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Influence of Nanopore Shapes on Thermal Conductivity of Two-Dimensional Nanoporous Material

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ABSTRACT

The influence of nanopore shapes on the electronic thermal conductivity (ETC) was studied in this paper. It turns out that with same porosity, the ETC will be quite different for different nanopore shapes, caused by the different channel width for different nanopore shapes. With same channel width, the influence of different nanopore shapes can be approximately omitted if the nanopore is small enough (smaller than 0.5 times EMFP in this paper). The ETC anisotropy was discovered for triangle nanopores at a large porosity with a large nanopore size, while there is a similar ETC for small pore size. It confirmed that the structure difference for small pore size may not be seen by electrons in their moving.

No MeSH data available.


ETC of MNMs with triangle nanopores along X and reverse-X directions
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Fig5: ETC of MNMs with triangle nanopores along X and reverse-X directions

Mentions: ETCs of MNM with triangle nanopores along X and reverse-X directions were compared in this part. The data are expressed according to the scaled pore size d* = d/l0 and the scaled ETC (reduced by the bulk ETC); l0 is the EMFP of the bulk material. The result was shown in Fig. 5. For most pore size d, there is not a linear relationship between ETC and the porosity, different from that happens in the microscale. This phenomenon was also discovered in our previous work [9]. As is to be expected, a larger nanopore size will lead to a larger ETC while porosity is fixed [9]. This is quite similar with the result got for LTC [1, 19, 20]. It shows that there is not an obvious ETC difference along X and reverse-X directions except at high porosity for large nanopore size. It can be understood by that the similar channel width should be responsible for the equal ETC along X and reverse-X directions at low porosity, while the nanopore can be treated as only defects. But for the MNMs with large porosity and large nanopore size, the structure difference between X and reverse-X directions can be seen by electrons in their moving while the size is large enough, so there will be a different ETC at large porosity in Fig. 5. This validates the result on the last paragraph that a shape difference for large nanopores will be seen by electrons in their moving. To further illustrate the different scattering effects for X and reverse-X directions, the electron distributions were shown in Fig. 6. The solid black circle and the hollow red circle in Fig. 6 represent the electron locations along X and reverse-X directions at a given time, respectively. The large electron distribution difference between X and reverse-X directions in Fig. 6a, b confirmed that there will be different electron scatterings for the MNM with a large porosity and a large pore size. And electrons along reverse-X directions distribute more uniformly than that along X direction in Fig. 6. It means that the electron transfer along reverse-X direction will be easier than along X direction. Thus, there is a larger ETC for reverse-X direction than for X direction in Fig. 5. For the MNM with a large porosity but a small pore size, the electron distribution looks similar along X and reverse-X directions in Fig. 6c. It confirmed that the structure difference for small pore size d* = 0.5 is too small to be seen by electrons in their moving.Fig. 5


Influence of Nanopore Shapes on Thermal Conductivity of Two-Dimensional Nanoporous Material
ETC of MNMs with triangle nanopores along X and reverse-X directions
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037102&req=5

Fig5: ETC of MNMs with triangle nanopores along X and reverse-X directions
Mentions: ETCs of MNM with triangle nanopores along X and reverse-X directions were compared in this part. The data are expressed according to the scaled pore size d* = d/l0 and the scaled ETC (reduced by the bulk ETC); l0 is the EMFP of the bulk material. The result was shown in Fig. 5. For most pore size d, there is not a linear relationship between ETC and the porosity, different from that happens in the microscale. This phenomenon was also discovered in our previous work [9]. As is to be expected, a larger nanopore size will lead to a larger ETC while porosity is fixed [9]. This is quite similar with the result got for LTC [1, 19, 20]. It shows that there is not an obvious ETC difference along X and reverse-X directions except at high porosity for large nanopore size. It can be understood by that the similar channel width should be responsible for the equal ETC along X and reverse-X directions at low porosity, while the nanopore can be treated as only defects. But for the MNMs with large porosity and large nanopore size, the structure difference between X and reverse-X directions can be seen by electrons in their moving while the size is large enough, so there will be a different ETC at large porosity in Fig. 5. This validates the result on the last paragraph that a shape difference for large nanopores will be seen by electrons in their moving. To further illustrate the different scattering effects for X and reverse-X directions, the electron distributions were shown in Fig. 6. The solid black circle and the hollow red circle in Fig. 6 represent the electron locations along X and reverse-X directions at a given time, respectively. The large electron distribution difference between X and reverse-X directions in Fig. 6a, b confirmed that there will be different electron scatterings for the MNM with a large porosity and a large pore size. And electrons along reverse-X directions distribute more uniformly than that along X direction in Fig. 6. It means that the electron transfer along reverse-X direction will be easier than along X direction. Thus, there is a larger ETC for reverse-X direction than for X direction in Fig. 5. For the MNM with a large porosity but a small pore size, the electron distribution looks similar along X and reverse-X directions in Fig. 6c. It confirmed that the structure difference for small pore size d* = 0.5 is too small to be seen by electrons in their moving.Fig. 5

View Article: PubMed Central - PubMed

ABSTRACT

The influence of nanopore shapes on the electronic thermal conductivity (ETC) was studied in this paper. It turns out that with same porosity, the ETC will be quite different for different nanopore shapes, caused by the different channel width for different nanopore shapes. With same channel width, the influence of different nanopore shapes can be approximately omitted if the nanopore is small enough (smaller than 0.5 times EMFP in this paper). The ETC anisotropy was discovered for triangle nanopores at a large porosity with a large nanopore size, while there is a similar ETC for small pore size. It confirmed that the structure difference for small pore size may not be seen by electrons in their moving.

No MeSH data available.