Synthesis And Application Of Mutil-Element Iron Family Metal Oxide Nano Materials

Ferrite magnetic nanomaterials have drawn an intense interest over the past two decades owing to their unavailable properties, such as small size effect, surface and interface effect, quantum size effect as well as macroscopic quantum tunneling effect. Due to the nanometer scale size and excellent properties, ferrite magnetic nanomaterials have important implications in the fields of electrode materials, catalysts, magnetic fluid, wave-absorbing materials, targeted bio-materials and high-density magnetic recording materials.In this paper, well dispersed ferrite magnetic nanomaterials are successfully prepared by modified low-temperature combustion synthesis method and innovative agar combustion synthesis method. Based on these, rare earth elements are doped to obtain cerium doped ferrite magnetic nanomaterials for the thermo-catalytic decomposition of ammonium perchlorate and the methods are developed for the preparation of multiple composite ferrites. Besides, the composite of ferrite magnetic nanomaterials and expanded graphite is also obtained by the simple and effective one-step low-temperature combustion synthesis method and the millimeter-wave attenuation performance of the product is researched. This paper studies the synthesis, and application of ferrite magnetic nanomaterials and the findings are listed below:(1)A fast and simple method combining traditional combustion synthesis method and sol-gel method was introduced for the synthesis of well dispersed ferrite magnetic nanomaterials, using metal nitrates as oxidizing agents, soluble hydrazine fuel as reducing agent, EDTA as complexing agents and ethylene glycol as dispersing agent. Based on Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis, the effect of fuel type, complexing agents amount, dispersing agent amount and calcination temperature on the size and morphology of the product were discussed. The results indicated that, uniformly dispersed ferrite magnetic nanomaterial with well-defined morphology was obtain under the following conditions:water-soluble hydrazine served as fuel,2 g complexing agents and 2 g dispersing agent amount was used, calcination temperature was 800℃ with calcination time of 2 h. Samples synthesized under the optimal conditions were bulky structure and well dispersed particles with the size range 40-80 nm. Furthermore, rare earth elements doped ferrite magnetic nanomaterials and multiple composite ferrites were researched.(2) A new method was developed to develop well dispersed ferrite magnetic nanomaterials, using agar as solvent, metal nitrates as oxidizing agents and soluble hydrazine fuel as reducing agent. Introduction of appropriate amount of agar facilitate keeping the looseness of the precursors throughout reaction process. Meanwhile, large amounts of gas during the combustion process of soluble hydrazine fuel can reduce the agglomeration of the traditional method, which conducive to the fast, simple, efficient and large-scale preparation of nanopowders with dood dispersibility.(3) Ce doped NiFe2O4 nanoparticles were prepared via sol-gel combustion synthesis method. The morphology and structure of the products were characterized by XRD, FTIR and TEM. The catalysis of products on thermal decomposition of AP was investigated by DSC. The results indicate that the products have a good dispersity, with crystallite size range from 30 to 60nm. As Ce content increase, nanoparticles can gradually decrease the thermal decomposition peak temperature of AP, so as to make total apparent decomposition heat increase obviously. When Ce content reaches 0.09, the nanoparticles can make the high-temperature decomposition peak value of AP decrease by 57.8℃, which presents good catalytic effect. This work provides an economical approach to fabricate highly catalytic nanoparticles by a simple production process.(4) NiFeaO4/expanded graphite (EG) composites are successfully prepared by low-temperature combustion synthesis method. The morphology, structure and millimeter wave (mmw) attenuation properties of the NiFe2O4/EG composites are investigated by X-ray diffraction (XRD), Fourier transform infrared Spectroscopy (FTIR), Raman spectra, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and mmw radar measurement device. The effects of fuel and stoichiometric ratio on the composites are also investigated. The results show that NiFe2O4/EG composites are uniform and have a good crystallinity. The composites possess better mmw attenuation properties than EG. The 3 and 8 mmw attenuation performances of NiFe2O4/EG composites are 8.5 dB and 14.6 dB respectively.