Patent Application
20220032369
The present disclosure relates to the formation of porous metals, and more particularly to the formation of 3D periodic porous materials having an engineered, hierarchical, multi-porosity structure.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Conventionally, nanoporous metals with uniform single level porosity have been fabricated by de-alloying methods from an alloy precursor. The performance of these materials in many applications often suffers from mass transport limitations, which is specifically true for monolithic macroscopic nanomaterials. In the extreme case, mass transport limitations limit reactions to the geometrical surface of the macroscopic monolithic material, thus leaving the majority of the internal surface within the nanoporous bulk material unused (see, for example
Hierarchical nanoporous gold has been realized using template methods, for example by injecting a target metal salt to replicate the structure of a hierarchical template (Lee et al. “Developing Monolithic Nanoporous Gold with Hierarchical Bicontinuity Using Colloidal Bijels” J Phys Chem. Lett., 2014, 5, 809). However, pore size distributions and sample dimensions are determined by the template which is difficult to tune at different levels of structures. Specifically, anisotropic templates are difficult to realize by nature's self-organization and self-assembly methods. For example, Lee and his co-workers (Lee et al., supra) used colloidal Bijels as template materials. By filling the template with HAuC14 and AgNO3 solutions with the desired composition, and then followed up with an annealing process to form the alloys and remove the template. Finally, a de-alloying process was used to remove Ag from AgAu alloys.
Bulk hierarchical nanoporous gold has also been prepared using a multi-step corrosion-deposition-annealing-de-alloying process (see Qi et al. “Hierarchical Nested-Network Nanostructure by De-alloying” ACS Nano, 2013, 7, 5948). The corrosion-deposition-annealing-de-alloying process is limited by the availability of suitable starting alloys. Solid solution alloys which present only a tiny fraction of binary alloys are so far the only reported system for this process. For example, Qi and Weissmueller (Qi et al., supra) chose a dilute AgAu alloy with the gold content of 5 atomic percent as a starting alloy, whereas the normal gold composition range for dealloying is 20-50 atomic percent. They then used an electrochemically controlled de-alloying process to partially remove Ag from the dilute AgAu alloy to form a nanoporous AgAu alloy with a high residual Ag content, which is enough to perform a second de-alloying process. It should be noted that the normal composition range for dealloying cannot achieve such a high residual Ag concentration, and therefore it is not possible to perform a second de-alloying process. The obtained nanoporous AgAu alloy was annealed at 30020 C. for 3 hours to form the upper hierarchy structure with a ligament size of ˜200 nm. A second de-alloying process introduces the lower level hierarchical structures with a size of ˜20 nm. However, this process also does not allow for the realization of anisotropic pore architectures required for directed mass transport.
In one aspect the present disclosure relates to a system for using a feedstock to form a three dimensional, hierarchical, porous metal structure with deterministically controlled 3D multiscale porous architectures. The system may comprise a reservoir for holding the feedstock, the feedstock including a rheologically tuned alloy ink. A printing stage may be included for receiving the feedstock. A processor including a memory may be included which is configured to help carry out an additive manufacturing printing process to produce a three dimensional (3D) structure using the feedstock in a layer-by-layer fashion, on the printing stage. A nozzle may be included for applying the feedstock therethrough onto the printing stage. A de-alloying subsystem may be included for further processing the 3D structure through a de-alloying operation to form a de-alloyed 3D structure having several distinct, differing pore length scales ranging from a digitally controlled macroporous architecture to a nanoporosity introduced by the de-alloying operation.
In another aspect the present disclosure relates to a system for forming a three dimensional, hierarchical, porous metal structure with deterministically controlled 3D multiscale hierarchical pore architectures. The system may comprise a printing stage and an additive manufacturing system having a processor and a nozzle. The additive manufacturing system may be configured to print a three dimensional (3D) structure in a layer-by-layer process by flowing a rheologically tuned ink through the nozzle onto the printing stage, and to build up the 3D structure in a layer-by-layer operation. The system may also include an annealing subsystem configured to anneal the 3D structure to remove the binder, and to form an alloyed 3D structure. The system may also include a de-alloying subsystem configured to de-alloy the alloyed 3D structure to form a hierarchical, nanoporous 3D structure having an engineered, digitally controlled macropore morphology with integrated nanoporosity.
In still another aspect the present disclosure relates to a system for forming a three dimensional, hierarchical, porous metal structure with deterministically controlled 3D multiscale hierarchical pore architectures. The system may comprise a printing stage, a rheologically tuned, flowable ink including a metal powder and a binder, and an additive manufacturing system having a processor for controlling a printing process. The additive manufacturing system may have a nozzle and may be configured to print a three dimensional (3D) structure in a layer-by-layer process by flowing the rheologically tuned ink through the nozzle onto the printing stage. In this manner the 3D structure is built up in a layer-by-layer printing operation. An annealing subsystem may be configured to anneal the 3D structure by heating the 3D structure for a predetermined time period to remove the binder, to form an alloyed 3D structure. A de-alloying subsystem may be included which is configured to de-alloy the alloyed 3D structure to form a hierarchical, nanoporous 3D structure. The hierarchical, nanoporous 3D structure has an engineered, digitally controlled macropore morphology with integrated nanoporosity.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
The present invention uses an additive manufacturing operation, in one example a DIW additive manufacturing process, to fabricate hierarchical nanoporous metal foams with deterministically controlled, application specific, 3D multiscale pore architectures. Arbitrary macroscopic architectures and sample shapes can be printed according to the application requirements. Moreover, the structure of two, three, or more distinct levels of porosity can be tuned independently which enables application specific multiscale architectures of virtually any geometric 3D shape.
Referring to
In
In this example the DIW operation using the Ag—Au alloy forming metal particle mixture (i.e., ink 18) forms an extrusion-based, room temperature manufacturing process. The Ag—Au ink 18 in this example was housed in a 3 cm×3 cm syringe barrel (EFD) (shown as nozzle 20a) attached by a Luer-Lok to a smooth-flow tapered nozzle (200 microns inner diameter, “d”). An air-powered electronically controlled fluid dispenser, in this example the ULTIMUS™ V, EFD (available from the Nordson Corp. of Westlake, Ohio), provided the appropriate pressure to extrude the ink 18 through the nozzle 20a. The extrusion process may be controlled by controlling the extrusion pressure and printing speed during the writing operation. The target patterns forming the 3D Au—Ag particle structure 28 in this example were printed using an x-y-z 3-axis air bearing positioning stage (model ABL 9000, available from Aerotech, Inc. of Pittsburgh, Pa.), whose motion was controlled by writing the appropriate G-code commands. The 3D Ag—Au metal particle structure 28 was printed in a layer-by-layer scheme onto silicon wafers with a nozzle height (h) of 0.7 d to ensure moderate adhesion to the substrate and between adjacent printed layers. This process enables the 3D Au—Ag metal particle structure 28 to be printed with virtually any 3D shape.
Referring to
As indicated in
The melt de-alloying process starts with the target alloy by putting it into a melting metal for certain time, and then taking it outside. Next, the treated piece may be exposed to an etching solution to remove the unwanted elements. The de-alloying in this example was performed by submerging the annealed structure 28a′ in concentrated HNO3 solution for two days. In this example the process described herein resulted in a hierarchical metal foam morphology, represented by illustration 28b′, with three distinct levels of pores (i.e., three distinct sections having differing porosities).
The system and method disclosed herein may be used to fabricate a 3D structure having multiple levels of porosity, and in one specific example three levels of porosity with a total porosity of 95% and a surface area of 5 m2/g, as shown in
Referring to
The present invention thus uses DIW additive manufacturing to fabricate hierarchical nanoporous metal foams with deterministically controlled 3D multiscale porosities. Arbitrary yet mechanically robust 2D or 3D shapes can be printed according to the specific needs of the application. Moreover, the printed structure with its two, three or more distinct levels of porosity can be tuned independently, in part by using the DIW operation, in part by controlling the ink's organic binder content, in part by controlling annealing of the structure and in part by controlling de-alloying of the structure, to create different architectures for different layers or sections of the 3D structure, which enables application specific multiscale architectures to be created. The ability of the present disclosure to create 3D metal foams with deterministic shapes and a macroscale porosity is expected to have significant impact in the fields of energy storage for batteries, catalysis, and more. The methods disclosed herein can be used to create structures such as filaments, films, and virtually any other type of three dimensional, monolithic or spanning free-form structures, where it is desired to have both high surface area and high electrical conductivity, in addition to two or more distinct pore size length scales.
It will also be appreciated that while the present disclosure has described a DIW process as being one example of the specific process being used to apply the ink 18, other fabrication processes in addition to DIW may be used as well. For example, the ink 18 may be used in more traditional extrusion-based processes where the architecture is not controlled by the motion of the nozzles with respect to the XYZ stage, but by the shape of the nozzle itself. Furthermore, the present disclosure is not limited to use with only a DIW process; virtually any form of additive manufacturing/3D printing method/process, for example and without limitation, Selective Laser Sintering, Selective Laser Melting, Binder Powder Bed Printing, Fused Deposition Modeling, Projection Microstereolithography, Electrophoretic Deposition, Screen Printing, Inkjet Printing, and other laser melting, sintering, or deposition processes may be used in place of a DIW process. Virtually any process capable of producing multi-metal component parts with a digitally controlled macropore architecture, which may then be annealed to form the alloy, and then de-alloyed to create the functional nanoporosity, is contemplated by the present disclosure.
It will also be appreciated that nanoporous metals can be prepared from typical binary and ternary alloys, or even from multi-composition alloys (i.e., more than three different elements). The less noble elements have a lower standard electrode potential compared with the more noble elements for aqueous de-alloying process. Typical elements that can be used as less noble components are the following: Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Zr, Nb, Mo, Cd, In, Sn, Pb, Bi and most or non-radioactive rare earth elements. Typical elements for the more noble elements to form nanoporous metals are: Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Ge, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sn, Ta, W, Os, Ir, Pt, Au, Pb, and Bi. Other elements such as Be, B, P, S, As, and Se can be used as additive elements. The typical element compositional range for the less noble element of the alloy is from 5 to 99 atomic percent and the rest are the more noble elements. If the alloy particles are available, then it would be possible to prepare the hierarchical nanoporous metals directly by using the alloy powders and binders to form the macroscopic architecture.
While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
This application is a divisional and claims the benefit and priority of U.S. patent application Ser. No. 15/790,810 filed on Oct. 23, 2017. The entire disclosure of the above application is incorporated herein by reference.
This invention was made with Government support under Contract No. DE-AC52-07NA27344 awarded by the United States Department of Energy. The Government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15790810 | Oct 2017 | US |
| Child | 17502538 | US |
