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boost in wear resistance thanks to silica nanoparticles. Researchers at the University of Arkansas (Fayetteville) treated PTFE films with silica nanoparticles to significantly reduce wear while maintaining low friction in tests. In a comparison of PTFE surfaces impregnated with silica nanoparticles versus pure PTFE films and bare stainless steel, the researchers found the composite films had greatly improved wear characteristics. All PTFE coatings were produced by dip coating type 316 stainless steel substrates. According to researcher Min Zou, associate professor, director of the university’s Nano Mechanics and Tribology Laboratory (NMTL), and holder of the 21st Century Professorship in Mechanical Engineering, the lab tested PTFE surfaces with two concentrations of 50-nm-diameter silica nanoparticles— 1.7 and 3.3 wt%—against a conventional PTFE surface and bare stainless steel. “Linear reciprocating wear tests were performed by repetitively rubbing the test samples against a chrome steel ball under an applied pressure up to 0.5 GPa,” Zou explains in an email. “The pure PTFE film failed immediately under 0.5 GPa pressure, while the composite film with 3.3-wt% silica lasted 300 cycles.” Zou and her team have continued their research with further development of the silica–PTFE composite material as well as testing of other types of nanoparticles in thin PTFE coatings, she reports. “The durability of the film has been increased four times compared to what we reported in this paper. If adding an adhesive layer, durability is increased 70 times.“ NMTL has developed a variety of nanoengineered surfaces with nanoscale topographies and chemistries to reduce friction and wear, change wetting properties of surfaces, and facilitate cell adhesion and growth in biomedical applications. Results of this work are reported in the paper “Wear-resistant PTFE/SiO2 nanoparticle composite films” in Tribology Transactions .n AFM image of 50-nm-diameter silica nanoparticles on PTFE surface. (Credit: M. Zou, University of Arkansas.) American Ceramic Society Bulletin, Vol. 92, No. 6 | www.ceramics.org 13


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