Search results for "engineering.material"
showing 10 items of 2352 documents
The effects of water absorption and salt fog exposure on agglomerated cork compressive response
2022
The replacement of synthetic foams with agglomerated cork in sandwich composites can meet the increasing environmental concerns. Its peculiar morphology and chemical composition lead to outstanding dimensional recovery that endorsed a broad investigation of its compressive behavior. The knowledge of neat material response is fundamental to obtain a reliable design dataset, but it is necessary to consider all the environmental factors (water, moisture and sunlight) that significantly modify material mechanical properties. In view of this, the present work investigates the effect of distilled and seawater absorption and salt fog exposure on the compressive behavior of two agglomerated corks w…
Electronic structure of p-type ultraviolet-transparent conducting CuScO2 films
2008
Abstract We investigate the electronic structure of CuScO 2 thin films grown on sapphire and mica substrates by pulsed laser deposition. X-ray diffraction and microanalysis confirm that the films have the expected delafossite crystal structure and stoichiometric proportions. The electronic structure is investigated by means of X-ray and ultraviolet photoelectron spectroscopy. Electronic states in the range 0–1350 eV are identified, making reference to theoretical density-of-states calculations up to 80 eV. Photoelectron spectra near the Fermi energy confirm the p-character of the films. Optical absorption spectroscopy shows that the films are transparent up to 3.7 eV and exhibit an intense …
Effects of high pressure thermal treatments in oxygen and helium atmospheres on amorphous silicon dioxide and its radiation hardness
2009
The effects of thermal treatments at similar to 400 degrees C in oxygen or helium atmospheres at similar to 180 baron the radiation hardness of amorphous SiO(2) are studied. The generation efficiency of several point defects under gamma irradiation is compared to that of the untreated material. All the effects on point defects generation here observed can be explained in terms of changes in the precursor sites. In particular it has been observed that the thermal treatments can change the precursors sites of point defects both through temperature and pressure related processes, not depending on the atmosphere, and through oxygen related processes creating oxygen excess sites. The presence of…
Optical properties of natural topaz
2013
The results of investigation of infrared, Raman and UV-Visible absorption spectra of natural topaz crystals from Ukraine before and after fast neutron irradiation are presented. We assume that the ~ 620 nm band in topaz crystals is associated with the presence of Cr 3+ , Fe 2+ and Mn 2+ impurities. The broad band with maxima at 650 cm -1 observed in Raman spectra for topaz irradiated by fast neutrons may be connected with lattice disorder. Exchange interaction between radiation defect and impurity ions during neutron irradiation leads to appearance of additional absorption band in UV-VIS spectra and bands broadening in infrared and Raman spectra of investigated crystals.
Intrinsic absorption threshold of stishovite and coesite
2004
Abstract The optical absorption spectra of the small mono-crystals samples of stishovite and coesite were studied at first. The intrinsic absorption threshold of stishovite is determined at 8.75 eV, being probably, highest in the family of different crystalline polymorph modifications of silicon dioxide. The absorption spectrum of stishovite is independent of temperature (studied in the range 290–450 K). The intrinsic absorption threshold of coesite mono-crystal situated near 8.6 eV at 293 K, coincides within experimental errors with that of α-quartz crystal, and depends on temperature, as used to be for the tetrahedron structured silicon dioxide crystalline modifications. A broad absorptio…
Channeling experiments at planar diamond and silicon single crystals with electrons from the Mainz Microtron MAMI
2020
Line structures were observed for (110) planar channeling of electrons in a diamond single crystal even at a beam energy of 180 MeV . This observation motivated us to initiate dechanneling length measurements as function of the beam energy since the occupation of quantum states in the channeling potential is expected to enhance the dechanneling length. High energy loss signals, generated as a result of emission of a bremsstrahlung photon with about half the beam energy at channeling of 450 and 855 MeV electrons, were measured as function of the crystal thickness. The analysis required additional assumptions which were extracted from the numerical solution of the Fokker-Planck equation. Prel…
The Bi sulfates from the Alfenza Mine, Crodo, Italy: An automatic electron diffraction tomography (ADT) study
2014
We report about three bismuth sulfates from mineralized quartz dikes from Alfenza (Crodo, Italy), two new phases and a rare mineral, cannonite, all growing on bismuthinite. The first new phase occurs as white, "hortensia-like" aggregates of pseudo-hexagonal platelets, with perfect basal cleavage, similar to 20 mu m wide and few micrometers thick. The approximate composition is Bi2O2(SO4), and cell parameters and symmetry, as determined by automatic diffraction tomography, are a = 22.0(4), b = 16.7(3), c = 15.9(3) angstrom, beta = 102.9(5)degrees, space group Pc or P2/c. A major stacking disorder is detected by HR-SEM images and electron diffraction data.The second new phase was detected onl…
Ferro-pedrizite, NaLi2(Fe2+ 2Al2Li)Si8O22(OH)2, a new amphibole-supergroup mineral from the Sutlug pegmatite, Tyva Republic, Russia
2015
Ferro-pedrizite, a new amphibole-supergroup mineral was discovered in the Sutlug pegmatite occurrence situated in the Targi River Basin, Tyva Republic, Eastern Sibera, Russia. The associated minerals are quartz, albite, microcline, spodumene, cassiterite, beryl, columbite-(Mn), fergusonite-β-(Y), fluorapatite, schorl, trilithionite and fluorite. Ferro-pedrizite forms dark grey-blue to violet-blue acicular and long prismatic crystals up to 2 × 5 × 50 mm and their aggregates. D meas = 3.16(1) g/cm3 (by hydrostatic weighing), 3.13(1) g/cm3 (by flotation in heavy liquids); D calc = 3.135 g/cm3. Ferro-pedrizite is optically biaxial (−), α = 1.614(3), β = 1.638(3), γ = 1.653(3), 2 V meas = 75(5)°…
Geochemistry of REE, Zr and HF in a wide range of pH and water composition: The Nevado del Ruiz volcano hydrothermal system (Colombia)
2015
International audience; The geochemical behaviour of Rare Earth Elements, Zr and Hf was investigated in the thermal waters of Nevado del Ruiz volcano system. A wide range of pH, between 1.0 and 8.8, characterizes these fluids. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The important role of the pH and the ionic complexes for the distribution of REE, Zr and Hf in the aqueous phase was evidenced. The pH rules the precipitation of authigenic Fe and Al oxyhydroxides producing changes in REE, Zr, Hf amounts and strong anomalies of Cerium. The precipitation of alunite and jarosite removes LREE from the solution, changing the REE distribution in acidic waters.Y–Ho and Z…
Electronic properties of Co2MnSi thin films studied by hard x-ray photoelectron spectroscopy
2009
This work reports on the electronic properties of thin films of the Heusler compound Co2MnSi studied by means of hard x-ray photoelectron spectroscopy (HAXPES). The results of photoelectron spectroscopy from multilayered thin films excited by photons of 2?8?keV are presented. The measurements were performed on (substrate/buffer layer/Co2MnSi(z)/capping layer) multilayers with a thickness z ranging from 0 to 50?nm. It is shown that high energy spectroscopy is a valuable tool for non-destructive depth profiling. The experimentally determined values of the inelastic electron mean free path in Co2MnSi increase from about 19.5 to 67?? on increasing the kinetic energy from about 1.9 to 6.8?keV. T…