Glassy Carbon - History

History

It was first observed in the laboratories of The Carborundum Company, Manchester, UK, in the mid-1950s by Bernard Redfern, the inventor, 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.

Redfern left The Carborundom Co., which officially wrote off all interests in the glassy carbon invention. Whilst 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 Alan 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.

Refern's contribution 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 and precursor samples exist.

UK patent application were filed in 11 Jan.1960 and US patent filed 9 Jan. 1961 (finalised as US patent 3,109,712). This prior art is not referenced in US 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 the son of Redfern.

Glassy/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, moldings 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 as the polymer, processed separately and subsequently give a perfect fit.

Some of the first ultrapure samples of Gallium Arsenide were zone refined in these crucibles. (Glassy carbon is extremely pure and unreactive to GaAs).

Doped/impure glassy carbon exhibited semiconductor phenomena.

Uranium carbide inclusions were fabricated (using U238 carbide at experimental scale).

On October 11, 2011, research conducted at the Carnegie Geophysical Laboratory led by Stanford’s Wendy L. Mao and her graduate student Yu Lin described a new form of glassy carbon formed under high pressure with hardness equal to diamond. Unlike diamond, however its structure is that of amorphous carbon so its hardness may be isotropic. Research is ongoing.