【作者】 魏范松；

【导师】 雷永泉；

【作者基本信息】 浙江大学 ， 材料学， 2002， 硕士

【摘要】 本文首先对AB5型混合稀土系贮氢电极合金的国内外研究进展进行了文献综述。在此基础上，本文选择了ABs型低Co合金ReNi3．5Coo．3Mno．3Alo．4Feo．5—xM，((x=0～0.4；M=Sn,Cr)和无Co合金ANixSno．3(A=La,Ml；x=4.5～5.2)为研究对象，采用XRD、SEM、EDS以及电化学测试等手段，比较系统的研究了Sn、Cr部分替代Fe、非化学计量比以及退火处理对合金相结构和电化学性能的影响。力求探索出一定的规律，从而为进一步优化合金成分，提高合金性能提供实验数据。 对铸态与退火态AB5型ReNi35Coo．3Mno．3Alo．4Feo．5-xSnx(x=0～0.4)低Co合金的研究表明：所有合金的主相均为LaNi5相结构，含Sn合金中均存在有LaNiSn第二相，而且第二相的含量随Sn含量的增加而增多。铸态合金的显微组织为粗大的树枝晶，真空退火(1000℃×5h)处理后，合金的树枝状组织结构消失。随x的增加，铸态和退火态合金的放氢平台宽度均变窄，合金的有效吸氢量减小。在x≤0.2范围内，所有合金的放氢平台压力均随x的增加而升高，进一步增加x，平台压力又下降。所有的铸态合金经2～3个循环即可活化，最大放电容量和循环稳定性均随x的增加单调下降，但含Sn合金的高倍率性能则随x的增加得到改善。退火处理会降低合金的活化性能和高倍率放电性能，提高循环稳定性，退火态合金的最大放电容量在x≤0.2范围内有所增加，其它成分范围内则下降。研究认为，无Sn退火态合金具有较好的电化学性能：最大放电容量为289.7mAh/g，600mA/g放电电流时的高倍率放电性能HRD600为51％，经250次充放电循环后的容量保持率为92.4％。在含Sn合金中以ReNi3．5Coo．3Mno 3Alo．4Feo．．3Sno．：退火态合金具有较好的综合性能：最大放电容量为249.3mAh/g，在600mA/g放电电流时的高倍率放电性能HRD600为55％，经250次充放电循环后的容量保持率S250为94.3％。 对铸态与退火态AB5型ReNi35Coo．3Mno．3Alo．dFeo．5-~Crx(x=0～0.4)低Co合金的研究表明：所有合金的主相均为LaNi5相结构，含Cr合金中还存在有LaNi第二相和富Cr第三相。经真空退火(1000℃×5h)后，LaNi5主相的衍射峰更为尖锐，合金中的第二和第三相仍然存在。随x的增加，铸态合金的显微结构组织由树枝状晶逐步向层片状或针状结构转变。退火处理后，合金中的树枝状、层状或针状组织结构消失。少量Cr部分替代Fe后会降低合金的放氢平台压力，但进一步增加x，对合金的放氢平台压力几乎没有影响，而平台宽度却逐渐变窄，倾斜度加大，有效放氢量下降。退火态合金的放氢P-C-T曲线更为平坦，平台变宽，有效放氢量有所增加。所有的铸态合金经1～2个循环即可活化，Cr部分替代Fe后会降低合金的最大放电容量和循环稳定性，随x的增加，含Cr合金的高倍率性能得到改善。退火处理会降低合金的活化性能和高倍率放电性能以及合Cr合金的最大放电容量，提高循环稳定性。研究认为，在所研究的含Cr合金中以 X二0．4成分的退火态合金性能较好，其最大放电容量为 20．ghah／g，在 600ha／g放电电流条件下的高倍率放电性能 io600为 31．4％，经 217次充放电循环后的容量保持率 5217为 85．3％。 对铸态与退火态 ANi雇．3（A＝La．MI；Xwt．5＊二）无 C。合金的研究表明：所有铸态合金的相结构均由LLis相（主相）和另一种CaCus结构的未知第二相组成。此外，在欠化学计量比合金k一、5冲还存在有LaNISn相。经950℃＼72h真空退火后，除欠化学计量比合金k＝4月仍存在LaNISn相外，其余合金均为单一的LaNis相，且Lallis相的衍射峰更为尖锐，半高宽变窄。铸态合金的显微结构组织为网状结构，退火处理后，合金中已无明显的网状结构。对所有铸态合金，偏高标准化学计量比均会改善合金电极的放氢平台特性，使平台压力略有升高。退火后合金的放氢P－C－T曲线更为平坦，平台变宽，有效放氢量有所增加。铸态合金的活化性能和高倍率性能较好，但循环稳定性较差，化学计量比对铸态合金的活化性能几乎没有影响。退火后合金的活化性能和高倍率变差，循环稳定性得到提高。用i替代La后会提高合金的活化性能，降低合金的最大放电容量。在所研究的合金中，以＊咖、。SO。退火态合金的容量保持率最高，SZ瓜达到了84．2％。研究认为，以退火态LaNis。SSpo．3合金具有较好的综合性能：最大放电容量为 31 0…g，在 600hajg放电电流时的高倍率放电性能 IIRD6。。为 66石％，经 200次充放电循环后的容量保持率 S。0。为 82．2 ％。更多还原

【Abstract】 In this thesis, the research and development of AB5-type mischmetal-based hydrogen storage electrode alloys have been reviewed, On this basis, low-Co AB5-type alloys ReNi3.5Coo3Mno3Alo.4Feo.5 - = 0-O.4;MSn, Cr) and Co-free AB5-type alloys ANi^Sno.3 （A=La, Mi.; x4.5-5.2） were chosen as objects of study. By means of XRD, SEM/EDS analysis and electrochernical measurements, the effects of the partial substitution of Fe by Sn and Cr, the stoichiometric ratio and annealing treatment on the phase structures and electrochemical performance of the alloys were studied systeimcally.For the ReNi35Co03Mn0.3A104 Feo.5..^Sn^x4i-0.4 alloys, both of the as-cast and annealed alloys consisted of the LaNi5 main phase and some LaNiSn second phase in Sn-containing alloys ,and the amounts of the second phase increased with the increase of the Sn content x, after annealed 5h at 1000 0C the second phase still remained, but the peaks of LaM5 phase became sharper and narrower. The as-cast alloys showed a typical coarse dendrite structure, but this structure disappeared after annealing. With the increase of x, the width of desorbing-hydrogen plateau narrowed, the available capacity of desorbing-hydrogen decreased. When x⁰.2, the desorbing-hydrogen equilibrium pressure of the alloys increased with the increase of x, but it decreased when x increased further. The as-cast alloys was activated in 2-3 cycles, with the increase of x , the maximum discharge capacity and cycling stability decreased, but the high-rate dischargeability of the Sn-containing alloys was improved. Annealing treatment decreased the activation and hi2h-rate dischargeability of the alloys, but improved the cycling stability. Annealing treatment increased the maximum capacity of the alloys when x 0.2,but decreased for other alloys. It was found that the annealed non-Sn-containing alloys showed the best overall electrochemical properties among all the alloys studied: its maximum discharge capacity Cmax289.7mAhIg. high-rate dischargeability HRD60051%, and the capacity retention reached 92.4% after 250 cycles. Among the Sn-containing alloys, the alloy of x⁰.2 showed better properties: its maximum discharge capacity Cmax=249.3rnAhlg, high-rate dischargeability HRD600-55%, and the capacity retention reached 94.3% after 250 cycles.For the ReNi35Co03Mn03A104 Fe0 s^Cr^x=0-0.4 alloys, both of the as-cast and annealed alloys consisted of the LaNi5 main phase arid some LaNi phase and Cr-rich phase in Cr-containing alloys. After annealed 5h at 10000C,the peaks of LaNi5 phase became sharper and narrower, but the second phases still remained. With the increase of x, the microstructure of the as-cast alloys changed from a typical coarse dendrite to a flake or needle structure, but all the structures disappeared after annealing. A small amount of Cr replacing Fe lowered the desorbing-hydrogen equilibrium pressure, but when x increased further, the value of x almost had no effect on the pressure. With theIIIincrease of x, the width of desorbing-hydrogen plateau narrowed, the slope of plateau increased, and the available capacity of desorbing-hydrogen decreased. After annealing, the P-C-T curves became flatter and broader, then the available capacity of desorbing-hydrogen increased .The as-cast alloys was activated in 1 -2 cycles, a small amount of Cr replacing Fe lowered the cycling stability and the maximum discharge capacity. With the increase of x, the high-rate dischargeability of Cr-containing alloys improved. Annealing treatment decreased the activation and high-rate dischargeability of the alloys, but improved the cycling stability. It was found that among the Cr-containing alloys, the alloy of x0.4 showed better properties: its maximum discharge capacity Cmax=20 1 .9mAh!g, high-rate dischargeability HRD600-3 1.4%, and the capacity retention 8217 reached 85.3% after 217 cycles.For the as-cast ANi^Sno3（ALa,M1;x=4.5-S.2） alloys, it consisted of the LaNi5 phase and an unknowing phase which also showed the CaCu5 structure, in addition, there was LaNi更多还原