Search

This study develop the solar tracking system of a nonelectric power source by using a metal hydride (MH) actuator with solar radiation drive. The proposed tracking system includes two MH reactors of the same shape that are placed perpendicular to the solar cell array. A shielding plate is installed between the MH reactors to interrupt the solar radiation from each MH reactor. The solar angle of direction changes when there is a temperature difference between the MH reactors. This is because a gap occurs in the equilibrium pressure of the hydrogen sealed hermetically in each reactor, and the actuator angle of direction follows the sun according to this pressure difference. This study also present the result of the proposed system after four months of testing. Moreover, this study examine the wind’s influence on the proposed MH actuator by applying heat fluid simulation. In order to achieve highly reliable solar tracking with the proposed system, excessive cooling by wind should be prevented by installing a windshield.

X-ray diffraction measurements were performed using synchrotron radiation at the SPring-8 facility and electrochemical techniques to investigate the effect of polishing methods and storage conditions on the crystal structure of air-formed oxide films and anodic oxide films formed on highly pure aluminum. Storage in an N 2 environment hinders local film breakdown during anodizing, and it was established that the X-ray diffraction measurements showed the presence of a γ-Al 2 O 3 in the anodic oxide film formed on mechanically polished (MP) specimens. Formation of γ-Al 2 O 3 during anodizing was inhibited by electropolishing because of the removal of the work-hardened layer that was formed on the MP by electro-polishing. The X-ray diffraction results do not show clear differences in the influence of the polishing method on the crystal structure of air formed oxide film. This is due to the very fast oxidation rate of the air-formed oxide film and very long storage times for the X-ray measurements. The anodic oxide film formed on aluminum, which has a very flat surface, shows color and the color depended on grain orientation. The electrochemical impedance of the MP specimen is slightly lower than that of the mechanically and then electrochemically polished specimen at the middle frequency range. This impedance difference may be due to formation of γ-Al 2 O 3 in the amorphous anodic oxide film and the thickness of the film. C.

“Environmental cell” microscopy was applied for surveying gas reaction of hydrides in magnesium base alloys, which are candidates for hydrogen storage materials in advanced hydrogen energy systems. In order to clarify the mechanism of hydrogenation process, in-situ experiment has been carried out by using a 200 kV transmission electron microscope (TEM) equipped with a newly developed environmental cell, which is capable to 0.1 MPa in the temperature range between R.T. and 200°C. When hydrogen gas reacted with magnesium powders, straightening of surface steps (60~70 nm in height) was observed, indicating that volume expansion occurred. In addition, the formation of MgH2 was indicated in selected-area-diffraction patterns (SADP). The precise study on this in-situ experiment, as well as its improvement, will be continued, with using transparent films.

NaAlH4 has a theoretical hydrogen capacity of 5.6 wt. % with two-step reaction, and the control of the reaction temperature and reversibility is a critical issue for onboard application. To clarify nano-structural details of decomposition of NaAlH4, the in-situ annealing experiment was carried out in a high resolution microscope. It was confirmed that NaAlH4 decomposed at between 200 and 300°C, resulted in formation of many gas bubbles at interface between the particle and oxide film. A reactive intermediate, Na3AlH6, may decompose in this temperature range. Sodium alanate particle was originally agglomeration of small nano-sized crystal with the size of 10 – 20 nm, and the crystal grain grew to 110 nm in diameter after completing decomposition at around 400°C. This is the first step for examination of the microstructural response of catalysts on hydrogen storage materials.

To clarify hydrogen effects on mechanical properties of pure vanadium, two kinds of tensile tests were performed using hydrogen charged miniature specimens at room temperature. One is with hydrogen charging prior to testing, and the other is with hydrogen charging during testing with continuous or intermittent methods. The cathodic hydrogen charging was carried out electrolytically in various concentrations of H2SO4 with different current densities. The hydrogen charged specimens were tested to obtain stress–strain curves. The fractography was performed by SEM, and hydride formation and microstructural change were examined by TEM. Hydrogen-induced softening and hardening in vanadium resulted from hydrogen charging. The variations in mechanical property of specimens depended on the amount of dissolved hydrogen, that was determined by hydrogen diffusion and hydrogen desorption. Dislocation motion also plays a role in the variation of flow stress.

Chemical and topological disorderings in the NiTi intermetallic compound during electron irradiation were studied using a combination of in situ irradiation inside a high-resolution high-voltage electron microscope and image analyses of molecular-dynamics-simulated atom configurations. It was found that metastable defect clusters formed during the chemical-disordering phase prior to topological disordering leading to amorphization. These planar defect clusters contributed to the characteristic diffuse scattering were also observed in selected-area diffraction patterns.

Temporal nanostructural fluctuations brought about by transient metastable atom-cluster formation during radiation-induced amorphizing transformation in the intermetallic compound NiTi, observed using a combination of high-resolution high-voltage electron microscopy and molecular dynamics simulation, were characterized in terms of power-law responses of non-equilibrium energy-dissipative systems. Within the framework of the multi-Lorentzian picture, the resultant power law also describes the multirelaxation time (i.e. cluster lifetime) distribution. In addition, a unified relation for the autocorrelation functions for such fluctuation phenomena is discussed.

Materials responses under non-equilibrium conditions, especially in the state far-from-equilibrium, have been attracting great interest. Although of limited use, there are some tools available for investigating the phenomena, e.g. theoretical approaches such as non-equilibrium thermodynamics or atomistic computer simulation. The present study centers on high-resolution TEM of ordered NiTi specimens subjected to ultra-high-speed plastic deformation at Hiroshima Institute of Technology. Various local non-equilibrium nano-phases were observed to form due to high-speed deformation. Image analysis using high-resolution electron microscopy (HREM) simulation and the FFT technique revealed that those meta-stable phases in the Ni–Ti system were R-phases (Ni4Ti3), O-phases (Ni3Ti2) and amorphous phases. The current study also elaborates on the formation and nature of deformation-induced lattice invariant shear bands. Our results suggest that ultra-high-speed deformation is a promising tool to study the material responses in far-from-equilibrium states.

We performed a dynamical-atomistic study of radiation-induced amorphization in the NiTi intermetallic compound using in situ high-resolution high-voltage electron microscopy and molecular dynamics simulations in connection with image simulation. Spatio-temporal fluctuations as non-equilibrium fluctuations in an energy-dissipative system, due to transient atom-cluster formation during amorphization, were revealed by the present spatial autocorrelation analysis.

The effects of hydrogen in vanadium, V–5Cr and V–5Ti have been evaluated by the change in surface and in microstructure and by the aspect of fractured surfaces. Hydrogen accumulation promotes local concentration of hydrides and assists the generation of stacking faults. Under increased stress, crack propagation occurs by the successive formation of crack fronts.

In situ tensile straining experiments have been carried out on thin films of the ordered intermetallic compound NiTi (B2 structure) in a high-voltage electron microscope. Real-time observations of stress-induced local amorphization of moving crack tips were followed by high-resolution transmission electron microscopy examination of nanocrystalline regions formed near the crack tip and in the region between the amorphous and crystalline regions. We have also independently confirmed the occurrence of local amorphization by ultra-high speed deformation at an atomistic level in bulk samples of the same NiTi sample. A fast Fourier transformation (FFT) image analysis technique was used to determine the root mean square displacement (RMSD) parameter within the nanocrystalline regions. The RMSD parameter increases to a critical fraction of the nearest neighbor distance of 0.12±0.01 as the amorphous region is approached, and this finding agrees with the generalized Lindemann melting criterion for amorphization pro...

In the Mo–Si system, there are three typical intermetallic compounds. In order to get insight into the phase stability under irradiation, interface structure and non-equilibrium phase formation in multilayer materials with several nanometers scale were investigated by means of high-voltage electron microscope. The initial structure was composed of crystalline Mo and amorphous Si layers, and transition layer existed at the interfaces. The thickness of transition layers is thicker at the Mo-on-Si than at the Si-on-Mo interface. While those structures were basically stable after thermal annealing up to 773 K, two types of amorphous layers developed during electron irradiation at room temperature: one is an amorphous-Si layer and the other is a Mo–Si mixing layer. And the radiation-induced amorphization was accompanied by anomalous shrinkage in the thickness of layers. It is suggested that those phenomena are related to non-equilibrium phase formation and biased diffusion process during irradiation.

We successfully isolated one microorganism (UMI-21) from Ulva, a green algae that contains starch. The strain UMI-21 can produce polyhydroxyalkanoate (PHA) from starch, maltotriose, or maltose as a sole carbon source. Taxonomic studies and 16S rDNA sequence analysis revealed that strain UMI-21 was phylogenetically related to species of the genus Massilia. The PHA content under the cultivation condition using a 10-L jar fermentor was 45.5% (w/w). This value was higher than that obtained after cultivation in a flask, suggesting the possibility of large-scale PHA production by UMI-21 from starch. A major issue for the industrial production of microbial PHAs is the very high production cost. Starch is a relatively inexpensive substrate that is also found in abundant seaweeds such as Ulva. Therefore, the strain isolated in this study may be very useful for producing PHA from seaweeds containing polysaccharides such as starch. In addition, a 3.7-kbp DNA fragment containing the whole PHA synthase gene (phaC) was obtained from the strain UMI-21. The results of open reading frame (ORF) analysis suggested that the DNA fragment contained two ORFs, which were composed of 1740 (phaC) and 564 bp (phaR). The deduced amino acid sequence of PhaC from strain UMI-21 shared high similarity with PhaC from Ralstonia eutropha, which is a representative PHA-producing bacterium with a class I PHA synthase. This is the first report for the cloning of the PHA synthase gene from Massilia species.

We have carried out an atomistic study of electron-induced amorphization of an ordered intermetallic compound NiTi by means of in-situ high-resolution high-voltage electron microscopy observations and molecular dynamics simulations. Both theoretical and experimental results show that metastable nanometre-size atomic clusters form and disappear during irradiation, so that a spatiotemporal fluctuation under amorphization is induced. Mean-lifetime measurements of these clusters demonstrate that high-energy particle irradiation provides a useful tool to study dynamic fluctuations of the local atomic structure in the non-equilibrium open systems.

Pure vanadium, V–5Cr, V–5Ti and V–5Cr–5Ti alloys doped with different amounts of hydrogen were tested under tension and observed under TEM in order to clarify the interaction between hydrogen and vanadium. Hydrogenated samples tested under tension showed a typical hydrogen-embrittlement behavior. TEM observation suggests that the embrittlement is caused by hydrogen diffusion at the triple point of grain boundaries, hydride formation and the subsequent generation of dislocations and micro-cracks.

In order to form the silicide at relatively low temperature, ion-beam-mixing was applied to Mo/Si and Ti/Si systems in a temperature range from room temperature to 473 K. After the irradiation of 1 MeV Si + , the cross-sectional specimens were examined by transmission electron microscopy and X-ray microanalysis. Crystalline silicide formation was achieved only in Mo/Si system irradiated to high dose at each temperature. The evaluation of interdiffusion coefficient indicated that the diffusion is predominant in the ion-beam-mixing process. The nucleation process of silicide and the phase stability are discussed.

ODS ferritic steels (13Cr–0.5Ti–0.2Y2O3) were prepared by the mechanical alloying method followed by the hot extrusion and several heat treatments including recrystallization. ODS steels with different heat treatment and a ferritic/martensitic (F/M) steel for the reference were irradiated to 12 dpa at 670–770 K in HVEM. After recrystallization, the dislocation density decreased with increasing grain size, however, the oxide particles did not show any obvious change in the size and the number density. During the electron-irradiation the microstructure was relatively stable, i.e. oxide particles showed good stability and the dislocation density remained almost constant. A limited void formation was observed in the specimens, and the suppressive effect due to dislocations with high number density was confirmed. From these results, the behavior of microstructure and the limited void formation in ODS steels have been discussed.

Acidic cupric sulfate solution, equilibrated with copper at 220°C, was injected into the same solution which was already placed in a large stainless reservoir.From the observation of the solution and the measurement of light transmittance through the solution, it was found that the solution was clear for a short while after injection and suddenly became turbid. The fact suggests that the homogeneous nucleation of copper take place after some induction period.The particle numbers formed per unit volume (N) could be approximately expressed as a function of supersaturation degree (S)N=S2.05×108.7From the observation of internal structure with TEM and SEM, it was found that copper particles were polycrystals which had radial internal structures.

In order to improve initial activation properties of TiFe alloy, simple ion implantation and ion mixing with the deposition of LaNi 5 were carried out at room temperature. The results show that argon-ion mixing caused extensive improvement of initial activation, wherein hydrogenation was easily effected at 373 K and 1 MPa. Those results are related to several irradiation effects; the re-crystallization of amorphous film of LaNi 5 and the local segregation of composed elements. Both of these irradiation effects greatly improve the initial hydrogenation process of TiFe alloy.

We have studied nanostructural fluctuations during electron irradiation in the ordered intermetallic compound NiTi by performing irradiation experiments with a high-resolution high-voltage electron microscope (HVEM) and molecular dynamics (MD) simulations. It was observed that atom clusters formed and disappeared repeatedly during irradiation, which results in the structural fluctuation. Comparing the experimental results with the MD simulations, we conclude that such spatio-temporal structural fluctuations under irradiation can be accounted for the evolution of metastable nanoclusters. The present study demonstrates the usefulness of high-resolution HVEM for in situ studies of dynamic, nanoscale fluctuation phenomena.

High-energy ion-beam mixing technique was applied for the surface modification of austenitic stainless steel, followed by electrochemical characterization and microstructural observation. The co-mixing of silicon and chromium resisted the passivation current to 1/1000 relative to the un-modified condition. The corrosion resistance improved remarkably. Microstructural observation revealed that the enhanced diffusion and induced amorphous structure introduced by the co-mixing of silicon and chromium, which played a very important role in the improvement of electrochemical behavior at surface.

Organic materials or polymers, which are widely used in electronic devices, are easily damaged by energetic ion or electron bombardment. Therefore, it is difficult to use conventional ion or electron beam processes for etching organic materials. In this study, a gas cluster beam possessing kinetic energy of the order of several hundred eV was used as a novel means to realize high-rate, low-damage etching. Polyethylene (PE) and polyvinyl chloride (PVC) were used as the target organic materials. Using a SF6 cluster beam, the etching depth suddenly increased when the nozzle gas pressure exceeded 0.6 MPa, as in the case of cluster beam formation. When the SF6 gas pressure in the nozzle was 1.2 MPa, the etching rates of PVC and PE were 2.88 μm/s and 1.62 μm/s, respectively. The dependence of the etching effect on cluster size was studied by varying the gas temperature. The etching depth of PVC increased with increasing average cluster size and intensity of the beam. The flow rate of the gas was constant; hence, etching of the organic materials did not occur because of the individual impact of the molecular beam. In fact, it occurred because of the neutral cluster, which had a large total kinetic energy. The energy per molecule of the gas cluster beam is of the order of several tens of meV; hence, high-rate, low-damage etching of organic materials can be potentially achieved.

Experimental condition to make fine copper powder by disproportionation reaction and the physical properties of powders obtained were studied.A 3 l-reactor to produce large amount of samples, similar to the 1 l-reactor described previously, was used. Fine copper powder (1-2μm) which was similar in shape and diameter to that with the 1 l-reactor was obtained.By use of the 3 l-reactor, the formation of larger copper powders more than 10μm which were surrounded with flat crystal surface planes could be achieved.Mixed powder, which consists 70% of large powder and 30% of small powder, showed the maximum tap density of 5.1g/cm3. Densely sintered product was obtained when mixed powders were sintered for 2.5 hours at 1, 000°C. Some results in thermomechanical analysis and SEM micrographs of sintered products are included.

One of impotent materials issues of Ti-Cr-V based hydrogen storage alloys is to improve cyclic degradation of storage capacity, which has been assumed to be the effect of internal stress. We focused on the sub-micron structure of this material, which can be accumulated during cyclic use. We used 24Ti-36Cr-40V alloy for the specimens, after FZ melting. Powered samples were fabricated by mechanical grinding under Ar environment. Vacuum annealing was carried out for reducing residual stress and lattice defects. PCT properties were tested at 293 K under 4.5 MPa. XRD and TEM were carried out for important samples. In the first cycle, the annealing resulted in the increasing of storage capacity, but in the second cycle the improving was disappeared. Comparing microstructures with and without annealing, complex dislocation structures were observed after cyclic hydrogenation. It is notable that dislocation free structure was some time observed in the fine grains of less than 0.1 micron, which suggests the possibility of fine structure without defect accumulation.

From the irradiation resistance and high-temperature strength, oxide dispersion strengthened (ODS) ferritic steels are candidate materials for advanced and fusion reactors. For the development of advanced steels the key issue is to homogenize nano-particles into matrix. Recent studies have indicated that Ti addition can homogenize Y-Ti complex particles into ferrite matrix, but the reason of the effect of additional elements has not been clarified. In this model study, we focus on the effect of additional elements, such as IV and V families and other oxide formers, which can control potentially the distribution of the oxide particles. The materials used in this study were based on Fe-9Cr-Y{sub 2}O{sub 3} alloys which were mechanical alloyed (MA) from the powder of Fe, Cr and Y{sub 2}O{sub 3}, which was added systematically with the element of Ti, Zr, Ta, V, Nb, Hf, Al, Si and others. Usually ODS fabrication process is required for hot extrusion, but we annealed up to 1150 C for simplify the microstructure. To evaluate the distribution of ODS particles; we used TEM equipped with EDS after electro-polishing or FIB techniques. (1) In the case of Si or Al addition, oxides were disappeared after MA process, which means Y{sub 2}O{sub 3}more » and other elements should be in solution at non-equilibrium condition. Two types of oxides of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} or SiO{sub 2} developed after the annealing at 850 C, but only complex oxides were developed after the annealing at 1150 C. This result suggests that the oxide formation is independent process for Y and Si or Al. (2) In the case of Ti addition, oxides also were disappeared after MA process, but developed after annealing at 1150 C. This means that Ti can stabilize complex oxides of Y and Ti, and enhance the fine distribution of the oxides comparing with simple Fe-9Cr-Y{sub 2}O{sub 3} alloy. (authors)« less

High-resolution and “environmental cell” microscopy were applied for surveying the reaction of hydrides in Vanadium and Magnesium based alloys, which are candidate for hydrogen storage materials of advanced hydrogen energy systems. For clarify the hydrogenation process, in-situ experiment was carried out by using 200 kV TEM equipped with a newly developed environmental cell, which is enable to observe transmitted image and electron-diffraction under gas reaction under hydrogen environment of 0.1 MPa at room temperature. In case of Vanadium, bending fringe was created under hydrogen-gas of 0.1 MPa, which means that hydrogen reaction is not so quick in this case, and the local stress due to the hydrogen solution caused the fringes. In case of Magnesium, the gas reacted with the powders and showed the swelling, where the surface steps with several ten nm become to more straight, and also SADP showed the formation of MgH2. In-situ experiment for hydrogenation reaction by using the environmental cell has started recently, therefore the precise studies will be continued, as well as its improvement, especially in the transparence films.

Ion-implantation was applied to the surface modification of ZrNi for improving the surface activation of hydrogen absorbing alloys. At the condition of low temperature, only implanted areas showed micro-cracks and pulverization. At high temperature, the reaction was very rapid and both implanted and shielded areas showed the pulverization. The results indicate hydrogen ion-implantation can enhance the activation of this alloy, and the roles of radiation-induced implanted hydrogen and surface film are discussed.

Cu etching was carried out at a low substrate temperature using a gas cluster ion beam (GCIB) under an acetic acid gas atmosphere. A very shallow Cu surface was oxidized by O2-GCIB irradiation. Reactions between copper oxide and acetic acid occurred, and the reaction products were desorbed by local heating owing to the O2-GCIB irradiation. Thus, Cu etching at a low substrate temperature (2-GCIB irradiation, the etching depth of Cu became almost 29 times higher than the depth achieved when the etching was carried out using O2-GCIB alone at an acceleration voltage of 5 kV. In addition to the etching of Cu, there was no surface roughening after O2-GCIB irradiation under acetic acid atmosphere.