Search results for "Metallurgy"
showing 10 items of 1419 documents
Development of a gas chromatography-mass spectrometry method for the determination of ultraviolet filters in beach sand samples
2014
An analytical method for the determination of eight fat-soluble ultraviolet (UV) filters in beach sand samples is presented for the first time. The method is based on a leaching process of the target compounds from sand samples using vortex mixer agitation and further centrifugation, followed by dispersive liquid–liquid microextraction (DLLME) of the supernatant and gas chromatography-mass spectrometry (GC-MS) analysis of the DLLME extract. The variables involved in the leaching and in the DLLME processes were studied to provide the best enrichment factors. In the first case, the leaching solvent type and volume, and the vortex mixer agitation time were studied. In the case of the DLLME, th…
Cr(III)/Cr(VI) speciation in aerosol particles by extractive separation and thermal ionization isotope dilution mass spectrometry
1997
An isotope dilution mass spectrometric (IDMS) method, using the formation of positive thermal ions, was developed for Cr(III) and Cr(VI) speciation in aerosol particles. Cr(III) and Cr(VI) spike species, enriched in 53Cr, were applied for the isotope dilution step. After leaching of filter collected aerosol samples by an alkaline solution at pH 13, species separation was carried out by extraction with a liquid anion exchanger in methyl isobutyl ketone. Cr(VI) in the organic phase was re-extracted into an ammoniacal solution and chromium was then isolated from both fractions of species by electrodeposition. Detection limits of 30 pg/m3 for Cr(III) and of 8 pg/m3 for Cr(VI) were achieved in a…
Speciation of selenium and tellurium in milk by hydride generation atomic fluorescence spectrometry
2004
A simple, fast and highly sensitive method has been developed for the differentiation of Se and Te into their (IV) and (VI) oxidation states in milk samples by HG-AFS. This procedure involves a previous leaching of milk slurries by sonication with aqua regia for 10 min. Se(IV) and Te(IV) were determined by analysis of the samples without a pre-reduction step; being total Se and Te determined after reduction with KBr. The method provides limit of detection values (LOD) of 0.012 and 0.023 ng ml−1 for Se(IV) and Te(IV) respectively. Average relative standard deviation values of 10.5%, 3.9%, 12% and 12.5% were found for the determination of Se(IV), Se(VI), Te(IV) and Te(VI) in milk samples cont…
Non-chromatographic speciation analysis of arsenic and antimony in milk hydride generation atomic fluorescence spectrometry
2003
Abstract A rapid, high sensitivity method has been developed for the determination of As(III), As(V), Sb(III) and Sb(V) in milk samples by using hydride generation atomic fluorescence spectrometry. The method is based on the leaching of As and Sb from milk through the sonication of samples with aqua regia followed by direct determination of the corresponding hydrides both before and after reduction with KI. It was confirmed by recovery experiments on spiked commercially available samples that neither the reduced nor the oxidized forms of the elements under study or mixtures of the two oxidation states were modified by the room temperature sample treatment with aqua regia. The methodologies …
Quantification of low levels of amorphous content in sucrose by hyperDSC.
2005
A method was developed for the quantification of low levels of amorphous content in sucrose with hyperDSC. The method was based on the fact that the change of specific heat at the glass transition is linearly proportional to the amorphous content. It was found out that as annealing time increased, the glass transition temperature moved to a higher temperature and the change of specific heat increased. DeltaC(p) for annealed totally amorphous sucrose was 0.761+/-0.012 Jg(-1) degrees C(-1). Synthetic mixtures with various proportions of crystalline and amorphous sucrose were prepared. The following linear regression between DeltaC(p) and amorphous content was obtained: DeltaC(p)=0.0075x - 0.0…
Structure determination of thin CoFe films by anomalous x-ray diffraction
2012
This work reports on the investigation of structure-property relationships in thin CoFe films grown on MgO. Because of the very similar scattering factors of Fe and Co, it is not possible to distinguish the random A2 (W-type) structure from the ordered B2 (CsCl-type) structure with commonly used x-ray sources. Synchrotron radiation based anomalous x-ray diffraction overcomes this problem. It is shown that as grown thin films and 300 K post annealed films exhibit the A2 structure with a random distribution of Co and Fe. In contrast, films annealed at 400 K adopt the ordered B2 structure.
A comparative study of heterostructured CuO/CuWO4 nanowires and thin films
2017
Authors are grateful to Reinis Ignatans for XRD measurements.
Mechanical and structural characterizations of gamma- and alpha-alumina nanofibers
2015
Abstract We investigate the applicability of alumina nanofibers as a potential reinforcement material in ceramic matrix compounds by comparing the mechanical properties of individual nanofibers before and after annealing at 1400 °C. Mechanical testing is performed inside a scanning electron microscope (SEM), which enables observation in real time of the deformation and fracture of the fibers under loading, thereby providing a close-up inspection of the freshly fractured area in vacuum. Improvement of both the Young's modulus and the breaking strength for annealed nanofibers is demonstrated. Mechanical testing is supplemented with the structural characterization of the fibers before and afte…
RF magnetron-sputtered coatings deposited from biphasic calcium phosphate targets for biomedical implant applications
2017
Bioactive calcium phosphate coatings were deposited by radio-frequency magnetron sputtering from biphasic targets of hydroxyapatite and tricalcium phosphate, sintered at different mass % ratios. According to Raman scattering and X-ray diffraction data, the deposited hydroxyapatite coatings have a disordered structure. High-temperature treatment of the coatings in air leads to a transformation of the quasi-amorphous structure into a crystalline one. A correlation has been observed between the increase in the Ca content in the coatings and a subsequent decrease in Ca in the biphasic targets after a series of deposition processes. It was proposed that the addition of tricalcium phosphate to th…
SPS-assisted preparation of the Magnéli phase WO2.90 for thermoelectric applications
2013
We describe the preparation and simultaneous consolidation of WO2.90 by spark plasma sintering (SPS). SPS allows for the direct manufacturing of large amounts of consolidated material. Synchrotron powder X-ray diffraction indicates that the material is single phase. Microstructure analysis indicates that the pellet is fully dense, allowing high-temperature thermoelectric properties to be reliably measured. The as-prepared samples of WO2.90 reach a ZT of 0.1 at 1100 K.