Understanding
Surface Chemistry for Improved Coatings
Development
Coatings are used to change the surface
properties of materials to enhance corrosion
and wear resistance, improve biocompatibility
or for decorative purposes, without significantly
altering the production cost or bulk properties
of the article. Of particular interest are
aqueous coating processes that are a simple
and cost effective way to modify a materials
surface. Despite the fact that these processes
have been known for over a century, comparatively
little is known about the surface chemistry
involved.
Our research focuses on developing an understanding
of the surface chemistry of the material
to be coated and the chemistry at the interface
of the substrate and coating. This knowledge
will be used to design appropriate surface
treatments for specific applications.
Our approach involves a combination of surface
characterization by traditional ultra-high
vacuum techniques such as X-ray photoelectron
spectroscopy and scanning auger microscopy,
as well as characterization of the liquid/solid
interface by techniques such as dynamic
contact angle, surface vibrational spectroscopy
and atomic force microscopy.
Current Research Projects:
1.
Surface Modification of Polymer Bio-materials:
Device associated infections are a significant
problem with the use of polymers as medical
implants and devices. The cause of these
infections is the adherence and colonization
of bacteria on the surface resulting in
biofilm formation. Surface modification
of the materials to inhibit bacterial colonization
of the surface without altering bulk properties
that affect the function of the material
would lead to improved function and lifetime
of medical devices. Our research focuses
on studying the dynamic nature of polymer
surfaces and polymer surface chemistry at
the liquid/polymer interface. This information
will be used to develop appropriate surface
treatments for production of biomaterials
with improved resistance to bacterial adhesion.
2.
Protective Coatings on Magnesium and its
Alloys: Magnesium and its alloys have a
high strength:weight ratio that make it
an ideal metal for automotive and aerospace
applications, where weight reduction is
of significant concern. Unfortunately, these
alloys are highly susceptible to corrosion.
The simplest way to avoid corrosion is to
coat the magnesium-based substrate to prevent
contact with the environment. The existing
processes for coating magnesium alloys do
not produce acceptable coatings on high
aluminum content magnesium alloys, which
are commonly used for die-cast automotive
components. Our research focuses on characterizing
the surface micro-chemistry of magnesium
alloys and under-standing its role in surface
film formation during pretreatment and coating
processes. This understanding will be used
to formulate pretreatment and coating baths
that produce coatings with optimum corrosion
resistance.
Recent
representative publications:
B.
Luan & J. Gray, (2003) “Acousto-Immersion
Coating and Process for Magnesium and its
Alloys” US Patent Granted –
In Press.
J.E.
Gray, P.R. Norton, & K.G. Griffiths
(2003) “Mechanism of Adhesion of Electroless-deposited
Silver on a Biomedical Poly (ether)urethane
. ”Thin Solid Films, submitted.
J.E.
Gray, P.R. Norton, & K.G. Griffiths
(2003) “Surface Modification of a
Biomedical Poly (ether)urethane by a Remote
Air Plasma” Applied Surface Science,
217: 210-222.[Pdf]
J.E.
Gray, P.R. Norton, R. Alnouno, M. Valvano,
& K.G. Griffiths (2003) “Biological
Efficacy of Electroless-deposited Silver
on Plasma Activated Polyurethane”
Biomaterials, 24(16): 2759-2765. [Pdf]
J.E.
Gray & B. Luan (2002)“Protective
Coatings on Magnesium and its Alloys –
A Critical Review” J. Alloys &
Compounds, 336: 88-113.[Pdf]
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