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Rear-detection photothermal technique for microscale thermal diffusivity measurement

wang, dihui (2019) Rear-detection photothermal technique for microscale thermal diffusivity measurement. Master's Thesis, University of Pittsburgh. (Unpublished)

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In nuclear reactors, a characteristic of irradiated nuclear fuel is that its microstructure is damaged by neutron irradiation, thus, the local changes of thermal diffusivity are existed. Additionally, extremely large temperature gradient ( ~1600K/cm) from the fuel centerline to the coolant result in similar gradient of thermal diffusivity. However, most existing thermal diffusivity measurement techniques do not have the high spatial resolution ability. Therefore, for better understanding the spatial distribution of nuclear fuel thermal diffusivity and minimizing the radiation exposure of experiment sample, the objective of this study is to develop a non-contact thermal diffusivity measurement technique with high spatial resolution for sample of micrometer-sized.
Based on photothermal reflectance technique (PRT), this study developed a new approach that the thermoreflectance signal is measured at the rear surface of the Focus ion
beam (FIB) fabricated micrometer-sized sample. An analytical model was built for this Rear-Detection Photothermal Reflectance Technique (RDPRT) to guide the experiment and optimize the FIB sample design. Metal with High absorptivity at heating laser wavelength was coated on the front surface of sample to ensure good energy absorption. Metal with high thermoreflectance coefficient at probe laser wavelength was coated on the rear surface of sample to ensure high signal to noise ratio of the measurement. An experimental measurement system was designed and built for the FIB sample. The experiment result shows good agreement to the literature value, with uncertainty under 6%. Sources of experimental uncertainty are analyzed qualitatively and quantitatively. The RDPRT enables thermal property measurement at a high spatial resolution for FIB sample and offers unique option for measurements of special materials, such as irradiated nuclear fuel or other irradiated materials to minimize radiation exposure.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBan, Heng
Committee MemberLee, Sangyeop
Committee MemberWang, Qingming
Date: 18 June 2019
Date Type: Publication
Defense Date: 29 March 2019
Approval Date: 18 June 2019
Submission Date: 1 April 2019
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 78
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Mechanical Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: Photothermal reflectance technique, rear-detection,micrometer-scale resolution,
Date Deposited: 18 Jun 2019 18:24
Last Modified: 18 Jun 2019 18:24

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