Search results for "Argon"
showing 10 items of 250 documents
Simulation of the influence of gas flow on melt convection and phase boundaries in FZ silicon single crystal growth
2015
Abstract Axisymmetric calculations of inert gas flow in a floating zone puller are carried out using an open source software package OpenFOAM. Transient axisymmetric melt flow in liquid silicon and quasi-stationary shape of silicon phase boundaries are calculated using a specialized program FZone. Additional heat losses at silicon surfaces caused by the gas flow are taken into account for argon and helium, while maintaining the height of molten zone by adjusting inductor current. Cooling causes an increase of electromagnetic force, heat sources and more intense melt flow, while crystallization interface deflection decreases. The shear stress of gas flow is found to be an order of magnitude …
Helium and Argon Line Broadening in the nu2 Band of CH4
2004
Abstract The spectra of the gaseous mixtures CH 4 –He and CH 4 –Ar were obtained in the spectral region 1400–1750 cm −1 with a resolution up to 0.003 cm −1 . Helium and argon pressure broadenings for the vibration–rotation lines of the ν 2 band of CH 4 have been estimated at room temperature for some lines in the P , Q , and R branches. These values were also calculated using the theoretical approach developed by Robert and Bonamy, extended to the case of tetrahedral molecules. The helium data have been found to be in a satisfactory agreement whereas a divergence of calculated and measured broadening coefficients has been evidenced in the case of argon. Simulations of the ν 2 band shapes of…
Vibrational spectroscopy of trans and cis deuterated formic acid (HCOOD): Anharmonic calculations and experiments in argon and neon matrices
2010
The absorption spectra of trans and cis conformers of deuterated formic acid (HCOOD) isolated in argon and neon matrices are analyzed in the mid-infrared and near-infrared spectral regions (7900–450 cm � 1 ). Vibrational excitation by narrow-band IR radiation is used to convert the lower-energy trans conformer to the higher-energy cis form. A large number of overtone and combination bands are identified. The results of anharmonic vibrational calculations (CC-VSCF) for both conformers are reported and compared to the experimental spectra.
Molecular dynamics investigation of the premelting effects of Lennard-Jones (111) surfaces
1987
Molecular dynamics simulations have been performed to study the premelting effects of noble-gas surfaces (argon) close to but below the bulk melting temperature. In particular, the increase of disorder as a function of temperature at (111) surface has been considered. The truncated Lennard-Jones (6-12) potential is used to describe the interactions between particles. Surface premelting has been analyzed by means of total energies, trajectory plots, mean sequare displacement functions, diffusion coefficients, vacancy concentrations and two-dimensional order parameters. The (111) surface starts to disorder by vacancy formation, which leads to the premelting of the surface layer far below the …
High Voltage Insulation and Gas Absorption of Polymers in High Pressure Argon and Xenon Gases
2018
High pressure gas time projection chambers (HPGTPCs) are made with a variety of materials, many of which have not been well characterized in high pressure noble gas environments. As HPGTPCs are scaled up in size toward ton-scale detectors, assemblies become larger and more complex, creating a need for detailed understanding of how structural supports and high voltage insulators behave. This includes the identification of materials with predictable mechanical properties and without surface charge accumulation that may lead to field deformation or sparking. This paper explores the mechanical and electrical effects of high pressure gas environments on insulating polymers PTFE, HDPE, PEEK, POM …
Experimental Investigation on the Use of Argon to Improve FMEP Determination through Motoring Method
2019
In the ever increasing challenge of developing more efficient and less polluting engines, friction reduction is of significant importance and its investigation needs an accurate and reliable measurement technique. The Pressurized Motoring method is one of the techniques used for both friction and heat transfer measurements in internal combustion engines. This method is able to simulate mechanical loading on the engine components similar to the fired conditions. It also allows measurement of friction mean effective pressure (FMEP) with a much smaller uncertainty as opposed to that achieved from a typical firing setup. Despite its advantages, the FMEP measurements obtained by this method are …
Sensing properties of assembled Bi2S3nanowire arrays
2015
Bismuth sulfide (Bi2S3) nanowires were grown in porous aluminium oxide template and a selective chemical etching was applied to transfer the nanowires to a solution. Well aligned nanowire arrays were assembled on pre-patterned silicon substrates employing dielectrophoresis. Electron beam lithography was used to connect aligned individual nanowires to the common macroelectrode. In order to evaluate the conductometric sensing performance of the Bi2S3 nanowires, current–voltage characteristics were measured at different relative humidity (RH) levels (5–80%) / argon medium. The response of the Bi2S3 nanowires depending of RH is found to be considerably different from those reported for other ty…
Development of microwave gas sensors
2011
Abstract This work presents a novel approach in gas detection by an original method of microwave transduction. The design of the sensor includes a coplanar grounded wave guide with a gas sensing material to study its sensitivity to ammonia in argon flux. The sensing material can play the role of the substrate or can be deposited as a thin layer on a microstrip structure used in electronics. Submitted to an electromagnetic excitation in microwave energies, the sensor response in the presence of a gas results in a specific modification of the reflected wave (real and imaginary parts). The goals of this study include an examination of the form of the sensitive material and its influence on the…
Gas sensing properties of multiwall carbon nanotubes decorated with rhodium nanoparticles
2011
International audience; In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O 2). The properties of these hybrid materials towards the room temperature detection of NO 2 , C 2 H 4 , CO, C 6 H 6 and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to avoid response saturation even at low gas/vapor concentrations. These desirable effec…
Oxidation of pentan-2-ol -Part II: Experimental and modeling study
2021
International audience; The oxidation of pentan-2-ol was investigated at high-pressure in a jet-stirred reactor and in a shock tube. Experiments in the JSR were carried out at 10 atm, between 500-1180 K, for five different equivalence ratios of = 0.35, 0.5, 1, 2, 4 and 1000 ppm of fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were quantified using Fourier transform infrared spectrometry (FTIR) and gas chromatography (GC). Ignition delay times were measured for pentan-2-ol/O 2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1070-1460 K and for equivalence ratios of = 0.5, 1 and 2. Ignition delay times of a…