Coconut Shell Carbon Hardness Number and Iodine Number

Coconut shell based activated carbons has Lower Ash Content, Higher Amount of Micropores, Higher Iodine Number, Excellent Hardness and it is very efficient in the removal of small size organic impurities.

Activated carbon from coconut shell has predominantly pores in micro pore range. Almost 85-90% surface area of coconut shell activated carbon exists as micro-pores. These small pores match the size of contaminant molecules in drinking water and therefore are very effective in trapping them.

Macro-pores are considered as an access point to micro-pores. Meso-pores do not usually play an important role in the adsorption unless the surface area of these pores is large, 400 m2/g or more. The predominance of micro-pores in coconut shell carbon gives it tight structure and provides good mechanical strength and hardness and also high resistance to resist attrition or wearing away by friction.

Coconut shell-based AC has the most micropores. Micropores are defined as pores less than 20-angstrom units (two nm) in diameter.  Coconut shell based carbons are excellent for Point of Use (POU) and Point of Entry (POE) applications because of lower ash content and excellent microporus structure.

The very large internal surface areas characterized by microporosity along with high hardness and low dust make these coconut shell carbons particularly attractive for water and critical air applications as well as point-of-use water filters and respirators.

Coconut Activated Carbon Hardness Number is around 98 but Bituminous Coal Activated carbons hardness number is only 85 – 90.

Some of other features which carbon industries, see as a great advantage in favour of coconut carbon are as follows:

  • Coconut is a renewable source of carbon
  • Coconuts grow throughout the year, with harvesting generally occurring 3-4 times in a year
  • Coconut tree can be preserved for many years

 

 

 

 

 

Pelletized Activated Carbon and Its Usages

Pellet activated carbon produced from coal, wood and coconut shell, either by high temperature steam activation or chemical activation under stringent quality control. With low ash content, large surface area, high mechanical hardness, high pore volume and chemical stability.

By varying manufacturing conditions, internal pore structures are created that impart unique adsorption properties specific to each product type. The choice of product for a specific application will vary due to differing impurities and process conditions.

Pelletized activated carbon is created by extruding activated carbon into cylindrical shaped pellets with diameters ranging from 0.8 to 5 mm. Their high activity and surface area make it ideal for many vapor phase applications. The uniformity of its shape makes it particularly useful in applications where low-pressure drop is a consideration.

Pelletized activated carbon provides lower pressure drop than granular activated carbon in fixed-bed purification of gases and vapors. The adsorptive capacity of pelletized carbon makes it ideal for removing a variety of contaminants from air and gas streams. Pellets are also an environmentally responsible product that can be reactivated through thermal oxidation and used multiple times for the same application.

Applications include gasoline vapor recovery for automotive applications, solvent recovery, air purification, odor control, catalysis and removal of corrosive gases.  Pelletized activated carbons are extremely hard, durable and low in dust content. They are particularly well suited for recovery of solvents and for evaporative emissions controls.

The pellets are available in different diameters and chemistry to meet a variety of application requirements.  Pelletized activated carbons specifically designed for gasoline vapor recovery. Customers can select activated carbon products with the proven physical properties and design flexibility needed to achieve optimum performance in their own canister systems.

The features and benefits of pelletized automotive carbons include the highest working capacity, low density, low flow restriction, low diurnal emissions, and superior durability.

Solvent Recovery, Air Purification, Acid Gas-Odor Control – Pelletized carbons are used for the control of organic pollutants in a variety of off-gas applications for environmental purposes. They are particularly well suited for use in solvent recovery systems where cyclohexanone is the solvent, and in systems with other solvents that see traces of heavy components that shorten the bed life of other types of carbons. They are also
used to purify many types of industrial and hydrocarbon gases in fixed beds or pressure swing adsorption applications such as natural gas purification and helium recovery.

Other Uses – Catalysis/Catalyst support

For Pelletized Activated Carbon Market place, please go to  http://www.acarbons.com/market-places/browse-ads/72/pelletized-activated-carbon/

The Pricing of Natural Graphite and the history of natural graphite

In the 4th millennium B.C., during the Neolithic Age in southeastern Europe, the Mariţa culture used graphite in a ceramic paint for decorating pottery.

Some time before 1565 (some sources say as early as 1500), an enormous deposit of graphite was discovered on the approach to Grey Knotts from the hamlet of Seathwaite in Borrowdale parish, Cumbria, England, which the locals found very useful for marking sheep.

During the reign of Elizabeth I (1533–1603),  Borrowdale graphite was used as a refractory material to line moulds for cannonballs, resulting in rounder, smoother balls that could be fired farther, contributing to the strength of the English navy. This particular deposit of graphite was extremely pure and soft, and could easily be cut into sticks.  Because of its military importance, this unique mine and its production were strictly controlled by the Crown.

The Pricing of Natural Graphite

Graphite prices are a function of 2 factors – flake size and purity – with large flake (+80 mesh), high Carbon (+94%) varieties commanding premium pricing.

Graphite Prices

There is a posted price for Graphite which provides a guideline with respect to longer term trends but transactions are largely based on direct negotiations between the buyer and seller. Prices exceeded USD$1,300/t in the late 80s but crashed to USD$600 -$750/t in the 90s as Chinese producers dumped product on the market. During this period there was essentially no exploration and as a result there are very few projects under development.

Graphite prices started to recover in 2005 and with average growt rates of 5% per annum over the past decade. They are currently well over USD$1,300/t with premium product rumoured to be selling at up to USD$3,000/t as the supply of large flake, high carbon graphite is tightening. Price appreciation is largely a function of the commodity super cycle and the industrialization of emerging economies as new, high growth applications such as Li-ion batteries are only beginning to have an impact on demand and consumption. Graphite prices have not yet experienced the price appreciation of other commodities and graphite must still be considered an overlooked and undervalued commodity in the context of the current super cycle.

Future Growth

New applications such as lithium-ion batteries, fuel cells and nuclear power have the potential to create significant, incremental demand growth in the future. For example, it takes 20 to 30 times more graphite than lithium to make lithium-ion batteries. The use of lithium-ion batteries is growing rapidly in consumer electronics, and they are now becoming popular in power tools and motor scooters, and growth will continue with the increased use of hybrid and fully electric vehicles. Each hybrid electric car uses about 22 pounds of graphite, while a fully electric auto uses about 110 pounds.

Types and varieties of Graphite

The principal types of natural graphite, each occurring in different types of ore deposits are:

There are three distinct types of natural graphite which occur in different kinds of ore deposits:

  1. Flake Graphite
  • Less common form of graphite
  • Carbon range of 85-98%.
  • Priced ~4X higher than amorphous graphite
  • Used in many traditional applications
  • Desirable for emerging technology graphite applications (e.g. Li-ion battery anode material)
  • Crystalline small flakes of graphite (or flake graphite) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken.
  • When broken the edges can be irregular or angular;
  1. Amorphous Graphite
  • Most abundant form of graphite
  • Comparatively low carbon content of 70-80%
  • No visible crystallinity
  • Lowest purity
  • Not of suitable quality for use in most applications
  1. High Crystalline Graphite (vein, lump or crystalline vein)
  • Only extracted from Sri Lanka
  • Carbon content of 90-99%
  • Scarcity and high cost restricts viability for most applications

4. Lump graphite (or vein graphite) occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin.

5.Highly ordered pyrolytic graphite refers to graphite with an angular spread between the graphite sheets of less than 1°.

*Synthetic graphite is a manufactured product made by high-temperature treatment of amorphous carbon materials. In the United States, the primary feedstock used for making synthetic graphite is calcined petroleum coke and coal tar pitch. This makes it very expensive to produce — up to 10 times the cost of natural graphite – and less appealing for use in most applications. The name “graphite fiber” is sometimes used to refer to carbon fibers or carbon fiber-reinforced polymer.

Graphene Nanoplatelets

Graphene nanoplatelets represent a new class of carbon nanoparticles with multifunctional properties.  Graphene nanoplatelets have a “platelet” morphology, meaning they have a very thin but wide aspect ratio.  This unique size and platelet morphology  makes these particles especially effective at providing barrier properties, while their pure graphitic composition makes them excellent electrical and thermal conductors.

Graphene Nanoplatelets (GNPs) consist of small stacks of graphene that can replace carbon fiber, carbon nanotubes, nano-clays, or other compounds in many composite applications. When they are added at 2-5wt% to plastics or resins they make these materials electrically or thermally conductive and less permeable to gasses, while simultaneously improving mechanical properties like strength, stiffness, or surface toughness.

Graphene nanoplatelets with an average thickness of the 5 – 10 nanometers are offered in varying sizes up to 50 microns. These interesting nanoparticles are comprised of short stacks of platelet-shaped graphene sheets that are identical to those found in the walls of carbon nanotubes, but in a planar form. Hydrogen or covalent bonding capability can be added through functionalization at sites on the edges of the platelets.

Enhanced barrier properties and improved mechanical properties (stiffness, strength, and surface hardness) can be achieved with the graphene nanoplatelets due to their unique size and morphology. The nanoplatelets are also excellent excellent electrical and thermal conductors as a result of their pure graphitic composition.

Graphene nanoplatelets are 6-8 nm thick with a bulk density of 0.03 to 0.1 g/cc, an oxygen content of <1% and a carbon content of >99.5 wt% and a residual acid content of <0.5 wt%, and are offered as black granules.

Graphene nanoplatelets

Graphene nanoplatelet aggregates are aggregates of sub-micron platelets with a diameter of <2 microns and a thickness of a few nanometers, a bulk density of 0.2 to 0.4 g/cc, an oxygen content of <2 wt% and a carbon content of >98 wt%, and are offered as black granules or black powder.

 

Graphene Nanoplatelets Properties

graphene-nanoplatelets-properties-chart

The main properties of Graphene Nanoplatelets are electrical conductivity, thermal conductivity, mechanical reinforcement, and gas barrier layers. GNPs properties can be influenced by its manufacturing methods. Our graphene nanoplatelets are made by exfoliating graphite down to 5-15 atomic layers.  The methods used vary but the typically used processes are chemical exfoliation (which adds defects to the product) or dry exfoliation with plasma.  Dielectric Barrier Discharge is a plasma process and is how our research grade GNPs are made. They enhance mechanical properties and are some of the highest electrically & thermally conductive carbon additive materials you can buy. They can be surface functionalized by introducing the desired species during the exfoliation process.

Graphene Nanoplatelets Applications

graphene-nanoplatelets-applications

Graphene Nanoplatelets applications are quickly advancing from the R&D lab to commercial scale products. They are extremely useful as nanoscale additives for resistive heaters, advanced composites, as an electrode in advanced batteries and ultra/super capacitors, as the conductive component in specialty coatings or adhesives, and as a component of e-inks or printable electronic circuits.

Wide Applicability Because of their unique nanoscale size, shape, and material composition, graphene nanoplatelets can be used to improve the properties of a wide range of polymeric materials, including thermoplastic and thermoset composites, natural or synthetic rubber, thermoplastic elastomers, adhesives, paints and coatings.

The graphene nanoplates are offered in a granular form that in water, organic solvents and polymers with the right choice of dispersion aids, equipment and techniques. Used alone, graphene nanoplatelets can replace both conventional and nanoscale additives while expanding the range of properties being modified. Other graphene nanoplatelets applications include exceptionally strong and impermeable packaging, better lubricants, and a recent publication even demonstrates that our conductive research grade GNPs, surface-treated with sensitized molecules, can be used to produce highly sensitive bio-sensors.

Used in combination with other additives, they help reduce cost and expand property modification. With graphene nanoplatelets, you can:

  •  Increase thermal conductivity and stability
  • Increase electrical conductivity
  • Improve barrier properties
  • Reduce component mass while maintaining or improving properties
  • Increase stiffness
  • Increase toughness (impact strength)
  • Improve appearance, including scratch and mar resistance
  • Increase flame retardance

Graphene Nanoplatelets Price

Graphene Nanoplatelets price is typically based on quality and volume.  Industrial grade GNPs are cheaper, have a larger number of layers, more defects in the structure, a lower specific surface area and range from $50- $75 per kg for commercial volumes (tonnage) and $15 for small quantities.  Research grade GNPs price range is from $65-$90 per kg for commercial volumes and $35-$40 per gram for small quantities.  The prices decline as volume increases.

Graphene Nanoplatelets Dispersions

Graphene Nanoplatelets come in various sizes and grades, and these particles disperse well in many systems depending on the host system. xGnP® Graphene Nanoplatelets are very thin, (5-10 nanometers in thickness) flat particles with quite large diameters.

Because of the flat shape of these particles, they are especially sensitive to van der Waals attractive forces and have a tendency to re-aggregate in the dry state. These granules are friable collections of individual platelets that prevent agglomerations and are easily broken with mechanical agitation.

We understand that our customers have different approaches to their developments and we work within many frameworks.

Various dispersions of  xGnP® Graphene Nanoplatelets can be ordered instead of bulk powder:

  • Aqueous
  • IPA
  • Organic Solvents
  • Resins and Custom

Graphene Nanoplatelets dispersions are available from Cheap Tubes Inc. Please let us know your requirements for solvent, surfactants, and loading ratios.  Graphene nanoplatelet disperison is typically achieved with an ultrasonic probe, a high shear mixer, or a 3 roll mill with the rollers rotating at different speeds to create shear.  Best practice is to add the surfactant right at the end of the dispersion process. Our plasma exfoliated graphene nanoplatelets disperse much more easily than competing products.  When present, functional groups are bonded to the edges of the individual graphene sheets to promote dispersion. Our functionalized graphene nanoplatelets are the right choice for many industrial applications and are available on the ton level. The available functionalized graphene nanoplatelets with O+ (all of the oxygen groups) COOH, NH2, N2, & F groups to chose from will enable compatibility with a wide range of industrial processes.

 

 

Graphene Oxide

Graphene Oxide and Reduced Graphene Oxide are available in powder form, as a dispersion, or as a spin coated film which is available in oxide or reduced forms. Please contact us today to discuss your needs. Some of our Graphene Oxide products are well suited to Ink Jet & 3D printing applications. Please call us to discuss your needs.

Graphite oxide, formerly called graphitic oxide or graphitic acid, is a compound of carbon, oxygen, and hydrogen in variable ratios, obtained by treating graphite with strong oxidizers. The maximally oxidized bulk product is a yellow solid with C:O ratio between 2.1 and 2.9, that retains the layer structure of graphite but with a much larger and irregular spacing.

The bulk material disperses in basic solutions to yield monomolecular sheets, known as graphene oxide by analogy to graphene, the single-layer form of graphite. Graphene oxide sheets have been used to prepare strong paper-like materials, membranes, thin films, and composite materials. Initially, graphene oxide attracted substantial interest as a possible intermediate for the manufacture of graphene. The graphene obtained by reduction of graphene oxide still has many chemical and structural defects which is a problem for some applications but an advantage for some others.

 

Graphene Oxide Properties

Graphene Oxide synthesis methods have been known for decades. Originally called graphite oxide, it is a compound of carbon, oxygen, and hydrogen in variable ratios. It is synthesized by exfoliating graphite with strong oxidizers, rinsed repeatedly until the the rinse water is PH neutral and then freeze dried to preserve solubility.  Many companies try to reduce the rinsing or skip the freeze drying but they are critical to success in using the product. The bulk product is a brownish/yellowish solid material that retains the layer structure of graphite but with a much larger and irregular spacing. Graphene oxide doesn’t require post production functionalization as it consists of graphene sheets with hydroxyl, carboxyl, & epoxide groups. It is highly soluble in Di water, NMP, DMF, THF, Ethanol, and other solvents that behave like water. GO can be reduced using several methods such as laser, microwave, electrochemically, hydrazine vapor treatment, or by annealing at temperatures from 250-400C in a forming gas (95% argon, 5% hydrogen) environment yielding the intrinsically high electrical and thermal conductivity of graphene.

Molecular Structure of Graphene Oxide

GO’s molecular structure is shown above. The functional groups are present on the edges of the flakes and on the top and bottom which helps impart GO with legendary solubility compared to most nanoscale particles. No surfactants are needed when dispersing into typical solvents such as Di Water, NMP, DMF, THF, DCB, or Ethanol.

Graphene Oxide Applications

Graphene Oxide applications are numerous due to its high solubility and the ability to reduce it to near perfect graphene.  This overcomes the well known dispersion problems with other nanomaterials enabling you to get the full benefits of nanoscale additives such as improved mechanical properties as well as enhanced conductivity.

Water purification – In 2016 engineers developed graphene-based films that can filter dirty/salty water powered by the sun. Bacteria were used to produce a material consisting of two nanocellulose layers. The lower layer contains pristine cellulose, while the top layer contains cellulose and graphene oxide, which absorbs sunlight and produces heat. The system draws water from below into the material. The water diffuses into the higher layer, where it evaporates and leaves behind any contaminants. The evaporate condenses on top, where it can captured. The film is produced by repeatedly adding a fluid coating that hardens. Bacteria produce nanocellulose fibers with interspersed graphene oxide flakes. The film is light and easily manufactured at scale

Coating – Optically transparent, multilayer films made from graphene oxide are impermeable under dry conditions. Exposed to water (or water vapor), they allow passage of molecules below a certain size. The films consist of millions of randomly stacked flakes, leaving nano-sized capillaries between them. Closing these nanocapillaries using chemical reduction with hydroiodic acid creates “reduced graphene oxide” (r-GO) films that are completely impermeable to gases, liquids or strong chemicals greater than 100 nanometers thick. Glassware or copper plates covered with such a graphene “paint” can be used as containers for corrosive acids.  Graphene-coated plastic films could be used in medical packaging to improve shelf life.

Related materials –Dispersed graphene oxide flakes can also be sifted out of the dispersion (as in paper manufacture) and pressed to make an exceedingly strong graphene oxide paper. Graphene oxide has been used in DNA analysis applications. The large planar surface of graphene oxide allows simultaneous quenching of multiple DNA probes labeled with different dyes, providing the detection of multiple DNA targets in the same solution. Further advances in graphene oxide based DNA sensors could result in very inexpensive rapid DNA analysis.

Recently a group of researchers, from university of L’Aquila (Italy), discovered new wetting properties of graphene oxide thermally reduced in ultra-high vacuum up to 900 °C. They found a correlation between the surface chemical composition, the surface free energy and its polar and dispersive components, giving a rationale to the wetting properties of graphene oxide and reduced graphene oxide.

Flexible rechargeable battery electrode – Graphene oxide has been demonstrated as a flexible free-standing battery anode material for room temperature lithium-ion and sodium-ion batteries. It is also being studied as a high surface area conducting agent in lithium-sulfur battery cathodes.

Graphene oxide lens – the excellent properties of newly discovered graphene oxide provide novel solutions to overcome the challenges of current planar focusing devices. Specifically, giant refractive index modification (as large as 10^-1), which is one order of magnitude larger than the current materials, between graphene oxide (GO) and reduced graphene oxide (rGO) have been demonstrated by dynamically manipulating its oxygen content using direct laser writing (DLW) method.

 

Reduced Graphene Oxide

Reduced GO first undergoes the typical synthesis process and then it is reduced which removes most of the surface functional groups as well as restores the molecular structure to one much closer to pristine graphene than GO.

There are a number of ways reduction can be achieved and is typically a chemical, thermal or electrochemical process. Some of these techniques are able to produce very high quality rGO, similar to pristine graphene, but can be complex or time consuming to carry out.

Common graphene reduction techniques are:

  • Treating GO with hydrazine hydrate and maintaining the solution at 100c for 24 hours
  • Exposing GO to hydrogen plasma for a few seconds
  • Exposing GO to another form of strong pulse light, such as those produced by xenon flashtubes
  • Heating GO in distilled water at varying degrees for different lengths of time
  • Directly heating GO to very high levels in a furnace
  • Directly heating GO in a microwave
  • Electrochemical methods
  • At 400C in a forming has atmosphere 95% argon, 5% hydrogen

Chemical reduction is a highly scalable method, unfortunately the reduced GO produced often has resulted in relatively poor yields in terms of surface area and electronic conductivity. Thermally reducing GO at temperatures of 1000℃ or more creates rGO that has been shown to have a very high surface area but the annealing process damages the structure of the GO when pressure between builds up and carbon dioxide is released. During reduction, there is a substantial reduction in the mass of the GO (figures around 30% have been mentioned) which creates imperfections and voids in the structure and interferes with its unique properties.

Electrochemical reduction of GO is a method that has been shown to produce very high quality RGO, almost identical in terms of structure to pristine graphene.

Once RGO has been produced, it can be selectively functionalized thus enabling its use in different applications. By treating RGO with other chemicals or by creating new compounds when combining RGO with other two dimensional materials, we can engineer the surface chemistry of the compound to the specific application.

Graphene Oxide Paper

Graphene Oxide Paper is relatively easy to make.  GO is known to disperse very easily due to the type and amount of functional groups on its surface. To make GO paper folks typically disperse the GO in a solvent such as water or an organic solvent and then using a 0.2um membrane filter, they pour the GO solution through a vacuum filtration apparatus and the membrane keeps the particles on top while the solvent is collected below.  When dry, the membrane can be removed leaving a free standing GO paper product. RGO paper can be made by similar methods but will require surfactants to stabilize it so it may be desirable to make the GO paper and then reduce it instead of adding surfactants.

 

Graphene manufacture

Graphite oxide has attracted much interest as a possible route for the large-scale production and manipulation of graphene, a material with extraordinary electronic properties. Graphite oxide itself is an insulator,  almost a semiconductor, with differential conductivity between 1 and 5×10−3 S/cm at a bias voltage of 10 V. However, being hydrophilic, graphite oxide disperses readily in water, breaking up into macroscopic flakes, mostly one layer thick. Chemical reduction of these flakes would yield a suspension of graphene flakes. It was argued that the first experimental observation of graphene was reported by Hanns-Peter Boehm in 1962. In this early work the existence of monolayer reduced graphene oxide flakes was demonstrated. The contribution of Boehm was recently acknowledged by Andre Geim, the Nobel Prize winner for graphene research.

Partial reduction can be achieved by treating the suspended graphene oxide with hydrazine hydrate at 100 °C for 24 hours, by exposing graphene oxide to hydrogen plasma for a few seconds, or by exposure to a strong pulse of light, such as that of a Xenon flash. Due to the oxidation protocol, manifold defects already present in graphene oxide hamper the effectiveness of the reduction. Thus, the graphene quality obtained after reduction is limited by the precursor quality (graphene oxide) and the efficiency of the reducing agent. However, the conductivity of the graphene obtained by this route is below 10 S/cm, and the charge mobility is between 0.1 and 10 cm2/Vs. These values are much greater than the oxide’s, but still a few orders of magnitude lower than those of pristine graphene. Recently, the synthetic protocol for graphite oxide was optimized and almost intact graphene oxide with a preserved carbon framework was obtained. Reduction of this almost intact graphene oxide performs much better and the mobility values of charge carriers exceeds 1000 cm2/Vs for the best quality of flakes. Inspection with the atomic force microscope shows that the oxygen bonds distort the carbon layer, creating a pronounced intrinsic roughness in the oxide layers which persists after reduction. These defects also show up in Raman spectra of graphene oxide.

Large amounts of graphene sheets may also be produced through thermal methods. For example, in 2006 a method was discovered that simultaneously exfoliates and reduces graphite oxide by rapid heating (>2000 °C/min) to 1050 °C. At this temperature, carbon dioxide is released as the oxygen functionalities are removed and explosively separates the sheets as it comes out.

Exposing a film of graphite oxide to the laser of a LightScribe DVD has also revealed to produce quality graphene at a low cost.

Graphene oxide has also been reduced to graphene in situ, using a 3D printed pattern of engineered E. coli bacteria.

 

 

 

 

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