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The "carbon sponge" made of graphene at Zhejiang University is very light and can easily be absorbed by the electrostatic charge on the glass rod. Dragonfly Photo
Not long ago, the research team of Tsinghua University released an invention of “smart graphene artificial throatâ€, which utilizes the advantages of porous graphene materials to create an integrated acoustic device that is suitable for wear and tear, and is expected to solve deaf-mute in the future. People's "speaking" problems.
Internationally, researchers at institutions such as the University of Cambridge in the United Kingdom reported that they have found a new way to “awaken†the superconductivity of graphene, which can be used to make supercomputers.
Graphene is currently the hottest new material. In the aviation field, people use “unique elements†to describe materials that are as light as air and hard as steel. Previously, titanium alloys were the ideal choice for this quality, and “rising stars†graphene was considered to be a step closer to the “rare element†of human dreams.
What is graphene?
The world’s thinnest, lightest, and strongest material is 100 times stronger than the strongest steel.
Like diamond, graphite is an existing form of carbon. The difference is that because of the different atomic structure, diamond is the hardest thing on earth, and graphite is one of the softest minerals, often made of graphite rods and pencil cores. Graphene is stripped from the graphite material and consists of only one layer of carbon atoms in the plane.
It can be said that one of the characteristics of graphene is its thinness, which is currently the thinnest material in the world. It is only one atom thick, about 0.3 nanometers, which is one hundred thousandth of the thickness of an A4 paper, and fifty of its hair. One ten thousandth. At the same time, it can conduct electricity. The speed of electrons in graphene reaches 1000 km/s, which is 1/300 of the speed of light. Thin, strong, conductive, thermally conductive... Graphene These characteristics give people a lot of imagination.
According to Dr. Kong Yuezheng, deputy director of the China National Semiconductors 55 Microwave Millimeter Wave Monolithic Integration and Module Circuit Key Laboratory, the hardness of graphene is very strong, which is 100 times stronger than the current strongest steel. Graphene also has very fast electronic operation speed. High, which is 10 times that of silicon, is very suitable for the development of next generation UHF electronic devices. In addition, graphene is also a master of heat conduction and is 10 times stronger than the most conductive metal silver.
The properties of graphene are also very "fun". For example, when a drop of water rolls on the surface of graphene, graphene can acutely "feel" the subtle motion and generate a constant current. This feature provides scientists with a new way of thinking to get electricity from the flow of water.
“Graphene can induce a single electron. The movement of charged particles on the surface of graphene can cause rapid movement of the electrons inside the graphene, enabling sensing and power generation processes.†said Lin Shisheng, associate professor at the School of Information and Electronic Engineering at Zhejiang University, said that graphite This property of alkene can be used in many applications such as energy and electronic sensing. For example, electricity can be generated by using an umbrella coated with graphene during rainy weather, or sensitive sensors can be made.
It is these comprehensive properties that have given graphene unprecedented attention. Some people have even begun to predict that the appearance of graphene will lead to an industrial revolution triggered by material progress.
How to get graphene
For the first time in the world, single-layer graphene is obtained by “gluing†the transparent plastic.
People acquired graphene for the first time, using a "simple and crude" approach.
Graphene itself exists in nature. Graphene is a thin layer of carbon atoms. A hexagonal ring is formed between atoms, and the rings form a honeycomb plane. It is graphite layered on one layer, graphite with a thickness of 1 mm contains about 3 million layers of graphene. The pencil gently strokes on the paper, leaving traces of several to several tens of layers of graphene. Previously, this two-dimensional structure of carbon has always existed in people's conjecture, but it is difficult to peel off the monolayer structure. The key problem is how to layer the graphite into very thin sheets.
Many people also have such experiences during their school days. When writing typos on paper, they use transparent tape to stick the typo. But no one thought that this is a simple way for people to discover the mysterious graphene.
The production of graphene is simply a matter of thinning graphite, not relying on cutting, not grinding, but on sticking. In 2004, Heim and Novoselov of the University of Manchester in the United Kingdom glued and tore apart a piece of graphite with transparent glue, and the thickness of the graphite piece gradually decreased, resulting in the formation of graphene with a thickness of only 0.335 nm. Only one atom thick graphene. This is the first time that a single layer of graphene has been obtained in the world, and the two scientists won the 2010 Nobel Prize in physics.
Dr. Wu Yun, a senior engineer of the China National Keystone Microwave Microwave Millimeter Wave Monolithic Integration and Module Circuit Key Laboratory, gave a presentation to the reporter. He stuck a small piece of graphite on top of the tape and then overlapped it. After being glued for half an hour, the tape was covered with gray graphite and then the tape was transferred to a clean wafer with tape.
Wu Yun said that none of the graphene is seen at this time, because graphene is not only very thin, but also has a transmittance of more than 97%. It is almost completely transparent, and the human eye cannot see it at all. To find it, you have to find it. Through special technical means. However, this is already a multi-layer graphite sheet, and the number of layers is determined by technical means, and finally the single-layer graphene produced can be found.
Experts say that this is just the first way to produce graphene. The mechanical peeling method, which evolved from the tape-paste method, is just a method of preparing graphene in the laboratory. At present, as technology advances, high-quality graphene can be produced more.
What does graphene bring?
Application of graphene material, mobile screen can be easily bent or even folded
The appearance of graphene is expected to bring surprises to our lives. The mobile phone can be charged “secondarilyâ€, the mobile phone screen can be easily bent or even folded. The car can use graphene conductive tires to avoid detonation due to frictional electrification...from the aerospace and electronic information to energy saving and environmental protection, using the characteristics of graphene, many It is likely that the field will change dramatically.
Replacing silicon with graphene can improve the performance of electronic chips. Researchers are currently introducing the production and application of graphene into the semiconductor industry. The graphene-induced technological revolution is likely to begin with our common small chip.
The basic material for electronic chips is silicon. However, with more and more dense components on the chip, the distance between two components on the highest-end chip is already less than 10 nanometers, which almost reaches the limit of silicon materials. What if you want to continue to improve performance? Researchers began to try to substitute graphene for silicon.
"The devices made from graphene can theoretically be up to ten times or even hundreds of times faster than silicon, and can be used on radars to dramatically increase the resolution of radars. There are also more extensive applications for communication and imaging." Said, moreover, the current R&D production equipment of graphene is the same as general semiconductor equipment production equipment. The existing technology development can be based on mature equipment and processes, laying the foundation for subsequent engineering development.
Researchers are still doing another big thing. They attached graphene to gold foil, which was only 50 nanometers thick, and then used a new approach to transfer the graphene intact to a soft plastic sheet.
Kong Yuelu said that graphene can be transferred to any substrate desired by scientific researchers through flexible methods, such as a plastic substrate dedicated to electronic devices, which is flexible and suitable for transistor preparation. Through special graphene transfer technology, gold foil with graphene is attached to a plastic sheet, and on this basis a certain functional electronic device is prepared on the plastic sheet. Crucially, such electronic devices can be easily bent. In the future, whether it is a foldable display screen or a wearable device that can be implanted into the human body, it is possible to realize such a graphene device.
Another area where graphene has high hopes is the storage of electrical energy. At the Tianjin Power Research Institute, researchers here are conducting research on the most advanced capacitors. Capacitors, like batteries, can be used to store electrical energy. Its advantage is that it can be charged quickly, it can be filled for a few minutes, and it can be used repeatedly for tens of thousands of times. However, it does not store as much electricity as a battery, and it can't be used in life by storing enough energy.
“This is a slurry of modified graphene that we have already prepared. Next, we will apply these pastes to the aluminum foil through a coating machine and become the positive electrode used in our graphene capacitors.†China Electronics 18 Dr. Ding Fei, deputy director of the National Defense Science and Technology Key Laboratory of Chemical and Physical Power Technology, said that capacitive materials have a crucial influence on the performance of capacitors. By further studying the modification of graphene materials, researchers are moving the capacitor's storage capacity closer to the battery. At the same time, its ultra-fast charging speed can bring more convenience to people's lives. “The modified graphene capacitors we are making can be full for a few minutes, and their energy density is expected to approach the energy density of existing lithium batteries after some time.â€
Energy density refers to the amount of energy stored in a certain space or mass of matter. The higher the energy density, the stronger the storage capacity of this material. According to Ding Fei, at present, the samples of modified graphene capacitors that they developed have an energy density that is more than 3 times that of conventional capacitors. Although still in the laboratory research stage, the powerful capabilities of graphene materials allow R&D teams to see the broad prospects for the application of modified graphene capacitors.
In the future, when charging facilities are becoming more and more perfect, electric cars use graphene batteries and it may take two or three minutes to fully charge the batteries.
According to Gao Tao, director of the China Electronics Technology Research Institute's 55th Division and the key laboratory of Microwave Millimeter Wave Monolithic Integration and Module Circuits, even under laboratory conditions, the magical properties of graphene are still not completely released. At the same time, there are still many challenges at the technical level, and there is still a long way to go for real large-scale applications. However, by strengthening the combination of demand and research, we have made important breakthroughs in the preparation of graphene materials and device development. Graphene, a new generation of strategic emerging materials, will greatly change people's lives.
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