Materials Science: Metals Overview

Study Notes

Materials are classified based on their atomic/molecular structure into families: metals, polymers, elastomers, ceramics, glasses, and hybrids.

Metallic solids are composed of atoms that share a "cloud" of valence electrons, known as metallic bonding.
Metallic bonding results in excellent thermal and electrical conductivity.
Metals exhibit high elastic stiffness, demonstrating resistance to deformation.
Pure metals are generally soft and ductile, capable of bending without breaking.
Metals possess high fracture toughness, resisting crack propagation.
Most metals are crystalline in structure. Amorphous metals, also known as metallic glass, are a notable exception.
Metals can be shaped, joined, and surface treated in various ways.
Strengthening methods for metals include:
- Alloying (mixing metals)
- Strain hardening (cold working)
- Heat treating

Dure metals are rarely found in nature in their pure metallic form.
Metals are typically extracted from their oxides.
Extraction involves reacting metal oxide with coke (carbon) in the presence of heat and/or electricity.
The general reaction process is: MxOy + S > XM + COy
- MxOy represents the metal oxide.
- S represents coke (carbon).
- XM represents the extracted metal.
- COy represents carbon monoxide.
For example, iron is extracted from iron oxide (Fe2O3) via the following reaction: Fe2O3 + 3C > 2Fe + 3CO
Producing one ton of iron requires approximately seven tonnes of raw materials, including two tonnes of iron oxide, one tonne of coke, 0.5 tonnes of limestone, and 3.5 tonnes of gases.

Elastomers are polymers with very long chains connected by cross-linking.
This structure enables them to undergo high elastic deformation without breaking or permanently deforming.
Elastomers exhibit low stiffness, typically 500 to 5000 times lower than metals .