Materials Science and Engineering

Topic 1: Nature of Materials

 Materials Science and Engineering?

Materials Science is about investigating the relationships that exist between the structures and properties of materials while Materials Engineering focuses on the basic of these structure-property correlations, designing or engineering the structure of a material to produce a predetermined set of properties. It is very important to study Materials Science and Engineering because materials are part of our daily living. We make use of various materials for an easier and comfortable living. It is important to select the right material for a certain object for it to optimize its function.

Importance of Engineering Materials

Because materials play the most important role in manufacturing. It is the material that is transformed. And it is the behavior of the material when subjected to the forces, temperatures, and other parameters of the process that determines the success of operation.

Types of Engineering Materials

• Metals

Metals are materials composed of one or more metallic elements (iron, aluminum, copper, gold, nickel, titanium, etc.) and non-metallic elements (carbon, nitrogen, oxygen, manganese, etc.) in relatively small amounts.

Characteristics of Metals

• Crystalline structure in the solid state, almost without exception [pic 1]
• Resistant to fracture
• Atoms held together by metallic bonding
• High strength and hardness, high electrical and thermal conductivity
• Generally ductile

• Ceramics

Ceramics are compounds of metallic and non-metallic elements. Some of the common ceramic materials include aluminum oxide or alumina (Al2O3), silicon dioxide or silica (SiO2), silicon carbide (SiC), and silicon nitride (Si3N4). There are also materials referred as traditional ceramics which are composed of clay minerals, cement, and glass.

Characteristics of Ceramics[pic 2]

• Most ceramics have crystal structure, while glass (SiO2) is amorphous
• Molecules characterized by ionic covalent bonding or both
• High hardness and stiffness, electrically insulating, refractory, and chemical inert

• Polymers

Most of the polymers are organic compounds that are chemically based on carbon, hydrogen, oxygen, nitrogen, and silicon. Polymers include the familiar plastics and rubber materials.

Characteristics of Polymers [pic 3]

• Many repeating mers in molecule held together by covalent bonding
• Polymers usually carbon plus one or more other elements: H, N, O and Cl
• Amorphous (glassy) structure or mixture of amorphous or crystalline
• Low density, high electrical resistivity, and low thermal conductivity, strength and stiffness vary widely

• Composites

A composite is composed of two (or more) individual materials, which come from the categories discussed above—viz., metals, ceramics, and polymers. The design goal of a composite is to achieve a combination of properties that is not displayed by any single material, and also to incorporate the best characteristics of each of the component materials. A large number of composite types exist that are represented by different combinations of metals, ceramics, and polymers. Furthermore, some naturally-occurring materials are also considered to be composites—for example, wood and bone.