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

• f carbon

 2-D crystalline, single

layer of carbon, sp2 hybridized carbon

 Basic building unit for

• ther 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

• xidation 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

• xygen content.

 Graphite oxide – This precursor to GO is a bulk solid made by

• xidation of graphite through processes that functionalize the basal

planes and increase the interlayer spacing.