Gas sensitiveness of polypyrrole films doped chemically in the gas phase

Electropolymerized polypyrrole films were electrochemically reduced and then chemically doped with one of PCl₃, SO₂, NO₂ or iodine vapour in the gas phase. These chemically-doped polypyrrole films showed a resistance decrease when they were exposed to electron-acceptor gases having electron affinities larger than those used in the chemical doping, except for one case of exposure of iodine-doped polypyrrole films to NO₂, where (although iodine has reportedly a larger electron affinity than NO₂) a resistance increase was seen, which was caused by a partial substitution of the doped iodine with exposed NO₂. The phenomenon is discussed in terms of the stabilization of gaseous species on adsorption. The present study suggests that a selective gas sensitivity may be attached to polypyrrole films if they are doped with an appropriate gas in advance.     

The relationship between acoustic emission signals and cutting phenomena in turning process

The development of intelligent manufacturing by using machine tools is advancing in leaps and bounds. To maintain accuracy in machining and in the interests of fail-safe operation, monitoring of the cutting state or the final machining is very important. Acoustic emissions (AE) comprise elastic stress waves produced as a result of the deformation and fracture of materials. By measuring the AE generated during a turning process, it is possible to estimate the state of the machining operation. The correlation between cutting phenomena and AE in a turning process was examined experimentally by using a steel workpiece and a cermet tool in a numerically controlled turning process. The process of formation of chips, the types of chip, and the shear angle all markedly affected the AE signals. There was a strong negative correlation between the shear angle and the AE signal level. Similar results were obtained for various feed rates and for workpieces of various degrees of hardness. Correlations related to surface roughness and to tool wear are also described that permit the evaluation of the state of the turning process.     

石英玻璃的化学机械磨削加工

为了实现石英玻璃基板的高效、高质量加工,进一步改善光掩模设备的性能,进行了石英玻璃化学机械磨削(CMG)加工技术的研究。通过在磨削过程中主动增强磨粒、结合剂以及磨削液与工件的化学反应,并使化学反应与机械去除作用形成动态平衡,从而消除因材料脆性去除而造成的表面损伤等,实现了大口径玻璃工件的高表面质量、高形状精度的加工。针对石英玻璃CMG加工的特点,开发了CMG专用砂轮及磨削液,利用正交实验法优化了石英玻璃CMG加工工艺参数,分析了CMG加工过程中磨削压力、砂轮转速、磨削液流量、pH值等因素对加工表面粗糙度及加工效率的影响,并利用优化后的工艺参数加工得到了Ra为0.795nm的石英玻璃表面。加工后基板的光学性能和化学机械抛光(CMP)加工基板的光学性能相同,能够满足光掩模设备的性能需求。     

Magnetization of friction surfaces and wear particles by tribological processes

The relationship between magnetization of a friction surface and wear phenomena is discussed for the case of rubbing of nickel on nickel. Experiments were performed by sliding-friction tests of the pin-on-block type. Magnetization of the friction surface was estimated by measuring changes in the magnetic flux density with a Tesla meter, and the effects of lubrication and various normal loads on changes in the magnetic flux density were examined. Also, the magnetic flux density of wear particles was examined for single particles and particle aggregates. The magnetization of the friction surface was found to be related to surface damage by transfer (adhesion). Individual wear particles and aggregates of fine wear particles were all magnetized in one direction by tribological action, showing that wear particles and transfer particles on the friction surface are the principal source of magnetization.     

Characteristic scales of two‐dimensional turbulence in polymer solutions

An experimental study has been performed to investigate the relationship between the extensional viscosity of polymers and the turbulent drag reduction. Self‐standing flowing soap film was used to generate two‐dimensional (2‐D) turbulent flow to eliminate shear stress. Two types of polymers having different flexibilities were added to the 2‐D turbulence. The effects of these polymers were visualized by the interference pattern of flowing soap films. The vortex deformation by adding polymers was analyzed by Fourier transformation and wavelet transformation. The scaling exponents of the power spectrum of interference patterns indicate that the mechanism of turbulence laminarization due to the extensional viscosity is anisotropic. A wavelet analysis reveals the high and low fluctuations of the polymer‐added flow. Results from wavelet analysis indicate disappearing of original vortices, and appearing of new structures in low frequency in 2‐D flow. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1854–1862, 2014     

Perpendicular oriented cylinders via directional coalescence of spheres embedded in block copolymer films induced by solvent annealing

Polystyrene-b-poly(methyl acrylate) (PS-b-PMA) block copolymer with PS volume fraction of 25.2 vol% was synthesized by atom transfer radical polymerization. Non-pretreated silicon wafers were used as the substrates to prepare perpendicular oriented PS cylinders in PMA matrix via solvent annealing which could induce the transformation of spheres to vertically oriented and hexagonally packed cylinders. The spherical microdomains were formed after the evaporation of solvents from the solutions of the block copolymer in selective solvents mixed from methanol, acetone and dichloromethane. The thickness of films could be as thick as 1000 nm, which were much thicker than usual cases and the cylinders came from the directional coalescence of the spheres, thus any pre-treatments of the substrates were not required for perpendicular orientation. The structures were characterized by small angle X-ray scattering (SAXS), transmission electron microscope (TEM), atom force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS).     

1-O-alkyl-2-(ω-oxo)acyl-sn-glycerols from shark oil and human milk fat are potential precursors of PAF mimics and GHB

This study examines the feasibility that peroxidation and lipolysis of 1-O-alkyl-2,3-diacyl-sn-glycerols (DAGE) found in shark liver oil and human milk fat constitutes a potential source of dietary precursors of platelet activating factor (PAF) mimics and of gamma-hydroxybutyrate (GHB). Purified DAGE were converted into 1-O-alkyl-2-acyl-sn-glycerols by pancreatic lipase, without isomerization, and transformed into 1-O-alkyl-2-oxoacyl-sn-glycerols by mild autooxidation. The various core aldehydes without derivatization, as well as the corresponding dinitrophenylhydrazones, were characterized by chromatographic retention time and diagnostic ions by online electrospray mass spectrometry. Core aldehydes of oxidized shark liver oil yielded 23 molecular species of 1-O-alkyl-sn-glycerols with short-chain sn-2 oxoacyl groups, ranging from 4 to 13 carbons, some unsaturated. Autooxidation of human milk fat yielded 1-O-octadecyl-2-(9-oxo)nonanoyl-sn-glycerol, as the major core aldehyde. Because diradylglycerols with short fatty chains are absorbed in the intestine and react with cytidine diphosphate-choline in the enterocytes, it is concluded that formation of such PAF mimics as 1-O-alkyl-2-(ω-oxo)acyl-sn-glycerophosphocholine from unsaturated dietary DAGE is a realistic possibility. Likewise, a C₄ core alcohol produced by aldol-keto reduction of a C₄ core aldehyde constitutes a dietary precursor of the neuromodulator and recreational drug GHB, which has not been previously pointed out.     

Redox properties of CeO2 and Pt-Rh/CeO2 studied by TAP method

Redox properties of CeO₂ and Pt-Rh/CeO₂ were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O₂. A portion of pulsed CO was oxidized to CO₂ and a portion of CO was adsorbed on the surface. Pulsing ¹⁸O₂ onto the catalyst which has surface species derived from CO, evolved CO₂ contained no ¹⁸O suggesting that the surface species will be carbonate ions.     

Development of ultra-deep HDS catalyst for production of clean diesel fuels

Cosmo Oil has successfully developed a new CoMo HDS catalyst, C-606A, for production of ultra-low sulfur diesel fuels. This catalyst was prepared by an impregnation method using a solution containing Co, Mo, P, and citric acid on a HY-Al₂O₃. The resulting catalyst air-dried only without calcination. The HDS activity was measured with straight-run light gas oil feedstocks under industrial hydrotreating conditions. C-606A had a three times higher HDS activity compared with the conventional CoMoP/Al₂O₃ catalyst. Commercial operation with C-606A has successfully demonstrated high performance. This catalyst has superior activity, which enables <10-ppm sulfur content in products in a commercial hydrotreater designed to produce 500-ppm sulfur diesel fuels.     

Rheological behavior and microstructure of bimodal suspensions of core‐shell structured swollen particles

The rheological behavior and microstructure of bimodal suspensions of core‐shell structured swollen particles have been examined with changing volume ratio of two different sized particles. As the volume fraction of large particles increases, the viscosity, degree of shear‐thinning, and the critical shear stress σ_c decreases, while the interparticle distance ξ of the microstructure increases. The suspensions exhibit single mode rheological behavior and have a single diffraction peak in the SAXS profiles. These results suggest that the bimodal suspensions of the core‐shell structured swollen particles behave likely to unimodal suspensions of hard spheres with alloy like single mode microstructure composed of hypothetical intermediate size particle. The relationship between σ_c and ξ can be represented as σ_c = 3kT/4πξ³, which corresponds to the dynamics of the Brownian hard sphere model with ξ being the particle diameter. These findings indicate that the shear‐thinning of the suspensions can be attributed to dynamical competition between the thermal motion and the hydrodynamic motion under shear flow and that the mechanism can be applied to bimodal suspensions of the swollen particles as well as unimodal suspensions of hard spheres. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 102: 2212–2217, 2006