bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Particle Collection on Single Fibres of Different Configurations
Authors: Schweers Elke , Umhauer Heninz , Löffler Frendrich
Published: December 2004

This presentation is part of a fundamental investigation into the influence of structural characteristics on particle collection in fibrous filters. The collection on single fibres has been experimentally determined, whereby different fibre configurations were set. For this purpose, particle fluxes upstream and downstream of the fibres were measured simultaneously using an optical particle counter which operates with two purely optically delineated measuring volumes and two detectors. The experimental results are compared with published values.
Strategies for Evaluating Boundary Fractal Dimensions by computer aided image analysis
Authors: Kaye Brian H. , Clark Garry G. , Kydar Yosef
Published: December 2004

For many profiles the values of the boundary fractals deduced by different exploration techniques are identical but the presence of deep fissures of convoluted structure can perturb the information gathered by the exploration technique. Data for different boundaries generated by different exploration techniques are used to illustrate the physical significance of the deduced fractal dimensions as evaluated using the different techniques. Heuristic programs for teaching an automated instrument to distinguish between different regions of ruggedness around a profile and to prevent “fractal rabbits” from appearing in the data are outlined. It is shown how the logic for removing fractal rabbits from the experimental data will also generate data on the presence of sharp edges on the profile. The possible occurrence of pseudo‐texture fractal dimensions from projection occlusion is discussed.
Obtaining Fractal Dimensions and Examining Boundaries by Coordinate Averaging
Authors: Adler Jeremy , Allen Martin
Published: December 2004

Problems with automated techniques for measuring boundary fractal dimensions using structured walks are described and a new method is proposed, coordinate averaging. The actual polygon generated by a structured walk is variable and depends upon the chosen starting point. This noise is apparent in the resulting Richardson plots. The use of multiple starting points enhances the Fast (equipaced) method but is less productive with the Hybrid (fixed step) method because the paths followed around the perimeter tend to converge. Coordinate averaging uses perimeters that have been mapped as a list of sequential coordinates. They are then examined by averaging every coordinate with an increasing number of neighbours. The resulting family of shapes progressively shed detail and can be used to generate fractal dimensions. Coordinate averaging appears to be free from the noise found with structured walks and is able to examine highly convoluted shapes. In addition it appears well suited to the examination of the homogeneity of boundaries and can follow the detailed evolution of individual features.
Characterization of Agglomerated and Aggregated Aerosol Particles Using Image Analysis
Authors: Einar Kruis F. , van Denderen Jos , Buurman Hans , Scarlett Brian
Published: December 2004

Accurate particle size characterization of aggregated and agglomerated particles is only possible by analysis of photographs. Both the primary particle size and the morphology of the aggregate are important experimental results. Since standard image analysis techniques for particle size analysis usually recognize only single particles, a new programme, called here Sparse Hough Transformation, was developed for the automated recognition of spherical particles within an aggregate. The method is shown to perform well, even for images with many overlapping particles. The structure of the aggregate is analysed using the fractal dimension, determined from the density‐density correlation function. Finite size effects, important when dealing with aggregates containing few primary particles, are taken into account by including a cut‐off function.
Flow Properties of Selected Pharmaceutical Powders from a Vibrating Spatula
Authors: Hickey Anthony J. , Concessio Neville M.
Published: December 2004

Studies have been performed to characterize the flow of certain powders of pharmaceutical interest from a vibrating spatula. Lactose, cromolyn sodium, sodium chloride and charcoal powders were prepared by milling or sieving. Jet milling yielded micronized powder (1–10 μm), which was recovered from the product jar or metal cyclone. Particles in the larger size ranges were prepared by sieving. Photomicrograph images of the products were obtained by scanning electron microscopy. All of the powders were subjected to flow studies from vibrating beds to a top loading pan balance. Cumulative mass versus time, flow profiles were plotted. Bulk flow properties, as reflected in mass flow rates (Mi), were assessed. Irregular flow patterns were obtained for lactose, cromolyn sodium and charcoal, whereas sodium chloride was free flowing. The lengths of the lines depicting cumulative mass versus time, for samples of each material, were estimated using the inswing structured walk technique. Stride lengths (γ) of 1–100 mm were employed. Fractal dimensions were obtained from graphs of the logarithm of the cumulative mass versus time line length plotted against the logarithm of the stride length. Thus, flow irregularities were indicated by fractal dimensions (δ).

In all of the powders studied, mass flow rates increased as the particle size increased. Sodium chloride did not exhibit fractal behavior (δ ≤ 1.007), as there were no flow irregularities. Lactose, cromolyn sodium and charcoal did not appear to exhibit fractal behavior (δ ≤ 1.010) at large stride lengths (γ = 15–100 mm). At small stride lengths (γ = 1–10 mm) these materials did exhibit fractal behavior (δ equals; 1.029–1.059) indicative of flow irregularity. This method may be used to numerically quantify uniformity of flow from a vibrating spatula, and would be useful in a number of industrial processes.
A Field Study of Three Collocated Ambient PM10 Samplers
Authors: Tsai Chuen‐Jinn
Published: December 2004

The performances of three ambient PM10 samplers were studied at three monitoring stations in Taiwan. It was found that differences in the daily measured PM10 concentrations of the SA 1200 and Wedding high‐volume samplers are now within ± 10% since the former now has a closer cut‐point to the latter than in the earlier SA 321 A model. The Wedding beta gauge automatic sampler was found to be applieable in rainy and humid weather conditions in Taiwan. Its daily PM10 concentrations are typically within ± 10% of those of the Wedding highvolume sampler. The particle loading effect of Wedding highvolume and beta gauge samplers was found to be important. To avoid sampling errors due to the loading effect with ambient PM10 samplers, they must be cleaned regularly at an interval depending on the ambient particulate level.
Interface analysis for the determination of the pH within the boundary layer at a cathode surface
Authors: Castle J. E. , Tremaine R. Tanner
Published: December 2004

The determination of pH value at a cathode surface requires the use of a technique capable of detecting the initial precipitation of a tracer ion. It is shown that XPS fulfils this role and that thicknesses of deposit may be estimated. The results can be correlated well with simple hydrodynamic theory and may be related to deposits formed on power station condenser tubes operating in sea water.
The significance of reduced thicknesses determined by XPS using the variable take‐off angle technique
Authors: Ebel Maria F.
Published: December 2004

The results of quantitative XPS analysis show a systematic change when the sample surface is covered by an overlayer. An accurate knowledge of the reduced thickness (x) of the total overlayer (e.g. oxide plus contamination) allows the quantification of such changes. The total reduced thickness (x) can be determined from the photoelectron signals of the substrate measured for different take‐off angles. It is found that this method can be applied for reduced thicknesses up to x = 3 with an error Δx estimated at less than 10%.
ESCA study of the effect of bivalent metal ions on lead ion selective electrode membrane
Authors: Young V. Y. , Kar Chaudhari Sunetra N. , Cheng K. L.
Published: December 2004

ESCA studies have been performed to investigate the exchange equilibria which occur between a lead ion selective electrode membrane containing multiple fixed sites due to surface degradation and various bivalent cations. The membranes have been exposed to solutions containing a single bivalent cation and to solutions containing Pb2+ and an equal amount of a second bivalent cation. The changes in surface speciation have been inferred from spectral intensity data. The possibility of obtaining exchange equilibrium constants from ESCA intensity data has been investigated.
A model for determining the composition of layer structured samples using XPS electron take‐off angle experiments
Authors: Hazell L. B. , Brown I. S. , Freisinger F.
Published: December 2004

A model is presented for interpreting the results of electron take‐off‐angle(ETOA) experiments in x‐ray photoelectron spectroscopy (XPS). The surface region of a solid is treated as a multilayer structure where each layer is of homogeneous but different composition. The model is used to derive the true composition of a solid from the apparent compositions obtained by quantification of the spectra taken at each take‐off‐angle. All the species present are treated simultaneously to yield the physical structure of the surface region, within a maximum sampling depth of ∼5–10 nm, with no loss of chemical information. The validity of the model is demonstrated using ETOA data from a single layer of oxidised single crystal silicon. The derived layer stoichiometry and thickness agrees with the results which can be obtained using intensity ratio calculations which are restricted to the single layer case. As an example of the potential use of the model the structure of a Langmuir–Blodgett (L–B) film of cadmium stearate deposited on the oxidised silicon surface is investigated.
Observation of ion nitriding on FeCr, FeNi and NiCr alloy surfaces in a glow discharge plasma
Authors: Wagatsuma Kazuaki , Hirokawa Kichinosuke
Published: December 2004

For FeCr, FeNi and NiCr alloys, iron nitriding in a glow discharge plasma was investigated by optical emission spectroscopy and Auger electron spectroscopy. The composition change in depth was provided by both techniques and, in addition, Auger nitrogen‐metal interatomic transitions give information about chemical environments surrounding N atoms. Chromium‐enrichment in the nitrided layers was observed from the variation both in the nitrogen‐KLL Auger lineshapes and in the depth profiles. The chemical composition in the layers was strongly affected by the alloyed chromium having a strong affinity with N in the chromium‐containing alloys.
RBS and SIMS characterization of tungsten silicide deposited by using dichlorosilane and tungsten hexafluoride
Authors: Gregory Richard B. , Lamartine Bruce C. , Wu T. H. Tom , Tompkins Harland G.
Published: December 2004

Rutherford back‐scattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS) were used to characterize tungsten silicide (WSix) which had been chemical vapor deposited using higher‐than‐normal temperatures and a new reactant. Silicon wafers were subjected to a flowing mixture of dichlorosilane (SiH2Cl2) and tungsten hexafluoride (WF6) with temperatures ranging from 450°C to 650°C. The conventional process uses SiH4 and WF6 with temperatures from 250°C to 400°C.

RBS analysis was performed on a matrix of samples produced to show silicon‐to‐tungsten ratios as functions of various deposition temperatures and reactant gas flow ratios. The Si/W ratios obtained ranged from 2.0 to 2.8 over the 450–650°C temperature range.

SIMS analysis provided the chlorine and fluorine distributions in the WSix films, again as functions of various deposition temperatures and flow ratios. This data showed fluorine concentrations on the order of 1 × 1016− 4 × 1018 cm−3, which are far lower than those concentrations observed for the conventional WF6/SiH4 chemistry (about 1 × 1020 cm−3).
Hydrogen detection at thin film—silicon interfaces
Authors: Jaworowski A. E.
Published: December 2004

The resonance depth profiling with 15N beams was used to measure the hydrogen content and diffusion at the aluminum/silicon interface and the near‐interface region of silicon. The formation of a subsurface hydrogen barrier in silicon has been directly observed. The hydrogen barrier formation appears to be a general effect and a property of the near‐surface of silicon, and probably other semiconductors. The observed hydrogen profiles indicate that hydrogen can be easily and inadvertently introduced into the aluminum/silicon interface region and produces a large build‐up of hydrogen concentration in the near‐interface region of silicon.
Auger parameter measurements of zinc compounds relevant to zinc transport in the environment
Authors: Dake L. S. , Baer D. R. , Zachara J. M.
Published: December 2004

This paper reports x‐ray generated photoelectron and Auger transition data for Zn compounds that have not been previously examined by XPS, with the objective of establishing a self‐consistent data base for Zn compounds of environmental and geochemical importance. Additional Zn compounds were analyzed to allow comparison with existing Zn data. Specimens analyzed include: hydrozincite (Zn5(OH)6(CO3)2), sphalerite (ZnS), smithsonite (ZnCO3), willemite (ZnSiO4), franklinite (ZnFe2O4), ZnO, Zn(OH)2, ZnCl2 and Zn metal. Where possible, this data has been related to previously reported values using Wagner chemical‐state (modified Auger parameter) plots. This self‐consistent data base has been used to identify the Zn solids that form on CaCO3 in Zn2+ –CaCO3 suspension.
Chemical and electronic properties of Pd/SnO2(110) model gas sensors
Authors: Fryberger T. B. , Erickson J. W. , Semancik S.
Published: December 2004

A model gas sensor system, Pd/SnO2(110), has been investigated using XPS, UPS, ISS and 4‐point conductivity measurements. The growth of Pd and its chemical interaction with the SnO2 surface were studied in the 0.1–10.0 monolayer equivalent (ML) regime. It was found that the Pd overlayer grows by clustering at 300 K and that the deposited Pd is primarily metallic by 3 ML. Heating Pd‐covered surfaces up to 800 K causes a decrease in the XPS Pd/Sn 3d intensity ratio, possibly due to further clustering of the overlayer above room temperature. Annealing did not, however, change the local metallic nature of the deposited Pd. The gas sensing behavior of these model interfaces was investigated by measuring the sheet conductance at different hydrogen pressures. The increase in conductance for a 3 ML Pd/SnO2(110) surface was 16 times greater than that for the Pd‐free surface at 10−5 Torr H2. This enhancement by Pd is duscussed in terms of a ‘spillover’ effect.
Cf‐252 particle desorption mass spectrometry of photo‐oxidized polystyrene
Authors: Quiñones Leticia , Schweikert Emile A.
Published: December 2004

Cf‐252 particle (plasma) desorption mass spectra are presented for polystyrene surfaces before and after exposure in air to UV light. The photo‐oxidation produces changes observed in both positive and negative ion spectra. Oxygen incorporation produces a slight increase in intensity of m/z+ 18 and 19 (H2O+ and H3O+) and m/z− 16 and 17 (O− and OH−). Also, the relative intensity of m/z+ 91 decreases after photo‐oxidation and is interpreted as the formation of a bond alpha to the benzene ring. New peaks are detected at m/z+ 226, 227 and 331, and are tentatively assigned to hydroperoxide‐containing structures. Other changes in the spectrum include the increase in intensity of m/z+ 77 and 105 arising from easily ionized fragments of the oxidation products of polystyrene.
Performance and application of the scienta ESCA300 spectrometer
Authors: Beamson G. , Briggs D. , Davies S. F. , Fletcher I. W. , Clark D. T. , Howard J. , Gelius U. , Wannberg B. , Balzer P.
Published: December 2004

The Scienta ESCA300 is a state‐of‐the‐art x‐ray photoelectron spectrometer with high intensity, and high energy and spatial resolution. This unique combination of features is made possible by the use of a high‐power rotating anode x‐ray source with monochromatization, high transmission and imaging electron optics and a multichannel detector. The first ESCA300 has been installed recently at ICI Wilton. We report on the performance of this instrument for conducting samples and as a microanalytical device. Also described are its performance for insulating samples (polymer films) and studies of charge compensation using the Bremsstrahlung‐induced electrons from an unmonochromated dual anode x‐ray source.
Ultrahigh lateral resolution spectromicroscopy beam line at ELETTRA (trieste)
Authors: Nataletti P. , Contarini S. , Gariazzo C. , Minnaja N. , Musicanti M. , Jark W. , Kiskinova M. , Melpignano P. , Morris D. , Rosei R.
Published: December 2004

This report presents the project for the development of a combined facility consisting of a high spatial resolution soft x‐ray scanning photoelectron microscope (SPEM) and a scanning tunnelling microscope (STM) that is going to be built in an ultrahigh vacuum (UHV) station on one of the undulator beam lines at ELETTRA, Trieste. The photon microprobe for SPEM will be generated using a zone plate diffraction optic. A special design of a spherical grating monochromator will provide the source for illuminating the zone plate. The emitted photoelectrons will be detected and analysed using a high‐energy resolution hemispherical analyser with a large acceptance angle. The performance of the SPEM is projected to be as follows:

(1) a photon spot size on the sample of ∼50 × 50 nm2;

(2) a tunable photon energy range of 200–800 eV, with an energy resolving power of 3000 at the carbon K‐edge;

(3) a photon flux in the spot that is > 109 photons s−1 (0.1% body wt.)−1.

The projected performance of the STM instrument ensures a lateral resolution better than 2 Å. The combination of SPEM and STM techniques will enable chemical and structural mapping within the same microscopic areas of the sample surface. Descriptions of the main beam line components together with some examples of possible applications of this unique tool are included in the paper.
A comparison of experimental and theoretically derived sensitivity factors for XPS
Authors: Ward R. J. , Wood B. J.
Published: December 2004

X‐ray photoelectron spectroscopy sensitivity factors for elements from lithium to zinc have been determined experimentally using standard compounds. These are found to differ quite considerably from those theoretically calculated using Scofield's photoelectric cross‐sections, but are in good agreement with other experimentally derived databases in the literature. It is concluded that Scofield's cross‐sections are in error and that a correction factor must be employed if they are to be used for the calculation of XPS sensitivity factors.
XPS study of the interface reactions between buffer layers for HTSC thin films and silicon
Authors: Behner H. , Wecker J. , Matthée Th. , Samwer K.
Published: December 2004

In this work we have studied the interface reactions during e‐beam evaporation of yttria‐stabilized zirconia (YSZ), yttria (Y2O3) and Y on Si(100) substrates by means of x‐ray photoelectron spectroscopy (XPS). A deposition process was developed for the heteroepitaxial growth of YSZ and Y2O3. A high amount of metallic Zr in the YSZ vapour results in an in situ reduction of the native silicon oxide layer, allowing the growth of high‐quality YSZ films even on uncleaned Si substrates. A similar in situ reduction process was achieved for the Y2O3 film growth on uncleaned substrates by a predeposition of metallic Y. The deposition of YBa2Cu3O7−δ (YBCO) films on YSZ/Y2O3/Si multilayers by dc magnetron sputtering resulted in critical current densities of the YBCO layer in excess of 2 × 106 A cm−2.
Joint use of XPS and Auger techniques for the identification of chemical state of copper in spent catalysts
Authors: Guerrero‐Ruiz A. , Rodríguez‐Ramos I. , Siri G. J. , Fierro J. L. G.
Published: December 2004

X‐ray photoelectron and x‐ray‐induced Auger spectroscopic analyses of various copper‐containing catalysts have been used to reveal the chemical state of copper during on‐stream in the dehydrogenation of methanol to methyl formate. Three catalyst systems have been selected for this purpose: (1) supported preparations (Cu/S, where S = ZrO2, SiO2, ZnO, MgO or graphite); (2) mixed oxides of the type LaMn1‐xCuxO3 (x = 0.4–0.6); (3) copper‐containing bentonite and sepiolite. The binding energies of the Cu 2p levels in all catalysts after reaction correspond to reduced Cu species, i.e. Cuo and/or Cu+. However, the precise differentiation between these reduced species is only feasible by measuring the Cu L3VV x‐ray‐induced Auger parameter. Acocordingly, the energies of the modified Auger parameter for type (1) and (2) catalysts were close to that of Cuo, while they correspond to Cu+ species for type (3) preparations.
Novel method for studying the kinetics of surface reactions at submonolayer exposures: Decomposition of acetic acid on palladium foil
Authors: Kelleter J. , Schüll G. , Kohl C. D. , Grüner U. , Kraft A. , Wollnik H.
Published: December 2004

The experimental set‐up for relaxation spectroscopy with a newly constructed time‐of‐flight mass spectrometer (ToF‐MS) is described. The response to single gas pulses is measured with the ToF‐MS, which is equipped with a special storing ion source and an electrostatic ion reflector. The gas pulses, with rise and fall times of less than 2 ms, are generated by a solenoid valve in a differentially pumped system. Conventional ToF instruments with ionization by electron pulses detect only a small fraction of the incoming molecules. Therefore our instrument with the storing (integrating) ion source is more sensitive, typically by a factor of 1000. Pulses of deuterated acetic acid (AcOD) with a length of 20 ms are used to produce exposures of 1/1000 monolayer (ML) per pulse on a polycrystalline Pd foil. On clean Pd the formation of CO2 is observed. An activation energy of 0.78 eV and a preexponential factor of 3 × 108 s−1 are derived from the transients in the temperature range between 550 and 650 K. After a total dose of 1 ML of AcOD the CO2 signal ceases and the AcOD signal emerges, yielding an activation energy of 0.44 eV and a pre‐exponential factor of 9 × 108 s−1. It is shown that even exposure to small doses of AcOD decreases the efficiency of CO2 formation. After a dose of 2 ML the CO2 formation is completely suppressed. To determine the energy and the pre‐exponential factor for the investigated surface reaction, an exposure dose of less than 1/100 ML is sufficient.
Surface studies of powder metallurgical stainless steel
Authors: Nyborg L. , Norell M. , Olefjord I.
Published: December 2004

The reaction products formed on the surfaces of gas‐atomized 12Cr steel powder are determined using ESCA and AES. It is shown that Cr and Mn oxide particles larger than about 10 nm are formed at high temperatures during atomization. At lower temperatures and during subsequent handling, the remainder of the powder surface is covered by a thin (<5 nm) layer of mainly Fe oxide. For particles larger than about 40 μm the average oxide thickness is about 5.5 nm, while smaller particles are less oxidized and also frequently covered by a thin (1 nm) S‐rich layer. On lowering the O2 availability, much less Mn, Cr and Fe oxides are formed and Si is oxidized instead. During hot isostatic pressing (HIPing), first Fe oxide and then Cr and Mn oxides are reduced as the temperature increases, while Si oxide particles are formed on the powder surfaces. Consequently, heating the powder in a temperature gradient causes reduction and oxidation at higher and lower temperatures respectively. The surface oxides on the particle boundaries provide sites for carbonitride precipitation. Local growth of manganese sulphide at 1200°C is noticed. The HIPing temperature should therefore be limited but high enough for reducing surface oxides and the pore system should be closed early during consolidation.
A surface study of the chemical pretreatment before coil coating of hot dip zinc‐coated steel
Authors: Hörnström S. E. , Hedlund E. G. , Klang H. , Nilsson J.‐O. , Backlund M. , Tegehall P.‐E.
Published: December 2004

Zinc‐coated steel strip is painted in coil‐coating plants in order to improve corrosion resistance and to provide a decorative surface. We have used Auger and x‐ray photoelectron spectroscopy to characterize the conversion coating formed during pretreatment of hot dip zinc‐coated steel prior to coil coating. The pretreatment process includes alkaline cleaning of the strip, alkaline oxidation and a chromic acid after‐rinse treatment. The composition and the chemical state of the surface have been examined after the different pretreatment steps.
A possible solution to the problem of compositional change with ion‐bombarded oxides
Authors: Bertóti Imre , Kelly Roger , Mohai Miklós , Tóth András
Published: December 2004

We have explored a new type of experiment in which the beam‐induced surface changes of MgO, SiO2, Al2O3, TiO2, V2O5 and MgAl2O4 are determined by XPS after ion bombardment at 2.5 keV with Ar+ or N2+. The initial bombardment, typically with Ar+, led to a combined surface cleaning and loss of O. Although the relative extents of these were difficult to establish, the result was in every case to define the composition in an N‐free situation. After a subsequent bombardment with N2+ the O content was distinctly lower than that after Ar+ impact, with the extra O deficiency in each case made up almost exactly by the N addition. For example, Al2O3 evolved from a nominal Al2O2.74 to a nominal Al2O2.20N0.48. The chemical state of this N was predominantly nitride‐type, indicative of MN bonds (M, metal). The observed replacement of MO bonds with MN bonds is disfavoured by thermodynamics and this, combined with the already mentioned tendency for the extra O loss to be closely matched by the N addition, together constitute a strong indication that the disturbed lattice is to some extent relaxing randomly. Interestingly, however, the extent by which N replaces O increases as the energy change calculated for this replacement decreases. This confirms, in agreement with a large body of earlier work, that the changes in the oxides are to some extent also chemically guided. The similarity to ion beam mixing and to ion‐beam‐induced grain growth is worth noting, where again one finds a mixture of ballistic (i.e. random) and chemically guided behaviour.
Auger analysis of Ni/Au/Te and Au/Te Ohmic Contacts on n‐GaAs
Authors: Bender H. , Wuyts K. , Watté J. , Silverans R. E.
Published: December 2004

The characterization of Ni/Au/Te and Au/Te contacts on n‐GaAs by Auger electron spectroscopy is studied by surface element mapping and depth profiling. Owing to the high lateral resolution of AES, important characteristics of these metallization schemes, which could not be detected by any other technique, are revealed. Comparison with other analysis technique is performed, yielding important insight into the mechanism of ohmic conductivity.
Spectroscopic ellipsometry characterization of anodic films on aluminium correlated with transmission electron microscopy and Auger electron spectroscopy
Authors: De Laet J. , Terryn H. , Vereecken J. , Vanhellemont J.
Published: December 2004

This paper reports the characterization of barrier‐type anodic oxide films on aluminium by means of spectroscopic ellipsometry. In order to show the capabilities of the technique for quantitative determination of the layer characteristics such as thickness, composition and interface structure, results based on ellipsometric data are correlated with results from transmission electron microscopy and Auger electron spectroscopy. Especially if measures are performed at multiple angles of incidence, ellipsometry allows an accurate determination of the thickness and the interfacial properties of the barrier layer.
X‐ray photoelectron spectroscopy of low‐temperature anodic silicon oxides
Authors: Galán L. , Montero I. , Rueda F. , Albella J. M.
Published: December 2004

Electron spectroscopy investigations of anodic silicon oxides grown over monocrystalline silicon and obtained at room temperature under different oxidation conditions are discussed and compared with thermal silicon oxide. In the first place, XPS shows that these oxides are essentially similar to thermal oxides with the same band gap, valence band spectra, plasma frequency, charge transfer and bulk mass density. However, there are also some important differences with respect to thermal oxides, related to the large density of structural defects, mainly OH and H2O, incorporated in the lattice during the growth process. In spite of the SiO2/Si interface appearing to be locally abrupt, this interface seems to be very rough. The anodic oxides have some oxygen excess and consequently the electronic polarizability of such materials is slightly smaller than that of thermal oxides. However, the most striking difference is the build‐up of a surface potential of 1.4–3.3 V upon x‐irradiation, even for thin, low‐resistivity anodic oxide films.
Multiple‐angle ellipsometric study of the interfacial layer in SiSiO2 structures
Authors: Paneva A. , Szekeres A.
Published: December 2004

The optical parameters of the interface layer formed during low‐temperature oxidation of Si substrates were studied by means of multiple‐angle ellipsometry at a fixed wavelength λ = 632.8 nm. By numerical modelling of single‐ and two‐layer systems, it was observed that the maximum of the ellipsometric angle sensitivity to the presence of the interfacial layer is achieved at oxide thicknesses less than 30 nm. It was found that the thickness of the interface layer is tint = 0.93 ± 0.2 nm and its refractive index is nint = 2.45 ± 0.2. A difference between the substrate refractive indices obtained for bare and oxidized silicon wafers was also observed and is attributed to the internal stresses induced in the SiSiO2 structures during oxidation.
On the interaction of silica xerogel thin films with oxidized aluminium or phosphate coatings on steel
Authors: Stoch A. , Stoch J.
Published: December 2004

XPS has been used to study the interaction between very thin layers of silica deposited by the sol–gel technique and coatings on metals of the simple oxide or the phosphate type. Samples were measured as‐received and after vacuum heating at 150–350°C. It has been found that silica xerogel below 500°C reacts with alumina and nickel oxide to form silicates. Compared with simple iron or zinc phosphates, mixed zinc‐iron phosphate coatings are more stable against heating and contain much more phosphorus. In this case silica surface deposits (1) reduced mass transfer and the ability for phosphate coating reconstruction, (2) limited phosphorus and/or water removal from the surface and (3) enhanced zinc segregation towards the surface.
Use of XPS and Ar+ depth profiling to determine the dispersion degree of Ni in Ni/TiO2 and Ni/SiO2 catalysts
Authors: Espinós J. P. , González‐Elipe A. R. , Fernández A. , Munuera G.
Published: December 2004

Two series of Ni/TiO2 and Ni/SiO2 catalysts prepared by different methods have been characterized by XPS and Ar+ sputtering. Depth profiles have been obtained from the intensity of the Ni 2p photoelectron peaks as a function of the sputtering time. The analysis has been carried out for samples in their precursor, calcined and reduced states, in order to obtain information on the changes in dispersion of the active phase through the whole activation process. In the case of reduced Ni/SiO2 catalysts, comparison with results by other techniques (i.e. H2 chemisorption, x‐ray diffraction and transmission electron microscopy) has shown that the sputtering method may give a semi‐quantitative assessment on the dispersion degree of nickel. However, for Ni/TiO2 catalysts in the SMSI state after reduction in H2 at 773 K only the Ar+ sputtering method was able to provide information on the distribution of nickel. In this case the depth profiles were consistent with partial solution of the nickel in the TiO2 matrix.
XPS study on barium‐promoted copper chromite catalysts
Authors: Bianchi C. L. , Cattania M. G. , Ragaini V.
Published: December 2004

Copper chromite catalysts are used nowadays in catalytic reactions during the incineration of organic air pollutants, which is a subject of growing interest in environmental safety. The aim of this work was to investigate by XPS the surface species, on a sample prepared by ourselves and to study the modifications of these species after various heat treatments. This study confirmed the deep surface transformation on the sample. We observed a complete reduction of the copper atoms from oxidation state II to I. In contrast, this behaviour is not followed by the chromium atoms, which are reduced to oxidation state III only to a small degree. This fact could be explained by the presence of barium which was introduced as a promoter in the catalyst.
Effects of elastic scattering on energy spectra of emitted and backscattered electrons
Authors: Borodyansky S.
Published: December 2004

The problem of elastic and inelastic scattering of Auger electrons, photoelectrons and backscattered electrons is investigated. The path length distribution functions for emitted and backscattered electrons are calculated analytically in different approximations for elastic scattering. The calculations are carried out on the basis of an invariant‐embedding approach. A procedure of background subtraction in AES/XPS in the presence of elastic scattering and a procedure of reflection electron energy‐loss spectra processing are also discussed.
Plasma‐polymerized films of trimethylsilane deposited on cold‐rolled steel substrates. Part 1. Characterization by XPS, AES and TOF‐SIMS
Authors: Sabata A. , van Ooij W. J. , Yasuda H. K.
Published: December 2004

Plasma‐polymerized coatings on metal substrates have been suggested as corrosion protection layers, but not much is known about the properties of these films and how these properties relate to the corrosion performance of coated metals. In this study, trimethylsilane plasma films were deposited on cold‐rolled steel (CRS) under different deposition conditions. Angular‐dependent XPS, AES and time‐of‐flight (TOF)‐SIMS were used to characterize the films. These three techniques were highly complementary in nature. All films were silicon‐based and the hydrocarbon content was a function of the deposition conditions. The AES depth profiles indicated that pretreatment of the substrate with oxygen had a significant effect on the type of film produced. Both TOF‐SIMS and XPS revealed that the surface of the film was different from the bulk. The surface was oxygen‐rich and was apparently modified upon exposure of the plasma film to the atmosphere. Both silicon and carbon were highly oxidized in the surface layers. Thus, these plasma films consist of at least three distinctly different regions: an interfacial region where the film is intimately mixed with the metal oxide; a bulk region with approximately the same elemental composition as the monomer; and a highly oxidized surface region. A correlation between the type of plasma film produced and the deposition conditions is discussed briefly.
Application of transmission Mössbauer spectroscopy to the surface study of Ni(II)–Fe(III) hydroxide electrocatalysts: Comparison with AES data
Authors: Kamnev Alexander A. , Angelov Venelin , Smekhnov Alexander A.
Published: December 2004

Transmission Móssbauer spectra of binary coprecipitated nickel(II)–iron(III) hydroxides (molar ratios 9:1 and 4:1) are analysed and compared with the results of AES analyses of their surface composition. A correlation between the data of the above techniques has been noted, indicating a redistribution of the components (i.e. Ni and Fe) in the surface layers, the latter being enriched with iron(III) as compared to the bulk. The results obtained are in good agreement with an excellent electrocatalytic activity of composite Ni–Fe hydroxide systems towards anodic oxygen evolution in alkaline electrolytes, taking into account a distinctly exhibited ‘surface’ electrocatalytic effect of ferric species on the nickel hydroxide electrode in the anodic oxygen evolution process revealed previously. Transmission Móssbauer spectroscopy has been shown to be a highly effective probe sensitive both to various bulk and surface effects related to the solid phases studied.
Segregation of phosphorus at the metal/scale interface during oxidation of Ni and Ni–20Cr
Authors: Kurbatov G. , Viefhaus H. , Grabke H. J.
Published: December 2004

The segregation of phosphorus at the metal/scale interface formed upon oxidation of Ni and Ni–20Cr at high temperatures was studied. Auger electron spectroscopy with high spatial resolution was used in combination with thermogravimetric measurements. The chemistry of the interface was related to its microstructure. The effects of oxidation procedure and surface preparation on the composition and microstructure of the interface were considered.

The incorporation of phosphorus in an oxidized state into the NiO scale formed at 700°C and 1000°C was revealed. The oxidation rate at 1000°C is retarded by segregated phosphorus.

The segregation of phosphorus at the metal/scale interface formed upon oxidation of Ni–20Cr alloy at high temperatures was observed for oxidation at low and at atmospheric oxygen pressures. Phosphorus and sulphur segregated at the interface retard the oxidation rate at the initial stage of oxidation at 1000°C and at atmospheric oxygen pressures.
Composite interface analysis using voltage contrast XPS
Authors: Miller James D. , Harris William C. , Zajac Gerry W.
Published: December 2004

Voltage contrast x‐ray photoelectron spectroscopy (XPS) was developed to characterize the interfacial bonding properties in carbon fiber‐reinforced polymer matrix composites. The differing electrical properties of the fiber and matrix allow biasing of the matrix and separation of the fiber and matrix signals in the XPS spectrum. The result is a quantitative measure of the relative amount of exposed fiber and exposed matrix at the fracture surface of a failed composite specimen. A parameter used to describe the interfacial bonding is defined as the ratio of the areas of the carbon 1s peaks from the fiber and matrix components and is referred to as the interfacial bonding ratio or Cf/Cm. Typical values of Cf/Cm for polyacrylonitrile‐based carbon fiber‐reinforced polymer matrix composites range from zero (excellent bonding) to three (poor bonding). The voltage contrast technique was used to demonstrate the effects of matrix resin chemistry, electrolytic oxidative fiber surface treatment, fiber processing temperature, fiber modulus and hydrothermal damage on interfacial bonding.
Spectroscopic studies of surface copper spinels. Influence of pretreatments on chemical state of copper
Authors: Sepúlveda A. , Márquez C. , Rodríguez‐Ramos I. , Guerrero‐Ruíz A. , Fierro J. L. G.
Published: December 2004

The nature of copper species of a series of alumina‐supported copper samples was investigated by the kinetics of reduction, x‐ray photoelectron spectroscopy, temperature‐programmed desorption‐mass spectrometry of chemisorbed NO and infrared spectroscopy of chemisorbed NO and CO probes. The role of these copper species was also examined in the catalytic decomposition of NO. The surface properties of copper were found to depend strongly on both Cu loading and calcination treatment. At Cu contents as low as 0.6 wt.%, Cu2+ ions from a well‐dispersed interacting phase at the alumina surface, which upon calcination forms a surface spinel CuAl2O4. At copper contents up to 3.2 wt.%, both the surface spinel CuAl2O4 and a segregated CuO phase were clearly distinguished. The partial reduction of these species upon thermal treatment under high vacuum, the ability of the surface sites to chemisorb NO and CO probes and their implications in the catalytic decomposition of NO are discussed.
X‐ray photoelectron spectroscopy study of aluminium surfaces prepared by anodizing processes
Authors: Cordier F. , Ollivier E.
Published: December 2004

X‐ray photoelectron spectroscopy was used to compare several pretreatments of aluminium surfaces used in aerospace and aircraft industry. These anodizing processes, which aim at preparing the metal surface for adhesive bonding or painting, all lead to the formation of an aluminium oxide layer. A set of aluminium samples representing the various steps of the processes was analysed by XPS. After curve fitting of the aluminium peak (Al 2p) and oxygen peak (O 1s) recorded at high energy resolution, and correction of charging effects, residual energy shifts between the spectra can be observed. This could be attributed to differences in the Fermi energy values between the treated aluminium surfaces. A classification based on this parameter of the relative Lewis acid–base character of these treated surfaces is proposed. The evolution of this parameter after exposure of the treated samples to a moist environment was also studied.
Processability of rigid poly(vinyl chloride) compounds I. Evaluation of extrusiometer data
Authors: Pukánszky Béla , Nagy Tibor T. , Kelen Tibor , Krall György , Tölgyesi‐Papp Emöke
Published: December 2004

The results of the extrusiometer measurements made on a great number of different rigid poly(vinyl chloride) (PVC) compositions are analyzed. The laboratory extruders used in the experiments can be considered to be isothermic. The output rate is proportional to the extrusion speed and almost independent of the composition. The other characteristics—torque, die and back pressure—significantly depend on the composition of the compounds. The back pressure proved to be proportional to the die pressure, and thus does not give additional information. Processability is well characterized by the dissipated energy which can be calculated from the difference of the total introduced mechanical energy and the energy required to transport the melt through the capillary. The dissipated energy is closely related to the fusion characteristics of the compounds.
Polycaprolactone as a permanent plasticizer for poly(vinyl chloride)
Authors: Deanin Rudolph D. , Zheng‐Bai Zhang
Published: December 2004

Polycaprolactone at moderate usage levels has been determined to provide desirable modifications of both rigid and plasticized poly(vinyl chloride). In rigid PVC it effected significant improvement in melt processing as well as good modulus, tensile strength, and kerosene resistance. Impact strength was not measurably altered, but heat‐distortion temperature was appreciably lowered. In flexible PVC, polycaprolactone contributed increased tensile strength and ultimate elongation, reduced volatility, and kerosene extraction. Lowering of modulus and flex temperatures were similar to conventional liquid polymeric plasticizers, but melt processability was not as good as lower‐molecular‐weight plasticizers.
Reinforced poly(vinyl chloride)—the ultimate rigid vinyl
Authors: Deanin Rudolph D. , Michaels George C.
Published: December 2004

Rigid poly(vinyl chloride) was reinforced with 10 to 40 phr of 1/4‐inch glass fiber. This improved flexural modulus up to 140 percent, flexural strength 40 percent, and heat‐deflection temperature 8°C; and reduced creep by 90–95 percent, and the coefficient of thermal expansion by 50 percent. Thus a typical Type I rigid vinyl with glass reinforcement had flexural modulus 1,164,000 psi, flexural strength 16,500 psi, notched Izod impact strength 5.1 fpi; creep only 12 percent of normal unreinforced material, coefficient of thermal expansion only 50 percent of normal unreinforced material, and heat‐deflection temperature 79°C. Such balance of properties elevates rigid vinyl from a commodity plastic up to an engineering thermoplastic, capable of much wider and more economical utilization in high‐performance applications.
Monomeric plasticizers for PVC medical devices: Safety and regulatory status
Authors: Group Edward F.
Published: December 2004

As the data base for phthalates and other monomeric plasticizer classes is broadened, and our understanding of toxic mechanisms and potential risks improves, it is anticipated that industry and government agencies alike will demonstrate that these products can be safely used. Progress will depend heavily on advancements in predictive animal testing science, and extrapolation of animal data to meaningful risk assessment in humans.

Future directions for testing initiatives are being determined, with a leadership role being played by CMA. Much exploratory work remains, but the focus will continue to narrow on areas critical to human risk assessment.
Morphology of mass PVC
Authors: Fischer Nicolas
Published: December 2004

The evolution of the morphology of the PVC grains during the mass polymerization of vinylchloride monomer (VCM) has been studied. After nucleation of primary particles, a rapid flocculation step occurs that leads to grains. Continued polymerization inside the grains results in a progressive reduction in the pore volumes. Continuing the reaction to completion, if appropriate by adding a further amount of monomer, causes densifying of the grains leading, in some cases, to vitreous grains, which therefore are related to the cleanliness of the reactors used. The changes in the size of the constituent compartment affect both the process of preparation and the processing of the final product: degassing rate of monomer, and plasticizing rate. Thus, control of the degrees of conversion, associated with perfect cleaning of the reactor, which is easy in the case of the new vertical reactors, constitutes the key factors in the reproducibility of the process and the quality of the PVC produced.
Effect in vitro and in vivo of a rat anti‐CD2 monoclonal antibody (LO‐CD2b) on pig‐to‐baboon xenogeneic cellular (T and natural killer cells) immune response
Authors: Dehoux Jean‐Paul , De La Parra Bernardo , Latinne Dominique , Bazin Hervé , Gianello Pierre
Published: December 2004

Abstract: Although hyperacute rejection of discordant xenogeneic grafts can be prevented, baboon or human anti‐pig cellular response may lead to acute xenograft rejection. Among the immune cellular actors participating in such a xenograft rejection are both T and natural killer (NK) cells. In the pre‐clinical model of pig‐to‐baboon discordant xenograft, there is however, a lack of specific immunological therapeutic agent, in particular antibaboon T‐cell monoclonal antibodies do not exist. We therefore developed a rat anti‐CD2 monoclonal antibody (LO‐CD2b) that recognizes both baboon and human CD2 + cells. In this study, we show that in vitro LO‐CD2b inhibits a pig‐to‐baboon mixed lymphocyte reaction, the direct cytotoxicity of baboon peripheral blood lymphocytes to pig aortic endothelial cells, as well as the baboon NK activity against K562 cell line. In vivo, LO‐CD2b produces a strong depletion of all peripheral CD2+ cells including NK CD2+ cells. In summary, LO‐CD2b represents an important immunological tool that can be used in the preclinical model of discordant pig‐to‐baboon vascularized xenograft.