Date of Award

12-2021

Document Type

Dissertation - Campus Access Only

Degree Name

Doctor of Philosophy (PhD)

Degree Discipline

Electrical Engineering

Abstract

Single-walled carbon nanotube (SWCNT) and poly (methyl methacrylate) (PMMA) nanocomposites have various potential applications including radiation detection. This work studied the response of a radiation sensor that was developed from functionalized and unfunctionalized SWCNT/PMMA nanocomposite thin films placed on an interdigitated electrode (IDE). The functionalized thin film devices are made of ferrocene doped SWCNTs, SWCNTs functionalized with carboxylic acid (COOH), and SWCNTs coated/ modified with copper.

This study focused on studying the effect of ionizing radiation (X-rays) in the real-time electrical resistance of thin film nanocomposites. The initial positive results observed in the previous study on X-ray radiation effect on MWCNT/PMMA can be reproduced. The SWCNT/PMMA nanocomposite was prepared using the solution blending method. The prepared thin film of nanomaterial composite in this study was cast on IDE to make the SWCNT/PMMA nanocomposite thin film device. A 160 KV X-ray source was used to irradiate the thin film device at different doses and dose rates. X-rays generated electrons and positive ions (equivalent to holes) in the nanocomposite film caused the reduction of the device’s resistance.

The electrical characterization of the device was performed using a Semiconductor Device Analyzer during the experiments. The results showed that heat treatment of irradiated nanocomposite devices caused rapid recovery. The heat treatment time of thin film device increased about linearly, increasing with the X-rays radiation dose. The thin film device was operated at dc voltage as low as 0.05 V and could reliably observe the radiation-induced change in electrical resistance. This study suggests that researchers could use SWCNT/PMMA thin film devices to detect X-rays radiation, with five times higher sensitivity than similar devices made with MWCNT/PMMA nanocomposite thin film in another study. The response of carboxylic acid functionalized and copper coated SWCNT/PMMA nanocomposite thin film devices to X-rays reduced compared to unfunctionalized SWCNT/PMMA nanocomposite with almost a factor or two for all dose rate conditions. The sensitivity of ferrocene doped SWCNT/PMMA was the highest of all other functionalized and unfunctionalized SWCNT/PMMA thin film devices at lower dose rates 2.13 krad/min and 1.08 krad/min. In contrast, a previous study showed the improved response of the functionalized MWCNT/PMMA nanocomposite devices to X-ray ionizing radiation compared to unfunctionalized MWCNT/PMMA nanocomposite devices for all dose rates. In addition, electrical characterization of thin SWCNT/PMMA film devices was performed using an Arduino Nano microcontroller board.

The results showed that an inexpensive, lightweight-designed prototype radiation sensor instrument consisting of using SWCNT/PMMA thin film nanocomposite can be produced by integrating the devices with a modest microcontroller. The thin film device (SWCNT/PMMA) was irradiated with gamma radiation (Cs-137) to study the low dose rate radiation effect on the device. There was no significant effect observed on the electrical resistance of the device due to gamma radiation. The device was interfaced with an Arduino nano microcontroller connected to a DHT11 temperature and humidity sensor to monitor humidity and change in resistance of the device under ambient conditions in real-time. When the device is open, resistance change is about -2.5% under ambient conditions. The decrease in resistance when the device is encapsulated is very small (about -0.1%). In addition, the result showed that the encapsulated device could be used to detect X-ray radiation. Future work may focus on encapsulating the device to isolate the device from the environment to reliably detect low dose rates.

Committee Chair/Advisor

Richard T. Wilkins

Committee Member

Irvin W. Osborne-Lee

Committee Member

John Fuller

Committee Member

Merlyn Pulikkathara

Committee Member

Justin Foreman, Penrose Cofie

Publisher

Prairie View A&M University

Rights

© 2021 Prairie View A & M University

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Date of Digitization

12/23/2024

Contributing Institution

John B Coleman Library

City of Publication

Prairie View

MIME Type

Application/PDF

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