Metallic, Polymeric, Ceramic, and Composite Materials
Classified in Chemistry
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Metallic Materials
Metallic materials are inorganic substances containing one or more elements. They may contain metals and also some non-metallic elements. The metallic elements include iron, copper, aluminum, nickel, magnesium, and titanium. Non-metallic elements include carbon, nitrogen, and oxygen.
Characteristics of Metal Components
- Have a crystalline structure
- Are good thermal and electrical conductors
- Many have mechanical resistance and are ductile at room temperature
- Can also exhibit high strength at elevated temperatures
A metal alloy is a combination of two or more metals. They are normally divided into two classes:
- Ferrous metals and alloys that contain a high percentage of iron
- Nonferrous metals and alloys containing no iron or relatively small amounts of iron
Polymeric Materials
Polymeric materials are formed by very large molecules with molecular weights ranging from a few thousand to millions of grams per mol. Most are organic polymers, i.e., containing carbon and hydrogen and often other non-metal atoms, especially oxygen and nitrogen.
Polymer Classification
Polymers can be classified into two groups:
- Thermoplastic polymers: Long chains that are not covalently connected to each other
- Thermoset polymers: Molecular chains strongly linked, making them rigid, strong, and more fragile than thermoplastics
Polymerization
Polymerization occurs when small molecules combine to produce larger molecules. The structure can be of long-chain (thermoplastic) or networks (thermosets). Thermoplastic materials are used to produce polyethylene plastic bags. Thermoset materials include resins and vulcanized rubber.
Ceramic Materials
Ceramic materials are inorganic, non-metallic materials consisting of metal and non-metal elements. They can be chemically bonded crystalline, amorphous, or mixtures thereof.
Features of Ceramic Materials
- High hardness and temperature resistance
- Low weight and good insulating properties
- Low toughness and ductility, mechanical fragility
- High melting temperature and high chemical stability
Composite Materials
Composite materials in engineering are generally defined as a material system comprising a mixture or combination of two or more micro or macro constituents that differ in shape and chemical composition and are essentially insoluble in each other.
Most Important Composites
- Fiber-reinforced plastic
- Concrete
- Asphalt
- Wood