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Modification of n-type and p-type semiconducting metal oxide gas sensors for the purpose of explosive detection

Horsfall, Lauren Amber; (2020) Modification of n-type and p-type semiconducting metal oxide gas sensors for the purpose of explosive detection. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis investigates three different heterojunction semiconducting metal oxide sensing sets, designed with unmodified, admixed and 2-layered sensors, build for the purpose of explosive detection. The base metal oxides chosen for this study were ZnO, WO3, CTO and SnO2. The metal oxides investigated were chosen based upon their previous sensitivity to test gases associated with explosives. The thesis aim was to introduce admixed and 2- layered sensors in order to improve the sensor performance in terms of sensitivity and selectivity. The sensing sets incorporated an n-n type sensing set and two n-p sensing sets in order to distinguish any increase in sensor response based upon metal oxide type. The three sensing sets were exposed to explosive vapours as well as test gases associated with explosives at a range of temperatures from 300 ̊C to 500 ̊C. The sensors were investigated in terms of their microstructure, response to temperature, sensitivity, selectivity, and sensing response and recovery times. Overall it was shown that modified sensors do improve sensor sensitivity and selectivity for a range of test gases. The admixed sensors showed improved response when detecting TNT, ammonia and nitromethane whilst the 2-layered sensors displayed heightened responses when exposed to TATP and DMNB when compared to the unmodified sensors. Both admixed and 2-layered sensors also successfully showed selectivity towards many explosive vapours including EGDN, nitroglycerine and NO2. It was demonstrated the modification also affected the responses produced by the sensors when exposed to humidity. Overall the unmodified, admixed and 2- layered sensors all showed positive stable responses as humidity increased when exposed to a range of explosive behaviours.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Modification of n-type and p-type semiconducting metal oxide gas sensors for the purpose of explosive detection
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Security and Crime Science
URI: https://discovery.ucl.ac.uk/id/eprint/10107642
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