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31.
S.J.C. Irvine A. Stafford M.U. Ahmed P. Prete R. Berrigan 《Progress in Crystal Growth and Characterization of Materials》1997,35(2-4):177-206
The development of II–VI MOVPE is reviewed, contrasting the narrow bandgap materials with the wide bandgap. Common issues are the need to grow the layers at lower temperatures than their III–V cousins in order to avoid point defects. This means that II–VI MOVPE occurs in a surface kinetic regime for precursor decomposition and has stimulated a lot of research on alternative precursors. The narrow bandgap II–VI growers have settled on dimethyl cadmium (DMCd) combined with diisopropyl telluride (DIPTe) and a liquid Hg source but wide bandgap growers are split between pyrolytic and photo-assisted growth. Recent progress in p-type doping has enabled the demonstration of some new devices, including two colour infrared detectors and the first MOVPE grown green emitting laser structure. The common theme appears to be hydrogen passivation of the Group V dopant and some novel precursor solutions to this problem are discussed. 相似文献
32.
Clayton HJ Harding LP Irvine JP Jeffery JC Riis-Johannessen T Laws AP Rice CR Whitehead M 《Chemical communications (Cambridge, England)》2008,(1):108-110
The reaction of a potentially tetradentate bis(pyridyl-thiazole) ligand with acetone is allosterically activated upon complexation with Cd(II) but deactivated by reaction with Cu(I), demonstrating metal-specific allosteric controlled reactivity. 相似文献
33.
Ruiz-Morales JC Canales-Vázquez J Savaniu C Marrero-López D Núñez P Zhou W Irvine JT 《Physical chemistry chemical physics : PCCP》2007,9(15):1821-1830
A new SOFC anode material based upon oxygen excess perovskite related phases has been synthesised. The material shows better electrochemical performance than other alternative new anodes and comparable performance to the state-of-art of the electrodes, Ni-YSZ cermets, under pure hydrogen. Furthermore, this material shows an enhanced performance under methane operation with high open circuit voltages, i.e. 1.2-1.4 V at 950 degrees C, without using steam excess. The effect of the anode configuration was tested in one and four layer configurations. The optimised electrode polarisation resistances were just 0.12 ohm cm(2) and 0.36 ohm cm(2), at 950 degrees C, in humidified H(2) and humidified CH(4), respectively. Power densities of 0.5 W cm(-2) and 0.35 W cm(-2) were obtained in the same conditions. A very low anodic overpotential of 100 mV at 1 A cm(-2) was obtained under humidified H(2) at 950 degrees C. Samples were tested for two days in reducing and oxidising conditions, alternating heating and cooling processes from 850 degrees C to 950 degrees C, showing stable electrode performance and open circuit voltages. The results show that the substituted strontium titanates are very promising anode materials for SOFC. 相似文献
34.
Apatite is a mineral with general formula M10(XO4)6Z2, where M are metallic elements such as Li+, Na+, K+, Ca2+, Sr2+, Ba2+, Ln3+ etc.; X=P, V, S, Si, Ge, Re, Cr etc; Z=F−, Cl−, I−, OH−, O2−, S2− etc. Some materials with apatite structure (S.G. P63/m) exhibit quite high cationic (Li+, H+ etc.) and/or anionic (F−, Cl− etc.) conduction. Recently, it was reported that some rare earth silicates, e.g., La10(SiO4)6O3, exhibit quite high oxide-ion conductivity. In this paper, we discuss chemical composition, structure, synthetic procedure
and ionic conduction of apatite-type materials. Recent improvements are briefly reviewed. High ionic conductivity has been
observed for both cation deficient, oxygen stoichiometric La9.33(SiO4)6O2 and cation stoichiometric, oxygen excess La10(SiO4)6O3 compositions. Grain boundary conductivity is usually low, which tends to dominate the impedance response. The resistance,
particularly the grain boundary resistance is also found to depend on pO2.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
35.
36.
K.Y. Wang A.C. Irvine C.T. Foxon D.A. Williams 《Journal of magnetism and magnetic materials》2009,321(8):971-973
We have studied current-driven domain wall motion in modified Ga0.95Mn0.05As Hall bar structures with perpendicular anisotropy by using spatially resolved polar magneto-optical Kerr effect microscopy and micromagnetic simulation. Regardless of the initial magnetic configuration, the domain wall propagates in the opposite direction to the current with critical current of 1-2×105 A/cm2. Considering the spin-transfer torque term as well as various effective magnetic field terms, the micromagnetic simulation results are consistent with the experimental results. Our simulated and experimental results suggest that the spin-torque rather than Oersted field is the reason for current-driven domain wall motion in this material. 相似文献
37.
Single phase polycrystalline BaZr0.3Ce0.5Y0.1Yb0.1O3 - δ electrolyte material was prepared by solid state reaction route. Rietveld analysis of the XRD data confirms the tetragonal symmetry in the I4/mcm space group with unit cell parameters of a = b = 6.0567(3) Å and c = 8.5831(5) Å. The addition of ZnO as a sintering additive was found to reduce the sintering temperature and enhance both overall sinterability and grain growth. Sintering temperature was reduced by 200–300 °C, and a very high relative density of about 98% was achieved at 1400 °C. Impedance spectroscopy in humidified 5% H2/Ar atmosphere shows that the protonic conductivity at 600 °C was 8.60 × 10?3 S cm?1. Thermal analysis performed in pure CO2 atmosphere shows very good chemical stability up to 1200 °C. Good biaxial flexure strength of 100–200 MPa was reported which makes this material a promising electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs). 相似文献
38.
Li2SnO3 has been synthesized at 1000 °C from Li2CO3 and SnO2 (high temperature form - HT) and it has also been prepared from ball-milled SnO2 and Li2CO3 at 650 °C (low temperature form - LT). The Li2SnO3 materials have been tested as a negative electrode for possible use in a Li-ion cell and their electrochemical behaviour
has been compared with that of SnO2. In theory, Li2SnO3 and SnO2 should be able to cycle the same number of lithium atoms per tin atom but on the initial discharge SnO2 has inserted more lithium than Li2SnO3. During the initial discharge of SnO2 and Li2SnO3, a side electrochemical reaction seems to be occurring. The resultant compound apparently inserts lithium reversibly for
potentials around 1 V; however, cycling from 0.02–2 V significantly degrades performance compared to 0.02–1 V. Li2SnO3 (HT) allows the de-insertion of more lithium than Li2SnO3 (LT) and SnO2 in the first charge.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
39.
Jean‐Marc Behr Scott Alexander Irvine Chaw‐Su Thwin Ankur Harish Shah Min‐Chul Kraun Bae Eyal Zussman Subbu Venkatraman 《Macromolecular bioscience》2020,20(3)
Mechanical mismatch between vascular grafts and blood vessels is a major cause of smaller diameter vascular graft failure. To minimize this mismatch, several poly‐l ‐lactide‐co‐ε‐caprolactone (PLC) copolymers are evaluated as candidate materials to fabricate a small diameter graft. Using these materials, tubular prostheses of 4 mm inner diameter are fabricated by dip‐coating. In vitro static and dynamic compliance tests are conducted, using custom‐built apparatus featuring a closed flow system with water at 37 °C. Grafts of PLC monomer ratio of 50:50 are the most compliant (1.56% ± 0.31?mm Hg?2), close to that of porcine aortic branch arteries (1.56% ± 0.43?mm Hg?2), but underwent high continuous dilatation (87 µm min?1). Better matching is achieved by optimizing the thickness of a tubular conduit made from 70:30 PLC grafts. In vivo implantation and function of a PLC 70:30 conduit of 150 µm wall‐thickness (WT) are tested as a rabbit aorta bypass. An implanted 150 µm WT PLC 70:30 prosthesis is observed over 3 h. The recorded angiogram shows continuous blood flow, no aneurysmal dilatation, leaks, or acute thrombosis during the in vivo test, indicating the potential for clinical applications. 相似文献
40.
In the reducing atmosphere of the SOFC anode at operating temperatures of 800 °C and above Nb2TiO7 is reduced to Nb1.33Ti0.67O4. This material displays very high electronic conductivity of >100 Scm−1, suitable for use in such applications as a current collector. It has a low thermal expansion coefficient of 3 × 10−6 K−1, however, which may cause problems due to mismatch with other SOFC components, e.g. YSZ. Doping with Fe2O3 successfully increased the thermal expansion to a maximum of 6 × 10−6 K−1. A conductivity of 140 Scm−1 at 900 °C in dry 5% H2/Ar, with an activation energy of 0.18 eV, was achieved for the Nb1.344Ti0.642Fe0.014O4, making it suitable for the use as a current collector. Conductivity runs in wet 5%H2/Ar showed lower conductivities of 15–18 Scm−1 and lower activation energies of 0.08 − 0.09 eV. Single cell tests of Nb1.33Ti0.67O4 showed power outputs of 5.5 − 7.2 mW·cm−2 at 850 °C, lower than for Ni with 150 − 200 mW·cm−2 at 850 °C, however, this material displayed much better stability at high temperatures than Ni.
Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献