Molecular beam epitaxial growth of SrO and CaO with RHEED intensity oscillation

SrO and CaO, related compounds of BSCCO superconductor, are grown onto SrTiO₃(100) substrates with molecular beam epitaxy(MBE) technique. During growth, the specular spots of RHEED patterns show intensity oscillations, indicating two dimensional growth. The periods of oscillations are utilized to calculate the atom fluxes. It is shown that sublimation processes of both Sr and Ca metals in the effusion cells are stable under the growth condition of oxide films. The periods of oscillations during the SrO growth are independent of substrate temperature, confirming that Sr atoms are oxidized immediately and stay on the substrate surface without re-evaporation. These informations are practically available for precise control of the atomic layer controlled MBE of BSCCO superconductor thin films.On leave from Superconductiivity Research Laboratory, ISTEC.     

Experimental characterization of high-speed impact damage behavior in a three-dimensionally woven SiC/SiC composite

This paper discusses high-speed impact damage in a three-dimensionally woven SiC/SiC composite (3D-CMC). The impact damage was introduced by a steel ball projectile in 3D-CMC plates with and without thermal exposure. The surface and internal damages were observed by optical microscopy and X-ray CT. A crater was observed on the collision surface. The X-ray CT measurement revealed that multiple pyramid-shaped cone cracks were generated beneath the crater when the impact speed was relatively low. At an impact speed exceeding the critical speed, a spall fragment was ejected from the back surface, while no internal damage was observed in the fragment. The spall fracture mode differed between the virgin and the thermally-exposed specimens. This difference is the result of embrittlement of the fiber/matrix interface due to oxidation of the carbon coating layer in the thermally-exposed specimen. In addition, it is found that z-yarns improve impact resistance by constraining delamination.     

Interphase transfer of tackifier between poly(butadiene) and poly(styrene-co-butadiene)

The interphase transfer behavior of poly(styrene-co-α-methyl styrene), which is known as a tackifier in rubber industry, is investigated using poly(butadiene) rubber (BR) and poly(styrene-co-butadiene) rubber (SBR). The films of pure rubbers and the blends with the tackifier were prepared by a solution-cast method using toluene as a solvent. Two sheets composed of different rubbers, in which the tackifier was mixed at least in one rubber sheet, were piled together and annealed beyond the glass transition temperature T _g of the tackifier. The transfer phenomenon of the tackifier between the sheets was evaluated by the peak shift in the tensile loss modulus E″ curve, ascribed to T _g of the rubbers, which was measured by the dynamic mechanical analysis. Moreover, crystallization temperature of BR was also employed as a measure of the transfer, because the tackifier retards the crystallization of BR. It is found that the tackifier moves from one rubber to another during annealing procedure to reduce severe localization. When the content is the same in each rubber, the tackifier immigrates from BR to SBR, suggesting a better miscibility with SBR. This behavior is attributed to the small difference in the solubility parameter between SBR and the tackifier as compared to that between BR and the tackifier.     

Synthesis of New Superconducting Pb-Based 1222 Cuprates Containing Sulfur in the (Pb0.75S0.25)Sr2(Eu2.0−x Ce x )Cu2O z System

We have synthesized new Pb-based 1222 cuprates containing sulfur in the (Pb_0.75S_0.25)Sr₂(Eu_2.0?x Ce _x )Cu₂O _z system. X-ray diffraction study shows that almost the single 1222 phase samples can be obtained for a considerable wide area of 0.3≤x≤1.2 in the composition of (Pb_0.75S_0.25)Sr₂(Eu_2.0?x Ce _x )Cu₂O _z . Next, the sample with x=0.4 after annealing under high-pressure O₂ is discovered to show an onset of the resistivity drop at about 31 K and to show an onset of diamagnetic signal at about 29 K. These phenomena clearly indicate that the sample is a new superconductor.     

Effect of molding pressure on fabrication of low-crystalline calcite block

We have reported that low-crystalline porous calcite block, which is useful as a bone substitute or a source material to prepare apatite-type bone fillers could be fabricated by exposing calcium hydroxide compact to carbon dioxide gas saturated with water vapor. In the present study, we investigated the effect of molding pressure on the transformation of calcium hydroxide into calcite and the mechanical strength of the carbonated compact. Transformation into calcite was almost completed within 72 h, however, a small amount of Ca(OH)₂ still remained unreacted at higher molding pressure because of incomplete penetration of CO₂ gas into the interparticle space due to dense packing of Ca(OH)₂ particles. On the other hand, high molding pressure resulted in an increase in diametral tensile strength (DTS) of the calcite compact formed. Critical porosity of the calcite block was calculated as approximately 68%.     

Vibration analysis of cubic rotary-linear piezoelectric actuator

Cubic design of a stator in a rotary-linear piezoelectric actuator is sophisticated and interesting, but the vibration theory of the cubic stator remains unclear when using the finite element method (FEM). In this paper, we analyze the vibration behavior of the cubic stator by applying the energy method, which distinguishes the component of mechanical energy. By changing the design of the stator (especially the length in the direction of the through-hole axis), we clarify how the vibration modes are in accordance at one equal frequency in cubic shape. The behavior of the vibration modes is discussed using conventional vibration theory of a beam and a plate.     

Internal stress behavior of the short ceramic fiber reinforced aluminum alloy under tensile deformation

The in situ measurement of phase stress under tensile deformation on an A6061 alloy reinforced with SiC whiskers (Al/SiCw MMC: Metal Matrix Composite) was performed using the X-ray diffraction technique. In order to raise a preciseness of measurements, we applied a profile fitting technique to separate the nearby located diffraction peak. Tensile deformation on elastic to plastic range was applied by four points bending device and discussed internal stress behavior in the short ceramic fiber reinforced MMC. Phase stress in Al matrix was increased linearly up to 2800×10⁻⁶ in strain and then saturated immediately. On the other hand phase stress in SiC whiskers shows an unstable stress behavior. It was decreased at first because of the Poisson's effect from Al matrix but reversed over 500×10⁻⁶ applied strain. The measured phase stress behavior in elastic region agreed with the calculations using micromechanics based on Eshelby/Mori–Tanaka model except for this unstable internal stress region. The macro stress behavior in plastic region was extremely small than that of the tensile test results. It supposed that the mechanism of strength is not so much the fiber reinforcing as the dispersion strengthening like the Orowan mechanism. Regarding the fatigue property, ΔK_th of the Al/SiC MMC, this was lower than that of the A6061 alloy. On the Al/SiCw MMC specimen, many micro void formations were observed around the fatigue crack tip even under the ΔK_th of A6061. It was considered that these were caused by the high gradient of residual stress on composite process and the unstable stress behavior in low ΔK region.     

950 keV, 3.95 MeV and 6 MeV X-band linacs for nondestructive evaluation and medicine

We are developing compact X-band linac X-ray sources for nondestructive evaluation and medicine. First, we develop a portable X-ray system by a 950 keV 9.4 GHz X-band linac to realize on-site inspection. We use a low power (250 kW) magnetron as an RF source for compactness of the whole system. Since the RF power source is quite small and the stored energy in the structure is also small, we faced the problem of beam loading and current/RF-power oscillation. We are analyzing the problem by the circuit model. We plan to use this system for erosion inspection of metal pipes of petrochemical complex. By adopting a side-coupling cavity design to avoid the oscillation, we have developed 6 MeV X-band (9.3 GHz) linac for pinpoint dynamic tracking cancer therapy. Furthermore, we are manufacturing 3.95 MeV X-band (9.3 GHz) linac X-ray source with flexible waveguides for on-site bridge inspection. Updated results and situations are presented.     

Fullerene Production in Tons and More: From Science to Industry

In the last decade, application of fullerenes has been proposed actively in a wide range of areas, and recent developments suggest that many of those applications are to be practical technologies. However, there has been no large-scale production enterprise for commercial usage of fullerenes. High production cost and limited availability of fullerenes have been the main obstacle in the development of the Fullerene Market. Improved flame-based technology leads to the most feasible process for mass production of fullerenes, since it is a continuous process and uses inexpensive hydrocarbons as its starting materials. In May 2003, we started fullerene production in tons and more to supply fullerenes with reasonable price as practical materials for industries.     

Thermodynamic properties for the quaternary system H2O + CH3OH + LiBr + ZnCl2

The thermodynamic properties (solubility, vapour pressure, density, viscosity, heat capacity and heat of mixing) of the H₂O + CH₃OH + LiBr + ZnCl₂ (9:1 H₂O:CH₃OH and 1:1 LiBr:ZnCl₂ by mass) system using H₂O + CH₃OH as the working media and LiBr + ZnCl₂ as the absorbents were measured. The solubility data were obtained in the temperature range from 270.35 to 389.55 K. The measurements of vapour pressure, density, viscosity and heat capacity were carried out at various temperatures and absorbent concentrations. The differential heat of dilution and differential heat of solution at 298.15 K were measured for solutionw with absorbent concentrations from 0 to 75.2 wt%. The integral heat of mixing data at 298.15 K were obtained from both sets of experimental data. The integral heats of mixing for this quaternary system showed exothermic behaviour. The vapour pressure data were correlated with an Antoine-type equation. An empirical formula for the heat capacity was obtained from experimental data. The experimental data for the basic thermodynamic properties of this quaternary system were compared with those of the basic H₂O + LiBr system.