Preparation And Characterizations Of Co-Zr-B Amorphous Nanoparticles

Amorphous metals (also known as metallic glasses), which have short-range ordered (instead of long-range ordered) atom arrangement and are free of defects such as grain boundaries and dislocations, have excellent mechanical strength properties superior to traditional alloys. Different from common metallic glasses, nanoglasses are a new type of amorphous materials consisting of nanometer-sized glassy regions connected with "glass-glass interfaces". The "interfaces" between adjacent glassy regions have an increased free volume compared with the glassy regions. Such unique structure has enhanced atoms mobility, thereby, affecting diffusion coefficient, viscosity, and creep properties of component atoms. In addition, the change of the average distance between atoms in nanoglasses, may also give rise to the variations of structure of outer electrons and interactions between atoms, consequently resulting in special magnetic and electric properties. So, it is crucial to prepare and study the properties of the magnetic materials with the unique structure. Consolidation of amorphous nanoparticles in ultra-high vacuum environment is an efficient way to produce nanoglasses. Therefore, this tries to prepare amorphous nanoparticles.Pronounced stress and bond will be introduced when consolidation of amorphous nanoparticles to prepare nanoglasses. Studies have shown that the introduction of stress could dampen the magnetic properties, whereas a subsequent annealing process would be useless to reduce this effect, and this degradation would not disappear until the magnetostrictive coefficient approaches zero. The magnetostrictive coefficient of Co-based amorphous alloys with a series of excellent soft magnetic properties is close to zero (below10-7), and the thermal stability of the Co-B amorphous alloy can be improved by introducing zirconium element. Thus, we choose the Co-Zr-B system as the research object.In this paper, amorphous Co-Zr-B nanoparticles were prepared by liquid reduction process using potassium borohydride as a reducer in the mixed solution of cobalt sulfate/cobalt chloride and zirconium sulfate/zirconium nitrate. The effects of the reaction environment temperature, ratio of metal ions, concentration of reducing agent, variety of dispersing agents, concentration of metal ions, and reacting environments on the structure, size and dispersion of the Co-Zr-B nanoparticles were analyzed. The Co-Zr-B nanoparticles were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and energy dispersive X-ray spectroscopy. The results show that the Co-Zr-B nanoparticles have amorphous structure, and the particle sizes are between5to800nanometers and partially form agglomerates. The Co-Zr-B amorphous nanoparticles with a good dispersity and an average size of11nm were obtained at the reaction environments temperature of20℃, the water to ethanol volume ratio of4:1, the Co2+to Zr4+ratio of10:1, the total Co2+and Zr4+concentration of0.09M, and0.5M KBH4.