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 thermal stability, high thermal conductivity, hardness (7 Mohs), low density, low electrical resistance, low friction, 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 , 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.
Redfern left The Carborundum Co., which officially wrote off all interests in the glassy carbon invention. While working at the Plessey laboratory 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 company set up a laboratory in Litchborough, and then a permanent facility at Caswell, Northamptonshire, which became Plessey Research Caswell and then the Allen Clark Research Centre.
Glassy carbon arrived at the Plessey as a fait accompli. The contribution of Redfern to the invention and production of glassy/vitreous carbon is acknowledged by his co-authorship of early articles,
Redfern's British patent application were filed on 11 January 1960 and he was the author of U.S. patent 3109712A, granted 5 November 1963, priority date 11 January 1960, filing date 9 January 1961. This came after the rescinded British patent. This prior art is not referenced in U.S. patent 4,668,496, 26 May 1987 for Vitreous Carbon. Patents were filed "Bodies and shapes of carbonaceous materials and processes for their production" and the name "Vitreous Carbon" presented to the product by Redfern's son.
Glassy or vitreous carbon was under investigation used for components for thermonuclear detonation systems and at least some of the patents surrounding the material were rescinded (in the interests of national security) in the 1960s.
Large sections of the precursor material were produced as castings, mouldings or machined into a predetermined shape. Large crucibles and other forms were manufactured.
Carbonisation took place in two stages. Shrinkage during this process is considerable (48.8%) but is absolutely uniform and predictable. A nut and bolt can be made to fit while in polymer form, processed separately but identically, and subsequently give a perfect fit.
Some of the first ultra-pure samples of gallium arsenide (GaAs) were zone refined in these crucibles, as glassy carbon is not reactive with GaAs.
Doped or impure glassy carbon exhibits semiconductor phenomena.
Vitreous carbon was fabricated with uranium carbide inclusions, on an experimental scale, using uranium-238.
On 11 October 2011, research conducted at the Carnegie Geophysical Laboratory led by Wendy Mao from Stanford, and her graduate student Yu Lin, described a new form of glassy carbon formed under high pressure, with hardness equal to diamond – a kind of diamond-like carbon. Unlike diamond, however its structure is that of amorphous carbon so its hardness may be isotropic. Research was ongoing .
Early structural models assumed that both sp2- and sp3-bonded atoms were present, but it is now known that glassy carbon is entirely sp2. More recent research has suggested that glassy carbon has a fullerenes-related structure.
It exhibits a conchoidal fracture.
Note that glassy carbon should not be confused with amorphous carbon. This from IUPAC:
Comparable reaction on platinum:
The difference of 2.1 V is attributed to the properties of platinum which stabilizes a covalent Pt-H bond.
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