Buffer gas

About: Buffer gas is a research topic. Over the lifetime, 3565 publications have been published within this topic receiving 47283 citations.

Laser induced fluorescence in nanosecond repetitively pulsed discharges for CO2 conversion

Abstract: A CO2 nanosecond repetitively pulsed discharge (NRP) is a harsh environment for laser induced fluorescence (LIF) diagnostics. The difficulties arise from it being a strongly collisional system in which the gas composition, pressure and temperature, have quick and strong variations. The relevant diagnostic problems are described and illustrated through the application of LIF to the measurement of the OH radical in three different discharge configurations, with gas mixtures containing CO2 + H2O. These range from a dielectric barrier NRP with He buffer gas, a less hostile case in which absolute OH density measurement is possible, to an NRP in CO2+H2O, where the full set of drawbacks is at work. In the last case, the OH density measurement is not possible with laser pulses and detector time resolution in the ns time scale. Nevertheless, it is shown that with a proper knowledge of the collisional rate constants involved in the LIF process, a collisional energy transfer-LIF methodology is still applicable to deduce the gas composition from the analysis of LIF spectra.

Arc process parameters for single-walled carbon nanotube growth and production: experiments and modeling.

Abstract: Collarets rich in single-walled carbon nanotubes (SWCNTs) have been grown using a direct current arc method. Arc process parameters such as current, pressure, and anode to cathode distance were varied experimentally and by modeling to provide an optimal working window. The best collaret yields were obtained when helium was used as a buffer gas. Mixing helium with argon in the buffer permits controlling nanotube diameters. In addition to an experimental study, a modeling approach was developed assuming local thermal equilibrium and homogenous and heterogeneous neutral chemistry. The gas-phase chemical model involves 81 neutral carbon species (C1, C2, . . ., C79, C60F, C70F) and 554 reactions with rates taken from data of Krestinin and Moravsky. Axial profiles of temperature, C atom, C2 radical, and fullerene distributions in the reactor are predicted as a function of process parameters. Carbon nanotube growth is considered by a set of surface reactions simulating open nanotube growth. Because nanotube surface chemistry is controlled by the local terminated bond and not by the bulk nanotube bond, a mechanistic approach based on the formal resemblance between the bonding and the structure of open nanotube and other carbon surfaces is proposed to explain nanotube growth. Predicted growth rates are in the range of 100 to 1000 microm/min.

Control of atmosphere surrounding crystal growth zone

Abstract: OF THE DISCLOSURE: The invention pertains to growth of silicon bodies from a melt and comprises enveloping the liquid/solid interface with a mixture of an inert gas and more than a trace amount of a carbon-containing gas. The carbon-containing gas may be a compound of carbon and oxygen such as CO or CO2, and oxygen gas also may be intro-duced to the growth zone.

Cleaning gas and method for cleaning vacuum treatment apparatus by flowing the cleaning gas

Abstract: A cleaning gas includes HF gas whose concentration is greater than or equal to 1 vol % and oxygen containing gas whose concentration ranges from 0.5 to 99 vol %. The oxygen containing gas includes at least one of O 2 gas, O 3 gas, N 2 O gas, NO gas, CO gas and CO 2 gas. The cleaning gas is employed to remove a deposited material generated in a vacuum treatment apparatus for producing a thin film of at least one of Ti, W, Ta, Ru, Ir, a compound thereof and an alloy thereof.