Abstract The terahertz (THz) time-domain spectroscopy technique was used to characterize the cooling process of solid n-alkanes. The THz waveforms of n-octadecane, n-nonadecane, n-eicosane, n-heneicosane, n-docosane, and n-pentacosane were obtained with the cooling time using the aforementioned noncontact optical method. The peak values of the THz signal were found to be related to the cooling temperature of n-alkanes. The THz wave was sensitive to the size and structure of particles in the liquid; therefore, the crystallization process of n-alkanes was monitored. An empirical equation based on signal attenuation was proposed to quantitatively distinguish the content change of structural order in the samples. Results present a new noncontact optical approach for characterizing wax crystallization via THz time-domain spectroscopy.
Keywordssolid n-alkanes terahertz (THz) time-domain spectroscopy cooling process
Chen Jiang obtained her B.Sc. degree from Hebei Normal University of Science and Technology in 2012. She is currently working toward a Ph.D. degree in Materials Science and Engineering at China University of Petroleum, Beijing, China. Her research interest includes terahertz detection of crude oil.
Honglei Zhan obtained his B.Sc. degree from Xiamen University in 2012. He is currently working toward a Ph.D. degree in Materials Science and Engineering at China University of Petroleum, Beijing, China. His research interest includes nano-petrophysics and terahertz metrology.
Kun Zhao obtained his B.Sc. degree in Physics from Nanjing University in 1992, his master’s degree from the Institute of Physics, Chinese Academy of Sciences in 1997, and his Ph.D. degree from the Chinese University of Hong Kong in 2001. He is currently a professor in optical engineering and the head of the Beijing Key Laboratory of Optical Detection Technology for Oil and Gas. His research interest includes oil and gas optics.
Cheng Fu obtained her B.Sc. degree from Yangtze University in 2011 and her master’s degree from China University of Petroleum, Beijing, China, in 2014. Her research interest includes the application of terahertz spectroscopy in crude oil.