Search results for "CHROMIUM"
showing 10 items of 494 documents
Usability of Cr-Doped Alumina in Dosimetry
2019
Dosimetry is a widespread material science field dealing with detection and quantification of ionizing radiation using electronic processes in materials. One of the main aspects that determines the performance of dosimeters is the type of defects the material contains. Crystalline lattice imperfections are formed around impurity ions, which may have a smaller or larger size, or different oxidation states compared to host ions. In this study, we show what effects Cr impurities have on the luminescent properties of alumina. Porous Al 2 O 3 : Cr microceramics synthesized using the sol-gel method showed a higher thermoluminescence response than a single crystal ruby. We have found that Cr 2 O 3…
Molecular Ruby under Pressure
2018
The intensely luminescent chromium(III) complexes [Cr(ddpd)2 ]3+ and [Cr(H2 tpda)2 ]3+ show surprising pressure-induced red shifts of up to -15 cm-1 kbar-1 for their sharp spin-flip emission bands (ddpd=N,N'-dimethyl-N,N'-dipyridine-2-yl-pyridine-2,6-diamine; H2 tpda=2,6-bis(2-pyridylamino)pyridine). These shifts surpass that of the established standard, ruby Al2 O3 :Cr3+ , by a factor of 20. Beyond the common application in the crystalline state, the very high quantum yield of [Cr(ddpd)2 ]3+ enables optical pressure sensing in aqueous and methanolic solution. These unique features of the molecular rubies [Cr(ddpd)2 ]3+ and [Cr(H2 tpda)2 ]3+ pave the way for highly sensitive optical pressu…
Mechanisms Involved by Reactive Elements upon High Temperature Chromia Scale Growth
2001
The influence of Y 2 O 3 , Pr 2 O 3 , Nd 2 O 3 , Sm 2 O 3 and Yb 2 O 3 coatings on Fe-30Cr alloy oxidation behaviour was investigated at 1000°C in air under atmospheric pressure. Isothermal exposures indicated that the Y 2 O 3 coating was the most protective after 100 hours. Pr 2 O 3 , Nd 2 O 3 and Sm 2 O 3 coatings were less effective, but the less beneficial effect was observed when Yb 2 O 3 coating was applied onto the Fe-Cr alloy surface. Two-stage oxidation experiments in 16 O 2 and then 18 O 2 were performed to get information about the chromia growth phenomena with and without reactive elements. The 18 O-tracer distribution was determined by secondary ion mass spectrometry (SIMS) and…
Photoelectrochemical monitoring of rouging and de-rouging on AISI 316L
2017
Electrochemical conditions for inducing rouging on surface of AISI 316L in quasi neutral aqueous solution are studied. Potentiostatic polarization at 0.6 V vs. SSC at pH ∼ 7 allowed growth of colourless passive films with a band gap slightly lower than that estimated for the oxide grown on the SS surface by air exposure due to chromium dissolution. Under stronger anodic polarization (UE = 1.5 V vs. SSC) coloured passive films are formed, mainly constituted by iron oxide according to their band gap (Eg = 2.0 eV). Etching in citric acid at 60 °C results to be effective in removing rouging.
Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr(III) passivation baths
2014
[EN] Conversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and e…
Magneto-Optical Properties of Electrodeposited Thin Films of the Molecule-Based Magnet Cr5.5(CN)12·11.5H2O
2011
Prof. E. Coronado , M. Makarewicz , J. P. Prieto-Ruiz , Dr. H. Prima-Garcia , Dr. F. M. Romero Instituto de Ciencia Molecular (ICMol) Universitat de Valencia C/Catedratico Jose Beltran, 2, 46980-Paterna, Spain E-mail: eugenio.coronado@uv.es; helena.prima@uv.es; fmrm@uv.es
Fabrication and characterization of chromium based single-electron transistors with evaporated chromium oxide barrier tunnel junctions
1999
We fabricated chromium based single-electron transistors comprising small-area Cr/CrOx/Cr tunnel junctions with an evaporated chromium oxide barrier. The transistors are fabricated using e-beam lithography with a bilayer resist and two-angle shadow evaporation. We describe the fabrication process and discuss the device characteristics.
MICRO-SCALE STUDY OF RESIDUAL STRESSES IN CR2O3 COATINGS SPRAYED BY APS
2020
International audience; Whichever the application field, every material forming process generates residual stresses on the surface. While they are likely to enhance the aimed properties of the final mechanical part, these stresses may also drastically reduce them and result in early failures. Therefore, understanding the residual stress state remains a major challenge when coating complex parts, especially as most characterization methods at the microscopic scale involve specific sample preparation procedures which may affect the residual stresses field. This work investigates the residual stress state that exists in chromium oxide coatings deposited via Atmospheric Plasma Spray (APS), usin…
Influence of long-term ageing in solution containing chloride ions on the passivity and the corrosion resistance of duplex stainless steels
2011
Abstract The influence of long-term ageing in NaCl on the passivity and the electrochemical behavior of UNS S32304 is studied. The passive film thickness, the Cr/Fe ratio and the chloride content were significantly increased after ageing. The chloride distribution depends on residual stresses, sample microstructure and surface preparation. Local electrochemical measurements revealed that pitting potentials are between 250–550 mV vs. SCE after electropolishing. The higher the chloride content, the lower the local pitting potential. It was also shown that the presence of chloride was balanced by the enrichment in chromium after ageing. Then no pitting potential could be measured.
Evaluation of a new Cr-free alloy as interconnect material for hydrogen production by high temperature water vapour electrolysis: Study in cathode at…
2012
International audience; For economic and ecological reasons, hydrogen is considered as a major energetic vector for the future. Hydrogen production via high temperature water vapour electrolysis (HTE) is a promising technology. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800 degrees C enables the use of metallic materials as interconnects. High temperature corrosion behaviour and electrical conductivity of a new Cr-free Fe-Ni-Co alloy were tested in cathode atmosphere (H-2/H2O) at 800 degrees C. The alloy exhibits a poor oxidation resistance but an excelle…