Silicon Carbide Monofilament-Reinforced Silicon Nitride or Silicon Carbide Matrix Composites

SiC-monofilament-reinforced SiC or Si₃N₄ matrix composites were fabricated by hot-pressing, and their mechanical properties and effects of filaments and filament coating layers were studied. Relationships between frictional stress of filament/matrix interface and fracture toughness of SiC monofilament/Si₃N₄ matrix composites were also investigated. As a result, it was confirmed experimentally that in the case of composites fractured with filament pullout, the fracture toughness increased as the frictional stress increased. On the other hand, when frictional stress was too large (>about 80 MPa) for the filament to be pulled out, fracture toughnesses of the composites were almost the same and not so much improved over that of Si₃N₄ monolithic ceramics. The filament coating layers were found to have a significant effect on the frictional stress of the SiC monofilament/Si₃N₄ matrix interface and consequently the fracture toughness of the composites. Also the crack propagation behavior in the SiC monofilament/Si₃N₄ matrix composites was observed during flexural loading and cyclic loading tests by an in situ observation apparatus consisting of an SEM and a bending machine. The filament effect which obstructed crack propagation was clearly observed. Fatigue crack growth was not detected after 300 cyclic load applications.     

Improvement of Cutting Performance of Silicon Nitride Tool by Adherent Coating of Thick Diamond Film

A thick diamond film was coated using two-stage microwave plasma CVD in the COH, system on a pretreated silicon nitride substrate for a cutting tool. The effects of acid treatment and microflawing treatment of the substrate on adherence of the film and cutting performance were investigated as well as the effects of two-stage CVD conditions. The combination of substrate pretreatment in a hot, strong acid solution of HF and HNO₃ and subsequent ultrasonic microflawing pretreatment with diamond grains resulted in the anchored deposition of CVD diamond into the micropores in the silicon nitride substrate. An excellent adherence of the diamond film to the substrate was attained by the two-stage CVD, which consists of a first CVD of fine diamond grains into the micropores and a second higher rate CVD of thick diamond film (thickness >30 pm). A dense layer composed of diamond-like carbon and silicon nitride was formed deep in the boundary region of the substrate during long CVD treatment. Long tool life of the silicon nitride chip coated with a thick diamond film was verified by a milling test using Al-20 wt% Si alloy as the work material.     

Synthesis of Lead Barium Niobate Powders and Thin Films by the Sol-Gel Method

Crack-free, dense, and transparent Pb_0.6Ba_0.4Nb₂O₆ (PBN60) thin films have been prepared by a sol-gel method with metal alkoxides and metal acetate. A homogeneous and stable precursor solution was obtained from Ba metal, Pb(CH₃COO)₂, and Nb(OEt)₅ in 2-methoxyethanol. PBN60 powder crystallized to the hexagonal phase at 600°C and then completely transformed to the orthorhombic phase of the tungsten bronze structure at 1250°C. The hexagonal phase was formed on SiO₂ glass, MgO(lOO), and sapphire(R) substrate at 600°C, while the orthorhombic phase was only on a sapphire(C) substrate. Orthorhombic PBN60 films with c -axis preferred orientation were successfully synthesized on sapphire(C) substrates at 600°C.     

Preparation,XAFS Characterization,and Catalysis of Platinum Nanowires and Nanoparticles in Mesoporous Silica FSM-16

Pt nanowires are prepared in mesoporous FSM-16 by photoreduction of H₂PtCl₆, while H₂-reduction of H₂PtCl₆/FSM-16 at 673 K gives Pt nanoparticles in FSM-16. The Pt nanowires and nanoparticles are characterized by physicochemical methods such as XAFS, TEM, XRD, and XPS. The formation mechanism of the Pt nanowires and the catalytic performance in the water–gas-shift reaction are also investigated.     

Development of 8‐in. oxide‐TFT‐driven flexible AMOLED display using high‐performance red phosphorescent OLED

An 8‐in. flexible active‐matrix organic light‐emitting diode (AMOLED) display driven by oxide thin‐film transistors (TFTs) has been developed. In‐Ga‐Zn‐O (IGZO)‐TFTs used as driving devices were fabricated directly on a plastic film at a low temperature below 200 °C. To form a SiO_x layer for use as the gate insulator of the TFTs, direct current pulse sputtering was used for the deposition at a low temperature. The fabricated TFT shows a good transfer characteristic and enough carrier mobility to drive OLED displays with Video Graphic Array pixels. A solution‐processable photo‐sensitive polymer was also used as a passivation layer of the TFTs. Furthermore, a high‐performance phosphorescent OLED was developed as a red‐light‐emitting device. Both lower power consumption and longer lifetime were achieved in the OLED, which used an efficient energy transfer from the host material to the guest material in the emission layer. By assembling these technologies, a flexible AMOLED display was fabricated on the plastic film. We obtained a clear and uniform moving color image on the display.     

Synthesis of organosiloxane-based inorganic/organic hybrid membranes with chemically bound phosphonic acid for proton-conductors

Proton conductive inorganic-organic hybrid membranes were synthesized from 3-glycidoxypropyltrimethoxysilane (GPTMS) and phosphonoacetic acid (PA) with various ratios by a sol-gel process. Self-standing, homogeneous, highly transparent membranes were synthesized. TG-DTA analyses indicated that these membranes were thermally stable up to 200 °C. The results of FT-IR and ¹³C NMR revealed that phosphonic acid groups of PA were chemically bound to organosiloxane network as a result of reaction between PA and GPTMS. The leach out of phosphonic acid groups from GPTMS-PA to water was reduced compared with phosphoric acid groups from GPTMS-H₃PO_4. The proton conductivity of the hybrid membranes increased with phosphonic acid content. The conductivity of GPTMS/PA with a 1/1.05 ratio at 130 °C was 8.7 × 10⁻² S cm⁻¹ at 100% relative humidity (RH).     

Passivation oxide film on Nd-Fe-B permanent magnets in borate buffer solution by ellipsometry

The passivation of Nd-Fe-B permanent magnet was investigated in neutral borate solution at pH 8.4. The thickness of the passive oxide film on the magnets was measured by ellipsometry and the composition was estimated by glow discharge optical emission spectroscopy (GD-OES).The passivation of the magnets takes place in the potential range between −0.2 and 1.0 V vs. Ag/AgCl/Sat. KCl. In the potential range, current density decays to the lower than 10⁻⁶ A cm⁻² after potentiostatic oxidation for 1800 s. The passive oxide film growth is assumed to be optically simulated from a model with a homogeneous film with complex refractive index, N = 2.1 − j0.086. The thickness estimated from the refractive index linearly increases with potential from 3.6 nm at −0.2 V to 7.8 nm at 1.0 V. The passive film growth follows the ionic migration model under high electric field, i.e., the Cabrera-Mott growth model. The ionic conductivity estimated from the model is about κ = 1.7 × 10⁻¹⁶ Ω⁻¹ cm⁻¹. The passive oxide film is preferentially composed of iron oxide/hydroxide. Boron and neodymium are, respectively, concentrated at the surface of the oxide film and at the inner layer in the oxide film.     

A Novel Prodrug of a γ‐Glutamylcyclotransferase Inhibitor Suppresses Cancer Cell Proliferation in vitro and Inhibits Tumor Growth in a Xenograft Mouse Model of Prostate Cancer

γ‐Glutamylcyclotransferase (GGCT) depletion inhibits cancer cell proliferation. However, whether the enzymatic activity of GGCT is critical for the regulation of cancer cell growth remains unclear. In this study, a novel diester‐type cell‐permeable prodrug, pro‐GA, was developed based on the structure of N‐glutaryl‐l ‐alanine (GA), by structure optimization using temporary fluorophore‐tagged prodrug candidates. The antiproliferative activity of pro‐GA was demonstrated using GGCT‐overexpressing NIH‐3T3 cells and human cancer cells including MCF7, HL‐60, and PC3 cells. By contrast, normal cells were not significantly affected by pro‐GA treatment. Moreover, pro‐GA administration exhibited anticancer effects in a xenograft model using immunocompromised mice inoculated with PC3 cells. These results indicate that the enzymatic activity of GGCT accelerates tumor growth and that GGCT inhibition is a promising therapeutic strategy for the treatment of GGCT‐overexpressing tumors.     

Photopyroelectric response of PTCa∕PEEK composite

A pyroelectric composite made of calcium modified lead titanate ceramic and polyether-ether-ketone high performance polymer was obtained in the film form by hot pressing the ceramic/polymer mixture into the desired composition. After polarization with a suitable electric field, a ceramic composite film (60% vol.) exhibited a pyroelectric figure of merit three times higher than that of a lead zirconate titanate ceramic. The material was used as infrared radiation sensor. The voltage responsivity decreases with the inverse of the frequency showing the same behavior of the thermally thick sensor. The reproducibility of the sensor responses was observed.     

Formation of a Rhenium-Base Coating on a Nb-Base Alloy

To protect Nb–5Mo–15W alloy against high-temperature oxidation a novel coating was developed involving electroplating of a Re–Ni film, followed by pack cementation with Cr and Al. The coating consisted of a duplex-layer structure, an inner (Re–Cr) or Re(Cr) layer and an outer Cr(Al) or NiAl layer. The Re–Ni film containing more than 70at.%Re, developed in the present investigation, is more useful than the conventional low Re–Ni film. The inner (Re–Cr) and Re(Cr) layer acts as a diffusion barrier between the Nb–5Mo–15W alloy substrate and the outer -Cr(Al) or -NiAl layer, which forms a protective -Al₂O₃ scale. The coated Nb–5Mo–15W alloy was oxidized in air at 1373K for up to 360ks, showing very good oxidation resistance.