Abstract Professors of Zhejiang University have made the world's "lightest material" - "all carbon aerogel" with an aqueous solution containing two nanomaterials, graphene and carbon nanotubes. A few days ago, there was news that the United States
Professors from Zhejiang University have made the world's "lightest material" - "all carbon aerogel" with an aqueous solution containing two nanomaterials, graphene and carbon nanotubes. 
A few days ago, it was reported that American scientists have developed a graphene-based micro-supercapacitor that can charge mobile phones and even cars within tens of seconds; a domestic listed company is also applying for graphene battery patents. Affected by these news, graphene concept stocks have been active recently.
In 2004, the physicists of the University of Manchester, André Heim and Konstantin Novoselov, succeeded in separating graphene from graphite in experiments, confirming that it can exist alone. Only six years later, the two won the 2010 Nobel Prize in Physics.
It is absolutely rare that a result is completed from the completion of the award to the Nobel Prize, only six years apart. This also explains the degree of attention of this work from one side.
Indeed, since the advent of graphene, scientists have quickly discovered the myriad magical properties of this material, and all parties have invested a lot of interest in its research and development. Some scientists even predict that graphene will "completely change the 21st century."
Only one layer of carbon atoms
"Two-dimensional structure" turns from imagination to reality
All of us are familiar with “graphite†because the pencil refill is made up of it and clay.
Graphite is composed of carbon. Under the electron microscope, it can be found that the structure of graphite is layered, and the carbon atoms of each layer are arranged in a tight honeycomb hexagonal grid, and the distance between layers is relatively large, and the interaction between layers is relatively large. It is weak and easily peels off each other to form a thin graphite sheet. The reason why the pencil is lightly stroked on the paper will leave a trace, which is the result of this loose pile.
It has long been thought that if a layer of graphite is peeled off, can you finally get a "two-dimensional" graphite sheet consisting of only a single layer of atoms? In 1987, someone officially named this ideal "two-dimensional" graphite sheet, called graphene.
This is almost an "ideal state" that can only occur in the physical work of textbooks. Until the beginning of the 21st century, the best performance that people achieved, the thinnest graphite sheets, was only to the level of dozens of atoms.
To make matters worse, as early as the 1930s, the famous Russian physicist Randall et al. had proved that the thermal motion fluctuations of two-dimensional materials would destroy their structures. Various failed attempts to prepare graphene experimentally seem to support this conclusion. For example, the thinner the graphite layer, the easier it is to curl into a spherical or columnar shape, and the planar structure cannot be maintained. Therefore, the preparation of graphene has been considered by many to be unsuccessful.
The Heim and Novoselov team stumbled upon a very simple method: they glued the two sides of the graphite layer with scotch tape and then tore them apart into two pieces. By repeating this process, thinner and thinner graphite flakes can be obtained, some of which consist of only one layer of carbon atoms - they produce graphene.
It sounds easy, but the real realization still has to overcome many difficulties, which is difficult for laymen to understand. The Heim experimental group prepared graphene for more than a year before and after, and the prepared graphene was only a few square micrometers, which could be observed with a high power microscope.
In a narrow sense, graphene refers to a single layer of graphite; in a broad sense, graphite having a layer number of less than 10 layers can be referred to as graphene. In recent years, attracted by its attractive application prospects, the method of developing large-scale industrial preparation of graphene has opened up a variety of ways, which can be roughly divided into physical methods and chemical methods, and many important breakthroughs have been obtained. However, this is still a very difficult job, as can be seen from the market price of graphene: graphite, which is so cheap everywhere, can be made ten times more expensive than gold.
The highest mechanical strength, the fastest electronic transmission
Magical features can subvert everyday experience
The "two-dimensional" graphene, which seems to exist only in the imagination, once it has been taken out, its magical nature can subvert many of our past daily experiences.
From the mechanical properties, the connection between the carbon atoms in graphene is very flexible. When an external mechanical force is applied, the carbon atom plane will be bent and deformed, so that the carbon atoms do not have to be rearranged to adapt to the external force, thus maintaining the structure. stable. Scientists have confirmed that graphene is the most intense material known in the world, harder than diamonds, and more than 100 times the strength of the world's best steel. The Royal Swedish Academy of Sciences used the analogy of the 2010 Nobel Prize in Physics: "Hammocks made from single-layer graphene can carry a 4 kg rabbit." Some people have said that since graphene is only a single layer of atoms and the transmittance is as high as 97.7%, if there is such a hammock, it is not only visible to the naked eye, but even to many instruments. What we see will be It is a rabbit hovering in midair. There are also estimates that if the graphene sheets are overlapped to the same thickness as the food wrap, they can carry a 2 ton car.
In terms of thermoelectric properties, in the "two-dimensional world" of graphene, electron motion has a very peculiar property, that is, the quality of electrons does not exist, and its conduction speed can reach 1/300 of the speed of light, far exceeding The speed of movement of electrons in a general conductor. In addition, the high perfectness of the graphene structure at room temperature makes the electron transport and the external field reaction super fast, which makes the graphene have extraordinary conductivity and thermal conductivity. More importantly, graphene can also be used to make transistors. Due to the high stability of the graphene structure, the transistor can still operate stably near the line of a single atom. Many people believe that graphene will become the successor of silicon, leading a new era of micro-scale in the field of technology.
In addition to its high strength and toughness, graphene has the ability to be impervious to water, airtight and resistant to strong acids and alkalis, making it an ideal material for making protective films. Graphene is both conductive and highly transparent, making it possible to create LCD screens, touch screens, and solar panels.
â– Extension
Application, there is unlimited possibilities
Due to the magical nature of the graphene material itself, its application is almost infinitely possible. Let's introduce some specific ideas that people talk about most.
Download a HD movie in one second
In June 2011, a research paper on graphene applications was published in the British journal Nature. Chinese American scientists have developed a modulator using nanomaterial graphene. Scientists say that this hair-optic optical modulator with only four percent of the hair has high-speed signal transmission capability, and downloading a high-definition movie in one second is just around the corner. . The breakthrough of this research is to solve the long-term industry by using graphene, the world's thinnest but hardest nano material, to make a high-speed, heat-insensitive, broadband, inexpensive and small-sized modulator. Unresolved issue.
Charge your phone and car in one minute
US researchers have recently announced a new type of battery they have developed that can fully charge a cell phone or even a car in less than a minute. Such a device called a micro graphene supercapacitor has a charging speed or a discharging speed 100 to 1000 times faster than a conventional battery. The researchers used lithium ions to quickly shuttle a large amount of motion between the graphene surface and the electrodes, and developed a new energy storage device that can reduce the charging time from a few hours in the past to less than a minute. The study was published in the recently published Nano Letters.
The researchers said that for supercapacitors, its "fast" is just a quantitative upgrade, and "small" is its greatest value. For a long time, miniaturization and miniaturization of electronic products have often encountered obstacles in energy storage systems. The large battery size drags down the flexibility and compactness of the entire product. The new supercapacitors not only have a small size, but can be easily integrated into other accessories.
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