Preparation And Properties Of Porous Metal Composite Oxide Films

Spinel type ferrite is one of the strongest branches of the ferrite development.Recently,the fabrication,structures,properties and applications of thin films have gained significance in the novel filmy materials science all over the world.Spinel type ferrite thin films have been paid much attention for their good thermal stability,mechanical wear-resisting,and well magnetic characteristic al.In this work,we present a new route for preparing porous spinel type ferrite films on silicon substrate by using LDH precursor film sintering and selective leaching technique.The structure,morphology and properties of the sample film were investigated.The main results are as follows:1 Fabrication of the porous spinel type ferrite films on silicon substrateFirstly,the LDH precursor films with dense LDH layer were prepared by static adsorption theory on surface sulfonated silicon substrate;further,this strategy involves calcination of the molecular precursor at high temperature; followed by selective leaching of the self-generated oxide from the resultant calcined films.The porous spinel type ferrite films(MgFe₂O₄,NiFe₂O₄, ZnFe₂O₄)on silicon substrate were fabricated with different pore size,unitary crystallite.2 Investigation of the LDH precursor films,metel composite oxide films and porous spinel type ferrite films with morphology and structuresThe surface morphology of the resulting films was characterized by scanning electron microscope(SEM),field emission scanning electron microscope(FESEM),atomic force microscopy(AFM),the composition of films was identified by means of X-ray diffractometer(XRD).Moreover,the effects of the annealing temperature and initial molar ratio M/Fe of LDH precursor on microstructure of the films were also investigated.The porous spinel type ferrite(MFe₂O₄)film presents a network-like surface morphology. XRD,AFM and FESEM images of the films provide evidence that the surface particle size of the film decreases with increasing initial molar ratio.3 Study on wetting property and magnetic property of porous spinel type ferrite films(MgFe₂O₄,NiFe₂O₄)The magnetic property of as-prepared porous ferrite film(MgFe₂O₄, NiFe₂O₄)was investigated with a vibration sample magnetometer,it can be concluded that the saturation magnetization value of the film increases with increasing initial molar ratio.Furthermore,temperature dependence of zero field cooled(ZFC,filled circles)and field cooled(FC,open circles) magnetization for 900℃-annealed porous MgFe₂O₄ films were investigated by SQUID-XL7 magnetometer at 100 Oe field.It can be observed that 900℃-annealed porous MgFe₂O₄ film possesses a blocking temperature(T_B) of 105K.Above the T_B,the FC and ZFC magnetization data exhibit the same trend.However,below the T_B,that is,low-temperature region,they diverge significantly.It is well known that the appearance of blocking temperature and unsaturated magnetization curve indicates the existence of superparamagnetic components originating from the small size effect of the magnetic grains.The wetting property of as-prepared porous ferrite film(NiFe₂O₄)was investigated with a video based contact angle meter;experiment results show that surface structures can greatly influence the hydrophobicity of the surface. Conventionally,there are two methods to produce the superhydrophobic surfaces.One is to modify the low surface energy stuff on the surface;the other is to produce mico and nano- structures on the surface.It can be concluded that the contact angle of the film increases with decreasing initial molar ratio.