scholarly journals Detection of Microplastic in Salts Using Terahertz Time-Domain Spectroscopy

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3161
Author(s):  
Jaeseung Im ◽  
Taewon Goo ◽  
Jugyoung Kim ◽  
Soobong Choi ◽  
Sung Ju Hong ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Optical Properties ◽  
Time Domain ◽  
High Density Polyethylene ◽  
Volume Ratio ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Practical Applications ◽  
Effective Medium Model

We report on a prototypical study of the detection of microplastic embedded in table salts by using terahertz time-domain spectroscopy. In the experiment, high-density polyethylene (HDPE) of sizes from 150 to 400 μm are used as a representative microplastic and mixed with table salts. Analyzing terahertz transmittance with an effective medium model, we extract various optical properties such as refractive index, absorption coefficient, and real/imaginary parts of the dielectric constant of the mixture. Consequently, the optical properties exhibit volume-ratio-dependence in 0.1–0.5 THz regimes. Especially, the refractive index and the real part of the dielectric constant possess monotonic frequency dependence, meaning that the quantities can be relevant indicators for the detection of the microplastic in terms of practical applications. Our work proves that terahertz time-domain spectroscopy can pave a way to recognize microplastic mixed with salts and be expanded for detecting various micro-sized particles.

scholarly journals Terahertz Time Domain Spectroscopy to Detect Different Oxidation Levels of Diesel Engine Oil

Lubricants ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 18 ◽  
Author(s):  
Ali Abdul-Munaim ◽  
Jan Ornik ◽  
Martin Koch ◽  
Dennis Watson
Keyword(s):  
Refractive Index ◽  
Diesel Engine ◽  
Time Domain ◽  
Measurement Method ◽  
Oxidation Time ◽  
Engine Oil ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Range

Diesel engine oil was subjected to thermal oxidization (TO) for six periods of time (0 h, 24 h, 48 h, 72 h, 96 h, and 120 h) and was subsequently characterized by terahertz time domain spectroscopy (THz-TDS). The THz refractive index generally increased with oxidation time. The measurement method illustrated the potential of THz-TDS when a fixed setup with a single cuvette is used. A future miniaturized setup installed in an engine would be an example of a fixed setup. For the refractive index, there were highly significant differences among the oxidation times across most of the 0.3–1.7 THz range.

Soot Optical Properties in the Terahertz Spectra Domain

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Fei Wang ◽  
Ting Xu ◽  
Zhishen Qiang ◽  
Qunxing Huang ◽  
Dong Liu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Time Domain ◽  
Wavelength Region ◽  
Optical Methods ◽  
Optical Data ◽  
Refractive Indices ◽  
Spectroscopy Technique ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Combustion Diagnostics

For understanding and accurately modeling combustion, the important questions are what species are present in the flame, and the spatial distribution and temperature of these species. Traditional optical methods used only the electromagnetic waves in the wavelength region from the ultraviolet region up to the infrared. Terahertz time-domain spectroscopy technique can be used for the combustion research as a novel tool. However, for some sooty combustion environments, the strong absorption, spectral interference from soot scattering, and fluorescence from large molecules must be considered. The optical properties of soot in the terahertz domain are the main basic data for terahertz application. In this paper, the terahertz time-domain spectroscopy technique was used to study the optical properties of flame soot within 0.2–1.6 THz. The complex refractive indices of the soot were deduced by the fixed-point iteration method. In order to validate the results, the complex refractive indices of the soot from the four different fuel flames were deduced. It was found that the complex refractive indices in the terahertz domain of the soot from the different fuel flames are very close to each other. The comparisons of complex refractive indices between the visible–IR domain and the terahertz domain indicate that the value of absorption index in terahertz domain is smaller than in IR domain, which implies that the terahertz wave will penetrate the sooty flame with smaller absorption than the IR rays. The results can provide the basic optical data of flame soot for the application of terahertz time-domain spectroscopy technique in the optical combustion diagnostics and extend the optical combustion diagnostics application area.

Evaluating Oil Potential in Shale Formations Using Terahertz Time-Domain Spectroscopy

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Yizhang Li ◽  
Xinyang Miao ◽  
Honglei Zhan ◽  
Wei Wang ◽  
Rima Bao ◽  
...  
Keyword(s):  
Refractive Index ◽  
Time Domain ◽  
Oil Shale ◽  
Powdered Material ◽  
Specimen Preparation ◽  
Evolutionary Stage ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
The Difference ◽  
Different Response

Optical assessment of oil shale using terahertz time-domain spectroscopy (THz-TDS) was carried out to study oil potential. Fischer assay testing was employed to obtain the oil yield of oil shale specimens to examine the difference of oil potential between oil shale samples from three regions: Beipiao, Barkol, and Huadian in China. Then, two types of specimens from each area were prepared for the optical tests and the results were compared. The refractive index (n) at 0.2–1.2 THz was derived; n decreased slowly with increasing frequency for all the specimens despite the oscillation pattern observed at lower frequencies. The specimen preparation method that mixed the powdered material led to minor differences between the specimens. The different response of kerogen to the terahertz pulse depending on the kerogen's evolutionary stage leads to a difference in the refractive index between the specimens from the various regions. This study indicates that using THz-TDS to evaluate the oil content in oil shale without inducing reaction within the specimen can be an effective method for resource exploration.

Accurate Complex Refractive Index with Standard Deviation of ZnTe Measured by Terahertz Time Domain Spectroscopy

2013 ◽  
Vol 52 (4R) ◽  
pp. 042401 ◽  
Author(s):  
Saroj R. Tripathi ◽  
Makoto Aoki ◽  
Masanori Takeda ◽  
Toshiaki Asahi ◽  
Iwao Hosako ◽  
...  
Keyword(s):  
Refractive Index ◽  
Standard Deviation ◽  
Time Domain ◽  
Complex Refractive Index ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy

scholarly journals Nondestructive Interface Morphology Characterization of Thermal Barrier Coatings Using Terahertz Time-Domain Spectroscopy

Coatings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 89 ◽  
Author(s):  
Dongdong Ye ◽  
Weize Wang ◽  
Jibo Huang ◽  
Xiang Lu ◽  
Haiting Zhou
Keyword(s):  
Refractive Index ◽  
Thermal Barrier Coatings ◽  
Time Domain ◽  
Thermal Barrier ◽  
Interface Morphology ◽  
Terahertz Time Domain Spectroscopy ◽  
Barrier Coatings ◽  
Time Domain Spectroscopy ◽  
Thickness Loss ◽  
Thz Waves

In this work, a terahertz time-domain spectroscopy (THz-TDS) system was used to measure the thickness of thermal barrier coatings (TBCs) and characterize the interface morphology of TBCs after erosion. Reflection mode, with an angle of incidence of 0, was used for inspection before and after erosion. The refractive index, thickness, and internal structure evolution tendency of the yttria-stabilized zirconia (YSZ) top coat were estimated under consideration of the interaction between the pulsed THz waves and the TBCs. The surface roughness of the top coat surface was considered for the errors analysis in the refractive index and thickness measurement. To reduce the errors introduced by the refractive index change after erosion, two mathematical models were built to assess the thickness loss. Then, the thickness loss was compared with results estimated by the micrometer inspection method. Finally, the basic erosion sample profile with Ra roughness was obtained, and the broadening of THz pulses were suggested as a possible measure for the top coat porosity change, showing that THz waves can be a novel online non-destructive and non-contact evaluation method that can be widely utilized to evaluate the integrity of TBCs applied to gas turbine blades.

Research of Beta-Endosulfan Based on THz Time-Domain Spectroscopy

2013 ◽  
Vol 718-720 ◽  
pp. 1060-1065 ◽  
Author(s):  
Zhe Liu ◽  
Xian Li ◽  
Fei Heng Yue ◽  
Lu Feng ◽  
Jin Hui Cai ◽  
...  
Keyword(s):  
Refractive Index ◽  
Organic Pollutants ◽  
Time Domain ◽  
Spectral Properties ◽  
Experimental Results ◽  
Good Match ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Characteristic Absorption ◽  
System Part

THz spectral properties between 0.2-1.5THz of beta-endosulfan, one of the persistent organic pollutants (POPs), are investigated based on the THz time domain system. Part of the characteristic absorption peaks are theoretically analyzed by Dmol3 modular program. The experimental results show that the average refractive index of beta-endosulfan in the THz waveband is about 1.005 and characteristic absorption peaks exist at 0.67, 0.80, 1.03, 1.14, 1.26 and 1.46THz. The absorption peaks at 0.67THz and 1.03THz have a good match with the theoretic absorption peak positions which appear at 0.72THz and 1.07THz calculated by Dmol3. The peaks at 0.67THz and 1.03THz may be caused by the torsion in B and C direction of beta-endosulfan crystal lattice, along with the translation in A direction. Compared with the experimental results of alpha-endosulfan, it can be seen clearly that these two isomers have completely different absorption peaks. For further it indicates that terahertz time domain spectroscopy (THz-TDS) has great application value in identifying isomers.

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