Basic Facts about Graphene
Posted: Dec 05, 2021
Graphene originally exists in nature, but it is difficult to peel off a single-layer structure. 1mm thick graphite contains about 3 million layers of graphene. People discovered graphite a long time ago, but it wasn't until 2004 that graphene was discovered. This is because theoretical studies starting from 70 years ago showed that a perfect two-dimensional crystal structure cannot exist stably in a non-absolute zero temperature environment.
In 2004, two British scientists obtained graphene through a very simple experimental method. They peeled off the graphite flakes from the highly oriented pyrolytic graphite, then glued the two sides of the flakes to a special tape, and peeled off the tape to split the graphite flakes in two. With continuous operations like this, the flakes are getting thinner and thinner, and finally a flake composed of only one layer of carbon atoms is obtained - this is graphene. Although theoretically impossible, it was successfully prepared in the experiment. This discovery immediately shocked the scientific community, and the two scientists jointly won the 2010 Nobel Prize in Physics.
Graphene has many magical properties, so it is called the "king of new materials". For instance, it is the thinnest material because it has only one atomic layer; it is the strongest material, theoretically 200 times stronger than steel; it is the material with the best electrical conductivity, having a conductivity of 1.6 times that of silver; it is the material with the best thermal conductivity, having a thermal conductivity of 13 times that of copper.
Graphene is one of the strongest materials. It also has good toughness, can be bent, and has super thermal and electrical conductivity, which makes its application prospects very broad. To name a few here: it can be used as a touch screen because it is transparent conductive film; it can also be used as an ultra-fast integrated circuit, because the electrons in it run very fast, and the electron mobility at room temperature is 10 times higher than that of silicon materials; it is a lightweight and high-strength material, which has a very broad application prospect in the aerospace field. Moreover, its electromagnetic shielding properties can also be used to make stealth aircraft, stealth materials, etc.
The human body can emit far-infrared light. Because graphene has an ultra-high carrier mobility, the electrons generated after the far-infrared light is projected on its surface and can be quickly collected. In this way, wearing glasses made of graphene lenses can see everything at night, and can also collect the user's own blood sugar, brain electricity and other physiological data. At the same time, because graphene has light transmittance, it can also be used as a display to project various information. When you travel, it can instantly display traffic information, nearby hotels, attractions, restaurants and other service information.
Graphene is generally divided into two categories: one is powder graphene, and the other is thin film graphene. The preparation methods of these two types of graphene are completely different, and the application fields and scenarios are also completely different.
In large-scale industrial preparation, graphene powder is generally obtained by chemical reaction to exfoliate the graphite layer. However, this kind of redox method often brings a lot of waste acid and waste water. For example, using concentrated sulfuric acid and potassium permanganate to cook graphite, it takes 50 kg of concentrated sulfuric acid, 3 kg of potassium permanganate and 1 ton of water to produce 1 kg of graphene.
As to the large-scale preparation method of thin-film graphene, the most representative one is the chemical vapor deposition technology, that is, the graphene is prepared layer by layer through high-temperature chemical reactions in a high-temperature furnace. For example, if methane is applied to the surface of copper foil at 1000 degrees Celsius, a single atomic layer graphene can be produced.
At present, what applications of graphene have been tried?
The first is new energy area. Graphene is used as a conductive additive for lithium-ion batteries to make the battery charge faster and increase the capacity. Secondly, graphene is added to the anti-corrosion coating to save the more expensive zinc content and improve the anti-corrosion performance. The third is the big health field, such as using its thermal conductivity to make eye masks, knee pads and other physiotherapy products.
In addition, graphene is also widely used in data communications, sensors, wearable devices, new energy and other fields. For example, an ultra-sensitive electronic sensor made of graphene can detect harmful gases, and a broadband image sensor made of graphene can simultaneously detect visible light and infrared light. Also, due to its ultra-high carrier mobility properties, graphene can be used with silicon-based semiconductors to produce superior performance photoelectronic detectors, night vision far-infrared detectors, logic circuit devices, etc.
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