| With the rapid development of electronic information technology, electronic devices become more and more powerful, chips more and more integrated, however,thermal failure is their main form of failure. Graphene, having excellent electrical,thermal, mechanical, optical properties, can effectively solve the problem of thermal chip failure, and play a significant role in the field of thermal controlling and micro-sensors. In recent years, many researchers were surprised to discover that thermal rectification phenomenon exists in grapheme, which will have a major significance in Thermal control, wiener device design, information transmission and so on. Research of thermal rectification of graphene nanoribbons(GNs) has become an important subject. Here, a variety of GNs thermal rectifier models are constructed by the form of defect, doping and different Angles, and their thermal conductivity and thermal rectification are studied by molecular dynamics(MD). The main works are shown as follows:(1) Nitrogen-doping around Triangle defect Graphene Nanoribbons(NTGNs)were constructed, and the effect of concentration of nitrogen doping beside defects and simulation temperature on thermal conductivity and thermal rectification was studied. The results show that: thermal conductivity reduces greatly when triangular defects appear in GNRs, but 0.85% nitrogen doping around defect can effectively improve its thermal properties, making thermal conductivity increase greatly.However, thermal conductivity began a slow decline with nitrogen doping continuing to increase. From thermal conductivity curve effected by temperature in different concentration of nitrogen, we find the effect of temperature on thermal conductivity becomes smaller as nitrogen doping concentration becomes higher. When triangle defect was introduced in GNRs, thermal rectification efficiency is more than 10%.However, 0.85% nitrogen doping around the triangle defect reduces thermal rectification efficiency a lot, based on which continuing to increase concentration of nitrogen doping makes thermal rectification efficiency has an increasing tend. In thisrespect the changing trend of thermal rectification is opposite to thermal conductivity.(2) Graphene nanoribbons with angles(AGNs) were constructed, and thermal conductivity and thermal rectification of which were studied. As well as, the effect of simulation temperature on thermal conductivity of 120°angle was studied. The results show that: when the angle appears, the thermal conductivity declines noticeably. As the angle growing, the rate of decline slows. thermal conductivity fluctuates after falling to the lowest point. With the angle increasing thermal rectification increases at first and then decreases, and the maximum reaches at 120 angle. For the 120 angle of AGNs, the impact of temperature on thermal rectification is remarkable. As temperature rises, thermal rectification significantly reduces.(3) Thermal characteristics of 120 angle GNs(120AGNs) were studied in detail,and it is mainly about the influence of Width and Length Difference of each arm,Hydrogenated GNs(HGNs) and Nitrogenated GNs(NGNs) on thermal conductivity and thermal rectification. The results show that: Width and Length Difference will all reduce the conductivity of 120 AGNs, but the influence of Width Difference is a little more. Width Difference can improve thermal rectification a lot, the maximum reaching 110.4%. However, Length Difference works a little on thermal rectification,and has a reduced role. The effect of HGNs and NGNs on the change trend of thermal conductivity with temperature is not large, but they has a greater impact on the overall thermal conductivity. HGNs reduce overall thermal conductivity of more than 20%,while NGNs will increase overall thermal conductivity by more than 70%.The above findings provide some referential value in electronics manufacturing,thermal management and thermal control。... |
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