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61.
Niobium diffusion in niobium-doped titanium dioxide 总被引:1,自引:0,他引:1
L. R. Sheppard A. J. Atanacio T. Bak J. Nowotny M. K. Nowotny K. E. Prince 《Journal of Solid State Electrochemistry》2009,13(7):1115-1121
The present work studied the self-diffusion coefficient of 93Nb in Nb-doped TiO2 single crystal (4.3 at.% Nb) at high oxygen activity [p(O2) = 21 kPa] over the temperature range 1,073 to 1,573 K. The diffusion-induced 93Nb concentration profile was determined by using secondary ion mass spectrometry (SIMS). The subsequently determined self-diffusion
coefficient of 93Nb exhibits the following temperature dependence:. This study builds upon a similar study performed previously for 93Nb tracer diffusion in undoped TiO2, and identifies the effect of compositional change on self-diffusion behaviour. The obtained activation energy has been considered
in terms of migration and formation enthalpies of titanium vacancies.
The present work is dedicated to Professor John Bockris on the occasion of his 85th birthday. His contribution to the progress
of modern electrochemistry is well-known to several generations of students and researchers who have been using his textbooks.
His specific contribution to the theory of photoelectrochemical water splitting is known to all working in this fascinating
area. 相似文献
62.
An expedient synthesis of orthogonally protected lysinoalanine from Aloc-protected Garner’s aldehyde
Cindy Körner Samuel E.M. Keegan Daniel C. Nicolau Tom D. Sheppard 《Tetrahedron letters》2010,51(49):6381-6383
An expedient synthesis of orthogonally protected lysinoalanine has been developed. We have prepared a novel Garner’s aldehyde derivative bearing an Aloc group; reductive amination of this aldehyde with Fmoc-Lys-OPMB gave the lysinoalanine skeleton. This was then transformed into an orthogonally protected lysinoalanine derivative suitable for the synthesis of side-chain bridged cyclic peptides by solid phase peptide synthesis methods. 相似文献
63.
C. J. R. Sheppard 《Optics Communications》1999,160(4-6):191-194
The three-dimensional (3D) pupil function for a high-aperture focusing system can be expressed in terms of Hertz or Debye potentials. The electromagnetic field in the focal region can be calculated directly from these. The Debye potential pupil function is given for optical systems obeying different conditions. 相似文献
64.
Confocal microscopy with serrated divided apertures is presented. Compared with using two smooth D-shaped apertures in confocal microscopy, the serrated divided apertures can suppress the out-of-focus central bright spot, thus increasing the efficiency of rejection of scattered light. Diffraction analysis shows that the serrated apertures maintain the optical sectioning strength while attenuating the background coming from far from the focal plane. In addition, the signal to background ratio (S/B) is also improved. 相似文献
65.
A three-dimensional reflectance scanning optical microscope based on the nonlinear optical phenomenon of second-harmonic generation is presented. A mode-locked Ti:sapphire laser producing <90-fs pulses at ~790nm was used, and the images were constructed by scanning of an object, which possessed local second-order nonlinearity, relative to a focused spot from the laser. The second-harmonic light at ~395nm generated by the specimen was separated from the fundamental beam by use of dichroic and interference filters and was detected by a photodiode. The technique was then used to characterize the distribution of second-order nonlinearity and microstructure of the nonlinear material lithium triborate. 相似文献
66.
The structures and relative configuration of three decipiene diterpenes from Eremophila decipiens have been established by degradation studies. These diterpenes possess the new tricyclic decipiane skeleton based on the tricyclo [5,3,1,05,11] undecane ring system. 相似文献
67.
Summary The gases evolved from geothermal fields, after condensation of H2O, CO2, H2S and NH3 in caustic solution, contain He, H2, Ar, O2, N2, CH4 and higher hydrocarbons. The analysis for the major components in these residual gas mixtures can be achieved by use of two simple gas chromatographs in parallel, and using 5Å molecular sieve. The separation of He and H2 to baseline is achieved by using low temperatures (30°C) coupled with a relatively long column; and the difficult separation of Ar and O2 is achieved by use of a cryogenically cooled column. The use of switching valves to backflush and bypass columns ensures that a minimum time for analysis can be achieved whilst retaining baseline separations of the He/H2 and Ar/O2 pairs. 相似文献
68.
J. A. Ferrara J. C. Seferis C. H. Sheppard 《Journal of Thermal Analysis and Calorimetry》1994,42(2-3):467-484
This investigation demonstrates that polyphenylene sulfide (PPS) crystallizes in a unique dual-mechanistic fashion in which 8% of the material by volume crystallizes instantaneously, while the remaining material crystallizes in a time dependent fashion. These rapid melt-crystallization kinetics are quantitatively modeled using a dual-mechanistic model approach which is based on the methodology first observed by Velisaris and Seferis in polyetheretherketone (PEEK) crystallization. The crystallization model is then used to accurately predict both isothermal and for the first time non-isothermal crystallization behavior over a wide spectrum of cooling rates utilizing the same model parameters. Specifically, this work identifies and models the initial fast crystallization kinetics of PPS. Additionally, the versatility of the Velisaris and Seferis dual-mechanistic model has been established with PPS, by simply showing that it is a special case of the generalized dual-crystallization kinetics methodology. 相似文献
69.
Robert N. Haszeldine Ronald Rowland Robin P. Sheppard Anthony E. Tipping 《Journal of fluorine chemistry》1985,28(3):291-302
Reaction of hexafluoropropene (HFP) with a series of alcohols under thermal, photochemical or peroxide-initiated conditions affords the 1:1 adducts CF3CHFCF2CR1R2OH (R1 = H, R2 = H, Me, Prn or CF3; R1 = Me, R2 = Me or Et) in high yield via a radical chain mechanism. Adduct are not formed with the alcohols (CF3)2CHOH and CF3CHFCF2CH2OH. Other 1:1 adducts of structure CHF2CF(CF3)CH2OH and CH3(C2H3CF2CHFCF3)CH2OH are formed as minor products in the methanol and -butanol reactions, respectively. 相似文献
70.
Ohne Zusammenfassung
Ins Deutsche übersetzt von Joh. Geiler. 相似文献