| With a research background of industrial production and application of metal nanopowders, metal-ceramics composite nanopowders fabricated by arc discharge method,the stabilization, oxidation resistance and application of the nanopowders are studied in this thesis.A series of objective materials encapsulated nanopowders are prepared by arc discharge. The phase composition,core-shell structure and morphology are characterized by X-ray diffraction(XRD) and transmission electron microscope(TEM).X-ray photoelectron spectroscopy(XPS),infrared spectrum(IR),oxygen content analysis and differential thermal-thermogravimetry analysis(DSC-TG) are used to analysis the surface layer,oxidation resistance.Magnetic behavior is investigated by using vibrating sample magnetometer(VSM). The conductive paste is prepared by using Cu-Ag composite nanopowders coated with terpineol (C10H18O) as conductive phase,the fabrication technology and conductive characters are also discussed.The magnetic liquid of the corrosion resistance and high viscosity is prepared using Ni,Fe nanopowders covered by carbon as magnetic-particles,the preparation technology and corrosion resistance are researched.A new stabilization method,called gas-liquid phase stability method for metal nanopowders by arc discharge is applied.The new method is mainly to solve the problem that the oxide layer of the nanopowders surface has a strong impact on conductibility during the preparing conduct paste by the metal nanaopowder.Cu-Ag composite nanopowders coated with terpineol are prepared by the new method.It turn out these nanopowders have double-shells structure,a thinner oxide layer is encapsulated by terpineol molecular layer.These nanopowders with double-shells structure show better oxidation resistance and conductibility comparing with single oxide layer structure.To aim at the problem that a lower saturation magnetization is always obtained under pure CH4 atmosphere by arc discharge.A great of free carbons in nanopowders play the most important role.We try to change the working atmosphere with 50%CH4+20%H2+30%Ar mixture atmosphere.The experiment shows 11wt%and 12wt%of free carbon content is decreased,saturation magnetization increased 5.1A·m2/kg and 45.5A·m2/kg for Ni and Fe nanopowders.The Mg nanopowders have ultra high surface activity,easy oxidation,flammability,easy burst and difficultly to be prepared in large quantity.A systematic preparation and stabilization technology to avoid these problems by arc discharge is researched in this thesis.The experiment results that the Mg nanopowders prepared in Ar,Ar+H2 and Ar+CH4 can be stabilized in Ar with little O2 and air.The Mg nanopowders prepared in Ar +CH4 atmosphere have the best stability and oxidation resistance.The energy exhaust and time consuming during preparing Mg based composite nanopowders by the mechanism alloying method are to be solved problem.A technology which Mg-Mg2Si-Si composite nanopowders are synthesized by arc discharge is developed.Pure Mg takes as a raw material and is prepared under the mixture with SiH4 atmosphere.The results show that the Mg-Mg2Si-Si composite nanopowders can be stabilized in Ar with little O2 and air.At room temperature and under atmospheric conditions,the more Mg2Si phases in powder, the better oxidation resistance.In flow air condition,the powders are evidently oxidized when temperature is higher than 410℃.There exist many problems to prepare TiC dispersion strengthening iron base nanopowders by the ball milling method such as energy exhaust and time consuming etc.Fe-TiC composite nanopowders are synthesized under different condition by arc discharge.Fe-Ti alloy is taken as a raw material,and is prepared the Fe-TiC composite nanopowders in mixture with CH4 atmosphere.The results show that the Fe-TiC composite nanopowders can be stabilized in Ar with little O2 and air.The composite nanopowders consist of Fe,TiC and little Fe3C.The morphology of composite nanoparticles owns two types.One is dumbell-like,another is polyhedron.The growth mechanism of composite nanoparticles obeys VLS.Thermodynamic calculation of chemical reaction in gas phases has been done to analyze the possibility of reactions.At room temperature and under atmospheric conditions,the more TiC phases in powder,the better oxidation resistance.In flow air condition,the powders are evidently oxidized when temperature is higher than 330℃.TiC nanoparticles are oxidized to dissolve at about 410℃.To aim at the problem that the cost of the conduct paste increase with the price of the precious metal,the preparation of the conduct paste for nanopowders of inexpensive metal is studied preliminarily.The conduct paste is synthesized by Cu-Ag composite nanopowders coated with terpineol as conduct phase and terpineol solvent additive ethylcellulose as bearer.A thick film with resistivity(1.10-2.16)×10-4Ω·cm can be obtained after the nanopowders conductive paste sintered at 180℃-200℃for 60 min-70 min under 1.33Pa.At present,there is no magnetic liquid with corrosion-resistant and high viscosity in our country.The preparation of magnetic liquid with corrosion resistant and high viscosity is studied preliminarily.Ni and Fe nanometer particle coated with carbon are to be magnetic particle,oleic acid as surfactant,miscible liquids of polyether oil and little silicone grease as base solution.The prepared magnetic liquid shows high resistant corrosion ability.The viscosity of magnetic liquid is 9Pa·S -25Pa·S at 25℃and 2Pa·S -16Pa·S at 85℃.The saturation magnetization of Ni magnetic liquid is 5.19A·m2/kg-17.83A·m2/kg and Fe magnetic liquid is 15.36A·m2/kg-59.88A·m2Z/kg. |
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