Self‐organization of striped pattern of refractive indices in photopolymer film

We report on a self‐organized striped pattern of refractive indices in a photopolymer film. Silicon oxide (SiO₂) particles (1.3‐μm diameter) were dispersed on a cover glass above a monomer mixture (bifunctional methacrylate monomer, cyanoethylmethacrylate, and 2,4,6‐trimethylbenzoyldiphenylphosphine oxide), and the sample was uniformly irradiated from a tube light source. The self‐organized striped pattern was observed inside a 0.45‐mm thickness photopolymer film. In contrast, no pattern was observed in a 0.45‐mm thickness sample photopolymerized without particles on a cover glass. The results suggest that the SiO₂ particles acted as “lenses” and produced a light distribution reflecting the shape of the light source used during the irradiation. The photopolymerization extended in depth according to the light distribution, and then the striped pattern was generated inside a medium. The photopolymer film with the striped pattern has an angular dependence in the transmittance as a result of the microstructure and can be applied to a flexible optical transmission filter. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3351–3358, 2004     

Formation of self-rolled polymer microtubes studied by combinatorial approach

This paper describes an experimental study of the polymer microtube formation in different fabrication conditions. A photolithography route is demonstrated for the fabrication of large amount of uniform and good quality polymer microtubes. TEM grids were used as mask and exposure of UV radiation was done in two steps to create asymmetric patterns. The diameter of tube was controlled by regulating the thickness of polymer layers, UV radiation dose and concentration of acidic solution. The results indicate that thickness of the bilayer film was the most dominating factor to determine the tube’s dimension, and diameter of the tubes increased with increase in the thickness of bilayer. The kinetics of the tube formation was studied with respect to acidity of the solution and UV dose. Rate of rolling increased with the acidity of the solution. Tube diameter and rate of rolling decreased with the increase of the UV exposure time. Films with two-dimensional gradients of layer thicknesses were prepared to study a broad range of parameters in a single experiment. The tubes were characterized in detail using optical microscopy and scanning electron microscopy. These polymer microtubes have potential applications in microfluidic devices and biotechnology field.     

Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity

~~Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity@魏刚$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @张元晶$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @熊蓉春$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China~…     

Extraction based on the flow-injection principle : Part 6. Film formation and dispersion in liquid—liquid segmented flow extraction systems

The dispersion mechanism in flow-injection extraction systems has been investigated. The phase with the highest affinity for the tubing material forms a thin film on the wall (e.g., 0.055 mm in a 0.7-mm i.d. PTFE tube with pentanol/water at a flow velocity of 11 cm s^?1). The film thickness increases linearly with increasing flow velocity and can be related to the viscosity/interfacial tension ratio in such a way that a low ratio indicates a thin film. The analyte is extracted into the film and into the adjacent segments. The film is stationary relative to the moving segments and this results in a backward transport of analyte molecules giving rise to dispersion. The thicker the film, the larger the dispersion. By decreasing the tube diameter and the flow velocity, lower dispersion results. Minimum dispersion is obtained for systems in which the phase carrying the analyte does not form the film.     

Controllable preparation of nanosized TiO<Subscript>2</Subscript> thin film and relationship between structure of film and its photocatalytic activity

TiO₂ nano-crystalline film and fixed bed photocatalytic reactor were prepared by the sol-gel process using tetrabutylorthotitanate as a precursor and glass tube as the substrate. XRD, AFM, SEM and thickness analysis results indicate that the preparation of nano-crystalline film can be controlled by optimizing experiment process. Under the optimized process, the phase of TiO₂ in film is anatase, and the grain size is 3–4 nm. The size of particles, which is about 20-80 nm, can be controlled. The thickness of monolayer film is in nanometer grade. The thickness and particles size in films growing on nanometer film can also be controlled in nanometer grade. As a result, the crack of film can be effectively avoided. Rhodamine degradation results using UV-Vis spectrophotometer show that the activity of nano-crystalline film in the photocatalytic reactor has a good relation with the diameter of TiO₂ particles, that is, the film shows high activity when the size is 20 –30 nm and greatly reduced when the size is above 60 nm. The activity of film does not decrease with the increase of film thickness, and this result indicates that nano-crystalline film has no ill influence on the transmissivity of ultraviolet light.     

Application of single-walled carbon nanotube body to unique emitter: a first-principles study

The field emission characteristics of the body for single-walled carbon nanotubes (SWNTs) are investigated by use of the first-principles calculations. We find that field emission property, chemical stability and binding energy of the tube body with the practical diameter are less sensitive to the tube diameter, morphology, and conductive characteristic, and conclude the emission features of the body film: consistence in emission sites, uniformity in emission energy distribution, predictability in emission effects and high emission stability, which are similar to those of graphite sheet or diamond film. These unique features guarantee the tube body to be applicable to flat panel displays with the same picture quality, cylindrical cathode and linear emitter.     

The dependence of the properties of liquid crystals on the film thickness and surface quality of capillary columns

Summary Glass capillary columns were prepared from non-deactivated and deactivated glass and coated with (2-methyl-4-[trans-4-n-propyl-cyclohexylcarbonyloxy]-benzoic acid-[4-n-heptyloxy-phenylester]) as the liqud phase, in different film thicknesses. The columns were tested using substances of different structures and polarities. It was verified that the capacity factors, retention indices and selectivity significantly depend on the thickness of the liquid crystalline stationary phase film and the quality of the tube, particularly in the case of columns with thin films. Trasition temperatures (melting and clearing point) of the liquid crystal are also dependent on these two factors.Dedicated to Professor J. F. K. Huber on the occasion of the his 60th birthday.     

Foam films in the presence of functionalized gold nanoparticles

Dry aqueous foams made of anionic surfactant (SDS) and spherical gold nanoparticles are studied by small angle X-ray scattering and by optical techniques. To obtain stable foams, the surfactant concentration is well above the critical micelle concentration. The specular reflectivity signal obtained on a very thin film (thickness 20 nm) shows that functionalized nanoparticles (17 nm typical size) are trapped within the film in the form of a single monolayer. In order to isolate the film behavior, investigations are made on a single film confined in a tube. The film thinning according to the ratio of functionalized nanoparticle and SDS micelles (1:1, 1:10, 1:100) is mainly governed by the structural arrangement of SDS micelles. In thick films, nanoparticles tend to form aggregates that disappear during drainage. In particular self-organization of nanoparticles (with different surface charge) inside the film is not detected.     

Dewetting of a sol-gel-derived thin film

We report on the dewetting of a thin film produced by the sol-gel method. In the early stages of dynamic morphological instability, the drying stress in the capillary wave model determines the linearly scaling behaviors of the characteristic wavelength with the initial film thickness and the square law dependence of the number density of the dewetted holes on the film thickness. These power law dependences are weaker than those observed in the case of the spinodal dewetting of a polymer thin film. The wavelength determined in the early stages also dominates the scaling behaviors of the average length of the sides and number density of the polygons and the diameter of the droplets of the dewetting pattern with the film thickness in the final stages of the dynamic instability. We also observed that further drying eventually induces wrinkles in the droplets, rim, and film, which have a characteristic wavelength that can be theoretically predicted.     

Corrosion and tribocorrosion behaviour of super‐thick diamond‐like carbon films deposited on stainless steel in NaCl solution

Super‐thick diamond‐like carbon (DLC) film is a potential protective coating in corrosive environments. In the present work, three kinds of DLC films whose thickness and modulation periods are 4 µm and 3, 21 µm and 17 and 21 µm and 7, respectively, were fabricated on stainless steel. The effect of different thickness and modulation periods on corrosion and tribocorrosion behaviour of the DLC‐coating stainless steel was investigated in 3.5 wt% NaCl aqueous solution by a ball‐on‐flat tribometer equipped with a three‐electrode electrochemical cell. The DLC‐coating stainless steel served as a working electrode, and its OCP and potentiodynamic polarization were monitored before and during rubbing. The wear–corrosion mechanism of the DLC films was investigated by SEM. The results showed that the increasing thickness can prolong significantly lifetime of DLC films in NaCl aqueous solution. In particular, the modulation period has a significant impact on the tribocorrosion resistance of the DLC super‐thick films. The study suggested that the increasing thickness of compressive stress layer could suppress film damage by reducing crack propagation rate. Thus, the super‐thick DLC film with thickness of 21 µm and 7 periods presented the best tribocorrosion resistance among all studied films. Copyright © 2016 John Wiley & Sons, Ltd.     

Water‐sorption behaviors of poly(3,4′‐oxydiphenylene pyromellitimide) films depending on the thickness variation

The effect of film thickness on the water‐sorption behaviors of poly(3,4′‐oxydiphenylene pyromellitimide) (PMDA‐3,4′ODA) films was gravimetrically investigated and interpreted with a Fickian diffusion model in films. The diffusion coefficient increased with increasing film thickness, whereas the water uptake and the activation energy decreased. Overall, the water‐sorption behaviors of PMDA‐3,4′ODA films are strongly dependent on the changes in morphological structure, which originated from the variation in the film thickness. As the film thickness increased, the molecular in‐plane orientation decreased, consequently leading to the increased diffusion coefficient and decreased activation energy. In contrast, the water uptake decreased with increasing film thickness because of the increase in the out‐of‐plane packing order. The diffusion coefficient and activation energy were strongly dependent on the in‐plane orientation in the films. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 669–676, 2001     

Internal Architecture of Zwitterionic Polymer Brushes Regulates Nonfouling Properties

In this work, we study how film thickness and chain packing density affect the protein‐resistant properties of polymer brushes in complex media. Polymer brushes based on dual‐functional poly(carboxybetaine acrylamide) (pCB) were prepared via surface‐initiated photoiniferter‐mediated polymerization. By adjusting UV radiation time and solvent polarity, pCB films with different thicknesses can be achieved and characterized using an ellipsometer. The packing density of pCB polymer chains is directly related to the swelling ratio of swollen to collapsed film thicknesses. Results showed that the dry film thickness alone, used often in the literature, is not sufficient to correlate with nonfouling properties and the chain packing density must be considered for the design of nonfouling surface coatings.     

Online preconcentration for the determination of lead, cadmium and copper by slotted tube atom trap (STAT)-flame atomic absorption spectrometry

An online sensitivity enhancement by using atom trapping in flame atomic absorption spectrophotometry was examined for increasing the residence time of the analyte atoms in the light path. For this purpose, various parameters of quartz tubes of the slotted tube atom trap were tested. The studied parameters include the internal diameter, the length of the upper slot and the wall thickness of quartz tube. The best sensitivities as high as 7-fold, 13-fold and 3-fold enhancement were achieved by the tubes having an internal diameter of 6 mm, an upper slot length of 1.0 cm and the wall thickness of 1.5 mm for lead, cadmium and copper, respectively. The limits of quantitation were found to be 30 ng mL(-1) for Pb and 3 ng mL(-1) for Cd and 30 ng mL(-1) for Cu by the optimized method. The achieved technique was applied to determine the concentrations of Pb, Cd and Cu in different plant leaves taken around cement and textile industries.     

黑膜厚度与膜表面张力关系的研究

用微干涉测量技术直接测定楔压等温线,研究了电解质浓度对阳离子表面活性剂TTAB在浓度大于cmc时形成黑膜厚度的影响及膜表面张力与溶液表面张力之间的差别.结果显示,黑膜厚度取决于楔压和电解质浓度,随着楔压的增加,液膜厚度减少至一定程度后几乎保持不变,表明黑膜类型的转化是阶跃式的,而电解质屏蔽了液膜两个表面电荷层间的排斥作用,故电解质浓度增加,液膜厚度变小.由楔压等温线得出的膜表面张力的结果说明一般黑膜的表面张力与溶液的表面张力并无明显差别.     

TiO2修饰的镍基光电极的制备及光电化学性能

通过溶胶 凝胶法，直接在导电的金属镍基上制备多孔TiO2纳米薄膜，利用STM观察电极的表面形貌，所制TiO2粒径约为20～80 nm，随着烧结温度的升高，TiO2纳米薄膜表面孔的数量增多、孔径增大.用循环伏安法分析了电极的光电化学性能，结果表明，电极的光电响应随烧结温度的升高和薄膜厚度的增加而增大.     

Influence of Nanoporosity and Roughness on the Thickness-Dependent Coercivity of Iron Nanonetworks

Summary.  We have studied the coercivity of magnetic nanonetworks as a function of thickness, nominal pore diameter, and surface/interface roughness in the thickness range of approximately 2 to 45 nm where a Néel-type domain wall has been theoretically predicted. Such magnetic nanonetworks have been prepared by sputtering iron on the walls of commercially available porous nano-channel alumina (NCA) membranes. The thickness dependence of coercivity has also been studied on films deposited on surface-oxidized Si and glass subtrates. These substrates are essentially non-porous and much smoother than NCAs. Our investigation shows that the coercivity of films deposited on Si and glass depends on the spatial fluctuation of thickness which arises from the roughness of the apparently smooth substrates. On the other hand, NCAs are found to be inherently quite rough, and films on NCAs show a complex thickness dependence which arises from the interplay between surface/interface roughness, domain pinning due to porosity, surface anisotropy, surface torques, and oxidation of the iron films. It was found that the growing films on NCA substrates led to partial filling up of the pore entrance, thereby reducing its effective diameter. The film growth also affects the roughness of the film, which in turn affects its coercivity. We propose a model for the thickness dependence of coercivity based on the pore fill-up geometry considering the effective pore diameter and the critical thickness at which the pore will be completely filled up. Experimental results on coercivity with thickness variation of iron network deposited on NCA generally agree with the suggested model. Received October 16, 2001. Accepted (revised) January 11, 2002     

First-principles calculations of AlN nanowires and nanotubes: atomic structures, energetics, and surface states

We explore the atomic and electronic structures of single-crystalline aluminum nitride nanowires (AlNNWs) and thick-walled aluminum nitride nanotubes (AlNNTs) with the diameters ranging from 0.7 to 2.2 nm by using first-principles calculations and molecular dynamics simulations based on density functional theory (DFT). We find that the preferable lateral facets of AlNNWs and thick-walled AlNNTs are {1010} surfaces, giving rise to hexagonal cross sections. Quite different from the cylindrical network of hexagons revealed in single-walled AlNNTs, the wall of thick-walled AlNNTs displays a wurtzite structure. The strain energies per atom in AlNNWs are proportional to the inverse of the wire diameter, whereas those in thick-walled AlNNTs are independent of tube diameter but proportional to the inverse of the wall thickness. Thick-walled AlNNTs are energetically comparable to AlNNWs of similar diameter, and both of them are energetically more favorable than single-walled AlNNTs. Both AlNNWs and AlNNTs are wide band gap semiconductors accompanied with surface states located in the band gap of bulk wurtzite AlN.     

Peculiarities of polyelectrolyte multilayer assembly on patterned surfaces

The layer-by-layer assembly of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) is studied on templates with imprinted arrays of microwells ranging from 2 to 25 μm and different aspect ratios. The thickness and microstructure of polyelectrolyte multilayers (PEMs) are measured using scanning electron microscopy. At 0.2 M ionic strength, the PEM film evenly coats the template both inside and outside the microwells. If the film is thinner than the critical value of about 400 nm, PEM microstructures collapse upon dissolving the template. Euler's model of critical stress is used to describe the collapse. At 2 M ionic strength, a substantially thinner PEM film is assembled inside the 25 μm wells than outside. If the well diameter is reduced to 7 and 2 μm, a much thicker PEM film is formed inside the microwells. These observations have been attributed to the changing of polyelectrolyte conformation in the solutions.     

Change in the interfacial reaction of Hf-silicate film as a function of thickness and stoichiometry

Medium energy ion scattering and high-resolution transmission electron microscopy are used to investigate the depth of the interfacial reaction of Hf-silicate film. The interfacial reaction is critically affected by the film thickness and the mole fraction of HfO(2) in silicate film. The interfacial compressive strain generated at the surface of the Si substrate is dependent on the film thickness during the postannealing process in film with a thickness of approximately 4 nm. Finally, the phase separation phenomenon demonstrates critically different behaviors at different film thicknesses and stoichiometries because the diffusion of Si from interface to surface is dependent on these factors. Moreover, the oxidation by oxygen impurity in the inert ambient causes SiO(2) top formation.     

Performance of open tubular columns as a function of tube diameter and liquid phase film thickness

Summary Wall-coated, open-tubular (capillary) columns prepared from different diameter tubing, with different liquid phase film thickness, are compared with each other and with packed and support-coated open-tubular columns. The comparison is based on the variation of the phase ratio and the capacity factor, and includes column efficiency (HETP, theoretical plate number), resolution, retention time, and sample capacity. Problems associated with the evaluation of the sample capacity are outlined. The influence of temperature on column performance is discussed in detail. Finally, the possibilities of short, wide-bore open-tubular columns prepared with a thick liquid-phase film are demonstrated.Parts of this paper were presented at the 35th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Atlantic City NJ, March 5–9, 1984, and at the 20th International Symposium on Advances in Chromatography, New York NY, April 16–18, 1984.