Preparation Of Fe-TiC Composite Nanopowder

Metal-ceramic composite material not only has the plasticity and tenacity of the metals,but also has the high toughness and high hardness of the porcelain.It is a kind of important material of engineering structure.In the currently there is less study on the iron base composite material which is widely used in the application of the engineering.So it is important for practical to make research and develop the choiceness of capability and low price.This thesis uses the method of D.C.arc to melt the binary Fe-Ti alloy in an atmosphere of argon gas,and then vaporize and agglomerate composite nanopowder of Fe-TiC in an atmosphere of He+CH₄ and H₂+CH₄+He.Analyse the phase structure of composite nanopowder of Fe-TiC by X-ray diffractometer.The transmission electron microscope (TEM) is used to analyse the morphology and size distribution of nanoparticle,the chemical analysis is used to confirm the content of Ti,C.Apparatus of Oxygen/nitrogen examination is used to confirm the oxygen content.Differential thermal and thermogravimetric analysis(DSC-TGA) is used to analyse oxidation characteristic.XRD analysis shows Fe-TiC composite nanopowder are composed by Fe,Fe₃C and TiC;when mass fraction of Fe in mother alloy under 10%,the component of powder is TiC single-phase,with increasing of mass fraction of Fe in mother alloy,the content of Fe and Fe₃C phases in powder also increased,but,the content of TiC phase decreased;when mass fraction of Fe in mother alloy is more than 95%,the TiC phase is disappear.TEM photo analysis indicates,Fe-TiC composite nanopowder have different kinds of shapes, such as dumb-bell shape particle formed by prism which two terminals combined hemisphere particles,polyhedron particle formed by a cube which every surface combined hemisphere particles.In addition,from TEM photo sphericity particles and cube particles could be seen.Those can be proved by electron diffraction pattern that sphere particle are Fe or Fe₃C,and cube particles are TiC.Energy spectrometer is used to analyse each part of dumb-bell shape particles in compound powder,it is shown that the middle part is TiC and the two terminal hemispheric particle is Fe.When the mass fraction of Fe in mother alloy are 25%and50%,the prepared Fe-TiC composite nanometer particle's particle size distribution is 5nm-80nm and 10nm-100nm.The growth mechanism of composite nanopowder is VLS mechanism,i.e.minute TiC solid state cores formed in gas phase are taken as center core,nanopowder are formed by process of Fe-Ti-C liquid alloy attaching, growing and graining on the center cores.Thermodynamic calculation indicates:when temperature is above 2420K in gas phase,TiC solid state core is formed first.When temperature is under 2420K,Fe₃C was formed by Fe and C.Oxygen content analysis indicates the more content of TiC in powder,the better inoxidizability of powder. DSC-TGA analysis indicated,the sample's oxidation obviously accelerated when temperature is upon 330℃,TiC is oxidized to dissolve at about 410℃.H₂ in work atmosphere could make the output of powder increase,but not make much influence in phase composition of powder.