The road to industrialization of graphene: What kind of material is this?

What kind of material is graphene? How many thorns are there on the road of graphene industrialization? Graphene is the first single-atom two-dimensional carbon film material invented by humans. With only one layer of atoms, the movement of electrons is confined to a plane, bringing new electrical properties to it. The road to graphene industrialization is still advancing, and it still does not give up on the road full of thorns.     Into the Jiaxing Zhongyi carbon 7000 square meters factory, neatly arranged dozens of high temperature furnaces and low temperature furnaces sintered high thermal conductivity graphite film. These furnaces produce raw materials for the production of heat-dissipating films for electronic products such as mobile phones.     Graphene is the first single-atom two-dimensional carbon film material invented by humans. With only one layer of atoms, the movement of electrons is confined to a plane, bringing new electrical properties to it. It is highly conductive, bendable, and mechanically strong, and looks like the future of magical materials.     In 2012, Konstantin Novoselov, who won the Nobel Prize for graphene, and his colleagues published an article in Nature to discuss the future of graphene. He believes that as a material, graphene "has a bright future and the road is tortuous." Although it may play a major role in the future, this scenario will not come before overcoming several major difficulties.     More importantly, considering the huge cost of industrial renewal, the benefits of graphene may not be enough to simply replace existing equipment – ​​its real future may be a new application tailored to its unique characteristics. .     Thermal conductivity: applications on mobile phones     What kind of material is this?     Graphene is transparent under visible light but impermeable to air. These characteristics make it ideal as a raw material for protective layers and transparent electronic products. If you add supercapacitors, information storage devices, high-performance composite materials, to catalyst carriers, drug delivery, etc., it is simply a change in the world's invention.     In the production workshop, the monthly production capacity of 15 synthetic graphite production lines can reach 60,000 square meters. After the calcined raw materials are calendered, back-coated, coated, and die-cut, they are finally formed into a piece of mobile phone cover-sized film for attaching to the screen of the mobile phone, the shield, the middle frame, the back cover, and the battery. On, to achieve the cooling function.     Prior to founding this company dedicated to the development of specialty functional materials in 2011, Li Ping, founder of Zhongyi Carbon, worked at the China Telecom Shanghai Research Institute. In the application field of high thermal conductivity graphite film, Zhongyi Carbon has researched and innovated from large-size graphite film, continuous coil material and multi-layer composite graphite film.     In response to the latest graphene concept, Li Ping said that Zhongyi Carbon has been continuously tracking and investing in research and development. The industry's first graphene mass production product graphene heat-dissipating film will soon be introduced to the market as an upgraded product of high thermal conductivity graphite film. The reporter saw at the scene that the thinnest thickness of the graphene heat-dissipating film can be 5 microns, which far exceeds the conventional thickness of the high-thermal graphite film of 25 microns. At the same time, the graphene heat-dissipating film has more powerful thermal conductivity. At present, the graphene heat-dissipating film has achieved the full production process of raw material preparation, surface chemical modification, dispersion, film formation, and subsequent die-cutting processing.     However, with the saturation of the smartphone industry, the entire industry is facing a decline in orders. Li Ping said: "The situation in the first half of this year was particularly bad. Many customers' orders were cut by 80%. But the second half of the year began to improve, and it is expected to be the same as last year. It will be much better to have new products next year. In this industry, only continuous innovation, Develop new products to prevent them from being eliminated by the market."     Biocompatible: detection reagents and implanted bones     Li Ping said that the company is also cooperating with the Chinese Academy of Sciences, Tongji University, East China University of Science and Technology and other research institutions, hoping to open up more applications in the future of graphene. “Biomedical is an area of ​​great concern to us, especially the application of graphene in biosensing and detection. Graphene has a very strong fluorescence quenching effect, which can improve the sensitivity of traditional bioassay methods by two to three orders of magnitude. At present, the most important challenge is safety assessment. Especially when graphene is introduced into the human body, it may react with proteins, affect metabolism, or cause apoptosis. These require a lot of work."     Li Ping said that the product is produced by using the biocompatibility of graphene. He said: "Chemical modification is the key. Because graphene oxide is rich in hydroxyl, carboxyl, epoxy and various reactive oxygen-containing groups, it has good biocompatibility and can be chemically modified through the surface of quantum dots. Self-assembly technology design special DNA or nucleic acid probes to generate electrochemical reactions or fluorescence energy resonances for certain proteins for rapid diagnosis. Just like antibody and antigen, biotin and avidin, DNA base pairing, are specific Very strong."     This idea is consistent with the idea of ​​Rice University physicist Ching-HwaKiang. Kiang and his friend JamesTour made graphene nanoribbons (GNRs) by decompressing carbon nanotubes. GNRs are strips of material that are several thousand times longer than the width. The shape of this material creates properties similar to proteins and DNA. This means that the folded state of the protein can be observed by this material. Researchers have found that GNRs, like DNA and proteins, spontaneously form wrinkles and circulation in solution, and can also form spirals, wrinkles or wraps.     This material is likely to be functionalized in the future for use in conjunction with DNA, proteins, and even cells. With such materials, both biomolecular detection and molecular medicine will become possible in the future. It may also be used for DNA sequencing. This material may change other areas of biomedical science in many ways.     Recently, scientists at Rice University have tried to weld nano-flakes to form a tough porous material. The researchers found through experiments that the focused ion beam microscope image showed a welded 3D graphene layer. This material meets the biocompatibility and material properties necessary for bone implant standards.     Pollickel Ajayan, a scientist at Rice University's Materials Laboratory, and colleagues used spark plasma sintering of graphene oxide sheets in Texas, Brazil, and India to achieve mechanical properties comparable to biocompatibility and titanium. A porous solid of bone substitute material.     The discovery was published in the Advanced Materials paper. Researchers believe that their technology will be able to create highly complex graphite shapes that take only a few minutes, and they believe that this process is easier to create special materials than special metal processing.     “We started thinking about bone implants because graphene is one of the most interesting materials, and it creates many possibilities because of its general biocompatibility,” said Chandra Sekhar Tiwary, a postdoctoral research associate at Rice University. Tiwary is also the co-first author of the paper. Another first author, Dibyendu Chakravarty, is from the Powder Metallurgy New Materials Research Center in Hyderabad, India. Tiwary said: "Four things are important: mechanical properties, density, porosity and biocompatibility."     New 3D printing materials     Researchers control the density of materials by changing the voltage on the nanoscale welds. Although the experiment was carried out at room temperature, the researchers also increased the sintering temperature to 200 to 400 degrees Celsius to make graphene solids of various densities. Tiwary said: "Experiments have shown that the best samples can be obtained at a local temperature of 300 ° C."     With the help of a colleague of Hysitron, a high-tech nanomanufacturing company in Minnesota, USA, the researchers repeatedly tested the load-carrying capacity of two to five layers of graphene by connecting with a scanning electron microscope and found that they were at 70 micro-bovines ( The micronewtons) are still very stable under pressure. In addition, they successfully cultured cells on the graphene material with the help of researchers at the MD Anderson Cancer Center at the University of Texas, demonstrating their biocompatibility. Surprisingly, the researchers also found that the sintering process has a deoxidizing function that can turn the graphene oxide sheets into pure two-layer graphite, which makes them more stable than single-layer graphite or graphene oxide.     Ajayan said that this experiment demonstrates how conventional techniques can be used to make unconventional materials. But an important premise is that two-dimensional materials can mass produce 3D materials with suitable density and strength. "The advantage of 2D materials is that they can be connected over a large surface area. You just have to overcome a small activation energy and increase the weld strength." Ajayan said, "The engineering structure and powerful interface between nano blocks is The biggest challenge to achieve these goals, but in this case, spark plasma sintering seems to be an effective way to add graphene sheets and make 3D graphite materials."     Tiwary also said that spark plasma sintering is commonly used in the industry together with ceramics to make complex parts. “This technology uses high pulse current to connect the solder pads in an instant. You only need high voltage, no high voltage or high temperature.” He said that nearly 50% of the materials they make are porous, half the density of ordinary graphite, only metal. One quarter of titanium. But it has enough compressive strength - 40 MPa, which meets the requirements of bone implants - the torsion in the bone can make it not dissolve in water.     There have been rumors that Nokia will use graphene sensor components in the future, and the sensor will be produced by Foxconn Taiwan. The new phone will be the first product of Nokia and Foxconn. In this regard, researchers at Nanyang Technological University in Singapore said: "The camera made of graphene photosensitive element is 1000 times more sensitive to light than ordinary CMOS, but at the same time the price is more than 5 times higher." However, the researchers It is said that Nokia is focusing on improving the image quality of photosensitive elements in strong light and low light, and adopting new photosensitive elements. If successful, it will have a huge impact on the industry.     However, as the technology matures, the cost of new materials will also be greatly reduced. Graphene 3D printing materials are a good proof. Just last month, Haydale Composite Solutions (HCS), a well-known subsidiary of the well-known graphene company and London-listed Haydale Graphene Industries (HGI), announced that it will work with thermoplastic 3D printed wire manufacturers Filamentprint and Fullerex to promote and sell graphene-reinforced aggregates. Lactic acid (PLA) wire is used in 3D printing. It is understood that this new 3D printed wire will be officially presented at the TCT additive manufacturing exhibition held this month.     At present, this 3D printing material has been used in several large 3D printing companies and has achieved good response. Gerry Boyce, Managing Director of HCS, said in a statement: "We are very excited to develop graphene-reinforced thermoplastics for 3D printing applications. These new materials have many advantages, including making parts harder, stronger and faster! Since then, printing speed has been an obstacle to the large-scale application of 3D printing technology. We are extremely excited to think about the prospect of manufacturing structural components directly from CAD in the future."     In addition to launching its first commercial graphene-reinforced PLA wire, the company is also researching graphene-enhanced 3D printed wires including ABS, nylon and PP (polypropylene) materials. In addition, the two companies can also develop custom-made graphene-reinforced thermoplastic wires to meet specific product requirements.     Konstantin Novoslov, a professor of the Nobel Prize in Physics and a professor at the University of Manchester in the UK, pointed out at the graphene special session of this year's MWC Mobile Communications Conference: "Graphene and other two-dimensional materials have unique properties. They provide a basic form for flexible and transparent electronic devices. One of the earliest applications is the use of two-dimensional materials in printed electronics, which will be used in mobile printed electronics."     However, the application of graphene does not have a clear path in the entire industry. “We have contacted many professors in higher education institutions. They have also written some interesting papers, but the problem is that they don’t understand the industry and the market. From research to product is an extremely complicated process. Graphene must become a kind of Electronic components have its practical application value. Successful cases in the laboratory may not be available on the production line." Li Ping said, "We still rely on our own researchers for research and development, combined with the development of the entire industry and Demand, but the cost of the product at the beginning is a problem."