NEWS | March 1, 2010

Dr. Irwin Singer Elected Fellow of the American Vacuum Society

By Daniel Parry

Research physicist, Dr. Irwin L. Singer, of the Naval Research Laboratory Surface Chemistry Branch, Chemistry Division, became a Fellow of the American Vacuum Society (AVS) at the society's annual meeting in San Jose, Calif., November 2009. Singer was cited for exceptional contributions to the fundamental understanding of tribology in the areas of surface modification, thin solid film lubrication, and third body processes in sliding interfaces.

Singer developed a rigorous, fundamental, chemical and physical understanding of sliding interfaces that led to the third body concept capable of explaining why hard coatings such as Titanium Nitride (TiN), Titanium Carbide (TiC), and diamond-like films could exhibit very low coefficients of friction as well as how Molybdenum disulfide (MoS2) structures act as lubricants. A pioneer in the application of auger and x-ray photoelectron spectroscopies for post mortem analysis of wear surfaces, Singer also developed an in situ micro-Raman tribometer in which he was able to visually and spectroscopically observe and characterize the third body materials that are formed in an operating sliding interface.

Beginning his career as an experimental physicist in the field of superconductivity, Singer's interest in the interface chemistry associated with electron tunneling and phonon scattering in thin films (Ph.D., 1976) brought him to the Naval Research Lab as a postdoctoral scientist, where he began investigating analytical techniques for studying surfaces and interfaces. In 1978, he became a member of the tribology section of the Surface Chemistry Branch at NRL and was named head of the section in 1983, stepping down in late 2008 to focus full-time on research.

Since arriving at NRL, Singer has been productive in many scientific and engineering-related fields, including tribology, vacuum and non-vacuum spectroscopies for surface analysis, surface treatments, and coatings and surface mechanical properties of metals, ceramics, plastics and elastomers. His crossover studies from physics to interface science began with investigations of low and high-energy ion- bombardment of surfaces. His work on ion implantation in metals in the late 1970s and early 1980s led to new approaches for studying wear rates with nanometer precision. He uncovered many of the chemical and mechanical mechanisms for friction and wear improvements of ion-implanted metals; most notably the process of vacuum carburization of metals implanted with high doses of reactive metals, e.g., Ti implanted steels. At the same time, he developed a reputation for dispelling myths of the supposed effectiveness of ion implantation on tribology. This understanding was guided by his unwavering persistence in attempting to understand the messy world of wear scars and debris resulting from dry sliding contact. This topic, which garnered him his first invited talks (of over 50 in his career) in 1983 and 1984, eventually led him to identify the role of third bodies in sliding processes. His study of third bodies, which is one of his hallmark contributions to tribology, continues today.

Throughout his roughly 30 year career at NRL, Singer has supervised 17 postdoctoral researchers, been on Ph.D. juries of seven students, hosted three university professors doing sabbaticals at NRL and himself taken three sabbaticals (1982, 1985 and 1992). In addition, he has been on the editorial board of three journals and has organized numerous conferences and symposia, most notably the highly regarded NATO institute on Fundamentals of Friction, at Braunlage, Germany, in August 1991. The institute brought together, for the first time, leading scientists and engineers in the field of friction with newcomers applying surface probe microscopies, molecular dynamics and other models to friction at the nanoscale. Much of the progress these past 20 years in micro and nanoscale understanding of friction can be traced back to the clarification of issues that came out of this two-week gathering.

Applying thermochemistry to problems of surface modification, adhesion and tribology, Singer exploited one of the new fields he studied during a sabbatical at Cambridge University, leading to the first of his two Berman Publication Awards for Applied Research in Chemistry at NRL in 1989. Singer also took advantage of the Cambridge studies to shift research directions into the tribology and modification of ceramic surfaces, which eventually led him into the field of hard coatings (e.g., TiN, diamond and diamond-like carbon-DLC) to which he still contributes. At the same time, he began working with a team of scientists and engineers in a Strategic Defense Initiative (SDI) program to develop solid lubricants for extreme environments. His investigations led to a better understanding of the friction behavior of solid lubricants and improved structural and bonding of MoS2 coatings deposited by ion beam assisted deposition.

In the 1990s, Singer began to focus on several fundamental aspects of friction processes, starting with some basic issues in the role of interfacial chemistry on friction. During a sabbatical year at Ecole Centrale de Lyon, he showed that monolayers of tribochemically reacted layers (e.g., of sulfur on molybdenum) provide so-called 'superlubricity,' meaning friction coefficients less than 0.01-the lowest value obtainable from standard MoS2 coatings and later identified gas-phase contributions to the 'superlubricity' of hydrogenated DLC coatings. He also designed numerous experiments that dispelled the notion that solid lubricant coatings operate similarly to a deck of 'weakly-coupled' cards. He instead showed that third bodies and third body reservoirs provide the basis for low friction and long life of solid lubricants. In support of this third body effect, he presented detailed microscopic (TEM) studies showing how both amorphous and randomly oriented MoS2 structures provided the same third body lubrication as layered MoS2 structures. Fighting the I'll believe it when I see it syndrome of the community, Singer initiated studies of in situ visualization of third body processes in sliding contacts. With the help of section members and several postdoctoral researchers, Singer produced a steady-stream of research that provides direct evidence that third bodies control friction processes in numerous low friction coatings, including MoS2 and diamond-like carbons.

During the 1990s, Singer was invited to participate in an Office of Naval Research/Navy workshop convened to find alternatives to toxic paints for keeping ship hulls free from sea-borne organisms and foulants. His contributions over the next eight years radically altered the understanding of both the mechanics of biofoulants release as well as the properties of biofoulant release coatings.

Since 2000, Singer has turned his attention to solving engineering problems facing the Navy by using tribological approaches. He has been active in both forming teams of scientists and performing the scientific studies needed to bring innovations to two high power devices: the homopolar motor and the electromagnetic gun (railgun).

The AVS is a scientific professional society focused on the science and technology of materials, interfaces and processing. Only members with five or more years of consecutive membership whom have made sustained and outstanding scientific and technical contributions are eligible for nomination. Election is limited to half of the membership percentage in any calendar year.