Thermoelectric materials can realize direct conversion of thermal energy and electric energy using the Seebeck effect and Peltier effect. They have the advantages of no noise, no pollution, high reliability and long service life, and have the advantages of exhaust gas waste heat, industrial waste heat, solar power generation and special refrigeration, etc. Wide application prospects. The conversion efficiency of thermoelectric materials is characterized by a dimensionless thermoelectric value of merit ZT (=S2σT/κ), where S and σ are the Seebeck coefficients and conductivity of the material, T is the absolute temperature, κ is the thermal conductivity, and S2σ is the power factor. High ZT thermoelectric materials require high Seebeck coefficients, high electrical conductivity, and low thermal conductivity (including electronic thermal conductivity κe and lattice thermal conductivity κph).
In recent years, carbon-based materials such as carbon nanotubes, carbon nanowires, and graphene have been successfully synthesized experimentally. Compared with traditional materials, carbon materials have the advantages of good environmental compatibility, rich carbon source, and ease of mass production. Carbon nanotubes have attracted extensive attention from researchers due to their unique structure and mechanical, electrical and thermal properties. While having excellent conductive properties, the thermal conductivity of carbon nanotubes is also very high, which greatly limits the application of thermoelectricity. It has been reported that attempts have been made to prepare carbon nanotubes as three-dimensional carbon materials in an attempt to increase their ZT values ​​by reducing their excessive thermal conductivity through strong interactions between the tubes. However, in these three-dimensional carbon materials, the structure of the carbon nanotubes is significantly distorted and their electrical properties are significantly reduced.
The Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences combined the first-principles calculations, Boltzmann transport theory, and molecular dynamics simulations to study the thermoelectric transport properties of a three-dimensional hybrid ordered carbon nanostructure network. It was found that the energy band structure of this ordered network structure is similar to that of carbon nanotubes. The band dispersion in the direction of the parallel tube diameter and the dispersion in the direction of the vertical tube diameter are basically zero. This energy band determines the electrical properties of the network structure. Close to carbon nanotubes. And using the Boltzmann transport theory to calculate this conjecture. Under suitable doping conditions, the carbon network structure can exhibit a higher Seebeck coefficient and moderate conductivity, and the power factor can be optimized to a higher level.
In terms of thermal conductivity, molecular dynamics simulations show that the bond between the tubes makes the thermal conductivity of the carbon network structure at least one order of magnitude lower than that of carbon nanotubes. Near 900 K, the optimized ZT value of (9,0) carbon network structure can reach 0.8, which is an order of magnitude higher than the optimized ZT value of carbon nanotubes. In addition, the thermal conductivity of the carbon network structure can be further reduced by a certain method, which will further improve the thermoelectric performance of the system. The results of this study provide an idea for the application of carbon materials in environmentally friendly high-performance thermoelectric materials. Related results have been published in the international journal RSC Adv. 4, 42234 (2014).
The research work was supported by the National Natural Science Foundation of China (11404350), the China Postdoctoral Foundation (2014M551782), the Natural Science Foundation of Ningbo (2014A610003) and the Ningbo Science and Technology Innovation Team (2014B82004).
Microscope Slides And Cover Slips
1. The glass slide is used to put the sample to be tested, and the cover glass is covered on the sample to be tested.
2. The glass slide is at the bottom, which is the carrier for the material you want to observe, that is, you want to put something on it.
3. The cover glass is smaller than the slide glass. The glass slide is mainly used to hold the observation objects. The cover glass is covered on the slide glass and used for fixing.
4. The glass slide is a thicker piece of glass in the transfer slide, which is used to carry the real object. The cover fragment is the small round or square thin one.
5. Mounting is a general term for a set of things, including slides, coverslips and loaded objects
6. The cover glass is square, the slide glass is rectangular, and the width is longer than the side of the cover glass.
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