The rise of nanometers

In the laboratory.

Huang Xiuyuan, wearing a full-coverage protective suit, is adjusting the thread angle of the nanowire textile machine.

After adjusting again and again, he weaved a piece of nanocloth, which is a product made of phosphorus nanowires and sulfur nanowires.

Specifically, it consists of two layers, one is a three-wire crossed phosphorus nanowire network woven at a specific angle, and the other is a 15-nanometer-thick sulfur nanowire network.

The surface is then covered with a layer of aluminum oxide through ion deposition to form a dense shell.

It looks like an ordinary aluminum oxide plate, but it actually has something going on inside.

After processing the composite board, he handed it to the assistant on the side: "Zhang Wei, take it for electric heating value testing."

The popular Zhang Wei on the side carefully took the composite plate and sent it to the material physical and chemical testing room of the laboratory to begin comprehensive testing.

Huang Xiuyuan followed to the testing room.

As several researchers conducted a series of tests on the composite panels, Qiao Qingshi, a researcher with a background in thermoelectric materials, wanted to speak, but found that his tongue seemed to be tied up.

Because the thermoelectric value of merit of the composite plate in front of them exceeded their expectations.

The so-called thermoelectric figure of merit is the thermoelectric conversion efficiency of the material, and its symbol is ZT. Among the thermoelectric materials currently discovered in the materials science community, the highest thermoelectric figure of merit is about 6. This is a material that can only be prepared in trace amounts in the laboratory.

In the understanding of Qiao Qingshi, Zhang Wei and others, in the current thermoelectric material world, several technical routes include two-dimensional multilayer films, superlattice, bismuth nanowires, carbon nanotubes, quantum well systems, The thermoelectric figure of merit of cat-eye-like structures, ferrosilicon tungsten alloys, etc. are all stuck at 6, and they do not have the technology for large-scale mass production.

The composite panel in front of them has a thermoelectric figure of merit as high as 11.37.

The thermoelectric figure of merit of large-scale mass-produced thermoelectric materials on the market is generally around 2.8 to 3.

The thermoelectric figure of merit of composite panels has reached about 3.79 to 4 times that of ordinary thermoelectric materials.

Many people don’t know what this means. The application fields of thermoelectric materials are mainly in thermoelectric power generation, thermoelectric refrigeration, sensors and thermostats.

For ordinary thermoelectric materials with a thermoelectric figure of merit between 2.8 and 3, the thermoelectric conversion efficiency in power generation is usually only about 6 to 8%.

When the thermoelectric figure of merit of the thermoelectric material increases to 11.37, this means that the efficiency of the thermoelectric generator will increase to about 24%.

Although the thermoelectric efficiency of this material is not comparable to the 30% efficiency of gallium arsenide solar panels, it is also not comparable to the steam turbines of thermal power stations.

However, thermoelectric materials have many advantages. For example, the structure is simple, and only the thermoelectric material itself, plus wires and switches are needed to use it.

In addition, the conditions for power generation are not too demanding. As long as there is a temperature difference, power generation can be generated.

"So that's it. This is a two-dimensional multi-layer film plus ultra-fine nanowires, and the three-wire cross-braiding angle of the phosphorus nanowires is probably using a quantum well system." Qiao Qingshi said to himself.

Huang Xiuyuan smiled and nodded: "Yes, it is the triple blessing, multi-layer film, ultra-fine nanowires, and quantum well system. The combination of the three reduces the thermal conductivity, and at the same time increases the electrical conductivity and Seebeck coefficient."

Qiao Qingshi's eyes were filled with shock.

There is a special formula for thermoelectric figure of merit ZT:

ZT=SσT/K (S is the Seebeck coefficient, σ is the electrical conductivity, T is the temperature, and K is the thermal conductivity).

From the formula, we can know that the factors that affect the thermoelectric figure of merit are the Seebeck coefficient, temperature, electrical conductivity and thermal conductivity.

The two most critical elements are electrical conductivity and thermal conductivity. If the thermoelectric figure of merit is to be improved, the electrical conductivity as the molecule must be high, and the thermal conductivity as the denominator must be as small as possible.

However, in reality, electrical conductivity and thermal conductivity are like Siamese twins. There are few materials that can satisfy high electrical conductivity and low thermal conductivity at the same time.

Qiao Qingshi was amazed: "Nano size will indeed amplify the quantum size effect, but Mr. Huang's idea is definitely a revolution in the field of thermoelectric materials."

"Stop flattering, haha." Huang Xiuyuan said with a smile.

Qiao Qingshi shook his head: "This is not flattery. When I was at the Chinese Academy of Sciences, my former boss spent tens of millions of dollars on the project to come up with ZT4.2, which was neither high nor low. As soon as your material came out, the Nobel Prize was awarded. It’s all possible.”

"Forget about the Explosives Award, that thing is just useless." Huang Xiuyuan picked up the composite plate: "Let's continue to discuss this material."

"Mr. Huang, do you still want to continue to improve?" Qiao Qingshi was a little uneasy.

"Science never ends, and I think there is still the possibility of continued improvement in sulfur nanowires."

"Research by many foreign teams has shown that ZT can be improved by using bismuth sulfide nanowires. Can we consider this?" Qiao Qingshi suggested.

But Huang Xiuyuan shook his head: "Bismuth metal is rare and expensive. It's okay to study it in the laboratory. But when it comes to industrial mass production, the cost is estimated to be sky-high."

"Uh..." Qiao Qingshi reacted immediately.

The main materials of the composite panels currently developed by Huang Xiuyuan are phosphorus, sulfur and alumina, all of which can be mass-produced.

Bismuth metal is less than silver. Although China has the largest bismuth reserves in the world, the problem is that this rare metal resource is not suitable for large-scale mass production.

If it is used in precision instruments and the like, you can still consider it.

The current phosphorus-sulfur-alumina composite plate has a thermoelectric figure of merit of 11.37, which is already very powerful and has the conditions for large-scale mass production.

Huang Xiuyuan thought about it and did not completely deny the direction of bismuth nanowires: "If you are interested, you can research this direction. Our company can still afford bismuth nanowires. If the effect is good, you can consider applying it to high-end products."

"Then I'll do some research."

There is a big discussion about the research and development of new thermoelectric materials.

During the discussion, Huang Xiuyuan led them to weave various types of thermoelectric materials. However, it is extremely difficult for the thermoelectric figure of merit to break through the new peak of 11.37.

For example, Qiao Qingshi mixed bismuth nanowires and sulfur nanowires to form a multi-layer nanowire network with a thickness of 27 nanometers.

During the testing process, the quantum size effect was further highlighted, increasing the density of electronic states at the edge of the band and enhancing the conductivity of the material.

At the same time, due to the reflection of the grain boundaries on the surface of the material, the phonon conduction in thermal conduction is blocked, thereby reducing the thermal conductivity.

The thermoelectric figure of merit has been increased from 11.37 to 14.28. The problem is that the material cost has also increased more than ten times.

Bismuth sulfide phosphorus-alumina composite materials are not cost-effective and can only be used in high-end products. For example, isotope thermoelectric generators for spacecraft are suitable for the use of this thermoelectric material.

In fact, Suiren Company has methods for mass production of nanowires and nanopowders in the application of various nanomaterials, so the company's material researchers are working hard to conduct in-depth research.

For example, on solar panels, the silicon nanowire network is combined with the silicon nano-coating to form nano-silicon wafers. The energy conversion efficiency reaches an extremely high level of 26.4%.

Moreover, after composite silicon nano-coating, the service life of nano-silicon wafers is very long, and the power generation efficiency can basically remain unchanged for more than ten years.

With the advancement of optoelectronic materials and thermoelectric materials, the two can actually be combined, because nano silicon wafers are transparent and can be combined together to utilize the light and heat energy of sunlight.

Thank you for your support, and thank you to book friends "Director 1249" and "Taoist Yuming" for their rewards (ω｀)

Third update!