Ceramics

The word ceramic is derived from the Greek word κεραμικός (keramikos). The term covers inorganic non-metallic materials whose formation is due to the action of heat. Up until the 1950s or so, the most important of these were the traditional clays, made into pottery, bricks, tiles and the like, along with cements and glass. The traditional crafts are described in the article on pottery. A composite material of ceramic and metal is known as cermet. The word ceramic can be an adjective, and can also be used as a noun to refer to a ceramic material, or a product of ceramic manufacture. Ceramics is a singular noun referring to the art of making things out of ceramic materials.

Many ceramic materials are hard, porous and brittle. The study and development of ceramics includes methods to mitigate problems associated with these characteristics, and to accentuate the strengths of the materials as well as to investigate novel applications.

The American Society for Testing and Materials (ASTM) defines a ceramic article as “an article having a glazed or unglazed body of crystalline or partly crystalline structure, or of glass, which body is produced from essentially inorganic, non-metallic substances and either is formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by the action of the heat.

Smectite is derived from the Greek word “smecktos”, meaning “soap”. The term “smectite” is used to describe a family of expanding 2:1 phyllosilicate minerals that have permanent layer charge between 0.2 and 0.6 charges per half unit cell. The smectite family encompasses clay minerals such as montmorillonite, beidellite, nontronite, saponite, and hectorite. Smectites are constructed of a single octahedral sheet sandwiched between two tetrahedral sheets, with the octahedral sheet sharing the apical oxygens of the tetrahedral sheets . Smectites are divided into two subgroups: dioctahedral, when only two of the three octahedral sites per half unit cell are occupied, and trioctahedral, when all three sites are populated .

Smectites are typically identified by X-ray diffraction. All Mg-saturated smectites give a 1.5 nm peak at 54% relative humidity. Beidellite give a 1.4 nm peak after the glycerol solvation from the vapor, whereas montmorillonite expand to 1.8 nm. Both expand to 1.7 nm after ethylene glycol solvation. K-saturated smectites give a 1.25 nm peak at 54% relative humidity, which reflects the hydration of the K⁺ ion and corresponds to a monolayer of H2O in the interlayer space. Smectite heat at 110 ^oC and kept 0% relative humidity yield a 1.0 nm peak that collapses slightly to 0.98 nm on heating.

a method for distinguishing between montmorillonite and beidellite or nontronite by heating Li-saturated clay at 220 ^oC. Subsequent liquid glycerol solvation results in a 0.95 nm XRD peak for montmorillonite, while nontronite and beidellite expand to 1.77 nm. A recent update of the method involves heating at 250 ^oC overnight followed by glycerol vapor solvation for 16 h at 90 ^oC .

Dioctahedral and trioctahedral smectites can be distinguished by observing the 060 XRD peak in randomly oriented samples. The dioctahedral smectites common in soils produce a peak near 0.150 nm, whereas the trioctahedral smectites inherited from parent material produce a peak near 0.154 nm .

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