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Enhancing metal oxide-based gas sensors for the detection of VOCs
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Ayyala, Sai Kiran (2022) Enhancing metal oxide-based gas sensors for the detection of VOCs. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3860888
Abstract
Metal oxide semiconductor (MOX) based gas sensors are very promising and widely commercialized gas sensing technology that has the potential to replace the conventional gas analysing instruments such as Gas chromatography and Mass spectroscopy. Though there are many advantages attributed to MOX sensors, there exists some limitations to the current technology – such as, humidity dependence, baseline drift, and poor sensitivity to trace level concentrations, and cross sensitivity. This thesis reports the investigations undertaken to overcome such limitations by using different strategies, while testing a wide range of relevant volatile organic compounds (VOCs) that are present in the environment.
Investigations were carried on Nickel oxide (NiO) thick films to achieve the humidity tolerance. Spin coated NiO thick film (10 μm) showed a stable and higher response towards ethanol (1.27) among the other VOCs while the baseline drift due to humidity was least when compared with other NiO sensors.
A heterojunction composite sensor was developed using ZnO and MoO3 materials to achieve fast, stable and high sensitivity towards trace levels of VOCs. The ZnO/MoO3 thick film sensor was able to detect different VOCs at ppb concentrations within 30 sec and the relative response was 12.84 and 9.27 for 200 ppb ethanol and methanol gases respectively, which was 4 times higher than its pristine counterparts. Ultraviolet (UV) light was illuminated onto different types of commercial MOX sensors and in-house fabricated MOX sensors with a focus to examine the effect of UV on the sensor performance – specifically, sensitivity, baseline drift due to humidity, response, and recovery time. The response time was reduced by 70 sec and 40 sec for the commercial MOX sensors, while the baseline drift due to humidity of AACVD deposited Chromium-Titanium Oxide was reduced by ~2% due to UV light. Finally, the fabricated MOX sensors were evaluated in a real-world application sensing the toxic VOCs that effuses from thermally abused Li-ion cells as an attempt to prevent from battery explosions.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TD Environmental technology. Sanitary engineering T Technology > TK Electrical engineering. Electronics Nuclear engineering T Technology > TP Chemical technology |
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Library of Congress Subject Headings (LCSH): | Metal oxide semiconductors, Gas detectors, Volatile organic compounds | ||||
Official Date: | August 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Covington, James A., 1973- | ||||
Format of File: | |||||
Extent: | xvi, 229 pages : colour illustrations | ||||
Language: | eng |
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