Numerical Study On Mechanical And Thermal Properties Of B/N-doped Graphyne

The doping of boron and nitrogen(BN)atoms into the graphyne can improve its absorbance and redox reaction ability greatly.However,the effects of the BN doping on the mechanical and thermal properties of the graphyne have not been reported.In this thesis,the mechanical and thermal properties of BN-doped graphyne are systematically investigated using the molecular dynamics method.The details are as follows:First,the effect of BN doping concentration on the mechanical properties of graphyne was analyzed.The results show that,when the temperature is 300 K(T=300K),the introduction of BN atoms into graphyne would induce the graphyne from brittle failure to ductile failure.With the microstructure analysis,it was found that the doping of BN atoms can lead to the formation of a large number of triangular structures in will be generated in the graphyne during the stretching process,which could hinder the crack propagation in graphyne.It was also found that when the doping concentration of BN atoms is lower than 50%(λ<50%),with the increase of BN doping concentration,the ultimate stress of graphyne materials shows a decreasing trend.When the BN doping concentration increases to 50%(λ≥50%),the ultimate stress will show a monotonically increasing trend with the decrease of the BN doping concentration.Next,the effect of temperature is discussed.As the temperature increases,graphyne will show more obvious plastic behavior.When50%<λ≤83.3%,the temperature has little effect on its mechanical behavior;and whenλ>83.3%,with the increase of temperature When the strain rate is high,the failure strain decreases rapidly;the strain rate has little effect on the graphyne,which is mainly manifested in the decreasing trend of the ultimate stress of the graphyne with the decrease of the strain rate.The mechanical properties of BN-doped graphyne nanotubes(GNTs)were further studied.Unlike two-dimensional graphyne,GNTs did not form triangular structures during the stretching process.When the doping concentration of BN was low(λ<50%),GNT shows a plastic failure,but the failure characteristics are not obvious.When 50%≤λ<83.3%,GNT has an obvious plastic failure stage.Whenλ≥83.3%,GNT shows brittle failure.The ultimate stress also decreased first and then increased with the doping of BN.With the increase in temperature,the ultimate stress of GNT gradually decreased,and the failure strain first decreased and then increased.When λ=100%,GNTs become boron nitride nanotubes,and the ultimate stress and failure strain decrease with the increase of temperature.The ultimate stress of GNT decreases with decreasing strain rate.Finally,the effect of BN doping on the thermal properties of graphyne and graphyne nanotubes was investigated.The results show that with the increase of BN doping concentration,the thermal conductivity of graphyne and graphyne nanotubes shows a trend of first increasing and then decreasing,and the change range is as high as 25%.