Metal‑glass bubble composites as adsorbent substrates for selected gas capture and methods for making the same

Abstract

Porous composite structures and compositions and methods for producing porous composite structures. The composition includes from 20 wt% to 80 wt% hollow glass bodies and from 20 wt% to 80 wt% metal particles, where wt% is based on a total combined weight of non-combustible inorganic particles in the composition.

Description

Attorney Docket No.: SP24-064MET L-GLASS BUBBLE COMPOSITES AS ADSORBENT SUBSTRATES FOR SELECTED GAS CAPTURE AND METHODS FOR MAKING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Serial No. 63 / 696122 filed on September 18, 2024, the content of which are relied upon and incorporated herein by reference in their entirety.TECHNICAL FIELD

[0002] The present disclosure relates to porous composite structures as adsorbent substrates for gas capture systems and methods for making the same.BACKGROUND

[0003] Increasing CO2 content in the atmosphere has been linked to global warming and is now considered a worldwide issue. In response to carbon trading incentives along with enacted and anticipated regulations of carbon emissions from flue gases and other CO2 point sources, significant efforts have been directed to improving the efficiency of CO2 capture technologies. There is also increased interest in direct air capture (DAC) systems that extract CO2 directly from the atmosphere. In particular, adsorption-based DAC systems wherein CO2 is adsorbed on a solid surface and subsequently released via system temperature and / or pressure swings, and then captured, are attracting interest for CO2 capture technologies. However, such DAC systems must be energy' efficient to process large amounts of air necessary to capture the relatively low concentration (roughly 400 ppm) of CO2 in the atmosphere.SUMMARY

[0004] In DAC systems employing temperature swing adsorption (TSA), CO2 adsorption onto solid surfaces (the sorbent) occurs at relatively low temperatures (e.g., ambient temperature) whereas CO2 desorption, i.e., regeneration of the sorbent, is induced by heating the system to weaken the attraction between CO2 molecules and the sorbent surface. In some conventional TSA regeneration processes, the system is heatedAttorney Docket No.: SP24-064 by purging with a hot gas (e.g., nitrogen) which directly contacts and heats the sorbent such that CO2 molecules adsorbed thereon are released. However, the use of a purging gas to heat the TSA system is associated with an unavoidable dilution of the desorbed CO2 stream, which is contrary to an intended purpose of DAC systems - to separate CO2 from the atmosphere in a concentrated form.

[0005] Another TSA regeneration process involves directly heating the sorbent bypassing electric current through the sorbent and exploiting Joule effect. Direct joule heating methods may result in a faster heat transfer rate, shorter desorption time, and reduced energy cost. Accordingly, there exists a need for electrically conductive adsorbent substrates that may be used in DAC systems for CO2 capture. Additionally, sorbents may be selective to additional and / or other gases than just carbon dioxide, such that such that the capture systems and methods described herein can be used for capturing gases other than carbon dioxide, such as other greenhouse gases.

[0006] Embodiments of the present disclosure are directed to metal-glass bubble composites as adsorbent substrates for CO2 or other selected gas capture systems and methods for making the same. The metal-glass bubble composites have a porous composite structure including a continuous, three-dimensional, and interconnected metallic phase that operates as a resistive heating element when subjected to a voltage potential. In embodiments, a sorbent coating may be provided on surfaces of the porous composite structure and configured to absorb heat, directly or indirectly, from the Joule-heated metallic phase. The heat absorbed by the sorbent coating may then be transferred to gas, e.g., CO2, molecules adsorbed on surfaces of the sorbent coating. Such embodiments may be advantageous because a non-electrically conductive sorbent material may be utilized in the sorbent coating, whereas existing DAC systems using direct Joule heating are ty pically limited to electrically conductive sorbent materials, e.g., activated carbon, which may be an undesirable design limitation for DAC systems.

[0007] Further embodiments of the present disclosure are directed to substrates including the porous composite structure, with or without a sorbent coating provided thereon. Further embodiments are directed to CO2 capture systems that include an adsorption / desorption unit with said substrate being integrated therein. Embodiments of the present disclosure are also directed to compositions for producing porous composite structures and methods of making porous composite structures.Attorney Docket No.: SP24-064

[0008] According to a first aspect of the present disclosure, a composition for producing porous composite structures comprises: from 20 wt% to 80 wt% hollow glass bodies; from 20 wt% to 80 wt% metal particles, wherein wt% is based on a total combined weight of the hollow glass bodies and the metal particles.

[0009] A second aspect includes the first aspect, comprising from 50 wt% to 80 wt% hollow glass bodies; and from 20 wt% to 50 wt% metal particles.

[0010] A third aspect includes either of the first or second aspects, where the metal particles comprise a metal selected from the group consisting of aluminum, copper, iron, nickel, cobalt, silver, alloys thereof, and combinations thereof.

[0011] A fourth aspect includes any one of the first through third aspects, wherein the hollow glass bodies have a wall thickness from 0.2 pm to 10 pm.

[0012] A fifth aspect includes any one of the first through fourth aspects, wherein: the hollow glass bodies comprise silica glass; and the metal particles comprise aluminum, aluminum alloy, or both aluminum and aluminum alloy.

[0013] A sixth aspect includes any one of the first through fifth aspects, wherein: the hollow glass bodies have a D50 diameter of greater than or equal to 1 pm and less than or equal to 100 pm; and the metal particles have a D50 diameter of greater than or equal to 1 pm and less than or equal to 100 pm.

[0014] A seventh aspect includes any one of the first through sixth aspects, further comprising from 2 wt% SA to 20 wt% SA binder, wherein wt% SA is weight percent by superaddition based on the total combined weight of the non-combustible inorganic particles in the composition. The binder can comprise cellulose, cellulose derivatives, polymer binders, or combinations thereof.

[0015] An eighth aspect includes any one of the first through seventh aspects, further comprising from 10 wt% SA to 50 wt% SA inorganic pore former.

[0016] A ninth aspect includes the eighth aspect, wherein the inorganic pore former comprises graphite particles.

[0017] A tenth aspect includes the ninth aspect, wherein the graphite particles have a D50 diameter of greater than or equal to 1 pm and less than or equal to 100 pm.

[0018] An eleventh aspect includes any one of the first through tenth aspects, further comprising a surfactant, a lubricant, an oil, or combinations thereof.Attorney Docket No.: SP24-064

[0019] A twelfth aspect includes any one of the first through eleventh aspects, further comprising from 2 wt% SA to 20 wt% SA lubricant.

[0020] A thirteenth aspect includes the twelfth aspect, wherein the lubricant comprises a mineral oil.

[0021] A fourteenth aspect includes any one of the first through thirteenth aspects, further comprising water in an amount from 20 wt% SA to 80 wt% SA.

[0022] A fifteenth aspect includes any one of the first through thirteenth aspects, further comprising water in an amount from 40 wt% SA to 55 wt% SA.

[0023] According to a sixteenth aspect of the present disclosure, a method of making a porous composite structure comprises: preparing the composition of any one of the first through fifteenth aspects; forming a green body from the composition; and firing the green body to produce the porous composite structure.

[0024] A seventeenth aspect includes the sixteenth aspect, wherein firing the green body comprises: ramping the green body to a peak firing temperature at a ramping rate of from 100 °C per hour to 500 °C per hour; holding the green body at the peak firing temperature for a peak firing time of less than 4 hours to produce the fired structure; and cooling the fired structure to produce the porous composite structure.

[0025] An eighteenth aspect includes the seventeenth aspect, wherein cooling the fired structure comprises cooling the fired structure to ambient temperature at a cooling rate of from 100 °C per hour to 500 °C per hour.

[0026] A nineteenth aspect includes either one of the seventeenth or eighteenth aspects, wherein the peak firing temperature is greater than or equal to 500 °C and less than or equal to 1000 °C.

[0027] An twentieth aspect includes any one of the seventeenth through nineteenth aspects, wherein the peak firing time is greater than or equal to 1 hour and less than or equal to 3 hours.

[0028] An twenty -first aspect includes any one of the seventeenth through nineteenth aspects, wherein: the peak firing temperature is greater than or equal to 800 °C and less than or equal to 1000 °C; and the peak firing time is less than or equal to 0.5 hours.

[0029] A twenty-second aspect includes any one of the seventeenth through nineteenth aspects or the twenty -first aspect, wherein the peak firing time is zero hours.Attorney Docket No.: SP24-064

[0030] A twenty-third aspect includes any one of the seventeenth through twenty-second aspects, wherein firing the green body is performed in an inert atmosphere.

[0031] A twenty-fourth aspect includes the twenty-third aspect, wherein the inert atmosphere comprises nitrogen gas.

[0032] A twenty -fifth aspect includes the sixteenth aspect, wherein firing the green body comprises: ramping the green body to a peak firing temperature at a ramping rate of from 2,500 °C per hour to 3,500 °C per hour; and holding the green body at the peak firing temperature for a peak firing time of from 0.5 hours to 3 hours to produce the fired structure; and cooling the fired structure to produce the porous composite structure.

[0033] A twenty-sixth aspect includes the twenty-fifth aspect, wherein cooling the fired structure comprises naturally cooling the fired structure to ambient temperature over a cooling time of from 1 hour to 3 hours.

[0034] A twenty -seventh aspect includes either of the twenty-fifth or twenty-sixth aspects, wherein the peak firing temperature is greater than or equal to 600 °C and less than or equal to 800 °C.

[0035] A twenty-eighth aspect includes any one of the twenty-fifth through twenty-seventh aspects, wherein firing the green body to produce the fired structure and cooling the fired structure to produce the porous composite structure is completed in a combined time of less than 10 hours.

[0036] A twenty -ninth aspect includes any one of the twenty -fifth through twenty-eighth aspects, wherein firing the green body is performed in an oxygenated atmosphere.

[0037] A thirtieth aspect includes any one of the sixteenth through twenty -ninth aspects, wherein forming the green body comprises extruding the composition into a honeycomb body comprising a plurality of elongate channels.

[0038] A thirty-first aspect includes the thirtieth aspect, wherein the honeycomb body comprises: a cell density of from 200 cells per square inch to 400 cells per square inch, where the cell density refers to a number of elongate channels per square inch of crosssection of the honeycomb body; and a web thickness of from 2 mils to 10 mils.

[0039] A thirty-second aspect of the present disclosure includes a green body formed from the composition of any one of the first through fifteenth aspects.Attorney Docket No.: SP24-064

[0040] A thirty-third aspect of the present disclosure includes a porous composite structure comprising a continuous, three dimensional, and interconnected metallic phase and a non metallic phase of sintered hollow glass bodies dispersed throughout the porous composite structure and intertwined with and / or interspersed through the metallic phase.

[0041] A thirty-fourth aspect includes the thirty-third aspect, wherein the non-metallic phase is a continuous, three-dimensional, and interconnected glass phase intertwined with the metallic phase.

[0042] A thirty -fifth aspect includes either of the thirty7-third or thirty-fourth aspects, wherein the porous composite structure comprises a porosity of greater than or equal to 50% and less than or equal to 85%, measured in accordance with ASTM D6761-07 (2012).

[0043] A thirty -sixth aspect includes any one of the thirty -third through thirty -fifth aspects, wherein the porous composite structure comprises a bulk density of greater than or equal to 0.5 g / cm3and less than or equal to 5.0 g / cm3. measured in accordance with ASTM D6761-07 (2012).

[0044] A thirty -seventh aspect includes any one of the thirty -third through thirty -seventh aspects, wherein the porous composite structure comprises a modulus of rupture of greater than or equal to 0.5 MPa to 10 MPa, measured in accordance with ASTM C1674-16.

[0045] A thirty-eighth aspect includes any one of the thirty-third through thirty-eighth aspects, wherein the porous composite structure comprises a median pore diameter dso of greater than or equal to 1 pm and less than or equal to 50 pm, measured by mercury porosimetry in accordance with ASTM D6761-07 (2012).

[0046] A thirty-ninth aspect includes any one of the thirty-fourth through thirty-eighth aspects, wherein: the metallic phase comprises metal particles of the composition that have been sintered together; and the non-metallic phase comprises reaction products of a portion of the metal particles of the composition and the hollow glass bodies of the composition.

[0047] A fortieth aspect includes the thirty -ninth aspect, wherein: the hollow glass bodies of the composition comprise silica glass; the metal particles of the compositionAttorney Docket No.: SP24-064 comprise aluminum; and the reaction products of the portion of the metal particles and the hollow glass bodies comprise silicon and alumina.

[0048] A forty -first aspect includes any one of the thirty-third through fortieth aspects, wherein the porous composite structure comprises: from 15 wt% to 50 wt% of a combined amount of aluminum and silicon, based on a total weight of a cry stalline portion of the porous composite structure; from 40 wt% to 70 wt% alumina, based on the total weight of the crystalline portion of the porous composite structure; and up to 20 wt% silica, based on the total weight of the crystalline portion of the porous composite structure.

[0049] A forty-second aspect includes any one of the thirty-third through forty -first aspects, wherein porous composite structure comprises from 5 wt% to 35 wt% aluminum, based on the total weight of the crystalline portion of the porous composite structure.

[0050] A forty -third aspect includes any one of the thirty -third through forty -second aspects, wherein porous composite structure comprises at least 10 wt% silicon, based on the total weight of the crystalline portion of the porous composite structure.

[0051] A forty -fourth aspect includes any one of the thirty -third through forty -third aspects, wherein the porous composite structure has a honeycomb shape comprising a plurality of elongate channels extending through at least a portion of the porous composite structure, wherein the porous composite structure has a cell density of less than or equal to 400 cells per inch and a web thickness between cells of from 2 mils to 10 mils, where the cell density refers to a number of elongate channels per square inch of cross-section of the porous composite structure.

[0052] According to a forty-fifth aspect of the present disclosure, a substrate comprises: the porous composite structure of any one of the thirty -third through forty-fourth aspects; and a sorbent coating supported on the porous composite structure, wherein the sorbent coating is configured to adsorb a selected gas, e.g., CO2 molecules.

[0053] According to a forty-sixth aspect of the present disclosure, a CO2 capture system comprising the substrate of the forty -fifth aspect, wherein the CO2 capture system comprises an adsorption / desorption unit and the substrate is integrated into the adsorption / desorption unit.Attorney Docket No.: SP24-064

[0054] Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0055] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0057] FIG. 1 schematically depicts a green body for forming metal-glass bubble porous composite structures, according to one or more embodiments shown and described herein;

[0058] FIG. 2 schematically depicts a metal-glass bubble porous composite structure as part of a heater assembly, according to one or more embodiments shown and described herein;

[0059] FIG. 3 is an SEM image of a metal-glass bubble porous composite structure, according to one or more embodiments shown and described herein; and

[0060] FIG. 4 is an SEM image of a metal-glass bubble porous composite structure, according to one or more embodiments shown and described herein.Attorney Docket No.: SP24-064DETAILED DESCRIPTION

[0061] Reference will now be made in detail to various embodiments of the compositions, porous composite structures, and methods of the present disclosure, some embodiments of 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 similar parts.

[0062] As used herein, the term “hollow glass bodies’" refers to particles comprising a shell that is made of glass and that surrounds an internal volume containing a substance that is not glass, such as air or other gas.

[0063] As used herein, the term “green body” refers to a structure formed of the compositions disclosed herein that has not been subjected to firing.

[0064] As used herein, the term “peak firing temperature” refers to the maximum temperature during the firing process, at which maximum temperature, the green body may be maintained for a period of time before being gradually cooled down to ambient temperature.Compositions for Producing Porous Composite Structures

[0065] Embodiments of the present disclosure are directed to compositions for producing porous composite structures that include hollow glass bodies and metal particles. The term “wt%,” when used with respect to a component of the compositions described herein, refers to the weight percent of the component based on a total combined weight of the hollow glass bodies and the metal particles in the composition. If the composition includes a non-combustible inorganic powder such as talc, the term “wt%,” when used with respect to a component of the compositions described herein, refers to the weight percent of the component based on a total combined weight of the hollow glass bodies, the metal particles, and the non-combustible inorganic powder in the composition.

[0066] The term “wt% SA,” when used with respect to a component of the compositions described herein, refers to weight percent by superaddition based on the total combined weight of the hollow glass bodies and the metal particles in the composition. If the composition includes a non-combustible inorganic particle powder such as clay, talc, etc. the term “wt% SA,” when used with respect to a component of theAttorney Docket No.: SP24-064 compositions described herein, refers to weight percent by superaddition based on the total combined weight of the hollow glass bodies, the metal particles, and the non-combustible inorganic particle powder in the composition.

[0067] In embodiments, a composition for producing porous composite structures comprises from 20 wt% to 80 wt% hollow glass bodies, from 20 wt% to 80 wt% metal particles, and from 2 wt% SA to 20 wt% SA binder. In embodiments, the compositions described herein may comprise from 50 wt% to 80 wt% hollow glass bodies and from 20 wt% to 50 wt% metal particles. As will be described in more detail herein, the mechanical properties, electrical properties, and characteristics of the porous microstructure of the porous composite structures produced from the compositions described herein may be controlled, in part, by adjusting the content of the hollow glass bodies and the metal particles.

[0068] The hollow glass bodies, also referred to as glass bubbles, microballoons, or hollow glass microspheres (HGMS), are commercially available, such as from Dennert Poraver GMBH. 3M, Zhongke Yah Technology, Ltd, Fibre Glast Developments Corp., Potters Industries LLC. and others. The compositions of the present disclosure and the porous composites structures made therefrom may include and / or be at least partially formed from a plurality of hollow glass bodies, where a “plurality ” of hollow glass bodies may refer to greater than or equal to 100, or even greater than or equal to 1000 hollow glass bodies. The hollow glass bodies may act as both a pore former and a main frame structure to provide a high porosity composite structure. The hollow glass bodies may have various shapes. The hollow glass bodies may be generally spherical or may have an irregular shape, such as having an oblong, elliptical, or potato-shape, for example.

[0069] It has now been discovered that these hollow glass bodies can be utilized in combination with metal particles in compositions for producing electrically conductive porous composite structures which may be used as porous media for adsorption / desorption units in CO2 capture processes. Porous structural features may be formed from tightly packing the hollow glass bodies together, bonding the hollow glass bodies to one another, and also breaching the hollow glass bodies (e.g., breaking, popping, fracturing, opening, or otherwise exposing hollow cores thereof) to produce voids in the porous composite structure. That is, the internal volume of individual hollowAttorney Docket No.: SP24-064 glass bodies may open into one another to form porous cavities that extend and interconnect through the overall porous composite structure and may open to surfaces thereof. Bonding and then breaching the hollow glass bodies may be accomplished by firing a green body formed from compositions comprising the hollow glass bodies to temperatures greater than the softening temperature of the glass of the hollow glass bodies.

[0070] By adjusting the content and characteristics (e.g., composition, particle size distribution, etc.) of the hollow glass bodies in the compositions described herein, the resulting microstructure of the porous composite structures may be controlled in terms of the porosity, mean pore size, and pore distribution. Accordingly, the compositions described herein allow for the production of porous composite structures having a wide range of permeability characteristics associated with the adjustable porous microstructure.

[0071] In embodiments, the compositions for producing porous composite structures include hollow glass bodies in an amount from 20 wt% to 80 wt%, from 25 wt% to 80 wt%. from 30 wt% to 80 wt%, from 35 wt% to 80 wt%, from 40 wt% to 80 wt%. from 45 wt% to 80 wt%, from 50 wt% to 80 wt%, from 55 wt% to 80 wt%, from 60 wt% to 80 wt%, or from 65 wt% to 80 wt%, based on a total combined weight of the noncombustible inorganics in the composition (e.g., the hollow glass bodies and the metal particles).

[0072] The size of the hollow glass bodies may be selected and characterized based on the diameter of the hollow glass bodies, which may be referred to as the diameter of the hollow glass body if the volume of the hollow glass body was arranged in a perfect spherical geometry. The size distribution of the hollow glass bodies may be characterized in terms of various statistical parameters of the size distribution, including the D50, D10, and D90 diameters. As used herein, the “D50” diameter of a group of particles corresponds to a 50% pass point, where particles making up 50% by volume of the group of particles have a diameter less than the D50 diameter. Similarly, the “D10” diameter of a group of particles corresponds to a 10% pass point, where particles making up 10% by volume of the group of particles have a diameter less than the D10 diameter. Similarly the “D90” diameter of a group of particles corresponds to a 90% pass point, where particles making up 90% by volume of the group of particles have a diameter lessAttorney Docket No.: SP24-064 than the D90 diameter. The size distribution of other components of the compositions described herein provided in particle form may be similarly characterized with DIO, D50, D90, and / or other D-values.

[0073] The hollow glass bodies of the compositions described herein may have a D50 diameter of greater than or equal to 1 pm, greater than or equal to 3 pm, greater than or equal to 5 pm. or even greater than or equal to 10 pm. The hollow glass bodies may have a D50 diameter of less than or equal to 100 pm. less than or equal to 50 pm, or even less than or equal to 40 pm. The hollow glass bodies may have a D50 diameter of from 1 pm to 100 pm, 1 pm to 50 pm, from 1 pm to 40 pm, from 3 pm to 100 pm, from 3 pm to 50 pm, from 3 pm to 40 pm, from 5 pm to 100 pm from 5 pm to 50 pm, 5 pm to 40 pm, from 10 pm to 100 pm, from 10 pm to 50 pm, or from 10 pm to 40 pm.

[0074] The particle size distribution of the hollow' glass bodies may be further characterized by the (D90-D10) / D50 ratio. The hollow' glass bodies may have (D90- D10) / D50 ratio of less than or equal to 2, less than or equal to 1.5, less than or equal to 1, less than or equal to 0.8, less than or equal to 0.4, less than or equal to 0.2. less than or equal to 0.1. or less than or equal to 0.06. In embodiments, the composition may include two or more different types or sizes of hollow' glass bodies (i.e., the composition is multi-modal at least with respect to the hollow glass bodies). In these embodiments, each type or size of hollow glass bodies may be characterized by a D50 diameter and (D90- D10) / D50 ratio such that the particle size distribution for the hollow glass bodies in the composition is multi-modal.

[0075] The hollow glass bodies incorporated into the composition and before firing (i.e., before breaching the hollow' glass bodies as discussed further herein) may have a density of greater than or equal to 0.1 g / cm3, such as greater than or equal to 0.3 g / cm3, where the density is the mass per volume, which includes the interior bubble volume of the hollow' glass bodies. The hollow glass bodies incorporated into the composition and before firing may have a density7of less than or equal to 1.5 g / cm3, such as less than or equal to 0.7 g / cm3. The hollow glass bodies before firing may have a density of from 0.1 g / cm3to 1.5 g / cm3, from 0.1 g / cm3to 0.7 g / cm3, from 0.3 g / cm3to 1.5 g / cm3, from 0.3 g / cn to 0.7 g / cnT, or from 0.5 g / cm3to 0.7 g / cm3.

[0076] The hollow glass bodies may have a w all thickness of the shell sufficient to enable the hollow glass bodies to withstand being formed into green bodies, such asAttorney Docket No.: SP24-064 through extrusion or molding, but thin enough to enable breaching of a majority of the hollow glass bodies during firing. In embodiments, the hollow glass bodies may have an average wall thickness of from 0.2 pm to 10 pm, or from 1 pm to 3 pm.

[0077] The hollow glass bodies may have an isostatic crush strength that is sufficient so that the hollow glass bodies do not break during the forming process, such as during extrusion. The isostatic crush strength of the hollow glass bodies depends on the shell thickness, particle size, and glass composition of the hollow glass bodies. In embodiments, particularly resilient hollow glass bodies are used, such as those having a mean isostatic crush strength of at least 1,000 psi (6.9 MPa), such as at least 2,000 psi (13.8 MPa), such as at least 3,000 psi (20.7 MPa) (see Measuring Isostatic Pressing Strength of Hollow Glass Microspheres by Mercury-inj ection Apparatus by Yun and Shou, Key Engineering Materials, vol. 544, pp. 460-5 (2013)).

[0078] The hollow glass bodies may include glass (e.g., consist of, consist mostly of by volume, comprise), such as silica glass, soda lime glass, borosilicate, or other glasses. In embodiments, the hollow glass bodies may comprise silica glass. The glass of the hollow glass bodies may be fully amorphous. In embodiments, the glass of the hollow glass bodies may be amorphous prior to heating, and subsequently may devitrify and / or crystallize during the firing process. For clarify, “glass” as used herein includes amorphous glass and / or at least partially devitrified glass with crystals.

[0079] According to embodiments, hollow glass bodies with high crystallinity at softening temperatures of the hollow' glass bodies, such as hollow glass bodies including more than 45% silica (SiCH) and / or CaSiCh, etc. by weight, may facilitate transformation processes from internal porosity to open connected porosity, as discussed below.

[0080] In embodiments, the glass of the hollow glass bodies may include more than 50 wt% SiC>2, such as from 50 wt% to 99 wt%, from 50 wt% to 95 wt%, from 50 wt% to 90 wt%, from 50 wt% to 85 wt%, from 55 wt% to 85 wt%, from 60 wt% to 85 wt%, or from 65 wt% to 85 wt% SiCh, based on the total weight of the glass.

[0081] In embodiments, the glass of the hollow glass bodies may include at least some CaO. such as at least 0. 1 wt% CaO. In embodiments, the glass of the hollow glass bodies may include at least some CaO, such as at least some but less than 10 wt%, less than 8 wt%, less than 6 wt%, less than 4 wt%, less than 2 wt%, or less than 1 wt% CaO, based on the total weight of the glass. In embodiments, the glass of the hollow- glass bodiesAttorney Docket No.: SP24-064 may include more than 6 wt% CaO, such as from 6 wt% to 10 wt%, from 6 wt% to 9 wt%. or from 6 wt% to 8 wt% CaO, based on the total weight of the glass.

[0082] In embodiments, the glass of the hollow glass bodies may include less than 13 wt% B2O3, such as from 2 wt% to 13 wt%, from 3 wt% to 13 wt%, from 4 wt% to 13 wt%, from 5 wt% to 13 wt%, or from 5.5 wt% to 13 wt% B2O3, based on the total weight of the glass.

[0083] In embodiments, the glass of the hollow glass bodies may include at least some AI2O3, such as at least some but less than 20 wt%, less than 15 wt%, less than 10 wt%, less than 5 wt%, less than 3 wt%, or less than 1 wt% AI2O3, based on the total weight of the glass.

[0084] In embodiments, the glass of the hollow glass bodies may include at least some Fe2C>3, such as at least some but less than 5 wt%, less than 3 wt%, less than 1 wt%, less than 0.5 wt%, or less than 0.1 wt% Fe20s, based on the total weight of the glass. In embodiments, the glass of the hollow glass bodies may be substantially free of Fe2C>3.

[0085] In embodiments, the glass of the hollow glass bodies may include less than 20 wt% Na2O. such as from 1 wt% to 20 wt%, from 1 wt% to 12 wt%, from 1 wt% to 1 1 wt%, or from 1.5 wt% to 11 wt% Na2O, based on the total weight of the glass. In embodiments, the glass of the hollow glass bodies may include greater than 10 wt%, greater than 12 wt%, greater than 14 wt%, greater than 16 wt%, or greater than 18 wt% Na2O, based on the total weight of the glass.

[0086] In embodiments, the glass of the hollow glass bodies may include at least some K2O, such as at least some but less than 5 wt%, less than 3 wt%, less than 1 wt%, or less than 0.5 wt% K2O, based on the total weight of the glass. In embodiments, the glass of the hollow glass bodies may be substantially free of K2O.

[0087] In embodiments, the glass of the hollow glass bodies may include at least some MgO, such as at least some but less than 5 wt%, less than 3 wt%, or less than 1 wt%, based on the total weight of the glass. In embodiments, the glass of the hollow glass bodies may be substantially free of MgO.

[0088] In embodiments, the glass of the hollow glass bodies is, is mostly, or includes soda lime, borosilicate, and / or aluminum silicate glass. Some exemplary glass compositions and corresponding attributes of various hollow glass bodies are provided in Tables 1 and 2.Attorney Docket No.: SP24-064Table 1 : Exemplary hollow glass body compositions (wt%)Table 2: Atributes of hollow glass bodies

[0089] Hollow glass bodies with different compositions can be used. In embodiments, the compositions for producing porous composite structures may include a plurality of different types of hollow glass bodies, such as glass bodies having different glass compositions or different physical attributes. The different physical attributes may include different median or average particle sizes, different softening temperatures, different particle size distribution, different density’, different shell thickness, different crush strength, or combinations of these. In embodiments, the composition may includeAttorney Docket No.: SP24-064 first hollow glass bodies and second hollow glass bodies, where the second glass bodies have one or more of a glass composition, median or average particle size, softening temperature, particle size distribution, density, shell thickness, crush strength, or combinations of these, that is different from the first hollow glass bodies.

[0090] The compositions of the present disclosure for making the porous composite structures may include an amount of the hollow glass bodies sufficient to produce a porous composite structure having a porosity of greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 42%, greater than or equal to 44%, greater than or equal to 46%, greater than or equal to 48%, greater than or equal to 50%, greater than or equal to 52%, greater than or equal to 54%, greater than or equal to 56%, greater than or equal to 58%. greater than or equal to 60%. greater than or equal to 62%, or greater than or equal to 64%.

[0091] As previously discussed, the compositions described herein include metal particles, which may upon firing a green body formed from the composition, form a continuous, three-dimensional, and interconnected metallic phase that operates as a resistive heating element when subjected to a voltage potential. In embodiments, the metal particles may be selected from the group consisting of aluminum, copper, iron, nickel, cobalt, silver, alloys thereof, and combinations thereof. However, other electrically conductive metal particles may be utilized. The metal particles may act as a rigid member to control shrinkage during firing of green bodies formed from the compositions described herein.

[0092] In embodiments, the metal particles comprise aluminum, aluminum alloy, or both aluminum and aluminum alloy. Metal particles formed from aluminum and aluminum alloys are desirable due to the low cost and availability of such materials. Further, the low density of aluminum is advantageous because the resulting continuous, three-dimensional, and interconnected metallic phase contributes less thermal mass to the porous composite structure, which reduces the energy7cost associated with temperature swing adsorption processes when utilizing the porous composite structure as a sorbent substrate for adsorption / desorption units in gas, e.g.. CO2. capture processes. Further, the high thermal conductivity of aluminum is advantageous both during firing, to reduce thermal gradients and associated potential for crack formation, and during use of the porous composite structure as an adsorbent substrate for adsorption / desorptionAttorney Docket No.: SP24-064 units in CO2 capture processes, as heat generated from the Joule effect is transported via the continuous aluminum phase to other regions of the porous composite structure to provide the thermal energy needed for CO2 molecules to desorb from the adsorbent surface.

[0093] In embodiments, the hollow glass bodies comprise silica glass and the metal particles comprise aluminum, aluminum alloy, or both aluminum and aluminum alloy. By using hollow glass bodies comprising silica in combination with metal particles containing aluminum, a displacement reaction between aluminum and silica takes place upon firing, as shown in Equation 1 below:4A1 + 3SiCh —> 3Si + 2AI2O3 Equation 1

[0094] The above displacement reduces the amount of aluminum available for the metallic phase of the porous composite structure and the extent to which the reaction takes place upon firing a green body formed from the composition can be controlled by the parameters of the firing process, such as the peak firing temperature, peak firing time, ramping rate, etc. This allows for control of the content and micro structure of the metallic phase in the porous composite structure along with the corresponding electrical properties of the substrate. Moreover, the displacement reaction of Equation 1 also results in formation of alumina (AI2O3), which has a higher thermal conductivity than silica and is thus beneficial during use of the porous composite structure as an adsorbent substrate for adsorption / desorption units in CO2 capture processes. Further, alumina is also more stable than silica and thus results in increased stability for the porous composite substrate when subjected to repeated adsorption — desorption cycles. The porous composite structures described herein may have working temperatures up to 500 °C.

[0095] In embodiments, the compositions for producing porous composite structures include metal particles in an amount from 20 wt% to 80 wt%, from 20 wt% to 75 wt%, from 20 wt% to 70 wt%, from 20 wt% to 65 wt%, from 20 wt% to 60 wt%, from 20 wt% to 55 wt%, from 20 wt% to 50 wt%, from 25 wt% to 50 wt%, or from 30 wt% to 50 wt%, based on a total combined weight of the non-combustible inorganics in the composition, i.e., the total weight of hollow glass bodies and the metal particles if these are the only non-combustible inorganics utilized. As used herein, non-combustible means that the material does not combust or bum at the temperatures used for firing. For example,Attorney Docket No.: SP24-064 hollow glass bodies, metal particles, as well as clay, talc, or other ceramic-forming precursors would generally be considered non-combustible inorganics, while graphite would be considered a combustible pore former.

[0096] The metal particles of the compositions described herein may have a D50 diameter of greater than or equal to 1 pm, greater than or equal to 3 pm, greater than or equal to 5 pm. or even greater than or equal to 10 pm. The metal particles may have a D50 diameter of less than or equal to 100 pm, less than or equal to 50 pm, or even less than or equal to 40 pm. The metal particles may have a D50 diameter of from 1 pm to 100 pm, 1 pm to 50 pm, from 1 pm to 40 pm, from 3 pm to 100 pm, from 3 pm to 50 pm, from 3 pm to 40 pm, from 5 pm to 100 pm from 5 pm to 50 pm, 5 pm to 40 pm, from 10 pm to 100 pm, from 10 pm to 50 pm, or from 10 pm to 40 pm.

[0097] The particle size distribution of the metal particles may be further characterized by the (D90-D10) / D50 ratio. The metal particles may have (D90-D10) / D50 ratio of less than or equal to 2, less than or equal to 1.5, less than or equal to 1, less than or equal to 0.8, less than or equal to 0.4, less than or equal to 0.2, less than or equal to 0.1, or less than or equal to 0.06. In embodiments, the composition may include two or more different types or sizes of metal particles such that the composition is multi-modal at least with respect to the metal particles. In these embodiments, each type or size of metal particles may be characterized by a D50 diameter and (D90-D10) / D50 ratio such that the particle size distribution for the metal particles in the composition is multi-modal.

[0098] As previously described, the compositions herein may include a binder. A binder is used to bond particles together to form a green body that can hold a honeycomb shape and provide structural integrity until the green body can be fired. In embodiments, the binder may be any kind of cellulose or cellulose derivatives. The binder can also be a polymer binder, such as but not limited to polyvinyl alcohol (PVA) polymers. In embodiments, the composition may include from 2 wt% SA to 20 wt% SA, from 2 wt% SA to 18 wt% SA, from 2 wt% SA to 15 wt% SA, from 5 wt% SA to 15 wt% SA, from 6 wt% SA to 14 wt% SA, or from 8 wt% SA to 14 wt% SA of the binder, wherein wt% SA is weight percent by superaddition based on the total combined weight of the noncombustible inorganics (e.g., the hollow' glass bodies and the metal particles, as well as any inorganic filler particles).Attorney Docket No.: SP24-064

[0099] In embodiments, the compositions may include a binder that comprises cellulose, cellulose derivatives, polymer binders, or combinations thereof. Cellulose derivatives may include, but are not limited to, methylcellulose, ethylhydroxy ethylcellulose, hydroxybutyl methylcellulose, hydroxymethylcellulose, hydroxypropyl methylcellulose, hydroxy ethyl 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 compositions, with methylcellulose and hydroxypropyl methylcellulose being excellent choices. Sources of cellulose-containing materials are METHOCEL™ cellulose products available from DOW® Chemical Co. In embodiments, the binder may include methylcellulose.

[0100] In some embodiments, combinations of cellulose derivatives may comprise mixtures of such materials with different molecular weights. Alternatively, the combination of cellulose derivatives may comprise different hydrophobic groups or different concentrations of the same hydrophobic group. Different hydrophobic groups may be, by way of non-limiting example, hydroxy ethyl or hydroxypropyl. The binder, in some embodiments, may be a combination of a hydroxyethyl methylcellulose binder and a hydroxy propyl methylcellulose binder. Other suitable combinations of binders may be used.

[0101] The compositions for producing porous composite structures may include water. The amount of water in the composition may be sufficient to enable the composition to be extruded or otherwise shaped or formed into the green body but not so much that the green body is unable to maintain its shape after formation. In embodiments, the compositions for producing porous composite structures may include water in an amount from 20 wt% SA to 80 wt% SA, from 20 wt% SA to 75 wt% SA, from 25 wt% SA to 75 wt% SA, from 25 wt% SA to 70 wt% SA, from 30 wt% SA to 70 wt% SA, from 30 wt% SA to 65 wt% SA, from 35 wt% SA to 65 wt% SA, from 35 wt% SA to 60 wt% SA, from 35 wt% SA to 55 wt% SA, or from 40 wt% SA to 55 wt% SA, wherein wt% SA is weight percent by superaddition based on the total combined weight of the noncombustible inorganics (e.g., hollow' glass bodies and the metal particles, and / or any inorganic filler particles).Attorney Docket No.: SP24-064

[0102] The compositions described herein may also include additives such as pore formers and processing aids, such as lubricants, surfactants, and / or plasticizers. In embodiments, the processing aids may act as rheology modifiers to make the compositions easier to extrude, to increase the extrusion rate, and / or to improve the quality7of the honeycomb-shaped porous composite structures formed from the compositions. The relative amounts of processing aids can vary depending on factors such as the nature and amounts of raw materials used, etc. Processing aids can comprise one or more of sodium stearate, stearic acid, oleic acid, linoleic acid, lauric acid, myristic acid, palmitic acid, and their derivatives, ammonium lauryl sulfate, or tall oil, for example. Further non-limiting examples of processing aids are Cs to C22 fatty acids, and / or their derivatives. Additional surfactant components that may be used with these fatty acids are Cs to C22 fatty esters, Cs to C22 fatty alcohols, and combinations of these. Non-limiting examples of oil lubricants used as processing aids include light mineral oil, com oil, high molecular weight polybutenes, polyol esters, a blend of light mineral oil and wax emulsion, a blend of paraffin wax in com oil, and combinations of these. In embodiments, the compositions include a surfactant, a lubricant, an oil. or combinations thereof.

[0103] The compositions may include processing aids in an amount from greater than 0 wt% SA to 20 wt% SA, such as from 0. 1 wt% SA to 20 wt% SA, from 0.1 wt% SA to 18 wt% SA, from 0.1 wt% SA to 16 wt% SA. from 0. 1 wt% SA to 14 wt% SA. from 0.5 wt% SA to 20 wt% SA, from 1 wt% SA to 20 wt% SA, from 2 wt% SA to 20 wt% SA, from 1 wt% SA to 14 wt% SA, from 3 wt% SA to 14 wt% SA, from 5 wt% SA to 14 wt% SA, from 7 wt% SA to 14 wt% SA, or from 9 wt% SA to 14 wt% SA, wherein wt% SA is weight percent by superaddition based on the total combined weight of the noncombustible inorganics (e.g., hollow glass bodies and the metal particles, and / or any inorganic filler particles). In embodiments, the composition may not include processing aids.

[0104] In embodiments, the compositions may include a lubricant in an amount from greater than 0 wt% SA to 20 wt% SA. such as from 0. 1 wt% SA to 20 wt% SA, from 0.1 wt% SA to 18 wt% SA, from 0.1 wt% SA to 16 wt% SA, from 0.1 wt% SA to 14 wt% SA, from 0.5 wt% SA to 20 wt% SA, from 1 wt% SA to 20 wt% SA, from 2 wt% SA to 20 wt% SA, from 1 wt% SA to 14 wt% SA, from 3 wt% SA to 14 wt% SA, fromAttorney Docket No.: SP24-0645 wt% SA to 14 wt% SA, from 7 wt% SA to 14 wt% SA, or from 9 wt% SA to 14 wt% SA, wherein wt% SA is weight percent by superaddition based on the total combined weight of the non-combustible inorganics (e.g., hollow glass bodies and the metal particles, and / or any inorganic filler particles). In embodiments, the lubricant may comprise mineral oil.

[0105] In embodiments, the compositions may include a pore former, such as an organic pore former, such as starch, flour (wood, shell, or nut flour), polymers such as polyethylene beads, and the like, and combinations of the aforementioned. Starches may comprise corn starch, rice starch, pea starch, sago starch, potato starch, and the like. However, in some embodiments, the composition may not include an organic pore former. Without wishing to be bound by theory, it is believed that the combustion of organic pore formers during firing may release large amounts of heat at undesirable times during the firing cycles, such as before the hollow glass bodies have bonded together and / or before the metal particles have begun to sinter to provide a rigid framework to support the porous composite structure.

[0106] In embodiments, the compositions may include an inorganic pore former, such as graphite. Without wishing to be bound by theory, it is believed that graphite may provide several advantages when used as a pore former in the compositions described herein. Initially, graphite has a high thermal conductivity which may, particularly when used in combination with metal particles having high thermal conductivity, reduce thermal gradients during firing and thus reduce the risk of cracking. Moreover, there may be residual levels of char in the porous composite structure after firing, which may beneficially increase the electrical conductivity of the porous composite structure. Further, relative to organic pore formers, which may combust before the glass begins to melt and / or devitrify, graphite may not begin to combust until later in the firing process, i.e., as the glass begins to melt and / or devitrify. Therefore, the use of graphite as a pore former may help to avoid shrinkage and retain the green body in a more rigid state until later into the firing process when the hollow glass spheres have begun to soften and bond with each other and the metal particles have begun to sinter together to form a more rigid framework throughout the porous composite structure. Accordingly, the use of graphite as an inorganic pore former may allow for increased ramping rates during firing and aAttorney Docket No.: SP24-064 significant reduction in the overall time required for firing the green bodies to form the porous composite structures.

[0107] In embodiments, the compositions described herein include graphite particles in an amount from 5 wt% SA to 50 wt% SA, from 10 wt% SA to 45 wt% SA, from 10 wt% SA to 40 wt% SA, from 15 wt% SA to 40 wt% SA, from 15 wt% SA to 35 wt% SA, from 20 wt% SA to 35 wt% SA, or from 20 wt% SA to 30 wt% SA, wherein wt% SA is weight percent by superaddition based on the total combined weight of the noncombustible inorganics (e.g., hollow glass bodies and the metal particles, and / or any inorganic filler particles).

[0108] The graphite particles of the compositions described herein may have a D50 diameter of greater than or equal to 1 pm, greater than or equal to 3 pm, greater than or equal to 5 pm, or even greater than or equal to 10 pm. The graphite particles may have a D50 diameter of less than or equal to 100 pm, less than or equal to 50 pm, or even less than or equal to 40 pm. The graphite particles may have a D50 diameter of from 1 pm to 100 pm, 1 pm to 50 pm, from 1 pm to 40 pm, from 3 pm to 100 pm, from 3 pm to 50 pm, from 3 pm to 40 pm. from 5 pm to 100 pm from 5 pm to 50 pm, 5 pm to 40 pm, from 10 pm to 100 pm, from 10 pm to 50 pm, or from 10 pm to 40 pm.

[0109] The particle size distribution of the graphite particles may be further characterized by the (D90-D10) / D50 ratio. The graphite particles may have (D90- D10) / D50 ratio of less than or equal to 2, less than or equal to 1.5, less than or equal to 1, less than or equal to 0.8, less than or equal to 0.4, less than or equal to 0.2, less than or equal to 0.1, or less than or equal to 0.06. In embodiments, the composition may include two or more different types or sizes of graphite particles such that the composition is multi-modal at least with respect to the graphite particles. In these embodiments, each type or size of graphite particles may be characterized by a D50 diameter and (D90- D10) / D50 ratio such that the particle size distribution for the graphite particles in the composition is multi-modal.

[0110] In addition to the above constituents, the compositions described herein may further include inorganic filler particles, e.g., in the form of a non-combustible inorganic powder, that acts as a rigid frame member having a high melting temperature to provide structural support during softening and modify the peak firing temperature to reduce shrinkage. In embodiments, the inorganic filler particles comprise oxides of the metalAttorney Docket No.: SP24-064 used in the metal particles (e.g., alumina corresponding to aluminum metal particles), the same oxides contained in the hollow glass bodies (e.g.. silica corresponding to silica- based hollow glass bodies), or a combination thereof. For example, the compositions described herein may comprise alumina, silica, and / or other non-combustible inorganic particle powders including, but limited to, oxides, hydroxides, and alumina- and / or silica-containing ceramic precursors such as clay and talc. However, in other embodiments, the compositions described herein are substantially free of non-combustible inorganic filler particles. In some aspects, the inorganic filler particles (non-combustible inorganic powder) may be provided in an amount from 0 wt% to 30 wt% with respect to a total weight of the non-combustible particles in the composition (e.g.. the metal particles, the hollow glass bodies, and any other non-combustible inorganics in the composition).[OHl] In embodiments, the compositions for producing porous composite structures may include inorganic filler particles up to about 30 wt%, such as from 0 wt% to 5 wt%, 0 wt % to 10 wt%, from 0 wt% to 15 wt%, from 0 wt% to 20 wt%, from 0 wt% to 25 wt%, or from 0 wt% to 30 wt%, based on a total combined weight of the non- combustible inorganics in the composition (i.e., the hollow glass bodies, the metal particles, and the inorganic filler particles. In embodiments wherein the composition includes inorganic filler particles in addition to metal particles and hollow glass bodies, the amount of the metal particles and / or hollow glass bodies will naturally be adjusted such that the total amount of metal particles, hollow glass particles, and inorganic filler particles equals 100 wt%. Accordingly, each of the metal particles and hollow glass bodies can be generally present in an amount of 20 wt% to 80 wt%, with respect to a total weight of non-combustible inorganics in the composition, provided that in embodiments comprising the inorganic filler particles that the maximum combined amount of the metal particles and hollow glass bodies is reduced by the weight of the inorganic filler particles. For example, if 0 wt% of inorganic filler particles are provided, then either of the metal particles or the hollow glass bodies could be present up to the maximum of 80 wt%. but if 30 wt% of inorganic filler particles were provided, then the maximum sum of the metal particles and hollow glass bodies would be 70 wt% (100 wt% total - 30 wt% inorganic filler particles = 70 wt% remaining for the metal particles and the hollow glass bodies together).Attorney Docket No.: SP24-064Methods of Making Porous Composite Structures

[0112] Embodiments of the present disclosure are also directed to methods of making porous composite structures from the compositions described herein. A method for making a porous composite structure may include preparing a composition in accordance with the present disclosure comprising hollow glass bodies and metal particles, forming a green body from the composition, and firing the green body to produce the porous composite structure. As will be described in more detail below, the mechanical properties, electrical properties, and characteristics of the porous microstructure of the porous composite structures may be controlled, in part, by adjusting parameters of the firing process. By controlling the composition and firing process, porous composite structures having a range of mechanical properties, electrical properties, and porosity features can be produced.

[0113] Preparing the composition may include combining the hollow glass bodies, metal particles, and any other components useful for formation of a formable (extrudable) mixture, such as the binder. Inorganic filler particles and / or one or more the above-described additives may also be combined into the composition. The constituents of the composition may be combined and mixed according to known methods. The hollow glass bodies, metal particles, binder, and any included additives may have any of the features, properties, or amounts previously described herein. The median pore size and the pore size distribution of the porous composite structure may be modified by changing the make-up of the composition. In particular, methods disclosed herein may include controlling the median pore size of the porous composite structure by changing a proportion of the metal particles to the hollow glass bodies in the composition. The median pore size may also be tuned by modifying the peak firing temperature, the hold / dwell time at the peak firing temperature (also referred to herein as the£'peak firing time”), the temperature ramping rate during heating, the temperature cooling rate during cooling, or combinations of these. In embodiments, increasing the peak firing temperature, increasing the hold / dwell time at the peak firing temperature, and decreasing the temperature ramping rate during heating may all increase the median pore size to the extent the whole structure is not completely melted. For example, increasing the peak firing temperature may result in an increased porosity' and / or reduced bulk density for resulting the porous composite structure.Attorney Docket No.: SP24-064

[0114] After preparation of the composition, the methods disclosed herein may include forming a green body comprising the composition. With reference now to FIG. 1, in embodiments, the composition may be formed into a green body 10 with a honeycomb shape having an outer wall 12 and a plurality of elongate channels 16 separated by channel walls 14 and extending through the green body 10 from a front face 18 to a rear face 20 opposite the front face along an axial direction 13 of the honeycomb shape. Forming the green body 10 may include extrusion, molding, tape-casting, rolling, calendaring, 3D printing, other forming process, or combinations of these. Extruding the green bodies may be particularly efficient for forming green bodies with through- channels (e.g., elongate channels 16) such as the honeycomb-shaped green body of FIG. 1, or other regular features in the respective green bodies. However, in other contemplated embodiments, such green bodies may be molded, tape-cast, or otherwise shaped or processed, which may also preserve integrity of the hollow glass bodies.Moreover, while the honeycomb shape of the green body 10 depicted in FIG. 1 has square cross-sectional shape and square-shaped channels 16. the cross-section of the green body and / or the channels 16 may have different shapes. For example, in other embodiments, the green body 10 may have a circular cross-sectional shape with channels 16 having triangular, heptagonal, hexagonal, octagonal, trapezoidal, diamond, circular, ellipsoidal, other polygonal shapes, or combinations of any of the aforementioned shapes.

[0115] In embodiments, the composition may be extruded to form the green bodies. Extrusion may be accomplished using a twin-screw extruder or other suitable extrusion machine. The composition comprising the hollow glass bodies and metal particles may be extruded at a rate and pressure to preserve integrity of most (e.g., more than 50%, more than 75%, more than 90%) of the hollow glass bodies. With that said, in other contemplated embodiments, extrusion rate and pressure may preserve integrity of many of the hollow glass bodies, but not most, such as less than 50%, but at least 25%, or at least 20%. Preserving the integrity of the hollow glass bodies may allow the hollow glass bodies to occupy relatively large volumes of space within the green bodies with voids between the hollow glass bodies and within the hollow glass bodies (i.e., the internal volume of the hollow glass bodies). The extrusion rates and pressures may vary depending upon the size of the hollow glass bodies, the glass of the hollow glass bodies,Attorney Docket No.: SP24-064 and the extruding device. In some embodiments, extrusion pressures may be in the range of less than 2500 psi, such as less than 2000 psi, and / or at least 500 psi.

[0116] Following forming of the green bodies from the composition, the green bodies are fired to produce the porous composite structures described herein. However, prior to firing the green bodies, the green bodies may be dried using any suitable dry ing method, such as, for example, RF drying, microwave drying, oven drying, or combinations thereof. Conditions and handling of the green bodies during the firing may be such that adjoining hollow glass bodies may physically interact with one another, such as directly bond to one another (e.g., sinter, weld, melt-into), but without fully losing their individual structures. Put another way, in such embodiments, the conditions and handling during firing may be such that the hollow glass bodies do not fully liquefy and / or completely lose structure, and instead become bonded to one another such that, in the aggregate, the resulting structure is cohesive and rigid.

[0117] Additionally, in embodiments, the conditions and handling of the green bodies during the firing may be such that many of the hollow glass bodies (e g., most, >50%, >60%. >70%, >80%, >90%, >95%, >99%) breach or break, such as by rupture from internal gas expansion and / or by devitrification or otherwise. The green bodies may be heated to a point that the hollow glass bodies lose integrity' and the glass of the hollow glass bodies shatters or is otherwise breached. In other contemplated embodiments, the hollow glass bodies may be breached by microwaves, sound, or other phenomena. Breaching the hollow glass bodies may be counterintuitive to those in industry, where hollow glass bodies may be relied upon to provide buoyancy and / or prevent inflow of materials into voids within the hollow glass bodies or through the hollow glass bodies. However, it has now been found that by breaching the hollow glass bodies contained in green bodies during firing, as disclosed herein, voids of the hollow glass bodies may be maintained and / or even enlarged and joined to one another to, in combination with a sintered metallic phase, create an electrically conductive porous composite structure.

[0118] In embodiments, the green bodies may be heated, such as by firing the green bodies in a furnace, by laser heating the green bodies, or by other heating methods. The heating may burn out, char, chemically transform, or otherwise influence the binder and the graphite particles (when included in the composition). In embodiments, the methods may include heating the green bodies to at least to a softening temperature of glass of theAttorney Docket No.: SP24-064 hollow glass bodies. However, the hollow glass bodies are not overheated, such as being heated well above a liquidus temperature of the glass, at which temperatures the hollow glass bodies may fully lose cohesion or structure. In embodiments, the firing of the green bodies may be performed in an inert atmosphere, such as with the green bodies in an inert gas, such as nitrogen. In other embodiments, the firing of the green bodies may be performed in air or other oxygenated atmosphere. In embodiments where the composition comprises graphite particles, firing green bodies formed therefrom in an oxygenated atmosphere may cause oxidation and / or removal of the graphite particles, and in some embodiments, the formation of electrically conductive char.

[0119] In embodiments, firing the green body may comprise ramping the green body to a peak firing temperature and then holding the green body at the peak firing temperature for a peak firing time to produce a fired structure, and then cooling the fired structure to produce the porous composite structure. The methods may include heating the green bodies to a peak firing temperature that is at least greater than or equal to a softening temperature of the glass and less than a liquidus temperature of the glass. Depending upon the glass composition and materials in the composition used to make the green bodies, the methods may include heating the green bodies to a peak firing temperature of at least 400 °C, at least 500 °C, at least 600 °C, at least 700 °C, at least 800 °C, or at least 900 °C. In embodiments, the peak firing temperature may be at most 1400 °C, at most 1300 °C. at most 1200 °C, at most 1100 °C. at most 1000 °C, at most 900 °C, at most 800 °C, at most 700 °C, or at most 600 °C. In embodiments, the peak firing temperature may be greater than or equal to 400 °C and less than or equal to 1200 °C, greater than or equal to 400 °C and less than or equal to 1100 °C, greater than or equal to 500 °C and less than or equal to 1100 °C, greater than or equal to 500 °C and less than or equal to 1000 °C, greater than or equal to 600 °C and less than or equal to 1000 °C, greater than or equal to 600 °C and less than or equal to 900 °C, greater than or equal to 600 °C and less than or equal to 800 °C, greater than or equal to 650 °C and less than or equal to 900 °C. or greater than or equal to 700 °C and less than or equal to 900 °C. In embodiments, the peak firing temperature may be about 700 °C.

[0120] In embodiments, firing the green bodies may include conducting the firing process to systematically heat the green body to the peak firing temperature. In embodiments, the firing process may include heating the green body to the peak firingAttorney Docket No.: SP24-064 temperature at a generally constant temperature ramping rate of from 50 °C per hour to 3,500 °C per hour, holding the green body at the peak firing temperature for no time at all or for a peak firing time of up to 10 hours, and then cooling the green body back to ambient temperatures. In embodiments, firing of the green body may comprise ramping the green body to the peak firing temperature at a ramping rate of between 50 °C per hour to 1,000 °C per hour, 100 °C per hour to 1,000 °C per hour, between 50 °C per hour to 800 °C per hour, between 100 °C per hour to 800 °C per hour, between 50 °C per hour to 600 °C per hour, between 100 °C per hour to 600 °C per hour, between 200 °C per hour to 600 °C per hour, between 200 °C per hour to 500 °C per hour, between 300 °C per hour to 500 °C per hour, between 300 °C per hour to 450 °C per hour, or between 350 °C per hour to 450 °C per hour.

[0121] In other embodiments, firing of the green body may comprise ramping the green body to the peak firing temperature at a ramping rate of at least 1,000 °C per hour, at least 1,200 °C per hour, at least 1,400 °C per hour, at least 1,600 °C per hour, at least 1,800 °C per hour, at least 2,000 °C per hour, at least 2,200 °C per hour, at least 2.400 °C per hour, at least 2,500 °C per hour, at least 2.600 °C per hour, at least 2,800 °C per hour, or at least 3,000 °C per hour. In embodiments, the firing of the green body comprises ramping the green body to the peak firing temperature at a ramping rate of greater than or equal to 1,000 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 1,200 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 1,400 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 1,600 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 1,800 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,000 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,200 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,400 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,500 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,600 °C per hour and less than or equal to 3,500 °C per hour, greater than or equal to 2,600 °C per hour and less than or equal to 3,400 °C per hour, greater than or equal to 2,700 °C per hour and less than or equal to 3,400 °C per hour, greater than or equal to 2,700 °C per hour and less than or equal to 3,300 °C per hour, greater than or equal to 2,800 °C per hour and less than or equal to 3,300 °C per hour,Attorney Docket No.: SP24-064 greater than or equal to 2,800 °C per hour and less than or equal to 3,200 °C per hour, greater than or equal to 2,900 °C per hour and less than or equal to 3,200 °C per hour, or greater than or equal to 2,900 °C per hour and less than or equal to 3,100 °C per hour.

[0122] In embodiments, firing the green body to produce the fired structure and cooling the fired structure to produce the porous composite structure may be completed in a combined time of less than 10 hours, less than 9 hours, less than 8 hours, less than 7 hours, less than 6 hours, or even less than 5 hours. As mentioned above, the use of graphite as an inorganic pore former may allow for increased ramping rates during firing and a significant reduction in the overall time required for firing the green bodies to form the porous composite structures. In embodiments, the composition comprises graphite and firing the green body formed from the composition comprises ramping the green body to the peak firing temperature at a ramping rate of greater than or equal to 2,500 °C per hour and less than or equal to 3,500 °C per hour.

[0123] In embodiments, firing of the green body may comprise ramping the green body to the peak firing temperature, holding the green body at the peak firing temperature for no time (zero hours) to produce a fired structure, and then cooling the fired structure to produce the porous composite structure. In embodiments, firing of the green body may comprise ramping the green body to the peak firing temperature and holding the green body at the peak firing temperature for a peak firing time of between 0.1 hours and 1 hour, between 0.1 and 0.9 hours, between 0.1 and 0.8 hours, between 0.1 and 0.7 hours, between 0.1 and 0.6 hours, or between 0.1 and 0.5 hours. In embodiments, the peak firing time may be less than 4 hours, less than 3.5 hours, less than 3 hours, less than 2.5 hours, less than 2 hours, less than 1.5 hours, less than 1 hour, or less than 0.5 hours.

[0124] In embodiments, the peak firing time may be greater than or equal to 0. 1 hours and less than or equal to 5 hours, greater than or equal to 0.5 hours and less than or equal to 5 hours, greater than or equal to 0.5 hours and less than or equal to 4 hours, greater than or equal to 0.5 hours and less than or equal to 3 hours, greater than or equal to 1 hour and less than or equal to 3 hours, greater than or equal to 1 hour and less than or equal to 2.5 hours, or greater than or equal to 1.5 hours and less than or equal to 2.5 hours. In embodiments, the peak firing time may be about 2 hours.

[0125] During the firing process, at least some of the hollow glass bodies may be devitrified such that the glass comprises one or more crystal phases. Moreover, asAttorney Docket No.: SP24-064 previously discussed, silica and other components of the glass may react with the metal of the metal particles to form additional crystal phases. That is, while the hollow body structure of the hollow glass bodies may remain intact or mostly intact (e.g., in a breached state), the constituents of these residual hollow bodies may include devitrified glass and / or additional crystal phases formed via reactions between the glass, metal particles, elements from the firing atmosphere, and / or other components of the compositions. That is, while composition of the green bodies may include amorphous hollow glass bodies, the hollow bodies remaining after firing may be glass-ceramics with cry stallinity greater than or equal to 45% by weight (wt%), such as greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, greater than or equal to 90 wt%, greater than or equal to 95 wt%, or even greater than or equal to 99 wt% crystallinity based on the total weight of the glass ceramics. In embodiments, the porous composite structure may comprise less than 50 wt%, less than 40 wt%, less than 30 wt%, less than 20 wt%, less than 10 wt%, less than 5 wt%. or even less than 1 wt% amorphous material based on the total weight of porous composite structure.

[0126] Following ramping the green bodies to the peak firing temperature and holding the green bodies at the peak firing temperature for a period of time (or no time, in embodiments) to produce the fired structure, the fired structure may then be cooled back to ambient temperature. In embodiments, the methods may include cooling the fired structure to a temperature that is at least 100 °C less than the temperatures to which the green body were heated during firing (i.e., peak firing temperature). In embodiments, the methods may include cooling the fired structure to a temperature less than 100 °C or even less than 50 °C, such as a temperature of from 20 °C to 100 °C, or from 20 °C to 50 °C. During the cooling, the adjoining residual hollow bodies, which may be less spherical at this point, may' remain physically' bonded to one another, such as directly or indirectly bonded. Indirect boding may refer to adjacent residual hollow bodies being bonded to each other through an intermediate bonding agent, such as the sintered metallic phase or residue of the binder or graphite added to the composition.

[0127] In embodiments, cooling the fired structure may comprise systematically cooling the fired structure to the ambient temperature. In embodiments, the cooling process may include cooling the fired structure to the ambient temperature at a generallyAttorney Docket No.: SP24-064 constant temperature cooling rate of from 100 °C per hour to 1,000 °C per hour, from 100 °C per hour to 800 °C per hour, from 100 °C per hour to 600 °C per hour, from200 °C per hour to 600 °C per hour, from 200 °C per hour to 500 °C per hour, from300 °C per hour to 500 °C per hour, from 300 °C per hour to 450 °C per hour, or from350 °C per hour to 450 °C per hour. In some embodiments, the fired structure may be cooled naturally to ambient temperature as opposed to systematically. For example, in embodiments wherein the firing is performed using an electric furnace, cooling the fired structure naturally may comprise the shutting off the electrical power and allowing the furnace to cool down naturally without any forced convection. In embodiments, the fired structures are naturally cooled to ambient temperature over a cooling time of from 1 to 5 hours, from 1 to 4 hours, from 1 to 3 hours, from 1 to 2.5 hours, from 1.5 to 2.5 hours, or from 1.5 to 2 hours.

[0128] In embodiments, cooling the fired structure may include dwelling the fired structure at temperatures greater than the ambient temperatures but less than the firing temperatures. In embodiments, cooling the fired structure may include dwelling the porous composite structures at an annealing temperature of the glass of the hollow glass bodies. Dwelling may occur at incremental steps, in some embodiments, or may be in the form of very gradual temperature declines within certain temperature ranges in other embodiments, both of which may allow for formation of crystals in the materials of the hollow glass bodies and / or may facilitate relaxing of residual stresses by annealing.

[0129] In embodiments, the methods disclosed herein for making the porous composite structures may include modifying the median pore size of the porous composite structure by changing the average and / or median particle size of the metal particles, the content of the metal particles, or both included in the composition. In embodiments, the methods may include changing the porosity of the porous composite structures by changing the average and / or median particle size of the metal particles, the content of the metal particles, or both included in the composition.Porous Composite Structures

[0130] The porous composite structures produced by the compositions and methods described herein include a continuous, three-dimensional, and interconnected metallic phase that extends throughout the porous composite structure. While the metallic phase may include isolated regions of sintered metal particles, the metallic phase is sufficientlyAttorney Docket No.: SP24-064 continuous and interconnected so as to make the porous composite structure electrically conductive. The porous composite structures also include a non-metallic phase dispersed throughout the porous composite structure and intertwined with and / or interspersed through the metallic phase. The non-metallic phase may exhibit some degree of continuity and interconnectedness, but generally not to the extent to which the metallic phase exhibits these characteristics. However, in some embodiments, both of the metallic phase and the non-metallic phase are each a continuous, three-dimensional, and interconnected phase that are intertwined together. The metallic and the non-metallic phases may together provide the porous composite structure with rigidity7while also defining porous cavities that extend and interconnect throughout the porous composite structure and may open to surfaces thereof.

[0131] In embodiments, the metallic phase may be formed by metal particles of the composition that were sintered together during the firing of the green body comprising the composition. In embodiments, the content and structural characteristics of the metallic phase may be controlled by adjusting the parameters of the firing process. For example, in embodiments wherein the glass of the hollow glass bodies reacts with the metal of the metal particles upon firing, increasing the peak firing temperature and / or the peak firing time may decrease the content of the metallic phase in the resulting porous composite structure due to more of the metal of the metal particles having reacted with components of the glass to form non-metallic material. Moreover, by adjusting the content and structural characteristics of the metallic phase, the electrical properties of the porous composite structure may in turn be controlled. For example, as shown herein by example, the electrical resistance for a given geometry and orientation of the porous composite structures may, for a given composition, be adjusted over a wide range (e.g., by a factor of 10, 15, 50, 100, 200, or even 400) by increasing the peak firing temperature so as to increase the rate of reaction between glass of the hollow glass bodies and metal of the metal particles. The electrical resistance of the porous composite structure may be similarly increased by increasing the peak firing time during the firing process so as to provide additional time for reaction between glass of the hollow glass bodies and metal of the metal particles.

[0132] In embodiments, the porous composite structure comprises the metallic phase in an amount from 5 wt% to 50 wt%, based on the total weight of the cry stalline portionAttorney Docket No.: SP24-064 porous composite structure. In embodiments, the porous composite structure comprises the metallic phase in an amount from 5 wt% to 50 wt%, from 5 wt% to 45 wt%, from 5 wt% to 40 wt%, from 8 wt% to 40 wt%, from 5 wt% to 35 wt%, or from 8 wt% to 35 wt%, based on the total weight of the crystalline portion porous composite structure. In embodiments, the metallic phase of the porous composite structure may make up at least 5 wt%. at least 8 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%, or at least 30 wt%.

[0133] The non-metallic phase of the porous composite structures may include one or more cry stal phases as well as amorphous (glass) material, and generally comprises all non-metallic constituents of the porous glass composites. In embodiments, the non-metallic phase comprises reaction products of a portion of the metal particles of the composition and the hollow glass bodies of the composition. The non-metallic phase may further comprise devitrified glass of the hollow glass bodies and / or reaction products of glass of the hollow glass bodies, metal of the metal particles, components of the firing atmosphere, binder, and any additives included in the composition. The non-metallic phase may further comprise residue and / or combustion products from the binder and any additives included in the composition (e g., graphite).

[0134] In embodiments, the porous composite structure may be produced by firing a green body having a composition where the hollow glass bodies comprise silica glass and the metal particles comprise aluminum. In such embodiments, the non-metallic phase may comprise reaction products of aluminum from the aluminum particles and silica from the hollow glass bodies. The reaction products of the aluminum and silica may include silicon and alumina (including corundum, in embodiments), which may formed in accordance with the displacement reaction shown above in Equation 1. In embodiments, silica and other components of the glass may react with aluminum to form aluminosilicate crystals, such as nepheline (Nad AI iSi iOie). which may also be formed by devitrification of the glass containing corresponding elements of such aluminosilicate crystals. Silica from the hollow glass bodies may also devitrify to form polymorphs of silica, such as cristobalite, and other alkali silicate materials, such as pseudowollastonite (CaSiCh). In embodiments, aluminum may also react with gaseous elements in the firing atmosphere, such as nitrogen in the formation of aluminum nitride, or oxygen in the formation of aluminum oxide. Silicon formed from the displacement reaction ofAttorney Docket No.: SP24-064Equation 1 may further react with carbon in the composition (e.g.. from the binder or graphite, if present), to form silicon carbide. Accordingly, the non-metallic phase of the porous composite structures may have a phase assemblage with an array of crystalline materials. The particular phase assemblage of the non-metallic phase may depend on the composition used to form the green body as well as parameters of the firing process. For example, compositions having a relatively lower amount of aluminum may be more likely to result in the formation of additional silicate phases such as cristobalite, nepheline, and pseudowollastonite.

[0135] In embodiments where the porous composite structure is produced by firing a green body having a composition where the hollow glass bodies comprise silica glass and the metal particles comprise aluminum, the resulting porous composite structure may comprise a combined amount of aluminum and silicon sufficient to achieve desired electrical properties for the porous composite structure. For example, by controlling the combined amount of aluminum and silicon in the porous composite structure, and amount and continuity’ of electrical conductive constituents of the porous composite structure may be achieved. In embodiments, the porous composite structure may comprise a combined amount of aluminum and silicon from 15 wt% to 50 wt%, from 15 wt% to 45 wt%, from 15 wt% to 40 wt%, from 15 wt% to 35 wt%, or from 15 wt% to 30 wt%, based on the total weight of the cry stalline portion porous composite structure. In embodiments, the porous composite structure may comprise a combined amount of aluminum and silicon of at least 15 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, or at least 45 wt%, based on the total weight of the crystalline portion porous composite structure.

[0136] In embodiments, the porous composite structure may comprise alumina in an amount from 40 wt% to 70 wt%, from 40 wt% to 65 wt%, from 40 wt% to 60 wt%, or from 40 wt% to 55 wt%, based on the total weight of the cry stalline portion porous composite structure. In embodiments, the porous composite structure may comprise alumina in an amount of at least 40 wt%, at least 45 wt%, at least 50 wt%, at least 55 wt%. or at least 65 wt%, based on the total weight of the crystalline portion porous composite structure.

[0137] In embodiments, the porous composite structure may comprise silicon in an amount from 1 wt% to 20 wt%, from from 5 wt% to 20 wt%, from 7Attorney Docket No.: SP24-064 wt% to 20 wt%, from 9 wt% to 20 wt%, from 10 wt% to 20 wt%, from 12 wt% to 20 wt%. from 12 wt% to 17 wt%, from 12 wt% to 16 wt%, or from 13 wt% to 16 wt%, based on the total weight of the crystalline portion of the porous composite structure. In embodiments, the porous composite structure may comprise silicon in an amount of at least 1 wt%, at least 3 wt%, at least 5 wt% at least 7 wt%, at least 9 wt%, at least 10 wt%, at least 12 wt%, at least 13 wt%. at least 14 wt%, or at least 15 wt%, based on the total weight of the crystalline portion of the porous composite structure.

[0138] The porous composite structures may have a high porosity of greater than or equal to 50% or greater than or equal to 70%, such as from 50% to 85% or from 70% to 85%, as determined by mercury intrusion porosimetry as discussed herein. The porosity of the porous composite structures may be modified by changing the relative amounts of the hollow glass bodies and metal particles in the composition. The porosity of the porous composite structures may also be modified by incorporating addition components such, as pore formers (e.g., graphite), into the composition. Further, the porosity of the porous composite structures may also be modified by adjusting parameters of the firing process, as described above. As used herein, porosity of the porous composite structure only includes pores that can be reached during mercury porosimetry and does not include closed pores.

[0139] The porous composite structures of the present disclosure may have a median pore size of from 1 pm to 50 pm, from 1 pm to 20 pm. from 1 pm to 16 pm, from 8 pm to 50 pm, from 8 pm to 20 pm, from 8 pm to 16 pm, from 12 pm to 50 pm, from 12 pm to 20 pm, or from 12 pm to 16 pm. The median pore size may refer to a dso value, which corresponds to a 50% pore size of a porous composite structure, as measured by mercury intrusion porosimetry in accordance with ASTM D6761-07 (2012). The median pore size can be tuned in the range of from 1 pm to 50 pm.

[0140] The porous composite structure may have a pore size distribution characterized by the ratio (dso-dioj / dso. The dso value refers to a median pore diameter of the porous composite structure at which 50% by volume of the cumulative pore volume of the porous composite structure has been intruded by mercury during a porosimetry measurement made in accordance with ASTM D6761-07 (2012). The dio value of the porous composite structure is equal to the pore diameter at which 10% by volume of the cumulative pore volume of the porous composite structure has been intruded by mercuryAttorney Docket No.: SP24-064 during a porosimetry measurement made in accordance with ASTM D6761-07 (2012). The d9o value of the porous composite structure is equal to the pore diameter at which 90% by volume of the cumulative pore volume of the porous composite structure has been intruded by mercury during a porosimetry measurement made in accordance with ASTM D6761-07 (2012). In embodiments, the porous composite structures including may have a pore size distribution with a (dso-dio) / d5o ratio of less than 0.5, such as less than or equal to 0.4. less than or equal to 0.3, less than or equal to 0.2, less than or equal to 0.1, or less than or equal to 0.06. In embodiments, the porous composite structure may have a pore size distribution with a (d5o-dio) / dso ratio of less than or equal to 0.5 or even less than or equal to 0.3.

[0141] The interconnected metallic phase of the porous composite structures described herein may enable increased mechanical strengths relative to other porous composite structures. Additionally, in embodiments wherein the metal particles comprise low-density metals (e.g., aluminum), the interconnected metallic phase formed therefrom may provide the porous composite structure with a high strength-to-weight ratio. The high strength-to-weight ratio of the porous composite structures described herein in combination with tunable electrical properties and porosity7makes the porous composite structures very7suitable as adsorbent substrates for CO2 capture systems and processes. In embodiments, the porous composite structures disclosed herein may have a modulus of rupture of greater than 0.3 megapascals (MPa), such as greater than or equal than 0.5 MPa, greater than or equal to 0.7 MPa, greater than or equal to 0.9 MPa, greater than or equal to 1.1 MPa, greater than or equal to 0.3 MPa, or even greater than or equal to 1.5 MPa, measured in accordance with ASTM Cl 674- 16. In embodiments, the porous composite structures may have a modulus of rupture of from 0.5 MPa to 10 MPa, such as from 0.5 MPa to 8 MPa, from 0.5 MPa to 5 MPa, from 0.5 MPa to 3 MPa, from 0.5 MPa to 2.5 MPa, from 0.5 MPa to 2 MPa, or from 0.7 MPa to 2 MPa, measured in accordance with ASTM D6272-17 (2020).

[0142] The porous composite structures described herein may also have lower density relative to other porous composite structures, particularly when low-density metal particles (e g., aluminum particles) are used, and possibly even more so when graphite particles are incorporated into the compositions used to produce the porous composite structures. As previously described, the use of graphite particles in the compositionsAttorney Docket No.: SP24-064 described herein may help reduce or avoid shrinkage during firing, and the oxidation and removal of graphite may contribute to additional porosity and a reduced bulk density’ for the porous composite structure. In embodiments, the porous composite structure (e.g., absent any coatings added thereto) can have a bulk density of less than or equal to 5.0 g / cm3, such as from 0.5 g / cm3to 5.0 g / cm3, from 0.5 g / cm3to 4.0 g / cm3, from 0.5 g / cm3to 3.0 g / cm3, from 0.5 g / cm3to 2.0 g / cm3, from 0.5 g / cm3to 1.0 g / cm3, from 0.5 g / cm3to 0.8 g / cm3, or from 0.6 g / cm3to 0.8 g / cm3.

[0143] As previously discussed, the porous composite structures described herein are electrically conductive. In embodiments, the porous composite structures may have an electrical resistance, measured in accordance with procedures described herein, of from 0.1 ohm to 10 kilohms, from 0.1 ohm to 5 kilohms, from 0.1 ohm to 1 kilohms, from 0. 1 ohm to 500 ohms, or from 0.5 ohm to 500 ohms.

[0144] With reference now to FIG. 2, in embodiments, the porous composite structures 100 described herein, like the exemplary' green bodies 10 described above fired to produce the porous composite structures, may have a honeycomb shape comprising an outer wall 102 and a plurality of elongate channels 106 separated by channel walls 104 and extending through the porous composite structure 100 from a front face 108 (e.g., an inlet face) to a rear face (not shown; e.g., an outlet face) opposite the front face along an axial direction (extends out of the page in FIG. 2) of the honeycomb shape. The outer wall may be provided with a skin 111 which can co-extruded with the green honeycomb body or applied after forming the green honeycomb body. The outer shape of the porous composite structure 100 can be a rectangular parallelepiped as is shown, and therefore may comprise a square or rectangular outer profile when viewed from the front face 108. However, other outer perimeter shapes can be used as described above, such as round, oval, triangular or tri-lobed, polygonal, and the like.

[0145] The porous composite structures may have a cell density of greater than or equal to 50 cells per square inch (cpsi), such as greater than or equal to 100 cpsi, greater than or equal to 200 cpsi, or greater than or equal to 300 cpsi. As used herein, the term “cell density” refers to the number of elongate channels of a honeycombed shaped porous composite structure per unit cross-sectional area of the honeycombed porous composite structure and is provided in units of cells per square inch. A cell refers to the transverse cross-section of an elongate channel.Attorney Docket No.: SP24-064

[0146] The porous composite structures may have a cell density of less than or equal to 400 cpsi. The porous composite structures disclosed herein may have a web thickness Tw of less than or equal to 10 mils (i.e. thousandths of an inch), such as no more than 8 mils, such as no more than 7 mils, such as no more than 6 mils, such as no more than 5 mils. The porous composite structures disclosed herein may have a web thickness of from 2 mils to 10 mils, from 2 mils to 8 mils, from 2 mils to 7 mils, from 2 mils to 6 mils, or from 2 mils to 5 mils. In embodiments, the porous composite structures may have a combination of cell density and web thickness (i.e., noted as: (cell density in cpsi) / (web thickness in mils)) of about 200 / 8. In other embodiments, the porous composite structures may have combinations of cell density and web thickness of 400 / 7, 400 / 6, 400 / 5, 400 / 4, 400 / 3, 400 / 2. 300 / 7, 300 / 6, 300 / 5, 300 / 4. 300 / 3, 300 / 2, 200 / 7, 200 / 6, 200 / 5, 200 / 4, 100 / 8, 100 / 7, 100 / 6, 100 / 5, 50 / 8, 50 / 7, or 50 / 6, where left of the ’7” is the cell density in cpsi and to the right of the ‘7” is the web thickness in mils.

[0147] In embodiments, the porous composite structures may have a cylindrical geometry and may have a diameter of greater than or equal to 2 inches, greater than or equal to 4 inches, greater than or equal to 6 inches, greater than or equal to 8 inches, greater than or equal to 12 inches, or greater than or equal to 24 inches. The diameter of the porous composite structure may be less than or equal to 64 inches or less than or equal to 36 inches. In embodiments, the porous composite structure may have a generally square, rectangular, or other polygonal geometry in cross-section, with sides of greater than or equal to 2 inches, greater than or equal to 4 inches, greater than or equal to 6 inches, greater than or equal to 8 inches, greater than or equal to 12 inches, or greater than or equal to 24 inches. The sides of the porous composite structure may be less than or equal to 64 inches or less than or equal to 36 inches. Other contemplated embodiments have other sizes or shapes. Such geometries may facilitate beneficial permeability, higher CO2 loading, and improved CO2 capture efficiency.Substrates for CO2 Capture Systems

[0148] The porous composite structures disclosed herein may be used as substrates for CO2 captures systems and processes. The substrates may include the porous composite structures having any of the features, compositions, and / or properties disclosed herein for the porous composite structures. In embodiments, a substrate may include the porous composite structure disclosed herein and a sorbent coating supported on the porousAttorney Docket No.: SP24-064 composite structure, wherein the sorbent coating is configured to adsorb CO2 molecules. In embodiments, the sorbent coating may include carbon-based sorbent materials such as, for example, biochar, hydrochar, activated carbon (AC), and / or carbon nanomaterials such as, for example, carbon nanotubes, fullrenes, graphite, graphene, carbon nanofilms, and / or carbon fibers. In embodiments, the sorbent coating may be selected from the group consisting of carbon-based adsorbent materials, natural zeolites, synthetic zeolites, carbonates (e.g.. sodium carbonate or calcium carbonate), polyethylenimine (PEI), amine-functionalized materials (e.g, amine-impregnated polymeric resins), metal oxides, non-metal oxides, metal-organic frameworks, and combinations thereof. The substrate may further include a housing that at least in part surrounds the porous composite structure and the coating.

[0149] Embodiments of the present disclosure also include CO2 capture systems including said substrates comprising the porous composite structures described herein, with or without a sorbent coating provided thereon. In embodiments, a CO2 capture system comprises an adsorption / desorption unit with the substrate integrated in the adsorption / desorption unit.

[0150] The porosity of the porous composite structures disclosed herein may enable a greater amount of sorbent material for CO2 capture to be loaded into the adsorption / desorption unit per unit volume of honeycomb-shaped porous composite structure. Enabling a greater amount of sorbent material for CO2 to be loaded per unit volume may enable a greater CO2 adsorption capacity per unit volume for the adsorption / desorption unit compared to other ty pes of porous media. The porous composite structures of the present disclosure may also have lower thermal mass compared to conventional structures used for TSA units, which may reduce energy consumption of the CO2 capture process by reducing the energy needed to heat the porous composite structure during CO2 desorption compared to conventional structures. Additionally, the porous composite structures disclosed herein may be less expensive compared to conventional structures typically used in CO2 capture processes. Finally, the electrical conductivity of the porous composite structures described herein enable the porous composite structure to function as a heater apparatus in TSA direct air capture systems, thereby avoiding the need to use a purging gas for the desorption of CO2 and regeneration of the sorbent material. In embodiments, a CO2 capture process may includeAttorney Docket No.: SP24-064 an adsorption / desorption unit and the porous composite structure may be integrated into the adsorption / desorption unit.

[0151] With reference again to FIG. 2, in embodiments, the porous composite structure 100 may function as a heater assembly 101, namely, as a resistive heating element of the heater assembly 101. For example, the continuous, three-dimensional, interconnected, metallic phase may provide continuous, three-dimensional, electrically conductive paths laterally across the body (in a direction perpendicular to the axial direction), such as between a first side 1 13 of the porous composite structure and a second side 115 of the porous composite structure opposite the first side 113, as shown in FIG. 2. For example, in this embodiment, the electrical connection is formed in a lateral direction corresponding to a width W of the porous composite structure 100, which is perpendicular to the axial direction (see e.g., line 13 in FIG. 1 indicating the axial direction for a corresponding green body). Accordingly, electrodes 117 with electrical leads 119 (optionally with insulators 118) can be attached to the respective opposite sides 113, 115 of the porous composite structure 100 and the continuous, three- dimensional, interconnected, electrically conductive metallic phase of the composite material of the walls 104 of the porous composite structure 100 can function as a resistor element. In this way, the porous composite structure 100 will heat up when an electrical potential (voltage) is applied across the electrodes 117. Thus, the metallic phase being interconnected throughout the porous composite structure 100 enables electrical current to pass through the walls 104, such that the porous composite structure 100 is electrically conductive between respective opposing sides 113, 115.

[0152] In embodiments, the electrical leads 119 may be connected to a control system (not shown) such that the porous composite structure 100 can be implemented as a resistive heater that can be integrated into an adsorption / desorption unit of a CO2 capture system, e.g., an direct air capture (DAC) system. In some embodiments, multiple heater assemblies 101 can be included in the DAC systems.

[0153] Construction and arrangements of the porous composite structures, assemblies, and structures, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, useAttorney Docket No.: SP24-064 of materials, colors, orientations) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary7embodiments without departing from the scope of the present inventive technology.

[0154] Unless stated otherwise, mechanical strength of the porous composite structures can be evaluated using a 4-point bending point bending test conducted according to ASTM Cl 674- 16. In conducting the mechanical strength testing herein, the samples are cut into 0.25 inch by 0.5 inch by 3.5 inch minibars. The 4-point bending test is accomplished using a 2 inch support span.

[0155] Unless stated otherwise, porosity, median pore volume, and pore size distribution herein are measured by mercury intrusion porosimetry in accordance with ASTM D6761-07 (2012).EXAMPLES

[0156] The embodiments described herein will be further clarified by the following examples. The following examples illustrate the formation of porous composite structures using the compositions and methods disclosed herein. The following examples are not intended to be limit the scope of the present disclosure.Materials

[0157] The hollow glass bodies used in the Examples of the present disclosure were one of H60 hollow glass microspheres obtained from Zhongke Yah Technology Co., Ltd., H50 hollow glass microspheres obtained from Zhongke Yali Technology Co., Ltd., or C100T hollow glass microspheres obtained from Zhongke Huaxing Co., Ltd . The glass composition of the hollow glass bodies is provided below in Table 3.Attorney Docket No.: SP24-064Table 3: Composition of H60, H50, and C100T Hollow Glass Microspheres

[0158] The metal particles used in used in the Examples of the present disclosure were aluminum particles that had been passed through a 325 mesh screen. The binder used in the Examples was Culminal 724 (methylhydroxy propyl cellulose). The graphite used was Asbury 4014. The lubricant used was mineral oil.Compositions

[0159] Table 4 below lists three compositions used in the Examples of the present disclosure.Attorney Docket No.: SP24-064Table 4: Exemplary Compositions* H60 Hollow Glass Microspheres* Cl GOT Hollow Glass Microspheres■t H50 Hollow Glass MicrospheresGreen Bodies

[0160] Green bodies were prepared for Compositions A and B by extruding each composition to a 1” by 1” square-shaped honeycomb having a cell density of 300 cpsi and a web thickness of 8 mil. Green bodies were prepared for Compositions C and D by extruding each composition to a 2” diameter cylindrical-shaped honeycomb having a cell density of 300 cpsi and a web thickness of 8 mil. The length of the honeycomb (i.e., the length along honeycomb axis 13 with respect to FIG. 1) for green bodies prepared from Compositions A and B was 1”. The length of the honeycomb for green bodies prepared from Composition D was 5”. The length of the honeycomb for green bodies prepared from Composition C was 3.2”. Prior to firing, the green bodies prepared from Composition C were cut along the diameter of the green bodies into two half cylinders. Firing Methods

[0161] For the green bodies prepared from Compositions A and B, four different firing methods (Firing Methods 1-4) were implemented using a retort furnace with an inert nitrogen atmosphere. Each of Firing Methods 1-4 involved ramping the green bodies (vertically oriented in furnace) to a peak firing temperature at a temperature ramping rate, holding the green bodies at the peak firing temperature for a peak firing time, and then cooling the fired structures to ambient temperature at a cooling rate of 400 °C per hour.Attorney Docket No.: SP24-064

[0162] For the green bodies prepared from Composition C, two different fast firing methods (Firing Methods FF1 and FF2) were implemented using an IBEX model furnace with an air atmosphere. The IBEX model furnace had a circular exhaust hole at the top with a roughly 3.5 cm diameter, and chamber dimensions of 20 cm x 20 cm * 15 cm. The half cylinder green bodies prepared for Composition C were placed flat side down on a fired ceramic honeycomb disk. Each of Fast Firing Methods FF1 and FF2 involved ramping the green bodies to a peak firing temperature at an increased temperature ramping rate (relative to Firing Methods 1-4), holding the green bodies at the peak firing temperature for a peak firing time, and then shutting off electrical power to the furnace and naturally cooling the fired structures to ambient temperature over a period of two hours.

[0163] For the green bodies prepared from Composition D, four firing methods (Firing Methods 5-8) were implemented using a gas furnace, with Firing Methods 5 and 8 involving an air atmosphere and Firing Methods 6 and 7 involving an air atmosphere with controlled oxygen content at 10% and 6%. respectively. Each of Firing Methods 5- 8 involved ramping the green bodies (vertically oriented in furnace) to a peak firing temperature at a temperature ramping rate, holding the green bodies at the peak firing temperature for a peak firing time, and then cooling the fired structures to ambient temperature at a cooling rate of 100 °C per hour.

[0164] Parameters of the firing methods used for Compositions A-D are shown below in Table 5:Attorney Docket No.: SP24-064Table 5: Example Firing MethodsProperties and Phase Assemblage for Produced Porous Composite Structures

[0165] The properties and phase assemblages for example porous composite structures produced using compositions described herein and in accordance with methods described herein are now discussed. Each of the porous composite structures produced for Compositions A-C was electrically conductive, as shown below via measured electrical resistance values. The electrical resistance measurements were performed using a multimeter where two electrodes of the multimeter were contacted with opposite sides of the porous composite structure with respect to a lateral direction perpendicular to the honeycomb axis 13 (see FIG. 1). A piece of copper foil was placed between each electrode and the surface of the porous composite structure to improve contact between the electrodes and the porous composite structure. Table 6 below provides, for each example porous composite structures, the firing method, porosity, median pore diameter (for select examples), bulk density, electrical resistance, and modulus of rupture (for select examples), each of which was determined in accordance with test methods described herein.Attorney Docket No.: SP24-064Table 6: Properties of Example Porous Composite StructuresND = not determined

[0166] FIG. 3 is an SEM image of Example A-700C corresponding to a porous composite structure produced by firing a green body of Composition A using Firing Method 1 (see Table 5). As can be seen from FIG. 3, the porous composite structures described herein include a continuous and interconnected metallic phase 202 and a non-metallic phase 204 which together define porous cavities that extend and interconnect throughout the porous composite structure and open to surfaces thereof.

[0167] FIG. 4 is an SEM image of Example D-600C corresponding to a porous composite structure produced by firing a green body of Composition D using Firing Method 5 (see Table 5). Like FIG. 3, FIG. 4 shows that the porous composite structuresAttorney Docket No.: SP24-064 described herein include a continuous and interconnected metallic phase 202 and a non-metallic phase 204 which together define porous cavities that extend and interconnect throughout the porous composite structure and open to surfaces thereof.

[0168] Table 7 below provides the crystalline phase assemblage for example porous composite structures formed from Compositions A and B. The weight percentages expressed in Table 7 as well as the identification of the various phases that are present is accomplished by the Reitveld refinement method, and are expressed as a percentage based on the total weight of the crystalline portion of the porous composite structure. Table 7: Phase Assemblages Example Porous Composite Structures (wt% based on cry stalline portion of the porous composite structure)

[0169] As can be seen from Tables 6 and 7, the compositions and firing methods used to make porous composite structures described herein may be adjusted to make electrically conductive porous composite structures having a range of properties corresponding to distinct microstructural characteristics and phase assemblages.

[0170] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Unless otherwise specified, a range of values, when recited, includes both the upper and lowerAttorney Docket No.: SP24-064 limits of the range as well as any sub-ranges therebetween. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0171] As used herein, the indefinite articles “a,” “an,” and the corresponding definite article “the” mean “at least one” or “one or more.” unless otherwise specified. It also is understood that the various features disclosed in the specification and the drawings can be used in any and all combinations.

[0172] It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0173] Reference throughout this specification to “one embodiment.” “certain embodiments,” “various embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in embodiments,” “in one or more embodiments,” “in certain embodiments,” “in various embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment, or to only one embodiment. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0174] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.

Claims

1. PCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-064CLAIMSWhat is claimed is:

1. A composition for producing porous composite structures, the composition comprising: from 20 wt% to 80 wt% hollow glass bodies; and from 20 wt% to 80 wt% metal particles, wherein wt% is based on a total combined weight of non-combustible inorganic particles in the composition.

2. The composition of claim 1, comprising: from 50 wt% to 80 wt% hollow glass bodies; and from 20 wt% to 50 wt% metal particles.

3. The composition of any one of claims 1-2, where the metal particles comprise a metal selected from the group consisting of aluminum, copper, iron, nickel, cobalt, silver, alloys thereof, and combinations thereof.

4. The composition of any one of claims 1-3, wherein the hollow glass bodies have a wall thickness from 0.2 pm to 10 pm.

5. The composition of any one of claims 1-4, wherein: the hollow glass bodies comprise silica glass; and the metal particles comprise aluminum, aluminum alloy, or both aluminum and aluminum alloy.

6. The composition of any one of claims 1-5, wherein: the hollow glass bodies have a D50 diameter of greater than or equal to 1 pm and less than or equal to 100 pm; and the metal particles have a D50 diameter of greater than or equal to 1 pm and less than or equal to 100 pm.PCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-0647. The composition of any one of claims 1-6, further comprising from 2 wt% SA to 20 wt% SA binder, wherein wt% SA is weight percent by superaddition based on the total combined weight of the non-combustible inorganic particles in the composition.

8. The composition of claim 7, wherein the binder comprises cellulose, cellulose derivatives, polymer binders, or combinations thereof.

9. The composition of any one of claims 1-8, further comprising from 10 wt% SA to 50 wt% SA inorganic pore former.

10. The composition of claim 9, wherein the inorganic pore former comprises graphite particles.

11. The composition of any one of claims 1-10, further comprising a surfactant, a lubricant, an oil, or combinations thereof.

12. The composition of any one of claims 1-11, further comprising from 2 wt% SA to 20 wt% SA lubricant.

13. The composition of any one of claims 1-12, comprising from 0 wt% to 30 wt% of inorganic filler particles.

14. A method of making a porous composite structure, the method comprising: forming a green body from the composition of claim 1; and firing the green body to produce the porous composite structure.

15. The method of claim 14, wherein firing the green body comprises: ramping the green body to a peak firing temperature at a ramping rate of from 100 °C per hour to 500 °C per hour; holding the green body at the peak firing temperature for a peak firing time of less than4 hours to produce the fired structure; and cooling the fired structure to produce the porous composite structure.PCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-06416. The method of claim 15, wherein cooling the fired structure comprises cooling the fired structure to ambient temperature at a cooling rate of from 100 °C per hour to 500 °C per hour.

17. The method of claim 15, wherein the peak firing temperature is greater than or equal to 500 °C and less than or equal to 1000 °C.

18. The method of claim 17, wherein the peak firing time is greater than or equal to 1 hour and less than or equal to 3 hours.

19. The method of claim 17, wherein: the peak firing temperature is greater than or equal to 800 °C and less than or equal to 1000 °C; and the peak firing time is less than or equal to 0.5 hours.

20. The method of claim 19, wherein the peak firing time is zero hours.

21. The method of any one of claims 14-20, wherein firing the green body is performed in an inert atmosphere.

22. The method of claim 21, wherein the inert atmosphere comprises nitrogen gas.

23. The method of any one of claims 14-22, wherein the composition further comprises from 10 wt% SA to 50 wt% SA graphite particles.

24. The method of claim 23, wherein firing the green body comprises: ramping the green body to a peak firing temperature at a ramping rate of from 2,500 °C per hour to 3,500 °C per hour; and holding the green body at the peak firing temperature for a peak firing time of from 0.5 hours to 3 hours to produce the fired structure; and cooling the fired structure to produce the porous composite structure.PCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-06425. The method of claim 24, wherein cooling the fired structure comprises naturally cooling the fired structure to ambient temperature over a cooling time of from 1 hour to 3 hours.

26. The method of claim 24, wherein the peak firing temperature is greater than or equal to 600 °C and less than or equal to 800 °C.

27. The method of claim 24, wherein firing the green body to produce the fired structure and cooling the fired structure to produce the porous composite structure is completed in a combined time of less than 10 hours.

28. The method of claim 24, wherein firing the green body is performed in an oxygenated atmosphere.

29. The method of any one of claims 14-28, wherein forming the green body comprises extruding the composition into a honeycomb body comprising a plurality of elongate channels.

30. The method of claim 29, wherein the honeycomb body comprises: a cell density of from 200 cells per square inch to 400 cells per square inch, where the cell density refers to a number of elongate channels per square inch of cross-section of the honeycomb body; and a web thickness of from 2 mils to 10 mils.

31. A green body formed from the composition of any one of claims 1-30.

32. A porous composite structure comprising: a continuous, three-dimensional, and interconnected metallic phase; and a non-metallic phase of sintered hollow glass bodies dispersed throughout the porous composite structure and intertwined with and / or interspersed through the metallic phase.

33. The porous composite structure of claim 32, wherein the non-metallic phase is a continuous, three-dimensional, and interconnected glass phase intertwined with the metallic phase.PCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-06434. The porous composite structure of any one of claims 32-33, comprising a porosity of greater than or equal to 50% and less than or equal to 85%, measured in accordance with ASTM D6761-07 (2012).

35. The porous composite structure of any one of claims 32-34, comprising a bulk density of greater than or equal to 0.5 g / cm3and less than or equal to 5.0 g / cm3, measured in accordance with ASTM D6761-07 (2012).

36. The porous composite structure of any one of claims 32-35, comprising a modulus of rupture of greater than or equal to 0.5 MPa to 10 MPa, measured in accordance with ASTM C1674-16.

37. The porous composite structure of any one of claims 32-36, comprising a median pore diameter dso of greater than or equal to 1 pm and less than or equal to 50 pm, measured by mercury porosimetry in accordance with ASTM D6761-07 (2012).

38. The porous composite structure of any one of claims 32-37, wherein: the metallic phase comprises metal particles that have been sintered together; and the non-metallic phase comprises reaction products of a portion of the metal particles and the hollow glass bodies.

39. The porous composite structure of claim 38, wherein: the hollow glass bodies comprise silica glass; the metal particles comprise aluminum; and the reaction products of the portion of the metal particles and the hollow glass bodies comprise silicon and alumina.

40. The porous composite structure of claim 39, comprising; from 15 wt% to 50 wt% of a combined amount of aluminum and silicon, based on a total weight of a crystalline portion of the porous composite structure; from 40 wt% to 70 wt% alumina, based on the total weight of the cry stalline portion of the porous composite structure; andPCT / US25 / 46518 16 September 2025 (16.09.2025)Attorney Docket No.: SP24-064 up to 20 wt% silica, based on the total weight of the crystalline portion of the porous composite structure.

41. The porous composite structure of claim 40, comprising from 5 wt% to 35 wt% aluminum, based on the total weight of the cry stalline portion of the porous composite structure.

42. The porous composite structure of any one of claims 40-41, comprising at least 10 wt% silicon, based on the total weight of the crystalline portion of the porous composite structure.

43. The porous composite structure of any one of claims claim 40-42, wherein the porous composite structure has a honeycomb shape comprising a plurality of elongate channels extending through at least a portion of the porous composite structure.

44. The porous composite structure of claim 43, wherein the porous composite structure has a cell density of less than or equal to 400 cells per inch and a web thickness between cells of from 2 mils to 10 mils, where the cell density refers to a number of elongate channels per square inch of cross-section of the porous composite structure.

45. A substrate comprising: the porous composite structure of any one of claims 32-44; and a sorbent coating supported on the porous composite structure.

46. The substrate of claim 45, wherein the sorbent coating is configured to adsorb CO2 molecules.

47. A CO2 capture system comprising the substrate of either one of claims 45-46, wherein the CO2 capture system comprises an adsorption / desorption unit and the substrate is integrated into the adsorption / desorption unit.

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