PREPARATION AND PROPERTIES OF HYDROGEN STORAGE MATERIAL TiFe WITH AMORPHOUS Si COATING

An evident improvement on activation properties of hydrogen storage was made by sput-tering an amorphous coating of commercial Si on TiFe alloy.SEM observation revealedan obvious difference between the morphologies before and after hydrogen storage forTiFe alloy with or without amorphous Si coating.It is believed that this may be quitea developable hydrogen storage material.     

Mechanical properties and microstructure of Fe3Al intermetallics fabricated by mechanical alloying and spark plasma sintering

Fabrication technology and mechanical properties of the Fe3Al based alloys were studied by spark plasma sintering from elemental powders （Fe-30Al, volume fraction, %） and mechanically alloying powders. The mechanically alloying powders were processed by the high-energy ball milling the elemental mixture powders with the milling time of 5, 8 and 10 min, respectively. The spark plasma sintering process was performed under the pressure of 50 MPa at 1 050 ℃ for 5 min. The phase identification by X-ray diffraction presents the Fe reacts with Al completely during the processing time. The samples are nearly full density （e.g. the relative density of sinter of raw powder is 99%）. The microstructure was observed by TEM. The mechanical properties were tested by three-point bending at room temperature in air. The results show that the mechanical properties are better （e.g. bend strength of 1 500 MPa ） than those of the ordinary Fe3Al casting.     

Effect of Al content on the phase structure and the hydrogenation characteristic of La(Mg_(1-x)Al_x) alloys

1. Introduction Hydrogen-absorbing materials like sodium alanates, advanced BCC alloys, and Mg-based al- loys have been widely investigated [1]. Mg-based alloys are attractive as potential hydrogen storage materials because of their high storage capacity and low cost [2-3]. The hydrogen desorption kinetics has been improved using various methods [4-6], espe- cially alloying. It was reported that the kinetics of hydriding and dehydriding of Mg-based alloys can be improved by alloying with rar…     

Effects of Al partial substitution for Ni on properties of LaNi5-xAlx

The hydrogen storage properties of four LaNi5-xAlx （x=0.25, 0.50, 0.75, 1.00） pseudobinary alloys were systematically studied. The characteristics of microstructure before and after hydrogenation, activation, kinetics and thermodynamics properties, as well the anti-combustibility properties of the four pseudobinary alloys were investigated. The results reveal that the alloys have excellent activation properties and kinetics properties. X-ray diffraction analysis of crystal lattice of the alloys show that the crystal structures of alloys do not change with the addition of AI in the range of 0≤x≤ 1, but the lattice constants slightly increase. It is found by measuring thermodynamic properties of the alloy-H2 systems that with increasing x value the equilibrium pressure, hydrogen-absorbing ability and hysteresis decrease, whereas the absolute value of the enthalpy increases. It is also found that the hydrogen absorbing velocity of the alloys decreases with increasing x value.     

Microstructure and mechanical properties of Mg-Zn-Gd-based alloys strengthened with quasicrystal and Laves phase

One kind of Mg3.5Zn0.6Gd-based alloy strengthened with quasicrystals was designed, and the effect of alloying elements on microstructure and mechanical properties of as-cast Mg-Zn-Gd alloy at room temperature and elevated temperatures were studied. The results indicate that MgZnCu Laves phase, which coexists with quasicrystal at grain boundary, emerges with the addition of copper element in Mg-Zn-Gd alloy. The strength of alloys exhibits the parabola curve with the increase of copper content. The alloy with 1.5% （mole fraction） Cu shows better mechanical properties at room temperature： tensile strength 176 MPa, yield strength 176 MPa and elongation 6.5%. The existence of MgZnCu Laves phase can effectively improve the heat resistance and elevated temperature properties of the alloy. The alloy with 1.5% Cu has better mechanical properties at 200℃ ： tensile strength 130 MPa and elongation 18.5%. The creep test of the alloys at 200℃ and 50 MPa for 102 h indicates that Mg3.5Zn0.6Gd alloy reinforced with quasicrystal has better creep properties than AE42, which can be further improved with the introduction of Laves phase in the alloy.     

Characteristics of mechanical alloyed Ni-Al powder for sintering

Mechanical alloying was employed to obtain high-activity Ni-AI powder. The effects of mechanical alloying on the microstructure and characteristics of milled powder with a normal composition of Ni-22.89 at.% AI-0.5 at.% B were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results show that a solution Ni （AI） was obtained after milling. During mechanical alloying, the milled powder obtains extra surface energy and crystalline energy because the crystallite size becomes free and the lattice strain increases with the milling time prolonging. Furthermore, about 0.5 mol% oxide in the particles were formed after milling, and this kind of dis- persed oxide is effective to improve the properties of the sintered alloy by dispersion strengthening. It is confirmed that Ni3AI alloy with outstanding properties has been prepared with mechanical alloyed powders.     

Hydrogen storage thermodynamics and dynamics of La-Mg-Ni-based LaMg_(12)-type alloys synthesized by mechanical milling

Nanocrystalline/amorphous LaMg_(12)-type alloyNi composites with a nominal composition of LaMg_(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C_(100)~a) and hydrogen absorption saturation ratio(R_(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R_(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R_(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.     

Effects of Cu addition on microstructure and mechanical properties of as-cast Mg-6Zn magnesium alloy

The application of Mg-Zn binary alloys is restricted due to their developed dendritic microstructure and poor mechanical properties. In this study, an alloying method was used to improve the mechanical properties of Mg-Zn alloy. The Mg-6Zn magnesium alloys microalloyed with varying Cu content(0, 0.8, 1.5, 2.0 and 2.5wt.%) were fabricated by permanent mould casting, and the effects of Cu content on the microstructure and mechanical properties of as-cast Mg-6Zn alloys were studied using OM, SEM, XRD and tensile tests at room temperature. The obtained results show that the addition of Cu not only can refine the grains effectively, but also can modify the eutectic morphology and improve the mechanical properties of the alloys. The main phases of the studied alloys include α-Mg, MgZn_2, Mg_2Cu and CuMgZn. When the content of Cu exceeds 0.8wt.%, Mg_2Cu phase appears. Meanwhile, the eutectic morphology is modified into dendritic shape or lamellar structure, which has an adverse effect on the tensile properties. Furthermore, among the investigated alloys, the alloy containing 0.8% Cu shows an optimalultimate tensile strength of 196 MPa, while the alloy with 1.5wt.% Cu obtains an excellent elongation of 7.22%. The experimental alloys under different Cu contents show distinguishing fracture behaviors: the fracture of the alloy with 0.8wt.% Cu reveals a mixed mode of inter-granular and quasi-cleavage, while in other investigated alloys, the fracture behaviors are dominated by cleavage fracture.     

Microstructure and mechanical properties of hypereutectic Al-Fe alloys prepared by semi-solid formation

The effects of alloying elements, electromagnetic stirring, reheating and semi-solid formation on the microstructure and mechanical properties of Al-Fe alloys prepared by semi-solid formation were studied. It was found that alloying elements and electromagnetic stirring can alter the morphology and growth mode of the iron-rich phase in Al-Fe alloys; and effectively refine the primary Al3Fe phase. In contrast to the microstructure obtained in conventional casting, the Al3Fe phase becomes thin short rod-like instead of thick needle-like; and the dendritic grain structure almost disappears in the semi-solid formation. The Al3Fe phase can be further refined through being dissolved or fused during subsequent reheating. It was also found that the larger extrusion ratio of semi-solid formation causes a greater crushing effect and therefore the Al3Fe phase is more refined and has more uniform distribution. Moreover, Al-Fe alloys prepared by semi-solid formation exhibit excellent mechanical properties at both room and high temperatures.     

Effects of V and Zr Additions on Microstructures and Mechanical Properties of Nb-Ti-Al-Base Alloys

Microstructures and mechanical properties of Nb-32Ti-7Al alloys containing different V and Zr contents were investigated. The microstructures were characterized using optical microscopy and scanning electron microscopy (SEM). The alloy with V and Zr presents single phase Nb solid solution (Nbss). Tensile testing was carried out at room temperature and 1373 K. The results show that these alloys have good ductility at room temperature. The strengths at room and high temperature increase with the addition of V...     

V＋TiFe0．85Mn0．15复相合金的储氢特性

研究了(100—x)％V x％ TiFe0．85Mn0．15(x＝50，60，70)(质量分数，下同)合金的储氢特性。讨论了添加TiFe0．85Mn0．15对钒基合金活化、吸放氢性能与组织结构的影响。研究表明，所有试验合金无需活化处理即可吸氢。在室温和4．0MPa下，40％V 60％TiFe0．85Mn0．15合金的有效氢容量达到207ml／g。     

Hydrogen storage properties of Mg-doped Ti_(1.2)Fe alloys synthesized by mechanical alloying

1　INTRODUCTIONHydrogenstoragematerials ,usedinhydrogensourcesystemsforfuelcellshavebeeninvestigatedduetotheirhighvolumetricdensity ,safety ,easyminiaturizationandconvenientoperation .Consider ingallkindsofhydrogenalloysasawhole ,AB typeTiFealloysareknowntobemuchmoresuitableforusingin portableormobilePEMFCbecauseofitshighreversiblehydrogenstoragecapacity ,whichismuchhigherthanthatofAB5 typealloys.Ontheotherhand ,theactivationpropertiesoftheTiFeal loysare poor .Forexample ,typically ,…     

V对贮氢合金微观结构和电化学性能的影响

为了开发AB5型稀土系低Co贮氢合金，研究了加V低Co贮氢合金M／Ni3．55Co0.3Mn0.4Al0．25Cu0．15Fe0.1Cr0.1Zn0.13Vx（x=0．02，0．05，0．08）V含量变化对放电容量、循环稳定性的影响机理。结果表明，加V低钴贮氢合金可以获得良好的综合电化学性能，但V的加入应严格控制。在本研究范围内，x=0．02的加V低钴贮氢合金具有最佳的综合电化学性能。     

Hydrogen storage properties of TiMn2-based alloys

Several TiMn₂-based C14 Laves phase alloys were prepared and their hydrogen storage properties studied in order to develop suitable materials for hydrogen storage tank or hydride heat pump applications. It was observed that the plateau characteristic of the stoichiometric alloy AB, was better than that of the non-stoichiometric one. The plateau pressure was effectively decreased by the partial substitution of Zr for Ti, while the slope was increased. The substitution effects of other transition elements, such as Cr, V, Cu, Fe, Ni for Mn, were also examined. It was found that Cr was suitable for decreasing the hysteresis, Cu could flatten the plateau with decreasing storage capacity, and V could effectively lower the plateau pressure without decreasing the storage capacity. The hydriding properties were found to be related to the lattice structures. Considering a careful balance of the substitution effects of the alloying elements, it was found that Ti_0.85Zr_0.15MnCr_0.8V_0.1Cu_0.1 alloy had very good plateau characteristics with considerably small hysteresis and high storage capacity.     

Mg2Ni型合金与AB5型稀土储氢合金纳米复合对电极性能的影响

对由两步法 (由机械合金化和烧结两个步骤组成 )制备的Mg2 Ni型储氢合金进行高能球磨处理 ,然后对球磨后的Mg2 Ni合金粉进行化学镀及与AB5型合金进行复合等处理。利用X射线衍射 (XRD)、扫描电镜(SEM)分析了经过处理的材料的微观结构 ,并用模拟电池法测定了该材料的电极性能 ,并讨论了化学镀和与AB5型储氢合金复合等因素对Mg2 Ni合金电极特性的影响     

机械合金化制备Mg-Ni基贮氢合金研究进展

本文在简要介绍机械合金化概念的基础上,综述了国内外采用机械合金化方法制备Mg-Ni基贮氢合金,特别是在多元合金化、复合贮氢合金、表面改性等方面的发展,并讨论了今后的发展方向.     

Ti-Cr基合金的储氢性能及晶体结构

研究了Ti1＋xCr1.2Mn0.8（x=0．0,0．1,0．2,0．3）系和Ti1＋xCr1.2Mn0.8-6My（M=Fe,Ni,Cu,V,VFe;x=0．0,0．1;y=0．1,0．3）系AB2型合金的储氢性能和晶体结构．XRD结果表明,合金主相为C14（MgZn2）型Laves相,可以保证较高的吸、放氢量．通过A侧过化学计量以及B侧用Fe,Ni,Cu,V,VFe分别替代部分Mn,增加了点阵常数和晶胞体积,降低了P—C—T曲线的滞后．由相应数据寻找出适合于金属氢化物氢压缩机的高压端储氢合金．结果表明,合金TiCr1．2Mn0．5Fe0．3与Ti1.1Cr1.2Mn0.5Cu0.3具有良好的储氢性能和压缩特性,可以作为性能优良的高压端储氢合金．     

镁基贮氢合金的制备

综述了镁基贮氢合金制备方法的研究进展，对熔炼法、机械合金化法、扩散法、氢化燃烧法、表面处理等几种主要制备镁基贮氢合金的方法的制备过程、影响因素、特点、优缺点等作了阐述，并论述了目前国内外采用不同制备方法所制得的部分镁基贮氢合金的充放氢性能和电化学性能。     

Ti基贮氢合金Ti0．3Zr0．225V0．25Mn0．3-xNi0．45＋x（x=0-0．25）的显微组织及电化学性能

为了改善Ti基贮氢合金的电化学性能，采用XRD，SEM及EDS分析了Ti0．3Zr0．225V0．25Mn0．3-xNi0．45＋x（x=，0．05，0．10，0．15，0．20，0．25）贮氢合金的相结构及相成分，并研究了合金的电化学性能。结果表明，合金均由六方结构的C14型Laves主相和立方结构的C15型Laves第二相构成；随着Ni替代量x的增大，合金的活化性能降低，而循环稳定性得到一定程度的改善。当Ni替代量x=0．05时，合金的放电容量达到最大，为426mAh／g，显示出很大的应用潜力.     

Si元素对Ti基储氢合金电化学性能的影响

为了改善Ti基储氢合金的电化学性能，采用Si元素部分替代Mn元素的方法，分析研究了Ti基储氢合金Ti03Zr0．225V0.25Mn0．25-xNi0.5Six的相结构及电化学性能。结果表明，合金均由六方结构的C14型Laves主相和立方结构的TiNi第二相构成；随着Si元素替代量x的增大，合金的活化性能降低，而循环稳定性得到很大程度的改善。