Materials and reaction mechanisms at anode/electrolyte interfaces for SOFCs

The present paper reviews anodic reaction mechanisms of porous cermet and model anodes at metal/oxide interfaces in solid oxide fuel cells (SOFCs). Some analytical results, electrochemical methods, and reaction models were presented at Ni–YSZ cermets and well defined model anodes. Isotope labeling/secondary ion mass spectrometry (SIMS) analysis techniques were applied to determine the oxygen surface reactivity of oxide electrolytes in reducing atmospheres. The technique was also applied to determine the catalytic activity of metal/oxide interfaces for CH₄ decomposition and reactivity with the reformed gases at the mesh or stripe shaped anodes on different oxides. Observed SIMS images and the electrochemical analyses were compared at the model anode/electrolyte interfaces.     

最有效的相容剂是两嵌段还是多嵌段聚合物？

采用Monte Carlo模拟方法研究了多嵌段聚合物在A／B／嵌段聚合物三组份体系作为相容剂使用的有效性．占总体积19％的A组份在体系中为分散相．模拟结果显示了两嵌段和多嵌段聚合物在界面上的聚集行为,以及如何影响这个不相容体系的相形为．两嵌段聚合物趋于直立在相界面上,而多嵌段聚合物更容易横跨在相界面上并占据较大的界面积．从而导致多嵌段聚合物更有效的阻止体系相分离的发生．     

The interfacial effects on the conductive performance of the composite films based on materials with electron and ionic conductors

Laminated and blending composites are designed to study the interfacial effects on the overall conductivity based on materials with different conductive mechanisms. The blends exhibit porous morphology because of the phase separation among the components, providing lager contacting areas between polymer chains and ions, and also more moving spaces for them, and hence their conductivity increases with the addition of polyaniline (PAN) to a maximum value of 0.075?S?cm^?1 at 75% PAN of polyvinyl butyral (PVB) (wt.%). The laminated films also show conductivity improvement, but inferior to that of blends from room temperature to 60?°C. The element parameters of the interfaces have great effects on their conductive performances as tested by the electrode/solid polymer electrolytes (SPE)/electrode model. The values of the electrode/SPEs interface are in the same magnification, while the value between PAN and PVB/polyethylene glycol₄₀₀/LiClO₄ layers is much bigger than those of the electrode/SPEs, providing the fact that the interface effect between different materials (metal/polymer, polymer/polymer) plays a vital role in determining their overall conductive performances.     

Grafting onto poly(ethylene terephthalate) driven by 172 nm UV light

The reactivity of the surface of poly(ethylene terephthalate) (PET) film under 172 nm UV irradiation (xenon excimer lamp) towards nitrogen-borne 1-octene, n-nonane and heptafluorodecene vapor was investigated. Materials receiving from 0 to 24 J/cm² of UV were examined by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF/SIMS), water and mineral oil contact angle measurement and atomic force microscopy (AFM). A uniform nanoscale layer developed on PET surface attributed to the grafting reaction between photolytically-produced polymer radicals and vapor phase molecules.     

A new approach for preventing charging up of soft material samples by coating with conducting polymers in SIMS analysis

Dynamic secondary ion mass spectroscopy (SIMS) analysis of soft materials such as polymer or biomaterial is one of challenging subjects due to the charge up effect brought from the irradiation of a primary ion beam, hampering the collection of secondary ions. Conventional methods against the charging up are the electron beam irradiation for charge compensation and surface coating with metal, normally gold. Those methods require a compromise analytical condition, reducing the primary ion beam current to suppress the range of the charging, which degrading the performances of the SIMS analyses. We have proposed that a thicker conductive layer, capable of delocalizing the charge onto the surface, should be put on a soft insulator sample to avoid charging up. The depth profile of the hair sample coated wholly with a polythiophen-based conducting polymer was successfully measured in longer time without any charging up even in the maximum current of the oxygen primary ion beam (O₂⁺: 7.5 keV, 400 nA) or using an electron beam compensation system. Thus, the proposed method coating with a conductive organic polymer against the charging issue would be expected as a breakthrough on SIMS analysis.     

Nano- and microstructured polymer LB layers: A combined AFM/SIMS study

Ultra thin structured polymer films have been prepared by horizontal precipitation Langmuir-Blodgett (HP-LB) method of polymer blends. In particular we used mixtures of two incompatible polymers, poly-2-vinylpyridine and polystyrene, the former giving the necessary surface activity for LB film formation. Upon spreading at the air-water interface, the blend forms different surface structures depending on the relative amount of the two components. By adjusting the experimental parameters it is possible to obtain relatively regular structures in the submicron size range, which can be transferred on a solid substrate. These systems have been investigated by means of SIMS and atomic force microscopy.     

Characterization of EUV periodic multilayers

Nanometric Co/Mg, Co/Mg/B₄C, Al/SiC and Al/Mo/SiC periodic multilayers deposited by magnetron sputtering are studied in order to correlate their optical performances in the extreme ultraviolet (EUV) range to their structural quality. To that purpose, our recently developed methodology based on high‐resolution X‐ray emission spectroscopy (XES) and X‐ray and EUV reflectometry is now extended to nuclear magnetic resonance (NMR) spectroscopy and time‐of‐flight secondary ions mass spectrometry (ToF‐SIMS). The analysis of the Co Lαβ and Mg Kβ emission spectra shows that the Co and Mg atoms within the multilayers are in a chemical state equivalent to that of the atoms in the pure Co and Mg references, respectively. But NMR spectra give evidence for a reaction between Co atoms and B and/or C atoms from B₄C. The Al and Si Kβ emission spectra do not reveal the formation of an interfacial compound in Al/SiC and Al/Mo/SiC. Only the roughness limits the optical quality of Al/SiC. The comparative analysis of the ToF‐SIMS spectra of Al/SiC and Al/Mo/SiC indicates that the structural quality is enhanced when Mo is introduced within the stack. Copyright © 2011 John Wiley & Sons, Ltd.     

Chemical depth profiling and 3D reconstruction of III–V heterostructures selectively grown on non‐planar Si substrates by MOCVD

The chemical characterization of novel 3D architectures with nanometre‐scale dimensions is extremely challenging. The chemical composition of InGaAs/AlAs quantum wells selectively grown in SiO₂ trenches, 100–300 nm wide, is studied. Combining high lateral resolution 3D ToF‐SIMS analysis and Auger measurements, the chemical composition of individual trenches was obtained confirming the uniformity of these III–V heterostructures. These results correlate well with an average approach using SIMS depth profiling. The effects of ion beam orientation on the surface topography of confined structures were highlighted. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Adsorption and spreading of polymers at plane interfaces; theory and molecular dynamics simulations

Nonequilibrium processes play a key role in the adsorption kinetics of macromolecules. It is expected that the competition between transport of polymer towards an interface and its subsequent spreading has a significant influence on the adsorbed amount. An increase of the transport rate can lead to an increase of the adsorbed amount, especially when the polymer has too little time to spread at the interface. In this study we present both molecular dynamics simulations and analytical calculations to describe some aspects of the adsorption kinetics. From MD simulations on a poly(ethylene oxide) chain in vacuum near a graphite surface, we conclude that the spreading process can, in first approximation, be described by either a simple exponential function or by first-order reaction kinetics. Combining these spreading models with the transport equations for two different geometries (stagnation-point flow and overflowing cylinder) we are able to derive analytical equations for the adsorption kinetics of polymers at solid-liquid and at liquid-fluid interfaces. Received: 18 July 1997 / Received in final form: 27 October 1997 / Accepted: 6 November 1997     

Quantification of a Ti(CxN1−x) based multilayer by Auger Electron Spectroscopy

Auger Electron Spectroscopy (AES) is an analytical technique sensitive to the surface of materials and providing elemental and chemical composition of conductive samples. The excellent spatial resolution and its quantification possibilities, even for light elements, make AES a commonly used technique to investigate surface and interfaces.TiN-like materials have a wide range of applications depending on their stoichiometry, but their composition is still complex (or at least not straightforward) to determine because of a strong overlapping of the Ti LMM with the N KLL Auger transitions. This quantification problem can be circumvented using computerised calculations as target factor analysis (TFA) to estimate the different nitrogen and titanium contributions in this peaks overlap. However, a more simple method, based on the study of Ti LMM and Ti LMV area ratio of pure TiN and TiC reference samples, is described in this paper and can be used to obtain the atomic composition of any titanium nitride based compound, whatever the complexity of the material. This method is an alternative to easily quantify TiN-like compounds by AES.As an illustration, a Ti(C_xN_1−x) based multilayer deposited on a hardmetal substrate was investigated. This quantification method was successfully used to evidence three different layers and the diffusion phenomenon at the interfaces between the layers. This study was completed with a quantitative SIMS depth profile that the high sensitivity and depth resolution allowed to measure the small variations of composition lower than the uncertainty of AES.     

Computer Simulations of Polymers Close to Solid Interfaces: Some Selected Topics

This paper presents a topical overview of molecular-dynamics and Monte Carlo simulations for polymer systems close to solid interfaces. The simulations utilize simplified coarse-grained models: The polymers are represented by bead-spring chains, and the walls by a crystalline layer of Lennard-Jones particles or by a smooth impenetrable barrier. This approach has two advantages. First, it reduces the complexity of the simulation. Often, it is only then possible that the interesting length and time scales can be studied at all. Second, the approach concentrates on generic features that are believed to determine the physics of the problem under consideration. The results of the simulation can thus help to single out those features which should be incorporated in an analytical treatment. In this paper, we want to illustrate the versatility of these models by applying them to a broad spectrum of different problems. The situations considered range from the adsorption of a polymer from dilute solution onto a wall, over the importance of sub-monolayer monomeric or polymeric lubricants for kinetic friction, to the crystallization or glass transition of dense polymer films.     

Low-dimensional physics of ultracold gases with bound states and the sine-Gordon model

We present 2D steady concentration profiles of confined layers of off-critical polymer blends. The layer rests on a solid substrate and has a flat free surface due to very high surface tension. The profiles correspond to non-linear steady solutions of the Cahn-Hilliard equation in a rectangular domain. The free polymer-gas interface is considered to be sharp, while the internal interfaces are diffuse. We explore the rich solution structure (including laterally structured layers, stratified layers, checkerboard structures, oblique states and droplets) as a function of mean concentration.     

3D-TOFSIMS characterization of black spots in polymer light emitting diodes

The occurrence and formation of black spots areas in PolyLED devices has been studied by time-of-flight SIMS (TOFSIMS). The composition, shape and position of the black spots is visualised by three-dimensional (3D)-TOFSIMS depth-profiling. It has been established that the formation of non-emissive spots is due to the growth of aluminium oxide clusters at the AlBa/polymer interface. Electron injection in the black spots is lost by the resulting local increase of the resistivity of the cathode.     

Origin of near constant loss (NCL) in ion conducting polymer blends

We report a novel observation pertaining to scaling behavior and near constant loss response in ion conducting polymer blends. This type of response evidenced by linear plot of conductivity spectrum at high frequency has rarely been reported for polymer blends. It is noted that at a fixed cation concentration in the polymer blends high frequency dielectric loss remains constant irrespective of temperature confirming near constant loss (NCL). However the onset of such response is prominent in sub-ambient temperature limit vis-à-vis ambient condition. It is also noted that low temperature NCL response depends on cation loading in the polymer blend matrix. These results, reported for the first time for an ion conducting polymer blend has been explained using Kramer–Kröinig (KK) and Haveriliak Negami (HN) equation.     

正常态金属与氧化物高温超导薄膜界面扩散特性分析

利用二次离子质谱(SIMS)技术,分析了Ag和A1与YBa_2Cu_3O_(7-x)(YBCO)超导薄膜接触界面互扩散.结果显示,它们有不同的互扩散特征.利用SIMS的分析结果,可以很好地理解经高温热处理后,Ag/YBCO和A1/YBCO样品具有不同界面电学性质的原因. 关键词：     

Molecular SIMS – A journey from single crystal to biological surface studies

The development of Static or Molecular secondary ion mass spectrometry (SIMS) is reviewed with particular reference to the journey made by the Manchester group and its collaborators. The earliest studies focussed on the application of static SIMS to single crystal surface studies. These studies successfully demonstrated that static SIMS delivered information on the delicate adsorbate state that mirrored that obtained by other surface science techniques. Subsequent application of the technique to studying the state and reactivity of bimetallic surfaces stimulated by collaboration with the Ertl group, demonstrated that static SIMS could be applied to the investigation of quite complex surface chemistry. This success stimulated the application of the technique to surface chemistry studies of much more complex systems such as polymers, ice mimics of polar stratospheric clouds, aerosols, culminating in biological systems. The need to enhance ion yields of the larger biological molecules led to the development and introduction of polyatomic primary ion beams, most notably based on C₆₀ buckminsterfullerene. This type of ion beam has transformed molecular analysis by SIMS. Not only have the yields of larger molecular ions been greatly increased, the bombardment induced damage that necessitated the static limit has been dramatically reduced such that for many materials the static limit requirement can be abandoned. A completely new analytical regime has opened up so that molecular depth profiling and 3D chemical imaging is possible. To fully realise the new capabilities for biological analysis a new generation of ToF-SIMS instrument is being developed that overcomes the compromises of pulsed beam instruments and that enables high mass resolution, high spatial resolution and high duty cycle to be attained simultaneously.     

Synchrotron PEEM and ToF‐SIMS study of oxidized heterogeneous pentlandite,pyrrhotite and chalcopyrite

Synchrotron‐based photoemission electron microscopy (PEEM; probing the surface region) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS; probing the uppermost surface layer) have been used to image naturally heterogeneous samples containing chalcopyrite (CuFeS₂), pentlandite [(Ni,Fe)₉S₈] and monoclinic pyrrhotite (Fe₇S₈) both freshly polished and exposed to pH 9 KOH for 30 min. PEEM images constructed from the metal L₃ absorption edges were acquired for the freshly prepared and solution‐exposed mineral samples. These images were also used to produce near‐edge X‐ray absorption fine‐structure spectra from regions of the images, allowing the chemistry of the surface of each mineral to be interrogated, and the effect of solution exposure on the mineral surface chemistry to be determined. The PEEM results indicate that the iron in the monoclinic pyrrhotite oxidized preferentially and extensively, while the iron in the chalcopyrite and pentlandite underwent only mild oxidation. The ToF‐SIMS data gave a clearer picture of the changes happening in the uppermost surface layer, with oxidation products being observed on all three minerals, and significant polysulfide formation and copper activation being detected for pyrrhotite.     

G-SIMS of thermosetting polymers

In this study, the gentle SIMS (G-SIMS) concept has been applied to thermosetting polymers. The polymer chosen is an epoxy resin based adhesive, which is commercially available as a two-part mixture. The G-SIMS spectra have been used alongside the static SIMS (SSIMS) spectra to aid in the identification of ions characteristic of the individual components present in each part of the two-part formulation. The G-SIMS spectra are shown to provide information that is not readily available from the SSIMS spectra. G-SIMS has been shown to be a viable technique for mixtures and is of potential use in characterising thermosetting polymers.     

利用红外光谱成像技术研究PP/PE共混物

利用红外光谱对不同比例条件下制备的PP PE共混物进行了研究 ,通过对PP ,PE的特征吸收峰的分析 ,发现聚丙烯 (PP)特征峰峰面积与聚乙烯 (PE)特征峰峰面积的比值与PP/PE共混物的质量比之间存在较好的对应关系。利用特征吸收峰面积之比 ,借助红外成像技术对PP纤维热压在PE薄膜上制备的样品的研究得到了复合共混物的分布信息 ,发现其成像结果与偏光显微镜的结果有很好的吻合。实验研究结果表明采用红外成像技术 ,利用特征吸收峰面积之比可以进行对聚合物共混物的分相行为的研究。     

Functionality of novel black silicon based nanostructured surfaces studied by TOF SIMS

A functionality of the novel black silicon based nanostructured surfaces (BS 2) with different metal surface modifications was tested by time-of-flight secondary ion mass spectrometry (TOF SIMS). Mainly two surface functions were studied: analytical signal enhancement and analyte pre-ionization effect in SIMS due to nanostructure type and the assistance of the noble metal surface coating (Ag or Au) for secondary ion formation. As a testing analyte a Rhodamine 6G was applied. Bi⁺ has been used as SIMS primary ions. It was found out that SIMS signal enhancement of the analyte significantly depends on Ag layer thickness and measured ion mode (negative, positive). The best SIMS signal enhancement was obtained at BS2 surface coated with 400 nm of Ag layer. SIMS fragmentation schemes were developed for a model analyte deposited onto a silver and gold surface. Significant differences in pre-ionization effects can play an important role in the SIMS analysis due to identification and spectra interpretation.