Advanced Materials Research Vols. 47-50

Abstract: Particulate reinforced 10 vol.% (TiB+TiC)/Ti-6Al-4V metal matrix composites (MMCs) were produced by in-situ synthesis using vacuum arc re-melting process, and the mechanical properties of the metal matrix composites were assessed by the small punch testing (SPT). Mechanical properties of the in-situ synthesized Ti MMCs were studied and compared with the Ti base alloy. From the test data, the fracture properties and equivalent fracture strain of the test materials were characterised. The fracture mechanism of the test samples was examined using scanning electron microscopy.

Abstract: Site-selective growth of multi-walled carbon nanotubes (MWCNTs) from an iron oxide nanoparticle catalyst patterned by drying-mediated self-assembly technique is present. The ethanol solution of the iron nitrate was employed as catalyst precursor. The silicon wafer was mounted catalyst precursor by dip-coating. After solvent evaporation at room temperature, the catalyst pattern formed. The catalyst pattern was subjected to chemical vapor deposition of ethanol vapor after oxidation of iron nitrate. The patterned array of MWCNTs was obtained with a dot size of around 5 (m and the distance between dots of about 25 (m. The locally-ordered patterns of MWCNTs were found. The present method offers a simple and cost-effective method to grow carbon nanotubes with self-assembled patterns.

Abstract: High-quality single-walled carbon nanotubes (SWNTs) are a key aspect in the emerging field nanotechnology. Although many approaches have been developed, the research on the synthesis of SWNTs is still needed. In this study, we report the synthesis of high-quality SWNTs by floating catalyst chemical vapor deposition, which employs ferrocene as the catalyst precursors. We obtained massive deposits at low temperature region. The deposits were characterized by scanning electron microscopy, transmission electron microscopy, and visual laser Raman spectroscopy. The Raman spectrum obtained from raw deposits shows clear radial breathing mode at the range from 180cm-1 to 300cm-1 and high-intensity graphite mode at 1577.7cm-1 with a shoulder at 1550.5cm-1, and almost no detectable peak around at 1545cm-1, which is induced by defects, is observed. These results indicate that the deposits are high-quality SWNTs.

Abstract: In the electroplating and water treatment fields, as the demand and expectation on an electrode with high productivity and high efficiency are getting increased, various electrodes(DSE) with higher reactivity and durability are being developed. This study is intended to analyze the characteristics of the produced electrodes and to establish the optimum manufacturing conditions for electrode being used that we mentioned. For improving the durability, the changes of reactivity and corrosion resistance are observed as adding Tantalum and/or another components (hereafter stated as “α”) and surface treatment of substrate(Ti). As a result, increasing the amount of Iridium, the reactivity of electrode increased, and increasing amount of Tantalum, the durability of electrode increased. And thus, it is found out that Iridium and Tantalum have the opposite role each on the electrode’s reactivity and durability. And adding α and surface treatment substrate, an electrode with excellent reactivity and durability and low oxygen evolution can be manufactured. In the water treatment field like sterilizing in a swimming pool and power-plant cooling water, the high efficiency of sodium-hypochlorite generation is surely guaranteed.

Abstract: The thin film resistors such as Ni-Cr alloy could be formed by the electrodeposition method for embedded passive device in printed circuit board. A kinetic study on the electrodeposition of nickel-chromium alloy on copper has been performed using a rotating disk geometry. Activation energies of nickel and chromium in the temperature range between 15°C and 35°C were 8.9kcal/mole and 3.5kcal/mole, respectively. The electrodeposition rate of nickel seems to be controlled partly by electrochemical reaction and partly by mass transport, namely mixed controlled. However, that of chromium seems to be controlled by mass transport. As the amount of chromium in deposit increased, the electric resistance of deposit surface increased. The maximum electric resistance of nickel-chromium alloy deposit was 78.6Ω /□.

Abstract: As the electrodeposition reaction is a heterogeneous reaction including both material transfer and electrochemical reaction, this study tries to find out the reaction mechanism about Ag electrodepostion used as semiconductor interconnection using rotating disk electrode system (RDE system). Considering the environmental problem, non-cyanide Ag electrodeposition solution has been carried out. With varying the process conditions of a certain range including the rotating speed of RDE, applied voltage, and temperature etc., obtained the electrodeposition rate of Ag according to the reaction time. The rate determining step was clarified with the activation energy(Ea) of the electrodeposition reactions for the each process conditions estimated from Arrhenius Plot. Activation energy of Ag in the temperature range between 18°C and 32°C was 3.2kcal/mole. The electrodeposition rate of Ag seems to be controlled mass transport. With the electrodepositon solution mentioned above, the characteristics of silver thin film and bottom-up filling capability were investigated by DC or pulsed electrodeposition method. Especially, the effects of additives on the properties of bottom-up filling of Ag were studied.

Abstract: Small interfering RNA (siRNA) holds potential as a therapeutic approach to silence targeted gene of disease, but siRNA has limited stability in vivo. Therefore, delivery system of siRNA is the key to siRNA therapeutic application. We attempted to develop a delivery system, which enables siRNA to demonstrate high stability and long blood circulation. We synthesized a series of bottlebrush-type copolymers (BBCs) possessing polycationic backbone (less than 30 wt%) and abundant water-soluble side chains (more than 70 wt%) as siRNA carrier. A siRNA complexed with the BBC was resistant to nuclease and stable in plasma. Especially, the BBC (10 wt% PLL and 90 wt% PEG) having higher grafting ratio (≈ 90 wt%) of water-soluble side chains showed 100-times enhanced stability of siRNA in mouse bloodstream in vivo. Surprisingly, even when the BBC and siRNA separately injected into mouse at 20 min interval, the BBC increased blood half life of the siRNA. These results suggest that the BBC has higher selectivity in its ionic interaction to siRNA than other anionic substance in blood components. To our knowledge, this is the first report of siRNA delivery carrier which prolonged blood circulation of siRNA without resource-consuming preparation process.

Abstract: A melt blending process was employed to prepare nano-composites based on thermoplastic polyurethane (TPU) and multi-walled carbon nanotubes (MWNT). The content of MWNT filled in TPU was increased till 40phr (parts per hundreds of rubber). Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the unmodified MWNT were dispersed uniformly in the TPU matrix beyond expectation. Dynamic mechanical thermal analysis (DMTA) test demonstrated that the nano-composites possessed greatly increased modulus, and the flowing temperature moved to higher temperature with increasing MWNT content. Moreover, the nano-composites exhibited improved wear resistance, evidently increased thermal conductivity, and prominently raised electrical conductivity that might mean the TPU/MWNT nano-composites have potential application as multi-functional materials.

Abstract: This paper discusses a smart temperature sensor system that comprises of a high performance quartz tuning fork temperature sensor, interface with CMOS circuitry and control algorithm for reconfiguration. The ideal thermo-sensitive cut for quartz tuning fork resonators is analyzed with the theory, and is optimized by FEM (Finite Element Method). The specific cut quartz tuning fork was fabricated using photolithography and the etching technology. And the tuning fork sensing element (4 3 2 . 0 1 mm × × ) is so small that can be housed in the capsule ( 6 2× Φ mm). The smart temperature sensor along with the interface IC to FPGA and special control algorithm may easily realize the sensor reconfiguration and the auto-calibration in the field. The experimental result indicates that the sensitivity of this sensor can reach C ppm o / 65 in the temperature range from-20 to 140 C o , it guarantees that precision is C o 01 . 0 , the resolution is C o 001 . 0 , and the response time is 1s.

Abstract: The recently performed investigations in continuum plastic-damage analysis of composite laminates by the authors showed that using a single hardening internal variable for damage and plasticity surfaces may prone to significant errors in response and failure load for some lay-ups. In this paper, the new technique of coupled continuum plastic-damage mechanics including multisurface dissipation potentials are employed to improve the results. The response and failure loads of the laminated composites with different lay-ups are predicted using elastic, damage, and damageplasticity conditions with single and multi surface plasticity and compared with the available experimental results.