Preparation And Study On The Properties Of CF/copper Matrix And CuO Nanowire/CF Composites

The lead free tin bronze matrix composite with chemical composition of Cu-4wt.%Sn-6wt.%Zn reinforced by carbon fibers (CF/tin bronze composite)is prepared bypowder metallurgy,and the mechanical,tribological and wear properties areinvestigated.The preparation and microwave absorbing properties of cupric oxidenanowire/carbon fiber composites (CuONW/CF composites)prepared by thermaloxidation are also investigated.(1)In order to prepare the high strength,anti-friction and anti-wear CF/tin bronzecomposite,the effects of plating solution PH,plating time and plating processes areinvestigated and the coated copper carbon fibers (Cu/CFs,2μm in thickness)areprepared.In addition,the Cu/CFs are used as starting reagent to prepare the effectivemicrowave absorption materials with the properties of wide frequency range,strongabsorption,low density and high resistivity.(2)The CF/tin bronze composites are prepared by warm pressing,repressing andre-sintering (powder metallurgy).The CF/tin bronze composites show high relativedensity,high hardness,high tensile strength,excellent anti-friction and anti-wearproperties.The hardness,tensile strength,friction and wear rate of 9 vol.% CF/tinbronze composites are better than that of the tin bronze ZQ663.In particular,the 9 vol.% CF/tin bronze composite has hardness of HV138.2 MPa,which is about 1.8 timeshigher than that of tin bronze 6-6-3.The 9 vol.% CF/tin bronze composite shows atensile strength of 302 MPa,which is about 1.68 times higher than that of tin bronzeZQ663.The wear rate of 9 vol.% CF/tin bronze composite is only 1% of that of tinbronze ZQ663.The friction coefficient of 9 vol.% CF/tin bronze composite is far lowerthan that of tin bronze ZQ663.Additionally,since lead in tin bronze is harmful to theenvironment and tin is a kind of valuable metal,CF/tin bronze composites eliminatelead and reduce tin addition in the composite matrix that show the excellent propertiesof the environment compatibility.(3)The CuONW/CF composites are synthesized by thermal oxidation of Cu/CFsat 400℃for 4 hours in air.The results of transmission electron microscope images indicate that the nanowires are about 50 nm in diameter and several microns in length.The magnetic properties of CuO nanowires are measured with a vibrating samplemagnetometer (VSM).It is interesting that the CuO nanowires on the carbon fibersshow ferromagnetic at room temperature.Agilent E8363B PNA vector networkanalyzer is used to measure microwave absorption property of CuONW/CFs.Theelectromagnetic parameter of 50 wt.% CuONW/CFs is measured by the coaxial linemethod at 1-18 GHz.The results show that the lowest reflectivity of CuONW/CFs is-32 dB (absorptivity＞99.9 %)at 7.9 GHz,and the corresponding thickness is 1.8 mm.The reflectivity of CuONW/CFs is less than-4 dB over the range of 2.5～18 GHz,-10dB over the range of 3～16.4 GHz and-20 dB over the range of 3～9.8 GHz.TheCuONW/CFs is thinner than those in other reports when the reflectivity is equivalent.(4)The CuONW/Co/CF composites are synthesized by thermal oxidation ofCu/CFs at 400℃for 4 hours in air.The thicknesses of cobalt and CuO are about 200and 50 nm,respectively.CuO nanowires (10 nm in diameter)and nanoparticles areobtained on the film surfaces.Due to the function of cobalt the saturation magnetizationvalue of CuO/Co/CF composites is raised to 28.7emu/g at an external field of 9 kOe,which is 1150 times higher than that of CuO/CF composites.The strongest reflectivityloss is further enhanced to-42.7 dB at 10.8 GHz for a layer of 2.0 thickness of thecomposites,and the strong absorption (RL＜-10 dB)is between 8.72 and 18 GHz withthe thickness of 1.3-2.2 mm.The reflectivity loss bandwidth of CuO/Co/CF compositesis more than 3 GHz when the thickness and absorption of materials are fixed.TheCuO/Co/CF composites are believed to be ideal for making a lightweight,strongabsorption and wide-frequency microwave absorbing materials.(5)The ZnO nanosheet/carbon fiber composites are synthesized by thermaloxidation of Zn/carbon fiber composites at 400℃for 4 hours in air.The opticalproperties were characterized with photoluminescence (PL)spectrum by RF-540 in 325nm.The results show that a broad orange-red emission covering range from 620nm to700nm by 325 excitation wavelength at room temperature.It is indicated that theorange-red emission is resulted from the interstitial carbon atoms of ZnOnanosheet/carbon fiber composites,and green emission results from the oxygen vacancies.(6)The nanosyringe-like and micromethane-like ZnMgO are synthesized byannealing the ZnMg alloy at 400℃for 4 hours in air.ZnMg alloys are prepared bycold press and sintering (powder metallurgy).The red shift from 500nm to 560nm ismore pronounced with increasing annealing temperature.The nanosyringe-like samplesexhibit broad green and yellow defect emission.The optical properties of ZnMgO arerelated to the morphologies.(7)The ZnSnO nanofibers are synthesized by thermal oxidation of ZnSn alloys.ZnSn alloys are prepared by powder metallurgy.The diameter and length of ZnSnOnanofibers are about 50nm and 60μm,respectively.The room temperaturephotoluminescence spectra of ZnSnO nanofibers show the near-band-edge emission at～391 nm and a broad green emission at～493 nm.(8)The radial structure CuO microspheres are synthesized by thermal oxidationof copper deposited on Indium Tin Oxides conducting glass.The microspheres areabout 6 microns in diameter.