Progress in terahertz nondestructive testing: A review

Abstract

Terahertz (THz) waves, whose frequencies range between microwave and infrared, are part of the electromagnetic spectrum. A gap exists in THz literature because investigating THz waves is difficult due to the weak characteristics of the waves and the lack of suitable THz sources and detectors. Recently, THz nondestructive testing (NDT) technology has become an interesting topic. This review outlines several typical THz devices and systems and engineering applications of THz NDT techniques in composite materials, thermal barrier coatings, car paint films, marine protective coatings, and pharmaceutical tablet coatings. THz imaging has higher resolution but lower penetration than ultrasound imaging. This review presents the significance and advantages provided by the emerging THz NDT technique.

Keywords

terahertz pulsed imaging (TPI) / nondestructive testing (NDT) / composite material / thermal barrier coating

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Acknowledgements

We would like to express our appreciation to the National Natural Science Foundation of China (Grant No. 51675103), Fujian Provincial Excellent Young Scientist Fund (Grant No. 2014J07007), Shanghai Natural Science Fund (Grant No. 18ZR1414200), and Research Project of State Key Laboratory of Mechanical System and Vibration (Grant No. MSV201807).

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