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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/80

Title: Quartz crystal microbalance/heat conduction calorimetry (QCM/HCC), a new technology capable of isothermal, high sensitivity, mass and heat flow measurements at a solid/gas interface
Authors: Shirazi, Hamid M.
Keywords: Temperature measuring instruments;Thermal diffusivity;Quartz crystal microbalances;Enthalpy
Issue Date: 7-Nov-2002
Publisher: Drexel University
Abstract: A new technology called the quartz crystal microbalance/heat conduction calorimeter (QCM/HCC) capable of simultaneous, high sensitivity mass change and heat flow measurements under isothermal conditions, was developed. The QCM/HCC consists of two highly sensitive sensors. A quartz crystal microbalance measures mass changes on its surface (to ±0.25ng/cm2), while a thermopile positioned between the WCM and a heat sink measures heat flows (to ±50nW) to and from the surface of the QCM. In the preliminary developmental stage the operation of the QCM/HCC was examined. The QCM/HCC setup was improved by the integration of a gas flow system and an isothermal housing. Different models describing the viscoelastic behavior of the coating of QCMs were employed to evaluate the mass sensitivity of the QCMs. In an attempt to minimize human supervision the operation of the QCM/HCC was fully automated by a LabView program. In the application phase the QCM/HCC was utilized in five separate experiments, each investigating one important system. The sorption/desorption enthalpies of six different organic vapors in two polyetherurethane (Tecoflex) thin films (0.78μm and 2.09μm) were measured. A linear salvation energy relationship (LSER) was established for Tecoflex. It was shown how the QCM/HCC could be used to determine thermodynamic parameters (∆sorptionH, Κ, ∆sorptionG, and ∆sorptionS) as well as kinetic information (diffusion coefficient) for sorption processes under isothermal conditions. The energetics of hydrogen sorption in a thin electrodeposited palladium film was investigated. The hydrogen sorption enthalpies were comparable to those measure by other investigators for the β-phase of hydrogen-palladium solid solution. The surface activity of the same palladium sample for catalytic hydrogenation of ethylene at ambient temperature was estimated from the heat flow measurements. The energetics of self-assembled monolayer formation (SAM) of nonylthiol on gold was measured directly for the first time. A model proposed for the breakdown of the enthalpy of SAM formation into three individual steps explained an observed increase in the magnitude of the ∆SAM formationH at higher surface coverage. Hydration/dehydration enthalpy of lysozyme was measured directly for the first time. The measured hydration enthalpies had a large magnitude at low water vapor activity but approached the enthalpy of condensation of water for higher water contents.
URI: http://dspace.library.drexel.edu/handle/1860/80
Appears in Collections:Drexel Theses and Dissertations

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