Temperature dependent optical properties of CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> perovskite by spectroscopic ellipsometry

© 2016 AIP Publishing LLC. Mixed organic-inorganic halide perovskites have emerged as a promising new class of semiconductors for photovoltaics with excellent light harvesting properties. Thorough understanding of the optical properties of these materials is important for photovoltaic device optimization and the insight this provides for the knowledge of energy band structures. Here we present an investigation of the sub-room temperature dependent optical properties of polycrystalline thin films of CH3NH3PbI3 perovskites that are of increasing interest for photovoltaics. The complex dielectric function of CH3NH3PbI3 in the energy range of 0.5-4.1 eV is determined between 77 K and 297 K using spectroscopic ellipsometry. An increase in optical permittivity as the temperature decreases is illustrated for CH3NH3PbI3. Optical transitions and critical points were analyzed using the energy dependent second derivative of these dielectric functions as a function of temperature

Symptomatic pulmonary cement embolism after pedicle screw polymethylmethacrylate cement augmentation: A case report and review

Background: In osteoporotic patients, a useful technique for significantly enhancing the strength of a pedicle screw is augmentation with polymethylmethacrylate cement. However, a rare complication of this procedure is a symptomatic pulmonary cement embolism. Case Description: A pedicle screw cement augmentation was performed in a middle-aged female for the failed back syndrome. When she developed symptomatic pulmonary cement emboli, she was successfully managed with conservative measures, including anticoagulation. Conclusion: Despite the increased use of cement augmentation for pedicle screw placement and the relatively high incidence of cement leakage into the prevertebral venous system, symptomatic cement pulmonary embolism remains rare. The management of such symptomatic CPE should be evaluated and treated based on both the size and location of the embolism. Here, we presented this case while reviewing three symptomatic and four asymptomatic cases from the literature. © 2020 Scientific Scholar. All rights reserved

Impact of microstructure on the electron-hole interaction in lead halide perovskites

Despite the remarkable progress in the performance of devices based on the lead halide perovskite semiconductor family, there is still a lack of consensus on their fundamental photophysical properties. Here, using magneto-optical transmission spectroscopy we elucidate the impact of the microstructure on the Coulomb interaction between photo-created electron-hole pairs in methylammonium lead triiodide (MAPbI₃) and the triple-cation lead mixed-halide composition, Cs₀.₀₅(MA₀.₁₇ FA₀.₈₃)₀.₉₅Pb(I₀.₈₃Br₀.₁₇)₃ (Cs: cesium, MA: methylammonium, FA: formamidinium) by investigating thin films with a wide range of grain sizes from tens of nanometers to microns. At low temperatures, in which thermal fluctuations of the interactions are frozen and the rotational disorder of the organic cation is negligible, the exciton binding energy and reduced effective mass of carriers remain effectively unchanged with grain size. We conclude that the microstructure plays a negligible role in the Coulomb interaction of the photo-created electron-hole pairs, in contrast to previous reports. This renewed understanding of the relationship between these fundamental electronic properties and the microstructure is critical for future fundamental studies and improving device design.The authors acknowledge support from the Australian Government through the Australian Renewable Energy Agency (ARENA) and the Australian Centre for Advanced Photovoltaics (ACAP). The views expressed herein are not necessarily the views of the Australian Government, and the Australian Government does not accept responsibility for any information or advice contained herein. S. D. S. acknowledges funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (FP7/2007-2013) under REA grant agreement number PIOF-GA-2013-622630. This work was partially supported by ANR JCJC project milliPICS, the Région Midi-Pyrénées under contract MESR 13053031, BLAPHENE project under IDEX program Emergence and Programme des Investissements d'Avenir under the program ANR-11-IDEX-0002-02, reference ANR-10-LABX-0037-NEXT. Part of the work has been supported by TERASPEC grant within IDEX Emergence program of University of Toulouse. Zhuo Yang and Nan Zhang hold a fellowship from the Chinese Scholarship Council (CSC). This work was supported by EPSRC (UK) via its membership to the EMFL (grant no. EP/N01085X/1). M. A. J. gratefully acknowledges Cambridge Materials Limited for a PhD scholarship

Measurement and Modeling of Particle Radiation in Coal Flames

This work aims at developing a methodology that can provide information of in-flame particle radiation in industrial-scale flames. The method is based on a combination of experimental and modeling work. The experiments have been performed in the high-temperature zone of a 77 kWth swirling lignite flame. Spectral radiation, total radiative intensity, gas temperature, and gas composition were measured, and the radiative intensity in the furnace was modeled with an axisymmetric cylindrical radiation model using Mie theory for the particle properties and a statistical narrow-band model for the gas properties. The in-flame particle radiation was measured with a Fourier transform infrared (FTIR) spectrometer connected to a water-cooled probe via fiber optics. In the cross-section of the flame investigated, the particles were found to be the dominating source of radiation. Apart from giving information about particle radiation and temperature, the methodology can also provide estimates of the amount of soot radiation and the maximum contribution from soot radiation compared to the total particle radiation. In the center position in the flame, the maximum contribution from soot radiation was estimated to be less than 40% of the particle radiation. As a validation of the methodology, the modeled total radiative intensity was compared to the total intensity measured with a narrow angle radiometer and the agreement in the results was good, supporting the validity of the used approach

Interfacial Reaction During High Energy Ball Milling Dispersion of Carbon Nanotubes into Ti6Al4V

The unique thermal and mechanical properties of carbon nanotubes (CNTs) have made them choice reinforcements for metal matrix composites (MMCs). However, there still remains a critical challenge in achieving homogeneous dispersion of CNTs in metallic matrices. Although high energy ball milling (HEBM) has been reported as an effective method of dispersing CNTs into metal matrices, a careful selection of the milling parameters is important not to compromise the structural integrity of CNTs which may cause interfacial reactions with the matrix. In this study, multi-walled carbon nanotubes (MWCNTs) were purified by annealing in argon and vacuum atmospheres at 1000 and 1800 °C, respectively, for 5 h to remove possible metallic catalyst impurities. Subsequently, 1, 2 and 3 wt.% MWCNTs were dispersed by adapted HEBM into Ti6Al4V alloy metal matrix. Raman spectroscopy (RS), x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectrometry and transmission electron microscopy techniques were used to characterize the as-received and annealed MWCNTs, as well as the admixed MWCNT/Ti6Al4V nanocomposite powders. The experimental results showed that vacuum annealing successfully eliminated retained nickel (Ni) catalysts from MWCNTs, while the adapted HEBM method achieved a relative homogeneous dispersion of MWCNTs into the Ti6Al4V matrix and helped to control interfacial reactions between defective MWCNTs and the metal matrix

Absorption, émission et réflexion du rayonnement électromagnétique par une paroi constituée de tubes parallèles jointifs

On se propose dans cette étude d'évaluer l'influence des deux phénomènes suivants : 1) macrorugosité d'une surface constituée de demi-tubes jointifs; 2) gradients locaux de température engendrés par un flux incident normal au plan des génératrices, sur la nature de l'émission et de l'absorption du rayonnement par ce faisceau de tubes. Cette étude permet de définir une température équivalente radiative que l'on exprime simplement en fonction des paramètres du problème afin d'en avoir une utilisation facile par la suite

Absorption, émission et réflexion du rayonnement électromagnétique par une paroi constituée de tubes parallèles jointifs

This paper describes an investigation of the effects of : 1) macro-rugosity of a wall constituted with joined parallel tubes; 2) local drops in temperature due to an incident flux normal to the generating lines, on the nature of emission and absorption of radiation by this bundle of tubes. As a result, an equivalent radiative temperature is defined. This temperature is simply expressed as a function of the various parameters of the system in order to be used easily afterwards.On se propose dans cette étude d'évaluer l'influence des deux phénomènes suivants : 1) macrorugosité d'une surface constituée de demi-tubes jointifs; 2) gradients locaux de température engendrés par un flux incident normal au plan des génératrices, sur la nature de l'émission et de l'absorption du rayonnement par ce faisceau de tubes. Cette étude permet de définir une température équivalente radiative que l'on exprime simplement en fonction des paramètres du problème afin d'en avoir une utilisation facile par la suite

Double-level myelopathy due to atlantoaxial dislocation (os odontoideum) and subaxial cervical spondylosis with angular kyphosis

Background: The surgical management of cervical spondylotic myelopathy (CSM) attributed to os odontoideum (OO with atlantoaxial instability atlantoaxial instability) and subaxial kyphosis together pose significant surgical challenges. Case Description: An elderly male presented with CSM/myelopathy and severe quadriparesis attributed to an unstable OO and 87° fixed, subaxial cervical kyphosis. After performing a 540° spinal cord decompression with atlantoaxial fixation, the patient did well. Conclusion: Double-level CSM due to an unstable OO and subaxial kyphosis is rare and typically requires combined 540° decompression and stabilization. © 2020 Scientific Scholar. All rights reserved