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.[1]

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 three-dimensional electrode in electrochemistry.[2] 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 and a 1cm3 graphite cube HP68-79
A large sample of glassy carbon, with 1 cm3 graphite cube for comparison
GlassyCarbon
A small rod of glassy carbon
Vitreos carbon crucible 2
Vitreous-glassy carbon crucibles

History

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.[3] But references to Redfern were not obvious in subsequent publications by Cowlard and Lewis.[4] Original boat crucibles, thick section rods and precursor samples exist.

Redfern's UK patent application were filed on 11 January 1960 and Bernard Redfern was the author of US patent US3109712A, granted 5 November 1963, priority date 11 January 1960, filing date 9 January 1961.[5] This came after the rescinded British patent. 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, a kind of diamond-like carbon. Unlike diamond, however its structure is that of amorphous carbon so its hardness may be isotropic. Research is ongoing.[6]

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. More recent research has suggested that glassy carbon has a fullerene-related structure.[7]

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."[1]

It exhibits a conchoidal fracture.

Electrochemical properties

Glassy carbon electrode (GCE) in aqueous solutions is considered to be an inert electrode for hydronium ion reduction:[8]

      versus NHE at 25 °C

Comparable reaction on platinum:

      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.[8]

Physical properties

Properties include 'high temperature resistance', hardness (7 Mohs), low density, low electrical resistance, low friction, and low thermal resistance.

Advantages

Due to their specific surface orientation, glassy carbon is employed as an electrode material for the fabrication of sensors. Glassy carbon paste, glassy carbon, carbon paste etc. electrodes when modified are termed as chemically modified electrodes.

See also

References

  1. ^ a b The entry for "Glass-like carbon" in IUPAC Goldbook.
  2. ^ Walsh, F.C.; Arenas, L.F.; Ponce de León, C.; Reade, G.W.; Whyte, I.; Mellor, B.G. (2016). "The continued development of reticulated vitreous carbon as a versatile electrode material: Structure, properties and applications". Electrochimica Acta. 215: 566–591. doi:10.1016/j.electacta.2016.08.103.
  3. ^ Lewis, J.C.; Redfern, B.; Cowlard, F.C. (1963). "Vitreous carbon as a crucible material for semiconductors". Solid-State Electronics. 6 (3): 251–254. Bibcode:1963SSEle...6..251L. doi:10.1016/0038-1101(63)90081-9.
  4. ^ Cowlard, F.C.; Lewis, J.C. (1967). "Vitreous carbon — A new form of carbon". Journal of Materials Science. 2 (6): 507–512. Bibcode:1967JMatS...2..507C. doi:10.1007/BF00752216.
  5. ^ https://www.google.com/patents/US3109712
  6. ^ New form of superhard carbon observed
  7. ^ Harris, P.J.F. (2003). "Fullerene-related structure of commercial glassy carbons" (PDF). Philosophical Magazine. 84 (29): 3159–3167. Bibcode:2004PMag...84.3159H. CiteSeerX 10.1.1.359.5715. doi:10.1080/14786430410001720363.
  8. ^ a b Sawyer, D. T.; Sobkowiak, A.; Roberts, J. L., Jr. (1995). Electrochemistry for Chemists (Second ed.). New York: John Wiley & Sons. ISBN 978-0-471-59468-0.

External links

2,8-Dihydroxyadenine

2,8-Dihydroxyadenine is a derivative of adenine which accumulates in 2,8 dihydroxy-adenine urolithiasis.

Allotropes of carbon

Carbon is capable of forming many allotropes due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades many more allotropes, or forms of carbon, have been discovered and researched including ball shapes such as buckminsterfullerene and sheets such as graphene. Larger scale structures of carbon include nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at very high temperatures or extreme pressures. Around 500 hypothetical 3-periodic allotropes of carbon are known at the present time according to SACADA

database.

Amorphous carbon

Amorphous carbon is free, reactive carbon that does not have any crystalline structure. Amorphous carbon materials may be stabilized by terminating dangling-π bonds with hydrogen. As with other amorphous solids, some short-range order can be observed. Amorphous carbon is often abbreviated to aC for general amorphous carbon, aC:H or HAC for hydrogenated amorphous carbon, or to ta-C for tetrahedral amorphous carbon (also called diamond-like carbon).

Carbon

Carbon (from Latin: carbo "coal") is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Three isotopes occur naturally, 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen.The atoms of carbon can bond together in different ways, termed allotropes of carbon. The best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form. For example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper (hence its name, from the Greek verb "γράφειν" which means "to write"), while diamond is the hardest naturally occurring material known. Graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure. They are chemically resistant and require high temperature to react even with oxygen.

The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of inorganic carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil, and methane clathrates. Carbon forms a vast number of compounds, more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. For this reason, carbon has often been referred to as the "king of the elements".

Carbon chauvinism

Carbon chauvinism is a neologism meant to disparage the assumption that the chemical processes of hypothetical extraterrestrial life must be constructed primarily from carbon (organic compounds) because carbon's chemical and thermodynamic properties render it far superior to all other elements.

Carbon paste electrode

A carbon-paste electrode (CPE) is made from a mixture of conducting graphite powder and a pasting liquid. These electrodes are simple to make and offer an easily renewable surface for electron exchange. Carbon paste electrodes belong to a special group of heterogeneous carbon electrodes. These electrodes are widely used mainly for voltammetric measurements; however, carbon paste-based sensors are also applicable in coulometry (both amperometry and potentiometry).

Chemically modified electrode

A chemically modified electrode is an electrical conductor (material that has the ability to transfer electricity) that has its surface modified for different electrochemical functions. Chemically modified electrodes are made using advanced approaches to electrode systems by adding a thin film or layer of certain chemicals to change properties of the conductor according to its targeted function.At a modified electrode, an oxidation-reduction substance accomplishes electrocatalysis by transferring electrons from the electrode to a reactant, or a reaction substrate.Modifying electrodes' surfaces has been one of the most active areas of research interest in electrochemistry since 1979, providing control over how electrodes interacts with their environments.

Cyclic voltammetry

Cyclic voltammetry (CV) is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is reached in a CV experiment, the working electrode's potential is ramped in the opposite direction to return to the initial potential. These cycles of ramps in potential may be repeated as many times as needed. The current at the working electrode is plotted versus the applied voltage (that is, the working electrode's potential) to give the cyclic voltammogram trace. Cyclic voltammetry is generally used to study the electrochemical properties of an analyte in solution or of a molecule that is adsorbed onto the electrode.

Electrochemical stripping analysis

Electrochemical stripping analysis is a set of analytical chemistry methods based on voltammetry or potentiometry that are used for quantitative determination of ions in solution. Stripping voltammetry (anodic, cathodic and adsorptive) have been employed for analysis of organic molecules as well as metal ions. Carbon paste, glassy carbon paste, and glassy carbon electrodes when modified are termed as chemically modified electrodes and have been employed for the analysis of organic and inorganic compounds.

Stripping analysis is an analytical technique that involves (i) preconcentration of a metal phase onto a solid electrode surface or into Hg (liquid) at negative potentials and (ii) selective oxidation of each metal phase species during an anodic potential sweep. Stripping analysis has the following properties: sensitive and reproducible (RSD<5%) method for trace metal ion analysis in aqueous media, 2) concentration limits of detection for many metals are in the low ppb to high ppt range (S/N=3) and this compares favorably with AAS or ICP analysis, field deployable instrumentation that is inexpensive, approximately 12-15 metal ions can be analyzed for by this method. The stripping peak currents and peak widths are a function of the size, coverage and distribution of the metal phase on the electrode surface (Hg or alternate).

Flow battery

A flow battery, or redox flow battery (after reduction–oxidation), is a type of electrochemical cell where chemical energy is provided by two chemical components dissolved in liquids contained within the system and separated by a membrane. Ion exchange (accompanied by flow of electric current) occurs through the membrane while both liquids circulate in their own respective space. Cell voltage is chemically determined by the Nernst equation and ranges, in practical applications, from 1.0 to 2.2 volts.

A flow battery may be used like a fuel cell (where the spent fuel is extracted and new fuel is added to the system) or like a rechargeable battery (where an electric power source drives regeneration of the fuel). While it has technical advantages over conventional rechargeables, such as potentially separable liquid tanks and near unlimited longevity, current implementations are comparatively less powerful and require more sophisticated electronics.

The energy capacity is a function of the electrolyte volume (amount of liquid electrolyte), and the power is a function of the surface area of the electrodes.

Glass

Glass is a non-crystalline, amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. The term glass, in popular usage, is often used to refer only to this type of material, which is familiar from use as window glass and in glass bottles. Of the many silica-based glasses that exist, ordinary glazing and container glass is formed from a specific type called soda-lime glass, composed of approximately 75% silicon dioxide (SiO2), sodium oxide (Na2O) from sodium carbonate (Na2CO3), calcium oxide (CaO), also called lime, and several minor additives.

Many applications of silicate glasses derive from their optical transparency, giving rise to their primary use as window panes. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels. These qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures. Because glass can be formed or moulded into any shape, it has been traditionally used for vessels: bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also been used for paperweights, marbles, and beads. When extruded as glass fiber and matted as glass wool in a way to trap air, it becomes a thermal insulating material, and when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass. Some objects historically were so commonly made of silicate glass that they are simply called by the name of the material, such as drinking glasses and eyeglasses.

Scientifically, the term "glass" is often defined in a broader sense, encompassing every solid that possesses a non-crystalline (that is, amorphous) structure at the atomic scale and that exhibits a glass transition when heated towards the liquid state. Porcelains and many polymer thermoplastics familiar from everyday use are glasses. These sorts of glasses can be made of quite different kinds of materials than silica: metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses (acrylic glass, polycarbonate or polyethylene terephthalate) are a lighter alternative than traditional glass.

M-DISC

M-DISC (Millennial Disc) is a write-once optical disc technology introduced in 2009 by Millenniata, Inc. and available as DVD and Blu-ray discs.

Molten-salt battery

Molten-salt batteries (including liquid-metal batteries) are a class of battery that uses molten salts as an electrolyte and offers both a high energy density and a high power density. Traditional "use once" thermal batteries can be stored in their solid state at room temperature for long periods of time before being activated by heating. Rechargeable liquid-metal batteries are used for electric vehicles and potentially also for grid energy storage, to balance out intermittent renewable power sources such as solar panels and wind turbines.

Overpotential

In electrochemistry, overpotential is the potential difference (voltage) between a half-reaction's thermodynamically determined reduction potential and the potential at which the redox event is experimentally observed. The term is directly related to a cell's voltage efficiency. In an electrolytic cell the existence of overpotential implies the cell requires more energy than thermodynamically expected to drive a reaction. In a galvanic cell the existence of overpotential means less energy is recovered than thermodynamics predicts. In each case the extra/missing energy is lost as heat. The quantity of overpotential is specific to each cell design and varies across cells and operational conditions, even for the same reaction. Overpotential is experimentally determined by measuring the potential at which a given current density (typically small) is achieved.

Poly(3,4-ethylenedioxythiophene)

Poly(3,4-ethylenedioxythiophene) or PEDOT (or sometimes PEDT; IUPAC name poly(2,3-dihydrothieno[3,4-b][1,4]dioxane-5,7-diyl)) is a conducting polymer based on 3,4-ethylenedioxythiophene or EDOT. Advantages of this polymer are optical transparency in its conducting state, high stability and moderate band gap and low redox potential. A large disadvantage is poor solubility, which is partly circumvented in the PEDOT:PSS composite, and the PEDOT-TMA material. Applications of PEDOT include electrochromic displays, antistatics, photovoltaics, electroluminescent displays, printed wiring, and sensors.The polymer is generated by oxidation. This process begins with production of the radical cation of EDOT monomer, [C2H4O2C4H2S]+. This cation attacks a neutral EDOT followed by deprotonation. The idealized conversion using peroxydisulfate is shown

n C2H4O2C4H2S + n (OSO3)22− → [C2H4O2C4S]n + 2n HOSO3−For commercial purposes, the polymerization is conducted in the presence of polystyrene sulfonate (PSS). The resulting composites, PEDOT coatings are deposited on a conductive support (Pt, Au, glassy carbon, indium tin oxide, etc.) in organic solvents or in aqueous suspensions.

Polycarbonyl

Polycarbonyl, (also known as polymeric-CO, p-CO or poly-CO) is a solid metastable and explosive polymer of carbon monoxide. The polymer is produced by exposing carbon monoxide to high pressures. The structure of the solid appears amorphous, but may include a zig zag of equally spaced CO groups.

Rotating disk electrode

A rotating disk electrode (RDE) is a hydrodynamic working electrode used in a three electrode system. The electrode rotates during experiments inducing a flux of analyte to the electrode. These working electrodes are used in electrochemical studies when investigating reaction mechanisms related to redox chemistry, among other chemical phenomena. The more complex rotating ring-disk electrode can be used as a rotating disk electrode if the ring is left inactive during the experiment.

Sudan I

Sudan I (also commonly known as CI Solvent Yellow 14 and Solvent Orange R), is an organic compound, typically classified as an azo dye. It is an intensely orange-red solid that is added to colourise waxes, oils, petrol, solvents, and polishes. Sudan I has also been adopted for colouring various foodstuffs, especially curry powder and chili powder, although the use of Sudan I in foods is now banned in many countries, because Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogens (not classifiable as to its carcinogenicity to humans) by the International Agency for Research on Cancer. Sudan I is still used in some orange-coloured smoke formulations and as a colouring for cotton refuse used in chemistry experiments.

Working electrode

The working electrode is the electrode in an electrochemical system on which the reaction of interest is occurring. The working electrode is often used in conjunction with an auxiliary electrode, and a reference electrode in a three electrode system. Depending on whether the reaction on the electrode is a reduction or an oxidation, the working electrode is called cathodic or anodic, respectively. Common working electrodes can consist of materials ranging from inert metals such as gold, silver or platinum, to inert carbon such as glassy carbon, boron doped diamond or pyrolytic carbon, and mercury drop and film electrodes. Chemically modified electrodes are employed for the analysis of both organic and inorganic samples.

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