Not long ago, Tsinghua University’s research team released an invention of "Smart Graphene artificial larynx", which makes use of the advantages of porous graphene materials to create an integrated acoustic device that is transceivable and wearable, and is expected to solve the "speaking" problem of deaf people in the future.
Internationally, researchers from institutions such as Cambridge University reported that they found a new way to "awaken" the superconductivity of graphene, and the awakened graphene can be used to manufacture supercomputers.
Graphene is the hottest new material at present. In the aviation field, people use "rare elements" to describe materials that are as light as air and as hard as steel. Previously, titanium alloy was considered as the ideal choice closest to this quality, while "rising star" graphene was considered as a step closer to the "rare element" of human dreams.
What is graphene?
At present, the thinnest, lightest and strongest material in the world is 100 times harder than the strongest steel.
Like diamond, graphite is a form of carbon. The difference is that, due to the different atomic structures, diamond is the hardest thing on earth, while graphite is one of the softest minerals, which are often made into graphite rods and pencil lead. Graphene is stripped from graphite material and only consists of a layer of carbon atoms on the plane.
It can be said that one of the characteristics of graphene is its thinnest material in the world, which is only one atom thick, about 0.3 nanometer, which is one-hundredth of the thickness of A4 paper and one-fifth of the thickness of hair. At the same time, it can conduct electricity, and the movement speed of electrons in graphene reaches 1000 km/s, which is 1/300 of the speed of light. Thin, strong, conductive and thermal … … These characteristics of graphene give people a lot of imagination.
Dr. Kong Yuechan, deputy director of the Key Laboratory of Microwave and Millimeter Wave Monolithic Integration and Modular Circuits of China Electric Power Department, said that the hardness of graphene is very strong, 100 times stronger than the strongest steel now; Graphene’s electron running speed is also very high, 10 times that of silicon, which is very suitable for developing the next generation of UHF electronic devices. In addition, graphene is also a master of heat conduction, which is 10 times stronger than the most thermally conductive metal silver.
The characteristics of graphene are also very "fun". For example, when a drop of water rolls on the surface of graphene, graphene can keenly "perceive" subtle movements and generate continuous current. This characteristic provides scientists with a new idea to obtain electric energy from the flow of water.
"Graphene can sense a single electron, and the movement of charged particles on the surface of graphene can cause the electrons in graphene to move rapidly, realizing the sensing and power generation process." Lin Shisheng, an associate professor at the School of Information and Electronic Engineering of Zhejiang University, said that this feature of graphene can be used in many applications in energy and electronic sensing, such as using an umbrella coated with graphene to generate electricity in rainy days, or making it into a sensitive sensing device.
It is these comprehensive properties that make graphene attract unprecedented attention, and some people even begin to predict that the appearance of graphene will lead an industrial revolution triggered by material progress.
How to obtain graphene
For the first time in the world, a single layer of graphene was obtained by "sticking" it with transparent glue.
The first time people got graphene, they used a "simple and rude" method.
Graphene itself exists in nature. Graphene is a thin layer of carbon atoms, and a hexagonal ring is formed between the atoms, and the rings are connected to form a honeycomb plane. It is graphite when stacked layer by layer, and graphite with a thickness of 1 mm contains about 3 million layers of graphene. Pencil lightly across the paper, leaving traces that may be several to dozens 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 single-layer structure. The key problem is how to stratify graphite into extremely thin slices.
Many people also had this experience when they were students. When they wrote typos on paper, they would use transparent tape to stick the typos off. But no one thought that it was such a simple method that people discovered the mysterious graphene.
To make graphene, simply speaking, it is necessary to thin graphite, not by cutting, not by grinding, but by sticking. In 2004, Heim and Novoselov of the University of Manchester in the United Kingdom repeatedly stuck and tore a graphite sheet with transparent adhesive, and the thickness of the graphite sheet gradually decreased, eventually forming graphene with a thickness of only 0.335 nm, that is, graphene with an atomic thickness. This is the first time in the world to get a single layer of graphene, so two scientists won the 2010 Nobel Prize in Physics.
Dr. Wu Yun, a senior engineer in the Key Laboratory of Microwave and Millimeter Wave Monolithic Integration and Modular Circuits of 55 China Electric Power Institute, gave a demonstration to the reporter. He stuck a small piece of graphite on the tape and then tore it overlapping. After sticking for half an hour, the tape was covered with gray graphite, and then the graphite was transferred to a clean silicon wafer with tape.
Wu Yun said, what we saw at this time was not graphene, because graphene is not only very thin, but also has a light transmittance of over 97%, which is almost completely transparent, and people can’t see it at all. To find it, we have to use special technical means. But this is already a multi-layer graphite sheet, and then the number of layers can be located and determined by technical means, and finally the single-layer graphene can be found.
Experts say that this is just the initial method of producing graphene. The mechanical stripping method, which evolved from the adhesive tape paper sticking method, is just a method for preparing graphene in the laboratory. At present, with the technological progress, high-quality graphene can be produced more.
What will graphene bring?
Using graphene material, the screen of mobile phone can be easily bent or even folded.
The appearance of graphene is expected to bring surprises to our lives. Mobile phone charging can be "second charging", mobile phone screen can be easily bent or even folded, and cars can use graphene static conductive tires to avoid deflagration caused by friction electrification … … From aerospace and electronic information to energy conservation and environmental protection, great changes are likely to take place in many fields by using the characteristics of graphene.
Using graphene instead of silicon can improve the performance of electronic chips. Researchers are currently introducing the production and application of graphene into the semiconductor industry, and the technological revolution triggered by graphene is likely to start with our common small chips.
The basic material of electronic chips is silicon. However, with the increasing density of components on the chip, the distance between the two components on the top chip is less than 10 nanometers, almost reaching the limit of silicon materials. What should I do if I want to continue to improve my performance? Researchers began to try to partially replace the role of silicon with graphene.
"Devices made of graphene can theoretically reach ten times or even hundreds of times the frequency of silicon, which can be applied to radar and greatly improve the resolution of radar. Moreover, it is widely used in communication and imaging. " Kong Yuechan said, moreover, the current R&D and production equipment of graphene is the same as that of ordinary semiconductor equipment, and 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 a gold foil with a thickness of only 50 nanometers, and then used a new method to completely transfer graphene to a soft plastic sheet.
Kong Yuechan said that graphene can be transferred to any substrate that researchers want through flexible methods, such as a special plastic substrate for electronic devices, which is flexible and suitable for the preparation process of transistors. Through the special graphene transfer technology, the gold foil with graphene is attached to the plastic sheet, and based on this, electronic devices with certain functions are prepared on this plastic sheet. Most importantly, 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 may be realized by such graphene devices.
Another highly anticipated application field of graphene is the storage of electric energy. In Tianjin Electric Power Research Institute, researchers here are conducting research on the most advanced capacitors. Capacitors, like batteries, can be used to store electric energy. Its advantage lies in its fast charging speed, which can be fully charged in a few minutes and can be reused for tens of thousands of times. But it doesn’t store as much electricity as a battery, and it can’t be used in life by storing enough electricity.
"This is the slurry made of modified graphene. Next, we will apply these slurries to aluminum foil through a coater and become the positive electrode for our graphene capacitor." Dr. Ding Fei, executive deputy director of 18 National Defense Science and Technology Key Laboratories of Chemical and Physical Power Technology in China Electric Power Department, said that capacitor materials have a vital impact on the performance of capacitors. Through the further modification of graphene materials, researchers are making the storage capacity of capacitors closer to the battery step by step, and at the same time, its ultra-fast charging speed can bring more convenience to people’s lives. "The modified graphene capacitor we are making can be fully charged in a few minutes, and its energy density is expected to be close to that of existing lithium batteries after a period of time."
Energy density refers to the amount of energy stored in a substance with a certain space or mass. The higher the energy density, the stronger the power storage capacity of this substance. According to Ding Fei, the energy density of the modified graphene capacitor they have developed has reached more than three times that of the traditional capacitor. Although it is still in the laboratory research stage, the powerful capabilities of graphene materials have enabled the R&D team to see the broad prospects for the application of modified graphene capacitors.
In the future, when the charging facilities are becoming more and more perfect, it may take two or three minutes for electric vehicles to fully charge with graphene batteries.
Gao Tao, director of No.55 Institute of China Electric Power Department and director of the Key Laboratory of Microwave and Millimeter Wave Monolithic Integration and Modular Circuits, believes that even under laboratory conditions, the magical properties of graphene have not been fully 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 application. However, by strengthening the combination of demand and research, important breakthroughs have been made in the preparation of graphene materials and device development. Graphene, a new generation of strategic emerging materials, will greatly change people’s lives.
Yu Jianbin Li Xiaohui Wujie
