Photocatalytic degradation of rhodamine B by anchored TiO2 nanowires

Rutile TiO2 nanowires anchored on silica were fabricated by annealing TiO2 nanoparticles dispersed on silicon or quartz substrate by means of a polystyrene nanosphere monolayer template at 1000 degrees C for 1 h without any catalyst. The diameter and length of the nanowires were 30-80 nm and 1-3 microm, respectively. The growth direction of the nanowires is [112]. The photocatalytic activities of TiO2 nanoparticles and anchored nanowires were evaluated. TiO2 nanowires had higher photocatalytic activity for rhodamine B than TiO2 nanoparticles.     

Fabrication of TiO2 nanotubes by atomic layer deposition and their photocatalytic and photoelectrochemical applications

The formation of TiO(2) nanotubes was conducted by atomic layer deposition (ALD) with tris-(8-hydroxyquinoline) gallium (GaQ(3)) nanowires as a template at different substrate temperatures, 50, 100, and 200?°C. TiO(2) nanotubes were formed only at 50 and 100?°C. Although a higher growth rate at 50?°C was observed, nanotubes with better uniformity, conformality, and less residual chloride were obtained at 100?°C because of a different formation mechanism. A photocatalysis test of TiO(2) nanotubes prepared by different cycle numbers at 100?°C was conducted. It showed that TiO(2) nanotubes prepared by 400 cycles of ALD and treated at 700?°C for 1 h to form anatase phase had the best photocatalytic performance. Compared with P-25, the nanotubes showed higher photocatalytic degradation of rhodamine B and water splitting efficiency.     

Effect of the prominent catalyst layer surface on reactant gas transport and cell performance at the cathodic side of a PEMFC

The cell performance enhancement of a proton exchange membrane fuel cell (PEMFC) has been numerically investigated with the prominence-like form catalyst layer surface of the same composition at the cathodic half-cell of a PEMFC. The geometries of the prominence-like form catalyst layer surface are assigned as one prominence, three prominences, and five prominences catalyst layer surfaces with constant distance between two prominences in the same gas diffusion layer (GDL) for the purpose of investigating the cell performance. To confine the current investigation to two-dimensional incompressible flows, we assume that the fluid flow is laminar with a low Reynolds number 15. The results indicate that the prominence-like form catalyst layer surface can effectively enhance the local cell performance of a PEMFC.     

Self-forming AlOx layer as Cu diffusion barrier on porous low-k film

The copper diffusion barrier properties of an ultrathin self-forming AlO_x layer on a porous low-k film have been investigated. Cu-3 at.% Al alloy films were directly deposited onto porous low-k films by co-sputtering, followed by annealing at various temperatures. Transmission electron microscopy micrographs showed that a ∼ 5 nm layer self-formed at the interface after annealing. X-ray photoelectron spectroscopy analysis showed that this self-formed layer was Al₂O₃. Sharp declines of the Cu and Si concentrations at the interface indicated a lack of interdiffusion between Cu and the porous low-k film for annealing up to 600 °C for 30 min. The leakage currents from Cu(Al)/porous low-k/Si structures were similar to as-deposited films even after a 700 °C, 5 min anneal while a Cu sample without Al doping failed at lower temperatures. Adding small amounts of Al to bulk Cu is an effective way to self-form copper diffusion layer for advanced copper interconnects.     

On the formation and photoluminescence of Si(1-x)Ge(x) nanoparticles

Si(1-x)Ge(x) nanoparticles were prepared from two annealed alloy ingots at the compositions of Si:Ge = 9.5:0.5 and 9:1 using a vapor condensation technique under Ar atmosphere. These nanoparticles are all spherical, and increasing the working pressure leads to an increased particle size and size dispersion. Comparing to the alloy ingots, the nanoparticles have a higher average content of Ge. In addition, increasing the working pressure also causes the Si(1-x)Ge(x) nanoparticles to become more Ge-rich. This can be ascribed to the lower melting point and higher kinetic energy of Ge than Si during the evaporation process. The photoluminescence of Si(1-x)Ge(x) nanoparticles ranges from visible light to infrared region, and the luminescence peak exhibits a red shift as the Ge content in the nanoparticles increases. This indicates that the incorporation of Ge into Si has a dominant effect in the radiative recombination process, in comparison with the constant luminescence peak position in the case of pure Si nanoparticles with similar size distribution.     

Fabrication of highly homogeneous Al‐doped TiO2 nanotubes by nanolamination of atomic layer deposition

Conformal parallel arrays of Al‐doped TiO₂ nanotubes were fabricated by atomic layer deposition. TiO₂/Al₂O₃ bilayered shells were grown on a polycarbonate template by various cyclic sequences of TiO₂ and Al₂O₃. The doping level of Al could be tuned by the fraction of cycle number of Al₂O₃. From the depth profiles measured by second ion mass spectrometry, Al is uniformly distributed across the thickness, which is also supported by the analyses of X‐ray diffraction, X‐ray photoelectron spectroscopy, and Raman spectroscopy. A uniform bulk solubility of ~7 at.% and the surface concentration of ~18 at.% were observed with the cycle ratio of Al₂O₃: TiO₂ at 0.04.     

Synthesis and properties of novel phosphorus‐containing bismaleimide/epoxy resins

A novel soluble phosphorus‐containing bismaleimide (BMI) monomer, bis(3‐maleimidophenyl)phenylphosphine oxide (BMIPO), was synthesized by the imidization of bis(3‐aminophenyl) phenylphosphine oxide, in which its structural characterization was identified with ¹H‐NMR, ¹³C‐NMR, and Fourier transform infrared spectra. The BMIPO resin, with five‐membered imide rings and high phenyl density, was an excellent flame retardant with a high glass‐transition temperature (T_g), onset decomposition temperature, and limited oxygen index. In phosphorus‐containing BMI/epoxy/4,4′‐methylene dianiline (DDM)‐cured resins, homogeneous products were obtained from all proportions without phase separation. Because of the higher reactivity of BMIPO/DDM relative to that of 4,4′‐bismaleimidodiphenylmethane (BMIM)/DDM, the increase in the BMIPO/BMIM ratio in this blending resin increased the recrosslinking hazards of the postcuring stage and so lowered the T_g value and thermal stability. The thermal stability of the BMI/epoxy‐cured system was lower than that of the epoxy‐cured system because of the introduction of a phosphide group into BMIPO, whereas for the T_g value and flame retardancy, the former was significantly higher than the latter: the higher the BMIPO content in the blend, the higher the flame retardancy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2080–2089, 2002; DOI 10.1002/app.10607     

Self-calibration of a general hexapod manipulator using cylinder constraints

This paper presents a novel self-calibration strategy for a general hexapod manipulator to overcome weaknesses and embrace merits of existing approaches. A commercial trigger probe and a cylindrical gauge block are adopted in the present approach. The algorithm is formulated to solve a nonlinear least squares problem that takes all measurement errors into account. The simulation results show that the proposed algorithm has the following advantages: (1) it is capable of calibrating the position and orientation of the gripper or spindle on the platform; (2) it completely avoids the unobservability of certain parameters due to mobility constraints on the passive joints; (3) the hardware of the calibration system is more compact and cost-effective than that adopted in the existing approaches; and (4) the algorithm is numerically robust, efficient and effective, while the calibrated parameter errors are expected to be with the same order of the measurement errors. Due to these merits, the present scheme is attractive for an autonomous hexapod manipulator when a great precision is required in a workspace of five degrees-of-freedom.     

Thermal degradation mechanism of poly(ether imide) by stepwise Py–GC/MS

The thermal degradation of poly(ether imide) (PEI) was studied through a combination of thermogravimetric analysis and stepwise pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) techniques with consecutive heating of the samples at fixed temperature intervals to achieve narrow temperature pyrolysis conditions. The individual mass chromatograms of various pyrolysates were correlated with pyrolysis temperatures to determine the pyrolysis mechanism. The major mechanisms were two‐stage pyrolysis, involving main‐chain random scission, and carbonization. In the first stage, the scission of hydrolyzed imide groups, ether groups, and isopropylidene groups produced CO+CO₂ and phenol as the major products and was accompanied by chain transfer of carbonization to form partially carbonized solid residue. In the second pyrolysis stage, the decomposition of the partially carbonized solid residue and remaining imide groups formed CO+CO₂ as the major product along with benzene and a small amount of benzonitrile. The yield of CO+CO₂ was the largest fraction in the total ion chromatogram of the evolved gas mixtures. Hence, the thermal stability of the imide group was identical to the maximum thermogravimetry loss rates in the two‐stage pyrolysis regions. Afterward, carbonization dominated the decomposition of the solid residue at high temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1151–1161, 2001     

Fabrication of TiN inverse opal structure and Pt nanoparticles by atomic layer deposition for proton exchange membrane fuel cell

A titanium nitride (TiN) inverse opal structure was fabricated on carbon paper as a support of Pt for application in proton exchange membrane fuel cell (PEMFC). Polystyrene spheres with different diameters were coated on carbon paper by spin coating in multilayers as a template. Titanium dioxide (TiO₂) thin film was then deposited on the template by atomic layer deposition (ALD). The TiN inverse opal structure was fabricated by direct nitridation of TiO₂ in flowing ammonia atmosphere at above 800 °C. Platinum nanoparticles were then deposited uniformly on TiN by ALD. The performances of PEMFC using Pt@TiN@carbon paper composite as electrodes were examined. The homemade electrodes showed at least 13 times higher platinum specific power density than commercial E-Tek electrodes.