Photoluminescence (PL) spectra properties of 0.5 and 2.0 mol % Al doped Bi₄Ge₃O₁₂ crystals in near-infrared (NIR) region were studied. A relative broad emission band can be found at 1189 nm in these Al doped Bi₄Ge₃O₁₂ under 808 nm laser diodes (LDs) excitation. The doped Bi₄Ge₃O₁₂ also exhibit emission band centered at about 1324 nm under 980 nm LDs excitation. The Al ions can play a helpful role in NIR emission of doped Bi₄Ge₃O₁₂ crystals.

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Al₂O₃–CaMgSi₂O₆ ceramics with different amount of CaMgSi₂O₆ additions were prepared by a conventional solid-state method, and the effects of CaMgSi₂O₆ addition on the sintering behavior and dielectric properties of Al₂O₃ ceramics have been investigated. CaMgSi₂O₆ was used as a liquid sintering aid to effectively lower the sintering temperature of Al₂O₃ ceramics and its addition resulted in the presence of CaAl₂Si₂O₈ and MgAl₂O₄ phases. However, the CaMgSi₂O₆ addition deteriorated the dielectric properties of Al₂O₃–CaMgSi₂O₆ ceramics because of the higher dielectric loss of the derived CaAl₂Si₂O₈ and MgAl₂O₄ compared with that of Al₂O₃ ceramics. After sintered at 1450°C, the Al₂O₃–CaMgSi₂O₆ ceramic with 10 wt % CaMgSi₂O₆ addition possessed dielectric properties of ε_r = 9.83, tan δ = 1.5 × 10⁻⁴ (1 MHz) and Q × f = 20,425 GHz (f₀ = 12 GHz).

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Nanosized aluminum nitride (AlN) powders were prepared by calcining δ-alumina (δ-Al₂O₃) nanopowders under a flow of acetonitrile (CH₃CN) diluted in argon. The nitridation process of δ-Al₂O₃ to AlN was monitored by powder X-ray diffraction patterns and ²⁷Al magic-angle spinning nuclear magnetic resonance spectroscopy. δ-Al₂O₃ began to be converted to AlN at 1050°C without δ-α alumina transformation and the conversion was completed at 1300°C. The cyanide radical, which was produced by thermal decomposition of CH₃CN, reacted with Al₂O₃ to form AlN. The cyanonitridation method can considerably mitigate the two main drawbacks of the carbothermal reduction and nitridation method: high reaction temperature and intimate mixing of Al₂O₃ with carbon. Cathodoluminescence spectra of the nanosized AlN powders obtained in this study showed an intense ultraviolet emission band at 376 nm.

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Anodic oxidation of a pure Al plate was carried out in aqueous solutions containing sulfuric acid (H₂SO₄), oxalic acid (H₂C₂O₄) and a percarboxylic acid-based additive at temperatures between 273 and 293 K for 0.6 to 9 ks under a constant current density of 300 A·m⁻² (3 A·dm⁻²). The microstructures and the mechanical properties of the obtained anodic oxide film were investigated to determine the optimum electrochemical condition. In the H₂SO₄ + additive bath, the film with a maximum thickness of approximately 100 µm was formed at 293 K for 7.2 ks. However, the surface hardness of the film decreased with increasing processing time and film thickness. To enhance the film hardness, the Al plate was anodized in the H₂SO₄ + H₂C₂O₄ + additive bath at lower temperatures, which resulted in higher Vickers hardness of 400–500 and excellent wear resistance for the thick film formed at 278 K for 7.2 ks. The film formed at 278 K in the H₂SO₄ + H₂C₂O₄ + additive bath had a typical cell structure with a nano-sized pore at the center of each cell. Compared with the film formed in the H₂SO₄ bath, the cells were almost uniform in size and the pore size in the cell was smaller. In addition, the occupation ratio of the pores in unit area of the film formed in the H₂SO₄ + H₂C₂O₄ + additive bath was smaller than that of the film formed in the H₂SO₄ bath. Such microstructural features are thought to be responsible for the high hardness of the anodic oxide thick film.

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This paper reports the elastic properties and structure of GeO₂–PbO–Bi₂O₃ ternary bulk glasses which were successfully prepared by melt quenching technique. The study was performed by ultrasonic measurements and Fourier transform infra red (FTIR) spectroscopy. Increasing values of density, ultrasonic velocity and elastic moduli were observed due to substitution of bismuth to lead atoms with fixed composition of GeO₂. Also, FTIR spectrum showed different profiles between samples with higher content of lead or bismuth. In Pb-rich samples all of the components contributed in the structure as network former; however, in Bi-rich samples lead and bismuth showed modifier behavior and the structure was depolymerized by adding of bismuth content.

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The optical surface plasmon resonance (SPR) phenomenon was used to detect the apatite formation on the titania films. The apatite formation on the anatase titania deposited by atmospheric chemical vapor deposition using a modified-simulated body fluid (m-SBF) solution was detected by the SPR method using a multilayer structure of titania/gold/chromium/optical glass. To contact both the titania surface and m-SBF solutions, flow channel made by silicone is put on the multilayer device surface. The m-SBF solution was injected to the flow channel, and then SPR angle was measured at each time. SPR angle was shifted by +0.03° after 13 min since the start of the injection. SPR angles increased with duration until 39 min. By assuming that apatite was flat, the deposition rate for apatite layer was calculated to 0.23 nm/h from the obtained SPR profiles. The SPR profiles after 39 min included some noise because apatite was formed as a non-uniform layer such as slit-like structure. These results indicate that the early growth of apatite formation on titania films can be detected by the multilayer SPR device.

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Aqueous dispersions of γ-alumina powder synthesized by homogeneous precipitation (HP) were investigated and compared with a commercial gamma alumina (TM300). As the isoelectric point (IEP) of the two powders was found to be at the same pH (8.5), the rheological properties of the suspensions were determined under controlled rate conditions, varying the pH and solid loading. It was found that the pH used in a suspension affects its rheological properties and consequently the final density of the slip cast body, obtaining the highest density for the heated bodies at pH values below the IEP. The pH limit to maintain Newtonian flow is dependent on the solid content and the type of alumina used. Thus, a TM300 35% solid-loaded suspension requires a pH of 4, whereas HP alumina requires only a pH of 3.75 to behave as a Newtonian fluid. Both suspensions were slip cast and the green bodies were heated at four distinct temperatures. Lastly, the relative densities of the heated bodies were measured by the Archimedes method, and in all cases, lower relative densities were obtained for HP alumina.

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Nano-composite particles were subjected to develop a high performance abrasive for glass polishing. We focused on nano-dispersion abrasives composed of two kinds of materials; one has a high chemical reactivity with glasses and the other has a high mechanical strength. High performance in glass polishing was expected by so-called chemical mechanical polishing (CMP) effect due to combination of these two materials. The nano-dispersed SrZrO₃/ZrO₂ composite particles were successfully synthesized by spray pyrolysis technique. The glass polishing using SrZrO₃/ZrO₂ nano-composite abrasives revealed that the removal rate was relatively high and that the polished surface was quite smooth. On the other hand, the mixed abrasive with SrZrO₃ and ZrO₂ showed much lower polishing properties than nano-composite abrasive. The nano-dispersed structure would be of great importance to achieve CMP effect by combination of two different materials.

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We have been developing a new route in synthesizing conductive alumina through gel casting method and then sintered in an inert environment. In this study, we fabricate a semi-conductive ceramics utilizing silica as the matrix and investigate the effect of this matrix on the basic properties for a semi-conductive ceramic body. The results were then compared to the gelcast alumina body sintered under inert atmosphere. Synthesize gelcast silica body gave a higher relative density and lower conductivity if compared to the gelcast alumina body sintered under inert atmosphere. This is because the gelcast silica during sintering, some silica matrix component attached to nano-carbon network (originating from polymers) form a SiC under inert atmosphere. This carbon-consuming process causes defects which inhibits graphitization and structural disorder onto the gelcast silica body.

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Highly efficient all solid state dye-sensitized solar cells (DSSC) were fabricated by the specific interaction of CuI with the NCS groups of the dye molecules and that of the counter electrodes. The specific interaction was studied using X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM). The counter electrode containing NCS groups was prepared by coating the PEG solution containing NCS groups. The counter electrode was connected with the the NCS groups of the dye molecules by CuI. The specific interaction between the CuI with the NCS groups of the dye molecules and that of the counter electrode facilitate the injection of the hole into the counter electrode to give the highly efficient all solid state DSSC. The DSSC were stable and exhibited high efficiency (4.2%). This DSSC has potential to be applied for practical use.

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Titania nanotubes (TNTs) were synthesized by a low-temperature chemical processing method and then hybridized with Pt nanoparticles (NPs) by a UV-light-induced photoreduction method using H₂PtCl₆. Optical band gap energy was slightly increased by the Pt NPs loading. Methylene blue (MB) removal test revealed that the both pure and Pt-loaded TNTs eliminated the MB under dark and UV-light irradiation conditions, showing the molecular adsorption property was kept even after the Pt loading. Ultraviolet (UV) light induced photocatalytic degradation of MB mainly underwent at the surface of TNT while Pt NPs accumulated photoinduced electron sufficiently. Pt-loaded TNTs exhibited higher performance of photocatalytic than non-Pt-loaded TNTs at the early stage of photodegradation of MB. It indicated that the Pt NPs worked well as co-catalysts with the TNTs. These results suggest that the present nanocomposite is suitable for elimination of molecules through the combination of two functions as molecular adsorption and photocatalytic reaction.

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