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.

Selected recent publications:

J.E. Gray, P.R. Norton and K.G. Griffiths

Mechanism of Adhesion of Electroless-Deposited Silver on a Biomedical Poly(ether)urethane.
Thin Solid Films, 484: 196-207 (2005)

B. Luan & J. Gray
Acousto-Immersion Coating and Process for Magnesium and its Alloys
US Patent Granted – In Press.(2003)

J.E. Gray, P.R. Norton, & K.G. Griffiths
Surface Modification of a Biomedical Poly (ether)urethane by a Remote Air Plasma
Applied Surface Science, 217: 210-222. (2003)

J.E. Gray, P.R. Norton, R. Alnouno, M. Valvano, & K.G. Griffiths
Biological Efficacy of Electroless-deposited Silver on Plasma Activated Polyurethane
Biomaterials, 24 (16): 2759-2765. (2003)

J.E. Gray & B. Luan
Protective Coatings on Magnesium and its Alloys – A Critical Review
J. Alloys & Compounds, 336: 88-113. (2002)