U.S. patent application number 12/005019 was filed with the patent office on 2010-11-04 for aluminum phosphate coatings.
Invention is credited to Krishnaswamy K. Rangan, Sankar Sambasivan, Kimberly A. Steiner.
Application Number | 20100279000 12/005019 |
Document ID | / |
Family ID | 33567250 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100279000 |
Kind Code |
A1 |
Sambasivan; Sankar ; et
al. |
November 4, 2010 |
Aluminum phosphate coatings
Abstract
Aluminophosphate compounds and compositions as can be used for
substrate or composite films and coating to provide or enhance,
without limitation, planarization, anti-biofouling and/or
anti-microbial properties.
Inventors: |
Sambasivan; Sankar;
(Chicago, IL) ; Steiner; Kimberly A.; (Chicago,
IL) ; Rangan; Krishnaswamy K.; (Evanston,
IL) |
Correspondence
Address: |
REINHART BOERNER VAN DEUREN S.C.;ATTN: LINDA KASULKE, DOCKET COORDINATOR
1000 NORTH WATER STREET, SUITE 2100
MILWAUKEE
WI
53202
US
|
Family ID: |
33567250 |
Appl. No.: |
12/005019 |
Filed: |
December 21, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10745955 |
Dec 23, 2003 |
7311944 |
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12005019 |
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60436063 |
Dec 23, 2002 |
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60436066 |
Dec 23, 2002 |
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Current U.S.
Class: |
427/62 ;
427/126.1; 427/240; 427/384 |
Current CPC
Class: |
C23C 18/1225 20130101;
C23C 18/1216 20130101; H01L 39/2461 20130101; C23C 18/1295
20130101; C23C 18/1208 20130101; C23C 18/1279 20130101; C23C
18/1241 20130101 |
Class at
Publication: |
427/62 ; 427/384;
427/240; 427/126.1 |
International
Class: |
B05D 5/12 20060101
B05D005/12; B05D 3/02 20060101 B05D003/02; B05D 3/12 20060101
B05D003/12 |
Goverment Interests
[0002] The United States government has certain rights to this
invention pursuant to Grant Nos. F49620-00-C-0022 and
F49620-01-C-0014 from AFOSR (Air Force Office of Scientific
Research) and DE-FG02-01ER83149, from the Department of Energy each
to Applied Thin Films, Inc.
Claims
1. A method of using an aluminophosphate compound to decrease
surface roughness, said method comprising: providing a precursor to
an aluminophosphate compound, said precursor comprising aluminum
ions and phosphate esters in a fluid medium; applying said
precursor medium to a substrate, said substrate having a first
surface roughness value; and treating said applied medium for a
time and at a temperature sufficient to provide a substantially
amorphous aluminophosphate compound on said substrate, wherein the
surface of said substrate is planarized and has a second roughness
value decreased compared to said first surface roughness value.
2. The method of claim 1 wherein said surface roughness value is
decreased at least by about 3-fold.
3. The method of claim 1 wherein said medium is applied by a
process selected from dip-coating, spraying, flow-coating and
spin-coating.
4. The method of claim 1 wherein said treated substrate has a
friction coefficient less than about 0.2.
5. The method of claim 4 wherein said substrate is selected from a
bearing and a gear.
6. The method of claim 1 wherein a biaxially-textured component is
deposited on said aluminophosphate compound.
7. The method of claim 6 wherein said component is selected from
magnesium oxide, yttria, and a yttria stabilized zirconia.
8. The method of claim 7 wherein an electromagnetic component is
deposited on said textured component.
9. The method of claim 8 wherein said electromagnetic component is
a superconducting YBCO layer.
10. The method of claim 1 wherein said treated substrate is exposed
to an environment inducing condition selected from oxidation and
corrosion.
11. The method of claim 1 wherein said substrate is selected from a
steel, a nickel-based alloy, a superalloy, titanium, a
titanium-based alloy, niobium, a niobium-based alloy, molybdenum
and a molybdenum-based alloy.
12. The method of claim 1 wherein said substrate is selected from
silicon, aluminum oxide, enamel, mullite, a glass, fused silica, a
silica-based refractory and a ceramic.
Description
[0001] This application is a continuation of and claims priority
benefit from application Ser. No. 10/745,955 filed Dec. 23, 2003
now issuing as U.S. Pat. No. 7,311,944 on Dec. 25, 2007 and
provisional application Ser. Nos. 60/436,063 and 60/436,066, each
filed on Dec. 23, 2002 and incorporated herein by reference in its
entirety; U.S. application Ser. No. 10/627,194 filed Jul. 23, 2003
from prior provisional application Ser. No. 60/398,265 filed Jul.
24, 2002; U.S. application Ser. No. 10/642,069 filed Aug. 14, 2003
from prior provisional application Ser. No. 60/403,470 filed Aug.
14, 2002; U.S. application Ser. No. 10/362,869 filed Feb. 21, 2003
from prior PCT application no. PCT/US01/41790 filed Aug. 20, 2001;
and U.S. application Ser. No. 10/266,832 filed Oct. 8, 2002 as a
continuation of application Ser. No. 09/644,495 filed Aug. 23, 2000
and issued as U.S. Pat. No. 6,461,415 on Oct. 8, 2002--each of
which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to modification of metal and
alloy, ceramic, and glass surfaces with an inorganic coating to
provide planarization, oxidation and corrosion protection of the
coated surfaces. This invention is also related to the coating on
solid supports (e.g., glass) providing one or more reactive sites
for the attachment of organic or inorganic molecules including but
not limited to aliphatic acids, organosilanes and biomolecules such
as oligonucleotides. Stable molecular attachment can provide
several desired mechanical, optical (second harmonic generation,
fluorescence and like), hydrophobic, hydrophilic, tribological,
biological (antimicrobial) and other properties to the solid
supports coated with the inventive material. This invention is also
related to chemically modifying the inventive material composition
to impart useful properties such as antimicrobial property.
BACKGROUND OF THE INVENTION
[0004] Advanced alloys, including nickel-based superalloys,
intermetallics of titanium-aluminum, niobium-aluminum,
titanium-silicon, molybdenum-silicon-boron and others are used
extensively for high temperature applications due to their
desirable mechanical properties. However, their environmental
durability in oxidizing or harsh environments is limited and
various surface modification techniques, including protective
coatings are employed to extend their lifetimes and/or use
temperatures. Due to presence of surface pits, scratches, pores, or
other abnormal surface features (more commonly known as pitting or
crevice corrosion), accelerated oxidation or corrosion is initiated
in these areas which eventually degrades the entire surface. If the
surfaces are prepared adequately, advanced alloys, that contain
aluminum for example, will form a uniform protective alumina scale
which limits further oxidation. However, if the thermally grown
scale is not uniform or contain other oxides, besides that of
aluminum, the protection is compromised and the alloys are subject
to rapid degradation at elevated temperatures. In addition, surface
grain boundary junctions are compositionally different compared to
the bulk composition which may also cause the oxide scale in those
regions to be different and perhaps less protective. Therefore,
there is a need for a suitable surface modification method that
will allow for the slow and steady formation of predominantly
alumina-rich (more preferably pure alumina scale) scale for
aluminum-containing alloys.
[0005] Similar arguments are valid for chromium-based steels and
other chromium-based alloys which are used in applications for
boilers, heat exchangers, recuperators, interconnect for solid
oxide fuel cells, automotive catalytic converters, and others as
apparent to those skilled in the art. In these applications, it is
desired to form a protective chromia scale which requires a minimum
level of chromium content in the alloy. Higher chromium content
makes the alloy more expensive and also results in compromise of
other important mechanical, thermal, and electrical properties of
alloys. Thus, there is a need for a protective coating for
chromium-based alloys and steels which will allow for the formation
of a dense and uniform protective scale of chromium oxide,
especially if it can be implemented for low chromium-containing
alloys.
[0006] Metal or alloy honeycomb structures are used in many
applications such as catalytic converters, radiators and heat
exchangers, and exterior bodies of space vehicles for thermal
protection. U.S. Pat. Nos. 5,411,711 and 5,146,743, among others,
discuss the metal foil catalytic converters for automotive systems.
Currently, most catalytic converters used in automotive exhaust
systems in the US use a ceramic honeycomb substrate loaded with a
precious metal catalyst. The ceramic honeycomb is used because it
can tolerate the hot exhaust environment without degradation. Alloy
foil honeycombs offer advantages over ceramic honeycombs in weight
and electrical conductivity. Most auto pollution occurs when the
engine is cold, generally after the engine is started. At low
temperatures the catalysts are not effective at reducing nitrogen
and oxidizing residual hydrocarbons. To alleviate this problem and
achieve overall reduced emissions, alloy foil catalytic converters
can be resistively heated to ensure that the catalysts are kept at
a temperature that allows them to function optimally. However,
these thin foils are prone to oxidation and corrosion in the
exhaust stream. Foils are particularly sensitive to oxidation
because the original alloy is so thin, that the buildup of a thick
oxide scale results in dimensional changes and changes in
mechanical properties. For this reason, expensive oxidation
resistant alloys are required. A thin oxidation resistant coating
that will not substantially increase the thickness of the foil will
be useful to reduce oxidation and corrosion, allowing the use of
less expensive alloys, while still allowing the use of resistive
heating to reduce emissions. Another such application is the
potential use of alloy foils is for thermal protection systems for
next-generation reusable launch vehicles for space travel. Present
inventive material can be used as the oxidation protection coatings
for these applications.
[0007] Currently, there are many ways to combat corrosion of
aluminum and ferrous alloys. They include painting, electroplating,
composite coverings, use of more corrosion resistant alloys,
anodizing and chromating the surfaces of metal. Many of these
processes are not environmentally friendly, cannot be maintained or
repaired in the field, are expensive, require significant
preparation of the substrate, and none offer the required
long-term, low maintenance protection. Past coating efforts have
primarily used relatively thick coatings (1-20 mils thick) to
combat salt corrosion. Anodizing of aluminum and chromate
conversion coating of aluminum and ferrous alloys are the most
effective technologies, but both are environmentally unfriendly and
require the use of toxic chemicals. Corrosion often occurs in areas
of surface defects of the alloy substrate. Pits and inhomogeneities
in the alloy composition cause accelerated corrosion. High strength
aluminum alloys in particular are subject to pitting corrosion
because of the influence of Cu-containing intermetallic particles.
The inhomogeneous distribution of Cu in the alloy microstructure
has been shown to be a major cause for low resistance to pitting or
stress corrosion cracking. Heterogeneous microstructures are
intentionally developed in commercial aluminum alloys to optimize
mechanical properties. Unfortunately, such microstructures make
aluminum alloys susceptible to localized corrosion during service
and complicate aqueous surface finishing processes. The standard
coating system uses a chromate conversion layer covered by organic
paints. Short term corrosion protection of metals and alloys from
corrosion due to moisture and other environmental factors is
currently achieved using organic layers. Time-consuming and
arduous, these organic coatings need to be removed before the
processing of metals and alloys like heating or melting or for
painting and other surface modifications.
[0008] Many metals, alloys and ceramics used in various
applications require a smooth surface finish which is often
accomplished by mechanical or chemical mechanical polishing means.
In addition to passivation of coated surfaces, it is also desired
to protect them from any environmental attack during processing or
surface modification or during service. Typically, anodization of
the surface with the formation of an alumina or chromia film is
done to passivate the surfaces. However, the aforementioned
procedures are expensive, labor intensive, and are environmentally
unsafe releasing toxic substances and generating toxic waste.
[0009] Physical vapor deposition (PVD) grown amorphous silicon
nitride film on metallic substrates are used for growth of single
crystal magnesium oxide films using ion-beam assisted deposition
(IBAD) whereby the growth is induced by e-beam evaporation,
sputtering or other PVD method with another ion-beam to induce
crystallographic alignment. Using this technique, biaxial texture
of magnesium oxide is attained over thicknesses within 100
Angstroms as opposed to direct IBAD growth of yttria stabilized
zirconia (YSZ) on highly polished polycrystalline metal or alloy
substrates (hereafter referred to as metal substrates) which
required growing much thicker films (over 1000 Angstroms) to attain
similar quality biaxial texture. The IBAD magnesium oxide films
served as good templates for further heteroepitaxial growth of
functional oxide films such as ferroelectrics, superconductors,
piezoelectric films, or other electronic films of the like. Thus,
the IBAD MgO approach served as a much faster and economical way of
producing biaxially textured or single crystal films on
polycrystalline metal substrates with amorphous interlayers (also
known as nucleation or adhesion layers).
[0010] It has been recently demonstrated that yttria served as a
much better amorphous template layer (grown by PVD) than silicon
nitride on highly polished metal/alloy substrates. Specifically,
the yttria/IBAD MgO approach was used to demonstrate the
architecture for growth of high quality High Temperature
Superconductor (HTS) films suitable as HTS coated conductors.
Specific disadvantages of this approach include: an expensive
(vacuum deposition process) low deposition rate process is required
for yttria amorphous layer formation, the use of thin yttria layer
is not an adequate diffusion barrier against diffusion of oxygen
and other metals to diffuse into the superconducting layer; thus, a
separate diffusion barrier layer is still required (currently
strontium ruthenate is being used as diffusion barrier), and prior
to deposition of yttria, the substrate roughness needs to be
tailored below 40 angstroms (preferably below 10 Angstroms) through
mechanical or electrical polishing methods. Thus there is a need
for an alternative material and associated thin film process
(preferably non-vacuum, low-cost, and high deposition rate) to
replace yttria and silicon nitride or other layers which is
multifunctional and performs better and can be deposited at lower
costs using a simple deposition process.
[0011] Low friction surfaces are required for many applications,
including bearings, bearing races, and gears. Low friction surfaces
can be imparted by depositing a low-friction material as a coating
or reducing the overall surface roughness of the substrate.
Although surface finish of metallic and ceramic parts can be
improved through mechanical polishing, pits and defects contained
on the surface cannot be effectively removed through any of the
standard polishing techniques. Deposition of extremely thin
amorphous films that exhibit low surface energy and provide
hermetic coverage with adequate thermal and microstructural
stability can be beneficial in maintaining a low friction surface
whereby the defects on the metal surfaces are effectively
sealed.
[0012] Biofouling of ship hulls is caused by microorganisms such as
slime, algae and bacteria, and macroorganisms such as barnacles,
mussels, clams and oysters which adhere to the hull of the ship.
Fouling increases drag on the hull, decreasing ship speed and often
significantly reducing fuel economy. One of the promising emerging
technologies is the nontoxic "foul-release" coating. These coatings
are based on the hypothesis that in surfaces with the weakest
attraction for bio-organisms, fouling will be slow and likely to
require the least amount of effort to release from the surface.
Fouling organisms adhere to the surfaces by secreting proteinaceous
adhesives. Materials with low surface energy will offer low
adhesion strength, resulting in poor attachment and easy to remove
fouling. The feasibility of this approach has been established by
researchers using fluorinated polymers, epoxy based and
silicone-based coatings. These coatings did foul, but fouling
bio-mass can be easily removed by fast-flowing water. However,
these polymer-based coatings have limited heat and UV light
resistance. Therefore, an inorganic coating with smooth and low
friction surface properties are highly desirable.
[0013] Microarrays are arrays of biomolecules such as
oligonucleotides that are spatially arranged and stably attached to
a surface of a solid support. Microarray technology is used for
parallel analysis of genes in a large scale, and has emerged as the
universal genetic analytical tool for use in a wide range of
biomedical applications. Commercial production of DNA chips has
been implemented by many companies while, in parallel, medical
researchers report exciting advances across many disciplines within
the field of medicine. These developments in microarray technology
offer tremendous promise to solving long-standing problems in
public health worldwide and also provide new avenues to combat the
more recent threats of bioterrorism.
[0014] The starting point or the basic building block for producing
biomolecular microarrays is a suitable solid template surface
(solid support material) upon which biological molecules can be
anchored or immobilized. Several patents have been issued on
functionalizing silicate glass and other surfaces. Numerous other
surface coatings have also been disclosed. Patents are also awarded
for novel solid supports, e.g. aluminosilicate, for immobilizing
nucleic acids. Characteristics of DNA microarrays are determined by
the surface properties such as chemical homogeneity, interaction
between surface and bio-molecules, surface roughness, density of
surface functionality, spacing between surface functional moieties,
amenability to DNA hybridization, and so forth. While the current
methods employ the use of soda-lime glass substrates, they are
prone to degradation over the long term and the surface chemistry
is not tailored to allow for suitable organic attachments. An
organic linker is used to attach the DNA or other biomolecule to
the surface of the substrate. Polylysine is a coating material
currently recommended and one of several used for glass slide
preparation, as known in the art. However, polylysine-coated glass
slides suffer from poor stability, extended curing cycles, and poor
reliability such that new surface methodologies are critically
needed to support the rapidly growing field of microarray
technology. For example, polylysine-coated slides need to be stored
for 14 days after coating for curing purposes and should be used
within four months due to degradation from oxidation. Typically, in
a batch of polylysine-coated slides, several are rejected because
of non-uniformity or opacity. In addition, the hybridized
microarrays cannot be stored over long time periods. Stability of
polylysine coating under UV light is also a concern.
[0015] Many alternative coatings to replace polylysine are being
investigated including aminosilanes, epoxy derivatives, aldehydes,
and others. While aminosilanes or their derivatives offer superior
stability, their low binding capacity has been a problem. Many of
these limitations stem from the lack of desirable inorganic surface
chemistry for bonding with organics. Organic groups functionalized
on soda-lime glass surfaces are not stable under even slightly
harsh conditions or chemical treatments and will degrade over time.
Organic molecules interact only weakly with soda-lime-silica
surfaces. Under humid or other conditions, sodium ions diffuse to
the surface of the glass and interact with organic molecules
resulting in degradation. Borosilicate or aluminosilicate glasses
have also been proposed, but they do not offer the ideal surface
chemistry for organic absorption.
[0016] Disinfecting and antimicrobial chemicals are commonly
employed to eradicate microbial growth and improve hygiene. The
adhesion of micro-organisms to surfaces is influenced by the
bio-adhesive characteristics of the fouling organism and surface
properties, such as its chemical composition and physical
characteristics of the surfaces like surface roughness. Fungi, such
as molds, yeasts and algae are visible in mass, but it can be
advantageous to eliminate them earlier, when contamination and the
consequential substrate deterioration has not yet become obvious.
Highly active cleaning chemicals may be toxic and aggressive and,
after repeated applications, degrade the surface and inactivate
bioactive systems. Another major problem is the evolution of
microbial strains which are resistant to disinfectants and
antimicrobial agents that are being used now. The issue of hygiene
is especially critical to contact surfaces present in food
processing, supply and catering chains, health and medical
establishments, animal husbandry, water and sewage operations as
well as in heating, ventilation and air conditioning systems.
[0017] The performance factors of antimicrobial coatings include
durability, retention of activity, and minimal degradation of
surface characteristics and appearance. The coatings must also show
resistance to heat, chemicals, solvents, staining, scratching, and
moist environments. They should preferably be non-toxic, odorless,
smooth, non-porous, easy or self clean, crack-free, avoid
discoloration, have good color retention and be UV resistant.
Several potential novel techniques are being developed to overcome
these problems. These include albumin affinity surfaces, surface
modification with blue dextran, silver ion incorporation in a
porous matrix, photocatalytic titanium dioxide, silicone
quarternary ammonium compounds and sacrificial coatings that are
alkali soluble or strippable and recyclable films. A multi-layer
film, fluoro/silicon containing resins, a dry paint film with
additive coating or additives incorporated, the incorporation of
cleaning agent activators, the design of surface and cleansing
system in tandem, tuned ultraviolet, ultrasound and ozone could
also be of value.
[0018] Among these antimicrobial techniques, there is a renewed
interest in silver ion incorporation into coatings and substrates
by researchers and companies. Several patents and publications have
recently appeared on the use silver ion incorporated substrates
like zeolites, polymers, ceramic sheets and polyelectrolyte films.
Silver compounds have been exploited for their medicinal properties
for centuries. It is an effective agent with low toxicity. Although
silver salts are effective antimicrobial agents, their use likely
results in unwanted adsorption of silver ions in epidermis cells
and sweat glands. To reduce the likelihood of silver-ion adsorption
into tissue, silver ions need to be incorporated into stable
substrates.
[0019] The hydrophobic effect plays an important role in the
defense against pathogens. In addition to the unfavorable surface
energy on the hydrophobic surfaces, microorganisms are also
deprived of the water necessary for germination and growth. Very
few microorganisms are known to survive in the absence of water.
Hence, hydrophobic property imparted on inventive material coated
surfaces may be regarded as the additional defense against
microbes. The combined effect of both bactericidal and hydrophobic
properties of inventive material coating will act as two lines of
defense against harmful microorganisms. A hydrophobic layer will
prevent or reduce the adhesion of microbials and help in easy
cleaning. In case of damage occurring to this hydrophobic layer
during service the antimicrobial agent loaded second layer will act
as second line of defense against microbes. Fiberglass insulation
is used extensively in building construction. Fiberglass is an
effective insulation, but is susceptible to moisture and can become
a point for bacteria and mold to grow. Mold and bacteria growth in
building materials causes indoor air pollution and can cause
sickness in the inhabitants of the building. A water-repellent
coating is desired to maintain dry conditions of the fiberglass
insulation. If the fiberglass is dry, then biological growth can be
prevented. Therefore, the combination of both hydrophobic and
antibacterial property in one embodiment will greatly help in
situation like this and others.
SUMMARY OF THE INVENTION
[0020] In light of the foregoing, it is an object of the present
invention to provide aluminophosphate compounds, compositions
and/or related composites or articles, together with methods for
their use and preparation, thereby overcoming various deficiencies
and shortcomings of the prior art, including those outlined above.
It will be understood by those skilled in the art that one or more
aspects of this invention can meet certain objectives, while one or
more other aspects can meet certain other objectives. Each
objective may not apply equally, in all its respects, to every
aspect of this invention. As such, the following objects can be
viewed in the alternative with respect to any one aspect of this
invention.
[0021] For purposes of the present invention, the phrase "inventive
material," mention thereof or reference thereto will be understood
to mean any of the present aluminophosphate compounds or
compositions, over the entire available range of Al:P
stoichiometries, as may be used in conjunction with a method,
composite, or article of this invention, and/or a film, layer or
coating associated therewith, or as otherwise provided below, such
compounds or compositions prepared or characterized as described
herein, such compounds and compositions as may be alternatively
expressed, respectively, as aluminum phosphate compounds and
compositions, and prepared, characterized and/or applied as
described in U.S. Pat. Nos. 6,036,762 and 6,461,415 and co-pending
application Ser. Nos. 10/627,194 and PCT/US03/36976, filed Jul. 24,
2003 and Nov. 19, 2003, respectively, and 10/642,069 and
PCT/US03/25542 filed Aug. 14, 2003, each of which is incorporated
herein by reference in its entirety. Without limitation, as
described herein and/or through one or more of the aforementioned
incorporated patents or applications, the inventive material can
include such aluminophosphate compounds and compositions comprising
dopants, particles and/or inclusions of carbon, silicon, metals,
metal oxides and/or other metal ions/salts--including
nonoxides--regardless of whether the aluminum content is
stoichiometric, less than stoichiometric or greater than
stoichiometric relative to phosphorous, on a molar basis.
Embodiments of the inventive materials are available under the
Cerablak trademark from Applied Thin Films, Inc.
[0022] The inventive material comprises aluminophosphate and can be
deposited as a thin film on substrates using a specially-designed
precursor solution that yields a unique form of amorphous aluminum
phosphate. U.S. Pat. Nos. 6,036,762 and 6,461,415 issued to
Sambasivan et. al and the above-referenced patent applications
provide details regarding the precursor synthesis and chemistry,
properties, and other processing details are provided. Various
additions or modifications to surfaces coated with the inventive
material are also considered embodiments of the present invention,
examples of which are provided below.
[0023] One of the objects of the invention is to provide a method
to deposit this inventive material coating as a thin, hermetic,
microstructurally dense, uniform, and transparent coating using
simple dip, spin, spray, brush or flow coating process. It is an
object of the invention is to use inventive material coatings to
passivate and protect metals and alloys from oxidation and
corrosion during processing and service at room and elevated
temperatures. Another object of the invention is to use the present
inventive material in conjunction with other coating materials. For
example, along with copper-chromium alloy coatings, the inventive
material coating can be used to protect against oxidation of
advanced copper-niobium alloys with less chromium content.
[0024] It is a further object of the invention to planarize metal
and alloy surfaces such that the smoothness of the resulting
surface is beneficial for rendering a low-friction surface which
should provide, for example, better wear characteristics. The
planarized surface may also be suitable for further deposition of
other functional layer(s) above, over or on top of the inventive
material coating whereby the substrate is protected during
processing of subsequent layers and the planarized surface provides
better quality overlayers. The smooth surface obtained due to the
planarization effect of the coating is also beneficial as
foul-release coatings for marine utilities.
[0025] Another object of the invention is that coatings of the
inventive material applied to metal, alloys, ceramic or glass
surfaces can be imparted with additional functions including but
not limited to hydrophobic, hydrophilic, antimicrobial, optical,
low-friction, anti-fouling, easy foul-releasing, mechanical and
self-cleaning properties by an additional layer of organic
molecules. Such surface modification of metal and alloy, ceramics
and glass surfaces with a substantially pore-free and smooth
inorganic film which is highly stable and with the additional
organic layer make the surface multifunctional and can provide a
comprehensive method of protection and other broad range of
applications.
[0026] Another object of present invention is to preferentially
attach or couple biomolecules and other organic molecules to films
or components of the inventive material, such molecules including,
but not limited to, polypeptides, polynucleotides or nucleic acids
onto inventive material surface, which is preferably obtained as a
coating on a solid support.
[0027] It is another objective of this invention to tailor the
inventive material coated surfaces with attachment of organic or
inorganic or combined molecules including, but not limited, to
alkyl amines, carboxylic acids and organosilanes. It is another
objective of this invention to use organic linker molecules
attached to inventive material surface for biomolecular array
preparation. It is another object of this invention to provide a
mask layer over inventive material layer, which can be selectively
removed chemically or photochemically. It is another object of this
invention to reduce or eliminate the fluorescence impurities
present in the solid substrates which interfere in DNA
hybridization analysis. It is another objective of this invention
to use inventive material coating as barrier for interaction of
attached biomolecules with detrimental species such as sodium ions
present in the substrates like soda-lime glasses. It is another
objective of this invention to tailor the hydrophobicity of the
inventive material surface coated on solid substrates, for example,
by selectively attaching suitable organic molecules. This will help
in processes such as DNA spotting from spreading. It is another
objective of this invention to coat the inventive material over
silicon surfaces, thus allowing the integration with DNA chip
technology. It is another object of this invention to mass produce
suitable solid supports to clean, consistent and durable solid
supports for bimolecular array. It is another object of this
invention to attach functionally derivatized DNA molecules onto
inventive material surface coated over solid substrates. It is
another object of this invention to modify conventional solid
substrates including but not limited to glass slides to be applied
for preparing consistent, clean, uniform, durable, and hard
surfaces suitable for microarrays.
[0028] Another object of present invention is to use inventive
material as the substrate or carrier for organic and inorganic
antimicrobial agents and in particular but not limited to silver
ions. Antimicrobial agents can also be incorporated within the
inventive material matrix and used as antimicrobial powder.
[0029] Another object of the present invention is the development
of a low-cost, durable, antimicrobial and corrosion resistant
coating material in one embodiment. Another objective is the
development of silver mixed-inventive material coated surfaces with
additional hydrophobic property through the attachment of a
suitable organic layer. Yet another objective of the present
invention is to use a porous overlayer to the inventive material
coating on substrates to impart large surface area to the surface
for intake of higher quantity of antimicrobial agents. The porous
layer will be loaded with antimicrobial agents such as, but not
limited, to silver ions. The porous layer can also be
functionalized by the uptake of selective organic compounds, for
example, adsorbed hinokitiol, tannin, lysozyme, protamine or sorbic
acid that can be released slowly for durable antimicrobial
activity.
[0030] Other objects, features, benefits and advantages of the
present invention will be apparent from this summary and its
descriptions of various embodiments, and will be readily apparent
to those skilled in the art having knowledge of various
corrosion/oxidation protection, anti-microbial, anti-biofouling and
bio-microarray coatings, films and/or applications. Such objects,
features, benefits and advantages will be apparent from the above
as taken into conjunction with the accompanying descriptions,
examples, data, figures and all reasonable inferences to be drawn
therefrom, alone or with consideration of the references
incorporated herein. These and other objectives, advantages, and
features of the invention will become apparent to those skilled in
the art upon reading the details of the invention as more fully
described below.
[0031] In accordance with the preceding and the inventive materials
referenced above and described elsewhere herein, the present
invention is, in part, a method of using an aluminophosphate
compound to decrease surface roughness. Such a method comprises (1)
providing a precursor to an aluminophosphate compound, the
precursor comprising aluminum ions and phosphate esters in a fluid
medium; (2) applying the precursor medium to a substrate having a
first surface roughness value; and (3) treating and/or heating the
applied medium for a time and at a temperature sufficient to
provide a substantially amorphous aluminophosphate compound on the
substrate. Application and subsequent treatment of the precursor
medium, as described herein, as well as in the aforementioned
incorporated references, provides a planarized substrate surface,
such planarization as can be determined by a decreased, second
roughness value, as compared to the aforementioned first surface
roughness value. Reference is made to several figures and
supporting examples. In preferred embodiments, the surface
roughness value can be decreased at least by about a factor of 3.
Alternatively, such a method can provide a treated substrate with a
friction coefficient less than about 0.2.
[0032] A precursor to the aluminophosphate compound can be applied
to the substrate using one or more techniques, as would be
understood by those skilled in the art. Dip-coating can be used
with good effect over a range of substrate materials and
configurations. Spraying, flow-coating and spin-coating can be used
with comparable effect, depending upon choice of substrate. Without
limitation, a substrate used in conjunction with a method or
composite of this invention can include a steel, a nickel-based
alloy, a superalloy, titanium, a titanium-based alloy, niobium, a
niobium-based alloy, molybdenum, a molybdenum-based alloy, silicon,
aluminum oxide, an enamel, mullite, a glass, fused silica, a
silica-based refractory and a ceramic material. Likewise, for
purposes of illustration and without limitation, such a substrate,
in particular those comprising a metal, alloy or ceramic material,
can be configured to provide a bearing, a gear, or a medical
implant component.
[0033] Further demonstrating the utility of this invention,
providing a suitable substrate, an aluminophosphate compound of
this invention can have deposited thereon a biaxially-textured
component such as but not limited to magnesium oxide, yttria and an
yttria-stabilized zirconia. With such embodiments of the
methodology and/or composites of this invention, a lattice-matching
and/or an electromagnetic component can be deposited on such a
textured component. As would be understood by those skilled in the
art made aware of this invention, such an electromagnetic component
can comprise a superconducting YBCO ceramic material.
[0034] In part, the present invention is also a composite
comprising a substrate, a substantially amorphous aluminophosphate
compound and an organic component attached to the aluminophosphate
compound. Typically, the aluminophosphate compound is on the
substrate, but can, optionally, be provided as an overlayer or
coating on another component deposited on the substrate.
Regardless, as described elsewhere herein, the organic component
can comprise a compound having synthetic, clinical and/or
diagnostic application. Such a biomolecule can be selected from but
is not limited to a protein or an amino acid residue thereof, a
polypeptide, a polynucleotide or a fragment, component or residue
thereof. As discussed elsewhere herein, such a composite and
associated methodology can be used for the coupling, attachment or
bonding interaction with a DNA fragment or component. Such coupling
or attachment of the aluminophosphate compound with a particular
biomolecule can be direct or via a molecular linker component.
Polylysine can be used as can other linker components known in the
art to those individuals made aware of this invention, such
components including a range of organosilane compounds. Examples of
the latter include difunctional aminosilane compounds which can be
used for the coupling or attachment of the range of biomolecules,
directly or by way of synthetic modification, to the
aluminophosphate compounds or compositions of this invention.
[0035] In part, the present invention can also include a
substantially amorphous composition comprising an aluminophosphate
compound and an antimicrobial component. Without limitation, the
antimicrobial component can be selected from silver, copper, zinc
and iron ions. Regardless, such an antimicrobial component can be
incorporated into such a composition over a range of effective
concentrations. However, depending upon desired effect, the ratio
of antimicrobial to aluminophosphate component can range from about
0.1:1 to about 1:1. As described elsewhere herein, such a
composition can be applied or deposited on a substrate, such a
composite can further comprise one or more organic components to
provide additional functional effect. Without limitation, such an
organic component can be selected from a fatty acid or a silane
compound to provide enhanced hydrophopicity. Alternatively,
enhanced effect can be achieved through choice of an appropriate
detergent or surfactant component, with incorporation of the metal
cations to provide antimicrobial effect and the organic anion to
enhance hydrophopicity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1. Schematic figure showing the ability of the
microstructurally dense and hermetic inventive material coating to
seal off surface defects and grain boundaries on a metal or alloy
specimen. (a) indicates a grain boundary, (b) indicates a pit and
(c) indicates a scratch in the surface. The inventive material
coating effectively seals such defects.
[0037] FIG. 2. Schematics showing typical architecture to develop
HTS films on a metal substrate. The respective layers are (a)
polycrystalline metal or alloy substrate, including but not limited
to Inconel, stainless steel, 1-624, and nickel chromium alloys, (b)
an inventive material coating, for passivating and planarizing the
substrate, (c) IBAD MgO or YSZ, (d) homoepitaxial MgO or YSZ, (e)
CeO.sub.2 and (f) HTS layer. FIG. 2A shows how the inventive
material can be used in the current architecture. FIG. 2B shows how
the inventive material can be used to reduce or eliminate the need
for the diffusion layer (d).
[0038] FIG. 3. Schematic showing the immobilization of biomolecules
on inventive material coated on solid substrates.
[0039] FIG. 4. Cross-sectional transmission electron micrograph
showing a well-adherent, thin, uniform, dense and hermetic film of
the inventive material deposited on the 304 stainless steel.
[0040] FIG. 5. Photograph of coated and uncoated Ti-46 alloy after
100 hours of exposure at 800.degree. C. in ambient air showing the
oxidation protection ability of the inventive material.
[0041] FIG. 6. Photograph of uncoated and coated nickel rods
exposed at 550.degree. C. for 115 hours in ambient air. Higher
reflectivity for the coated nickel relative to uncoated sample is
readily apparent. A coating of the inventive material not only
provides the desired oxidation protection, but the hermetic nature
of the coating also provides protection of the substrate from
environmental attack during service from various contaminants in
the atmosphere such as sulfur, chlorine, acids, salt, and
moisture.
[0042] FIG. 7. Schematic showing the planarization effect of a
coating of the inventive material on relatively rough surfaces.
[0043] FIG. 8. Comparative photographs showing antimicrobial
susceptibility test with e. coli, bacterial growth inhibition (A) a
slide coated with an inventive material comprising silver ions and
(B) `control` sample, glass slide coated with inventive material
and not loaded with antimicrobial silver ions.
[0044] FIG. 9. Grazing angle Fourier Transform Infrared reflectance
spectrum of an embodiment of the inventive material coated on a
stainless steel sample and cured at 500.degree. C. for 5
minutes.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
[0045] As mentioned above, the present invention relates to an
aluminophosphate compound/composition with a variable aluminum to
phosphorus ratio which is stable to high temperature. Without
limitation, the molar ratio of aluminum to phosphorus can range
from about 0.5:1 to about 10:1, preferably ranging from about 1:1
to about 4:1, most preferably ranging from about 1:1 to about 2:1.
Films, layers and/or components of the inventive material are
available using an inexpensive chemical precursor solution that
deposits a uniform, hermetic, transparent thin film by a simple
dip, paint, spray or flow coating process, such precursor(s) and
methods of deposit as are more fully described in the
aforementioned patent and application references.
[0046] Present inventive material offers a) excellent protection
against oxidation, b) the formation of stable protective oxide
scales, and c) adequate sealing of defects (such as pits) on alloy
surfaces such that accelerated oxidation is prevented during the
early stages of exposure (see FIG. 1 for a schematic representation
of the effect of inventive material coating metal and alloy
substrates). Among these, the most relevant and innovative
attribute, without wishing to be bound by theory, is the ability of
the inventive material to promote formation of a dense, continuous
and protective oxide scale underneath during early stages of
oxidation. It is apparent from studies on stainless steel that a
dense chromia-rich scale is formed preferentially in coated
materials compared to a highly porous iron-rich scale for uncoated
specimens. In the latter case, extensive oxidation is observed with
subsequent spallation of the scales. An order of magnitude
difference in oxide scale thickness was observed between coated and
uncoated AUS 304 substrate coupons.
[0047] Inventive material coatings on nickel-based superalloys and
titanium alloys may extend turbine lifetimes, limit failure, and
allow higher operational temperatures with minimal additional cost.
Inventive material coating on alloy foils reduces oxidation and
corrosion which may find application with metal foil catalytic
converters. In addition, a component (e.g., a film) of the
inventive material may be used to protect other alloy and metal
specimens from oxidation and corrosion. The coating process is
simple, scalable, and amenable to field repair. Protection from
oxidation at elevated temperatures has been demonstrated for a
number of alloy substrates including titanium alloys, nickel-based
alloys, steel, cast iron, and inconel.
[0048] In addition to protecting alloys from oxidation during
service conditions, the present inventive material can be used to
protect alloys from oxidation during hot forming. Metals and alloys
are sometimes heated (strengthening or case hardening) for forming
to produce a specific shape for future use. The mechanism of
protection is the same as protection at use conditions, although
the heat treatment is relatively short (a few minutes to hours),
and the coated alloy may or may not be intended for use at high
temperature.
[0049] In addition to depositing the coating using a clear
precursor solution, powders can be made and dispersed in the
solution to form a slurry coating. The coating is then applied in
the same manner as the clear solution. Powders can also be thermal
sprayed onto a substrate. Black, gray color of various shades or
white powders of the inventive material can be used as pigments and
dispersed in a paint medium and used in coating surfaces.
[0050] The inventive material coating can be used as part of a
multilayered coating system. Coatings of other compositions can be
deposited either underneath or over the inventive material coating.
One example of this embodiment of the invention is the use of
inventive material coating as an oxidation barrier between an alloy
substrate and a thermal barrier coating. Thermal barrier coatings
are used to reduce the temperature of an alloy substrate, but do
not offer significant oxidation protection. A component coating of
the inventive material can be applied underneath the thermal
barrier coating to reduce oxidation of the substrate.
[0051] The inventive material can be used as multilayers to tailor
desired properties with varying chemistries or microstructrures in
each layer to form a functionally-graded structure or to produce
thicker layers to increase the protection ability against corrosion
and anti-tarnishing. The inventive material coating can be used to
retain or improve the heat and light reflectivity of coated
surfaces substantially at low as well as elevated temperatures.
[0052] The planarization induced by inventive material will be
useful for a number of applications including those requiring wear
resistance or low friction surfaces. In addition, the smooth
amorphous surface can also serve as a template (due to better
adhesion characteristics with deposited overlayers of organic or
polymeric or ceramic materials) for growth of additional layers for
adding functionality. For example, amorphous template layers are
desired for growth of textured films for electronic applications.
In particular, growth of biaxially textured superconductor films is
desired for long length high temperature superconducting (HTS)
tapes. Several patents have been issued related to using ion beam
assisted deposition (IBAD) to create a biaxially textured oxide
template on metal/alloy or amorphous (silica/Si) substrates,
including U.S. Pat. Nos. 6,383,989 and 6,312,819, each of which is
incorporated herein by reference.
[0053] Presently, both silicon nitride and yttria are used as
amorphous "nucleation" or "adhesion" in the IBAD or Inclined
Substrate Deposition (ISD) approaches. Thus, there is a need for an
alternative material and associated thin film process (preferably
non-vacuum, low-cost, and high deposition rate) to replace yttria
and silicon nitride or other layers which is multifunctional and
performs better and can be deposited at reduced costs. Inventive
material produced using a dip-coating or other solution-based
process offers an excellent opportunity to replace existing
amorphous template technologies for IBAD film growth. By a simple
dip-coating process, the inventive material can be deposited as a
microstructurally dense, hermetic, thin (50 nm-1 .mu.m), pin-hole
free, uniform, and smooth film at relatively high rates in one
pass. The inventive material coating is a better alternative
because of the low cost coating process, high throughput, thermally
stable and durable nature of the coating, and will provide
excellent protection to substrate, but may also be suitable for
etching to pattern the semiconductor layers for solar array
applications.
[0054] Inventive material coatings suitable as an IBAD template
layer have several advantages over current technology. As a
hermetic coating, the inventive material seals off pits, scratches,
and other defects typically found even on well-polished substrates
which can be corrosion-active and may affect the texture quality of
IBAD film in those areas. Deposition of inventive material on metal
or alloy or ceramic surfaces also induces a planarizing or
smoothening effect so that the surface roughness can be
significantly reduced which may allow for reduced polishing effort.
Inventive material is a highly inert and stable high temperature
material with low oxygen diffusivity. The diffusion barrier
characteristics are very important so that diffusion of metal
species into the functional oxide layer is limited during high
temperature growth of the oxide layer. Typically, the multilayer
stack will contain a buffer layer on top of the IBAD layer to
prevent diffusion of metal species into the functional layer (See
FIG. 2, for the schematics showing typical architecture to develop
HTS films on a metal substrate).
[0055] Thus, the inventive material can serve as an excellent
template for IBAD growth for a number of applications including,
but not limited to, HTS coated conductors, ferroelectrics,
piezoelectrics, optoelectronics or electro-optics. It also has a
low dielectric constant so that it can be integrated easily into
silicon-based technology and used as a gate dielectric layer for
silicon-based semiconductors. Biaxially textured or single crystal
films of piezoelectric ceramics are being targeted for adaptive and
flexible structures for aerospace and other applications. The
inventive material deposited on flexible metal/alloy foil
substrates will offer corrosion and oxidation resistance while
serving as a stable and inert template for IBAD growth of
piezoelectric films, thus creating a stable adaptive wing or other
structures with high electromechanical coupling (due to high
quality texture) produced at much lower costs as compared to
current methods. The IBAD process can also be used to produce
single crystal or biaxially textured films on flexible metal foil
substrates suitable for solar cell applications. Single crystal
germanium and GaAs layers are desired on metal foil substrates for
solar arrays. The current approach is to use polycrystalline
semiconductor layers on metal or polymer substrates, limiting the
solar conversion efficiencies. The IBAD approach may be ideally
suited to produce textured layers.
[0056] Growth of epitaxial conductive oxide electrode layers is
desired on amorphous substrates (such as ruthenium oxide) for use
in actuators and other devices; inventive material can serve as an
excellent template on silicon. Although thermally grown silica
films on silicon may be suitable for the same purpose, growing a
100 nm silica scale on silicon by thermal oxidation require very
high temperature processing and long scale formation times which
also induces stresses so that the microstructure and morphology of
the oxide scale is not optimal for subsequent growth of oxides.
With the inventive material, at a low deposition temperature, a
nominal 100 nm thick film, which is uniform, hermetic, and dense
can be grown within few minutes by curing above 350-500.degree.
C.
[0057] Planarization can be induced on relatively rough surfaces by
depositing multiple layers of coatings of the inventive material,
where each coating has a lower surface roughness than the coating
underneath. Coatings of the inventive material were deposited on
4340 steel coupons and the friction coefficient was found to be
.about.0.1-0.14. In addition to the low friction properties, the
inventive material has a low surface energy of 32 dyne/cm. With
organic molecules attached to the inventive material surface, the
surface energy can be lowered even further.
[0058] The surface of inventive material coatings can be further
tailored by the purposeful deposition of organic overlayers. The
use of functional organic overlayers on metal or alloy substrates
has many applications, including but not limited to the use of
organic catalysts on metal reactor vessels. Without wishing to
bound by any theory the adsorption of organics may result from the
presence of active adsorption sites on the inventive material
surface. These active organic attachment sites may be attributed to
the presence of unsaturated aluminum ions (bonded to three or less
oxygen atoms) or P doublebond 0 moieties (P.dbd.O), or Al--OH
and/or P--OH groups on the surface of the inventive material.
Further Al--O--Al and A--O--P bridging groups, present on the
surface resulting from the pyrolysis of the precursor solution can
also render the inventive material highly reactive. Molecular
water, alcohol, acetone or ether can dissociatively adsorb on these
sites upon atmospheric exposure resulting in reactive Al--OH and
P--OH groups. These reactive hydroxyl groups can also be formed on
the inventive material surface purposely by treating with dilute
acid or other chemical methods that are familiar to those skilled
in art. The organic attachment is very stable and durable toward
subsequent chemical, thermal, and mechanical treatments
[0059] Thus, the inventive material offers a new and unique glass
surface chemistry which has tremendous promise for use in
biomolecule immobilization. The attractive attributes of inventive
material include the nature of the glassy material and the simple
dip coating process used to develop a thin, uniform, dense,
hermetic, and transparent film (see FIG. 3, for a schematic
representation of microarray using inventive material coated
substrates). The coating also provides the benefit to seal off any
surface flaws or defects, thus providing a very uniform and
consistent surface chemistry which is essential for microarray and
other biotechnological applications.
[0060] Another aspect of this invention is the preservation of an
inorganic surface prior to biomolecular deposition. Normal
procedures for using soda lime glasses include extensive cleaning
and inspection of surfaces to ensure scratch and contaminant-free
surfaces prior to polylysine deposition. These procedures are
tedious and time-consuming and are prone to manual errors and can
cause unknown failures on precious DNA samples and hence raises
concern with the current approach. In comparison, immediately after
forming inventive material coatings, they can be masked with a
surfactant layer which may include but is not limited to oleic acid
layers, which provide excellent coverage and a hydrophobic surface
which repels water and other contaminants (non-stick coating).
These masked layers can be easily removed just prior to organic
deposition such that a pristine surface of the inventive material
is exposed for producing consistent and high quality organic or
biomolecular overlayers. Such an approach cannot be used to protect
sodalime glasses since the bonding with organics is fairly weak and
surfaces tend to get hydroxylated to form silanol groups as opposed
to organic adsorption. High quality coatings of the inventive
material with organic layers on glass can also provide
self-cleaning glass products suited for architectural windows and
automotive applications.
[0061] Two other alternative approaches are possible for attachment
of biomolecules on an inventive material surface. One method
involves developing a suitable organic anchor layer which has
functional groups for subsequent bonding with DNA or other
biomolecules. The coupling, attachment and/or bonding of the
organic layer with an inventive material coating is fairly robust
as it can be tailored with a carboxylic or amino terminating
groups. A second alternative is to use the inventive material as a
stable buffer layer for use in conjunction with linker molecules,
compounds or moieties including the currently-used polylysine-based
coating systems. The compounds/compositions offer important
benefits of this invention compared to the current system via
providing a chemically inert surface, strong bonding with
polylysine, and superior surface morphology not limited to smooth,
dense, and nearly defect-free surface.
[0062] The inventive material and/or precursor solution with metal
cations including, but not limited to silver, copper and zinc can
be used in antimicrobial coatings. Inventive material mixed with
antimicrobial agents coated surface can act as antimicrobial on
contact. Organic antimicrobial agents can also be attached onto the
inventive material surface owing to the strong and unique affinity
of inventive material for organic molecules. Antimicrobial agents
not limited to antimicrobial surfactants can also be adsorbed on to
surfaces coated with inventive material. These will act both as
antimicrobial and hydrophobic surfaces. End groups of surfactants
can be alkyl, or trifluoro alkyl groups. Trifluoro end groups are
preferred for higher hydrophobicity. Dry conditions because of a
hydrophobic surface will help in preventing microbial growth. Metal
cation salts of surfactants not limited to silver salts of acid
surfactants (e.g. silver salt of oleic acid) can also be used as
the adsorption layer on the inventive material coating to enhance
the antimicrobial activity. Not wishing to be bound by any theory,
it is believed that the carboxyl group is attached to aluminum
cation and silver ion to phosphate group. Since the inventive
material can be coated by a simple process, and not limited to dip
coating, on a variety of substrates, several fields of applications
can be exploited. Applications of antimicrobial coatings are listed
in Table 1. These are only representative examples and not
exhaustive list of potential applications of the present
invention.
TABLE-US-00001 TABLE 1 Property Substrates Applications
Antimicrobial, Glass Windows, Cell Cultures, Anchoring substrate
Micro array Protein adsorption Antimicrobial, and Steel Building
Construction corrosion (push-plates, kick-plates, towel dispensers,
escalators, door knobs, light fixtures, bath room components, Air-
handling duct systems) Antimicrobial Aluminum Serving trays, salad
bars, Refrigerators, Coolers, Food packaging. Antimicrobial Floor
Tiles Serving counters, food preparation surfaces, animal shelters
Antimicrobial Ti and Ti- Surgical instruments, based alloys,
Catheters, Guidewires, Stainless Introducers, Shunts, Tubes, steel,
Endoscopes, Blades, Needles, Platinum, Coiling wire, PTCA stylets,
Nitinol Mandrel wire Microbially Marine/ Against growth of
bacteria, Influenced Corrosion Aquaculture algae, fungus, mold, and
(& salt corrosion) mildew under water (swimming pool)
[0063] For some applications, it is possible to tailor the
inventive material composition to alter its mechanical
(nanocomposite films), thermal (improve conductivity through
inclusions), electrical (add cationic solutions to precursor to
improve electrical conductivity), optical, chemical properties, and
biological properties (antimicrobial) thus enhancing the product
capabilities and performance. In the case of metallic surfaces,
bioactive inventive material surfaces can serve dual purpose:
corrosion resistance and antimicrobial coating. Such
multifunctional coatings are highly desired. Other approaches
include forming a porous layer of aluminum phosphate layer over a
hermetic coating of the inventive material. The porous layer can be
loaded with a desired amount of antimicrobial agents including, but
not limited to, organic antimicrobial agents such as hinokitiol,
tannin, lysozyme, protamine and sorbic acid and inorganic ions such
as silver, copper or zinc. These agents can be released slowly for
antimicrobial activity. Silver ion embedded in an inventive
material coating on glass substrate showed antibacterial activity
against E. coli bacteria preventing the growth of the bacteria
around the coated glass surface. This property can be exploited in
destroying microbes or preventing the growth thereof.
EXAMPLES OF THE INVENTION
[0064] The following non-limiting examples and data illustrate
various aspects and features relating to the compounds,
compositions, composites, articles and/or methods of the present
invention. In comparison with the prior art, the present compounds,
compositions and/or methods provide results and data which are
surprising, unexpected and contrary thereto. While the utility of
this invention is illustrated through the use of several
aluminophosphate compounds/compositions and films/coatings thereof,
it will be understood by those skilled in the art that comparable
results are obtainable with various other compounds, compositions
and stoichiometries, as are commensurate with the scope of this
invention.
Example 1
[0065] A preferred method for depositing a component film/coating
of the inventive material coating is with a clear chemical
precursor solution, with the solution preferably containing an
aluminum salt and phosphate esters in an organic solvent. A
solution used to deposit inventive material coatings with a 2 to 1
molar ratio of aluminum to phosphorus is made by dissolving 264 g
of Al(NO.sub.3).sub.3.9H.sub.2O in 300 mL ethanol. In a separate
container, 25 g P.sub.2O.sub.5 is dissolved in 100 mL ethanol.
These solutions are mixed together. The resulting solution is
diluted with ethanol to a concentration of about 0.2 moles Al/L
solution.
Example 2
[0066] 1''.times.2'' 304 stainless steel foil is coated with the
precursor solution of Example 1. The sample is heated at
500.degree. C. for 15 minutes in a preheated furnace. A small part
of this heat treated sample is prepared for transmission electron
microscopic study of cross section of the inventive material
coating on the substrate. FIG. 4 shows the thickness of the coating
to be about 100 nm. The inventive material coating is well-adhered
to the stainless steel surface, and the micrograph demonstrates the
continuous, dense and hermetic nature of the coating.
Example 3
[0067] Titanium-based alloys tend to oxidize readily, causing
changes in the desired properties of the alloy. Titanium can be
alloyed with other elements (aluminum, for example) to increase
oxidation resistance, but mechanical properties may suffer. An
ultra-thin coating which can protect titanium alloys from oxidation
is greatly desired. The inventive material has been shown to
protect titanium aluminide alloys from oxidation. The solution
described in Example 1 is deposited on a Ti-46Al coupon and cured
by heating at 600.degree. C. for 2 minutes. Samples coated by this
method were exposed to 800.degree. C. in ambient air for 100 hours,
along with an uncoated sample. The weight change from oxidation was
significantly lower for the coated specimens. FIG. 5 shows a
photograph of coated and uncoated samples after the test.
[0068] Weight change after 800.degree. C., 100 hour exposure in
ambient air (mg/cm.sup.2)
[0069] coated sample 1 0.000034
[0070] coated sample 2 0.000033
[0071] uncoated sample 0.017
Example 4
[0072] A coupon of Ti-6Al-4V was dipped into a chemical precursor
solution as described in Example 1. The coating was dried with cool
air and heat treated at 600.degree. C. for 2 minutes in a preheated
furnace. The coupons were then exposed to ambient air at
800.degree. C. for 100 hours. The weight change from oxidation was
orders of magnitude lower for the coated specimen.
[0073] Weight change after 800.degree. C., 100 hour exposure in
ambient air (mg/cm.sup.2)
coated sample 0.000077 uncoated sample 0.027
Example 5
[0074] Oxidation protection of nickel has been demonstrated with a
film/coating component of the inventive material. The coating will
help passivate the nickel or nickel alloy substrate such that
protection against high temperature oxidation or protection against
corrosive environments such as salty or sulfur or
chlorine-containing atmospheres, is imparted. A nickel rod was
dipped into a chemical precursor solution as described in Example 1
and dried in flowing air. The coated rod, along with an uncoated
control specimen, was annealed in ambient air at 550.degree. C. for
115 hours. The uncoated sample showed a dark oxide film, while the
coated sample retained the metallic luster of the original rod
(FIG. 4).
Example 6
[0075] Metal and alloy surfaces have varying surface finishes and
roughness depending on the desired application, cost of preparation
and other factors. Many metal and alloy surfaces are grit-blasted
before coating to clean off prior surface preparations or existing
corrosion residues. A coupon of type 304 stainless steel is grit
blasted to give a rough surface finish. The solution described in
Example 1 is deposited on the surface through dip coating. The
coating is dried in flowing air and cured with an IR lamp for 5
minutes. Optical microscopy showed that the coating substantially
covers the sample and is essentially crack-free. The coupon of
annealed, along with an uncoated coupon at 1100.degree. C. for 4
hours in a furnace. The coated coupon shows significantly less
weight gain from oxidation than the uncoated coupon.
[0076] Weight change after 1100.degree. C., 4 hour exposure in
ambient air (mg/cm.sup.2)
Coated sample 6.52 Uncoated sample 26.34
Example 7
[0077] The inventive material can be used to planarize or smoothen
a variety of substrates. The solution of Example 1 is deposited on
an alloy substrate. Atomic force microscopic measurements were
performed on coated and uncoated samples to determine the root mean
square (rms) roughness. The uncoated alloy has a rms roughness of
21 nm. The rms roughness decreases to 7 nm upon application of the
coating.
Example 8
[0078] Inventive material coatings on metal and silicon substrates
can be used for subsequent growth of epitaxial layers for
electronic applications. Specifically, this example relates to use
of inventive material coating as a template layer for producing
high current carrying high temperature superconducting (HTS) tapes.
A piece of C-276 nickel-base alloy or Hastelloy foil having an
initial "as-received" rms roughness of 570 .ANG. is dipped in the
solution of Example 1. The coated foil is dried in flowing air and
heat treated at 570.degree. C. for 1 minute in a preheated furnace.
The rms roughness is reduced to below 140 .ANG. for a nominal
thickness of 100 nm for the inventive material coating. FIG. 7
shows a schematic of the planarized surface.
Example 9
[0079] Using an ion-beam assisted electron beam deposition process,
a thin oxide of yttria stabilized zirconia (YSZ) (thickness ranging
from 50-100 nm) with substantial biaxial texture is grown on the
surface of the inventive material coating of Example 7. A thin
cerium oxide layer (10-20 nm) with substantial biaxial texture is
grown on top of YSZ to provide a lattice-matching template for
subsequent growth of 1-2 .mu.m high temperature superconducting
YBCO film by electron beam deposition. The entire multilayer stack
represents a HTS coated conductor architecture which can be
produced in long lengths.
Example 10
[0080] Inventive material coated substrate of Example 7 is used to
deposit a 100 .ANG. layer of MgO using ion-beam assisted e-beam
deposition process which has substantial biaxial texture.
Subsequent layers of cerium oxide and YBCO films are deposited as
described in Example 8. Note that the inventive material coating is
serving both as a adhesion/planarization layer as well as an
effective diffusion barrier. Thus, a separate diffusion barrier
layer of YSZ or other oxide may not be necessary to avoid diffusion
of species from substrate into YBCO that will degrade
superconducting properties. With this architecture, the YBCO layer
will have substantially improved texture and uniformly textured
over large areas and will carry high critical current densities as
desired in related HTS applications.
[0081] In another embodiment of this example, a multilayer coating
of inventive material can be deposited with varying aluminum to
phosphorous ratios such that the adhesion is further improved and
the planarization is further improved. These improvements will
result in a more mechanically robust HTS coated conductor with
consistent properties over long lengths.
[0082] In yet another embodiment of this example, the same
procedure described herein can be followed to develop a stack using
silicon as a substrate. Inventive material coated silicon
substrates can be used as templates for growth of IBAD YSZ or MgO
layers with substantial biaxial texture. These epitaxial layers can
then serve as templates for further growth of HTS, ferroelectric,
piezoelectric, or other functional layers comprising of oxides with
cubic symmetry. The inventive material layers can also serve as
dielectric layers for silicon-based devices.
[0083] In yet another embodiment of this example, the as-received
substrate with rms roughness values of about 570 .ANG. is
mechanically polished, using a lapping technique, to reduce the
roughness value to below about 400 .ANG., more preferably below
about 300 .ANG. and most preferably below about 200 .ANG. and then
the inventive material coating (about 100 nm thick) is deposited
(either as a single layer or multiple layers) to further reduce the
roughness below about 70 .ANG., preferably below 40 .ANG. and more
preferably below about 20 .ANG. and most preferably below about 10
.ANG.. The highly smooth amorphous surfaces can then serve as
templates for IBAD growth of oxides using a physical vapor
deposition technique.
Example 11
[0084] In addition to resistance to oxidation and corrosion at
elevated temperatures, inventive material coatings can protect
against atmospheric corrosion at lower temperatures. Lab tests for
salt corrosion resistance are carried out in a salt fog chamber,
according to ASTM standard B 117. A coupon of aluminum alloy 6061
was dipped in the composition of Example 1 and retracted. The
coupon was dried in flowing air and heat treated at 500.degree. C.
for 2 minutes. This coupon, along with an uncoated coupon was
placed in a salt fog chamber for 170 hours. The coated coupon
showed significantly less corrosion than the coated coupon (FIG.
7).
Example 12
[0085] Titania nanoparticles are know to exhibit desired optical or
mechanical properties as a bulk material or when incorporated into
a film. A transparent host matrix for the titania nanoparticles is
required if transmission of light to the titania particles is
desired. Titania nanoparticles can be produced in an inventive
material precursor solution by the addition of titanium
isopropoxide solution. 4 mL of titanium isopropoxide is added to
9.8 mL water and 0.2 mL nitric acid to produce a solution with a
cloudy appearance (partially hydrolyzed). This solution is added to
the solution of Example 1 to produce a titania containing precursor
of the inventive material.
Example 13
[0086] A coating of an inventive material containing titania
nanoparticles can be deposited on a substrate, including but not
limited to steel or glass or fused silica. A piece of 304 stainless
steel is dipped in the solution of Example 11 and removed. The
coating is dried with cool air and heat treated to 800.degree. C.
for 1/2 hour. The resulting coating is hermetic and optically
transparent.
Example 14
[0087] Zirconia inclusion in a film are desired to induce certain
desirable optical or mechanical properties. A nanocomposite of the
inventive material and zirconia can also be made. 1.49 g
ZrO(NO.sub.3).sub.3.xH.sub.2O was dissolved in 10 mL of ethanol. In
a separate beaker, 6.46 g P.sub.2O.sub.5 was dissolved in 70 mL
ethanol. In another beaker 59.9 g Al(NO.sub.3).sub.3.9H.sub.2O was
dissolved in 140 mL ethanol. All three solutions were mixed
together and stirred. A clear solution resulted. The solution was
dried at 150.degree. C. in a convection oven to form a gel powder
and annealed to 1000.degree. C. for 1 hour. Crystals of tetragonal
ZrO.sub.2 and predominately inventive material were identified by
x-ray diffraction.
Example 15
[0088] A coating of the inventive material with zirconia
nanoparticles is deposited on 304 stainless steel by dipping in the
solution of Example 13. The coupon is dried in flowing air and heat
treated to 800.degree. C. for 20 min to produce a nanocomposite
coating.
Example 16
[0089] With reference to the precursor of Example 1, the ethanolic
P.sub.2O.sub.5 solution is added to the ethanolic nitrate solution.
0.1 g of AgNO.sub.3 solid is dissolved in 10 mL of the mixed
solution.
Example 17
[0090] A coated glass specimen prepared with a treated
aluminophosphate compound of Example 16 is placed onto a Petri dish
containing E. coli bacterial strain. A control petri dish without
the slide is also prepared. Both slides are kept at 35.degree. C.
for 2 days. After two days, silver/inventive material coated glass
showed no bacterial growth around the slide as compared to the
control experiment showing the growth along the strain streaks
Example 18
[0091] A 1'.times.2'' stainless steel foil was dipped into the
composition of example 1. The coupon was cured at 500.degree. C.
for 5 minutes in a preheated furnace. The resulting coating was
highly reflective.
[0092] FIG. 9 shows the 80 Grazing angle FTIR spectrum of the cured
stainless steel foil recorded using Perkin-Elmer Spectrum One FTIR
spectrometer. Strong absorption peak centered near 1207 cm.sup.-1
along with a broad peak centered near 735 cm.sup.-1 were observed.
These peaks are due to phosphate and Al--O--P group vibrations. The
peak near 830 cm.sup.-1 is also observed which may be due to
Al--O--Al bonding groups. Those skilled in the art will understand
that these peak positions can vary in the range 1280 cm.sup.-1-1180
cm.sup.-1 and 860 cm.sup.-1-700 cm.sup.-1 depending on the curing
temperatures, composition of the precursor solution, coated
substrate and other conditions. Peak intensities also can vary
based on the coating, curing and other conditions.
* * * * *