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Cracks developed by tensile loading in the Si thin film deposited on the Ti–50.3Ni (at%) substrate were closed by the shape memory effect of the substrate. The interfacial layer formed after annealing at 873 K between the Si thin film and the substrate was essential for the shape memory effect-induced crack closure. Cracks which formed during lithiation in the Si thin film annealed at 873 K after deposition were closed by delithiation followed by heating up to 373 K.

Ternary Ti-Nb-Zr alloys were prepared by a magnetron sputtering method with porous structures observed in some of them. In bulk, in order to control the porous structure, a space holder (NH4HCO3) is used in the sintering method. However, in the present work, we show that the porous structure is also dependent on alloy composition. The results from Young&rsquo, s modulus tests confirm that these alloys obey d-electrons alloy theory. However, the Young&rsquo, s modulus of ternary thin films (&asymp, 80&ndash, 95 GPa) is lower than that for binary alloys (&asymp, 108&ndash, 123 GPa). The depth recovery ratio of ternary Ti-Nb-Zr thin films is also higher than that for binary &beta, Ti-(25.9&ndash, 34.2)Nb thin film alloys.

It is well-known that the behavior of shape memory alloys (SMAs) depends on varying the temperature and dynamic loading frequency. However, the relationship between SMA behavior and cyclic loads has not been clearly discussed. This relationship is very important in the field of seismic application of SMAs. Therefore, this study arranges several dynamic tensile tests of martensitic and austenitic SMA bars. The parameters of the tests are the initial strain of the SMA bars, the number of cycles, and the loading frequency. The hysteretic curves of the stress–strain relation are measured, and the mechanical properties of the residual strain, Young's modulus is varied at first, but becomes stable after 250 cyclic loading. However, the damping ratio decreases continuously when the number of loading cycles increased. It is found that the initial strain and loading frequency do not affect the mechanical properties significantly. Only the residual strain is influenced by the amount of initial strain but not the loading frequency.

Nanostructured implant materials are considered as promising future biomaterials. Specifically, titanium based nanomaterial is the mostly used implant materials in orthopedic, dental and vascular surgeries. Due to the advantage of nanoscale features, treatment with nano porous and nano bump surface features have shown enhanced biocompatibilities, such as adhesion, proliferation and differentiation for bone and vascular cells. In addition, nanotoxicity issue with immune cells (macrophages) is currently paramount interest for determining subsequent tissue cellular response on implanted biomaterials. In this review, we demonstrated altered cellular interaction of bone, vascular cells on nanostructured titanium based alloys/materials through systematic controlling of nanoscale surface features, such as porosity and nanobumps. All this knowledge will be beneficial for both understanding and designing nanostructured biomaterials for increasing biocompatibility, thus, all these endeavors will lead increment of functionality of biomaterials and will eventually prolong the life time of implanted biomaterials.

Mo is added to Ti–Nb alloys in order to enhance their superelasticity. The shape memory properties of Ti–(12–28)Nb–(0–4)Mo alloys are investigated in this paper. The Ti–27Nb, Ti–24Nb–1Mo, Ti–21Nb–2Mo and Ti–18Nb–3Mo alloys exhibit the most stable superelasticity with a narrow stress hysteresis among Ti–Nb–Mo alloys with Mo contents of 0, 1, 2 and 3 at.%, respectively. The ternary alloys reveal better superelasticity due to a higher critical stress for slip deformation and a larger transformation strain. A Ti–15Nb–4Mo alloy heat-treated at 973 K undergoes (2 1 1)〈1 1 1〉-type twinning during tensile testing. Twinning is suppressed in the alloy heat-treated at 923 K due to the precipitation of the α phase, allowing the alloy to deform via a martensitic transformation process. The Ti–15Nb–4Mo alloy exhibits stable superelasticity with a critical stress for slip deformation of 582 MPa and a total recovery strain of 3.5%.

Silicon thin film annealed at 973 K for 7.2 ks after being deposited on a Ti–50.3Ni(at%) substrate was not detached from the substrate after 2.2% tensile deformation, which was ascribed to a diffusion bonding between the Si film and substrate. The B2–B19′ transformation start temperature ( M s ) of the Ti–Ni substrate with Si thin film increased by annealing, which was ascribed to a tensile stress developed by the difference in thermal expansion coefficient between the Si film and substrate.

Spatially varying temperature profile generated by the Joule heating of a Ti–45Ni–5Cu (at%) alloy wire was investigated by experiment and analysis. The Joule heating is a simple and effective method to fabricate shape memory alloy (SMA) actuators for proportional control. By applying a voltage drop of 1.338 V, a temperature gradient between 504 K and 413 K was obtained experimentally over a length of 30 mm SMA wire. A closed-form expression derived from a simple analytic model was suggested to predict the temperature profile, and the result of the finite element analysis was also provided. Finally, it is demonstrated that the Joule heated specimen shows a low shape recovery rate of 0.02%/K and a unique Luders-type deformation with a progressively increasing stress level from 340 MPa to 380 MPa.

Melt overflow improved the workability and shape memory characteristics of a Ti–20Ni–30Cu (at.%) alloy by suppressing the formation of TiCu phase and introducing crystallographic defects such as dislocations. The fracture stress and strain of the alloy strip prepared by melt overflow were 445 MPa and 7.6%, respectively, which were larger than those of the alloy rod fabricated by conventional casting. Transformation hysteresis of the strip was 3.8 K under 120 MPa, which was much smaller than that of the rod.

The nano-sized cobalt powders were prepared using a pulsed wire evaporation method. The cobalt powder had a spherical shape with a diameter of less than 200 nm. A cobalt electrode was prepared from the nano-sized cobalt powder, acetylene black and polyvinylidene fluoride. During the first discharge, the Li/Co cell showed a plateau potential of 0.7V and a capacity of 440mAh/g. The nano-sized Co electrode had a stable reversible lithium storage capacity of approximately 280mAh g−1 after 30 cycles.

By annealing Ni film/Li film/Ti–50Ni alloy in O 2 atmosphere, we fabricated a superelastic electrode consisting Ti–LiNiO 2 film as a cathode material and TiNi substrate as a current collector. The electrode with partial shape memory effect and superelasticity exhibited a high operating voltage of 3.7 V and a good reversibility of Li ion. An increased M S of TiNi alloy in the electrode was attributed to a compressive stress imposed by TiO 2 and Li 0.98 Ni 0.7 Ti 0.3 O 1.92 layers.

Ni sulfides were formed by reacting Ni substrates with gaseous sulfur, and then their microstructures were investigated. Ni sulfides consisted of four distinct layers, i.e., the topmost thin film layer (I), dense thick film layer (II), coarse particulate layer (III), and innermost fine particulate layer (IV). XRD and electrochemical analyses demonstrated that layers I, II and IV were NiS 2 , NiS and Ni 3 S 2 , respectively and layer III was a transient layer where Ni 3 S 2 was converted into NiS by Ni 3 S 2 + S → NiS reaction.

The sodium/copper sulfide (Na/Cu 2 S) rechargeable batteries are investigated using 1 M NaCF 3 SO 3 -TEGDME liquid electrolyte at room temperature. The first discharge curve of Na/Cu 2 S cells shows a slope shape without plateaus potential region. The first discharge capacity is 294 mAh g −1 and decreases to 220 mAh g −1 after 20 cycles. The discharge process can be explained by intercalation of sodium into Cu 2 S phase without phase separation of Cu 2 S.

Lithiated nickel oxide films were thermally synthesized using Ni / Li / Ni films at various temperatures between 873 K and 1123 K. Structural and electrochemical properties of the synthesized films were investigated by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and galvanostatic charge–discharge half-cell tests between 4.5 V and 2.5 V. Lithiated nickel oxide films with the composition near stoichiometric LiNiO 2 could be obtained under annealing conditions (973–1073 K, 1 h). Surfaces of synthesized films consisted of some particles and became smoother with an increase in annealing temperature. Particles with the sharpest edge were formed at 1023 K. Cells with synthesized electrodes showed reversible Li ion transfer and clear voltage plateaus in charge–discharge curves that can confirm the phase transformation of LiNiO 2.

The shape memory alloy strips of Ti 50 Ni 30 Cu 20 and Ti 50 Ni 25 Cu 25 have been fabricated by arc melt overflow technique. Their microstructures and shape memory characteristics were investigated by means of X-ray diffraction (XRD), optical microscopy and differential scanning calorimetry (DSC). The microstructure of the as-cast strips exhibited columnar grains normal to the strip surface. XRD analysis showed that the martensitic transformation of B2–B19 occurred in the alloy strips. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2–B19 transformation were observed to be 4.9°C and 1.8% in Ti 50 Ni 30 Cu 20 alloy strip and 3.5°C and 1.7% in Ti 50 Ni 25 Cu 25 alloy strip. The as-cast strip of Ti 50 Ni 25 Cu 25 alloy also showed a perfect superelasticity and its stress hysteresis was as small as 14 MPa. These mechanical properties and shape memory characteristics of the alloy strips were ascribed to B2–B19 transformation and the controlled microstructures produced by rapid solidification of the arc melt overflow process.

In order to clarify the effect of annealing on the shape memory behavior of Ti -50.85at.% Ni alloy, the deformation and transformation behavior were investigated using tensile tests and differential scanning calorimeter (DSC). The martensitic transformation temperature increases with increasing annealing temperature until it reach as a maximum, and then decreases with further increasing annealing temperature. This can be rationalized by interaction between the distribution of Ti 3 Ni 4 precipitates and recovery of cold-worked structure. The R-phase transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with a further increase of annealing temperature. This is attributed to the change of Ni content in the matrix caused by precipitation of Ti 3 Ni 4. The critical stress for slip decreases rapidly with increasing annealing temperature, influenced by interaction between the distribution of Ti 3 Ni 4 precipitates and recovery of cold-worked structure.

The relationship between the parent phase grain size and the B2–B19 martensitic transformation start temperature ( M s ) was investigated in a Ti–30Ni–20Cu alloy ribbon fabricated by melt spinning. The average grain size of the ribbons increased from 0.7 to 1.2 μm with increasing crystallization temperature from 748 to 823 K without significant compositional change and precipitation. M s increased from 308 to 317 K with increasing crystallization temperature from 748 to 823 K, which was ascribed to the increase in grain size.

The shape memory alloy strips of Ti50Ni15Cu35 and Ti50Ni10Cu40 had been fabricated by arc melt overflow. Their microstructures and shape memory characteristics were investigated by means of X-ray diffraction, optical microscopy and differential scanning calorimetries. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that one-step martensitic transformation of B2-B19 occurred in the alloy strips. According to the DSC analysis, it was known that the martensitic transformation temperature (Ms) of B2→B19 was 71.2°C in Ti50Ni15Cu35 and 64.5°C in Ti50Ni10Cu40 alloy strip, respectively. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be 4.9°C and 1.4% in Ti50Ni15Cu35 alloy strip. However, Ti50Ni10Cu40 alloy strip was so brittle that its mechanical properties could not be measured.

Microstructures, shape memory characteristics and the superelasticity of Ti–45Ni–5Cu (at.%) alloy ribbons were investigated by transmission electron microscopy, thermal cycling tests under constant load and tensile tests. Coherent Ti2Ni particles less than 13 nm in diameter are formed when the melt spinning temperature is higher than 1773 K. The ribbons with coherent Ti2Ni particles do not show a residual elongation, which may be ascribed to the increase due to the coherent Ti2Ni particles of the critical stress for slip deformation by the coherent Ti2Ni particles. Almost perfect superelastic recovery is found in the ribbons containing coherent Ti2Ni particles, while only partial superelastic recovery is observed in Ti2Ni particle-free ribbons.

Ni and Ti sulfides are formed on the surface of a Ti 50 Ni 50 alloy by annealing the alloy at 873 K for 0.24-72 ks under the sulfur pressure of 160 kPa, and then microstructures, martensitic transformation behavior, shape memory characteristics, superelasticity and electrochemical properties are investigated by means of scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, thermal cycling tests under constant load and tensile tests. NiS 2 particles are formed first on the surface of the alloy, and then are grown and coalesced with increasing annealing time. When annealing time is longer than 1.2ks, in addition to NiS 2 , Ti 8.2 S 11 sulfide is formed, and therefore the surface sulfide layers is consisted of NiS 2 and Ti 8.2 S 11 . A Ti 50 Ni 50 alloy with the surface sulfide layers shows the shape memory effect and superelasticity clearly. A Ti 50 Ni 50 alloy with the surface sulfide layers shows clear discharge behavior with an increase of annealing time. Multi-voltage plateaus of 1.89, 1.70 and 1.42 V are observed at a cell with electrode annealed for 1.2 ks and an additional plateau at 2.0 V appeared at cells of 3.6 and 10.8 ks. NiS 2 is not transformed into pure Ni and Li 2 S during discharging process directly but is transformed by way of intermediate phases such as NiS and Ni 3 S 2 .

The discharge properties of a Na/Ni 3 S 2 cell using 1 M NaCF 3 SO 3 in tetra(ethylene glycol)dimethyl ether liquid electrolyte were investigated at room temperature. The products were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Electrochemical properties of Na/Ni 3 S 2 cells were also presented by cyclic voltammetry and the galvanostatic current method. Na/Ni 3 S 2 cells have an initial discharge capacity of 420 mAh g -1 with a plateau potential at 0.94 V versus Na/Na + . After the first discharge, Ni 3 S 2 and Na react at room temperature and then form sodium sulfide (Na 2 S) and nickel. Sodium ion can be partially deintercalated from Na 2 S charge reaction. The discharge process can be explained as follows: Ni 3 S 2 + 4Na ↔ 3Ni + 2Na 2 S.

Nanostructured Ti-Ni alloys were prepared by cold working followed by annealing, and then their shape memory characteristics and superelasticity were investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM), thermal cycling tests under constant load and tensile tests. Morphology of amorphous phases induced by cold working depended largely on the amount of cold working. They had domain like shape in the 40% cold rolled alloy, while had mainly wide band shape in the 70% cold rolled alloy. In 40% cold rolled alloy, the average grain size increased from 27 nm to 80 nm with increasing annealing temperature from 573 K to 673 K. Transformation elongation increases with raising annealing temperature, which was ascribed to the increase in grain size reducing the constraints of grain boundaries. Transformation hysteresis increased rapidly with raising annealing temperature up to 623 K, above which they almost keep constant, which was ascribed to the small grain size and large constraints of grain boundaries.

Microstructures and deformation behaviour of Ti-45Ni-5Cu and Ti-46Ni-5Cu alloy ribbons prepared by melt spinning were investigated by transmission electron microscopy, thermal cycling tests under constant load and tensile tests. Spherical Ti2Ni particles coherent with the B2 parent phase were observed in the alloy ribbons when the melt spinning temperature was higher than 1773 K. Average size of Ti2Ni particles in the ribbons obtained at 1873 K was 8 nm, which was smaller than that (10 nm) in the ribbons obtained at 1773 K. Volume fraction of Ti2Ni phase in the ribbons obtained at 1873 K was 40%, which was larger than that (20%) in the ribbons obtained at 1773 K. The stress required at temperatures of Af + 10 K for the stress-induced martensitic transformation increased from 93 MPa to 229 MPa and apparent elastic modulus of the B2 parent phase increased from 56 GPa to 250 GPa with increasing the melt spinning temperature from 1673 K to 1873 K in Ti-45Ni-5Cu alloy ribbons. The critical stress for slip deformation of the ribbons increased by coherent Ti2Ni particles, and thus residual elongation did not occur even at 160 MPa, while considerable plastic deformation occurred at 60 MPa in the ribbons without Ti2Ni particles. Almost perfect superelastic recovery was found in the ribbons with coherent Ti2Ni particles, while only partial superelastic recovery was observed in the ribbons without coherent Ti2Ni particles.

This study evaluates the strain-dependence of Clausius–Clapeyron relation of the stress-induced martensitic transformation in a Ti–50.8 at.% Ni. The transformation strain is altered by means of pseudoelastic cycling. It is found that the σ–T linearity coefficient of the relation is greater for the reverse transformation than for the forward transformation, consistent with the smaller transformation strain of the reverse transformation, and that the coefficient increases with mechanical cycling, resulting from decreases of the transformation strains caused by the mechanical cycling. The thermodynamic analysis indicates that the reduction in transformation strain with cycling is caused partially by a reduction in the transformation volume and partially by a reduction in the degree of orientation of the martensite variant.

A flexible wire Li battery was fabricated using a thermal-sulfurized Ti–Ni alloy as a cathode material. Sulfides formed by the sulfidation had a layered structure consisting of NiS 1.97 , NiS and Ti 8.2 S 11 . Sulfur pressure was an important factor to control the sulfur content in the sulfide and the thickness of the sulfurized layers. No apparent changes in thermal and mechanical properties were found after the sulfidation of the Ti–Ni alloy at 80 kPa. The shape memory effect and the superelasticity still remained after the sulfidation. The discharge capacity of sulfurized Ti–Ni alloy applied to the Li battery was measured to be over 400 mAh/g-NiS 1.97 until the fifth cycle. The initial discharge capacity of our homemade wire battery with 1 mm of diameter and 100 mm of length was 0.66 mAh-cell.

Effect of partial thermal cycling through incomplete B2 → B19′ martensitic transformation on the transformation behaviour of NiTi was investigated. This investigation was carried to assess the property stability of NiTi during operation in applications involving repeated transformation cycles. Partial thermal or mechanical cycling has been considered a remedy for more stable operation in such applications. It was observed that on equal transformation volume basis partial transformation cycling was less damaging compared to full transformation cycling. This observation is indicative that less structural damages are created during the early stages of the B2 → B19′ martensitic transformation and that incomplete transformation cycling has certain advantage in minimising the shift of shape memory properties of NiTi.

Ti 50 –Ni 30 –Cu 20 alloy ribbons without any crystal phases have been fabricated at the wheel velocities of 55 m/s and the melt spinning temperature of 1500 °C by melt spinning process. Their microstructures and shape memory characteristics were investigated by means of optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The crystallization temperature was measured to be 440 °C. The crystallized ribbon exhibited fine microstructure after annealed at 440 °C for 10 min and was deformed up to about 6.8%. During thermal cycle with the applied stress of 220 MPa, transformation hysteresis and elongation associated with a B2–B19 transformation were observed to be 4 and 3.6%. The ribbons showed a perfect superelasticity and their stress hysteresis was as small as 20 MPa which was attributed to the single pair martensite variants in small grains. This controlled microstructure was achieved by a proper heat treatment of amorphous ribbons in Ti 50 –Ni 30 –Cu 20 alloy.

To develop the battery with low cost and high energy density, Na/FeS2 battery was prepared using FeS2 powder synthesized by mechanical alloying. With increasing the milling time from 20 to 60 h, the size of FeS2 powder decreased from 0.85 to 0.55 μm. The discharge capacity of Na/FeS2 battery depended on the synthesizing condition of FeS2 powder. The FeS2 electrode prepared by 30 h milling showed the highest discharge capacity of 447 mAh g−1-FeS2. The discharge capacity decreased continuously by repeated charge–discharge cycling, and remained 70 mAh g−1-FeS2 after 50th cycles. The Na/FeS2 cell could be used as a rechargeable battery at room temperature.

Transformation behavior and shape memory characteristics of temperature gradient anneal (TGA) treated and thermo-mechanically treated (TMT) Ti–47Ni–3Cu(at.%) alloys were investigated by means of differential scanning calorimetry and thermal cycling tests under constant load. Both TGA treated and TMT Ti–47Ni–3Cu alloys showed B2–B19' transformation behavior. The change in Ms * by 23 K was developed in the TGA treated Ti–47Ni–3Cu alloy along the length of the sample (150 mm). TGA treated Ti–47Ni–3Cu alloy showed perfect shape memory effects. The temperature dependence of elongation (de/dT) of a TGA treated specimen was in the range of 0.02–0.09% K−1 depending on the amount of applied stress, which was small compared to that of a TMT specimen (0.01–0.18% K−1). The temperature dependence of elongation (de/dT) of the TGA treated specimen on cooling is almost the same as that on heating, while de/dT of the TMT specimen on cooling is much smaller than that on heating (0.68% K−1).

Six batches of Ti50Ni50-xCux alloy (x=0–25) were prepared by a melt overflow process and strips of about 550 μm thickness were fabricated by rapid solidification. Microstructures and shape memory characteristics were investigated by means of x-ray diffraction (XRD), optical microscopy, differential scanning calorimetry and thermal cycling tests under a constant load. The microstructures of the as-cast strips exhibited columnar grains normal to the strip surface. XRD showed B2–B19' martensitic transformation in the Ti50Ni50 binary alloy strip, while B2–B19 martensitic transformation in all the ternary alloy strips. The transformation temperature (Ms) increased with Cu-content. During cycle deformation with an applied stress of 60 MPa, the smallest transformation hysteresis and the largest elongation associated with the B2–B19 transformation were observed to be 3.5% in Ti50Ni25Cu25 alloy strip and 3.02% in Ti50Ni40Cu10 alloy strip.

Li0.98Ni0.7Ti0.3O1.92 (LNTO) cathode material for Li ion batteries was thermally synthesized using Ni/Li/TiNi film and Li/TiNi film. Structural and electrochemical properties of the synthesized electrodes were investigated by means of x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and galvanostatic charge?discharge half-cell test. A large amount of LNTO was synthesized in a Ni/Li/TiNi system compared to a Li/TiNi system, and the Ni film in the Ni/Li/TiNi system restrained Li leakage during thermal synthesis at high temperature. The surface of the annealed Ni/Li/TiNi film consisted of a peel-off layer part (Li2O2) and an exposed surface part (LNTO). A cell with LNTO electrode synthesized in the Ni/Li/TiNi system showed 103?mAh?cm?2 initial discharge capacity and 83% of capacity retention after 10 cycles.

A novel design of the functionally graded near-equiatomic NiTi shape memory alloys that exhibit expanded ranges of transformation temperature and stress is developed. The approach utilises the sensitivity of the alloys' thermomechanical properties with respect to heat treatment conditions. The functionally graded properties are achieved by anneal within a temperature gradient after cold work, thus to create a continuous structural variation. The optimum annealing temperature range for the Ti–50.5 at.% Ni alloy is determined to be 630–800 K. Gradient-anneal of the alloy wire in this temperature range resulted in varying thermal transformation behaviour along its length and unique Luders-type deformation behaviour with a positive stress gradient for both the forward and the reverse transformations. Such behaviour enhances the functionality of the alloy for actuation applications.

Ni sulfides were formed on a Ni-deposited Ti–50.0Ni(at) alloy by annealing under a sulfur pressure of 100 kPa at 673 K for 0.36 ks. Martensitic transformation, superelasticity and electrochemical properties were characterized using different techniques. Ni sulfides consisting of NiS and NiS2 of thickness 0.8 μ m were formed by a reaction between Ni and S. Some spherical particles and pores were found in the sulfides. A Ti–50.0Ni alloy with Ni sulfide surface layers showed a two-stage B2–R–B19' transformation behavior. A partial superelasticity with a superelastic recovery ratio of 78% found in a current collector showed a clear discharge behavior with a voltage plateau between 1.3–1.6 V. Discharge capacities of the Ni sulfide cathode decreased largely from 700 to 510 mAh(g-NiS2)−1 with increasing number of cycles up to 3, above which it decreased gradually.

Carbon nanotubes (CNTs) have been synthesized through chemical vapor deposition in argon gas atmosphere using Fe–2.5%Mo alloyed nanoparticles as a catalyst and H2/CH4 gas mixture as a reaction gas. Fe–2.5 wt.%Mo alloyed nanoparticles with average diameter of 7, 20, 45 and 85 nm are prepared by the chemical vapor condensation process using the pyrolysis of iron pentacarbonyl (Fe(CO)5) and molybdenum hexacarbonyl (Mo(CO)6). The morphologies of the CNTs are controlled by adjusting the nanoparticle size, reaction gas ratio and reaction temperature. With decreasing nanoparticle size under the same experimental conditions, the degree of crystalline perfection increases gradually and the morphologies of the carbon nanotubes vary from multi wall carbon nanotubes to single wall carbon nanotubes. Also, the ratio of reaction gas has an effect on the morphology and the degree of crystallinity of CNTs. In this work, it is suggested that morphology, diameter and degree of crystallinity of CNTs could be controlled by adjusting the reaction gas ratio, reaction temperature and catalyst size.

Ti-51Ni(at%) and Ti-40Ni-10Cu(at%) alloy wires with diameters of 0.3mm, 0.5mm and 0.7mm were prepared by drawing the alloy ingots fabricated by vacuum induction melting. Heating rates of the wires were investigated by measuring changes in temperatures of them while applying currents in the range of 1 A and 6 A to them and cooling rates were investigated by measuring changes in temperatures of them after cutting currents. Heating rate increased with increasing the amount of current, while cooling rate was kept constant. Both heating rate and cooling rate increased with decreasing diameter of wire. This suggested that high amount of current and small wire diameter were required for high heating and cooling rate. Comparing Ti-50Ni alloy wires with Ti-40Ni-10Cu alloy wires, heating rates of the latter was faster than that of the former, although cooling rates were almost same. This suggested that Ti-40Ni-10Cu alloy wires is better than Ti-50Ni alloy wires for the applications requiring high actuating rates.

Si film electrodes for Li micro-film batteries were fabricated on a Cu substrate and a Ci/Cu film. In the structural properties, FE-SEM observation demonstrated difference in surface morphologies of Si films with different under layers. Surface of the Si film deposited consists of clusters and average size of the cluster was 165 nm for Si/Cu film and 80 nm for Si/C/Cu film. Si film has amorphous phase in spite of different under layers; Cu substrate and C/Cu film. In the electrochemical properties, the carbon-inserted film showed a good cycleability compared with Si/Cu electrode. It is believed that the insertion of carbon film as a buffer film absorbed the stress generated during charge-discharge process and improved cycle performance of Si anode electrode.

Deformation behavior of temperature gradient anneal(TGA) treated Ti-50.0Ni(at%) alloys were investigated by means of thermal cycling tests under constant load and tensile tests. TGA treated Ti-Ni alloy wires showed a sequential deformation behavior along the length of the specimen since the stress required for the B2-B19’ transformation increased with decreasing annealing temperature. Considerably large residual elongation(about 0.4 %) occurred in the TGA treated Ti-Ni alloy under the applied stress of 80 MPa, which is ascribed to the fact that yield stress of the sample annealed at 823 K is lower than the stress required for the B2-B19’ transformation of the sample annealed at 658 K.

Ti–Ni and Ti–Ni–Cu alloy ribbons have been prepared by single roll melt spinning, and then martensitic transformation behaviours were investigated by means of transmission electron microscopy, differential scanning calorimetry and X-ray diffraction. In 51Ti–49Ni(at.%) alloy ribbons, Ti 2 Ni particles of a size less than 50 nm with the coherent interface with the matrix were found, while they were not found in 50Ti–50Ni alloy ribbons. In 49Ti–46Ni–5Cu and 50Ti–45Ni–5Cu alloy ribbons, Ti 2 Ni particles of size less than 30 nm with coherent interface with the matrix were found. Coherent Ti 2 Ni particles induced the R phase transformation in Ti–Ni alloys, and consequently transformation occurred in two-stages, i.e., B2–R–B19. Coherent Ti 2 Ni particles induced the B19 martensite in a Ti–45Ni–5Cu alloy, and consequently transformation occurred in two-stages, i.e., B2–B19–B19′. The change in transformation behaviour was ascribed to strain fields developed around coherent Ti 2 Ni particles.

Ti 50 Ni 30 Cu 20 (at.%) alloy ribbons have been fabricated by melt spinning and then their microstructures and shape memory characteristics were investigated by means of X-ray diffraction optical and transmission electron microscopies and differential scanning calorimetry. In these experiments particular attention has been paid to change the velocity of cooling wheel from 33 m/s to 55 m/s to control the thickness of ribbons. Microstructural analysis of melt-spun ribbons showed that the proportion of amorphous solidification at the chilled side of the ribbon increased with wheel. The perfect amorphous ribbon was produced in Ti 50 Ni 30 Cu 20 alloy when the ribbon was fabricated at the wheel velocity of 55 m/s and the melt spinning temperature of 1500 °C. After annealing the amorphous ribbons at 440 °C for 10 min, they were crystallized with fine grains of B19 phase. The effect of these microstructural changes on martensitic transformation behaviours is discussed.

Various physical, chemical and mechanical methods, such as inert gas condensation, chemical vapor condensation, sol-gel, pulsed wire evaporation, evaporation technique, and mechanical alloying have been used to synthesize nanoparticles. Among them, chemical vapor condensation(CVC) represents the benefit for its applicability to almost materials because a wide range of precursors are available for large-scale production with a non-agglomerated state. In this work, iron nanoparticles and nanowires have synthesized by chemical vapor condensation(CVC) process, using iron pentacarbonyl(Fe(CO)5) as precursor. The effects of processing parameters on the morphology, microstructure and size of iron nanoparticles and nanowires were studied. Iron nanoparticles and nanowires having various diameters were obtained by controlling the inflow of metallic organic precursor. Both nanoparticles and nanowires were crystallized. Characterization of obtained nanoparticles and nanowires were investigated by using a field emission scanning electron microscopy, transmission microscopy and X-ray diffraction.

TiNi shape memory alloy (SMA) thin sheets with a thickness of 120 μm were fabricated by the method of bonding and cold rolling and subsequent heat treatment of elemental Ti and Ni foils. The annealing temperature and time have been investigated with regard to their effects on the phase composites and microstructures of the as-roll-bonded Ti/Ni multilayers. It is found that the TiNi phase which shows shape memory effect is easily to be synthesized by the subsequent heat treatment even though it was preformed by annealing at a relatively low temperature of 650 °C and for a short time of 6 h. The shape memory effect has been examined by DSC for the fabricated TiNi thin sheets and it reveals a good martensitic and reverse transformation behavior from B2 to B19′ of M s at around 60 °C and transition hysteresis of about 30 °C. A tensile test at the temperature above A f revealed that recovery strains of average 1.5% in superelasticity has been obtained for the TiNi thin sheets.

A Ti-Ni alloy compositionally graded along the thickness direction in order to obtain a shape change over a wide temperature range, which is beneficial to the actuator for precise position control, was prepared by spark plasma sintering (SPS) after stacking Ti-Ni alloy ribbons in the sequence of Ti-51Ni, Ti-50Ni, Ti-49Ni and Ti-48Ni (at%) followed by annealing. Then, the microstructure and martensitic transformation behavior were investigated by using FE-SEM, DSC and thermal cycling tests under a constant load. The inter-ribbon defects observed after SPS due to insufficient diffusional bonding between the ribbons were eliminated by post-SPS annealing at 1023 K for 36 ks. The compositionally graded sample showed compositional variation of 1.5 at% Ti along the thickness direction (- 120 μm) and a martensitic transformation temperature window as large as 91 K on cooling and 79 K on heating. A recoverable elongation of 0.9% was obtained under a stress of 80 MPa and the deformation rate, which is defined as the ratio of the recoverable elongation to the temperature range where the elongation occurred was 0.015%/K in the compositionally graded sample.

Si film electrodes were deposited onto Cu foil current collectors fabricated with well-formed CuO nanostructures. The structural and electrochemical properties of the Cu foils oxidized for 1, 3, and 6 h and of the Si film electrodes were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), and charge/discharge tests. The morphologies and XRD profiles suggested that the oxidized Cu foils consisted of a top CuO layer and a bottom Cu2O layer. The surface roughness of the Cu foils decreased with increasing oxidation time since the flower-like CuO nanostructures weakly adhered to the surface were easily detached by ultrasonic cleaning. The cycle performance of the Si film electrode with the rougher CuO layer rapidly deteriorated, whereas the flat Cu2O layer showing a relatively high electric conductivity induced the formation of a dense Si film and improved the electrochemical performance of the Si film electrode.

In this study superelasticity and corrosion characteristics of 50Ti–(45-X)Ni–5Cu–XMo alloys have been investigated by means of electrical resistivity measurements, X-ray diffraction, tensile tests, polarization tests, and optical microscopy. Substitution of Mo for Ni in a Ti–45Ni–5Cu alloy induces the B2–B19 transformation and the stability of the B19 martensite increases with an increase in Mo content. Superelastic recovery of 50Ti–(45-X)Ni– 5Cu–XMo alloys increases from 33 to 91% with an increase in Mo-content from 0 to 0.5%. The 50Ti–(45-X)Ni–5Cu–XMo alloys show small stress hysteresis below 100 MPa. The pitting potential of 50Ti–(45-X)Ni–5Cu–XMo alloys also increases with the increase in Mo content.

The low temperature behaviors of Li/TEGDME/S cell was examined using discharge curves, SEM and impedance spectra. The first discharge capacity of Li/S cell with tetra(ethylene glycol) dimethyl ether (TEGDME) electrolyte was 1303 mAh g −1 -sulfur at 20 °C, but 357 mAh g −1 -sulfur at low temperature of −10 °C. The low temperature discharge characteristic is improved by adding 1,3-dioxolane (DOXL) and methylacetate (MA) to TEGDME electrolyte. The optimum composition of mixed electrolyte is MA–DOXL–TEGDME (5:47.5:47:5, v/v). The Li/S cell using the optimum electrolyte has the first discharge capacity of 994 and 1342 mAh g −1 -S at −10 and 20 °C, respectively.

We investigated self-discharge characteristics of Li/S batteries using tetra ethylene glycol dimethylether (TEGDME) electrolyte. The open circuit voltages (OCV) and discharge curves were measured as a function of storage time. The self-discharge of the Li/S battery depended on current collectors. Li/TEGDME/S batteries with stainless steel (SUS) current collector showed the highest self-discharge rate of 59% per month. The self-discharge rate of Li/TEGDME/S battery using Al current collector is 34% during initial 80 days, but only 36% after 360 days storage. The discharge capacity decreases only 2% from 80 to 360 days. The self-discharge of Li/S battery using Al current collector is severe during initial 80 days, but is not an important factor after 80 days. Average self-discharge rate of Li/TEGDME/S battery using Al current collector is 3% per month for 1 year.

Conventional lead-rubber bearings may have a problem of instability and unrecovered deformation with a strong ground motion. As a way of solving the problem, this study proposes a new concept of an isolation device in which shape memory alloy wires are incorporated in an elastomeric bearing. A three-span continuous steel bridge was used for seismic analyses to compare the performance of lead-rubber and the proposed bearings. The proposed bearings limit the deck relative displacement effectively with strong ground motions and recover almost original undeformed shape.

Ti–45Ni–5Cu (at.%) alloy ribbons have been fabricated by melt spinning at various melt spinning temperatures with a linear velocity of 31.0 m/s, and shape memory characteristics and superelasticity were investigated by means of thermal cycling tests under constant load and tensile tests. The ribbons obtained at the melt spinning temperatures above 1673 K showed two-stage deformation corresponding to the B2-B19-B19′ transformation. The temperature gap between M ′ s (the B2-B19 transformation start temperature) and M s (the B19-B19′ transformation start temperature) increased with increasing the melt spinning temperature. Transformation hysteresis associated with the B2-B19 transformation was measured to be about 12 K, irrespective of the melt spinning temperature. The ribbons with the melt spinning temperature higher than 1723 K showed perfect superelasticity. Stress hysteresis associated with the B2-B19 transformation was less than 45 MPa, which was ascribed to a formation of single-pair martensitic variants in each grain.

Stabilization of the B19 martensite by rapid solidification in a Ti–45Ni–5Cu (at.%) alloy has been investigated by means of differential scanning calorimetry and transmission electron microscopy. Rapid solidification process induced the B2–B19 transformation prior to formation of the B19′ martensite, and thus the two-stage B2–B19–B19′ transformation occurred in as-spun Ti–45Ni–5Cu alloy ribbons. Inducement of the B19 martensite was ascribed to the formation of Ti2Ni particles coherent with the B2 matrix. With increasing Ti content from 49 to 51 at.%, the temperature range where the B19 martensite exists was expanded from 7 to 25 K, which was attributed to an increase in volume fraction of Ti2Ni particles from 10 to 55% and a decrease in the size from 16 to 5 nm.

Transformation behaviors and shape memory characteristics of Ti50Ni30Cu20 (at.%) alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry, X-ray diffraction, and optical microscopy. The alloy was solidified as amorphous ribbon by a melt spinning process. After annealed at 440 °C for 10 min, the crystallized ribbon was deformed up to about 6.8% in ductile manner. A temperature hysteresis associated with the B2–B19 transformation was observed to be 4 K. These properties are mainly attributed to the controlled microstructures of the alloy ribbon.

Solidification structures and shape memory characteristics of Ti–30 at.% Ni–20 at.% Cu alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change the ejection temperature of the melt from 1350 to 1500 °C and the velocity of cooling wheel from 33 to 55 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on solidification structures and martensitic transformation behaviors is discussed.