialite. In some embodiments, the first crystalline phase further comprises MgTi₂O₅. In some embodiments, the second crystalline phase comprises cordierite. In some embodiments, the ceramic material further comprises a third crystalline phase containing a third refractory material. In some embodiments, the third crystalline phase comprises andalusite.

[0067] In the third aspect, the ceramic material disclosed herein includes: a first crystalline phase comprising a first refractory material, the first crystalline phase having a first melting point; and a second crystalline phase comprising a second refractory material, the second crystalline phase having a second melting point lower than the first melting point, wherein the second crystalline phase comprises a particle size greater than 4,000 µm. 2 Domain size, greater than 2500 µm 2 The average domain size was determined by electron backscatter diffraction (EBSD). In some embodiments, the first crystalline phase comprises tialite. In some embodiments, the first crystalline phase further comprises MgTi2O5. In some embodiments, the second crystalline phase comprises cordierite. In some embodiments, the ceramic material further comprises a third crystalline phase containing andalusite.

[0068] In a fourth aspect, the composite ceramic material disclosed herein comprises: a first crystalline phase comprising aluminosilicate, the first crystalline phase having a first melting point and a first maximum domain size in a selected cross-sectional plane; and a second crystalline phase comprising cordierite, the second crystalline phase having a second melting point lower than the first melting point and having a second maximum domain size in the selected cross-sectional plane, wherein the ratio of the second maximum domain size to the first maximum domain size is 6.0 or greater. In some embodiments, the ratio of the second maximum domain size to the first maximum domain size is 7.0 or greater; in some embodiments, it is 8.0 or greater; in some embodiments, it is 10.0 or greater; in some embodiments, it is 15 or greater; and in some embodiments, it is 20 or greater.

[0069] In some embodiments, the domain size of the second crystal phase is greater than 5,000 µm. 2 This was measured using electron backscatter diffraction (EBSD).

[0070] In some embodiments, the first crystalline phase constitutes at least 50% by volume of the material. In some embodiments, the second crystalline phase constitutes less than 50% by volume of the material. In some embodiments, the first crystalline phase constitutes at least 50% by volume of the material, and the second crystalline phase constitutes less than 50% by volume of the material.

[0071] In some embodiments, the first crystalline phase primarily comprises aluminosilicate tungstate. In some embodiments, the first crystalline phase comprises various refractory materials in solid solution with each other. In some embodiments, the first crystalline phase comprises MgTi2O5 in solid solution with aluminosilicate tungstate.

[0072] In some embodiments, the ceramic material further includes a third crystalline phase. In some embodiments, the third crystalline phase includes andalusite. In some embodiments, the first crystalline phase includes pseudo-alumina brookite, the second crystalline phase includes cordierite, and the third crystalline phase includes andalusite. In some embodiments, the first crystalline phase includes pseudo-alumina brookite and MgTi2O5; and in some of these embodiments, the first crystalline phase includes pseudo-alumina brookite and MgTi2O5 in a solid solution with each other.

[0073] In some embodiments, the second crystalline phase primarily comprises cordierite. In some embodiments, the second crystalline phase is essentially composed of cordierite. In some embodiments, the second crystalline phase is cordierite.

[0074] In some embodiments, the first crystalline phase comprises primarily a piezite crystal structure.

[0075] In a fifth aspect, this document discloses a method for manufacturing an article comprising a composite ceramic material, the method comprising: heating a body comprising a starting mixture, the starting mixture comprising a first refractory material or a precursor thereof (or both) and a second refractory material or a precursor thereof (or both), wherein, if a first refractory material precursor is present, the heating is sufficient to cause at least some of the precursor to reactively form the first refractory material, and if a second refractory material precursor is present, the heating is sufficient to cause at least some of the precursor to reactively form the second refractory material, and the heating is sufficient to cause at least some of the first refractory material to melt and to come into contact with at least some of the second refractory material without causing the second refractory material to melt during the heating process; and then cooling the body to form a composite ceramic material comprising a first crystalline phase comprising the first refractory material and a second crystalline phase comprising the second refractory material, wherein the second crystalline phase comprises a particle size greater than 5000 µm. 2 The domain size was measured by electron backscatter diffraction (EBSD).

[0076] In some embodiments, not all of the second refractory material present during heating melts. In some of these embodiments, the unmelted second refractory material provides nucleation sites for the epitaxial domain growth of the second crystalline phase.

[0077] In some embodiments, at least 10% of the second refractory material present during heating melts during heating; in some embodiments, at least 20%; in some embodiments, at least 50%; in some embodiments, 90%; and in some embodiments, all of the second refractory material present during heating melts during heating.

[0078] In some embodiments, the mixture further includes one or more pore-forming materials; in some of these embodiments, heating causes the one or more pore-forming materials to burn off from the mixture, thereby imparting an average bulk porosity to the ceramic material. In some embodiments, the average bulk total porosity is 40% or greater.

[0079] In some embodiments, the first crystalline phase has a first melting point, and the second crystalline phase has a second melting point lower than the first melting point.

[0080] In some embodiments, the highest temperature reached by the mixture during heating is less than the first melting point. In some embodiments, the highest temperature reached by the mixture during heating is between 1300°C and 1450°C.

[0081] In some embodiments, the first crystalline phase comprises tialite. In some embodiments, the first crystalline phase primarily comprises tialite. In some embodiments, the first crystalline phase comprises various refractory materials in solid solution with each other. In some embodiments, the first crystalline phase comprises MgTi2O5 in solid solution with tialite.

[0082] In some embodiments, the composite ceramic material further includes a third crystalline phase. In some embodiments, the third crystalline phase includes a third refractory material. In some embodiments, the third crystalline phase includes andalusite. In some embodiments, the first crystalline phase includes pseudo-alumina and MgTi2O5. In some embodiments, the first crystalline phase includes pseudo-alumina, MgTi2O5, and andalusite in a solid solution with each other.

[0083] In some embodiments, the second crystalline phase includes cordierite. In some embodiments, the second crystalline phase mainly includes cordierite. In some embodiments, the second crystalline phase is essentially composed of cordierite. In some embodiments, the second crystalline phase is cordierite.

[0084] In some embodiments, a cordierite precursor is present in the starting mixture. In some embodiments, the starting mixture is substantially free of cordierite.

[0085] In some embodiments, the first crystalline phase comprises a predominantly brookite crystal structure. In some embodiments, at least a majority of the first crystalline phase provides a multi-branched solid-state network, and at least some of the second crystalline phase is positioned directly adjacent to one or more branches of the solid-state network.

[0086] In some embodiments, cooling includes causing the body to cool at a rate of 80°C / hour or less, in some embodiments it is 50°C / hour or less, in some embodiments it is 40°C / hour or less, and in some embodiments it is 20°C / hour or less.

[0087] In some embodiments, cooling includes causing the body to cool at a rate of 80°C / hour or less when at least a portion of the body temperature is greater than 120°C. In some embodiments, cooling includes causing the body to cool at a rate of 80°C / hour or less when at least a portion of the body temperature is greater than 110°C. In some embodiments, cooling includes causing the body to cool at a rate of 80°C / hour or less when at least a portion of the body temperature is greater than 1000°C.

[0088] Example

[0089] The various implementation methods described above are further illustrated by the following examples.

[0090] Now refer to ceramic materials containing a high percentage of aluminum titanate (AT), materials, or matrices as disclosed herein, which may include aluminum titanate (stabilized aluminum titanate, such as aluminum titanate stabilized by magnesium titanate) and cordierite, wherein cordierite has a very large domain structure. In these matrices, the coefficient of thermal expansion (CTE) is lower than that of matrices containing similar components but with smaller domain structures. The low CTE of such composite ceramic materials disclosed herein depends on both the cordierite and AT phases for their low CTE. A lower CTE can help open the operating window for such materials. Both the AT and cordierite phases have anisotropic thermal parameters. For example, Figure 1 This illustrates the lattice expansion of both AT and cordierite. Both phases exhibit a single axis that shows negative expansion upon heating. Controlling the orientation of these phases within the cell structure is one way to achieve the material's thermal properties. The anisotropy of lattice expansion can also be a source of internal micro-stress and micro-cracks at the grain level, which can also lead to favorable thermal expansion properties. In various applications such as high-temperature environments (e.g., engine exhaust gas, where temperature variations can be hundreds of degrees Celsius), materials with lower CTE generally survive better during use. Across various applications, the lower the CTE, the better the material performance.

[0091] Figure 2 A schematic diagram showing the orthorhombic structure of cordierite crystals, and the associated expansion along each axis.

[0092] Figure 3 This diagram schematically illustrates the orthorhombic structure of cordierite crystals. The left-hand diagram shows the crystal orientation, where the c-axis of cordierite's negative expansion is oriented in the image plane. The right-hand diagram shows the crystal orientation, where the c-axis of cordierite's negative expansion is oriented perpendicular to the image plane. The c-axis in cordierite is parallel to the length of the prismatic crystal. The a- and b-axis are perpendicular to the c-axis and to each other.

[0093] In some embodiments disclosed herein, the particulate filter or catalyst substrate may comprise a ceramic body, such as a honeycomb structure comprising one or more ceramic materials, said ceramic materials comprising multiple or several different crystalline phases or materials, such as aluminum titanate (with or without magnesium titanate) and feldspar or cordierite and other smaller amounts of phases. In various embodiments, the main crystal structure of AT is referred to as argillaceous tungsten.

[0094] The specific crystalline material of aluminum titanate is called pseudo-titanium aluminate. Pure pseudo-titanium aluminate is not thermodynamically stable below approximately 1200°C. To prevent decomposition of AT during high-temperature use, in some embodiments, AT can be stabilized with, for example, MgTi₂O₅, which forms a solid solution with Al₂TiO₅ and is also present in the titanium aluminate crystal structure. In these embodiments, cordierite has been found to be a highly favorable second phase for achieving the desired physical properties (e.g., low CTE, high porosity, and / or high strength, which are required for applications such as particulate filters). Cordierite has been found to have a surprisingly large influence on the physical properties of the material. In these AT embodiments, materials with the lowest CTE can be achieved by creating very large domain structures in cordierite. These domain structures, in their largest form, can be limited only by macroscopic physical boundaries, such as the network width in a honeycomb structure. Furthermore, these cordierite domains were found to possess the surprising property of being encapsulated or encapsulating ilmenite material, and that while the cordierite domains appear non-adjacent in 2D space, they are actually adjacent in 3D space. Therefore, in these embodiments, the provided aluminum titanate-containing material (with or without magnesium titanate or iron titanate) also contains cordierite, which was found to have a large domain structure (or “large domains”). These domain structures can be measured using electron backscatter diffraction (EBSD). The measurement method involves vacuum impregnating a porous ceramic honeycomb into an epoxide, allowing the epoxide to cure, and then polishing it to a high-quality final product either parallel to the honeycomb extrusion direction (long section) or perpendicular to the honeycomb extrusion direction (cross section). A thin metallic coating is applied to the polished cross section to minimize the charge, and EBSD is performed using field emission scanning electron microscopy (FESEM). The electron backscattering diffraction pattern at each point in the micrograph can be compared with known crystal structure information determined by powder X-ray diffraction data to provide information on crystal type and orientation with sub-micron spatial resolution. Post-processing of EBSD data allows for the mapping of crystal regions with similar crystallographic test orientations by creating texture composition maps, where the colors indicate the orientation of the crystal of interest (AT or cordierite) relative to the negative expansion direction of the sample surface. Image analysis can then be used to determine regions with equivalent spherical diameters of similar crystallographic test orientations. Because the regions are discontinuous in 2D space, directly measuring the domain size using standard EBSD techniques is largely impractical.

[0095] In these AT / cordierite examples, the main phase is the relatively inert argillaceous borosilicate. In some embodiments, cordierite can be obtained from the material forming the cordierite phase, which can be heated to the melting point of cordierite to aid nucleation and the formation of large domains. Furthermore, in some embodiments, because the main phase is the relatively inert argillaceous borosilicate, the regions where the cordierite phase forms are separated, thereby reducing the nucleation area and resulting in large domains.

[0096] In some implementations, it has been found that, for example, if the duration of the top holding temperature during the firing cycle is shortened for cost-saving reasons, the CTE of the fired product increases compared to a longer top holding firing period; however, if the proportion of the top holding temperature in the cycle is shortened, while everything else remains the same, a lower CTE can be achieved again by implementing a cooling portion of the firing cycle with a lower cooling rate. "Top holding" refers to the highest kiln temperature setpoint for a specified time according to the firing scheme, or the highest kiln temperature at which the vessel is exposed inside the kiln.

[0097] Table 1

[0098] Example 1: Aluminous pseudopantheite with a large cordierite domain

[0099] A composite ceramic material comprising alumina pseudoborosilicate and large cordierite was prepared according to the materials in Example 1 of Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 1 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0100] Figure 4 The regions / domains showing similar cordierite orientations corresponding to the image analysis from the EBSD data in Table 1 are shown.

[0101] Example 2: Aluminosilicate pseudopanthene from slowly cooled ore with large cordierite domains

[0102] The composite ceramic material comprising pseudo-ilmenite and large cordierite was prepared according to Example 2 in Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 2 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0103] Figure 5 Showing regions / domains with similar cordierite orientations corresponding to the image analysis from EBSD data in Table 2.

[0104] Example 3 (Comparative Example): Alumina pseudo-titanium ore with cordierite domain obtained from rapid cooling

[0105] A composite ceramic material comprising pseudo-ilmenite and large cordierite was prepared according to the materials in Example 3 of Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 3 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0106] Figure 6 The images in Table 3 show regions / domains with similar cordierite orientations based on the image analysis of the EBSD data.

[0107] Example 4 (Comparative Example): Alumina pseudo-titanium ore with cordierite domain obtained from rapid cooling

[0108] A composite ceramic material comprising pseudo-ilmenite and large cordierite was prepared from the materials in Example 4 of Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 4 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0109] Figure 7 The images shown in Table 4 depict regions / domains with similar cordierite orientations based on the image analysis of the EBSD data.

[0110] Example 5 (Comparative Example): Alumina pseudo-titanium ore with large cordierite domains from rapidly cooled samples: small cordierite domains

[0111] A composite ceramic material comprising alumina pseudoborosilicate and large cordierite was prepared according to the materials in Example 5 of Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 5 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0112] Figure 8 The images in Table 5 show regions / domains with similar cordierite orientations based on the image analysis of the EBSD data.

[0113] Example 6 (Comparative Example): Aluminous pseudo-titanium ore with cordierite domain

[0114] A composite ceramic material comprising alumina pseudoborosilicate and large cordierite was prepared from the materials in Example 6 of Table 1. The batch material was extruded, dried, and then fired according to the conditions of Example 6 in Table 1. Cross-sectional images were analyzed from EBSD data. Table 1 shows representative regions of the first 10 images corresponding to the largest cordierite domain. Table 1 also shows the average domain size of the first 10.

[0115] Figure 9 The images shown in Table 6 depict regions / domains with similar cordierite orientations based on the image analysis of the EBSD data.

[0116] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Therefore, this specification is intended to cover modifications and variations of the various embodiments described herein, and such modifications and variations fall within the scope of the appended claims and their equivalents.

Claims

1. A method for manufacturing ceramic articles, comprising: The main body is formed from the starting mixture, the starting mixture comprising: at least one of a first refractory material or a precursor thereof, and at least one of a second refractory material or a precursor thereof; The main body is heated to a temperature range of 1300°C to 1450°C at a heating rate, such that if a first refractory material precursor is present, the heating causes the reactivity of at least some of the precursor to form a first refractory material, and if a second refractory material precursor is present, the heating causes the reactivity of at least some of the precursor to form a second refractory material. as well as When at least a portion of the body reaches a temperature greater than 1000°C, the body is cooled at a cooling rate of 80°C / hour or less to form a ceramic article, the ceramic article comprising a first crystalline phase containing a first refractory material and a second crystalline phase containing a second refractory material, the second crystalline phase comprising a crystal phase greater than 5000 µm. 2 The domain size was measured by electron backscatter diffraction (EBSD); as well as Wherein, the ratio of the maximum domain size of the second crystal phase to the maximum domain size of the first crystal phase is 6.0 or greater.

2. The method as described in claim 1, wherein, The heating rate is 60°C / hour to 130°C / hour.

3. The method as described in claim 1, wherein, The cooling rate is less than or equal to 20°C / hour.

4. The method of claim 1, wherein, The second crystalline phase comprises a particle size greater than 30,000 µm. 2 The size of the domain.

5. The method of claim 1, wherein, The ratio of the second maximum field size to the first maximum field size is 15 or greater.

6. The method of claim 1, wherein, The ratio of the second maximum field size to the first maximum field size is 20 or greater.

7. The method of claim 1, wherein, Heating causes at least some of the first refractory material to melt and come into contact with at least some of the second refractory material, which is done without causing the second refractory material to melt during heating.

8. The method of claim 1, wherein, The first crystalline phase includes aluminosilicate.

9. The method of claim 8, wherein, The first crystalline phase includes MgTi2O5, which is in solid solution with aluminosilicate.

10. The method of claim 1, wherein, The second crystalline phase includes cordierite.

11. The method of claim 1, wherein, The first crystalline phase has a first melting point, and the second crystalline phase has a second melting point lower than the first melting point.

12. The method of claim 11, wherein, During the heating process, the highest temperature reached by the initial mixture is lower than the first melting point.

13. The method of claim 1, wherein, Ceramic products include polyaluminum andalusite.

14. The method of claim 1, wherein, The starting mixture contains an aqueous solvent.

15. The method of claim 1, wherein, The starting mixture contains one or more pore-forming materials.

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