TY - JOUR
T1 - Surface characteristics of selected carbon materials exposed to supercritical water
AU - Ashraf, Ali
AU - Dastgheib, Seyed A.
AU - Mensing, Glennys
AU - Shannon, Mark A.
N1 - Funding Information:
The authors are grateful for the support provided by U.S. Department of Energy, National Energy Technology Laboratory (Cooperative Agreement DE-NT0005343), Illinois Clean Coal Institute (Project 08-1/US-3), and National Science Foundation (Water CAMPWS Center). Material characterization tests were carried out in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the U.S. Department of Energy under grants DE-FG02-07ER46453 and DE-FG02-07ER46471 , and MNMS (Micro-Nano-Mechanical Systems) cleanroom in the Department of Mechanical Science and Engineering at the University of Illinois at Urbana Champaign.
PY - 2013
Y1 - 2013
N2 - 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.
AB - 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.
KW - Carbon
KW - Characterization
KW - Graphite
KW - Hydrophobicity
KW - Supercritical water
KW - Surface chemistry
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U2 - 10.1016/j.supflu.2013.01.017
DO - 10.1016/j.supflu.2013.01.017
M3 - Article
AN - SCOPUS:84874691297
SN - 0896-8446
VL - 76
SP - 32
EP - 40
JO - Journal of Supercritical Fluids
JF - Journal of Supercritical Fluids
ER -