11,298 research outputs found
Magnetic proximity-enhanced Curie temperature of Cr-doped Bi2Se3 thin films
Full text linkBeam time awarded on ID32 at the ESRF (Proposal No. HC-1282) and on I10 at the Diamond Light Source (Proposal No. SI-10207) are acknowledged. T.H. acknowledges the John Fell Oxford University Press (OUP) Research Fund. A.A.B. was supported by Diamond Light Source and together with L.J.C.M. by EPSRC through Doctoral Training Awards.We report a study on the transition temperature TC of Cr-doped topological insulator thin films, where an increase in the ferromagnetic onset can provide a pathway towards low-power spintronics in the future. Arrott plots, measured by surface-sensitive x-ray magnetic circular dichroism at the Cr L2,3 edge as a function of field at various low temperatures, give a TC ≈ 7K for the pristine surface. This is comparable to the bulk value of the film, which means that there is no indication that the spontaneous magnetization is different near the surface. Evaporation of a thin layer of Co onto the pristine surface of the in-situ cleaved sample increases the ordering temperature near the surface to ∼19K, while in the bulk it rises to ∼10K. X-ray absorption spectroscopy shows that Cr enters the Bi2Se3 host matrix in a divalent state, and is unchanged by the Co deposition. These results demonstrate a straightforward procedure to increase the transition temperature of doped topological insulators.Peer reviewe
Electron Microscopy Characterization of Ni-Cr-B-Si-C Laser Deposited Coatings
Full text linkDuring laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.
Review of Creep Cavitation and Rupture of Low Cr Alloy and its Weldment
Full text linkThis paper presents a review of creep cavitation and rupture of low Cr alloy and its weldment, particular in the heat-affected zone (HAZ). Creep damage is one of the serious problems for the high temperature industry. One of the computational approaches is continuum damage mechanics which has been developed and applied complementary to the experimental approach and assists in the safe operation. However, the existing creep damage constitutive equations are not developed specifically for low stress. Therefore, in order to form the physical bases for the development of creep damage constitutive equation, it is necessary to critically review the creep cavitation and rupture characteristics of low Cr alloy and its weldment
Effects of Cr/Al underlayer on magnetic properties and crystallography in CoCrPtTa/Cr/Al thin films
No full textThe effects of Cr/Al underlayers on the magnetic properties of CoCrPtTa films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by using Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCrPtTa grains, and the refinement of CoCrPtTa grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCrPtTa/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCrPtTa grains
Simultaneous photocatalytic Cr(VI) reduction and 2,4,6-TCP oxidation over g-C3N4 under visible light irradiation
No full textIn this study, a rapid reduction of Cr(VI) and degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in a simultaneous manner was reported through the catalysis of g-C3N4 under visible light (lambda > 420 nm) irradiation. The effects of initial concentration of reactants, dissolved O-2 and pH value were investigated systematically. It indicated that, under the optimized concentration, the Cr(VI) reduction and 2,4,6-TCP oxidation could be accomplished in couple of hours in the presence of g-C3N4. And also, the O-2 involvement and low pH value were able to significantly improve the removal rate of Cr(VI) and 2,4,6-TCP. In addition, the reaction mechanism was investigated through monitoring the reduced states of Cr(VI) and active oxygen intermediates formed during photoreaction by ESR and XPS, as well as determining the degradation products of 2,4,6-TCP by HPLC-MS. The results supported that the redox reactions of Cr(VI) and 2,4,6-TCP can be performed simultaneously via a synergistic oxidation-reduction mechanism in the presence of g-C3N4 under visible light irradiation. (C) 2013 Elsevier B.V. All rights reserved.In this study, a rapid reduction of Cr(VI) and degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in a simultaneous manner was reported through the catalysis of g-C3N4 under visible light (lambda > 420 nm) irradiation. The effects of initial concentration of reactants, dissolved O-2 and pH value were investigated systematically. It indicated that, under the optimized concentration, the Cr(VI) reduction and 2,4,6-TCP oxidation could be accomplished in couple of hours in the presence of g-C3N4. And also, the O-2 involvement and low pH value were able to significantly improve the removal rate of Cr(VI) and 2,4,6-TCP. In addition, the reaction mechanism was investigated through monitoring the reduced states of Cr(VI) and active oxygen intermediates formed during photoreaction by ESR and XPS, as well as determining the degradation products of 2,4,6-TCP by HPLC-MS. The results supported that the redox reactions of Cr(VI) and 2,4,6-TCP can be performed simultaneously via a synergistic oxidation-reduction mechanism in the presence of g-C3N4 under visible light irradiation. (C) 2013 Elsevier B.V. All rights reserved
Predicting the geographical distribution of plant communities in complex terrain: a case study in Fushian Experimental Forest, northeastern Taiwan.
No full textIdentifying the scale thresholds for field-data extrapolation via spatial analysis of landscape gradients.
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