Can graphene masks prevent haze

1. Mechanical properties The mechanical properties of graphene are very strong, and its mechanical tensile strength reaches 130GPa, which is equivalent to 100 times that of steel. Theoretically calculated, if the effective connection thickness of graphene can reach one millimeter, it can support the weight of an elephant. Where does its strong mechanical properties come from? As we said at the beginning-structure determines properties. It is a two-dimensional structure, and the chain between carbon and carbon is very strong.There are three neighbors around each carbon. The carbon bond formed by these three neighbors is very short and very strong, which supports the high mechanical properties of graphene. 

2. Electrical properties Its electrical properties are worth mentioning. Its electron mobility can reach 200,000cm^2/Vs, which is one hundred times that of silicon. What is electron mobility? It means how fast electrons can run in this material. The conductivity of a material is determined by two things. One is how fast the electrons run in it, and the second is how many electrons run in it. You can imagine a highway. What is the speed limit on this highway? How fast can the car run? The number of cars running on it determines the capacity of this highway. So in the manufacture of electronic devices, we often hope to have a high capacity, so that the computing speed of the device can be accelerated. Second, its current density tolerance is very large. For example, we have a commonly used wire, such as a metal wire copper wire. We pass current. If the voltage increases and the current increases to a certain extent, the current will burn the copper wire. But graphene's ability to resist burning is very high, it can reach 1 million times that of copper!If we use graphene as a conductor, the weight of the conductor can be greatly reduced. A recent discovery shows that if a double-layer graphene is rotated at an angle, some superconductivity will occur. However, it has a shortcoming in electrical properties, which is its zero energy band gap. The energy band [4] is related to the existence of a semiconductor. If this energy band is appropriate, it is a good semiconductor. Since graphene has a zero energy band, it is not a semiconductor, but a metallic property, so it is still difficult to make electronic devices. Scientists are overcoming the problems caused by these zero energy bands. 

3. Density and large specific surface area Graphene is a very dense material. Because its bonds are very short, the distance between atoms is very close, only 0.142nm. In other words, even small molecules and atoms such as hydrogen and helium cannot pass through it. It is a very good barrier material with a specific surface area of ​​2630m^2/g, which means that its area is very large. Let's look at the middle picture, which is a foam-like structure made of graphene. It can support itself, but it is very light.We put it on a dogtail grass, and the dogtail grass doesn't seem to have any structural changes. We can use these graphenes to make some filtering materials. By opening some small holes of controllable size on them, we can separate different gases or liquids. For example, the separation of salt in seawater and the separation of oxygen and nitrogen in the air. 

4. Properties of light and heat The properties of light in graphene, because there is only one carbon source, only one layer of carbon atoms, its transmittance can reach 97.7%, which means that one layer of carbon atoms can absorb 2.3% of light. Is this big or small? In fact, it is a very strong light absorption. We can completely absorb light with about 50 layers of graphene. This is difficult for other materials. But graphene can, we only need one layer of it, which makes it very useful. Graphene has very good thermal conductivity. There are currently two main ways of thermal conductivity. One is called electronic thermal conductivity, that is, if a material is very conductive, its thermal conductivity is often also very good, such as copper and aluminum.But there is another material that does not rely on electrical conductivity for thermal conductivity. It relies on phonons, that is, the speed of sound wave propagation. In graphene, the speed of sound wave propagation can reach 22km/s, so it has a very good thermal conductivity.