退火方式对La_(0.75)Mg_(0.25)Ni_(3.44)Co_(0.2)Al_(0.03)Ti_(0.03)合金的电化学性能影响

为了研究不同退火方式对La0.75Mg0.25Ni3.44Co0.2Al0.03Ti0.03铸态合金的电化学性能影响,设计最终退火温度为1223K,并采用不同保温程序对合金进行退火处理。X射线衍射(XRD)与扫描电镜(SEM)分析一段、两段保温法退火后合金的结构与性能结果表明,铸态及退火后合金由LaNi5,(La,Mg)2(Ni,Co,Al)7相以及少量LaNi2、TiNi3相组成,且退火后合金中(La,Mg)(Ni,Co,Al)3相出现。前者微观组织较后者均匀,并且前者的放电容量、放电效率好于后者。一段保温法更有利于改善合金的循环稳定性。     

纳米晶Mg2-xTixNi0.8Cr0.2四元合金的气态储氢性能

纳米晶Mg2-xTixNi0.8Cr0.2(x=0.05,0.10,0.15,0.20)四元合金由纯Mg,Ti,Ni,Cr粉在773 K经4h烧结后机械球磨而成.该合金具有良好的活化性能和吸氢动力学性能.合金在393 K,4.0 MPa氢压条件下,2min内便可以完成总吸氢量的75%(质量分数)以上,Mg1.95Ti0.05Ni0.8C0.2最大吸氢量可达到3.35%.在493 K,0.1 MPa条件下可快速放氢,Mg1.80Ti0.20Ni0.8Cr0.2在18 min内便可完成放氢过程,总放氢量为2.17%.所有合金具有良好的低温吸氢性能,353 K时Mg1.85Ti0.15Ni0.8Cr0.2合金最大吸氢量可达到2.08%.XRD分析结果显示,Ti替代Mg后,合金中主要存在Mg2Ni与Ni两相,另外,还有微量的Mg与TiNi相,TiNi相弥散分布在合金中,对合金的吸放氢性能有一定的催化作用.     

Structure and Electrochemical Hydrogen Storage Properties of as-Milled Mg-Ce-Ni-Al-Based Alloys

At room temperature,crystalline Mg-based alloys,including Mg_2 Ni,MgNi,REMg_(12) and La_2 Mg_(17),have been proved with weak electrochemical hydrogen storage performances.For improving their electrochemical property,the Mg is partially substituted by Ce in Mg-Ni-based alloys and the surface modification treatment is performed by mechanical coating Ni.Mechanical milling is utilized to synthesize the amorphous and nanocrystalline Mg_(1-x)Ce_xNi_(0.9)Al_(0.1)(x=0,0.02,0.04,0.06,0.08)+50 wt%Ni hydrogen storage alloys.The effects made by Ce substitution and mechanical milling on the electrochemical hydrogen storage property and structure have been analyzed.It shows that the as-milled alloys electrochemically absorb and desorb hydrogen well at room temperature.The as-milled alloys,without any activation,can reach their maximal discharge capacities during first cycling.The maximal value of the 30-h-milled alloy depending on Ce content is 578.4 mAh/g,while that of the x=0.08 alloy always grows when prolonging milling duration.The maximal discharge capacity augments from337.4 to 521.2 mAh/g when milling duration grows from 5 to 30 h.The cycle stability grows with increasing Ce content and milling duration.Concretely,the S_(100) value augments from 55 to 82% for the alloy milled for 30 h with Ce content rising from 0 to 0.08 and from 66 to 82% when milling the x=0.08 alloy mechanically from 5 to 30 h.The alloys' electrochemical dynamics parameters were measured as well which have maximum values depending on Ce content and keep growing up with milling duration extending.     

苯溶液中球磨La2Mg16Ni合金的储氢性能

对苯溶液中球磨的La2Mg16Ni合金的储氢性能进行了研究。XRD和SEM分析表明：球磨后合金颗粒粒径减小，且有明显的非晶化趋势；由合金和有机苯溶剂在球磨过程中形成的EDA(electron donor-acceptor)体系极大地提高了合金的活化性能；球磨后的合金即使在低温下也具有良好的吸氢速率；延长球磨时间，可改善合金的吸氢性能。     

La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx贮氢合金的相结构和电化学性能

研究了Mn替代Ni对La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx(x=0,0.3,0.6,0.9)贮氢合金相结构和电化学性能的影响。XRDRietveld全谱拟合分析表明:Mn替代改变了合金的物相组成和物相的丰度。LaNi3相消失,αLa2Ni7相丰度的变化表现为先增加(x=0,0.3)后减少(x=0.6,0.9),LaMgNi4相和La5Ni19相的丰度则随合金中Mn含量x的增加而增加。Mn替代Ni降低了合金的贮氢容量、最大电化学放电容量和活化性能,La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3合金电极表现出最好的电化学循环稳定性,合金的高倍率放电性能随Mn含量的增加降低,这归因于交换电流密度(I0)和氢扩散系数(D)的降低。     

La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0～0.4)贮氢合金的循环稳定性

为了提高La-Mg-Ni系贮氢合金的循环稳定性,以Al部分替代Ni,采铸造及快淬工艺制备了La0.7Mg0.3Ni2.55-xCo0.45Alx(x=0,0.1,0.2,0.3,0.4)电极合金,研究了Al替代量及快淬工艺对合金微观结构及电化学循环稳定性的影响。X射线衍射分析结果表明:铸态及快淬态合金具有多相结构,包括(La,Mg)Ni3相、LaNi5相和一定量的LaNi2相;Al替代使铸态合金中LaNi2相的量显著增加,但对快淬态合金中LaNi2相的相丰度影响不显著。电化学测试结果表明:随Al替代量的增加,合金的循环寿命大幅度提高;快淬处理可以提高合金的循环寿命,但随Al替代量的增加,淬速对循环寿命的影响减小。     

放电等离子烧结技术制备La0．7Mg0．3Ni2．5Cox贮氢合金性能研究

用放电等离子烧结技术（SPS）制备La0．7Mg0．3Ni2．5Cox（x=O．1,0．2,0．3,0．4,0．5）贮氢合金。采用X射线衍射、三电极测试体系和交流阻抗法研究了合金的相结构、贮氢性能和电化学性能。结果表明：合金为多相结构,主相为（La,Mg）2Ni,和（La．Mg）Ni3相;该系列贮氢合金的贮氢容量随x值的增大先增后减,在x=0．4时贮氢容量达1．37％。最大放电容量为365．4mAh／g。合金的活化性能好（活化次数均为1次）,随着x值的增加,贮氢合金的放氢平台压力升高,合金电极表面电荷转移速率增大。     

Mn元素对储氢合金(La_(0.78)Mg_(0.22))(Ni_((0.9-x))Co_(0.1)Mn_x)_(3.5)的结构及电化学性能的影响

感应熔炼法制备了(La_(0.78)Mg_(0.22))(Ni_((0.9-x))Co_(0.1)Mn_x)_(3.5)(x=0.00,0.01,0.03,0.05,0.07)合金,并在氩气气氛下,以1 173 K温度退火处理。XRD相结构分析表明,合金具有多相结构,随着Mn含量的不同分别含有:La_2Ni_7相、LaNi_5相和LaNi_3相。P-C-T性能测试表明,合金在3 MPa压力和298 K温度下的吸氢量高达1.6 wt.%。电化学测试表明,合金放电容量随着Mn含量的增大而减小,由x=0时的394.2 mAh/g下降到x=0.07时的363.3 mAh/g,充放电循环性能是先下降,后上升,再下降。合金的倍率性能随着Mn含量的增加先上升,后下降,然后又上升。当放电电流密度为3 000 mA/g时,高倍率性能由x=0时的201.6 mAh/g变为x=0.07时的182.9 mAh/g。研究表明当x=0.03时合金具有比较好的综合性能。     

Co替代Ni改善纳米晶和非晶Mg2Ni型合金的贮氢动力学

为了改善Mg2Ni型合金的贮氢动力学性能,用Co部分替代合金中的Ni,用快淬技术制备了Mg2Ni1？xCox（x=0,0.1,0.2,0.3,0.4）贮氢合金。用XRD、HRTEM表征了快淬态合金的微观结构,用自动控制的Sieverts设备测试了合金的吸放氢动力学性能,用程控电池测试仪测定了合金薄带的电化学贮氢动力学。结果表明：Co替代Ni提高了Mg2Ni型合金的非晶形成能力,合金的非晶化程度随着Co含量的增加而增加。此外,Co替代Ni显著地改善了合金的贮氢动力学,当Co含量从0增加到0.4时,快淬态（15m/s）合金在5min内的吸氢饱和率从81.2%增加到84.9%,20min的放氢率从17.60%增加到64.79%,氢扩散系数从1.07×10-11cm2/s增加到2.79×10？11cm2/s,极限电流密度从46.7mA/g增加到191.7mA/g。     

La1＋xMg2-xNi9（x=0，0．5，1．0，1．5）合金的储氢性能及电化学性能研究

利用高频熔炼方法制备了La1＋xMg2-xNi9（x=0，0．5，1．0，1．5）系列合金，并对其进行了XRD分析和储氢容量及电化学性能测定。结果表明：随着La含量增大，合金中LaNi5和（La，Mg）Ni3相转变为LaNi3相，且Mg2Ni相出现，晶胞体积也增大，合金的储氢容量和电化学性能提高；当x=1．5时，Mg2Ni相消失，合金的储氢性能有所下降。当x=1．0时，即La2MgNi9合金具有较好的储氢容量及电化学容量。     

Zr在Mg2Ni储氢合金中的作用

采用感应熔炼法制备了Mg2Ni1-xZrx(x=0、0.2、0.4)合金,研究了Zr的添加对Mg系储氢合金储氢性能的影响。对合金的成分和微观组织进行分析,结果表明,Zr较难融入到合金,但是Zr能使得合金晶粒得到细化,且合金中都有Mg2Ni相的形成,有利于吸氢反应的进行。利用PCT测试仪测定了合金的储氢性能,结果表明:添加Zr元素的添加能有效降低Mg2Ni的吸放氢温度,并能有效提高提高合金的吸氢量,最高吸氢量达到4.91wt%。     

含锆镁基储氢合金的合成及其电化学性能

用固相扩散法合成了Mg2-xZrxNi (x=0, 0.2, 0.3, 0.4, 0.5, 0.6)系列合金. XRD结构分析表明 主相仍为Mg2Ni; Zr替代Mg使合金的微晶结构发生了改变, 趋于非晶化; 添加Zr的合金的容量比由扩散法合成的合金的容量有所提高; 合金中添加Zr, 提高了电极的放电容量, 增大了放电平台; 特别是Zr 对六方晶系Mg2Ni合金结构中Mg的部分取代大幅度提高了电极的循环寿命, 未经任何处理的 Mg1.4Zr0.6Ni合金电极经25个循环后, 放电容量仅衰减4.11%, 表明添加Zr对提高合金的循环寿命具有重要的作用.     

Mg67-xCaxNi33 (x=0, 5, 10, 15, 20, at%)合金的物相及储氢性能研究

采用感应熔炼、甩带结合机械球磨法制备了Mg67-xCaxNi33(x=0,5,10,15,20,at%)储氢合金。研究了Ca含量及制备工艺对合金相结构和储氢性能的影响。结果表明,制备工艺(熔炼,熔炼+球磨,熔炼+甩带+球磨)对储氢合金的物相组成影响不大,而含Ca的合金经过甩带后容易形成非晶。不含Ca的Mg67Ni33合金主要由Mg2Ni相组成,并含有少量的Mg相;随着Ca含量升高,合金中的Mg2Ni相逐渐减少,而MgNi2相和Mg2Ca相逐渐增加。当Ca含量增加到20at%时,Mg47Ca20Ni33则主要由MgNi2和Mg2Ca组成,几乎没有Mg2Ni生成。P-C-T测试结果表明,在573K下,Mg67-xCaxNi33合金的最大吸氢量随着合金中Ca含量的升高而降低,这主要是由于Mg2Ni相含量减少造成的。吸氢后的Mg67Ni33主要由Mg2NiH4组成,而含Ca合金吸氢后则主要由Mg2NiH4、CaH2和不吸氢的MgNi2相组成。     

熔盐保护熔炼法制备La_2Mg_(17)合金及其储氢性能

采用熔盐保护熔炼法(SMPMS)成功制备了La2Mg17储氢合金.SEM和EDS研究发现,熔炼时液相在凝固过程中形成微观成分不均匀的非平衡组织.通过PCT性能测试发现,合金在523～623 K时可逆吸放氢量大于4.3%(质量分数, 下同).动力学分析结果表明,合金在473～623 K时具备良好的氢化动力学性能,并且在523 K时出现氢化速率极大值(25 s内吸氢3.2%).丰富的表面裂纹改善了合金的储放氢性能.     

La_(0.7)Mg_(0.3)Ni_(2.8)Co_(0.5-x)Fe_x系列合金的制备及其储氢性能

在制备La-Ni-Co-Fe中间合金的基础上,采用机械合金化方法制备La0.7Mg0.3Ni2.8Co0.5-xFex(x=0,0.1,0.2,0.3,0.4,0.5)系列储氢合金,研究在不同球磨时间下储氢合金的物相、微观形貌和电化学性能及元素置换对其储氢性能的影响。结果表明:La0.7Mg0.3Ni2.8Co0.5合金的主相为LaNi5相,La0.7Mg0.3Ni2.8Co0.5-xFex系列储氢合金球磨40 h和80 h后,主相为LaNi5相和少量LaMg2Ni9相;且随着球磨时间的增加,合金晶粒变细小,La0.7Mg0.3Ni2.8Co0.5合金的最大放电容量呈变大的趋势,从142.4 mA.h/g增加到157.5 mA.h/g,La0.7Mg0.3Ni2.8Co0.2Fe0.3合金的最大放电容量从150.7mA.h/g增加到162.1mA.h/g,合金具有较好的循环稳定性能。     

Hydrogen Storage Thermodynamics and Dynamics of Nd–Mg–NiBased Nd Mg_(12~-)Type Alloys Synthesized by Mechanical Milling

Nanocrystalline and amorphous Nd Mg_(12~-)type Nd Mg_(11)Ni+ x wt% Ni(x=100, 200) hydrogen storage alloys were synthesized by mechanical milling. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The gaseous hydrogen absorption and desorption properties were investigated by Sieverts apparatus and differential scanning calorimeter connected with a H_2 detector. Results show that increasing Ni content significantly improves hydrogen absorption and desorption kinetics of the alloys. Furthermore,varying milling time has an obvious effect on the hydrogen storage properties of the alloys. Hydrogen absorption saturation ratio(R~a_(10); a ratio of the hydrogen absorption capacity in 10 min to the saturated hydrogen absorption capacity) of the alloys obtains the maximum value with varying milling time. Hydrogen desorption ratio(R~d_(20), a ratio of the hydrogen desorption capacity in 20 min to the saturated hydrogen absorption capacity) of the alloys always increases with extending milling time. The improved hydrogen desorption kinetics of the alloys are considered to be ascribed to the decreased hydrogen desorption activation energy caused by increasing Ni content and milling time.     

Gaseous and electrochemical hydrogen storage behaviors of nanocrystalline and amorphous Nd-added Mg_2Ni-type alloys

Melt spinning technology was used to prepare the Mg2Ni-type(Mg24Ni10Cu2)100-xNdx(x = 0, 5, 10, 15,20) alloys in order to obtain a nanocrystalline and amorphous structure.The effects of the spinning rate on the structures and gaseous and electrochemical hydrogen storage behaviors of the alloys were investigated.The analysis of X-ray diffraction(XRD), transmission electron microscope(TEM), and scanning electron microscope(SEM) linked with energy-dispersive spectroscopy(EDS)reveals that all the as-cast alloys hold a multiphase structure, involving the main phase Mg2 Ni and some secondary phases such as Mg6 Ni, Nd5Mg41, and Nd Ni.The as-spun Nd-free alloy displays an entire nanocrystalline structure,whereas the as-spun Nd-added alloys hold a nanocrystalline and amorphous structure, and the amorphization degree visibly increases with the spinning rate increasing.The melt spinning ameliorates the hydrogen storage performances of the alloys dramatically.When the spinning rate rises from 0(the as-cast was defined as the spinning rate of 0 m s-1) to 40 m s-1, the discharge capacity increases from 86.4 to 452.8 m Ah g-1, the S20(the capacity maintain rate at 20 th cycle) value increases from53.2 % to 89.7 %, the hydrogen absorption saturation ratio(Ra5, a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increases from36.9 % to 91.5 %, and the hydrogen desorption ratio(Rd10,a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) increases from16.4 % to 47.7 % for the(x = 10) alloy, respectively.     

退火热处理对Nd0.75Mg0.25(Ni0.8Co0.2)3.5储氢合金结构和性能的影响

采用中频感应熔炼制备Nd0.75Mg0.25(Ni0.8Co0.2)3.5储氢合金,在0.03 MPa氩气氛围进行退火,退火温度分别为850,900和950 ℃,保温时间均为7 h。分别对合金的电化学性能、气态储氢性能和合金的微观结构进行研究。结果表明,合金在退火热处理前后的相组成没有发生明显变化,主相均为Ce2Ni7型(Nd,Mg)2(Ni,Co)7相和CaCu5型NdNi5相。合金中晶粒尺寸随着退火温度的升高而增大,相界面则减少,退火消除晶格应力、增加成分均匀性、增加储氢容量;同时有部分Mg在热处理过程中损失导致储氢容量的下降。900 ℃热处理使得Nd0.75Mg0.25(Ni0.8Co0.2)3.5合金表现出较好的储氢性能,最大电化学放电容量为359 mAh/g,合金电极在100次循环后容量保持率为90.3%,气态储氢容量达到1.65%（质量分数,下同）。     

Mg_(50)Ni_(50-x)Ti_x合金的吸放氢性能

研究了Mg50 Ni50 -xTix 合金的非晶形成能力与非晶合金电极的吸放氢性能。结果表明 :在Mg50 Ni50 -xTix合金中 ,当Ti替代Ni元素的量低于 1 5% (摩尔分数 )时 ,机械合金化能够得到几乎单一的非晶态合金 ;用Ti替代Ni形成的三元非晶合金能降低镁镍合金的平衡氢压 ;少量的Ti替代能改善合金的电化学吸放氢容量 ,使合金电极的吸放氢循环稳定性得到提高。这被认为是在三元合金中钛元素减缓了合金中镁元素的氧化腐蚀进程所致。     

La替代Mg对Mg2Ni型合金电化学贮氢性能的影响

用快淬工艺制备了纳米晶和非晶Mg2Ni型Mg2 -xLaxNi (x=0,0.2,0.4,0.6)贮氢电极合金,获得长度连续,厚度约为30μm,宽度约为25 mm的薄带.用XRD、SEM和HRTEM分析了快淬合金薄带的微观结构,测试了合金薄带的电化学性能及电化学交流阻抗谱(EIS).快淬无La合金具有典型的纳米晶结构,...