Thermoelectric materials rookie: porous material The future green equipment count on it?
This is a different porous layer (gradient porous material) of cascade structure diagram. Each layer includes a set of indirect distribution, the same size hole (here only shows a group of such particles).
Hot cars, or fever laptop, each machine and equipment are in your life by heat loss wasted a lot of energy. But to be able to heat and electric energy conversion of electric heating device may be able to take advantage of waste heat green technology energy efficiency. To enhance the efficiency of the sustainable development of the future is very necessary. Now, a new study shows that the porous material - that is, how to become a thermoelectric materials pointed out how to use this material in the future production of thermoelectric devices.
National research center in Athens, Greece (Demokritos) Dimitris Niarchos said, produce all the energy in the world, about 70% in the form of heat consumption. He and in the same research center of Roland Tarkhanyan will be released their analysis results at the American association of physics (AIP) issue of the journal APLMaterials.
In order to create a can make full use of the technology of heat, researchers around the world have been trying to create more efficient thermoelectric materials. A promising material to full size about a micron (ten minus six meters) to about minus nine meters (10) is a nanometer pore. Niarchos said: "long-short thermoelectric technology can significantly improve the efficiency of the thermoelectric. So it can be used as a viable method to collect waste heat".
Using the phonon heat and vibration of quantitative unit (as heating particles) through the material. When phonon ran into a hole, it will distract, loss of energy. Therefore, phonon cannot effectively carry heat by multi-layer materials. As a result, the coefficient of thermal conductivity of the material will be lower. And this one low thermal conductivity will improve the efficiency of thermoelectric conversion. The more material hole, the coefficient of thermal conductivity is lower, the more suitable for thermoelectric materials.
But Niarchos says, so far, researchers have not systematically simulate porous materials is how to keep a low coefficient of thermal conductivity. So he and Roland Tarkhanyan studied four simple model of micro/nano porous structure of the thermal conductivity. He also said that this analysis is how to design this kind of material used for thermoelectric devices provide general direction.
Overall, the researchers found that when the smaller the hole, the more dense, the lower the thermal conductivity. Niarchos said their computing results fit well with other experiment data. They also say, micro/nano porous materials basically than non-porous materials heat - electricity conversion is several times higher.
First model described by the material is full of holes, the diameter of the hole from micron to nanometer size; The second model is a multi-layer material description. Due to the material of each layer of the hole and the other layers of the scale of the hole is different, so its porosity is special; The third model describes a material composed of three dimensional cubic lattice, cubic lattice hole the same size; The fourth is another of the model of multilayer materials, the materials of each layer contains a cubic lattice, cubic lattice hole size is the same, but the hole size of each layer is different.
Through the analysis, the first model and the fourth model than the second low coefficient of thermal conductivity of the model. The third model seems to be the best, because its thermal conductivity coefficient of thermal conductivity than the fourth model is still lower.
But Niarchos said, in addition to the first model, the rest of the model is unrealistic. Because the second, three, four models show are holes perfect combination of an ideal state. In reality, accurately create the completely same size of the hole is not possible. Therefore, the first model is most likely to implement.
But he also said that all the models shows the importance of porosity in thermoelectric materials. On the general analytical formula of simple model, in addition to the need for effective lattice conductive coefficient of porous materials for fast and accurate calculation, also need a systematic analysis on the material.
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