Phthalocyanie, one of the most common organic semiconductor molecules, was molecularly modified and its electronic structure was investigated by means of visible spectroscopy, photoelectron emission analysis and molecular orbital calculations. The exchange of π-conjugating carbon and nitrogen atoms in the four-fold macrocyclic ring of zinc phthalocyanine (ZnPc) yielded tetrapyrido-tetraazaporphyrinatozinc (ZnTAP(Py)4) and tetrabenzporphyrinatozinc (ZnTBP). The replacement of the four aza nitrogen atoms in the meso position of ZnPc with the methine groups resulted in a pronounced Soret band in the absorption spectrum of ZnTBP due to the change in its frontier orbital distribution. The ionization potential increased in the order of ZnTBP<ZnPc<ZnTAP(Py)4, accordingly to the caluculeated electronic energy levels of the highest occupied molecular orbitals. Electronic delocalization at the pyridine groups in ZnTAP(Py)4 lowered the molecular orbital energies, which also leaded to the observed n-type behavior as compared to the p-type conduction of phthalocyanines.
This paper describes radical-source molecular beam epitaxial growth of ZnO films on a-plane sapphire substrates. Reflection high-energy electron diffraction observation and x-ray diffraction measurement show that single-crystalline ZnO (0001) films without any rotational domains are obtained on the sapphire substrates. Photoluminescence spectra measured at 300K exhibit an intense emission peak from free excitons. Hall measurement shows that phonon scattering becomes dominant with increasing temperature and a relatively high electron mobility of -100cm2/Vs with a low residual electron density of -4×1017cm-3 at 300K is achieved.
The improvement of piezoelectric thick films formed on Si substrates is required to develop piezoelectric microactuators. In fabricating Pb(Zr, Ti)O3-Pb(Zn, Nb)O3 (PZT-PZN) films on Si, it is important to lower the firing temperature of thick films and use buffer layers on Si to prevent the reaction of Si and Pb in the PZT-PZN films. Two kinds of additives, PbO-Ge2O3 (PGO) and Bi2O3-ZnO, were evaluated to obtain dense films by firing at a low temperature of 850°C. Buffer layers of Al2O3/SiO2 and Al2O3/TiO2/SiO2 were also evaluated from point of view of densification and electrical properties of the films. The ferroelectric and piezoelectric properties increased as the films became denser, and excellent properties were obtained as follows for films with Bi2O3-ZnO additives formed on Pt/Al2O3/TiO2/SiO2-coated Si: dielectric constant 1350, Curie temperature 300°C, remanent polarization 30.9μC/cm2 and piezoelectric constant d31 121pm/V.
Electron beam lithography is a highly flexible method to fabricate micro-optical elements. However, the long exposure time is the largest problem, which derived from the lack of the sensitivity in electron beam resist. Instead of conventional carbon-based resists, physical properties of polydimethylsiloxane (PDMS) and poly [dimethylsiloxaneco-methylvinylsiloxane] (PMVS) for electron beam were investigated. As a result, these polysiloxanes exhibited a much higher sensitivity of 1.5 and 0.9μC/cm2, respectively and adequate γ value of 1.3. We succeeded in fabricating a four-level computer generated hologram on a glass substrate with ITO film using PMVS in 1/10 exposure time compared with conventional resists.
We have developed new micromachined opposing nano probes for electrical measurement of biomolecules. Since comb-drive micro actuators were integrated and connected to the nano probes electrically isolated from silicon piece, it will enables us to measure electro-mechanical characteristics of a biomolecule such as piezoelectricity. The probe structure was defined by etching of a 25[μm]-thick silicon-on-insulator wafer (SOI) using an inductively coupled plasma reactive ion etching apparatus (ICP-RIE). To obtain the tip radius of less than 10[nm] and to align two probe tips, new process sequence was designed by combining wet anisotropical etching of silicon with the ICP-RTE. Another type with probes directing outward was also developed.
Thermal barrier coating (TBC) was applied to Co based superalloy specimens, where bond coat was CoNiCrAlY deposited by high velocity oxygen fuel (HVOF) spraying and top coat was 8 mass% yttria stabilized zirconia (YSZ) by atmospheric plasma spraying. After heat cycles with different holding temperature, holding time at the maximum temperature and heat cycle numbers, edge indent tests of the specimens were carried out to measure the delamination energy of the coating. The results showed that the delamination energy Ed once increased and then decreased with increase in heat cycle numbers. The Ed was lower than those obtained from holding tests at high temperature. The delamination life of TBC was calculated by combining the effects of heat cycles (thermal fatigue) and holding time (oxide growth) on the damage of interface using the strain parallel to the substrate. The predicted delamination life coincided relatively well with experimental one.
This paper describes both experimental and FEM analytical studies on performance evaluation of RC beams bonded with FRP sheet considering putty lining between concrete surface and FRP sheet, Young's modulus of epoxy adhesive and FRP sheet material (Carbon or Aramid fiber). Loading tests on RC beam specimen and bond tests were performed and differences in performance considering these factors were evaluated. The constitutive law of spring model between concrete surface and FRP sheet was evaluated from the bond tests as the cut-off model for relationship between bond force and relative displacement. And this model was applied to FEM analysis of RC beam, and its suitability was verified through comparison with experimental results.
Three point bending (rectangular bar) specimen was made from sintered Al2O3/SiC composite and commercial Al2O3. A semi-elliptical surface crack 100μm in diameter (aspect ratio≈0.9) was introduced on the sample by indentation method. The sample was subjected to the following crack-healing treatment; Al2O3/SiC composite (temperature: 1573K, crack-healing time: 1h), and monolithic Al2O3 (temperature: 1373K or 1723K, crack-healing time: 1h). Monolithic Al2O3 was able to recover strength of cracked sample by heat treatment at 1723K. The recovery was caused by the secondary sintering process. However, the cracked sample recovered strength slightly by the heat treatment at 1373K. The incomplete strength recovery of cracked sample was caused by the removal of tensile residual stress ahead of crack. The Al2O3/SiC composite exhibited large crack-healing ability. The bending strength of the cracked Al2O3/SiC sample was about 180MPa. By the crack-healing treatment, the strength recovered up to about 850MPa. And also, crack-healed Al2O3/SiC sample exhibited very high static and cyclic fatigue limit of 600MPa and 700MPa, respectively. From these test results, it can be concluded that Al2O3/SiC has excellent crack-healing ability and the crack-healing is a desirable technology for the structural integrity of Al2O3/SiC.
To evaluate arbitrary shaped defects or cracks parallel to an interface, a formula is proposed in terms of √area parameter for the maximum stress intensity factors. Here “area” is the projected area of the defect or crack. First, the results for an elliptical crack parallel to a bimaterial interface are considered with varying the distance, aspect ratio of the crack, and combinations of material's constants systematically. Second, the stress intensity factors of an interface crack and a crack in a functionally graded material are also investigated. It is found that the maximum stress intensity factors normalized by √area are almost independent of the crack aspect ratio. They are given in a form of formula useful for engineering applications.
To evaluate corrosion of reinforcing steel by the attack of chloride ion in concrete under high temperature, influence of temperature on diffusion coefficient of chloride ion in concrete was investigated. At first, two types of test equipments, immersion test type and diffusion cell method type, were manufactured. They were able to control condition of high temperature. Using these equipments, chloride ion diffusion tests were conducted. In the tests, temperature were controlled from 25 to 90°C. Water cement ratios of specimens were changed from 40 to 60%. The result of the tests showed that diffusion coefficient of chloride ion was affected significantly by temperature. The relationship between temperature and diffusion coefficient depended on Arrhenius' equation. The diffusion coefficient decreased as water cement ratio decreased. The tendency does not change even in high temperature. Based on the tests results, equations for evaluating diffusion coefficients of chloride ion in concrete as a function of temperature were proposed.
A method for measuring large surface strains of three-dimensional bodies under tension is proposed, which utilizes the scattered light technique with polymer coating. A major advantage of this method is that interference fringes at the boundary between a real specimen and coatings can be observed directly. The difference in normal strains and shear strain on the surface of real specimen in axisymmetric tension problems can be calculated from three kinds of scattered-light fringe patterns obtained by three different incidences of polarized light. For the demonstration of effectiveness of this method, surface strains of solid and circumferentially notched cylindrical specimens made of aluminum alloy were measured under uniaxial tension. For the unnotched specimen, measured longitudinal strains were well consistent with ones calculated from the elongation of the gauge length. For the notched specimen, distributions of the measured normal and shear strains on the notch surface were well consistent with FEM analyses.
Recently, the position sensitive detector (PSD) has been becoming popular as a detector for X-ray stress measurement. However, little information is available in the literature regarding the effects of systematic errors on the stress measurement using the PSD. Therefore, the authors have developed a modeling of the Ω assembly X-ray stress analyzer enabling us to simulate the stress measurement under the various conditions including specimen mis-setting and mis alignment of collimator and detector. In this paper, stress measurement of Fe powder specimen under mis-setting and/or collimator misalignment was conducted by an Ω assembly X-ray stress analyzer using PSPC. It was found that the X-ray stresses experimentally obtained were well coincident with those calculated by the simulation, though the stress distribution on specimen surface was taken into account. As the conclusion, it is confirmed that the modeling and simulation can estimate X-ray stress under various systematic errors and that the simple methods proposed based on the studies using the simulation are effective for approximation of the stress error under various systematic errors.
The experimental method of caustics is a useful technique for the determination of the stress intensity factor K. In this paper, the stress intensity factors under mode I, II and III loadings are measured by the method of caustics, and the effect of those loading modes on the measurement accuracy is experimentally and numerically examined. Furthermore, a numerical method based on the 3-D finite element method (3D-FEM), which can directly simulate the caustic images, is proposed. As a result, it is found that the minimum initial curve radius rmin0 obtained in this study depends on the type of loading that is of mode I or mode II. In the case of mode III loading, however, the measured value of K agrees with the theoretical one regardless of the change of the initial curve radius r0. And the simulated results are in good agreement with the experimental images.