Showing 2 results for Crystal Orientation
M. Ghanbari, M. R. Aboutalebi, S. G. Shabestari,
Volume 11, Issue 2 (6-2014)
Abstract
Geometrical design of the spiral crystal selector can affect crystal orientation in the final single crystal
structure. To achieve a better understanding of conditions associated with the onset of crystal orientation in a spiral
crystal selector, temperature field was investigated using three-dimensional finite element method during the process.
Different geometries of spiral crystal selector were used to produce Al- 3 wt. % Cu alloy single crystal using a
Bridgman type furnace. The Crystal orientation of the samples was determined using electron backscattered
diffraction (EBSD) and optical microscopy. Analysing the temperature field in the crystal selector revealed that, the
orientation of growing dendrites against liquidus isotherm in the spiral selector was the reason for crystal
misorientation which differs in various selector geometries. Increasing the take-off angle from 35° up to 45° increases
the misorientation with respect to <001> direction. Further increase of take-off angle greater than 45° will decrease
the crystal misorientation again and the efficiency of the selector to produce a single grain is decreased.
D. Gharailou, A. Abbasi,
Volume 12, Issue 3 (9-2015)
Abstract
Effect of electro migration on crystal structures of platinum nanowire (Nano bridge) during Nano-gap
formation is investigated by means of Transmission Electron Microscopy (TEM). Selected area diffraction patterns as
well as bright field images are used for this investigation. There were severely recessions in the polycrystalline Nano
bridge and crystal structures around the nanogap changed completely during electro migration. Due to Joule heating,
original small crystal with random orientation disappeared and newly crystals with a preferred orientation grew. They
have [111] orientations (respect to beam direction) with slight misorientations. α and θ was defined to calculate the
misorientation and used to represent Nano-gap formation mechanism. The calculation gives the breaking of Nano
bridge occurred along grain boundaries in most of Nano bridges. The controlling system during eletromigration may
affect on the shapes of tips so that the shape of tips in Nano bridges, in which feedback control is applied, is more
symmetric than others. The effect of temperature on atomic diffusivity might be the reason of the behaviour. {422}
could be a preferred surface plane for mass transport in platinum Nano bridge in which atoms move along it
