Glassy carbon
Encyclopedia
Glassy carbon, also called vitreous carbon, is a non-graphitizing 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.
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 an 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.
Note that glassy carbon should not be confused with amorphous carbon
. This from IUPAC: "Glass-like carbon cannot be described as amorphous carbon because it consists of two-dimensional structural elements and does not exhibit ‘dangling’ bonds."
It exhibits a conchoidal fracture
.
Comparable reaction on platinum:
The difference of 2.1 V is attributed to the properties of platinum which stabilizes a covalent Pt-H bond.
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
which combines glassy and ceramic properties with those of graphite. The most important properties are high temperature resistance, hardness (7 Mohs
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
), 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
Electrochemistry
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...
, 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.
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 SellotapeSellotape
Sellotape is a British brand of transparent, cellulose-based, pressure sensitive adhesive tape, and is the leading brand of clear, pressure sensitive tape in the United Kingdom. Sellotape is generally used for joining, sealing, attaching and mending...
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
Plessey
The Plessey Company plc was a British-based international electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after the second world war by acquisition of companies and formed overseas companies...
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 an 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
Amorphous carbon
Amorphous carbon or free, reactive carbon, is an allotrope of carbon that does not have any crystalline structure. As with all glassy materials, some short-range order can be observed...
so its hardness may be isotropic. Research is ongoing.
Structure
The structure of glassy carbon has long been a subject of debate. Early structural models assumed that both sp2- and sp3-bonded atoms were present, but it is now known that glassy carbon is 100% sp2. However, more recent research has suggested that glassy carbon has a fullerene-related structure.Note that glassy carbon should not be confused with amorphous carbon
Amorphous carbon
Amorphous carbon or free, reactive carbon, is an allotrope of carbon that does not have any crystalline structure. As with all glassy materials, some short-range order can be observed...
. This from IUPAC: "Glass-like carbon cannot be described as amorphous carbon because it consists of two-dimensional structural elements and does not exhibit ‘dangling’ bonds."
It exhibits a conchoidal fracture
Conchoidal fracture
Conchoidal fracture describes the way that brittle materials break when they do not follow any natural planes of separation. Materials that break in this way include flint and other fine-grained minerals, as well as most amorphous solids, such as obsidian and other types of glass.Conchoidal...
.
Electrochemical properties
Glassy carbon electrode (GCE) in aqueous solutions is considered to be an inert electrode for hydronium ion reduction:- H3O+(aq) + e-
H
(aq) Eo= −2.10 V versus NHEStandard hydrogen electrodeThe standard hydrogen electrode , is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials...
at 25 °C
Comparable reaction on platinum:
- H3O+(aq) + Pt(s) + e-
Pt:H(s) Eo= 0.000 V versus NHE at 25 °C
The difference of 2.1 V is attributed to the properties of platinum which stabilizes a covalent Pt-H bond.
External links
- HTW, supplier's website, for Glassy Carbon SIGRADUR