| X2YZ-type Heusler alloy is a kind of new predominant material and it has caught people’s attention because of its unique crystal structure and a variety of physicochemical properties.Currently, researchers have been prepared many Heusler alloys with different structures and excellent performance by molecular beam epitaxy, arc melting, sputtering, ball milling,high-temperature hydrogen reduction and other methods. In this work, we prepared Heusler alloy Co2 FeSn and Ni2 CoAl nanoparticles by diffusion-assisted method which was low cost, simple and easy to controled, and we tried to prepare Ni2 CoSn nanoparticles by using this method. We have studied the influence of experimental conditions on product’s structure, morphology and chemical composition during the preparation, and make a preliminary exploration on magnetic of products.The diffusion method and the combination of diffusion method with other methods in this paper can be extended to the synthesis of other ternary alloys. Not only can it lay a foundation for further research of Heusler alloy preparation, but also has far-reaching significance in properties study of Heusler alloys nanoparticles.In this thesis, we firstly prepared Heusler alloy Co2 FeSn nanoparticles by low-temperature diffusion method. Before diffusion, we prepared Co2 Fe alloy and Sn nanoparticles by reduction method, we discussed some of the factors of Co2 Fe binary alloys preparation. Then the two substances are used to be diffusion material, and focused on the factors when we prepared Co2 FeSn ternary alloy by diffusion method, the factors are as follows: temperature, time,concentration, proportion of raw materials, particle size, and so on. A series of experiments showed that we could prepared the Co2 FeSn Heusler nanoparticles with A2 type, spherical-like shape and particles size range from 5 to 10 nm,when we took these experiment conditions(the total raw materials concentration is 0.1 M, the molar ratio of Sn/Co2 Fe is 3:1,the reaction temperature is 230 ℃ and the reaction time is 24 h). VSM measurement indicated that the saturation magnetization at room temperature of Co2 FeSn was 93 emu/g, and the corecivity was75 Oe. We concluded that the magnetic characteristics of Co2 FeSn nanoparticles were consistent with the theoretical calculation, and the Co2 FeSn nanoparticles had a higher saturationmagnetization and a lower corecivity compared with other simial alloys.Secondly, we tried to prepared Ni2 CoSn alloy by low temperature diffusion method. Our raw materials Ni2 Co nanoparticles were prepared by hydrothermal reduction and Sn nanoparticles was prepared by liquid reduction. We used these two substances to diffuse at different diffusion time,raw materials contentration, the molar ratio of Sn/Ni2 Co, but the products has contained Ni-Sn impurity phase.At last, the Ni2 CoAl alloy nanoparticles were prepared by the combination of hydrothermal method and low temperature diffusion method. In the hydrothermal system, Al nanoparticles were added to the system in advance. The influence of Al concentration, temperature and time was investigated, and we can conclude that the Ni2 CoAl can be obtained at these condition(the molar ratio of Al/Ni2 Co is 3, the reaction temperature is 250℃, and the reaction time is 96 h). On the magnetic characterization, the saturation magnetization of Ni2 CoAl nanoparticles was 66 emu/g and the coercivity was 173 Oe at room temperature. |
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