Carbon Allotropes: A carbon atom can form various types of allotropes. In 3D structures, diamond and graphite are the allotropes of carbon. Carbon also forms low-dimensional (2D, 1D or 0D) allotropes collectively known as carbon nanomaterials. Examples of such nanomaterials are 1D carbon nanotubes (CNTs) and 0D fullerenes. In the list of carbon nanomaterials, graphene is known as 2D single layer of graphite.
Carbon Allotropes: Carbon, the common element in organic compounds, is known to exist in two allotropic forms, diamond and graphite. In 1985, a third form of carbon called fullerenes was discovered. Fullerenes are large carbon cage molecules considered to be three-dimensional analogues of benzene. The most abundant form of fullerenes is Buckminster fullerene (C60) with 60 carbon atoms arranged in a spherical structure. A C60 molecule, also known as Buckyball or Buckminsterfullerene, is about 7 Å in diameter. C60 molecules condense to form a solid of weakly bound molecules. This crystalline state is called fullerites.
Carbon nanotubes (CNTs) are made by rolling up of sheet of graphene into a cylinder. These nanostructures are constructed with length-to-diameter ratio of up to (1.32 × 108):1 that is significantly larger than any other material. As their name suggests, the diameter of nanotube is in the order of few nanometers, while they can be up to 18 centimeters in length. CNTs are most promising candidates in the field of nanoelectronics, especially for interconnect applications. Metallic CNTs have aroused a lot of research interest for their applicability as VLSI interconnects due to high thermal stability, high thermal conductivity, and large current carrying capability. A CNT can carry current density in excess of 103 MA/cm2, which can enhance the electrical performance as well as eliminate electro migration reliability concerns that plagues current nanoscale Cu interconnects.
Both CNTs and GNRs (graphene nano ribbons) can be understood as structures derived from a graphene sheet. A graphene sheet is a single layer of carbon atoms packed into 2D honeycomb lattice structure. CNT, considered as rolled-up graphene sheet, have the edges of the sheet joint together to form a seamless cylinder. CNTs can be classified to zigzag and armchair structures.
For armchair CNTs, the chiral indices n1 and n2 are equal while for zigzag CNTs, n1 or n2 = 0. For other values of indices, CNTs are known as chiral. Depending upon their different structures, CNTs can exhibit metallic or semiconducting properties. The armchair CNTs are always metallic, whereas zigzag CNTs are either metallic or semiconducting in nature. Statistically, a natural mix of CNTs will have 1/3rd metallic and 2/3rd semiconducting chiralities. Depending on the number of concentrically rolled-up graphene sheets, CNTs are also classified to single-walled (SWNT), double-walled (DWNT), and Multiwalled CNTs (MWNT). The structure of SWNT can be conceptualized by wrapping a one-atom-thick layer of graphene into a seamless cylinder. MWNT consists of two or more numbers of rolled-up concentric layers of graphene. DWNT is considered as a special type of MWNT wherein only two concentrically rolled up graphene sheets are present.
Synthesis of Carbon Nanotubes
Carbon Allotropes: Chemical vapor deposition is the method with the most promise for mass production of carbon nanotubes. It operates at much lower temperatures, and produces nanotubes in greater quantities than arc discharge or laser vaporization.
Nanoshel is the master of synthesis of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) by the Catalytic Chemical vapor deposition. Carbon nanotubes (CNTs) are unique nanostructures with remarkable electronic and mechanical properties and have attracted tremendous interest worldwide. Catalytic chemical vapor deposition (CCVD) is currently the most promising technique to produce carbon nanotubes (CNTs) at large-scale, low cost and on a dedicated place on a substrate. The method consists in the decomposition of a carbon containing gas over a supported catalyst. Contrasting with the abundant types of carbon sources used for the growth of CNTs, their synthesis is restricted to the thermal decomposition reaction of the carbon source. The optimization of growth parameters remains mostly empirical.
Arc-evaporation synthesis, also known as electric arc discharge, has long been known as the best method for synthesizing fullerenes, and it also generates the highest quality carbon nanotubes. Nanoshel also synthesize multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) by the arc discharge method. The high temperature of the arc enables the formation of CNTs of a very high structural quality suitable for fundamental research. They often exhibit properties, close to the ones predicted by theory.
Functionalization of CNTs
More, the potential applications require an extended functionalization of Carbon nanotubes to make them process able and to tune their properties functionalization of CNTs with any group creates the new type or new class of material with new properties. Functionalization may as well help to separate semi conducting tubes from metallic ones, to purify nanotubes.
Nanoshel is working on the modification of carbon nanotubes with various functional groups to enhance the properties, capability of CNTs for newer applications. Also, Nanoshel Commercially deals with industries working on both CNTs and functionalized CNTs as per the requirement.
Carbon Allotropes: Research team of Scientists at Nanoshel is working on SLAC battery. They are trying to discover new electrolyte material for quick charging and slow discharging. New electrolyte material may be organic or inorganic. Research team use MWCNT’s at predefined composition to enhance the storage power of battery. The aim of our team is to synthesize high power and compact sized battery and we are working on it.