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Full-Text Articles in Engineering

Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov May 1999

Novel One-Phase Synthesis Of Thiol-Functionalized Gold, Palladium, And Iridium Nanoparticles Using Superhydride, Chanel K. Yee, Rainer Jordan, Abraham Ulman, Henry White, Alexander H. King, Miriam Rafailovich, Jonathan Sokolov

Alexander H. King

A new, facile, general one-phase synthesis for thiol-functionalized gold, palladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the solvent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticles, HRTEM of drop-cast particle-films revealed the formation of spherical particles of d = 4 ± 0.3 nm average size. Electron diffraction shows fcc packing arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans conformation, adopting orthorhombic packing as confirmed by FTIR spectroscopy. Particles are arranged in a discrete solidlike assembly with a correlation …


Incommensurate And Commensurate Antiferromagnetic Spin Fluctuations In Cr And Cr Alloys From Ab Initio Dynamical Spin Susceptibility Calculations, Duane D. Johnson, J. Pulter, B. Ginatempo, E. Bruno, J. B. Staunton Apr 1999

Incommensurate And Commensurate Antiferromagnetic Spin Fluctuations In Cr And Cr Alloys From Ab Initio Dynamical Spin Susceptibility Calculations, Duane D. Johnson, J. Pulter, B. Ginatempo, E. Bruno, J. B. Staunton

Duane D. Johnson

A scheme for making ab initio calculations of the dynamic paramagnetic spin susceptibilities of solids at finite temperatures is described. It is based on time-dependent density functional theory and employs an electronic multiple scattering formalism. Incommensurate and commensurate antiferromagnetic spin fluctuations in paramagnetic Cr and compositionally disordered Cr95V5 and Cr95Re5 alloys are studied together with the connection with the nesting of their Fermi surfaces. We find that the spin fluctuations can be described rather simply in terms of an overdamped oscillator model. Good agreement with inelastic neutron scattering data is obtained.


Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor Jan 1999

Resistivity, Thermopower And The Correlation To Infrared Active Vibrations Of Mn1.56co0.96ni0.48o4 Spinel Films Sputtered In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor

Alexander H. King

Mn1.56Co0.96Ni0.48O4 spinel was sputter deposited using a series of oxygen partial pressures. Electrical resistivity versus temperature and thermopower versus temperature measurements at each oxygen partial pressure were made. The variations of the thermopower and resistivity with oxygen partial pressure are consistent with a change in the ratio of Mn3+ to Mn4+ cations, which occurs due to changes of oxygen content of the material. The weak temperature dependence of the thermopower indicates small polaron hopping is the charge transport mechanism. Combining the models of Mott and Schnakenberg to analyze the transport data, we find that the Debye temperature (or frequency) is …


Infrared Optical Properties Of Mn1.56co0.96ni0.48o4 Spinel Films Sputter Deposited In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor Jan 1999

Infrared Optical Properties Of Mn1.56co0.96ni0.48o4 Spinel Films Sputter Deposited In An Oxygen Partial Pressure Series, Rand Dannenberg, S. Baliga, R. J. Gambino, Alexander H. King, A. P. Doctor

Alexander H. King

Mn1.56Co0.96Ni0.48O4 spinel films were sputter deposited onto silicon substrates using a series of oxygen partial pressures. Fourier transform infrared transmission and reflectance, and Raman scattering measurements were made. The 1–25 μm wavelength range was examined using these optical techniques. The complex index of refraction was calculated for this entire wavelength range. Infrared active vibrations were analyzed using multiple oscillator analysis, Kramers–Kronig analysis, and derivative reflectance spectroscopy. The Raman and infrared active lattice vibrations were observed to shift with increasing oxygen partial pressure during film deposition, and were consistent with the earlier published shift in Debye frequency calculated from resistivity data. …


Conductivity Of A Periodic Particle Composite With Spheroidal Inclusions, Nicola Harfield Jan 1999

Conductivity Of A Periodic Particle Composite With Spheroidal Inclusions, Nicola Harfield

Nicola Bowler

The effective electrical conductivity of a two-phase material consisting of a lattice of identical spheroidal inclusions in a continuous matrix is determined analytically. The inclusions are located at the node points of a simple-cubic lattice and the axis of rotation of each spheroid coincides with one of the lattice vectors, such that the spheroids are aligned with each other and with the lattice. With an electric field applied in the direction of the rotation axes of the spheroids, the electric potential is found by solving Laplace's equation. The solution is found by analytically continuing the interstitial field into the particle …