Electrochemical Properties Of Ti Research Articles

Influence of the calcination temperature and ionic liquid used during synthesis procedure on the physical and electrochemical properties of Ti/(RuO2)0.8–(Sb2O4)0.2 anodes

The development of synthesis methods to produce efficient anodes for wastewater treatment systems is an important industrial issue. Here, we describe the synthesis and the physical and electrochemical characterization of Ti/(RuO2)0.8–(Sb2O4)0.2 anodes prepared by thermal decomposition. The electrodes were prepared using three calcination temperatures (500, 550 and 600 °C) and using 2-hydroxyethylammonium acetate (2HEAA) and methyl-imidazolium hydrogensulfate ((HMIM)HSO4) ionic liquids (IL) as solvents for the precursors solutions. Both ionic liquids used were characterized in terms of water content and viscosity. The 2HEAA IL is almost 10 times more viscous than the (HMIM)HSO4 IL. The anodes developed were electrochemically characterized by cyclic voltammetry, morphology factor, electrochemical impedance spectroscopy and accelerated service lifetime tests. The electrodes synthesized using the 2HEAA IL have superior electrocatalytic properties and electrochemical stability than those made using the (HMIM)HSO4 IL. In addition, the anodes made using the 2HEAA IL as solvent have more homogenous surfaces and higher crystallinity degree than those made using the (HMIM)HSO4 IL. Among the studied calcination temperatures, combining 550 °C and the 2HEAA IL results in more compact and rough electrode surfaces with the highest electroactive areas and electrochemical stability. Thus, the temperature of 550 °C is suitable for the synthesis of mixed metal oxide (MMO) anodes. The electrodes synthesized using the 2HEAA IL are more efficient in the electrochemical oxidation of the Reactive Yellow 186 dye than those made using the (HMIM)HSO4 IL. Consequently, the viscosity of the IL used has great influence on the performance of the synthesized anodes. In addition, the high viscosity of the 2HEAA IL results in a lower number of calcinations steps to produce the anodes and, hence, lower production cost. Viscous ionic liquids are therefore promising for the production of MMO anodes via thermal decomposition methods.

Synthesis and Electrochemical Properties of Ti-Si Alloys Prepared by Mechanical Alloying and Heat Treatment

The aim of this work was to study the synthesis and electrochemical properties of Ti 2 wt %-Si alloys prepared by mechanical alloying (MA) and heat treatment. The MA process was performed under Ar atmosphere. The structural, morphological, and compositional evolutions during the milling and subsequent heat treatment were investigated by X-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. The electrochemical behavior was evaluated by open circuit potential and linear sweep voltammetry measurements. The results showed that the MA process promotes the formation of a supersaturated α-Ti-Si solid solution. During heat treatment, the Si remaining in the mechanically alloyed powders and the Si from the α-Ti-Si supersaturated solid solution reacted with Ti to form Ti-Si intermetallic compounds. These compounds have a fine and homogeneous distribution in the α-Ti matrix, which cannot be achieved by conventional casting methods. Additionally, the electrochemical evaluations revealed that the mechanically alloyed and heat-treated Ti 2 wt %-Si powders have better corrosion resistance in 1.63 M H2SO4 than the pure Ti and MA Ti-Si samples. This is likely due to the particular microstructure produced during the milling and subsequent heat treatment.

Ti@δ-MnO2 core-shell nanowire arrays as self-supported electrodes of supercapacitors and Li ion batteries

δ-MnO2 is a promissing electrode material of supercapacitors and Li ion batteries (LIBs) owing to its low cost, layer structure and composite valence of Mn. However, the unfavorable electronic conductivity of δ-MnO2 restricts its rate capability in both of the two devices. Herein, a vertically standing Ti nanowire array modified with δ-MnO2 nanoflakes is prepared by a electrodeposition method, and the electrochemical properties of Ti@δ-MnO2 nanowire arrays in supercapacitors and LIBs are investigated. The results show that, the arrays have a capacity of 195Fg−1 at 1.0Ag−1 and can cycle more than 10000 rounds at 10Ag−1 as electrodes of supercapacitors. On the other hand, the arrays behave good rate capability as LIB cathodes, which can release a capacity of 70mAhg−1 at 10C rate charge/discharge. We suggest that, the good electronic conductivity owing to the core-shell structure and the facilitated mass transport supplied by the array architecture are responsible for the enhanced rate performances in the two devices.

Improvement of the hydrogen storage properties and electrochemical characteristics of Ti 0.85VFe 0.15 alloy by Ce substitution

The effect of Ce substitution for Ti on the microstructure, hydrogen absorption characteristics and electrochemical properties of Ti 0.85− x Ce x VFe 0.15 ( x = 0, 0.02 and 0.05) is studied in detail. In the Ti–V–Fe series, the composition Ti 0.85VFe 0.15 which crystallizes in single phase BCC structure shows the highest hydrogen storage capacity of 3.7 wt%. In the present study, the effect of Ce addition (2 and 5 at%) on the hydrogen absorption properties of Ti 0.85VFe 0.15 has been investigated by X-ray diffraction, electron probe microanalysis (EPMA) and pressure–composition isotherm studies. The hydrogen absorption capacity is found to be higher for the Ce substituted alloys. The alloys Ti 0.85VFe 0.15, Ti 0.83Ce 0.02VFe 0.15 and Ti 0.80Ce 0.05VFe 0.15 show maximum hydrogen storage capacities of 3.7, 4.02 and 3.92 wt%, respectively. Kinetic studies show that the hydrogen absorption is quite fast for all the three alloys and they reach near saturation value in about 120 s. Electrochemical studies of the Ce (2 at%) substituted alloy, Ti 0.83Ce 0.02VFe 0.15 show higher electrocatalytic activity for the hydrogen electrode reactions as compared to Ce-free parent compound, Ti 0.85VFe 0.15.

Structure and electrochemical property of ball-milled Ti 0.26Zr 0.07Mn 0.1Ni 0.33V 0.24 alloy

In present study, high-energy ball-milling (HEBM) is used in order to improve the cyclic stability and other electrochemical properties of Ti 0.26Zr 0.07Mn 0.1Ni 0.33V 0.24 alloy. The effect of the milling time on crystallographic and electrochemical characteristics of the alloy has been investigated systematically. From X-ray diffraction (XRD) patterns, it can be found that the ball-milled alloys retain their respective phase structures with increasing the ball-milling time from 30 min to 180 min. Electrochemical studies show that the cyclic stability of the ball-milled alloys is noticeably improved after charge–discharge cycles. The capacity retention rate C 40/ C max after 40 cycles increases from 46.3% ( t = 30 min) to 78.3% ( t = 180 min), although the maximum discharge capacity of the ball-milled alloys decreases moderately. Both electrochemical impedance spectra (EIS) and Potentiostatic discharge technique studies indicate that the electrochemical kinetics of the ball-milled alloys is improved with increasing the ball-milling time.

Effect of Mechanical Milling on the Structure and Electrochemical Properties of Ti2Ni Alloy in an Alkaline Battery

Mechanical milling (MM) has been used to treat the crystalline Ti2Ni alloy prepared by solid-state sintering. Changes of the structure, morphology, and electrochemical properties were investigated. The particle size of the alloy decreases first and then increases after the milling. Moreover, MM contributes to a decrease in grain size and the formation and increase of the amorphous phase by increasing the milling time, resulting in improvements of the antipulverization ability and cycle life after the milling. The result of linear polarization indicates that the exchange current density, determined by the competition between the specific surface area and amorphous phase, increases first and then decreases. The amorphous phase is beneficial to hydrogen diffusion according to the result of potential-step measurement. The electrochemical properties of Ti2Ni alloy are significantly improved by the non-equilibrium processing technology.

Structures and electrochemical characteristics of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0–0.1) hydrogen storage alloys

Microstructures and electrochemical properties of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0, 0.025, 0.05, 0.075, 0.10) electrode alloys have been investigated. The results of XRD analysis show that the alloys are mainly composed of V-based solid solution phase with body centered cubic (bcc) structure and C14 Laves phase with hexagonal structure. The addition of Mo element can improve the activation characteristics, maximum discharge capacity and cyclic durability for the electrode alloys. The discharge capacity of the electrode alloys increases with changing x from 0.025 to 0.10 within temperature region from 303 to 343 K. The results show that the discharge property of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo 0.075 electrode alloy at high temperature is the best, and its maximum discharge capacity is 633 mAh g −1 at 343 K. However, the high-rate dischargeability decreases and the self-discharge rate increases for Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0–0.10) electrode alloys with increasing Mo content. Electrochemical impedance spectroscopy (EIS) shows that the charge-transfer resistance at the surface of the alloy electrodes increases obviously with increasing Mo content.

An improvement on cycling stability of Ti–V–Fe-based hydrogen storage alloys with Co substitution for Ni

In this work, the effects of Co substitution for Ni on the microstructures and electrochemical properties of Ti 0.8Zr 0.2V 2.7Mn 0.5Cr 0.6Ni 1.25− x Co x Fe 0.2 ( x = 0.00–0.25) alloys were investigated systematically by XRD, SEM and electrochemical measurements. The structural investigations revealed that the main phases of all of the alloys were the C14 Laves phase in a three-dimensional network and the V-based solid solution phase with a dendritic structure. The lattice parameters and unit cell volumes of the two phases gradually increased with the increase of Co concentration. The relative abundance of the C14 Laves phase slightly increased from 47.3% to 49.6%, accordingly that of the V-based solid solution phase decreased, with the increase of x from 0.00 to 0.25. The crystal grain of the V-based solid solution phase was obviously refined after Co substitution. The electrochemical investigations showed that the proper substitution of Co for Ni improved the cycling durability of the alloy electrodes mainly due to the suppression of both the pulverization of the alloy particles and the dissolution of the main hydrogen absorbing elements (V and Ti) into the KOH solution. The cycling stability of the alloy electrode with x = 0.1 was 79.8% after 200 cycles. However, the maximum discharge capacity ( C max) was decreased from 340.5 to 305.6 mAh g −1, and the high rate dischargeability (HRD) gradually decreased from 66.8% to 55.0% with increasing x from 0.00 to 0.25.

Crystal structural and electrochemical properties of Ti 0.17Zr 0.08V 0.35Cr 0.10Ni 0.30− xMn x ( x = 0–0.12) alloys

To get the Ni–MH batteries used within wide temperature with high discharge capacity, the crystal structural and electrochemical properties of Ti 0.17Zr 0.08V 0.35Cr 0.10Ni 0.30− x Mn x ( x = 0–0.12) alloys were investigated. The partial substitution of Ni by Mn remains the crystal structure of these alloys, and they are still composed of bcc phase and C14 Laves phase. Both the lattice parameter and phase abundance of bcc phase decrease slightly, however, those of C14 Laves phase increase. The discharge capacity, the exchange current density and limit current density of these alloy electrodes at 298 K enhance obviously, but the electrochemical cyclic stability, the rate dischargeability and the polarization resistance decrease with increasing Mn content. Also, the electrochemical properties of these alloy electrodes at 273 K and 343 K were examined. The results show that Ti 0.17Zr 0.08V 0.35Cr 0.10Ni 0.25Mn 0.05 ( x = 0.05) compound has a good performance, which maybe has a potential application within the wide temperature.

The effect of particle size on the electrode performance of Ti–V-based hydrogen storage alloys

The effect of particle size ranging from 100 mesh to below 500 mesh on the electrochemical properties of Ti 0.8 Zr 0.2 V 2.7 Mn 0.5 Cr 0.8 Ni x ( x = 0.75 , 1.75 ) hydrogen storage alloy electrodes was investigated. SEM observation on the surface of the alloy electrodes after charge/discharge cycles revealed that the abilities of anti-pulverization and anti-corrosion of the x = 0.75 alloy were much lower than those of the x = 1.75 alloy. For both of the two alloys, the electrode performance is affected markedly by the particle size. With the increase of the initial particle size, the initial discharge capacity of the alloy electrode decreases and the pulverization of the alloy particles aggravates, especially for the particles of the x = 0.75 alloy with size larger than 400 mesh, the size of which was minimized obviously compared with their initial size. However, the maximum discharge capacity and the cycling stability almost do not correlate to the initial particle size but relate with their actual particle size. As the actual particle size decreases, the maximum discharge capacity increases and the cycling stability declines.

Investigation of microstructure and electrochemical properties of Ti 0.8Zr 0.2V 2.7Mn 0.5+ xCr 0.8Ni 1.5− x hydrogen storage alloys

The effects of partial substitution of Mn for Ni on the structural and electrochemical properties of Ti 0.8Zr 0.2V 2.7Mn 0.5+ x Cr 0.8Ni 1.5− x ( x = 0.0–0.4) hydrogen storage alloys have been systematically investigated. It is found by XRD and Rietveld analysis that all of the alloys consist of a C14 Laves phase with a hexagonal structure and a V-based solid solution phase with a BCC structure. With increasing x, the abundance of the C14 Laves phase increases, but the abundance of the V-based phase decreases progressively. The electrochemical measurements indicate that the maximum discharge capacity of the alloy electrode increases first from 324.8 mAh/g ( x = 0.0) to 356.4 ( x = 0.2) and then decreases to 310.0 mAh/g ( x = 0.4). But the cyclic stability of the alloy electrode deteriorates with increasing Mn content. Moreover, the results of electrochemical impedance spectroscopy (EIS), linear polarization, anodic polarization and potentiostatic discharge tests indicate that the exchange current density I 0, the limiting current density I L and the hydrogen diffusion coefficient D all increase first and then decrease with increasing x. The high rate dischargeability (HRD) of the alloy electrode varies in the same manner. An optimum overall performance is obtained when x = 0.1.

Structure and electrochemical properties of Ti 0.25V 0.35Cr 0.40− xNi x ( x=0.05–0.40) solid solution alloys

The structure and electrochemical properties of Ti 0.25 V 0.35 Cr 0.40−x Ni x (x=0.05 –0.40) solid solution alloys have been studied in the paper. It is found that these alloys consist of a main solid solution phase with body centered cubic (bcc) structure and a little TiNi-based secondary phase. The solid solution alloys show easier activation behavior at 313 K as a negative electrode material for MH–Ni battery. With changing x from 0.05 to 0.30, the discharge capacity and the high-rate dischargeability increase. The discharge capacity increases with increasing temperature. The maximum discharge capacity is 240 mA h / g at 313 K for x=0.30 and 280 mA h / g at 343 K for x=0.15.

A study of pulsed high flux Ti, Mo, V and Y ion implantation for surface modification of resistances in wear, corrosion and oxidation

The resistances to wear, corrosion and oxidation of implanted H13 steel using pulsed Ti and Y ions were studied. The Ti and Y ions were produced from a metal vapor vacuum source (MEVVA). The instantaneous beam current was from 0.3 to 1 A and energy was from 25–50 keV. The target temperature was raised to 300°C for a flux of 38 μA cm −2 and to 600°C for a flux of 76 μA cm −2. The hardness of Ti-implanted steel increases with ion dose and decreases with ion flux. The wear resistance of Ti-implanted steel is 3–3.7 times that for the unimplanted steel. Precipitates of Fe 2Ti were observed by X-ray diffraction and high energy electron microscopy (HVEM). The size and amount of Fe 2Ti increases with increasing ion dose and ion flux. The oxidation barrier of Y-implanted H13 steel formed during oxidation at 800°C for 10 min was measured by RBS. The oxidation rate of Y-implanted steel was 8–10 times less than the unimplanted steel. The electrochemical properties of Ti and Y implanted steel in 1 mol H 2SO 4 or solution of NaCl were studied. The results show that the Y implantation is effective for improvement of corrosion inhibition of H13 steel, GCr15 and 304 stainless steel.

Methanol oxidation in acid on ordered NiTi

A 50–50 ordered NiTi alloy is shown to form a passivating layer that makes it electrochemically stable in acid solution and to be an electrocatalyst for the methanol oxidation reaction. To elucidate the reaction pathways, the electrochemical properties of Ti and Ni electrodes were compared with those of NiTi and Pt electrodes. Alloying Ti with Ni suppresses the corrosion reaction on Ni electrodes in acid by shifting the potential for Ni2+ion dissolution to a value above that at which the Ni2+ ions at the surface are converted to Ni3+ ions. NiTi electrodes, like Ni and Ti electrodes, form oxyhydroxide films at anodic potentials, and the thickness of the film increases with applied anodic voltage. Methanol oxidation occurs on the oxyhydroxide films. Dissociative chemisorption requires a potential sufficiently anodic of the flat-band potential of the film composition at the surface, or threshold potential Eth for the creation of surface Ni3+ ions, for electron transfer to take place via tunnelling across a Schottky barrier to either a conduction band, in the case of Ti, or an Ni3+/2+ redox band in the case of Ni. In the case of NiTi, the former mechanism appears to be operative at lower potentials, the latter at higher potentials. The reaction is completed with an attack by water on a surface carboxy group, which also requires electron tunnelling across a depletion layer. Methanol oxidation on NiTi is more active than on Ti or Ni, and it is completed at a potential E < 1.23 V. A distinction was found between p-type and n-type oxyhydroxide layers. The n-type layers, formed only occasionally, gave cyclic voltammograms which resembled those obtained on elemental platinum.