Laser Absorption (laser + absorption)

Distribution by Scientific Domains

Terms modified by Laser Absorption

  • laser absorption spectroscopy

  • Selected Abstracts


    Measurements of High-Temperature Silane Pyrolysis Using SiH4 IR Emission and SiH2 Laser Absorption.

    CHEMINFORM, Issue 9 2004
    Eric L. Petersen
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    OH concentration time histories in n -alkane oxidation

    INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2001
    D. F. Davidson
    OH radical concentration time histories were measured behind reflected shocks in the oxidation of four n -alkanes: propane, n -butane, n -heptane, and n -decane. Initial reflected shock conditions of these measurements were 1357,1784 K, 2.02,3.80 atm, with fuel concentrations of 300,2000 ppm, and equivalence ratios from 0.8 to 1.2. OH concentrations were measured using narrow-linewidth ring-dye laser absorption of the R1(5) line of the A,X (0,0) transition at 306.5 nm. These concentration time-history measurements were compared to the modeled predictions of eight large n -alkane oxidation mechanisms currently available in the literature and the kinetic implications of these measurements are discussed. These data, in conjunction with recent measurements of n -alkane ignition times and ethylene yields in n -alkane pyrolysis experiments, also performed in this laboratory, provide a unique database of species concentration time histories for n -alkane mechanism validation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 775,783, 2001 [source]


    Direct Laser Sintering of Al2O3,SiO2 Dental Ceramic Components by Layer-Wise Slurry Deposition

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006
    André Gahler
    This publication presents a solid freeform fabrication technique for ceramics in the alumina,silica system by layering binder-free, high-loaded ceramic slurries, followed by selective laser sintering. The low melting silica phase and the reaction sintering between silica and alumina favor the rapid prototyping of pure ceramic parts. On the basis of electroacoustic and viscosity measurements, stable slurries from Al2O3/SiO2 powder mixtures and water with a high fluidity have been prepared for the layer deposition with a doctor blade like in tape casting. Layers with a thickness of about 100 ,m were processed. It was found in laser parameter studies that ceramic parts can only be obtained using special alumina contents and laser parameters. But the biphasic approach may allow greater flexibility in the processing regime than is afforded by the use of just one material. The microstructure of these parts depends mainly on the temperature gradient induced by the laser absorption and thermal conduction. The wet shaping facilitates laser-sintered parts with a relatively high density, which could be increased by a thermal post-treatment. [source]


    Pulsed Laser Polymerization of Alkyl Acrylates: Potential Effects of the Oxygen Presence and High Laser Power,

    MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2006
    Patrice Castignolles
    Abstract Summary: Unexpected difficulties are encountered in the determination of propagation rate coefficients (kp) in free radical polymerization of alkyl acrylates by pulsed laser polymerization (PLP), mainly due to intramolecular transfer to polymer.1 This article is focused on the role played by the high laser power in these difficulties and the possible reactions of mid-chain radical with residual oxygen. Removing the oxygen by simple bubbling of nitrogen is sufficient to avoid alteration of the polymerization kinetics of acrylates by residual oxygen under PLP conditions. Moreover, no degradation of polymer (or solvent) has been detected after irradiation with the high laser power typically used in PLP experiments. However, it has been shown that this high laser power completely prevents from having a temporally and spatially homogeneous radical concentration in the PLP cell. A model is proposed here to simulate the pulsed laser polymerization taking initiator consumption and laser energy absorption into account. According to our simulation results, this non-negligible initiator consumption and laser power absorption can indeed have a positive influence, i.e., it favors the obtainment of a bimodal molar mass distribution fulfilling the IUPAC consistency criteria. This observation may contradict the idea that PLP-SEC is not suitable to determine accurate kp values for acrylates above 20,30,°C. Instantaneous MMDs formed after N pulses. Simulation taking initiator consumption and laser absorption into account. [source]