Materials Science

Scientifics and engineers deal with material development of materials and its sythesis and processing. "Synthesis" means how materials are fabricated from chemical substances. This science is concerned with:

1. Composition.

2. Microstructure.

3. Synthesis and processing.

4. Performance/Cost relation of materials.

 Classification of materials

1. Metals and alloys.

2. Ceramics and glasses.

3. Polymers.

4. Semiconductors.

5. Composites.

Metals and alloys

Some examples are: steel, aluminum, magnesium, zinc, cast iron, titanium, copper and nickel. They have metallic bond. It can also be metallic+covalent (iron) or metallic+ionic. They are electropositive (reason for oxidation). Non-directional bonds.

Properties:

1. Good electrical and thermal conductivity.

2. High resistance.

3. High stiffness.

4. Are ductile.

5. High impact resistance.

Ceramics and glasses

These are crystalline and inorganic materials. Sand and rocks are examples of natural ceramics. They are used to produce thermal insulation and as abrasives due to their porosity. Most of ceramics behave as brittle materials (it means they are delicate and could break easily due to an impact). Glasses are amorphous materials. It means they don't have a regular and periodic array of atoms. Covalent or covalent+ionic (silica) bonds. Salts have ionic bonds. Also, bonds are directional. Silica based. Low ductility.  Low electrical conductivity.

Polymers

Organic materials. Are made by chains of monomers that result from the polymerization process. In thermoset polymers the molecular chains are connected rigidly, while in thermoplastic polymers they are not. Covalent (between monomers) and van der Waals bonds (between polymer chains).

Semiconductors

Like Silicon and Germanium. They are used in electronic devices. The electrical conductivity of semiconductors is between that of ceramic and metallic materials. It is controlled to produce transistors and diodes. A semiconductor is an insulator that can be transformed into a conductor.

Composites

They combine the properties of two or more materials to produce a single material with properties that can't be found in other materials. Concrete and glass fiber reinforced parts are examples of composite materials.

Classification by their most important function

Structural

Steel and alloys, aluminum and alloys, concrete, wood, etc.

Intelligent materials

PZT: a ceramic compound with a piezoelectric effect (it produces a voltage when deformed) or changes shape when an external electric field is applied. Ultrasonic transducers and piezoelectric resonators are made using this material. Ni-Ti alloy (also called nitinol, present Shape Memory effect. At one temperature it can be deformed and at "Transformation temperature" it recovers its original shape), MR fluids (Magnetorheological Fluid. A fluid whose viscosity varies when varying an applied magnetic field to it) and polymer gels (materials that show a response when they are subjected to external environmental changes) also belong to this classification.

Optic materials

Examples are: SiO2 (Silicon Oxide), GaAs (Gallium Arsenide, Arseniuro de Galio), Al2O3 (Aluminium Oxide) , YAG (Yttrium Aluminium Garnet), ITO (Indium Tin Oxide).

Magnetic materials

Fe (iron), Fe-Si, Co-Pt-Ta-Cr (thin films used in magnetic data storage devices).

Energetic and environmental technology

UO2 (Uranium Dioxide, nuclear fuel), Ni-Cd (Nickel-Cadmium, for batteries), ZrO2 (Zirconium Dioxide, for fuel cell membranes), LiCoO2 (Lithium Cobalt Oxide, for use in Li-Ion batteries), amouphous Si:H (amorphous silicon for solar cells).

 Electronic materials

Si (silicon, for the manufacture of integrated circuits, i.e. printed silicon waffers), GaAs, Ge, PZT, Al, Cu, W (Wolfram or Tungsten), conductor polymers.

Biomedical materials

Hydroxylapatite (it is used as a filler to replace amputated bone), titanium alloys, stainless steel alloys, PZT, Memory Effect alloys.

Aerospace materials

C-C composites (carbon fiber reinforcement in a matrix of graphite) , SiO2, amouphous silicon, Al alloys, superalloys, Zerodur TM (extremely low expansion glass).

Material classification based on their structure

"Structure" means the array of atoms of a material. Materials can be classified as:

1. Crystalline materials: its atoms are organized periodically.

a) Monocrystalline materials.

b) Policrystalline materials: the grain boundaries also affect the properties of the material.

2. Amorphous materials: its atoms don't have the long-range order that is characteristic of a crystal.