Microstructure of alloy MlNi_(3.75)Co_(0.75)Mn_(0.3)Al_(0.2) (Ml—La-rich mischmetal) during electrochemical hydriding-dehydriding process

1　INTRODUCTIONIt s well known that the hydrogen absorptionand desorption cycling in the LaNi5 based AB5 type alloys always induces high isotropic or aniso tropic strains and therefore accelerates the rate ofpulverization, which has been considered as themain reason for the degradation of hydrogen stor age alloys in the electrochemical cycling[1]. There fore, it s necessary to study the properties of thehydrogen cycling induced strains and other strain related microstructu…     

Effects of sputtering conditions on electrochemical behavior and physical properties of Ni-Mo alloy electrode

1 Introduction Many transition metal alloys with binary and ternary compositions have been studied as hydrogen evolution reaction electrodes in water electrolysis[1- 6]. The activity of such metal alloys for the hydrogen evolution reaction depends on at l…     

Microstructure and storage properties of low V-containing Ti–Cr–V hydrogen storage alloys prepared by arc melting and suction casting

The microstructure and hydrogen storage properties of low V content （Ti0.46Cr0.54）100-xVx （x = 2.5-7.1, at%） and （TiyCr1-y）95V5 （y= 0.38-0.54） alloys were investigated. These alloys were prepared by arc melting and copper mould suction casting. The structures of as-cast （Ti0.46Cr0.54）100-xVx （x = 2.5, 5.0, and 7.1） alloy ingots evolve with V contents from pure Laves-（x = 2.5） to dual-phase TiCr2-BCC structures （5.0 and 7.1）, whereas the suction-cast （Ti0.46Cr0.54）100-xVx （x =2.5, 5.0, and 7.1） alloys only contain single BCC phase. The suction-cast alloy rod （Ti0.46Cr0.54）95V5, containing only 5.0 at% V is shown to possess the optimum hydrogen absorption capacity, with the maximum hydrogen content of 3.14 wt%. Furthermore, the hydrogen storage properties of the suction-cast low V alloys （TiyCr1-y）95V5 （y = 0.38-0.54） are sensitive to Ti/Cr ratios and only those alloys with Ti/Cr ratios close to the CN14 cluster [TiTCrs] have good hydrogen storage properties.     

Electrochemical properties of M1Ni_(3.5)Co_(0.6)Mn_(0.4)Al_(0.5)–x wt%Mm_(0.89)Mg_(0.11)Ni_(2.97)Mn_(0.14)Al_(0.20)Co_(0.54)composites

In order to improve the overall electrochemical properties of AB5-type storage alloys, the new type composite alloys M1Ni3.5Co0.6Mn0.4Al0.5–x wt% Mm0.89-Mg0.11-Ni2.97Mn0.14Al0.20Co0.54(x = 0, 5, 10; M1 means mischmetal) were prepared by means of ball milling. The composite alloys are shown to be single La Ni5 phase by X-ray diffraction(XRD) patterns. The maximum discharge capacity slightly increases from 315 m Ah g-1for M1Ni3.5Co0.6Mn0.4Al0.5to 324 m Ah g-1(x = 5) and325 m Ah g-1(x = 10). The addition of AB3-type La–Mg–Ni-based alloy has a positive effect on the cycle stability.With the addition of Mm0.89Mg0.11Ni2.97Mn0.14-Al0.20Co0.54 alloy, the exchange current density(I0), the limiting current density(IL), and the diffusion coefficient of hydrogen(D) of the alloy electrodes increase, leading to a corresponding improvement of the high rate dischargeability.     

Hydrogen storage properties of V＋TiFe0.85Mn0.15 multi—phase alloys made by mechanical alloying

The mechanical alloying technique was used to make multi-phase alloys V TiFe0.85Mn0.15.Their hydrogen storage properties were characterized and compared with that of the polycrystalline alloys made by casting.It was found that the ball milled alloys can absorb hydrogen at room temperature in the first cycle without prior activation.The 40% V 60% TiFe0.85Mn0.15 alloy made by mechanical alloying shows the best hydrogen storage property with the valid hydrogen capacity up 50 220mL/g at 293K and 4.0MPa, and the P-C-T behavior is also improved.The XRD and EDX analyses also show that the phase of these alloys contains.V,TiFe,γ-TiMnx,TiFe2 and α-FeV.The composition of these phases affects significantly the hydrogen storage properties of alloys.     

MICROSTRUCTURE AND ELECTROCHEMICAL CHARACTERISTICS OF Zr_(0.9)Ti_(0.1)(Ni_(1.1)Mn_(0.7)V_(0.2))_x METAL HYDRIDE ELECTRODE

The crystal structure, the phase composition and the electrochemical characteristics of Zr0.9Ti0.1(Ni1.1Mn0.7V0.2)x (x=0.90, 0.95, 1.00, 1.05) alloys were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that all alloys are multiphase with C15 Laves phase as a main phase along with C14 phase and some secondary phases. And the amounts of the C14 phase and secondary phases in the four alloys increases with decreasing x. The results indicated that the various stoichiometric ratios have great effects on the electrochemical characteristics such as the maximum discharge capacity, discharge rate capability and self-discharge properties etc. for Zr0.9Ti0.1(Ni1.1Mn0.7 V0.2)X (x=0.90, 0.95, 1.00, 1.05) alloys. The hyper-stoichiometric Zr0.9 Ti0.1(N1.1Mn0.7 V0.20)1.05 exhibits the maximum discharge capacity of 332mAh-g-1. The C14 phase and secondary phases seems to improve discharge rate capability of the alloys.     

Electrochemical properties of CeMg_(11)Ni+x% Ni composites (x=0,50, 100 and 200) prepared by ball-milling

1　INTRODUCTIONMagnesium and magnesium based alloys arepromising hydrogen storage materials because oftheir absorbability of hydrogen in large quantities,low specific gravity, rich mineral resources, lowmaterial cost and so on. Nevertheless, their hy drides are too stable to be used at room tempera ture[1]. It seems impossible for application of crys talline Mg based alloys in nickel hydrogen batter ies.It is well known that amorphous alloys havemany advanta…     

Corrosion of New Zirconium Claddings in 500 ℃/10.3 MPa Steam: Effects of Alloying and Metallography

With the aim of improving corrosion resistance of rod cladding for in-service and accident conditions, six new zirconium alloys(named N1–N6) have been designed.The contents of Sn and Nb were optimized for better behavior at high-temperature pressurized water, and Fe, Cr, V, Cu or Mo elements were added to the alloys to adjust the corrosion behavior.The current work focused on the rapid corrosion behavior in 500 ℃/10.3 MPa steam for up to 1960 h, aiming to test the corrosion resistance at high temperature.The structure of matrix and properties of second-phase particles(SPPs) were characterized to find the main differences among these alloys.All the six alloys exhibited better corrosion resistance than N36, and N1 was shown to have the best performance.A careful analysis of the corrosion kinetics curves revealed that Cr was beneficial for severe condition.Elements Fe, Cr, V, Cu or Mo aggregated into SPPs with different concentrations and structures.This was demonstrated to be the main reason for different corrosion resistance.Due to good processing control, all alloys had a uniform structure and a uniform distribution of SPPs.As for N4, N6 and N36, the existing of large-size SPPs(450 nm) might be a contributing factor of the relatively poor corrosion resistance.     

Influence of Cr or Co doping on electrode properties of V2.1TiNi0.5Hf0.05 hydrogen storage alloy

The microstructures and electrode properties of Cr or Co-doped V2.1 TiNi0.5 Hf0.05 M0.113 （M = Cr, Co） hydrogen storage alloys were investigated. It is found that all alloys consist of a main phase of V-based solid solution with b. c. c. structure and a secondary phase of C14-type Laves phase with a three-dimensional network structure. After the doping of Cr or Co into V2.1 TiNi0.5 Hf0.05, the abundance and unit cell volume of the main phase decrease, and those of the secondary phase increase. The electrochemical measurements show that the discharge capacities of Cr-doped V2. 1 TiNi0. 5 Hf0. 05 Cr0. 113 alloy and Co-doped V2. 1 TiNi0. 5 Hf0.05 Co0. 113 alloy are less than that of V2. 1 TiNi0. 5- Hf0.05 alloy, but their cycle stability and high-rate dischargeability are improved markedly. The results show that Cr or Co doping into V2. 1 TiNi0.5 Hf0.05 alloy is significantly beneficial for the cycling stability.     

Densities of molten Ni-（Cr,Co, W） superalloys

In order to obtain more accurate density for molten Ni-（Cr, Co, W） binary alloy, the densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys were measured with a sessile drop method. It is found that the measured densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys decrease with increasing temperature in the experimental temperature range. The density of alloys increases with increasing W and Co concentrations while it decreases with increasing Cr concentration in the alloy at 1 773-1 873 K. The molar volume of Ni-based alloys increases with increasing W concentration while it decreases with increasing Co concentration. The effect of Cr concentration on the molar volume of the alloy is little in the studied concentration range. The accommodation among atomic species was analyzed. The deviation of molar volume from ideal mixing shows an ideal mixing of Ni-（Cr, Co, W） binary alloys.     

MAGNETIC PROPERTIES AND CRYSTALLIZATION OF AMORPHOUS ALLOYS Co_(90-x)Cr_xZr_(10)

Curie temperature of amorphous alloys Co_(90-x)Cr_x Zr_(10) decreases linearly with increas-ing x.Average magnetic moment per magnetic atom Co or Cr is 1.51 μB or -3.62 μBrespectively.The temperature dependence of spontaneous magnetization at low temper-atures is in agreement with Bloch's T~(3/2) law.The spin wave stiffness constant decreaseswith increasing x from 4 to 20.The range of interaction is 2—3 atoms for x=4 andnearest neighbour atom for x=20.The crystallization temperature increases mono-tonically with increasing x.It may relate to the average number of outer electrons peratom.The crystalline phase components of heat-treated alloys were analyzed by X-raydiffration and thermomagnetic measurement.     

The electrochemical hydrogen storage characteristics of as-spun nanocrystalline and amorphous Mg_(20)Ni_(10-x)M_x(M=Cu,Co, Mn;x=0–4) alloys

In this paper, we comprehensively investigate the influences of M(M=Cu, Co, Mn) substitution for Ni on the structures and electrochemical hydrogen storage characteristics of the nanocrystalline and amorphous Mg20Ni10-xMx(M=Cu, Co, Mn; x = 0–4) alloys prepared by melt spinning. The as-spun(M=None, Cu) alloys display an entire nanocrystalline structure, whereas the as-spun(M=Co, Mn) alloys hold a mixed structure of both nanocrystalline and amorphous when x = 4(M content). These results indicate that the substitution of M(M=Co, Mn) for Ni facilitates the glass formation in Mg2Ni-type alloy. All the as-spun alloys have the Mg2 Ni major phase, but M(M=Co, Mn) substitution brings on some secondary phases,such as Mg Co2, Mg phases for M=Co, and Mn Ni, Mg phases for M=Mn. The substitution of M(M=Cu, Co, Mn)for Ni also makes a positive contribution to the cycle stability of the alloys in the following orders:(M=Cu) [(M=Co) [(M=Mn) for x = 1 and(M=Co) [(M=Mn)[(M=Cu) for x = 2–4. Meanwhile, it notably enhances the discharge capacity of the alloys in the sequence of(M=Co) [(M=Mn) [(M=Cu). As for the high rate discharge ability, it visibly upgrades with the growing of M content for(M=Cu, Co), while it grows at first and then declines for(M=Mn).     

Theoretical analysis of β-LaNi5Hx（5≤x≤8）： structure and energetics

The calculations of total energy, band structure, and electronic density of states and Mulliken population analysis of β-LaNi5Hx（5≤x≤8） were performed by adopting the method of total energy based on the density functional theory. The augmented plane wave function was selected as the basis set in combination with ultra-soft pseudo-potential technology. The influence of the amount of H absorbed in alloys was discussed in terms of geometry, electronic structure and thermodynamic derived from calculated results. The results show that the amount of H absorbed and the preferred site occupation of the absorbed hydrogen atoms were controlled by the position of H- bands and the energy gap between H-bands and conduction bands. The β-phase hydrides of LaNi5 are most stable when hydrogen atom capacity coating in the range of 6 ～ 7.     

DEGRADATION BEHAVIORS OF NEW TYPE TiV-BASED HYDROGEN STORAGE ELECTRODE ALLOYS

The degradation behaviors of the TiV-based multiphase hydrogen storage alloy Ti0.8,Zr0.2V3.2Mn0.64 Cr0.96Ni1.2 during electrochemical cycling in alkaline electrolyte have been studied by XRD, SEM, EIS and AES measurements. XRD analysis indicates that the alloy consists of a C14-type Laves phase and a V-based solid solution. The lattice parameters of both phases are increased after discharged with cycling, which indicates that more irreversible hydrogen remains not discharged in the alloy. It should be responsible for the decrease of discharge capacity. SEM micrographs show that after 10 electrochemical cycles, a large number of cracks can be observed in the alloy, existing mainly in the V-based solid solution phase. Moreover, after 30 cycles, the alloy particles are obviously pulverized due to the larger expansion and shrinkage of cell volumes during hydrogen absorption and desorption, which induces the fast degradation of the TiV-based hydrogen storage alloys. EIS and AES measurements indicate that some passive oxide film has been formed on the surface of alloy electrode, which has higher charge-transfer resistance, lower hydrogen diffusivity, and less electro-catalytic activity. Therefore it can be concluded that the pulverization and oxidation of the alloy are the main factors responsible for the fast degradation of the TiV-based hydrogen storage alloys.     

ELECTRON RADIATION INDUCED VOID SWELLING AND GRAIN BOUNDARY SEGREGATION IN AN Fe-Cr-Mn AUSTENITIC ALLOY

The behavior of void swelling and segregation in Fe-15Cr-xMn alloys and an alloy con-taining small amount of W and V was investigated by electron-irradiation.The compositionalanalysis in the irradiated regions including grain boundaries was performed.The resultdts showthat there are many common features of irradiuation tehavior in the Fe-Cr-Mn andFe-Cr-Ni systems while there are some significant differences,In the Fe-Cr-Mn alloy sys-tems void swelling was rematrkably suppressed and at the same time the radiation-inducedsegregation was also retarded,furthermore,the segregation was strongly retarded in anFe-15Cr-15Mn alloy containing small amount of W and V.The results also show that Ni re-placed by Mn does not in general confer immunity from either swelling or phase instabilities.The phase instability is due to the different diffusion behavior of Ni and Mn in reponse to theoperation of the inverse-Kirkendall effecr.Fe segregates to the microstructural sinks in theFe-Cr-Mn alloys.The segregation of Fe often leads to the formation of ferrite.This fact isbeneficial to reducing the swelling rate and segregation on the grain boundaries.     

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…     

Effect of stoichiometric ratio upon electrochemical properties of AB5-type alloys

In order to evaluate the effect of stoichiometric ratio upon electrochemical properties of AB5-type hydrogen storage alloys, a series of alloys Mm0.8La0.2（Ni4.0Mn0.2Al0.3Co0.37Fe0.13）a （a=0.90-1.08） were prepared and the electrochemical properties were tested. Mm0.8La0.2Ni4.0Mn0.2Al0.3Co0.37Fe0.13 was one of some new low cobalt AB5-type hydrogen storage alloys which had been researched to have good electrochemical properties. The results show that the stoichiometric ratio has great effects on the electrochemical properties of alloys. And the effects were investigated in detail. When stoichiometric ratio x〈5.3, the activation performances of alloys are all good. But when stoichiometric ratio x〉5.3, the activation performances are decreased evidently. When stoichiometric ratio x〈5.3, the discharge capacities of alloys are linearly increased with the increase of stoichiometric rati0. When stoichiometric ratio x〉5.3, the discharge capacities of hydrogen storage alloys decrease linearly rapidly by the raise of stoichiometric rati0. Overstoichiometry is good to the cycle lives of alloys. When stoichiometric ratio is between 4.8 and 5.4, voltage platforms of alloys tend to increase linearly with the increasing ofx. When x〉5.4, the increase of stoichiometric ratio leads to the decrease of voltage platform of alloys.     

Effects of Mn Content on Mechanical Properties of FeCoCrNiMn_x (0≤x≤0.3) High-Entropy Alloys: A First-Principles Study

Effects of Mn content on mechanical properties of FeCoCrNiMn_x(0 ≤x≤0.3) high-entropy alloys(HEAs) are investigated via first-prmciples calculations combining EMTO-CPA method.Related physical parameters,including lattice constant.elastic constants,elastic modulus,Pugh's ratio,anisotropy factors,Poisson's ratio,Cauchy pressure,Vickers hardness,yield strength,and energy factor,are calculated as a function of Mn content.The results show that the resistances to bulk,elastic,and shear deformation decrease with increasing Mn content.Pugh's ratio B/G indicates that the ductility of FeCoCrNiMn_x HEAs has a remarkable reduction between 22 and 24% of Mn content.Meanwhile,Cauchy pressure suggests that the atomic bonding transforms from metallic to directional characteristic from 22 to 24% of Mn content.Vickers hardness and yield strength of FeCoCrNiMn HEA are intrinsically larger than those of FeCoCrNi HEA.Dislocation nucleation easily occurs in FeCoCrNiMn HE A compared to FeCoCrNi HEA,and large dislocation width in FeCoCrNiMnO_2 HE A results in low stacking-fault energy,which easily induces twinning deformation.This work provides a valuable msieht for further theoretical and experimental study on the mechanical properties of FeCoCrNiMn_x(0≤x≤0.3) HEAs.     

Performance of hydrogen storage of carbon nanotubes decorated with palladium

Carbon nanotubes(CNTs) decorated with palladium were synthesized and applied to hydrogen storage of gas phase. The results show that the amount of hydrogen storage of the decorated CNTs is up to 3.9 % (mass fraction), of which, almost 85％ H2 can be desorbed at ambient temperature and pressure, while the non-decorated CNTs has a poor performance of hydrogen storage(only about 0.5% H2, mass fraction). These indicate that it is feasible to enhance the performance of hydrogen storage of CNTs by further decoration with hydrogen-storing metals or alloys.     

A new high strength and high tolerance-resistance A1-Li alloy

In order to develop a new high strength and high tolerance-resistance Al-Li alloy which can be used in aerospace industry, the effects ofmicroalloying elements such as Mg, Ag, Mn and Zn on the mechanical properties of Al-Cu-Li alloys were studied. The results show that the strengthening effects of Mg＋Ag and Mg＋Zn additions are higher than those of the individual Mg, Ag or Zn addition. The element Mn can also bring some extent strengthening effects on the alloys, but it has nothing to do with the other microalloying elements present or not. Finally, a new Al-Li alloy with Mg＋Zn＋Mn additions was developed, which possesses high strength and high tolerance-resistance promising properties for aerospace applications.