WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7150

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COAR Access Rights: search.filters.coarAccessRights.open accessSubject: search.filters.subject.Elevated temperature

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  • Article
    Citation - WoS: 16
    Citation - Scopus: 17
    Investigation of the High Temperature Dry Sliding Wear Behavior of Graphene Nanoplatelets Reinforced Aluminum Matrix Composites
    (SAGE Publications, 2021) Martin, Seçkin; Kandemir, Sinan; Antonov, M.
    In this study, graphene nanoplatelets (GNPs) with a thickness of 50-100 nm have been utilized to improve the mechanical and tribological properties of A360 alloy due to their extraordinary mechanical properties and solid lubricant nature. For the investigation of tribological properties, ball-on disc tests were carried out at various temperatures including room temperature (RT), 150 °C, and 300 °C. According to the hardness and ball-on-disc test results, the nanocomposite samples reinforced with GNPs exhibited improved hardness and wear resistance. The improvement in the wear behavior of nanocomposites was referred to the temporarily formed solid lubricant film of harder GNPs during the wear, and hence coefficient of friction (COF) and volume loss were considerably reduced. Abrasive-adhesive, oxidative, and mild-to-severe were found to be main wear mechanisms at RT, 150 °C, and 300 °C, respectively. Overall, the results show that the nanocomposites fabricated by casting method combined with mechanical stirring and ultrasonication have promising wear performance, especially at elevated temperatures. This may suggest that these developed materials could be potential candidates to be used in the engineering applications requiring high temperature wear performance. © The Author(s) 2020.
  • Article
    Citation - WoS: 25
    Citation - Scopus: 25
    Conformational and Aggregation Properties of a Pegylated Alanine-Rich Polypeptide
    (American Chemical Society, 2011) Top, Ayben; Roberts, Christopher J.; Kiick, Kristi L.
    The conformational and aggregation behavior of PEG conjugates of an alanine-rich polypeptide (PEG-c17H6) were investigated and compared to that of the polypeptide equipped with a deca-histidine tag (17H6). These polypeptides serve as simple and stimuli-responsive models for the aggregation behavior of helix-rich proteins, as our previous studies have shown that the helical 17H6 self-associates at acidic pH and converts to β-sheet structures at elevated temperature under acidic conditions. In the work here, we show that PEG-c17H6 also adopts a helical structure at ambient/subambient temperatures, at both neutral and acidic pH. The thermal denaturation behavior of 17H6 and PEG-c17H6 is similar at neutral pH, where the alanine-rich domain has no self-association tendency. At acidic pH and elevated temperature, however, PEGylation slows β-sheet formation of c17H6, and reduces the apparent cooperativity of thermally induced unfolding. Transmission electron microscopy of PEG-c17H6 conjugates incubated at elevated temperatures showed fibrils with widths of ∼20-30 nm, wider than those observed for fibrils of 17H6. These results suggest that PEGylation reduces β-sheet aggregation in these polypeptides by interfering, only after unfolding of the native helical structure, with interprotein conformational changes needed to form β-sheet aggregates.