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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Design, Modeling, and Thermal Characterization of Temperature Gradient Gas Chromatography Micro-Columns

Schnepf, Parker David 31 July 2018 (has links)
This thesis presents a thermal gradient gas chromatography (TGGC) system that is implemented on a micro-scale. The GC column is approximately 20 cm long and is fabricated out of silicon with 21 nickel thin-film heaters evenly placed along the length of the column. Computational heat transfer models using ANSYS Mechanical APDL predict heating and cooling rates up to 32,000 deg C/min and 3,600 deg C/min, respectively. These results are verified through testing an experimental silicon channel. A PI controller which uses resistance measurements to calculate thin-film temperature is used for obtaining dynamic thermal gradient control. This controller is shown to possess a characteristic rise time of approximately 0.3 seconds with less than 4% overshoot and precision to within less than a degree. These characteristics present this system as a highly favorable candidate for a micro-GC column with resolution similar to that of conventional GC.
2

Gas Chromatography Micro-Chip with High Temperature Interface and Silk Screen Heaters

Vilorio, Carlos R. 11 August 2020 (has links)
There has been substantial market demand for a portable Gas Chromatography (GC) system. Throughout the years, much progress has been made on fabricating a micro system that works as well as a benchtop system. Unfortunately, even though many substrates, channel types, channel widths, temperature control systems, and interface solutions have been attempted, existing versions of the micro-GC still fall short of the ideal. This thesis presents the design, fabrication, and testing of a silicon based micro-GC column that presents a solution for interfacing and heating of the chip. A polyimide resin is used to create a durable high temperature low thermal mass interface with the chip, while a silk screen method is demonstrated for easy printing of heaters. Chromatogram results are shown in both Temperature Program and Thermal Gradient runs.
3

Thermal Gradient Characterization and Control in Micro-Fabricated Gas Chromatography Systems

Foster, Austin Richard 01 May 2019 (has links)
In order to make gas chromatography (GC) more widely accessible, considerable effort has been made in developing miniaturized GC systems. Thermal gradient gas chromatograpy (TGGC), one of the heating methods used in GC, has recieved attention over the years due to it's ability to enhance analyte focusing. The present work seeks to develop high performance miniaturized GC systems by combining miniaturized GC technology with thermal gradient control methods, creating miniaturized thermal gradient gas chromatography (µTGGC) systems. To aid in this development a thermal control system was developed and shown to successfully control various µTGGC systems. DAQ functionality was also included which allowed for the recording of temperature and power data for use in modeling applications. Thermal models of the various µTGGC systems were developed and validated against the recorded experiemental data. Thermal models were also used to aid in decisions required for the development of new µTGGC system designs. The results from the thermal models were then used to calibrate and validate a stochastic GC transport model. This transport model was then used to evaluate the effect of thermal gradient shape on GC separation performance.

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