| Diamond-like carbon(DLC)thin films have attracted much interest due to their unique properties such as high hardness,low friction,good wear resistance,optical transparency and high chemical inertness.Due to these excellent properties,DLC films have been widely used for several critical applications such as protective coatings for magnetic recording disks,cutting tools,optical components and micro electromechanical devices(MEMs).However,there are some problems such as high internal stress,poor adhesion between film and substrate,unstable tribological properties and so on.At present,researchers at home and abroad mainly solve these problems by building composite structures,and have achieved some results.In this paper,Ni/DLC multilayers with different modulation periods and DLC films doped with different Ni content were prepared by RF magnetron sputtering.The effects of modulation period and Ni content on the chemical composition,microstructure and properties of DLC films were investigated.The tribological properties and field emission properties of DLC films were mainly studied,and the related mechanisms were discussed.The main achievements are as follows:(1)Ni/DLC multilayers with different modulation periods were successfully deposited by RF magnetron sputtering.The interface between the substrate and the layers was well bonded.The hardness of the films first increases and then decreases with the increase of the modulation period.When the modulation period is 710 nm,the hardness of the films is the highest.This is mainly due to the good overall compatibility between the sublayers,and the minimum grain size of Ni sublayer in A3film is 4.0 nm,which has the effect of fine grain strengthening.(2)The tribological properties of Ni/DLC multilayers in air were investigated.It was found that the films had good wear resistance.With the increase of modulation period,the tribological properties of the films were enhanced first and then weakened.The best tribological properties of A3 films are attributed to its excellent mechanical properties,the highest hardness,the strongest crack propagation resistance and deformation resistance.During the friction process,the accumulation of friction heat between the friction contact surfaces and the catalysis of Ni lead to the graphitization of the film.(3)The field emission properties of Ni/DLC multilayers were investigated.With the increase of the modulation period,the turn-on electric field of the films first decreases and then increases.It is found that the field emission properties of the films can be enhanced by adjusting the modulation period reasonably.The field emission properties of the films with the modulation period of 710 nm are the best.(4)A series of DLC composite films with different Ni content were prepared at different Ni target power.With the increase of Ni target power,the hardness of the films first increases and then decreases.When the Ni target power is 30 W,the hardness of the films is the highest,which is mainly attributed to the nano enhancement effect of Ni particles.At the same time,it is found that the elastic recovery of the films can be improved by doping Ni particles.(5)The tribological properties of Ni/DLC doped films in air were investigated.The results show that A2 film has the best tribological properties under 2 N load,mainly due to its highest hardness.Under 5 N load,A3 film has the best tribological properties.Under the action of alternating stress,sp~2C changes to sp~3C in the wear scar,and the hardness and wear resistance of the film are improved.(6)The field emission properties of Ni/DLC composite films were investigated.With the increase of Ni target power,the turn-on electric field of the films first decreases and then increases.A2 film has the best field emission properties,mainly due to the best sp~2/sp~3 hybrid carbon ratio of A2 film. |
PDF Full Text Request