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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2639-2642 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new technique is developed and described which allows the measurement of dendrite growth velocities in undercooled melts in an electromagnetic levitation facility. The triggering of nucleation at the bottom of the liquid drop (=beginning of growth at t=t*) and the end of recalescence (=end of growth at t=t++) are detected by a capacitance proximity sensor and a photodiode, respectively. Dendrite growth velocities are determined as the ratio 2R0/(t++−t*), where 2R0 denotes the vertical diameter of the drop. First results on pure Ni demonstrate the capability of the method to produce less scattered data than other techniques.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 13 (1992), S. 65-74 
    ISSN: 1572-9567
    Keywords: image processing ; levitation ; microgravity ; metals ; surfacetension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An improved method for measuring the surface tension of liquid metals is proposed. It makes use of the electromagnetic levitation technique for levitating a liquid metal droplet and of digital image processing to evaluate the surface oscillations of the droplet. The oscillation frequencies determine the surface tension. This paper contains a discussion of the theoretical background and a description of the experimental setup. In addition, preliminary results on FeNi samples in 1g and microgravity are presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 13 (1992), S. 199-210 
    ISSN: 1572-9567
    Keywords: evaporation ; high temperature ; levitation ; liquid metals ; microgravity ; pyrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Containerless materials processing of liquid metals with the use of electromagnetic levitation requires contactless temperature measurement by pyrometry. For high temperatures and under high-vacuum conditions, the vapor pressure of the levitated metal drop increases, leading to evaporation losses of the sample material. This flux condenses on the cold parts of the experimental apparatus including the window in front of the pyrometer. As a result, the intensity of radiation reaching the pyrometer decreases, which is erroneously interpreted as a decrease in temperature. Several methods to protect the pyrometer against contamination have been proposed. In this paper, we report experimental tests of the concepts of shielding windows and mirror optics placed into the optical path between the sample and the pyrometer. Temperature measurements with a periscopic mirror system are also presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 14 (1993), S. 573-584 
    ISSN: 1572-9567
    Keywords: density ; electrical conductivity ; electromagnetic levitation ; emissivity ; liquid metals ; microgravity ; specific heat ; surface tension ; undercooling ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the advent of containerless processing techniques such as electromagnetic levitation, it is now possible to study the properties of high-temperature liquid metalsin situ by applying sophisticated noncontact diagnostics, such as pyrometry and high-speed videography. Thermophysical properties of interest are, e.g., specific heat, thermal conductivity, and viscosity. Applying containerless processing, it is also possible to undercool the melt because of the lack of container-induced nucleation sites. This gives access to a metastable region of the phase diagram. The knowledge of thermophysical data in this region is very important, because undercooling plays a major role in any solidification process. The degree of undercooling not only determines the growth velocity, but also is crucial in selecting the eventually obtained metastable solid phase. In this paper, some recent developments are surveyed relating to the noncontact measurements of emissivity, specific heat, electrical conductivity, density, surface tension, and viscosity, as well as a discussion of possible experiments in microgravity.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 26 (1991), S. 2997-3003 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An improved method for measuring the surface tension of liquid metals is proposed. Surface oscillations of an electromagnetically levitated liquid metal droplet are observed by a video camera and digital image processing is used to evaluate the spectrum of oscillations. A discussion of the theoretical background and a description of the experimental apparatus are presented. In addition, preliminary results on an FeNi sample, and an outlook for future experiments, including the measurement of viscosity, are given.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 11 (1992), S. 330-333 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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