Probing the Role of Surface Defects and Disorder on the Tribology of Nanoscopic Contacts

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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.