Analysis of graphene properties, applications and development status

Recently, China Graphene Standardization Forum released the world's first commercial graphene femtosecond fiber laser. This product solves the key technical problems of large-scale low-cost transfer of graphene and interaction of graphene with light field strength. For a time, graphene has received much attention in the field of laser technology.

In 2004, two Russian-born British scientists successfully separated graphene from graphite. Graphene combines the best quality materials in the world. Graphene is undoubtedly the most dazzling of all the 'stars' of the past decade and even decades. If the 20th century is the century of silicon, the magical graphene is the darling of the new material of the 21st century.

Although it has not been found for less than ten years, graphene has been causing a round of turbulence in the scientific and industrial circles. As people's understanding of it gradually became clear, its mysterious veil was uncovered as much as it was at the beginning—thin and hard, good transparency, strong thermal conductivity, high electrical conductivity, stable structure, and electron migration speed fast, can observe the quantum Hall effect at room temperature.

From hypothesis to reality

The discovery of graphene is significant because it creates many 'records'

Graphene is a basic unit material constituting carbon allotropes such as graphite, charcoal, carbon nanotubes and fullerenes, and is a two-dimensional crystal.

The structure of graphene has always been considered to exist only in theory and cannot be stably present alone. Until 2004, British physicists Andre Heim and Konstantin Novoselov successfully separated graphene from graphite, confirming that it can exist alone.

Initially, the scientist stripped the graphite sheet from the graphite and then glued the two sides of the sheet to a special tape. The tape was peeled off to divide the graphite sheet into two. Through repeated operations, the graphite sheets become thinner and thinner. Finally, they obtained a sheet consisting of only one layer of carbon atoms, which is graphene.

With the 'creative experiment in two-dimensional graphene materials', the two scientists jointly won the 2010 Nobel Prize in Physics.

The discovery of graphene is significant because it creates many “records”.

Graphene is the thinnest material in the world.

'Graphite is only 0.34 nanometers thick, and the thickness of 100,000 layers of graphene is roughly equal to the diameter of a hair strand, which is invisible to the naked eye. Haofei Shi, deputy director of the Micro-Nano Manufacturing and System Integration Research Center of the Chongqing Research Institute of the Chinese Academy of Sciences, described this in an interview with the Journal of the Chinese Academy of Sciences.

Graphene is the most intense substance known to man.

It is harder than diamonds and is 100 times stronger than the best steel in the world.

Physicists at Columbia University used diamond-made probes to test the resistance of graphene. The maximum pressure that can be withstrated per 100 nanometers before the particles of the graphene samples were broken began to reach 2.9micro-N. This means, If you make a bag made of graphene, it will be able to withstand about two tons of items.

Graphene has extremely low resistivity and electron migration is extremely fast.

In graphene, electrons can migrate very efficiently, with a migration rate of only one-third of the speed of light, much higher than in conventional semiconductors and conductors such as silicon and copper.

Electronics seem to have no mass inside the graphene, and the movement speed is very fast. Changyu Zeng, a professor at the University of Science and Technology of China, said that the characteristics of electron energy that will not be depleted make this material have extraordinary characteristics.

Another feature of the material is to surprise material scientists, the material is almost completely transparent, and the light transmittance is above 97%.

In 2012, IBM USA successfully developed the first integrated circuit made of graphene wafers, which made the special electrical properties of graphene show the application prospects. Hongjun Gao, an academician of the Chinese Academy of Sciences, said: “Graphene materials have excellent electrical properties and are expected to be used in the manufacture of next-generation high-performance electronic devices.”

Guiding the technological revolution

Worldwide, the craze for graphene research and applications continues to surge

The mysterious and magical special properties of graphene make people full of illusions about its application.

In China, the application research on graphene is in full swing.

China is at the forefront of the basic research and industrialization of graphene, and many research teams have made breakthroughs in the performance research and preparation technology of graphene. Among them, the graphene film preparation technology of the Chongqing Institute of Green Intelligent Technology of the Chinese Academy of Sciences was transferred at a price of 210 million Yuan, which made researchers and developers eager to move.

Worldwide, the craze for graphene research and applications continues to surge.

According to statistics from Cambridge Intellectual Property Corporation, as of May this year, a total of 9,218 graphene patents have been approved and are being applied worldwide, and the number of patent applications has increased fourfold in the past five years; since 2004, graphite The research papers in the field of olefins are exponentially increasing. The total number of papers has exceeded 20,000 so far, and in 2012 alone, it exceeded 6,000.

Never a material has been widely used in various fields like graphene. Changyi Zeng felt that although there are no real graphene products available at home and abroad, but it is the closest material to many “stars” materials.

Ultra-light body armor, super light conversion efficiency laser weapon, ultra-thin ultra-light aircraft, ultra-thin foldable mobile phone, high-strengthspecial materials, high-performance energy storage and sensors, super capacitors, and even more imaginative space elevators, More and more future devices based on graphene materials have entered the research field of scientists.

Among them, the application of transparent electrodes is the most attractive. Graphene's good electrical conductivity and light transmission properties make it a very good application prospect in transparent conducting electrodes. Changjun Zeng said that now touch screens, liquid crystal displays, organic photovoltaic cells, organic light-emitting diodes, etc. in electronic products require good transparent conductive electrode materials.

The traditional conductivity electrode uses indium tin oxide, which is relatively brittle and is relatively easy to damage.

In contrast, graphene is not only harder but also better in performance.

“Indium tin oxide light pass rate is relatively low, with graphene, the display screen will be brighter.” Changjun Zeng said that the application of graphene in transparent electrodes will greatly reduce the cost of electronic equipment, and make it more energy-efficient and clearer. 'A decade, graphene can certainly be commercialized in transparent electrodes'.

More than 97% of the light transmission rate has brought about changes in the application of transparent electrodes, and it has also made it possible to upgrade the solar industry.

According to experts, the current solar panels on the market are basically polycrystalline silicon, and its photoelectric conversion rate is about 30%, while the photoelectric conversion efficiency of graphene solar technology is as high as 60%, which is twice that of the existing polysilicon solar technology.

Recently, the Massachusetts Institute of Technology and Apple have released research reports on the possibility of graphene as a solar cell to provide energy for electronic devices. Apple has filed a patent application for the purpose of carrying graphene solar energy in electronic equipment. The battery provides a solution.

Zhaoping Liu, a researcher at the Institute of Materials Technology and Engineering of the Chinese Academy of Sciences, said in an interview with the Journal of the Chinese Academy of Sciences that graphene microchips can form two-dimensional conductive contact with particles of active materials of lithium-ion batteries and construct a three-dimensional conductive network in the electrodes can greatly improve the overall performance of the battery.

Preliminary experimental results show that the lithium cobalt oxide battery with graphene conductive agent has a capacity higher than 3% and the discharge capacity has increased from 72% to 92% compared with the conventional battery.

Breakthrough preparation technology

Preparation technology is one of the roadblocks for graphene to enter the application field and realize industrialization

Despite the increasingly thorough research on graphene by domestic and foreign scientists, the results of their application are constantly emerging. However, there are few real graphene materials available on the market.

The preparation technology is one of the roadblocks for graphene to enter the application field and realize industrialization. The high-cost preparation technology has pushed up the market price of graphene, and its price once reached 5,000 Yuan per gram, which is more than ten times that of gold.

Hongjun Gao bluntly stated at the Xiangshan Science Conference on the topic of graphene held at the end of last year. China still faces great challenges in the research field of graphene preparation methods. 'The challenge lies mainly in how to prepare high-quality single crystal materials with large area and controllable impurity defects and how to improve the graphene processing technology of the existing silicon-based process fusion. 'In spite of this, Chinese scientists have still achieved a major breakthrough in the development of graphene preparation technology. Zhaoping Liu led the research team through years of efforts to develop graphene industrial preparation technology, reducing the manufacturing cost of graphene from 5,000 Yuan per gram to 3 Yuan per gram, directly bringing a large number of orders from foreign customers.

At the beginning of this year, Chongqing Institute of Green and Intelligent Technology of the Chinese Academy of Sciences announced the preparation of 15-inch single-layer graphene, and successfully applied a graphene transparent electrode to a resistive touch screen to prepare a 7-inch graphene touch screen.

It is worth mentioning that the above two research teams have jointly established a professional graphene production company with Shanghai Nanjiang Group to produce graphene microchips and graphene films respectively.

The research team of Changjun Zeng, the National Laboratory of Microscale Material Science, has taken a different approach. The conventional graphene growth based on gaseous carbon source needs to reduce the high temperature of 1000 °C to 300 °C, creating the lowest temperature for graphene chemical vapor deposition.

With the upgrading of graphene preparation technology, the conditions for industrial production are also maturing, and it is believed that new products made of graphene will continue to emerge in the next few years, Changyu Zeng said.

The page contains the contents of the machine translation.