September 25, 2015
Nearly all interactions with materials occur at the surface. Consequently, surface coatings are primarily responsible for the optical, electrical, chemical, biological, and mechanical properties of many devices. Since they occupy so little volume, coatings are a cost effective method for improving the capability or performance of a system. Perhaps equally important is their historical role in protecting structural materials from corrosion and other types of degradation. This talk will discuss coating technologies developed at JHU/APL that address these demands through the development of multifunctional materials that change their properties in response to the environment. To this end, we present a corrosion inhibitor-filled microcapsule that confers self-healing properties to chemical agent resistant coatings (CARC). Used in conjunction with zinc-rich primers, it can prolong the lifetime of galvanic protection afforded by the sacrificial zinc. Under the right conditions, on-demand passivation of exposed steel delays the onset of corrosion for 6 weeks in a salt fog chamber, compared to hours for a conventional paint and 1 week for a zinc-rich paint. Electrochemical impedance spectroscopy reveals how the mechanism of chemical passivation working in conjunction with cathodic protection is better than either strategy alone. We will then present inorganic coatings with the capacity to undergo self-repair even in the absence of liquid-filled microcapsules. The silica matrix has much greater resistance to elevated temperatures, wear, and ultraviolet degradation than conventional polymer coatings. These coatings also perform thermal management functions, which are capable of achieving sub-ambient cooling in direct sunlight. The simple reduction in temperature reduces the rate of corrosion as much as many complex corrosion inhibition chemistries.
Dr. Benkoski received his Ph.D. in 2003 under the supervision of Prof. Ed Kramer, where he studied “The Molecular Mechanisms of Polymer Fracture” at UC Santa Barbara. Shortly thereafter he received a NSF MPS-DRF Distinguished International Postdoctoral Research Fellowship to develop a platform for light-regulated, reusable protein sensors at Chalmers University of Technology in Gothenburg, Sweden. He was then awarded a postdoctoral fellowship at NIST from the National Research Council to develop novel techniques for generating hierarchical material structures through self-assembly at photocurable oil/water interfaces. He now serves as Principal Scientist in the Research and Exploratory Development Department at the Johns Hopkins University Applied Physics Laboratory where he heads a large research program devoted to the development of stimuli-responsive materials through scalable self-assembly techniques. His programs include: self-healing paint, inorganic low solar absorbance coatings, hierarchically structured conformal coatings for stem cell scaffolds, sub-10 nm lipid nanoparticles for topical drug delivery, magnetically actuated artificial cilia self-assembled from cobalt nanoparticles, hydrogel paints with antifouling and drag reduction properties, and adhesives for adipose tissue. Dr. Benkoski recently received the 2014 Outstanding Young Scientist Award from the Maryland Academy of Sciences, he is a two-time Inventor of the Year from the Johns Hopkins Applied Physics Laboratory, his self-healing paint is being considered for deployment on the US Marine Corps’ new Joint Light Tactical Vehicle, and he recently represented JHU/APL when his work on low solar absorbance inorganic coatings was highlighted by the American Chemical Society for their conference press release.