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1.
Phase structure and electrochemical properties of the Ml1−xMgxNi2.80Co0.50Mn0.10Al0.10 (x = 0.08, 0.12, 0.20, 0.24, 0.28) (Ml = La-rich mixed lanthanide) alloys were studied. X-ray diffraction (XRD) analysis and Rietveld refinement show that the alloys consist mainly of LaNi5 and (La,Mg)Ni3 phase. Due to variation in phases of the alloys, the maximum discharge capacity, the high rate dischargeability (HRD), and the low temperature dischargeability increase first and then decrease. The maximum discharge capacity increases from 322 mAh g−1 (x = 0.08) to 375 mAh g−1 (x = 0.12), and then decreases to 351 mAh g−1 (x = 0.28) with increasing x. As the case of x = 0.20, HRD at 1200 mA g−1 and discharge capacity at 233 K reaches 41.7% and 256 mAh g−1, respectively. The cycling stability is improved by substituting La with Ml and B-site multi-alloying, and the capacity retention of Ml0.72Mg0.28Ni2.80Co0.50Mn0.10Al0.10 at the 200th cycle is 71%. 相似文献
2.
For (Ti1−xVx)2Ni (x = 0.05, 0.1, 0.15, 0.2 and 0.3) ribbons, synthesized by arc-melting and subsequent melt-spinning techniques, an icosahedral quasicrystalline phase was present, either in the amorphous matrix or together with the stable Ti2Ni-type phase. With increasing x values, the maximum discharge capacity of the alloy electrodes increased until reached 271.3 mAh/g when x = 0.3. The cycling capacity retention rates for these electrodes were approximately 80% after a preliminary test of 30 consecutive cycles of charging and discharging. Ti1.7V0.3Ni alloy electrode displayed the best high-rate discharge ability of 82.7% at the discharge current density of 240 mA/g. 相似文献
3.
The melt-spinning technique is applied to the preparation of the nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2Ni1−xMnx (x = 0, 0.1, 0.2, 0.3, 0.4). The as-spun alloy ribbons possessing a continuous length, a thickness of about 30 μm and a width of about 25 mm were prepared. The structures of the as-spun alloy ribbons are characterized by XRD and TEM. The electrochemical performances of the as-spun alloy ribbons are measured by an automatic galvanostatic system. The results show that no amorphous structure is detected in the as-spun Mg2Ni alloy, whereas the as-spun Mg2Ni0.6Mn0.4 alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni notably intensifies the amorphous forming ability of the Mg2Ni-type alloy. The amorphization degree of the as-spun alloys containing Mn increases with increasing spinning rate. The melt spinning also significantly enhances the electrochemical performances such as the discharge capacity and the electrochemical cycle stability of the Mn-containing alloys. Furthermore, the high rate dischargeability (HRD) of the (x ≤ 0.1) alloys increases with an increase in the spinning rate, while for the (x ≥ 0.2) alloys, the HRD exhibits a maximum value at a particular spinning rate, and it varies with the change in Mn contents of the alloys. 相似文献
4.
The structure and electrochemical properties of TiV1.1Mn0.9Nix (x = 0.1-0.7) solid solution electrode alloys have been investigated. It is found that these alloys mainly consist of a solid solution phase with body centered cubic (bcc) structure and a C14 Laves secondary phase. The solid solution alloys show easy activation behavior, high temperature dischargeability, high discharge capacity and favorable high-rate dischargeability as a negative electrode material in Ni-MH battery. The maximum discharge capacity is 502 mAh g−1 at 303 K when x = 0.4. Electrochemical impedance spectroscopy (EIS) test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with increasing Ni content. 相似文献
5.
We report the effect of Cu2+ ion on CaAl2O4 with different molar concentrations of 0.0, 0.4 and 0.8 M prepared by simple combustion method. The materials have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR) and scanning electron microscopy (SEM). DC electrical conductivity has also been measured to study the electrical behavior of the materials. The XRD patterns confirm the formation of single-phase CaAl2O4 along with some impurity phases like CaAl4O7, CaAl12O19 and Ca12Al14O33. The FT-IR spectra show the stretching and bending vibrations of the synthesized compounds. DC electrical conductivity of the Ca1−xCuxAl2O4 is found to vary from 26.46 × 10−4 to 515.68 × 10−4 S cm−1 for x = 0.0 to x = 0.8 at the measuring temperature of 1000 °C. SEM images show the morphological features of the compounds. 相似文献
6.
The effect of Mn content on the crystal structure and electrochemical characteristics of La0.7Mg0.3Ni2.975−xCo0.525Mnx (x = 0, 0.1, 0.2, 0.3, 0.4) alloys has been studied systematically. The results of the Rietveld analyses show that all these alloys mainly consist of two phases: the La(La,Mg)2Ni9 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCu5-type structure. The pressure-composition isotherms shows that the partial substitution of Mn for Ni results in lower desorption plateau pressure and steeper pressure plateau of the alloy electrodes. For a Mn content of x = 0.3, the electrochemical performances, including specific discharge capacity, high rate chargeability (HRC) and high rate dischargeability (HRD), of the alloy are preferable. Moreover, the data of the polarization resistance Rp and the exchange current density I0 of the alloy electrodes is consistent with the results of HRC and HRD. The hydrogen diffusion coefficient D increases with increasing Mn content, and thereafter increases the low temperature dischargeability (LTD) of the alloy electrodes. 相似文献
7.
Gang Deng Mingda Tao Chaoling Wu Xiangqian Shen Heng Yang 《Electrochimica acta》2009,54(15):3910-3914
La(1−x)SrxFeO3 (x = 0.2,0.4) powders were prepared by a stearic acid combustion method, and their phase structure and electrochemical properties were investigated systematically. X-ray diffraction (XRD) analysis shows that La(1−x)SrxFeO3 perovskite-type oxides consist of single-phase orthorhombic structure (x = 0.2) and rhombohedral one (x = 0.4), respectively. The electrochemical test shows that the reaction at La(1−x)SrxFeO3 oxide electrodes are reversible. The discharge capacities of La(1−x)SrxFeO3 oxide electrodes increase as the temperature rises. With the increase of the temperature from 298 K to 333 K, their initial discharge capacity mounts up from 324.4 mA h g−1 to 543.0 mA h g−1 (when x = 0.2) and from 147.0 mA h g−1 to 501.5 mA h g−1 (when x = 0.4) at the current density of 31.25 mA g−1, respectively. After 20 charge-discharge cycles, they still remain perovskite-type structure. Being similar to the relationship between the discharge capacity and the temperature, the electrochemical kinetic analysis indicates that the exchange current density and proton diffusion coefficient of La(1−x)SrxFeO3 oxide electrodes increase with the increase of the temperature. Compared with La0.8Sr0.2FeO3, La0.6Sr0.4FeO3 electrode is a more promising candidate for electrochemical hydrogen storage because of its higher cycle capacity at various temperatures. 相似文献
8.
The effect of La/Ce ratio on the structure and electrochemical characteristics of the La0.7−xCexMg0.3Ni2.8Co0.5 (x = 0.1, 0.2, 0.3, 0.4, 0.5) alloys has been studied systematically. The result of the Rietveld analyses shows that, except for small amount of impurity phases including LaNi and LaNi2, all these alloys mainly consist of two phases: the La(La, Mg)2Ni9 phase with the rhombohedral PuNi3-type structure and the LaNi5 phase with the hexagonal CaCu5-type structure. The abundance of the La(La, Mg)2Ni9 phase decreases with increasing cerium content whereas the LaNi5 phase increases with increasing Ce content, moreover, both the a and cell volumes of the two phases decrease with the increase of Ce content. The maximum discharge capacity decreases from 367.5 mAh g−1 (x = 0.1) to 68.3 mAh g−1 (x = 0.5) but the cycling life gradually improve. As the discharge current density is 1200 mA g−1, the HRD increases from 55.4% (x = 0.1) to 67.5% (x = 0.3) and then decreases to 52.1% (x = 0.5). The cell volume reduction with increasing x is detrimental to hydrogen diffusion D and accordingly decreases the low temperature dischargeability of the La0.7−xCexMg0.3Ni2.8Co0.5 (x = 0.1-0.5) alloy electrodes. 相似文献
9.
Ibro Tabakovic Venkateswara Inturi Jeremy Thurn Mark Kief 《Electrochimica acta》2010,55(22):6749-6754
Electrodeposition of Ni1−xFex (x = 0.1-0.9) films was carried out from a chloride plating solution containing saccharin as an organic additive at a constant current density (5 mA/cm2) and a controlled pH of 2.5. X-ray diffraction studies revealed the existence of an fcc, or γ phase, in the range of 10-58 wt.% Fe, a mixed fcc/bcc phase in the range of 59-60 wt.% Fe, and a bcc, or α phase in the range of 64-90 wt.% Fe. The saturation magnetization, Bs, of electrodeposited Ni1−xFex alloys at the room temperature was found to increase with the increase of Fe-content and follows the Slater-Pauling curve, but deviates from as-cast bulk NiFe alloys. The coefficient of thermal expansion, CTE, of electrodeposited alloys at room temperature also deviates from as-cast bulk NiFe alloys. Annealing of α-Ni36Fe64 alloy results in a martensitic α → γ phase transformation, which takes place between 300 and 400 °C. It was demonstrated that thermal treatment above 400 °C was necessary to obtain magnetic and mechanical properties similar to those to conventional Invar alloy. Annealing of α-Ni36Fe64 alloy at 700 °C brings about a decrease of Bs from 1.75 to 0.45 T. By controlling the annealing conditions of α → γ martensitic transformation, it is possible to adjust the CTE of Ni36Fe64 alloy over the broad limits from 2.7 to 8.7 × 10−6/°C. 相似文献
10.
Cation substituted bismuth vanadate possesses high oxygen ion conductivity at lower temperatures. The ionic conductivity of this material at 300 °C is 50–100 times more than any other solid electrolyte. Three phases (α, β, γ) are observed in the substituted compound; α and γ are low and high conducting phase, respectively. Samples of Bi4V2−xCuxO11−δ (x = 0–0.4) were prepared by solid-state reaction technique. Impedance spectroscopy measurements were carried out in the frequency range of 100 Hz to 100 kHz using gold sputtered cylindrical shaped pellets to obtain bulk ionic conductivities as a function of the substitution and temperature. The change of slopes observed in the Arrhenius plots is in agreement with the phase transitions for all the compositions. The highest ionic conductivity of the Cu-substituted compound was observed in Bi4V1.8Cu0.2O11−δ which is attributed to its lower activation energy. Microstructural studies indicated the stabilization of high temperature γ-phase at low temperature in those samples whose ionic conductivity observed was higher. 相似文献
11.
The structure and electrochemical properties of LiNixMn2−xO4 cathode materials for lithium ion batteries were studied by the means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), cyclic voltammetry, and galvanostatic charge-discharge tests. The cathodes with different Ni contents (LiNixMn2−xO4, x = 0.1, 0.2, 0.3, 0.4, and 0.5) were synthesized by a spray-drying method and showed a single-phase spinel structure without any impurity. The amount of Ni has a large effect on the electrochemical characteristics. Capacity values of different voltage ranges (4- and 5-V ranges) change obviously with amount of Ni-doped. Also, the total discharge capacities increase with the Ni content, and all of them have good cycle stability. 相似文献
12.
Mohammad Javad Nasr Isfahani Parisa Nasr IsfahaniKlebson Lucenildo Da Silva Armin FeldhoffVladimir Šepelák 《Ceramics International》2011,37(6):1905-1909
NiFe2−xBixO4 (x = 0, 0.1, 0.15) nanopowders were synthesized via sol-gel method. The precursor gels were calcined at 773 K in air for 1 h to obtain the pure nanostructured NiFe2−xBixO4 spinel phase. The crystal structure and magnetic properties of the substituted spinel series of NiFe2−xBixO4 have been investigated by means of 57Fe Mössbauer spectroscopy, transmission electron microscopy and alternating gradient force magnetometry. Mössbauer spectroscopic measurements revealed that Bi3+ cations tend to occupy octahedral positions in the structure of the substituted ferrite, i.e., the crystal-chemical formula of the as-prepared nanoparticles may be written as: (Fe)[NiFe1−xBix]O4 (x = 0, 0.1, 0.15), where parentheses and square brackets enclose cations on sites of tetrahedral and octahedral coordination, respectively. Selective area electron diffraction studies provided evidence that the samples of the NiFe2−xBixO4 series, independently of x, exhibit the cubic spinel structure. The values of the saturation magnetization and the coercive field of NiFe2−xBixO4 nanoparticles were found to decrease with increasing degree of bismuth substitution. 相似文献
13.
Ibro Tabakovic Jie Gong Steve Riemer Venkatram Venkatasamy Mark Kief 《Electrochimica acta》2010,55(28):9035-9041
Electrodeposition of 0.5 μm thick CoxFe1−x (x = 0.33-0.87) films was carried out from a sulfate/chloride plating solution containing saccharin as an organic additive at constant current density and a controlled pH 2.3. The increase of Fe2+ concentrations in plating solution resulted in an increase of Fe-content and tensile stress in CoxFe1−x films, which is accompanied by a decrease of plating rate. Several possible origins for generation of tensile stress include the following: interfacial stress between CoFe films and Cu-substrate, crystal texture and grain size, coalescence and stress evolution during film growth, and hydrogen adsorption/desorption. The adsorption/desorption mechanism of hydrogen seems to be the most likely dominant stress mechanism. The relationship between increase of the tensile stress and decrease of plating rate was discussed. 相似文献
14.
The effect of partial substitution of Co for Ni on the structure and electrochemical properties of the thus formed La2Mg(Ni1−xCox)9 (x = 0.1-0.5) quaternary alloys was investigated. All alloys are consisted of a main phase with hexagonal PuNi3-type structure and a few impurity phases (mainly La2Ni7 and LaNi). The increase of Co content in the alloys leads to an increase in both the cell volume and the hydride stability, and leads to a noticeable decrease in cell volume expansion rate (ΔV/V) on hydriding. The discharge capacity of the alloys at 50 mA/g increases slightly with the increase of Co content and passes though a maximum of 404.5 mAh/g at x = 0.2. As the Co content increases, the high-rate dischargeability of the alloy electrodes at 800 mA/g (HRD800) decreases sharply from 72.8 (x = 0) to 24.5% (x = 0.5), yet the decrease of HRD800 of the alloy electrodes with lower Co substitution (with x ≤ 0.2) is much milder. The slower decrease of HRD800 (from 72.8 to 64.2%) of the alloys with x from 0 to 0.2 is mainly attributed to the decrease of eletrocatalytic activity for charge-transfer reaction, the more rapid decrease of the alloys with x > 0.2 is mainly attributed to the lowering of the hydrogen diffusion rate in the bulk of alloy. The cycling capacity retention rate (S100) of the alloys increase greatly with increasing of Co content, increasing from 60.2% for the alloy with x = 0 to a much higher value of 87.9% for the alloy with x = 0.5. The improvement in cycling stability is attributed to the lower cell volume expansion on hydriding. 相似文献
15.
R. Gimenes M.R. BaldisseraM.R.A. da Silva C.A. da SilveiraD.A.W. Soares L.A. PerazolliM.R. da Silva M.A. Zaghete 《Ceramics International》2012,38(1):741-746
In this work the microstructure and magnetic properties of Mn-Zn ferrites powders were investigated. MnxZn1 − xFe2O4 powders where x = 0.2; 0.35; 0.5; 0.65; 0.8 and 1.0 were obtained by citrate precursor method. Citrate resin precursor was burned on air atmosphere at 400 °C for 3 h. Mn-Zn powders were calcined at 950 °C during 150 min under inert atmospheres: N2 and rarefied atmosphere. Thermal analysis of precursor resin, phase evolution and microstructure of Mn-Zn ferrites powders were investigated by TG, DTA, XRD and SEM techniques. The powders calcined under rarefied atmosphere show spinel cubic structure and contamination of α-Fe2O3, while powders calcined under N2 presents only the spinel cubic structure. Particle size was observed by SEM ranging from 80 to 150 nm. The magnetic properties were measured employing a vibrating sample magnetometer (VSM). It was observed that the saturation magnetization Ms increased with the increase of Mn content. The Ms of Mn0.8Zn0.2Fe2O4 calcined on rarefied atmosphere and Mn0.8Zn0.2Fe2O4 calcined on N2 was 23.31 emu g−1 and 56.23 emu g−1, respectively. 相似文献
16.
Iron is a key element in the development of Co-free AB5-type hydrogen storage alloys. The aim of this work is to systematically investigate the effects of Fe and Co on the electrochemical properties of LaNi4.6−xMn0.4Mx (M = Fe or Co, x = 0, 0.25, 0.5 and 0.75) hydrogen storage alloys under relatively low temperatures (273, 253 and 233 K). The results showed that substitution of Fe for Ni reduced the low temperature electrochemical performance much more seriously than that of Co. Exchange current density (I0), charge-transfer resistance (Rct) and hydrogen diffusion coefficient (D) were determined based on the study of linear polarization, electrochemical impedance spectrum (EIS) and galvanostatic discharge, respectively. Both the hydrogen diffusion in the bulk of alloy particles and the electrochemical reaction at the alloy electrolyte interface were found to be greatly limited as the decrease of temperature. During the EIS analysis, interestingly, we found that the semicircle in the high frequency region increased dramatically with the decrease of temperature. The electrochemical process corresponding to this semicircle was proposed to be related to the oxide layer on the surface of alloy particles. Novel explanations of EIS response in metal hydride electrodes were proposed accordingly. 相似文献
17.
To improve the cathodic performance of olivine-type LiMnPO4, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn1−xMxPO4 (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO4 was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn2P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn0.99Mg0.01PO4/C was 146 mAh/g at 0.1 mA/cm2 and 125 mAh/g even at 2.0 mA/cm2. 相似文献
18.
Rajjab Ali Muhammad Azhar Khan Azhar Mahmood Adeel Hussain Chughtai Amber Sultan Muhammad Shahid Muhammad Ishaq Muhammad Farooq Warsi 《Ceramics International》2014
Ca–Ni co-substituted samples of nanocrystalline spinel ferrites with chemical formula Mg1−xCaxNiyFe2−y O4 (x=0.0–0.6, y=0.0–1.2) were synthesized by the micro-emulsion method and were annealed at 700 °C for 7 h. The synthesized samples were characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM) and dielectric measurements. The XRD and FTIR analysis reveals that single phase samples can be achieved by substituting Ca and Ni ions at Mg and Fe sites respectively in cubic spinel nano-ferrites. The crystallite size of the synthesized samples was found in the range 29–45 nm. The saturation magnetization (Ms) increases from 9.84 to 24.99 emu/g up to x=0.2, y=0.4 and then decreases, while the coercivity (Hc) increases continuously from 94 to 153 Oe with the increase in dopants concentration. The dielectric properties of these nano materials were also studied at room temperature in the frequency range 100 MHz to 3 GHz. The dielectric parameters were found to decrease with the increased Ca–Ni concentration. Further the peaking behavior was observed beyond 1.5 GHz. The frequency dependent dielectric properties of all the samples have been explained qualitatively on the basis of the Maxwell–Wagner two-layer model according to Koop's phenomenological theory. The enhanced magnetic parameters and reduced dielectric properties make the synthesized materials suitable for switching and high frequency applications, respectively. 相似文献
19.
Evolution of the local structure and electrochemical properties of spinel LiNixMn2−xO4 (0 ≤ x ≤ 0.5)
A series of Ni substituted spinel LiNixMn2−xO4 (0 ≤ x ≤ 0.5) have been synthesized to study the evolution of the local structure and their electrochemical properties. X-ray diffraction showed a few Ni cations moved to the 8a sites in heavily substituted LiNixMn2−xO4 (x ≥ 0.3). X-ray photoelectron spectroscopy confirmed Ni2+ cations were partially oxidized to Ni3+. The local structures of LiNixMn2−xO4 were studied by analyzing the and A1g Raman bands. The most compact [Mn(Ni)O6] octahedron with the highest bond energy of Mn(Ni)O was found for LiNi0.2Mn1.8O4, which showed a Mn(Ni)O average bond length of 1.790 Å, and a force constant of 2.966 N cm−1. Electrolyte decomposition during the electrochemical charging processes increased with Ni substitution. The discharge capacities at the 4.1 and 4.7 V plateaus obeyed the linear relationships with respect to the Ni substitution with the slopes of −1.9 and +1.9, which were smaller than the theoretical values of −2 and +2, respectively. The smaller slopes could be attributed to the electrochemical hysteresis and the presence of Ni3+ in the materials. 相似文献
20.
The structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% LaNi5 (x = 0, 1, 5 and 10) hydrogen storage alloys have been investigated systematically. XRD shows that the matrix phase structure of V-based solid solution phase with a BCC structure and C14 Laves phase with hexagonal structure is not changed after adding LaNi5 alloy. However, the amount of the secondary phase increases with increasing LaNi5 content. Field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS) shows that the C14 Laves phase contains more Zr and the white lard phase has a composition close to (Zr, Ti)(V, Cr, Ni, La)2. The electrochemical measurements show that the hysteresis effect decreases dramatically with increasing x. The activation performance, the low temperature dischargeability, high rate dischargeability and cyclic stability of composite alloy electrodes increase greatly with increasing x. The maximum discharge capacity first increases as x increases from 0 to 5 and then decreases when x increases further from 5 to 10. The improvement of the electrochemical characteristics caused by adding LaNi5 seems to be related to formation of the secondary phase. 相似文献