1.2 Family of Materials

Metals and nonmetals should be the first of material classification by atomic bonding nature. Then along with civilization and material development, organic materials are isolated from nonmetals' family. Therefore, the nonmetal materials are divided into inorganic materials and organic materials; the latter usually refers to carbon-based materials generally made of covalently bonded carbon, hydrogen, oxygen, and nitrogen, etc, with minor species also containing elements of halogen, sulphur and phosphor. Nevertheless, some carbon-containing compounds are traditionally considered as inorganic, such as carbon monoxide, carbon dioxide, carbonates, cyanides, cyanates, carbides, since their components and properties are very similar to other inorganic materials.

Sometimes, we also typically identify materials either as structural materials or functional materials, with mechanical or opto-electro-magneto/thermal properties to be considered, respectively. And according to the nature of chemical bonding or components, these functional materials can be further divided into four main families: Metals (e.g., steel), Polymers (e.g., plastics), Ceramics (e.g., porcelain), and Composites (e.g., glass-reinforced plastics). Additionally, considering atom stacking mode, there are crystalline, polycrystalline and amorphous materials; by conductivity, there are insulator, semiconductor, conductor and superconductor; according to space scale, there are bulky, nanomaterials and thin films; in terms of availability, there are natural and artificial materials; etc.