Quantitative Surface Analysis Research Articles

Correlative Fractography: Combining Scanning Electron Microscopy and Light Microscopes for Qualitative and Quantitative Analysis of Fracture Surfaces

Correlative fractography is a new expression proposed here to describe a new method for the association between scanning electron microscopy (SEM) and light microscopy (LM) for the qualitative and quantitative analysis of fracture surfaces. This article presents a new method involving the fusion of one elevation map obtained by extended depth from focus reconstruction from LM with exactly the same area by SEM and associated techniques, as X-ray mapping. The true topographic information is perfectly associated to local fracture mechanisms with this new technique, presented here as an alternative to stereo-pair reconstruction for the investigation of fractured components. The great advantage of this technique resides in the possibility of combining any imaging methods associated with LM and SEM for the same observed field from fracture surface.

Functionalized Magnetic Nanoparticles for the Detection and Quantitative Analysis of Cell Surface Antigen

Cell surface antigens as biomarkers offer tremendous potential for early diagnosis, prognosis, and therapeutic response in a variety of diseases such as cancers. In this research, a simple, rapid, accurate, inexpensive, and easily available in vitro assay based on magnetic nanoparticles and magnetic cell separation principle was applied to identify and quantitatively analyze the cell surface antigen expression in the case of prostate cancer cells. Comparing the capability of the assay with flow cytometry as a gold standard method showed similar results. The results showed that the antigen-specific magnetic cell separation with antibody-coated magnetic nanoparticles has high potential for quantitative cell surface antigen detection and analysis.

Vacuum laser-produced plasma for analytical application in fusion technologies

LIBS is a well established tool for qualitative, semi-quantitative and quantitative analysis of surfaces, with micro-destructive characteristics and some capabilities for stratigraphy. In this work, the depth profiling capabilities of LIBS has been checked by determining the composition of multilayered samples simulating the plasma facing components fusion device covered with co-deposited impurity layers. A new experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working at low pressure and remotely.

Tribological characterization of polyvinyl alcohol hydrogel as substitute of articular cartilage

Polyvinyl alcohol (PVA) hydrogels are considered as promising biomaterials to substitute damaged articular cartilage due to their excellent biocompatibility, high permeability to fluids and low friction coefficient against smooth and wet surfaces. The study aims to demonstrate that under tribological loading mimicking in vivo conditions, PVA hydrogel/natural articular cartilage consists in a particular combination of mating surfaces with friction and wear characteristics compatible with the application as articular joints. Hydrogel membranes having approximately 1mm thickness were processed from PVA aqueous solutions (Aldrich Mw 89000–98000g/mol, 99% hydrolized), with 10% (w/w) concentration of polymer in solution, to be used as tribological samples against bovine articular cartilage. In order to ensure the natural properties and resistance of the tissue, articular cartilage samples were collected from condyles and prepared with ∼4mm subchondral bone. Tribological tests were performed on a pin-on-plate tribometer with a linear reciprocating geometry in the presence of distilled water and phosphate buffered saline solution (PBS) at 37°C. The reciprocating sliding frequency and stroke length were kept constant at 1Hz and 8mm, respectively. Contact pressures ranging from 1MPa to 5MPa were applied. For each experiment the friction coefficient was determined and the dominant wear mechanisms analyzed by SEM. The topography of hydrogel membranes in the hydrated state was evaluated with AFM microscopy for quantitative and qualitative analysis of worn surfaces. Results show that PVA hydrogel present excellent tribological performance against natural articular cartilage with very low friction coefficient values (≈0.02 to 0.05) combined with the preservation of both mating surfaces.

Systematic calculation of the surface excitation parameters for 22 materials

Quantitative surface analysis requires knowledge of surface excitations by electrons. These excitations are characterized by the surface excitation parameter (SEP) which represents the surface excitation probability while an electron moves across a solid surface. In this work, a systematic calculation of a SEP database has been performed for 22 materials, including metals, oxides and semiconductors, for electron energies between 100 eV and 5000 eV, and for angles α of incidence/emission between 0.5o and 89.5o with respect to the surface normal. Surface excitations are considered for both sides of a solid–vacuum interface when an electron is incident on or emitted from a surface. These SEPs represent not only the appearance of surface excitations but also the inhibition of bulk excitations. Four common SEP formulas are evaluated, and we present best‐fit parameters for the most satisfactory formula. SEP can then be readily determined for about 22 materials and various energies and electron incidence or emission angles. Copyright © 2012 John Wiley & Sons, Ltd.

Analysis of Phase Distribution in Thin Surface Layers Comparable to the Penetration Depth of X-Rays

After hydrogen concentration, gradients in austenitic-type stainless steels, formed during electrochemical charging and followed by hydrogen loss during aging at room temperature, surface stresses, and martensitic phases α′-bcc and e-hcp, developed. Phase quantitative X-ray surface analysis of distributions of martensitic phases in a thin layer, comparable to the penetration depth of X-rays, based on diffraction data taken for various diffraction reflections (2θ, Bragg’s angles) and with various radiations (λ-wavelengths) was applied for various degrees of the type steel in the surface layers. An examination of the relationships between γ-phase transitions in a number of stainless steels and their γ stability revealed that the stability of the γ phase increased (S stability factor changed from 26.5 in AISI 321 to 44 in AISI 310), the amount of α′-martensites (from 25 pct in AISI 347 to 0 pct in AISI 310) decreased, and e-martensites (from 48 pct in AISI 310 to 77 pct in AISI 321) increased, while the depth (from 6.2 μm in AISI 321 to 3 μm in AISI 310) of the martensitic phases decreased. Deformation and fracture experiments were carried out at room temperature in a high-resolution transmission electron microscope with single-axis tilt tensile stage and environmental cell. The principal effect of hydrogen was to decrease the stress required for dislocation motion, for phase transformation of the austenite, and for crack propagation. Formation of e- and α′-martensite was noted along the fracture surfaces and in front of the crack tip. The cracks propagated through the e-martensite plates, which formed along the active slip planes, while α′ phase was always found in the high stress regions.

X-ray Photoelectron Spectroscopic Study on the Anodic Passivity of Sputterdeposited W-Ta Alloys in 12 M HCl

The role of a simultaneous additions of tungsten and tantalum on the anodic passivity of the passive films of the sputter-deposited nanocrystalline W-xTa alloys was studied using immersion tests, electrochemical measurements and X-ray photoelectron spectroscopic (XPS) analysis. The formation of spontaneous passive film on the alloys, which is composed of double oxyhydroxide of tungsten and tantalum ions are responsible for their higher corrosion resistance than those of the alloy-constituting elements in 12 M HCl solution open to air at 30°C. The quantitative surface analysis by XPS is clarified that the improved anodic passivity of the alloys than those of alloy-constituting elements is based on the formation of new anodic passive oxyhydroxide films composed of W6+ and Ta5+ ions. These films have higher protectiveness and stability than those of passive oxyhydroxide films of alloy-constituting elements, that is, oxyhydroxides of hexavalent tungsten and pentavalent tantalum after potentiostatic polarization for 1 h in 12 M HCl.DOI: http://dx.doi.org/10.3126/njst.v12i0.6492 Nepal Journal of Science and Technology 12 (2011) 139-148

Research into the causes cracking of aluminum alloys of Al - Cu during mechanical machining

The aim of the work was carried out research on the causes cracking formed aluminum work pieces in the assortment of rods, which sometimes occur in the mechanical machining (turning, drilling) for alloys of Al-Cu. A typical representative for the machining of aluminum alloys is AlCu4MgMnPb alloy, most of which performs heat treatment for hardening increases the ultimate strength. For the given alloy were carried out qualitative and quantitative fractographic analysis of fracture surfaces after machining in order to determine possible causes cracking of the material and thus his insufficient strength. This paper clearly documented that the fractographic analysis methods can clearly and in the extent required to provide answers to the causes of insufficient strength of the material when cutting. At the same time points out the possible causes of cracks in this alloy in machining and ways for their elimination.

Remote-LIBS characterization of ITER-like plasma facing materials

The occurrence of several plasma-wall interaction processes, eventually affecting the overall system performances, is expected in a working fusion device chamber. Monitoring the changes in the composition of the plasma facing component (PFC) surface layer, as a result of erosion and redeposition mechanisms, can provide useful information on the possible plasma pollution and fuel retention. To this aim, suitable diagnostic techniques able to perform depth profiling analysis of the superficial layers on the PFCs have been developed. Due to the constraints commonly found in fusion devices, the measuring apparatus must be non invasive, remote and sensitive to light elements. These requirements make LIBS (Laser Induced Breakdown Spectroscopy) an ideal candidate for on-line monitoring the walls of current and of next generation (as ITER) fusion devices. LIBS is a well established tool for qualitative, semi-quantitative and quantitative analysis of surfaces, with micro-destructive characteristics and some capabilities for stratigraphy. In this work, LIBS depth profiling capability has been verified for the determination of the composition of multilayer structures simulating plasma facing components covered with deposited impurity layers. A new experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working in vacuum conditions and remotely, two noticeable properties for an ITER-relevant diagnostics. A quantitative analysis has been carried out in determining the elemental composition of the ITER-like samples.

Quantitative MAS NMR characterization of the LiMn1/2Ni1/2O2 electrode/electrolyte interphase

The conditions in which degradation processes at the positive electrode/electrolyte interface occur are still incompletely understood and traditional surface analytical techniques struggle to characterize and depict accurately interfacial films. In the present work, information on the growth and evolution of the interphases upon storage and cycling as well as their electrochemical consequences are gathered in the case of LiNi1/2Mn1/2O2 with commonly used LiPF6 (1M in EC/DMC) electrolyte.The use of 7Li, 19F and 31P MAS NMR, made quantitative through the implementation of empirical calibration, is combined with transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) to probe the elements involved in surface species and to unravel the inhomogenous architecture of the interphase. At room temperature, contact with the electrolyte leads to a covering of the oxide surface first by LiF and lithiated organic species are found on the outer part of the interphase. At 55°C, not only the interphase proceeds in further covering of the surface but also thickens resulting in an increase of 240% of lithiated species and the presence of –POF2 fluorophosphates. The composition gradient within the interphase depth is also strongly affected by the temperature.In agreement with the electrochemical performance, quantitative NMR surface analyses show that the use of LiBOB-modified electrolyte results in a Li-enriched interphase, intrinsically less resistive than the standard LiPF6-based interphase, comprised of a mixture of resistive LiF with non lithiated species.

Self-correlation function for determination of geometrical parameters in Nanoporous Anodic Alumina Films

Self-correlation functions have been applied to top-view high-resolution scanning electron microscopy micrographs of anodic alumina nanoporous arrays in order to determine their ordering degree and geometrical parameters; as a result, self-correlation images were obtained. These images are formed in the real space and can be used to make quantitative and qualitative surface analysis. The developed method for surface analysis has been applied to three series of porous anodic alumina films grown using sulphuric acid based electrolytes with concentrations of 3, 10, and 20 wt% and applying voltages from 25 down to 5 V. Significant changes in ordering degree, interpore distances, and pore diameters have been observed. In addition, in this study, the existence of an anodization window for self-ordering regimes for each acid concentration used in the electrolytic solution is also revealed.

Reconstruction and quantitative analysis of metallic surfaces with pits based on improved stereo image matching method

A stereo image matching method is developed for the solution of the problem of reconstruction of surfaces with corrosion defects. Special attention is given to the problem of improvement of mathematical models of an objective function and methods for its optimization in the presence of shaded regions in the images of a metal surface, which are observed in the investigation of pit-like defects. The proposed method is used for the quantitative analysis of the depth and shape of local pitting corrosion.

X-ray Photoelectron Spectroscopic Study on the Anodic Passivity of Sputter-deposited W-Nb Alloys in 12 M HCl Solution

The effect of a simultaneous additions of tungsten and niobium on the anodic passivity of the surface films of the sputter-deposited amorphous/nanocrystalline W-xNb alloys was studied using corrosion tests, electrochemical measurements and X-ray photoelectron spectroscopic (XPS) analyses. The formation of spontaneous passive film on the alloys, which is composed of double oxyhydroxides of Wox and Nb5+ ions, is responsible for their higher corrosion resistance than those of the alloy-constituting elements in 12 M HCl solution open to air at 30°C. The quantitative surface analysis by XPS clarifies that the improved anodic passivity of the alloys than those of alloy-constituting elements is based on the formation of new double oxyhydroxide anodic films composed of W6+ and Nb5+ ions. These anodic passive films have higher protectiveness and stability than those of the anodic passive oxyhydroxide films of alloy-constituting elements, that is, oxyhydroxides of hexavalent tungsten and pentavalent niobium after potentiostatic polarization for 1 h in 12 M HCl at 30°C.Keywords: W-Nb alloys; Sputter deposition; Polarization curve; Passivity; Surface analysis.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i3.7207 J. Sci. Res. 3 (3), 467-480 (2011)

Pd/MWCNTs catalytic activity in the formic acid electrooxidation dependent on catalyst surface treatment

The catalytic activity in the formic acid (HCOOH) electrooxidation reaction of the Pd multiwall carbon nanotubes (MWCNTs) supported catalyst, prepared by a microwave-assisted polyol method, treated under different gas atmospheres, and temperatures (200 and 300 °C), was investigated. Their respective catalysts surface characterization proceeded in UHV using the electron spectroscopy methods. Content of constituents, i.e., Pd nanoparticles, C and O, was examined quantitatively. Content of Pd phases and chemical forms of C atoms was analyzed assuming respective binding energy (BE) values to Pd 3d and C 1s X-ray photoelectron spectra (XPS) spectra fitted to Gaussian–Lorentzian components. Surface structure was examined from the 3D nanostructure analysis by quantitative analysis of surfaces by electron spectroscopy (QUASES). Catalytic activity of Pd/MWCNTs after various surface treatments was attributed to different surface content and forms of Pd nanoparticles, and PdOx/C overlayer morphology, coverage, and thickness.

Antibody-Mediated Self-Limiting Self-Assembly for Quantitative Analysis of Nanoparticle Surfaces by Atomic Force Microscopy

Quantification of very low density molecular coatings on large (60 nm) gold nanoparticles (AuNPs) is demonstrated via the use of antibody-mediated self-limiting self-assembly of small and large AuNPs into raspberry-like structures subsequently imaged by atomic force microscopy (AFM). AFM imaging is proposed as an automated, lower-cost, higher-throughput alternative to immunostaining and imaging by transmission electron microscopy. Synthesis of large AuNPs, containing one of three ligand molecules in one of three stoichiometries (1, 2, or 10 ligands per AuNP), and small probe AuNPs with one of three antibody molecules in a one antibody per AuNP ratio, enabled a range of predicted self-limiting self-assembled structures. A model predicting the probability of observing a given small to large AuNP ratio based on a topography measurement such as AFM is described, in which random orientational deposition is assumed and which accounts for the stochastic synthesis method of the library AuNPs with varied ligand ratios. Experimental data were found to agree very well with the predictive models when using an established AFM sample preparation method that avoids drying-induced aggregation.

The Storing Matter technique: Application to PVC using Au and Ag collectors

AbstractThe Storing Matter technique has been developed to perform quantitative surface analysis with high sensitivity. This technique consists in decoupling the sputtering of the specimen from the subsequent analysis step. In the recently developed prototype instrument, the sample surface is sputtered by an ion beam and the emitted particles are deposited at submonolayer level on a dedicated collector under UHV conditions. In a second step, the matter deposited on the collector is analyzed by SIMS in dynamic or static mode. The chemical nature of the collector surface is chosen with regard to the subsequent SIMS analysis (high or low work function to enhance positive or negative ionization, metallic overlayer for optimized organic information by cationization, etc.) by depositing thin films by electron beam evaporation.This paper presents the first results obtained on PVC samples with the Storing Matter prototype instrument. The chosen collector surfaces were Au and Ag, which are known to enhance cationization in static SIMS. The positive mass spectra obtained from Storing Matter deposits on these collectors were compared to those recorded on a PVC reference sample, on a PVC sample covered with a thin metallic overlayer, on a PVC thin film deposited on a metal substrate, and on the pristine collectors. This study showed that the Storing Matter technique allows for a clear identification of the PVC deposit on the Ag collector, while identification was impossible in the case of the Au collector due to a high degree of organic contaminations on the pristine collector. Copyright © 2010 John Wiley & Sons, Ltd.

The Storing Matter technique: application to polymer samples using Ag collectors

AbstractThe Storing Matter technique has been developed to perform quantitative surface analysis with high sensitivity. This technique consists in decoupling the sputtering of the specimen from the subsequent analysis step. In the recently developed prototype instrument, the sample surface is sputtered by an ion beam and the emitted particles are deposited at submonolayer level on a dedicated collector under UHV conditions. In a second step, the matter deposited on the collector is analyzed by SIMS in dynamic or static mode. The chemical nature of the collector surface is chosen with regard to the subsequent SIMS analysis (high or low work function to enhance positive or negative ionization, metallic overlayer for optimized organic information by cationization, etc.) by depositing thin films by electron beam evaporation.This paper presents the first results obtained on polymer samples (PMMA, PVC and PS) with the Storing Matter prototype instrument. The chosen collector surface was Ag, which is known to enhance cationization in static SIMS. The positive mass spectra obtained from Storing Matter deposits on Ag collectors were compared to those recorded on polymer reference samples and on the pristine Ag collectors. This study showed that the Storing Matter technique allows for a clear identification of the PMMA and PVC deposits while enhancing the secondary ion intensities in the higher‐mass range with respect to a conventional static SIMS analysis of the polymer. Copyright © 2010 John Wiley & Sons, Ltd.

Comparison of MeV monomer ion and keV cluster ToF‐SIMS

AbstractRecent results1 show the potential of using monomer primary ions accelerated to several MeV with a tandem accelerator to achieve the necessary secondary ion yields to image large (above 1 kDa) molecules with submicron lateral resolutions. The Surrey ion Beam Centre (Surrey IBC) has designed a time‐of‐flight secondary ion mass spectrometer (ToF‐SIMS) combined with a 2 MV Tandem accelerator to investigate the characteristics of the desorption of secondary ions by the impact of fast, heavy, primary ions. The application of this MeV‐ToF‐SIMS technique is intended to eventually image biomolecules in the subcellular regime without the need for matrix application associated with other mass spectromery techniques, such as Matrix Assisted Laser Desorption ionisation (MALDI). A discussion is given to point out the merits of using a combination of Particle‐Induced X‐ray Emission Spectrometry (PIXE) and Rutherford Backscattering (RBS) with the MeV‐ToF‐SIMS measurement to improve quantification and sensitivity of this surface analysis technique. We also present data from highly focused MeV primary ions to directly compare results obtained using keV cluster‐SIMS to measure various biological materials using ToF‐SIMS through sputtering in both the nuclear and electronic stopping regimes. Our findings show that the mass spectra obtained with MeV ions in the electronic stopping regime show similarities to those acquired with more conventional keV ion beams (e.g. Bi+, Bi3+, Bi5+ and C60+). MeV‐ToF‐SIMS has the potential for becoming a widely used quantitative surface analysis technique in the many ion beam analysis facilities already conducting‐high energy ion beam analyses. Copyright © 2010 John Wiley & Sons, Ltd.

Micromorphology of Epicuticular Waxes and Epistomatal Chambers of Pine Species by Electron Microscopy and White Light Scanning Interferometry

High-resolution imaging and quantitative surface analysis of epicuticular waxes and epistomatal chambers of pine species were performed by field emission scanning electron microscopy and white light scanning interferometry. Both juvenile and adult needles were collected from the two-year-old seedlings of Pinus rigida and Pinus densiflora and subjected to surface observations. Epicuticular wax structures developed on the cuticle layer as well as in the epistomatal chambers and appeared to occlude the cavities in the two pine species. The stomata of P. densiflora were characterized by more distinctly raised rings around openings than P. rigida. The most common epicuticular wax structures of the two pine species included tubules with terminal openings and coiled rodlets. Wax platelets were deposited on epistomatal chambers. Either rodlets or tubules seemed to be longer and thicker in P. rigida than those in P. densiflora. White light scanning interferometry revealed quantitative surface profiles, demonstrating more ridged (ca. 4 μm high) stomatal apertures and nearly twofold deeper (ca. 20 μm deep) epistomatal chambers of P. densiflora than those of P. rigida. These results suggest that white light scanning interferometry can be applied to unravel the quantitative surface features of epicuticular sculptures on plant leaves.

Functional mapping of the anti-idiotypic antibody anti-TS1 scFv using site-directed mutagenesis and kinetic analysis

Recombinant antibodies may be engineered to obtain improved functional properties. Functional mapping of the residues in the binding surfaces is of importance for predicting alterations needed to yield the desired properties. In this investigation, 17 single mutation mutant single-chain variable fragments (scFvs) of the anti-idiotypic antibody anti-TS1 were generated in order to functionally map amino acid residues important for the interaction with its idiotype TS1. Residues in anti-TS1 determined to be very important for the interaction were identified, Y32L, K50L, K33H, and Y52H, and they were distributed adjacent to a centrally located hydrophobic area, and contributed extensively to the interaction energy (≥2.5 kcal/mol) in the interaction. Quantitative ELISA assays, BIAcore technologies and three-dimensional surface analysis by modeling were employed to visualize the consequences of the mutations. The expression levels varied between 2 - 1,800 nM as determined by ELISA. All the 17 scFvs displayed higher dissociation rates (60 - 1,300 times) and all but two of them also faster association rates (1.3 - 56 times). The decrease in affinity was determined to be 1.6 - 12,200 times. Two of the mutants displayed almost identical affinity with the wild type anti-TS1, but with a change in both association and dissociation rates. The present investigation demonstrates that it is possible to generate a large panorama of anti-idiotypic antibodies, and single out a few that might be of potential use for future clearing and pre-targeting purposes of idiotypic-anti-idiotypic interactions.