What is Graphene? | Introduction, Properties and Applications - News4u95

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Wednesday, 13 May 2020

What is Graphene? | Introduction, Properties and Applications

Graphene

Graphene is the name for an atomic thick honeycomb sheet of carbon atoms. It is a component of other graphite materials. Harder than diamond, but harder than rubber. It is stronger than steel but lighter than aluminum. Graphene is the most powerful known material.

Its high electron mobility is 100 times faster than silicon. It has twice the thermal conductivity of the diamond. The conductivity is 13 times that of copper. It absorbs only 2.3% of the reflected light. Due to its impermeability, even the smallest atoms (helium) cannot pass through a defect-free single-layer graphene sheet. A surface area of   2630 square meters/gram means that less than 3 grams can cover the entire soccer field.

Graphene is the basic building block of other graphite materials. It is also a conceptually new class of materials, so-called two-dimensional (2D) materials with only one atom in thickness.

Graphene is also very attractive for the fabrication of mixed-dimensional van der Waals heterostructures that can be performed by hybridizing graphene with 0D quantum dots or nanoparticles, 1D nanostructures such as nanowires and carbon nanotubes, or 3D bulk materials.

Graphene

Properties of Graphene

Electrical Properties

One of the reasons why nanotechnology researchers working towards molecular electronics are so excited about graphene is its electronic properties. It is one of the best conductors on earth. The unique atomic arrangement of carbon atoms in graphene allows electrons to move very fast and easily without significantly increasing the chances of scattering them, saving valuable energy normally lost in other conductors.

Scientists have discovered that graphene is capable of conducting electricity even at a nominally zero carrier concentration limit because electrons do not appear to slow down or localize. Electrons traveling around the carbon atom interact with the periodic potential of the graphene honeycomb lattice. This creates new quasiparticles that have lost their mass or rest mass. In other words, the conduction of graphene does not stop. We also found that they move much faster than the electrons in other semiconductors.

Mechanical Properties

The striking and unique mechanical properties of graphene, its stiffness, strength, and toughness are one of the reasons why graphene stands out as an individual material and as a reinforcing agent in composites. They occur due to the stability of sp2 bonds that form a hexagonal lattice and resist various in-plane deformations.

Hardness

The fracture forces obtained from the experiments and simulations were almost the same, and the experimental The value of the second elastic stiffness was 340 ± 50 N m-1. This value corresponds to Young's modulus of 1.0 ± 0.1 TPA, assuming an effective thickness of 0.335 nm.

Strength

Defect-free monolayer graphene is considered to be the strongest material ever tested at a strength of 42 N m-1. This corresponds to an intrinsic strength of 130 GPa.

Toughness

Fracture toughness, a property highly relevant to engineering applications is one of the most important mechanical properties of graphene, measured as a critical stress intensity factor of 4.0 ± 0.6 MPa.

Applications of Graphene

Energy Storage and Solar Cells

Graphene-based nanomaterials have many promising applications in energy-related fields. Some recent examples: Graphene improves both the energy capacity and charge rate of rechargeable batteries. Activated graphene makes supercapacitors with excellent energy storage. Graphene electrodes could lead to a promising approach to making cheap, lightweight, and flexible solar cells. Multi-functional graphene mats are promising substrates for catalytic systems.

The researchers also discovered an important and unexpected relationship between the chemical/structural defects of graphene as a host material for electrodes and its ability to suppress dendrite growth. Batteries can cause electrical short circuits, overheating, and fire.

Due to the excellent transport properties of electrons and very high carrier mobility, direct bandgap monounsaturated materials such as graphene and other transfer metal decalcogenides and black phosphorus can be used in low cost, flexible and highly efficient photovoltaic devices. It shows great potential. They are the most promising materials for advanced solar cells.

Sensor Applications

Functionalized graphene holds great promise for biological and chemical sensors. Already, researchers have shown that by combining the characteristic 2D structure of graphene oxide with super permeability to water molecules, devices can be detected at unprecedented rates.

Scientists have discovered that chemical vapors alter the noise orbits of graphene transistors, activating the selective gas sensing of many vapors in a device made of pure graphene. The graphene surface does not need to be activated.

A rather cool approach is to connect passive wireless graphene nanosensors to biomaterials via silk bioabsorption, as shown by tooth graphene nanosensor tattoos monitoring oral bacteria.

Researchers have also begun to use graphene foam, a three-dimensional structure of interconnected graphene sheets, very highly conductive. These structures hold great promise as gas sensors and biosensors for disease detection.

Electronics Applications

Graphene has a unique combination of properties such as mechanical flexibility, high electrical conductivity and chemical stability, ideal for next-generation electronics. Combining this with inkjet printing gives you a cheap and scalable path to harness these properties in real-world technology.

Transistor and Memory

Some of the most promising applications for graphene are electronics, detectors, and thermal management. The first graphene field-effect transistors-both bottom and top gate-have already been demonstrated. At the same time, the level of electronic low-frequency noise must be reduced to acceptable levels in order for the transistor to be useful in analog communication or digital applications.

Graphene-based transistors are considered to be potential successors to some of the silicon components currently in use. The fact that electrons can travel faster through graphene than through silicon indicates the potential for this material for terahertz computing.

In the ultimate nanoscale transistor, electrons avoid collisions. That is, the current flow is virtually unobstructed. Ballistic conduction enables incredibly fast switching devices. Graphene has the potential to achieve ballistic transistors at room temperature.

Graphene has the potential to revolutionize electronics and replace the silicon materials used today, but with the Achilles heel. Pristine graphene is a semimetal and lacks the bandgap needed to function as a transistor. Therefore, it is necessary to design the band gap of graphene.

Experiments have demonstrated the benefits of graphene as a platform for flash memory, demonstrating that it may exceed the performance of current flash memory technology by taking advantage of the intrinsic properties of graphene.

Flexible and Elastic Foldable Electronics

Flexible electronics rely on bendable substrates and truly collapsible electronics require a foldable substrate with very stable conductors that can withstand folding.

That is, in addition to a foldable substrate such as paper, the conductors deposited on this substrate must also be foldable. To that end, researchers have demonstrated a manufacturing process for folding graphene circuits based on paper substrates.

Graphene's excellent conductivity, strength and elasticity make it possible to create circuits on flexible plastic substrates for applications such as stretchable electronics.

Scientists have devised a chemical vapor deposition (CVD) method to turn graphene sheets into porous, three-dimensional foams with extremely high conductivity. By impregnating this foam with a siloxane-based polymer, researchers have made a composite material that can be twisted, stretched, and bent without compromising it's electrical or mechanical properties.

Photo Detector

Researchers have demonstrated that graphene can be used in telecommunications applications, and that it's weak, the universal optical response can translate into advantages for ultrafast photonics applications. They also found that graphene could potentially be used as a saturable absorber with a wide range of optical responses from ultraviolet, visible, infrared to terahertz.

The use of graphene for optoelectronics applications are of great research interest. Graphene-based photodetectors have been realized previously and graphene's suitability for high bandwidth photodetection has been demonstrated at 10 GBit / s optical data links.

One new approach is based on the integration of graphene into optical microcavities. Increasing the electric field amplitude inside the cavity absorbs more energy and significantly increases the optical response.

Coating

Coating objects with graphene can be used for a variety of purposes. For example, researchers have shown that graphene sheets can be used to create superhydrophobic coating materials that exhibit stable superhydrophobicity under both static and dynamic conditions, thereby forming highly water-repellent structures.

Graphene is also the world's thinnest known coating to protect metals from corrosion. It has been found that graphene, whether made directly on copper or nickel or transferred to another metal, provides protection against corrosion.

Researchers have demonstrated the use of graphene as a transparent conductive coating for photonic devices, demonstrating that its high transparency and low resistivity make this two-dimensional crystal ideal for electrodes in liquid crystal devices (LCDs).



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