Basic Research On Processing Of Metal And Carbon Materials By Femtosecond Laser

The interaction of femtosecond laser with materials has become a hot topic in recent years due to its ultra-short pulse,peak power and uniqueness of "cold machining".The interaction between femtosecond laser and metal/carbon materials are studied in this paper and the new materials produced by their interaction have better properties.Firstly,laser trimming becomes one of powerful tools for precise manufacturing of alloy resistors which is widely used in electrical vehicles,electrical controlling and appliances and other fields.Fe-Cr-Al alloy is a kind of thermocouple alloy with high resistivity and low resistance-temperature coefficient.Fe-Cr-Al alloy resistance has high precision and large range of resistance(100 u ?-100 ?).Therefore,the Fe-Cr-Al alloy resistance is used as the metal material in this paper.Secondly,carbon nanomaterials,such as nano-diamond,carbon nanotubes and graphene,have wide application prospects in supercapacitors,aerospace equipment,microelectronic components,military materials,semiconductors,water purification and functional fillers.And carbon materials that cannot be synthesized at room temperature can be produced by pulsed laser liquid phase irradiation.Therefore,this paper adopts laser liquid phase ablation method to study carbon materials and diamond is selected as the carbon material.The main contents of this paper are as follows:1.This paper compares the influence of the same laser(femtosecond laser modulated resistance and nanosecond laser modulated resistance)on the resistance value of the alloy resistance sheet.The resistance change was systematically investigated as a function of cutting lengths and the cutting depths of different laser powers for both lasers.The experiments show that the femtosecond laser trimming has a higher precision of the resistance adjustment than nanosecond laser trimming.This paper analyzes whether the resistance value of the alloy resistance sheet will change when it is slightly etched by the polarized light of femtosecond laser in different directions.And the range of resistor values change in the S-polarized light direction of femtosecond laser is more than that in the p-polarized light direction.2.The periodic ripple structure was investigated at the focus position above,on or beneath surface,respectively,when the femtosecond laser interacts with Fe-Cr-Al alloy resistance.When femtosecond laser interacts with Fe-Cr-Al alloy resistance sheet,the changes of the periodic fringe structure generated at different focusing positions(above,below and above the surface)were studied.The results shows that laser focused on different heights relative to the sample surface induced significant changes of surface morphology.The period of the low frequency ripple structure(LFRS)on the ablated groove bottom is about 600 nm-700 nm when the laser is just focused right on the surface but changes to 490-560 nm when focused above or beneath the surface.The period of high frequency ripple structure(HFRS)is about100 nm-380 nm at the vertical direction of LFRS.The period of low frequency ripples on the outside of groove is smaller than that on the groove bottom for all three focusing cases.The period of the low frequency ripple structure is not sensitive to the laser power.3.The interaction between femtosecond laser and diamond was studied.The diamond suspension of deionized water was irradiated by femtosecond laser by pulsed laser liquid phase irradiation method.In the experiment of irradiation liquid phase diamond by femtosecond laser,it is found that the suspension of diamond can be clarified by femtosecond laser.The average particle size of diamond decreases and a small amount of non-diamond carbon is produced.At the same time,laser irradiation of diamond suspension can reduce the agglomeration of nano-sized diamond and prolong the agglomeration deposition time.In addition,a method of removing graphite and amorphous carbon was found in the purification process of diamond.