Search results for "Radiation"
showing 10 items of 5298 documents
Luminescence, vibrational and XANES studies of AlN nanomaterials
2007
Abstract The paper reports comparative studies on synthesized aluminium nitride nanotubes, nanoparticles and commercially available micron-sized AlN powder using different spectroscopic techniques: cathodoluminescence measurements (CL), X-ray absorption near edge spectroscopy (XANES) and Fourier-transform infrared spectroscopy (FTIR). Crucial distinctions in CL spectra are observed for nano- and microsized aluminium nitride powders; systematic shift of the IR absorption maximum has been detected for nanostructured aluminium nitride as compared to commercial samples. Through XANES experiments on Al K-edge structural differences between nano- and bulk AlN are revealed, intensity of features i…
Semipermeable membrane to retain platinum atoms in the electrodeposition process of alpha spectrometry sources
1998
Abstract In earlier work alpha sources electrodeposited on stainless steel backings were analyzed by X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS) finding that during the electrodeposition process large quantities of platinum from the anode were deposited on the cathode surface jointly with the actinides. In the present work, a method to retain platinum atoms using an electrodeposition cell with a semipermeable membrane located between anode and cathode is proposed and tested. The XRF and RBS of alpha sources electrodeposited using this method show that there is less platinum on the stainless steel backing, thereby improving the quality of sources to be measured …
Chalcogen adsorption and surface magnetism
2000
Abstract Investigations concerning the electronic and magnetic properties of oxygen and sulfur adsorbed on magnetized surfaces were carried out by means of angle and spin resolving photoelectron spectroscopy. Iron(110), a polycrystalline iron alloy, and an amorphous metallic glass (Fe 79 B 16 Si 5 ) served as ferromagnetic substrates. Exchange splittings of the O 2p and S 3p derived levels could be detected, demonstrating a magnetic coupling between the chemisorbate and iron. This observation presents a prerequisite for an induced magnetic moment within the adsorbate overlayer. For sulfur an adsorbate-induced structure only in the minority spin channel near the Fermi level was observed whic…
Orbital mapping of carbon thin films by XANES-spectromicroscopy
2000
Abstract A laterally resolved micro-XANES study (X-ray absorption near edge structure) of amorphous carbon, hydrogen terminated CVD-diamond (100) and highly oriented pyrolytic graphite (HOPG) is presented. The results were obtained by means of a photoemission electron microscope. Using this technique the well-known spectral features of carbon in its different chemical states (sp 2 , sp 3 ) could be recorded. The sp 2 /sp 3 content of the films was extracted from the spectra. Images, taken at X-ray energies corresponding to maxima (π*, C–H*) of the unoccupied density of states in these spectra, map the lateral distribution of the different orbitals at the sample surface. This study revealed …
Thermoluminescence properties of AlN ceramics
1998
Abstract The paper describes thermoluminescence (TL) properties of AlN:Y 2 O 3 ceramics irradiated with ionising radiation. A high TL sensitivity of AlN:Y 2 O 3 ceramics to radiation encouraged a study of the AlN ceramics for application as a dosimetric material. The paper presents experimental data on: glow curve, emission spectrum, dose response, energy dependence, influence of heating rate and fading rate. The measured TL characteristics were compared with those of well-known, widely used TLDs, i.e. LiF:Mg,Ti, LiF:Mg,Cu,P and Al 2 O 3 :C. It is concluded that AlN:Y 2 O 3 ceramics showing a radiation sensitivity which is approximately 50 times greater than that of LiF:Mg,Ti is an interest…
About complexity of the 2.16-eV absorption band in MgO crystals irradiated with swift Xe ions
2020
Abstract The precise study of the accumulation and subsequent thermal annealing of the defects responsible for the complex absorption band around 2.16 eV, being under discussion in the literature for a long time, has been performed in highly pure MgO single crystals exposed to 0.23-GeV 132Xe ions with a fluence of Φ = 5 × 1011 − 3.3 × 1014 ions/cm2. Three Gaussian components with the maxima at 2.16, 2.02 and 2.40 eV have been considered as a measure of so-called D1, D2 and D3 defects. Similar to the F and F+ centers, the concentration of these defects increases at high fluences without saturation marks, thus confirming their radiation-induced nature (involvement of novel Frenkel defects). T…
Investigation of a Ge nanoparticle film by means of electron stimulated photon emission spectroscopy
2014
Abstract Electron stimulated photon emission spectroscopy was used for the study of the electronic structure of Ge nanoparticles. A nanoparticle film was prepared by thermal deposition on a quartz substrate. Photon emission was stimulated by electron bombardment at energies of several hundred electron volts. Electron field emission from a W-tip was used at tip voltage U t = 100–600 eV. A spectrometer in combination with a liquid nitrogen cooled charge-coupled device (CCD) camera was used for light detection. Light emission spectra were measured in the energy range 1.18–4.2 eV. They are characterized by features at ∼1.6 and ∼3.1 eV. A comparison with light emission spectra obtained with ano…
Electronic exchanges between adsorbed Ni atoms and TiO2(110) surface evidenced by resonant photoemission
2011
Abstract Nickel was deposited on stoichiometric TiO2(1 1 0) surface in the 0.02–2.1 equivalent monolayer (eqML) range and analyzed by means of photoemission and resonant photoemission. In the case of very low coverage (lower than 0.1 eqML), deposited nickel reacts with the surface through an electronic transfer from nickel atoms towards titanium ions. This exchange caused the filling of unoccupied Ti3d states leading to the increase of a peak in the TiO2 band gap. These states can be better characterized through resonant photoemission experiments at the Ti 3p → 3d absorption edge: for very low coverage, these states in the TiO2 band gap have resonant behavior of Ti3d electrons rather than N…
Novel epoxy formulations for high energy radiation curable composites
2005
Abstract It has been widely recognised that high energy radiation can be effectively applied to the cure of epoxy resins in applications as composite matrices or structural adhesives with improvements in product quality and/or reduction in production costs. In the presence of suitable initiators, polymerisation of epoxies occurs via cationic mechanism, thus restricting the choice of the resin system components to species which do not contain electron donor groups. The present investigation is aimed to identify suitable co-monomers to be formulated with an epoxy resin, resulting in different cure reaction kinetics and application properties of the cured resin. In particular, four different a…
Spectroscopy of an optical excited Ga doped SiO2 surface
2007
Abstract We present the first spectroscopical analysis of the Ga/SiO2 surface interaction in hot environment. This interaction gives rise to inclusions of Ga atoms inside the silica matrix that produce structural changes and modify the SiO2 optical characteristics. This paper discusses both the time- and the frequency-resolved spectra of the fluorescence emission following UV pulsed laser excitation of the so “doped” silica in the range 15,000–28,000 cm−1. The investigation is completed by the electron paramagnetic resonance (EPR) spectra of two high-purity synthetic silica samples of commercial origin after thermal treatment in presence and in absence of a Ga atmosphere.