Surface characteristics of selected carbon materials exposed to supercritical water

Ali Ashraf, Seyed A. Dastgheib, Glennys Mensing, Mark A. Shannon

Research output: Contribution to journalArticlepeer-review

Abstract

Interactions of supercritical water (SCW) with several carbon (including polycrystalline graphite, highly ordered pyrolytic graphite (HOPG), pyrolytic carbon, and diamond) and selected ceramic materials under oxic or anoxic conditions are investigated. Wettability and surface/material properties of samples, before and after the SCW exposure, are characterized with sessile drop contact angle measurement, profilometry, XPS, XRD, and ToF-SIMS. All tested ceramic materials became more hydrophilic during the SCW exposure, mainly due to hydrolysis reactions. Carbon samples exposed to oxic SCW became more hydrophilic as a result of surface oxidation. Carbon materials, except HOPG and diamond, became more hydrophobic when exposed to anoxic SCW because of degradation of hydrophilic oxygen functionalities. HOPG and diamond became more hydrophilic after anoxic SCW exposure mainly due to the removal of hydrophobic hydrocarbon contaminants. Hydrophobicity of different carbon samples exposed to SCW are explained based on the abundance of surface hydrophilic sites (i.e., oxygen functionalities, reactive carbon dangling bonds or defects), hydrocarbon impurities, and surface roughness.

Original languageEnglish (US)
Pages (from-to)32-40
Number of pages9
JournalJournal of Supercritical Fluids
Volume76
DOIs
StatePublished - 2013

Keywords

  • Carbon
  • Characterization
  • Graphite
  • Hydrophobicity
  • Supercritical water
  • Surface chemistry

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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