FeGa／BTO／FeGa层状复合结构中的磁电效应

采用区域熔炼法制备了FeGa磁致伸缩材料并测量了其磁致伸缩性能。利用该材料制备了FeGa/BTO／FeGa层状复合结构，并对该样品的磁电性能进行了系统研究。结果表明．该材料在共振频率95kHz下．磁电性能高于低频下性能7～10倍。磁电电压随直流偏磁场的变化发生明显变化，出现5．97×10^1A／m的优化偏置场，这主要是由FeGa层的压磁系数q随偏磁场的变化所致。3层复合材料的磁电系数与交流驱动场变化呈线性关系。另外，较薄的BTO压电层可以提高压应力，从而获得较高的磁电性能。

Effects of La substitution on microstructure and hydrogen storage properties of Ti−Fe−Mn-based alloy prepared through melt spinning

The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermodynamics of TiFe-type Ti−Fe−Mn-based alloy were investigated.The as-spun alloys hold the TiFe single phase,which transforms to TiFeH_(0.06),TiFeH,and TiFeH_(2) hydrides after hydrogenation.La substitution promotes the formation of micro-defects(such as dislocations and grain boundaries)in the alloys,thus facilitating hydrogen diffusion.In addition,the hydrogen storage kinetics properties are improved after introducing La element.With the rise of La content,the hydrogen storage capacity decreases firstly and then increases,but the absolute value of hydriding enthalpy change(|ΔH|)increases firstly and then reduces.When x=0.01,the maximum value of|ΔH|is obtained to be(25.23±0.50)kJ/mol for hydriding,and the alloy has the maximum hydrogen absorption capacity of(1.80±0.04)wt.%under the conditions of 323 K and 3 MPa.

Electrochemical hydrogen storage performance of as-cast and as-spun RE-Mg-Ni-Co-Al-based alloys applied to Ni/MH battery

The La-Mg-Ni-Co-Al-based AB2-type La0.8-xCe0.2YxMgNi3.4Co0.4Al0.1(x=0,0.05,0.1,0.15,0.2)alloys were prepared via melt spinning.The analyses of the X-ray diffraction(XRD)and scanning electron microscopy(SEM)proved that the experimental alloys contain the main phase LaMgNi4 and the second phase LaNi5.Increasing Y content and spinning rate lead to grain refinement and obvious change of the phase abundance without changing phase composition.Y substitution for La and melt spinning make the life-span of the alloys improved remarkably,which is attributed to the improvement of anti-oxidation,anti-pulverization and anti-corrosion abilities.In addition,the discharge capacity visibly decreases with increasing the Y content,while it firstly increases and then decreases with increasing spinning rate.The electrochemical kinetics increases to the optimum performance and then reduces with increasing spinning rate.Moreover,all the alloys achieve to the highest discharge capacities just at the initial cycle without activation.

Hydrogen storage behavior of nanocrystalline and amorphous La-Mg-Ni-based LaMg_(12)-type alloys synthesized by mechanical milling

Nanocrystalline and amorphous LaMg11Ni+x%Ni(x=100,200,mass fraction)alloys were synthesized by mechanicalmilling.The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system.The gaseous hydrogen absorption and desorption properties were investigated by Sievert’s apparatus and differential scanningcalorimeter(DSC)connected with a H2detector.The results indicated that increasing Ni content significantly improves the gaseousand electrochemical hydrogen storage performances of the as-milled alloys.The gaseous hydrogen absorption capacities andabsorption rates of the as-milled alloys have the maximum values with the variation of the milling time.But the hydrogen desorptionkinetics of the alloys always increases with the extending of milling time.In addition,the electrochemical discharge capacity andhigh rate discharge(HRD)ability of the as-milled alloys both increase first and then decrease with milling time prolonging.

Effects of spinning rate on structures and electrochemical hydrogen storage performances of RE-Mg-Ni-Mn-based AB_2-type alloys

La was partially substituted by Ce with the aim of improving the electrochemical hydrogen storage performances ofLa1–xCexMgNi3.5Mn0.5 (x=0, 0.1, 0.2, 0.3, 0.4) alloys, and melt spinning technology was adopted to fabricate the alloys. Theidentification of XRD and SEM reveals that the experimental alloys consist of a major phase LaMgNi4 and a secondary phase LaNi5.The growth of spinning rate results in that the lattice constants and cell volume increase and the grains are markedly refined. Theelectrochemical measurement shows that the as-cast and spun alloys can obtain the maximum discharge capacities just at the firstcycle without any activation needed. With the increase of spinning rate, the discharge capacities of the alloys first increase and thendecline, whereas their cycle stabilities always grow. Moreover, the electrochemical kinetic performances of the alloys first increaseand then decrease with spinning rate growing.

Microstructure, hydrogen storage thermodynamics and kinetics of La_5Mg_(95-x)Ni_x(x=5, 10, 15) alloys

The microstructure, hydrogen storage thermodynamics and kinetics of La5Mg95-xNix (x=5, 10, 15) ternary alloys with different Ni contents were investigated. The evolutions of the microstructure and phase of experimental alloys were characterized by X-ray diffractometry and scanning electron microscopy. The hydrogen storage kinetics and thermodynamics, and P-C-I curves were tested using a Sievert apparatus. It is found that increasing Ni content remarkably improves hydrogen storage kinetics but reduces the hydrogen storage capacity of alloys. The highest hydrogen absorption/desorption rate is observed in the La5Mg80Ni15 alloy, with the lowest hydrogen desorption activation value being 57.7 kJ/mol. By means of P-C-I curves and the van’t Hoff equation, it is determined that the thermodynamic performance of the alloy is initially improved and then degraded with increasing Ni content. The La5Mg85Ni10 alloy has the best thermodynamics properties with a hydrogenation enthalpy of -72.1 kJ/mol and hydrogenation entropy of -123.2 J/(mol·K).

Hydrogen storage performances of as-milled REMg_(11)Ni(RE=Y, Sm) alloys catalyzed by MoS_2

To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these alloys were measured by various methods,such as XRD,TEM,automatic Sievert apparatus,TG and DSC.The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure.The RE=Y alloy shows a larger hydrogen absorption capacity,faster hydriding rate,lower initial hydrogen desorption temperature,superior hydrogen desorption property,and lower hydrogen desorption activation energy,which is thought to be the reason of its better hydrogen storage kinetics,as compared with RE=Sm alloy.

Effect of Al Addition on Microstructure,Magnetic Properties,and Mechanical Properties of(Fe_(7)3Ga_(27))_(99.8)Tb_(0.2)Alloy

(Fe_(73)Ga_(27−x)Al_(x))_(99.8)Tb_(0.2)(x=0,1,2,3,4,5)alloys were prepared by vacuum arc furnace to investigate the effect of Al addition on the microstructure,magnetic properties,and mechanical properties of alloys.Results show that the phase structure of the alloys is still A2 phase and Tb_(2)Fe_(17) phase,and the metallographic structure is composed of cellular crystal and columnar dendrite.The decrease in lattice constant,the intensification of(100)orientation,and the generation of Tb_(2)Fe_(17) phase at the grain boundary exert significant effect on the magnetostrictive properties.The fracture morphology of the alloys is intergranular brittle fracture and cleavage fracture,and the causes of fracture occurrence include the segregation of Tb and Al elements.The parallel magnetostrictive strain(λ_(∥))of(Fe_(73)Ga_(24)Al_(3))_(99.8)Tb_(0.2)alloy peaks at 1.04×10^(−4).It is worth noting that compared with those of(Fe_(73)Ga_(27))_(99.8)Tb_(0.2)alloy,theλ_(∥)and elongation of(Fe_(73)Ga_(26)Al_(1))_(99.8)Tb_(0.2)alloy increase by 18.3%and 53.4%,respectively.Besides,(Fe_(73)Ga_(26)Al_(1))_(99.8)Tb_(0.2)alloy possesses the characteristics of high saturation magnetization(Ms),low remanent magnetization(M_(r)),and coercivity(H_(c)),which is beneficial to reduce the cost in actual production,but its tensile strength and Vickers hardness decrease to a certain extent.Therefore,the investigation on the micro-mechanism of Al addition on Fe-Ga alloys is of great significance for the development of Fe-Ga alloy devices.