Search results for "Microstructure"
showing 10 items of 707 documents
Reaction Sequence in the Preparation of NiAl2O4 Spinel-Mullite Composites by Sol-Gel
2005
NiAl 2 O 4 spinel-mullite composites were prepared by simultaneous replacement of Al by Ti and/or Ni in 3:2 stoichiometric mullite. Specimens having nominal compositions 3(Al 2-2x Ni x Ti x O 3 ).2SiO 2 (x = 0, 0.025, 0.05, 0.2) and 3(Al 2-x M x O 3) .2SiO 2 (M = Ni 2+ or Ti 4+ and x = 0.05) were synthesized by sol-gel techniques, which provide homogeneous gels in the SiO 2 -Al 2 O 3 system. Gel structures investigated by infrared (IR) spectroscopy revealed the formation of Al-O-Si bonds in dried gels. The reaction sequence of gel-derived glasses, previously obtained by preheating gels at 750°C for 3 h, was evaluated by X-ray powder diffraction (XRD) and ultraviolet-visible (UV-vis) spectro…
Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation.
2011
Abstract In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10–15% for female adults and 1–3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni–Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni–Cr dental alloys. Microstructure characterization, corrosion r…
Design of All-Normal Dispersion Microstructured Optical Fiber on Silica Platform for Generation of Pulse-Preserving Supercontinuum Under Excitation a…
2017
We investigated numerically the possibility of all normal dispersion fiber design for near-infrared supercontinuum generation based on a standard air-silica microstructure. The design procedure includes finding of target dispersion profile and subsequent finding of appropriate geometrical fiber design by inverse dispersion engineering. It was shown that the tailoring of dispersion profile could increase the spectral width of generated supercontinuum while maintaining perfect spectral flatness. Conditions necessary for wide and flat supercontinuum generation as well as restrictions imposed by chosen materials were discussed. As a result of design and optimization procedure, an air-silica des…
High magnification SEM observations for two types of granularity in a high burnup PWR fuel rim
1998
Abstract Rim microstructure of an UO2 pellet irradiated up to 61 GWd/tU, observed with high magnification scanning electron microscopy, presented two types of subgrains: polyhedral and round subgrains. Round subgrains were also observed on the surface of fabrication pores along the pellet radius. These round-shaped subgrains seem to be associated to free surface rearrangement. This new type of round subgrains was proved to be independent of the rim effect. Observations of the fuel structure in the vicinity of rim area evidenced two types of defects specific to rim effect: planar defects and small intergranular pores. Hypothesis is made that the accumulation of planar defects could generate …
Optical frequency domain reflectometer distributed sensing using microstructured pure silica optical fibers under radiations
2016
International audience; We investigated the capability of micro-structured optical fibers to develop multi-functional, remotely-controlled, Optical Frequency Domain Reflectometry (OFDR) distributed fiber based sensors to monitor temperature in nuclear power plants or high energy physics facilities. As pure-silica-core fibers are amongst the most radiation resistant waveguides, we characterized the response of two fibers with the same microstructure, one possessing a core elaborated with F300 Heraeus rod representing the state-of-the art for such fiber technology and one innovative sample based on pure sol-gel silica. Our measurements reveal that the Xray radiations do not affect the capaci…
ODS ferritic steels obtained from gas atomized powders through the STARS processing route: Reactive synthesis as an alternative to mechanical alloying
2018
Authors acknowledge ALBA synchrotron (Spain) for the provision of beamtime on the beam line BL22-CLAESS (Proposal 2016081797). Transmission electron microscopy observations were accomplished at Centro Nacional de Microscopía Electrónica, CNME-UCM. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Financial support from Basque Government through the ELKARTEK ACTIMAT 2016 project is also acknowledged.
Radiation defects in doped alkali halide microstructures
2000
Abstract Photostimulated luminescence (PSL) has been measured in KBr and KI systems doped with Tl and In. The size of grains in microstructures varied from 0.1 to 1.0 μm. Specifics of the photostimulated luminescence mechanisms in these systems are analysed from the viewpoint of their application in miniaturized optoelectronic and photonic devices, including optical chips.
Construction of two large-size four-plane micromegas detectors
2015
We report on the construction and initial performance studies of two micromegas detector quadruplets with an area of 0.5 m$^2$. They serve as prototypes for the planned upgrade project of the ATLAS muon system. Their design is based on the resistive-strip technology and thus renders the detectors spark tolerant. Each quadruplet comprises four detection layers with 1024 readout strips and a strip pitch of 415 $\mu$m. In two out of the four layers the strips are inclined by $\pm$1.5$^{\circ}$ to allow for the measurement of a second coordinate. We present the detector concept and report on the experience gained during the detector construction. In addition an evaluation of the detector perfor…
The role of yttrium and titanium during the development of ODS ferritic steels obtained through the STARS route: TEM and XAS study
2018
Abstract Oxide Dispersion Strengthened Ferritic Steels (ODS FS) are candidate materials for structural components in future fusion reactors. Their high strength and creep resistance at elevated temperatures and their good resistance to neutron radiation damage is obtained through extremely fine microstructures containing a high density of nanometric precipitates, generally yttrium and titanium oxides. This work shows transmission electron microscopy (TEM) and extended X-ray absorption fine structure (EXAFS) characterization of Fe-14Cr-2W-0.3Ti-0.24Y ODS FS obtained by the STARS route (Surface Treatment of gas Atomized powder followed by Reactive Synthesis), an alternative method to obtain O…
Experimental visualization of inoculation using a charged colloidal model system
2012
Inoculation is widely used to tune the microstructure of a polycrystalline solid from the melt and thus its material properties. We present here a systematic time resolved experimental study of inoculation in a charged colloidal model system investigating the changes of the crystallization scenario upon adding spherical seeds and show that the nucleation kinetics solely determines the resulting microstructure.