Solidification And Crystalline Imperfections Question & Answer Sample

Question #1: Graphical illustration of energy changes during the formation of the nucleus in homogeneous solidification phenomenon.

The solidification phenomenon of a metal starts with the formation of nuclei in a liquid melt, the nuclei forms a stable nuclei in the same melt, and finally formation of the solidified structure of grained crystals. The structure is illustrated in the following diagrams.
Figure 1. Solidification process

Question #2: Comparison between homogeneous and heterogeneous nucleation

In the homogenous nucleation, the nuclei are synthesized from metal solidifying atoms. In heterogeneous nucleation, the nucleating agents are the impurity atoms as well as the container surfaces

Question #3: Production of large silicon single crystals

The large silicon single crystals are generated by the use of pure silicon seed crystals in a silicon melt in the Czochralski process.

Question #4: What are a metal alloy and solid solution?

A metal alloy can be described as the mixture of more than one metals.
A solid solution is a solid alloy that is formed by more than one elements that are atomically dispersed in one phase structure.

Question #5: Description and illustration of vacancy, divacancy, and interstitialcy point defect imperfections

Vacancy (point defect), it is an atomic space with a missing atom.
Divacancy, it is a defect in a crystal pack with two missing atoms
Interstitialcy, it is a point defect where an atom is occupying the interstitial space in the neighboring atoms.
Figure 2. Vacancy and Interstitialcy

Question #6: what are volume defects (three-dimensional defects)?

They include precipitates, often involving impurities, voids that may be filled or not filled with air. Special types of volume defects are stacking fault tetrahedral and dislocation clusters.

Question #7: Scanning tunneling microscope (STM), modes of operation, and dimensional resolution.

An STM is a device that images surface at atomic levels. Tunneling is the main principle of operation arising from quantum mechanics. An object hitting on an impenetrable barrier does not pass. But electrons that have atomic mass and wavelike features pass by tunneling principle.