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, as well as for high temperature crucibles and as a component of some prosthetic devices, and can be fabricated as different shapes, sizes and sections.

The names glassy carbon and vitreous carbon have been introduced as trademarks; therefore, IUPAC does not recommend their use as technical terms.

Vitreous carbon can also be produced as a foam. It is then called reticulated vitreous carbon (RVC). This foam was first developed in the mid to late 1960s as a thermally insulating, microporous glassy carbon electrode material. RVC foam is a strong, inert, electrically and thermally conductive, and corrosion resistant porous form of carbon with a low resistance to gas and fluid flow. Due to these characteristics, the most widespread scientific use of RVC is as electrode in electrochemistry . Additionally, RVC foams are characterized by an exceptionally high void volume, high surface area, and very high thermal resistance in non-oxidising environments, which allows for heat sterilization and facilitates manipulation in biological applications.

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. Using this phenolic resin, crucibles were produced. Crucibles were distributed to organisations such as UKAEA Harwell.

Bernard 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, UK, and then a permanent facility at Caswell, near Blakesly, UK. Caswell became the Plessey Research Centre and then the Allen Clark Research Centre. Glassy carbon arrived at the Plessey Company Limited as a fait accompli. Redfern was assigned J.C. Lewis, as a laboratory assistant, for the production of glassy carbon. F.C. Cowlard was assigned to Redfern's department later, as a laboratory administrator. Cowlard was an administrator who previously had some association with Silane (Silane US Patent assignee 3,155,621 3 Nov 1964). Neither he nor Lewis had any previous connection with glassy carbon. The contribution of Bernard Redfern to the invention and production of glassy / Vitreous carbon is acknowledged by his co-authorship of early articles. But references to Redfern were not obvious in subsequent publications by Cowlard and Lewis. Original boat crucibles, thick section rods and precursor samples exist.

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