Black technology starts from the steel suit

Chapter 172 172 Two-digit thermoelectric figure of merit

Time flies very fast, and three months have passed in a blink of an eye.In the past three months, for Wang Feng, the biggest achievement is not that the zt value of the thermoelectric material they studied has broken through double digits, but that his theory has gone a step further and can be published as a phased result. up.

"Professor Wang, can we really not publish this part of the results?" Liu Yihang asked impatiently. He cannot be blamed for this matter. No matter who it is, he will not be in the mood to be named on such a major achievement. It is calmer than the current Liu Yihang.

"Not yet. Although we have applied for domestic patents, it will take some time for international patents, but it should be soon. You don't need to panic." Wang Feng comforted.

"I'm not panicking. After all, can a cooked duck fly?" Liu Yihang smiled a little embarrassingly, but despite what he said, he was really worried that the cooked duck would fly. Nothing new.

"Don't worry, I can't guarantee that in other places, but in our institute, what I say can still be nailed down." Wang Feng, as a young man who has been working hard in academia for many years , of course, know very well what the other party is worried about.

However, there is no way around this. Although he does hope that his paper will be published as soon as possible and his results will be shared with everyone, when it comes to specific interests, all honors must be compromised for it.

So it is still not possible at the moment. If it only involves breakthroughs in natural science, then he will naturally be willing to share it.After all, this kind of cause concerns all mankind and does not involve any specific interests.

But it involves specific achievements, and it is impossible for him to publish it before it is converted into a patent. This not only involves real money in scientific research investment, but also involves future profit distribution. In this kind of matter, any possible troubles will be infinitely magnified, even rising to the height of the country.

In this kind of matter, no matter how careful you are, you can't be too careful. After all, how big is the interest involved? This matter, even a Nobel Prize winner in economics, can't calculate it. It takes a huge team to figure it out. OK.

Let's take a simple example to understand:
Traditionally, the engine emits a considerable amount of heat when powering a car. What if we could use this part of the heat from the engine to generate electricity like the heat from a power station?With the continuous improvement of thermoelectric materials, this energy-saving solution may be widely used.

At that time, we can use the lost heat to power the car's electrical equipment. You can use the electric energy to charge the car's battery. Even if the conversion rate is higher, we can directly use the heat to power the motor. It is more converted into kinetic energy.

At present, the conversion efficiency of traditional car engines is only 30%, and the other heat will be dissipated as waste heat. If part of this heat can be used, even if it is only 10%, this also means that our car air conditioners It can be replaced with more powerful equipment without affecting the power of the car.

However, this is very difficult. Scientists have studied many materials in the past 60 years to explore their thermoelectric potential law and the efficiency of converting heat into electrical energy.But so far, the energy conversion efficiency of most materials is too low to realize large-scale applications.

It can be said that the thermoelectric figure of merit of the current materials has no way to break through the value of 3, and most of them are hovering at 2.Of course, this refers to the situation under normal conditions. Under other conditions, there are still ways to do it. For example, the recent breakthrough was made under the action of a strong magnetic field. It's just frying cold rice.

In 2018, physicists at the Massachusetts Institute of Technology, his alma mater, discovered a method that can significantly improve the thermoelectric conversion capacity of materials, and published this theoretical method in the journal Science Advances.

They used this method to create new materials that were tested to be five times more thermoelectrically efficient than the best thermoelectric materials currently available, and could theoretically convert twice as much energy, but only in theory, of course.

"If this material performs exactly as we expect, then many things that are inefficient now will become more efficient in the future," said Brian Skinner, a postdoc at MIT's Research Laboratory of Electronics. You may find in your car that there are some small thermoelectric recovery devices that take away the waste heat released by the car engine and then use this energy to charge the battery. These devices can also be placed around power plants, which were previously used by nuclear reactors. Or waste heat from coal-fired power plants can be recycled back into the grid."

This is a very good wish, and it can be regarded as a big pie for investors. Although it looks beautiful, it is difficult to eat.

Unless they can simplify the conditions for transformation.For example, reduce the condition of strong magnetic field to general, magnetic field conditions that can be achieved by ordinary equipment, or even the conditions that can be achieved by permanent magnets.

How a material's electrons behave under temperature differences determines how efficiently the material uses heat to generate electricity.When one side of a thermoelectric material is heated, electrons are excited inside the material, and electrons jump from the hot side to accumulate on the cold side.The accumulation of these electrons can generate a measurable voltage across the hot and cold sides of the material.

Materials that have been studied so far generate little thermoelectric energy, in part because electrons are difficult to be excited thermally.In most materials, electrons exist in specific energy bands or energy ranges.Between each band is a gap, a small energy range where electrons cannot exist.Injecting electrons with sufficient energy to cross the band gap and physically transport electrons across materials is a very challenging task.

Skinner and Liang Fu decided to study the thermoelectric potential of a class of materials known as topological semimetals.Topological semimetals differ from most other solid materials such as semiconductors and insulators in that they are unique in that they have a zero bandgap.This is an energy structure that allows electrons to easily jump to higher energy bands when heated.

Scientists generally consider topological semimetals to be a relatively new class of materials synthesized in the lab, but which don't generate much thermoelectric power.When a topological semimetal is heated on one side, electrons become energized and accumulate on the other side.But when these negatively charged electrons hop to higher energy bands, they leave behind so-called "holes": positively charged particles that also pile up on the cold edge of the material, canceling out the effect of the electrons, resulting in the resulting energy rare.

Simply put, the positive and negative offset each other, which is embarrassing.

(End of this chapter)