12035-60-8Relevant articles and documents
The effect of an electric field on the microstructural development during combustion synthesis of TiNi-TiC composites
Graeve, Olivia A.,Munir, Zuhair A.
, p. 79 - 87 (2002)
The role of an externally imposed (contacting) electric field on the microstructural development during the synthesis of TiC-TiNi composites was investigated. Using elemental reactants, composites with 60 and 70 vol% TiNi were synthesized by the self-propagating combustion method. The field had a direct effect on the velocity and temperature of the combustion wave, and had an influence on the particle size of the TiC phase formed within the TiNi matrix. The average particle size increased by at least a factor of two (from about 2.5 to 5.5 μm for the 60 vol% TiNi samples and from 1.5 to 3.0 μm for the 70 vol% TiNi samples) as the field strength was increased from zero to about 5 V cm-1. Although higher temperatures and wave velocities result in higher temperature gradients and thus an anticipation of shorter residence time at the highest temperatures, the presence of a liquid phase has apparently a more direct effect on TiC particle growth. In cases where no liquid is present the results are different, as will be reported in a subsequent paper.
Effect of Zr additions on the electrode characteristics of nanocrystalline TiNi-type hydrogen storage alloys
Makowiecka,Jankowska,Okonska,Jurczyk
, p. 303 - 307 (2005)
The effect of Zr on the structure and electrochemical properties of nanocrystalline TiNi-type alloys was studied. These materials were prepared by mechanical alloying (MA) followed by annealing. It was found that the respective replacement of Ni in nanocrystalline TiNi by Zr, and by Zr and Fe improved not only the discharge capacity but also the cycle life of these electrodes. In the nanocrystalline TiNi0.875Zr0.125, a powder discharge capacity up to 135 mA h g-1 was measured on the 10th cycle (at 40 mA g-1 discharge current). The studies show that the electrochemical properties of Ni-MH batteries are a function of the microstructure and the chemical composition of the used electrode materials.
Studies of electrochemical properties of TiNi alloy used as an MH electrode - I. Discharge capacity
Wang,Lei,Wang
, p. 3193 - 3207 (1998)
The electrochemical properties of TiNi alloy used as an MH electrode were investigated. A mathematical model for the electrochemical discharge capacity of TiNi electrode was developed. The model was used to study the effects of various parameters on the discharge capacity, and cycle life. The predicted results from the model fit well with the experimental results. Increasing the discharge current density and charge/discharge cycling current density decreases the discharge capacity, but a high charge/ discharge cycling current density increases the cycle life of the hydride electrode. Increasing the exchange current density, or the diffusion coefficient of hydrogen or reducing the particle size increases the discharge capacity. Upon increasing the discharge current density the controlling steps of discharge capacity change from hydrogen diffusion in α phase (including oxide film) to the charge-transfer reaction on the hydride electrode surface. However for the TiNi alloy electrode the discharge capacity still depends mainly on the diffusion ability of hydrogen even at high discharge current density (200 mA/g). There exists an optimum dissolved hydrogen content of the α phase, Coptαβ, at which the discharge capacity reaches a maximum value. Also Coptαβ increases with increasing discharge current density.
Production of NiTi shape memory alloys via electro-deoxidation utilizing an inert anode
Jiao, Shuqiang,Zhang, Linlin,Zhu, Hongmin,Fray, Derek J.
, p. 7016 - 7020 (2010)
NiTi shape memory alloys (SMA) with equiatomic composition of Ni and Ti were prepared by electro-deoxidation, in molten calcium chloride, at 950 °C. Constant voltage electro-deoxidation was conducted using a NiTiO3 cathode, and either a carbon anode or a novel CaRuO3/CaTiO 3 composite inert anode. Both anode materials successfully allowed NiTi shape memory alloy to be obtained. The primary difference is that molecular oxygen was produced on the inert anode, instead of environmentally undesired CO2 greenhouse gases on the carbon anode. Indeed, it was found that carbon could successfully be substituted with conductive calcium titanate-calcium ruthenate composites for electro-deoxidation. Furthermore, DSC was used to analyze the phase transformation of NiTi shape memory alloys, with results revealing the existence of reversible martensite-austenite phase transformations during the cooling and heating process.
Two-stage transformation of aluminum-containing NiTi
Matsumoto, Hitoshi,Abe, Hiroshi,Morikawa, Yuki
, p. 24 - 30 (2002)
Measurements of electrical resistivity, ultrasonic velocity and attenuation for equiatomic NiTi and Ni50Ti49Al1 were performed in order to characterize the thermoelastic martensitic transformation during cooling. The NiTi shows a one-stage transformation, essentially, because a premartensitic phenomenon is negligibly faint. The ultrasonic anomalies in NiTi appear near the temperature at a faint resistivity-peak, which correspond to lattice softening at the start temperature of martensitic transformation from the high-temperature phase to the low-temperature phase. The resistivity of Ni50Ti49Al1 has a negative temperature coefficient over the wide temperature range from room temperature to154K, and indicates a large peak. Such an anomaly in resistivity corresponds to an enhanced premartensitic phenomenon, where ultrasonic anomalies caused by a two-stage transformation are observed which accompany a large change in electrical resistivity. However, a resistivity peak in the aluminum-containing NiTi is formed at lower temperature than those at ultrasonic anomalies by over 40K, and the temperature at the resistivity peak is not one characterizing the transformation behavior. It proved helpful to measure the ultrasonic properties in comparison with the electrical resistivity in order to characterize successive transformations in the temperature range of a premartensitic phenomenon of NiTi enhanced by addition of aluminum.
Tokumoto, Madoka
, (1980)
Isothermal section of the phase diagram of the La-Ni-Ti ternary system at 673 K
Jingqi, Liu,Ke, Geng
, p. 121 - 123 (2000)
The isothermal section of the phase diagram of the ternary system La-Ni-Ti was investigated by X-ray diffraction, differential thermal analysis, optical microscopy and electron microscopy techniques. It consists of 14 single-phase regions, 25 two-phase re
Pore characteristics of porous NiTi alloy fabricated by combustion synthesis
Li,Rong,Li
, p. 259 - 262 (2001)
Biomedical porous NiTi shape memory alloy (SMA) is a promising implant material. The pore characteristics, such as pore morphology and distribution, mean pore size and porosity of porous NiTi SMA fabricated by combustion synthesis were investigated in this paper by optical microscopy, scanning electron microscopy (SEM), image processing and density determination and the mechanism of pore formation was proposed. The result indicated that pore morphology and distribution of porous NiTi SMA exhibited features of isotropy or anisotropy, depending upon preheating temperature during synthesis. Mean pore size and porosity range was 300-600 μm and 60-64% respectively, and open porosity ratio was bigger than 90% which indicates that porous NiTi SMA is suitable for biomedical application.
Optical properties and electronic structures of B2 and B19′ phases of equiatomic Ni-Ti alloys
Rhee, Joo Yull,Harmon,Lynch
, p. 1878 - 1884 (1999)
The dielectric functions of equiatomic Ni-Ti alloys were measured by spectroscopic ellipsometry in the energy range of 1.5-5.4 eV at ～423 and at ～25 K. The peak at ～2.26 eV in the B19′ (monoclinic structure) optical conductivity spectrum has a slightly larger magnitude than in the B2 (cubic CsCl structure) phase, while the shoulder at ～3.5 eV becomes weaker and almost indiscernible upon martensitic transformation. A new structure develops at ～2.85 eV in the B19′ phase; however, it is also very weak. The band structures and the optical conductivity were calculated in both phases using the linearized-augmented-plane-wave method within the local-density approximation. k points near the Γ-X-M plane in the B2 phase and the corresponding k-points in B19′ phase contribute significantly to all three structures. The difference between the two spectra is due to the transitions between the folded-back bands from the B2 phase because of the larger unit cell of the B19′ phase and the change in the electronic energy spectrum near the Fermi level. The overall optical properties of Ni-Ti alloys in the measured energy range are rather insensitive to the martensitic transformation because the states far from the Fermi level are mainly involved in the interband transitions. 1999 The American Physical Society.
Nanocrystalline titanium-type metal hydride electrodes prepared by mechanical alloying
Jurczyk,Jankowska,Nowak,Jakubowicz
, p. 265 - 269 (2002)
Mechanical alloying (MA) was employed to produce nanocrystalline TiFe1-xNix alloys (x=0, 0.25, 0.5, 0.75 and 1.0). XRD analysis showed that, after 25 h of milling, the starting mixture of the elements had decomposed into an amorphous phase. Following annealing in high purity argon at 750°C for 0.5 h, XRD confirmed the formation of the CsCl-type structures with crystallite sizes of about 50 nm. These materials were used as negative electrodes for a Ni-MHx battery. With increasing nickel content in TiFe1-xNix, the material shows an increase in discharge capacity which passes through a maximum for x=0.75. In the nanocrystalline TiFe0.25Ni0.75 powder, discharge capacities of up to 155 mA h g-1 (at 40 mA g-1 discharge current) were measured. The titanium-based hydrogen storage alloys are attractive for secondary batteries, because of inexpensive raw materials.
Electrochemical properties of sealed Ni-MH batteries using nanocrystalline TiFe-type anodes
Jankowska,Jurczyk
, p. L9-L12 (2004)
Mechanical alloying (MA) process was introduced to produce nanocrystalline TiFe0.25Ni0.75 and TiNi alloys. XRD analysis showed that, firstly, after 20 h of milling, the starting mixture of the elements had transformed into an amorphous phase and, secondly, the annealing in high purity argon at 700°C for 0.5 h led to formation of the CsCl-type structures with a crystallite size of about 25 nm. These materials were used as negative electrodes for sealed nickel-metal hydride (Ni-MH) batteries. The results show that the sealed battery using the nanocrystalline TiFe0.25Ni 0.75 alloy has about 1.5 times the capacity of the TiNi one.
Enhancement of a peak in electrical resistivity of NiTi alloy in early stage of transformation cycles
Matsumoto, Hitoshi
, p. 132 - 136 (2004)
For a better understanding of the transformation behavior on the equiatomic NiTi alloy, the measurement of electrical resistivity was performed in the early stage of transformation cycles, and was compared with the calorimetric measurement. A faint peak in electrical resistivity is observed during the first cooling, at which the temperature is much higher in comparison with the exothermic peak. With increasing transformation cycles, the peak in electrical resistivity is enhanced, at which the temperature is close to the start temperature of the transformation from the intermediate phase to the low-temperature phase. The transformation and the reverse one show a thermal hysteresis of 30 K, and the low-temperature phase is transformed directly to the high-temperature phase, even with increasing transformation cycles. An increase in electrical resistivity with the transformation is detected in the temperature range of the low-temperature phase, which is attributable to the defects induced during the transformation. It is thought on the transformation in the early stage of transformation cycles that the transformation-induced defects play complicated roles such as the electron scattering and the stabilization of the intermediate phase to result in a peak in electrical resistivity.
Microstructure of TiNi shape-memory alloy synthesized by explosive shock-wave compression of Ti-Ni powder mixture
Han, Xiaodong,Zou, Wenhui,Wang, Renhui,Jin, Sing,Zhang, Ze,Li, Tongchun,Yang, Dazhi
, p. 4723 - 4729 (1997)
Cylinders of TiNi shape-memory alloy were synthesized from mixtures of equiatomic fine irregular titanium and nickel powders by explosive-wave compression with a detonation velocity of about 6500 m s 1. B2 type parent phase, R phase, B19′ type martensite, Ti2Ni, Ti3Ni4 and Ti2Ni3 phases were observed in this as-synthesized material. In the B2 matrix high density dislocations existed. The Burgers vectors of many dislocations were determined to be parallel to 〈111〉 directions. The R phase variants formed (001) B2 twinning structure. The substructure of the B19′ martensite was (001) B19′ type I twin and stacking faults on the (001) B19′ plane. When increasing the temperature of the as-synthesized material in a differential scanning calorimeter, no B19′ → R → B2 transitions were observed on the temperature range -50 to 100°C. However, B2 → B19′(R) transitions occurred during the cooling cycle. After heat treating the specimen at 800°C for 1 h and then ageing at 400°C for 10 min, both B2 → R → B19′ and B19′(R) → B2 phase transitions were observed.
Aoki, K.,Masumoto, T.,Kamachi, M.
, p. 33 - 42 (1985)
The electronic and electrochemical properties of the TiFe-based alloys
Szajek,Jurczyk,Jankowska
, p. 285 - 292 (2003)
Ti(Fe,M)-based alloys (M = Ni, Mo, Cr, Co) were mechanically alloyed (MA) under an argon atmosphere to synthesize nanostructured materials. XRD analysis showed that, after 25 h of milling, the starting mixture of the elements had decomposed into an amorphous phase. Following the annealing in high purity argon at 750 °C for 0.5 h, XRD confirmed the formation of CsCl-type structures with crystallite sizes of about 30 nm. These materials were used as negative electrodes for a Ni-MHx battery. The alloying elements of the 3d transition metals, Ni, Mo, Cr and Co, were substituted for iron atoms, and the structural, electronic and electrochemical properties were studied. With increasing nickel content in TiFe1-xNix, the material showed an increase in discharge capacity which passed through a maximum for x = 3/4. In the nanocrystalline TiNi0.6Fe0.1Mo0.1Cr0.1Co0.1 powder, a discharge capacity of up to 135 mA h g-1 (at 40 mA g-1 discharge current) was measured. For this composition the capacity degraded much more slowly with cycling in comparison to other studied compositions. The electronic structure was studied by the tight-binding version of the linear muffin-tin method in the atomic sphere approximation (TB-LMTO ASA). In the TiFe1-xNix alloys, increasing the content of the Ni impurities extended the valence bands and increased the density of states at the Fermi level. Similar effects were observed for the TiNi1/2Fe1/8Mo1/8Cr1/8Co1/8 system. Mechanical alloying proved to be a suitable procedure for obtaining TiFe-based alloy electrodes for Ni-MHx batteries. Elsevier Science B.V. All rights reserved.
Experimental investigation in the quaternary systems Ti-Ni-Al-N and Ti-Ni-Al-O
Huneau,Ding,Rogl,Bauer,Ding,Bohn
, p. 71 - 77 (2000)
The experimental evaluation of phase equilibria in the Ti-Ni-Al-N and Ti-Ni-Al-O phase diagrams are based on alloy samples, which were prepared of elemental powder blends by argon-levitation melting in a Hukin crucible. The experimental investigation employed X-ray powder diffraction, metallography, SEM, and EMPA techniques in the as-cast state as well as after annealing at 900°C. Two quaternary compounds Ti3NiAl2N and Ti3NiAl2O deriving from the filled Ti2Ni type (η phase) were observed. The novel phases are in equilibrium with the Ti2Ni-type solid solution phase (Ti(1-x)Al(x))2Ni, which exhibits a maximum solubility of 14 at % Al in binary Ti2Ni. Atom order in all these phases was monitored by quantitative X-ray powder diffraction (Rietveld analyses). The difference of X-ray spectra among the various phases deriving from parent Ti2Ni type was analyzed and the complex atom site occupation mode was discussed in terms of the general classification scheme for η phases. (C) 2000 Academic Press.
Electrochemical stability of orthopedic porous NiTi shape memory alloys treated by different surface modification techniques
Wu, Shuilin,Liu, Xiangmei,Hu, Tao,Jiang, Jiang,Chu, Paul K.,Yeung,Chung,Chu,Xu, Zushun,Lu,Cheung,Luk
, p. C187-C194 (2009)
The complex surface morphology and large exposed surface area induce electrochemical instability on porous NiTi shape memory alloys in human body fluids. Consequently, leaching of toxic nickel ions from the alloys impede wider applications of the material
The thermochemical behavior of some binary shape memory alloys by high temperature direct synthesis calorimetry
Meschel,Pavlu,Nash
, p. 5256 - 5262 (2011/06/25)
The standard enthalpies of formation of some shape memory alloys have been measured by high temperature direct synthesis calorimetry at 1373 K. The following results (in kJ/mol of atoms) are reported: CoCr (-0.3 ± 2.9); CuMn (-3.7 ± 3.2); Cu3Sn
