Search results for "Absorption"

On the Possibility of Miniature Diamond-Based Magnetometers Using Waveguide Geometries

2018

Micromachines 9(6), 276 (2018). doi:10.3390/mi9060276

Production and Characterization of Oxyhydroxyapatites

2018

The amount and alignment of hydroxyl ions influence the bioactivity of hydroxyapatite. Hydroxyl ions in hydroxyapatite are the most mobile and upon heating are the first to leave the lattice to form oxyhydroxyapatite. This work describes a method for producing hydroxyapatite with different amounts of hydroxyl ions, and reports on the changes in Fourier transform infrared absorption at increasing level of dehydroxylation. Detailed analysis of spectra in the 500 – 700 cm-1 range showed a peak shift for the hydroxyl ion absorption line at 632 cm-1 to 637 cm-1 and an increase in the wavenumber for the phosphate line at 575 cm-1.

Quantum chemical simulations of the optical properties and diffusion of electron centres in mgo crystals

1996

Semiempirical quantum chemical simulations have been undertaken to obtain the self-consistent atomic and electronic structure of the two basic electron defects in MgO crystals: F+ and F centres (one and two electrons trapped by an 0 vacancy, V,). The calculated absorption and luminescence energies agree well with the experimental data; the excited states of both defects are found to be essentially delocalised over nearest-neighbour cations. The activation energy for diffusion is found to increase monotonically in a series V, --f F+ --f F centre (2.50 eV, 2.72 eV and 3.13 eV, respectively).

Luminescence and Transient Optical Absorption in CdWO<sub>4</sub>

1997

Evidence for a Double Doping Regime in Nd:YAG nanopowders

2009

Nanopowders of Yttrium Aluminium Garnet doped with neodymium (Nd:YAG) were investigated by X-Ray Absorption Fine Structure (XAFS) at the Nd LIII-edge in the 1.3 - 20.8 % doping range. XANES spectra appear similar in the full range of the Nd concentration. However, a significant decrease in the white line intensity of XANES is revealed as the quantity of Nd doping ions increases. Plotting the white line intensity as a function of Nd doping ions reveals two linear trends with two different slopes, identifying a threshold value where the neodymium concentration reaches 5 at.% This experimental finding provides support for the existence of a double doping regime in Nd:YAG nanopowders.

Raman Imaging of Single Carbon Nanotubes

2000

[19] The single crystals of the Bu4NBr0.6I1.4Cl salt, were obtained by addition of IBr to a solution of Bu4NCl in ethanol at a reagent ratio of 1:0.5. Stoichiometry of the anion has been found by EDX. Based on a Raman study the anion consists of the I2Br ‐ (band at 140 cm ‐1 ), IBr2 ‐ (band at 150‐ 176 cm ‐1 ), BrICl ‐ (band at 225 cm ‐1 ), and ICl2 ‐ (band at 250‐263 cm ‐1 ) trihalide anions. [20] The X-ray diffraction data from single crystals for both trihalide salts were measured using an Enraf Nonius CAD4 diffractometer with graphite monochromatic Mo Ka radiation (k = 0.71073 a) at room temperature. Unit cell parameters of the new a¢¢¢- crystal were determined from a leastsquares analy…

XAFS study of short range order in the heavily disordered MoxW1−wO3 oxides

1995

We have done comparative XAFS analysis on the MoK and WL 3 edges of polycrystalline Mo x W 1-x O 3 solid solutions. It was found that their structures are closely related to corner-shared WO 3 -type for x<0.9 while α-MoO 3 -type structure is present for x≥0.9. The obtained structural parameters for the first shell around metal ions allow to distinguish several structural phase transitions due to the change of composition. A set of subshells within the first shell was found, and they are in good agreement with Raman data

Sorption properties of torrefied wood and charcoal

2014

AbstractPre-treating biomass by torrefaction is assumed to improve the material's storage properties because of reducing hydrophilicity. In order to assess the effect of sorption on storage properties, the adsorption of water vapour and capillary absorption of liquid water in torrefied and charred spruce and birch were studied. In addition, the chemical changes were evaluated through Fourier Transform Infrared (FT-IR) spectroscopy. Adsorption decreased notably as severity of treatment increased, as was expected due to degradation of the wood constituents, namely hemicelluloses and amorphous cellulose. Capillary absorption increased with increasing severity in spruce samples while birch show…

Hygrothermal ageing of reprocessed polylactide

2012

[EN] The influence of an accelerated hygrothermal ageing simulation test on a commercial PLA and its three subsequent mechanically-reprocessed materials was studied. The analysis was focused on the water diffusion kinetics and the physico-chemical changes induced by the hygrothermal degradation. Water diffusion proceeded faster than chain relaxation processes, as defined by a Case II absorption model. It was proved that the water diffusion rate decreased with subsequent reprocessing cycles and increased with higher hygrothermal ageing temperatures. Hydrolytic chain scission provoked significant molar mass decays and consequent general losses of thermal and mechanical performance. The rearra…

Probing the Size Effect of Co2FeGa-SiO2@C Nanocomposite Particles Prepared by a Chemical Approach

2010

In this contribution, we report the chemical synthesis of carbon coated, silica supported Co2FeGa (Co2FeGa-SiO2@C) nanocomposite particles. The particle size of Co2FeGa particles can be tuned by varying the amount of silica supports. The dependences of the crystal structure and magnetic properties on particle size have been investigated by synchrotron radiation based X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, transmission electron microscope (TEM), 57Fe Mossbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co2FeGa Heusler nanoparticles is found to be ∼17 nm by correlating the TEM derived par…