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A twin boundary is a defect that introduces a plane of mirror symmetry in the ordering of a crystal. For example, in cubic close-packed crystals, the stacking sequence of a twin boundary would be ABCABCBACBA. On planes of single crystals, steps between atomically flat terraces can also be regarded as planar defects.
The formation and migration of twin boundaries is partly responsible for ductility and malleability of fcc metals. [26] Twin boundaries are partly responsible for shock hardening and for many of the changes that occur in cold work of metals with limited slip systems or at very low temperatures.
In mixed oxidation state materials like magnetite, antiphase domains and antiphase domain boundaries can occur as a result of charge-ordering even though there are no changes in atom locations. [4] For example, the reconstructed magnetite (100) surface contains alternating Fe II pairs and Fe III pairs in the first subsurface layer. [ 4 ]
Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a telltale sign of the presence of defects. [5]
Spontaneous nanowire formation by non-catalytic methods were explained by the dislocation present in specific directions [20] [21] or the growth anisotropy of various crystal faces. More recently, after microscopy advancement, the nanowire growth driven by screw dislocations [22] [23] or twin boundaries [24] were demonstrated.
The time frequency approach for machine fault diagnosis can be divided into two broad categories: linear methods and the quadratic methods. The difference is that linear transforms can be inverted to construct the time signal, thus, they are more suitable for signal processing, such as noise reduction and time-varying filtering.
Triangles and squares mark positions of the topological defects. A Wigner crystal is the solid (crystalline) phase of electrons first predicted by Eugene Wigner in 1934. [ 1 ] [ 2 ] A gas of electrons moving in a uniform, inert, neutralizing background (i.e. Jellium Model ) will crystallize and form a lattice if the electron density is less ...
The stacking-fault energy (SFE) is a materials property on a very small scale. It is noted as γ SFE in units of energy per area.. A stacking fault is an interruption of the normal stacking sequence of atomic planes in a close-packed crystal structure.