I. Discovery of Graphene
Graphene is a new material that has just been discovered for more than ten years. We say discovery instead of invention here because there is graphene in nature. We often say that graphite is widely distributed in nature. They are made of graphene, but people have never taken out a piece of graphene. Only when two British scientists successfully prepared a single piece of graphene can we study graphene in depth. Of course, these two scientists won the Nobel Prize. At the same time, the method of preparing graphene by two scientists is also a story of scientific innovation.
When it comes to preparation in chemistry, it is often a pile of bottles, bottles and cans, and various reagents. Through a complex chemical reaction process, a substance is finally obtained. But the initial preparation of graphene, just like children playing house, can be completed only with graphite and tape. Graphite is like a thousand layers of cake stacked with graphene. If we can uncover them layer by layer, we will get graphene. However, the thickness of a layer of graphene is very small, which is not only invisible to the naked eye, but also indistinguishable under the microscope. So it is impossible to remove it like adhesive. However, two British scientists came up with an idea. Two tapes were attached to both sides of graphite, and then it was uncovered, so that many layers of graphene could be attached. Then stick it on with two tapes, uncover it, and the graphite becomes thinner again. This repeated operation can make the graphite like a thousand layers of cakes thinner and thinner, and finally there is only one layer left, which is graphene. Such a piece of graphene is a honeycomb-like fine mesh structure, which is called two-dimensional crystal material in the industry. If we get such graphene, we can study it. Many friends have heard this story. Let me briefly talk about the properties and applications of graphene.
Second, the properties and applications of graphene
1. The ideal graphene material has unlimited potential.
The first special property of graphene is its powerful mechanical properties. Generally speaking, graphene is one of the strongest materials found so far. With the same thickness of steel cable and rope made of graphene, the force of breaking the steel cable will increase by 200 times before the graphene rope can be broken. At the same time, the density of graphene is only one third to one quarter of that of steel. In science fiction, space elevator is regarded as the standard of the future world, but how to make this kind of elevator is also a difficult problem. If the elevator is driven by steel cables, hundreds or even tens of thousands of kilometers of steel cables can be rolled by themselves without connecting the elevator car. The most likely material to become the cable of space elevator is the cable made of graphene or carbon nanotubes.
If graphene is used to make a film with the thickness of plastic wrap, it will be as soft as plastic wrap, but it is not easy to tear it. It has been calculated that if you want to pierce a piece of plastic wrap made of graphene with a needle tip, you have to stand an elephant on the needle. At the same time, perfect graphene is an almost absolutely airtight material, and even the lightest hydrogen and helium can't pass through the gaps of graphene. If you can make the perfect graphene tire in the future, you can almost never need to pump up. Even if the car rolls on the nail, it is difficult to puncture the tire. Of course, it is not always safe, it will wear out over time, and it will fight poison with poison. In other words, although graphene is good, it is not without flaws.
According to this ability, graphene will be widely used in the future. For example, the space field has begun to plan graphene materials as fuel tanks, and spacesuits made of graphene will be very sci-fi.
These applications sound good, but they are far from practical applications. Because the biggest problem here is the production of graphene. In fact, graphene itself is not difficult to produce. There are many methods to extract graphene in nature. On Taobao, you can buy a catty of graphene for more than 100 yuan. But if you buy such graphene, you can't do those things mentioned above. All you can buy is graphene powder, and the real graphene film is very expensive. Just like diamonds, the bigger the diamond, the more valuable it is. There are a lot of miniature diamonds in the smoke produced by candle burning. You never thought that the smoke produced by burning candles would be expensive. Similarly, the price of graphene powder is not high, but if it is made into a large-area graphene film, it will be valuable.
Nowadays, it is not easy to produce palm-sized graphene films in industry, because the production of macromolecules is not as simple as pressing steel plates or producing plastic films. Graphene is a molecule no matter how big it is. As we all know, the bigger the molecule, the more complex it is, and the more difficult it is to produce. In other words, graphene is not produced by a bunch of carbon atoms, but by chemical reaction. The larger the area, the more difficult it is to synthesize. However, the magic is one foot high and the road is ten feet high. Now we have many ways to produce graphene. In 20 12 years, Sony Corporation of Japan has been able to produce graphene composite reels with a width of 20 cm and a length of 100 m, but the price of this material is almost the same as that of gold. In order to make graphene widely used in the future, the production cost must be continuously reduced.
But even if we can produce a large area of complete graphene, we still can't make the tires we just mentioned. Our ideal graphene is a perfect structure without defects, but the actual graphene is more or less defective, and the larger the area, the more defects. A large area of perfect graphene materials can't be done at present, and even if it can be done, the price will be outrageous. A perfect graphene tire is definitely much more expensive than the most expensive car, which is not affordable for our average consumers. Teacher Dongcheng once imagined that Spider-Man's clothes were probably made of graphene and carbon nanotubes. Interested friends can guess how clothes use materials on the earth to realize the functions of Spider-Man clothes. Find time, let's talk about the implementation method.
2. In reality, graphene also has a lot of room to play.
Some friends may say that they seem to have been fooled. Graphene can't be used at all, and it's not like this. Graphene is not only strong, but also has many properties that can be used now. Graphene, for example, has strong thermal conductivity. How strong is it? Let's make a simple analogy. In the metal world, the strongest thermal conductivity is silver, followed by copper. Generally, our notebook computers use copper to transfer the heat generated by CPU and graphics card. Thermal conductivity is stronger than silver. If the diamond is big enough to be as long as a small ruler, we can hold this end of the ruler with our hands and melt the ice with the other end of the diamond. The thermal conductivity of graphene is 1.5 times that of diamond, that is, it is stronger than diamond. Some mobile phone manufacturers have begun to try to use graphene materials to cool their mobile phones.
In addition, graphene has very good conductivity and is the best semiconductor material at present. In addition, graphene is soft and transparent, which makes it very suitable for flexible devices. For example, by applying graphene materials, solar panels that can be bent can be produced. Graphene can also be used to make flexible screens and touch screens, which can overcome the shortcoming that mobile phones can't bend for fear of falling. In the future, there will be more and more mobile phones that can bend. At present, all countries are tackling the problem of graphene flexible chips. Once the research and development is successful, flexible wearable devices and transparent mobile phones that can only be seen in many movies will no longer be dreams. China Peking University's research team developed carbon-based chips and used carbon nanotubes as transistors. The future development direction is to develop flexible carbon-based chips based on graphene.
Graphene can be used to manufacture electrode materials for lithium ion batteries. Compared with traditional graphite materials, graphene has much better performance, higher storage capacity and longer service life. However, the cost of graphene is much higher than that of ordinary graphite, which has a great impact on the cost of batteries. Whether graphene can be widely used in the future depends on whether the production cost of graphene can be greatly reduced. The conductivity of graphene can be further enhanced. For example, adding some elements to transform the conductivity can make it a very good conductor, or putting graphene into liquid helium can greatly improve the conductivity. All these determine that graphene will have a very good application prospect.
Large pieces of graphene are widely used, but it does not mean that small pieces of graphene are useless. Let's talk about the application of graphene powder. Graphene powder, technically called graphene powder, also has the properties of graphene and can be widely used. Now, these applications have already entered the market.
Graphene powder still has good electrical and thermal conductivity, and its structure is still very strong and not easy to wear. Therefore, such materials are often added to other materials to enhance the performance of other materials. For example, graphene powder can be added to lubricating oil to bring better lubrication effect to construction machinery and reduce mechanical damage; The coating added with graphene has better anticorrosion effect; Clothing, paint or floor added with graphene can prevent static electricity accumulation because of its conductivity; Adding graphene into heat-resistant polyethylene plastic pipe for floor heating can conduct heat better and improve the utilization rate of heat; Graphene added to clothes has certain far-infrared radiation function and so on. In a word, graphene powder can be widely used in military, aerospace, construction machinery, household clothing, environmental management, medicine and other fields. We will introduce some application scenarios later.
Third, China's graphene technology has a leading edge.
As a big country in science and technology, China has always paid attention to the layout of science and technology fields. Teacher Dongcheng has always had a view that although our country has a certain gap with the western developed countries in the field of traditional science and technology, in many emerging fields of science and technology, China is keeping up with the world trend, and even has achieved a leading position in some fields. As patriots, we shouldn't "eat dragon fruit and spit seeds" and don't demand perfection in everything.
While not relaxing R&D in the traditional scientific and technological field, China has been paying more attention to R&D's investment in emerging technologies. For example, in the field of graphene materials, although it was the earliest breakthrough in Britain, countries are also studying it, but the research results in China are very gratifying. At the national level, graphene materials and rare earth materials have been given great policy support as key industrial fields for future development. According to statistics, the number of graphene-related papers published by Chinese researchers ranks first in the world, more than that of the United States. The number of patents also far exceeds that of the United States, ranking first in the world. According to statistics, from 20 16 to 20 18, China applied for 229 12 graphene patents and the United States applied for 84 1 piece. In terms of quantity, the advantage is still obvious. It can be seen that various industries in China attach importance to graphene materials. Coupled with the huge application market in China, it is not surprising that China will complete the carbon material revolution at the earliest in the future.
Under the guidance of national policies, a large number of domestic enterprises carry out business and research and development around graphene materials, and related products are sold in large quantities. Of course, some of these products are excellent functional products, which bring convenience to our lives, and some are gimmicks that hype graphene, which are not as magical as advertised. I hope everyone will keep their eyes open and avoid being fooled. Later, I will introduce some real applications and refute some gimmicks.