U.S. patent application number 16/047663 was filed with the patent office on 2018-12-06 for particulates for additive manufacturing techniques.
The applicant listed for this patent is Delavan Inc.. Invention is credited to Sameh Dardona, Tahany Ibrahim El-Wardany, Anais Espinal, Michael A. Klecka, Wayde R. Schmidt, Ying She.
Application Number | 20180347036 16/047663 |
Document ID | / |
Family ID | 57994642 |
Filed Date | 2018-12-06 |
United States Patent
Application |
20180347036 |
Kind Code |
A1 |
She; Ying ; et al. |
December 6, 2018 |
PARTICULATES FOR ADDITIVE MANUFACTURING TECHNIQUES
Abstract
A particulate for an additive manufacturing technique includes
metallic particulate bodies with exterior surfaces bearing a
polymeric coating. The polymeric coating is conformally disposed
over the exterior surface that prevents the underlying metallic
body from oxidation upon exposure to the ambient environment by
isolating the metallic particulate bodies from the ambient
environment. Feedstock materials for additive manufacturing
techniques, and methods of making such feedstock, are also
disclosed.
Inventors: |
She; Ying; (East Hartford,
CT) ; Klecka; Michael A.; (Vernon, CT) ;
El-Wardany; Tahany Ibrahim; (Bloomfield, CT) ;
Espinal; Anais; (West Hartford, CT) ; Schmidt; Wayde
R.; (Pomfret Center, CT) ; Dardona; Sameh;
(South Windsor, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Delavan Inc. |
West Des Moines |
IA |
US |
|
|
Family ID: |
57994642 |
Appl. No.: |
16/047663 |
Filed: |
July 27, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14822713 |
Aug 10, 2015 |
10041171 |
|
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16047663 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2998/10 20130101;
B22F 2999/00 20130101; B22F 2999/00 20130101; B22F 2999/00
20130101; B22F 2202/17 20130101; B22F 2201/01 20130101; B22F
2201/10 20130101; B22F 1/0062 20130101; B22F 1/0062 20130101; B22F
9/22 20130101; B22F 9/22 20130101; B22F 3/008 20130101; B01J
2208/0053 20130101; B01J 2208/00061 20130101; B01J 3/00 20130101;
C09D 183/04 20130101; B22F 2998/10 20130101; B33Y 70/00 20141201;
B01J 8/1827 20130101; H01B 1/22 20130101; C23C 16/442 20130101;
C23C 14/12 20130101; B01J 8/1836 20130101 |
International
Class: |
C23C 16/442 20060101
C23C016/442; H01B 1/22 20060101 H01B001/22; B01J 3/00 20060101
B01J003/00; B01J 8/18 20060101 B01J008/18; C09D 183/04 20060101
C09D183/04; C23C 14/12 20060101 C23C014/12 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS STATEMENT
[0001] This invention was made with government support under
Contract No. DE-AR-0000308 awarded by the Department of Energy. The
government has certain rights in the invention.
Claims
1. A particulate for an additive manufacturing technique, particles
of the particulate comprising: a particulate body having a surface;
and a polymeric coating disposed over the surface of the
particulate body, wherein the particulate body includes a metallic
material prone to oxidation upon exposure to the ambient
environment, wherein the polymeric coating forms a barrier
isolating the particulate body from the ambient environment.
2. The particulate as recited in claim 1, wherein the particulate
body includes only elemental copper.
3. The particulate as recited in claim 1, wherein the coating
includes polydimethylsiloxane.
4. The particulate as recited in claim 1, wherein the particulate
body is oxide-free.
5. The particulate as recited in claim 1, wherein an interface
between the particulate body and the polymeric coating is metallic
oxide-free.
6. A particulate feedstock for an additive manufacturing technique
including particulate as recited in claim 1, wherein the feedstock
has greater flowability than uncoated copper particulate.
7. The particulate feedstock for an additive manufacturing
technique including particulate as recited in claim 1, wherein the
particulate is brighter than uncoated copper particulate.
8. A conductor formed from particulate as recited in claim 1,
wherein the conductor has porosity that is less than a porosity of
a conductor formed from particulate composite of elemental copper
and copper oxide.
9. A method of making particulate for an additive manufacturing
technique, the method comprising: receiving a metallic particulate
at a fluidized bed apparatus; flowing a reducing gas through the
metallic particulate; flowing a drying and degassing gas through
the metallic particulate; and flowing a coating gas from vessel
containing a polymeric material maintained at a polymeric material
vaporization temperature through the metallic particulate, wherein
the metallic particulate is maintained at a coating temperature
that is less than the polymeric material vaporization temperature
to encapsulate the metallic particulate with polymeric material
coatings, particles of the particulate having: a particulate body
having a surface; and a polymeric coating disposed over the surface
of the particulate body, wherein the particulate body includes a
metallic material prone to oxidation upon exposure to the ambient
environment, wherein the polymeric coating forms a barrier
isolating the particulate body from the ambient environment.
10. The method as recited in claim 9, wherein the metallic
particulate is maintained at a drying and degassing temperature
while the drying and degassing gas is flowed therethrough at a
temperature that is lower than a reducing temperature at which the
metallic particulate is held while the reducing gas is flowed
therethrough.
11. The method as recited in claim 9, wherein the metallic
particulate is maintained at coating temperature while the coating
gas is flowed therethrough that is less than a drying and degassing
temperature at which the metallic particulate is held while the
drying the degassing temperature is flowed therethrough.
12. The method as recited in claim 9, wherein the coating gas is
flowed from a vessel containing polymeric material that is
maintained at a polymeric material vaporization temperature that is
greater than a coating temperature at which the metallic
particulate is maintained while the coating gas is flowed
therethrough.
13. The method as recited in claim 9, wherein flowing a reducing
gas through the metallic particulate includes removing
substantially all oxygen from oxidized portions of the metallic
particulate prior to flowing the coating gas through the
particulate material.
14. The method as recited in claim 9, wherein flowing a degassing
and drying gas flow through the metallic particulate includes
removing water vapor generated during the reducing process from the
metallic particulate.
15. The method as recited in claim 9, wherein flowing a drying and
degassing gas through the metallic particulate and flowing the
coating gas through the metallic particulate include flowing an
inert gas from a common inert gas source.
16. The particulate as recited in claim 1, wherein the polymeric
coating encapsulates the particulate body.
17. The particulate as recited in claim 1, wherein the polymeric
coating encapsulates the entirety of the surface of the particulate
body.
18. The particulate as recited in claim 1, wherein the polymeric
coating is condensed over the surface of the particulate body.
19. The particulate as recited in claim 1, wherein the polymeric
coating is condensed over the entirety of the surface of the
particulate body.
20. An additive manufacturing technique, comprising: receiving a
metallic particulate at a fluidized bed apparatus; flowing a
reducing gas through the metallic particulate; flowing a drying and
degassing gas through the metallic particulate; and flowing a
coating gas from vessel containing a polymeric material maintained
at a polymeric material vaporization temperature through the
metallic particulate, wherein the metallic particulate is
maintained at a coating temperature that is less than the polymeric
material vaporization temperature to encapsulate the metallic
particulate with polymeric material coatings, particles of the
particulate having: a particulate body having a surface; and a
polymeric coating disposed over the surface of the particulate
body, wherein the particulate body includes a metallic material
prone to oxidation upon exposure to the ambient environment,
wherein the polymeric coating forms a barrier isolating the
particulate body from the ambient environment; and forming a
conductor from the coated particulate using an additive
manufacturing technique, the conductor having porosity that is less
than a porosity of a conductor formed from particulate composite of
elemental copper and copper oxide.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present disclosure relates to particulates and methods
of making particulate materials, and more particularly to
particulate feedstock for additive manufacturing techniques.
2. Description of Related Art
[0003] Additive manufacturing techniques are commonly used to
fabricate articles by depositing successive layers on a substrate.
Additive manufacturing systems typically scan a high-density energy
source like a laser or electron beam over a powder according to a
predetermined two-dimensional slice of an article geometry.
Application of the high-density energy to the particulate fuses the
particulate into a layer, which is integral with the underlying
substrate. Once a given scan is completed, additional particulate
is generally deposited over the fused layer, and succeeding layers
thereafter fused overtop the preceding layers. Subsequent layers
are added over one another until the article is fully developed, at
which time the article is removed from the substrate. In some
additive manufacturing techniques physical properties of the
article can be influenced by the composition of the particulate
used in the additive manufacturing technique as well as interaction
of particulate constituents with the fusing process.
[0004] Such conventional methods and systems have generally been
considered satisfactory for their intended purpose. However, there
is still a need in the art for improved particulates and methods of
making particulate for additive manufacturing techniques. The
present disclosure provides a solution for this need.
SUMMARY OF THE INVENTION
[0005] A particulate for an additive manufacturing technique
includes metallic particulate bodies (i.e. particles) with exterior
surfaces coated with a polymeric material. The polymeric material
is conformally disposed as a relatively thin coating over the
exterior surface that prevents the underlying metallic body from
oxidation upon exposure to the ambient environment by isolating the
metallic particulate bodies from the ambient environment.
[0006] In certain embodiments, the metallic material of the
particulate body can include copper, aluminum, nickel, alloys
thereof, or any other suitable metallic material. The metallic
material can include elemental copper. In an illustrative exemplary
embodiment the metallic material includes elemental copper free
from copper oxide. In this respect exterior surfaces of the
metallic body are free from copper oxides, like cupric oxide and
cuprous oxide, such that additively manufactured articles formed
from the particulate have low porosity.
[0007] In accordance with certain embodiments, the polymeric
material can be disposed over the entire exterior surface of the
particulate bodies. The polymeric material can include
polydimethylsiloxane. The polymeric material can disposed over an
elemental surface that is substantially free of oxygen. The
polymeric material can be disposed in a layer with a thickness that
is about one nanometer. In the illustrative exemplary embodiment
the polymeric material is disposed over an exterior surface that is
elemental copper and is oxide-free.
[0008] It is also contemplated that a feedstock for an additive
manufacturing technique can include particles as described above.
The feedstock can have reflectivity (or brightness) that is greater
than that of elemental copper and/or elemental copper bearing a
copper oxide layer. The feedstock can be more flowable than
elemental copper and/or elemental copper bearing an oxide layer. In
this respect, an angle of repose of a given amount of particulate
may be smaller (i.e. form a less steep pile) than the angle of
repose of equivalent amounts of elemental copper particulate and/or
the angle of repose for elemental copper particulate bearing oxide
layers.
[0009] A method of making a particulate for an additive
manufacturing technique includes receiving metallic particulate at
a fluidized bed apparatus. The metallic particulate is reduced by
flowing a reducing gas through the metallic particulate while the
metallic particulate is maintained at a reducing temperature,
thereby converting metallic oxides of the metallic particulate to
elemental material. A drying and degassing gas is then flowed
through the metallic particulate while the metallic material is
maintained at a drying and degassing temperature, thereby removing
water vapor generated by reduction of the metallic oxides. A
coating gas including an inert gas and a vaporized polymeric
material is then flowed through the metallic particulate while the
metallic particulate is maintained at a coating temperature,
thereby causing the polymeric material to deposit on the metallic
particulate as discrete particle polymeric coatings. It is
contemplated that the inert gas bearing the polymeric material
flows to the metallic material from a polymeric material reservoir
maintained at polymeric material vaporization temperature, a
temperature differential between the inert gas bearing the
vaporized polymeric material and the metallic particulate
facilitating development of the discrete particle coatings.
[0010] In certain embodiments the drying and degassing temperature
of the metallic particulate can be less than the reducing
temperature of the metallic particulate. The coating temperature of
the metallic temperature can be less than the drying and degassing
temperature of the metallic particulate. The polymeric material
vaporization temperature can be less than the reducing temperature
of the metallic particulate. The polymeric material vaporization
temperature can also be greater than the drying and degassing
temperature of the metallic particulate. In an exemplary embodiment
of the method the metallic particulate reducing temperature can be
about 500 degrees Celsius, the metallic particulate degassing and
drying temperature is between about 150 and 200 degrees Celsius,
the metallic particulate coating temperature is about 50 degrees
Celsius, and the polymeric material vaporization temperature can be
about 240 degrees Celsius.
[0011] In certain embodiments receiving the metallic particulate
can include receiving a copper particulate material having a copper
oxide layer. The reducing gas can include hydrogen gas, and the
reducing gas can be flowed through the metallic material for a
reducing time interval of about twelve (12) hours. The drying and
degassing gas can include an inert gas like nitrogen, helium,
argon, or any other suitable inert gas, and can be flowed through
the metallic material for a drying and degassing interval of about
two (2) hours. The coating gas can include an inert gas and a
polymeric material, and can be flowed through the metallic material
for a coating interval of about two (2) hours.
[0012] These and other features of the systems and methods of the
subject disclosure will become more readily apparent to those
skilled in the art from the following detailed description of the
preferred embodiments taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] So that those skilled in the art to which the subject
disclosure appertains will readily understand how to make and use
the devices and methods of the subject disclosure without undue
experimentation, embodiments thereof will be described in detail
herein below with reference to certain figures, wherein:
[0014] FIGS. 1A-1D are schematic views of an exemplary embodiment
of particulate for an additive manufacturing process constructed in
accordance with the present disclosure, showing a metallic body
with oxide having the oxide reduced, cooled, and coated with a
polymeric material;
[0015] FIG. 2 is a side elevation view of feedstock for an additive
manufacturing process including the particulate of FIG. 1, showing
an angle of repose of the feedstock relative to those of elemental
copper particulate and copper particulate bearing copper oxide;
[0016] FIG. 3 is a schematic view of an apparatus for making the
particulate of FIG. 1, showing a fluidized bed apparatus;
[0017] FIG. 4 is a schematic view of a method for making
particulate and feedstock for an additive manufacturing process;
and
[0018] FIGS. 5A and 5B are perspective views of conductors
constructed using an additive manufacturing technique, FIG. 5A
showing a conductor fabricated without decomposing copper oxide
deposits within (or on) the copper particulate and FIG. 5B showing
a conductor fabricated using copper powder prepared using an
embodiment of the methods described herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject disclosure. For purposes of explanation and
illustration, and not limitation, a partial view of an exemplary
embodiment of particulate in accordance with the disclosure is
shown in FIG. 1 and is designated generally by reference character
100. Other embodiments of particulate, feedstock, apparatus for
making particulate and feedstock, and methods of making particulate
and feedstock in accordance with the disclosure, or aspects
thereof, are provided in FIGS. 2-5B, as will be described. The
systems and methods described herein can be used for making
additively manufactured articles with low porosity using metallic
particulate prone to oxidation.
[0020] Referring to FIGS. 1A-1D, a particulate 100 for an additive
manufacturing technique is shown undergoing reduction and coating
development operations. With reference to FIG. 1A, particulate 100
includes a particulate body 102. Particulate body 102 has a surface
104 and includes an elemental metallic material 106. Particulate
body 102 also includes an oxide 108 of metallic material 106. It is
contemplated that metallic material 106 includes a material like
copper, aluminum, nickel, iron or any other suitable material that
is prone to oxidation upon exposure to the ambient environment. In
the illustrated exemplary embodiment, metallic material 106 is
elemental copper that is substantially pure and contiguous
throughout particulate body 102. Oxide 108 includes an oxide of
copper, like cupric oxide and/or cuprous oxide, disposed over
surface 104 of particulate body 102.
[0021] With reference to FIG. 1B, particulate 100 is shown in a
flow of reducing gas. In illustrated exemplary embodiment, the
reducing gas includes a flow of substantially pure hydrogen
(H.sub.2) that flows through particulate 100 by traversing both
particulate body 102 and oxide 108. With respect to oxide 108, the
reducing gas extracts and carries away oxygen from the oxide,
leaving elemental copper. Subsequent to reduction, particulate 100
is comprised solely of elemental copper. While undergoing
reduction, particulate 100 is maintained at a reducing temperature
for a reducing time interval. In an exemplary embodiment, copper
particulate is maintained at about 500 degrees Celsius for a
reducing time interval being about twelve (12) hours, reducing
copper oxide layers that may have developed on the copper
particles. As will be appreciated, other reducing temperatures and
reducing time intervals may be utilized as suitable for the
metallic material forming the metallic particulate 100.
[0022] With reference to FIG. 1C, particulate 100 is shown in a
drying and degassing gas flow that includes nitrogen (N.sub.2). The
drying and degassing gas flow includes an inert gas like nitrogen
(illustrated), helium, argon, or any other suitable inert gas, and
carries away water vapor that may be generated during the reduction
process. This prevents water vapor that may have been generated
from interaction of the hydrogen gas with oxides of the metallic
material forming particulate 100 from forming new oxides within
particulate 100. While undergoing drying and degassing, particulate
100 is maintained at drying and degassing temperature that is less
than the metallic particulate reduction temperature. In an
exemplary embodiment, copper particulate is maintained at drying
and degassing temperature between about 100 degrees Celsius and
about 150 degrees Celsius while an inert gas is flowed through the
reduced copper particles for a drying and degassing time interval
of about two (2) hours. As will be appreciated, other drying and
degassing temperatures and time intervals may be utilized as
suitable for metallic material forming metallic particulate
100.
[0023] With reference to FIG. 1D, particulate 100 is shown in a
flow of coating gas. The coating gas includes an inert gas and a
polymeric material, the inert gas being nitrogen (N.sub.2) and the
polymeric material A being polydimethylsiloxane in the illustrated
exemplary embodiment. As the coating gas traverses both particulate
body 102 a polymeric coating 110 develops over surface 104 of
particulate 100. Polymeric coating 110 develops as a relatively
thin coating extending about substantially the entirety of surface
104 of particles of particulate 100, and in a contemplated
embodiment develops with a thickness t that is about one (1)
nanometer. In the exemplary embodiment, copper particulate is
maintained at a temperature of about fifty (50) degrees Celsius
while a coating gas including polydimethylsiloxane (PDMS) is flowed
through particles forming particulate 100 during a coating time
interval of about two (2) hours. As will be appreciated, other
coating temperatures and/or coating time intervals may be utilized
as suitable for the polymeric material and the metallic material
forming the metallic particulate.
[0024] The coating gas flows between a vessel 340 (shown in FIG. 3)
containing polymeric material A. Polymeric material A is maintained
at a polymeric material vaporization temperature. This allows
vaporized polymeric material A to be taken up by an inert gas
provided to vessel 340 and borne thereby to a fluidized bed
apparatus 310 (shown in FIG. 3) containing particulate 100 at the
coating temperature. The coating temperature is less than the
polymeric material vaporization material, causing polymeric
material A to cool and coat surfaces of the discrete particles to
form polymeric coating 110 over substantially the entire surface of
discrete particles forming particulate 100. It is contemplated that
differential between the polymeric material vaporization
temperature of polymeric material A and the coating temperature of
particulate 100 can be as high as 190 degrees Celsius, though
higher temperature differentials are within the scope of the
present disclosure.
[0025] Coating particulate 100 with relatively thin polymeric
coatings such as illustrated can prevent oxidation of metallic
material 106 included therein by hermetically isolating metallic
material 106 from water vapor and/or other contaminates to which
particulate 100 may be exposed during storage, handing, and/or use
in additive manufacturing techniques that could influence the
porosity of articles formed using the particulate. Such thin
polymeric coatings can be vaporized during fusing and prior to
particulate 100 solidifying, thereby preventing polymeric material
A from becoming incorporated into the article and/or potentially
influencing the mechanical or electrical properties of the article
formed by the additive manufacturing technique.
[0026] In embodiments, polymeric material A includes PDMS. PDMS, in
a relatively thin coating (e.g. about one (1) nanometer), renders
coated particulate 100 inert when exposed to the ambient
environment. Coating particulate 100 with a material like PDMS can
also improve the handling properties of the material, such as its
flowability, the coating tending to reduce the tendency of the
particles to develop static charges from contact with other
particles that otherwise would cause the particles to weakly bond
with one another. Flowability may include the ability of the powder
to flow at a given rate or the amount of resistance encountered by
particles as they move in a shared general direction at different
rates.
[0027] With reference to FIG. 2, a feedstock 200 for an additive
manufacturing process is shown. Feedstock 200 includes a
particulate 100 having a polymeric coating 110 that includes PDMS.
Particles coated with PDMS are more flowable than both uncoated
particles formed solely from the underlying elemental material and
oxides of the underlying material. As a consequence, feedstock 200
has a smaller angle of repose than the underlying particulate
material in elemental form as well as oxides of the underlying
particulate material. For example, as shown in FIG. 2, the angle of
repose of PDMS coated copper particulate is smaller than the angle
of repose of both copper particulate and oxidized copper
particulate. This can simplify handling feedstock 200, simplifying
manufacture of components additively manufactured therefrom. It can
also allow for fabrication, using additive manufacturing
techniques, structures with relatively fine feature sizes--such as
features found in motors including copper-containing
components.
[0028] With reference to FIG. 3, a fluidized bed apparatus 300 is
shown for reducing and coating particulate 100 and generating
feedstock 200 (shown in FIG. 2). Aspects of fluidized bed apparatus
300 are described in U.S. Patent Application No. 61/815,359, U.S.
Patent Application No. 61/931,295, and U.S. Patent Application No.
61/980,681, each of which is incorporated herein by reference in
their entirety, and which is assigned to the Applicant of the
instant application. Particulate 100, which may have an oxides
layer, is received within in a fluidized bed apparatus 310.
Particulate 100 is therein maintained at the reducing temperature
and a reducing gas is flowed through particulate 100 for the
reducing time interval. The reducing gas flow reduces the oxide
layer, e.g. oxide layer 108 (shown in FIG. 1A), to elemental form.
The reducing gas can be pure hydrogen, a hydrogen gas mixture,
carbon monoxide or any other suitable gas, and is provided to
fluidized bed apparatus 310 from a reducing gas source 320.
[0029] Once particulate 100 is reduced, the drying and degassing
gas flow is provided from a gas source 330 to fluidized bed
apparatus 310. While the drying and degassing gas flow is provided
to fluidized bed apparatus 310, particulate 100 is maintained at
the drying and degassing temperature. The drying and degassing
temperature is less than the reducing temperature and is provided
for drying and degassing time interval that is sufficient to carry
away substantially all water vapor disposed within particulate 100
and which may develop as a result of the reducing process.
[0030] Subsequent to drying and degassing particulate 100, the
coating gas is provided to fluidized bed apparatus 310 by flowing
an inert gas through a vessel 340 containing polymeric material A.
Polymeric material A is maintained at the polymeric material
vaporization temperature within vessel 340, and the inert gas
supplied to vessel 340 can be the same gas as used for drying and
degassing particulate 100. This simplifies the process of coating
particulate 100 by allowing a single inert gas source, e.g. gas
source 330, to provide inert gas for both drying and degassing
particulate 100 as well as an inert gas bearing polymeric material
A to fluidized bed apparatus 310.
[0031] With reference to FIG. 4, a method of making particulate is
indicated generally by reference numeral 400. As shown with box
410, method 400 includes receiving particulate, e.g. particulate
100 (shown in FIG. 1A) in a fluidized bed apparatus, e.g. fluidized
bed apparatus 310 (shown in FIG. 3). The particulate can include
both an elemental material and oxides of the elemental material. As
shown with box 420, a reducing gas is thereafter flowed through the
particulate while the particulate is maintained at a reducing
temperature. A drying and degassing gas flow is then flowed through
the particulate, as shown with box 430. Once the particulate has
been dried and degassed by the drying and degassing gas flow, a
coating gas is flowed through the particulate as shown with box
440. The coating gas includes a polymeric material and an inert
gas, and the particulate is maintained at a coating temperature
that is less than the polymeric material vaporization temperature
such that a polymeric coating forms over substantially the entire
surface of respective particles within particulate disposed within
the fluidized bed apparatus.
[0032] With reference to FIGS. 5A and 5B, a conductor 10 and a
conductor 20 each fabricated using an additive manufacturing
technique are shown. Referring to FIG. 5A, conductor 10 has a
copper body 12 that is interrupted by one or more voids 14. Voids
14, indicated with relatively lightly shaded surface portions in
FIG. 5A, are associated with the liberation of oxygen from copper
oxide when exposed to a high density energy source during fusing,
and generally increase the electrical resistance and reduce the
thermal conductivity of conductor 10 relative to solid conductor
having the same geometry and having contiguous elemental
copper.
[0033] Referring to FIG. 5B, conductor 20 is shown. Conductor 20
has substantially the same geometry as conductor 10 (shown in FIG.
5A) and includes a body 22 that is formed from contiguous elemental
copper. Conductor 20 is formed from particulate as described
herein, and includes substantially no voids not withstanding having
been fused by exposure to the same high density energy source as
conductor 10 (shown in FIG. 5A). Absence of copper oxide deposits
within (and/or on) particulate used to form conductor 20 provides
an electrical resistance that is lower and a thermal conductivity
that is higher than that of conductor 10 (shown in FIG. 5A).
[0034] Additive manufacturing techniques can allow for deposition
of copper with a predetermined feature size. However, some copper
particulates can form a relatively thin layer of copper oxide,
i.e., cuprous oxide and cupric oxide, on exterior portions of the
copper particles. The copper oxide can be an artifact of the copper
manufacturing process or can be the result of exposure of the
copper particulate to the ambient environment. Such copper oxides
can decompose into copper and oxygen at temperatures encountered
during powder fusing in some additive manufacturing techniques,
potentially causing voids to develop in the fused layer due to the
tendency of oxygen to expand rapidly. Porosity in turn can change
the properties of the article developed using the additive
manufacturing technique, such as reducing the conductivity of a
conductor developed using the technique.
[0035] In embodiments described herein, particulates for additive
manufacturing techniques prone to oxidation are ruggedized such
that they are less likely to form oxide layers on their exterior
surfaces. This renders the particulate less apt to oxidize upon
exposure to the ambient environment, simplifying handling of the
particulate. For example, in certain embodiments copper particulate
including copper oxide is reduced to elemental copper particulate
the elemental copper particulate is encapsulated in a conformal
barrier material. The barrier material may include a polymeric
material that provides both isolation from the ambient environment
as well as improves the flowability of the copper particulate.
[0036] In certain embodiments, reduction of the oxidized
particulate can occur in a fluidized bed system. The reduction can
occur in the presence of a reducing gas, such high-purity hydrogen,
a hydrogen gas mixture, carbon monoxide or any other suitable
reduction gas. The reduction can also entail the use of an inert
gas, which is preheated in the shell side between an outer tubing
and inner tubing of the fluidized bed system prior to entering the
charge chamber from below to a preheat temperature that is in the
range of 150 to 200 degrees Celsius. Examples of suitable inert
gases include nitrogen, helium, and argon.
[0037] The methods and systems of the present disclosure, as
described above and shown in the drawings, provide for particulates
with superior properties including improved purity. While the
apparatus and methods of the subject disclosure have been shown and
described with reference to preferred embodiments, those skilled in
the art will readily appreciate that changes and/or modifications
may be made thereto without departing from the scope of the subject
disclosure.
* * * * *