Showing papers by "National Institute of Advanced Industrial Science and Technology published in 1982"

Observation of Surface Cracks with Scanning Acoustic Microscope

Abstract: Surface cracks introduced in soda lime glass and MgO single crystal have been examined with a 200‐ and 420‐MHz scanning acoustic microscope. A fringe pattern was observed around the cracking line on the surface which could not be observed with an optical microscope. A simplified model is proposed in which fringe formation is due to the interference between the leaky surface wave reflected by the crack and the specularly reflected wave at the surface or the leaky surface wave that did not reach the crack. By monitoring these fringes, a Hertzian crack in soda lime glass with a depth as small as 25 μm was detected. The direction of crack orientation relative to the surface normal was also obtained from the asymmetrical contrast distribution of the fringes.

Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts

Abstract: Kinetics and hydrogen-deuterium isotope effects in the methanation of adsorbed CO molecules on a Ni/SiO/sub 2/ catalyst were precisely measured by using pulse surface reaction rate analysis (PSRA). When a CO pulse was injected into flowing hydrogen, it was immediately adsorbed on the catalyst and gradually hydrogenated to CH/sub 4/ and H/sub 2/O. The amounts of CH/sub 4/ and H/sub 2/O produced by the hydrogenation of the adsorbed CO were determined up to various times, and it was found that CH/sub 4/ and H/sub 2/O were produced at the same rate. When O/sub 2/ instead of CO was injected, H/sub 2/O was immediately produced. From these results, the rate-determining step of the reaction was found to be C-O bond dissociation of an adsorbed CO molecule or a partially hydrogenated CO species. By PSRA, the rate constant for the C-O bond dissocition process per adsorbed CO molecule (k/sub H/) was determined at various temperatures, and the Arrhenius parameters of the rate constant were obtained. The rate constant in flowing deuterium (k/sub D/) was also determined. it was found that k/sub D/ is considerably larger than k/sub H/, indicating an inverse isotope effect. The average value of k/sub H//k/sub D/ was 0.75.more » From these results, it was concluded that adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but it is partially hydrogenated before C-O bond dissociation under the conditions of the PSRA experiment. 8 figures.« less

Monte Carlo particle simulation of GaAs submicron n+-i-n+ diode

Abstract: Monte Carlo particle simulation of a GaAs submicron n+-i-n+ diode showed that the electron transport in the diode is almost ballistic in nature, so long as the electron energy is below 0.36 eV. A maximum electron velocity of 1 × 108 cm s−1 was observed at certain conditions. Effects of the electron backscattering from the anode n+-layer are also discussed.

Kinetics, isotope effects, and mechanism for the hydrogenation of carbon monoxide on supported nickel catalysts

Abstract: Kinetics and hydrogen-deuterium isotope effects in the methanation of adsorbed CO molecules on a Ni/SiO/sub 2/ catalyst were precisely measured by using pulse surface reaction rate analysis (PSRA). When a CO pulse was injected into flowing hydrogen, it was immediately adsorbed on the catalyst and gradually hydrogenated to CH/sub 4/ and H/sub 2/O. The amounts of CH/sub 4/ and H/sub 2/O produced by the hydrogenation of the adsorbed CO were determined up to various times, and it was found that CH/sub 4/ and H/sub 2/O were produced at the same rate. When O/sub 2/ instead of CO was injected, H/sub 2/O was immediately produced. From these results, the rate-determining step of the reaction was found to be C-O bond dissociation of an adsorbed CO molecule or a partially hydrogenated CO species. By PSRA, the rate constant for the C-O bond dissocition process per adsorbed CO molecule (k/sub H/) was determined at various temperatures, and the Arrhenius parameters of the rate constant were obtained. The rate constant in flowing deuterium (k/sub D/) was also determined. it was found that k/sub D/ is considerably larger than k/sub H/, indicating an inverse isotope effect. The average value of k/sub H//k/sub D/ was 0.75.more » From these results, it was concluded that adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but it is partially hydrogenated before C-O bond dissociation under the conditions of the PSRA experiment. 8 figures.« less

Monte Carlo simulation of GaAs submicron n+-n-n+ diode with GaAlAs heterojunction cathode

Abstract: A Monte Carlo simulation program has been developed to simulate the motion of electrons in a submicron GaAs diode with a Ga1−xAlxAs heterojunction cathode. It is shown that the hot electron injection through the heterojunction cathode is effective to increase the mean electron velocity of carriers.

Observation of Subsurface Flaws with Scanning Acoustic Microscope

Abstract: To establish the effective detection and identification of cracks and precipitations on and under solid surfaces, a comparative study has been made on acoustic micrographs of such flaws using a scanning acoustic microscope. It has been found that different modes of acoustic waves contribute to the detection of different types of flaws.