Terahertz Testing Technique for Fiber-Reinforced Composite Materials

Zhong, Shuncong, and Walter Nsengiyumva. "Terahertz Testing Technique for Fiber-Reinforced Composite Materials." In Nondestructive Testing and Evaluation of Fiber-Reinforced Composite Structures, pp. 273-314. Springer, Singapore, 2022.

for full paper see https://link.springer.com/chapter/10.1007/978-981-19-0848-4_6

Abstract

Terahertz (THz) systems constitute an effective tool for the NDT&E community for the testing and characterization of fiber-reinforced composite materials. However, their systems are still very complicated and expensive to commercialize. Also, establishing the inspection limits for the vast majority of fiber-reinforced composite structures is still not achieved because this technique is relatively new in the area of material testing and evaluation. Nevertheless, this technique presents several advantages including the fact that it can see “through” the defects in thin composites and examine the underlying fabric of the material, overcoming the shadowing effect that is commonly observed with other NDT techniques such as ultrasonic testing and most of the radiographic testing techniques. Although the technology had been deferred for many years because of the inadequacy of its emission and detection devices, the so-called “THz gap”, this problem has recently been addressed thanks to the development of highly performing semiconductors and ultrafast electronics. To date, extremely short pulses required for the energy frequency of the THz waves can be achieved, suggesting that spatial resolution of the inspection levels higher than those of the normal microwave-based NDT techniques can be reached using THz systems. A lot has been done but much still needs to be done, particularly because there are no reported studies on the inspection of moisture uptake in fiber-reinforced composite structures nor are there any studies that confidently inspect conductive materials using THz waves. Indeed, this would be a highly valued milestone to the literature if it was achieved. In applications involving the inspection of thick composites and sandwich structures, THz systems do not, unfortunately, provide reliable inspection results owing to the attenuation and/or the scattering effects of the THz waves in thick sections.

… Although tremendous progress has been made in the THz technology in recentyears, typically the signal-to-noise ratio (SNR) is somewhat smaller except whenusing some of the most advanced THz systems such as Teraview (TeraView TPS …

Multifunctional Elastic Nanocomposites with Extremely Low Concentrations of Single-Walled Carbon Nanotubes

Novikov, Ilya V., Dmitry V. Krasnikov, Anton M. Vorobei, Yaroslav I. Zuev, Hassaan A. Butt, Fedor S. Fedorov, Sergey A. Gusev et al. "Multifunctional Elastic Nanocomposites with Extremely Low Concentrations of Single-Walled Carbon Nanotubes." ACS Applied Materials & Interfaces (2022).

for full paper see https://pubs.acs.org/doi/abs/10.1021/acsami.2c01086

Abstract

Stretchable and flexible electronics has attracted broad attention over the last years. Nanocomposites based on elastomers and carbon nanotubes are a promising material for soft electronic applications. Despite the fact that single-walled carbon nanotube (SWCNT) based nanocomposites often demonstrate superior properties, the vast majority of the studies were devoted to those based on multiwalled carbon nanotubes (MWCNTs) mainly because of their higher availability and easier processing procedures. Moreover, high weight concentrations of MWCNTs are often required for high performance of the nanocomposites in electronic applications. Inspired by the recent drop in the SWCNT price, we have focused on fabrication of elastic nanocomposites with very low concentrations of SWCNTs to reduce the cost of nanocomposites further. In this work, we use a fast method of coagulation (antisolvent) precipitation to fabricate elastic composites based on thermoplastic polyurethane (TPU) and SWCNTs with a homogeneous distribution of SWCNTs in bulk TPU. Applicability of the approach is confirmed by extra low percolation threshold of 0.006 wt % and, as a consequence, by the state-of-the-art performance of fabricated elastic nanocomposites at very low SWCNT concentrations for strain sensing (gauge factor of 82 at 0.05 wt %) and EMI shielding (efficiency of 30 dB mm–1 at 0.01 wt %).

EMI-shielding efficiency of the nanocomposites in the THz range was tested using a time-domain spectrometer (TeraView TPS 3000). Both disk shaped samples with a thickness of 0.5 mm (the same were used for impedance tests) and thin film samples were used for testing, ranging in thickness from 0.1–0.2 mm, depending on the SWCNT loading in the nanocomposites.

Spatially inhomogeneous operation of phase-change memory

Kim, Dasol, Soobin Hwang, Taek Sun Jung, Min Ahn, Jaehun Jeong, Hanbum Park, Juhwan Park, Jae Hoon Kim, Byung Joon Choi, and Mann-Ho Cho. "Spatially inhomogeneous operation of phase-change memory." Applied Surface Science (2022): 153026.

for full paper see https://www.sciencedirect.com/science/article/abs/pii/S0169433222005931

Abstract

Rapid changes in the electrical resistance depending on the phases (amorphous and crystal) are one of the most promising bases for universal memory. Phase-change region is spatially inhomogeneous during memory operation in a unit cell because Joule heat for the phase-change is generated at the interface between the metal and compounds. However, delicate optimization of the electrical and thermal properties at the interface is underexplored compared to the bulk. In this study, we modulate the electrical and thermal conductivities by incorporating oxygen in Ag-In-Sb-Te, superior memory compounds where oxygen is chosen for high accessibility and efficiency for the modulation of conductivity. We further analyze the oxidation and crystallization process at the atomic level. Based on the results, we successfully improve the memory performances such as speed, energy, signal ratio, and reliability simultaneously by inserting the oxygenated layer as an interfacial layer. Our study proves that there is considerable room to optimize memory performance at the interface.

Experimental 

… The optical conductivities of AIST with various thicknesses were obtained from THz-TDS using a Teraview TPS3000 under a N 2 purged state. The time-domain signal after sample transmission has the information of the sample conductivity.....

Terahertz Dielectric Characterization of Low-Loss Thermoplastics for 6G Applications

Zhai, Min, Alexandre Locquet, and D. S. Citrin. "Terahertz Dielectric Characterization of Low-Loss Thermoplastics for 6G Applications." International Journal of Wireless Information Networks (2022): 1-6.

for full paper see https://link.springer.com/article/10.1007/s10776-022-00554-x

Abstract

Common thermoplastics, namely, polycarbonate (PC), poly (methyl methacrylate) (PMMA), and acrylonitrile butadiene styrene (ABS) are low-cost materials with potential applications in emerging 6G communications systems, ranging from microelectronics packaging to metasurfaces for reflectors and filters. In addition, low-loss materials are also needed for more pedestrian applications, such as packaging for entire handheld devices, subassemblies, and high-frequency windows where low-cost is key and long lifetime might not be a requirement. In this work, we utilize terahertz time-domain spectroscopy from 500 GHz to 2 THz to characterize the dielectric properties and loss tangent for each thermoplastic above. The plastics investigated have refractive index (∼ 1.6–1.7) in the 6G band with low dispersion. The absorption, however, increases at high frequencies as is common in disordered materials, highlighting a key challenge for 6G. Nonetheless, in absolute terms, all the thermoplastics studied present low-loss performance compared with (higher–index) common glasses and ceramics within the entire frequency range, suggesting that they are promising candidates for selected applications for future 6G systems.

… The transmission measurements in this work were performed using a commercial pulsed broadband THz time-domain spectroscopy (TDS) system (TPS Spectra 3000 from TeraView Ltd, UK). Compared to vector network analyzers (VNA), another …

Terahertz-infrared spectroscopy of wafer-scale films of single-walled carbon nanotubes treated by plasma

 Zhukov, S. S., E. S. Zhukova, A. V. Melentev, B. P. Gorshunov, A. P. Tsapenko, D. S. Kopylova, and Albert G. Nasibulin. "Terahertz-infrared spectroscopy of wafer-scale films of single-walled carbon nanotubes treated by plasma." Carbon 189 (2022): 413-421.

for full paper see 

https://www.sciencedirect.com/science/article/abs/pii/S0008622321012355

Abstract

We investigated terahertz-infrared electrodynamic properties of wafer-scale films composed of plasma-treated single-walled carbon nanotubes (SWCNTs) and films comprising SWCNTs grown with different lengths. The spectra of complex conductance of the films were measured at frequencies 5–20 000 cm−1 and in the temperature interval 5–300 K. Terahertz spectral response of films of pristine SWCNTs is well described with the Drude conductivity model and a plasmon resonance located at ≈100 cm−1. Stepwise treatment of the films with oxygen plasma led to a gradual suppression of the Drude spectral weight from the low-frequency side. For films with the nanotubes shorter than 1 μm, i.e., close to electrons mean free path and localization length, scattering of charge carriers at the nanotubes edges is shown to additionally contribute to the carriers scattering rate and to the damping of plasmon resonance. The temperature coefficient of ac resistance (ac TCR) in both kinds of films is found to strongly increase in amplitude during cooling and frequency decrease. The values of ac TCR increase in films with longer time of plasma treatment and nanotubes with shorter length but reach saturation in films with exposure time longer than ≈100 s or composed from SWCNTs shorter than 1 μm.

.....complex (amplitude and phase) transmission coefficient measured with the TeraView time-domain......