Thermal Conductivity Of Nanoribbons Research Articles

Research Progress on Thermal Conductivity of Graphdiyne Nanoribbons and its Defects: A Review.

Graphdiyne has a unique pi-conjugated structure, perfect pore distribution and adjustable electronic properties of sp2, sp hybrid planar framework. Due to the presence of acetylenic bonds, it has more excellent properties compared to grapheme, such as a unique structure-dependent Dirac cone, abundant carbon bonds and a large bandgap. As one of the important raw materials for nanodevices, it is extremely important to study the thermal properties of graphdiyne nanoribbon. This paper mainly introduces and discusses recent academic research and patents on the preparation methods and thermal conductivity of graphdiyne nanoribbons. Besides, the applications in engineering and vacancy defects in the preparation process of graphdiyne are described. Firstly, taking thermal conductivity as an index, the thermal conductivity of graphdiyne with various vacancy defects is discussed from the aspects of length, defect location and defect type. In addition, the graphdiyne nanoribbons were laterally compared with the thermal conductivity of the graphene nanoribbons. The thermal conductivity of graphdiyne with defects increases with the length and width, which is lower than the intrinsic graphdiyne. The thermal conductivity of the acetylene chain lacking one carbon atom is higher than the one lacking the benzene ring. Typically, the thermal conductivity is larger in armchair than that of zigzag in the same size. Moreover the thermal conductivity of nanoribbons with double vacancy defects is lower than those nanoribbons with single vacancy defects, which can also decrease with the increase of temperature and the number of acetylene chains. The thermal conductivity is not sensitive to shear strain. Due to the unique structure and electronic characteristics, graphdiyne has provoked an extensive research interest in the field of nanoscience. Graphdiyne is considered as one of the most promising materials of next-generation electronic devices.

Thermal characteristics of graphene nanosheet with graphane domains of varying morphologies

In this paper, thermal characteristics of graphene nanosheet embedded with graphane quantum dots (QDs) are investigated using Non-Equilibrium Molecular Dynamics (NEMD) method. Thermal conductivity of nanoribbon is demonstrated to be tunable by manipulating the geometrical characteristics of graphane QDs without changing the amount of hydrogenation. Graphane QDs of larger circumferences cause more deterioration in heat transfer due to the scattering of phonons occurred at the graphene-graphane interface. As a result, nanoribbon with graphane QDs possesses higher thermal conductivity than that with random hydrogenation of same amount. Under fixed circumferences, the length-to-width ratio of QD is revealed to be the most important causes of deterioration in thermal conductivity. Graphane QDs of high length-to-width ratio have smaller deterioration effect on thermal conductivity. Combing the effect of circumference and length-to-width ratio, the thermal difference between nanoribbons with graphane QDs of different shapes can be sufficiently interpreted. The demonstrated mechanism can be applied for the optimization of nanodevices fabricated from hydrogen functionalized graphene.

Thermal rectification and phonon scattering in asymmetric silicon nanoribbons

Thermal rectification is an interesting phenomenon and has important potential applications in improving the thermal management of electronics and saving energy. Exploring thermal rectification phenomena and understanding the mechanism are very necessary and important. This paper reports the investigation of the thermal conductivity and thermal rectification of asymmetric silicon nanoribbons by the non-equilibrium molecular dynamics simulation. The results indicate that the thermal conductivity of the nanoribbon is only on the order of 100 Wm−1K−1. Thermal rectification is observed in silicon nanoribbons at different temperatures, geometry aspects, and ribbon length. The thermal conductivity is apparently larger when heat flows from the thin end to the thick end. The larger the aspect ratio of the thick end to thin end is, the larger the thermal rectification. The rectification coefficient does not change much in the ribbon length ranges from 8.1 nm to 21.7 nm. The longitudinal phonon scattering in the silicon nanoribbon at different frequency is investigated by the phonon wave packet dynamic simulation. The results show that the phonon transmission coefficient is sensitive to frequency and transverse phonons are generated during the scattering. Decreasing the thin end width will reduce the transmission coefficient due to the scattering at the slope boundary.

Influence of chemisorption on the thermal conductivity of graphene nanoribbons

The thermal conductivity of graphene nanoribbons (GNRs) functionalized by the chemical attachment of methyl and phenyl groups at random positions is calculated using reverse nonequilibrium molecular dynamics. The GNRs exhibit a rapid drop in thermal conductivity with increasing degree of functionalization; a functional group coverage regime of as little as 1.25% of GNR atoms reduces the thermal conductivity by about 50%. The thermal conductivity of nanoribbons with zigzag edges is more sensitive in the degree of functionalization than nanoribbons with armchair edges. The simulation results indicate that the rapid drop in thermal conductivity is a consequence of the higher angular momentum of functional groups, which rotate the unsupported sp 3 bonds and thus reduce the phonon mean free paths.