Prediction of oven-dry density of wood by time-domain terahertz spectroscopy

Holzforschung ◽  
2014 ◽  
Vol 68 (1) ◽  
pp. 61-68 ◽  
Author(s):  
Tetsuya Inagaki ◽  
Ian D. Hartley ◽  
Satoru Tsuchikawa ◽  
Matthew Reid
Keyword(s):  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Effective Medium Theory ◽  
Wood Products ◽  
Wall Material ◽  
Thz Radiation ◽  
Dry Density ◽  
Submillimeter Range ◽  
Time Domain Spectroscopy ◽  
Good Spatial Resolution

Abstract Wood is relatively transparent to terahertz (THz) radiation with wavelengths in the submillimeter range. This radiation has a high potential for sensing and imaging wood with a good spatial resolution. THz is especially sensitive to moisture content, fiber alignment, and density – all of which are critical in the manufacturing of wood products. In this work, a systematic study was undertaken on 46 very different wood species by means of THz time-domain spectroscopy with density determination in focus. The dielectric response of wood was modeled based on the Maxwell-Garnett effective medium theory. The dielectric function of the cell wall material was found to be extremely consistent over this large number of species with very different properties. This renders possible to determine wood density by THz time-domain spectroscopy. A strong correlation between the measured and predicted densities has been observed for all the samples investigated.

scholarly journals Terahertz Time-Domain Spectroscopy of Graphene Nanoflakes Embedded in Polymer Matrix

2019 ◽  
Vol 9 (3) ◽  
pp. 391 ◽  
Author(s):  
Anton Koroliov ◽  
Genyu Chen ◽  
Kenneth M. Goodfellow ◽  
A. Nick Vamivakas ◽  
Zygmunt Staniszewski ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Time Domain ◽  
Thz Radiation ◽  
Complex Conductivity ◽  
Frequency Range ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Graphene Nanocomposites ◽  
Graphene Nanoflakes ◽  
Exfoliated Graphene

The terahertz time-domain spectroscopy (THz-TDS) technique has been used to obtain transmission THz-radiation spectra of polymer nanocomposites containing a controlled amount of exfoliated graphene. Graphene nanocomposites (1 wt%) that were used in this work were based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) matrix and were prepared via a kilo-scale (suitable for research and development, and prototyping) in-situ polymerization. This was followed by compression molding into 0.3-mm-thick and 0.9-mm-thick foils. Transmission electron microscopy (TEM) and Raman studies were used to confirm that the graphene nanoflakes dispersed in a polymer matrix consisted of a few-layer graphene. The THz-radiation transients were generated and detected using a low-temperature–grown GaAs photoconductive emitter and detector, both excited by 100-fs-wide, 800-nm-wavelength optical pulses, generated at a 76-MHz repetition rate by a Ti:Sapphire laser. Time-domain signals transmitted through the nitrogen, neat polymer reference, and 1-wt% graphene-polymer nanocomposite samples were recorded and subsequently converted into the spectral domain by means of a fast Fourier transformation. The spectral range of our spectrometer was up to 4 THz, and measurements were taken at room temperature in a dry nitrogen environment. We collected a family of spectra and, based on Fresnel equations, performed a numerical analysis, that allowed us to extract the THz-frequency-range refractive index and absorption coefficient and their dependences on the sample composition and graphene content. Using the Clausius-Mossotti relation, we also managed to estimate the graphene effective dielectric constant to be equal to ~7 ± 2. Finally, we extracted from our experimental data complex conductivity spectra of graphene nanocomposites and successfully fitted them to the Drude-Smith model, demonstrating that our graphene nanoflakes were isolated in their polymer matrix and exhibited highly localized electron backscattering with a femtosecond relaxation time. Our results shed new light on how the incorporation of exfoliated graphene nanoflakes modifies polymer electrical properties in the THz-frequency range. Importantly, they demonstrate that the complex conductivity analysis is a very efficient, macroscopic and non-destructive (contrary to TEM) tool for the characterization of the dispersion of a graphene nanofiller within a copolyester matrix.

Determination of pesticides in a flour substrate by chemometric methods using terahertz spectroscopy

2018 ◽  
Vol 10 (42) ◽  
pp. 5097-5104 ◽  
Author(s):  
Binghua Cao ◽  
Hui Li ◽  
Mengbao Fan ◽  
Wei Wang ◽  
Mengyun Wang
Keyword(s):  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Chemometric Methods ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy

Terahertz time-domain spectroscopy combined with chemometrics is utilized to identify imidacloprid and carbendazim in a flour substrate.

scholarly journals Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors

2019 ◽  
Vol 9 (13) ◽  
pp. 2704 ◽  
Author(s):  
Kai-Henning Tybussek ◽  
Kevin Kolpatzeck ◽  
Fahd Faridi ◽  
Sascha Preu ◽  
Jan C. Balzer
Keyword(s):  
Laser Diode ◽  
Time Domain ◽  
Dynamic Range ◽  
Laser System ◽  
Industrial Applications ◽  
Thz Radiation ◽  
Full Potential ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Fabry Perot

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

Application of Terahertz Spectroscopy and Imaging

2010 ◽  
Vol 5 (4) ◽  
pp. 123-129
Author(s):  
Mu Kaijun ◽  
Zhang Cunlin
Keyword(s):  
Time Domain ◽  
Quartz Crystal ◽  
Terahertz Spectroscopy ◽  
Thz Radiation ◽  
Radiation Polarization ◽  
Air Plasma ◽  
Thz Imaging ◽  
Terahertz Time Domain Spectroscopy ◽  
Security Applications ◽  
Angle Of Rotation

We examined the feasibility of Terahertz time-domain spectroscopy (THz-TDS) using a 4-mm-thick quartz crystal to extract the angle of rotation of THz radiation polarization induced by a two-color laser in air plasma. We also used the THz-TDS technique to identify explosives and melamine in mixtures. In addition, we presented a new opto-mechanical scanner for security applications using the method of passive THz imaging

scholarly journals Transformation and dehydration kinetics of methylene blue hydrates detected by terahertz time-domain spectroscopy

RSC Advances ◽  
2017 ◽  
Vol 7 (66) ◽  
pp. 41667-41674 ◽  
Author(s):  
Shihan Yan ◽  
Hua Zhang ◽  
Zhongbo Yang ◽  
Mingjie Tang ◽  
Mingkun Zhang ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Dehydration Kinetics ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Absorption ◽  
Kinetics Of ◽  
Absorption Features ◽  
Crystalline Hydrates

Three methylene blue crystalline hydrates were identified by terahertz spectroscopy according to their different THz absorption features.

scholarly journals Terahertz Time-domain Spectroscopy as a Novel Tool for Crystallographic Analysis in Cellulose: Cellulose I to Cellulose Ii, Tracing the Structural Changes Under Chemical Treatment

2021 ◽  
Author(s):  
Han Wang ◽  
Hiroki Kataoka ◽  
Satoru Tsuchikawa ◽  
Tetsuya Inagaki
Keyword(s):  
Absorption Coefficient ◽  
Time Domain ◽  
Structural Changes ◽  
Crystalline Lattice ◽  
Thz Radiation ◽  
Cellulose Ii ◽  
Cellulose I ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Thz Absorption

Abstract Terahertz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose crystallography research, as THz radiation detects most intermolecular vibrations and responds to the phonons of crystalline lattices. In this study, we traced the transformation of the cellulose crystalline lattice from cellulose I to cellulose II by THz-TDS and X-ray powder diffraction. Cellulose II was obtained by treating cellulose I with NaOH of different concentrations (0 wt%–20 wt%, at 2 wt% intervals). The THz absorption coefficient spectra of cellulose II showed three characteristic peaks (at 1.32 THz, 1.76 THz, and 2.77 THz). The THz absorption coefficient spectra of cellulose II treated with 20-wt% NaOH and cellulose I without NaOH treatment were fitted by a seventh-order Fourier series. Thus, the THz absorption coefficient spectra of samples treated with NaOH of other concentrations could be considered a combination of these two fitted profiles of cellulose I and cellulose II, multiplied by different coefficients. Furthermore, the coefficients could reflect the relative contents of cellulose I and cellulose II in the samples.

Investigation of Dielectric Properties of Polymers and their Discrimination Using Terahertz Time-Domain Spectroscopy with Principal Component Analysis

2016 ◽  
Vol 71 (3) ◽  
pp. 456-462 ◽  
Author(s):  
Muhammad Mumtaz ◽  
Ahsan Mahmood ◽  
Sabih D. Khan ◽  
M. Aslam Zia ◽  
Mushtaq Ahmed ◽  
...  
Keyword(s):  
Spectral Range ◽  
Time Domain ◽  
Principal Component ◽  
Component Analysis ◽  
Thz Radiation ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Styrene Acrylonitrile ◽  
Characteristic Features ◽  
First Time

Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2–2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.

scholarly journals Study of 2,4-D Spectral Characteristics and Its Detection in Zizania Latifolia Using Terahertz Time-Domain Spectroscopy

2019 ◽  
Vol 9 (11) ◽  
pp. 2248
Author(s):  
Pengcheng Nie ◽  
Chengyong Cai ◽  
Fangfang Qu ◽  
Lei Lin ◽  
Tao Dong ◽  
...  
Keyword(s):  
Time Domain ◽  
Density Functional ◽  
Terahertz Spectroscopy ◽  
Spectral Characteristics ◽  
Geometry Optimization ◽  
Main Peak ◽  
Terahertz Time Domain Spectroscopy ◽  
Zizania Latifolia ◽  
Time Domain Spectroscopy ◽  
2,4 Dichlorophenoxyacetic Acid

2,4-Dichlorophenoxyacetic acid (2,4-D) is a common plant growth regulator, which can remain in food and, with long-term consumption, threaten human health. Therefore, it is necessary to propose an effective detection method. Terahertz time-domain spectroscopy technique (THz-TDS) has good advantages in the quantitative and qualitative analysis of most biomolecules due to its rich fingerprint characteristics. In this paper, density functional theory (DFT) was applied to geometry optimization and frequency vibration calculation of 2,4-D, and THz-TDS was used to quantitatively detect 2,4-D in Zizania latifolia. The results showed that there were three characteristic absorption peaks of 2,4-D at 1.36, 1.60, and 2.38 THz, respectively, and the theoretical spectra were in good consistency with experimental spectra, with slight discrepancies. Additionally, the absorption peak at 1.36 THz had the best absorption characteristics and was chosen as the main peak for 2,4-D quantitative analysis. It was demonstrated that the limits of detection (LOD) of 2,4-D in Zizania latifolia were found to be as low as 5%, the absorbance intensity at 1.36 THz showed a good linear relationship (R2 = 0.9854) with 2,4-D concentration from 5% to 30%, and the recovery was 93.29%–98.75%. Overall, this work enriched the fingerprint database of pesticide molecules on the basis of terahertz spectroscopy and could provide a technical support for the detection of 2,4-D in food by terahertz spectroscopy.

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