Graphene- A Miracle Material Allotropes Of Carbon Diamond - PowerPoint PPT Presentation

Graphene- A Miracle Material

Allotropes Of Carbon  Diamond  Graphite  Fullerene

What is Graphene?  Graphene is an allotrope of carbon  2-D crystalline, single layer of carbon, sp 2 hybridized carbon  Basic building unit for other allotropes like graphite, CNTs  Hexagonal (Honeycomb) like structure

Brief History  Theory was first proposed in 1947 by P.R.Wallace  But in 2004,graphene was successfully produced by Andre Geim And Konstantin Novoselov  In 2010,Both got Noble Prize in physics for discovery of graphene

Why is this material so special?  Hardest material known  Thinnest compound known to man at one atom thick, the lightest material known  Best conductor of heat at room temperature  Best conductor of electricity known

Mechanical Properties  Bond length is 0.142 nm long  Strongest material ever discovered  Ultimate tensile strength of 130 gigapascals compared to 400 megapascals for structural steel  Very light at 0.77 milligrams per square meter, paper is 1000 times heavier  Single sheet of graphene can cover a whole football field while weighing under 1 gram  Also, graphene is very flexible, yet brittle(preventing structural use)

Electronic Properties  Dirac Points are the transition between the valence band and the conduction band  Graphene is a zero-gap semiconductor, because its conduction and valence bands meet at the Dirac points  It is the best conductor of electricity known

Production Methods  Chemical Vapour Deposition where a gas containing carbon (such as Methane) is broken down and reassembled on a hot metallic surface into a sheet of graphene.  Solution Exfoliation where graphite is blasted into small fragments of graphene using ultrasonic energy.

TYPES OF GRAPHENE  Graphene oxide (GO) – Chemically modified graphene prepared by oxidation and exfoliation. Graphene oxide is a monolayer material with a high oxygen content.  Few-layer graphene (FLG) or multi-layer graphene (MLG) – a 2D,sheet-like material, either as a free-standing flake or substrate- bound coating, consisting of a small number (between two and about 10) of well-defined, countable, stacked graphene layers of extended lateral dimension.  Reduced graphene oxide (rGO) – Graphene oxide (as above) that has been reductively processed by chemical, thermal, microwave, photo- chemical, photo-thermal or microbial/bacterial methods to reduce its oxygen content.  Graphite oxide – This precursor to GO is a bulk solid made by oxidation of graphite through processes that functionalize the basal planes and increase the interlayer spacing.