Strain Engineering For Thermal Properties Of Carbon-based Film Materials

To meet various requirements and working conditions,it is essential to regulate the thermal conductivity on demand.For instance,one can maximize the thermal conductivity in cooling applications while minimize it in thermoelectric applications.Therefore,it is of great significance to tune the thermal conductivity of materials on demand in engineering application.Usually,the thermal conductivity of graphene can be tuned via strain engineering,doping,surface decorating,tailoring etc.Among all the available modulation techniques,strain engineering is regarded as the most promising one owing to its repeatable operations even at nanoscale.For example,this method is easier to operate in practical application,and the irreversible changes of the structure in the regulation process is not easy to happen.Meanwhile,it is able to adjust the thermal conductivity in a large range.In this work,we performed molecular dynamics simulations to systematic examine the local strain field engineering and global strain on thermal properties of low dimensional materials.The research results can be summarized as follows:(1)Graphene nanoribbons are very sensitive to the local strain field in terms of the interfacial thermal resistance with a maximum enhancement factor of 1.5 at the strain of10%.The interfacial thermal resistance is found to depend linearly on the local strain.Next,this phenomenon is thoroughly explained by micro-structure deformation,heat flux scattering,and phonon density of state overlapping.The results clearly confirms that the local strain engineering is a useful technique to tune the interfacial thermal resistance of graphene nanoribbons or other two-dimensional materials with ease.(2)The thermal conductivity of diamond nanothread forest was studied.We find a strong anisotropic thermal property in this structure,i.e.the thermal conductivity in thread direction is over 300 times of that in the perpendicular direction.It can be seen that the thermal conductivity in the thread direction exhibits strong length dependence,while there is no size effect in the perpendicular direction.(3)The effects of uniaxial tensile and compressive strain on the thermal conductivity of diamond nanthread forests were studied.The thermal conductivity decreases with increasing compressive/tensile strain in the thread direction.When the diamond nanothread forest is subjected to compressive loading in the perpendicular direction,the thermal conductivity increasing.Next,this phenomenon is thoroughly explained by micro-structure deformation,and phonon dispersio.Our findings provide useful guideline to use diamond nanothread forest in thermal management equipment.