Chapter 350: Insufficient Materials, Graphene Will Make up for It!
When in doubt, use quantum mechanics; when you don’t have enough imagination, use parallel universes.
This is a very popular phrase on the Internet, which means that when you encounter something or a question that you can’t solve, just say “quantum mechanics”.
In the material world, there is actually a similar phrase.
If you don’t have enough materials, graphene will do the job.
Graphene is called “all-round material” by people in the material world.
It is a carbon material with a “two-dimensional honeycomb lattice structure” of carbon atoms tightly stacked into a single layer, with excellent optical, electrical and mechanical properties. It has adaptability and important application prospects in almost most application fields such as materials science, micro-nano processing, energy, biomedicine, and drug delivery.
This is a material that has become popular, and many ordinary people know about it.
Of course, the performance of graphene materials is also amazing.
Its strength and hardness even exceeds that of diamonds, and can reach 100 times that of high-quality steel. A one-centimeter-thick plate made of it can allow a five-ton adult elephant to stand steadily on it without collapsing and breaking.
For example, in terms of light transmittance, the light transmittance of ordinary glass is only about 89%, while the light transmittance of graphene can reach 97.7%, so it is almost transparent to the naked eye.
If graphene is used to make the battery screen of mobile phones and computers, the screen can be folded almost at will, and even folded into tofu blocks and put in pockets will not affect its performance.
In terms of electrical conductivity and thermal conductivity, there is currently no traditional material that can surpass graphene.
In addition, graphene materials are also a major direction in the field of superconductivity research.
In 2018, researchers represented by Cao Yuan of MIT and his mentor, MIT physicist Pablo Jarillo Herrero, published a paper in Nature magazine, showing the team's research results on graphene.
When the overlapping angle of two graphene sheets is close to 1.1°, the band structure will be close to a zero-dispersion band, causing this band to transform into a Mott insulator when it is half-filled.
And this kind of superconductivity after rotating and charging the stacked graphene.
In addition, graphene has extremely high mobility electrons, which makes it possible to realize pairing of electrons like in superconductors, making it one of the future materials for studying high-temperature superconductivity and even room-temperature superconductivity.
However, it is very difficult to break through room-temperature superconductivity in graphene.
Even more than a decade later, Xu Chuan has not heard of any country that can manufacture graphene high-temperature superconducting materials. High-temperature graphene superconductivity is still under laboratory exploration, let alone room-temperature superconductivity.
Of course, the potential of graphene superconducting materials is huge.
On the one hand, as long as a method is found, a two-dimensional material such as graphene can be molded like plasticine, round, square, long, flat, lined, or hollow.
On the other hand, it lies in the current carrying capacity of graphene materials.
There are also differences between superconducting materials and superconducting materials.
The stronger the current carrying capacity, the stronger the magnetic field and various properties it can provide.
In this regard, graphene has great potential.
The only reason that limits the application of this top-quality material is that industrial production is too difficult.
At present, there is no method that can produce high-quality graphene in large quantities and stably.
However, for now, Xu Chuan does not want the superconductivity of graphene materials. He only needs the excellent physical properties of graphene to assist in improving the toughness of high-temperature copper-carbon-silver composite superconducting materials.
As for the current problem that graphene cannot be mass-produced, it is not a problem that he needs to worry about.
If it is applied to superconducting materials, small-batch manufacturing is enough.
How to reduce costs, how to productize, and how to make profits from it are all things that the industrial and commercial sectors need to consider, and have nothing to do with him as a scholar.
Compared with the doped zirconium oxide atoms mentioned by Academician Zhang Pingxiang, Xu Chuan is more optimistic about using graphene materials as whisker (fiber) toughening materials to make up for the toughness of high-temperature copper-carbon-silver composite materials.
Because for a superconducting material, if the crystal structure between the materials breaks, it will cause a gap in the superconducting energy gap, and a gap in the superconducting energy gap will cause a sharp decrease in superconducting performance in all aspects.
But the core of whisker (fiber) toughening technology actually comes down to the chemical bonds of the material.
As we all know, most metal materials are prone to plastic deformation because metal bonds have no directionality.
In materials such as ceramics, the bonds between atoms are covalent bonds and ionic bonds, and covalent bonds have obvious directionality and saturation.
In this case, the repulsion is very large when the same-sign ions of the ionic bond approach each other, so ceramics mainly composed of ionic crystals and covalent crystals have very few slip systems and generally break before slip occurs. (High school knowledge, don't say you don't understand it!)
This is the fundamental reason for the brittleness of ceramic materials at room temperature, and the properties of high-temperature copper-carbon-silver composite superconducting materials are very similar to ceramic materials.
However, whisker (fiber) toughening technology can make up for this well. When whiskers or fibers are pulled out and broken, they consume a certain amount of energy, which is conducive to preventing the expansion of cracks and improving the fracture toughness of materials.
To put it simply, when you want to break a chopstick, there is a thin film on the chopstick, which can absorb the force from your arm, thereby maintaining the shape of the chopstick inside.
Of course, the specific situation of using graphene to toughen whiskers (fibers) will be more complicated.
Because the combination of graphene and high-temperature copper-carbon-silver composite superconducting materials is not a simple mixture, it is more like a composite material, organically combined through an extremely thin interface.
In this case, the chemical bonds in graphene are likely to replace the doped carbon atom bonds in the copper-carbon-silver composite material.
The reason why Xu Chuan chose to use graphene as a toughening material is also because of this consideration.
Graphene is a pure single-layer, 'two-dimensional honeycomb lattice structure' carbon material. Its organic combination with the interface of copper-carbon-silver material does not change the composition of the high-temperature copper-carbon-silver composite superconducting material.
So theoretically, it is still possible to achieve the goal of using graphene to toughen whiskers (fibers).
As for whether it can be done specifically, it depends on the results of the experiment.
In the Chuanhai Materials Laboratory, Xu Chuan and Zhang Pingxiang started from their own optimistic directions and studied how to solve the problem of insufficient toughness of high-temperature copper-carbon-silver composite superconducting materials.
On the other hand, Gao Hongming, who had left to prepare the parameter information of the domestic controlled nuclear fusion experimental reactor, came back.
It not only brought the detailed parameters of the experimental reactors in major domestic controlled nuclear fusion research institutes, but also brought a list of domestic manufacturers that are qualified and capable of producing high-temperature copper-carbon-silver composite superconducting materials.
Xu Chuan first looked at the detailed parameters of the experimental reactors in major domestic controlled nuclear fusion research institutes.
This is related to the actual measurement of the plasma turbulence control model.
In the office, Xu Chuan flipped through the information brought by Gao Hongming.
To be loose, there are currently more than a dozen controlled nuclear fusion research institutes in China, but there are only eleven fusion reactors.
This number is indeed quite large, but in fact, most of these eleven fusion reactors are just experimental reactors or even device reactors.
The so-called experimental reactor refers to an experimental device that can meet the most basic experimental needs of plasma experiments.
And the device reactor, needless to say, it can't even do an ignition experiment.
In the information brought by Gao Hongming, there are currently only two fusion reactors in China that are capable of ignition and operation experiments.
They are the magnetic confinement fusion tokamak device 'EAST' of the Institute of Plasma Physics of the Academy of Sciences and the inertial confinement fusion device 'Shen Guang' of the Ninth Institute of Engineering.
The means of inertial confinement are completely different from those of magnetic confinement.
Magnetic confinement can be understood as allowing high-temperature plasma to flow and fuse in the device to form high temperature.
Inertial confinement uses the inertia of matter to put a few milligrams of mixed gas or solid of deuterium and tritium into a small ball with a diameter of about a few millimeters.
Then a laser beam or particle beam is uniformly injected from the outside, and the spherical surface evaporates outward due to the absorption of energy. Under its reaction, the inner layer of the spherical surface is squeezed inward to form a high-temperature environment, allowing these milligrams of mixed gas of deuterium and tritium to explode and generate a lot of heat energy.
If three or four such explosions occur per second and continue continuously, the energy released is equivalent to a million-kilowatt power station.
Simply put, inertial confinement is similar to the explosion of a hydrogen bomb, and then heat energy is absorbed from the explosion energy to generate electricity.
It is just a smaller scale and more controllable one.
This method has no meaning for the plasma turbulence control model studied by Xu Chuan, because the fusion methods are completely different.
So after excluding the inertial confinement fusion device ‘Shen Guang’ of the 9th Institute of Engineering, the only experimental reactor he could choose was the ‘EAST’ magnetic confinement fusion tokamak device.
The ‘EAST’ magnetic confinement fusion tokamak device, also known as the fully superconducting tokamak nuclear fusion experimental device, created plasma operation experiments of more than 50 million degrees and 100 million degrees Celsius in 2016 and 2018 respectively.
In 2017, it achieved a record of stable 101.2 seconds of steady-state long pulse high confinement plasma operation.
In China, it is the undisputed leader in the field of controlled nuclear fusion, and even in the world, it is one of the top experimental reactors.
However, except for ‘EAST’, other fusion devices are somewhat unsatisfactory.
Xu Chuan did not expect that at the end of 2019, the field of controlled nuclear fusion in China would still be like this.
Indeed, from a technical point of view, in the field of controlled nuclear fusion, China is already one of the top batches, and the various technologies are still quite good overall.
But in the field of experimental reactors, there are indeed some rare ones.
Except for the ‘EAST’ magnetic confinement fusion tokamak device, there are currently no other experimental reactors that can do ignition experiments.
The famous KTX fusion reactor of HKUST, HL-2A and HL-2M experimental reactors are still under construction and unfinished.
Even the Tokamak 2, which is the closest to completion, will have to wait until the end of 20 years.
And even if it is completed, it is not capable of carrying out ignition experiments immediately. It will take at least one to two years to complete various tests, and after at least two or three rounds of ignition experiments, it is possible to test the plasma turbulence model.
This situation made Xu Chuan smile helplessly.
Now it seems that he has no choice at all.
The only thing to be thankful for is that the parameters of the ‘EAST’ magnetic confinement fusion tokamak device are quite excellent.
The main part of the EAST device is 11 meters high, 8 meters in diameter, and weighs 400 tons. It consists of six major components, including ultra-high vacuum chamber, longitudinal field coil, poloidal field coil, internal and external cold screens, external vacuum Dewar, and support system.
It has 16 large "D"-shaped superconducting longitudinal field magnets, which can generate a longitudinal field magnetic field intensity of 3.5T; 12 large poloidal field superconducting magnets can provide magnetic flux changes ΔФ≥ 10 volts per second; through these poloidal field superconducting The magnet will be able to generate a plasma current of ≥ 1 million amperes; the duration can reach more than 1000 seconds, and the temperature will exceed 100 million degrees under high-power heating
This series of parameters is quite excellent even in the whole world.
With excellent equipment, coupled with the plasma turbulence mathematical model, even if it is only a phenomenological level model, Xu Chuan is confident of breaking the current record of the longest operating time of a tokamak device.
Even chasing stellarator runtime records is not out of the question.
After reading the information in his hand, Xu Chuan gently shook his head and sighed: "I didn't expect that the development of controllable nuclear fusion in China would be like this."
On the sofa, Gao Hongming leaned forward and asked nervously: "Isn't there anyone who meets the requirements?"
Xu Chuan nodded, shook his head, and said: "There are some that meet the requirements, but only one. The EAST device in Luyang meets the requirements from the data. As for the others, they don't work."
Hearing this, Gao Hongming breathed a sigh of relief and said with a smile: "As long as there is one that meets the requirements, the leader of the EAST device is Academician Chen Mingji. He is also the person in charge of our country's connection with the ITER international fusion project. I will follow up here. I will go and communicate with Academician Chen.”
Xu Chuan nodded, thought for a while and then said: "I should have gone there in person, but recently I was studying how to optimize high-temperature copper-carbon-silver composite superconducting materials with Academician Zhang Pingxiang, and I really couldn't get away from it. "
"Well, I'll ask Academician Peng Hongxi to go with you. It seems to be more serious. After all, if you want to use other people's equipment, you also need to modify the control model. For controllable nuclear fusion, it is also a big deal. "
Gao Hongming smiled and nodded, saying: "It doesn't matter. You can do your research first. I believe Academician Chen will understand."
After a pause, he continued: "By the way, regarding the work you previously communicated with Mr. Qin about the production of high-temperature copper-carbon-silver composite superconducting materials, I will also provide information on the manufacturers that are qualified and capable of producing it. I brought it here by the way, do you want to take a look first?"
Xu Chuan nodded and took the information from Gao Hongming. Just as he was about to look through it, he thought for a while and said, "By the way, I just looked at the information. The 'EAST' magnetic confinement fusion tokamak device still uses niobium." Titanium alloys as superconducting materials.”
"About this application for the 'EAST' magnetic confinement fusion tokamak device, you can discuss it with Academician Chen. I will not get it for free, and will make some compensation."
"If he is willing, I can provide him with the first batch of high-temperature superconducting materials for free after the high-temperature copper-carbon-silver composite superconducting materials are produced. I believe that the performance of high-temperature copper-carbon-silver composite superconducting materials can make 'EAST' magnetic confinement fusion tokamak device goes one step further."
PS: I got my computer back this afternoon, but it’s too late. I’ll do a double update tomorrow, and ask for a monthly ticket (it’ll be more than 500 yuan to fix it, woo woo ┗( T﹏T )┛,)