U.S. patent application number 14/712626 was filed with the patent office on 2015-11-12 for functionally graded coatings and claddings for corrosion and high temperature protection.
The applicant listed for this patent is Modumetal, Inc.. Invention is credited to Rajendra Kumar Bordia, Brian Flinn, Christina A. Lomasney, John D. Whitaker.
Application Number | 20150322588 14/712626 |
Document ID | / |
Family ID | 43063528 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150322588 |
Kind Code |
A1 |
Lomasney; Christina A. ; et
al. |
November 12, 2015 |
Functionally Graded Coatings and Claddings for Corrosion and High
Temperature Protection
Abstract
The present disclosure describes functionally graded coatings
and claddings for corrosion and high temperature protection.
Inventors: |
Lomasney; Christina A.;
(Seattle, WA) ; Whitaker; John D.; (Seattle,
WA) ; Flinn; Brian; (Seattle, WA) ; Bordia;
Rajendra Kumar; (Seattle, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Modumetal, Inc. |
Seattle |
WA |
US |
|
|
Family ID: |
43063528 |
Appl. No.: |
14/712626 |
Filed: |
May 14, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13323431 |
Dec 12, 2011 |
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14712626 |
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PCT/US2010/001677 |
Jun 11, 2010 |
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13323431 |
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61186057 |
Jun 11, 2009 |
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Current U.S.
Class: |
428/418 ;
204/471; 204/509; 428/425.8; 428/447; 428/457; 428/461;
428/469 |
Current CPC
Class: |
Y10T 428/31692 20150401;
C25D 5/20 20130101; C25D 21/12 20130101; Y10T 428/31529 20150401;
Y10T 428/31678 20150401; C25D 13/00 20130101; C25D 5/18 20130101;
C25D 15/02 20130101; C25D 5/50 20130101; Y10T 428/31605 20150401;
Y10T 428/31663 20150401; C25D 21/14 20130101 |
International
Class: |
C25D 13/00 20060101
C25D013/00 |
Claims
1. A method for producing a functionally-graded coating,
comprising: (a) exposing a mandrel or a substrate to be coated to
an electrolyte containing one or more metal ions, and containing
one or more ceramic particles, polymer particles, pre-ceramic
polymer particles, active fillers, or a combination thereof; (b)
applying an electric current and changing in time one or more of:
an amplitude of the electrical current, an amplitude of an
electrical potential, an electrolyte temperature, a relative
concentration of metal ions or particles in the electrolyte, or an
electrolyte agitation, to change a ratio of an electrodeposited
species; and (c) promoting growth of the functionally-graded
coating until a desired thickness of the coating is achieved, the
electrodeposited species being varied throughout the desired
thickness of the coating.
2. (canceled)
3. The method of claim 1, further comprising heat treating the
coating to cause partial or complete sintering of a pre-ceramic
polymer applied to said mandrel or substrate by said applying of
said electric current.
4. The method of claim 3, where the heat treating has a heat
treatment temperature between 200 degrees C. to 1300 degrees C.
5-6. (canceled)
7. The method of claim 1, wherein said one or more metal ions are
selected from the group consisting of: Ni, Zn, Fe, Cu, Au, Ag, Pd,
Sn, Mn, Co, Pb, Al, Ti, Mg, and Cr.
8. The method of claim 1, wherein the ceramic particles are chosen
from metal oxides, carbides, nitrides, or combinations thereof.
9-12. (canceled)
13. The method of claim 1, wherein the polymer particles comprise
one or more of: epoxy, polyurethane, polyaniline, polyethylene,
poly ether ether ketone, polypropylene, and siloxane; wherein the
pre-ceramic polymer particles comprise one or more of: siloxides,
silences, silanes, organosilanes, siloxanes, polyhedral oligomeric
silsesquioxanes, polydimethylsiloxanes, and polydiphenylsiloxanes;
and/or wherein the active fillers comprise one or more of: titanium
disilicide, yittrium disilicide, nickel disilicide, niobium
disilicide, tantalum disilicide, vanadium disilicide, chromium
disilicide, and molybdenum disilicide.
14.-24. (canceled)
25. A coating prepared by the method of claim 1.
26. An electrodeposited corrosion-resistant functionally-graded
coating, comprising: an interior first region of metal; and an
exterior second region of polymer, pre-ceramic polymer, or ceramic,
wherein a non-discrete region is disposed between the first region
and the second region, the non-discrete region being a combination
of the first region and the second region.
27. The functionally-graded coating of claim 26, wherein said
non-discrete region has a monotonically increasing metal
concentration gradient.
28. The functionally-graded coating of claim 26, wherein said
non-discrete region has a monotonically decreasing metal
concentration gradient.
29. The functionally-graded coating of claim 26, wherein said
functionally-graded coating is corrosion-resistant or substantially
corrosion resistant, is heat resistant or substantially heat
resistant, and/or wear resistant or substantially wear
resistant.
30-31. (canceled)
32. The functionally-graded coating of claim 26, wherein said metal
comprises one or more metal ions selected from the group consisting
of: Ni, Zn, Fe, Cu, Au, Ag, Pd, Sn, Mn, Co, Pb, Al, Ti, Mg, and
Cr.
33. The functionally-graded coating of 26, wherein said ceramic
comprises one or more metal oxides, carbides, nitrides, or
combinations thereof.
34-37. (canceled)
38. The functionally-graded coating of claim 26, wherein the
polymer comprises one or more of: epoxy, polyurethane, polyaniline,
polyethylene, poly ether ether ketone, polypropylene, and siloxane;
and wherein the pre-ceramic polymer comprises one or more of:
siloxides, silences, silanes, organosilanes, siloxanes, polyhedral
oligomeric silsesquioxanes, polydimethylsiloxanes, and
polydiphenylsiloxanes.
39. (canceled)
40. The functionally-graded coating of claim 26, further comprising
a first substrate disposed proximate to a second substrate
comprising iron, copper, zinc, aluminum, titanium, nickel,
chromium, graphite, carbon, cobalt, lead, epoxy, or composites or
alloys thereof.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/186,057, filed Jun. 11, 2009, tilted
Functionally Graded Coatings and Claddings for Corrosion and High
Temperature Protection, incorporates herein by reference in its
entirety.
[0002] A process for depositing functionally graded materials and
structures is described for manufacturing materials that possess
the high temperature and corrosion resistant performance of
ceramics and glasses, while at the same time eliminating the common
mismatches encountered when these are applied to structural metal
or composite substrates. An example of the structure of a
functionally graded coating is shown in FIG. 1. An example of the
functionally graded coating structure applied to a pipe is shown in
FIG. 2.
[0003] Electrolytic deposition describes the deposition of metal
coatings onto metal or other conductive substrates and can be used
to deposit metal and ceramic materials via electrolytic and
electrophoretic methods. Electrodeposition which is a low-cost
method for forming a dense coating on any conductive substrate and
which can be used to deposit organic primer (i.e. "E-coat"
technology) and ceramic coatings.
[0004] The embodiments described herein include methods and
materials utilized in manufacturing functionally graded coatings or
claddings for at least one of corrosion, tribological and high
temperature protection of an underlying substrate. The technology
described herein also is directed to articles which include a wear
resistant, corrosion resistant and/or high temperature resistant
coating including a functionally-graded matrix.
[0005] One embodiment provides a method which will allow for the
controlled growth of a functionally-graded matrix of metal and
polymer or metal and ceramic on the surface of a substrate, which
can corrode, or otherwise degrade, such as a metal.
[0006] Another embodiment provides a method which includes the
electrophoretic deposition of controlled ratios of ceramic
pre-polymer and atomic-scale expansion agents to form a ceramic
(following pyrolysis). This form of electrophoretic deposition may
then be coupled with electrolytic deposition to form a hybrid
structure that is functionally graded and changes in concentration
from metal (electrolytically deposited) to ceramic, polymer or
glass (electrophoretically deposited).
[0007] Embodiments of the methods described here provide a
high-density, corrosion and/or heat resistant material (e.g.,
ceramic, glass, polymer) that is deposited onto the surface of a
substrate to form a functionally-graded polymer:metal,
ceramic:metal, or glass:metal coating. The result is a coating, of
controlled density, composition, hardness, thermal conductivity,
wear resistance and/or corrosion resistance, that has been grown
directly onto a surface.
[0008] The functionally-graded coating made according to the
methods disclosed herein may be resistant to spallation due to
mismatch in any of: coefficient of thermal expansion, hardness,
ductility, toughness, elasticity or other property (together
"Interface Property"), between the substrate and the ceramic,
polymer, pre-ceramic polymer (with or without fillers) or glass
(together "Inert Phase") as the coating incorporates a material at
the substrate interface, which more closely matches the Interface
Property of the substrate.
[0009] In general, coatings made according to methods described
herein are resistant to wear, corrosion and/or heat due to the
hard, abrasion-resistant, non-reactive and/or heat-stable nature of
the Inert Phase.
[0010] Polymer-derived ceramics that incorporate active fillers
(e.g., TiN, Ti disilicide, and others) to improve density, have
shown promise as a way to process a variety of Inert Phases, which
are more dense than polymer-derived ceramics which do not
incorporate these fillers. Polymer-derived ceramic composites have
been demonstrated for applications, including--oxidation resistance
and thermal barriers, due to their high density and low open-pore
volume (e.g., the ceramic has less than 1, 5, 10, 20, 30, 40, or 50
percent voids based on volume). See, J D Toney and R K Bordia,
Journal of European Ceramic Society 28 (2008) 253-257. These
polymer-derived ceramics can be electrophoretically deposited.
Electrophoretic deposition is a two-step process. In a first step,
particles suspended in a liquid are forced to move towards one of
the electrodes by applying an electric field to the suspension
(electrophoresis). In a second step (deposition), the particles
collect at one of the electrodes and form a coherent deposit on it.
Since the local composition of the deposit is directly related to
the concentration and composition of the suspension at the moment
of deposition, the electrophoretic process allows continuous
processing of functionally graded materials. Polymer-derived
ceramics is the method used in commercial production of
Nicalon.RTM. and Tyranno fibers.
[0011] In embodiments, the technology of this disclosure includes
the use of electrochemical deposition processes to produce
composition-controlled functionally-graded coating through chemical
and electrochemical control of the initial suspension. This
deposition process is referred to as Layered Electrophoretic and
Faradaic Deposition (LEAF). By controlling the composition and
current evolution during the deposition process, LEAF affords the
means to engineer step-graded and continuously graded compositions;
see Figs. and reference graphs that show dependence of Ni and Si as
a function of solution chemistry and current density. Control of
current evolution and direction of the electric field also offers
the possibility to orient anisotropic powders allowing intimate
control of both the density AND the morphology of the Inert Phase
(e.g., the content and organization of added ceramic, polymer or
glass materials incorporated into an electrodeposited
functionally-graded coating). For example, in one embodiment by
controlling current evolution and the direction of the electric
field in a solution including pre-ceramic polymer, the resulting
density of ceramic can be varied through the coatings to produce a
varying morphology of ceramic/metal composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an illustration of a functionally graded
material.
[0013] FIG. 2 is an illustration of a pipe based on functionally
graded material shown in FIG. 1.
[0014] FIG. 3 is graph illustrating mass loss of a substrate per
area over time for several materials exposed to concentrated
sulfuric acid at 200 degrees C.
[0015] FIG. 4 illustrates Active Filler Controlled Pyrolysis.
[0016] FIG. 5 illustrates LEAF electrophoretic deposition process
on a fiber mat.
[0017] FIG. 6 illustrates the concentration of Si and nickel in
deposits found by changing the current density. Si is the left most
member of each bar graph pair and nickel the right most member of
each bar graph pair measured at a specific current density
[0018] FIG. 7 illustrates the concentration of Ni in the emulsion
increases from left to right. Si is the left most member of each
bar graph pair and nickel the right most member of each bar graph
pair prepared with the noted solution concentration of nickel.
DETAILED DESCRIPTION
[0019] Polymer-derived ceramics have shown promise as a novel way
to process low-dimensional ceramics, including matrices, fibers and
coatings. Polymer-derived ceramic composites have been demonstrated
for applications including oxidation barriers, due to their high
density and low open-pore volume. See, Torrey and R K Bordia,
Journal of European Ceramic Society 28 (2008) 253-257.
[0020] The Active Filler Controlled Pyrolysis (AFCoP),
polymer-derived ceramics offer many benefits over tradition ceramic
processing methods including: [0021] Liquid form with low
crosslinking temperature [0022] High purity reactants [0023]
Tailorable composition, microstructure, nanostructures and
properties [0024] Ability to produce crystalline and beta-SiC
phases
[0025] Pure polymer-derived ceramics suffer from certain
performance limitations. One such limitation is the occurrence of
volume shrinkage--up to 50%, upon sintering. To prevent this, and
in order to increase the density of PDC matrices, the AFCoP process
is employed, as shown in FIG. 4.
[0026] To produce fully-dense ceramic matrices, the active-filler
additive can be occluded into the liquid polymer prior to casting
and sintering. During sintering, this additive acts as an expansion
agent, resulting in a fully dense part with near zero volume loss
(e.g., there are no voids present). Active fillers include Si, Al,
Ti and other metals, which on pyrolysis form SiC, Al2O.sub.3 or
TiSi.sub.2, for example. One of the limitations of this process, as
it is practiced currently, is the limited reactivity of the
fillers. In many cases, due to kinetic limitations, even for the
finest available powders, the filler conversion is incomplete. As
will be shown in the processes described herein, the reactive
"filler" and the polymer will mixed at molecular scale leading to
highly efficient conversion of the filler to the product phase.
[0027] Polymer-derived ceramics and in particular, AFCoP ceramics,
have shown promise as a novel way to process a variety of ceramics
forms, including matrices, fibers and coatings. Polymer-derived
ceramic composites have been demonstrated for applications,
including-oxidation resistance and thermal barriers, due to their
high density and low open-pore volume. See, J D Torrey and R K
Bordia, Journal of European Ceramic Society 28 (2008) 253-257. In
the some embodiments of this disclosure the AFCoP concept and the
LEAF deposition process are combined to enable a manufacturing
capability which can produce tailorable, low-cost,
ultra-high-performance SiC.sub.f/SiC composites and parts.
[0028] The Layered Electrophoretic And Faradaic (LEAF) production
process employed herein enables the low-cost production of tailored
ceramic matrices. A schematic of one embodiment of that process
described in Scheme A.
##STR00001##
[0029] Starting from SiC powders and fiber, a first portion of the
LEAF process consists in depositing either direct SiC powders,
pre-ceramic polymer emulsions (including active fillers) or a
combination of these onto the SiC fiber. Electrophoretic deposition
is a two-step process. In a first step, particles suspended in a
liquid are forced to move towards one of the electrodes by applying
an electric field to the suspension (electrophoresis). In a second
step (deposition), the particles collect at one of the electrodes
and form a coherent deposit on it. Since the local composition of
the deposit is directly related to the concentration and
composition of the suspension at the moment of deposition, the
electrophoretic process allows continuous continuous processing of
functionally graded materials.
[0030] A variety of substrates may be employed to prepare the
compositions described herein. In one embodiment, the compositions
are prepared by the LEAF electrophoretic deposition process
outlined above on fiber mat as illustrated in FIG. 5.
[0031] The LEAF process offers the ability to reliably produce
composition-controlled "green" (not yet sintered) ceramic through
chemical and electrochemical control of the initial suspension. By
shaping the starting fiber, which serves as a mandrel, LEAF
provides a means to manufacture free standing parts of complex
geometry, and hybrid, strength-tailored materials.
[0032] By controlling the composition and current evolution during
deposition process, LEAF affords the means to engineer step-graded
and continuously graded compositions. Control of current evolution
and direction of the electric field also offers the possibility to
orient anisotropic powders allowing intimate control of both the
density AND the morphology of the ceramic deposit.
[0033] Layer thickness can be controlled by, among other things,
the application of current in the electrodeposition process. In
some embodiments current density may be varied within the range
between 0.5 and 2000 mA/cm.sup.2. Other ranges for current
densities are also possible, for example, a current density may be
varied within the range between: about 1 and 20 mA/cm.sup.2; about
5 and 50 mA/cm.sup.2; about 30 and 70 mA/cm.sup.2; 0.5 and 500
mA/cm.sup.2; 100 and 2000 mA/cm.sup.2; greater than about 500
mA/cm.sup.2; and about 15 and 40 mA/cm.sup.2 base on the surface
area of the substrate or mandrel to be coated. In some embodiments
the frequency of the wave forms may be from about 0.01 Hz to about
50 Hz. In other embodiments the frequency can be from: about 0.5 to
about 10 Hz; 0.02 to about 1 Hz or from about 2 to 20 Hz; or from
about 1 to about 5 Hz.
[0034] In some embodiments the electrical potential employed to
prepare the coatings is in the range of 5V and 5000 V. In other
embodiments the electrical potential is within a range selected
from 5 and 200 V; about 50 and 500 V; about 100 and 1000 V; 250 and
2500 V; 500 and 3000 V; 1,000 and 4,000 V; and 2000 and 5000 V.
[0035] In addition to direct electrophoretic deposition of SiC
pre-polymers onto SiC fibers, studies have also demonstrated the
co-deposition of densification additives. This is similar to the
AFCoP process described above. These active-filler additives allow
low-temperature densification without any detrimental effects on
the fibers, as many densification additives can be sintered well
below the re-crystallization temperature of the SiC.sub.f. See, A.
R. Boccaccini et al., Journal of European Ceramic Society 17 (1997)
1545-1550. By combining these additives into the LEAF process, it
is possible to produce high density and density graded ceramic
matrices.
[0036] Density gradation allows for the design and development of a
highly optimized SiC-fiber:SiC-matrix interface. Density gradation
provides a means for balancing the optimization of the interface
strength, while still maintaining a high density, and in some
embodiments gas impermeable and hermetically sealed matrix. Gas
impermeability is especially important in corrosion protection
where a high level of gas diffusion through the coating may result
in substrate attack. The LEAF process enables control and gradation
of density such that a high density region near the substrate may
protect the substrate from attack while a low density region near
the surface may reduce the thermal conductivity of the coating.
[0037] It is believed to be possible to join non oxide ceramics
using preceramic polymers with active fillers based on the work of
Borida. See, J D Toney and R K Bordia, Journal of European Ceramic
Society 28 (2008) 253-257. In regard to the embodiments described
herein, refinement of the microstructure of ceramics joined by the
LEAF processes leads to higher bond strengths In one embodiment of
the technology, a sample composition can be controlled by
controlling the voltage. Specifically, by slowly transitioning from
a low voltage electrolytic deposition regime to a high voltage
electrophoretic deposition regime it may be possible to create a
functionally-graded material that gradually changes from metal to
ceramic or polymer. The same could be achieved by controlling the
current to selectively deposit ionic (metal) species and/or charged
particle (Inert Phase) species. To create a metal:ceramic
functionally graded SiC composite material would significantly
increase the corrosion-resistance, wear-resistance, toughness,
durability and temperature stability of a ceramic-coated
structure.
[0038] In another embodiment, the coating composition can be
functionally-graded by modifying the metal concentration in the
electrolyte solution during electrochemical deposition. This
approach affords an additional means to control the composition of
the functionally-graded coating, and allows for deposition to occur
at relatively lower current densities and voltages, which produced
a better quality in the deposited composites. The standard cathodic
emulsion system, where the emulsion particles comprise polymer,
pre-ceramic polymer, ceramic or a combination thereof, can be
adjusted by adding increasing amounts of nickel to the solution.
This embodiment is described in Example #3.
[0039] In other embodiments, this disclosure provides a corrosion
resistant coating, which changes in composition throughout its
depth, from a high metal concentration at the interface with the
substrate to which it is applied to an Inert Phase at the
surface.
[0040] In another embodiment, the present disclosure provides a
heat resistant coating, which changes in composition throughout its
depth, from a high metal concentration at the interface with the
substrate to which it is applied to an Inert Phase at the
surface.
[0041] As used herein "Inert Phase" means any polymer, ceramic,
pre-ceramic polymer (with or without fillers) or glass, which can
be electrophoretically deposited. This Inert Phase may include
Al.sub.2O.sub.3, SiO.sub.2, TiN, BN, Fe.sub.2O.sub.3, MgO, and
TiO.sub.2, SiC, TiO, TiN, silane polymers,
polyhydriromethylsilazane and others.
[0042] In some embodiments, ceramic particles may include of one or
more metal oxides that can be selected from Zr.sub.xO.sub.x,
YtO.sub.x, Al.sub.xO.sub.x, SiO.sub.x, Fe.sub.xO.sub.x, TiO.sub.x,
MgO where x=1-4, and include mixed metal oxides with the structure
M.sub.xY, where M is a metal and Y is Zr.sub.xO.sub.x, YtO.sub.x,
Al.sub.xO.sub.x, SiO.sub.x, Fe.sub.xO.sub.x, TiO.sub.x, MgO. In
another embodiment, M is selected from Li, Sr, La, W, Ta, Hf, Cr,
Ca, Na, Al, Ti, Zr, Cs, Ru, and Pb.
[0043] As used herein, "metal" means any metal, metal alloy or
other composite containing a metal. These metals may comprise one
or more of Ni, Zn, Fe, Cu, Au, Ag, Pd, Sn, Mn, Co, Pb, Al, Ti, Mg
and Cr. In embodiments where metals are deposited, the percentage
of each metal may independently be selected. Individual metals may
be present at about 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10,
15, 20, 25, 30, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90,
95, 98, 99, 99.9, 99.99, 99.999 or 100 percent of the
electrodeposited species/composition.
[0044] In other embodiments, the coating can have a coating
thickness that varies according to properties of the material that
is to be protected by the coating, or according to the environment
that the coating is subjected to. In some embodiments, the coating
can range from 0.2 and 250 millimeters, and in other embodiments
the range can vary from 0.2 to 25 millimeters, 25 to 250
millimeters, or be greater than about 25 millimeter and less than
about 250 millimeters. In still other embodiments, the coating
thickness can range from 0.5 to 5 millimeters, 1 to 10 millimeters,
5 to 15 millimeters, 10 to 20 millimeters, and 15 to 25
millimeters. In still other embodiments, the overall thickness of
the functionally-graded coating can vary greatly as, for example,
between 2 micron and 6.5 millimeters or more. In some embodiments
the overall thickness of the functionally-graded coating can also
be between 2 nanometers and 10,000 nanometers, 4 nanometers and 400
nanometers, 50 nanometers and 500 nanometers, 100 nanometers and
1,000 nanometers, 1 micron to 10 microns, 5 microns to 50 microns,
20 microns to 200 microns, 200 microns to 2 millimeters (mm), 400
microns to 4 mm, 200 microns to 5 mm, 1 mm to 6.5 mm, 5 mm to 12.5
mm, 10 mm to 20 mm, 15 mm to 30 mm.
[0045] The functionally graded coatings described herein are
suitable for coating a variety of substrates that are susceptible
to wear and corrosion. In one embodiment the substrates are
particularly suited for coating substrates made of materials that
can corrode and wear such as iron, steel, aluminum, nickel, cobalt,
iron, manganese, copper, titanium, alloys thereof, reinforced
composites and the like.
[0046] The functionally graded coatings described herein may be
employed to protect against numerous types of corrosion, including,
but not limited to corrosion caused by oxidation, reduction. stress
(stress corrosion), dissolution, dezincification, acid, base,
sulfidation and the like.
[0047] The functionally graded coatings described herein may be
employed to protect against thermal degradation. In one embodiment,
the coatings will have a lower thermal conductivity than the
substrates (e.g., metal surfaces) to which they are applied.
[0048] The coatings described herein may be employed to protect
against numerous types of corrosion, including, but not limited to
corrosion caused by oxidation, reduction. stress (stress
corrosion), dissolution, dezincification, acid, base, sulfidation
and the like. In one embodiment, the coatings are resistant to the
action of strong mineral acid, such as sulfuric, nitric, and
hydrochloric acids.
EXAMPLES
Example 1
[0049] Preparation of a functionally graded coating comprising a
Inert Phase and a metal formed utilizing a combination of
electrolytic (faradaic) and electrophoretic deposition includes the
following steps: [0050] 1. Acquire the desired substrate material
and cut it to its appropriate size [0051] 2. Sand the substrate on
a circular sander using three steps to achieve a 600 Grit finish
[0052] a. 120 Grit [0053] b. 420 Grit [0054] c. 600 Grit [0055] 3.
Attrition Mill TiSi.sub.2 powder for 10 or more hours. [0056] a.
Add isopropanol to the TiSi.sub.2 powder to aid in grinding [0057]
b. The longer the time period the smaller the particle size [0058]
c. Rinse with isopropanol [0059] d. Dry at 100 C for 8 hours [0060]
4. Mix the Pre-ceramic Polymer with the solvent [0061] a.
Pre-ceramic Polymer, Polyhydridomethysilazane (PHMS): 5.25 g [0062]
b. Add to Solvent, n-Octane: 6.25 mL [0063] c. Add an
electrodepositable metal species (e.g. Ni) to the slurry [0064] d.
The total Volume ratio of slurry : n-Octane is 3:5 [0065] 5. Mix
TiSi.sub.2 powder at 30% volume with PHMS from step 4 to create
slurry [0066] 6. Ball mill slurry for 4 hours with 200, 5/32''
diameter glass beads [0067] 7. Dissolve the Ru.sub.3(CO).sub.12
catalyst in n-Octane [0068] a. Ru.sub.3(CO).sub.12: 2.63 mg [0069]
b. n-Octane: 6.25 mL [0070] c. Combine the mixture with the slurry
[0071] 8. Ball mill for the entire slurry from step 7 for 30
minutes [0072] 9. Dip-coat the slurry onto the prepared substrate
[0073] a. Dip substrate into slurry [0074] b. Apply a current to
affect electrolytic deposition of the metal content of the coating
[0075] c. Increase the current to affect electrophoretic deposition
of the ceramic content of the coating [0076] d. Attach the
substrate to the Instron head [0077] e. Optionally dip into the
substrate into the slurry and remove it at a rate of 50 cm/min
[0078] 10. Cross-link the samples in humid air [0079] a. Hang the
dipped substrates in a jar filled 1/5 with water [0080] b.
Temperature: 150 C [0081] c. Time: 2 hours [0082] 11. Pyrolyze the
dipped samples with flowing air [0083] a. Hang the samples from a
ceramic stand and place them in the oven [0084] b. Ramp rate: 2
C/min [0085] c. Hold temperature: 800 C [0086] d. Hold Time: 2
hours [0087] e. Ramp down: 2 C/min [0088] 12. Remove the completed
sample from the oven.
[0089] The resistance of a TiSi.sub.2 filled and an unfilled
coating to degradation by 200 degree C. concentrated sulfuric acid
is shown in FIG. 3. A standard of Alloy 20 and 316 stainless steel
are provide for reference. The filled coating showed the least loss
of weight.
Example 2
[0090] Toughness Improvements Employing LEAF Processes To
Incorporate a Low-Content of Metal Binder Into Composites
[0091] In order to improve toughness, the LEAF processes a
low-content of a metal binder (e.g., nickel in this Example) may be
incorporated into composites. As shown in FIG. 6, the concentration
of nickel in deposits can be controlled by changing the current
density employed.
Example 3
[0092] A Functionally Graded Coating
[0093] In order to create a functionally-graded coating, a standard
nickel plating bath was added to the polymer emulsion in 1%
increments by volume up to 10%.
[0094] Samples were subsequently exposed to a DC current for a
fixed period. The bath was stirred and agitated at the conclusion
of each test in order to ensure proper solution mixing and
suspension.
[0095] The observations attained from the optical image of the
samples were confirmed by the EDX compositional analysis. The Ni
composition of the coating was increasing as the Ni concentration
in solution increased. These results once again demonstrate the
feasibility of creating a functionally graded ceramic:metal
composite material by controlling the concentration of metal and
Inert Phases in the electrolyte during the deposition process.
[0096] In addition, the data demonstrated that the silicon content
in the deposit remain constant over time. This result is to be
expected as a result of the voltage driven nature of
electrophoretic deposition, and a constant current density and
similar voltages were used for the samples. The nickel emulsion
system can be optimized through concentration alteration and
current and voltage modulation to create a structural material
suitable for corrosion resistant, wear resistant, heat resistant
and other applications.
Example 4
[0097] Nickel, a siloxane-based pre-ceramic polymer particles and
ceramic SiC particles are added to an organic electrolyte Note that
in this case, the polymer is not deposited as an emulsion, but
rather directly as a lacquer. A cathode and an anode were connected
to a power supply. The substrate was connected to the cathode and
inert anodes were connected to the anode. A potential was applied
across the anodes and cathode, which potential ramped from a low
voltage (around 5-100V) to a high voltage (about 100-1000V). The
high voltage was held for a period of time. In an SEM of the
resulting structure, where gray masses are the SiC fibers the
darker gray areas are a mixed matrix of SiOC and SiC. SiOC is
present due to the heat treatment in an environment in which oxygen
was present. The white areas are where the nickel was able to
infiltrate into the cracks and reinforce the structure of the
material.
[0098] The addition of the SiC filler particles into the
pre-ceramic polymer led to the densification and, strengthening of
the specimen by reducing shrinkage on formation. The sub-micron
size of the filler particles facilitated the flow and migration of
the matrix around the SiC fibers. The upper-right corner of the
image contains a zoomed in view of the interface around a fiber.
Any gaps present were filled and strengthened by the nickel metal
deposition.
[0099] Fiber break analysis was performed on a selection of samples
that contained the functionally graded metal:SiC structure to
determine the toughness and fracture characteristics of various SiC
bundles. The toughness of the fiber matrix can be determined
through the visual inspection of fiber pull-out during fracture.
This is observed in SEM images of the fracture surface of a dipped
coated ceramic bundle cross-linked at 500.degree. F. for 2
hours.
[0100] The above descriptions of embodiments of methods and
compositions are illustrative of the present technology. Because of
variations which will be apparent to those skilled in the art,
however, the technology is not intended to be limited to the
particular embodiments described above.
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