This thesis examines the mechanical, and adhesive properties of graphene and explores using graphene as a gas separation membrane. A pressurized blister test was used to measure both the in-plane mechanical properties and adhesion energy of monolayer and few layer graphene suspended over a circular cavity in silicon oxide. The adhesion energy between graphene and silicon oxide was found to be 0.45 ± 0.02 J m-2 for monolayer graphene and 0.31 ± 0.03 J m-2 for samples containing two to five graphene layers. These values are larger than the adhesion energies measured in typical micromechanical structures and are comparable to solid-liquid adhesion energies. We attribute this to the extreme flexibility of graphene, which allows is to conform to the topography of even the smoothest substrates, thus making its interaction with the substrate more liquid like than solid like. In addition we found that the in-plane mechanical properties are consistent with previously reported values.
We also show that ultraviolet-induced oxidative etching can create pores in micrometer-sized graphene membranes, and the resulting membranes can be used as molecular sieves. A pressurized blister test, similar to that used for testing the mechanical properties, and mechanical resonance are used to measure the transport of a range of gases (H2, CO2, Ar, N2, CH4, and SF6) through the pores. The experimentally measured leak rate, separation factors, and Raman spectrum agree well with models based on effusion through a small number of angstrom-sized pores.
Lastly, we work toward creating large scale gas separation membranes from chemical vapor deposition (CVD) grown graphene films. CVD graphene films are grown on copper foils and transferred to a polymer support or suspended over openings in copper. Films are measured in a time lag permeation apparatus to get gas permeation and ideal gas separation factors.
|Advisor:||Bunch, Joseph S.|
|Commitee:||Murray, Todd W., Pellegrino, John, Stoykovich, Mark P., Xiao, Jiangliang|
|School:||University of Colorado at Boulder|
|School Location:||United States -- Colorado|
|Source:||DAI-B 74/12(E), Dissertation Abstracts International|
|Keywords:||Adhesion, Gas separations, Graphene, Mechanics, Molecular sieving|
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