U.S. patent application number 15/640400 was filed with the patent office on 2018-01-18 for low stress property modulated materials and methods of their preparation.
The applicant listed for this patent is Modumetal, Inc.. Invention is credited to Zhi Liang Bao.
Application Number | 20180016694 15/640400 |
Document ID | / |
Family ID | 41402491 |
Filed Date | 2018-01-18 |
United States Patent
Application |
20180016694 |
Kind Code |
A1 |
Bao; Zhi Liang |
January 18, 2018 |
LOW STRESS PROPERTY MODULATED MATERIALS AND METHODS OF THEIR
PREPARATION
Abstract
The technology described herein sets forth methods of making low
stress or stress free coatings and articles using electrodeposition
without the use of stress reducing agents in the deposition
process. The articles and coatings can be layered or nanolayered
wherein in the microstructure/nanostructure and composition of
individual layers can be independently modulated.
Inventors: |
Bao; Zhi Liang; (Seattle,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Modumetal, Inc. |
Seattle |
WA |
US |
|
|
Family ID: |
41402491 |
Appl. No.: |
15/640400 |
Filed: |
June 30, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13003283 |
Jan 24, 2012 |
9758891 |
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PCT/US2009/049847 |
Jul 7, 2009 |
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15640400 |
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61078668 |
Jul 7, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 5/18 20130101; C25D
17/10 20130101; C25D 5/10 20130101; C25D 3/20 20130101; C25D 3/665
20130101; C25D 5/16 20130101 |
International
Class: |
C25D 5/10 20060101
C25D005/10; C25D 5/16 20060101 C25D005/16; C25D 3/20 20060101
C25D003/20; C25D 3/66 20060101 C25D003/66; C25D 17/10 20060101
C25D017/10; C25D 5/18 20060101 C25D005/18 |
Claims
1.-46. (canceled)
47. An article comprising: a low stress coating that has less than
400 MPa of stress, the low stress coating comprising at least two
nanolayers comprising: a first nanolayer comprising a first
material having a first composition and a first nanostructure
defined by one or more of a first average grain size, a first grain
boundary geometry, a first crystal orientation, and a first defect
density, wherein the first material comprises a first alloy; and a
second nanolayer comprising a second material having a second
composition and a second nanostructure defined by one or more of a
second average grain size, a second grain boundary geometry, a
second crystal orientation, and a second defect density, wherein
the second material comprises a second alloy, wherein at least one
of the first average grain size is different from the second
average grain size, the first grain boundary geometry is different
from the second grain boundary, the first crystal orientation is
different from the second crystal orientation, the first defect
density is different from the second defect density, or a
combination thereof.
48. The article of claim 47, wherein the first composition is
different than the second composition.
49. The method of claim 47, wherein the stress is less than 300
MPa.
50. The method of claim 47, wherein the stress is less than 200
MPa.
51. The article of claim 47, wherein the first alloy comprises a
first mixture of two or more metals and the second alloy comprises
a second mixture of the two or more metals.
52. The article of claim 51, wherein at least one of the two or
more metals is independently selected from the group consisting of:
molybdenum, tungsten, nickel, iron, cobalt, copper, zinc,
manganese, platinum, palladium, rhodium, iridium, gold, aluminum,
magnesium, and silver.
53. The article of claim 51, wherein the two or more metals are
independently selected from the group consisting of: molybdenum,
tungsten, nickel, iron, cobalt, copper, zinc, manganese, platinum,
palladium, rhodium, iridium, gold, aluminum, magnesium, and
silver.
54. The article of claim 47, further comprising a substrate.
55. The article of claim 54, wherein the substrate is solid.
56. The article of claim 54, wherein the substrate is
conductive.
57. The article of claim 54, wherein the substrate is porous.
58. The article of claim 54, wherein the substrate is
non-conductive.
59. The article of claim 47, wherein the at least two nanolayers
comprise a plurality of alternating layers.
60. The article of claim 59, wherein the first nanolayer has a
first tensile strength, a first percentage of elongation, a first
hardness, a first ductility, and a first impact toughness; the
second nanolayer has a second tensile strength, a second percentage
of elongation, a second hardness, a second ductility, and a second
impact toughness; and at least one of the first tensile strength is
different from the second tensile strength, the first percentage of
elongation is different from the second percentage of elongation,
the first hardness is different from the second hardness, the first
ductility is different from the second ductility, and the first
impact toughness is different from the second impact toughness.
61. The article of claim 59, wherein the plurality of alternating
layers comprises a plurality of first nanolayers comprising the
first nanolayer, and a plurality of second nanolayers comprising
the second nanolayer.
62. The article of claim 61, wherein the plurality of first
nanolayers comprises stress free materials and the plurality of
second nanolayers comprises low stress materials.
63. The article of claim 61, wherein the plurality of first
nanolayers comprises low stress or stress free materials and the
plurality of second nanolayers comprises uncontrolled stress
materials.
64. The article of claim 47, wherein the first nanolayer has a
grain size ranging from about 0.5 nanometers (nm) to about 100 nm,
and the second nanolayer has a grain size greater than 1,000
nm.
65. The article of claim 47, wherein the at least two nanolayers
independently have a thickness ranging from about 0.5 nm to about
1,000 nm.
66. The article of claim 47, wherein the at least two nanolayers
independently vary in thickness, nanostructure, microstructure,
stress, or a combination thereof.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 13/003,283 filed Jan. 7, 2011, which is a U.S. National Stage
Application of International Application No. PCT/US2009/049847
filed Jul. 7, 2009, which claims the benefit of U.S. Provisional
Application No. 61/078,668 filed Jul. 7, 2008, all of which are
hereby incorporated by reference in their entirety.
BACKGROUND
Stress Free Material Using Control of Electrodepositing Process
[0002] One difficulty with the preparation of coatings articles
produced by electrodeposition processes arises from the internal
stress in the electrodeposited materials that can lead to the
failure of coatings and articles. A variety of means have been used
to reduce the stress in electrodeposited materials including the
use of stress reducing agents such as saccharin in nickel plating,
and thiourea for copper plating. The ability to electrodeposited
materials, and particularly metals, in stress free or low stress
form without the use of additives that can negatively impact the
performance of electrodeposited materials could provide an advance
to the material science of electroplating and electroforming of
coatings and articles.
SUMMARY OF THE DISCLOSURE
[0003] This disclosure provides electrodeposition processes for the
application of low stress or stress free coatings and the
preparation of low stress or stress free articles. The low stress
and stress free coatings and electroformed articles may be prepared
as a single material that is unlayered, or as an electroformed
coating or article that is comprised of layered or nanolayered
metal(s) or metal alloy(s) without the use of additives for the
reduction of stress.
[0004] In one embodiment the technology described herein is
directed to a method of applying a low stress or stress free
coating to substrate, or of electroforming a low stress or stress
free article using electrodeposition comprising the steps of:
applying an electrical current to said substrate, said current
having a time varying current density, wherein the current density
is controlled as a function of time, said function of time
comprised of two or more cycles wherein each cycle independently
has a first time period and a second time period. In this
embodiment the value of said current density during said first time
period is greater than zero, and the value of the current density
during said second time period is less than zero, provided that the
ratio, .beta..sup.A, which is defined as the ratio of the area
bounded by the function and a line representing zero current
density for said first period divided by the absolute value of the
area bounded by the function and a line representing zero current
density for said second period, is greater than 1.
[0005] In another embodiment the technology described herein is
directed to a method of applying a low stress or stress free
coating to substrate, or of electroforming a low stress or stress
free article using electrodeposition comprising the steps of:
[0006] (a) providing a bath including one or more
electrodepositable species; [0007] (b) providing a substrate to be
coated; [0008] (c) at least partially immersing the substrate in
the bath, the substrate being in electrical communication with a
power supply; and [0009] (d) applying an electrical current to said
substrate, said current having a time varying current density. In
this embodiment the current density is controlled as a function of
time, and the function of time is comprised of two or more cycles
wherein each cycle independently has a first time period and a
second time period,
[0010] where the value of said current density during said first
time period is greater than zero, and the value of the current
density during said second time period is less than zero, provided
that the ratio, .beta..sup.A, which is defined as the ratio of the
area bounded by the function and a line representing zero current
density for said first period divided by the absolute value of the
area bounded by the function and a line representing zero current
density for said second period is greater than 1.
[0011] Embodiments described herein also provide coatings and
articles comprising stress free or low stress materials
electrodeposited without the use of stress reducing additives by
the methods described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The drawings are not necessarily to scale; emphasis is being
placed upon illustrating the principals of the disclosure.
[0013] FIG. 1 illustrates one cycle of a generic function used to
control the current density in the electrodeposition of low stress
or stress free coatings or electroform low stress or stress free
articles. The figure indicates the area bounded by the function and
a line representing zero current density for said first period by
the "A" and the area bounded by the function and a line
representing zero current density for said second period by "B,"
which are used to determine the ratio .beta..sup.A.
[0014] FIG. 2 Illustrates an alternative set of terminology that
may be used to describe the generic function used to control the
current density in the plating process, particularly where the
function used is a sine wave function. Positive values of J
(current density) are cathodic and reducing, whereas negative
values are anodic and oxidizing. For net electrodeposition to take
place with a sine wave function the value of .beta. must be greater
than one (i.e. J.sub.offset must be greater than zero).
DETAILED DESCRIPTION
[0015] Materials deposited by electrodeposition must have low
stress to avoid cracking or peeling in the plating process or
subsequent use. Moreover if the electrodeposited materials contain
thin or narrow features, then the stress must be tensile as
compressive stress would likely result in buckling of the material.
A good deal of stress is intrinsic to the plating process, and some
systems such as Ag and Fe--Ni are notorious for their high stress.
See e.g., Marc J. Maldou "LIGA and Micromolding" Chapter 4, The
MEMS Handbook, 2.sup.nd edition, CRC Press, Edited by Mohamed
Gad-el-Hak (2006). While it is possible to relieve stress from
electrodeposited materials by using stress reducing agents during
their deposition, such agents not only add to the cost of final
product, perhaps more importantly they can affect the performance
and properties of the deposited materials.
[0016] The processes described herein provide, among other things,
an electrodeposition process that produces low stress coatings
without the use of stress reducing agents. Embodiments of the
processes described herein may be used to electroform articles
where the process employs a mandrel as a substrate that can be
separated from the electrodeposited materials. The processes may
also be used to form a coating on a substrate that is comprised of
a single layer of low stress or stress free electrodeposited
material and in some embodiments, the process can be used to form
multiple layers or graded layers of electrodeposited materials, one
or more of which are layers of low stress or stress free
electrodeposited materials.
[0017] Stress in a coating or layer may refer to the tendency of a
material to curl or deform, causing it to peel away from the
substrate onto which it is deposited. Tensile and compressive
stresses in a coating or layer result in concave and convex
delamination, respectively. Stress in an electrodeposited coating
or article may be evaluated by any suitable means in the known in
the art. For purposes of this disclosure, low stress coatings and
articles are those that can maintain contact with a rigid substrate
during electrodeposition when the bond strength is less than 400
MPa, or, more preferably less than 350 MPa, 300 MPa, 250 MPa, 200
MPa, 150 MPa, 100 MPa, 60 MPa, 40 MPa, 30 MPa, 20 MPa, or 10 MPa.
For the purposes of this disclosure stress free means that the
coating or article has a level of stress that is at, or below, the
level of measurement, and which does not affect the ability of the
article to maintain contact with the substrate during
electrodeposition.
[0018] The stress of an electrodeposited material also may be
characterized using conventional methods such as the bent strip
method and commercially available testing equipment such a Model
683 deposit stress analyzer, available from Specialty Testing and
Development Co., PA. For purposes of this disclosure, low stress
coatings, layers, and articles have less than 400 MPa, or, more
preferably less than 350 MPa, 300 MPa, 250 MPa, 200 MPa, 150 MPa,
100 MPa, 80 MPa, 60 MPa, 40 MPa, 30 MPa, 20 MPa, or 10M Pa of
stress as assessed by the bent strip method. For the purposes of
this disclosure, where a bent strip test is employed as means of
assessing stress, "stress free" means that the coating, layer or
article has a level of stress that is at, or below, the level of
measurement in the bent strip test.
[0019] For the purposes of this disclosure, "electrodeposition"
defines a process in which electricity drives formation of a
deposit on an electrode (e.g., a substrate) at least partially
submerged in a bath including a component or species, which forms a
solid phase upon either oxidation or reduction. The terms
electrodeposition or electrodeposited include both electrolytic
deposition (e.g., reduction of metal ions to metals) and
electrophoretic deposition.
[0020] For the purposes of this disclosure, "electrodepositable
species" define the constituents of a material deposited using
electrodeposition. Electrodeposited species include, without
limitation, metal ions forming a metal salt. Particles which are
deposited in a metal matrix formed by electrodeposition, polymers
and metal oxides can also be electrodeposited. Organic molecules
(e.g., citric acid, malic acid, acetic acid, and succinic acid) may
also be co-deposited with other electrodepositable species.
[0021] For the purpose of this disclosure, current density is the
current (generally in amperes) per unit area of a substrate upon
which material is to be electrodeposited. Where current densities
are stated to be positive, they are cathodic (reducing) currents
and negative current densities are anodic (oxidizing) currents.
[0022] For the purpose of this disclosure, the average current
density for an electrodeposition process is taken as the integral
of the current density versus time curve describing the process,
divided by the total time and has the units of charge per unit area
per unit time. Average current density can be calculated for one or
more cycles of the function used to control current density in the
electrodeposition processes described herein.
[0023] For the purpose of this disclosure, nanolayered means
layered material having at least one layer with at least one
dimension (usually thickness) greater than 0.5 nm and less than
1,000 nm.
[0024] For the purpose of this disclosure, an electrolyte can be an
aqueous solution or an ionic liquid, either of which may comprise
one or more electrodepositable species.
[0025] In one embodiment a method of producing low stress or stress
free coatings on a substrate, or of electroforming an article on a
substrate (e.g., a mandrel) using electrodeposition comprises:
[0026] applying an electrical current to said substrate, said
current having a time varying current density, [0027] wherein the
current density is controlled as a function of time, said function
of time comprised of two or more cycles wherein each cycle
independently has a first time period and a second time period,
[0028] where the value of said current density during said first
time period is greater than zero, and the value of the current
density during said second time period is less than zero, provided
that the ratio, .beta..sup.A, which is defined as the ratio of the
area bounded by the function and a line representing zero current
density for said first period divided by the absolute value of the
area bounded by the function and a line representing zero current
density for said second period, is greater than 1.
[0029] In another embodiment a method of producing low stress or
stress free coating to substrate, or of electroforming an article
on a substrate (e.g., a mandrel) using electrodeposition comprises:
[0030] (a) providing a bath including one or more
electrodepositable species; [0031] (b) providing a substrate to be
coated; [0032] (c) at least partially immersing the substrate in
the bath, the substrate being in electrically communication with a
power supply; and [0033] (d) applying an electrical current to said
substrate, said current having a time varying current density,
[0034] wherein the current density is controlled as a function of
time, said function of time comprised of two or more cycles wherein
each cycle independently has a first time period and a second time
period, and where the value of said current density during said
first time period is greater than zero, and the value of the
current density during said second time period is less than zero,
provided that the ratio, .beta..sup.A, which is defined as the
ratio of the area bounded by the function and a line representing
zero current density for said first period divided by the absolute
value of the area bounded by the function and a line representing
zero current density for said second period, is greater than 1.
[0035] While the description provided in FIG. 1 is not to be viewed
as limiting the type of functions that may be employed to produce
low stress or stress free coatings and articles by
electrodeposition, that figure illustrates exemplary functions that
may be employed to produce low stress or stress free materials
through electrodeposition. The embodiments described above may be
better understood by reference to that figure.
[0036] As positive current density is defined as a reducing
cathodic current for the purposes of this disclosure, ratio
.beta..sup.A (Beta based on the integrated areas) must be greater
than 1 for a cycle in order for there to be a net deposition of
reducible materials (e.g. metal cations) at the cathode in the
methods forming low or stress free coatings and articles described
herein.
[0037] The value of .beta..sup.A may effectively be any value
greater than 1 and less than infinity for any cycle of the of the
method but more typically .beta..sup.A will be between a value that
is greater than 1 and less than 100, or greater than 1.001 and less
than 100, or greater than 1.01 and less than 100, or greater than
1.05 and less than 100, or greater than 1.1 and less than 100. In
some embodiments the value of .beta..sup.A is greater than a value
selected from 2, 4, 8, 10, 20, 50, 100, 200, 400, 800, 1,000, or
10,000; in such embodiments the value of .beta..sup.A may be
limited by an upper value of 100,000. In other embodiments the
value of the ratio .beta..sup.A may have a value greater than 1, or
1.01, or 1.05 or 1.1 and less than a value independently selected
from 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.8, 1.9, 2,
2.2, 2.4, 2.6, 2.8, 3.0, 3.5, 4, 6, 8, 10, 15, 20, 25, 50, 100,
200, 400, 800, 1,000, or 10,000. In some embodiments the value of
.beta..sup.A within a range selected from: 1.01 to 2, 1.01 to 1.7,
1.01 to 1.6, 1.01 to 1.5, 1.01 to 1.4, 1.01 to 1.3, 1.01 to 1.2,
1.1 to 1.5, 1.1 to 1.6, 1.1 to 1.7, 1.1 to 1.8, 1.3 to 1.5, 1.3 to
1.7, 1.3 to 1.9, 1.5 to 1.7, 1.5 to 1.8, 1.5 to 1.9, 1.5 to 2.0,
1.6 to 1.9, 1.6 to 2, 1.7 to 1.9, 1.8 to 2, 1.5 to 8, 1.5 to 6, 2
to 40, 2 to 20, 2 to 10, 4 to 40, 1.1 to 50, or 2 to 50.
[0038] The number of cycles, each of which includes first period of
electrodeposition and a second period of oxidation (etching or
dissolution), used to apply a coating or to prepare an article
using the methods described herein depends upon the thickness of
the desired coating or article and the characteristics of the cycle
employed (e.g., total passed charge and .beta..sup.A which
represents the ratio of the material deposited to the material
removed in a cycle). In some embodiments the function used in the
electrodeposition process has 3 or more cycles, 10 or more cycles,
50 or more cycles, 100 or more cycles, 200 or more cycles, 500 or
more cycles, 1,000 or more cycles, 2,000 or more cycles, 5,000 or
more cycles, 10,000 or more cycles, 20,000 or more cycles, 50,000
or more cycles, 100,000 or more cycles, 200,000 or more cycles,
400,000 or more cycles, 500,000 or more cycles, 750,000 or more
cycles, or 1,000,000 or more cycles.
[0039] While current density is controlled as a function of time in
the electrodeposition processes described herein, the function for
the individual cycle need not, but can, be the same. In some
embodiments the function is identical for each cycle (although
other parameters including the temperature and plating bath
composition can be varied). In other embodiments the same function
may be applied for one cycle or over a series of consecutive cycle
followed by the application of a different function (with or
without a change in the other parameters). In some embodiments the
function applied for the low stress or stress free
electrodeposition process is identical for 2, 3, 4, 5, 10, 20, 50,
100, 250, 500, 1,000, 5,000, 10,000, 20,000, 50,000, 100,000,
200,000, 500,000 consecutive cycles and the other plating
parameters are also held constant (do not change). In other
embodiments, the function applied for the low stress or stress free
electrodeposition process is identical for 2, 3, 4, 5, 10, 20, 50,
100, 250, 500, 1,000, 5,000, 10,000, 20,000, 50,000, 100,000,
200,000, 500,000 consecutive cycles and one or more, or two or
more, or three or more plating parameters (e.g., plating
temperature, bath composition, or the concentration of the
electrodepositable species in the bath) varied for one or more of
the cycles.
[0040] In another embodiment the function employed for the
electrodeposition processes described herein has 2, 3, 4, 5, 7, 10,
15, 20, 25, 50, 100, 200, 500, or 1,000 consecutive cycles wherein
the function is employed in the electrodeposition process is not
identical for those consecutive cycles. In one variation the
function is varied between a first function and a second function
for alternate cycles. In another variation the function is varied
from a first function to second function to a third function over
three consecutive cycles.
[0041] In some embodiments the value of the ratio .beta..sup.A can
be varied. In such embodiments, .beta..sup.A may be varied for 2,
3, 4, 5, 10, 20, 50, 100, 250, 500, 1,000, 5,000, 10,000, 20,000,
50,000, 100,000, 200,000, 500,000 or more consecutive cycles. In
those embodiments where .beta..sup.A is increased or decreased from
a first value to a second value by incrementally changing
.beta..sup.A, the disclosed methods may be used to create coatings
or articles that vary from a first property or composition to a
second property or composition in a continuous fashion (e.g.,
graded materials).
[0042] The functions describing the change in current density with
respect to time for a cycle of electrodeposition may be of
virtually any form. In some embodiments the function is one that
has a discontinuous first derivative with respect to time. Such
functions include square wave, rectangular wave, triangular wave,
or saw tooth wave forms possessing a DC offset. In other
embodiments the function describing the change in current density
with respect to time may have a continuous first order derivative.
In other embodiments such functions may have a continuous first
order derivative with respect to time. Functions with continuous
first order derivatives include shifted sine wave, shifted cosine
wave, and other periodic wave type functions possessing a DC
offset.
[0043] Shifted sine wave functions, which are a special case of the
general wave forms used to control the current density, may be
described using three parameters, the offset current density, the
frequency and the peak to peak current density used for the plating
process. See FIG. 2, which describes the terms that can be used
with a "shifted sine wave" that has been shifted vertically on the
current density axis by the application of an offset current
density. For shifted sine wave functions a value .beta., which is
the ratio of the peak cathodic current density to the absolute
value of the peak anodic current density may be defined. See FIG. 2
and associated text.
[0044] Where shifted sine or shifted cosine wave forms are used
they are offset such that ratio .beta..sup.A or .beta. will be
greater than 1, resulting in net electrodeposition of material at
the cathode. In other embodiments the sine or cosine waves may be
modified such that the amplitudes for the wave forms in the range
of 0.degree. to 180.degree. and the range 180.degree. to
360.degree. degrees is different, resulting in a .beta..sup.A that
is greater than one.
[0045] In some embodiments wave forms other than shifted sine waves
and square (rectangular) waves with DC offsets may be employed, and
part or all of any method described herein may be conducted
provided that the wave form utilized is not a sine wave or a square
(rectangular) wave with a DC offset. Hence, any of the methods of
this disclosure may be carried out with the proviso that when
current density is controlled as a function of time, the function
is not a sine wave or a square or rectangular wave form.
[0046] The length of time for each cycle of the electrodeposition
processes described herein may be the same or different, with the
length of time varying independently for each cycle. In some
embodiments the function describing the deposition process may have
1 to 4,000, 1 to 2,000, 1 to 800, 1 to 400, 1 to 200, 1 to 100, 1
to 10, 2 to 50, 3 to 75, 10 to 200, 50 to 300, or 100 to 400 cycles
per second (Hz). In general, the frequency of the wave form (e.g.,
sine wave, square wave, or triangular wave) will vary from about
0.01 to about 1,000 Hz, with ranges typically being from about 10
to about 400 Hz.
[0047] The peak anodic and cathodic currents, which are the maximum
currents applied to a substrate during the periods of
electrodeposition and oxidation (etching) during each cycle of the
functions used to control current density, may also be modulated.
Generally the absolute value of peak cathodic and anodic currents
can be independently varied from about 1 to about 2,000
mA/cm.sup.2, with typical ranges being from about 10 to about 300
mA/cm.sup.2 or from about 60 to about 100 mA/cm.sup.2.
[0048] The methods of electrodepositing low stress or stress free
coating or electroforming articles may be used with a broad variety
of electrodepositable species. In some embodiments the bath used
for electrodeposition may contain only one electrodepositable
species. In some embodiments where the bath contains only one
electrodepositable species the electrodepositable species is
selected from the group consisting of: nickel, iron, cobalt,
copper, zinc, manganese, platinum, palladium, rhodium, iridium,
gold, aluminum, magnesium, and silver. In some embodiments where
the bath contains only one electrodepositable species the
electrodepositable species is selected from the group consisting
of: nickel, cobalt, copper, zinc, manganese, platinum, palladium,
rhodium, iridium, gold, aluminum, magnesium, and silver. In other
embodiments where the electrolyte bath contains only one
electrodepositable species the electrodepositable species is
selected from the group consisting of: nickel, cobalt, manganese,
platinum, palladium, rhodium, iridium, and silver. In still other
embodiments where the bath contains only one electrodepositable
species the electrodepositable species is selected from the group
consisting of: nickel, cobalt, copper, zinc, manganese, gold, and
silver.
[0049] In still other embodiments, the methods of electrodepositing
low stress or stress free materials may be practiced with the
proviso that the electrodepositable species is not iron when the
bath (electrolyte) contains only one electrodepositable species of
metal; in such embodiments the bath (electrolyte) may further not
include stress reducing agents (e.g., thiourea or saccharin).
[0050] In some embodiments the electrolyte bath (electrolyte) used
for electrodeposition may contain two or more, or three or more, or
four or more electrodepositable species. In some embodiments where
the bath (electrolyte) contains two or more, or three or more, or
four or more electrodepositable species, at least one
electrodepositable species is selected from the group consisting
of: molybdenum, tungsten, nickel, iron, cobalt, copper, zinc,
manganese, platinum, palladium, rhodium, iridium, gold, aluminum,
magnesium, and silver. In other embodiments at least one
electrodepositable species is selected from the group consisting
of: molybdenum and tungsten. In embodiments, where the bath
(electrolyte) for electrodeposition contains two or more, or three
or more, or four or more electrodepositable species, the methods of
electrodepositing low stress or stress free materials may be
practiced with the proviso that the electrodepositable species is
not iron.
[0051] In some embodiments the material to be deposited is an alloy
comprising nickel having greater than about 60% 70%, 75% 80%, 85%
90% or 95% of the electrodeposited material as nickel on a weight
basis. In other embodiments the material to be deposited will be an
alloy comprising nickel and iron having greater than about 55%,
60%, 70%, 75% 80%, 85% 90% or 95% of the electrodeposited material
as the iron with the remainder made up of either nickel, or nickel
and up to 5% other metals on a weight basis.
[0052] In another embodiment the material to be deposited is an
alloy comprising chromium, iron, and optionally nickel. In such
alloys the chromium is present as 11-25% of the electrodeposited
material, nickel is present from 0-20% of the electrodeposited
materials, with the remainder made up of either iron, or iron and
up to 5% other metals on a weight basis.
[0053] In still another embodiment the material to be deposited is
an alloy comprising copper and zinc. In such alloys the copper is
present at 1-95% of the electrodeposited material, preferably
between 50% and 80%, with the remainder made up of either zinc, or
zinc and up to 10% other metals on a weight basis.
[0054] In still another embodiment the material to be deposited is
an alloy comprising copper and tin. In such alloys the copper is
present at 1-95% of the electrodeposited material, preferably 11%
to 13%, with the remainder made up of either tin, or tin and up to
10% other metals on a weight basis.
[0055] In yet another embodiment the material to be deposited is an
alloy comprising copper and aluminum. In such alloys the copper is
present at 1-25% of the electrodeposited material, with the
remainder made up of either aluminum, or aluminum and up to 10%
other metals (such as magnesium) on a weight basis.
[0056] In one embodiment chromium may be electrodeposited alone or
as an alloy wherein chromium comprises greater than 50% of the
electrodeposited material on a weight basis. In methods of
electrodepositing chromium the chromium may be electrodeposited
from either a Cr.sup.+3 or Cr.sup.+6 salt.
[0057] One embodiment provide for the electrodeposition of chromium
as an alloy with iron, wherein the chromium comprises 1%-75% of the
electrodeposited material on a weight basis with the remainder made
up of either iron, or iron and up to 10% other metals on a weight
basis. In such an embodiment the chromium may be electrodeposited
from a Cr.sup.+3 salt.
[0058] In still other embodiments, the material to be
electrodeposited is an alloy comprising a metal selected from
molybdenum, tungsten, nickel, iron, cobalt, copper, zinc,
manganese, platinum, palladium, rhodium, iridium, gold, aluminum,
magnesium, and silver; wherein greater than about 40%, 50% 60% 70%,
75% 80%, 85%, 90%, or 95% of the electrodeposited alloy is
comprised of the selected metal.
[0059] Other embodiments provide for the electrodepositing of iron
with an organic molecule (e.g., citric acid, malic acid, acetic
acid, or succinic acid). In such embodiments the organic molecule
may comprise up to 2% of the total weight of the deposited material
with the remainder made up of either iron, or iron and up to 10%
other metals on a weight basis.
[0060] In some embodiments where the system (electrolyte) contains
one or more electrodepositable species, those species may be the
same electrodepositable species for the entirety of
electrodeposition processes (the same species for all cycles). In
other embodiments where the system contains one or more
electrodepositable species, the composition of the bath used for
electrodeposition may be changed so that different species or
mixtures of electrodepositable species are present for different
portions of the electrodeposition processes (i.e., to form a
material that is compositionally modulated throughout its growth
direction).
[0061] In addition to varying composition of the electroplating
media (bath), a variety of electrodeposition parameters can be
modulated while still electrodepositing low stress or stress
coatings or electroforming low stress or stress free articles. In
some embodiments one or more of the electrodeposition parameters
that can be modulated in one or more independently selected cycles,
(whether those cycles are consecutive or not) are selected from:
peak positive current density; the length of time of said first
time period; the peak negative current density; the length of time
of said second time period, the average current density,
electrodeposition temperature (temperature of the bath) or the
composition of the electrodeposition media (e.g., electrodeposition
bath) may be. In other embodiments, one or more, or two or more,
parameters selected from: the peak positive current density; the
length of time of said first time period; the peak negative current
density; the length of time of said second time period, or the
average current density may be modulated in one or more, or two or
more, independently selected cycles. In still other embodiments,
one or more, or two or more, parameters selected from the
temperature of the electrodeposition media (bath) or the
composition of said the bath may be modulated in one or more, or
two or more, independently selected cycles.
[0062] Embodiments of the methods described herein may be employed
to produce low stress or stress free coatings and articles that may
consist of one layer (material having a single type of structure
and composition) in addition to coatings and articles that are
layered or nanolayered. Layers and nanolayers present in the
coatings and articles described herein need not arise from single
cycles of the function used to control the electrodeposition
process, instead, layers or nanolayers may arise from the
application of numerous cycles of a function used to control
electrodeposition. Thus, in some embodiments, the methods described
herein may be used to develop layered or nanolayered coatings and
articles by utilizing different wave forms in combinations. For
example, a single composition may be deposited as a low stress or
stress free layer utilizing numerous cycles of a sine wave
function, followed by the deposition of a next layer of the same
composition utilizing numerous cycles of a saw tooth wave form.
Alternatively, low stress or stress free layers may be built up by
the application of numerous cycles of specific function describing
the electrodeposition of a first composition followed by the use
numerous cycles of the same function to apply a layer of different
composition or a layer of the same composition at a different
temperature.
[0063] Embodiments of the methods described herein are particularly
useful as they permit the electrodeposition and electroforming of
low stress or stress free coatings and articles without the use of
stress reducing agent; however, where desirable it is possible to
use the methods describe above in combination standard
electrodeposition process that either do not control stress or use
stress reducing agents. Thus, in addition to the deposition of
layers of a substance (e.g., a metal) using low stress or stress
free electrodeposition as described herein, it is possible to
deposit layers of low stress or stress free materials utilizing
stress reducing agents or by standard electrodeposition (e.g., DC
electroplating). In some instances, such as where control of defect
propagation or the direction of corrosive decomposition of coatings
is desired, it may be desirable to prepare layered or nanolayered
materials that have repeating (e.g., alternating) layers of: stress
free and low stress materials; low stress or stress free materials
alternated with layers of uncontrolled stress materials; or layers
of stress free, low stress and uncontrolled stress materials.
[0064] A variety of substrates for electrodeposition may be
employed in the methods described herein. While the substrate may
comprise a solid, conductive material (such as a metal object to be
coated), other substrates are also possible. For example, instead
of being solid, the substrate may be formed of a porous material,
such as a consolidated porous substrate, such as a foam, a mesh, or
a fabric. Alternatively, the substrate can be formed of an
unconsolidated material, such as, a bed of particles, or a
plurality of unconnected fibers.
[0065] In some embodiments, including for example, embodiments
which utilize electrodeposition, the substrate is generally formed
from a conductive material or a non-conductive material which is
made conductive by metallizing. In other embodiments, the substrate
may be a semi-conductive material, such as a silicon wafer, or a
nonconductive material, such as a ceramic or plastic composite.
Where it is desirable to prepare an article through the use of
electroforming, a solid conductive mandrel that can be separated
from the electroformed materials may be employed (i.e., titanium or
stainless steel mandrel).
[0066] The electrodeposition methods described herein may be used
without etching substrates prior to the application of low stress
coatings without the use of additives in the electrodeposition
process (e.g., the bath) to relieve stress. The methods of coating
a substrate described herein may be utilized without the use of
etching by electrical current, that is to say the application of a
net negative (anodic current) to the substrate prior to (or
immediately prior to) the application of a low stress coating.
Similarly, the methods of coating a substrate described herein may
be utilized without the use of etching by chemical means prior to
(or immediately prior to) the application of a low stress coating
without the use of additive to relieve stress.
[0067] Some embodiments of this present disclosure are directed to
a coating or article produced by the methods of electrodepositing
low stress or stress free materials described herein that do not
require the use of stress reliving agents. In some embodiments, a
coating or article comprises a single low stress or stress free
layer of electrodeposited materials that has not been deposited
using stress reducing agents.
[0068] In other embodiments, a low stress or stress free coating or
article of the present technology comprises: a first material
having a first composition and defined by one or more of a first
composition, a first average grain size, a first grain boundary
geometry, a first crystal orientation, and a first defect density;
and a second material having a second composition and a second
nanostructure defined by one or more of a second composition, a
second average grain size, a second grain boundary geometry, a
second crystal orientation, and a second defect density. In still
another embodiment, a low stress or stress free coating comprises:
a first material having a first composition and a first
nanostructure defined by one or more of a first composition, a
first average grain size, a first grain boundary geometry, a first
crystal orientation, and a first defect density; and a second
material having a second composition and a second nanostructure
defined by one or more of a second composition, a second average
grain size, a second grain boundary geometry, a second crystal
orientation, and a second defect density; with the proviso that the
second composition is the same as the first composition while one
of the first average grain size differs from the second average
grain size, the first grain boundary geometry differs from the
second grain boundary geometry, the first crystal orientation
differs from the second crystal orientation, and the first defect
density differs from the second defect density.
[0069] In some embodiments, property modulated coatings and
articles are provided comprising a plurality of alternating layers,
in which one or more of those layers are low stress or stress free
layers that have specific mechanical properties, such as, for
example, tensile strength, elongation, hardness, ductility, and
impact toughness, and where the specific mechanical properties are
achieved by altering the nanostructure of those layers. Examples of
such are provided in Examples 1 and 2.
[0070] In general, tensile strength may be controlled through
controlling frequency of a signal used for electrodepositing a
material. In general, percentage of elongation of a material can
also be controlled through frequency. In general, hardness,
ductility, and impact toughness can be controlled through
controlling deposition temperature. Other methods for controlling
tensile strength, elongation, hardness, ductility and impact
toughness are also envisioned.
[0071] The structure of low stress and stress free electrodeposited
materials may also be controlled in order to produce materials with
desired properties. Smaller grain sizes, which can range, e.g.,
from about 0.5 nanometers to about 100 nanometers, generally will
yield layers that exhibit high impact toughness. Large grain sizes,
which generally will be greater than 1,000 nanometers, such as, for
example, 5,000 or 10,000 nanometers, will generally produce layers
that provide greater ductility. Of course, the grain sizes will be
relative within a given group of layers such that even a grain size
in the intermediate or small ranges described above could be deemed
large compared to, e.g., a very small grain size or small compared
to a very large grain size.
[0072] Generally, such grain sizes can be controlled through
process parameters, such as, for example deposition temperature
(e.g., electrodeposition bath temperature). To modulate grain size
utilizing temperature control, a first layer defined by large
grains can be formed by increasing the deposition temperature and a
second layer defined by smaller grains can be formed by decreasing
the temperature.
[0073] The thickness of the individual layers in the coatings and
articles can range from about 0.1 nanometer to about 10,000
nanometers or more. Layer thickness may range from about 5
nanometers to 50 nanometers, although varied thicknesses are
expressly envisioned. Coatings and articles prepared by the methods
described herein may contain a single layer or any number of
desired layers, including a number of layers within a range
selected from: 2-10, 10-20, 20-30, 30-50, 50-100, 2-500, 100-500,
2-1,000, 500-1,000, 1,000-5,000 5,000-10,000, or 2-10,000 or even
more layers. Each layer may be independently created with a desired
composition, thickness, and nanostructure/microstructure and with
each layer being independently chosen to be of a low stress or
stress free nature.
[0074] The coatings and articles described herein may be used
separately or as part of other coatings and articles and may be
incorporated into laminated structures. In addition, the methods of
preparing low stress or stress free coatings and articles utilizing
the electrodeposition methods described herein, may be used in
conjunction with other methods of preparing low stress or stress
free coatings and articles. Such methods include the use of
chemical deposition such as electroless (auto-catalytic) deposition
or plating, chemical vapor deposition, or physical vapor
deposition. Such processes may be advantageous where it is
difficult to electrodeposit specific metals such as aluminum,
titanium, and magnesium.
EXAMPLES
[0075] The following examples are merely intended to illustrate the
practice and advantages of specific embodiments of this disclosure;
and are not intended in any way to limit or illustrate any limits
of the methods, articles or embodiments described herein.
Example 1: Low Stress Electrodeposition of Iron
[0076] Deposition of iron layers in a low stress or stress free
form may be accomplished using an offset sine wave to control
current density in the electrodeposition process. The beta value is
defined as the ratio of peak cathodic to peak anodic current
densities; alternately, .beta..sup.A is defined as the ratio
cathodic charge density (integral of the cathodic portion of j(t)
with respect to time) to the anodic charge density (integral of the
anodic portion of j(t) with respect to time). At low beta value
(<1.8), the electroplated iron layers have low hardness and high
ductility.
[0077] The electroplating system includes a tank, electrolyte of
FeCl.sub.2 bath with or without CaCl.sub.2, computer controlled
heater to maintain bath temperature, a power supply, and a
controlling computer. The anode is low carbon steel sheet, and
cathode is titanium plate which will make it easy for the deposit
to be peeled off. Carbon steel can also be used as the cathode if
the deposit does not need to be peeled off from the substrate.
Polypropylene balls are used to cover the bath surface in order to
reduce bath evaporation.
The process for producing an iron laminate is as follows: [0078] 1.
Prepare a tank of electrolyte consisting of 2.0 M FeCl.sub.2 plus
1.7 CaCl.sub.2 M in deionized water. [0079] 2. Adjust the pH of the
electrolyte to -0.5-1.5 by addition of HCl. [0080] 3. Control the
bath temperature at 60.degree. C. [0081] 4. Clean the titanium
substrate cathode and low carbon steel sheet anode with deionized
water and immerse both of them into the bath. [0082] 5. To start
electroplating a high ductility layer, turn on the power supply,
and controlling the power supply to generate a shifted sine wave
with a beta of 1.26 (.beta..sup.A=1.50) by setting the following
parameters: 250 Hz with a peak cathodic current density of 43
mA/cm.sup.2, and a peak anodic current density of -34 mA/cm.sup.2
applied to the substrate (i.e., a peak to peak current of 78
mA/cm.sup.2 with a DC offset of 4.4 mA/cm.sup.2). Continue
electroplating for an amount of time necessary to achieve the
desired high ductility layer thickness. [0083] 6. Remove the
substrate and deposit from the bath and immerse in DI water for 10
minutes and blow it dry with compressed air. [0084] 7. Peel the
deposit from the underlying titanium substrate to yield a
free-standing low stress iron sheet.
Example 2: Electrodeposition of Low Stress High Elongation
Nickel-Iron Alloy
[0085] Low stress or stress free Ni--Fe alloys can be
electrodeposited using a shifted sine wave with a defined .beta.
value (see FIG. 2 and associated text). At low beta values
(<1.3), the electroplated iron-nickel alloy layers have low
hardness, low stress, larger grain size, and high elongation, while
at high beta (>1.5), the plated iron-nickel alloy layers have
higher hardness, smaller grain size and lower elongation. At beta
value of (<1.25), the deposited Ni--Fe alloy film's stress is
almost zero, which makes it possible to obtain low stress and
ductile Ni--Fe alloy deposits without sulfur co-deposition caused
by adding stress reducing additives such as saccharin. The low
stress Fe--Ni deposit makes it possible to deposit very thick
layers. It is also possible to deposit onto semiconductors and low
adhesion substrates such as conductively coated non-conductive
mandrels. Because no sulfur containing additives are used, it is
possible for these Ni--Fe alloy deposits to be used at high
temperature environments without brittleness caused by co-deposited
sulfur.
[0086] For electrodeposition of Ni--Fe alloys the system includes a
tank, an electrolyte of a mixture of FeCl.sub.2 and NiCl.sub.2, a
computer controlled heater to maintain bath temperature, a power
supply, and a controlling computer. The anode is an Ni--Fe alloy
plate. Any conductive material can be used as the cathode, however,
where titanium is used as the cathode, the deposit can be removed
from its surface. Carbon steel can be used as the cathode if the
deposit does not need to be removed from the substrate.
Polypropylene balls are used to cover the bath surface in order to
reduce bath evaporation.
Electrodeposition of the Ni--Fe laminate is conducted as follows:
[0087] 1. A tank (bath) of electrolyte consisting of a mixture of
1.0 M FeCl.sub.2 and 1.0 M NiCl.sub.2 in deionized water is
prepared. [0088] 2. The pH of the electrolyte is adjusted to 0.8 by
addition of HCl. [0089] 3. The bath temperature is maintained at
50.degree. C. [0090] 4. The substrate cathode (metals, alloys,
semiconductors, or conductively coated non-conductive mandrels) and
the Fe--Ni alloy anode are cleaned with deionized water and
immersed in the electrolyte bath. [0091] 5. Electroplating of a low
stress, high ductility layer is started by providing power to the
electroplating power supply, and controlling the power supply to
generate a shifted sine wave with a .beta. value of 1.25 by setting
the following parameters: 250 Hz with a peak-to-peak current
density of 60 mA/cm.sup.2, a DC offset current density 3.3
mA/cm.sup.2. Electroplating is continued for an amount of time
necessary to achieve the desired thickness. [0092] 6. The substrate
bearing the electrodeposited Fe--Ni alloy is removed from the bath
and immerse in deionized water for 10 minutes and blown dry with
compressed air. [0093] 7. The electrodeposited Ni--Fe alloy is
removed by peeling it from the underlying substrate to yield a
free-standing nickel-iron film. Alternatively, the deposited
nickel-iron alloy may be left as a deposit on the substrate.
Example 3: Electrodeposition of Low Stress Ni Films Using Shifted
Sine Wave
[0094] Electrodeposition of nickel films may be accomplished using
a shifted sine wave similar to that employed in Example 2. At low
beta values (<1.3) electroplated nickel films have low hardness,
low stress, larger grain size, and high elongation, while at high
beta (>1.5), the plated nickel films have higher hardness,
smaller grain size and lower elongation. At beta value of
(<1.25), deposited Ni films have almost zero stress, which makes
it possible to obtain low stress and ductile Ni deposits without
sulfur co-deposition from stress reducing additives such as
saccharin. The low stress of Ni deposit electrodeposited using the
embodiments disclosed herein makes it possible to deposit very
thick layers. By controlling the wave form used to deposit nickel
in a low stress or stress free format, it is also possible to
electrodeposited nickel onto low adhesion substrates such as
conductively coated non-conductive mandrels. Because no sulfur
containing additives are used, it is possible for these Ni deposits
to be used in high temperature environments without becoming
brittle due to co-deposited sulfur.
[0095] For electrodeposition of nickel the system includes a tank,
an electrolyte of NiCl.sub.2, a computer controlled heater to
maintain bath temperature, a power supply, and a controlling
computer. The anode is a nickel plate. Any conductive material can
be used as the cathode. However, where titanium is used as the
cathode, the deposit can be removed from its surface. Carbon steel
can be used as the cathode if the deposit does not need to be
removed from the substrate. Polypropylene balls are used to cover
the bath surface in order to reduce bath evaporation.
The process for producing an iron deposit is as follows: [0096] 1.
A tank (bath) of electrolyte consisting of a mixture of 1.0 M
NiCl.sub.2 in deionized water is prepared. [0097] 2. The pH of the
electrolyte is adjusted to 0.8 by addition of HCl. [0098] 3. The
bath temperature is maintained at 50.degree. C. [0099] 4. The
substrate cathode (metals, alloys, semiconductors, or conductively
coated non-conductive mandrels) and the nickel anode are cleaned
with deionized water and immersed in the electrolyte bath. [0100]
5. Electroplating of a low stress, high ductility layer is started
by providing power to the electroplating power supply, and
controlling the power supply to generate a shifted sine wave with a
.beta. value of 1.25 by setting the following parameters: 250 Hz
with a peak-to-peak current density of 60 mA/cm.sup.2, a DC offset
current density 3.3 mA/cm.sup.2. Electroplating is continued for an
amount of time necessary to achieve the desired thickness. [0101]
6. The substrate bearing the electrodeposited nickel is removed
from the bath and immersed in deionized water for 10 minutes and
blown dry with compressed air [0102] 7. The electrodeposited nickel
is removed by peeling it from the underlying substrate to yield a
free-standing nickel film. Alternatively, the deposited nickel may
be left as a deposit on the substrate.
* * * * *