Huang Haojie flipped through the information on ion hair and photon hair one by one, many of these materials are theoretical papers, of course, there are still a lot of practical applications in ion hair.

Mi Lijia, the Sun Country, and the Xizhou Alliance all have ion-emitting satellites or probes, especially in the deep-space probe, plutonium isotope batteries can only fly for decades with ion-emitting satellites.

Otherwise, those probes that fly for decades will not have the means to use chemical fuel engines.

I watched it for a long time, but there are still very few useful people to solve the heat problem of nuclear fusion miniaturization.

However, ionic hair and photon hair are still very potential, Huang Haojie asked Zhong:

"I remember if we had an ion engine research institute?"

[Yes, the Ion Engine Research Institute is in Keelung City, the director is Zhou Botong, and the chief engineer is Mishima Ji. ］

"Zhou Botong?" Huang Haojie raised his head curiously.

［╭(′?? o ?? ′)╭?? It is a knowledgeable and versatile Bo. ］

"......Forehead" Huang Haojie was suddenly embarrassed, and quickly changed the topic:

"I sent the No. 5, 6, and 7 small reactors in my laboratory to the Ion Engine Research Institute, so that they could study ion engines for nuclear fusion, and by the way, even the task of photonic engines was given to them."

[Okay.] ］

After Huang Haojie instructed this matter, he focused his attention on thermoelectric power generation, which is a simple and direct power generation technology.

There is no need for complicated equipment, as long as a special material called "thermoelectric material" is applied to the temperature difference at both ends - for example, one end is 27 degrees Celsius cold water, the other end is 100 degrees Celsius boiling water, this temperature difference of 73 degrees Celsius can make this material emit a certain amount of electricity.

With so many advantages and great potential, why is it that so few people have heard of applications?

Because there is a fatal flaw in thermoelectric power generation - the efficiency is too low.

The existing best temperature difference power generation materials, its thermal efficiency is only less than half of the conventional thermal power plant, than the efficiency of geothermal power generation is lower than that of geothermal power generation (geothermal power generation efficiency is about 6~18%), such a low thermal efficiency, those capitalists are not stupid forks, how can they do this kind of loss-making business.

However, when Huang Haojie flipped through a paper published in Nature, he found that this paper gave him a lot of inspiration.

The paper was published by a research team led by Prof. Ernst Bauer of the Technical University of Vienna, Austria.

The data in the paper shows that they have doubled the coefficient of merit (ZT), a key performance indicator for thermoelectric power generation materials.

They developed thermoelectric materials with a thermoelectric merit factor of up to 5 to 6, compared to about 2.5 to 2.8 for the best materials before.

Huang Haojie immediately paid attention to it, and asked Zhong to collect the team's information on thermoelectric materials, and after a while, a large amount of information appeared in his holographic computer.

In order to improve the efficiency of thermoelectric power generation, the ZT value of the thermoelectric material must be increased, and only if the ZT value reaches or exceeds 4 can this technology have commercial value. However, more than 100 years have passed since the discovery of the thermoelectric effect, and scientists have a hard time attaining even 3.

Why is it so hard to increase the ZT value of thermoelectric materials? This starts with the thermoelectric effect itself, the physical principle on which thermoelectric power generation technology depends.

There are a certain number of carriers (such as electrons or holes) in a metal or semiconductor, and the density of these carriers will change with temperature, if the temperature at one end of the object is high and the other end is low, there will be different carrier densities in the middle of the same object.

As long as the temperature difference between the two ends of the object can be maintained, the carriers can continue to diffuse, so as to form a stable voltage, which is the principle of temperature difference power generation.

The efficiency of thermoelectric power generation depends on three important properties of thermoelectric materials:

First, the Seebeck coefficient (the ability of a material to generate electromotive force in the presence of temperature differences), the higher the Seebeck coefficient, the higher the electromotive force generated at the same temperature difference, which means that the more electricity can be generated.

Second, electrical conductivity (the conductivity of the material), the higher the conductivity, the easier it is for electrons to diffuse inside the material.

Third, thermal conductivity (thermal conductivity of the material), the higher the thermal conductivity, the faster the heat can be transferred from the hot end to the cold end, so that the temperature difference on which the temperature difference power generation depends disappears, and the electromotive force disappears.

Obviously, for thermoelectric materials, the stronger the first two capabilities, the better, while the weaker the latter, the better.

The coefficient of merit of thermoelectric power ZT is the set of these three parameters: the higher the Seebeck coefficient, the higher the electrical conductivity, and the lower the thermal conductivity, the higher the ZT value and the higher the efficiency of the material for thermoelectric power generation.

Therefore, the key to the study of thermoelectric materials is how to increase the ZT value of the material, that is, to achieve a high Seebeck coefficient and electrical conductivity while achieving a low thermal conductivity.

However, it is very difficult to optimize all three parameters at the same time. Because these three properties are interrelated, the promotion of one property is often accompanied by the weakening of indicators of another, or even both, nature.

In general, increasing the Seebeck coefficient of a material decreases its electrical conductivity. This interrelated nature of the three parameters has made the development of thermoelectric materials slow.

However, the relationship between the three parameters, "one loses and one prospers", is not completely absolute.

This "community of interests" also has a "traitor" - thermal conductivity, more precisely, part of it. The thermal conductivity of a material consists of two parts, which are the electronic thermal conductivity and the phonon thermal conductivity.

Among them, the former is closely related to conductivity and is a member of the "community of interests"; However, phonon thermal conductivity is the only parameter that determines the properties of thermoelectric materials and has no effect on all other parameters in the ZT value.

The idea of the team at the University of Vienna is to reduce the overall thermal conductivity by reducing the phonon thermal conductivity without affecting the electronic thermal conductivity of the material.

Specific to the microscopic level of the material, it is to enhance the scattering of phonon through some special structures without affecting the electron transport, so as to only reduce the phonon thermal conductivity of the material, but not change other parameters.

Beginning in 2013, after years of research, they discovered a material that could achieve both high electron thermal conductivity and low phonon thermal conductivity.

With an alloy of iron, vanadium, tungsten and aluminium overlaid on a silicon crystal, ZT values of up to 5 to 6 were achieved, doubling the ZT value from the best available level.

Under normal circumstances, this alloy composed of four elements, iron, vanadium, aluminum, and tungsten, has a very regular structure, for example, there must be only iron atoms next to vanadium atoms, and the same is true for aluminum atoms, and the distance between two adjacent atoms of the same element is always the same.

However, when scientists combined a thin layer of this material with a silicon material substrate, something magical happened.

Although the atoms still maintain the structure of the original cubes, the positions of the atoms have changed drastically from each other.

What used to be a vanadium atom may now be an iron atom or an aluminum atom; And next to an aluminum atom should be an iron atom, but now it may still be an aluminum atom, or even a vanadium atom.

Moreover, this change in the position of the individual atoms is completely random and irregular.

This combination of ordered and disordered crystal structures gives the material its unique properties:

Electrons can still have their own special paths, "freely" shuttling in the crystal, so that the electrical conductivity and electron thermal conductivity are not affected; However, the heat conduction-dependent phonon migration is blocked by irregular structures, resulting in a significant decrease in phonon thermal conductivity.

In this way, the temperature difference between the hot and cold ends is maintained, and the resulting potential difference does not disappear.

The team at the University of Vienna also achieved the coveted goal of keeping the electron thermal conductivity of thermoelectric materials unchanged and phonon thermal conductivity decreasing, thereby significantly increasing the ZT value to 6.

And theoretically, if the topology of the relevant conceptual material can be changed, a ZT value of 20 will no longer be just a dream.

If the ZT value reaches 6, the thermal efficiency will reach about 12%, and if the ZT value can be increased to 20, the thermal efficiency can be compared to that of a steam turbine.

Compared with the temperature difference power generation equipment and steam turbines, the structure is extremely simple, such as the plutonium isotope battery mentioned above, which is the temperature difference power generation battery.

However, in terms of materials science, Huang Haojie is not as good as the orthodox Li Xiangthem, and he hurriedly sent a research project to the Institute of Materials, asking the Institute of Materials to develop a thermoelectric material with a ZT value of about 20.

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