Three-dimensional microstructures having a three-dimensional porosity network and methods of making the same

Abstract

Provided herein are three-dimensional microstructures including a three-dimensional porosity network and methods of making the same. The three-dimensional porosity network includes a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof. The method includes spreading a layer of a powder feedstock (e.g., a powder with optional decomposable space-holder materials) by binder-jet printing, over a build surface, selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock to form a composite green part, with the sequential process repeated for the entirety of composite green part's height, curing the binder material to form a cured composite green part, removing excess powder feedstock from the cured composite green part; and sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional microstructure comprising the three-dimensional porosity network.

Description

Attorney Docket No. 06527-2600560THREE-DIMENSIONAL MICROSTRUCTURES HAVING A THREE- DIMENSIONAL POROSITY NETWORK AND METHODS OF MAKING THE SAMECROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to United States Provisional Application No.63 / 777,241, filed March 25, 2025, the disclosure of which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTIONField of the Invention

[0002] Provided herein are three-dimensional microstructures including a three-dimensional porosity network and a method of making a three-dimensional micro structure comprising a three-dimensional porosity network, wherein the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.Description of Related Art

[0003] Metal, ceramic, or composite porous structures may be used as filters for liquid streams or gas streams to remove particulates, sediments, and / or pathogens, or to allow for directional flow. These metal, ceramic, or composite porous structures can also be used for heat exchangers, light-weight structural components, and / or for energy or gas storage applications. However, these metal and ceramic porous structures, which are made from powder feedstock by traditional techniques, are limited to simple shapes.

[0004] It would be desirable to have metal and ceramic porous structures, made from a powder feedstock, that have three-dimensional geometries, potentially combining porous macrochannels with a tunable three-dimensional micro-porosity network to maximize the surface area, and thus permeability and efficiency, while reducing the size and weight of the filter.SUMMARY OF THE INVENTION

[0005] Provided herein is a method of making a three-dimensional micro structure having a three-dimensional porosity network. The method includes spreading a layer of a powder feedstock, by binder-jet printing, over a build surface; selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock to form a composite green part, wherein a process of spreading a layer of powder feedstock and sequentially depositing a layer of binder material is repeated for an entirety of a height of the16BX9540.DOCXAttorney Docket No. 06527-2600560composite green part; curing the binder material to form a cured composite green part; removing excess powder feedstock from the cured composite green part; and sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional microstructure comprising the three-dimensional porosity network. The three-dimensional porosity network comprises a layered porosity network, an isotropic porosity network, a complex-shaped porosity network, or combinations thereof.

[0006] Also provided herein is a three-dimensional microstructure. The three-dimensional micro structure comprises a three-dimensional porosity network dispersed within a sintered solid matrix. The sintered solid matrix comprises a sintered metal material, a sintered ceramic material, a sintered composite material, or mixtures thereof. The three-dimensional porosity network comprises a layered porosity network, a complex- shaped porosity network, an isotropic porosity network, or combinations thereof.

[0007] The three-dimensional microstructures described herein and formed from the foregoing method may be used as filters, flow restrictors, and / or structural components.

[0008] This disclosure is further described in the following numbered clauses:

[0009] Clause 1: A method of making a three-dimensional microstructure comprising a three-dimensional porosity network, the method comprising: spreading a layer of a powder feedstock, by binder-jet printing, over a build surface; selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock to form a composite green part, wherein a process of spreading a layer of powder feedstock and sequentially depositing a layer of binder material is repeated for an entirety of a height of the composite green part; curing the binder material to form a cured composite green part; removing excess powder feedstock from the cured composite green part; and sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional micro structure comprising the three-dimensional porosity network, wherein the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.

[0010] Clause 2: The method of clause 1, wherein the powder feedstock of each layer may be the same or different.

[0011] Clause 3: The method of clause 1, wherein the binder material of each layer may be the same or different.

[0012] Clause 4: The method of any one of clauses 1 to 3, wherein the powder feedstock comprises a metal powder, a ceramic powder, a composite powder, or a mixture thereof.26BX9540.DOCXAttorney Docket No. 06527-2600560

[0013] Clause 5: The method of clause 4, wherein the powder feedstock comprises a metal powder.

[0014] Clause 6: The method of clause 4 or 5, wherein the metal powder comprises a metal selected from the group consisting of silver, gold, platinum, copper, nickel, tin, titanium, iron, cobalt, chromium, zinc, manganese, niobium, molybdenum, gallium, zirconium, aluminum, tungsten, combinations thereof, and alloys thereof.

[0015] Clause 7: The method of clause 5 or 6, wherein the metal powder is a functionalized metal powder.

[0016] Clause 8: The method of any one of clauses 5 to 7, wherein the metal powder comprises a diameter of 2 microns (pm) or greater.

[0017] Clause 9: The method of clause 4, wherein the powder feedstock comprises a ceramic powder.

[0018] Clause 10: The method of clause 9, wherein the ceramic powder comprises clay, alumina, zirconia, silicon carbide, silicon nitride, silicon dioxide, sand, silica, tungsten carbide, mullite, titania, cordierite, aluminum titanate, hydroxyapatite, metakaolin (calcined clay), fly ash, or combinations thereof.

[0019] Clause 11: The method of clause 9 or 10, wherein the ceramic powder is a functionalized ceramic powder.

[0020] Clause 12: The method of any one of clauses 9 to 11, wherein the ceramic powder comprises a diameter of 2 pm or greater.

[0021] Clause 13: The method of clause 4, wherein the powder feedstock comprises a composite powder.

[0022] Clause 14: The method of clause 13, wherein the composite powder comprises a metalceramic composite powder, a core-shell powder, a metal organic framework (MOF) powder, or mixtures thereof.

[0023] Clause 15: The method of clause 13 or 14, wherein the composite powder is a functionalized composite powder.

[0024] Clause 16: The method of any one of clauses 13 to 15, wherein the composite powder comprises a diameter of 2 pm or greater.

[0025] Clause 17: The method of any one of clauses 1 to 16, wherein the powder feedstock further comprises a decomposable space-holder material.

[0026] Clause 18: The method of clause 17, wherein the powder feedstock comprises from 1 volume percent (vol. %) to 99 vol. % of metal powder or ceramic powder and from 1 vol. % to 99 vol. % of the decomposable space-holder material.36BX9540.DOCXAttorney Docket No. 06527-2600560

[0027] Clause 19: The method of clause 17 or 18, wherein the decomposable space-holder material comprises decomposable polymer particles, a natural material, a low-melting point metal, or combinations thereof.

[0028] Clause 20: The method of clause 19, wherein the decomposable space-holder material comprises decomposable polymer particles.

[0029] Clause 21: The method of clause 19 or 20, wherein the decomposable polymer particles are poly (methyl methacrylate) (PMMA) particles.

[0030] Clause 22: The method of any one of clauses 1 to 21, wherein the binder material comprises a polymer, a solvent, or combinations thereof.

[0031] Clause 23: The method of any one of clauses 1 to 22, wherein the binder material further comprises decomposable particles, evaporable particles, metal particles, ceramic particles, composite particles, or a mixture thereof.

[0032] Clause 24: The method of clause 23, wherein the decomposable particles, evaporable particles, metal particles, ceramic particles, or composite particles comprise a diameter of less than 2 pm, such as less than or equal to 1.5 pm, such as less than or equal to 1 pm, such as less than or equal to 800 nanometers (nm), such as less than or equal to 600 nm, such as less than or equal to 400 nm, such as less than or equal to 200 nm, such as less than or equal to 100 nm, or such as less than or equal to 50 nm.

[0033] Clause 25: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a metal powder and the binder material comprises a polymer.

[0034] Clause 26: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a metal powder and a decomposable space-holder material and the binder material comprises a polymer.

[0035] Clause 27: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a metal powder and the binder material comprises a solvent.

[0036] Clause 28: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a metal powder and a decomposable space-holder material and the binder material comprises a solvent.

[0037] Clause 29: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a ceramic powder and the binder material comprises a solvent.

[0038] Clause 30: The method of clause 30, wherein the solvent is water.

[0039] Clause 31 : The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a ceramic powder and a decomposable space-holder material and the binder material comprises a solvent.46BX9540.DOCXAttorney Docket No. 06527-2600560

[0040] Clause 32: The method of clause 31, wherein the solvent is water.

[0041] Clause 33: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a ceramic powder and the binder material comprises a polymer.

[0042] Clause 34: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a ceramic powder and a decomposable space-holder material and the binder material comprises a polymer.

[0043] Clause 35: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a composite powder and the binder material comprises a polymer.

[0044] Clause 36: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a composite powder and a decomposable space-holder material and the binder material comprises a polymer.

[0045] Clause 37: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a composite powder and the binder material comprises a solvent.

[0046] Clause 38: The method of any one of clauses 1 to 24, wherein the powder feedstock comprises a composite powder and a decomposable space-holder material and the binder material comprises a solvent.

[0047] Clause 39: The method of any one of clauses 1 to 38, further comprising, prior to sintering the cured composite green part, heating the cured composite green part to a sufficient temperature for a sufficient time to decompose the binder material and the decomposable space-holder material, when present.

[0048] Clause 40: The method of any one of clauses 1 to 39, further comprising, after sintering, coating the three-dimensional porosity network of the three-dimensional micro structure with a coating composition.

[0049] Clause 41: The method of clause 40, wherein the coating composition comprises a liquid carrier and solid particles, wherein the solid particles are dispersed in the liquid carrier.

[0050] Clause 42: The method of clause 41, wherein the solid particles comprise a diameter of 5 pm or less.

[0051] Clause 43: The method of clause 41 or 42, wherein the solid particles reduce a pore size of the three-dimensional porosity network.

[0052] Clause 44: The method of clause 40, wherein the coating composition comprises a functional compound.

[0053] Clause 45: The method of clause 44, wherein the functional compound comprises an antimicrobial compound, a catalytic compound, a metal organic framework (MOF) compound, or combinations thereof.56BX9540.DOCXAttorney Docket No. 06527-2600560

[0054] Clause 46: The method of any one of clauses 40 to 45, further comprising heating the coating composition to form a dried coating in the three-dimensional porosity network.

[0055] Clause 47: The method of any one of clauses 40 to 46, wherein the three-dimensional porosity network is coated by dipping the three-dimensional micro structure in the coating composition.

[0056] Clause 48: A three-dimensional micro structure comprising a three-dimensional porosity network prepared according to the method of any one of clauses 1 to 47.

[0057] Clause 49: A three-dimensional microstructure comprising: a three-dimensional porosity network dispersed within a sintered solid matrix, wherein the sintered solid matrix comprises a sintered metal material, a sintered ceramic material, a sintered composite material, or mixtures thereof, and wherein the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.

[0058] Clause 50: The three-dimensional microstructure of clause 49, wherein the three-dimensional porosity network comprises a layered porosity network.

[0059] Clause 51: The three-dimensional micro structure of clause 50, wherein the three-dimensional porosity network is formed from alternating layers of high porosity and layers of the sintered solid matrix.

[0060] Clause 52: The three-dimensional microstructure of clause 51, wherein the layers of the sintered solid matrix comprise a density that is greater than the layers of high porosity and further comprise fine channel porosity and bulk porosity throughout the sintered solid matrix.

[0061] Clause 53: The three-dimensional microstructure of clause 51 or 52, wherein each layer of high porosity connects to each layer of the sintered solid matrix through a plurality of sintered interconnections.

[0062] Clause 54: The three-dimensional micro structure of clause 49, wherein the three-dimensional porosity network comprises an isotropic porosity network.

[0063] Clause 55: The three-dimensional micro structure of clause 54, comprising a plurality of large pores dispersed within the sintered solid matrix, wherein the large pores are interconnected through a series of fine channels dispersed throughout the sintered solid matrix.

[0064] Clause 56: The three-dimensional micro structure of clause 55, wherein the plurality of large pores is randomly dispersed within the sintered solid matrix.

[0065] Clause 57: The three-dimensional micro structure of clause 49, wherein the three-dimensional porosity network comprises a complex- shaped porosity network.66BX9540.DOCXAttorney Docket No. 06527-2600560

[0066] Clause 58: The three-dimensional micro structure of any one of clauses 49 to 57, wherein the sintered solid matrix comprises a sintered metal material.

[0067] Clause 59: The three-dimensional micro structure of clause 58, wherein the sintered metal material comprises silver, gold, platinum, copper, nickel, tin, titanium, iron, cobalt, chromium, zinc, manganese, niobium, molybdenum, gallium, zirconium, aluminum, tungsten, combinations thereof, and alloys thereof.

[0068] Clause 60: The three-dimensional micro structure of clause 59, wherein the sintered metal material is a magnetocaloric material.

[0069] Clause 61: The three-dimensional micro structure of any one clauses 49 to 57, wherein the sintered solid matrix comprises sintered ceramic material.

[0070] Clause 62: The three-dimensional micro structure of clause 61, wherein the sintered ceramic material comprises clay, alumina, zirconia, silicon carbide, silicon nitride, silicon dioxide, sand, silica, tungsten carbide, mullite, titania, cordierite, aluminum titanate, hydroxyapatite, metakaolin (calcined clay), fly ash, or combinations thereof.

[0071] Clause 63: The three-dimensional micro structure of any one of clauses 49 to 57, wherein the sintered solid matrix comprises a sintered composite material.

[0072] Clause 64: The three-dimensional micro structure of clause 63, wherein the sintered composite material comprises a metal-ceramic composite material.

[0073] Clause 65: The three-dimensional micro structure of any one of clauses 49 to 64, comprising a hydraulic diameter of less than or equal to 10 pm.

[0074] Clause 66: The three-dimensional micro structure of any one of clauses 49 to 65, comprising a hydraulic diameter of less than or equal to 1 pm.

[0075] Clause 67: The three-dimensional micro structure of any one of clauses 49 to 66, wherein the three-dimensional porosity network comprises a coating.

[0076] Clause 68: The three-dimensional microstructure of clause 67, wherein the coating further reduces the pore size of the three-dimensional porosity network.

[0077] Clause 69: The three-dimensional microstructure of clause 67, wherein the coating comprises a functional compound.

[0078] Clause 70: The three-dimensional micro structure of clause 69, wherein the functional compound comprises an antimicrobial compound, a catalytic compound, a MOF compound or combinations thereof.

[0079] Clause 71: The three-dimensional micro structure of any one of clauses 49 to 70, wherein the three-dimensional micro structure comprising the three-dimensional porosity network is a filter.76BX9540.DOCXAttorney Docket No. 06527-2600560

[0080] Clause 72: The three-dimensional microstructure of clause 71, wherein the filter is a filter for removing particulates from a gas stream.

[0081] Clause 73: The three-dimensional microstructure of clause 72, wherein the filter is formed from a powder feedstock comprising a metal powder.

[0082] Clause 74: The three-dimensional microstructure of clause 72, wherein the filter is formed from a powder feedstock comprising a ceramic powder.

[0083] Clause 75: The three-dimensional microstructure of clause 71, wherein the filter is a filter for removing fine sediment, pathogens, or combinations thereof from a water stream.

[0084] Clause 76: The three-dimensional microstructure of clause 75, wherein the filter is formed from a powder feedstock comprising a metal powder.

[0085] Clause 77: The three-dimensional microstructure of clause 75, wherein the filter is formed from a powder feedstock comprising a ceramic powder.

[0086] Clause 78: The three-dimensional micro structure of any one of clauses 49 to 70, wherein the three-dimensional micro structure comprising the three-dimensional porosity network is a flow retarder.

[0087] Clause 79: The three-dimensional microstructure of clause 78, wherein the three-dimensional microstructure comprising the three-dimensional porosity provides directional flow.

[0088] Clause 80: The three-dimensional micro structure of any one of clauses 49 to 70, wherein the three-dimensional microstructure comprising the three-dimensional porosity is a structural material.BRIEF DESCRIPTION OF THE DRAWINGS

[0089] For a more complete understanding of the description provided herein and the advantages thereof, reference is now made to the brief descriptions below, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0090] FIG. l(a)-(d) are images showing the effect of sintering time on the three-dimensional porosity network after sintering for (a) 6 hours, (b) 4 hours, (c) 3 hours, and (d) 4 hours, each at 1270 °C.

[0091] FIG. 2 is a plot of relative bulk density as a function of sintering temperature for three-dimensional microstructures made from a powder feedstock including spherical metal powder and PMMA particles (from 0 to 70 vol. %) as a decomposable space-holder material.86BX9540.DOCXAttorney Docket No. 06527-2600560

[0092] FIG. 3 is a plot of relative Archimedes density as a function of sintering temperature for three-dimensional microstructures made from a powder feedstock including irregularly shaped metal powder and PMMA particles (from 0 to 70 vol. %) as a decomposable spaceholder material.

[0093] FIG. 4(a)-(c) are images showing the effect of heating temperature, before sintering, on the three-dimensional porosity network at (a) 650 °C, (b) 450 °C, and (c) 250 °C, each heated for 2 hours.

[0094] FIGS. 5A-5C are exemplary layered porosity networks according to the invention.

[0095] FIG. 6 includes cross-sectional images of exemplary three-dimensional microstructures having layered porosity networks according to the invention.

[0096] FIG. 7 is an exemplary isotropic porosity network according to the invention.

[0097] FIG. 8 is a cross-sectional image of a three-dimensional micro structure having an isotropic porosity network according to the invention.

[0098] FIG. 9 is a schematic depicting three levels of pore structure.

[0099] FIG. 10 is a cross-sectional image of an exemplary three-dimensional micro structure having an oriented three-dimensional porosity network according to the invention.

[0100] FIG. 11 is a schematic depicting the process of coating the three-dimensional porosity network, where (a) shows the three-dimensional porosity network without a coating, (b) shows the three-dimensional porosity network coated with a coating composition, and (c) shows the three-dimensional porosity network with the final dried coating.

[0101] FIG. 12 is a schematic depicting anisotropic flow for a layered porosity network according to the invention.

[0102] FIG. 13 is a graph of particle size vs. volume fraction for gas atomized Inconel® 625 metal powder (GA), water atomized Inconel® 625 metal powder (WA), and PMMA powder particles.

[0103] FIGS. 14A and 14B are graphs depicting powder properties, specifically the powder density as a function of PMMA content in the powder feedstock (FIG. 14 A) and the relative density as a function of PMMA content in the powder feedstock (FIG. 14B).

[0104] FIG. 15 is a graph of green relative density of a cured composite green part as a function of PMMA content in the water atomized (WA) and gas atomized (GA) metal powder feedstock.

[0105] FIGS. 16A and 16B are graphs depicting properties of the sintered three-dimensional microstructure, specifically the relative Archimedes density as a function of sintering temperature and varying PMMA content in the powder feedstock containing WA (FIG. 16 A)96BX9540.DOCXAttorney Docket No. 06527-2600560and the relative porosity as a function of sintering temperature and varying PMMA content in the powder feedstock containing WA (FIG. 16B).

[0106] FIGS. 17A and 17B are graphs depicting properties of the sintered three-dimensional microstructure, specifically the relative Archimedes density as a function of sintering temperature and varying PMMA content in the powder feedstock containing GA (FIG. 17A) and the relative porosity as a function of sintering temperature and varying PMMA content in the powder feedstock containing GA (FIG. 17B).

[0107] FIGS. 18A and 18B are graphs depicting surface roughness of the three-dimensional microstructures as a function of PMMA content in the powder feedstock containing WA (FIG.18A) or GA (FIG. 18B), at two different sintering temperatures.

[0108] FIG. 19 includes scanning electron micrographs of three-dimensional microstructures prepared from powder feedstocks containing WA or GA and PMMA particles.

[0109] FIG. 20 includes cross section images of micro-computed tomography scans of binder jetted and sintered Inconel® 625 parts, where (a), (b), and (c) were parts sintered at a high temperature and had 0 vol. %, 30 vol. %, and 60 vol. % of PMMA particles, respectively, in the powder feedstock and (d), (e), and (f) were parts sintered at a low temperature and had 0 vol. %, 30 vol. %, and 60 vol. % PMMA particles, respectively, in the powder feedstock.DESCRIPTION OF THE INVENTION

[0110] The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. While the description is designed to permit one of ordinary skill in the art to make and use the invention, and specific examples are provided to that end, they should in no way be considered limiting. It will be apparent to one of ordinary skill in the art that various modifications to the following will fall within the scope of the appended claims. The present invention should not be considered limited to the presently disclosed embodiments, whether provided in the examples or elsewhere herein.

[0111] The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as approximations as though the minimum and maximum values within the stated ranges are both preceded by the word “about”. In this manner, slight variations above and below the stated ranges (e.g., ± 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.5%) can be used to achieve substantially the same results as values within the ranges. Also, unless indicated otherwise, the disclosure of ranges is intended as a continuous range including every value between the minimum and maximum values. For example, a stated range of “1 to 10” should be considered to include any and all subranges 106BX9540.DOCXAttorney Docket No. 06527-2600560between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, e.g., 1 to 3.3, 4.7 to 7.5, 5.5 to 10, and the like.

[0112] As used herein “a” and “an” refer to one or more.

[0113] As used herein, the terms “comprising”, “comprise”, or “comprised”, and variations thereof, are open ended and do not exclude the presence of other elements not identified. In contrast, the term “consisting of’ and variations thereof is intended to be closed, and excludes additional elements in anything but trace amounts.

[0114] As used herein, spatial or directional terms, such as “left”, “right”, “inner”, “outer”, “above”, “below”, “over”, “under”, and the like, relate to the invention, are provided solely for ease of description and illustration, and do not imply directionality, unless specifically required for operation of the described aspect of the invention. It is to be understood that the invention can assume various alternative orientations and, accordingly, such terms are not to be considered as limiting.

[0115] Provided herein is a method of making a three-dimensional micro structure comprising a three-dimensional porosity network. The method comprises spreading a layer of a powder feedstock, by binder-jet printing, over a build surface; selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock to form a composite green part, wherein a process of spreading a layer of powder feed stock and sequentially depositing a layer of binder material is repeated for an entirety of a height of the composite green part; curing the binder material to form a cured composite green part; removing excess powder feedstock from the cured composite green part; and sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional micro structure comprising the three-dimensional porosity network. The three-dimensional porosity network of the three-dimensional micro structure comprises a layered porosity network, a complex- shaped porosity network, an isotropic porosity network, or combinations thereof.

[0116] As used herein “binder-jet printing”, is an additive manufacturing process in which a binder material is selectively deposited onto a layer of powder particles, where the binder material and the powder particles are bonded together to form a three-dimensional part, one layer at a time. A binder-jet printer is a device or system used for binder-jet printing.

[0117] The method comprises spreading a layer of a powder feedstock, by binder-jet printing, over a build surface.116BX9540.DOCXAttorney Docket No. 06527-2600560

[0118] As used herein “build surface”, is a movable platform in which the powder feedstock is applied and the composite green part is built upon. The build surface may be any material that the cured composite part may be easily removed from. The build surface is a movable surface and may move along a y-axis.

[0119] The layer of the powder feedstock may be evenly applied over the build surface by a recoating blade.

[0120] The powder feedstock may comprise a metal powder.

[0121] The metal powder comprises at least one metal. For example, the metal of the metal powder may include, but is not limited to: silver, gold, platinum, copper, nickel, tin, titanium, iron, cobalt, chromium, zinc, manganese, niobium, molybdenum, gallium, zirconium, aluminum, tungsten, combinations thereof, and alloys thereof. For example, the metal powder may be a nickel-chromium alloy powder, such an Inconel® 625 powder. For example, the metal powder may be a copper powder. For example, the metal powder may be stainless steel. The metal powder may comprise a magnetocaloric material.

[0122] The metal powder may be a functionalized metal powder. For example, the metal powder may comprise a functional coating on the surface of the metal powder particles. Exemplary functional coatings suitable for the metal powder include, but are not limited to, antimicrobial coatings, catalytic coatings, metal organic framework (MOF) coatings, and combinations thereof.

[0123] The metal powder may be a spherical powder.

[0124] The metal powder may comprise an irregular shape.

[0125] The metal powder may comprise any diameter that can be deposited by the binder-jet printer. For example, the metal powder may comprise diameter of 2 microns (pm) or greater.

[0126] Alternatively, the powder feedstock may comprise a ceramic powder.

[0127] The ceramic powder may include, but is not limited to, clay, alumina, zirconia, silicon carbide, silicon nitride, silicon dioxide, sand, silica, mullite, titania, cordierite, aluminum titanate, hydroxyapatite, tungsten carbide, metakaolin (calcined clay), fly ash, or combinations thereof.

[0128] The ceramic powder may be a functionalized ceramic powder. For example, the ceramic powder may comprise a functional coating on the surface of the ceramic powder particles. Exemplary functional coatings suitable for the ceramic powder include, but are not limited to, antimicrobial coatings, catalytic coatings, MOF coatings, and combinations thereof.

[0129] The ceramic powder may be a spherical powder.

[0130] The ceramic powder may comprise an irregular shape.126BX9540.DOCXAttorney Docket No. 06527-2600560

[0131] The ceramic powder may comprise any diameter that can be deposited by the binderjet printer. For example, the ceramic powder may comprise diameter of 2 pm or greater.

[0132] Alternatively, the powder feedstock may comprise a composite powder.

[0133] The composite powder may include, but is not limited to, a metal-ceramic composite powder, a core-shell powder, a MOF powder, or mixtures thereof.

[0134] The composite powder may be a functionalized composite powder. For example, the composite powder may comprise a functional coating on the surface of the composite powder particles. Exemplary functional coatings suitable for the composite powder include, but are not limited to, antimicrobial coatings, catalytic coatings, MOF coatings, and combinations thereof.

[0135] The composite powder may be a spherical powder.

[0136] The composite powder may comprise an irregular shape.

[0137] The composite powder may comprise any diameter that can be deposited by the binderjet printer. For example, the composite powder may comprise diameter of 2 pm or greater.

[0138] The powder feedstock may further comprise a decomposable space-holder material. As used herein “decomposable space-holder material” means a material that evaporates or burns off during the one or more heating processes, leaving a void where it previously occupied.

[0139] The decomposable space-holder material may comprise a natural material. For example, the decomposable space-holder material may include, but is not limited to salts (e.g., table salt), sucrose (e.g., table sugar), cellulose materials (e.g., sawdust), starch, or combinations thereof.

[0140] The decomposable space-holder material may comprise a low melting point metal powder. For example, the decomposable space-holder material may include, but is not limited to a copper powder, a bronze powder, or mixtures thereof.

[0141] The decomposable space-holder material may comprise decomposable polymer particles. The decomposable polymer particles may be synthetic polymer particles. The decomposable polymer particles may be natural polymer particles. For example, the polymer of the decomposable polymer particles may include, but is not limited to: poly(methyl methacrylate) (PMMA), polyethylene glycol (PEG), polystyrene, polydimethylsiloxane, poly (lactic acid), natural rubber, starch, and combinations thereof. In one non-limiting embodiment, the decomposable polymer particles may be PMMA particles.

[0142] The decomposable space-holder material may comprise any diameter that can be deposited by the binder-jet printer. For example, the decomposable space-holder powder may136BX9540.DOCXAttorney Docket No. 06527-2600560comprise diameter of 2 pm or greater. The size of the decomposable space-holder material may be selected based on the desired three-dimensional porosity network.

[0143] The powder feedstock may consist of a metal powder (i.e., 100 volume percent (vol. %) metal powder).

[0144] The powder feedstock may consist of a ceramic powder (i.e., 100 vol. % ceramic powder).

[0145] The powder feedstock may consist of a composite powder (i.e., 100 vol. % composite powder).

[0146] The powder feedstock may comprise a metal powder and a decomposable space-holder material, wherein the amount of decomposable space-holder material present in the powder feedstock is selected based on the desired three-dimensional porosity network of the three-dimensional microstructure. For example, the powder feedstock may comprise the metal powder in an amount ranging from 1 vol. % to 99 vol. % and may comprise the decomposable space-holder material in an amount ranging from 1 vol. % to 99 vol. %. For example, the powder feedstock may comprise 99 vol. % decomposable space-holder material and 1 vol. % metal powder. For example, the powder feedstock may comprise 95 vol. % decomposable space-holder material and 5 vol. % metal powder. For example, the powder feed stock may comprise 90 vol. % decomposable space-holder material and 10 vol. % metal powder. For example, the powder feed stock may comprise 80 vol. % decomposable space-holder material and 20 vol. % metal powder. For example, the powder feed stock may comprise 70 vol. % decomposable space-holder material and 30 vol. % metal powder. For example, the powder feed stock may comprise 60 vol. % decomposable space-holder material and 40 vol. % metal powder. For example, the powder feed stock may comprise 50 vol. % decomposable spaceholder material and 50 vol. % metal powder. For example, the powder feed stock may comprise 40 vol. % decomposable space-holder material and 60 vol. % metal powder. For example, the powder feed stock may comprise 30 vol. % decomposable space-holder material and 70 vol. % metal powder. For example, the powder feed stock may comprise 20 vol. % decomposable space-holder material and 80 vol. % metal powder. For example, the powder feed stock may comprise 10 vol. % decomposable space-holder material and 90 vol. % metal powder. For example, the powder feedstock may comprise 5 vol. % decomposable space-holder material and 95 vol. % metal powder. For example, the powder feedstock may comprise 1 vol. % decomposable space-holder material and 99 vol. % metal powder

[0147] The powder feedstock may comprise a ceramic powder and a decomposable spaceholder material, wherein the amount of decomposable space-holder material present in the 146BX9540.DOCXAttorney Docket No. 06527-2600560powder feedstock is selected based on the desired three-dimensional porosity network of the three-dimensional micro structure. For example, the powder feedstock may comprise the ceramic powder in an amount ranging from 1 vol. % to 99 vol. % and may comprise the decomposable space-holder material in an amount ranging from 1 vol. % to 99 vol. %. For example, the powder feedstock may comprise 99 vol. % decomposable space-holder material and 1 vol. % ceramic powder. For example, the powder feedstock may comprise 95 vol. % decomposable space-holder material and 5 vol. % ceramic powder. For example, the powder feed stock may comprise 90 vol. % decomposable space-holder material and 10 vol. % ceramic powder. For example, the powder feed stock may comprise 80 vol. % decomposable spaceholder material and 20 vol. % ceramic powder. For example, the powder feed stock may comprise 70 vol. % decomposable space-holder material and 30 vol. % ceramic powder. For example, the powder feed stock may comprise 60 vol. % decomposable space-holder material and 40 vol. % ceramic powder. For example, the powder feed stock may comprise 50 vol. % decomposable space-holder material and 50 vol. % ceramic powder. For example, the powder feed stock may comprise 40 vol. % decomposable space-holder material and 60 vol. % ceramic powder. For example, the powder feed stock may comprise 30 vol. % decomposable spaceholder material and 70 vol. % ceramic powder. For example, the powder feed stock may comprise 20 vol. % decomposable space-holder material and 80 vol. % ceramic powder. For example, the powder feed stock may comprise 10 vol. % decomposable space-holder material and 90 vol. % ceramic powder. For example, the powder feedstock may comprise 5 vol. % decomposable space-holder material and 95 vol. % ceramic powder. For example, the powder feedstock may comprise 1 vol. % decomposable space-holder material and 99 vol. % ceramic powder.

[0148] The powder feedstock may comprise a composite powder and a decomposable spaceholder material, wherein the amount of decomposable space-holder material present in the powder feedstock is selected based on the desired three-dimensional porosity network of the three-dimensional micro structure. For example, the powder feedstock may comprise the composite powder in an amount ranging from 1 vol. % to 99 vol. % and may comprise the decomposable space-holder material in an amount ranging from 1 vol. % to 99 vol. %. For example, the powder feedstock may comprise 99 vol. % decomposable space-holder material and 1 vol. % composite powder. For example, the powder feedstock may comprise 95 vol. % decomposable space-holder material and 5 vol. % composite powder. For example, the powder feed stock may comprise 90 vol. % decomposable space-holder material and 10 vol. % composite powder. For example, the powder feed stock may comprise 80 vol. % decomposable 156BX9540.DOCXAttorney Docket No. 06527-2600560space-holder material and 20 vol. % composite powder. For example, the powder feed stock may comprise 70 vol. % decomposable space-holder material and 30 vol. % composite powder. For example, the powder feed stock may comprise 60 vol. % decomposable space-holder material and 40 vol. % composite powder. For example, the powder feed stock may comprise 50 vol. % decomposable space-holder material and 50 vol. % composite powder. For example, the powder feed stock may comprise 40 vol. % decomposable space-holder material and 60 vol. % composite powder. For example, the powder feed stock may comprise 30 vol. % decomposable space-holder material and 70 vol. % composite powder. For example, the powder feed stock may comprise 20 vol. % decomposable space-holder material and 80 vol. % composite powder. For example, the powder feed stock may comprise 10 vol. % decomposable space-holder material and 90 vol. % composite powder. For example, the powder feedstock may comprise 5 vol. % decomposable space-holder material and 95 vol. % composite powder. For example, the powder feedstock may comprise 1 vol. % decomposable space-holder material and 99 vol. % ceramic powder.

[0149] The method comprises selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock. The layer of binder material directly contacts at least a portion of the layer of powder feedstock. The binder material may be deposited over the entire layer of the powder feedstock. Alternatively, the binder material may be deposited over select areas of the layer of the powder feedstock. The deposition of the binder material over at least a portion of the layer of the powder feedstock binds the powder feedstock and the binder material together to form a composite green part. As used herein, “composite green part” means a part that contains the bonded powder feedstock and binder material, but the part un- sintered.

[0150] The binder material is applied from a nozzle that passes over the layer of the powder feedstock. The binder material is deposited from the nozzle as a liquid. The binder material is deposited from the nozzle according to a predetermined pattern or a design (e.g., a Computer-Aided Design (CAD) model).

[0151] The binder material may be any material that binds to the powder feedstock during printing and is subsequently removed (e.g., by evaporation or burning off) during the one or more heating processes, for example during a heating step and / or during sintering.

[0152] The binder material may comprise a polymer, a solvent, or combinations thereof.

[0153] For example, the binder material may comprise a polymer, such as a synthetic or a natural polymer. Suitable polymers for the binder material are not particularly limited and may include polyurethane, polyethylene, polypropylene, acrylic, epoxy, furan, phenolic polymers,166BX9540.DOCXAttorney Docket No. 06527-2600560or combinations thereof. The binder material may comprise natural polymers, such as wax, gums, polysaccharides, biopolymers (e.g., pectin), geopolymers (e.g., sodium silicate and sodium hydroxide), or combinations thereof. The polymer is selected such that the polymer bums off during the one or more heating processes.

[0154] For example, the binder material may comprise a solvent. Suitable solvents for the binder material are not particularly limited and may include organic solvents and water. The organic solvent is selected such that the solvent evaporates during the one or more heating processes.

[0155] The binder material may further comprise decomposable particles, evaporable particles, metal particles, ceramic particles, composite particles, or a mixture thereof. The particles, when present, may be selected such that the particles bum off during the one or more heating processes, such as during a heating step and / or during sintering, and leave voids where they previously occupied. The particles, when present, may also be selected such that they enhance the sintering process, or may be removed in an additional post-treatment step, such as etching, to reveal another porosity level.

[0156] The decomposable particles, evaporable particles, metal particles, ceramic particles, or composite particles may be particles having a diameter that cannot be included in the layer of powder feedstock due to size. For example, the particles may have a diameter of less than 2 pm. For example, the particles may comprise a diameter of less than or equal to 1.5 pm, such as less than or equal to 1 pm, such as less than or equal to 900 nanometers (nm), such as less than or equal to 800 nm, such as less than or equal to 700 nm, such as less than or equal to 600 nm, such as less than or equal to 500 nm, such as less than or equal to 400 nm, such as less than or equal to 300 nm, such as less than or equal to 200 nm, such as less than or equal to 100 nm, or such as less than or equal to 50 nm.

[0157] In one non-limiting embodiment, the powder feedstock comprises a metal powder and the binder material comprises a polymer.

[0158] In another non-limiting embodiment, the powder feedstock comprises a metal powder and a decomposable space-holder material and the binder material comprises a polymer. For example, the powder feedstock may comprise an Inconel® 625 powder and PMMA particles.

[0159] In another non-limiting embodiment, the powder feedstock comprises a metal powder and the binder material comprises a solvent, such as water.

[0160] In another non-limiting embodiment, the powder feedstock comprises a metal powder and a decomposable space-holder material and the binder material comprises a solvent, such176BX9540.DOCXAttorney Docket No. 06527-2600560as water. For example, the powder feedstock may comprise an Inconel® 625 powder and PMMA particles.

[0161] In another non-limiting embodiment, the powder feedstock comprises a ceramic powder and the binder material comprises a polymer.

[0162] In another non-limiting embodiment, the powder feedstock comprises a ceramic powder and a decomposable space-holder material and the binder material comprises a polymer.

[0163] In another non-limiting embodiment, the powder feedstock comprises a ceramic powder and the binder material comprises a solvent, such as water.

[0164] In another non-limiting embodiment, the powder feedstock comprises a ceramic powder and a decomposable space-holder material and the binder material comprises a solvent, such as water.

[0165] In another non-limiting embodiment, the powder feedstock comprises a composite powder and the binder material comprises a polymer.

[0166] In another non-limiting embodiment, the powder feedstock comprises a composite powder and a decomposable space-holder material and the binder material comprises a polymer.

[0167] In another non-limiting embodiment, the powder feedstock comprises a composite powder and the binder material comprises a solvent, such as water.

[0168] In another non-limiting embodiment, the powder feedstock comprises a composite powder and a decomposable space-holder material and the binder material comprises a solvent, such as water.

[0169] In the binder-jet printing process, the process of spreading a layer of powder feedstock and sequentially depositing a layer of binder material is repeated for the entirety of the composite green part’s height.

[0170] For example, after the powder feedstock is bound together with the binder material in a print layer, the build platform moves downward (e.g., along a y-axis) and the recoating blade spreads another even layer of the powder feedstock onto the previously printed layer. A layer of the binder material is then selectively deposited over at least a portion of the layer of the powder feedstock. This sequential process is repeated until the desired composite green part is obtained.

[0171] The powder feedstock of each layer may be the same. Alternatively, the powder feedstock of each layer may be different. Based on the composition of the powder feedstock, the powder feedstock of each layer may be spread to have the same height (i.e., the same 186BX9540.DOCXAttorney Docket No. 06527-2600560thickness). Alternatively, based on the composition of the powder feedstock, the powder feedstock of each layer may be spread to have the different heights (i.e., different thicknesses). Depositing specific mixtures of powder feedstock for different layers allows for porosity networks having directionality and tunable flow resistance in-between layers.

[0172] The binder material of each layer may be the same. Alternatively, the binder material of each layer may be different.

[0173] During the binder-jet printing process, the composite green part remains encapsulated in excess powder feedstock, which is an accumulation of the layers of powder feedstock that were not contacted with and bound to the binder material.

[0174] The method comprises, after forming the composite green part, curing the binder material of the composite green part to form a cured composite green part. As used herein, “cured composite green part” means that the part contains the bonded powder feedstock and hardened binder material, but the part remains un-sintered. This curing process hardens the binder material so that the part can be handled for further processing.

[0175] For example, the composite green part may be heated to a sufficient temperature for a sufficient time to cure (e.g., harden) the binder material. For example, the composite green part may be heated to a temperature of less than or equal to 200 degrees Celsius (°C), such as less than or equal to 150 °C, or such as less than or equal to 100 °C, to cure the binder material. Alternatively, the composite green part may be left at room temperature (e.g., 25 °C) for a time sufficient to cure (e.g., harden) the binder material. The composite green part is cured while remaining encapsulated in excess powder feedstock.

[0176] Alternatively, the composite green part may be subjected to radiation, such as ultraviolet radiation, to cure (e.g., harden) the binder material.

[0177] The method comprises, after forming the cured composite green part, removing excess powder feedstock from the cured composite green part. The cured composite green part is removed from the excess powder feedstock. In addition, any unbound powder feedstock positioned within the cured composite green part is removed. For example, the unbound powder feedstock positioned within the cured composite green part may be removed by pressurized air.

[0178] The method comprises, after removing the excess powder feedstock from the cured composite green part, sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional microstructure comprising the three-dimensional porosity network.196BX9540.DOCXAttorney Docket No. 06527-2600560

[0179] The cured composite green part is sintered at relatively high temperature. The sintering step is a powder densification step that results in the consolidation of the powder particles. For example, the cured composite green part may be sintered at a temperature ranging from 1150 °C to 1320 °C, or such as from 1170 °C to 1290 °C. The cured composite green part may be sintered for a time ranging from several minutes to several hours. For example, the cured composite green part may be sintered for at least 2 hours, for at least 3 hours, for at least 4 hours, for at least 5 hours, or for at least 6 hours. The cured composite green part may be sintered in an inert gas atmosphere (e.g., argon, hydrogen, natural gas, or combinations thereof) or may be sintered in a vacuumed atmosphere.

[0180] The sintering process of powders requires high temperatures and occurs in a sequential manner with the smallest pores shrinking and breaking up first, followed by the intermediate sized pores, and finally the largest sized pores. Therefore, sintering can be used to control the final porosity of the three-dimensional porosity network.

[0181] The sintering time, sintering temperature, and sintering atmosphere are selected depending upon the desired three-dimensional porosity network of the three-dimensional microstructure, the composition of the powder feedstock, the presence or absence of the decomposable space-holder material, as well as the desired pore size distribution, pore connectivity, pore location, and pore homogeneity. An exemplary effect of sintering time on the resulting three-dimensional porosity network is shown in FIG. 1.

[0182] As non-limiting examples, FIGS. 2 and 3 show the effect of sintering temperature on the resulting relative bulk density for three-dimensional microstructures prepared from various powder feedstocks. The powder feedstocks of FIG. 2 included only spherical Inconel® 625 metal powder (i.e., 100 vol. % metal powder) or included spherical Inconel® 625 metal powder (i.e., 30 vol. % to 90 vol. %) in combination with PMMA particles (i.e., 10 vol. % to 70 vol. %), as the decomposable space-holder material. The powder feedstocks of FIG. 3 included only irregularly shaped Inconel® metal powder (i.e., 100 vol. % metal powder) or included irregularly shaped Inconel® 625 metal powder (i.e., 30 vol. % to 90 vol. %) in combination with PMMA particles (i.e., 10 vol. % to 70 vol. %), as the decomposable space-holder material. As shown in FIG. 2, as the sintering temperature increases, the relative Archimedes density also increases, with the three-dimensional microstructures reaching a relative Archimedes density of between approximately 92% to 99% after sintering at a temperature of 1290 °C. As shown in FIG. 3, as the sintering temperature increases, the relative Archimedes density also increases, with the three-dimensional microstructures reaching the highest relative Archimedes density of between approximately 90% to 96% after sintering at a temperature of 1260 °C.206BX9540.DOCXAttorney Docket No. 06527-2600560

[0183] The method may optionally further comprise, prior to sintering the cured composite green part, heating the cured composite green part to a sufficient temperature for a sufficient time to decompose the binder material and the decomposable space-holder material, when present. This heating step is performed at elevated temperatures, where the heating temperature and heating time is dependent upon the composition of the binder material and / or the presence and composition of the decomposable space-holder material. This optional heating step bums-off and / or evaporates the binder material and the decomposable space-holder material, when present, prior to the sintering step.

[0184] For example, the cured composite green part may be heated to a temperature of less than or equal to 700 degrees Celsius (°C), such as less than or equal to 650 °C, such as less than or equal to 600 °C, such as less than or equal to 550 °C, such as less than or equal to 500 °C, such as less than or equal to 450 °C, such as less than or equal to 400 °C, such as less than or equal to 350 °C, such as less than or equal to 300 °C, or such as less than or equal to 250 °C.

[0185] The cured composite green part may be heated for a time ranging from several minutes to several hours. For example, the cured composite green part may be heated for at least 30 minutes, for at least 1 hour, for at least 2 hours, for at least 3 hours, for at least 4 hours, for at least 5 hours, or for at least 6 hours.

[0186] The inclusion of the heating step prior to sintering, as well as the heating temperature, heating time, and heating atmosphere, depends upon the desired three-dimensional porosity network of the three-dimensional microstructure. For example, when the binder material and / or decomposable space-holder material are not burned-off or evaporated in the heating step, the resulting three-dimensional porosity network of the three-dimensional microstructure may contain much finer connected porosity, as compared to a three-dimensional porosity network of a three-dimensional micro structure in which the cured composite green part was heated in this heating step. An exemplary effect of heating temperature on the resulting three-dimensional porosity network is shown in FIG. 4.

[0187] The three-dimensional porosity network of the three-dimensional microstructure comprises a layered porosity network, a complex- shaped porosity network, an isotropic porosity network, or combinations thereof.

[0188] As used herein, “a layered porosity network” means alternating layers of a denser matrix (i.e., metal or ceramic) with induced fine channel and bulk porosity and highly porous layers that interconnect the dense matrix layers through the few metal particles that act as interconnections (e.g., pillars) in-between dense layers and ensure structural integrity.216BX9540.DOCXAttorney Docket No. 06527-2600560

[0189] As used herein, “an isotropic porosity network” means a large porosity connected through fine channels in a denser matrix (i.e., metal or ceramic), with no specific orientation and randomly distributed porosity.

[0190] As used herein, “a complex-shaped porosity network” means a porosity network that is formed from three types of pores, including (i) interstices between the particles in the printed layers controlled by the shape and size of the particles, (ii) particle packing defects in the layers created by inefficient particle packing and the decomposable space- holder material (when present) and (iii) interlayer porosity created by the printing process. The complex shaped porosity can be formed in three-dimensions via local binder-jet printing process modifications.

[0191] For example, the three-dimensional porosity network of the three-dimensional microstructure may comprise a layered porosity network. Exemplary three-dimensional porosity networks comprising a layered porosity network are shown in FIGS. 5A-5C and 6. In FIG. 5A, the three-dimensional porosity network is a layered porosity with alternating porous and dense channels. In each of FIGS. 5B and 5C, the three-dimensional porosity network is a layered porosity with alternating regions of high and low density. The three-dimensional network of FIG. 5A would provide the highest flow rates and permeability, while the three-dimensional network of FIG. 5C would provide the lowest permeability rates (e.g., for filtration purposes). FIG. 6 shows layered porosity over a plurality of layers, where the layered porosity was obtained by including varying amounts of a decomposable space-holder material (e.g., PMMA particles) in each layer.

[0192] For example, the three-dimensional porosity network of the three-dimensional microstructure may comprise an isotropic porosity network. Exemplary three-dimensional porosity networks comprising isotropic layered porosity are shown in FIGS. 7 and 8. In each of FIGS. 7 and 8, the three-dimensional porosity network includes large pores and fine connecting channels. As shown in FIG. 8, the large pores of the isotropic porosity network may be formed from the inclusion and degradation of packing of the decomposable spaceholder material (e.g., PMMA particles) in the powder feedstock and the fine connecting channels of the isotropic porosity network as a result of evaporation during sintering.

[0193] Three levels of pore structure that determine the three-dimensional porosity network include packing interstices, packing defects, and interlayer defects are shown in FIG. 8.

[0194] Packing interstices form between powder particles in the layer of the powder feedstock and lead to the smallest pores. The size and shape of the resulting pores are controlled by the shape, size, and size distribution of the powder particles within the powder feedstock.226BX9540.DOCXAttorney Docket No. 06527-2600560

[0195] Packing defects also form between powder particles in the layer of the powder feedstock, but as shown in FIG. 9, are larger in size than the pores created by the packing interstices. Packing defects may be intrinsic to the printing process (e.g., controlled by the deposition rate of the layer of the powder feedstock, controlled by the spreading speed of the layer of the powder feedstock, and / or controlled by the binder material). Alternatively, packing defects may be created by inefficient particle packing or including the decomposable spaceholder material in the powder feedstock.

[0196] Interlayer defects occur at the layer interfaces due to the packing of the powder feedstock material and is a result of the binder-jet printing process. These interlayer defects tend to be larger than both the packing interstices and the packing defects, as shown in FIG. 9, and can be further increased in size by incorporating the decomposable space-holder material into alternating or specific layers.

[0197] If the printed layers (i.e., a layer of powder feedstock bonded to a layer of binder material) do not contain defects that extend through the printed layer, the permeability of the three-dimensional porosity network will be controlled by the interconnecting packing interstices in the printed layers. These are the finer pores which lead to the lowest permeabilities of the three-dimensional porosity network. For example, depending on the particle size of the powder feedstock used in the binder-jet printing process, the interconnecting packing interstices may result in hydraulic diameters below 1 pm. Subsequent sintering and / or heating prior to sintering will lead to the break-up of these pore interstices to further decrease the hydraulic diameter of the three-dimensional porosity network.

[0198] When the print layers (i.e., a layer of powder feedstock bonded to a layer of binder material) contain packing defects, the permeability of the three-dimensional porosity network will depend upon the connectivity of the packing defects. If the packing defects are isolated from one another, the packing defects will be connected by smaller packing interstices, making the permeability of the three-dimensional porosity network not much higher than that of a three-dimensional porosity network formed from print layers without defects. However, when the packing defects become connected, such as through connecting throats, the connected throats control the hydraulic diameter of the three-dimensional porosity network, which can lead to permeabilities that are at least an order of magnitude higher than that of a three-dimensional porosity network formed from print layers without packing defects.

[0199] In addition, the packing defects may connect adjacent printed layer interfaces. In these conditions, the size, shape, and orientation of the packing defects will control the connectivity of the packing defects and the size of the throats, and ultimately the permeability of the three- 236BX9540.DOCXAttorney Docket No. 06527-2600560dimensional porosity network. Decomposable space-holder materials can be added to the powder feedstock to control the packing defect populations and ultimately the permeability of three-dimensional porosity network of the three-dimensional microstructure.

[0200] Densification during sintering can cause the pore structures within the print layers to become isolated from the interlayer defects, making the connected pore structures directional along the low-density print layer interfaces or the low-density print layers that are prepared with high fractions of the decomposable space-holder material. This creates an oriented three-dimensional porosity network that has a lower tortuosity, resulting in higher flow rates along the layer interfaces than a comparable homogeneous material. An exemplary three-dimensional micro structure having an oriented three-dimensional porosity network is shown in FIG. 10.

[0201] The method may further comprise, after sintering, coating the three-dimensional porosity network of the three-dimensional microstructure with a coating composition.

[0202] The three-dimensional porosity network of the three-dimensional microstructure may be coated to further decrease the pore size or hydraulic diameter of the three-dimensional porosity network, as shown in FIG. 11. For example, the hydraulic diameter of the three-dimensional porosity network may be reduced to less than 1 pm using a coating composition.

[0203] The coating composition may comprise a liquid carrier and solid particles, wherein the solid particles are dispersed in the liquid carrier.

[0204] The solid particles of the coating composition may comprise a diameter of 5 pm or less, such as 4 pm or less, such as 3 pm or less, such as 2 pm or less, such as 1 pm or less, such as 900 nm or less, such as 800 nm or less, such as 700 nm or less, such as 600 nm or less, such as 500 nm or less, such as 400 nm or less, such as 300 nm or less, such as 200 nm or less, such as 100 nm or less, such as 50 nm or less, or such as 10 nm or less.

[0205] The three-dimensional porosity network of the three-dimensional microstructure may be coated to functionalize the three-dimensional porosity network. For example, the coating composition may comprise a functional compound, which may include, but is not limited to an antimicrobial compound, a catalytic compound, a MOF compound, or combinations thereof.

[0206] After applying the coating composition to the three-dimensional porosity network, the three-dimensional microstructure may be heated to form a dried coating in the three-dimensional porosity network. When the coating composition comprises solid particles, the solid particles remain within the three-dimensional porosity network, as shown in FIG. 11(c), after heating.246BX9540.DOCXAttorney Docket No. 06527-2600560

[0207] The three-dimensional porosity network may be coated by dipping the three-dimensional micro structure in any of the coating compositions described herein. The three-dimensional microstructure may be dipped in the coating composition for a time sufficient for the coating composition to sufficiently coat the three-dimensional porosity network.

[0208] The three-dimensional microstructures prepared according to the method described herein includes the three-dimensional porosity network dispersed within a sintered solid matrix. The sintered solid matrix comprises a sintered metal material, a sintered ceramic material, a sintered composite material, or mixtures thereof and the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.

[0209] The three-dimensional porosity network of the three-dimensional micro structure prepared according to the method described herein, can be tuned using alternations in the powder feedstock (e.g., the inclusion of decomposable space-holder materials and / or selection of the size and shape of the metal powder or ceramic powder) in combination with the intrinsic intralayer powder packing voids (i.e., interstitial defects and packing defects), interlayer printing defects, printing parameters, and / or sintering parameters to vary the hydraulic pore diameter, and thus permeabilities, that span several orders of magnitude, as well as allowing for directional channeling. Burning off the decomposable space-holder material (when present), sintering the cured composite green part, and optionally coating the three-dimensional porosity network can further enhance the functionality of the three-dimensional microstructures by creating three-dimensional microstructures having controlled connected porosity, strong sintered connections, and / or functionalized properties (e.g., antibacterial properties).

[0210] The three-dimensional microstructures comprising the three-dimensional porosity network described herein also minimize weight, while simultaneously maximizing surface area.

[0211] The three-dimensional microstructures comprising the three-dimensional porosity network described herein may be used as porous structures.

[0212] For example, the porous structures may be used as filters for gas streams or liquid streams.

[0213] Alternatively, the porous structures may be used for heat exchangers, light-weight structural components, thermal insulation, acoustic insulation, and / or for energy or gas storage applications.256BX9540.DOCXAttorney Docket No. 06527-2600560

[0214] For example, the three-dimensional microstructures comprising the three-dimensional porosity network described herein may be used as a filter for removing particulates from an exhaust gas stream. These filters may be printed from a powder feedstock comprising metal powders. Alternatively, these filters may be printed from a powder feedstock comprising ceramic powders. Alternatively, these filters may be printed from a powder feedstock comprising composite powders.

[0215] For example, the three-dimensional microstructures comprising the three-dimensional porosity network described herein may be used as a filter for removing fine sediment, pathogens (e.g., bacteria, viruses, and / or parasites), and combinations thereof from a liquid stream, such as a water stream. These filters may be printed from a powder feedstock comprising metal powders, such as a copper. Alternatively, these filters may be printed from a powder feedstock comprising ceramic powders, such as clay. Alternatively, these filters may be printed from a powder feedstock comprising composite powders. The three-dimensional microstructures comprising the three-dimensional porosity network described herein may be used as a flow retarder, such as a flow retarder for gas streams or liquid streams, since the flow resistance of the three-dimensional porosity network can be finely tuned. The three-dimensional microstructure comprising may provide directional flow.

[0216] The flow resistance of the three-dimensional porosity network can be controlled through the particle size and size distribution of the powder feedstock, the addition of decomposable space-holder materials in the powder feedstock, particle morphology of the powder feedstock, and / or sintering parameters.

[0217] As shown in FIG. 12, when the three-dimensional porosity network comprises a layered porosity network, the three-dimensional porosity network can provide anisotropic flow. As used herein, “anisotropic” means having a physical property that has a different value when measured in different directions.

[0218] As shown in FIG. 12, for a layered porosity network, when the direction of flow of the gas stream or the water stream is from left to right through the three-dimensional porosity network, the gas stream or liquid stream has low resistance as it passes through the pores (e.g., a throat structure) and a high resistance as it passes through the densified metal, ceramic, or composite portion. When the direction of flow of the gas stream or the liquid stream is from the top of the three-dimensional porosity network, the gas stream or liquid stream has low resistance as it passes through the pores (e.g., the throat structure), but has high resistance as it is passes through the densified metal, ceramic, or composite portion.266BX9540.DOCXAttorney Docket No. 06527-2600560

[0219] The present invention is described in the following illustrative, non-limiting examples. Numerous possible modifications and variations will be apparent to those skilled in the art. EXAMPLESExample 1

[0220] Spherical gas or irregular water atomized Inconel® 625 powders were each mixed with PMMA powder for one hour to form the powder feedstock. Powder mixtures with 0-70 vol. % PMMA were prepared by mixing 500 grams of the corresponding ratio. The powder feedstock was characterized for particle size, particle size distribution, and morphology. The apparent and tapped densities of the powder feedstock were measured following ASTM B527-22 standard but manually tapping the powder container. The relative densities were calculated by normalizing by the density of the composite powder.

[0221] The gas atomized Inconel® 625 (GA) / PMMA mixtures were composed of spherical particles with varying size distributions, while the water atomized Inconel® 625 (WA) / PMMA mixtures included a combination of irregular and spherical shapes and particle size, as shown in FIG. 13. This effect was directly reflected in the powders apparent and tapped density behavior.

[0222] The nominal apparent and tapped density of the powder mixtures decreased with increasing PMMA content in a nearly linear trend, with about 0.6 grams per cubic centimeter (g / cm3) between the two measurements, and 1 g / cm3between the GA and WA mixtures. However, this trend shows a combined effect of the powder mixture density and powder characteristics (size and shape). From the rule of mixtures, it is known that increasing values of PMMA, will result in smaller powder density. However, when normalizing the apparent and tapped densities by the respective composite densities to calculate the packing fraction, a nearly opposite trend was observed for the relative values.

[0223] For both types of mixtures, the GA and WA mixtures, the measurements reflected a near constant 10% increase after tapping. For WA mixtures, increasing the PMMA content resulted in an increased density, as the morphology had a dominant effect over particle size, with the spherical polymer particles contributing to the better packing in contrast with the irregular metal particles. For GA mixtures, there was an original decrease in apparent and relative density upon addition of 10 vol. % PMMA, which then leveled off until 50 vol. % additions, after which the values decreased again. The powder density and the relative densities as a function of PMMA content are provided in FIGS. 14A and 14B, respectively.

[0224] Binder-jet printing was carried out in an ExOne Innovent printer for powder feedstocks containing between 0-30 vol. % PMMA. Binder-jet printing was carried out in an ExOne XI- 276BX9540.DOCXAttorney Docket No. 06527-2600560Lab printer for powders with more than 50 vol. % PMMA. Printing parameters included 150 pm layer thickness and 65% binder material saturation. The binder material was a solvent provided by ExOne or was an aqueous binder provided by ExOne.

[0225] Curing was performed at 100 °C for 6 hours. The cured composite green part was depowdered and the green density was measured geometrically with a Mitutoyo caliper (3 measurements for each orientation per sample). Sintering was carried out in a Lindberg BlueM tube furnace. The sintering temperatures were chosen based on each powder’ s expected solidus temperature and ranged from 1170 °C to 1290 °C.

[0226] After sintering, density was measured through the Archimedes principle, dimensional changes were measured with calipers, surface characterization was performed with a scanning electron microscope equipped with energy-dispersive spectroscope, and the multi-line surface profile irregularities were measured with an optical profilometer. The profile (P) and not the roughness (P) was measured to account for the large and intermediate-scale defects. Sample cross-sections were prepared through metallography by grinding and polishing with colloidal silica. Mechanical integrity of the three-dimensional microstructure’s compressive behavior was performed through spherical indentation.

[0227] A similar behavior and magnitude to the relative apparent density of the powder feedstock was also observed for the green density of the as-printed and cured parts, where the relative density (normalized by the composite density) increased for the WA mixture as the addition of spherical PMMA particles improved the packing, but decreased for the GA mixtures, as shown in FIG. 15.

[0228] The density increased for all PMMA contents with increasing temperature, with a common overlap of the 10 and 20 vol. % PMMA samples, and a general order of decreasing density for increasing PMMA content within each temperature. However, at high temperatures it was noticed that there was a temperature at which the porosity created by 10 and 20 vol. % PMMA is lost, and the same density was achieved as the 100 vol. % Inconel® 625 samples (1245 °C for WA and 1275 °C for GA). At high temperatures, it was also noticed that there was a large discontinuity in the densification behavior of samples containing 60 and 70 vol.% PMMA, as it increases from 36 to 76% within 15 °C difference for WA mixtures, and from 50 to 98% for GA mixtures. At this temperature, partial melting, massive shrinkage, and major pore closure occurs and the remaining porosity is expected to be isolated. At the maximum sintering temperature partial melting was observed for all samples. The sintered density and porosity of the sintered parts formed from the WA mixtures are provided in FIGS. 16A and286BX9540.DOCXAttorney Docket No. 06527-260056016B, respectively. The sintered density and porosity of the sintered parts formed from the GA mixtures are provided in FIGS. 17A and 17B, respectively.

[0229] To observe the surface behavior of the samples, upon sintering and evaporation of the PMMA particles, surface roughness at the top surface (i.e., the top surface during printing and sintering) was examined. All the PMMA fractions of the minimum and the maximum temperature without partial melting were examined. For the WA mixture, Pzvalues remained nearly constant until 70 vol. % PMMA where there was a 50% increment, but in all cases the higher sintering temperature appeared to result in higher surface irregularity (FIG. 18 A). For the GA mixtures, there was a continuous increment in surface roughness with increasing PMMA volume with the lower sintering temperature having a slightly higher Pzvalue, but within deviation of the higher sintering temperature (FIG. 18B). For the 70 vol.% PMMA sample, there is an inversion of the trend and a large measurement deviation (FIG. 18B).

[0230] The roughness profiles showed that two major defects were present: (1) horizontal straight lines produced by the binder deposition; and (2) surface depression, commonly deeper at the sample center and particularly noticeable at the high PMMA loadings, and at higher sintering temperature. The second defect seemed to be enhanced by the presence of the PMMA particles and may be attributed to the evaporation of PMMA during sintering.

[0231] Further analysis of the surface included observation of necking sites and carbide formation at a much finer scale (FIG. 19). As Inconel® 625 is a carbide former based on its alloying elements, it was expected that the decomposition of PMMA during burnout would introduce carbides.

[0232] High temperature sintered Inconel® 625 parts produced from a powder feedstock having 0 vol. %, 30 vol. %, and 60 vol. % PMMA particles (FIG. 20(a)-(c), respectively) and low temperature sintered Inconel® 625 parts produced from a powder feedstock having 0 vol. %, 30 vol. %, and 60 vol. % PMMA particles (FIG. 20(d)-(f), respectively) were imaged using micro-computed tomography, where porosity appears as the darker gray in the images and the solid material appears as white or light grey in the images. At high sintering temperatures, feedstock powder particles were more difficult to identify within the solid material (white or light grey in the images) since sintering has progressed. At low sintering temperatures, individual feedstock particles were visible since they only necked with each other. With an increasing amount of PMMA particles used as decomposable space-holder during printing, larger voids were seen within the cross sections. In addition, the larger porosity was connected via fine porosity that was present between the feedstock powder particles even without any296BX9540.DOCXAttorney Docket No. 06527-2600560PMMA decomposable space-holder. At higher sintering temperatures, and 60 vol. % PMMA, there was no visible fine porosity left.Prophetic Example 1

[0233] Gasoline particulate filters are required for direct injection engines which have been introduced to give high specific power, low fuel consumption, and fast catalyst light-off capability compared to port injection engines. However, direct injection into the piston cylinder results in higher particulate concentrations in the exhaust. These filters involve challenging thermomechanical conditions and so durable metal filters are required.

[0234] A three-dimensional microstructure, to be used as a gasoline particulate filter, having a high flow rate structure will be made by including a decomposable space-holder material in the powder feedstock to control the packing defects in the layer of powder feedstock.Prophetic Example 2

[0235] Ceramic water filters with high efficacy against fine sediment and pathogens, such as bacteria and parasites, have higher durability and higher resistance to chemical antifouling strategies than equivalent polymer membranes. Such filters can be used to clean drinking water and also wastewater that is consequently released back into surface water.

[0236] A three-dimensional microstructure, to be used as a filter for water, will be made from a powder feedstock comprising clay and that will be sintered at a temperature as low as 900°C. The three-dimensional microstructure, to be used as a filter for water, will have a low hydraulic diameter, such as below 10 pm. This will be done by controlling the packing defects in the layer of powder feedstock and by coating the three-dimensional porosity network, after sintering, with a clay slip.Prophetic Example 3

[0237] A three-dimensional microstructure having oriented pore structures that have lower tortuosity will be made. The resulting micro structure will result in high figure of merit values for high flow rate filter applications. This will be done by sintering the structures into late intermediate stage sintering to reduce the permeability through the print layers, so that the flow occurs in the interlayer regions and / or through layers made with high content of decomposable space-holder material.Prophetic Example 4

[0238] A three-dimensional microstructure, to be used for directional heat transfer, will be made.306BX9540.DOCXAttorney Docket No. 06527-2600560Prophetic Example 5

[0239] A layered three-dimensional micro structure will be made. The layered microstructures will be made by different functional metallic materials (e.g., metallic materials that change temperature when a magnetic field is applied). These materials are magnetocaloric materials and are used as higher efficiency cooling materials in refrigeration.Prophetic Example 6

[0240] A three-dimensional microstructure, to be used as a light-weight structural material, will be made. The three-dimensional micro structure will be stronger in one direction verses another direction. Alternatively, the three-dimensional microstructure will have complexshaped porosity networks that are parallel or perpendicular to the load directions.Prophetic Example 7

[0241] A three-dimensional microstructure, to be used in energy storage applications, will be prepared. For example, the three-dimensional microstructure can be used in batteries to provide high surface area anode or cathode surfaces.

[0242] Prophetic Example 8

[0243] A three-dimensional microstructure, to be used for hydrogen gas storage or hydrogen gas transmission, will be prepared. The three-dimensional micro structure will be prepared to have a three-dimensional porosity network to provide directional hydrogen gas flow.

[0244] Prophetic Example 9

[0245] A three-dimensional microstructure, to be used as a thermal insulation material, will be prepared. The three-dimensional micro structure will be prepared to have a three-dimensional porosity network, where air trapped within the three-dimensional porosity network can reduce heat transfer.

[0246] Prophetic Example 10

[0247] A three-dimensional microstructure, to be used as a sound insulation material, will be prepared. The three-dimensional micro structure will be prepared to have a three-dimensional porosity network, where sound waves can be absorbed by the three-dimensional porosity network.

[0248] Although representative processes and articles have been described in detail herein, those skilled in the art will recognize that various substitutions and modifications may be made without departing from the scope of what is described and defined by the appended claims.316BX9540.DOCX

Claims

Attorney Docket No. 06527-2600560What is Claimed Is:

1. A method of making a three-dimensional microstructure comprising a three-dimensional porosity network, the method comprising:spreading a layer of a powder feedstock, by binder-jet printing, over a build surface;selectively depositing a layer of a binder material, by binder-jet printing, over at least a portion of the layer of the powder feedstock to form a composite green part,wherein a process of spreading a layer of powder feedstock and sequentially depositing a layer of binder material is repeated for an entirety of a height of the composite green part;curing the binder material to form a cured composite green part; removing excess powder feedstock from the cured composite green part; and sintering the cured composite green part for a sufficient time at a sufficient temperature to generate the three-dimensional micro structure comprising the three-dimensional porosity network,wherein the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.

2. The method of claim 1 , wherein the powder feedstock of each layer may be the same or different, andwherein the binder material of each layer may be the same or different.

3. The method of claim 1 or 2, wherein the powder feedstock comprises a metal powder, a ceramic powder, a composite powder, or a mixture thereof.

4. The method of claim 3, wherein the powder feedstock comprises a metal powder.

5. The method of claim 3 or 4, wherein the metal powder comprises a metal selected from the group consisting of silver, gold, platinum, copper, nickel, tin, titanium, iron, cobalt, chromium, zinc, manganese, niobium, molybdenum, gallium, zirconium, aluminum, tungsten, combinations thereof, and alloys thereof.326BX9540.DOCXAttorney Docket No. 06527-26005606. The method of claim 4 or 5, wherein the metal powder is a functionalized metal powder.

7. The method of claim 3, wherein the powder feedstock comprises a ceramic powder.

8. The method of claim 7, wherein the ceramic powder comprises clay, alumina, zirconia, silicon carbide, silicon nitride, silicon dioxide, sand, silica, tungsten carbide, mullite, titania, cordierite, aluminum titanate, hydroxyapatite, metakaolin (calcined clay), fly ash, or combinations thereof.

9. The method of claim 8 or 9, wherein the ceramic powder is a functionalized ceramic powder.

10. The method of claim 3, wherein the powder feedstock comprises a composite powder.

11. The method of claim 10, wherein the composite powder comprises a metal-ceramic composite powder, a core-shell powder, a metal organic framework (MOF) powder, or mixtures thereof.

12. The method of claim 10 or 11, wherein the composite powder is a functionalized composite powder.

13. The method of any one of claims 3 to 12, wherein the metal powder, the ceramic powder, or the composite powder comprises a diameter of 2 microns (pm) or greater.

14. The method of any one of claims 1 to 13, wherein the powder feedstock further comprises a decomposable space-holder material.

15. The method of claim 14, wherein the powder feedstock comprises from 1 volume percent (vol. %) to 99 vol. % of metal powder or ceramic powder and from 1 vol. % to 99 vol. % of the decomposable space-holder material.336BX9540.DOCXAttorney Docket No. 06527-260056016. The method of claim 14 or 15, wherein the decomposable space-holder material comprises decomposable polymer particles, a natural material, a low-melting point metal, or combinations thereof.

17. The method of claim 16, wherein the decomposable space-holder material comprises decomposable polymer particles.

18. The method of claim 16 or 17, wherein the decomposable polymer particles are poly (methyl methacrylate) (PMMA) particles.

19. The method of any one of claims 1 to 18, wherein the binder material comprises a polymer, a solvent, or combinations thereof.

20. The method of any one of claims 1 to 19, wherein the binder material further comprises decomposable particles, evaporable particles, metal particles, ceramic particles, composite particles, or a mixture thereof, wherein the decomposable particles, evaporable particles, metal particles, ceramic particles, or composite particles comprise a diameter of less than 2 pm, such as less than or equal to 1.5 pm, such as less than or equal to 1 pm, such as less than or equal to 800 nanometers (nm), such as less than or equal to 600 nm, such as less than or equal to 400 nm, such as less than or equal to 200 nm, such as less than or equal to 100 nm, or such as less than or equal to 50 nm.

21. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a metal powder and the binder material comprises a polymer.

22. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a metal powder and a decomposable space-holder material and the binder material comprises a polymer.

23. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a ceramic powder and the binder material comprises water.346BX9540.DOCXAttorney Docket No. 06527-260056024. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a ceramic powder and a decomposable space-holder material and the binder material comprises water.

25. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a composite powder and the binder material comprises a polymer.

26. The method of any one of claims 1 to 20, wherein the powder feedstock comprises a composite powder and a decomposable space-holder material and the binder material comprises a polymer.

27. The method of any one of claims 1 to 26, further comprising, prior to sintering the cured composite green part, heating the cured composite green part to a sufficient temperature for a sufficient time to decompose the binder material and the decomposable space-holder material, when present.

28. The method of any one of claims 1 to 27, further comprising, after sintering, coating the three-dimensional porosity network of the three-dimensional microstructure with a coating composition.

29. The method of claim 28, wherein the coating composition comprises a liquid carrier and solid particles, wherein the solid particles are dispersed in the liquid carrier.

30. The method of claim 29, wherein the solid particles comprise a diameter of 5 pm or less.

31. The method of claim 29 or 30, wherein the solid particles reduce a pore size of the three-dimensional porosity network.

32. The method of claim 28, wherein the coating composition comprises a functional compound.356BX9540.DOCXAttorney Docket No. 06527-260056033. The method of claim 32, wherein the functional compound comprises an antimicrobial compound, a catalytic compound, a metal organic framework (MOF) compound, or combinations thereof.

34. The method of any one of claims 28 to 33, further comprising heating the coating composition to form a dried coating in the three-dimensional porosity network.

35. The method of any one of claims 28 to 34, wherein the three-dimensional porosity network is coated by dipping the three-dimensional microstructure in the coating composition.

36. A three-dimensional microstructure comprising a three-dimensional porosity network prepared according to the method of any one of claims 1 to 35.

37. A three-dimensional micro structure comprising:a three-dimensional porosity network dispersed within a sintered solid matrix, wherein the sintered solid matrix comprises a sintered metal material, a sintered ceramic material, a sintered composite material, or mixtures thereof, andwherein the three-dimensional porosity network comprises a layered porosity network, a complex-shaped porosity network, an isotropic porosity network, or combinations thereof.

38. The three-dimensional microstructure of claim 37, wherein the three-dimensional porosity network comprises a layered porosity network.

39. The three-dimensional microstructure of claim 38, wherein the three-dimensional porosity network is formed from alternating layers of high porosity and layers of the sintered solid matrix.

40. The three-dimensional microstructure of claim 39, wherein the layers of the sintered solid matrix comprise a density that is greater than the layers of high porosity and further comprise fine channel porosity and bulk porosity throughout the sintered solid matrix.366BX9540.DOCXAttorney Docket No. 06527-260056041. The three-dimensional microstructure of claim 39 or 40, wherein each layer of high porosity connects to each layer of the sintered solid matrix through a plurality of sintered interconnections.

42. The three-dimensional micro structure of claim 37, wherein the three-dimensional porosity network comprises an isotropic porosity network.

43. The three-dimensional micro structure of claim 42, comprising a plurality of large pores dispersed within the sintered solid matrix, wherein the large pores are interconnected through a series of fine channels dispersed throughout the sintered solid matrix.

44. The three-dimensional microstructure of claim 43, wherein the plurality of large pores is randomly dispersed within the sintered solid matrix.

45. The three-dimensional micro structure of claim 37, wherein the three-dimensional porosity network comprises a complex-shaped porosity network.

46. The three-dimensional micro structure of any one of claims 37 to 45, wherein the sintered solid matrix comprises a sintered metal material.

47. The three-dimensional micro structure of claim 46, wherein the sintered metal material comprises silver, gold, platinum, copper, nickel, tin, titanium, iron, cobalt, chromium, zinc, manganese, niobium, molybdenum, gallium, zirconium, aluminum, tungsten, combinations thereof, and alloys thereof.

48. The three-dimensional micro structure of claim 46, wherein the sintered metal material is a magnetocaloric material.

49. The three-dimensional microstructure of any one claims 37 to 45, wherein the sintered solid matrix comprises sintered ceramic material.

50. The three-dimensional micro structure of claim 49, wherein the sintered ceramic material comprises clay, alumina, zirconia, silicon carbide, silicon nitride, silicon376BX9540.DOCXAttorney Docket No. 06527-2600560dioxide, sand, silica, tungsten carbide, mullite, titania, cordierite, aluminum titanate, hydroxyapatite, metakaolin (calcined clay), fly ash, or combinations thereof.

51. The three-dimensional microstructure of any one of claims 37 to 45, wherein the sintered solid matrix comprises a sintered composite material.

52. The three-dimensional micro structure of claim 51, wherein the sintered composite material comprises a metal-ceramic composite material.

53. The three-dimensional micro structure of any one of claims 37 to 52, comprising a hydraulic diameter of less than or equal to 10 pm.

54. The three-dimensional micro structure of any one of claims 37 to 52, comprising a hydraulic diameter of less than or equal to 1 pm.

55. The three-dimensional micro structure of any one of claims 37 to 54, wherein the three-dimensional porosity network comprises a coating.

56. The three-dimensional microstructure of claim 55, wherein the coating further reduces the pore size of the three-dimensional porosity network.

57. The three-dimensional microstructure of claim 55, wherein the coating comprises a functional compound.

58. The three-dimensional micro structure of claim 57, wherein the functional compound comprises an antimicrobial compound, a catalytic compound, a MOF compound, or combinations thereof.

59. The three-dimensional microstructure of any one of claims 37 to 58, wherein the three-dimensional micro structure comprising the three-dimensional porosity network is a filter.

60. The three-dimensional micro structure of claim 59, wherein the filter is a filter for removing particulates from a gas stream.386BX9540.DOCXAttorney Docket No. 06527-260056061. The three-dimensional microstructure of claim 59, wherein the filter is a filter for removing fine sediment, pathogens, or combinations thereof from a liquid stream.

62. The three-dimensional microstructure of any one of claims 37 to 58, wherein the three-dimensional microstructure comprising the three-dimensional porosity network is a flow retarder.

63. The three-dimensional micro structure of claim 62, wherein the three-dimensional micro structure comprising the three-dimensional porosity provides directional flow.

64. The three-dimensional microstructure of any one of claims 37 to 58, wherein the three-dimensional micro structure comprising the three-dimensional porosity is a structural material.396BX9540.DOCX

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