Glassy carbon

Glass-like carbon, often called glassy carbon or vitreous carbon, is a non-graphitizing, or nongraphitizable, carbon which combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resistance, hardness (7 Mohs), low density, low electrical resistance, low friction, low thermal resistance, extreme resistance to chemical attack, and impermeability to gases and liquids. Glassy carbon is widely used as an electrode material in electrochemistry, for high-temperature crucibles, and as a component of some prosthetic devices. It can be fabricated in different shapes, sizes and sections. The names glassy carbon and vitreous carbon have been registered as trademarks, and IUPAC does not recommend their use as technical terms. A historical review of glassy carbon was published in 2021. Glassy carbon was first observed in the laboratories of The Carborundum Company, Manchester, UK, in the mid-1950s by Bernard Redfern, a materials scientist and diamond technologist. He noticed that Sellotape he used to hold ceramic (rocket nozzle) samples in a furnace maintained a sort of structural identity after firing in an inert atmosphere. He searched for a polymer matrix to mirror a diamond structure and discovered a resole resin that would, with special preparation, set without a catalyst. Crucibles were produced with this phenolic resin, and distributed to organisations such as UKAEA Harwell. Redfern left The Carborundum Co., which officially wrote off all interests in the glassy carbon invention. While working at the Plessey Company laboratory (in a disused church) in Towcester, UK, Redfern received a glassy carbon crucible for duplication from UKAEA. He identified it as one he had made from markings he had engraved into the uncured precursor prior to carbonisation—it is almost impossible to engrave the finished product. The Plessey Company set up a laboratory, first in a factory previously used to make briar pipes in Litchborough, and then a permanent facility at Caswell, Northamptonshire; this site became Plessey Research Caswell and then the Allen Clark Research Centre.