WO2022026236A1 - Aluminum titanate-feldspar ceramic bodies, batch mixtures, and methods of manufacture - Google Patents

Abstract

Aluminum titanate-feldspar ceramic bodies are provided. The aluminum titanate-feldspar ceramic body comprises a first crystalline phase containing aluminum titanate and a second crystalline feldspar phase. Body further exhibits CTE (x 10^-7/ºC measured from RT to 800ºC) ≤ 0.54 (%P) + 4.22 (MgO wt%) – b, wherein CTE is coefficient of thermal expansion, %P is average bulk porosity, and 20 ≤ b ≤ 25. Batch mixtures including sources of alumina, titania, silica, strontia and/or calcia, and magnesia are provided. Sources of magnesia comprising spinel in an amount greater than or equal to 1.8 wt% (e.g., from 1.8 wt% and 9.6 wt%) are disclosed. Methods of manufacture of ceramic bodies including green and ceramic honeycomb bodies are provided, as are other aspects.

Description

ALUMINUM TITANATE-FELDSPAR CERAMIC BODIES, BATCH MIXTURES, AND METHODS OF MANUFACTURE

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63/058665 filed on July 30, 2020, the content of which is relied upon and incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to ceramic bodies, more particularly aluminum titanate-feldspar ceramic bodies, batch mixtures used to form such ceramic bodies, and methods of manufacture of such ceramic bodies.

BACKGROUND

[0003] Formed ceramic bodies, for example porous ceramic honeycomb bodies, may be used in a variety of applications. Such formed ceramic honeycomb bodies may be used, for example, as catalyst supports for carrying out catalyzed reactions, as sorbents, or as particulate filters useful in the capture of particulates from fluids such as gas or liquid streams.

SUMMARY

[0004] In accordance with various embodiments of the disclosure, an aluminum titanate (AT)-feldspar ceramic body is provided. The ceramic body is relatively resistant to decomposition of aluminum titanate (e.g., into titania and alumina, such as rutile and/or corundum phases) when exposed to high temperatures (e.g., above 700°C) in the presence of copper oxide -containing coatings or other copper-oxide sources.

[0005] In accordance with some embodiments of the disclosure, an AT-feldspar ceramic body is provided. The AT-feldspar ceramic body can exhibit excellent combinations of low CTE and high resistance to decomposition when heated in the presence of a copper-oxide source. [0006] In accordance with further embodiments of the disclosure, an AT-feldspar ceramic body is provided that exhibits excellent combinations of low CTE, high porosity, and high resistance to decomposition when heated in the presence of a copper-oxide source.

[0007] In accordance with various other embodiments of the disclosure, aluminum titanate- feldspar forming batch mixtures including spinel are disclosed.

[0008] In accordance with other embodiments of the disclosure, methods of manufacture of aluminum titanate-feldspar ceramic bodies are disclosed wherein a source of magnesia is spinel and is provided as a component in the batch mixture in an amount greater than 1.8 wt%, based on a total weight of inorganic materials in the batch mixture. In some embodiments, the source of magnesia comprises spinel provided in an amount of greater than 1.8 wt%, from 1.8 wt% to 9.6 wt%, or even from 1.8 wt% to 3.6 wt%, based on a total weight of the inorganic materials in the batch mixture.

[0009] In accordance with other example embodiments of the disclosure, an aluminum titanate-feldspar ceramic body is disclosed. The aluminum titanate-feldspar ceramic body comprises a first crystalline phase containing aluminum titanate and a second crystalline phase of feldspar; wherein the body is characterized by CTE (10⁷/°C at RT to 800°C) < 0.54* (%P) + 4.22*MgO (wt%) - b, where RT refers to room temperature (25°C), %P is average bulk porosity of the porous ceramic material of the ceramic body, and 20 < b < 25.

[0010] Further, the aluminum titanate-feldspar ceramic body can have a decomposition rate of aluminum titanate in the presence of 0.15 wt% of a copper oxide -containing coating on the ceramic body that corresponds to less than 7.0 wt% growth of a rutile phase after heating at 1, 100°C for 4 hours, as compared to an uncoated body of the same composition.

[0011] In accordance with another example embodiment of the disclosure, a method of manufacturing an aluminum titanate-feldspar ceramic body is disclosed. The method of manufacturing comprises forming a batch mixture of inorganic materials from sources of: alumina, titania, silica, one or more of a strontia or calcia, and magnesia, wherein the source of magnesia comprises spinel provided in an amount greater than or equal to 1.8 wt% based on a total weight of the inorganic materials in the batch mixture; forming a green body from the batch mixture; and firing the green body to form the aluminum titanate-feldspar ceramic body, wherein the aluminum titanate-feldspar ceramic body further comprises: a first crystalline phase comprising aluminum titanate and magnesium dititanate, a second crystalline phase comprising feldspar, wherein the aluminum titanate-feldspar ceramic body is characterized by CTE (10⁷/°C at RT to 800°C) < 0.54* (%P) + 4.22*MgO (wt%) - b, wherein CTE is coefficient of thermal expansion measured from room temperature (25°C) to 800°C, %P is average bulk porosity of the porous ceramic material of the ceramic body, and 20 < b < 25. The %P and wt% values are to be entered as their percentage numbers between 0 and 100 (for example a ceramic body having 50% porosity and 1.5 wt% MgO would have the %P value entered as “50” not “0.5” and the MgO wt% entered as “1.5” not “0.015”). Bulk porosity referred to herein can be measured by mercury intrusion porosimetry (MIP) or the Archimedes method (all measured values of bulk porosity provided herein, e.g., in Tables 2A-2B, were obtained by MIP).

[0012] As described herein, the aluminum titanate may decompose under certain circumstances (e.g., in the presence of transition metal oxides, such as copper oxide) into rutile and corundum phases, and thus, the decomposition rate of the aluminum titanate can be determined based on the growth of one or both of these phases. In some embodiments, the aluminum titanate-feldspar ceramic body can further comprise a decomposition rate of the aluminum titanate in the presence of 0.15 wt% of a copper oxide-containing coating on the aluminum titanate-feldspar ceramic body that corresponds to less than 7.0 wt% growth of the rutile phase after heating at 1, 100°C for 4 hours. In some embodiments, the source of magnesia comprises spinel provided in an amount from 1.8 wt%to 9.6 wt%, or even from 1.8 wt%to 3.6 wt%, based on a total weight of the inorganic materials in the batch mixture.

[0013] In various embodiments described herein, the aluminum titanate-feldspar ceramic bodies are formed from AT-feldspar forming batch mixtures. The AT-feldspar forming batch mixture, comprises inorganic materials provided in the batch mixture in amounts, on an oxide weight basis (“owt%”), of: alumina from 40 owt% to 56 owt%; titania from 22 owt% to 50 owt%; silica from 1.8 owt% to 22 owt%; one or more of strontia and calcia in a combined owt% from 1.0 owt% to 16 owt%; and magnesia in an amount of greater than or equal to 0.5 owt%, wherein the source of magnesia comprises spinel (MgAhCri). and wherein oxide weight percentage of each inorganic material is based upon a total weight of inorganics present in the batch mixture.

[0014] In some embodiments, the source of magnesia comprises spinel (MgAhCri) and the spinel provides the magnesia in an amount, on a weight percent oxide basis, from 0.5 owt% to 2.73 owt%, or even from 0.5 owt%to 1.5 owt%.

[0015] Additional features of the present disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments disclosed herein. Both the foregoing general description and the following detailed description provide numerous examples and are intended to provide further explanation of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIGs. 1 and 2 schematically illustrate perspective views of honeycomb ceramic bodies, respectively unplugged and plugged, formed from an AT-feldspar forming batch mixture according to one or more embodiments of the disclosure.

[0017] FIG. 3 illustrates a flowchart of a method of manufacture of an AT-feldspar ceramic body according to one or more embodiments of the disclosure.

[0018] FIG. 4 illustrates a partially cross-sectioned side view of an extruder apparatus useful in the manufacture of green honeycomb bodies from AT-feldspar forming batch mixtures according to one or more embodiments of the disclosure.

[0019] FIG. 5 is a graph showing the growth in wt% Rutile phase present at various MgO inclusions in oxide weight % when the AT-Feldspar ceramic body is subjected to heating at 1, 100°C for 4 hours in the presence of a copper-containing coating as compared to an untreated (uncoated) body under the same heating conditions according to various embodiments of the disclosure.

[0020] FIG. 6 is a graph showing CTE (x 10⁷/°C) versus average bulk porosity (%P) for an example AT-Feldspar ceramic honeycomb body having a level of spinel addition that contributes approximately 0.68 owt% of MgO, as well as data points for comparative examples derived from Mg(OH)2, MT2, and talc in amounts that contribute similar amounts of MgO, as indicated.

[0021] FIG. 7 is a graph showing CTE (x 10⁷/°C from RT to 800°C) versus average bulk porosity (%P) for an example AT-Feldspar ceramic honeycomb body having an oxide weight level of spinel batch mixture addition to provide the indicated 1.02 owt% of MgOas compared to comparative examples for other types of batch inclusions (1.04 owt% from Mg(OH)2 and 1.05 owt% from talc).

[0022] FIG. 8 is a graph showing CTE (x 10⁷/°C from RT to 800°C) versus average bulk porosity (%P) for an example AT-Feldspar ceramic honeycomb body having relatively higher oxide weight levels of spinel batch mixture addition (as compared to the amounts in FIGs. 6 and 7), as well as data points for MgO in the indicated amounts provided by MT2 and talc.

[0023] FIG. 9 is a graph showing CTE (x 10⁷/°C from RT to 800°C) versus average bulk porosity (%P) for example AT-Feldspar ceramic honeycomb bodies having various oxide weight levels of spinel batch mixture addition according to various embodiments of the disclosure.

[0024] FIG. 10 is a graph showing median pore diameter (interchangeably herein as MPD or d50) versus average bulk porosity (%P) for example AT-Feldspar ceramic honeycomb bodies having various oxide weight levels of spinel batch mixture addition and being fired at different top soak temperatures according to various embodiments of the disclosure.

DETAILED DESCRIPTION

[0025] Embodiments of the disclosure relate to aluminum titanate-feldspar containing ceramic bodies, such as aluminum titanate-feldspar ceramic honeycomb bodies, batch mixtures used to form the aluminum titanate-feldspar ceramic bodies, green honeycomb bodies formed from such batch mixtures, as well as methods of manufacture of the green honeycomb bodies and aluminum titanate-feldspar ceramic honeycomb bodies.

[0026] In some ceramic honeycomb body embodiments of such as particulate fdters, aluminum titanate (“AT”) ceramic materials may be used. One process used in the manufacture of such AT ceramic honeycombs involves forming a batch mixture, forming a green honeycomb body such as by extrusion of the batch mixture through an extrusion die to produce a green honeycomb body, and firing the green honeycomb body in a furnace to produce the AT crystalline phase in the ceramic honeycomb body. In some embodiments, the ceramic composition can include an AT phase and a feldspar phase (hereinafter “AT-feldspar”).

[0027] Degradation of the coefficient of thermal expansion (CTE) due to exposure to high temperatures is one issue potentially faced by some AT-feldspar honeycombs, which may be undesirable, as high CTE values may in some instances result in cracking of the ceramic honeycomb body during use. As described herein, currently disclosed embodiments may be beneficial for maintaining low CTE values even when used in high temperature scenarios, e.g., in an exhaust aftertreatment system.

[0028] An example of a ceramic honeycomb body 100 is illustrated in FIG. 1, which honeycomb body 100 comprises intersecting walls 102 forming a plurality of channels 104. The channels 104 extend axially and can be parallel to one another so as to extend from a first end 105 to a second end 107 (e.g., an inlet end and an outlet end for exhaust gas or other fluid to be treated by the honeycomb body 100). A skin 108 may be formed on an outside peripheral surface of the honeycomb body 100.

[0029] In some embodiments, such as shown in FIG. 2, at least some channels 104 formed by the intersecting walls 102 of the AT-Feldspar ceramic honeycomb body 100 are plugged with plugs 206 to form a plugged ceramic honeycomb body 200 that can be used as part of a particulate filter. Plugging with plugs 206 can be performed using any conventional plugging method and plugging material. Some channels 104 not plugged at the first end 105 can be plugged at the second end 107, and channels not plugged at the second end 107 can be plugged at the first end 105, thereby forcing fluid flow through the plugged body 200 to travel through the porous ceramic material of the intersecting walls 102 and trap particulate matter in the channels 104. Any suitable plugging pattern or arrangement can be used. In some embodiments, the plugged ceramic honeycomb body 200 comprises at least some channels 104 that are entirely unplugged along their length, i.e., the plugged ceramic honeycomb body 200 can be a partial filter (comprise both plugged and unplugged channels).

[0030] Aluminum titanate materials (AT) have been used where high heat capacity is desired, such as in diesel particulate filter applications. In such applications, burnout of captured soot can create a substantial amount of internal heat. This high heat can, in some instances cause cracking of the diesel particulate filter. In current applications, AT is not used as its lone crystal state, but rather in conjunction with other materials such as with an alkaline- earth feldspar phase, cordierite phase, or mullite crystalline phase. Examples of such AT- containing ceramics including a alkaline-earth feldspar crystalline phase are described in US6,620,751, US6,942,713, US7,259,120, US7,249,164, US7,976,768, US7,977,266, and US9,272,956, for example. Examples of cordierite-aluminum titanate compositions are described in US8,394,167, US8,673,045, and US9,079,799. Examples of aluminum titanate- mullite compositions are described in US4,483,944.

[0031] In some embodiments, the second crystalline feldspar phase in the aluminum titanate - feldspar (AT-feldspar) ceramic honeycomb bodies comprises one or both of a strontium -containing feldspar and a calcium -containing feldspar, such as a combined strontium (Sr)- and calcium (Ca)-containing feldspar (e.g., strontium-containing and calcium-containing feldspar in solid solution).

[0032] Conventional aluminum titanate - feldspar materials have advantages of high strength and high heat capacity, but this may come at the expense of relatively-low thermal stability in comparison to some other ceramic material. At lower temperatures of less than about 700°C, AT is kinetically stable. However, at temperature above about 700°C and up to about 1,200°C, conventional aluminum titanate - feldspar materials are prone to decomposition in the presence of transition metal oxides, such as copper oxide. One advantage of the present AT-feldspar ceramic body is that it can be used in both high and low porosity applications. Previously, CMAT was used in high porosity applications. Thus, the present AT-feldspar ceramic bodies according to this disclosure can now be used for high porosity (e.g., > 50%) by using spinel as the magnesia source. The present AT-feldspar ceramic bodies can also be used in low porosity (e.g., <40% or < 50%).

[0033] Without wishing to be bound by theory, it is believed that the increased thermal instability offered by the embodiments disclosed herein is because of a substantial stabilized magnesium titanate phase in the currently disclosed embodiments, while conventional AT- feldspar ceramic honeycomb bodies lack the stabilizing magnesium titanate or other stabilizing titanate phase. In the presence of certain transition metals and/or transition metal oxides, such as copper-containing metal oxide coatings at temperatures even as low as about 700°C, the conventional AT-feldspar material can decompose. In particular, in the presence of copper- containing metal oxides used in catalysts for Selective Catalyst Reduction (SCR) applications, decomposition of the AT phase may be particularly severe. Any decomposition causes conversion to corundum and rutile phases and thus can cause relatively-high CTE in the ceramic honeycomb body over time when exposed to such heat. Such high CTE in the conventional AT-feldspar ceramic honeycomb body is generally undesirable and may cause cracking over time due to exposure to such high temperatures during use.

[0034] For example, when a copper-containing coating, such as a Cu zeolite coating, is used as a catalyst coating on such a conventional AT-feldspar ceramic honeycomb body, the ceramic body can decompose and crack when exposed to such high temperatures. Cu zeolite coatings may be used on ceramic honeycomb bodies to remediate NOx gases from an exhaust stream. It would be therefore advantageous to have an AT-feldspar material that has relatively low CTE and that is temperature stable, i.e., that does not decompose appreciably when exposed to such high temperatures in the presence of copper oxide -containing coatings. Some of the copper oxide-containing materials may be received on the ceramic body by other means other than coatings. In some embodiments, the present AT-feldspar material has relatively low CTE, relatively-high bulk porosity (%P), and is sufficiently temperature stable when exposed to high temperatures in the presence of exposure to copper-containing materials, such as coatings or other from other sources.

[0035] Previous efforts have attempted to make such AT-feldspar that is temperature stable, such as by the use of transition metals and transition metal oxides such as by inclusion of iron oxide to form iron titanate in solid solution with the aluminum titanate. However, the CTE was either relatively high (e.g., >25 x 10⁷/°C or even >40 x 10⁷/°C from RT to 800°C) or if lower, then either desired filter properties were not achieved, and/or temperature stability at temperature and in the presence of copper oxide during use was not present. However, it is desired to have a ceramic body with CTE <25 x 10⁷/ °C (RT to 800°C), which does not degrade appreciably upon exposure to high temperatures (e.g., up to 1200°C). Further, the ceramic body should have be able to support high porosities, e.g., at least 50% porosity. Different sintering aids, such as LaiCh, Y2O3, CeCh, and their combinations were tried as well. Even Zr and Zn oxides in AT-Feldspar were tried to lower CTE. Different ways of adding the magnesium was tried, including talc, magnesium titanate (MgTiiCE). and Mg(OH)2. However, none of these methods were effective to reduce CTE, while providing excellent temperature stability at the same time.

[0036] Thus, in accordance with embodiments disclosed herein, a ceramic honeycomb body having and AT-feldspar phase composition that is magnesium titanate-stabilized is provided that exhibits not only relatively-low CTE (e.g., CTE (RT to 800 °C) < 25 x 10⁷/°C, or even CTE (RT to 800 °C) < 12 x 10⁷/°C), can have useful porosities for fdter applications, but that is also temperature stable by exhibiting relatively low amounts of decomposition when exposed to high temperatures in the presence of copper-oxide containing materials, such as copper-oxide containing catalyst coatings. According to embodiments, an aluminum titanate- feldspar ceramic body is provided that is characterized by CTE (10⁷/°C at RT to 800°C) < 0.54* (%P) + 4.22*MgO (wt%) - b, where 20 < b < 25. In some embodiments, b is at least 20, at least 21, at least 22, or at least 23. In some embodiments, b has a value of 25, 24, 23, 22, 21, or even 20, including ranges including any of these values as end points, such as from 20 to 24, 20 to 23, 20 to 22, 20 to 21, 21 to 25, 21 to 24, 21 to 23, 21 to 22, 22 to 25, 22 to 24, 22 to 23, 23 to 25, or 23 to 24.

[0037] Thus, in accordance with one or more aspects of the disclosure, an AT-feldspar ceramic body that is stabilized against Cu zeolites is provided, so it can be used in SCR applications. In accordance with one or more further aspects, an AT-feldspar ceramic body is provided that exhibits a combination of relatively-low CTE, desirable fdter porosity, and excellent temperature stability in terms of its decomposition rate in the presence of copper oxides when heated. In other aspects, batch mixtures (interchangeably, “batch compositions”) useful in the formation of AT-feldspar ceramic honeycomb bodies are provided that include spinel (Mg AI2O4) in defined wt% as an ingredient in a batch mixture used to form the ceramic honeycomb body. In yet further embodiments, green honeycomb bodies and methods of manufacture of AT-feldspar ceramic honeycomb bodies are provided. These and other aspects of the disclosure will be fully described with reference to FIGs. 1-10 herein.

Methods of manufacture of AT-Feldspar ceramic bodies

[0038] Methods of manufacture of the aluminum titanate-feldspar ceramic bodies exhibiting low CTE, desirable porosity, and excellent temperature stability are disclosed herein. Various methods of manufacture of aluminum titanate-feldspar ceramic honeycomb bodies are described with reference to FIGs. 3 and 4 and as otherwise as disclosed herein. [0039] More particularly, a method 300 in FIG. 3 comprises, in block 302, forming a batch mixture (e.g., a batch mixture 445 in FIG. 4) of inorganic materials from sources of: alumina, titania, silica, and magnesia. As described herein, the inventor has discovered that when the source of magnesia comprises spinel (MgAhCri) provided in a specific amount (wt%), that an excellent combination of relatively-low CTE and temperature stability in the presence of copper oxide occurs. Further, desirable bulk porosities (e.g., %P of 40% to 65%) are achieved in some embodiments. In particular, it was discovered that if the amount of spinel in the batch mixture is too low, that desired temperature stability in the presence of copper oxide is not achieved, and if the amount of spinel addition to the batch mixture is too high, then CTE (RT to 800°C) becomes too high (e.g., above 25 x 10⁷/ °C). In particular, it was discovered that spinel addition should be provided in the batch mixture an amount of greater than or equal to 1.8 wt%, from 1.8 wt% to 9.6 wt%, or even from 1.8 wt% to 3.6 wt%, based on a total weight of the inorganic materials in the batch mixture. In another manner of understanding the addition, the spinel can be added in an amount to result in greater than or equal to 0.5 owt%, from 0.5 owt% to 2.73 owt%, or even 0.5 owt% to 1.5 owt% of MgO in the batch mixture, wherein owt% is oxide weight percentage based on the total inorganic oxides present, and thus correspondingly result in greater than or equal to 0.5 wt%, from 0.5 wt% to 2.73 wt%, or even 0.5 wt% to 1.5 wt% of MgO in the ceramic honeycomb body. It is noted that MgO may not be present in its pure form in the final ceramic body, since the MgO may be incorporated into other phases, such as in the magnesium dititanate (MgTriCE) phase, and thus the wt% of MgO for the ceramic body as referred to herein is understood to include MgO that has been incorporated in the other phases. Oxides as referred to herein include both binary oxides, i.e., compounds having oxygen with one other element such as alumina (AI2O3), as well as complex oxides, i.e., compounds having oxygen with a group of multiple elements such as aluminum titanate (AI2T1O5) or cordierite (MgiAUSisOiii).

[0040] In some embodiments, the aluminum titanate-feldspar forming batch mixture 445 comprises inorganic materials provided in amounts, on an oxide weight basis, of: alumina from 40 owt% to 56 owt%; titania from 22 owt% to 50 owt%; silica from 1.8 owt% to 22 owt%; one or more of strontia and calcia in a combined owt% from 1.0 owt% to 16 owt%; and magnesia in an amount of greater than or equal to 0.5 owt%, wherein the source of magnesia comprises spinel (MgAhCri). and wherein oxide weight percentage of each inorganic material is based upon a total weight of inorganics present in the batch mixture. Since the owt% of oxides in the batch mixture should match the wt% of those oxides in the fired ceramic article, the oxide weight percentages of the components of the batch mixture can be determined from analysis of the resulting phases, e.g., identified by XRD analysis of the ceramic body. In other embodiments, the aluminum titanate-feldspar forming batch mixture 445 comprises spinel (MgAhCri) to provide an amount of MgO in an amount from 0.5 owt% to 2.73 owt%, or even in an amount from 0.5 owt% to 1.5 owt%.

[0041] In other embodiments aluminum titanate-feldspar forming batch mixture 445 comprises alumina from 42 owt% to 50 owt%; titania from 30 owt% to 36 owt%; silica from 10.0 owt% to 10.5 owt%; and one or more of strontia and calcia in a combined owt% from 6 owt% to 10 owt%.

[0042] In order to form the batch mixture 445, inorganic particulate material sources containing alumina, titania, silica, and one or more alkaline-earth containing compounds providing a strontia and/or calcia source are blended with particulate spinel, and optionally a rare-earth source. The rare-earth source can be lanthanum oxide (LaiCh) or other suitable rare- earth source such as a rare earth from the lanthanide series or yttrium. To these dry inorganic particulates one or more optional pore former materials may be added, such as graphite and/or starch as a super addition (SA) to the inorganic particulate materials. In addition, a methylcellulose-containing organic binder is added, and all the dry ingredients can be well mixed and intimately blended using a plow mixer or other mixing implement.

[0043] After mixing and blending, the wet ingredients such as a liquid vehicle (e.g., water) and other processing liquid aids (e.g., fatty acid) can be added and mulled together, which can help impart plastic formability and green strength to the raw materials of the batch mixture 445. For example, the materials can be mulled into a paste-like consistency using a muller. After initial mixing, the batch mixture is added into a material supply port 443 of an extruder apparatus 400, and further plasticized in the extruder apparatus 400 (FIG. 4). This plasticized AT-feldspar-forming batch mixture can be extruded through an extrusion die 444, and then cut, dried, and fired as will be described further herein.

[0044] The method 300 further comprises, in block 304, forming a green body (e.g., a green body 100G in FIG. 4) from the batch mixture. The green body (e.g., the green body 100G) can be formed to have any suitable form, shape, or structure. One example embodiment of forming the green body is shown in FIG. 4, which forms a honeycomb green body 100G of a shape of the honeycomb ceramic body 100 as shown in FIG. 1, for example. That is, the ceramic honeycomb body 100 can be formed from the green honeycomb body 100G by performing further manufacturing steps on the green honeycomb body 100G, such as drying and firing steps. Thus, the honeycomb green body 100G, like the ceramic honeycomb body 100 that is formed from the honeycomb green body 100G, also comprises intersecting walls 102 forming a plurality of channels 104 and the skin 108 on an outside peripheral surface of the green honeycomb body 100G.

[0045] The forming of the green honeycomb body 100G can be by using any suitable extrusion systems or methods, such as an extrusion die 444 shown in FIG. 4. The extruder apparatus 400 can be of any suitable type, such as a twin-screw extruder as shown in FIG. 4, or optionally a hydraulic ram extrusion press, or any other suitable extruder apparatus. However, any other suitable method of forming the green honeycomb body 100G can be used.

[0046] Batch mixture 445 can be introduced to the extruder apparatus 400 either continuously or intermittently. The extrusion die 444 in accordance with various embodiments described herein is coupled at the downstream side of a barrel 440 of the extruder 400 and can be configured as part of an extrusion assembly 409 to extrude the batch mixture 445 into a desired shape of the green honeycomb extrudate from which the green honeycomb body 100G is cut (and therefor the desired shape of the ceramic honeycomb body 100 after firing the green honeycomb body 100G). The extrusion die 444 can be coupled to the barrel 440 by any suitable means, such as bolting, clamping, or the like. The extrusion die 444 can be preceded by other extruder structures, such as a particle screen, a screen support, a homogenizer, or the like, e.g., to facilitate the formation of a desired rheology or flow type, such as a steady plug-type flow front, before the batch mixture 445 reaches the extrusion die 444.

[0047] The batch mixture 445 exits the extruder apparatus 400 from the extrusion die 444 in a longitudinal direction 442 as a green honeycomb extrudate, which green honeycomb extrudate is cut by a suitable cutting implement 448, such as a rotating saw blade, laser, wire, vibratory blade, or other suitable cutting implement. The green honeycomb extrudate is cut to a desired length L for the green honeycomb body 100G, which can then be transported on a tray 446, conveyor (not shown), and/or other transportation device for further processing steps such as drying. As described above, the green honeycomb body 100G can be transported to a dryer apparatus, dried and subsequently fired to form the AT-feldspar ceramic honeycomb body 100 shown in FIG. 1.

[0048] In some embodiments described herein, the skin 108 of the green honeycomb bodies 100G can be co-formed from the same batch mixture 445 and at the same time as the matrix portion (comprising the walls 102) of the green honeycomb body 100G. The AT-feldspar batch mixture 445, as described below, can be a mixture of inorganic materials, organic materials, and one or more liquids. For example, the containing the AT-feldspar batch mixture 445 can comprise inorganic sources of alumina, titania, silica, and magnesia, wherein the source of magnesia comprises spinel. The AT-feldspar batch mixture 445 can contain other inorganic materials, such as alkaline-earth containing compounds (e.g., SrCCb and CaCCb) to produce the feldspar phase and one or more rare earth additives as a sintering aid, such as lanthanum oxide to aid in lowering the sintering temperature. Other suitable sintering aids may be used.

[0049] The organic materials can comprise a methylcellulose organic binder, optionally a pore former, and/or other processing additives (oils, plasticizers, etc.). As a result of the forming of the honeycomb green body 100G from the AT-Feldspar-forming batch mixture 445, in some embodiments, the honeycomb green body 100G can comprise inorganic sources comprising an alumina source, a titania source, a silica source, and a magnesia source, wherein the magnesia source comprises spinel. The spinel can be provided in an amount of greater than or equal to 1.8 wt%, from 1.8 wt%to 9.6 wt%, or even from 1.8 wt%to 3.6 wt%, based on the total weight of inorganic materials in the batch mixture 445.

[0050] Once the green body is formed, the method 300 comprises, in block 306, firing the green body (e.g., the green body 100G) to form the AT-feldspar ceramic honeycomb body (e.g., the honeycomb body 100 of FIG. 1). In some embodiments, the aluminum titanate- feldspar ceramic body comprises: a first crystalline phase comprising aluminum titanate (AhTiCF or tialite) and magnesium dititanate (MgTiiCF). and a second crystalline phase of feldspar (SrxCa(l-x)AkSi208). [0051] For example, following formation of the green honeycomb body 100G, the green honeycomb body 100G can then be dried and fired using conventional drying and firing apparatus to produce the AT-feldspar ceramic honeycomb body 100, wherein an example AT- feldspar ceramic honeycomb body 100 shown in FIG. 1. Upon being provided to the tray 446, the tray 446 with green honeycomb body 100G can be provided to a dryer apparatus and dried, such as dryer apparatus described in US9,335,093, US9,038,284, US7,596,885, and US6,259,078, for example. Any suitable conventional drying apparatus can be used for drying, such as RF drying, microwave drying, oven drying, or any combination thereof. The green honeycomb body 100G can initially be cut to a desired length L by cutting implement 448 or optionally can be cut to an intermediate log length, dried, and then cut to the desired length L after drying. Thus, in this instance of being cut to a log length, multiple dried green honeycomb bodies 100G can be provided from each log length. A dried green body as used herein means dried to contain less than 10% water by weight.

Alumina Source

[0052] In forming the aluminum titanate-feldspar forming batch mixture 445, the batch mixture contains an alumina source. The alumina source can comprise monohydrate alumina, trihydrate alumina, or calcined alumina, for example. As should be recognized, some portion of the alumina in the batch mixture 445 can come from the spinel addition. Other suitable sources of alumina can be used. The alumina source can comprise a median particle diameter of from 5 pm and 30 pm, or even from 10 pm to 20 pm, for example.

[0053] The alumina source can be present in any amount suitable for producing the desired AT-feldspar composition. In various embodiments, the alumina source(s) can provide alumina in the batch mixture in at least 30 wt%, based on the total weight of the inorganics in the batch mixture 445. For example, in certain embodiments, the alumina source provides alumina in the batch mixture 445 in an amount of from 30 wt% to 55 wt%, or even 35 wt% to 50 wt%, based on the total inorganics in the batch mixture 445.

Titania Source

[0054] In various embodiments, the titania source in the batch mixture 445 can comprise one or more inorganic compounds containing titanium. Non-limiting sources of titania include, for example, titanium dioxide, such as rutile phase titanium dioxide or anatase phase titanium dioxide.

[0055] The titanium source can be present in any amount suitable for producing the desired AT-feldspar ceramic composition. In various embodiments, the titania source provides titania in the batch mixture in 30 wt% or more, based of the total weight of the inorganic materials of the batch mixture 445. In some other embodiments, the titania source provides titania in the batch mixture of from 30 wt% to 36 wt% based on the total weight of inorganics of the batch mixture 445. The titania source can have a median particle size of less than 10.0 pm, for example. In certain embodiments, the median particle diameter of the titania source can be from 0.1 pm to 5.0 pm, or even from 0.1 pm to 0.5 pm, for example.

Silica Source

[0056] According to some embodiments of the disclosure, the honeycomb-forming batch mixture 445 can comprise a silica source comprising a silica-containing compound. The silica source can comprise silica (SiC ), for example. The silica source may be present in any amount suitable for producing the desired AT-feldspar composition. In various embodiments, the silica source provides silica in the batch mixture that is at least 5 wt% of the total weight of the inorganics in the batch mixture 445. For example, in certain embodiments, the silica source can provide silica in the batch mixture 445 that is from 5 wt% to 15 wt% ,or even from 9 wt% to 12 wt%, based on the total inorganics in the batch mixture 445. The silica source can have a median particle size of greater than 2 pm, and between 5 pm to 40 pm, or even between 15 pm to 30 pm, for example.

Magnesia Source

[0057] The magnesia source can comprise magnesium aluminate (spinel). As shown in FIG. 6, the inventor discovered that the use of magnesium hydroxide (Mg(OH)2), talc (Mg3Si40io(OH)2), and magnesium titanate (designated herein as “MT2”, having chemical formula MgTnCri) as batch additions in amounts that provide a comparable wt% of MgO (e.g., each providing from 0.62 owt% to 0.69 owt% in FIG. 6) can form ceramic honeycomb bodies that can have unacceptably high CTE at desired average bulk porosity levels for fdter applications. Unexpectedly, when using the magnesia source comprising spinel in the defined amounts, it resulted in substantially lower CTE (CTE < 25.0 x 10-7/ °C, or even CTE < 12.0 x 10-7/ °C when measured from RT to 800°C), and in some cases a 50% reduction in CTE is provided as compared to magnesium hydroxide (Mg(OH)2), talc (Mg3Si40io(OH)2), and magnesium titanate (MgThCE) as batch additions at comparable porosities. In various embodiments, spinel (MgAhOr) as a magnesia source can be provided in the batch mixture 445 in an amount that is greater than 1.8 wt%, from 1.8 wt%to 9.6 wt%, or even from 1.8 wt% to 3.6 wt% of the total weight of the inorganics in the batch mixture 445. In the way of another measure, the magnesia source comprising spinel provides magnesia (MgO) in the batch mixture 445, on a weight percent oxide basis (owt%), that is from greater than or equal to 0.5 owt%, such as 0.5 owt% to 1.5 owt%, or even 0.5 owt% to 2.73 owt%, based on the total oxide weight of the inorganics in the batch mixture 445, wherein owt% is weight percentage on an oxide basis. The spinel as a magnesia source in the batch mixture 445 can have a median particle size of from about 5 pm and 30 pm, or even 10 pm to 25 pm, for example.

Alkaline Earth

[0058] An alkaline earth compound can be added to the batch mixture 445. Alkaline earth compound may include a source of strontium and/or calcium. The alkaline earth compound can be provided in an amount of from 3.0 wt% to 15.0 wt%, or even 8.0 wt% to 11.0 wt%, based on the total weight of all the inorganics in the batch mixture 445. For example, in some embodiments, a combination of a SrO source and a CaO source may be used. The strontium oxide source may be strontium carbonate (SrCCh). The calcium oxide source may be calcium carbonate (CaCCh). Calcium carbonate (CaCCh) may be provided in an amount from 1.0 wt% to 2.0 wt%. The source of strontia in the batch mixture 445 can comprise from 3 wt% to 15 wt% of SrCCh, based upon a total weight of inorganics in the batch mixture 445. The source of calcia in the batch mixture 445 can comprise from 0 wt% to 5 wt% of CaCCh, based upon a total weight of inorganics in the batch mixture 445. In some embodiments, when SrO and CaO sources are used in combination, SrC03 can be provided in an amount of 7.0 wt% to 9.0 wt%, based on the total weight of all the inorganics in the batch mixture 445. As an alternate measure, one or more of the strontia source (e.g., SrC03) and the calcia source (e.g., CaC03), can be added to the batch mixture in amounts that provide a combined (sum) of strontia (SrO) and calcia (CaO) together, on a weight percent oxide basis (owt%), from 1.0 owt% to 16 owt%, or even from 6 owt% to 10 owt%. Accordingly, the ceramic body can comprise a combined weight of SrO and CaO from 1.0 wt% to 16 wt%, or even from 6 wt% to 10 wt%. Sintering Aid

[0059] In the batch mixtures 445 shown, a sintering aid can comprise a rare-earth material. The rare-earth sintering aid can be added to the batch mixture 445 in an amount of 2.0 wt% or less, based on the total weight of all the inorganics in the batch mixture 445. The rare earth sintering aid can be a lanthanum oxide material, for example. Other suitable rare earth sintering aids can comprise other oxides from the lanthanide series or yttrium oxide, or combinations of the aforementioned.

Pore Former(s)

[0060] In order to achieve the relatively-high average bulk porosity (%P > 40%) the batch mixture 445 can contain a suitable amount of one or more pore former materials to aid in tailoring the average bulk porosity (%P) as well as the median pore diameter dso and the pore size distribution of the ceramic honeycomb body 100. A pore former is a fugitive material, which evaporates or undergoes vaporization by combustion during drying and/or firing of the green honeycomb body 100G and is completely removed upon firing to obtain a desired high average bulk porosity (%P), which can be coupled with a desired MPD (dso) and pore size distribution in the ceramic honeycomb body 100.

[0061] Any suitable pore former material can be used, such as, without limitation, carbon, graphite, starch, flour (wood, shell, or nut flour), polymers such as polyethylene beads, and the like, and combinations of the aforementioned. Starches can comprise com starch, rice starch, pea starch, sago starch, potato starch, and the like. Other suitable starches can be used.

[0062] When used, the one or more pore formers can have a median particle diameter (d_P5o) in the range of from 10 pm to 70 pm, or even from 12 pm to 50 pm. In some embodiments, combinations of graphite and starch in the honeycomb-forming batch mixture 445 can aid in providing relatively-high average bulk porosity (%P>40%) in combination with suitable microstructural properties for particulate filters, while also reducing cracking during firing ramp up. The pore former as described herein is provided in the batch mixture 445 in a weight percent by super addition (“wt% SA”) based upon 100% of the weight of the inorganics present in the batch mixture 445.

[0063] In some example embodiments, the pore former can be provided in the batch mixture 445 in an amount of up to 40 wt% SA, such as from 0 wt.%SA to 40 wt% SA. In some embodiments, to form AT-feldspar ceramic honeycomb bodies 100 having about 6 wt% SA to 40 wt% SA, for example, 20% < %P < 65%, wherein wt% SA is weight percent by superaddition (SA) based on the total weight of the inorganics in the batch mixture 445. A suitable amount of pore former can be selected in the batch mixture 445 along with appropriate sizes of inorganics and firing cycle to achieve the desired average bulk porosity (%P).

[0064] In some embodiments, the pore former comprises a combination of starch and graphite. Embodiments can include, for example, a starch:graphite ratio of between 2.5: 1.0 and 3.5: 1.0. For example, in the embodiments shown in Table 1A-1B, combinations of starch of from 0 wt% SA to 21 wt% SA and graphite of from 0 wt% SA to 7 wt% SA can be used in the batch mixture 445. Such combinations of starch and graphite can provide excellent combinations of high average bulk porosity (%P) and relatively high median pore size (dso) useful for filtration applications, while providing reduced cracking during initial firing ramp phase of firing the green honeycomb bodies 100G.

[0065] The weight of the pore former (wpf) in the batch composition mixture 445 is computed as the wpf = wi ^c wt%SA/100, wherein wi is the total weight of inorganic raw materials batch composition mixture 445. In some embodiments, the starch can have a median particle diameter (d_P5o) in the range from about 12 pm to 45 pm, or from about 20 pm to 35 pm in other embodiments. The graphite can have a median particle diameter (d_P5o) in the range from about 25 pm to 40 pm in some embodiments.

Organic Binder

[0066] In some embodiments, the batch mixture 445 can include an organic binder. The organic binder can be a cellulose-containing material. For example, the cellulose-containing material may be, but not limited to, methylcellulose, ethylhydroxy ethylcellulose, hydroxybutyl methylcellulose, hydroxymethylcellulose, hydroxypropyl methylcellulose, hydroxyethyl methylcellulose, hydroxybutylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium carboxy methylcellulose, and mixtures thereof. Methylcellulose and/or methylcellulose derivatives are especially suited as organic binders for use in the batch mixture 445, with methylcellulose and hydroxypropyl methylcellulose being excellent choices.

[0067] In some embodiments, combinations of cellulose-containing materials may comprise mixtures of such materials with different molecular weights. Alternatively, the combination of cellulose-containing materials may comprise different hydrophobic groups or different concentrations of the same hydrophobic group. Different hydrophobic groups may be, by way of non-limiting example, hydroxyethyl or hydroxypropyl. The organic binder, in some embodiments, may be a combination of a hydroxyethyl methylcellulose binder and a hydroxypropyl methylcellulose binder. Other suitable combinations of organic binders may be used.

[0068] The amount of organic binder provided in the batch mixture 445 can range from 3.0 wt% SAP to 8.0 wt% SAP, or even from 3.0 wt% SAP to 6.0 wt% SAP, wherein SAP is based on a superaddition to the total weight of the inorganics plus pore formers that are present in the batch mixture 445.

Other Processing Aids

[0069] The batch mixture 445 may optionally further include other additives, for example rheology modifiers, dispersants, surfactants, or lubricants. Non-limiting examples of additives include fatty acid. Fatty acid may be added in an amount from 0.5 wt% SAP and 1.5 wt% SAP Water may be added in an amount between 10 wt% SAP and 50wt% SAP, based on a weight of the total dry ingredients (inorganics and organic binder) in order to develop the desired plasticity.

Aluminum Titanate-Feldspar Body

[0070] The aluminum titanate-feldspar ceramic honeycomb body according to some embodiments is characterized by the equation:

CTE (10 °C at RT to 800°C) < 0.54* (%P) + 4.22*MgO (wt%) - b, wherein b >

20

In some embodiments, 20 < b < 25.

[0071] The walls 102 of the AT-feldspar ceramic honeycomb body 100 can have a low decomposition rate in the presence of a copper oxide-containing material. For example, after firing, AT-feldspar ceramic honeycomb bodies were tested for resistance to decomposition of the AT phase by soaking block portions thereof containing only walls in a CuNCb solution, drying them, and then heating to 1,100°C for 4 hours. Samples are then measured for CuO content and phases using XRD. The process included coating until the ceramic honeycomb bodies had about 0.15% CuO on them, which is a typical catalyst coating weight. When the AT phase is not stabilized, a large amount of rutile phase appears/grows when subjected to the 1,100°C for 4 hours (e.g., about 8 wt%-12 wt%, or even 10 wt%-12 wt% rutile or higher appears). For purposes of this disclosure, it is considered that the material has sufficient stability if less than 7.0 wt% rutile phase growth appears when heated to 1,100°C for 4 hours. For the AT feldspar ceramic honeycomb bodies 100, at least 0.5 wt% MgO (oxide wt%) is added to the batch mixture 445 in order to stabilize the resulting AT phase against excessive decomposition.

[0072] In particular, the decomposition rate in the presence of 0.15 wt% of a copper oxide- containing coating on the walls 102 of the AT-feldspar ceramic body 100 should be such that it corresponds to less than 7.0 wt% growth of a rutile phase after heating at 1,100°C for 4 hours, based on an XRD analysis. This is one suitable method for determining the extent of decomposition of the aluminum titanate in the AT-feldspar ceramic honeycomb body 100 at temperature, as its decomposition forms rutile phase. The rutile phase growth at temperature (e.g., over 700°C and less than 1200°C) over time can provide a suitable measure of the decomposition rate of the ceramic materials of the walls 102 that are subjected to the copper oxide-containing coating. The percentage growth of rutile phase present in the ceramic body 100 can be determined by a simple subtraction method. The growth is expressed as follows:

Growth of rutile phase = rutile wt% after heating to 1 , 100°C for 4 hours minus original rutile wt% before such heating

[0073] One method of determining rutile phase growth can involve providing a coating on a cut-out representative block section of the AT-feldspar ceramic honeycomb body 100, such as having sides of length 25mm x 25 mm x 25 mm and containing only walls 102 with a suitable copper-oxide containing material. In the present growth-determination method, the cut-out representative block section is dipped in a Cu(N03)2-3(H20) solution having 0.03 molar concentration of Cu²⁺ and then dried. Second and even third applications can be undergone until an approximate 0.15 wt% of a copper oxide -containing coating on the cut-out representative block section is achieved. The coated cut-out representative block section is then fired at 1,100°C for 4 hours in a furnace. Subsequently, the coated cut-out representative block section is ground and undergoes elemental analysis and x-ray diffraction (XRD) to determine that the wt% of the copper oxide (CuO) is sufficient and the wt% growth of rutile material. Of course, if a copper-zeolite coated honeycomb ceramic body 100 is provided, the coated ceramic body can be fired at 1, 100°C for 4 hours in a furnace and then XRD analysis can be performed to analyze the growth of rutile and similar elemental analysis can be done to determine the amount of CuO.

[0074] The firing of the honeycomb body (e.g., in accordance with block 306 of FIG. 3) can comprise firing (heating) in a suitable furnace or kiln, such as a tunnel kiln. During the firing of the green body 100G, after drying thereof, the green body 100G is heated at a predefined heating ramp rate and then held at a top soak temperature for a specified period of time to produce the desired crystalline phases and pore microstructure (at least porosity % and median pore diameter (MPD), and then ramped down at a suitable cooling rate to avoid cracking during the cooling. The heating ramp rate during firing may be, in some embodiments, greater than l°C/min, greater than 5°C/min, greater than 10°C/min, or even greater than 20°C/min. In certain embodiments, the heating rate during the firing is greater than 2°C/min and less than 20°C/min.

Top Soak Temperature

[0075] The firing of the green body 100G can be carried out at a top soak temperature. For example, the green body 100G may be fired in any suitable furnace or kiln (including tunnel kiln) and after the ramp, held at a top soak temperature of at least 1390°C, and for example from 1390°C to 1430°C in some embodiments. In other embodiments, the green body 100G may be held at a top soak temperature of at least 1420°C, and for example, the top soak temperature during firing can be from 1420°C to 1430°C. The slightly higher firing temperature can help lower the CTE appreciably.

[0076] The firing of the green body 100G is carried out at the top soak temperature for a firing time of greater than 10 hours, or even from 10 hours to 20 hours in some embodiments. At the end of the top soak, the formed AT-feldspar ceramic body 100 can be cooled at a suitable cooling rate so as to avoid cracking during cooling. The cooling rate can vary based on the volume (size of the ceramic honeycomb body), but can be accomplished at a cooling rate after top soak of greater than 2°C/min. In certain embodiments, the cooling rate after the top soak comprises a cooling of greater than 5 °C/min, a cooling of greater than 10 °C/min, or even greater than 20 °C/min. [0077] Upon firing, the ceramic body 100 can comprise a solid solution of aluminum titanate (AT) and magnesium dititanate (MT2). In particular, the ceramic body 100 may have a solid solution of aluminum titanate and MT2 wherein the MT2 comprises no more than 20% MT2, or even no more than 15% MT2 in the solid solution in some embodiments, based upon a total (100 wt%) weight of the solid solution in the ceramic body 100. Further, according to various embodiments, the solid solution can include a pseudobrookite crystal structure.

Batch Mixtures and Crystalline Phases

[0078] Tables 1A and IB below illustrate several examples of batch mixtures 445 useful in the formation of the AT-feldspar ceramic honeycomb body 100. In the batch mixture 445, sources of alumina, titania, silica, and magnesia (spinel) are provided together with SrO and/or CaO sources. Other materials may be included in the batch mixture for making the AT-feldspar ceramic body 100, such as a rare-earth sintering aid, an organic binder (e.g., methylcellulose), one or more pore formers, and one or more liquids, such as fatty acid and water (e.g., deionized water). Tables 1A-1B provide a single value for feldspar phase as the combined sum of the Ca- containing and Sr-containing feldspar, as Sr-containing and Ca-containing feldspars were indistinguishable from each other (e.g., without wishing to be bound by theory, believed to be in solid solution, resulting in a combined, or mixed, phase of Sr- and Ca- feldspar) in the x-ray diffraction (XRD) analysis that was performed to obtain the phase wt% values in the Tables.

[0079] Table 1A - Example Batch Mixtures and crystalline phases for AT-feldspar ceramic bodies.

[0080] Table IB - Example Batch Mixtures and crystalline phases for AT-feldspar ceramic bodies (Continued).

[0081] As can be seen, the aluminum titanate-feldspar ceramic body comprises a first crystalline phase containing aluminum titanate, and a second crystalline phase of feldspar. The first crystalline phase containing aluminum titanate comprises a combined substantially-pure solid solution crystalline phase of aluminum titanate and magnesium dititanate in an amount of at least 70 wt%, such as from 70 wt% to 80 wt%, from 70 wt% to 78 wt%, from 73 wt% to 78 wt%, or from 73 wt% to 76 wt%, based on a total weight of inorganics in the ceramic body. The combined phase can have a pseudobrookite structure. The first crystalline phase containing aluminum titanate can comprise less than 15 wt% magnesium dititanate, or even less than 12 wt% magnesium dititanate, based on a total weight of inorganics in the ceramic body.

[0082] The second crystalline phase of feldspar comprises, as shown, a combined strontium and calcium feldspar. The combined strontium and calcium feldspar is provided in an amount of at least 20 wt%, such as from 20 wt% to 25 wt%, or from 22 wt% to 24 wt%, based on a total weight of inorganics in the ceramic body. The aluminum titanate-feldspar ceramic body may comprise a third crystalline phase of rutile. The third crystalline phase of rutile can comprise less than or equal to 5.0 wt%, less than or equal to 4.0 wt%, less than or equal to 3 wt%, such as from 0 wt% to 5 wt%, from 0 wt% to 4 wt%, or from 0 wt% to 3 wt%, based on based on a total weight of inorganics in the ceramic body.

[0083] Table 2A - Example CTE and Pore Structure for AT-feldspar ceramic honeycomb bodies. CTE is measured from RT (25°C) to 800°C.

[0084] Table 2B - Example CTE and Pore Structure for AT-feldspar ceramic honeycomb bodies.

[0085] Tables 2A-2B above illustrate example AT-feldspar forming batch mixtures, firing conditions, and properties (CTE and pore microstructure) of AT-feldspar ceramic bodies 100 according to the disclosure.

Ceramic Body Structure and Properties

[0086] The AT-feldspar ceramic body 100 can comprise an intersecting porous wall structure having porous walls 102 (FIGs. 1 and 2) comprising a porous AT-feldspar ceramic suitable for exhaust treatment, such as when used as a catalyst support and/or for filtration purposes. Thus, the walls 102 of the AT-feldspar ceramic body 100 can contain a suitable weight of a copper-containing catalyst, such as a Cu-Zeolite-containing coating provided thereon and therein. Other suitable copper-containing catalyst coatings may be used for Selective Catalytic Reduction (SCR) filter applications. In some embodiments, SCR is an active emissions control system that can inject a liquid-reductant agent through a special catalyst into the exhaust stream of a diesel engine. The reductant source is usually automotive- grade urea, otherwise known as Diesel Exhaust Fluid (DEF). The DEF sets off a chemical reaction with a copper-containing catalyst coating that converts nitrogen oxides into nitrogen, water and tiny amounts of carbon dioxide (CO2). In some SCR embodiments, DEF is not used. SCR filters can achieve substantial NOx reductions.

[0087] In some embodiments, the AT-feldspar ceramic honeycomb body 100 can comprise about 0.15 wt% of a copper oxide -containing coating on the walls 102 of the AT-feldspar ceramic honeycomb body 100, based on a total weight of the walls 102 of the body 100 plus coating. Thus, for example, a portion of the body 100 comprising all walls 102 can contain about 0.15 wt% of a copper oxide contained in a coating on the portion, based on a total weight of the portion comprising all walls of the body.

[0088] In some embodiments, the AT-feldspar ceramic honeycomb body 100 produced using the batch mixture 445 described herein can exhibit low coefficient of thermal expansion (“CTE”) when measured between room temperature (RT) and 800°C, as well as desired average bulk porosity (%P). Thus, the AT-feldspar ceramic honeycomb body 100 can contain desirable combinations of relatively-low CTE (measured from RT to 800°C) and average bulk porosity (%P). Moreover, the AT-feldspar ceramic honeycomb body 100 can exhibit desirable ranges of median pore diameter (MPD). [0089] For example, as shown in FIG. 9 for the AT-feldspar ceramic body 100 made from batch mixtures comprising various levels of spinel addition, CTE (RT to 800°C) increases with average bulk porosity (%P) in a range of 0.5-1.0 points per percentage of bulk porosity (%P). The different lines represent different levels of spinel additions (in oxide wt%) leading to MgO content (shown from 0.14 owt% to 2.73 owt%). FIG. 9 shows the CTE results for various levels of spinel additions to AT where the stoichiometry of the AT-feldspar ceramic material is held constant at approximately 72 wt% pseudobrookite, with the remaining phases being feldspar and corundum. When amounts of spinel additions contributing up to 1.0 owt% MgO content are added to the batch mixture, the resulting CTE of the fired article does not increase appreciably as compared to lower amounts of spinel. However, as the amount of spinel adds greater than 1.36 owt% MgO, a CTE penalty (measurably higher CTE) was identified. However, it is estimated to be thermodynamically stable at that level, but no more than about 1.0 owt% MgO is needed to be thermodynamically stable. However, up to about 1.5 owt% can be tolerated in some cases, particularly where lower porosity is used in the honeycomb body (e.g., %P of less than 40% or 50%).

[0090] Thus, an oxide weight range of 0.5 owt% to 1.5% owt% MgO from spinel can be sufficient to protect the material from decomposition as specified herein and at the same time provide reasonably low CTE for average bulk porosities (%P) of interest. However, as can be seen, the addition of 2.73 owt% MgO to the batch mixture results in a higher CTE for the fired ceramic body than may be desired for some particulate filter applications. However, such a high level of MgO addition is not needed to achieve suitably low rates of decomposition of the AT-containing phase when exposed to heat in the presence of copper-oxide containing coatings (See FIG. 5). Thus, in some embodiments, the range of oxide weight range of from 0.5 owt% to 1.5% owt% MgO from spinel is sufficient to protect the AT-feldspar ceramic material from decomposition (e.g., when exposed to copper-oxide containing coatings at 1,100°C for four hours) and also provide suitably-low CTE (RT to 800°C). In some embodiments, suitably-high average bulk porosity, e.g., %P > 50%, may be also achieved.

[0091] In one aspect, the AT-feldspar ceramic honeycomb body 100 can have a relationship of CTE (RT to 800°C), average bulk porosity (%P), and MgO in wt% as expressed by the equation:

CTE (xl0 °C at RT to 800°C) < 0.54* (%P) + 4.22*MgO (wt%) - b, wherein b > 20. In some embodiments, 20 < b < 25. Above about 1.5 owt% spinel in the batch mixture 445, it becomes apparent that for average bulk porosity (%P) ranges of interest for particulate filters (e.g., 40%-65%) the CTE (RT-800°C) may become too large. Below about 0.5 oxide wt% of spinel in the batch mixture 445, the ceramic material decomposes too much when heated at 1,100°C for 4 hours in the presence of 0.15 wt% copper-containing coating, thus resulting in a growth of the rutile phase of greater than 7.0 wt% as compared to rutile phase wt% pre-heating.

[0092] Thus, in one aspect, the AT-feldspar ceramic honeycomb body 100 can have a decomposition in the presence of 0.15 wt% of a copper oxide -containing coating on the walls 102 of AT-feldspar ceramic honeycomb body 100 that results in less than or equal to 7.0 wt% growth of a rutile phase after exposure to heat at 1,100°C for 4 hours.

[0093] FIG. 5 illustrates two examples of AT-feldspar ceramic honeycomb bodies 100 that were fired at top soak temperatures of 1395°C for 16 hours and 1425°C for 16 hours and after formation and cooling of the AT-feldspar ceramic honeycomb body 100, block portions as described herein were coated with 0.15 wt% of a copper-containing coating. The coated wall- containing block portions of the AT-feldspar ceramic honeycomb bodies 100 were then subjected to heat at 1,100°C for 4 hours. The ceramic phases are then analyzed using x-ray diffraction (XRD) testing to determine the amount of rutile phase that is present, which is representative of decomposition of the AT phase. As can be seen, for a desirable amounts of MgO wt% in the ceramic body of greater than or equal to 0.5 wt%, from 0.5 wt% to 1.5 wt%, or even 0.5 wt% to 2.73 wt%, provided by using spinel in the batch mixture 445, the wt% growth of the rutile phase in the wall-containing portion of the body 100 over the same body prior to heating is less than or equal to 7.0 wt%.

[0094] Viewed another way, the wt% growth (y) of the rutile phase in the wall-containing portion of the body 100 as a function of MgO wt% (x) over an untreated body of the same composition can be expressed by the equations:

Fired @1395°C y < 0.11 e ^{88 14x}

Fired @1425°C y < 0.09 e ^{105 23x}

As will be shown in other plots, as the MgO owt% from spinel becomes large, the CTE at RT to 800°C can become relatively high (e.g., > 15.0 x 10⁷/°C).

[0095] FIG. 6 illustrates several examples of the AT-feldspar ceramic honeycomb bodies that were fired at top soak temperature of from 1395°C to 1425°C for 16 hours. After formation and cooling of the AT-feldspar ceramic honeycomb bodies and coating with a suitable weight of a copper-oxide-containing coating (of 0.15 wt%) as described herein, a wall-containing block portion of the bodies 100 are subjected to further heating at 1,100°C for 4 hours. Each example used a different MgO source providing MgO at approximately the same oxide wt% (approx. 0.68 owt% from spinel, 0.62 owt% from Mg(OH)2, 0.68 owt% from “MT2”, and 0.69 owt% from talc are shown). The coated wall-containing block portion of the bodies were then analyzed for the relationship between CTE and average bulk porosity (%P). CTE was measured using a method wherein a representative part of the body was heated to 1,000°C and then the coefficient of thermal expansion (CTE) was measured from RT to 800°C. Average bulk porosity %P was measured using mercury intrusion porosimetry (MIP).

[0096] As can be seen from FIG. 6, the use of this amount of spinel in the batch mixture 445 consistently resulted in lower CTE (RT to 800°C) at any particular level of average bulk porosity (%P) as compared to comparable addition amounts of other sources of MgO, such as Mg(OH)2, MT2, and talc. Thus, by addition of an effective, but low level of MgO from different sources shows how much lower the CTE can be made when spinel is used in the batch mixture 445 as compared to Mg(OH)2, MT2, and talc. In particular, the relationship between CTE (RT to 800°C) and average bulk porosity (%P) of a wall -containing portion the AT-feldspar ceramic body 100, at 0.68 owt% MgO from spinel can be expressed by the equation of the line 650 as follows:

CTE (x 10 °C) < 0.54(%P) - 20.1.

[0097] FIG. 7 illustrates examples in which the indicated levels of MgO are added from different magnesia sources ( 1.02 owt% from spinel, 1.05 owt% from talc, and 1.04 owt% from Mg(OH)2). In particular, FIG. 7 shows how much lower the CTE (RT-800°C) can be made to be when spinel is used as compared to Mg(OH)2 and talc as the MgO source. For example, at 1.02 owt% MgO from spinel, the relationship between CTE and %P can be expressed as line 752 as follows:

CTE (x 107°C) < 0.54(%P) - 18.7.

[0098] FIG. 8 illustrates examples adding MgO in the indicated amounts from different magnesia sources. In particular, FIG. 8 shows how much lower the CTE (RT-800°C) can be made to be when spinel is used as compared to MT2 and talc as the MgO source. For example, at 2.73 owt% MgO from spinel, the relationship between CTE and %P can be expressed as line 854 as follows:

CTE (x 10 °C) < 0.54(%P) - 11.5.

When 1.36 owt% MgO from spinel, the relationship between CTE and %P can be expressed as line 855 as follows:

CTE (x 107°C) < 0.54(%P) - 17.3.

[0099] FIG. 9 illustrates examples adding various levels of MgO from spinel as the magnesia source. In particular, FIG. 9 shows the levels of CTE (RT-800°C) that can be achieved when spinel is used as the MgO source. For example, at 1.50 owt% MgO from spinel, the relationship between CTE and %P can be expressed as line 956 as follows:

CTE (x 107°C) < 0.54(%P) - 16.7.

[0100] In the various embodiments described herein, the batch mixture 445 can be extruded into a green honeycomb body 100G (e.g., FIG. 4) having, like the fired ceramic counterpart, a plurality of intersecting walls 102 forming channels 104 via extrusion through an extrusion die 444 (FIG. 4) as described herein. The as-fired walls 102 can have wall thicknesses of from 8 pm to 12 pm in transverse thickness and the AT-Feldspar ceramic honeycomb body 100 can have a post-firing cell density of from 100 cpsi to 500 cpsi. Although it is submitted that wall thickness of from 4 pm to 15 pm and cell densities of from 100-1000 cpsi will have substantially similar properties.

[0101] According to embodiments described herein, the AT-Feldspar ceramic honeycomb bodies 100 produced using the batch mixtures 445 can have average bulk porosities of from about 20% to 65%, for example, depending at least in part on the amount and type of pore former used. As shown in the tables, aluminum titanate-feldspar ceramic bodies having average bulk porosities from 23% to 61% are produced using the batch mixtures 445 described herein. D50 can range from 10 pm to 21 pm, for example (See FIG. 10 illustrating ranges of porosity and MPD that provide useful average bulk porosity and pore microstructures for particulate filter applications. Furthermore, AT-Feldspar ceramic honeycomb bodies 100 produced using the batch mixtures 445 can have a coefficient of axial thermal expansion (“Axial CTE”) of less than 12. Ox 10^_7/°C from room temperature (RT) to 800°C, for average bulk porosities %P less than or equal to 50% (See FIG. 9), for example. [0102] It is to be understood that both the foregoing general description and the detailed description provided by the examples provided herein are explanatory and are not intended to be restrictive. The accompanying figures, which are incorporated in and constitute a part of this specification, are not intended to be restrictive, but rather illustrate various embodiments of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure.

[0103] It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope thereof. Thus, it is intended that the present disclosure covers the modifications and variations of this disclosure provided they come within the scope of the claims and their equivalents.

Claims

CLAIMS WHAT IS CLAIMED IS:

1. An aluminum titanate-feldspar ceramic body, comprising: a first crystalline phase containing aluminum titanate; a second crystalline phase of feldspar; and CTE (x 10-⁷/°C) < 0.54 (%P) + 4.22 (MgO wt%) - b, wherein CTE is a coefficient of thermal expansion, %P is average bulk porosity as determined by mercury intrusion porosimetry, and b > 20.

2. The aluminum titanate-feldspar ceramic body of claim 1, wherein 20 < b < 25.

3. The aluminum titanate-feldspar ceramic body of either one of claims 1 or 2, having a decomposition rate of the aluminum titanate in a presence of 0.15 wt% of a copper oxide- containing coating on walls of the aluminum titanate-feldspar ceramic body that corresponds to less than or equal to 7.0 wt% growth of a rutile phase after heating at 1100°C for 4 hours.

4. The aluminum titanate-feldspar ceramic body of any one of claims 1-3, wherein CTE < 12.0 x 10⁷/°C from RT to 800°C when %P is < 50%.

5. The aluminum titanate-feldspar ceramic body of any one of claims 1-4, wherein the second crystalline phase of feldspar comprises a combined strontium and calcium feldspar.

6. The aluminum titanate-feldspar ceramic body of claim 5, wherein ceramic body comprises the combined strontium and calcium feldspar is in an amount of from 22 wt% to 24 wt%.

7. The aluminum titanate-feldspar ceramic body of any one of claims 1-6, wherein the first crystalline phase comprises a solution of aluminum titanate and magnesium dititanate.

8. The aluminum titanate-feldspar ceramic body of claim 7, wherein the first crystalline phase comprises less than 15 wt% of the magnesium dititanate.

9. The aluminum titanate-feldspar ceramic body of claim 8, wherein the ceramic body comprises less than 12 wt% of the magnesium dititanate.

10. The aluminum titanate-feldspar ceramic body of any one of claims 1-9, wherein the ceramic body comprises the first crystalline phase in an amount from 70 wt% to 80 wt%.

11. The aluminum titanate-feldspar ceramic body of any one of claims 1-10, wherein the ceramic body comprises < 5.0 wt% of a third crystalline phase of rutile.

12. The aluminum titanate-feldspar ceramic body of any one of claims 1-11, wherein an average bulk porosity of the aluminum titanate-feldspar ceramic body, as determined by mercury intrusion porosimetry, is from 20% to 65%.

13. The aluminum titanate-feldspar ceramic body of any one of claims 1-12, wherein MgO is present in an amount of greater than or equal to 0.5 wt%.

14. The aluminum titanate-feldspar ceramic body of any one of claims 1-13, wherein MgO is present in an amount of from 0.5 wt% and 1.5 wt%.

15. The aluminum titanate-feldspar ceramic body of any one of claims 1-14, wherein MgO is present in an amount of from 0.5 wt% and 2.73 wt%.

16. The aluminum titanate-feldspar ceramic body of any one of claims 1-15 wherein a median pore diameter is from about 10 pm to about 21 pm.

17. A method of manufacturing an aluminum titanate-feldspar ceramic body, comprising: forming a batch mixture of inorganic materials from sources of: alumina, titania, silica, one or more of a strontia or calcia, and magnesia, wherein the source of magnesia comprises spinel in an amount greater than or equal to 1.8 wt% based on a total weight of inorganic materials in the batch mixture; shaping a green body from the batch mixture; and firing the green body to convert the green body into the aluminum titanate-feldspar ceramic body, wherein the aluminum titanate-feldspar ceramic body further comprises: a first crystalline phase comprising aluminum titanate and magnesium dititanate, and a second crystalline phase comprising feldspar.

18. The method of manufacturing of claim 17, wherein CTE (x 10⁷/°C) < 0.54 (%P) + 4.22 (MgO wt%) - b, wherein CTE is coefficient of thermal expansion measured from 25°C to 800°C, %P is average bulk porosity as determined by mercury intrusion porosimetry, and b > 20.

19. The method of manufacturing of claim 18, wherein 20 < b < 25.

20. The method of manufacturing of any one of claims 17-19, wherein the spinel is in an amount from 1.8 wt% to 9.6 wt%, based on a total weight of inorganic materials in the batch mixture.

21. The method of manufacturing of any one of claims 17-20, wherein the spinel is in an amount from 1.8 wt% to 3.6 wt%, based on a total weight of inorganic materials in the batch mixture.

22. The method of manufacturing of any one of claims 17-21, further comprising a third crystalline phase of rutile.

23. The method of manufacturing of any one of claims 17-22, further comprising a decomposition rate of the aluminum titanate in a presence of 0.15 wt% of a copper oxide- containing coating on the aluminum titanate-feldspar ceramic body that corresponds to less than or equal to 7.0 wt% growth of the phase of rutile after heating at 1100°C for 4 hours.

24. The method of any one of claims 17-23, wherein the source of strontium comprises from 3 wt% to 15 wt% of SrCCh, based upon a total weight of inorganics in the batch mixture.

25. The method of any one of claims 17-24, wherein the source of calcium comprises from 0 wt% to 5 wt% of CaCCh, based upon a total weight of inorganics in the batch mixture.

26. The method of any one of claims 17-25, further comprising a rare earth sintering aid in an amount of less than or equal to 2.0 wt%, based upon a total weight of inorganics in the batch mixture.

27. The method of any one of claims 17-26, wherein the batch mixture comprises, on an oxide weight basis (owt%): alumina from 40 owt% to 56 owt%; titania from 22 owt% to 50 owt%; silica from 1.8 owt% to 22 owt%; one or more of strontia and calcia in a combined owt% from 1.0 owt% to 16 owt%; and magnesia in an amount of greater than or equal to 0.5 owt%, wherein the source of magnesia comprises spinel (MgAhCri), and wherein oxide weight percentage of each inorganic material is based upon a total weight of inorganics present in the batch mixture.

28. The method of any one of claims 17-27, wherein the firing of the green body comprises firing at a temperature of at least 1390°C.

29. The method of claim 28, wherein the top soak temperature is from 1390°C to 1430°C.

30. The method of claim 28, wherein the firing of the green body is carried out at the top soak temperature for a firing time from 10 hours to 20 hours.

31. An aluminum titanate-feldspar forming batch mixture, comprising inorganic materials in the batch mixture in amounts, on an oxide weight basis (owt%), of: alumina from 40 owt% to 56 owt%; titania from 22 owt% to 50 owt%; silica from 1.8 owt% to 22 owt%; one or more of strontia and calcia in a combined owt% from 1.0 owt% to 16 owt%; and magnesia in an amount of greater than or equal to 0.5 owt%, wherein the source of magnesia comprises spinel (MgAkCri), and wherein oxide weight percentage of each inorganic material is based upon a total weight of inorganics present in the batch mixture.

32. The aluminum titanate-feldspar forming batch mixture of claim 31, wherein the spinel (MgAkCri) provides the magnesia, on a weight percent oxide basis, in an amount from 0.5 owt%to 2.73 owt%.

33. The aluminum titanate-feldspar forming batch mixture of claim 31, wherein the spinel (MgAkCri) provides the magnesia, on a weight percent oxide basis, in an amount from 0.5 owt%to 1.5 owt%.

34. The aluminum titanate-feldspar forming batch mixture of any one of claims 31-33, comprising: the alumina from 42 owt% to 50 owt%; the titania from 30 owt% to 36 owt%; the silica from 10.0 owt%to 10.5 owt%; and the one or more of strontia and calcia in a combined owt% from 6 owt% to 10 owt%.

35. A green honeycomb body manufactured from the aluminum titanate-feldspar forming batch mixture of any one of claims 31-34.