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CAS NUMBER: 7782-42-5
MOLECULAR FORMULA: C
Amorphous carbon is free, reactive carbon that has no 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).
Amorphous carbon is the primary starting material for the synthesis of organic semiconductors used in solar cells, perovskites, and bio/pharma applications.
High purity Amorphous carbon for use in thermal evaporation systems as either electron acceptors, n-type semiconductors, or interface layers.
Amorphous carbon is used in foundry, Amorphous carbon is greasy, stains well and has the ability to adhere to hard surfaces, creating a thin film on the surface.
In mineralogy, amorphous carbon is the name used for coal, carbide-derived carbon, and other impure forms of carbon that are neither graphite nor diamond.
In a crystallographic sense, however, the materials are not truly amorphous but rather polycrystalline materials of graphite or diamond within an amorphous carbon matrix.
Commercial carbon also usually contains significant quantities of other elements, which may also form crystalline impurities.
With the development of modern thin film deposition and growth techniques in the latter half of the 20th century, such as chemical vapour deposition, sputter deposition, and cathodic arc deposition, it became possible to fabricate truly amorphous carbon materials.
True amorphous carbon has localized π electrons (as opposed to the aromatic π bonds in graphite), and its bonds form with lengths and distances that are inconsistent with any other allotrope of carbon.
Amorphous carbon also contains a high concentration of dangling bonds; these cause deviations in interatomic spacing (as measured using diffraction) of more than 5% as well as noticeable variation in bond angle.
The properties of amorphous carbon films vary depending on the parameters used during deposition.
The primary method for characterizing amorphous carbon is through the ratio of sp2 to sp3 hybridized bonds present in the material.
Amorphous carbon consists purely of sp2 hybridized bonds, whereas diamond consists purely of sp3 hybridized bonds.
Amorphous carbons that are high in sp3 hybridized bonds are referred to as tetrahedral amorphous carbon, owing to the tetrahedral shape formed by sp3 hybridized bonds, or as diamond-like carbon (owing to the similarity of many physical properties to those of diamond).
Experimentally, sp2 to sp3 ratios can be determined by comparing the relative intensities of various spectroscopic peaks (including EELS, XPS, and Raman spectroscopy) to those expected for graphite or diamond.
In theoretical works, the sp2 to sp3 ratios are often obtained by counting the number of carbon atoms with three bonded neighbors versus those with four bonded neighbors.
Although the characterization of amorphous carbon materials by the sp2-sp3 ratio may seem to indicate a one-dimensional range of properties between graphite and diamond, this is most definitely not the case.
Research is currently ongoing into ways to characterize and expand on the range of properties offered by amorphous carbon materials.
Amorphous carbon, short for quenched carbon, is claimed to be a type of amorphous carbon that is ferromagnetic, electrically conductive, harder than diamond, and able to exhibit high-temperature superconductivity.
A research group led by Professor Jagdish Narayan and graduate student Anagh Bhaumik at North Carolina State University announced the discovery of Amorphous carbon in 2015.
They have published numerous papers on the synthesis and characterization of Amorphous carbon, but as of late 2020, there is no independent experimental confirmation of this substance and its properties.
According to the researchers, Amorphous carbon exhibits a random amorphous structure that is a mix of 3-way (sp2) and 4-way (sp3) bonding, rather than the uniform sp3 bonding found in diamonds.
Amorphous carbon is melted using nanosecond laser pulses, then quenched rapidly to form Q-carbon, or a mixture of Q-carbon and diamond.
Amorphous carbon can be made to take multiple forms, from nanoneedles to large-area diamond films.
The researchers also reported the creation of nitrogen-vacancy nanodiamonds and Amorphous carbon, as well as the conversion of Amorphous carbon into diamond and h-BN into c-BN at ambient temperatures and air pressures.
The group obtained patents on q-materials and intended to commercialize them.
Amorphous carbon (a-C), including carbon black and activated charcoal, can be obtained through incomplete combustion of plant and animal substances.
In consideration of a rapid development in a-C-reinforced nanocomposites, this chapter reviews current research and relevant techniques for the manufacture and application of a-C and its nanocomposites.
On the basis of their superior and unique properties, these materials have been used in various applications for textile, plastic, and health-care industries as well as in the fields of gas and water filtering, electrical applications, and food packaging.
Amorphous carbon is a carbon material without long-range crystalline order.
Short-range order exists, but with deviations of the inter-atomic distances and/or inter-bonding angles with respect to the graphite lattice as well as to the diamond lattice.
The term amorphous carbon is restricted to the description of carbon materials with localized π-electrons.
Deviations in the Amorphous carbon distances >5 (i.e. ± Δx/X0 > 0.05, where X0 is the inter-atomic distance in the crystal lattice for the sp2 as well as for the sp3 configuration) occur in such materials, as well as deviations in the bond angles because of the presence of “dangling bonds”.
Amorphous carbons usually give single symmetric signals when using continuous wave (CW)-EPR. Spin concentrations are evaluated by comparing the signal intensity with that of a standard sample.
The magnetic field position of the signal corresponds to the ‘g-value’ of the paramagnetic species which derives from the free electron value of 2.00023 as a result of increases in spin–orbit interactions.
Because heteroatoms induce strong spin–orbit interactions, g-values measure the presence of heteroatoms included in the radical content of carbon.
Amorphous carbon can be classified into soft carbon and hard carbon according to the degree of difficulty in graphitization.
Amorphous carbon, also known as graphitizable carbon, is a transitional carbon that can be converted to graphitized carbon by heat treatment at temperatures above 2000°C.
Amorphous carbon is mainly derived from pyrolysis of organic polymers and petroleum asphalt.
Compared with graphitized carbon, the degree of graphitization of soft carbon is low, the grain size is small, and the interplanar spacing is large, which also facilitates the insertion and removal of sodium ions during charge and discharge, and is favorable for compatibility with the electrolyte. Despite this, some of the shortcomings of soft carbon itself limit Amorphous carbons use in batteries, mainly due to lower specific capacity and severe voltage hysteresis.
Hard carbon is difficult to graphitize even at temperatures above 3000°C.
The precursor is the thermal decomposition of hot melt resins, such as some phenolic resins and cellulose present in plants, mainly pyrolytic carbon, resin carbon, and carbon black.
Hard carbon has a single Amorphous carbon layer, which is more spaced than the soft carbon layer, which is more conducive to the diffusion of sodium ions.
In addition, abundance of lattice defects in the atomic layer provides more active sites for sodium ions, so hard carbon has a larger specific capacity.
However, lattice defects also bring some disadvantages while increasing the capacity.
Amorphous carbons are difficult to escape after being embedded in the lattice defects of the atomic layer, which brings about a problem that the first charge and discharge reversible specific capacity loss is large, and the first coulomb efficiency is low.
Heteroatoms in hard carbon also cause more severe voltage hysteresis than soft carbon.
At the same time, hard Amorphous carbon has no obvious charging and discharging platform, which also makes the output voltage of the battery unstable.
An amorphous Amorphous carbon material consisting of small polycyclic aromatic carbon sheets with a high density of sulfonic acid sites is one of promising solid replacements for sulfuric acid catalyst.
Such a material can be readily prepared by incomplete carbonization of sulfopolycyclic aromatic hydrocarbons or sulfonation of incompletely carbonized organic compounds, and exhibits remarkable catalytic performance as a stable catalyst for various liquid-phase acid-catalyzed reactions.
Amorphous carbons, however, cannot be synthesized by sulfonation of familiar carbon materials such as graphite, carbon black, graphitized carbon fiber, activated carbon or glassy carbon.
Amorphous carbon is a noncrystalline solid allotropic form of carbon.
There is no long-range order in the positions of the carbon atoms, but some short-range order is observed. Chemical bonds among atoms are a mixture of sp2 and sp3 hybridized bonds with a high concentration of dangling bonds.
Because amorphous carbon is thermodynamically in a metastable state and the ratio of sp2 and sp3 hybridized bonds is variable, the properties of amorphous carbon vary greatly depending on the formation methods and conditions.
Amorphous carbon is often abbreviated as “a-C”.
Other forms—such as carbon black, charcoal, lampblack, coal, and coke—are sometimes called amorphous, but X-ray examination has revealed that these substances do possess a low degree of crystallinity.
Diamond and graphite occur naturally on Earth, and they also can be produced synthetically; they are chemically inert but do combine with oxygen at high temperatures, just as amorphous carbon does.
Fullerene was serendipitously discovered in 1985 as a synthetic product in the course of laboratory experiments to simulate the chemistry in the atmosphere of giant stars.
Amorphous carbon was later found to occur naturally in tiny amounts on Earth and in meteorites.
Amorphous carbon is also synthetic, but scientists have speculated that it could form within the hot environments of some planetary cores.
Amorphous carbon has attracted intense research interest due to its tunable properties and importance in applications.
Due to Amorphous carbons bonding flexibility, as sp, sp2 or sp3 hybridized, carbon forms many amorphous structures. Sp2-bonded glassy carbon inherits short-/medium-range graphitic order and is electrically conductive, and its structural disorder results in advantageous properties such as high hardness and strength combined with low density.
However, synthesis of sp3-hybridized amorphous carbon remains a challenge, in contrast to the situation for silicon and germanium, which easily form amorphous structures6.
Amorphous carbon with sp3 bond concentration up to near 100% may inherit the short-/medium-range order of crystalline diamond and is expected to inherit also its superior properties.
The addition of even a small number of sp3 bonds in amorphous carbon can significantly modify its properties.
Amorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions.
Amorphous carbon is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite.
Amorphous carbon is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent.
Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation.
This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.
Amorphous carbon has a wide range of properties that are primarily controlled by the different bond hydridisations possible in such materials.
Amorphous carbon allows for the growth of an extensive range of thin films that can be tailored for specific applications.
Amorphous carbons can range from those with high transparency and are hard diamond-like, through to those which are opaque, soft and graphitic-like.
Amorphous carbons with a high degree of sp3 bonding giving the diamond-like properties are used widely by industry for hard coatings.
Application areas including field emission cathodes, MEMS, electronic devices, medical and optical coatings are now close to market.
Amorphous carbons in amorphous carbon have been drawn together to produce this comprehensive commentary on the current state and future prospects of this highly functional material.
The properties of amorphous carbon vary significantly with sample density and the details of its atomic structure strongly affect the material's properties.
Computational approaches are being developed in the group to better understand the microscopic structure of various amorphous carbons at the atomic level and to predict properties of these materials relevant for experimental work and technological applications.
Amorphous carbon is free, reactive carbon that does not have any crystalline structure.
True amorphous carbon has localized π electrons (as opposed to the aromatic π bonds in graphite), and its bonds form with lengths and distances that are inconsistent with any other allotrope of 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.
These materials are then called hydrogenated amorphous carbon. As with all 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.
The properties of various types of amorphous carbon and hydrogenated amorphous carbon are reviewed with particular emphasis on the effect of atomic structure on the electronic structure.
Amorphous carbon is shown how the proportion of sp3 and sp2 sites not only defines the short-range order but also a substantial medium-range order.
Medium-range order is particularly important in amorphous carbon because it is the source of its optical gap, whereas short-range order is usually sufficient to guarantee a gap in other amorphous semiconductors.
The review discusses the following properties: short-range order and the radial distribution function, the infrared and Raman spectra, mechanical strength, the electronic structure, photoemission spectra, optical properties, electron energy-loss spectra, core-level excitation spectra, electrical conductivity, electronic defects and the electronic doping of hydrogenated amorphous carbon.
Amorphous carbon (a-C) thin films were deposited on quartz substrate at different deposition temperature by thermal chemical vapor deposition (CVD) method using natural precursor `camphor oil'.
All samples were grown in fixed conditions except the deposition temperature was varied from 400°C to 800°C.
Amorphous carbon thin films were characterized by using UV-Vis spectroscopy, I-V measurement, Raman spectroscopy and Atomic Force Microscopy (AFM).
The UV-Vis analysis was used to obtain the optical band gap. The optical bang gap was decreased from 1.0eV to 0.1eV with the increasing the deposition temperature.
The electrical conductivity of Amorphous carbon thin films increased as the deposition temperature increased.
The sp 2 and sp 3 -bonded carbon amount in Amorphous carbon structure could effect the optical band gap of the Amorphous carbon thin films.
Amorphous carbon thin films were found to be dependent on the deposition temperature and amount of sp 2 and sp 3 bOnded carbon.
Generally we can characterize the amorphous structures by the high degree of short range order and absence of long range order.
From the energetic point of view, atoms in an amorphous crystal are not bonded ideally, they are subject to important stresses and distortions.
The energy of an amorphous solid is thus higher than that of a pure crystal.
There are two specific amorphous form of carbon: the diamond-like amorphous carbon and the graphite-like amorphous carbon ($a-C$).
These two structures can be distinguished clearly by their macroscopic and microscopic properties.
The former has higher density, is transparent and much harder than the latter.
From the microscopic point of view, the ratio of fourfold, diamondlike bonds to threefold, graphite-like bonds ($sp^3/sp^2$) will determine the kind of structure we obtain.
This ratio is strongly affected by the way the amorphous solid is prepared and depends on temperature and pressure.
In order to describe an amorphous structure the following characteristics can be used: a coordination number, a radial distribution function, an angular distribution function.
The coordination number $z$ is the number of nearest neighbor atoms.
For example, $z$ is 4 for the Amorphous carbon structure, or 12 for the FCC structure.
For perfect lattices, the coordination number has no real significance but for more complex structures, like amorphous lattices, it plays a crucial role in the determination of the amorphous structure type.
Amorphous carbon films were synthesized on top of polyethylene terephthalate (PET) substrates using atmospheric-pressure glow (APG) plasma CVD equipment which we originally designed and set up.
By varying dielectric constant of the plate, the deposition rate of the Amorphous carbon films was controlled.
From the oxygen transmission test, the resulting PET coated with thin carbon films exhibited high gas barrier property.
Using the material with high dielectric constant, we finally synthesized a nearly complete gas barrier films at the deposition rate of 15 sec.
Amorphous carbon has a wide range of properties that are primarily controlled by the different bond hydridisations possible in such materials.
This allows for the growth of an extensive range of thin films that can be tailored for specific applications.
Films can range from those with high transparency and are hard diamond-like, through to those which are opaque, soft and graphitic-like.
Films with a high degree of sp3 bonding giving the diamond-like properties are used widely by industry for hard coatings.
Application areas including field emission cathodes, MEMS, electronic devices, medical and optical coatings are now close to market.
Experts in amorphous carbon have been drawn together to produce this comprehensive commentary on the current state and future prospects of this highly functional material.
USES:
-textile
-plastic
-health-care industries as well as in the fields of gas and water filtering
-electrical applications, and food packaging
APPLICATIONS:
Carbon nanopowder was used in the comparative studies of oxidative treatment to carbon nanoparticles.
Non graphitic carbon may be used in lithium ion batteries in the form of coating.
A very important filler in the rubber industry and next to titanium dioxide, the most important pigment, printing inks, toners, single-ply roofing, inks, paints and plastics.
PROPERTIES:
Physical properties of amorphous carbon (a-C) thin films prepared by electron-gun evaporation on glass substrates have been studied.
The electron gun method is a simple alternative technique to prepare films of this material, in vacuum or in controlled atmospheres like N2, with important physical properties.
The main experimental parameter varied for different growths was the source-substrate distance.
The structural, vibrational, and electrical properties of such films are reported here.
A comparison between a-C and N-doped a-C films prepared with the same technique was made.
Amorphous carbon films have graphitic character with a carrier density up to 1.2 x 1022 cm-3 and in a-C:N films high conductivity values up to 1.0 x 103 Ω-1cm-1 were measured.
Amorphous carbon is a disordered metastable form of elemental carbon (although it can also be doped, intentionally or unintentionally, with other elements, most notably hydrogen).
As a testament to the incredible flexibility of C to form chemical bonds (which is at the root of the sheer complexity of organic molecules and life itself), a-C is made up of a mixture of C atoms with different environments: sp (as in acetylene), sp2 (as in graphite) and sp3 (as in diamond), depending on how many neighbors each C atom has.
Amorphous carbon is of high interest in research and industry because its mechanical and electronic properties can be tuned between those of graphene/graphite and diamond, by adjusting the sp2/sp3 ratio.
Amorphous carbon nitride thin films have been grown by plasma decomposition of a feedstock of CH4 and N2.
In the films with higher nitrogen concentration, the infrared absorption spectra are dominated by NH2 modes and give strong evidence of a polymeric structure.
The optical absorption and photoluminescence spectra show that nitrogen incorporation decreases the bandgap and increases the structural order of these thin films.
PROPERTIES:
-AppearanceAppearance: Black solid
-Melting Point: 3652 - 3697 °C (sublimes)
-Boiling Point: 4200 °C
-Density: 2.267 g/cm3
-Electronegativity: 2.55 Paulings
-Heat of Vaporization: 128 K-Cal/gm atom at 4612 °C
-Thermal Conductivity: 119-165 W/m/K
PROPERTIES:
-Quality Level: 100
-form: nanopowder
-particle size: <100 nm (TEM)
-surface area: spec. surface area >100 m2/g (BET)
-InChI: 1S/C
-InChI key: OKTJSMMVPCPJKN-UHFFFAOYSA-N
SYNONYM:
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