GRAPHENE BASIC PROPERTIES
Graphene as a revolution in the development of fundamentally new materials
Graphene can be described as “surprising phenomenon is near”. It is a two-dimensional modification of carbon, one of the most abundant elements in the universe, or rather, one of the carbon structures. The secret is as follows: graphene is a monolayer of carbon atoms connected in a two-dimensional crystal lattice. Thickness of the layer is exactly one atom (the smallest possible atomic size). Over the past ten years, many properties of graphene have been discovered which are uncharacteristic of solid state physics. It is called a wonder material.
Why this relatively new material is so wonderful?
One of the main attractions of graphene is that its addition to almost any material gives the latter absolutely fantastic properties which did not previously exist, including strength, durability and resistance to external influences. Graphene, as a hardening additive in only a few percent, is able to radically change the basic properties of all known base materials (metals, cement, ceramics, polymers, paints, coatings, glass, etc.)
Graphene is the most durable material on the Earth. It is 300 times stronger than steel. A sheet of graphene of 1 sq. meter and only one atom thick can hold an object weighing 4 kilograms. Graphene, like a napkin, can be bent, rolled, stretched. The paper napkin is torn in the hands, but this won’t happen with graphene.
Because its two-dimensional structure graphene is a very flexible material, which allows it to be used, for example, for weaving threads and other rope structures. At the same time, a thin graphene “rope” will be similar in strength to heavy steel rope.
Graphene has high electrical conductivity. He has almost no resistance. The speed of electrons in graphene is 10,000 km/s, although in conventional conductor the speed of electrons is on the order of 100 m/s. At the same time, graphene is almost transparent (usually this property excludes good conductivity) and is easily stretched by 20%. When graphene is added, for example, to a metal wire, the electrical resistance of the latter is noticeably reduced.
But the main wonder property is that at absolute subtlety it is stable, atomic bonds do not disintegrate, as, in theory, two-dimensional materials should have. It turned out that the atoms are held together due to special vibrations.
Today graphene is increasingly being used in the energy sector. It improves the properties of lithium-ion batteries, the battery becomes more capacious and the charging time is reduced.
Graphene has a high electrical capacity. Specific energy capacity of graphene approaches 65 kWh/kg. This value is 47 times more than that of currently widespread lithium-ion batteries.
At present, researchers from many countries are working on a graphene-polymer battery. Spanish scientists have made significant progress in this matter. The battery they created has energy capacity hundreds of times higher than that of the currently existing batteries. It is used to equip electric cars. A car with a graphene battery installed can travel thousands of kilometers without stopping. Only 8 minutes needed to recharge an electric battery when the battery is completely discharged.
German engineers from KarlsruherInstitut für Technologie and the Estonian company Sketenton Tech have created graphene-based batteries that can be charged in 15 seconds.
It is expected that the fastest growing segment will be the graphene application in energy storage: the average annual growth forecast is 90%. Graphene electrodes are widely used in energy storage devices such as electromagnetic supercapacitors and batteries (Li-ion, Li-air, lead-acid and fuel cells), due to their high energy density and fast charge.
Graphene will give a fresh impulse to development of alternative energy. Graphene solar cells produce energy with minimal illumination, even in cloudy weather and during rain.
The use of graphene in hydrogen energetics is very promising.
Here are just some of the directions of its possible application:
- accumulation and storage of hydrogen in graphene materials (the possibility of creating reversible hydrogen storage systems based on them, combining high capacity, stability and the possibility of rapid hydrogen release under conditions acceptable for practical use);
- the use of chemical and heat-resistant membrane materials based on graphene, which make it possible to create new gas separation membranes which provide high permeability and selectivity and are promising for the purification of hydrogen in the process of its production from natural gas;
- significant improvement of polymer membranes characteristics, which are currently mostly used in industry, with the help of small additives of graphene materials;
- the use of graphene-like materials as carriers of nanoparticles or as functional additives in the composition of the electrocatalytic layer of fuel cells with a polymer-electrolyte membrane, which allows improving their characteristics, as well as increasing the activity and stability of the electrocatalyst in the oxygen release reaction;
- creation of electrodes based on graphene coated with catalytic nanoparticles (high corrosion resistance, large surface area and high conductivity).
Graphene materials have such advantages as high electrocatalytic activity, high conductivity, excellent mechanical properties – strength, high flexibility, large specific surface area and low weight, which makes it possible to store an electric charge, ions or hydrogen.
Graphene coated with metal oxide is an effective catalyst for next-generation hydrogen fuel cells.
Graphene materials can replace expensive platinum catalysts.
Graphene nanocomposites can serve as effective components of thermal management, providing effective thermal stabilization and heat removal from hydrogen fuel cells.
Graphene has a high thermal conductivity, 10 times more that of copper. It exceed wolfram in boiling point (3700°C).
Graphene has almost full optical transparency. It absorbs only 2.3% of the light. For comparison, ordinary glass absorbs about 10% of the light. For this reason, manufacturers of monitors and solar panels are interested in it, because it is important to obtain a conductive layer of maximum transparency for them.
The graphene film allows water molecules to pass through and at the same time retains all the others, which allows it to be used as a water filter.
Graphene is the lightweight material, about 100 times lighter than water. It is inert to the environment; multilayer graphene can absorb radioactive waste.
Because there is Brownian motion (thermal vibrations) of carbon atoms in graphene sheet, it is able to “produce” electrical energy.
Graphene is the basis for assembling various not only separate two-dimensional materials, but also multilayer two-dimensional heterostructures.
When salt water flows through a graphene sheet, the latter is able to generate electrical energy by converting the kinetic energy of salt water flow into electrical energy (electrokinetic effect).
All of the above mentioned properties of graphene gave an impulse to extensive research on the possibility of its use in various fields of knowledge.
Because graphene makes it possible to obtain principally new materials, it is quite possible that we are on the eve of creating a new “Mendeleev periodic table”. Its creation, of course, will take many years, but its appearance is inevitable!