| Owing to higher hydrogen-absorbing capacity, higher electrochemical Hydro-gen storage capacity, lower density, lower cost, lower environmental loading and good platforms of absorption and desorption of hydrogen, etc., Magnesium-based hydrogen storage alloy is one of the most promising hydrogen storage material. Replacement-diffusion method due to the simplicity of equipment and operation, resulting alloy powder is easy to activate, better hydrogen absorption and desorption kinetics performance, etc., is an effective method for the preparation of magnesium-based hydrogen storage alloy. However, reacting with magnesium intensely, water can not be as a magnesium-substituted reaction solvent. Ionic liquids with lower volatility, higher thermal stability, larger liquid state range, wider electrochemical window, soluble inorganic and many other advantages can be used as good alternative solvents for preparing bimetallic powder with chemical replacement method.Magnesium copper, magnesium nickel bimetallic powder is an intermediates for preparing a magnesium-based hydrogen storage alloy, and is the key step of preparing magnesium copper, magnesium nickel hydrogen storage alloys.Therefore, this paper uses replacement method in ionic liquids controlled preparation of a specific component of magnesium-transition metal (nickel, copper, etc.) bimetallic powders, Specific studies including:The prepared ionic liquids BMIC, using infrared spectroscopy, water testing, electrochemical testing and other means of its structure and properties were characterized. The results showed that:synthetic ionic liquids is the target ionic liquid, the water content of the ionic liquid can be controlled under three thousandths, electrochemical window of2.8V to meet the needs of magnesium displacement react with a transition metal.Response surface experiments by central composite design and single-factor experiment, reaction time, stirring speed on copper replacement ratio significantly; optimization of reaction conditions temperature100℃, reaction time4h, stirring speed200r/min. The results of experimental determination of the dynamic behavior of the magnesium displacement reaction with copper in the ionic liquid BMIC show that is the first order kinetic reaction rate equation data, at100℃, the reaction rate constant k=0.285h’1, impacted by stirring the reaction rate, temperature, initial concentration of copper ion, so stirring, increased the temperature, reduced the initial concentration of Cu (Ⅱ) ion can improve the reaction rate constant. Arrhenius equation by fitting the reaction rate constant and temperature relationships, obtain the apparent activation energy13.6kJ/mol, indicates that the replacement process is mainly controlled by diffusion, copper ion diffusion rate constant is ke=0.022. Evans showed that the concentration of nickel ions in solution in the range of0.005-0.5mol/L, the reaction rate is governed by diffusion of copper magnesium replacement control, consistent with the experimental results.The experimental determination of the dynamic behavior of BMIC ionic liquid magnesium displacement reaction with nickel, the results showed the same first-order reaction kinetic data rate equation, at100℃reaction rate constant k=0.171h"1, impacted by stirring the reaction rate, temperature, initial concentration of copper ion, by stirring, increasing the temperature was, reducing the initial concentration of nickel (Ⅱ) ion can improve the reaction rate constant. Arrhenius equation by fitting the reaction rate constant and temperature relationships, obtain the apparent activation energy24.83kJ/mol, indicates that the replacement process is mainly controlled by diffusion, nickel ion diffusion rate constant is ke-0.013. Evans figure showed that the concentration of nickel ions in solution in the range of0.005-0.5mol/L, the substitution reaction of nickel magnesium were diffusion controlled rate consistent with the experimental results.The resulting displacement of different magnesium copper, magnesium, nickel alloy powder heat treatment, XRD result indicate that we can get Mg2Ni alloys。... |
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