Use Of XPS Research Articles

Optimization of sound insulation of flat panel photobioreactors for bioenergy facades

Flat panel photobioreactors consisting of different layers of glass panes, designed to allow heat and microalgae biomass production in a water layer by solar radiation at the facade of buildings (i.e. bioenergy facade), were acoustically examined and further developed for increased sound insulation against external noise exposure. The sound insulation was first examined by simulations on double-, triple- and four-skin bioreactor variants. Parameters such as the distance between panes, the number and types of layers, as well as the material and thickness of the glass panes, were varied. Especially the influence of decoupling layers and an airlift on the sound reduction index was evaluated. Based on the simulation results, a modular prototype was developed which could be converted into a double-, triple- or four-skin structure as required. The sound reduction of these was studied in an acoustic window laboratory experimentally. The highest measured weighted sound reduction index of 51 dB was obtained with a four-skin photobioreactor variant with four glass pane layers and a water layer. The weighted sound reduction indexes for alternative four-skin opaque prototype variants with a plasterboard layer were 2—3 dB lower. The double- and triple-skin variants achieved 43—47 dB. The use of XPS as insulation material in the outer air layers of the triple- and four-skin variants reduced the weighted sound reduction index by 2 dB. The airlift needed for turbulent mixing of the microalgae had no effect on the sound insulation but increased the average ambient noise level by up to 10 dB. With 51 dB, the four-shell photobioreactor prototype achieves sound insulation class 5 according to the german regulation VDI 2719 for windows and thus fulfills the function of a sound insulation element in the facade of buildings or in a soundproof wall.

Arctic transmission oil

The tasks of the development of the Far North, the Arctic and the Antarctic require ensuring the operability of equipment units in low temperatures. To solve this problem, it is necessary to develop lubricants using new synthetic oils, a distinctive feature of which are low pour points. On the basis of polyethylsiloxane fluid and petroleum oil, we have developed a gear oil for the Arctic latitudes, which is efficient at temperatures down to -75 ° C (TMarktic). It is shown TMarktic’s antifriction properties are better than those of TSgip helicopter tail gear oil. The combined use of XPS and IR-Fourier methods for the analysis of the friction surface made it possible to conclude that the formation of the boundary film involves both antiwear additive molecules, which are part of the modified oil, due to the P-O, P=O, S=O bonds, so and molecules of polyethylsiloxane liquid due to C-O and Si-O bonds. Secondary surface structures are formed by TMarctic oil on the surface of iron oxide and include hydrocarbon and siloxane fragments. The high antiwear and extreme pressure properties of TMarktic are due to free sulfur and bound in iron sulfide.

X-ray Photoelectron Spectroscopic Study of Some Organic and Inorganic Modified Clay Minerals.

Layered clay systems intercalated with inorganic and organic compounds were analyzed to highlight how XPS can provide information on the different environments surrounding a particular atom as well as provide discernments on the size, coordination, and structural and oxidative transformations of the intercalating/pillaring compounds. XPS data on the intercalation of urea and K-acetate in low- and high-defect kaolinite revealed the interaction of the intercalating group NH2 with the siloxane functional groups in the interlayer surface. The intercalation of HDTMA in Mt demonstrated the use of XPS in monitoring the change in conformation assumed by alkylammonium intercalating compounds in Mt with increasing CEC. Studies on the pillaring of Mt by Al13 and Ga13 by XPS allowed determination of the coordination of the pillaring compound within the Mt layer. Lastly, the intercalation of hexacyanoferrate in hydrotalcite demonstrated the capability of XPS in following changes in the oxidation state of the iron compound. These were gleaned from interpretation of the shifts in binding energies and presence of multiplet splitting in the XPS of the component elements of the minerals or the intercalating compounds.

The Effects of Polystyrene Species and Fiber Direction on Thermal Conductivity of Plywood

Thermal conductivity of wood material is superior to other building materials because of its porous structure. Thermal conductivity is used to estimate the ability of insulation of material. Thermal conductivity of wood material has varied according to wood species, direction of wood fiber, specific gravity, moisture content, resin type, and addictive members used in manufacture of wood composite panels. The aim of study was to determine the effect of polystyrene species and fiber direction on thermal conductivity of plywood panels. In the study, two different wood types (black pine and spruce), two different fiber directions (parallel and perpendicular to the plywood fiber direction), two different types of insulator (expanded polystyrene-EPS and extruded polystyrene-XPS) and phenol formaldehyde glue were used as the adhesive type. Thermal conductivity of panels was determined according to ASTM C 518 & ISO 8301. As a result of the study, the lowest thermal conductivity values were obtained in the perpendicular fiber direction of the spruce plywood using XPS as insulation material. The use of XPS as an insulation material in plywood has given lower thermal conductivity values than EPS.

Selective deoxygenation of biomass volatiles into light oxygenates catalysed by S-doped, nanosized zinc-rich scrap tyre char with in-situ formed multiple acidic sites

In this paper, we report the unique properties and catalytic performance of scrap tyre char, an otherwise low-value waste derivative on the selective deoxygenation of biomass volatiles (derived from flash pyrolysis of lignocellulosic biomass at 500 °C) into value-added light oxygenates including furfural and phenol. Due to the inclusion of sulphur (S) and zinc oxide (ZnO) as additives during the prior tyre manufacturing process, the pyrolysis-derived tyre char is rich in both organically bound S and nano-sized zinc sulphide (ZnS) that are highly dispersed within the carbonaceous matrix. Detailed characterisations of the fresh and spent catalysts have been conducted to elaborate the unique mechanisms, upon the use of XPS, TEM-SAED, XAS, NEXAFS, Pyridine-FTIR, and NH3-TPD. As has been confirmed, multiple acidic sites are present in tyre char, including organically bound S serving as a weak Brønsted acid and nano-sized ZnS being a strong Lewis acid. The former acid is active for dehydration, whilst the latter one mainly catalyses the decarboxylation and decarbonylation reactions. Upon the interaction with adsorbed oxygen-bearing species and water molecules, the ZnS-centered active acid site can in-situ transform into a ZnSOx-centered super strong acid site, which is a Brønsted acid that is able to enhance the deoxygenation extent remarkably. More interestingly, the organic S enables an in-situ sulphidation of the less active ZnO on the catalyst surface, thereby enabling a continuous exposure of bio-oil vapour to the highly active ZnS and its sulphate derivative. This in turn enlarges the lifetime of the catalyst and its strong stability upon cyclic tests.

Efficient recycling of carbon fibers from amine-cured CFRP composites under facile condition

With an excellent combination of high strength, lightweight, and thermal stability, carbon fiber-reinforced polymer (CFRP) composites are ideal for applications in various demanding fields. The global consumption of CFRP composites continues to increase, and it is estimated that approximately 3000 tonnes of CFRP waste are generated annually. Mostly, the CFRP composites can be classified into two categories: thermoset composites and thermoplastic composites. However, the recycling of industrial thermoset composites is a daunting challenge due to their highly cross-linked thermosetting polymer matrix. In this study, an innovative strategy was developed for recycling amine-cured CFRP composites with a binary alkali catalytic system of monoethanolamine containing 10 wt% potassium hydroxide under facile conditions. The degradation ratio of CFRP composites reached 98.82% after processing at 160 °C in 90 min. The surface of recovered carbon fibers (CFs), as observed by SEM and AFM, appeared smooth, and there was a slight increase in the surface wettability as tested by dynamic contact angle measurements. Furthermore, the use of XPS demonstrated some surface oxidation, while single fiber filament testing suggests a small decrease in the tensile strength of 6.5%.

International standardization and metrology as tools to address the comparability and reproducibility challenges in XPS measurements

The status of standardization related to x-ray photoelectron spectroscopy (XPS, ESCA) at ASTM International (Subcommittee E42.03) and ISO (TC 201) is presented and commented upon in a structured manner. The survey also identifies other active bodies, here VAMAS Technical Working Area 2 and the Surface Analysis Working Group at the International Meter Convention, contributing to prestandardization research and metrology of XPS and reports their specific activities. It is concluded that existing standardization is delivering good practices in the use of XPS and has a high potential to avoid the recently observed erroneous use, misapplications, and misinterpretation by new and inexperienced users of the method—which seems to be the main reason for the “reproducibility crisis” in the field of XPS applications. A need for a more proactive publicizing of international documentary standards by experienced XPS users, specifically those who are involved in standardization, is identified. Because the existing portfolio of standards addressing the use of XPS is not complete, future standardization projects planned or already ongoing are mentioned. The way the standardization bodies are identifying future needs is shortly explained.

Fabrication of superhydrophilic surface on metallic nickel by sub-nanosecond laser-induced ablation

The alterations of wettability on metallic nickel surface by sub-nanosecond laser (1 ns, 1064 nm) induced surface modification was investigated. An approximate linear relation between surface contact angles (CAs) and accumulated fluence was established, which shows that with proper combinations of laser parameters, CA would reduce significantly from its initial value (∼96°) to approximately 3.1°. The microscopic inspection and roughness test reveal that the surface roughness on irradiated areas would increase remarkably due to the distribution of micro/nanoparticels and cracks that induced by laser ablation, which consequently improve the hydrophilic performance effectively. On the other hand, elemental analyses by use of XPS demonstrate that the nickel dioxides and nickel hydroxides were generated as the main components covering the self-organized structures. Such increasement in oxygen content, especially the growth of NiO and hydroxyl group provides a prerequisite in the transformation of nickel from initial hydrophobicity to hydrophilicity. And the integrated effects of surface morphology, roughness and chemistry ultimately led to the formation of super-wettability. The investigation indicates that, the sub-nanosecond laser is an effective tool to transform the metallic nickel into functional material with a highly hydrophilic surface by creating controllable topographical features and chemical properties on its surface.

Application of a new thermal insulation layer to subgrade

The use of thermal insulation has great potential for preventing frost damage to roads in seasonally frozen areas, in fact more so than in permafrost. With the aim of recycling the vast quantities of waste coal fly ash and rubber tyres in north-east China, a new combined thermal insulation layer consisting of extruded polystyrene (XPS) board and modified soil (silty clay modified with fly ash and crumb rubber) is proposed. Field tests on an insulated test section and an uninsulated control section were designed to assess the thermal performance of the sections over the change of time and depth. The thermal characteristics and the effect and mechanism of the layer were investigated. Finite-element analysis was used to evaluate its long-term performance. The results showed that the temperature regime of the subgrade varied regularly. The combined thermal insulation layer effectively protected the road surface from cold and heat erosion, elevating the freezing depth to the upper surface of the combined layer. Furthermore, the thermal insulation effect was greater for the combined layer than the use of XPS only. The finite-element analysis showed that the impact on cold resistance was more evident in the road shoulder and roadway centre than on the slope toe, and the layer will still perform normally after 50 years.

The impact of the scanning XPS microprobe on industrial applications of X-ray photoelectron spectroscopy

We will review the evolution of x-ray photoelectron spectroscopy (XPS / ESCA) instrumentation and applications that led to the development of the scanning XPS microprobe, describe its unique capabilities, and how they have impacted the use of XPS for industrial applications.

Characterization of film materials in wafer processing technology development by XPS

A brief introduction reviews the changes that have occurred in semiconductor wafer processing, which, coupled with developments in X ray Photoelectron Spectroscopy, XPS, instrumentation, have led to XPS becoming a primary materials analysis tool in this industry. Three specific examples illustrating the use of XPS and Angle resolved XPS, ARXPS, are then presented. These are nitridation processing of high k gate material (HfO2 based); the monitoring of Al content and chemistry in a 10A TiAlN film (a metal gate add on process to high k); and deposition of diamond-like amorphous C films (a candidate for hard mask applications in DRAM, NAND flash, and NOR flash memories).

Nickel Particles Selectively Confined in the Mesoporous Channels of SBA-15 Yielding a Very Stable Catalyst for DRM Reaction

A series of four Ni catalysts supported on SBA-15 and on a high SiO2 surface area have been prepared by modified impregnation (ImU) and deposition-precipitation (DP) methods. The catalysts have been extensively characterized, including in situ XAS (bulk sensitive) and XPS (surface sensitive) techniques, and their catalytic activities evaluated in the dry reforming reaction of methane (DRM). The combined use of XPS and XAS has allowed us to determine the location of nickel particles on each catalyst after reduction at high temperature (750 °C). Both Ni/SiO2-DP and Ni/SBA-15-DP catalysts yield well-dispersed and homogeneous metallic phases mainly located in the mesoporosity of both supports. On the contrary, the Ni/SiO2-ImU and Ni/SBA-15-ImU catalysts present a bimodal distribution of the reduced nickel phase, with nickel metallic particles located out and into the mesoporous structure of SiO2 or the SBA-15 channels. The Ni/SBA-15-DP catalyst was found the most stable and performing system, with a very low level of carbon deposition, about an order of magnitude lower than the equivalent ImU catalyst. This outstanding performance comes from the confinement of small and homogeneous nickel particles in the mesoporous channels of SBA-15, which, in strong interaction with the support, are resistant to sintering and coke deposition during the demanding reaction conditions of DRM.

Use of XPS to clarify the Hall coefficient sign variation in thin niobium layers buried in silicon

Si/Nb/Si trilayers formed with 9.5 and 1.3nm thick niobium layer buried in amorphous silicon were prepared by magnetron sputtering and studied using XPS depth-profile techniques in order to investigate the change of Hall coefficient sign with thickness. The analysis of high-resolution (HR) XPS spectra revealed that the thicker layer sample has sharp top interface and metallic phase of niobium, thus holes dominate the transport. In contrast, the analysis indicates that the thinner layer sample has a Nb-rich mixed alloy formation at the top interface. The authors suggest that the main effect leading to a change of sign of the Hall coefficient for the thinner layer sample (which is negative contrary to the positive sign for the thicker layer sample) may be related to strong boundary scattering enhanced by the presence of silicon ions in the layer close to the interface/s. The depth-profile reconstruction was performed by SESSA software tool confirming that it can be reliably used for quantitative analysis/interpretation of experimental XPS data.

Surface Analysis of Li-Ion Electrode-Electrolyte Interfaces: Insights By a Surface Science Approach

Electrode-electrolyte interfaces play a key role for the performance and degradation of electrochemical devices such as lithium-ion cells. Side reactions at cathode-electrolyte interfaces result in the formation of a solid-electrolyte interface (SEI) layer, resulting in loss or performance due to lithium loss and increase in surface layer resistance. Over the past years, the cathodic SEI layer has been subject to extensive investigation, focused on the correlation between composition and battery cycling parameters. Yet, open questions remain with regard to formation mechanisms and properties. Most investigations on SEI layers have been performed by post mortem analysis of composite electrode surfaces by photoelectron spectroscopy (XPS). XPS gives information on the chemical structure by way of core level electron binding energies. Despite of the standard use of XPS for SEI analysis, unambiguous identification of the different phases is often not straightforward as binding energy shifts are encountered. Moreover, the post mortem analysis of composite materials is not ideally suited to investigate the SEI on the active material, as emissions from the other materials in the electrode (carbon, binder) add complexity. Nevertheless, such data on the SEI composition of composite electrodes are often used to propose reaction mechanisms on SEI-formation and side reactions (electrolyte oxidation) occurring at the surface of the active materials. Improved insights into SEI-composition and side reactions require experiments that address binding energies and interaction of single material surfaces with components of the electrolyte. We prepare model interfaces of LCO (LiCoO2) thin film electrodes with components of the SEI, artificial SEI-layers, as well as with solvents, and analyze them with surface analysis methods [1]. In such experiments, the SEI or electrolyte-related components are deposited as top phase either by thin film deposition or low temperature adsorption, and analysis is performed by photoelectron spectroscopy (XPS, UPS, SXPS) and high resolution electron energy loss spectroscopy (HREELS). Usually, the preparation is performed stepwise with intermediate analysis in order to investigate the interface formation in detail with respect to chemical structure, electronic structure and space charge effects. In this contribution, we present our results with respect to the deposition of several solid compounds such as lithium oxide and LiPON, as well as the exposure to several solvents (water, diethyl carbonate, etc.). In most cases, the formation of interface and/or gradient layers is observed. For the substrate-related binding energies we usually note a shift to higher values which is attributed to space charge layer formation in the LiCoO2 (band bending downwards). Also, we find indications that binding energies from nominally identical overlayer compounds and those related to the substrate are differently positioned against each other depending on the preparation method. Possible causes for this are charging effects, differences in the overlayer compound´s Fermi-level, or presence of interfacial dipoles. Mechanistic insights regarding the formation of cathode-electrolyte interfaces and of ionic interfaces in general are discussed [2][3]. [1] R. Hausbrand, D. Becker, and W. Jaegermann, Progress in Solid State Chemistry 42 (2014) [2] A. Schwöbel, W. Jaegermann, and R. Hausbrand, Solid State Ionics, in press. [3] D. Becker, et al., Journal of Physical Chemistry C, 118 (2014)

Use of XPS to Quantify Thickness of Coatings on Nanoparticles.

XPS and other surface sensitive methods are being increasingly used to extract quantitative information about organic and inorganic coatings and contamination on nanoparticles. The extraction of coating thickness requires information about particle diameter from other measurements, such as electron microscopy, combined with a model that includes the physical processes associated with XPS. Advantages of using XPS include the sensitivity to very thin coatings (or surface contamination) and the ability to extract important information about organic layers. Single particle information from electron microsocpy combined with XPS sensitivity in determining composition make a powerful combination for nanoparticle anlaysis.

SPECIES FORMED ON IRON SURFACE DURING REMOVAL OF COPPER IONS FROM AQUEOUS SOLUTIONS

The subject of the research covered in this paper is the removal of copper (Cu 2+ ) cations from water at low pH (initial values of pH 3 and 6) by means of zero-valent iron. The chemical states and atomic concentrations of solids formed on the surface of zero-valent iron, and the type of deposited polycrystalline substances have been analyzed with the use of XPS and XRD. The type of process causing the copper removal from water at low pH, corresponding to the effect of acid mine drainage, has been identified by analyzing the changes of physicochemical parameters and specified chemicals content in water. Cu 2+ was removed from water for the initial pH of 6 was much more effective than at lower pH. The formation of CuxFe3-xO4 , where x≤1, and to a lesser degree Cu2O, Cu 0 and/or CuO and/or Cu2S, were the basic processes of the removal of copper at almost neutral pH of water (pH about 6), while the formation of copper in metallic form and Cu2O, as well as probably CuO, were the basic processes for lower pH (pH about 3). The adsorption of Cu 2+ on the surface of shell covering square-shaped cold-rolled steel sheet cell was an additional process causing the removal of copper from water at almost neutral pH.

Functionalization and defunctionalization of single walled carbon nanotubes: Electrochemical and morphologic consequences

Electrochemical oxidation and subsequent electrochemical reduction of single walled carbon nanotubes was carried out by cyclic voltammetry. Using methods of Raman and absorption spectra it was revealed that oxidation of SWCNT electrodes leads to significant disruption of electronic structure of nanotubes; the structure can be substantially restored in the course of subsequent cathodic polarization. The quantitative relationship between the concentration of various oxygen-containing functional groups present on the pristine surface, electrochemically oxidized and subsequently reduced single walled carbon nanotubes was demonstrated with the use of XPS. It was shown that upon application of anodic potentials, functionalization of metallic SWCNTs proceeds deeper than in the case of semiconductor ones. The correlation between the degree of functionalization of SWCNT electrodes and kinetic parameters of electron transfer were studied using redox couples: [Ru(NH3)6]2+/3+, [Fe(CN)6]4−/3−, and Fe2+/3+. The essential growth of the electron transfer rate constant observed for couple Fe+2/+3 was suggested to results from the coordination of iron ion to oxygen from functional groups, formed at water electrolysis. It was demonstrated that the maximum rate constant for the system is reached at the medium functionalization degree.

Influence of the Content and Distribution of Vanadium in the M1 Phase of the MoVTe(Sb)NbO Catalysts on their Catalytic Properties in Light Alkanes Oxidation

Phase-pure MoVTe(Sb)NbO mixed oxides, with an M1 structure, and various compositions were prepared, characterized and tested as catalysts for the oxidative dehydrogenation of ethane, in order to study the influence of vanadium content and its distribution over the crystallographic sites on the catalytic properties of these oxides. A linear variation in catalytic activity was observed, as a function of the total vanadium content. This property, which has already been demonstrated for propane oxidation, is shown to remain unaffected by the alkane reaction, the nature of the propene α-dehydrogenation elements (Te or Sb), the presence or absence of niobium. The use of XPS to study the surface composition of the catalysts allowed a direct proportionality to be established between the rate of ethane conversion and the V5+ surface content, thus explaining the first correlation observed with bulk V content. This result also emphasizes the fact that a maximum level of intrinsic catalytic activity can be found, and that high vanadium content might be detrimental to this activity, or to the stability of the catalysts. Finally, crystallographic data found in the literature are used to further interpret and discuss these results.

Combined use of SA‐XPS, XRD and SEM + EDS for the micro‐chemical characterisation of Ag‐based archaeological artefacts

The precious metallic artefacts are particularly interesting from a historical, artistic and economical point of view because they were used as jewels, amulets or artistic items and also for currency, medium of exchange and form of saving. By means of the combined use of XPS, X‐ray diffraction, SEM + energy dispersive spectrometry and optical microscopy, the micro‐chemical surface structure of the corrosion products grown on archaeological Ag‐based artefacts has been investigated in the present work. The obtained results allowed the identification of the corroding agents coming from the surrounding environment where the artefacts have been found, stored or exhibited. The experimental findings highlight the role of chloride ions that are present in the patina as chloroargyrite or corrode the copper islands scattered in the alloy giving rise to the formation of the dangerous species such as atacamite and paratacamite. Furthermore, the results shown different corrosion behaviours with the outermost layers enriched of S, Ca, Al, Si and Fe demonstrating the relationship between some soil constituents and surface alloy corrosion products giving rise to the formation of different compounds. Copyright © 2014 John Wiley & Sons, Ltd.

Ambient-Pressure “Tender” X-Ray Photoelectron Spectroscopy (APXPS) for in Situ study of Liquid-Solid Interface of Pt Foil in 6 M KF

not Available.