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College Park, Maryland      June 6 - 10 , 2004

T2-C6 (2:45 PM): A New In-Situ Vapor Sorption Apparatus for SANS Measurements

Man-Ho Kim (NIST Center for Neutron Research; Department of Materials Science and Engineering, University of Maryland), Charles J. Glinka (NIST Center for Neutron Research)

An apparatus for quantitative in-situ vapor phase sorption, based on a prototype developed by NISTís Polymers Division [1], has been constructed for SANS measurements. The apparatus facilitates determining pore size distributions of microporous materials, enhancing scattering contrast in structural studies of semi-crystalline polymers, and the adsorption and desorption of solvent mixtures in porous media for rapid contrast variation with a single sample. The apparatus consists of a temperature-controlled titanium sample cell with demountable quartz windows and variable path length of 1 mm to 5 mm. The cell has ports for evacuating or admitting vapor to the sample space while monitoring and controlling absolute pressure. The apparatus can also be used to continuously flow a carrier gas through the sample. Mass flow controllers in the system allow the carrier gas to mix specific molar ratios of saturated vapor from two temperature-controlled solvent reservoirs to provide continuous control of the H/D ratio in the vapor reaching the sample. Examples of vapor condensation in microporous silica and the selective absorption of deuterated vapor in semi-crystalline polyethylene will be shown to demonstrate the performance of the apparatus.

[1] Ronald C. Hedden, Hae-Jeong Lee, and Barry J. Bauer , Langmuir, 2004, 20, 416-422

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