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The mysterious birth of glassy carbon: How did Bernard Redfern discover this strange material?
Glass carbon, also known as glassy carbon or vitreous carbon, is a non-graphitizable carbon material that combines the properties of glass and ceramics with the characteristics of graphite. Its main properties include high thermal stability, high thermal conductivity, hardness (7 on the Mohs scale), low density, low electrical resistance, low friction, extremely high resistance to chemical attack, and impermeability to gases and liquids. This material is widely used as an electrode material in electrochemistry, a high-temperature crucible, and as a component of certain prosthetic limbs. Glassy carbon can be produced in different shapes, sizes, and cross-sections, and the terms "glassy carbon" and "glassy carbon" have been registered as trademarks, while IUPAC does not recommend their use as technical terms. With the publication of a historical review of glassy carbon in 2021, the origins of this material have attracted widespread attention.
Historical BackgroundGlass carbon first appeared in the laboratories of The Carborundum Company in Manchester, England, where it was discovered by materials scientist and diamond technology expert Bernard Redfern in the mid-1950s. He noticed that the tape used to hold a sample of ceramic (rocket nozzle) to the furnace floor transformed into an unusual structure after sintering in an inert atmosphere and retained its original shape.
Redfern then explored a polymer matrix to mimic the diamond structure and discovered a phenolic resin that, after a special treatment, would solidify without a catalyst. Crucibles made from this resin are distributed to many organizations, such as UKAEA Harwell. However, Redfern left Carbone and the company officially terminated all interest in the glassy carbon invention.
Plessey's development
While working at the Plessey laboratory in Towset, England, Redfern received a glassy carbon crucible from UKAEA and recognised it as one he had made earlier, as he had engraved the uncarbonised precursor with mark. The company established laboratories in Litchborough and later established permanent facilities in Caswell, Northamptonshire, which became Plessey Research Caswell and the Allen Clark Research Centre. The development of glassy carbon at Plessey is a matter of course, and although Redfern's contribution to the invention and production of glassy carbon is acknowledged, reference to him in subsequent publications by Cowlard and Lewis is not obvious.
Redfern filed a UK patent application on January 11, 1960, and was later granted US Patent 3,109,712A on November 5, 1963.
Material properties and applications
Glass carbon has a very uniform and predictable shrinkage rate, which allows precise fittings to be made in the polymer state. Some of the early ultrapure GaAs samples were zone purified in these crucibles because glassy carbon is not reactive toward GaAs. In addition, doping of glassy carbon also exhibits semiconductor phenomena.
Its porous form, called reticulated vitreous carbon (RVC), was first developed in the mid-1960s as a thermally insulating and microporous vitreous carbon electrode material. These properties make RVCs very useful in electrochemistry, especially as three-dimensional electrodes.
Structure and electrochemical properties
The structure of glassy carbon has long been controversial. Early structural models assumed the presence of both sp2- and sp3-bonded atoms in glassy carbon, but it is now known that glassy carbon is entirely sp2-bonded.
In electrochemistry, glassy carbon is considered to be an inert electrode for the reduction of hydroxide ions in aqueous solution. These features make it indispensable in sensor manufacturing. Due to its specific surface orientation, glassy carbon is used to fabricate various types of modified electrodes and exhibits good stability in biocompatible applications such as dental implants.
With the advancement of science and technology and the deepening of material research, the application scope and technology of glassy carbon are still expanding and evolving. The unique combination of ceramics and glass-like materials undoubtedly creates countless possibilities in the fields of modern science and engineering.
As we reflect again on this scientist’s contribution and the potential applications of this material, we can’t help but ask, how will future technological innovations change the way we understand and use this material?
