299,474 research outputs found
Using combined XRD-XRF analysis to identify meteorite ablation debris
In this research paper, X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectrometry has been used to determine the mineralogical and elemental composition of a stone sample recovered from a location near village Lehri in district Jhelum, Pakistan. The test data is compared with previous findings (as reported in literature and included in references) to identify this sample stone as part of a meteorite ablation debris
X-ray diffraction as a tool for the determination of the structure of double-walled carbon nanotube batches
The average structure of double-walled carbon nanotube DWCNT samples can be determined by x-ray diffraction XRD. We present a formalism that allows XRD patterns of DWCNTs to be simulated and we give researchers the tools needed to perform these calculations themselves. Simulations of XRD patterns within this formalism are compared to experimental data obtained on two different DWCNT samples, produced by chemical vapor deposition or by peapod conversion i.e., high-temperature peapod annealing. For each sample, we are able to determine structural aspects such as the number of walls, the diameter distribution of inner and outer tubes, the intertube spacing, and the bundled structure
Surface versus bulk characterization of the electronic inhomogeneity in a VO_{2} film
We investigated the inhomogeneous electronic properties at the surface and
interior of VO_{2} thin films that exhibit a strong first-order metal-insulator
transition (MIT). Using the crystal structural change that accompanies a VO_{2}
MIT, we used bulk-sensitive X-ray diffraction (XRD) measurements to estimate
the fraction of metallic volume p^{XRD} in our VO_{2} film. The temperature
dependence of the p was very closely correlated with the dc
conductivity near the MIT temperature, and fit the percolation theory
predictions quite well: (p - p_{c})^{t} with t = 2.00.1
and p_{c} = 0.160.01. This agreement demonstrates that in our VO
thin film, the MIT should occur during the percolation process. We also used
surface-sensitive scanning tunneling spectroscopy (STS) to investigate the
microscopic evolution of the MIT near the surface. Similar to the XRD results,
STS maps revealed a systematic decrease in the metallic phase as temperature
decreased. However, this rate of change was much slower than the rate observed
with XRD, indicating that the electronic inhomogeneity near the surface differs
greatly from that inside the film. We investigated several possible origins of
this discrepancy, and postulated that the variety in the strain states near the
surface plays an important role in the broad MIT observed using STS. We also
explored the possible involvement of such strain effects in other correlated
electron oxide systems with strong electron-lattice interactions.Comment: 27 pages and 7 figure
XRD and EDS Investigations of Metal Matrix Composites and Syntactic Foams
Metal matrix composites (MMCs) of different composition were produced and
investigated by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS)
analysis. Firstly unidirectionally reinforced MMCs were produced using two type
carbon fibre reinforcement and commercial purity aluminium matrix. In MMCs the
interface layer has significant effect on the mechanical properties of the composites
therefore need to be correctly explored. The investigations showed chemical
composition changes in the composites, especially at the interface layers. In the case
of carbon fibre reinforced composites Al4C3 phase was formed. The amount of Al4C3
depended on the temperature and the time at temperature of the composite during
production and on the quality of carbon fibres. As the second investigated MMC, SiC
fibre reinforced aluminium matrix composite wires were produced by continuous
pressure infiltration. In SiC reinforced MMC wires the effect of interface diffusion was
observed. After long term thermal ageing at 300°C alumina was formed and Si and Ti
of SiC fibres moved into the matrix. Finally, metal matrix syntactic foams were
manufactured which are particle-reinforced composites, but also known as porous
materials (foams), because they contain high amount of hollow ceramic
microspheres. Four type hollow spheres from different suppliers with different
chemical composition and mean diameters were used. In syntactic foams an
exchange reaction took place between the aluminium alloy matrix and the Si content
of ceramic inclusions. The reaction resulted in significant alumina formation
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