Chapter 398 God Is Helping Them!

After receiving the data from Zhao Guanggui, Xu Chuan carefully read through it.

The irradiation problem of high-energy neutron beams has always been a century-old problem that the whole world has been studying.

The most troublesome thing about high-energy neutrons is not the radiation they carry, but that they can collide with the nuclei of different elements.

When neutrons collide with various nuclei, "neutron excitation" will occur, producing unstable isotopes, making the material radioactive and damaging the structure of the material.

Simply put, some are like the original material is a family of four, two neutrons + two protons form a loving family.

Then the external high-energy neutron hits the nucleus and forcibly inserts into it like a mistress, and then the family is broken up and imperfect.

At present, the scientific community deals with the problem of neutron irradiation, generally using neutron slowing materials and slow neutron absorbing materials to stop neutron irradiation.

Among them, neutron slowing materials are divided into heavy and light elements, and heavy elements are mainly common metal materials such as lead, tungsten, and barium.

They can block fast neutrons, reduce the energy of neutron beams, and make them slow neutrons.

Neutrons slowed by heavy elements need to be further slowed by light elements before they can be absorbed by slow neutron absorbing materials.

This step is mainly processed using high-polyhydrogen materials such as water, paraffin, and polyethylene.

Slow neutrons treated with light elements can be completely absorbed and eliminated by lithium- or boron-containing materials, such as lithium fluoride, lithium bromide, and boron oxide.

Otherwise, even the slower neutrons are destructive to materials or human organisms.

It is so troublesome to deal with neutrons alone, and the first wall material of controlled nuclear fusion has to withstand high temperatures, deuterium and tritium high-energy particles, gamma rays, ion pollution and other problems.

Even if the materials constructed by atomic circulation technology and radiation gap bands have the ability to absorb radiation and rays, it is quite difficult to find a material that can allow neutrons to pass through, face high temperatures, and maintain self-repair.

Especially after excluding the option of metal materials, it is even more difficult.

After all, there are not many non-metallic materials that can withstand thousands of degrees of high temperature.

Ceramic materials count as one, carbon materials count as one (graphite, diamond, etc. are also carbon materials), and composite materials count as one, but there are many types of these, and only some of them are available.

At present, these are the non-metallic materials that can withstand temperatures above 3,000 degrees Celsius.

And as first-wall materials, these materials basically have their own defects.

So when Xu Chuan heard Professor Zhao say that the new materials they developed may have the potential to be used in first-wall materials, he was quite surprised.

After all, it has only been two or three months since he officially issued the order to study first-wall materials.

Even if he pointed out the direction and related methods at the beginning, and there was also the assistance of the material calculation mathematical model of the Sichuan Hai Materials Research Institute, this speed was a bit too fast.

It took Xu Chuan more than ten minutes to carefully read the data in his hand.

From the information in his hand, Zhao Guanggui and his team developed a carbon nanotube + carbon fiber reinforced silicon carbide + hafnium oxide-based composite material.

From the property point of view, it is similar to a high-temperature resistant composite ceramic material, and has the properties of most high-temperature resistant ceramic materials.

The difference is that because the main structure is carbon nanotube and carbon fiber reinforced silicon carbide material, the thermal conductivity has been greatly improved compared with ceramic materials.

The thermal conductivity of ordinary ceramic materials is between 0.5-1W/m·K, while the thermal conductivity of this composite material is 52.11W/m·K, which exceeds the 40W/m·K of graphite.

Of course, the thermal conductivity of 50W/m·K is nothing in some special ceramics.

For example, the thermal conductivity of silicon carbide (SiC) ceramic substrate can reach 120-4K, and the thermal conductivity of aluminum nitride (AlN) ceramic substrate is 170-230 W/mK.

These two ceramic substrates are considered to have the best thermal conductivity among ceramic substrates, but their high temperature resistance is not enough.

Most silicon carbide will melt when it exceeds 1600 degrees, and although aluminum nitride can be stabilized to 2200 degrees at most, it still cannot meet the requirement of 3000 degrees.

Of course, if the temperature is just not up to standard, the temperature can still be maintained by water cooling equipment. The key point is the damage to the metal bond caused by neutron irradiation.

Although alumina is a ceramic material, the aluminum metal bond is the core supporting bond, and the damage to the metal bond caused by neutron irradiation is particularly obvious.

As for carbon nanotube materials and carbon fiber materials, although they can withstand temperatures exceeding 3,000 degrees in an oxygen-free environment, the absorption problem of pure carbon materials on deuterium and tritium raw materials is too serious.

As a result, pure carbon materials, such as graphene and carbon nanotubes, are difficult to apply to the first wall.

As for the reinforced composite material developed by Zhao Guanggui and his team, it can withstand ultra-high temperatures exceeding 3,400 degrees Celsius in an oxygen-free environment.

This value, if compared among pure metals, can only be compared with tungsten.

If it is an alloy, it is still some distance away from the melting point of 4215 degrees Celsius of tantalum hafnium pentacarbide (Ta4HfC5).

However, it is enough to be applied to the first wall of a controlled nuclear fusion reactor.

The most critical thing is the absorption of deuterium and tritium raw materials. This can be seen from the test results. This composite material will not react with the material itself unless the high-energy deuterium and tritium ions hit the surface of the material out of control.

Putting the document in his hand on the table, Xu Chuan looked up at Zhao Guanggui and asked with interest:

"It's interesting. From the cross-sectional electron microscope image of the material, it seems that the atomic circulation technology and the radiation gap band structure have caused the carbon nanotubes to combine with the hafnium oxide substrate. The chemical bonds of the carbon nanotubes replaced the oxygen chemical bonds of the hafnium oxide substrate, forming a uniquely ordered carbon nanotube·hafnium crystal structure."

"And this uniquely ordered carbon nanotube·hafnium crystal structure should be the key point of this composite material's high temperature resistance and no longer absorbing deuterium and tritium ions."

"Is there a special process for this aspect?"

For him, the detailed data of a material are all in front of him, and it is not difficult to determine where the core key point of this material is.

At present, this composite material is a carbon nanotube·hafnium crystal structure with a special structure, which he has never seen before.

Zhao Guanggui nodded and said, "We did an inspection, but the results are not ideal. We can't separate the crystal structure you mentioned. We can't reproduce this uniquely ordered carbon nanotube-hafnium crystal structure using carbon nanotubes and hafnium oxide alone."

"So for now, we can only get the test data of this material, and the core crystal structure data can't be obtained."

After the test data of this material came out, someone in the research team had the same idea as Xu Chuan, speculating that this unique crystal structure was at work.

It's just that there is no way to separate this special structure later, so there is no way to confirm whether it is playing a core enhancement role.

Hearing this, Xu Chuan touched his chin and thought about it.

If it can't be separated, it's indeed impossible to judge, but this doesn't have a big impact, as long as the material can be used.

From the test data, whether it is thermal conductivity, high temperature resistance, or strength, ordinary physical properties meet the requirements of the first wall material.

Of course, the more critical point is not these ordinary performances, but the resistance to high-energy particles of deuterium and tritium, gamma rays, ion pollution, and the most critical resistance to neutron irradiation and other high-energy fields.

The former is not a big problem, the atomic cycle technology and the radiation gap band structure have been verified.

There are also tests reflected in the data. Although it has not been completed, it can be seen that it is quite excellent.

As for the latter, the latter has not been tested yet.

Neutron irradiation experiments are not so easy to do.

He asked with interest: "How did you think of this material?"

He saw traces of the two material construction technologies of 'atomic cycle' and 'radiation gap band' in the information in his hand.

The most obvious is the special crystal structure gap band presented in the cross-sectional structure diagram, which is the crystal structure used to absorb β radiation.

Hearing this question, Zhao Guanggui smiled a little embarrassed and said, "Strictly speaking, the idea of ​​this material is not actually my own."

"After you arranged for me to study carbon materials last time, I went to Professor Han Jin and Academician Peng to learn about the two technologies you developed, atomic circulation technology and radiation gap band."

"During the discussion, Professor Han Jin mentioned the radiation power semiconductor conversion material you developed when studying nuclear waste. Considering that the first wall will also face the problem of strong radiation, I think it is possible to dope some silicon carbide materials into carbon nanomaterials as impurities to manufacture semiconductors, which are used to export the electrical energy converted from radiation heat energy, thereby maintaining the material itself to a certain extent.”

“We conducted research along this route, and then gradually added additional hafnium oxide materials as reinforcing agents with the help of the material model from the Chuanhai Materials Research Institute.”

"Unexpectedly, hafnium oxide and carbon nanotubes as reinforcing agents have undergone unexpected changes. The two formed a special crystal structure, which not only reduced the thermal conductivity of the carbon material, but also brought new changes. The shortcomings of carbon materials absorbing deuterium and tritium raw materials are optimized.”

Hearing this, Xu Chuan was a little surprised and asked, "So it's just luck?"

After a pause, he continued with a smile: "Of course, in materials science, luck is also a part of strength."

Zhao Guanggui scratched his head in embarrassment.

Indeed, apart from some empirical processes, this material research and development can be said to be completely unexpected.

No one expected that after hafnium oxide is added as an additive to carbon materials, with the assistance of atomic recycling technology, a unique carbon nanotube-hafnium crystal structure will be formed.

Not to mention researchers like them, even the material calculation model from the Sichuan and Hai Materials Research Institute did not predict this.

After all, the initial addition of the hafnium oxide substrate with the help of the model was just to increase the strength of the carbon material.

It can only be said that even supercomputers cannot predict the complex reactions in the field of materials.

Or in other words, God is helping them!

Avoiding this topic, Zhao Guanggui swallowed his saliva and continued with some nervousness and worry: "From the test data, the other properties of this material except neutron irradiation should have met the requirements of the first wall material. The rest depends on how it performs when facing neutron irradiation."

The selection of first wall materials for controllable nuclear fusion reactors can be said to be one of the most complex problems of all, ranking in the top three.

The difficulty is no less than the control of high-temperature plasma turbulence and tritium self-sustainment.

As for which of these three problems is more difficult, it depends on the opinions of different people. It's not an easy problem to solve anyway.

Xu Chuan thought for a while and said: "Carbon and silicon can maintain strong stability and integrity when faced with neutron irradiation. The only worry lies in this new type of carbon nanotube hafnium crystal structure. How stable it is when faced with neutron irradiation.”

"Although it maintains its stability in the face of the impact of high-energy deuterium and tritium particles and strong radiation, the decay properties of hafnium metal make me a little worried. It may not be able to hold up when faced with neutron irradiation. "

Thinking that it might not be possible to talk about the materials that others worked so hard to create, Xu Chuan quickly added: "Of course, these are just theoretical analyzes I made based on the data. The specific results still need to be seen from the experimental data."

"After the Dawn Device is repaired in the next year, let's test materials like yours first. Maybe we'll be really lucky this time?"

"If the test results are good, construction of the demonstration reactor can begin."

Hearing this, Zhao Guanggui's breathing became much faster.

If he can make a key contribution to the construction of the demonstration reactor, there should be no pressure to be elected as an academician next year.

But after thinking about it, he quickly calmed down and swallowed nervously.

The neutron irradiation experiment is the real key. If this cannot be maintained, all previous efforts and excellent performance will be in vain.

And what the big guy in front of me said is actually fine.

Hafnium is the main additive element in heat-resistant alloy materials, while hafnium dioxide is a ceramic material with a wide bandgap and high dielectric constant, which is why they chose it as an additive and catalyst this time.

But hafnium has a big flaw when it comes to neutron irradiation.

That is, hafnium has a very friendly attitude towards neutrons. To put it simply, hafnium can absorb neutrons, and its efficiency is hundreds of times that of ordinary materials.

In a nuclear fission reactor, uranium serves as nuclear fuel, and the ideal material for the uranium rod sheath is a material with added hafnium metal.

Because hafnium has an extremely high absorption rate of neutrons, only a small amount of hafnium is needed to greatly reduce the transparency of neutrons released during nuclear fission.

From this point of view, I am afraid that there may be huge problems with the materials this time.

Thinking about it, Zhao Guanggui's smile became a little bitter and he said: "Hafnium element has a very high absorption rate of neutrons. Zirconium alloy with added hafnium material is used for uranium rod protective sheaths."

"From this critical point of view, I am afraid that this material cannot pass neutron irradiation."

Xu Chuan smiled and said: "There is still a possibility, but I don't think it is big."

After a slight pause, he continued: "But we are not without hope. The hafnium element has an extremely high absorption rate of neutrons, but don't forget that it also has an almost twin brother metal element."

"Perhaps you can try zirconium metal. Zirconium and hafnium belong to the VB group of the periodic table of chemical elements. They have very similar chemical properties and are two metal types that coexist together in nature."

"Perhaps you can try using zirconium oxide as additives and catalysts. If my guess is correct, this should be feasible."

Hearing this, Zhao Guanggui's eyes suddenly brightened, and he quickly continued: "The most important thing is that the absorption rate of zirconium for neutrons is extremely low. In zirconium with sufficient purity, neutrons can easily penetrate it."

Xu Chuan said with a smile: "Yes, the absorption rate of zirconium nuclei for neutrons is very low. The only problem is that it can absorb hydrogen. In the same way, the isotopes of hydrogen, deuterium and tritium, will also be absorbed."

"However, as an additive, its amount is not very large. A slight loss of deuterium and tritium is acceptable in exchange for the stability of the first wall."

Zhao Guanggui nodded quickly and said, "I'll go back and prepare the experiment again!"

PS: I went to get the MRI results in the morning. There is only one update today and two updates tomorrow.