According to scientists, it is easy to find the raw material of graphite on the earth, and graphene is the strongest substance known to mankind, and it will have many fascinating development prospects. It can not only develop and manufacture ultra-light aircraft materials as thin as paper, but also manufacture ultra-tough bulletproof vests, and even open the door of "Alibaba" for manufacturing "space elevator" cables. American researchers say that one of the biggest obstacles to the "space elevator" is how to make a cable that is 23,000 miles long and strong enough to connect from the ground to the space satellite. American scientists have confirmed that graphene, the strongest substance on earth, is completely suitable for making space elevator cables! It will be much cheaper for humans to enter space through the "space elevator" than through rockets. In order to encourage scientists to invent tough materials for manufacturing space elevator cables, NASA had previously offered a reward of $4 million.
Produce supercomputers instead of silicon
Scientists have found that graphene is still the best conductive material known at present. This characteristic of graphene is especially suitable for high frequency circuits. High-frequency circuit is the leader of modern electronic industry. Some electronic devices, such as mobile phones, are required to use higher and higher frequencies because engineers are trying to fill more and more information into signals. However, the higher the working frequency of mobile phones, the higher the calorific value, so the promotion of high frequency is greatly limited. Due to the appearance of graphene, the development prospect of high frequency enhancement seems infinitely broad. This makes it have great application potential in the field of microelectronics. Researchers even regard graphene as a substitute for silicon and can be used to produce future supercomputers.
photonic sensors
Graphene can also be used as a photon sensor in a larger market to detect the information carried in optical fibers. Now, this role is still played by silicon, but the era of silicon seems to be coming to an end. In June 5438+10 last year, a research group of IBM unveiled their graphene photodetector for the first time. Next, people have to look forward to solar cells and liquid crystal displays based on graphene. Because graphene is transparent, electrodes made of graphene have better light transmittance than other materials.
Other applications
Graphene can also be used in transistors, touch screens, gene sequencing and other fields, which is expected to help physicists make new breakthroughs in the field of quantum physics research. Researchers in China found that bacterial cells could not grow on graphene, while human cells were not damaged. Graphene can be used to make bandages, food packaging and even antibacterial T-shirts. Photoelectrochemical cells made of graphene can replace metal-based organic light-emitting diodes, because graphene can also replace the traditional metal graphite electrode of lamps, which is easier to recycle. This material can not only be used to develop and manufacture ultra-light airplane materials as thin as paper, but also make ultra-tough body armor, and even make the 23,000-mile-long space elevator that scientists dream come true.
Graphene-characteristics
Electronic transportation
Schematic diagram of graphene structure Before the discovery of graphene, most (if not all) physicists thought that thermodynamic fluctuations did not allow any two-dimensional crystal to exist at a finite temperature. Therefore, its discovery immediately shocked the condensed matter physics community. Although both theoretical and experimental circles believe that the perfect two-dimensional structure can not exist stably at non-absolute zero, single-layer graphene was prepared in the experiment. These may be attributed to the microscopic distortion of graphene at the nanometer level.
Graphene also shows abnormal integer quantum Hall behavior. Hall conductance =2e2/h, 6e2/h, 10e2/h ... are odd multiples of quantum conductance and can be observed at room temperature. This behavior is interpreted by scientists as "electrons obey relativistic quantum mechanics in graphene, and there is no rest mass".
electrical conductivity
The structure of graphene is very stable. So far, researchers have not found that graphene lacks any carbon atoms. The connection between carbon atoms in graphene is very flexible. When mechanical external force is applied, the surface of carbon atoms is bent and deformed, so that carbon atoms do not need to be rearranged to adapt to the external force, thus maintaining structural stability. This stable lattice structure makes carbon atoms have excellent conductivity. When electrons in graphene move in orbit, they will not be scattered due to lattice defects or the introduction of foreign atoms. Because of the strong interatomic force, even if the surrounding carbon atoms collide at room temperature, the interference of electrons in graphene is very small.
The biggest feature of graphene is that the speed of electrons in it reaches 1/300 of the speed of light, far exceeding the speed of electrons in general conductors. This makes the properties of electrons in graphene, or more accurately, "charge carriers", very similar to those of relativistic neutrinos.
Graphene is quite opaque: it can absorb about 2.3% of visible light. This is also the embodiment of carrier relativity in graphene.
mechanical character
Graphene is the strongest substance known to mankind, harder than diamond and stronger than the best steel in the world 100 times. Physicists at Columbia University have conducted a comprehensive study on the mechanical properties of graphene. During the experiment, they selected some graphene particles with the size of 10-20 micron as the research object. The researchers first placed these graphene samples on a thin crystal plate with holes drilled on the surface, and the diameters of these holes ranged from 1 to 1.5 microns. After that, they used a probe made of diamond to put pressure on the graphene placed on the holes to test their endurance.
The researchers found that before the particles of graphene samples began to disintegrate, the maximum pressure they could bear per 100 nm actually reached about 2.9 micro-Newton. According to the calculation of scientists, this result is equivalent to applying a pressure of 55 Newton to break the graphene with a length of 1 m. If physicists can make graphene (thickness about 100 nm) equivalent to ordinary food plastic packaging bags, it will take about 20,000 newtons to break it. In other words, if the packaging bag is made of graphene, it can bear about two tons of items.
Interaction of electrons
Using the world's most powerful artificial radiation source, physicists from the University of California, Columbia University and Lawrence Berkeley National Laboratory have discovered a new secret of graphene characteristics: there are strong interactions between electrons in graphene and between electrons and honeycomb grids.
Scientists use the Advanced Light Source (ALS) electron synchrotron at Lawrence Berkeley National Laboratory. The brightness of light radiation produced by this accelerator is equivalent to 65.438+0 billion times of medical X-ray intensity. Using this strong light source, scientists found that the electrons in graphene not only have strong interaction with honeycomb lattice, but also have strong interaction with electrons. [ 1]
Graphene-research results
China
Supported by the National Natural Science Foundation of China, the Ministry of Science and Technology and the China Academy of Sciences, Cheng Huiming and Ren's research team from the Advanced Carbon Materials Research Department of Shenyang National (Joint) Laboratory of Materials Science of China Academy of Sciences have made a series of new progress in the controllable preparation, structural characterization and physical properties of graphene, and related research results have been published in international journals.
This paper was selected as the "highlight" of this issue by ACSNano magazine of American Chemical Society and introduced emphatically. At the same time, it was selected as the outstanding scientific research achievement of Chinese mainland and Hongkong by Nature-China. Dr. Wycliffe, a commentator in the chemical field of Nature-China magazine, wrote: "Ren and Cheng Huiming of China Academy of Sciences and their collaborators have proposed a fast, nondestructive and large-area optical method for graphene characterization, which is helpful to determine and prepare ideal graphene samples suitable for application."
South Korea
In July 2009, Korean researchers discovered a method to prepare large-size graphene films.
The latest graphene film prepared by researchers from Sungkyunkwan University and Samsung Institute of Advanced Technology in Korea has a thickness of 1 cm and a transmittance of 80%. In the process of bending or stretching, it will not break and its electrical characteristics will not change. Their achievements were published in the online edition of the British journal Nature on June 65438+1October 65438+April. [ 1]
Application of Graphene
Graphene is widely used, from electronic products to body armor, paper making, and even future space elevators.
1. "Space elevator" cable
According to scientists, it is easy to find the raw material of graphite on the earth. Graphene is the strongest substance known to mankind, and it will have many fascinating things.
Development prospect of space elevator. It can not only develop and manufacture ultra-light aircraft materials as thin as paper, but also manufacture ultra-tough bulletproof vests, and even open the door of "Alibaba" for manufacturing "space elevator" cables. American researchers say that one of the biggest obstacles to the "space elevator" is how to make a 23,000-mile-long and strong enough cable from the ground to the space satellite. American scientists have confirmed that graphene, the strongest substance on earth, is completely suitable for manufacturing space elevator cables.
It will be much cheaper for humans to enter space through the "space elevator" than to ascend into space through rockets. In order to encourage scientists to invent tough materials for manufacturing space elevator cables, NASA had previously offered a reward of $4 million.
2. Produce supercomputers instead of silicon
According to scientists, graphene has a series of unique characteristics besides being extremely strong. Graphene is also the best conductive material known at present, which makes it have great application potential in the field of microelectronics. Researchers even regard graphene as a substitute for silicon and can be used to produce future supercomputers.
IBM announced that it has developed the fastest graphene field effect transistor (FET) in the world, which can operate at the frequency of 26GHz. Researchers at Thomas Hospital. The Watson Research Center of the company also predicts that the higher electron mobility of carbon element is expected to make this material exceed the limit of silicon and enter the terahertz field at a speed exceeding 100GHz.
Graphene-Winning the Nobel Prize
20 10 10 years 10 On 5 October, two scientists from Manchester University in England, Konstantin Novoselov and Andre Geim, won the 20 10 Nobel Prize in Physics for their research on graphene. [2]
Graphene-partial graphene research results
At the International Conference on Materials Science held in the United States on June 5438+February 1 2009, Fujitsu Research Institute of Japan announced that they had made thousands of transistors from graphene. Researchers at Fujitsu Research Institute blow raw gas onto a substrate coated with iron as a catalyst in advance, and make large-area graphene films on this substrate. The preparation of large-scale graphene has always been a difficult problem. Fujitsu made high-quality graphene films with a diameter of 7.5 cm by the above method. On this basis, electrodes and insulating layers are configured to make graphene transistors. Due to the large area of graphene, Fujitsu has made thousands of transistors on it. Graphene transistor has lower power consumption and faster operation speed than silicon transistor, and can make semiconductor devices with excellent performance. If the technology is improved, it is expected to further expand the area of graphene, so that more transistors and graphene integrated circuits can be made, which creates conditions for the production of high-end electronic products. In June165438+1October, 2009, Northeastern University and Huijin University discovered that graphene can generate terahertz electromagnetic waves. Researchers have made graphene films on silicon substrates, and irradiated infrared rays onto the graphene films, which can emit terahertz light in a short time. If we can continue to improve the technology and further improve the intensity of light source in the future, we can develop high-performance lasers. The research team used organic gas to make a layer of carbon-silicon compound on silicon substrate. Then, heat treatment is performed to grow graphene thin films. Graphene thin films can emit terahertz light from graphene only by irradiating infrared rays in a very short time. At present, the team is committed to developing devices that can seal light particles inside and increase the intensity of light sources, hoping to develop terahertz lasers that can work near room temperature. 20 10 rice university in the United States made a single molecule sensor with this graphene quantum dot. Rice University combines graphene sheets with a layer of helium to form graphite alkanes. Graphene is an insulator. Helium transforms graphene from a conductor to an insulator. The researchers removed the helium islands on both sides of the graphene sheet, forming tiny conductive graphene traps surrounded by graphite alkane insulators. Conductive graphene wells can be used as quantum wells. The semiconductor characteristics of quantum dots are better than bulk silicon devices. This technology can be used to manufacture chemical sensors, solar cells, medical imaging equipment or nanoscale circuits.
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