1,551 research outputs found
Mechanism of operation of the TFE-bonded gas-diffusion electrode
Mathematical analytical model predicts the performance of an electrode as a function of certain measurable physical characteristics. Concept assumes the catalyst particles form porous electrically conductive agglomerates which are completely flooded with electrolyte
Development of cathodic electrocatalysts for use in low temperature H2/O2 fuel cells with an alkaline electrolyte Second quarterly report, Oct. 1 - Dec. 31, 1965
Cathodic electrocatalysts for use in low temperature hydrogen-oxygen fuel cells with an alkaline electrolyte-corrosion resistance and activity testing of materials and element
Polar optical phonons in core-shell semiconductor nanowires
We obtain the the long-wavelength polar optical vibrational modes of
semiconductor core-shell nanowires by means of a phenomenological continuum
model. A basis for the space of solutions is derived, and by applying the
appropriate boundary conditions, the transcendental equations for the coupled
and uncoupled modes are attained. Our results are applied to the study of the
GaAs-GaP core-shell nanowire, for which we calculate numerically the polar
optical modes, analyzing the role of strain in the vibrational properties of
this nanosystem
Resonant hyper-Raman scattering in spherical quantum dots
A theoretical model of resonant hyper-Raman scattering by an ensemble of
spherical semiconductor quantum dots has been developed. The electronic
intermediate states are described as Wannier-Mott excitons in the framework of
the envelope function approximation. The optical polar vibrational modes of the
nanocrystallites (vibrons) and their interaction with the electronic system are
analized with the help of a continuum model satisfying both the mechanical and
electrostatic matching conditions at the interface. An explicit expression for
the hyper-Raman scattering efficiency is derived, which is valid for incident
two-photon energy close to the exciton resonances. The dipole selection rules
for optical transitions and Fr\"ohlich-like exciton-lattice interaction are
derived: It is shown that only exciton states with total angular momentum
and vibrational modes with angular momentum contribute to the
hyper-Raman scattering process. The associated exciton energies, wavefunctions,
and vibron frequencies have been obtained for spherical CdSe zincblende-type
nanocrystals, and the corresponding hyper-Raman scattering spectrum and
resonance profile are calculated. Their dependence on the dot radius and the
influence of the size distribution on them are also discussed.Comment: 12 pages REVTeX (two columns), 2 tables, 8 figure
Several new catalysts for reduction of oxygen in fuel cells
Test results prove nickel carbide or nitride, nickel-cobalt carbide, titanium carbide or nitride, and intermetallic compounds of the transition or noble metals to be efficient electrocatalysts for oxygen reduction in alkaline electrolytes in low temperature fuel cells
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