U.S. patent application number 13/439300 was filed with the patent office on 2012-10-11 for methods for providing high-surface area coatings to mitigate hydrocarbon deposits on engine and powertrain components.
This patent application is currently assigned to BASF Corporation. Invention is credited to Christopher R. Castellano, Marc J. Froning, Michael P. Galligan, Wieland Koban, Xinqing Ma, Kenneth E. Voss.
Application Number | 20120258254 13/439300 |
Document ID | / |
Family ID | 46966321 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120258254 |
Kind Code |
A1 |
Ma; Xinqing ; et
al. |
October 11, 2012 |
Methods For Providing High-Surface Area Coatings To Mitigate
Hydrocarbon Deposits On Engine And Powertrain Components
Abstract
Provided are methods related to preventing hydrocarbon residue
buildup in engine, exhaust-gas-system or powertrain components.
Prevention is achieved by applying coating of a mixed metal oxide
via a suspension plasma spray.
Inventors: |
Ma; Xinqing; (East Windsor,
CT) ; Galligan; Michael P.; (Cranford, NJ) ;
Castellano; Christopher R.; (Ringoes, NJ) ; Koban;
Wieland; (Mannheim, DE) ; Froning; Marc J.;
(Tolland, CT) ; Voss; Kenneth E.; (Somerville,
NJ) |
Assignee: |
BASF Corporation
Florham Park
NJ
|
Family ID: |
46966321 |
Appl. No.: |
13/439300 |
Filed: |
April 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61472319 |
Apr 6, 2011 |
|
|
|
Current U.S.
Class: |
427/453 |
Current CPC
Class: |
C23C 4/11 20160101; C23C
4/06 20130101; C23C 4/10 20130101 |
Class at
Publication: |
427/453 |
International
Class: |
C23C 4/10 20060101
C23C004/10 |
Claims
1. A method of applying a coating to an engine, exhaust-gas-system
or powertrain component, the method comprising suspension plasma
spraying a coating a mixed metal oxide onto an engine,
exhaust-gas-system or powertrain component, wherein the coating
contains a component that oxidizes hydrocarbons.
2. The method of claim 1, wherein the component that oxidizes
hydrocarbons prevents residue buildup.
3. The method of claim 2, wherein the engine, exhaust-gas-system or
powertrain component is selected from the group consisting of
turbocharger, valve, piston, piston fireland, firedeck, compressor
housing, intake port, injection nozzle, shroud, swirl generator,
combustion chamber and combinations thereof.
4. The method of claim 3, wherein a surface of the engine,
exhaust-gas-system or powertrain component that is prone to residue
buildup is sprayed.
5. The method of claim 4, wherein the coating comprises a mixed
metal oxide, the mixed metal oxide comprising at least two metals
selected from the group consisting of Al, Ti, Ce, Pr, La, Y, Nd, Mn
and combinations thereof.
6. The method of claim 5, wherein the coating further comprises a
precious metal.
7. The method of claim 6, wherein the precious metal comprises
Pd.
8. The method of claim 1, wherein the coating is catalytically
active to remove carbonization residue.
9. A method of applying a coating to an engine, exhaust-gas-system
or powertrain component, the method comprising suspension plasma
spraying a coating onto an engine, exhaust-gas-system or powertrain
component, wherein the coating comprises a mixed metal oxide
comprising at least two metals selected from the group consisting
of Al, Ti, Ce, Pr, La, Y, Nd, Mn, Zr and combinations thereof.
10. The method of claim 9, wherein the coating is catalytically
active for the oxidation of hydrocarbons.
11. The method of claim 9, wherein the engine, exhaust-gas-system
or powertrain component is selected from the group consisting of
turbocharger, valve, piston, piston fireland, firedeck, compressor
housing, intake port, injection nozzle, combustion chamber and
combinations thereof.
12. The method of claim 11, wherein a surface of the engine,
exhaust-gas-system or powertrain component that is prone to residue
buildup is sprayed.
13. A method of applying a coating to an engine, exhaust-gas-system
or powertrain component, the method comprising: forming a
suspension by dispersing mixed metal oxide particles in a liquid;
feeding and injecting the suspension into a plasma torch or plume;
and plasma spraying of the suspension towards the surface of an
engine, exhaust-gas-system or powertrain component.
14. The method of claim 13, wherein the suspension plasma is
sprayed onto a surface of the engine, exhaust-gas-system or
powertrain component that is prone to residue buildup.
15. The method of claim 13, wherein the mixed metal oxide comprises
at least two metals selected from the group consisting of Al, Ti,
Ce, Pr, La, Y, Nd, Mn, Zr and combinations thereof.
16. The method of claim 13, wherein forming a suspension further
comprises dispersing a precious metal in the liquid.
17. The method of claim 16, wherein the precious metal comprises
Pd.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) to Provisional U.S. Patent Application No. 61/472,319,
filed Apr. 6, 2011, which is hereby incorporated by reference in
its entirety.
TECHNICAL FIELD
[0002] The invention relates generally to the field of combustion
engines, and specifically to coatings for preventing hydrocarbon
residue buildup on engine, exhaust gas system and powertrain
components.
BACKGROUND
[0003] Internal combustion piston engines with carburetor or fuel
injection usually have several cylinders, and one or more
axially-moving pistons enclose a combustion chamber where
combustion of a fuel-air mixture occurs.
[0004] A pervasive problem with these internal combustion engines
is the formation of carbonization residues from unburnt fuel and/or
lube oil. These residues are bituminous and, in part, highly
complex mixtures of hydrocarbons. The residues are deposited and
accumulate on various engine and powertrain structural components.
This includes valves, piston surfaces, intake ports, injection
nozzles, and the upper surface of the combustion chamber. These
carbonization residues may accumulate to such an extent, especially
on intake valves, that they produce undesired changes in the fluid
dynamics or closing behavior of the valve. Carbonization residues
can also have very negative effects on other component surfaces of
the combustion chamber (e.g., the piston working surfaces).
[0005] Furthermore, known ways of applying coats have not been
satisfactory. For example, air spray techniques have been used.
However the coatings formed from air spray are not durable.
Conventional plasma spray techniques generally provide inactive
coatings, and it can be difficult to apply precious metals using
conventional plasma spray. Thus, there is a need for a new
technique of applying coatings, particularly those that can prevent
the formation of carbonization residues.
SUMMARY
[0006] Embodiments of the invention pertains to methods for
applying a coating of mixed metal oxides comprising at least two of
Al, Ti, Ce, Pr, La, Y, Nd, Zr and Mn. Specific embodiments pertain
a coating comprising a mixture of Al, Ce, Zr, La, Pr, and Pd.
[0007] Accordingly, one aspect of the invention relates to a method
of applying a coating to an engine, exhaust-gas-system or
powertrain component, the method comprising suspension plasma
spraying a coating a mixed metal oxide onto an engine,
exhaust-gas-system or powertrain component, wherein the coating
contains a component that oxidizes hydrocarbons. In one embodiment,
the component that oxidizes hydrocarbons prevents residue buildup.
In one or more embodiments, the engine, exhaust-gas-system or
powertrain component is selected from the group consisting of
turbocharger, valve, piston, piston fireland, firedeck, compressor
housing, intake port, injection nozzle, shroud, swirl generator,
combustion chamber and combinations thereof.
[0008] In one or more other embodiments, a surface of the engine,
exhaust-gas-system or powertrain component that is prone to residue
buildup is sprayed. In other embodiments still, the coating
comprises a mixed metal oxide, the mixed metal oxide comprising at
least two metals selected from the group consisting of Al, Ti, Ce,
Pr, La, Y, Nd, Mn and combinations thereof. In another variant, the
coating further comprises a precious metal. In a further
embodiment, the precious metal comprises Pd. In yet another
embodiment, the coating is catalytically active to remove
carbonization residue.
[0009] A second aspect of the invention pertains to a method of
applying a coating to an engine, exhaust-gas-system or powertrain
component. The method comprises suspension plasma spraying a
coating onto an engine, exhaust-gas-system or powertrain component,
wherein the coating comprises a mixed metal oxide comprising at
least two metals selected from the group consisting of Al, Ti, Ce,
Pr, La, Y, Nd, Mn, Zr and combinations thereof. In one embodiment,
the coating is catalytically active for the oxidation of
hydrocarbons. In another embodiment, the engine, exhaust-gas-system
or powertrain component is selected from the group consisting of
turbocharger, valve, piston, piston fireland, firedeck, compressor
housing, intake port, injection nozzle, combustion chamber and
combinations thereof. In yet another embodiment, a surface of the
engine, exhaust-gas-system or powertrain component that is prone to
residue buildup is sprayed.
[0010] A third aspect of the invention pertains to a method of
applying a coating to an engine, exhaust-gas-system or powertrain
component. The method comprises forming a suspension by dispersing
mixed metal oxide particles in a liquid, feeding and injecting the
suspension into a plasma torch or plume, and plasma spraying of the
suspension towards the surface of an engine, exhaust-gas-system or
powertrain component. In one embodiment, the suspension plasma is
sprayed onto a surface of the engine, exhaust-gas-system or
powertrain component that is prone to residue buildup. In another
embodiment, the mixed metal oxide comprises at least two metals
selected from the group consisting of Al, Ti, Ce, Pr, La, Y, Nd,
Mn, Zr and combinations thereof. In a further embodiment of this
aspect, forming a suspension further comprises dispersing a
precious metal in the liquid. In another embodiment, the precious
metal comprises Pd.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows an SEM image of a cross section of a suspension
plasma coating applied to a substrate in accordance with one or
more embodiments of the invention; and
[0012] FIGS. 2-9 show graphical data of several samples applied by
various coating techniques.
DETAILED DESCRIPTION
[0013] Before describing several exemplary embodiments of the
invention, it is to be understood that the invention is not limited
to the details of construction or process steps set forth in the
following description. The invention is capable of other
embodiments and of being practiced or being carried out in various
ways.
[0014] Residue buildup occurs as a result from unburned
hydrocarbons, lubricant oil and soot. The problem of residue
buildup can occur on the surfaces of various engine, exhaust gas
system and powertrain components. This includes, but is not limited
to the turbocharger, valve, piston, piston fireland, fire deck,
compressor housing, intake port, injection nozzle, shroud, swirl
generator and combustion chamber.
[0015] One aspect of the invention relates to a coating that
prevents deposit buildup on engine and powertrain components. An
embodiment of the invention pertains to an article component
comprising an engine or powertrain component and a coating applied
to the engine or powertrain component.
[0016] Without a coating, the engine or powertrain component would
have at least some of its surface exposed to hydrocarbons. The
coating comprises a mixed metal oxide, which is comprised of at
least two metals selected from the group consisting of Al, Ti, Ce,
Pr, La, Y, Nd, Zr and Mn. In another embodiment, the coating also
comprises a precious metal. In yet another embodiment, the coating
is catalytically active to the oxidation of hydrocarbons. In a
specific embodiment, the coating comprises Pd and another component
selected from those provided above.
[0017] Another aspect of the invention relates to methods for
applying the coating described herein using a suspension plasma
spray. In a specific embodiment, the invention pertains to a method
of applying a coating to an engine, exhaust-gas-system or
powertrain component, the method comprising suspension plasma
spraying a coating onto an engine, exhaust-gas-system or powertrain
component, wherein the coating oxidizes hydrocarbons to prevent
residue buildup. In a further embodiment, standard catalytic wash
coat slurry is used. This can be used to obtain a durable
high-surface area coating that prevents deposit buildup.
[0018] In one or more embodiments, the technique for coating the
catalytic powder to the surface of the component. Standard plasma
spray techniques significantly reduce surface area and thus
diminish the catalytic activity of the material. Typical washcoat
techniques suffer from insufficient durability of the coating.
Suspension plasma spray coating provides a solution as it provides
high surface area coatings with strong durability at the same time.
One or more embodiments of the suspension plasma techniques
described herein provide several advantages not yet addressed in
the prior art. For example, the coatings applied via suspension
plasma spraying exhibit much more stability as compared to air
spray coatings. Additionally, such suspension plasma spray coatings
exhibit more catalytic activity than conventional plasma spray
techniques. Yet another advantage is that it can be difficult to
apply precious metals using conventional plasma techniques, but
much easier using suspension plasma.
[0019] A related embodiment pertains to a method of applying a
coating to an engine, exhaust-gas-system or powertrain component,
the method comprising suspension plasma spraying a coating onto an
engine, exhaust-gas-system or powertrain component, wherein the
coating comprises a mixed metal oxide comprising at least two
metals selected from the group consisting of Al, Ti, Ce, Pr, La, Y,
Nd, Mn, Zr and combinations thereof. In a specific embodiment, only
the surface of the engine, exhaust-gas-system or powertrain
component that is prone to residue buildup is sprayed. In one or
more embodiments, the component has grooves or indentations on the
surface of the component. In another embodiment, the coating also
comprises a precious metal, for example, Pt, Pd, Rh and/or Au. In a
specific embodiment, the precious metal comprises Pd. In one or
more embodiments, the coating is catalytically active to remove
hydrocarbon deposits on engine components. In a specific
embodiment, the coating comprises Pd and another component selected
from those provided above. In another embodiment, a post-deposition
or post-impregnation process may be used to enhance the coating. In
order to reduce the overall precious metal content of the coating,
post-impregnation can be used such that the precious metal would be
present at the surface only. The other ceramic layer would only
provide the surface adhesion to the metal, like a bond coat. One
advantage of one or more of the suspension spray coatings described
herein is the ability to apply the full coating in a single step,
even those containing precious metal.
[0020] A third aspect of the invention relates to a method of
applying a coating to an engine, exhaust-gas-system or powertrain
component, the method comprising: suspending a mixed metal oxide in
a suspension; atomizing the slurry with suspended mixed metal oxide
into a suspension plasma as described further below; and spraying
the suspension plasma onto a engine, exhaust-gas-system or
powertrain component. Optionally, the suspension plasma may be
sprayed only onto the surface of the engine, exhaust-gas-system or
powertrain component that is prone to residue buildup. The mixed
metal oxide may comprise at least two metals selected from the
group consisting of Al, Ti, Ce, Pr, La, Y, Nd, Zr and Mn.
[0021] According to one or more embodiments, the metal oxides are
in particulate form. In specific embodiments, particles of high
surface area, e.g., from about 100 to 500 square meters per gram
("m.sup.2/g") surface area, specifically from about 150 to 450
m.sup.2/g, more specifically from about 200 to 400 m.sup.2/g, are
desired so as to better disperse the catalytic metal component or
components thereon. The first layer refractory metal oxide also
desirably is mesoporous and has a high porosity of pores up to 1456
Angstroms radius, e.g., from about 0.75 to 1.5 cubic centimeters
per gram ("cc/g"), specifically from about 0.9 to 1.2 cc/g, and a
pore size range of at least about 50% of the porosity being
provided by pores of 50 to 1000 Angstroms in radius. For alumina
particles, it may be desirable to utilize a high surface area
mesoporous gamma alumina, for example GA-200.
[0022] Exemplary suspension plasma spray methods according to one
or more embodiments involve several process steps. First, solid
particles are dispersed into a liquid and kept in suspension during
the process. Second, the suspension is fed and injected into a heat
source. Next, the solid particles in suspension are at least
partially melted and impact on a surface of an article to form a
deposit. The heat source in plasma spraying can include, but is not
limited to electric arc plasma, RF plasma or microwave plasma.
Suitable examples of suspension plasma spraying are described in
U.S. Pat. Nos. 5,609,921, 6,277,448, and 4,376,010, the entire
content of each patent being incorporated herein by reference.
[0023] Suspension plasma spraying, according to one or more
embodiments, involves a plasma spray deposition method for
producing a material deposit onto a substrate. The method can
comprise producing a plasma discharge; providing a suspension of a
material to be deposited, this suspension comprising small solid
particles of that material dispersed into a liquid or semi-liquid
carrier substance; atomizing the suspension into a stream of fine
droplets and injecting the stream of fine droplets within the
plasma discharge; and by means of the plasma discharge, (a)
vaporizing the carrier substance, (b) agglomerating the small
particles into at least partially melted drops, (c) accelerating
these drops, and (d) projecting the accelerated drops onto the
substrate to form the material deposit.
[0024] The probe atomizes the suspension into a stream of fine
droplets and injects this stream of droplets generally centrally of
the plasma discharge. The suspension is then sheared and thereby
atomized, and injected in the plasma discharge under the form of
fine droplets through the opening. Although an example of
suspension plasma spraying process and apparatus have been
described hereinabove, the present invention is not limited to the
process as apparatus described, and alternative atomizing processes
are available to shear the suspension.
[0025] The stream of fine droplets travels through the plasma
discharge to reach the substrate. As the droplets of suspension
travel from the opening to the substrate, these droplets are
subjected to several physicochemical transformations. The
suspension is typically composed of small solid particles suspended
and dispersed into a solvent or other liquid or semi-liquid carrier
substance. When the fine droplets of suspension reach the plasma
discharge, the solvent first evaporates and the vapor thus formed
decomposes under the extreme heat of the plasma. The remaining
aerosol of small solid particles then agglomerate into drops which
are either totally or partially melted and/or vaporized. The plasma
discharge accelerates the molten drops, which accumulate kinetic
energy. Carried by this kinetic energy, the drops hit the
substrate. The plurality of drops form on the substrate a layer of
partially or totally melted drops partially overlapping one
another.
[0026] In another example of a suspension plasma spray process, a
solid-liquid state suspension is prepared in which solid particles
with appropriate particle sizes are selected or processed. Suitable
particle sizes are in the range of nano-meters to micron-meters,
preferably less than one micron. If necessary, the particle sizes
can be reduced in a high energy process, such as ball milling. If
multiple supports are used, then this step is repeated as many
times as necessary to achieve the desired final slurry (suspension)
composition. A few additives may be added in very small quantities
to achieve the required properties for coating, such as: binders,
defoamers, suspension agents, and anti-microbials. Then, the solid
particles are dispersed into a liquid, for example, by using
mechanical agitation manner such as with a stirrer or circulating
pump. The particles should be suspended well and uniform during
suspension preparation and plasma spraying. Before use, a
suspension will be checked for solids % content and adjusted if
necessary for the coating method. Depending on the degree of
settling during storage, a suspension may be stirred or agitated
before coating.
[0027] The suspension is delivered from a storage container to an
injection device which is aligned a plasma torch, for example, in
vertical alignment. The feeding and injection of the suspension is
controlled by parameters such as flow rate and delivery pressure.
While the suspension is injected and penetrated into the plasma
torch/plume, the liquid is vaporized and the solid particles are
heated and at least melted partially. Directed by the dynamic force
of the plasma torch, the melted particles are directed toward a
substrate and finally deposit on the surface of the substrate.
Plasma spray parameters can affect the properties of the deposited
material. Such parameters include but are not limited to plasma
working gases and their compositions, pressure and flow rate,
plasma power and the distance between the suspension injection
location and the surface of the article.
[0028] According to an embodiment of the invention, suspension
plasma spraying can be to apply adherent, catalytic coatings to any
metallic surface such as aluminum or various steels. Compared to
traditional dip coating processes, limited material types can be
used to provide adherent coatings, such as ceramic or fecralloy
substrates. By using suspension plasma spraying, a wider variety of
substrates can be utilized.
[0029] The application process may be used to apply a protective
coating to any deposit-prone engine or powertrain component or
surface thereof. This includes, but is not limited to, the
turbocharger, valve, piston, piston fireland, firedeck, compressor
housing, intake port, injection nozzle and combustion chamber. In a
specific embodiment, the coating is applied to a metallic surface
of the engine or powertrain component.
EXAMPLES
Example 1
[0030] A sample was prepared by suspension plasma spraying an
alumina and ceria-based coating onto a sandblasted, stainless steel
substrate. The exact composition of the coating was 30:70
ceria:alumina with 0.6 weight % platinum, which the platinum
deposited onto the alumina. FIG. 1 is an SEM image of the coating
in cross section with elemental mapping using EDS. FIG. 1 also
shows the porosity of the coating, which is shown as the black
areas. The suspension plasma coated sample showed extraordinary
durability. The sample was subjected to thermal-shock stress
methods--4-h of lab aging, cycling through 30 seconds of heat
(900.degree. C..+-.20.degree. C. flame exhaust) followed by 30
seconds in 110.degree. C. cooling air--and no signs of degradation
or cracks are visible as shown in FIG. 1. In addition to mechanical
durability, the suspension plasma spray coated sample showed a high
catalytic durability. In repeated tests, the samples retained their
catalytic activity and no aging of the catalyst (as determined
signal decrease) could be found when repeating the measurement at
least 10 times. The SEM image demonstrates how the coating remains
adhered, even after treatment, and does not even show any visible
cracking.
Examples 2A (Comparative) and 2B
[0031] Examples 2A and 2B both comprised a 50:50 molar ratio on a
metals basis of Al.sub.2O.sub.3:CeO.sub.2. Prior to mixing the
alumina and ceria, 0.20 wt % Pt was added to the ceria. Example 2A
was applied via an air spray technique onto a test planchette, and
is considered comparative because of its application method.
Example 2B was applied via suspension plasma spraying.
Examples 3A (Comparative) and 3B
[0032] Examples 3A and 3B both comprised a 50:50 molar ratio on a
metals basis of Al2O3:CeO2. Prior to mixing the alumina and ceria,
0.45 wt % Pt was added to the ceria, and 0.15 wt % Pt was added to
the alumina, for a total Pt content of 0.6 wt %. Example 3A was
applied via an air spray technique onto a test planchette, and is
considered comparative because of its application method. Example
3B was applied via suspension plasma spraying.
Examples 4A (Comparative) and 4B
[0033] Examples 4A and 4B both comprised a 50:50 molar ratio on a
metals basis of Al2O3:CeO2. Prior to mixing the alumina and ceria,
0.60 wt % Pt was added to the alumina. Example 4A was applied via
an air spray technique onto a test planchette, and is considered
comparative because of its application method. Example 4B was
applied via suspension plasma spraying.
[0034] For all examples 2-4, on the planchette, soot and oil were
applied to the surface, and a temperature ramp was applied in air.
Combustion product CO and CO.sub.2 development were measured.
Planchettes with soot/oil mixture on the surface of the planchettes
were placed in a furnace. The furnace was ramp in temperature at
15.degree. K/min. The gas temperature right above the planchettes
was measured by means of an additional type K thermocouple. The
gases above the planchettes are extracted with a nozzle. This gas
was analyzed for CO and CO.sub.2 using an Uras 14, Advance Optima
module from ABB which uses infrared light. From this measurement,
the catalytic activity of the coating for hydrocarbon oxidation was
deduced. The test was repeated 5 times for each test planchette.
FIGS. 2A-B, 3A-B and 4A-B show the CO.sub.2 signal for Examples
2A-B, 3A-B and 4A-B, respectively. Similarly, FIGS. 5A-B, 6A-B and
7A-B show the CO signal for Examples 2A-B, 3A-B and 4A-B,
respectively. As can be seen in FIGS. 2-7, the samples applied via
suspension plasma spraying performed at least as well as the
samples applied via air spray. Whereas the signal for the
suspension spray coatings stayed almost constant for all of the
tests, the air-sprayed samples showed only a little aging (e.g. an
increasing of the peak signal temperature of about 40.degree. C. as
compared to freshly prepared samples).
Example 5
Comparative
[0035] A coating comprising 100% ceria was applied onto a test
planchette using a conventional plasma spray. It is considered
comparative because of the method with which coating was
applied.
Example 6
Comparative
[0036] A coating of pure aluminum was prepared on a test
planchette. The test planchette consists of pure aluminum, and is
free of any coating. It thus serves as a comparative example, and
is representative of, for example, a turbocharger aluminum
surface.
Example 7
Comparative
[0037] A coating comprising 100% ceria was applied onto a test
planchette using an air spray technique. This is considered a
comparative example because of the method with which the coating
was applied.
Example 8
Comparative
[0038] A coating comprising 100% Zirconia was applied onto a test
planchette using a conventional plasma spray technique. It is
considered comparative because of the method with which coating was
applied.
Testing of Comparative Examples 5-8
[0039] On the planchette, soot and oil were applied to the surface,
and a temperature ramp was applied in air. Combustion product CO
and CO.sub.2 development were measured. Planchettes with soot/oil
mixture on the surface of the planchettes were placed in a furnace.
The furnace was ramp in temperature at 15 K/min. The gas
temperature right above the planchettes was measured by means of an
additional type K thermocouple. The gases above the planchettes are
extracted with a nozzle. This gas was analyzed for CO and CO.sub.2
using an Uras 14, Advance Optima module from ABB which uses
infrared light. From this measurement, the catalytic activity of
the coating for hydrocarbon oxidation was deduced.
[0040] In FIG. 8 the CO signal is displayed, and in FIG. 9 the
CO.sub.2 signal is shown. From FIGS. 8 and 9, it can clearly be
seen that the ceria, when plasma sprayed, does not enhance the
oxidation of the lube oil. The combustion activity is almost the
same as for the catalytically inactive zirconia or a pure, uncoated
aluminum surface. There is almost no CO.sub.2 signal below
400.degree. C., but a strong CO signal around 425.degree. C. This
means the combustion of the lube oil is incomplete, and residues
(precursors for deposit buildup) continue to be burnt off around
425.degree. C. In contrast, the air sprayed ceria shows a strong
CO.sub.2 signal around 325.degree. C. and no CO peak around
425.degree. C., meaning the lube oil burns off completely. That is,
no residues or deposits will be left over. The signal above
500.degree. C. stems in both cases from the carbon black initially
applied onto the planchette.
[0041] While the air sprayed coating shows at least some catalytic
activity, it has no durability, as shown in the previous examples.
After a few tests, the coating will lose its activity and even peel
off the surface. Thus, the most advantageous method is suspension
spray, which has been shown to provide both, activity and
durability.
[0042] Reference throughout this specification to "one embodiment,"
"certain embodiments," "one or more embodiments" or "an embodiment"
means that a particular feature, structure, material, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the invention. Thus, the
appearances of the phrases such as "in one or more embodiments,"
"in certain embodiments," "in one embodiment" or "in an embodiment"
in various places throughout this specification are not necessarily
referring to the same embodiment of the invention. Furthermore, the
particular features, structures, materials, or characteristics may
be combined in any suitable manner in one or more embodiments.
[0043] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It will be apparent to those
skilled in the art that various modifications and variations can be
made to the method and apparatus of the present invention without
departing from the spirit and scope of the invention. Thus, it is
intended that the present invention include modifications and
variations that are within the scope of the appended claims and
their equivalents.
* * * * *