WO2024211131A1

WO2024211131A1 - Manufacturing honeycomb heater body

Info

Publication number: WO2024211131A1
Application number: PCT/US2024/021557
Authority: WO
Inventors: Zhihui Lv; Yiting QIN; Danhong ZHONG
Original assignee: Corning Incorporated
Priority date: 2023-04-06
Filing date: 2024-03-27
Publication date: 2024-10-10

Abstract

A method of manufacturing an electrical heater body is provided. The method comprises forming one or more hydrophobic regions in a honeycomb body by applying a hydrophobic solution. The honeycomb body comprises a plurality of channels extending axially through the honeycomb body. The method further comprises coating the honeycomb body with a metal slurry. The one or more hydrophobic regions repel the metal slurry to form an electrically conductive region and one or more electrically non-conductive regions in the honeycomb body. In embodiments, the method further comprises arranging, prior to forming the one or more hydrophobic regions, one or more masking elements on a face of the honeycomb body. The method may further comprise removing, prior to coating the honeycomb body with the metal slurry, the one or more masking elements from the face of the honeycomb body.

Description

MANUFACTURING HONEYCOMB HEATER BODY

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. 63/457541, filed on April 6, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.

Field of the Disclosure

[0002] This disclosure relates to heater assemblies that comprise honeycomb bodies, in particular honeycomb bodies having electrically conductive and electrically non-conductive regions, methods for manufacturing such heater assemblies, and exhaust aftertreatment systems comprising such heater assemblies.

Background

[0003] Pollution abatement systems, such as exhaust aftertreatment systems coupled to an internal combustion engine, e.g., that of an automobile or other vehicle, may include heater assemblies to provide supplemental heat in order to assist in operation of the system. For example, catalyst materials used in catalytic converters or other catalyst-containing aftertreatment components may require a sufficient minimum temperature to initiate catalytic reaction, which may be referred to as catalyst light off.

[0004] In the case of internal combustion engines, heat can also be supplied from the exhaust flow itself, but it may take some amount of time for the exhaust temperature to be raised sufficiently each time the engine is first turned on, which may be referred to as cold start of the engine. Even if the system is arranged for the exhaust flow to heat the catalyst to its light off temperature within a few seconds, these first few seconds after a cold start can contribute significantly to the overall emissions of the engine, and may even constitute the majority of emissions of the engine. Accordingly, supplemental heat provided by a heater assembly can considerably reduce the time it takes for the catalyst light off temperature to be achieved, thereby reducing emissions, particularly after cold start events. Summary of the Disclosure

[0005] Generally, in one aspect, a method of manufacturing an electrical heater body is disclosed. The method comprises forming one or more hydrophobic regions in a honeycomb body by applying a hydrophobic solution. The honeycomb body comprises a plurality of channels extending axially through the honeycomb body.

[0006] The method further comprises coating the honeycomb body with a metal slurry. The one or more hydrophobic regions repel the metal slurry to form an electrically conductive region and one or more electrically non-conductive regions in the honeycomb body.

[0007] In embodiments, the method further comprises arranging, prior to forming the one or more hydrophobic regions, one or more masking elements on a face of the honeycomb body. The method further comprises removing, prior to coating the honeycomb body with the metal slurry, the one or more masking elements from the face of the honeycomb body.

[0008] In embodiments, at least one of the one or more masking elements comprises aplastic tape or sheet. The plastic tape or sheet may be mylar, polypropylene (PP), or polyethylene (PE) . [0009] In embodiments, the method further comprises curing the honeycomb body prior to removing the one or more masking elements.

[0010] In embodiments, the electrically conductive region comprises an electrically conductive serpentine path.

[0011] In embodiments, the hydrophobic solution comprises a hydrophobic material. The hydrophobic material may be perfluoropolyether (PFPE) solution or siloxane resin solution.

[0012] In embodiments, the metal slurry is an aqueous solution formed by water and a metal powder. The metal powder may comprise copper, steel, chromium, nickel, an iron alloy, a chromium alloy, a nickel alloy, or a nickel-chromium alloy. Coating the honeycomb body with the metal slurry may impregnate a portion of the honeycomb body corresponding to the electrically conductive region with the metal powder.

[0013] In embodiments, the method further comprises forming, via extrusion or additive manufacturing, the honeycomb body.

[0014] In embodiments, the honeycomb body comprises a porous ceramic material. The porous ceramic material may be cordierite.

[0015] In embodiments, applying the hydrophobic solution to the honeycomb body includes pulling the hydrophobic solution through the plurality of channels via vacuum suction. [0016] In embodiments, the method further comprises sintering the metal slurry to form a monolithic conductive structure within the electrically conductive region of the honeycomb body.

[0017] Generally, in another aspect, an electrical heater body is disclosed. The electrical heater body comprises a plurality of channels extending axially through the electrical heater body. The electrical heater body is divided into an electrically conductive region and one or more electrically non-conductive regions. The electrically non-conductive regions are defined by a monolithic non-conductive structure. The electrically conductive region of the electrical heater body comprises a monolithic conductive structure supported by the monolithic non- conductive structure.

[0018] In embodiments, the electrically conductive region comprises an electrically conductive serpentine path.

[0019] In embodiments, both the monolithic non-conductive structure comprises a porous ceramic material.

[0020] In embodiments, the monolithic conductive structure comprises copper, steel, chromium, nickel, an iron alloy, a chromium alloy, a nickel alloy, or a nickel-chromium alloy. [0021] Generally, in another aspect, an electrical heater assembly is disclosed. The electrical heater assembly comprises the electrical heater body coupled to a pair of electrodes at opposite ends of the electrically conductive region.

[0022] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description, serve to explain principles and operation of the various embodiments.

Brief Description of the Drawings

[0023] FIG. 1 is a cross-sectional side view of an exhaust aftertreatment assembly according to embodiments disclosed herein. [0024] FIG. 2 is a front view of an electrical heater assembly having a serpentine design formed by a plurality of electrically insulating slots, according to embodiments disclosed herein.

[0025] FIG. 3 is an isometric view of a heater body having a serpentine design formed by a plurality of electrically insulating slots, according to embodiments disclosed herein.

[0026] FIG. 4A is a cross-sectioned microstructural photograph of a subsection of a heater body, according to embodiments disclosed herein.

[0027] FIG. 4B is an enlarged, cross-sectioned, microstructural photograph of a first wall segment of a heater body, according to embodiments disclosed herein.

[0028] FIG. 4C is an enlarged, cross-sectioned, microstructural photograph of a second wall segment of a heater body, according to embodiments disclosed herein.

[0029] FIG. 5 is a front view of an electrical heater assembly having a serpentine design formed by a plurality of electrically insulating virtual slots, according to embodiments disclosed herein.

[0030] FIG. 6 is a front view of a plurality of masking elements applied to a face of a honeycomb body, according to embodiments disclosed herein.

[0031] FIG. 7 is a front view of a single masking element applied to a face of a honeycomb body, according to embodiments disclosed herein.

[0032] FIG. 8 is a front view of a honeycomb body following the application of a hydrophobic solution to form a serpentine electrically conductive region, according to embodiments disclosed herein.

[0033] FIG. 9 is a front view of a honeycomb body following the application of a metal slurry, according to embodiments disclosed herein.

[0034] FIG. 10 is a front view of a honeycomb body following the sintering of the metal slurry, according to embodiments disclosed herein.

[0035] FIG. 11 is a front view of a honeycomb body following the application of hydrophobic solution to form a non-serpentine electrically conductive region.

[0036] FIG. 12A shows front, bottom, and side views of a honeycomb body following the application of hydrophobic solution, according to embodiments disclosed herein.

[0037] FIGS. 12B shows front, bottom, and side views of a honeycomb body following the application of a water-based dye, according to embodiments disclosed herein. [0038] FIG. 13 shows front, bottom, and side views of a honeycomb body following the application of a metal slurry, according to embodiments disclosed herein.

[0039] FIGS. 14A and 14B are microscopic images of channels of a honeycomb body following the application of a metal slurry, where one of the two channels was previously coated with a hydrophobic solution, according to embodiments disclosed herein.

[0040] FIG. 15 is a flowchart of a method for manufacturing an electrical heater body, according to embodiments disclosed herein

Detailed Description of Embodiments

[0041] Reference will now be made in detail to exemplary embodiments which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the exemplary embodiments.

[0042] Numerical values, including endpoints of ranges, can be expressed herein as approximations preceded by the term “about,” “approximately,” or the like. In such cases, other embodiments include the particular numerical values. Regardless of whether a numerical value is expressed as an approximation, two embodiments are included in this disclosure: one expressed as an approximation, and another not expressed as an approximation. It will be further understood that an endpoint of each range is significant both in relation to another endpoint, and independently of another endpoint.

[0043] Modifications of the disclosure will occur to those skilled in the art and to those who make or use the disclosure. Therefore, it is understood that the embodiments shown in the drawings and described herein are merely for illustrative purposes and not intended to limit the scope of the disclosure, which is defined by the following claims, as interpreted according to the principles of patent law, including the doctrine of equivalents.

[0044] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to also include the specific value or end-point referred to. [0045] Directional terms as used herein — for example up, down, right, left, front, back, top, bottom — are made only with reference to the figures as drawn and are not intended to imply absolute orientation. As used herein, the term “radial” refers to directions perpendicular to the indicated axial direction that extend from the center point (e.g., see center axis C in FIG. 2) of a shape to or toward the outer perimeter of the shape, regardless of the shape of the component or feature with respect to which the radial direction is used. Similarly, the term “diameter” as used herein is not limited to circular shapes, but instead refers to the longest dimension of a component that passes through the center point (center axis) of the shape of that component. For example, a radial distance of a square-shaped component can be measured as the straight- line distance from the center point (center axis) to an intersection with one of the walls of the square, while the diameter of a square refers to the longest dimension diagonally across the square. The terms “cross-sectional width” or “cross-sectional dimension” may also be used to refer to these directions perpendicular to the axial direction.

[0046] Fluid treatment systems, such as automobile exhaust aftertreatment systems or other pollution abatement systems, can comprise a supplemental source of heat to facilitate operation, such as faster catalyst light-off in the case of catalyst-containing systems. For example, heat can be supplied by an electric heater (e.g., arranged to transfer heat to the catalyst material) or an electrically heated catalyst substrate (e.g., an electrically conductive substrate that is carrying a catalytic material). For example, a heater can be arranged upstream of a catalyst substrate and heat the catalyst by providing heat to the flow of exhaust (or supplemental air flow), which in turn heats the catalyst. Aftertreatment systems employing supplemental heat can be provided to reduce emissions in gasoline, diesel, and/or hybrid vehicles to assist in ensuring fast and consistent light-off of the catalyst during operation of the corresponding engine, particularly after cold-start of the engine.

[0047] In order to heat the flow of exhaust, a voltage is applied to opposing ends of a heater body of the electrical heater. This voltage generates current flowing through portions of the heater body, which in turn causes resistive heating in the portions of the heater body where the current flows. However, simply applying a voltage may result in uneven and/or insufficient heating due to an uneven distribution of the current flow throughout the heater body, as current naturally flows to the shortest path(s) of least resistance. Previous embodiments have addressed this uneven and/or insufficient current distribution through the creation of non-conductive air gaps to force the current to travel through the heater body in a path many times longer than the diameter of the heater body, such that the overall resistance between the electrodes can be made high enough to reach sufficient temperatures. These non-conductive air gaps are often created by cutting slots into the heater body. However, cutting these slots weakens the physical structure of the heater body. Further, the cut-out slots may also require the use of insulated slot separators to prevent adjacent segments from pinching together (resulting in a short circuit). [0048] The present disclosure improves upon the previous designs by selectively coating a monolithic, electrically nonconductive structure with an electrically conductive material (such as metal). Rather than removing structurally significant portions of the heater body to more uniformly distribute current, the present disclosure creates a similar distributive effect by using this selective coating to create a monolithic, electrically conductive structure in a desired pattern. Accordingly, the strength of the monolithic, electrically nonconductive structure is preserved, while the resistive heat generated by the current is sufficiently distributed throughout the heater body.

[0049] Referring now to FIG. 1, a fluid treatment assembly 10 is illustrated, e.g., which can be arranged as part of an exhaust system of an automobile. The fluid treatment assembly 10 comprises an outer housing 12 (which may be alternatively referred to as a “can”), such as formed in a generally tubular shape (e.g., a hollow tube) from metal or suitable material. The outer housing 12 has an inlet 14, e.g., which can be connected in fluid communication with the exhaust manifold of an internal combustion engine, and an outlet 16, e.g., which can be connected in fluid communication with a tail pipe of an automobile.

[0050] Exhaust from an engine or other fluid flow (the fluid flow to be treated generally referred to herein as “exhaust”) can be treated (e.g., one or more pollutants removed or abated) as the exhaust is flowed from the inlet 14 to the outlet 16 through the assembly 10. To this end, the assembly 10 further comprises a heater assembly 18 and an aftertreatment component 20 located between the inlet 12 and the outlet 14. For example, the aftertreatment component 20 can be a catalyst-loaded substrate, a particulate filter, or a catalyst-loaded particulate filter. For example, catalyst substrates and particulate filters can comprise a porous ceramic honeycomb body having an array of walls that form a plurality of fluid flow paths or channels extending axially (in the direction of exhaust flow and/or perpendicular to the end faces of the body) through the body.

[0051] As described in more detail herein, the heater assembly 18 can be a resistance heater that provides supplemental heat in order to facilitate functionality of the aftertreatment component 20, e.g., by quickly initiating light-off of catalytic material disposed in or on the walls of the heater assembly 18 and/or the aftertreatment component 20. For example, the heater assembly 18 can comprise, or otherwise be connected to, electrodes 22. The electrodes 22 can be arranged extending through the housing 12 in order to connect the heater assembly 18 to a power source, such as a vehicle battery. As shown in FIG. 1, the electrodes 22 can extend radially through the housing 12. However, the electrodes 22 can alternatively extend axially through the housing 22 and/or one could extend radially while the other extends axially. In this way, the heater assembly 18 can be arranged to generate heat via Joule heating when the heater assembly 18 is connected to a power source and a corresponding voltage is applied to flow current through the walls of the heater assembly 18. The electrodes 22 are shown in FIG. 1 as being arranged on opposite sides of the heater assembly 18 (e.g., spaced 180° apart with respect to the exterior of the heater assembly 18), but can be arranged at other locations or angles.

[0052] In embodiments disclosed herein, such as shown in FIG. 1, the heater assembly 18 is positioned upstream (relative to the direction of exhaust flow) of the aftertreatment component 20 in order to increase the temperature of the exhaust flow and/or provide direct heating to the aftertreatment component 20. This in turn increases the temperature of the aftertreatment component 20, such as the temperature of the catalytic material carried by the aftertreatment component 20, as the exhaust flows through the aftertreatment component 20. In some embodiments, the heater assembly 18 and the aftertreatment component 20 can be effectively combined into a single device by directly loading the body of the heater assembly 18 with a catalyst. Such arrangements useful for heating a catalyst material may be referred to as an electrically heated catalyst, or EHC.

[0053] A vehicle exhaust system can be created by connecting additional lengths of piping (not shown) to the assembly 10 at the inlet 14 (e.g., extending between the inlet 14 and the engine exhaust manifold) and outlet 16 (e.g., extending from the outlet 16 to the tail pipe). Depending on the design or configuration of the exhaust system, which vary vehicle to vehicle, the various components and/or lengths of piping can have different diameters at different positions along the flow path through the exhaust system.

[0054] The heater assembly 18 and the aftertreatment component 20 can be held in place, supported, and/or contained within the housing 12 in any suitable manner. For example, the body of the heater assembly 18 can be held in place and supported via one or more retainers 24, e.g., retaining rings. The aftertreatment component 18 can be supported by similar retainers and/or supported by a mat 26, such as an inorganic fiber mat, which assists in protecting the aftertreatment component, such as from vibrations or thermal expansion forces exerted on the aftertreatment component 20 during operation.

[0055] Referring now to FIGS. 2-3, previous embodiments of the heater assembly 18 are illustrated. Consistent with the disclosure herein, these previous embodiments illustrated and/or described herein can be used as, or incorporated in, the heater assembly 18 in the fluid treatment assembly 10 (as shown in FIG. 1), and combinations of the features of the embodiments illustrated or described herein can be used together for the heater assembly 18 in the assembly 10. FIG. 2 depicts a front view of a circular face of a cylindrical heater body 30, while FIG. 3 depicts an isometric view of the cylindrical heater body 30 comprising two circular faces, a curved side surface, and a plurality of axially extending channels.

[0056] As described further herein, the heater assembly 18 comprises a heater body 30 comprised of electrically conductive material that extends in a serpentine current-carrying path 32 (or simply, “serpentine path”) between a pair of electrodes 22. A portion of the serpentine path 32 for the heater body 30 is identified by a dashed lined and the reference numeral 32 in FIG. 2. As described further herein, the serpentine path 32 for the heater body 30 results from a plurality of slots 34 extending into the body 30 from an outer periphery 36 of the heater body 30.

[0057] Current flow along the serpentine path 32 of the heater body 30 can be achieved via electrodes, such as the electrodes 22 at opposite ends of the serpentine path 32. The electrodes 22, or portions thereof, can be integrally formed with the heater body 30, or separately attached, such as via mechanical fastening or welding, for example at corresponding electrode attachment sites. In this way, an electrical connection can be established along the serpentine path 32 through the heater body 30 via the electrodes 22 secured at the opposite ends. For example, the properties of the heater body 30, such as the dimensions of the heater body 30, the length of the serpentine path 32, the area of the electrically conductive material of the heater body 30 available for current flow per unit length along the serpentine path, and/or resistivity of the material of the honeycomb body 30, can be set with respect to a targeted or selected voltage intended to be applied across the electrodes 22 in order to generate heat via resistance heating as electrical current passes through the material of the heater body 30. [0058] In embodiments, the heater body 30 is arranged with respect to a selected voltage (e.g., a voltage available for use by the heater assembly 18 from a vehicle’s battery) to reach a temperature suitable for catalyst light off, such as between about 700°C and 1000°C, although other temperatures can be targeted based on the application of the heater assembly 18 and/or the thermomechanical properties of the material selected for the heater body 30.

[0059] In embodiments, the material ofthe heater body 30 comprises athermally conductive, high porosity ceramic material, such as cordierite as a monolithic electrically non-conductive structure 202 (see FIGS. 4B and 4C) that extends through both the electrically conductive and non-conductive regions of the heater body 30 (see the electrically non-conductive regions 134 and electrically conductive regions 136 shown in FIG. 10). To form the conductive regions, the monolithic electrically non-conductive structure 202 is impregnated with an electrically conductive metal powder, e.g., a high melting temperature metal. The metal powder may be copper, steel, chromium, nickel, an iron alloy, a chromium alloy, an iron-chromium alloy, a nickel alloy, an iron-nickel alloy, a tungsten-cobalt alloy, or a nickel-chromium alloy. In some embodiments, an iron-chromium alloy such as an Fe, Cr, and Al containing alloy, (e.g., a FeCrAl alloy) is used for the metal powder. Alternatively, in some embodiments, the electrically conductive metal is a nickel-chromium containing alloy, such as an austenitic nickel-chromium containing alloy. An example of an austenitic nickel-chromium containing alloy is commercially available from Specialty Materials Corporation under the name INCONEL®, which can be about 50% to 58% nickel by weight and 17% to 23% chromium by weight, based on the total metal weight. Fe-Cr-Al, Fe-Cr, and Fe-Al alloys may be particularly useful in some embodiments due to their low cost and/or high resistance to heat, oxidation, and corrosion.

[0060] Following the impregnation of the metal powder, a sintering process can be performed to transform the metal powder into a monolithic electrically conductive structure 204 (see FIGS. 4B and 4C). That is, when the metal powder particles are loaded into a pore network of the monolithic electrically non-conductive structure 202 to a high enough degree, the particles will be sintered together to form the monolithic electrically conductive structure 204. In this way, the electrically non-conductive regions 134 can be formed by the monolithic electrically non-conductive structure 202, while the electrically conductive regions 136 can be formed by the monolithic electrically conductive structure 204 supported by the monolithic electrically non-conductive structure 202 (e.g., the monolithic electrically conductive structure 204 intertwining around, in, and through the pore network of a porous ceramic material of the monolithic electrically non-conductive structure 202). Advantageously, and as will be demonstrated with respect to FIGS. 6-14B the monolithic electrically non-conductive structure 202 enables the creation of both electrically non-conductive and conductive regions 134, 136 without the need for slots 34 to be formed (e.g., cut) into an improved heater body 175 (as compared to the slots 34 physically formed in the heater body 30 of FIGS. 2 and 3), which enables the improved heater body 175 to exhibit enhanced strength relative to heaters having slots (such as heater body 30).

[0061] As current supplied by the electrodes 22 travels through the heater body 30 via the monolithic conductive structure, the resistive nature of the ceramic generates heat, which travels through the heater body 30. Advantageously, the back-and-forth traversal of the serpentine designs described herein enables the current carrying path length for the heater body 30 to be many times longer than the diameter of the heater body, such that the overall resistance of the heater body 30 between the electrodes 22 can be made high enough to reach sufficient temperatures, while maintaining a compact size to the heater body 30.

[0062] In the illustrated embodiments, the heater body 30 comprises an array or matrix of intersecting walls 40, which form a plurality of channels 42 (fluid flow paths) extending in an axial direction through the heater body 30, and thus is of the type that may be referred to as a honeycomb body. The aforementioned monolithic conductive structure is formed within the intersecting walls 40 through the impregnation of metal powder within the walls and the subsequent sintering process to form the structure. The channels 42 provide flow paths that enable a fluid to flow through the heater body 30 (e.g., a flow of exhaust fluid), while the intersecting walls 40 act as electrically resistive elements to generate heat when a voltage is applied to the body 30 and also provide surface area for heat exchange with the fluid flow. Each of the sections of the walls 40 that are enclosed together to define a flow channel 42 may be referred to herein as a cell. Accordingly, in FIGS. 2 and 3, the array of walls 40 define a corresponding array of square-shaped cells, which together create the honeycomb design for the body 30. However, the walls 40 can be arranged in other patterns to form the channels 42 with any other desired cross-sectional shape (the shape perpendicular to the axial direction), such as hexagonal, triangular, or other polygon. Furthermore, in lieu of cells and channels 42 having regular and/or repeating geometric shapes, the body 30 can comprise irregularly shaped and sized openings. [0063] FIG. 4A is a cross-sectioned microstructural photograph of a subsection of a heater body 30. The pictured subsection shows four intersecting walls 40a-d. An enlarged portion of a first wall 40a is shown in FIG. 4B, and an enlarged portion of a second wall is shown in FIG. 4C. The walls 40a-d comprise a composite material of aspects of a porous, ceramic or glass monolithic electrically non-conductive structure 202 and aspects of a metallic monolithic electrically conductive structure 204. The aspects of the monolithic electrically non-conductive structure 202 are shown as dark gray areas in FIGS. 4A-4C, while the aspects of the monolithic electrically conductive structure 204 are shown as light gray areas. The aspects of the monolithic electrically conductive structure 204 at least partially fill in an internal, interconnected porosity 206 of the aspects of the monolithic electrically non-conductive structure 202. The walls 40a-d can additionally comprise pores or voids (which may be a combination of open and closed porosities due to the presence of the aspects of the monolithic electrically conductive structure 204) as the remaining portion of the internal interconnected porosity 206 that is not filled by the aspects of the monolithic electrically conductive structure 204. This interconnected porosity 206 is represented by the black areas in FIGS. 4A-4C. Thus, the internal, interconnected porosity 206 of the aspects of the monolithic electrically non- conductive structure 202 initially includes (before the addition of the aspects of the monolithically electrically conductive structure 204) both the black (unfilled) areas in FIGS. 4A-4C and the light gray areas that are later occupied by the aspects of the monolithic electrically conductive structure 204.

[0064] Further, FIG. 4C shows an electrical connection or current carrying path 208 passing through the second wall 40b, between opposite surfaces 210, 212 of the second wall 40b. Since the monolithic electrically conductive structure 204 is three-dimensional, many more connections pass through the second wall 40b, but cannot be seen in the cross-sectional view of FIG. 4C. In some cases, the aspects of the monolithic electrically conductive structure 204, and therefore the current-carrying path, traverse in a direction perpendicular to the plane in which the cross-section was taken.

[0065] Furthermore, in some embodiments, aspects of the monolithic electrically conductive structure 204 also provide a continuous current carrying path in a direction that extends along the walls 40, such as within the interior of the walls 40. For example, as shown in FIG. 4C, dotted and dashed path 214 illustrates a continuous, electrically conductive connection provided along an interior of the second wall 40b. In some embodiments, aspects of the monolithic electrically conductive structure 204 are also located on the exterior surfaces of the walls 40 (such as the surfaces 210, 212 of the second wall 40b), to also carry current along the exterior surface of the walls 40. For example, FIG. 4A shows that a comparatively heavy concentration of the conductive material of the monolithic electrically conductive structure 204 can be present at the intersection of the walls 40a-d, which may be advantageous to promote electrical connection between multiple different walls 40, such as walls 40 extending in two or more different directions. The arrangements and configurations shown in FIGS. 4A-4C are described in greater detail in co-pending International Patent Application No. PCT/US2022/038439, filed July 27, 2022.

[0066] As mentioned above, the heater body 30 of FIGS. 2 and 3 comprises the slots 34, which create disconnections, e.g., gaps, in the heater body 30 to break electrical conductivity at certain locations in the body 30. For example, the slots 34 sever, break, disconnect, or otherwise electrically isolate portions of the body 30 from each other, thereby forcing electrical current to flow in the designated serpentine path 32 around these disconnected portions. For example, the slots 34 can be air gaps achieved by cutting the heater body 30. Each of the slots 34 comprises an open end 44 where the slot 34 intersects with the outer periphery 36 of the body 30, and a terminal end 46 at which the slot 34 terminates within the heater body 30.

[0067] As shown in FIG. 2, the slots 34 extend across the body 30 altematingly from opposite sides of the body 30, such that the material of the body 30 (e.g., intersecting walls 40) is connected together in a serpentine pattern that doubles back on itself across the body 30 multiple times.

[0068] Accordingly, the electrical disconnections caused by the slots 34 enables the current path length between the electrodes 22 to be increased, as the electrical current is forced to traverse back and forth across the body 30 multiple times instead of flowing in a straight line directly between the electrodes 22. Since the overall resistance of the heater body 30 is dependent (in part) on the overall current-carrying path length between the electrodes 22, the electrical resistance of the heater assembly 18 can be set, at least in part, by selecting the dimensions, locations, and number of slots 34 (thereby setting the parameters of the serpentine current-carrying path). For example, as described herein, the serpentine design enables the heater body 30 to be formed as a relatively small, thin disc of a desirable metal alloy or other material while also generating temperatures in the hundreds of degrees Celsius. Alternatively, other types of disconnections and body designs may be used to increase the current path between the electrodes 22.

[0069] In embodiments, with respect to the axial direction, the heater body 30 is at most 1 inch thick, at most 0.75 inches thick, at most 0.5 inches thick, such as from 0. 1 inches to 1 inch, from 0. 1 inches to 0.75 inches, from 0. 1 inches to 0.5 inches, or from 0.25 inches to 0.5 inches. In embodiments, the diameter (or widest dimension perpendicular to the axial direction) is at most 10 inches, at most 9 inches, at most 8 inches, at most 7 inches, at most 6 inches, at most 5 inches, at most 4 inches, such as from 4 inches to 10 inches, although the size of the heater body can be arranged based on the particular application, such as to correspond generally to the cross-sectional size of the catalyst substrate or fdter with which the heater is used.

[0070] In some examples, and as illustrated in FIGS. 2 and 3, the heater body 30 is a honeycomb structure comprising a plurality of axially extending channels 42 formed by an array of intersecting walls 40. Such a heater body 30 can be created from a metal -ceramic composite. The heater body 30 implements a serpentine design 32, such that the total electrical resistance of the heater body 30 generates heat sufficient to increase the temperature of exhaust gas flowing through the heater body 30 to a level required by an exhaust aftertreatment system. Further, the serpentine design 32 results in more uniform heating, as current applied by electrodes 22 will be forced to travel around the non-conductive portions of heater body 30. The serpentine design 32 is often achieved by cutting slots 34 in the heater body 30. However, the cutting process may introduce defects into the heater body 30, particularly at the tips of slots, resulting in poor mechanical properties. Further, the precision cutting process required to cut the slots 34 is typically expensive. While cutting into the heater body 30 prior to sintering may reduce cost, the slots 34 may crack or otherwise deform during sintering. Beyond the manufacturing process, the cut-out slots 34 may reduce the durability of the heater body 30, as the slots 34 introduce weak points into the heater body 30. These weak points may lead to failures during hot vibration or frequent heating and cooling cycles.

[0071] As an alternative to the cut-out slots 34 of FIGS. 2 and 3, FIG. 5 illustrates the concept of electrically non-conductive regions 134. The electrically non-conductive regions 134 can be considered to be “virtual slots” in that the non-conductive regions 134 perform a similar function as the slots 34 to electrically isolate or disconnect portions of the previously described heater body 30 from each other, but are virtual because no slots are actually formed. Instead, the heater body 30 comprises the monolithic electrically non-conductive structure 202 continuously throughout conductive and non-conductive regions without the need to cut or remove material or otherwise form the heater body 30 to have the cut-out slots 34. The electrically non-conductive regions 134 are regions of the heater body 30 of a heater assembly 18 which are not electrically conductive. Thus, electrical current supplied by the electrodes 22 is forced to travel around the electrically non-conductive regions 134 in a similar manner as cut-out slots 34. Similar to the cut-out slots 34 of FIGS. 2 and 3, each of the electrically non- conductive regions 134 comprises a peripheral end 144 where the virtual slot 134 intersects with the outer periphery 36 of the body 30, and a terminal end 146 at which the virtual slot 134 terminates within the heater body 30.

[0072] While several methods of forming the electrically non-conductive regions 134 may exist (such as filling or coating the electrically non-conductive regions 134 with non- conductive polymer), the present disclosure provides for applying a hydrophobic material at selected areas corresponding to virtual slots through a spraying process. The hydrophobic material prevents a metal coating or slurry from impregnating the monolithic electrically non- conductive structure 202 with metal powder at those selected areas. The hydrophobic materials may include perfluoropolyether (PFPE) solution or siloxane resin solution. Further, the hydrophobic material may be a temporary coating applied for the selected areas which is removed following the application of the metal coating or slurry (such as by burning the hydrophobic material off during the sintering process). This spraying process eliminates the high costs associated with cutting a heater body, and also improves the durability of the heater body when compared to a heater body with cut-out slots. Further, the spraying process reduces time and material requirements associated with fdling the heater body with non-conductive material.

[0073] FIGS. 6-14B demonstrate the formation of an improved heater body 175 through the aforementioned selective spraying process. FIG. 6 illustrates a plurality of masking elements 102a-o affixed to a face 108 of a monolithic electrically non-conductive structure 202 formed as a cylindrical honeycomb body 100. The masking elements 102a-o are configured to prevent hydrophobic solution 140 (see FIG. 8) from reaching the covered portions of the honeycomb body 100. The masking elements 102a-o may be plastic tape or plastic sheet, such as mylar, polypropylene (PP), or polyethylene (PE). In other examples, the masking elements 102 may be any other removable coating or material capable of shielding the covered portions of the face 108 of the honeycomb body 100 from the hydrophobic solution 140. Further, while FIG. 6 depicts the masking elements 102a-o as fifteen discrete elements, in other examples, any appropriate number of masking elements 102 may be used. For example, in FIG. 7, the plurality of masking elements 102a-o are replaced with a single masking element 102 having a customized shape corresponding to the plurality of masking elements 102a-o of FIG. 6.

[0074] In this example, the honeycomb body 100 comprises an array of intersecting walls 240 formed through extrusion or additive manufacturing. The array of intersecting walls 240 form a plurality of axially extending channels 242. The intersecting walls 240 may be formed from a high porosity ceramic material, such as cordierite. The masking elements 102a-o in the example of FIGS. 6 and 7 combine to form a masked serpentine path 132 on a circular face 108 of the honeycomb body 100. However, in other examples, the masking elements 102 may be arranged to form one or more non-serpentine patterns.

[0075] While the masking elements 102a-o cover a significant portion of the face 108 of the honeycomb body 100, the masking elements 102a-o also form a plurality of exposed portions 104. When the hydrophobic solution 140 is sprayed on the face 108 of the heater body 100, only the walls 240 and channels 242 of the exposed portions 104 will receive the hydrophobic solution 140. Thus, the exposed portions 104 correspond to the electrically non-conductive regions 134 of FIG. 5. The hydrophobic solution 140 will prevent the metal coating or slurry 142 (see FIG. 9) from impregnating the walls 240 and channels 242 of the exposed portions 104 with metal powder, thereby forming a plurality of electrically non-conductive regions 134 (see FIG. 9). These electrically non-conductive regions 134 will therefore force electrical current provided by a pair of electrodes 22 (see FIG. 10) to travel in an electrically conductive serpentine path 32 (see FIG. 10).

[0076] In some examples, the hydrophobic solution 140 is applied to the honeycomb body 100 by a vacuum suction process. In this suction process, a vacuum pulls the hydrophobic solution 140 through the channels 42 of the exposed portions 104 of the honeycomb body 100, covering the walls 240 of the channels 242 with the hydrophobic solution 140 in the process. In some alternative examples, rather than applying masking elements 102 to the honeycomb body 100, the vacuum is configured to selectively generate suction only at the areas of the honeycomb body 100 corresponding to the exposed portions 104 of FIGS. 6 and 7. This selective suction may be achieved by masking portions of the vacuum itself (such as portions of an inlet valve), rather than portions of the honeycomb body 100. [0077] Following the application of the hydrophobic solution 140, the masking elements 102a-o are removed, resulting in the formation of a plurality of hydrophobic portions 106a-g of the honeycomb body 100 as shown within dashed lines in FIG. 8. As noted above, rather than cutting out slots 34 (see FIGS. 2 and 3) or fdling in the cells 242 with non-conductive material, the hydrophobic solution 140 prevents metal coating or slurry 142 from impregnating the hydrophobic portions 106 with metal powder. In some examples, the honeycomb body 100 is cured prior to removing the masking elements 102 shown in FIGS. 6 and 7.

[0078] FIG. 9 illustrates the honeycomb body 100 with a plurality of electrically non- conductive regions (also referred to as virtual slots) 134a-g following the application of metal slurry 142. The metal slurry 142 may be applied by any appropriate means, such as via dip coating or wash coating processes. The metal slurry 142 is preferably an aqueous solution formed by water and metal powder, such as copper, steel, chromium, nickel, an iron alloy, a chromium alloy, a nickel alloy, or a nickel-chromium alloy. While the metal powder impregnates the majority of the monolithic electrically non-conductive structure 202 forming the honeycomb body 100, the hydrophobic solution 140 of hydrophobic portions 106a-g (see FIG. 8) prevents the metal powder from impregnating the portions of the honeycomb body 100 within the electrically non-conductive regions 134a-g. Accordingly, while the walls 240 and channels 242 (or portions thereof) within the electrically non-conductive regions 134a-g are thermally conductive, these walls 240 and channels 242 are not electrically conductive.

[0079] Similarly, the majority of the honeycomb body 100 is impregnated by the metal powder and therefore, following sintering, may be considered an electrically conductive region 136 formed as a monolithic electrically conductive structure 204 (see FIG. 10). The example of FIG. 9 illustrates the electrically conductive region 136 as a continuous, serpentine pattern within a dash-dotted line. However, the electrically conductive region 136 may be formed into other shapes or patterns depending on the required application. Further, some honeycomb bodies 100 may comprise more than one electrically conductive region 136.

[0080] FIG. 10 illustrates an improved electrical heater assembly 218 formed with an improved honeycomb body 175 following a sintering process. The sintering process forms a monolithic electrically conductive structure 204 within the honeycomb body 100 from the metal powder deposited by the metal slurry 142. The monolithic electrically conductive structure 204 is formed within the walls 240 and channels 242 of the monolithic electrically non-conductive structure 202 of the honeycomb body 100 within the electrically conductive region 136. The monolithic electrically conductive structure 204 enables an electrical current applied to the honeycomb body 100 by a pair of electrodes 22 to follow a serpentine path 232, similar to the serpentine path 32 illustrated in FIG. 2. As shown in FIG. 10, a pair of electrodes 22 are affixed to the honeycomb body 100 at opposite ends of the electrically conductive region 136. Further, the sintering process bums off any remaining hydrophobic material found on the walls 240 or in the channels 242 of the electrically non-conductive regions 134a-g.

[0081] FIG. 11 illustrates a variation of the heater body 175 of FIG. 10 with an electrically conductive region 136 and a plurality of electrically non-conductive regions 134a-d. In this example, the electrically conductive region 136 is not arranged in a serpentine configuration. Rather, the plurality of electrically non-conductive regions 134a-d are configured as four radial virtual slots extending from the outer periphery 236 of the honeycomb body 100 towards the center of the honeycomb body 100. As with the virtual slots of the previous embodiments, the electrically non-conductive regions 134a-d of FIG. 11 lengthen the path of electrical current flowing through the electrically conductive region 136.

[0082] Example honeycomb bodies were prepared generally in accordance with the above description and as further described below. FIGS. 12A-14B illustrate validation of the method of manufacturing described above. FIG. 12A shows the top face 108a, bottom face 108b, and side faces 108c,d of a monolithic electrically non-conductive structure 202 that was prepared according to one experiment. In this experiment, a hydrophobic solution 140 was sprayed on two hydrophobic portions 106a,b (defined with dashed lines) of the monolithic electrically non- conductive structure 202, such that the hydrophobic solution 140 covers the walls 240 and channels 242 within the hydrophobic portions 106a,b. In FIG. 12B, the monolithic electrically non-conductive structure 202 was sprayed with a water-based dye to demonstrate the effectiveness of the hydrophobic solution 140. As can be seen in FIG. 12B, the dye fails to adhere to the hydrophobic portions 106a,b of the monolithic electrically non-conductive structure 202. FIG. 13 shows the same monolithic electrically non-conductive structure 202 of FIG. 12A coated with a metal slurry 142. As shown in FIG. 13, and similar to the dye of FIG. 12B, the metal slurry 142 fails to adhere to hydrophobic portions 106a, b of the monolithic electrically non-conductive structure 202. FIGS. 14A and 14B show microscopic images of adjacent channels 242 in the monolithic electrically non-conductive structure 202, where hydrophobic solution 140 has been applied to channel A, but not to channel B. [0083] Since the hydrophobic solution was only applied to channel A, channel A was accordingly representative of a channel intended to be part of the non-conductive region (where deposition of the metal particles is hindered or prevented) and channel B was representative of a channel intended to be part of the conductive region (where deposition of the metal particles is permitted). In this experiment, copper was used as a metal powder, although other high melting point temperature metals could be used to form the heater body 175 as described herein. [0084] An analysis of the chemical composition found in each of channel A and channel B was performed to assess the effectiveness of the hydrophobic solution in preventing metal particles from being deposited in the intended non-conductive regions. That is, the amount of metal particles deposited in channels A and B can be used to assess how electrically conductive the material in each channel is (with more metal being deposited corresponding to a more conductive region). Accordingly, Table 1 contains information regarding chemical elements found in each channel. In particular, Table 1 contains the atomic percentage, atomic ratio, and concentration of carbon, oxygen, magnesium, aluminum, silicon, and copper (with the copper being representative of the metal powder that would be used to create the conductive regions).

Table 1

[0085] As demonstrated by Table 1, the elemental composition of Channel A and B is very similar, with the exception of copper. As Channel A has been coated with hydrophobic solution 140, the metal slurry 142 was unable to impregnate the walls of the channel with the copper to the same degree as Channel B. Accordingly, Table 1 further demonstrates the effectiveness of the hydrophobic solution 140.

[0086] FIG. 15 is a flowchart of a method 900 of manufacturing an electrical heater body. The method 900 comprises forming 902 one or more hydrophobic regions in a honeycomb body by applying a hydrophobic solution. The honeycomb body comprises a plurality of channels extending axially through the honeycomb body. The method 900 further comprises coating 904 the honeycomb body with a metal slurry. The one or more hydrophobic regions repel the metal slurry to form an electrically conductive region and one or more electrically non-conductive regions in the honeycomb body.

[0087] In some optional embodiments, the method 900 further comprises arranging 906, prior to forming the one or more hydrophobic regions, one or more masking elements on a face of the honeycomb body. The method 900 further comprises removing 908, prior to coating the honeycomb body with the metal slurry, the one or more masking elements from the face of the honeycomb body.

[0088] In some optional embodiments, the method 900 further comprises curing 910 the honeycomb body prior to removing the one or more masking elements.

[0089] In some optional embodiments, the method 900 further comprises forming 912, via extrusion or additive manufacturing, the honeycomb body.

[0090] In some optional embodiments, the method 900 further comprises sintering 914 the metal slurry to form a monolithic conductive structure within the electrically conductive region of the honeycomb body.

[0091] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claimed subject matter. Accordingly, the claimed subject matter is not to be restricted except in light of the attached claims and their equivalents.

Claims

Claims What is claimed is:

1 . A method of manufacturing an electrical heater body, comprising: forming one or more hydrophobic regions in a honeycomb body by applying a hydrophobic solution, wherein the honeycomb body comprises a plurality of channels extending axially through the honeycomb body; and coating the honeycomb body with a metal slurry, wherein the one or more hydrophobic regions repel the metal slurry to form an electrically conductive region and one or more electrically non-conductive regions in the honeycomb body.

2. The method of claim 1, further comprising: arranging, prior to forming the one or more hydrophobic regions, one or more masking elements on a face of the honeycomb body; and removing, prior to coating the honeycomb body with the metal slurry, the one or more masking elements from the face of the honeycomb body.

3. The method of claim 2, wherein at least one of the one or more masking elements comprises a plastic tape or sheet.

4. The method of claim 3, wherein the plastic tape or sheet is mylar, polypropylene (PP), or polyethylene (PE).

5. The method of claim 2, further comprising curing the honeycomb body prior to removing the one or more masking elements.

6. The method of claim 1, wherein the electrically conductive region comprises an electrically conductive serpentine path.

7. The method of claim 1, wherein the hydrophobic solution comprises a hydrophobic material, and wherein the hydrophobic material is perfluoropolyether (PFPE) solution or siloxane resin solution.

8. The method of claim 1, wherein the metal slurry is an aqueous solution formed by water and a metal powder.

9. The method of claim 8, wherein the metal powder comprises copper, steel, chromium, nickel, an iron alloy, a chromium alloy, a nickel alloy, or a nickel-chromium alloy.

10. The method of claim 8, wherein coating the honeycomb body with the metal slurry impregnates a portion of the honeycomb body corresponding to the electrically conductive region with the metal powder.

11. The method of claim 1, further comprising forming, via extrusion or additive manufacturing, the honeycomb body.

12. The method of claim 11, wherein the honeycomb body comprises a porous ceramic material.

13. The method of claim 12, wherein the porous ceramic material is cordierite.

14. The method of claim 1, wherein applying the hydrophobic solution to the honeycomb body includes pulling the hydrophobic solution through the plurality of channels via vacuum suction.

15. The method of claim 1, further comprising sintering the metal slurry to form a monolithic conductive structure within the electrically conductive region of the honeycomb body.

16. An electrical heater body comprising a plurality of channels extending axially through the electrical heater body, wherein the electrical heater body is divided into an electrically conductive region and one or more electrically non-conductive regions, wherein the electrically non-conductive regions are defined by a monolithic non-conductive structure and the electrically conductive region of the electrical heater body comprises a monolithic conductive structure supported by the monolithic non-conductive structure.

17. The electrical heater body of claim 16, wherein the electrically conductive region comprises an electrically conductive serpentine path.

18. The electrical heater body of claim 16, wherein the monolithic non-conductive structure comprises a porous ceramic material.

19. The electrical heater body of claim 16, wherein the monolithic conductive structure comprises copper, steel, chromium, nickel, an iron alloy, a chromium alloy, a nickel alloy, or a nickel-chromium alloy.

20. An electrical heater assembly comprising the electrical heater body of claim 16 coupled to a pair of electrodes at opposite ends of the electrically conductive region.