University:
York University
Course:
CHEM 1100 | Chemistry and Materials Science for Engineers
Academic year:

2021
Views:

158

Pages:

2
Author:

Nick T.

Increasing temperature causes surface island of atoms to grow. The equilibrium vacancy concentration increases via atom motion from the crystal to the surface, where they join the island. Low energy electron microscope MgO (magnesium oxide defects) Vacancy, kink, adatom, step, terrace Unsaturated atoms: don't have full coordination with other atoms, bonding from all sides, more chemically active, easy to move around, less bond. Atoms can move along these steps after thermal treatment. Dots? Rows? Atoms? Guess where is the d-spacing? Pure metal with only one type of atom does not exist. In alloys, impurities are added intentionally to impact specific properties. Example: Sterling silver (92.5%) with copper (7.5%) is used to make jewelry. Gold and platinum are inactive chemically. Why add copper to silver? Silver in nature is very soft and bendable, so we add copper to improve its corrosion and mechanical properties. When adding impurities to form solid solutions, we are close to the limit of solid solubility. When impurities are added into the host material and crystal structure is maintained with no new crystals formed, the impurity is randomly spread in the material. Solid solution: Solid in solid with no new formation of crystals, new grains or phases are made, and new compositions and arrangements of atoms are made while maintaining composition.