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  • 1
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    Pressure concentrations due to plastic deformation of thin films or gaskets between anvils (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Plastic deformation of either a sample or a gasket between diamond anvils leads to large pressure concentrations, i.e., the maximum pressure can be many times the average pressure. This behavior is discussed using elementary plasticity theory for the case where the pressures are sufficiently low that the yield stress can be assumed not to vary with pressure. It is then shown that the pressure concentration factor can be even much larger when the yield stress of the sample at the highest pressure is much greater than the yield stress at the lowest pressure. This is illustrated with solid xenon where it is shown that the assumption that Nelson and Ruoff made about the pressure distribution in their xenon samples is incorrect. The pressure distribution is shown to be much steeper than assumed. Thus, the pressure they observed electrical conduction in xenon was above 1 Mbar.
    Keywords: ENGINEERING (GENERAL)
    Type: Journal of Applied Physics; 53; Oct. 198
    Format: text
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  • 2
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    The relation of the yield stress of high-pressure anvils to the pressure attained at yielding and the ultimate attainable pressure (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A sensitive microprofilometer was used to determine the onset of yielding in the anvils of a supported opposed anvil device for the case of 3% cobalt-cemented tungsten carbide as the anvil material. In addition, it is shown how the commencement of yielding in boron carbide pistons, the yield strength being known, can be used to obtain the transition pressure to a conducting phase in gallium phosphide. The transition pressures of bismuth and gallium phosphide are obtained and it is found that these transitions are extremely close to the maximum attainable pressure in, respectively, a maraging steel and a 3% cobalt-cemented tungsten carbide.
    Keywords: ENGINEERING (GENERAL)
    Type: Journal of Applied Physics; 50; Feb. 197
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  • 3
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    Analysis of resistance-versus-pressure relations for the diamond indentor-anvil system (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Pressures in excess of 1.4 Mbars have been attained by Ruoff and Wanagel (1977) by pressing tiny spherical diamond indentors (tip radius of 2 microns or less) against a diamond anvil. This system has been used for resistance-vs-pressure measurements as follows. A thin (200 A) coherent layer of a conductor, e.g., palladium, can be sputtered on the tip and on the anvil and electrical leads can then be attached to these at points remote from the contact area. Then a thin layer of the sample to be studied can be evaporated, sputtered, or placed on the anvil. When the indentor is pressed against the sample, the resistance changes as the pressure increases and as the contact radius increases. This paper analyzes the resistance-vs-pressure relationship for three different types of resistivity-vs-pressure behavior.
    Keywords: ENGINEERING (GENERAL)
    Type: Journal of Applied Physics; 50; Apr. 197
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  • 4
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    Etching of diamond with argon and oxygen ion beams (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The angular dependences of the sputter yield of (100) single crystal diamond under argon and oxygen ion beams were investigated. For argon ion beams a large increase in the sputter yield was observed as the angle of incidence was increased from the normal, with a maximum occurring at approximately 60 deg from the normal. The magnitude of the increase and the angle at which the maximum was observed were dependent on the ion energy and species. The shape of the yield versus angle of incidence curve indicated the presence of a highly damaged surface layer. Large deviations from this curve were observed where ion incidence was along channeling directions. Studies with oxygen ion beams showed almost no angular dependence for 500 eV ions while at an energy of 1000 eV the angular dependence was similar to that for argon ions. At normal incidence the yield for 500 eV oxygen ions was seven times larger than that for 500 eV argon ions. For 1000 eV oxygen and argon ions the corresponding ratio is only 2.5. Implications for mechanisms of inert and reactive ion etching are discussed. Application of the data to ion beam shaping of diamond tips for ultrahigh pressure research is discussed.
    Keywords: ENGINEERING (GENERAL)
    Type: Journal of Vacuum Science and Technology A (ISSN 0734-2101); 2; 477-480
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  • 5
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    Linear ruby scale and one megabar (1979)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The accuracy and validity of certain techniques used in studying high-pressure transitions have been investigated. Experiments which place upper limits of about 20 GPa and about 50 GPa on pressures practically attainable using uniaxial supported opposed anvil devices with tungsten carbide pistons and uniaxial opposed flat anvil diamond devices, respectively, are reported. Direct static determinations of the transition pressures of GaP by two different methods are described. The values obtained indicate that the linear ruby scale increasingly overestimates the transition pressure as the pressure rises above 10 GPa. It is further shown that the use of shock-based marker materials, such as silver, as the basis of pressure measurement in X-ray diffraction studies leads to bulk moduli of cubic carbides which are in extreme disagreement with expected values.
    Keywords: ENGINEERING (GENERAL)
    Type: High-pressure science and technology; Sixth International Conference; Jul 25, 1977 - Jul 29, 1977; Boulder, CO
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  • 6
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    A split sphere 60,000 ton press (1979)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A split sphere press which can have a total force of 60,000 tons applied to its exterior by a 0.55 GPa hydrostatic pressure vessel is described. The inner anvils are made of tungsten carbide and show considerable plastic deformation under load. Much greater pressures, in the 100 GPa range, are possible if diamond tipped anvils are used. Because of the uniformly loaded multi-anvil arrangement, the diamond tips can be maintained under a high degree of compressive load and therefore prevent fracture which may occur in a conventional opposed anvil arrangement. Press operation on CdS, ZnSe, ZnS, GaP, and BP samples is described, and their resistance versus external pressure on the sphere are plotted.
    Keywords: ENGINEERING (GENERAL)
    Type: High-pressure science and technology; Sixth International Conference; Jul 25, 1977 - Jul 29, 1977; Boulder, CO
    Format: text
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