It has been estimated that $100 billion is lost annually in the US due to energy losses through mechanisms of adhesion, friction and wear. The objective of the research supported by this award is to generate a clear understanding of how defect nucleation (e.g. bond breaking and molecular packing defects) at native and organosilane functionalized oxide surfaces, influences friction, adhesion and wear of interfaces. Wear of materials such as silica and alumina will be studied using atomic force microscopy (AFM). These studies will enable us to directly follow defect nucleation on the atomic scale and develop predictive models for wear. Additionally, as friction and adhesion between real surfaces in sliding contact are dominated by the interactions of nanoscaled surface asperities (ca. 10 50 nm), a measurement platform based on silica nanoparticles of controlled size will be developed. The interactions of an AFM tip with these well defined surfaces asperities will readily mimic the conditions found at true asperity-asperity contacts, allowing for the influence of asperity size on the efficacy of organosilane based lubricants under varying environmental conditions to be determined.
If successful, this work will guide the engineering of new molecular based lubricants and enhance microdevice design capabilities. Students participating in the project will gain broad education and training in areas critical for the continued development of US technological competitiveness, including materials science, engineering and surface chemistry. The work will be disseminated broadly through presentations by the PI and students via informal public science talks, conferences and departmental seminars. Training will be augmented by collaborations with national labs such as NIST, providing students with a diverse educational experience. Aspects of the work will also be incorporated as demonstrations for elementary school students and in a graduate level instrumental methods boot camp for chemistry, materials science and engineering students.
It has been estimated that ~ $100 billion is lost annually in the US due to energy losses through mechanisms of adhesion, friction and wear. As such, understanding the fundamental properties that underlie the control of friction and adhesion on the atomic and molecular level is of paramount importance to the design and integration of materials into technologies that can aid in reducing these energy costs. As the sliding surfaces in most machined parts are not atomically smooth, much of the damage and energy loss in machines occurs at these rough (asperity-asperity) contacts that dominate friction and wear, with many of these contacts being as small as 10 nm. As such in this work we developed a simple platform in which we could create interfaces with controlled nanometer scale asperities and used atomic force microscopy (in which a sliding contact of similar dimension is rubbed over the surface) to examine the frictional and adhesive properties of such junctions. We combined these studies with chemical techniques such as infrared spectroscopy to examine how molecules could be assembled on these rough surfaces and evaluate their capacity to act as molecular lubricants based on their extent of molecular disorder and their ability to trap weakly bound molecules which could at a self-healing lubricant layers. Building on our understanding of the fundamental interactions between materials such as nanoasperties and nanoparticles, we partnered with Huntsman Corporation to also investigate how unique nanomaterials such as graphene oxides could be incorporated into polymers such as polyurethane, which is a ubiquitous building material, to make composite materials with an eye toward the improvement of the polymers mechanical and thermal stabilities. The students trained on this highly interdisciplinary project garnered a wealth of experience in surface chemistry, physics and engineering, along with the experience of how fundamental research can impact industrial research through partnership with Hunstman Corporation. Outreach activities developed through this project included participation in the "lunch with a scientist program," in which our students would go to local elementary schools to carryout lunchtime science talks and demonstrations. We also developed a nanotechnology tour stop during our Chemistry Open House each year in which the public can visit our labs and learn about nanoscience and nanotechnology.
