Current effects on neck growth in the sintering of copper spheres to copper plates by the pulsed electric current method

The effect of a pulsed dc on the sintering of copper spheres to copper plates was investigated. It was shown that the current had a marked effect on neck growth between the spheres and the plates. The enhancement of sintering under the effect of the current was attributed to electromigration. Microstructural observations on fracture surfaces of necks formed under high currents showed considerable void formation. It was also observed that the current resulted in increased evaporation and the formation of bunched evaporation steps. Formation of these steps and their location relative to the neck were consistent with current density distributions. The results of this investigation provide direct evidence for the role of the current in the sintering in the pulse electric current sintering method. (c) 2007 American Institute of Physics

Crystallization of metallic glasses under the influence of high density dc currents

The effect of a dc current on the crystallization of Vit1A (Zr42.6Ti12.4Cu11.25Ni10Be23.75) and PCNP (Pd40Cu30Ni10P20) metallic glasses was investigated. Samples were isothermally annealed with and without the current, at 623 and 577 K for the two glasses, respectively. Small-angle neutron scattering analyses showed that in the absence of a current, the annealed Vit1A samples were amorphous, but the imposition of a current enhanced the crystallization process, increasing both the size and volume fraction of the crystallites. Similar general observations were seen for the PCNP glass. Differential scanning calorimetry patterns of Vit1A samples indicate a lower thermal stability of samples annealed with a current. (C) 2004 American Institute of Physics

Biofuel as an alternative source of energy

New sources of energy have to replace fossil fuels because of a-man made ecological catastrophe. In this article there is a question of biofuel as an alternative source of energy in the world. The types of this renewable source of energy are revealed and analyzed. This paper quantify biofuel by presentation what it is, advantages and disadvantages of using this type of energy and how it uses. There is an investigation of future of biofuel

Directional electromigration-enhanced interdiffususion in the Cu–Ni system

The effect of a dc on the interdiffusivity D in the Cu-Ni system was investigated over the temperature range of 650-850 degrees C and at current densities in the range of 0-1000 A cm(-2). Interdiffusivities were calculated using the Sauer-Freise-den Broeder method and the values calculated in the absence of a current were in agreement with previously published results. The influence of the current on D depended on its direction relative to the two interfaces in the trilayered Cu-Ni-Cu samples. When the electronic flow was from Ni to Cu (cocurrent interface), the interdiffusivity showed a marked increase relative to copper content but was unchanged when the electronic flow was from Cu to Ni (countercurrent interface). The increase of D in the cocurrent interface depended on concentration and temperature. At lower temperatures, the increase becomes significant at higher copper concentrations but for the same value of current density, the increase is apparent at lower concentrations. The effective activation energy of interdiffusivity depended on concentration and decreased with the application of a current. The decrease was largest for higher copper concentrations. The results are interpreted in terms of a proposed vacancy-atom interaction for copper with the implication that the electron wind effect on Cu is counteracted by the effect of vacancies. (c) 2007 American Institute of Physics