Graphene – the new wonders it is creating in design fields now-a-days is enormous. It is on its way to replace silicon in many cases. Now its turn of silicon based batteries to convert them into new graphene based super batteries.

 

WHAT IS GRAPHENE? :

Graphene is an allotrope of carbon, whose structure is one-atom-thick planar sheets of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice.

It shows many properties like high electrical conductivity and high storage capacity of voltage. The exciting properties of graphene are usually only applicable to the material that consists of one or two layers of the graphene sheets. Whilst synthesis of any number of layers is possible, the thicker layers have properties closer to the more common bulk graphite.

For device applications one- and two-layer graphene needs to be precisely identified apart from the substrate and regions of thicker graphene.

Exfoliated graphene sheets up to ~100 μm in size can be routinely identified by optical microscopy. However, the situation is much more complicated in the case of the epitaxial graphene grown on silicon carbide wafers with a diameter up to 5 inches where the straightforward identification of the graphene thickness is difficult using standard techniques.

This research shows that EFM, which is one of the most widely accessible and simplest implementations of scanning probe microscopy, can clearly identify different graphene thicknesses.

 

GRAPHENE REPLACING SILICON ON NANO CIRCUITARY:

Scientists have made a breakthrough toward creating nanocircuitry on graphene, widely regarded as the most promising candidate to replace silicon as the building block of transistors. They have devised a simple and quick one-step process based on thermo chemical nanolithography (TCNL) for creating nanowires, tuning the electronic properties of reduced graphene oxide on the nanoscale and thereby allowing it to switch from being an insulating material to a conducting material.

Scientists who work with nanocircuits are enthusiastic about graphene because electrons meet with less resistance when they travel along graphene compared to silicon and because today’s silicon transistors are nearly as small as allowed by the laws of physics. Graphene also has the edge due to its thickness — it’s a carbon sheet that is a single atom thick. While graphene nanoelectronics could be faster and consume less power than silicon, no one knew how to produce graphene nanostructures on such a reproducible or scalable method. That is until now.

On the macroscale, the conductivity of graphene oxide can be changed from an insulating material to a more conductive graphene-like material using large furnaces.

Now, the research team used TCNL to increase the temperature of reduced graphene oxide at the nanoscale, so they can draw graphene-like nanocircuits. They found that when it reached 130 degrees Celsius, the reduced graphene oxide began to become more conductive.

The research team tested two types of graphene oxide — one made from silicon carbide, the other with graphite powder.

“I think there are three things about this study that make it stand out,” said William P. King, associate professor in the Mechanical Science and Engineering department at the University of Illinois at Urbana-Champaign. “First, is that the entire process happens in one step. You go from insulating graphene oxide to a functional electronic material by simply applying a nano-heater. Second, we think that any type of graphene will behave this way. Third, the writing is an extremely fast technique. These nanostructures can be synthesized at such a high rate that the approach could be very useful for engineers who want to make nanocircuits.”

The simple conversion from graphene oxide to graphene is an important and fast method to produce conducting wires. This method can be used not only for flexible electronics, but it is possible, sometime in the future, that the bio-compatible graphene wires can be used to measure electrical signals from single biological cells.

 

Graphene Nanocomposite is a Bridge to Better Batteries:

For an electric vehicle, you need a lightweight battery that can be charged quickly and holds its charge capacity after repeated cycling. This is applicable to any electronic circuit and is also same in the case batteries which are used in several gadgets. If this secondary battery’s storage capacity exceeds beyond limitation, then its making reality must be done with graphene only.

            In this study of reproducing graphene for battery purposes, the team assembled alternating layers of graphene and tin to create a nanoscale composite. To create the composite material, a thin film of tin is deposited onto graphene. Next, another sheet of graphene is transferred on top of the tin film. This process is repeated to create a composite material, which is then heated to 300˚ Celsius (572˚ Fahrenheit) in a hydrogen and argon environment. During this heat treatment, the tin film transforms into a series of pillars, increasing the height of the tin layer.

These set of pillars lead to a high voltage storage component i.e., battery. But as we know, graphene is atomic layered composition and if the layers are kept side by side then there is a possibility that all the graphene layers merge to form graphite again. This graphite is nothing but lead in our daily used pencils and is almost an insulator and do not have any properties that this atomic layered graphene possess.

Hence to keep the layers separate from each other, scientists conducted various experiments and found out the repelling properties of graphene with water.

To keep it straight… We can say that…

Graphene layers which are placed one beside the other are repelled by keeping some water molecules between them as these water molecules create some sort of repelling force between graphene layers through which the maximum voltage storage capacity of graphene can be retained.

Hence we may think that silicon all over the world would be replaced by graphene compositions and their durability and efficiency are increased.

 

courtesy: Sciencedaily.com, Howstuffworks.com and newscientist.com

Posted by

Gopi Chand( MGIT ECE 4th year)

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