Tuesday, 10 July 2018

Proton irradiation induced changes in glass and polyethylene terephthalate substrates for photovoltaic solar cells

Čermák, J., L. Mihai, D. Sporea, Y. Galagan, J. Fait, A. Artemenko, P. Štenclová, B. Rezek, M. Straticiuc, and I. Burducea. "Proton irradiation induced changes in glass and polyethylene terephthalate substrates for photovoltaic solar cells." Solar Energy Materials and Solar Cells 186 (2018): 284-290.
… The results are presented in the form of the ratio S irradiated non-irradiated . THz spectroscopy was performed by a TPS3000 spectrometer (TeraView) in the spectral range 0.06–2 THz using a spectral …
Abstract
An alkaline earth boro-aluminosilicate glass (Eagle XG), a soda-lime glass, and a light-weight polyethylene-terephthalate (PET) foil, used as typical substrates for photovoltaics, were treated by an energetic proton beam (3 MeV, dose 106–107 Gy) corresponding to approx. 30 years of operation at low Earth orbit. Properties of the irradiated substrates were characterized by atomic force microscopyoptical absorption, optical diffuse reflectance, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and terahertz (THz) spectroscopy. Minimal changes of optical and morphological properties are detected on the bare Eagle XG glass, whereas the bare PET foil exhibits pronounced increase in optical absorption, generation of photoluminescence, as well as mechanical bending. On the other hand, the identical substrates coated with Indium-tin-oxide(ITO), which is a typical material for transparent electrodes in photovoltaics, exhibit significantly higher resistance to the modifications by protons while ITO structural and electronic properties remain unchanged. The experimental results are discussed considering a potential application of these materials for missions in space.

for full paper https://www.sciencedirect.com/science/article/pii/S0927024818303568




Monday, 9 July 2018

Visualization of subsurface damage in woven carbon fiber-reinforced composites using polarization-sensitive terahertz imaging

Dong, Junliang, Pascal Pomarède, Lynda Chehami, Alexandre Locquet, Fodil Meraghni, Nico F. Declercq, and D. S. Citrin. "Visualization of subsurface damage in woven carbon fiber-reinforced composites using polarization-sensitive #terahertz imaging." NDT & E International (2018).

for full paper see https://www.sciencedirect.com/science/article/pii/S0963869518301610

Abstract
Polarization-sensitive #terahertz imaging is applied to characterize subsurface damage in woven carbon fiber-reinforced composite laminates in this study. #Terahertz subsurface spectral imaging based on #terahertz deconvolution is tailored and applied to detect, in a nondestructive fashion, the subsurface damage within the first ply of the laminate caused by a four-point bending test. Subsurface damage types, including matrix cracking, fiber distortion/fracture, as well as intra-ply delamination, are successfully characterized. Our results show that, although the conductivity of carbon fibers rapidly attenuates terahertz propagation with depth, the imaging capability of #terahertz radiation on woven carbon fiber-reinforced composites can nonetheless be significantly enhanced by taking advantage of the #terahertz polarization and terahertz deconvolution. The method demonstrated in this study is capable of extracting and visualizing a number of fine details of the subsurface damage in woven carbon fiber-reinforced composites, and the results achieved are confirmed by comparative studies with X-ray tomography.

… thickness direction). The commercial THz time-domain spectroscopy (TDS) system (Teraview TPS Spectra 3000), which was employed in this study, is shown schematically.....

for more information about TeraView see https://www.azom.com/equipment-details.aspx?EquipID=4411

Experimental Gouy phase shift compensation in Terahertz time-domain spectroscopy

Koleják, Pierre, Kamil Postava, Martin Micica, Petr Kuzel, Filip Kadlec, and Jaromír Pištora. "Experimental Gouy phase shift compensation in Terahertz time-domain spectroscopy." Photonics and Nanostructures-Fundamentals and Applications(2018).

Abstract
Terahertz time-domain spectroscopy experiments are usually carried out with focused beams. In this case the Gouy phase shift modifies the retrieved dielectric spectra of thick samples [Opt. Express 18, 15338 (2010)]. We show that a significant influence of the Gouy shift occurs also in commercial THz spectrometers where the focusing conditions may be a priori unknown. A method of experimental compensation of the Gouy shift influence is described and demonstrated.

… In this work we use the time domain spectrometer TeraviewTPS Spectra 3000, which uses 90 fs pulses at 780 nm delivered by the second harmonic of Er:doped fiber laser …Scheme of the measuring system (TPS spectra 3000 from Teraview company) with the … 

For more information about TeraView see https://www.azom.com/equipment-details.aspx?EquipID=4411

for full paper see https://www.sciencedirect.com/science/article/pii/S1569441017303048

Thursday, 5 July 2018

Predicting the Structures and Associated Phase Transitions Mechanisms in Disordered Crystals via a Combination of Experimental and Theoretical Methods

Ruggiero, Michael T., Johanna Kölbel, Qi Li, and J. Axel Zeitler. "Predicting the Structures and Associated Phase Transitions Mechanisms in Disordered Crystals via a Combination of Experimental and Theoretical Methods." Faraday Discussions (2018).

Abstract

Disordered materials make up a large portion of condensed phase systems, but the difficulties in describing their structures and molecular dynamics limit their potential applications. Disordered crystalline systems, also known as plastic crystals, offer a unique perspective into these factors because the system retains a degree of crystallinity, reducing the degrees of freedom that must be explored when interpreting the results. However, while disordered crystals do diffract X-rays, it is difficult to fully resolve a meaningful crystalline structure, with the best scenario resulting in lattice parameters. In this study, we use a combination of experimental terahertz time-domain spectroscopy, and theoretical solid-state ab initio density functional theory and molecular dynamics simulations to fully elucidate the structures and associated dynamics of organic molecular solids. The results highlight that this combination provides a complete description of the energetic and mechanistic pathways involved in the formation of disordered crystals, and highlights the importance of low-frequency dynamics on their properties. Finally, with structures fully determined and validated by the experimental results, recent progress into anharmonic calculations, namely the quasi-harmonic approximation method, enables full temperature and pressure-dependent properties to be understood within the framework of the potential energy hyper-surface structure.



"A corresponding pellet containing pure polyethylene was also made to act as a standard blank for absorption measurements. All experimental THz-TDS spectra were obtained using a commercial TeraPulse 4000 spectrometer (TeraView Ltd., Cambridge,UK). Variable-temperature measurements were performed using a liquid nitrogen cryostat (Janis, Massachusetts, USA) equipped with a externally controlled heating element (Lakeshore 330, Ohio, USA)."


For information about Janis see https://www.janis.com/

A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging

Pei, Chunlei, Hungyen Lin, Daniel Markl, Yao-Chun Shen, J. Axel Zeitler, and James A. Elliott. "A quantitative comparison of in-line coating thickness distributions obtained from a pharmaceutical tablet mixing process using discrete element method and terahertz pulsed imaging." Chemical Engineering Science (2018).

Abstract

The application of terahertz pulsed imaging (TPI) in the in-line configuration to monitor the coating thickness distribution of pharmaceutical tablets has the potential to improve the performance and quality of the spray coating process. In this study, an in-line TPI method is used to measure coating thickness distributions on pre-coated tablets during mixing in a rotating pan, and compared with results obtained numerically using the discrete element method (DEM) combined with a ray-tracing technique. The hit rates (i.e. the number of successful coating thickness measurements per minute) obtained from both terahertz in-line experiments and the DEM/ray-tracing simulations are in good agreement, and both increase with the number of baffles in the mixing pan. We demonstrate that the coating thickness variability as determined from the ray-traced data and the terahertz in-line measurements represents mainly the intra-tablet variability due to relatively uniform mean coating thickness across tablets. The mean coating thickness of the ray-traced data from the numerical simulations agrees well with the mean coating thickness as determined by the off-line TPI measurements. The mean coating thickness of in-line TPI measurements is slightly higher than that of off-line measurements. This discrepancy can be corrected based on the cap-to-band surface area ratio of the tablet and the cap-to-band sampling ratio obtained from ray-tracing simulations: the corrected mean coating thickness of the in-line TPI measurements shows a better agreement with that of off-line measurements.

For full paper see https://www.sciencedirect.com/science/article/pii/S0009250918304172






… the terahertz in-line measurement. A TPI Imaga 2000 system (TeraView Ltd., Cambridge, UK) was used to perform the off-line measurements as described in detail by Shen and Taday (2008). During the measurement, each...... 


Also see https://www.azom.com/equipment-details.aspx?EquipID=4411


Monday, 2 July 2018

Investigating elastic relaxation effects on the optical properties of functionalised calcium carbonate compacts using optics-based Heckel analysis

Bawuah, Prince, Anssi-Pekka Karttunen, Daniel Markl, Cathy Ridgway, Ossi Korhonen, Patrick Gane, J. Axel Zeitler, Jarkko Ketolainen, and Kai-Erik Peiponen. "Investigating elastic relaxation effects on the optical properties of functionalised calcium carbonate compacts using optics-based Heckel analysis." International journal of pharmaceutics 544, no. 1 (2018): 278-284.

for full paper see https://www.sciencedirect.com/science/article/pii/S0378517318302710

The group used a terahertz  a Terapulse 4000 spectrometer (Teraview Ltd., Cambridge, UK) in transmission mode.
Abstract
Heckel analysis is a widely used method for the characterisation of the compression behaviour of pharmaceutical samples during the preparation of solid dosage formulations. The present study introduces an optical version of the Heckel equation that is based on a combination of the conventional Heckel equation together with the linear relationship defined between the effective terahertz (THz) refractive index and the porosity of pharmaceutical tablets. The proposed optical Heckel equation allows us to, firstly, calculate the zero-porosity refractive index, and, secondly, predict the in-die development of the effective refractive index as a function of the compressive pressure during tablet compression. This was demonstrated for five batches of highly porous functionalised calcium carbonate (FCC) excipient compacts. The close match observed between the estimated in-die effective refractive index and the measured/out-of-die effective THz refractive index supports the validity of the proposed form of the equation. By comparing the measured and estimated in-die tablet properties, a clear change in the porosity and hence, the effective refractive index, due to post-compression elastic relaxation of the FCC compacts, has been observed. We have, therefore, proposed a THz-based compaction setup that will permit in-line monitoring of processes during tablet compression. We envisage that this new approach in tracking powder properties introduced in this preliminary study will lead to the onset of further extensive and detailed future studies.