In order to realize the practical application of TiAl alloys in automobile industry, the possibility of decreasing cost of engine components by applying low-cost and recycled raw materials, in place of expensive elemental powders, was investigated. The TiAl exhaust valves with a relative density of 99% were made from chip Al and sponge Ti/Titanium Hydride (TiH₂) through the Mechanical Alloying-Pulse Discharge Sintering technique (MA-PDS). The sintered specimens from the sponge TiH₂/chip-Al system have the same level of fracture strength as those sintered from the powdered Ti/Al system, although the commercial price of TiH₂ is only one third that of Ti powder and the price of chip Al is one sixteenth that of Al powder. XRD results showed that specimens from the TiH₂/chip-Al system consisted of duplex phases of TiAl and Ti₃Al, which is identical with that of specimens from the Ti/Al powder system. On the other hand, the specimens from sponge-Ti/chip-Al system with the lowest cost have slightly lower mechanical properties caused by the unexpected coarse Al-rich phase.

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Angular dependence of the B-K edge in hexagonal BN (h-BN) has been quantitatively characterized using transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) in terms of the ratio of π^* and σ^* peaks. The dependence of the peak ratio on the scattering angle has been observed with two different values of the collection angle, 0.78 and 4.2 mrad. Under these conditions, the peak ratio of π^*⁄σ^* decreases with the increase of the scattering angle up to as much as the Bragg angle. As the angle approaches the fundamental reflection, the peak ratio re-increases, which may be attributable to the elastic scattering effect on the Bragg reflection. A change of the peak ratio in energy-loss spectra has been confirmed by the calculated peak ratio estimated by DV-Xα method.

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A study of the heat treatment behavior of lattice defects in Verneuil-grown SrTiO₃ crystals is described. Heat treatment in this study was made in atmospheric air at 1500°C for 240 h in total. The sample crystals before and after the heat treatment were investigated by X-ray topography. The observation of the sample crystals shows that the rearrangement of dislocations and the strain relaxation of the whole crystals were greatly effected by the heat treatment. In addition to those changes, the generation of new defects such as slip bands and oxygen vacancy clusters was observed.

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The synthesis of vapor-grown carbon fibers (VGCFs) using the nanocrystalline Fe₉₁Zr₇B₂ alloy as a novel catalyst, and the growth process of these VGCFs, have been investigated. We selected the nanocrystalline Fe₉₁Zr₇B₂ alloy as a novel catalyst for VGCF synthesis. The nanocrystalline Fe₉₁Zr₇B₂ alloy with fine bcc-Fe grains (∼20 nm) was prepared by a melt-spinning technique followed by annealing at 873 K for 5 min. VGCFs with a width ranging from 50 to 300 nm and a maximum length of about 6 μm were successfully prepared, by using a nanocrystalline Fe₉₁Zr₇B₂ alloy annealed at 873 K under a 80%CO–20%H₂ mixture. From HREM observation, it was found that the catalyst particle was made of fine bcc-Fe grains, and the VGCF consisted of graphite platelets with the spacing 0.396 nm, that were stacked in a direction parallel to the base of the catalyst particle and perpendicular to the fiber axis. The growth process of the VGCF using the nanocrystalline Fe₉₁Zr₇B₂ alloy can be described by two major stages, i.e., “the separation of catalyst particles” and “fiber growth.”

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The electromagnetic wave absorption properties of BaZn_2xFe_10.8+4x(Sn_0.5Mn_0.5)_1.2O_19+8x (x=0.25∼0.75) sintered bodies, consisting of BaM and BaZn₂W-type hexaferrite phases, were studied. The relative complex permittivity values hardly changed, with respect to composition (x). In the frequency dispersion of the relative complex permeability of some of the samples, two peaks were observed at frequencies centred around 14 and 17 GHz. The intensities of these permeability peaks at 14 and 17 GHz, increased and decreased with increasing x, respectively. The Reflection Loss (R.L.) was less than −20 dB, and almost the same matching thickness (d_m) was obtained in all of the samples. However, the bandwidth for R.L.≤−20 dB (ΔF) was affected by changes in composition (x), and the BaZnFe_12.8(Sn_0.5Mn_0.5)_1.2O₂₃ sample sintered at 1473 K for 10 h in air, exhibited a maximum value of ΔF=2.2 GHz, with a relatively small matching thickness of d_m=1.0 mm. When compared with a BaM-type single phase sintered body (BaFe₉(Ti_0.5Mn_0.5)₃O₁₉, d_m=0.6 mm, ΔF=0.1 GHz), the d_m was slightly larger but ΔF became wider. It is concluded that using a two-phase microstructure composed of M and W-type hexaferrite, is an effective method of expanding ΔF.

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The coherent transmission properties of armchair SWNTs with finite length are studied with the help of real space Green’s function method. In the linear conductance study, we find that SWNTs indeed act as genuine quantum wires: the conductance peak occurs in existence of resonant tunneling through a discrete electron level that is aligned with the Fermi energy E_f of the electrodes. The doubling of the conductance peaks observed in a recent experiment is numerically verified. We also find that there exist negative differential conductance region for larger bias voltage and similar transmission behavior for armchair SWNTs in the non-linear conductance study.

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γ-TiAl alloys were implanted with Nb ions with energy of 50 keV at a dose of 1.2×10²¹ ions/m². Cyclic oxidation testing on as-received and Nb⁺-implanted TiAl alloys was conducted at 1123 K in air with a flow velocity of 12 mm/s. At the initial oxidation stage, a TiO₂/Al₂O₃ mixed scale is formed on the as-received TiAl alloys whereas for Nb⁺-implanted TiAl alloys, an Al₂O₃-rich layer is observed present in the scale. During the cyclic oxidation test for up to 1100 ks, severe scale spallation occurs on as-received TiAl alloys. In contrast, Nb⁺-implanted TiAl alloys exhibit excellent cyclic oxidation resistance in flowing air.

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Vanadium-based alloys with BCC structure are known to absorb high content of protium. The reduction of costs of the alloys requires to lower V content and to have higher protium capacity. The decrease of the V content in the alloys appears to form Laves phases, which results in reduced protium capacity. It is expected that BCC former addition to the alloys will form BCC phase with less V content inhibiting formation of Laves phase. The effects of the addition of BCC former elements such as Nb, Ta, Mo, and W on protium absorbing properties and the phases of Cr–Ti–V–M alloys have been studied. It has been found that Nb, Ta, and Mo additions are effective in forming BCC structures with improved homogeneity of the alloys, resulting in flattening the slope of plateau region of their PCT curves.

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The changes in pressure-composition isotherms, structural and magnetic properties upon cyclic hydrogen absorption-desorption have been investigated for LaNi₅ and LaNi_4.7Al_0.3 in order to identify the origin of their performance degradation. The hydrogen storage capacity of LaNi₅ was observed to degrade by 35% after cycling for 2000 times whereas the degradation for LaNi_4.7Al_0.3 under the same cycling condition was only 13%. Magnetic measurements showed the presence of superparamagnetic Ni precipitates in these degraded samples. Assuming that the precipitation of Ni is the result of disproportionation, our magnetic measurements yield a degradation of 13% for the LaNi₅ sample and 9% for the LaNi_4.7Al_0.3 sample, respectively. Hence, the degradation observed for LaNi_4.7Al_0.3 can be mostly explained by taking into account the disproportionation reaction during cycling. On the contrary, the calculated degradation of LaNi₅ explains only ∼1⁄3 of the experiment. Our structural analysis suggests that the excess portion of degradation in LaNi₅ could be due to the evolution of stable protume sites in LaNi₅.

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In order to take multiple behavior of both mobile and immobile dislocations into account, Reaction-Diffusion equation is employed and a stress-strain curve is calculated. Characteristic three stages of a stress-strain curve are reproduced. The serration observed in the early stage of the deformation is interpreted based on the microscopic inhomogeneous multiplication process of dislocations leading to self-organization.

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The preparation of Nb-doped PbZrO₃ thin films by pulsed laser deposition and the effects of the Nb-doping on the dielectric properties of PbZrO₃ thin films have been investigated. By optimizing film deposition conditions and annealing temperatures, the 3 mol% Nb-doped PbZrO₃ thin films was successfully prepared under the partial oxygen pressure of 2 or 5 Pa followed by the rapid thermal annealing at 873 K for 1 min. From X-ray diffractometry, the PbZrO₃ phase was found to be crystallized without any preferred orientation. The 3 mol% Nb-doped PbZrO₃ film exhibited a double hysteresis loop with a transition field (antiferroelecric to ferroelectric phase) of 208×10⁵ V/m and saturation polarization of 20×10⁻² C/m². It was found that the Nb-doping might contribute to reduce the transition field and polarization of PbZrO₃ thin films. In addition, the Nb-doped PbZrO₃ film with a thickness of 185 nm showed a ferroelectric hysteresis loop with the parameters of Ps=22×10⁻² C/m², Pr=17×10⁻² C/m², and Ec=320×10⁵ V/m.

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The effects of “training” and ausforming on the morphology of stress-induced martensite and its reversion behavior to austenite in Fe–14Mn–6Si–9Cr–5Ni and Fe–28Mn–6Si–5Cr (mass%) alloys have been studied using atomic force microscopy (AFM), with the aim of clarifying the mechanism of the improvement of the shape memory effect. It is found that uniformly distributed thin martensite plates with a single variant nature are formed in a grain for both of the trained and ausformed samples. Those martensite plates can almost completely revert to the parent phase by shearing process, which is opposite to that of the forward transformation. This complete reverse transformation produces a perfect shape memory effect.

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Al–Al₃Ti in-situ composites with various mol%Ti of 0, 6.25, 9.40 and 12.5 were fabricated by sintering the mixed elemental powder using pulse discharge sintering process. Full density was achieved, especially for the low Ti content composites by this sintering process, except for the Al–12.5Ti composite, for which a longer sintering time is required. It was found that inducing Al₃Ti phase into Al alloy is an effective way in improving the Young’s modulus. The composites with Ti content lower than 9.4 mol%, show a Young’s modulus of around 110 GPa while maintaining reasonable ductility. Further increase in Ti content may lead to a brittle material at room temperature due to the excessive Al₃Ti volume fraction, though the Young’s modulus can be further increased.

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Based on a Heisenberg model with exchange parameters extracted from ab initio calculations, Monte Carlo (MC) simulations are carried out to study the finite-temperature properties of the L1₀ ordered FeAu superlattice. The magnetization and the specific heat are calculated as the functions of temperature, and the Curie temperature is determined by the ab initio-MC method. These results are discussed in connection with experiments and previous theoretical studies.

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The ternary compound Ti₃SiC₂ possesses an unusual combination of metallic and ceramic properties, such as, high electrical conductivity, good oxidation resistance and remarkable refractoriness. Stoichiometric mixtures of the elemental Ti, Si and C powders were heated under various conditions and the reactions among the powders were investigated to determine the processing conditions for the synthesis of Ti₃SiC₂. It was found that the formation reaction of Ti₃SiC₂ from the mixed elemental powders was very related to the formation of a eutectic liquid phase in the Ti–Si system. Porous compacts of high-purity Ti₃SiC₂ were produced by reactively sintering the powder compacts of the elemental powder premixes at 1673 K, and were readily pulverized to fine powder.

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The effect of titanium content (23.8–27.9 mol%) and vanadium content (0–6 mol%) on the microstructure and ductility of L1₂-type titanium trialuminide (AlMn)₃Ti(V) alloys has been examined by laser optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and three point bending test. The alloys used in this study exhibited a single-phase microstructure of titanium trialuminide with the L1₂ structure after a heat-treatment at 1500 K for 24 h, irrespective of the addition of vanadium. However, pores which were formed during the homogenization treatment, have been observed, and the density and size of the pores were dependent on the alloy composition. Among high Ti alloys containing more than 25.7 mol%Ti, the addition of 4 mol%V is optimum for ductility. The alloys containing less than 25.3 mol%Ti exhibited higher ductility than the high Ti alloys, and the alloys with 6 mol%V exhibited the maximum ductility, about 0.86% bending strain. The decrease of titanium content and/or pore size increases the ductility of the single phase alloys in quaternary (AlMn)₃Ti(V) alloys.

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Different from the continued hardening of Cr phase in Cu–15Cr in situ composites, the micro hardness of Cr phase in Cu–15Cr–0.5Fe in situ composites decreases with increasing drawing strain when drawing strain exceeds 1.6. In order to investigate the mechanism of the Cr softening caused by drawing, TEM (transmission electron microscopy) observations were made on the Cr fibre obtained at different drawing strains. It was found that the dislocation density in the deformed Cr phase in Cu–15Cr–0.5Fe in situ composites decreases with drawing strain increasing from 4.5 to 6.9, which is the result of the dynamic recovery, and the reason of the softening of Cr.

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The protium absorption-desorption properties of Ti–V–Cr–(Mn, Ni) alloys were investigated in conjunction with Mn, Ni and V contents and heat-treatment conditions. The compositions studied were (1) Ti–35V–(37–x)Cr–xM (M=Mn and Ni; 0≤x≤15), and (2) Ti–xV–Cr–M (M=Mn and Ni; 15≤x≤45) in which the content of Ti, Cr, and M was fixed at a ratio of 28:32:5. The addition of Ni reduced the protium storage capacity and increased the plateau pressure due to the formation of a Ti₂Ni secondary phase, and to the incorporation of Mn into the BCC matrix phase. Increasing the V content was found to be an effective way of stabilizing the BCC phase, and thereby increasing the protium storage capacity. For Ti–V–Cr–Ni alloys, the slope of the plateau region was also improved by increasing the V content. In addition, the Mn-added alloy after annealing at 1573 K exhibited an almost uniform BCC solid solution and a storage capacity as high as 2.6 mass%; however, the Ni-added alloy still contained the Ti₂Ni phase. The addition of Mn was found to be an effective way of decreasing the slope of the plateau region.

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The higher order regular solution model was extended to include the exchange interaction between the collinear magnetic moments of metallic atoms and chemical interaction between nonmetallic and metallic atoms. Using the extended model, the dependency of hydrogen solubility on temperature in ferromagnetic metal Ni was investigated, and it was found that magnetization does not favor the dissolution of hydrogen.

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Heavily porous FeSi₂ bulky materials for thermoelctric conversion elements have been developed via a spark plasma sintering process. FeSi₂ bulky materials with a porosity ratio of about 45% were molded into U-type thermoelectric conversion elements in which the p-type and n-type FeSi₂ were separated by insulating glass fiber sheets. The Doping elements used were Co and Mn. Ag mesh electrodes were firmly attached, simultaneously by the sintering process, to the surface of the sintered products. A thermoelectric power of 0.5–0.7 mV/K at 300–500 K and an apparent internal resistivity of 3.99×10⁻³ Ωm at 448–479 K have been obtained, which shows a potential for use in power generation by gas-combustion and heat-exchange type thermoelectric processes.

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The 1s core level energy is calculated for a few hypothetical structures of C_xN_1−x including α-C₃N₄, β-C₃N₄ and graphitic-C₃N₄ by using the all-electron mixed-basis approach. The results are compared with the XPS measurement of a diamond film irradiated with N₂⁺ ions. The comparison suggests that the irradiated film is amorphous C_xN_1−x whose local structure is similar to β-C₃N₄ or graphitic-C₃N₄.

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A thick intermetallic compound Al₃Ti layer was formed on a Cu or Ti substrate by a novel coating process, using combustion synthesis of a ball-milled Al–Ti powder mixture. The relation between the initial Ti particle sizes and heat treatment conditions required to react with Al completely was estimated by a spherical model incorporating diffusion kinetics to obtain homogeneous compound layer free from unreacted elements. Based on the calculated relation, a homogeneous Al₃Ti layer was formed by using finely ball-milled powder particles with a microstructure such that Ti particles less than 1.0 μm are dispersed in the Al matrix. This layer had almost the same wear property and hardness as that of a cast Al₃Ti.

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By using a simulated-annealing technique with a tight-binding molecular-dynamics, optimized structures of neutral and positively- and negatively-charged Ti clusters are determined for the number of atoms n=2–16. It is found that the clusters with the sizes of n=7, 9, 13 and 15 are specifically stable compared to those with the other sizes. These magic numbers agree well with the experimental results of time of flight mass spectrometry and collision induced dissociation with Xe. The physical origin of the magic numbers is discussed.

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A direct observation has been conducted to study the local corrosion of solid silica at the surface of molten silicon. The maximum local corrosion depth of solid silica (linear loss, ΔL/mm) has been measured in relation to various influencing factors. The thermodynamic analysis has been done for the corrosion reactions. Transfer pass of oxygen during corrosion procedure was analyzed based on these thermodynamics and kinetics. Up-and-down oscillation of molten silicon meniscus in the local corrosion zone has been confirmed. It is revealed that the main cause of the local corrosion for solid silica is the Marangoni effect caused by the surface tensions gradient, which is the result of the gradient of oxygen concentration along the meniscus surface of molten silicon formed in the vicinity of SiO₂(s)–Si(l)-gas three phases boundary.

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With the purpose of developing thick metal/metal graded-boundary materials, the fabrication experiment of Cr/Steel graded-boundary materials was carried out using a laser beam and an electron beam. In order to produce a compositionally graded boundary region between the substrate steel and the added Cr metal, a series of surface alloying treatments were performed with both a CO₂ laser beam and an electron beam. A Cr sheet was placed on a commercial low carbon steel, and then a CO₂ laser beam was irradiated on the surface to produce a homogeneous alloyed layer. On this first surface-alloyed layer, another Cr sheet was placed and then the CO₂ laser beam was used again to produce a second surface-alloyed layer. Four sequential repetitions of the laser surface alloying treatment resulted in a compositionally graded region with about a 2 mm thickness from 60%Cr and 40%Fe in the surface region to 0%Cr and 99%Fe in the substrate. Similar procedures were carried out by an electron beam surface alloying treatment to produce Cr/Steel graded-boundary material. Four sequential surface-alloying treatments resulted in a compositionally graded region with a thickness of about 1 mm from 60%Cr and 40%Fe in the surface region to 0%Cr and 99%Fe in the substrate. In both cases, no visible root porosities were found in the graded-boundary region. Since the structures of both the high Cr graded-boundary region and the substrate were both BCC, there was almost no volume change and thus no appreciable cracks were formed in the boundary region between the alloyed layers and the substrate even after rapid cooling.

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