First Principles Study On The Adsorption Performance Of Silver-based Composite Solder Enhanced By Element-doped Graphen

Graphene has a single-layer two-dimensional structure and unique physical and chemical properties,so graphene is currently considered as an ideal reinforcement material for high-performance composite materials.Graphene,as the reinforcing phase of the silver based composite filler,can reduce the contact angle between the filler and the substrate,the coefficient of thermal expansion and refine the microstructure,so as to enhance the strength of the filler.It is very important to reduce the difference of thermal expansion coefficient between the filler metal and graphene so as to improve the adsorption performance between the filler metal and graphene.Therefore,based on the first principle calculation method of density functional theory,supported by the software package,this paper studies the influence of rare earth elements Ce,W and CeW co-doped in graphene on the adsorption performance between graphene and silver,and studies the influence of the adsorption behavior of silver on element doped graphene on the electronic characteristics and adsorption performance of the system.The main achievements are as follows:(1)The adsorption behavior of Ag on the surface of graphene was studied by the first principle method.The adsorption properties,band structure,density of state and electron density of difference of the three adsorption systems(Top-site,Hollow-site and Bridge-site)were studied.It is found that the adsorption behavior and structure change of Ag on graphene surface are similar in three highly symmetrical adsorption positions.Because the intrinsic graphene is not doped with other atoms and does not destroy the grid equilibrium of C atom,the adsorption behavior of silver atom at different highly symmetrical positions has little effect on the band structure,so the effect of different adsorption positions on the band structure of the system can be ignored.The bonding type between Ag and graphene is physical adsorption.In terms of charge transfer and adsorption energy,the adsorption energy of Ag on the T-site of graphene is the largest,and the amount of charge transfer is the largest.Therefore,compared with the other two adsorption sites,the geometry of Ag on the T-site of graphene is the most stable and the adsorption effect is the strongest.(2)In order to improve the aggregation of graphene caused by the weak adsorption between graphene and silver,we doped alloy elements to improve the adsorption of graphene on silver based filler.We studied the influence of Ce doped graphene(Ce-Gra)and tungsten doped graphene(W-Gra)on the adsorption behavior of Ag on graphene surface,and calculated the energy band structure,density of States and electron density difference,etc.The results show that the adsorption height of silver is the smallest,the absolute value of adsorption energy is the largest,and the charge transfer between silver and graphene is the largest,which shows that the adsorption of Ag at the top of Ce-Gra is more stable.By studying the band structure and density of states of the adsorption system,it is found that the adsorption type between Ag and Ce-gra is chemical adsorption,and the doping type is N-type doping.Similarly,for W-Gra system,we have studied three kinds of highly symmetrical adsorption sites,and found that the adsorption type between Ag and W-Gra is chemical adsorption,the doping type is P-doping,and B-site is the most stable adsorption site with the strongest adsorption.(3)The influence of CeW co-doped on the adsorption behavior of Ag on the surface of graphene was studied.The properties of the system,such as geometry,adsorption energy,band structure,density of states and electron density difference were also studied.It is found that Ag in the four adsorption systems is close to the surface of graphene after optimization,forming chemical adsorption,and the doping type is N-doping.The absolute value of the adsorption energy of W-top is greater than that of Ce,and a new density of states peak is generated near the Fermi level in the W-top adsorption system.Because the impurity level introduced by doping is closer to the Fermi level than other adsorption systems,the adsorption performance of co-doped system is significantly enhanced after the adsorption of Ag at W-top.The results of single atom or atoms co-doped show that element doping can effectively improve the adsorption performance between graphene and silver base filler,and make the distribution of graphene between silver base filler more uniform,greatly improving the strengthening effect of graphene in silver base filler.