Material

A material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified based on their physical and chemical properties, or on their geological origin or biological function. Materials science is the study of materials and their applications.

Raw materials can be processed in different ways to influence their properties, by purification, shaping or the introduction of other materials. New materials can be produced from raw materials by synthesis.

In industry, materials are inputs to manufacturing processes to produce products or more complex materials.

Classification by use

Materials can be broadly categorised in terms of their use, for example:

• Building materials are used for construction
• Building insulation materials are used to retain heat within buildings
• Refractory materials are used for high-temperature applications
• Nuclear materials are used for nuclear power and weapons
• Aerospace materials are used in aircraft and other aerospace applications
• Biomaterials are used for applications interacting with living systems

Material selection is a process to determine which material should be used for a given application.

Classification by structure

The relevant structure of materials has a different length scale depending on the material. The structure and composition of a material can be determined by microscopy or spectroscopy.

Microstructure

In engineering, materials can be categorised according to their microscopic structure:

• Ceramics: non-metal, inorganic solids
• Glasses: amorphous solids
• Metals: pure or combined chemical elements with specific chemical bonding behavior
• Polymers: materials based on long carbon or silicon chains
• Hybrids: combinations of multiple materials, for example composites.

Larger-scale structure

In foams and textiles, the chemical structure is less relevant to immediately observable properties than larger-scale material features: the holes in foams, and the weave in materials.

Classification by properties

Main article: Material properties

Materials can be compared and classified by their large-scale physical properties.

Mechanical properties

Mechanical properties determine how a material responds to applied forces.

Examples include:

• Stiffness
• Strength
• Toughness
• Hardness

Thermal properties

Materials may degrade or undergo changes of properties at different temperatures. Thermal properties also include the material's thermal conductivity and heat capacity, relating to the transfer and storage of thermal energy by the material.

Other properties

Materials can be compared and categorised by any quantitative measure of their behavior under various conditions. Notable additional properties include the optical, electrical and magnetic behavior of materials.

See also

• Hyle, the Greek term, relevant for the philosophy of matter
• Matter
• Category:Materials