Improvement of Hydrogen Storage Properties of La0.6M0.4Ni4.8Mn0.2 Alloys

Investigation has been carried out to find the effects of Nd substitution and Cu addition on the hydrogen storage properties of AB5-type alloy with a multicomponent La0.6M0.4Ni4.8Mn0.2 (M=Y, Nd) system. La0.6Y0.4Ni4.8Mn0.2,which was used in an air-conditioning system, showed poor hysteresis and sloping characteristics, which led to a decrease concerning the coefficient of performance of the system. By the substitution of Nd for Y, the hydrogenstorage capacity increased, and the plateau pressure decreased a little, but the hydrogen absorption kinetics decreased dramatically. Cu addition can effectively improve the kinetics of hydride formation without changing the hydrogen storage capacity of La0.6Nd0.4Ni4.8Mn0.2. It has been found that La0.6Nd0.4Ni4.8Mn0.2Cu0.1 alloy showed good hydrogen storage characteristics for metal hydride air-conditioning system. The results showed that, for each component of La0.6Mo.4Ni4.8Mn0.2, the effective hydrogen storage capacity increased with decrease of the unit cell parameter c/a and the hydrogen absorption plateau pressure increased with decrease of the parameter a.     

La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2合金的储氢性能研究

针对两种新型稀土型储氢合金La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2的储氢特性进行研究分析。实验表明,相同温度下,La0.5Y0.5Ni4.8Mn0.1Al0.1和La0.5Y0.5Ni4.8Al0.2合金的PCT曲线基本重合,且都具有优良的吸氢动力学性能;相比之下,后者的滞后系数要小于前者,吸氢量较大,吸氢速率也较快,故其储氢性能较优。300次吸放氢循环实验结果表明,La0.5Y0.5Ni4.8Al0.2合金的吸氢动力学性能虽然略有下降,但抗粉化性能较好。     

Mn替代Ni对(La0.8Nd0.2)2Mg(Ni0.9-xCo0.1Mnx)9合金储氢及电化学性能的影响

在Ar保护下采用磁悬浮感应熔炼制备(La0.8Nd0.22)Mg(Ni0.9-xCo0.1Mnx)9(x=0,0.05,0.1,0.15)合金,系统研究了元素替代及退火处理对合金相结构、吸放氢性能及电化学性能的影响。结果表明,合金相主要由(La,Nd)Ni5相、LaMg2Ni9相和(La,Nd2)Ni7相组成,当x=0.15时,(La,Nd)2Ni7相消失。随着Mn取代量的增加,合金的储氢量、放电容量先增加后减小,Mn的添加提高了合金的充放电循环稳定性。经1073K退火处理后合金的放电容量得到提高,循环稳定性能得到明显改善。     

Effect of Preparation Technique on Microstructure and Hydrogen Storage Properties of LaNi_(3.8)Al_(1.0)Mn_(0.2) Alloys

La Ni3.8Al1.0Mn0.2 alloy was prepared by vacuum induction melting and melt-spinning.The effects of different preparation techniques of the as-cast,cast then annealed,as-spun and spun then annealed alloys on the microstructure and hydrogen storage properties were investigated.The results indicated that the non-Ca Cu5 phases in the alloy became tinier and more dispersive after annealing or melt-spinning compared to those of the as-cast one.But in the spun then annealed alloy,the non-Ca Cu5 phases disappeared and only a single-phase with Ca Cu5 type structure was found.For all the alloys,the cell volume was increased in an order of as-cast spun then annealed cast then annealed as-spun,and the change of plateau pressure showed the opposite trend with that of the cell volume.The plateau could be flattened after melt-spinning or annealing,and the spun then annealed alloy showed the minimum plateau slope.The absorption kinetics of the alloy was promoted after melt-spinning or annealing.It is suggested that the change in cell volume and compositional homogeneity resulting from different preparation techniques contribute to the difference of the hydrogen storage properties of the investigated alloys.     

退火处理对A2B7型La0.63(Pr0.1Nd0.1Y0.6Sm0.1Gd0.1)0.2Mg0.17Ni3.1Co0.3Al0.1储氢合金相结构和电化学性能的影响

利用高频感应熔炼法制备La0.63(Pr0.1Nd0.1Y0.6Sm0.1Gd0.1)0.2Mg0.17Ni3.1Co0.3Al0.1储氢合金,对铸态合金在900℃下退火热处理24h。结构分析表明,铸态合金微观组织由CaCu5型结构、Ce5Co19型结构及Ce2Ni7型结构三相组成,而退火合金则是单相Ce2Ni7型结构。铸态和退火合金电极均具有良好的活化性能,退火合金电极放电曲线更为平坦和宽阔。两种合金电极腐蚀电位基本一致,但铸态合金电极腐蚀电流更大。合金经过退火后其电极循环稳定性(S100=83.5%)明显优于铸态合金电极(S100=69%)。在100次电化学充放电循环内,低容量充电时,退火合金电极容量不衰减,合金电极容量衰减的充电容量临界点为活化最大放电容量(Cmax)的90%。铸态和退火合金电极动力学性能差别不大,铸态合金电极高倍率放电主要由氢在其体相中扩散控制,退火合金电极高倍率放电则主要由其表面电荷转移控制。     

镨含量对（La,Pr,Nd）Ni3.5Co0.8Mn0.4Al0.3合金电化学性能的影响

目前广泛采用的镍－金属氢化物电池负极材料多为ＬａＮｉ５基合金。本实验研究了稀土中镨含量分别为０、１０％、２０％、３０％、４０％和５种（Ｌａ，Ｐｒ，Ｎｄ）Ｎｉ３．５Ｃｏ０．８Ｍｎ０．４Ａｌ０．３合金的电极性能。发现稀土中镨含是来２０％和３０％的合金比其它成分手合金具有更高的放电容量，更好的电极稳定性。选用镨含量为１７％的富镧混合稀土制备了成分为ＭｌＮｉ３．５Ｃｏ０．８Ｍｎ０．４Ａｌ０．３的电极合金，     

Electrode Characteristics of MmNi_5-based Alloys for Nickel-Metal Hydride Batteries

Negative electrodes of the Ni-metal hydride battery were made from hydrogen storage alloy Mm0.9Ti0. 1Ni3. 9Mn0.4Co0.4Al0.3 mod fied by coating with Ni or mixing with Co powder. The cell volume expansion of hexagonal structure was about 12 % after coating with 11 % Ni on the alloy Surface,When this alloy was mixed with Co powder. the discharge capacity and the utilization efficiency of the hydrogen storage alloy increased. When the alloy was coated with 11 wt-% Ni and also mixed with 10 wt-% Co powder. the capacity decay for a small sealed cylindrical cell (AA size. 1 Ah) was only about 4 % after 200 cycles     

MlNi_4Co_(0.6)Al_(0.4)储H_2合金表面吸H_2的TDS研究

用热脱附谱 (TDS)对不同表面处理的富La混合储H2 合金MlNi4 Co0 6Al0 4 粉末样品进行H2 气吸附和脱附特性的比较和研究。未经表面处理的粉末样品 ,只测到一个H2 脱附峰 (α峰 ) ,脱附温度在 40 0K左右 ;经 6molKOH溶液 ,在 80℃下处理 6h的MlNi4 Co0 6Al0 4 粉末样品 ,有 2个H2 热脱附峰 (β峰和γ峰 ) ,脱附温度分别在 5 40和 6 30K处 ;而用 6molKOH 0 0 2molKBH4 溶液处理后 ,则有 3个H2 热脱附峰 (α峰 ,β峰和γ峰 ) ,脱附温度分别在 40 0 ,5 30和 6 40K处。TDS研究表明 ,热碱加还原的处理使材料表面对H2 气吸附的活性和容量提高 ,并使各个吸附态的扩散和转变更加容易。     

Ti-Cr-Mn-M(M=V、Fe、Ni、Cu)合金的储氢性能

为改善Ti(Cr-Mn)2 AB2型合金的储氢性能,采用A侧过化学计量和过渡金属部分替代Mn进行多元合金化,系统研究了Tix(Cr-Mn-M)2(x=1.0,1.1;M=V、Fe、Ni、Cu)合金的储氢性能.研究结果表明,V、Fe、Ni、Cu部分替代Mn进行多元合金化后,合金主相仍保持C14(MgZn2)型Laves相,合金晶胞体积增大.合金化元素部分替代Mn后合金的活化性能得到明显改善,合金吸放氢量增大,吸放氢压力滞后减小.除Fe使合金放氢平台压力有所升高外,其余合金化元素均使合金的吸放氢平衡压力有不同程度的降低,这是由于合金的晶胞体积增大所致.在所形成的合金中,以Ti1.1Cr1.2Mn0.5CuO0.3的综合性能最好,其室温下吸放氢量分别达到1.95%和1.72 9,6(质量分数).采用该合金与自制的轻质高压储氢容器(工作压力为40MPa)复合组成金属氢化物复合式高压储氢器,对其储氢密度的计算结果表明,当储氢合金的填充量(体积分数)达到0.20时,该复合式储氢器总的体积储氢密度将提高57%.     

Effect of substituting Ni with Cu on the cycle stability of La0.7Mg0.3Ni2.55−xCo0.45Cux (x = 0–0.4) electrode alloy prepared by casting and rapid quenching

In order to improve the cycle stability of the La–Mg–Ni system (PuNi₃-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu. Hydrogen storage alloys La_0.7Mg_0.3Ni_2.55−xCo_0.45Cu_x (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and the quenching rate on the microstructures and the cycle stability of the as-cast and quenched alloys were investigated in detail. The results obtained by X-ray diffraction show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni₃ phase, the LaNi₅ phase and the LaNi₂ phase, and the amount of the LaNi₂ phase increased with the increase of the Cu content. The substitution and rapid quenching have an inappreciable influence on the phase compositions of the alloys, but both obviously changed the phase abundances of the alloys. The results derived by transmission electron microscopy confirm that the substitution of Cu for Ni is favourable for the formation of an amorphous phase in the as-quenched alloys. The results obtained by the electrochemical measurement indicate that substituting Ni with Cu improved the cycle stability. When the Cu content increases from 0 to 0.4, the cycle lives of the as-cast and rapidly solidified alloys increased from 72 cycles to 88 cycles and from 100 cycles to 122 cycles, respectively.     

机械合金化制备Mg76-xTi12Ni12Mnx（x=2,4,6,8）合金及其贮氢性能研究

利用机械合金化法制备了Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金,并研究了Mn添加量对合金贮氢性能的影响。结果表明,在Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金中合金相主要由Mg2Ni和Ti2Ni相组成,合金最大贮氢量分别为3.47%、3.32%、3.60%和3.11%(质量分数,下同),合金氢化物的分解热依次为-79.2kJ/mol、-78.0kJ/mol、-73.7kJ/mol和-73.6kJ/mol,添加Mn可降低合金氢化物的稳定性,改善其热力学性能,非晶化不利于提高合金的贮氢性能。     

双辊淬冷法制备稀土镍基贮氢合金及其晶粒尺寸和电化学性能

使用双辊淬冷技术制备了LaNi5基AB5型贮氢合金,用扫描电镜和X射线衍射确定合金的晶粒尺寸,用恒电流充放电方法确定合金的电化学容量及其循环稳定性.结果表明, 制备的合金具有均匀的纳米晶结构;在64mA/g(约0.2C)的电流密度下,合金放电容量高达336mAh/g,而在640mA/g(约2C)的电流密度下,合金放电容量仍达312mAh/g,经400次循环后容量保持约80%.另外,还研究了La含量对合金容量和循环稳定性的影响,合金容量在La 含量<60%范围内,随La含量增加而增加,La含量从60%增至80%,合金容量保持不变, 但是合金循环稳定性随La含量增加而减少.     

正极材料zLi2MnO3·（1-z）LiNi0.4Mn0.4Co0.2O2的合成与性能

富锂锰过渡金属层状正极材料以其成本低、安全、容量高受到广泛关注,X射线衍射（XRD）和电化学性能测试显示以共沉淀结合煅烧成功合成富锂层状正极材料zLi2MnO3.（1-z）LiMn0.4Ni0.4Co0.2O2（z=0.2,0.4,0.6）。其中z=0.4组分的放电容量达到210mAh/g（2-4.8V,0.05C）,远高于z=0.6组分,而经20个充放电循环的稳定性也优于z=0.2组分。微分容量分析表明z=0.2组分中因Ni/（Co＋Mn）比值较大和Li2MnO3含量较少可能导致其容量逐渐衰减。z=0.6则因所含LiMn0.4Ni0.4Co0.2O2量较少,造成其放电容量较低;z=0.4拥有最佳Li2MnO3及LiMn0.4Ni0.4Co0.2O2组合使其容量和循环性能最好。     

铸态La0.75Mg0.25Ni3.3Co0.2Six(x=0～0.2)电极合金的电化学与动力学性能

为了提高La-Mg-Ni系A2B7型贮氢合金的电化学循环稳定性,添加少量的Si,用铸造工艺制备了La0.75 Mg0.25 Ni3.3 Co0.2 Six(x＝0、0.05、0.1、0.15、0.2)贮氮合金,分析并测试了其微观结构和电化学性能,以及高倍率放电能力,交流阻杭等动力学性能.结果表明,合金具有多相结构,主相...     

添加Al对稀土系贮氢电极合金高温性能的影响

系统研究了添加Al的贮氢电极合金在高温下的电化学性能，结果表明：以Al部分替代稀土系贮氢合金中的Ni，使氢化物电极的平衡分解压降低，低高温下的放电容量升高，自放电降低，改善高倍率放电性能和循环稳定性。     

La-Mg-Ni系A5B19超晶格负极材料相结构及电化学性能EI北大核心CSCD

感应熔炼制备La0.8-xCexMg0.2 Ni 3.8(x=0,0.1,0.3,0.5),研究Ce替代部分La对La4MgNi19超晶格负极材料相结构及电化学性能的影响。研究表明,La4MgNi19合金相由LaNi5,(La,Mg)2Ni7,(La,Mg)5Ni19(3R-Ce5Co19)相组成。加入Ce后,(La,Mg)2Ni7相消失,出现2H-Pr 5Co 19结构的(La,Mg)5Ni19相,同时随着Ce替代量的增多,(La,Mg)5Ni19相含量增多,LaNi5相随之减少,Ce加入有利于形成A5B19相,特别是形成2H-Pr5Co19结构。电化学放电容量随着x值的增加呈现先增后减趋势,x=0.1时样品的电化学放电容量380.36 mAh/g最佳。合金电极活化次数、容量保持率和倍率放电性能随着Ce含量增加而增大。H在合金中的扩散速率是影响其倍率放电性能主要因素。     

Lax Cey Prz Nd1-xy-z Ni3.55 Co0.75 Mn0.4 Al0.3储氢合金中稀土元素配比规律的研究

应用均匀试验设计法设计LaxCeyPrzNd1-x-y-zNi3.55Co0.75Mn0.4Al0.3(0＜x,y,z＜1)储氢合金的成分,通过大量的、统一的实验,来研究不同稀土配比的合金与其容量、电压、循环稳定性等电化学性能之间的关系,重点应用模式识别的人工智能方法分析实验数据并建立了相关的模型,结果显示出很好的规律性.     

A microscopic model for the different Tc(x) dependence in REBa2Cu3O6+x HTc-superconductors containing different RE-ions

Replacing Y in YBa₂Cu₃O_6+x by the larger ions Nd or La increases the critical oxygen content for the transition from antiferromagnetic to superconducting behavior from x=0.4 to 0.6. From the analysis of the NQR spectra of the Cu(1) sites at different x follows a change of the interaction in the oxygen pairs connected by a Cu(1) ion from attractive for Y to repulsive for La.     

Zr1-xTix(Ni0.6Mn0.3V 0.1Cr0.05)2(x=0～0.5)Laves相储氢合金的电化学性能

本文研究Zr1-xTix(Ni0.6 Mn0.3V0.1Cr0.05)2(x=0,0.1,0.2,0.3,0.4,0.5)系Lav es相储氢电极合金的气态P-C-T性能、晶体结构及电化学性能.XRD分析表明,Ti合金化使 Zr基储氢合金主相从C15相转变为C14相.当x>0.2时,第二相Zr7Ni10相消失, 并出现TiNi相.Ti合金化使Zr基储氢合金中C15相和C14相的晶格常数线性递减.气态P-C-T 测试表明,Ti合金化从x=0增加至x=0.5时合金的吸放氢平台压力升高约10倍,但降低了储氢合金的最大储氢容量.电化学测试表明,Ti合金化有利于改善Zr基储氢合金的活化性能, 这与Ti在KOH溶液中易于溶解有关,但过高的Ti含量降低了合金电极的循环稳定性.Zr1 -xTix(Ni0.6Mn0.3V0.1Cr0.05)2合金的电化学容量和高倍率放电性能均随合金中Ti含量的增加先上升后下降,这与合金的相结构组成有很大关系 .     

Hydrogen storage properties and phase structures of RMg2Ni (R = La,Ce, Pr,Nd) alloys

RMg₂Ni alloys were prepared by inductive melting where R is rare earth (R = La, Ce, Pr, Nd). X-ray diffraction (XRD) patterns revealed a single-phase composition of RMg₂Ni phase when R was one of the three elements (La, Pr, Nd), and a double-phase composition of CeMg₂Ni and CeMg₃ phases when R was Ce. In the hydriding process, RMg₂Ni phases transformed to rare earth hydrides (R-H) and Mg₂NiH₄ phase, and for CeMg₃ phase, it is decomposed to CeH_2.74 and MgH₂ phases. The enthalpy change of Mg₂Ni phase in RMg₂Ni alloys during the hydriding/dehydriding process was smaller compared with that of pristine Mg₂Ni alloy, which could be attributed to the existence of R-H. The hydrogen storage properties of RMg₂Ni alloys changed with different R compositions in R-H. At 573 K, the NdMg₂Ni alloy had the highest hydrogen storage capacity and dehydriding plateau, and the descending order of hysteresis was PrMg₂Ni < NdMg₂Ni < CeMg₂Ni < LaMg₂Ni, which suggested that the PrMg₂Ni alloy exhibited a better cycling stability and reversibility than the other three alloys. At 523 K, the uptake time of RMg₂Ni alloys to reach 90% of the maximum hydrogen storage capacity was 75 s, 34 s, 65 s and 52 s, respectively, compared with 110 s of pristine Mg₂Ni alloy. Therefore, we believed the R-H in the alloys not only improved their thermodynamic properties but also accelerated their hydriding kinetics.