Conductive And Shielding Properties Of Nano-Copper Thin Film Deposited On Carbon Fibers

Carbon fiber(CF) is a fiber with high performances, which has high specific strength, highspecific modulus, high temperature resistance, corrosion resistance, fatigue resistance, creepresistance, electrical conductivity, small thermal expansion coefficient of heat transfer and so on.Because of these excellent performances, it has been widely used in high fields of aviation andaerospace.In this paper, nano-copper thin film was deposited by magnetron sputtering on carbon fiberfelts, being prepared for flexible electromagnetic shielding materials. To improve the fastness ofsubstrate and thin film, the low-temperature plasma pretreatment was applied. The chemicalcomposition and elemental content of nano-copper thin film deposited on carbon fiber felts wereapplied by the methods of X-fluorescence spectrum analyzer (EDX) and X-ray diffractioninstrument(XRD); in order to study the influence of the main processing parameters on nano-copperthin films, atomic force microscope (AFM) and scanning electronic microscope (SEM) were used toanalyse the surface morphology of nano-copper thin films; in order to study the influence of themain processing parameters on the electrical conductivity and electronmagnetic shielding efficiencyof nano-copper thin films deposited on carbon fiber felts, four-probe tester and vector networkanalyzer were used. The conclusions are as follows:(1) Plasma pretreatment has two effects on the carbon fiber felt surface: one is the etchingeffect, and another is the surface activation effect; SEM images showed that, after the plasmapretreatment, grooves of carbon fiber felts became deeper, part of which even were linked.Nano-copper particles and carbon fibers had enhanced mechanical occlusion effect. Although thetensile strength of single carbon fiber decreased by9.2%after the plasma pretreatment, it was stillin the acceptable range;(2) At the condition of the sputtering power140W, pressure2.0Pa, sputtering time30min,nano-copper film crystallization was in good condition, whose degree of crystallinity was up to40.85%; EDX analysis showed that thickness of nano-copper film increased, at the same time themass percentage and the atomic percentage of nano-copper particles increased when the sputteringtime extended;(3) The relationship of the processing parameters and the surface morphology of nano-copperthin film was as follows: with different sputtering time, the surface morphology of thin film werequitely different, when the sputtering time increased, the surface roughness of thin film decreased,and Cu particles became smaller and more uniformed, this was mainly because follow-up particleswith high energy bombarded large gathering particles into many smaller islands when reaching thefilm surface;(4) The relationship of the sputtering process parameters and conductive properties ofcopper-deposited carbon fiber felts is as follows: when the sputtering power was small, with thesputtering power increasing, the sheet resistance and resistivity of carbon fiber felts had adecreasing trend, and when it was more than180W, the two had little change; with the sputteringpressure increasing, the two first decreased and then increase; when less than60min, the sheet resistance and resistivity rapidly increased with the sputtering time decreasing; when more than60min, the two had little change;(5) The relationship of sputtering process parameters and electromagnetic shielding efficiencyof copper-deposited carbon fiber felts is as follows: with the sputtering time increasing, theshielding effectiveness of copper-deposited carbon fiber felts gradually increased; in the range of300MHz to1500MHz, the SE maintained the basic stability in the high state; with the sputteringtime90min, its SE value was up to44dB; organization of fabrics and weight per square meter hadan impact on the shielding effectiveness, in the range of300kHz to1200MHz, the SE value ofplain weaves,twill weaves and satin weaves were all more than50dB, and the SE value of copper-deposited carbon fiber felts was better than that of unidirectional carbon cloths; after magnetronsputtering, the shielding efficiency of carbon fiber felts improved144%.