Search results for "absorption."
showing 10 items of 2682 documents
Evolution of the structural and optical properties from cobalt cordierite glass to glass-ceramic based on spinel crystalline phase materials
2007
Co 2+ -containing cordierite stoichiometric glasses have been prepared by melting colloidal gel precursors. After controlled thermal processing in the range of temperatures between 900 and 1300 C different polycrystalline, almost single phase materials displaying l-, a-, and b-cordierite crystalline forms were synthesized. In addition, spinel glass-ceramic materials were also prepared from the base glasses. All these materials were characterized by X-ray powder diffraction and infrared spectroscopy. Room temperature (RT) absorption and emission spectra of Co 2+ – cordierites and – spinel-glass material have allowed determining the local environment of the Co 2+ in the crystalline structure …
Series of charge transfer complexes obtained as crystals in a confined environment
2021
A series of charge transfer complexes (CTCs) were successfully formed by solvent free processing techniques, using the 1,2,4,5-tetracyano benzene (TCNB) as πA molecule and a series of p-dihydroquinones (H2Qs) as πD counterparts. Additionally to the classical co-evaporation techniques, we obtained CTCs in less than an hour, in a very simple confined environment, between two 100 μm – spaced glass plates. A systematical study by Raman spectroscopy on crystals highlighted the CTCs formation. Moreover, three new crystalline structures were obtained, namely TCNB-H2Q that crystallizes in columns connected to each other by H-bonds, while with the methoxy- and dimethoxy-H2Qs the CTC forms crystals w…
Modeling of the hydrogen sorption kinetics in an AB2 laves type metal hydride alloy
2021
Abstract Hydrides of the AB2 Laves type alloys (A=Zr, Ti; B = transition metal – Fe, Co, Ni, Mn, Cr, V) have been extensively studied as materials for the storage of gaseous hydrogen. They contain up to 4 H atoms/formula unit AB2, thus achieving reversible H storage capacities in the range between 1.5 and 2.0 wt% H and offering high rates of hydrogen charge and discharge, thus making them suitable for designing efficient hydrogen stores operating at ambient conditions. In the present study, we performed an experimental study and modeling of the thermodynamics and the kinetics of interaction in the AB2-hydrogen system. The experimental data was collected by studying a model alloy with a comp…
Electrochemical Investigation of Hydrogen Evolution and Absorption Phenomena in Nickel Based Electrodes
1996
Due to its potential for industrial applications, hydrogen absorption in metals has attracted continuous interest. Understanding the hydrogen chemistry in metals is crucial due to the significance of hydrogen-metal interactions in important industrial and technical applications such as catalysis, H-fuel containment, corrosion and embrittlement of metals and rechargeable metal hydride batteries [1–2].
Local electronic structure rearrangements and strong anharmonicity in YH3 under pressures up to 180 GPa
2021
The authors acknowledge the ESRF program committee (Grenoble, France) for the opportunity to perform XAFS and XRD measurements. We are grateful to Prof. Dr Marek Tkacz from the Institute of Physical Chemistry, PAS Kasprzaka 44/52, 01-224 Warsaw, Poland, for high quality YH3 samples and to Dr. José A. Flores-Livas for a fruitful discussion. A.P.M. and A.A.I. acknowledge the Russian Foundation for the Basic Research (grant No 18-02-40001_mega) for financial support. J.P., A.K., and I.P. would like to thank the support of the Latvian Council of Science project No. lzp-2018/2-0353. ISSP UL acknowledge the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-20l 6-2017-TeamingPh…
Highly sensitive optical hydrogen sensor using circular Pd-coated singlemode tapered fibre
2001
A novel optical hydrogen sensor, based on the absorption change of the evanescent fields in a circular Pd-coated singlemode tapered fibre is presented. The proposed sensor is polarisation independent and its sensitivity is adjustable by means of the taper diameter, interaction length, and/or light wavelength. A simple light transmission measurement setup is used to test the sensor. The sensor is suitable for the detection of low hydrogen concentrations with high sensitivity and fast time response. Transmission changes as high as 60% are demonstrated.
The electronic structure of zircon-type orthovanadates: Effects of high-pressure and cation substitution
2012
The electronic structure of four ternary-metal oxides containing isolated vanadate ions is studied. Zircon-type YVO4, YbVO4, LuVO4, and NdVO4 are investigated by high-pressure optical-absorption measurements up to 20 GPa. First-principles calculations based on density-functional theory were also performed to analyze the electronic band structure as a function of pressure. The electronic structure near the Fermi level originates largely from molecular orbitals of the vanadate ion, but cation substitution influence these electronic states. The studied ortovanadates, with the exception of NdVO4, undergo a zircon-scheelite structural phase transition that causes a collapse of the band-gap energ…
Analytic JV-Characteristics of Ideal Impurity PV-Cells
2017
In this article the mathematical modeling of idealized impurity photovoltaic cells is greatly simplified through the derivation of analytic JV-characteristics. The resulting expressions are also facilitating the intuitive understanding of such photovoltaic devices. The new model is used to investigate the sensitivity of impurity photovoltaic cells to the absorption band width, the impurity related absorptivity and the external radiative efficiency. It is found that impurities with narrow absorption bands or low absorptivity can greatly reduce the efficiency of the device, even if they are fully radiative and have energy levels situated at optimal positions in the band gap. It is also found …
Synthesis of cubic and hexagonal NaYF4:Er3+
2012
Up-conversion luminescence process, which is related to absorption of several light photons (usually infrared) followed by emission of light in the visible or even ultraviolet spectral regions, has attracted interest of scientists due to its potential practical use in various applications including biolabels, temperature sensors, light sources etc. Although observable in d- and f-ions doped materials, the highest efficiency of up-conversion luminescence is usually attained in lanthanides doped hosts. Among huge variety of materials suitable as up-conversion hosts the most prominent is considered to be NaYF4, both due to its low phonon energy and multisite nature of the crystalline lattice. …
Mass absorption indices of various types of natural aerosol particles in the infrared
2010
The mass absorption index of aerosol particles has been measured in the 2-17-microm wavelength region. The measurements were performed on films of aerosol particles that were collected by an automatic jet impactor at polluted and various uncontaminated remote sites. All but marine aerosols possess strong absorption bands in the transparent part of the atmospheric long-wave spectrum, indicating marked influence of aerosol particles on the radiation budget of the atmosphere.