Engineering topics

Kobashi, K.

Publications and source records attributed to Kobashi, K..

5 records

NASA NTRS2001

Proceedings of the Sixth Applied Diamond Conference/Second Frontier Carbon Technology Joint Conference (ADC/FCT 2001)

These are the Proceedings of the Sixth Applied Diamond Conference/Second Frontier Carbon Technology Joint Conference hosted by Auburn University from August 6 to 10, 2001. The diamond CVD process was first reported by Dr. Spitsyn in 1981 and Prof. S. Iijima reported his discovery of carbon nanotubes in 1991. In the past years, both diamond-related materials and novel carbon materials have attracted considerable interest by the scientific, technological, and industrial community. Many practical and commercial products of diamond materials are reported in these proceedings. A broad variety of applications of carbon nanotubes and novel carbons have also been explored and demonstrated. Having more than 200 invited and contributing papers by authors from over 20 countries for presentations at ADC/FCT 2001 clearly demonstrates that these materials, due to the combination of their superior properties, are both scientifically amazing and economically significant.

Tzeng, Y.↗

NASA NTRS1985

Raman spectra of solid benzene under high pressure

Raman spectra of solid benzene have been measured at room temperature up to about 140 kbar, using the diamond anvil cell. Effort has been focused upon the lattice vibration spectra at pressures above that of phase II. It is found that a change in slopes occurs in the frequency-pressure curves at about 40 kbar. Furthermore, a new band appears above 90 kbar. These features probably correspond respectively to the II-III phase transition, which has been reported previously, and a III-IV phase transition, reported here for the first time.

Thiery, M.-M.↗

NASA NTRS1983

Prediction of structures and magnetic orientations in solid alpha and beta-O2

A quasi-harmonic-lattice-dynamics method coupled with a pattern-recognition optimization scheme is used to determine the minimum energy structures and magnetic orientations of solid oxygen. It is shown that the magnetic interaction is responsible for the stability of alpha-O2 with respect to beta-O2 at zero temperature and pressure. The calculated alpha-O2 lattice parameters, magnetic orientations, and sublimation energy are in good agreement with experiment. Phonon dispersion curves are calculated at vector k not equal to zero and the acoustic sound velocities are determined. The rms translational and orientational fluctuations from equilibrium are also calculated. The beta-O2 phase is described by constraining the magnetic moments so that the magnetic Hamiltonian preserves the hexagonal symmetry of the crystal. The calculated lattice parameters are in good agreement with the experiments, and a three-sublattice, quasi-helical magnetic orientation is predicted from structural and energetic considerations.

Etters, R. D.↗

NASA NTRS1983

Calculation of high-pressure phase transitions in solid N2 and the pressure dependence of intramolecular mode frequencies

A calculation that minimizes the energy of solid N2 with respect to a rhombohedral distortion of the Pm 3n structure shows that a low-temperature phase transition occurs into the R 3c calcite structure at P = 19.2 kbar with a volume change of 0.125 cu cm/mole. This transition agrees with recent Raman scattering measurements. Another transition from R 3c into R3(bar)m is predicted at P = 67.5 kbar, with a volume change of 0.1 cu cm/mole. The pressure dependence of the intramolecular mode frequencies for the R 3c structure are in reasonably good agreement with the two main branches observed experimentally.

Chandrasekharan, V.↗

NASA NTRS1982

Predictions for partial and monolayer coverages of O2 on graphite

Monolayer properties of O2 on graphite are calculated using a pattern recognition, optimization scheme. Equilibrium monolayers are predicted at two different densities with properties in agreement with recent X-ray diffraction, specific heat, and neutron scattering data. Properties of the extremely low density regime are calculated using a model based upon a distribution of two-dimensional O2 clusters. The results are consistent with experimental evidence.

Pan, R. P.↗