Thin flakes of titanium dioxide have been synthesized through a novel route via exfoliation of a layered precursor. A protonic oxide of H x Ti2- x /4□ x /4O4·H2O (x ∼ 0.7; □, vacancy) was delaminated into colloidal single sheets (thickness 0.75 nm) by being interacted with a bulky organic amine, (C4H9)4NOH. The resulting titania sol was freeze-dried to produce a gel in a thin filmlike texture. The gelation took place by reassembling 10−20 titanate sheets and consequently yielding lamellar aggregates. Upon heating above 400 °C, the gel was transformed into titanium dioxide (anatase) in thin flaky morphology (20−30 nm in thickness versus ∼μm in the lateral dimension). Intermediates at various stages of the synthetic process as well as the final product were examined by applying various characterization techniques such as X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM, TEM), FT-IR and Raman spectroscopies, thermogravimetry, and elemental analysis. The flaky particulates were aggregated in a disordered fashion to make an open microstructure. Nitrogen gas physisorption measurements revealed that the material was meso- to macroporous having a BET surface area of 40−110 m2 g-1. Photocatalytic activity for the material was demonstrated for a degradation reaction of aqueous trichloroethylene.

Fast microtomography combined with local crack driving force analysis has been employed to analyze crack-tip stress/strain singularities in an aluminum alloy. The application of fast microtomography has made it possible to observe real crack initiation and propagation behaviors without intermediate unloading. The details of a crack and its local propagation behaviors are readily observed with this technique along with evidence of microstructure/crack interactions. After a preliminary investigation of the achieved spatial resolution, we show that conventional stationary and growing crack singularities can be quantitatively validated by deriving the local crack opening displacement. This is to our knowledge the first three-dimensional validation of conventional fracture mechanics during a real time continuous experiment that has been mainly developed via surface observations so far. We also reveal that there is a spatial transition from a stationary crack singularity to a growing crack singularity in addition to the well-known temporal transition that occurs with the onset of crack propagation. Local crack propagation behaviors are also discussed on the basis of this validation. To separate the effects of complex crack geometry from those of microstructure, we also perform an image-based numerical simulation.

A new type of 150 mm vertical 4H-SiC epitaxial reactor with high-speed wafer rotation has been developed. Multiple resistance heaters ensure uniform radial temperature distribution throughout a 150-mm-diameter wafer. Enhancement of the growth rates is realized by high-speed wafer rotation under a relatively high system pressure, and growth rates of 40–50 µm/h are achieved on 4° off 4H-SiC substrates, maintaining a low defect density and a smooth surface without macrostep bunching. Excellent thickness and doping uniformities are simultaneously obtained for a 150-mm-diameter wafer at a high growth rate of 50 µm/h.

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We developed a near-infrared (NIR) superluminescent diode (SLD) based on self-assembled InAs quantum dots (QDs) and demonstrated high-axial-resolution optical coherence tomography (OCT) imaging using this QD-based SLD (QD-SLD). The QD-SLD utilized InAsQDs with controlled emission wavelengths as a NIR broadband light emitter, and a tilted waveguide with segmented electrodes was prepared for edge-emitting broadband electroluminescence (EL) spanning approximately 1-1.3 m. The bandwidth of the EL spectrum was increased up to 144 nm at a temperature of 25°C controlled using a thermoelectric cooler. The inverse Fourier transform of the EL spectrum predicted a minimum resolution of 3.6 m in air. The QD-SLD was subsequently introduced into a spectral-domain (SD)-OCT setup, and SD-OCT imaging was performed for industrial and biological test samples. The OCT images obtained using the QD-SLD showed an axial resolution of ~4 m, which was almost the same as that predicted from the spectrum. This axial resolution is less than the typical size of a single biological cell (~5 m), and the practical demonstration of high-axial-resolution OCT imaging shows the application of QD-SLDs as a compact OCT light source, which enables the development of a portable OCT system.