Preparation Of The Heusler Alloy Nanoparticles

Heusler alloys have attracted great interest due to the diversity of the structure and physical properties. Heusler alloys can be prepared by the arc melting, high temperature hydrogen reduction, molecular beam epitaxy, sputtering and other means. In this work, the solution reduction method has been used to prepare Co2FeSn Heusler nanoparticles. The synthesis of Co2FeGa and the related binary alloy nanoparticles have been also investigated. A clear understanding of this novel material system would pave the way for potential applications.First, the systematic study on the synthesis of Co2FeSn nanoparticles were performed. Using hydrazine hydrate, NaBH4and NaH2PO2as reducing agent, Co2FeSn nanoparticles were prepared via a solution reduction process. The effects of the reducing agent, synthesis temperature, the concentration of alkaline solution and the reaction duration time on the structure and composition of the final products were investigated. Co2FeSn nanoparticles has been successfully prepared using the reducing agent NaH2PO2at room temperature. The structure, morphology and magnetic properties of the samples have been characterized by X-ray diffraction, Scanning electron microscopy and Vibrating sample magnetometer. XRD data indicates the B2-type cubic structure of the prepared Co2FeSn nanoparticles. The particle size of is in the range of10-100nm. Magnetic measurement reveals that the obtained Co2FeSn nanoparticles are soft magnetic. The solid phase method and the high temperature solution reduction method were also used in the preparation of Co2FeSn nanoparticles. By using solid phase method, the mixture of Co2.9Sn2and Co1.5FeSn0.5O4were obtained at200-800℃for3-130h. By using high temperature solution reduction, the cubic FeSnO(OH)5phase were obtained at250-300℃for10min-1h.Using hydrazine hydrate as reducing agent, we tried to synthesize Co2FeGa nanoparticles via solution reduction method. It was found that the ability of reduction can be enhanced by increasing the temperature and alkaline concentration of the solution. The final product is the mixture phase of Co and CoxFeY, the element Ga was not detected.The last part of my work is the investigation of the effect of alkaline in the preparation of Cobalt-Tin, Iron-Tin, Nickel-Tin, Nickel-Iron and Nickel-Cobalt alloy nanoparticles using solution reduction method. In the prepare of Cobalt-Tin nanoparticles, the content of hydroxide in the final product decreased gradually with the weakening of alkaline. We get the the mixture phase of Sn and CoxFeY while the concentration of NaOH equal to or less than0.5M. For the preparation of Iron-Tin nanoparticles, the hydroxide and oxide contained in the sample decreased gradually with the weakening of alkaline. When the concentration of NaOH was lower(be equal to) than the0.5M, the sample is Sn and Fe. For the preparation of NiSn nanoparticles, a mixture of Sn, NiCXand NixSnYwas obtained when the concentration of NaOH is0.005-5M; the sample is amorphous when the concentration of KOH is25M. For the preparation of Ni2Fe and Ni2Co nanoparticles, the samples were amorphous when the concentration of NaOH is0.005-5M; the hydroxide apperaed when the concentration of KOH is25M. The variation of the chemical composition and the morphology of the product with the change of alkaline were also shown.