Fabrication of Functionally Graded Carbon Nanotube‐Reinforced Aluminum Matrix Composite

Functionally graded carbon nanotube (CNT)‐reinforced aluminum (Al) matrix composites have been successfully fabricated by a powder metallurgy route. The gradient layers containing different amounts of CNT additions showed different microstructures and hardness. Each layer demonstrated good adhesion, with no serious pores or microcracks. We controlled the characteristics of the bulk composite by the efficient design of each CNT gradient layer. The functionally graded material concept offers a feasible approach to fabricating Al‐CNT nanocomposites.     

Sol-gel synthesis and characterization of nanostructured TiO2/gamma-Al2O3 composite membranes

Nanostructured TiO2/gamma-Al2O3 composite membranes with various compositions were prepared by sol-gel method. The structural and textural properties of the composite membranes could be modified by the mixing ratio of boehmite sol and titania sol, and calcination temperature. The existence of alumina in the composite membranes retarded anatase-to-rutile phase transformation, resulting in stabilization of textural properties. Defect-free composite membranes were confirmed by gas permeation test.     

Improved oxygen diffusion barrier properties of ruthenium-titanium nitride thin films prepared by plasma-enhanced atomic layer deposition

Ru-TiN thin films were prepared from bis(ethylcyclopentadienyl)ruthenium and tetrakis(dimethylamino)titanium using plasma-enhanced atomic layer deposition (PEALD). The Ru and TiN were deposited sequentially to intermix TiN with Ru. The composition of Ru-TiN films was controlled precisely by changing the number of deposition cycles allocated to Ru, while fixing the number of deposition cycles allocated to TiN. Although both Ru and TiN thin films have a polycrystalline structure, the microstructure of the Ru-TiN films changed from a TiN-like polycrystalline structure to a nanocrystalline on increasing the Ru intermixing ratio. Moreover, the electrical resistivity of the Ru0.67-TiN0.33 thin films is sufficiently low at 190 microomega x cm and was maintained even after O2 annealing at 750 degrees C. Therefore, Ru-TiN thin films can be utilized as a oxygen diffusion barrier material for future dynamic (DRAM) and ferroelectric (FeRAM) random access memory capacitors.     

Preparation of self-assembled zinc oxide nanoparticles multilayer films under ultrasonic irradiation

Zinc oxide nanoparticles were synthesized and self-assembled on the reactive surface of a glass slide functionalized with (3-mercaptopropyl)-trimethoxysilane under ultrasonic irradiation. The structure, morphology, and optical property of the zinc oxide nanoparticles were investigated by TEM, XRD, and UV-vis spectroscopy. The functionalized glass slide was soaked in an aqueous solution which dispersed zinc oxide nanoparticles under ultrasonic irradiation. Zinc oxide multilayer films grew up to several layers (up to 5 layers) depending on the immersion time. The self-assembled zinc oxide nanoparticles multilayer films were characterized using UV-vis spectroscopy and SEM. Ultrasonic irradiation was an efficient method to make multilayer films on the functionalized glass slide with zinc oxide nanoparticles.     

Synthesis and characterization of 3-[131I]iodo-L-tyrosine grafted Fe3O4@SiO2 nanocomposite for single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI)

In this study, we have successfully developed 3-[131I]iodo-tyrosine grafted Fe3O4@SiO2 nanocomposites for dual potential tumor imaging agent for SPECT and MRI. Fe3O4 nanoparticle was synthesized through thermal decomposition and Fe3O4@SiO2 was prepared by reverse microemulsion method. After conjugating aminopropyltriethoxysiliane, L-tyrosine was introduced by amide coupling reaction. Finally, [131I]iodide was labeled on L-tyrosine grafted Fe3O4@SiO2 nanocomposite by aromatic iodination using chloramine-T.     

Synthesis and properties of siloxane-containing hybrid hydrogels with alpha,omega-functionalized macromers

Siloxane-containing transparent hybrid hydrogels, coupled with high oxygen permeability and moderate equilibrium water content (EWC), were successfully obtained through free radical bulk copolymerization of hydrophobic and hydrophilic monomers. Due to obvious incompatibility of hydrophobic tris(trimethylsiloxy)-3-methacrryloxypropylsilane (TRIS) and hydrophilic 2-hydroxyehtyl methacrylate (HEMA) or N-vinyl pyrrolidone (NVP) monomers, alpha,omega-methacrylate terminated poly(dimethyl siloxane) (PDMS) macromer was employed as a compatibilizer in the formulations, resulting in high optical transmittance (> 90% at 400 nm) of the hybrid hydrogels. Although properties such as EWC and oxygen permeability of the hybrid hydrogels could be tailored over a wide range, the formulations with the PDMS macromer could not increase both EWC and oxygen permeability of the hybrid hydrogels without sacrificing one of them. For controlling these two properties simultaneously, an amphiphilic alpha,omega-methacrylate terminated PEO-PDMS-PEO triblock copolymer was synthesized as a surface-active macromer, and showed its usefulness in controlling phase separation and improving oxygen permeability and EWC, at the same time, of the hybrid hydrogels.     

Chemical and electronic properties of Ba/bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) interfaces for organic light-emitting diodes

The chemistry, electronic structure, and electron-injecting characteristics at the interfaces that were formed between bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (BAlq) and barium (Ba) were investigated using ultraviolet photoemission spectroscopy, near-edge X-ray absorption fine structure spectroscopy, X-ray photoemission spectroscopy, and current-voltage-luminance measurements. The device performance of organic light-emitting diodes (OLEDs), which have a glass/ITO/MoO3/2-TNATA/NPB/BAlq/Ba/Au structure, was significantly improved by inserting a Ba coverage (thetaBa) of 0.2 nm between BAlq and the cathode. For thetaBa'S that were thicker than 0.2 nm, however, even though the electron-injecting barrier heights at the Ba-on-BAlq interfaces were all 0.1 eV, the device performance of the OLEDs with Ba at the interface was degraded with increasing thetaBa. This result indicates that the device performance is largely dependent on the interfacial chemical degradation of the BAlq molecule itself, rather than the electron-injecting barrier height that is determined by the width and chemical structure of the interface, and the formation of barium-induced new gap states at the Ba-on-BAlq interface.     

Synthesis of B4C nanobelts in porous SiC bodies

B4C nanobelts were synthesized in porous SiC bodies, which had a sponge structure. The interconnected pore size of the SiC bodies was around 600 microm. The raw materials used for the B4C nanobelts were B2O3 for boron and phenolic resin and carbon black for carbon. The nanobelts grew fully inside the porous SiC when heat treated at 1400 degrees C for 1 h using LiCl as a volatilizing agent and cobalt as a catalyst. The thickness of the rhombohedral B4C nanobelts ranged from 0.1 to 1 microm, and their width was 0.5 to 10 microm. The length of the grown B4C belts was up to several hundreds of micrometers, and their growth direction was [110]. These single crystal nanobelts did not show any structural defects such as stacking faults, steps and twins. The low temperature synthesis in this study is attributed for the clean surface. It is suggested that the nanobelts were nucleated by the VLS mechanism, and then grew by the VS mechanism.     

Radio frequency source power-induced ion energy impact on SiN films deposited using a room temperature SiH4-N2 plasma

Using a SiH4-N2 plasma, silicon nitride films were deposited at room temperature. The impact of source power ranging from 500 to 900 W and ion energy are investigated. The film properties examined include a deposition rate, a refractive index, and a surface roughness. Ion energy diagnostics was conducted to explore the relationships between ion energy and film properties. A variation in ion energy with source power was quite complex. By contrast, a decrease in ion energy flux was observed for a decrease in the source power. An increase in the deposition rate with the decrease in source power was attributed to enhanced ion energy. The refractive index strongly correlated with low ion energy flux. A decrease in surface roughness in the range of 500-700 W was related to larger ion energy. The deposition rate, refractive index, and surface roughness were varied in the range of 0.27-0.35 nm/sec, 1.690-1.739, and 6.7-52.5 nm, respectively.     

Molecular dynamics study of nano mass transfer in a vibrating cantilevered carbon-nanotube

We investigate the nano mass transfer in an ultrahigh frequency carbon-nanotube-resonator encapsulating a nanocluster via classical molecular dynamics simulations. When the carbon-nanotube-resonator vibrated, the encapsulated copper nanocluster more rapidly approached the end of the cantilevered carbon-nanotube-resonator. Such phenomena were due to the migration of the encapsulated copper nanocluster due to the centrifugal force induced by the vibrating nanotube resonator. So the resonance frequency change could be time-dependently found. For the movable copper nanocluster in carbon nanotube resonator, the vibrational spectra when the copper nanocluster inside the carbon nanotube resonator rapidly settled at the capped edge were different from those obtained when the copper nanocluster continuously oscillated inside the carbon nanotube resonator. Such results showed that the frequency of the carbon-nanotube-resonator encapsulating the movable copper nanocluster could be adjusted by controlling the mean position of the oscillating copper nanocluster. The movable nanocluster inside a carbon-nanotube can be applied to a nanotube-based data storage media by sensing the position of the nanocluster.