Great Country Academician

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

The irradiation of high-energy neutron beams has been a century-old problem that has been studied all over the world.

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 atomic nuclei, there will be a phenomenon of "neutron excitation", which will produce unstable isotopes, make the material radioactive, and damage the structure of the material.

To put it simply, it looks like the original material is a family of four, two neutrons + two protons form a loving family.

Then the foreign high-energy neutrons collide with the atomic nucleus, and they are inserted into it like a little three, and then the family is broken up and imperfect.

At present, the scientific community deals with neutron irradiation problems, and generally uses neutron moderator materials and slow neutron absorbing materials to intercept neutron irradiation.

Among them, neutron moderator materials are divided into two types: heavy and light elements, and the heavy elements are mainly common metal materials such as lead, tungsten, and barium.

They block fast neutrons, reducing the energy of the neutron beam so that it becomes slow.

The neutrons moderated by heavy elements need to be further moderated by light elements before they can be absorbed by slow neutron absorbing substances.

This step is mainly processed with high-hydrogen-poly materials such as water, paraffin, and polyethylene.

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

Otherwise, even the slowest neutrons can be destructive to materials or human organisms.

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

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

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 high temperatures of thousands of degrees.

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

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

These materials, as the first wall materials, basically have their own defects.

So when Professor Zhao said that the new material they developed might have the potential to be applied to the first wall material, Xu Chuan was quite surprised.

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

Even if he pointed out the direction and related methods from the beginning, with the assistance of the material calculation mathematical model from the Chuanhai Materials Research Institute, this speed is a bit too fast.

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

Judging from the information in hand, what Zhao Guanggui and his colleagues developed is a carbon nanotube + carbon fiber reinforced silicon carbide + hafnium oxide-based composite material.

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

The difference is that because the main structure is carbon nanotubes and carbon fiber reinforced silicon carbide materials, 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, and 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 substrates can reach 120-490 W/m·K, and the thermal conductivity of aluminum nitride (AlN) ceramic substrates 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 up to 2200 degrees, it still cannot meet the requirement of 3000 degrees.

Of course, if only the temperature is not up to standard, the temperature can still be maintained through water cooling equipment. The key point is the destruction of metal bonds by neutron irradiation.

Although alumina is a ceramic material, the aluminum-metal bond is the core support bond, and the damage to the metal bond 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 problem of pure carbon materials absorbing deuterium-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 the others, it can withstand ultra-high temperatures exceeding 3,400 degrees Celsius in an oxygen-free environment.

If this value is compared in pure metals, it can be compared with tungsten.

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

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

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

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 cycle technology and the radiation gap structure lead to the combination of carbon nanotubes and hafnium oxide substrates. The chemical bonds of carbon nanotubes replace the oxygen of hafnium oxide substrates. chemical bonds, forming a uniquely ordered carbon nanotube hafnium crystal structure."

"And this uniquely ordered carbon nanotube hafnium crystal structure should be the key point for this composite material to withstand high temperatures and no longer absorb deuterium-tritium ions."

"Is there a check on the process specifically for this?"

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

The composite material right now is a carbon nanotube hafnium crystal structure with a special structure, which he has never seen before.

Zhao Guanggui nodded, and said: "I did an inspection, but the results were not satisfactory. We couldn't separate out the crystal structure you mentioned, and we couldn't reproduce this unique crystal structure with carbon nanotubes and hafnium oxide alone. Ordered carbon nanotube hafnium crystal structure."

"So at present, only the detection data of this material can be obtained, and the crystal structure data of the core inside cannot be obtained."

After the detection 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 in the follow-up, and there is no way to confirm whether it is playing a core strengthening role.

Hearing this, Xu Chuan stroked his chin and began to think.

If it cannot be separated, it is indeed impossible to judge, but the impact is not great, as long as the material can be used.

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

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

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

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

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

Experiments with neutron irradiation are not so easy to do.

Interested to ask: "How did you come up with this material?"

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

The most obvious is the special crystal structure gap zone shown on the cut-away structure diagram, which is the crystal structure for absorbing beta radiation.

Hearing this question, Zhao Guanggui smiled a little embarrassedly, and said, "Strictly speaking, the idea of ​​this kind of material is actually not something I thought of alone."

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

"During the discussion, Professor Han Jin mentioned the radiative power semiconductor conversion material you developed when you were studying nuclear waste. Considering that the first wall will also face the problem of strong radiation, I think carbon nanomaterials can be doped with some carbonization The silicon material is used as an impurity to manufacture a semiconductor, which is used to derive the electrical energy converted from radiant heat energy, thereby maintaining the stability coefficient of the material itself to a certain extent."

"Do research from this route, and then gradually add other hafnium oxide materials as reinforcing agents with the help of the material model of Chuanhai Materials Research Institute."

"Unexpectedly, the hafnium oxide and carbon nanotubes used as a reinforcing agent had an unexpected change. The two formed a special crystal structure, which not only reduced the thermal conductivity of the carbon material, but also brought new changes. Optimized the shortcomings of carbon materials to absorb deuterium and tritium raw materials."

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

After a pause, he then smiled and said, "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, the material development this time can be said to be an accident.

No one thought that after hafnium oxide was added to carbon materials as an additive, with the assistance of atomic cycle technology, a unique carbon nanotube hafnium crystal structure would be formed.

Let alone researchers like them, even the material calculation model of the Chuanhai Materials Research Institute did not speculate on this point.

After all, adding the hafnium oxide substrate with the power of the model at the beginning is just to increase the strength of the carbon material.

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

Or in other words, this is God helping them!

Avoiding this topic, Zhao Guanggui swallowed, and continued nervously and worriedly: "From the test data, this material should meet the requirements of the first wall material except for the neutron irradiation. The rest depends on its performance when it is exposed to neutron radiation."

The material selection of the first wall of a controllable nuclear fusion reactor can be said to be one of the most complicated problems among all problems, and it can be ranked in the top three.

The difficulty is not weaker than the control of high-temperature plasma turbulence and tritium self-sustainment.

As for which of these three problems is more difficult, it is a matter of opinion. It's not a problem to solve anyway.

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

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

Thinking of saying that other people's hard-working materials might not work, Xu Chuan quickly added: "Of course, these are just my theoretical analysis based on the data. The specific results still need to look at the experimental data."

"After the dawn device is repaired in the next year, I will do a test on your material first. Maybe we are really lucky this time?"

"If the test results are excellent, the demonstration reactor can be built."

Hearing this, Zhao Guanggui's breathing became more rapid.

As for the construction of the demonstration reactor, if he can make a key contribution here, there should be no pressure to be selected as an academician in the coming year.

But after thinking about it, he quickly calmed down again, swallowing a little nervously.

The neutron irradiation experiment is the real key, if this is not supported, all previous efforts and excellent performance will be in vain.

And what the big guy in front of him said was actually okay.

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

But hafnium has a big defect when facing neutron irradiation.

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

In nuclear fission nuclear reactors, uranium acts as nuclear fuel, and the ideal material for the sheath of uranium rods is the material added with hafnium metal.

Because hafnium has a very high absorption rate of neutrons, only a small amount of hafnium needs to be added to reduce the transparency of neutrons released during nuclear fission.

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

Thinking about it, Zhao Guanggui's smile became a bit bitter, and he said, "Hafnium element has a very high absorption rate of neutrons, and the zirconium alloy added with hafnium material is used for the protective sleeve of uranium rods."

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

Xu Chuan smiled, and said, "There is still a possibility, but I guess it's not big."

After a slight pause, he continued: "However, we are not hopeless. The hafnium element has a very high absorption rate for neutrons, but don't forget that it also has a brother metal element that is almost a twin."

"Maybe you can try zirconium metal. Zirconium and hafnium belong to the VB group of the periodic table of chemical elements. Their chemical properties are very similar, and they are two types of metals that coexist in nature."

"Maybe you can try to use zirconia as an additive and a catalyst. 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 zirconium has an extremely low absorption rate for neutrons. In zirconium with sufficient purity, neutrons can easily penetrate through it."

Xu Chuan said with a smile: "That's right, the zirconium nucleus has a very low absorption rate of neutrons. The only problem is that it can absorb hydrogen. Similarly, hydrogen isotopes deuterium and tritium will also be absorbed."

"However, as an additive, its amount will not be very large. It is acceptable to lose some deuterium and tritium in exchange for the stability of the first wall."

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

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