Electrochemical characterization of electrodeposited chromium and nickel-chromium layers on a steel substrate

Chromium was deposited on steel specimens and on electroplated steel specimens covered with a Watts nickel layer. The influence of the substrate and of the crack pattern of the electrodeposited chromium layer on the passivation and the reactivation behaviour has been studied by means of potentiodynamic polarization curve measurements and cyclic voltammetry. In the results of the above mentioned electrochemical measurements a strong influence of the substrate was found for a cracked chromium layer deposited on the steel specimen and for a cracked chromium layer deposited on a 30 m Watts nickel layer. No influence of the substrate was found in the case of a crack-free chromium layer deposited on the steel substrate or on a Watts nickel layer. It is thus possible to determine whether the chromium layer is cracked or crack free by recording a polarization curve or a cyclic voltammogram for a chromium-plated system. A mechanism is proposed for the passivation and repassivation of cracked chromium layers electrodeposited on a steel substrate or on a Watts nickel layer.     

Effects of magnesium content in the feed on cataract development in Shumiya cataract rat

Cataract is a phenomenon in which the eye becomes opaque resulting in severe visual impairment, and senile cataract is the most common cause of blindness in the world. We investigated the effect of magnesium (Mg) supplementation on cataract development using shumiya cataract rat (SCR). The SCR were fed on either a low Mg (Mg 50 mg/kg), standard Mg (Mg 500 mg/kg), or high Mg (Mg 5000 mg/kg) diet from aged 5 to 15 weeks. The growth curve of SCRs fed on a low Mg diet was the same as that of SCRs fed on a standard diet. The growth curve of SCRs fed on a high Mg diet was significantly suppressed in comparison with those fed on a standard diet. The opacification of lenses from SCR fed on a standard Mg diet started at 11 weeks of age. The opacification of lenses from SCR fed on a high Mg diet was similar to that from SCR fed on a standard Mg diet. On the other hand, the low Mg diet accelerated the onset of cataract development, and the opacity started at 10 weeks of age. In addition, the calcium ion (Ca2+) content in SCR lenses fed on a low Mg diet significantly increased in comparison with that in lenses from SCR fed on a standard Mg diet. These results suggest that Mg deficiency causes acceleration of cataract development in SCR, probably due to a rise in the Ca2+ content in the lens.     

Experimental study of a liquid film flowing over a perforation

Perforations are one of the recognized geometrical features that contribute to liquid redistribution in corrugated sheet packings. Our experimental study focuses on a simplified but relevant configuration: a thin liquid film flowing on either side of a vertical plate with a circular perforation. We focus on the curtain mode when the liquid fills the perforation. Confocal chromatic imaging reveals a capillary ridge upstream of the perforation, an inertial ridge downstream, and a varicose capillary wave standing on the liquid curtain. We show that the wavelength is selected such that the velocity of the wave both satisfies Taylor's dispersion relation and matches the curtain local speed. We examine the effect of perforation size, supply conditions, and liquid properties on the curtain transition. Lastly, we propose a simple model based on a momentum balance that describes the effect of these parameters on the Reynolds number at which curtain forms.     

Sedimentation from surface currents generated by particle-laden jets

In this paper, we develop a theoretical model for the dynamics and deposition patterns from surface currents generated by axisymmetric particle-laden jets. Our model incorporates the interaction between the particles in the environment and the continuing jet. We show that this interaction plays a central role in the evolution of the behaviour of the jet and on the sedimentation patterns on the surrounding floor. We consider surface currents generated by the impingement of the turbulent jet on both a free surface and on a solid surface. Our theoretical predictions are successfully compared with data from laboratory experiments. For the case of a jet impinging on a free surface, we also examine the evolution of the concentration of particles in the environment and in the surface current until steady state is attained. Finally, we propose a simple analytical expression for the sedimentation rate on the floor in the case of a dilute jet.     

Difference points in reactive and extractive cascades, V: Determining reaction distribution from separatrix manifolds

The effect of reaction distribution policy on a reactive column profiles is analyzed. We find that the extent reaction on a single reactive stage can greatly influence the feasibility and termination of subsequent non-reactive stages. We develop a method to quantitatively predict when perturbing the amount of reaction on a single stage will subsequently force the column profile to become infeasible or otherwise fail to meet global design targets. To predict such behavior we rely on the map of stable invariant manifolds over the saddle branch of an isoreflux pinch point curve. We show how this method can be used to select reactive stages and distribute reaction over a column section profile to meet certain design criteria. We also show how this method can be used to find limits on overall extent reaction within a column or extent reaction on a single stage.     

Phase and Texture Evolution in Chemically Derived PZT Thin Films on Pt Substrates

The crystallization of lead zirconate titanate (PZT) thin films was evaluated on two different platinum‐coated Si substrates. One substrate consisted of a Pt coating on a Ti adhesion layer, whereas the other consisted of a Pt coating on a TiO₂ adhesion layer. The Pt deposited on TiO₂ exhibited a higher degree of preferred orientation than the Pt deposited on Ti (as measured by the Full Width at Half Maximum of the 111 peak about the sample normal). PZT thin films with a nominal Zr/Ti ratio of 52/48 were deposited on the substrates using the inverted mixing order (IMO) route. Phase and texture evolution of the thin films were monitored during crystallization using in situ X‐ray diffraction at a synchrotron source. The intensity of the Pt₃Pb phase indicated that deposition on a highly oriented Pt/TiO₂ substrate resulted in less diffusion of Pb into the substrate relative to films deposited on Pt/Ti. There was also no evidence of the pyrochlore phase influencing texture evolution. The results suggest that PZT nucleates directly on Pt, which explains the observation of a more highly oriented 111 texture of PZT on the Pt/TiO₂ substrate than on the Pt/Ti substrate.     

The effect of substituents on the adsorption of alkenes on (111) Pt and Pd surfaces: a theoretical study

The coordination modes of ethylene, propene, 1- and 2-butenes, 2-methyl-2-butene, and styrene on a Pt(111) or a Pd(111) surface have been compared on the basis of extended Hückel calculations. The presence of methyl substituents induces a uniform decrease in the binding energies of the alkenes, both on Pt and on Pd. The phenyl group yields the same result on Pt but, on the contrary, gives a stronger adsorption mode on Pd. The interpretation of these results is based on the balance between attractive and repulsive interactions, the role of the latter being predominant. This trend in binding energy is related to the decrease of the hydrogenation reactivity of olefins upon substitutionin the case of a competitive reaction.     

Chromium coating on partially tin precoated steel sheet

Controlling the amount of chromium to be deposited on tin and iron substrates is important for the production of special steel sheet for welded can material, partially tin precoated and then fully coated with chromium. The deposition behaviour of chromium on tin and iron substrates was studied by means of the polarization behaviour of tin and iron in a chromium coating bath. For stable deposition, a higher current density is required on tin than on iron due to the higher hydrogen over-voltage on tin. Ageing in air after tin coating and preliminary electrolysis under the potential range of reduction of Cr⁶⁺ to Cr⁰ in a chromium coating bath are effective in facilitating the formation of a cathode film and encouraging the deposition. A study on a continuous coating line showed that the amount of chromium to be deposited on tin and iron can be industrially controlled by a process involving a lower current density in the first step and a higher current density in the second.     

Influence of subphase on the orientation of helical peptides at interface

Boc-(l-Leu-Aib)_n-OBzl (n=8, 12, 16; OBzl represents benzyl ester) was spread on water or a mixture of water and methanol (1/1 v/v) and the orientation of the helical peptides on subphase was investigated by FTIR-reflection-absorption spectroscopy. When the peptides were spread at a liquid phase on subphase, the peptides took a vertical orientation, which was not attainable by compression of peptide monolayers initially spread at a gas phase on subphase. However, the peptide monolayers on water could not be transferred on gold with keeping the vertical orientation. On the other hand, when the peptides were spread on a mixture of water and methanol, the orientation of helical peptides was closer to vertical than that on water and the monolayers were transferred repeatedly on gold to form multilayers with a vertical orientation. The suppression of orientation change upon transfer of the peptide monolayer is considered to be due to reduction of electrostatic interaction between the peptide and the image dipole when the peptide is spread on a mixture of water and methanol.     

A Model for the Diffusion of Moisture in Adhesive Joints. Part II: Experimental

The concentration dependence and temperature dependence of the diffusion coefficient, as discussed in Part I, are validated with literature data on poly(styrene) and on poly(vinylacetate). The effect on diffusivity, of a uniaxial tensile stress state and of a biaxial tensile stress state, is measured with permeation tests on stretched poly(ethyleneterephthalate) (PET) films. The influence of semi-crystallinity is briefly discussed. Further, diffusivity measurements under a tensile stress state, under a compressive stress state, and under a pure shear stress state are performed on Ultem^® polyimide films, using a modified sorption technique. Good agreement between theoretical predictions and experiment is found. Finally, predictions by the solubility model discussed in Part I are compared with data on low density polyethylene and on Ultem polyimide.     

温度均匀器不同安装间距对辊道窑窑内温度场的影响

为了进一步研究温度均匀器之间不同安装间距对辊道窑窑内温度场的影响，对某辊道窑烧成带内气体温度场进行了数值模拟。模拟计算结果表明，温度均匀器之间不同间距对窑内温度的均匀效果不同，适当增加均匀器之间的间距可以获得更好的均匀窑温效果。     

预钙化加速类骨磷灰石在镍钛合金表面生长的电化学阻抗谱

通过酸碱处理活化NiTi合金表面,在模拟体液中仿生生长类骨磷灰石层以改善其生物相容性.采用电化学阻抗谱研究了预钙化对加速磷灰石沉积的影响,并基于双层模型建立了电子等效电路.结果表明:随着在模拟体液中浸泡时间的延长,化学处理的NiTi合金表面类骨磷灰石不断生长,并且添加预钙化试样浸泡3 d,即可在合金表面生长出均匀完整的类骨磷灰石层,而未预钙化试样表面沉积物稀少.对应电子等效电路中,预钙化试样电阻值明显大于未预钙化试样的,显示预钙化促进了活化NiTi合金表面类骨磷灰石的生长.     

Experimental study of the effect of maldistribution at the structured packing inlet on the freon mixture separation efficiency

The results of an experimental study of the effect of the initial maldistribution over a structured packing on the separation efficiency of a binary freon mixture are considered. The study was performed in a distillation column 0.9 m in diameter on a mixture of R114 and R21 freons. The results on the efficiency of freon mixture separation, the pressure drop on the packing, and the distribution of the local liquid flow rate under the packing are presented. The experimental results showed that the rotation angle of structured packed layers have a significant effect on the efficiency of mixture separation in the case of maldistribution.     

Catalytic grafting: A new technique for polymer–fiber composites I. Polyethylene–asbestos composites

In this work we present a new technique to prepare polyolefin-fiber composites. This technique is based on chemical anchoring of a catalyst on reinforcing agents containing OH groups on their surface and then conducting an olefin polymerization on the supported catalyst. This technique offers the possibility to approach the challenging problems encountered in polymer composites, namely, the reinforcement-matrix adhesion, the dispersion, and the wetting of the reinforcement by the resin. As a first part of a systematic research, we report on the procedure of fixation of titanium tetrachloride on the surface of asbestos fibers and the Ziegler-Natta polymerization of ethylene on the surface-modified fibers. The procedure as well as the structure and properties of the composite were investigated by means of FTIR, atomic absorption, SEM, solvent extraction, and tensile testing. The experimental results show that the Ziegler-Natta catalyst can be efficiently anchored on the surface of the fibers to conduct successful polymerization and to “synthesize” a new class of polymer composites.     

Oxidation of carbon monoxide on poly-oriented and single-crystalline platinum electrodes over a wide range of pH

The oxidative stripping of pre-adsorbed carbon monoxide has been studied on poly-oriented platinum, and on Pt(1 1 1), Pt(1 0 0) and Pt(1 1 0) single-crystal electrodes in phosphate buffer solutions as a function of pH, both stripping voltammetry and chronoamperometry. It was found that the stripping peak potential has a tendency to decrease as a function of pH until a pH of ca. 10–11, which is ascribed to a weaker adsorption of phosphate on platinum with increasing pH. Above a pH of ca. 11, the stripping peak appears to stay constant or increase, depending on the surface structure. We hypothesize that this may be due to the fact that above a pH of ca. 10–11, the main product of carbon monoxide oxidation is carbonate, which may be block active sites on the surface. By comparison with the stripping on the single-crystalline Pt, the stripping voltammetry on the poly-oriented Pt electrode appears as a convolution of the oxidation on the different facets. A similar conclusion is drawn for the chronoamperometry experiments, and it is suggested that this may be the main reason for the asymmetrical transients observed on the poly-oriented Pt electrodes, as well as on other strongly heterogeneous Pt electrodes that have been studied in the literature.     

A pH sensor based on electric properties of nanotubes on a glass substrate

We fabricated a pH-sensitive device on a glass substrate based on properties of carbon nanotubes. Nanotubes were immobilized specifically on chemically modified areas on a substrate followed by deposition of metallic source and drain electrodes on the area. Some nanotubes connected the source and drain electrodes. A top gate electrode was fabricated on an insulating layer of silane coupling agent on the nanotube. The device showed properties of an n-type field effect transistor when a potential was applied to the nanotube from the top gate electrode. Before fabrication of the insulating layer, the device showed that the p-type field effect transistor and the current through the source and drain electrodes depend on the buffer pH. The current increases with decreasing pH of the CNT solution. This device, which can detect pH, is applicable for use as a biosensor through modification of the CNT surface.     

Dye distribution in the dyeing of mixed denier polyester fabrics

Microfibre polyester is sometimes blended with higher denier fibres to achieve good aesthetic effects at lower cost. Two polyester yarns of 1.4 and 0.7 denier were dyed singly and together with a range of depths of CI Disperse Blue 79, and the dye distribution over the course of the dyeings was examined. The uptake is initially greater on the microfibre, but as dyeing is continued the distribution becomes more even, and eventually the same concentration of dye is present on both fibres. Based on the common observation that a given concentration of dye produces a lighter shade on a microfibre, the redistribution of dye during the process causes a continuing shade change even though the bath exhaustion is constant. A mixture of three dyes produced a stable hue on a fabric of 1.0 denier polyester after 20 min at a fixed dyeing temperature, but when dyed on a fabric of 1.0 and 0.5 denier yarns, a change in hue continued for more than 60 min.     

Electrochemical activity of thiahelicenes: Structure effects and electrooligomerization ability

Thiahelicenes are polycondensed heteroaromatic molecules characterized by a chiral helix-like structure including multiple thiophene units, with a lowering effect on the oxidation potentials and a shrinking effect on the band gaps. As a consequence they can be regarded as electrochemically and optically active conducting materials, exhibiting interesting properties under electrical or magnetic polarization, and are under study for non-linear optics (NLO) applications. The present extensive investigation on 11 thiahelicenes with different chain length and functionalization (including the first example of a thiahelicene with perfluorinated alkyl chains) together with the precursor benzodithiophene provides a deep insight on the structure vs. electrochemical activity relationship within this attractive compound class, focusing on both electron transfer (ET) properties and oligomerization ability (hinging on free α positions on terminal thiophene groups).     

Numerical analysis of the flow around a system of bodies behind the shock wave

The incidence of a shock wave on a system of cylinders and spheres is numerically simulated. Flow regimes around a system of bodies are described, and a parametric analysis of the examined phenomenon is performed. Based on numerous computations, a chart of flow regimes is composed, which includes flow patterns with an individual shock wave and with a collective shock wave, depending on the free-stream Mach number and on the distance between the bodies.