纳米级包覆层厚度对染料敏化太阳电池中电子注入效率和电子寿命的影响

选取氧化钐作为包覆材料, 采用浸渍法对已烧结好的纳米TiO₂多孔薄膜电极进行修饰, 并将其应用于染料敏化太阳电池中, 研究了纳米级氧化钐包覆层厚度及均匀性对染料敏化太阳电池中电子注入效率和电子复合过程的影响和作用机制. 结果表明, 包覆层厚度对电子注入效率和电子复合具有明显影响, 且电子注入效率和电子寿命随包覆层厚度的增加而呈现相反的变化趋势, 包覆层厚度在0.4 nm以内, 电池性能最好.     

THE EFFECT OF EC ON ORIENTATION AND RELAXATION OF PP OBTAINED VIA DYNAMIC PACKING INJECTION MOLDING

As a long term project aiming at engineering plastics based on polypropylene (PP), in this work, we report the effect of ethylene-cellulose (EC) on the orientation and relaxation of PP obtained via dynamic packing injection molding (DPIM). 2d-WAXD results showed that PP with a highly oriented structure and a shish-kebab structure were achieved by DIPM, leading to an increase of tensile strength from 35.0MPa to 48.6MPa. The degree of orientation of PP was increased by adding only 1% of EC, resulting in a further increase of tensile strength from 48.6MPa to 53.8MPa. Shish was found to exist not only in the oriented layer but also in the core of the sample after adding EC, as evidenced by DSC result.This was understood as due to the overall decrease of viscosity by the addition of EC, thus an increasing of shear rate. Higher shear rate can favor the orientation of molecules and continuous growth of shish structure, resulting in a change of shish distribution along the sample thickness. On the other hand, the relaxation mode of shish in the melt recrystallization of PP is also greatly affected by the presence of EC. A retarded relaxation of PP macromolecules was seen.Even more, SEM results showed that EC could form the short fibers in PP matrix along the shear flow direction. Compared with the morphology obtained by conventional injection molding, a much better dispersion and easy break-up of EC in PP matrix were observed for samples obtained by dynamic packing injection molding.     

Direct measurement of molecular motion in freestanding polystyrene thin films

An optical photobleaching technique has been used to measure the reorientation of dilute probes in freestanding polystyrene films as thin as 14 nm. Temperature-ramping and isothermal anisotropy measurements reveal the existence of two subsets of probe molecules with different dynamics. While the slow subset shows bulk-like dynamics, the more mobile subset reorients within a few hundred seconds even at T(g,DSC) - 25 K (T(g,DSC) is the glass transition temperature of bulk polystyrene). At T(g,DSC) - 5 K, the mobility of these two subsets differs by 4 orders of magnitude. These data are interpreted as indicating the presence of a high-mobility layer at the film surface whose thickness is independent of polymer molecular weight and total film thickness. The thickness of the mobile surface layer increases with temperature and equals 7 nm at T(g,DSC).     

Polymeric surfactants in latex technology: polystyrene–poly(ethylene oxide) block copolymers as stabilizers in emulsion polymerization

Polystyrene–poly(ethylene oxide) PS–PEO di- and triblock copolymers have been used as stabilizers in the emulsion polymerization of styrene and styrene–butylacrylate for the preparation of “hairy latexes”. The polymerization kinetics and the efficiency of these polymeric surfactants were correlated with the molecular characteristics of the block copolymer. It was shown that the efficiency decreased with increasing molecular weight and PS content of the block copolymer. The PEO frige, with a thickness of 4–25 nm, on the latex particle surface could be characterized and it was shown by differential scanning calorimetry (DSC) that water is strucured in that PEO layer. Film formation with “hairy latexes” was also examined both by DSC and thermomechanical analysis. The properties and application possibilities, such as in controlled latex flocculation, have been reviewed.     

Control of Alq3 wetting layer thickness via substrate surface functionalization

The effects of substrate surface energy and vapor deposition rate on the initial growth of porous columnar tris(8-hydroxyquinoline)aluminum (Alq3) nanostructures were investigated. Alq3 nanostructures thermally evaporated onto as-supplied Si substrates bearing an oxide were observed to form a solid wetting layer, likely caused by an interfacial energy mismatch between the substrate and Alq3. Wetting layer thickness control is important for potential optoelectronic applications. A dramatic decrease in wetting layer thickness was achieved by depositing Alq3 onto alkyltrichlorosilane-derivatized Si/oxide substrates. Similar effects were noted with increasing deposition rates. These two effects enable tailoring of the wetting layer thickness.     

STS investigations to describe corrosion procedures on thin CrN layers

To represent the corrosion characteristics of thin hard material layers, CrN layers, which were magnetron sputtered, have been exposed to solutions with chloride or sulfate ions. The alterations of the layer surfaces were examined. Static immersion tests were carried out ex-situ in 1 mol L(-1) NaCl or 1 mol L(-1) Na(2)SO(4) solution over a period of 14 months. For in-situ measurements, the layers were inserted into the electrochemical cell of an EC STM as the working electrode. The sample potential was altered cyclically. At the same time, voltammograms were taken and the topography alteration was observed.Alterations in the surface structure were documented as hybrid information resulting from changes in topography and the chemical consistency or the thickness of the oxide layers. These modifications were demonstrated with scanning tunnelling spectroscopy before and after the treatment with solutions. Several chemical phases (initial state and oxide layers) were distinguished with raster tunnelling spectroscopy (measurements I(V) and I(z)). The evaluation of the I(z) spectroscopy showed that the tip was in mechanical contact with the sample if an oxide layer of greater thickness has existed.Exemplary XPS investigations demonstrated corrosive alterations of the CrN layers due to oxidation. Asymmetry and peak locations suggest that in addition to Cr(2)O(3) and CrN a complex mixture of different chromium oxides such as Cr(2)O(3) and Cr(OH)( x) exists.     

Self-assembly of polymer and molybdenum oxide into lamellar hybrid materials

We report on self-assembly of polymer and molybdenum oxide chains into a new class of lamellar hybrid materials. Aqueous ammonium molybdate and polyvinyl alcohol (PVA) or carboxymethyl cellulose (CMC) were used as the starting materials. Ammonium molybdate was hydrolyzed into layered molybdenum oxide under acidified conditions. The organic polymer chains and the inorganic molybdenum oxide layers self-assemble and pack into new hybrid composites. Scanning electron microscope (SEM) images and polarized microscopy show that these two new materials have typical lamellar structure. Transmission electron microscope (TEM) images show that the layer thickness is about 100 nm. X-ray diffraction (XRD) data confirm the formation of inorganic molybdenum oxide. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) data gave thermal behavior of these composites. The mechanism of this hybrid reaction and the templating function of polymers were discussed in this paper. A special entropy effect was discovered when polymer was used as guest species. This entropy effect makes polymers preferential candidates as guest species rather than small molecules when fabricating organic/inorganic layered hybrid materials. We believe that this opens a new way to create organic/inorganic hybrid superstructures.     

Investigation of mechanical properties of anodized aluminum using dilatometric measurements

Mechanical properties of anodized aluminum were studied using the results of dilatometric measurements of thermal expansion of anodized Al (the symmetric structure Al(2)O(3)-Al-Al(2)O(3)). The 100-microm-thick Al(2)O(3 )oxide layer was formed in 4% aqueous solution of oxalic acid in the galvanostatic regime at a current density of 20 mA cm(-2). Measurements of thermal expansion of anodized Al (Al and Mg alloy of 2.7-3.2%, and 0.3-0.6% Mn, and 0.5-0.8% Si) with the thickness of initial Al from 0.6 to 3.7 mm and ceramic from Al(2)O(3) in the temperature range of 20-500 degrees C were conducted using an automatic quartz dilatometer. Intrinsic stress in the Al layer, the values of the modulus of elasticity, and the porosity of Al oxide formed on Al of different thickness are calculated.     

Oxide and nitride protective layers on stainless steel studied by AES,WDS and XPS

Protective surface layers on AISI 321 stainless steel were prepared by thermal treatments at two different temperatures in air and two controlled atmospheres. Different oxide and/or nitride layers were formed. Surface morphology of the layers was investigated by scanning electron microscopy (SEM). Auger electron spectroscopy (AES) depth profiling of the samples was performed. Since depth profiling suggested layer thicknesses of the order of hundreds of nanometres, an attempt was made to obtain some fast, averaged information about the layer compositions using wavelength dispersive spectroscopy (WDS) at two different beam energies to obtain probing depths best suited to the layer thickness. X‐ray photoelectron spectroscopy (XPS) profiling of one layer was also performed to obtain information about the chemical states of the elements inside the layer. The analysed samples showed considerable differences with respect to their surface morphology, oxide/nitride layer thicknesses, compositions and layer–metal interface thickness. Copyright © 2007 John Wiley & Sons, Ltd.     

Mechanism of interaction of pyrite with hematite as simulation of slagging and fireside tube wastage in coal combustion

Iron-bearing minerals have been recognised as a mayor source of fire-side wall slagging in pulverised fuel boilers, which not only reduces the thermal efficiency of heat transfer of the exchangers surface, but also affects its integrity as a result of corrosion and erosion. Nevertheless, the root cause of adhesion and growing of deposits has not been clearly addressed. Our approach suggests that differential scanning calorimetry (DSC) combined with simultaneous thermogravimetry can follow the chemical reaction between pyrite and the outer layer of iron oxide on tubewalls. The changes in composition are followed by X-ray diffraction (XRD). The results indicated that the mechanism of wetting and adherence of molten pyrite over iron oxides is chemically induced: both di and mono iron sulphides interact with the oxide layer, changing the oxidation state of iron in oxide scale, from hematite to magnetite. This would imply a change in the protective ability of the scale as well as a great increment in corrosion tendency.     

Chemical stability of (NH4)2S-passivated InP(001) surfaces – investigations by XPS and XPD

UV/ozone supported surface oxidation of wet chemically cleaned and sulfurized InP(001) was investigated using XPS in order to study the chemical stability of (NH₄)₂S-passivated surfaces. Sulfur coverages of about one monolayer thickness were not sufficient to completely passivate the InP surface against oxidation. Similar oxides of the substrate components were observed at the surfaces. Evidence for surface passivation was found in the chemical stability of incorporated sulfur (In-S bonds), the lower growth rate of the oxide layer and its reduced thickness at comparably large UV/ozone exposures. The oxide layer was found to be amorphous at all stages of the oxidation process, as was proved by X-ray photoelectron diffraction.     

砷化镓半导体表面自然氧化层的X射线光电子能谱分析

用X射线光电子能谱(XPS)，测量了Ga3d和As3d光电子峰的结合能值，指认了砷化镓(GaAs)晶片表面的氧化物组成，计算了表面氧化层的厚度，定量分析了表面的化学组成；比较了几种不同的砷化镓晶片表面的差异。结果表明：砷化镓表面的自然氧化层主要由Ga2O3、As2O5、As2O3和单质As组成，表面镓砷比明显偏离理想的化学计量比，而且，氧化层的厚度随镓砷比的增大而增加；溶液处理后，砷化镓表面得到了改善。讨论了可能的机理。     

聚环氧乙烷的双层片晶

聚环氧乙烷(M_n=7000)的双层片晶形态用透射电镜和差示扫描量热计进行了研究。在结晶温区54—56℃,现察到双层片晶,高于这个温区,同时看到双层片晶及单层片晶,低于这个温区,只看到单层片晶。双层片晶的熔点稍高于单层片晶。根据非整数次折迭链晶向整数次折迭链晶的转变,讨论了双层片晶和单层片晶的生长过程。在双层片晶界面上的H键降低了表面自由能,这是形成双层片晶的主要原因。     

Metal anodes oxidation rate forecasted by results of electrolysis

This work represented the results from electrolysis tests of low-melting cryolite-alumina melts at temperatures of 790 and 850°C using metal anodes based on Cu-Fe-Ni and Cu-Al. The duration of experiment was at least 72 h. With these results, oxide layer dissolution/erosion rate and anodic material oxidation depth was calculated in arbitrary units (alloy cm/year) with examples of extrapolated (forecasted) experimental data of oxidation depth and oxide layer thickness for a long period. The oxide layer formed on the anode surface by electrolysis of the studied materials was found to decelerate further oxidation all over the period of tests.     

Modulation of Tenoxicam release from hydrophilic matrix: modulator membrane versus rate-controlling membrane

This paper describes the preparation of two layered device comprising of tenoxicam containing layer and a drug free membrane layer based on Geomatrix Technology. Our device based on bilaminated films which produced by a casting/solvent evaporation technique. The drug-hydroxypropyl methylcellulose (HPMC) layer was covered by drug free membrane layer composed of a mixture of different ratios of HPMC and ethyl cellulose (EC). The prepared devices were evaluated for thickness, weight, drug content uniformity, water absorption capacity and in-vitro drug release. The films were also evaluated for appearance, smoothness and transparency. The influence of drug free membrane layer composition and thickness on the drug release pattern was studied on 12 devices (D1 to D12). The results indicate that, the release of drug from HPMC matrixes without the drug free membrane layer was fast and follows diffusion controlled mechanism. The release of drug from the devices D1, D4, D9 and D12 follow the same mechanism, while the release of drug from other devices become linear with time (zero order) and extended for long time especially when thickness and the ratio of EC was increased in the drug free membrane layer. From this study it is concluded that, changing the geometry of drug layer by addition of drug free membrane layer and changing its composition and thickness plays an important role in determining whether the drug free membrane layer is rate-controlling or modulator membrane. Hence it can facilitate the development of different pharmaceutical products with different release pattern.     

Small-angle neutron scattering study of adsorbed pluronic tri-block copolymers on laponite

The adsorption of selected poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymers on synthetic clay particles (laponite) has been investigated. The adsorbed amount and distribution of polymer was determined as a function of relative block composition and size, using the technique of contrast variation small-angle neutron scattering. The pluronic molecules appear to adsorb via a preferential segregation of hydrophobic PPO segments at the surface, with hydrophilic PEO segments dangling into solution. The effect of the PPO segments is substantial with large increases in adsorbed amount and layer thickness as the anchor fraction decreases/PEO chain length increases. This is in direct contrast to the behavior observed for PEO homopolymer adsorption (of much higher molecular weights) where the adsorbed amount and layer thickness are smaller and change little with molecular weight.     

Atomic and electronic structure of the surface of porous silicon layers

Atomic and electronic structure of the surface layers of porous silicon was studied by the methods of the near fine structure spectroscopy at the edge of X-ray absorption and ultrasoft X-ray emission spectroscopy. The thickness of the oxide layer and the degree of distortion of silicon-oxygen tetrahedra in this layer were estimated. The thickness of the surface oxide layer on the amorphous layer covering the nanocrystals of porous silicon that was kept during one year is several times greater than the thickness of the natural oxide in the single crystal silicon wafers. Distortion of the silicon-oxygen tetrahedron, the basic structural units of the silicon oxide, is accompanied by elongation of Si-O bonds and an increase in the Si-O-Si bond angles.     

A DSC study of PVAC-PMMA two-stage emulsion polymers

Core-shell polymer colloids were produced by a two-stage emulsion polymerization technique. The polymers thus formed were investigated by means of differential scanning calorimetry (DSC). The DSC thermograms show two separate glass transition regions of the core and the shell component with positions unchanged regardless of chemical composition. Increases in specific heat capacity at the glass transition temperature of both components are lower than theoretical values calculated from the net chemical composition. From these results, it is possible to estimate i) the chemical composition of the interfacial layer and ii) the interfacial layer thickness. This interfacial layer thickness is in the order of 2–7 nm.Part 7 of Polymerizations in the Presence of Seeds     

双槽法电沉积Cu/Ni多层纳米线有序阵列

以多孔阳极氧化铝（AAO）为模板，采用双槽法电沉积工艺制得高度有序的Cu/Ni多层纳米线阵列。利用扫描电镜（SEM）和透射电镜（TEM）对Cu/Ni多层纳米线进行了表征，观察到纳米线表面平滑，多层结构清晰，各子层厚度均匀，直径约为 100 nm，与AAO模板孔径基本一致。由选区电子衍射（SAED）照片可知，多层纳米线中Cu层和Ni层均为单晶结构。振动样品磁强计（VSM）测试结果表明，Cu/Ni多层纳米线阵列具有明显的垂直磁各向异性，外加磁场垂直和平行于AAO模板表面时，磁滞回线的矩形比分别为 0.701 和 0.101 ，矫顽力分别为 589 Oe和 202 Oe。通过控制铝阳极氧化工艺及电沉积时间，可获得不同直径、不同子层厚度的Cu/Ni多层纳米线阵列。     

SIMS depth profiling, line scanning and imaging analyses of the oxide layer on in-reactor corroded cladding specimens with high lateral resolution

The distribution of the reactor water components lithium and boron in the oxide layer of in-reactor corroded Zircaloy fuel rod cladding specimens was investigated by depth profiling, line scanning and imaging analyses using secondary ion mass spectrometry (SIMS). The exact thickness of the oxide layer on the specimens was measured by scanning electron microscopy (SEM). The SIMS analyses showed that lithium and boron were not homogeneously distributed in the oxide layer. The peak concentration of lithium was found close to the reactor water/oxide interface of the specimens whereas boron showed no relevant variations in the bulk of the oxide layers investigated. The concentration of both elements decreased rapidly at a significant distance close to the oxide/metal interface. Conclusions were drawn to improve the understanding of the in-reactor corrosion process of fuel rod claddings consisting of zirconium based alloys.