title: Membrane gas diffusion measurements with MRI.
abstract: Gas transport across polymeric membranes is fundamental to many filtering and separation technologies. To elucidate transport mechanisms, and understand the behaviors of membrane materials, accurate measurement of transport properties is required. We report a new magnetic resonance imaging (MRI) methodology to measure membrane gas phase diffusion coefficients. The MRI challenges of low spin density and short gas phase relaxation times, especially for hydrogen gas, have been successfully overcome with a modified one-dimensional, single-point ramped imaging with T(1) enhancement, measurement. We have measured the diffusion coefficients of both hydrogen gas and sulfur-hexafluoride in a model polymeric membrane of potential interest as a gas separator in metal hydride batteries. The experimental apparatus is a modified one-dimensional diaphragm cell which permits measurement of the diffusion coefficient in experimental times of less than 1 min. The H(2) gas diffusion coefficient in the membrane was 0.54 +/- 0.01 mm(2)/s, while that of sulfur-hexafluoride was 0.14 +/- 0.01 mm(2)/s, at ambient conditions.
authors.affiliation: MRI Centre, Department of Physics, University of New Brunswick, Fredericton, NB, Canada E3B 5A3.
authors.forename: Ziheng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Ouriadov
authors.forename: Chris
authors.initials: C
authors.lastname: Willson
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Balcom
mesh_terms: D000465:Algorithms; D004058:Diffusion; D017022:Flow Injection Analysis / Q000379:methods; D005740:Gases / Q000032:analysis* / Q000737:chemistry*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008567:Membranes, Artificial; D016062:Porosity; D014462:Ultrafiltration / Q000379:methods*
chemical_list: D005740:Gases; D008567:Membranes, Artificial