Can graphene become the core material of new era technology?

 　　Throughout the history of the development of the world, it is the evolutionary history of a material. The emergence of each new material leads the development of an era and changes the way of life of human beings.

　　Not only Bing Dundun, but also graphene, known as the "king of new materials", was brought to the attention of the Winter Olympics. The interior of the seats, carpets and other products of the Beijing Winter Olympics viewing platform are all applied with a new type of graphene flexible heating fabric material, which can adjust the temperature while keeping the temperature evenly above 20 degrees Celsius. The ceremonial clothing for the Winter Olympics awards also uses the inner liner of the second-generation graphene textile flexible heating material, which can raise the temperature to the comfortable temperature of the human body within 30 seconds.

　　Graphene is a new material in which carbon atoms connected by sp hybridization are tightly packed into a single-layer two-dimensional honeycomb lattice structure. Graphene has excellent optical, electrical, and mechanical properties, and has important application prospects in materials science, micro-nano processing, energy, biomedicine, and drug delivery, and is considered to be a revolutionary material in the future.

future use

　　The future of technology is limitless, and graphene can help us achieve that future sooner than we ever thought possible.

　　Here are a few profound inventions to look forward to in the near future:

air fuel

　　A British team led by Nobel laureate Andre Heim has shown that graphene can be used as a proton exchange membrane in fuel cells.

　　The discovery surprised everyone, because no one expected that these membranes would allow protons to pass through their tight, one-atom-thick hexagonal structures. In addition, graphene membranes could be used to screen hydrogen out of the atmosphere, enabling mobile fuel cells to run on air alone.

more drinking water

　　Graphene could help solve the world's water crisis. Membranes made from graphene can be large enough to let water through, but small enough to filter out salts. In other words, these membranes could revolutionize desalination technology.

　　In fact, a type of graphene has been shown to be so effective in water filtration that it made a water sample in Sydney Harbour safe to drink after one pass through the filter.

　　Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) uses "graphair" to make seawater drinkable after a single treatment.

a world without rust

　　Because it is practically impermeable, a coating of graphene could one day be used to eliminate corrosion and rust. This is important because the estimated global cost of corrosion is $2.5 trillion per year.

　　The researchers also suggested the use of glassware or copper plates covered with graphene coatings as containers for strong corrosive acids.

Preserve your artwork without fading

　　Graphene has several material advantages: it can be produced in large, thin sheets; it blocks UV light and is impermeable to oxygen, moisture and other corrosive agents.

　　The researchers believe that layered on top of a piece of art, it can prevent irreversible fading due to light and oxidants such as air. Their findings show that a single protective layer can prevent fading by up to 70 percent.

Why hasn't the magic material been taken over?

　　Work still needs to be done before the material can be widely adopted. Several production issues need to be addressed before more advanced sectors choose to implement.

　　One of the current challenges in mass production revolves around chemical vapor deposition (CVD). While it's the best way to produce single-layer graphene, it's not ideal at scale.

　　These challenges also make mass production expensive. It costs about $100 to produce one gram of graphene. Even so, the methods used to produce graphene on a large scale produce low-quality products and release carbon into the environment.

Graphene-based inks add touch sensor and circuit functionality to printed textiles.

future points of contention

　　All countries in the world attach great importance to and raise graphene to an unprecedented height, investing a lot of manpower, material and financial resources to seize this strategic highland. The European Commission has listed graphene as one of only two "flagship projects for future emerging technologies". The United States also regards graphene as a strategic industry that supports future technological development as important as 3D printing technology. China also clearly proposed to actively develop graphene materials in the "Twelfth Five-Year" Development Plan for the New Materials Industry.

1. Application-oriented graphene preparation method

　　The micromechanical lift-off method,

　　Geim et al., used an oxygen plasma beam to etch microgrooves with a width of 20 μm to 2 mm and a depth of 5 μm on the surface of highly oriented pyrolytic graphite. Then, the graphite flakes are repeatedly peeled off from the graphite with transparent glue, put into the acetone solution for ultrasonic oscillation, and then the single-crystal silicon wafer is put into the acetone solvent. Due to van der Waals force or capillary force, the single-layer graphene will be adsorbed on the silicon wafer. , so that a single layer of graphene was successfully prepared.

　　The method directly exfoliates few-layer or single-layer graphene from graphite, which is simple and easy to implement, does not require harsh experimental conditions, and the obtained graphene maintains a perfect crystal structure, with few defects and high quality.

　　Epitaxial growth method

　　This method uses single crystal 6H-SiC as raw material, and after etching treatment with hydrogen, it is heated by electron bombardment under high vacuum to remove oxides.

　　The graphene prepared by the method has high electrical conductivity and is suitable for electronic devices that require high electrical properties. The main disadvantage is that this method will produce difficult-to-control defects and polycrystalline domain structure, it is difficult to obtain long-range ordered structure, and it is difficult to prepare graphene with a large area and thickness. In addition, the preparation conditions are harsh, the cost is high, and the separation is difficult to carry out under high pressure and vacuum conditions.

　　Graphite intercalation method

　　This method uses natural flake graphite as raw material, uses alkali metal elements as intercalation agent, and obtains graphite intercalation compounds through the mixing reaction of intercalation agent and graphite. The graphite intercalation compound accelerates the exfoliation process of graphite from two aspects. First, the intercalation of the intercalant increases the interlayer distance of graphite and weakens the van der Waals forces between the graphite layers. Secondly, after the insertion of alkali metals such as lithium and potassium, an electron is input into the graphite lattice, which makes the crystal face negatively charged, and generates electrostatic repulsion, which makes the graphite crystal easy to peel and separate.

　　

　　Solution exfoliation method

　　Solvent exfoliation method is to disperse graphite in a solvent to form a low-concentration dispersion liquid, use ultrasonic or high-speed shearing to weaken the van der Waals force between the graphite layers, insert the solvent between the graphite layers, and perform layer-by-layer exfoliation to prepare out graphene.

　　The liquid phase exfoliation method can prepare high-quality graphene. The entire liquid phase exfoliation process does not introduce chemical reactions, which avoids the introduction of structural defects on the graphene surface, which provides high-quality graphene for the application of high-performance electronic devices. The main disadvantage is that the yield is very low, which is not suitable for large-scale production and commercial applications.

　　Chemical Vapor Deposition (CVD) method

　　This method is the main method for large-scale preparation of semiconductor thin film materials in industry by reacting substances in a gaseous state at a relatively high temperature and chemically reacting. Graphene is prepared by CVD method by heating at high temperature to decompose the gas into carbon atoms and hydrogen atoms, and annealing to deposit carbon atoms on the surface of the substrate to form graphene.

　　The future of technology is limitless, and graphene can help us make it happen sooner than we ever thought possible.

　　Redox method

　　The redox method can be simplified into three steps of "oxidation-exfoliation-reduction". The reduction reaction of graphene oxide is carried out at high temperature or in a reducing solution to restore the perfect two-dimensional sp2 hybrid structure of graphene to obtain graphite. alkene products.

　　The main preparation methods of graphene are summarized from the aspects of product quality, cost performance, environmental friendliness, purity, yield and industrialization prospects. It can be seen that, compared with other preparation methods with complex operation, high cost or low yield, the redox method can produce high-quality graphene in a large amount and efficiently, and the process is relatively simple.

2. Status and problems of domestic graphene preparation

　　So far, the industrialization of graphene has made important progress. Domestic enterprises such as Ningbo Moxi Technology, Changzhou Sixth Element Materials Technology, Dongguan Hongna New Material Technology, Shanghai Xinchi Energy Technology, Xiamen Kaina Graphene Technology, Shenzhen Beterui New Energy Materials and other enterprises have become the pioneers of large-scale graphene production. By. Although graphene production lines above the ton level have been built, there are still many problems to be solved in the process of graphene marketization and productization.

　　Up to now, the large-scale production and application of high-quality graphene has not yet been realized. The main reason is that the various excellent properties of graphene can only be manifested when the quality of graphene is very high. With the increase of the number of layers and the accumulation of internal defects, many excellent properties of graphene will be reduced. Graphene products generally have problems such as uneven size and number of layers, low content of single-layer graphene, specific surface area far below the theoretical value, and inability to classify. Therefore, the current commercial graphene products cannot meet the special needs of graphene in various application fields, which seriously hinders the large-scale application of graphene with high performance and high added value.

　　To sum up, the future development direction of graphene is to focus on completing the controllable classification of the number and size of graphene layers, and to realize the targeted application of graded graphene products in different fields, so that graphite can be effectively used. The high value-added characteristics of graphene, reduce the application cost, realize the large-scale industrial application of new two-dimensional graphene materials, and rapidly promote the development of my country's leading graphene in the world.

　　What is the future of graphene? Li Yichun, Secretary General of China Graphene Industry Technology Innovation Strategic Alliance, believes: "Although there are disputes in the industry, but technological innovation, anything can happen, we must have an open mind."