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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2838-2846 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The first radial mode of a cylindrical resonator was excited in extracavity and intracavity configurations employing a modulated 3.39 μm HeNe laser. The resonance curves were measured as a function of pressure by a computer-controlled method and fitted to Lorentzian profiles. Measurements were performed for C2H4, CH3Cl, CH3F, C2H6, and CH4, where the optical absorption coefficient determined by transmission experiments increases from C2 H4 to CH4 . From the signal strengths and the Q factors of the resonances the so-called photoacoustic signal (PAS) was determined and compared with theory. Good agreement between theory and experiment was observed for all extracavity measurements and in the case of intracavity experiments with low optical losses in the laser resonator. In order to describe the large discrepancies between the experimentally determined PAS and the existing theory for high losses, improved models were developed, which are based on an inhomogeneous distribution of laser power in the optical cavity. Deviations from these models were found near threshold. The PAS observed above threshold is attributed to amplified spontaneous emission.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 227-238 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A noncontact all-optical method for surface photoacoustics is described. The surface acoustic waves (SAWs) were excited employing a KrF laser and detected with a Michelson interferometer using a 633-nm HeNe laser. Due to an active stabilization scheme developed for the interferometer a surface displacement of 0.2 A(ring) could be detected. The materials investigated included pure materials such as polycrystalline aluminum, and crystalline silicon; films of gold, silver, aluminum, iron, and nickel on fused silica; and a-Si:H on Si(100). In the case of pure materials the shape of the acoustic pulse and the phase velocity were determined. The dispersion of the SAW phase velocity observed for the film systems was used to extract information on the film thickness, density, and transverse and longitudinal sound velocity. Models for the theoretical treatment of film systems and the calculation of dispersion curves are presented.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Organometallics 11 (1992), S. 267-269 
    ISSN: 1520-6041
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 18 (1999), S. 1135-1137 
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 19 (2000), S. 157-158 
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 28 (1998), S. 1179-1188 
    ISSN: 1572-8838
    Schlagwort(e): functionally graded materials ; porous electrodes ; current distribution ; infiltration processing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The present paper lays the theoretical foundations of a new production process for functionally graded materials (FGMs). The process is based on the evolution of porosity gradients in porous electrodes which undergo electrochemical dissolution or deposition. The electrodes with graded porosity serve as preforms for the production of graded composites by infiltration processing. A one-dimensional macroscopic model of the porous electrode has been used for the prediction of the porosity gradients. A numerical approach allows utilization of experimentally determined current–potential curves for nonporous electrodes, with the incorporation of changes of the pore structure during the course of the electrode reaction, to predict the porosity gradients. For porous copper cathodes and anodes the results of this model are compared with experimentally observed polarization behavior and porosity distributions for different current densities and electrolyte conductivities.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 35 (2000), S. 477-486 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A novel processing route is presented that is capable of manufacturing composites with continuous gradients in chemical composition. This route is based on an electrochemical gradation and subsequent infiltration of porous preforms and allows production of a variety of functionally graded materials and geometries. The method allows flexible adjustment of the retained gradients by adjusting experimental parameters. Relevant electrode kinetics are cast into a macroscopic model which provides a predictive capacity for the gradients obtained. Tungsten/copper gradient materials with different gradation profiles were produced and a comparison of the observed with the calculated gradients was carried out.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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