3,192 research outputs found
Transmission X-ray microscopy : a new tool in clay mineral floccules characterization
No full textEffective flocculation and dewatering of mineral processing streams containing clays are microstructure dependent in clay-water systems. Initial clay flocculation is crucial in the design and for the development of a new methodology of gas exploitation. Microstructural engineering of clay aggregates using covalent cations and Keggin macromolecules have been monitored using the new state of the art Transmission X-ray Microscope (TXM) with 60 nm tomography resolution installed in a Taiwanese synchrotron. The 3-D reconstructions from TXM images show complex aggregation structures in montmorillonite aqueous suspensions after treatment with Na+, Ca2+ and Al13 Keggin macromolecules. Na-montmorillonite displays elongated, parallel, well-orientated and closed-void cellular networks, 0.5–3 μm in diameter. After treatment by covalent cations, the coagulated structure displays much smaller, randomly orientated and openly connected cells, 300–600 nm in diameter. The average distances measured between montmorillonite sheets was around 450 nm, which is less than half of the cell dimension measured in Na-montmorillonite. The most dramatic structural changes were observed after treatment by Al13 Keggin; aggregates then became arranged in compacted domains of a 300 nm average diameter composed of thick face-to-face oriented sheets, which forms porous aggregates with larger intra-aggregate open and connected voids
Improve QoS of Mobile Multimedia Streaming via Cross-Layer Predictive Packet Transmission over MIPv4
No full textMicrostructural evolution and microhardness variations in a Cu–36Zn–2Pb alloy processed by high-pressure torsion
No full textA coarse-grained Cu–36Zn–2Pb alloy with an initial grain size of ~54 µm was processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa through 1–10 turns, and the evolution of microstructure and microhardness was investigated. Analysis by X-ray diffraction (XRD) showed that in HPT processing the β'-phase transforms to an α-phase and a {111} texture is formed. Microscopic examination showed that dislocations were first formed at equivalent strains of not more than ~25 and when the equivalent strain increased to ~40 there was evidence for twins and secondary twinning. Fine grains were formed with an increase in equivalent strain to ~100 and with further straining these refined grains acted as precursors for additional grain refinement. The refined equiaxed grain size was ~250 nm after HPT through an equivalent strain of ~100 and the results show the microhardness reached a saturation value of ~220 Hv
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View synthesis for kinetic depth X-ray imaging
No full textThis thesis reports the development and analysis of feature based synthesis of transmission X-ray images. The synthetic imagery is formed through matching and morphing or warping line-scan format images produced by a novel multi-view X-ray machine. In this way video type sequences, which periodically alternate between synthetic and detector based views, may be formed. The purpose of these sequences is to provide depth from motion or kinetic depth effect (KDE) in a visual display; while the role of the synthesis is to reduce the total number of detector arrays, associated collimators and X-ray flux per inspection. A specific challenge is to explore the bounds for producing synthetic imagery that can be seamlessly introduced into the resultant sequences. This work is distinct from the image collection and display technique, termed KDEX, previously undertaken by the Imaging Science Group at NTU. The ultimate aim of the research programme in collaboration with The UK Home Office and The US Dept. of Homeland Security is to enhance the detection and identification of threats in X-ray scans of luggage. A multi-view „KDEX scanner‟ was employed to collect greyscale and colour coded image sequences of 30 different bags; each sequence comprised of 7 perspective views separated from one another by 10. This imagery was organised and stored in a database to enable a coherent series of experiments to be conducted. Corresponding features in sequential pairs of images, at various different angular separations, were identified by applying a scale invariant feature transform (SIFT)
High thermal stability of high indium content InGaN films grown by pulsed laser deposition
No full textThermal stability on the structural and optical properties of high
indium content InGaN films grown using pulsed laser deposition (PLD) was
investigated through long-duration and high-temperature annealing. X-ray
diffraction and cathode- luminescence measurements of the 33% indium
InGaN revealed no differences in the line-shape and peak position even after
annealing at 800�C for 95 min; similar structural stability was found for the
60% samples after annealing for 75 min. The higher thermal stability is
attributed to nanoscale InN domains with different orientations create
mixed-polarity InGaN/InN interfaces, resulting in higher activation energies
at interfaces and increasing the thermal stability of the material. Furthermore,
the InGaN films were subjected to metalorganic chemical vapor deposition
treatment to regrow a GaN layer; results are promising for the development
of high thermal stability InGaN films using the PLD technique
Effects of eutectic modifier and high-pressure torsion processing on microstructure and corrosion resistance of hypoeutectic Al-7Si alloy
No full textHigh-pressure torsion (HPT) has recently been proven as an effective technique to produce bulk ultrafine-grained materials. Both strontium-modified and unmodified Al-7Si alloys were processed by HPT under an applied pressure of 6.0 GPa for different numbers of torsional revolutions and then exposed to a 3.5 wt.% NaCl solution for open-circuit potential measurements followed by electrochemical impedance spectroscopy and potentiodynamic polarization curve tests. The results exhibit that corrosion resistance of both Al-7Si and Al-7Si-Sr alloys in NaCl solution is enhanced upon high torsion strains of HPT processing compared with that of the as-received sample, but the improvement in corrosion resistance for Al-7Si alloy is more significantly than the Sr-modified alloy, which is possibly due to the increased HPT-induced active sites, the homogenous microstructure and the breakage of brittle coarse silicon particles and intermetallic phases demonstrated by microstructure and microhardness measurements. The corroded samples were further characterized with scanning electron microscopy and energy dispersive X-ray spectroscopy to examine the effect of grain refinement on corrosion mechanism of the Al-7Si alloy
Regioselective addition of chalcogenol to an η3-propargyl/allenyl complex via formation of the carbon-chalcogen bond leading to new chalcogenoxyallyl species
No full textMicrohardness and corrosion properties of hypoeutectic Al-7Si alloy processed by high-pressure torsion
No full textHigh-pressure torsion (HPT) was used to produce hypoeutectic Al-7Si alloy samples having a range of microstructures to investigate the effect of the grain refinement on its corrosion behaviour in 3.5 wt. % NaCl solution for the first time. Optical microscopy measurements reveal that with the HPT processing increased from 1/4 to 10 revolutions under an applied pressure of 6.0 GPa, brittle coarse silicon particles and intermetallic phases were effectively broken into ultrafine-grained particles and redistributed homogeneously into the Al-rich matrix. Open-circuit potential and polarization curves results exhibit that corrosion resistance of the Al-7Si alloy in NaCl solution was significantly enhanced upon high torsion strains, with corrosion rate reduced from 7.41 ?m y–1 for the as-received sample to 1.68 ?m y–1 for the 10-turn processed sample. Electrochemical impedance spectroscopy analysis combined with characterization of the corroded samples using scanning electron microscopy and energy dispersive X-ray spectroscopy indicates that the enhancement in corrosion performance of the Al-7Si alloy is due to the breakage of coarse silicon particles and intermetallic phases, the microstructure homogeneity and the increased HPT-induced active sites. It is demonstrated that microstructure refinement through HPT processing can significantly improve both microhardness and corrosion properties of the Al-7Si alloy
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