Ceramics and Glasses
Ceramics and glasses are inorganic, non-metallic solids — crystalline ceramics and amorphous glasses — whose strong ionic and covalent bonding gives high hardness, thermal and chemical stability, and a wide range of electrical and optical behaviour.
Definition
Ceramics and glasses are inorganic, non-metallic materials, either crystalline (ceramics) or amorphous (glasses), bonded by ionic and covalent forces, and characterised by hardness, thermal stability, electrical insulation or controlled function, and intrinsic brittleness.
Scope
This area covers the chemistry of inorganic non-metallic materials: the structure and formation of glasses through vitrification of a supercooled liquid; the crystalline structural and functional ceramics, including oxides, carbides, and nitrides, used for their mechanical, thermal, electrical, and optical properties; and the powder processing and sintering by which ceramic components are consolidated into dense bodies. It connects bonding and microstructure to the brittleness, refractoriness, and functional response of these materials.
Sub-topics
Core questions
- What distinguishes a glass from a crystalline ceramic?
- How does bonding give ceramics their hardness, refractoriness, and brittleness?
- How are functional ceramics tailored for electrical and optical roles?
- How are ceramic powders consolidated into dense components?
Key concepts
- Glass transition
- Network formers and modifiers
- Oxide, carbide, and nitride ceramics
- Brittleness and fracture
- Sintering and densification
- Functional ceramics
Key theories
- Glass formation by vitrification
- When a melt is cooled fast enough to bypass crystallisation, it becomes an increasingly viscous supercooled liquid that freezes into an amorphous solid at the glass transition; network-forming oxides build the random three-dimensional network characteristic of glass.
- Bonding, microstructure, and ceramic properties
- Strong, directional ionic-covalent bonds make ceramics hard, stiff, and thermally and chemically stable but also brittle, because there are few ways to deform without breaking bonds; microstructure, especially porosity and grain size, then controls strength and function.
Clinical relevance
Ceramics and glasses are essential across technology: structural ceramics provide wear- and heat-resistant components, functional ceramics serve as capacitors, sensors, and solid electrolytes, optical glasses form lenses and fibres, and bioceramics are used in implants — applications all rooted in the bonding and microstructure described here.
History
Ceramics and glasses are among the oldest engineered materials, but their scientific understanding is recent: Zachariasen's 1932 random-network theory explained glass structure, and Kingery's mid-twentieth-century work established ceramic science by linking processing, microstructure, and properties, turning an empirical craft into a quantitative materials discipline.
Key figures
- W. David Kingery
- William Houlder Zachariasen
Related topics
Seminal works
- callister2018
- kingery1976
- shelby2005
Frequently asked questions
- Is glass a solid or a liquid?
- Glass is a solid. It is amorphous, lacking the long-range crystalline order of most solids, and it forms by freezing a supercooled liquid at the glass transition. The old claim that glass flows over centuries is a misconception; at room temperature its viscosity is far too high for measurable flow.
- Why are ceramics strong but brittle?
- The same strong, directional ionic and covalent bonds that make ceramics hard and stable also leave few mechanisms for plastic deformation. Without easy dislocation motion, applied stress concentrates at flaws and propagates cracks, so ceramics fail by brittle fracture rather than bending.