U.S. patent application number 17/502538 was filed with the patent office on 2022-02-03 for hierarchical porous metals with deterministic 3d morphology and shape via de-alloying of 3d printed alloys.
The applicant listed for this patent is Lawrence Livermore National Security, LLC. Invention is credited to Juergen BIENER, Wen CHEN, Eric DUOSS, Zhen QI, Christopher SPADACCINI, Marcus A. WORSLEY, Jianchao YE, Cheng ZHU.
Application Number | 20220032369 17/502538 |
Document ID | / |
Family ID | 66169669 |
Filed Date | 2022-02-03 |
United States Patent
Application |
20220032369 |
Kind Code |
A1 |
QI; Zhen ; et al. |
February 3, 2022 |
HIERARCHICAL POROUS METALS WITH DETERMINISTIC 3D MORPHOLOGY AND
SHAPE VIA DE-ALLOYING OF 3D PRINTED ALLOYS
Abstract
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 have a reservoir for holding the
feedstock, the feedstock including a rheologically tuned alloy ink.
A printing stage may be used for receiving the feedstock. A
processor may be incorporated which has a memory, and 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 used 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.
Inventors: |
QI; Zhen; (Tracy, CA)
; BIENER; Juergen; (Castro Valley, CA) ; CHEN;
Wen; (Livermore, CA) ; DUOSS; Eric; (Danville,
CA) ; SPADACCINI; Christopher; (Oakland, CA) ;
WORSLEY; Marcus A.; (Hayward, CA) ; YE; Jianchao;
(Tracy, CA) ; ZHU; Cheng; (Livermore, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lawrence Livermore National Security, LLC |
Livermore |
CA |
US |
|
|
Family ID: |
66169669 |
Appl. No.: |
17/502538 |
Filed: |
October 15, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15790810 |
Oct 23, 2017 |
11173545 |
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17502538 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 10/00 20141201;
B22F 2998/10 20130101; Y02P 10/25 20151101; B22F 10/38 20210101;
B22F 10/62 20210101; B22F 10/10 20210101; B33Y 40/00 20141201; B22F
2301/255 20130101; B22F 10/20 20210101; B22F 3/1121 20130101; B22F
3/1146 20130101; B22F 3/1115 20130101; B22F 2998/10 20130101; B22F
10/20 20210101; B22F 2003/248 20130101; B22F 2003/244 20130101;
B22F 2998/10 20130101; B22F 10/20 20210101; B22F 2003/248 20130101;
B22F 2003/244 20130101 |
International
Class: |
B22F 3/11 20060101
B22F003/11; B33Y 10/00 20060101 B33Y010/00; B33Y 40/00 20060101
B33Y040/00; B22F 10/10 20060101 B22F010/10; B22F 10/38 20060101
B22F010/38; B22F 10/62 20060101 B22F010/62 |
Goverment Interests
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] 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.
Claims
1. A system for using a feedstock to form a three dimensional,
hierarchical, porous metal structure with deterministically
controlled 3D multiscale porous architectures, the system
comprising: an reservoir for holding the feedstock, the feedstock
being formed as a rheologically tuned alloy ink; a printing stage
for receiving the feedstock; a processor including a memory and
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 for applying the feedstock therethrough onto the printing
stage; a de-alloying subsystem 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 dealloying operation.
2. The system of claim 1, wherein the feedstock comprises an alloy
powder.
3. The system of claim 1, wherein the rheologically tuned alloy ink
comprises an ink formed from a plurality of different metal powders
and a binder.
4. The system of claim 1, wherein the additive manufacturing
printing process comprises a direct ink writing (DIW) process.
5. The system of claim 1, wherein the additive manufacturing
printing process comprises at least one of: a direct ink writing
(DIW) process; a selective laser sintering process; a selective
laser melting process; a binder powder bed printing process; a
fused deposition modeling process; a projection
microstereolithography process; an electrophoretic deposition
process; a screen printing process; and an inkjet printing
process.
6. The system of claim 3, wherein the rheologically tuned alloy ink
comprises an ink formed from silver powder and gold powder.
7. The system of claim 6, wherein the rheologically tuned alloy ink
comprises also comprises an organic binder.
8. The system of claim 1, further comprising an annealing subsystem
for performing an annealing operation on the 3D structure prior to
performing the de-alloying operation.
9. The system of claim 8, wherein the annealing subsystem is
configured to heat the 3D structure to 0.99%-0.7% of a melting
temperature of an alloy being used to form the 3D structure.
10. The system of claim 9, wherein the annealing subsystem is
configured to maintain the 3D structure heated for between 1 hour
to 24 hours.
11. The system of claim 1, wherein the de-alloying subsystem
enables submerging the 3D structure in an aqueous solution for a
predetermined time.
12. A system for forming a three dimensional, hierarchical, porous
metal structure with deterministically controlled 3D multiscale
hierarchical pore architectures, the system comprising: a printing
stage; an additive manufacturing system including a processor
having a nozzle, and 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; an annealing subsystem
configured to anneal the 3D structure to remove the binder, and to
form an alloyed 3D structure; and 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.
13. The system of claim 12, wherein the rheologically tuned ink
comprises an ink from a plurality of metal powders and a
binder.
14. The system of claim 12, wherein the annealing subsystem is
configured to heat the 3D structure to 99%-0.7% of the melting
temperature of an alloy to be formed as the alloyed 3D
structure.
15. The system of claim 14, wherein the annealing subsystem is
further configured to heat the 3D structure for a predetermined
time period from between 1 hour to 24 hours.
16. The system of 12, wherein the de-alloying subsystem is
configured to enabling submerging the alloyed 3D structure in a
solution.
17. A system for forming a three dimensional, hierarchical, porous
metal structure with deterministically controlled 3D multiscale
hierarchical pore architectures, the system comprising: a printing
stage; a rheologically tuned, flowable ink including a metal powder
and a binder; an additive manufacturing system including a
processor for controlling a printing process, and also having a
nozzle, and 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, to build up the 3D
structure in a layer-by-layer printing operation; an annealing
subsystem 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; and 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.
18. The system of claim 17, wherein the metal powder of the
rheologically tuned ink comprises a mixture of a plurality of
different metal powders and the binder.
19. The system of claim 17, wherein the annealing subsystem is
configured to heat the 3D structure to 99%-0.7% of the melting
temperature of an alloy to be formed as the alloyed 3D structure,
for a predetermined period of time.
20. The system of claim 19, wherein the de-alloying subsystem is
configured to enabling submerging the alloyed 3D structure in an
aqueous solution for a predetermined period of time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] 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.
FIELD
[0003] 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.
BACKGROUND
[0004] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0005] 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 FIG. 1). This limitation can
be overcome by introducing a hierarchical structure with at least
two levels of pore sizes: 1) large pores which act as mass
transport "highways" that allow the reactants to diffuse to small
pores, while 2) nanosized pores provide high surface area and thus
are responsible for functionality.
[0006] 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.
[0007] 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 .about.200
nm. A second de-alloying process introduces the lower level
hierarchical structures with a size of .about.20 nm. However, this
process also does not allow for the realization of anisotropic pore
architectures required for directed mass transport.
SUMMARY
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0013] FIG. 1 is a diagram illustrating the mass transport
limitations of prior art non-hierarchical nanoporous materials
formed through conventional de-alloying methods;
[0014] FIG. 2 shows a simplified diagram illustrating how various
metal particle clays, together with a solvent, may be mixed
together to form an ink that may be used in a direct ink writing
(DIW) process;
[0015] FIG. 3 is a simplified diagram of using the ink shown in
FIG. 2 in a DIW operation to form a 3D structure in a
layer-by-layer process;
[0016] FIG. 4 shows a 3D printed Au--Ag alloy structure after an
annealing operation has been performed to burn off the binder
material and to alloy the metal components of the ink;
[0017] FIG. 5 shows a 3D printed, hierarchical porous structure
created through a de-alloying process, which leaves a 3D structure
having a plurality of distinct porosity length scales
[0018] FIG. 6 shows a cross sectional view of a portion of the
hierarchical 3D structure shown in FIG. 5 to illustrate the
increase in mass transport and accessible contact area of the
material for charge carriers, as compared to the prior art 3D
structure of FIG. 1;
[0019] FIG. 7 shows Scanning Electron Micrographs at different
magnifications of an example 3D structure created using the
teachings of the present disclosure, in which the 3D structure has
three distinct porosity length scales;
[0020] FIGS. 8-11 illustrate examples of complexly shaped 3D
structures that may be created using the teachings of the present
disclosure;
[0021] FIG. 12 shows a cyclic voltammetry graph illustrating the
electrochemical surface area of a hierarchical 3D structure created
using the teachings of the present invention compared to a
conventionally created unimodal 3D structure with the same
thickness;
[0022] FIG. 13 shows a graph comparing the electrical current
response of hierarchical (solid lines) and non-hierarchical (dash
lines) nanoporous gold electrodes in response to a sudden change of
the applied electrochemical potential from E.sub.i=0 V to E.sub.F
wherein the different colors from top to bottom represent different
values of E.sub.F ranging from 0.1V to 0.6V; it can be seen that
the hierarchical structure charges always faster compared to the
unimodal nanoporous gold; and
[0023] FIG. 14 is a high level flowchart summarizing basic
operations that may be performed in forming hierarchical nanoporous
metal foams and other 3D structures.
DETAILED DESCRIPTION
[0024] 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.
[0025] 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.
[0026] Referring to FIGS. 2-5, an additive manufacturing process,
in this example a direct ink writing (DIW) additive manufacturing
method, may be used to deposit filaments of rheologically tuned
alloy "inks" made from desired metal powder mixtures, in a
predefined geometry, for example a net-shaped, porous form. At FIG.
2, a metal particle mixing operation is performed. In this example
gold clay 12 and silver clay 14 are mixed together as powders with
a solvent(s) acting as an organic binder 16. However, it will be
appreciated that other combinations of metal powders may be
selected, and the present disclosure is not limited to use with
only Au and Ag powders. In this example, however, the specific
quantities and/or ratio of Au and Ag (e.g., metal powders) may be
selected, along with the quantity of organic binder(s) 16, and
mixed together as colloids/particles to tune the rheological
properties of the composition. The composition forms an ink 18
after being mixed. Thus, the operations performed in FIG. 2 may be
thought of as a "mixing" or powdered metal ink preparation process.
Changes to the metal powder mixing ratio (e.g., Au powder from Au
clay 12 and Ag powder from Ag clay 14) allow adjustment of the
metal alloy composition formed during a subsequent DIW/annealing
process. Alternatively, premade alloy particles with the desired
metal component composition can be mixed with the binder (i.e.,
solvent) 16 to prepare the alloy ink.
[0027] In FIG. 3, an ink reservoir 20 may be used to hold the ink
18 and supply the ink to a nozzle 20a of a DIW system 22. The
present disclosure is not limited to any particular construction of
DIW system, but in this example the DIW system 22 includes a
computer controlled processor 24 and a memory 26. The DIW system
uses the nozzle 20a to form a 3D printed, structure 28 in a
"layer-by-layer" fashion. The 3D structure 28 formed initially by
the DIW system 22 may be termed a "green part" to indicate that
further manufacturing operations are to be performed on the parts.
Illustration 28' in FIG. 3 illustrates a plan view showing one
example of the porosity of the 3D structure 28 formed by printed
metal particle ink filaments that form a lattice-like
structure.
[0028] 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.times.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.TM. 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.
[0029] Referring to FIG. 4, after the 3D Au--Ag metal particle
structure 28 (i.e., green part) is printed using the DIW process,
the structure may be heated to anneal it, to form the alloy by
interdiffusion of the different metal particles, and burn off the
organic binder 16. Depending on the alloy melting point, the
annealing temperature varies. Generally, anywhere from 0.99-0.7 of
the melting temperature of the alloy to be formed may be used as
the annealing temperature. The annealing time may also be varied as
this variable depends on the particle size used in the alloy, and
the annealing temperature. The annealing time may thus range from 1
hour to 24 hours. Smaller particles and higher annealing
temperatures require a shorter time to form a homogenous alloy. In
this example the annealing was performed by heating the structure
28 to 85020 C. using a heating rate of 1020 C./minute, and annealed
at this temperature for twelve hours to remove the organic binder
16 and allow the Ag and Au to form an alloy. The annealed structure
28a' is shown in FIG. 4 as well.
[0030] As indicated in FIG. 5, the annealed structure 28a' is then
de-alloyed. The de-alloying process may be performed by any
suitable process (e.g., free-corrosion, electrochemical
de-alloying, etc.). The de-alloying process is often carried out in
aqueous solution for free and electrochemical de-alloying
processes. Various types of acid and alkaline solution with the
concentration from 1% to its saturated form can be used for a free
corrosion process. For an electrochemical de-alloying process,
besides the acid and alkaline solution, a neutral solution such as
NaCl, KCl, etc., with a concentration from 0.1 M to its saturated
form may be selected for electrochemical de-alloying process
controlled by a potentiostat or power source (battery) with two or
three electrode setups. For certain elements to form nanoporous
structures such as Si, Ti, V, Cr, Fe, Co, Ga, Sn, Ta, Pb, and Bi, a
melt de-alloying process may be used along with choosing a metallic
element which does not mix with the target element.
[0031] 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). FIG. 6 shows a simplified cross-sectional illustration
of a portion of the 3D structure 28b' of FIG. 5 to illustrate the
hierarchical pore architecture of the structure. Portions 30 of the
3D structure 28b' may form macropores that operate as engineered
mass transport "highways" or paths, while portions 32 form
nanopores that provide the increased interior surface area that is
exposed to reactants (ions or neutral species), and thus helps to
provide high (electro)catalytic reactivity.
[0032] 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 m.sup.2/g, as shown in FIG. 7. FIG.
7 illustrates a portion of a 3D structure formed using the system
and method of the present disclosure having a distinct first level
macroscale porosity 34, a distinct second level mesoscale porosity
36 and a distinct third level nanoscale porosity 38, while having a
total porosity of 95% and a surface area of 5 m.sup.2/g. If
desired, the engineered macroscale porosity can be made anisotropic
to direct mass transport in applications that require directional
mass transport (for example flow battery electrodes). The system
and method of the present application may be especially useful in
enabling manufacture of complex 3D structures that would be
difficult and/or impossible to create using previously available
manufacturing techniques. Further examples are 3D structures 40-46
made using the teachings of the present disclosure as shown in
FIGS. 8-11 respectively.
[0033] FIG. 12 shows a graph illustrating that the
electrochemically accessible surface area of a 3D structure created
using the teachings of the present disclosure is similar to that of
a conventional unimodal 3D structure. FIG. 13 shows a graph
illustrating faster charging response as a consequence of a sudden
jump of the applied electrochemical potential of 3D structures
created using the teachings of the present disclosure, as compared
to that of a conventional unimodal 3D structure.
[0034] Referring to FIG. 14, the above described operations
performed using the teachings of the present disclosure are
summarized in flowchart 100. At operation 102, if an ink is to be
formed (i.e., rather than using a pre-prepared feedstock), then the
ink may be formed by mixing selected quantities of two or more
powdered metals together with an organic binder. At operation 104
an additive manufacturing operation is then performed to create a
3D metal particle structure. At operation 106 an annealing
operation is performed to burn off the organic binder and to form
the alloy 3D structure. At operation 108 a de-alloying operation is
then performed on the annealed 3D structure which creates a 3D
structure having a hierarchical metal foam architecture with
several distinct pore sizes.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
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