材料期刊网

在CaCl_2熔盐中,利用固体透氧膜(SOM)法直接电解混合氧化物NiO-CeO_2制备CeNi_5合金,并与熔盐电解法(FFC)进行了对比.阴极的制作方法与FFC法相同,阳极为碳饱和Cu(或Sn)液,采用只允许氧离子通过的透氧膜隔开阴极和阳极,这样可以采用较高的电解电压(3.5 V)以获取更高的电解速率.研究了SOM法制备CeNi_5合金的可行性和影响因素,如电解温度、电解时间,以及产物的相组成和形貌等.结果表明:通过SOM法,NiO-CeO_2可完全还原为CeNi_5.电解中间产物的相组成分析表明,CeNi_5的形成过程为:NiO首先还原为Ni,与随后生成的CeOCl反应生成CeNi_5.SOM法与FFC法对比表明,2.5 g的烧结试样采用SOM法电解3 h可电解完全,电流效率为75.5%,能耗为4.03 kW·h/kg;采用FFC法需12 h才能电解出纯的CeNi_5合金,其电流效率为26.1%,能耗为10.27 kW·h/kg.相比于FFC法,SOM法具有更好的工业化应用前景.

Ce-Ni base alloy CeNi_5 is often used as the hydrogen storage alloy in Ni-H batteries. Its application is more or less limited by the high cost in the traditional preparing process. Therefore, lots of researchers have paid more attention to develop a novel process with high production efficiency and low cost. The goal of the present research was to demonstrate the technical viability of a new process (solid-oxygen-ion conducting membrane process, I.e., SOM process) for the production of CeNi_5 alloy directly from its oxide precursors. This process was improved on the basis of FFC process (Fray-Farthing-Chen Cambridge process): (1) the preparation of cathode was the same as that in FFC process, (2) Cu (or Sn) liquid saturated with carbon was used as anode separated from the melt by a yttria-stabilized zirconia tube in which only oxygen-ion was permeated to prevent the side reactions and decomposition of molten salts taking place until a voltage as high as 3.5 V. This paper was focused on the preparation of hydrogen storage alloy CeNi_5 by SOM process, some parameters such as molten salt temperature, electrolytic time, configurations and phase compositions of products were investigated. The results show that NiO-CeO_2 pellets can be completely reduced to CeNi_5 alloy by SOM process. The analysis of phase compositions of intermediate products indicates that the reduction of NiO-CeO_2 starts from NiO, it reduces firstly into Ni, then reacts with newly-formed CeOCl and finally forms CeNi_5. The comparison of FFC and SOM processes shows that for SOM, NiO-CeO_2 pellet (2.5 g) can be completely reduced to CeNi_5 after electrolyzed for 3 h, and the current efficiency is 75.5%, the electrolysis energy consumption is only as low as 4.03 kW·h/kg; while for FFC, it takes 12 h for the same pellet to be reduced to pure CeNi_5, and the current efficiency is 26.1% but the electrolysis energy consumption is 10.27 kW·h/kg. It could be concluded that SOM process has a bright future for industrial application.