Design and Testing of a Micro Thermal Conductivity Detector (TCD) System

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This work describes the design, simulation, fabrication and characterization of a microfabricated thermal conductivity detector to be used as an extension of the {micro}ChemLab{trademark}. The device geometry was optimized by simulating the heat transfer in the device, utilizing a boundary element algorithm. In particular it is shown that within microfabrication constraints, a micro-TCD optimized for sensitivity can be readily calculated. Two flow patterns were proposed and were subsequently fabricated into nine-promising geometries. The microfabricated detector consists of a slender metal film, supported by a suspended thin dielectric film over a pyramidal or trapezoidal silicon channel. It was demonstrated that the ... continued below

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75 pages

Creation Information

SHOWALTER, STEVEN K.; CRUZ, DOLORES; GELBARD, FRED; MANGINELL, RONALD P.; ADKINS, DOUGLAS R.; KOTTENSTETTE, RICHARD et al. March 1, 2003.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA
    Place of Publication: Albuquerque, New Mexico

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Description

This work describes the design, simulation, fabrication and characterization of a microfabricated thermal conductivity detector to be used as an extension of the {micro}ChemLab{trademark}. The device geometry was optimized by simulating the heat transfer in the device, utilizing a boundary element algorithm. In particular it is shown that within microfabrication constraints, a micro-TCD optimized for sensitivity can be readily calculated. Two flow patterns were proposed and were subsequently fabricated into nine-promising geometries. The microfabricated detector consists of a slender metal film, supported by a suspended thin dielectric film over a pyramidal or trapezoidal silicon channel. It was demonstrated that the perpendicular flow, where the gas directly impinges on the membrane, creates a device that is 3 times more sensitive than the parallel flow, where the gas passed over the membrane. This resulted in validation of the functionality of a microfabricated TCD as a trace-level detector, utilizing low power. the detector shows a consistent linear response to concentration and they are easily able to detect 100-ppm levels of CO in He. Comparison of noise levels for this analysis indicates that sub part per million (ppm) levels are achievable with the selection of the right set of conditions for the detector to operate under. This detector was originally proposed as part of a high-speed detection system for the petrochemical gas industry. This system was to be utilized as a process monitor to detect reactor ''upset'' conditions before a run away condition could occur (faster than current full-scale monitoring systems were able to achieve). Further outlining of requirements indicated that the detection levels likely achievable with a TCD detector would not be sufficient to meet the process condition needs. Therefore the designed and fabricated detector was integrated into a detection system to showcase some technologies that could further the development of components for the current gas phase {micro}ChemLab as well as future modifications for process monitoring work such as: pressurized connections, gas sampling procedures, and packed columns. Component integration of a microfabricated planar pre-concentrator, gas-chromatograph column and TCD in the separation/detection of hydrocarbons, such as benzene, toluene and xylene (BTX) was also demonstrated with this system.

Physical Description

75 pages

Source

  • Other Information: PBD: 1 Mar 2003

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  • Report No.: SAND2003-0954
  • Grant Number: AC04-94AL85000
  • DOI: 10.2172/809627 | External Link
  • Office of Scientific & Technical Information Report Number: 809627
  • Archival Resource Key: ark:/67531/metadc738892

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  • March 1, 2003

Added to The UNT Digital Library

  • Oct. 18, 2015, 6:40 p.m.

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  • April 11, 2016, 2:12 p.m.

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SHOWALTER, STEVEN K.; CRUZ, DOLORES; GELBARD, FRED; MANGINELL, RONALD P.; ADKINS, DOUGLAS R.; KOTTENSTETTE, RICHARD et al. Design and Testing of a Micro Thermal Conductivity Detector (TCD) System, report, March 1, 2003; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc738892/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.