Study On The Preparation And Performances Of Low-dimensional Nickel-based Composite Metal Oxides

Because of the effects of small size,surface-interface and quantum size and the unique optical,electro and magnetic properties,nanoscaled materials have attracted wide attention.Recently,low-dimensional nanoscaled materials have been extensively studied around the world since the discovery of carbon nanotube and graphene.Due to the tunable chemical composition and structure,composite metal oxides offer promising applications in the fields of catalysis,energy storage and sensors.On account of the complexity of structure and composition,the controllable preparation of composite metal oxides remains a challenging topic.This thesis mainly focus on the synthesis and performances of low-dimensional nickel-based composite metal oxides and the detailed research contents were listed as follows:(1)Nickel-cobalt composite oxides nanotubes were synthesized by an electrospinning technique with soluble inorganic salts and polyvinylpyrrolidone as the starting materials.The morphology and structure were characterized by thermogravimetric analysis,X-ray Powder Diffraction,N2 adsorption-desorption isotherms,transmission electron microscopy,selected area electron diffraction,scanning electron microscopy and X-ray photoelectron spectroscopy.The obtained nickel-cobalt composite oxides possess uniform nanotube morphology,surface area of 61.1m2/g,average outer diameter of 100 nm,inner diameter of 60 nm and the wall thickness of 20 nm.Moreover,the catalytic test on thermal decomposition of ammonium perchlorate shown that the obtained composite nanotube achieves an superior catalytic performance(one exothermic interval,decomposition temperature of 260℃)to the bulk one(two exothermic intervals,decomposition temperature of 415℃).(2)The electrospinning method mentioned in above section was successfully applied to the synthesis of LaNiO3 nanotubes,indicating of a generality of the electrospinning method towards the preparation of composite metal oxides nanotubes.Detailed investigations was carried out to study the mechanism of formation process,in which the morphology evolution was traced by TEM and SEM.Based on the characterization results,a possible formation mechanism was proposed to interpret the formation of nanotube.The proposed mechanism is that the outer surface of the nanofibers would firstly crystallize during thermal treatment of the as-made precursors,meanwhile,the internal ions migrated outward,leading to the nanotube structure in the final material.(3)Porous NiCo2O4 nanosheets were fabricated by a newly explored ion-exchange method in mild conditions with the Mg(OH)2 as the starting material.The obtained NiCo2O4 nanosheets achieved a superior cycling stability after 2000 cycles(capacitance retention of 90%)under current density of 10 A/g,which can be attributed to the remaining Mg2+ in the final materials,enhancing the stability of the microstructure of the obtained NiCo2O4 nanosheets.