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  • Open Access


    Computer Simulation of Fundamental Behaviors of Point Defects, Clusters and Interaction with Dislocations in Fe and Ni

    E. Kuramoto, K. Ohsawa, T. Tsutsumi1

    CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 193-200, 2002, DOI:10.3970/cmes.2002.003.193

    Abstract In order to investigate the interaction of point defects with a dislocation, an interstitial cluster or a SFT (stacking fault tetrahedron), computer simulation has been carried out in model Fe and Ni crystals. The capture zone (the region where the interaction energy is larger than kT) was determined for various interactions. Calculated capture zone for T =500°C for SIAs (crowdion and dumbbell) around a straight edge dislocation is larger than that for a vacancy in both Fe and Ni. Capture zones for Ni are larger than those for Fe, suggesting that Ni (fcc) has a More >

  • Open Access


    Production of Carbon Nanotubes-Nickel Composites on Different Graphite Substrates

    Munther Issa K,ah1, Jean-Luc Meunier2

    FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.2, pp. 123-136, 2009, DOI:10.3970/fdmp.2009.005.123

    Abstract Multi walled carbon nanotubes (MWCNTs) were synthesized on different graphite types covered with thin layer of nickel catalyst by catalytic chemical vapour deposition using acetylene as hydrocarbon source. The produced carbon nanotubes were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The shape, quantity and diameter of the MWCNTs are shown to be affected by the type of the graphite substrate, the growth temperature and the hydrocarbon source flow rate. The diameters of the produced MWCNTs were ranged between 43 and 80 nm for pyrolytic (PYROID) and polycrystalline More >

  • Open Access


    The Colossal Piezoresistive Effect in Nickel Nanostrand Polymer Composites and a Quantum Tunneling Model

    Oliver K. Johnson1, Calvin J. Gardner1, David T. Fullwood1, Brent L.Adams1, Nathan Hansen2, George Hansen2

    CMC-Computers, Materials & Continua, Vol.15, No.2, pp. 87-112, 2010, DOI:10.3970/cmc.2010.015.087

    Abstract A novel nickel nanostrand-silicone composite material at an optimized 15 vol% filler concentration demonstrates a dramatic piezoresistive effect with a negative gauge factor (ratio of percent change in resistivity to strain). The composite volume resistivity decreases in excess of three orders of magnitude at a 60% strain. The piezoresistivity does decrease slightly as a function of cycles, but not significantly as a function of time. The material's resistivity is also temperature dependent, once again with a negative dependence.
    The evidence indicates that nickel strands are physically separated by matrix material even at high volume fractions, and More >

  • Open Access


    Statistics of High Purity Nickel Microstructure From High Energy X-ray Diffraction Microscopy

    C.M. Hefferan1, S.F. Li1, J. Lind1, U. Lienert2, A.D. Rollett3, P. Wynblatt3, R.M. Suter1,3

    CMC-Computers, Materials & Continua, Vol.14, No.3, pp. 209-220, 2009, DOI:10.3970/cmc.2009.014.209

    Abstract We have measured and reconstructed via forward modeling a small volume of microstructure of high purity, well annealed nickel using high energy x-ray diffraction microscopy (HEDM). Statistical distributions characterizing grain orientations, intra-granular misorientations, and nearest neighbor grain misorientations are extracted. Results are consistent with recent electron backscatter diffraction measurements. Peaks in the grain neighbor misorientation angle distribution at 60 degrees (∑3) and 39 degrees (∑9) have resolution limited widths of ≈ 0.14 degree FWHM. The analysis demonstrates that HEDM can recover grain and grain boundary statistics comparable to OIM volume measurements; more extensive data sets More >

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