Search results for "Aluminium"
showing 10 items of 548 documents
Ultraplāni anodēta alumīnija oksīda pārklājumi un to pielietojumi
2014
1 ANOTĀCIJA Ultraplāni anodēta alumīnija oksīda pārklājumi un to pielietojumi. Raimonds Popļausks, zinātniskais vadītājs Dr. ķīm. Donāts Erts. Promocijas darbs veltīts aktuālām problēmām par ultraplāna anodētā alumīnija oksīda pārklājumu iegūšanu uz dažādām virsmām un to pielietojumiem. Darbā izstrādātas metodikas atkārtojamu liela laukuma (virs 1 cm2) ultraplānu anodētā alumīnija oksīda masku ar variējamiem poru diametriem, starpporu attālumiem un biezumiem iegūšanai un pārnešanai uz dažādām virsmām, kā arī nanodaļiņu masīvu sensoru pielietojumiem iegūšanu caur šīm maskām. Izstrādāta metode ultraplānu anodētā alumīnija oksīda masku iegūšanai lai iegūtu nanodaļiņu masīvus ar diametru zem 20…
Neutron irradiation influence on magnesium aluminium spinel inversion
2002
Abstract Grown by the Verneuil method MgO · nAl2O3 single crystals and natural spinel crystal have been studied using X-ray diffraction and photoluminescence spectra. The fast neutron irradiation of magnesium aluminium spinel leads to the lattice parameter decrease. The bond lengths of Mg–O and Al–O vary with the u-parameter and the lattice parameter. On the other hand, the bond lengths are related with the inversion parameter. Using changes of the lattice parameter during irradiation we have calculated the inversion parameter, which is 15–20%. In the luminescence spectra, the fast neutron radiation (fluence 1016 cm−2) produces an increase in the intensity ratio of the N- to R-lines by 5–20…
Actinide Sorption Studies Using the Isotopes237Np and239Np
2008
The sorption of Np(V) on γ-Al2O3 and the reference clay mineral kaolinite was studied in batch experiments in the presence and absence of ambient CO2 with 0.1 M NaClO4 as background electrolyte. The short-lived isotope 239Np (t1/2 = 2.36 d) was used instead of 237Np (t1/2 = 2.14 × 106 a) to study the sorption behaviour of Np(V) at environmentally-relevant concentrations, i.e., 7 pM Np. In addition, 239Np served as tracer to measure sorption isotherms over six orders of magnitude in neptunium concentration. γ-Al2O3 served as a reference for clay minerals like kaolinite to investigate the interaction of Np(V) with aluminol groups, which are crucial binding sites of clays.
The positron distribution in a layered stack sample studied with the use of positron lifetime spectroscopy
2011
Abstract Computer simulation using GEANT4 codes indicates an enhancement of the fraction of implanted positrons stopped in the denser regions of a layered sample. However, positron lifetime measurements performed for layers of pure aluminum, silver and gold foils do not reveal this effect, indicating instead that backscattering plays an important role in determining the positron implantation profile in layered and/or heterogeneous samples.
Measurement of the beam-helicity asymmetry in photoproduction of π0η pairs on carbon, aluminum, and lead
2020
The beam-helicity asymmetry was measured, for the first time, in photoproduction of $\pi^{0}\eta$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for $\pi^{0}\eta$ pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the $D_{33}$ partial wave with the $\eta\Delta(1232)$ intermediate state.
Oxygen-related defects and energy accumulation in aluminum nitride ceramics
2001
Abstract Features of oxygen-related defects in the AlN crystalline lattice were studied. Spectral characteristics of photoluminescence and photostimulated luminescence under the UV light irradiation of AlN ceramics were examined. The results obtained allow us to propose the mechanisms of luminescence and radiation-induced energy accumulation in AlN.
Molecular dynamics simulation of the damage production in Al (110) surface with slow argon ions
1986
We have developed a molecular dynamics simulation program to gain more insight into the sputtering process, especially the damage produced by it. We have studied the sputtering of aluminium (110) surface with argon ions. The Morse pair potentail was used for Al−Al interaction, the Lennard-Jones potential for Ar−Ar interaction and both the Moliere potential and the universal potential of Ziegler et al. for Ar−Al interaction. An electronic friction term proportional to the particle velocities was also used. The studied incident argon ion energies and angles were 200 and 400 eV and 0° (normal), 25°, 45° and 75°, respectively. The calculated sputtering yield and the overall shape and the mean d…
H−ZSM-5 Modified Zeolite: Quantum Chemical Models of Acidic Sites
2007
A ZSM-5 fragment, containing 52 tetrahedral moieties, each of them formed by one silicon or one aluminum atom surrounded by four oxygen atoms, was employed to model (52T systems) by quantum chemical calculations (i) the influence of the positions of the acidic sites on the energetics of 22 aluminum monosubstituted and bisubstituted 52T acidic zeolite (H-ZSM-5) systems and (ii) the local adsorption properties and acidic strength of the corresponding -OH sites. The energetics and the structural properties of simpler acid H-ZSM-5 systems containing only five Tetrahedral moieties (5T systems) were also modeled for comparison. B3LYP/6-31G(d,p) partial geometry optimization routines were performe…
Revisiting the metallothionein genes polymorphisms and the risk of oral squamous cell carcinoma in a Brazilian population
2020
Background Metallothioneins (MTs) gene polymorphisms have been associated with the ability of free radical scavenging and detoxification of heavy metals leading to cancer development. Our aim was to revisit, in a Brazilian population, single-nucleotide polymorphisms (SNPs) of the MT gene family previously associated with oral squamous cell carcinoma (OSCC). Material and Methods A case-control investigation with 28 OSCC patients and 45 controls was conducted, using conventional risk factors (tobacco use and alcohol consumption) as covariates. SNPs genotyping for rs8052334 (MT1B), rs964372 (MT1B), and rs1610216 (MT2A) was performed by PCR-RFLP, and SNPs for rs11076161 (MT1A) were analyzed by …
Surface modifications induced by pulsed-laser texturing—Influence of laser impact on the surface properties
2014
Abstract Laser cleaning technology provides a safe, environmentally friendly and very cost effective way to improve cleaning and surface preparation of metallic materials. Compared with efficient cleaning processes, it can avoid the disadvantages of ductile materials prepared by conventional technologies (cracks induced by sand-blasting for example) and treat only some selected areas (due to the optical fibers). By this way, laser technology could have several advantages and expand the range of thermal spraying. Moreover, new generations of lasers (fiber laser, disc laser) allow the development of new methods. Besides a significant bulk reduction, no maintenance, low operating cost, laser f…