Time-of Flight Secondary Ion Mass Research Articles

Solute Enrichment in the Fusion Zone during Resistance Spot Welding of a Third Generation Advanced High Strength Steel

Resistance spot welding is a critical joining technique in automobile assembly. The load carrying properties of spot welds are generally accepted to correlate with weld diameter, which increases with increasing weld current or duration. The formation of a softened layer, or weld halo, surrounding the fusion zone in a spot-welded third generation (Gen3) advanced high strength steel (AHSS) was recently reported in the literature. To optimize weld performance by schedule design, it is necessary to understand the halo formation characteristics and potential impacts. Accordingly, welding of a Gen3 AHSS was performed using weld times between 130 – 1300 ms. Microhardness mapping characterized weld microhardness and the evolution of the halo during welding. Electron probe microanalysis and timeof-flight secondary ion mass spectrometry enabled measurement of solute distributions through the weld halo, while scanning electron microscopy was used for microstructural characterization. The solidified structure was examined using light-optical microscopy, and with the microhardness and compositional data, used to infer the mechanism by which the halo forms during welding. It was found that the halo develops due to solute rejection from a cellular solidification front that advances towards the center of the fusion zone while weld current is applied. Extended weld times increase the size of the weld halo and the solute content of the inner fusion zone. The decrease in weld halo microhardness and the increase in inner fusion zone microhardness is largely explained by the changes in local carbon content associated with halo formation.

Extrinsic oxygen defects in SnO/SnO2 heterostructure for efficient NO2 gas detection

High selectivity and fast response in the detection of NO2 are key factors in protecting human health in life-threatening environments. The p-n SnO/SnO2 heterostructure is a promising material as a metal oxide for effective chemical reactions with a target gas. It has a synergistic effect on the intrinsic semiconducting properties and the formation of an interfacial electric field in the heterojunction. The extrinsic oxygen vacancies in the SnO/SnO2 structure enhance the chemical reaction in the sensing property. In this study, we developed a defect-SnO/SnO2 heterostructure-based NO2 gas sensor. It shows excellent sensing performances with a high response of 100.86, fast response time of 5.83 s, and superior selectivity (approximately 23 times higher than those of other target gases) in the detection of 50 ppm NO2 at 150 °C. Raman and electron paramagnetic resonance (EPR) results supported the presence of oxygen vacancies in the defect-rich SnO/SnO2 crystal and X-ray photoelectron spectroscopy (XPS) and time-of flight secondary ion mass spectrometry (ToF-SIMS) analyses described the role of SnO/SnO2 heterostructure with oxygen defects as an effective electron donor for the adsorbed oxygen molecules and NO2 target gas. We believe that the direct formation of oxygen vacancies in the SnO/SnO2 heterostructures is a significant reference for the development of high-performance NO2 gas sensors.

Characterization of Sr2Fe1,5Mo0,5O6-δ Based Solid Oxide Electrolysis Cells

Hydrogen electrodes of solid oxide electrolysis cells (SOEC) are typically made of Ni-YSZ cermet. Despite having excellent catalytic activity Ni-based electrodes suffer from poor redox stability and Ni volatility [1]. Sr2Fe1,5Mo0,5O6-δ (SFM) mixed ionic- and electric conducting (MIEC) double perovskite has been proposed as promising hydrogen electrode material for solid oxide electrolysis cells (SOEC) because of its excellent catalytic properties and good conductivity. In this study SOEC single cells were prepared using SFM hydrogen electrode and (La0,6Sr0,4)0,99Co0,96Ti0,04O3-δ (LSCT) as well as (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) air electrodes [2, 3].Studied cells were prepared using 19 mm 10Sc1CeSZ electrolyte substrates. Screen printed 6 μm thick Ce0.9Gd0.1O1.95 (GDC) layer was applied to both sides of the cell to prevent formation of insulating SrZrO3 layer. GDC layer was sintered to the electrolyte at 1300°C for 5h. SFM or 50%SFM/50%GDC electrode layer with 0,52cm2 surface area was screen printed to the GDC layer and was sintered at 1200°C and at 1150°C to optimize electrode composition and thermal treatment program of electrode. Afterwards LSCT or LSCF oxygen electrodes were screen printed to the other side of the cell and sintered at 1100°C for 2 h. Finally, cells were characterized using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and time-of flight secondary ion mass spectrometry (TOF-SIMS).Impedance spectroscopy analysis showed that cells with 50%SFM/50%GDC hydrogen electrode sintered at 1150°C and LSCT oxygen electrode had highest current densities, reaching 1,59 A/cm2 at 1,5V and 850°C with 67,5% water in hydrogen electrode compartment. However, stability of the cells needs to be further investigated. With TOF-SIMS analysis it became apparent that Sr is moving through GDC intermediate layer and poorly conducting phases are formed in the GDC/10Sc1CeSZ boundary.[1] C. Singhal, K. Kendall (Eds.), High-Temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications, Elsevier, Oxford, 2003.[2]Bernadet, C. Moncasi, M. Torell, A. Tarancon, High-performing electrolyte-supported symmetrical solid oxide electrolysis cells operating under steamelectrolysis and co-electrolysis modes, Int. J. Hydrogen Energy 45 (2020)14208–14217[3]Sanna, W. Zhang, P. Costamagna, P. HoltappelsSynthesis and electrochemical characterization of electrospun nanofiber cathodes for intermediate- temperature solid oxide fuel cells Int. J. Hydrog. Energy (2020), pp. 1-14

Submicron 3-D mass spectrometry imaging reveals an asymmetric molecular distribution on chemotaxing cells.

Background: Dictyostelium discoideum is a ~10 µm diameter unicellular eukaryote that lives on soil surfaces. When starved, D. discoideum cells aggregate into streams of cells in a process called chemotaxis. In this report, we studied D. discoideum cells during chemotaxis using 3D - mass spectrometry imaging (3D-MSI). Methods: The 3D-MSI consisted of the sequential generation of 2D molecular maps using burst alignment coupled to delayed extraction time-of flight secondary ion mass spectrometry (TOF-SIMS) combined with a soft sputtering beam to access the different layers. Results: Molecular maps with sub-cellular high spatial resolution (~300 nm) indicated the presence of ions at m/z = 221 and 236 at the front and sides, but reduced levels at the back, of cells moving toward of aggregation streams. The 3D-MSI also detected an ion at m/z = 240 at the edges and back, but reduced levels at the front, of aggregating cells. Other ions showed an even distribution across the cells. Conclusions: Together, these results demonstrate the utility of sub-micron MSI to study eukaryotic chemotaxis.

Selective depression of Pb2+-activated sphalerite by potassium ferricyanide in Pb-Zn sulfides flotation separation

The depression of sphalerite in the flotation separation of galena and sphalerite is usually difficult, especially when sphalerite is activated by Pb2+ ions dissolved from lead-bearing minerals. In this study, the cheap, efficient, and environmentally friendly regent of potassium ferricyanide (K3[Fe(CN)6]) was used for the first time to efficiently separate galena from Pb2+-activated sphalerite at neutral pH. Micro-flotation experiments, adsorption tests, contact angles, zeta potential analysis, X-ray photoelectron spectroscopy (XPS) analysis, and time-of-flight secondary ion mass (ToF-SIMS) were performed to investigate the depression mechanism of K3[Fe(CN)6]. The micro-flotation test results showed that K3[Fe(CN)6] had a considerable depression effect on Pb2+-activated sphalerite. Adsorption tests showed that competitive adsorption between K3[Fe(CN)6] and sodium butyl xanthate (SBX) on the sphalerite surface reduced the amount of SBX adsorbed on the surface of Pb2+-activated sphalerite, thereby depressing sphalerite. Contact angles analysis indicated that K3[Fe(CN)6] treatment reduced the contact angle of Pb2+-activated sphalerite surface and weakened its hydrophobicity, providing a favorable condition for the separation of galena and Pb2+-activated sphalerite. Zeta potential measurements suggested that the K3[Fe(CN)6] effectively prevented the adsorption and interaction of sodium butyl xanthate (SBX) on the surface of Pb2+-activated sphalerite. Time-of-flight secondary ion mass (ToF-SIMS) and XPS analysis indicated that K3[Fe(CN)6] could chemisorb onto the Zn sites on the surface of Pb2+-activated sphalerite and form hydrophilic precipitates containing Zn3[Fe(CN)6]2, Zn3K2[Fe(CN)6]2, and Pb(OH)2, which further generate a hydrophilic passivation layer, and reduced the floatability of Pb2+-activated sphalerite.

Behavior of cation vacancies in single-crystal and in thin-film SrTiO3 : The importance of strontium vacancies and their defect associates

Solid-state diffusion experiments were used to probe the behavior of cation vacancies in the perovskite oxide ${\mathrm{SrTiO}}_{3}$. Two types of nominally undoped (effectively acceptor-doped) ${\mathrm{SrTiO}}_{3}$ systems were studied: (1) single crystals and (2) epitaxial thin films with different Sr/Ti stoichiometries produced by pulsed laser deposition. As diffusion sources, thin films of the perovskite oxide ${\mathrm{BaZrO}}_{3}$ were employed, and diffusion anneals were carried out in air at $1323\ensuremath{\le}T/\mathrm{K}\ensuremath{\le}1523$ for single crystals and at $1073\ensuremath{\le}T/\mathrm{K}\ensuremath{\le}1223$ for thin films. Sample analysis by means of time-of flight secondary ion mass spectrometry (ToF-SIMS) yielded diffusion coefficients of Ba and Zr in ${\mathrm{SrTiO}}_{3}\phantom{\rule{4pt}{0ex}}({D}_{\mathrm{Ba}}$ and ${D}_{\mathrm{Zr}})$. Diffusion profiles in single-crystal samples showed the expected error-function form and yielded ${D}_{\mathrm{Ba}}\ensuremath{\approx}{D}_{\mathrm{Zr}}$ at each temperature, and hence, activation enthalpies of diffusion that are approximately the same, at $(3.0\ifmmode\pm\else\textpm\fi{}0.4)$ eV and $(2.8\ifmmode\pm\else\textpm\fi{}0.4)$ eV. Diffusion profiles in the thin-film samples were unexpectedly complex, showing multiple error-function features. They also yielded ${D}_{\mathrm{Ba}}\ensuremath{\approx}{D}_{\mathrm{Zr}}$ at each temperature, however, but no clear trend was found as a function of Sr/Ti ratio. Comparing results for the two systems, we conclude that the concentration of cation vacancies is orders of magnitude higher in our thin-film samples than in the single crystals. Our results also provide experimental evidence that oxygen vacancies, ${\mathrm{v}}_{\mathrm{O}}^{\ifmmode\bullet\else\textbullet\fi{}\ifmmode\bullet\else\textbullet\fi{}}$, can decrease the activation enthalpy of strontium-vacancy migration by forming ${({\mathrm{v}}_{\mathrm{O}}{\mathrm{v}}_{\mathrm{Sr}})}^{\ifmmode\times\else\texttimes\fi{}}$ defect associates, and we derive an analytical model for the cation diffusivity as a function of temperature and defect concentrations.

Protein microarrays: The future of allergy diagnosis? Optimization of coating and printing of allergen arrays used with fluorescent humanised basophil reporter cell line NFAT-DsRed RBL

Up-to-date, in vitro allergy diagnosis techniques rely on the detection of allergen-specific Immunoglobulin E (sIgE). Protein microarrays enable the simultaneous screening of hundreds of sIgEs using only a small amount of serum. However, they do not always report clinically relevant sIgE. Combining protein arrays with humanised rat basophilic leukaemia (RBL) reporter cells that provide a biological readout, we aim to develop a high-throughput amenable, clinically relevant allergy diagnosis platform. Here, we demonstrate the effectiveness of different extracellular matrix (ECM) proteins to facilitate RBL cell attachment on various polymer-coated slide surfaces. We also determine printed protein stability using time-of flight secondary ion mass spectrometry (ToF-SIMS). Lastly, we demonstrate the ability of this system to detect an allergic response. Aldehyde-, epoxy- and amine-coated glass slides were coated with 10 μg/mL vitronectin, fibronectin or laminin for 48 hours at 37 ͦ C and with 10 μg/mL collagen for 48 hours at 4 ͦ C. After incubation, NFAT-DsRed RBL cells were cultured on each surface for 72 hours. The number of adherent cells was assessed every 24 hours using 1 μg/mL Hoechst 33342 solution. Next, the following proteins diluted in PBS to a final concentration of 1mg/mL, goat anti-human IgE, timothy grass pollen extract, human serum albumin, k-casein from bovine milk or the above mentioned proteins diluted with 10% fibronectin, were printed in triplicate onto the different polymer-coated slides using a XYZ3200 dispensing workstation (Biodot). Printed proteins were characterized by ToF-SIMS before and after washing the surfaces with deionized water. Finally, cells were sensitized overnight with human IgE. Cell activation was assessed using fluorescence microscopy after 24h incubation onto the protein printed surfaces. Treatment of the aldehyde- and epoxy-coated slides with different ECM proteins had no significant effect on cell adhesion compared to control (cells only). The amine coated surfaces showed higher printed protein stability compared to aldehyde and epoxy ones. Lastly, cell activation was higher on the epoxy slides after printing 10% fibronectin containing protein solution compared to control (protein only). The epoxy-coated slides would consist the optimum platform to assess cell activation and potentially detect an allergic response.

Advanced protection against environmental degradation of silver mirror stacks for space application

Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications. Hereby, we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO2 and Al2O3 coatings in conditions of accelerated aging by sulfidation. The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate. Accelerated aging was performed in dry and more severe wet conditions. Optical micrographic observations, surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and reflectivity measurements were combined to comparatively study the effects of degradation. The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions.

The Complementary Role of ToF-SIMS in the Assessment of Imiquimod Permeated into the Skin from a Microemulsion Dosage Form

The assessment of drug permeation into/across the skin is traditionally accomplished using Franz diffusion cells with subsequent analysis by conventional chromatographic methods such as HPLC and more recently using advanced imaging techniques. In this context, time of flight-secondary ion mass spectrometry (ToF-SIMS) offers distinctive advantages in mapping drugs within skin with high sensitivity and chemical specificity without the need for fluorescent tags or radiolabels. The work in this paper uses the combination of conventional and advanced methods to evaluate imiquimod permeation into the skin. This approach provides complementary and detailed information regarding the permeated mass, the permeation depth and the spatial distribution and localisation of drugs within skin. Imiquimod is an immune modulator drug approved by the FDA for the treatment of superficial basal cell carcinoma (BCC) but not the nodular lesions. As other studies have reported that Aldara™ cream (imiquimod 5% w/w) has some limitations in the treatment of nodular BCC lesions due to the cream’s inability to deliver imiquimod into the deeper more invasive nodular lesions, an enhancement of imiquimod permeation is thought to be useful to overcome these limitations. Therefore, an attempt to improve delivery of imiquimod into the deeper skin layers using microemulsions was investigated. Imiquimod microemulsions were formulated and characterised in our previous work are now tested for skin permeation enhancement. However, the assessment of imiquimod permeation from the formulated microemulsions using HPLC and ToF-SIMS demonstrated a limited ability of the microemulsions to improve delivery of imiquimod over Aldara™ cream. This was attributed to the poor release of imiquimod from the microemulsion formulas due to the high affinity of imiquimod for the oil phase and the encapsulation of the oil droplets by the S/Co-S mixture. This is thought to be, the first time that ToF-SIMS has been used to assess permeation of imiquimod from a microemulsion dosage form.

Applicability of TOF-SIMS for the assessment of lipid composition of cell membrane structures

Langmuir–Blodgett lipid films and plasma membranes of glioma cells were analyzed using timeof-flight secondary ion mass spectrometry (TOF-SIMS). Bi3 + primary ion beam was determined to be most efficient in various experimental setups. TOF-SIMS was shown to be applicable for a quantitative analysis of model lipid structures, as well as plasma membranes of glioma cells U87MG in vitro. A combination of atomic-force microscopy and scanning electron microscopy yielded the depth resolution of ~10–20 nm for cell surface scanning by primary ion beam.

MgO Implanted in Rat Tibia Bone Marrow is Osteoinductive through the Formation of a Matrix, Containing Hydroxyapatite

Healing of rat tibia after intramedullary implantation of MgO was analysed by Environmental Scanning Electron Microscopy (ESEM) and Energy-Dispersive X-ray spectroscopy (EDX). The results indicated the formation of hydroxyl-apatite (HA) in the entire intramedullary space after 1 week of healing. Then, corroded Mg, MgO and MgCO3 were incubated with DMEM in vitro for 24 h and the surface of the material was analysed by EDX and Time-of-Flight Secondary Ion Mass (ToF-SIMS). The chemical analysis of the Mg corrosion products indicate that HA is formed at the material surface and that MgCO3 was an efficient catalyzer of HA formation

Characterization of endotoxins on orthopaedic fixation screws, using physicochemical surface analyses.

The objective of this study was to determine if surface analysis techniques could be used to detect endotoxin on stainless steel malleolus screws. New malleolus screws were compared to ones that had been coated in purified lipopolysaccharide (LPS) or Artificial Test Soil (ATS) containing lipopolysaccharide. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and time-of flight secondary ion mass spectrometry (TOF-SIMS) were used to assess the fixation screws surface. Organic material was visualized on the LPS and ATS-LPS inoculated screws but not on the new unsoiled screws. This was further supported by the peaks observed at masses between 40 and 100 D in TOF-SIMS spectra of the LPS and ATS-LPS inoculated screws. After deconvolution of N1s high resolution XPS spectra, the LPS inoculated screws showed amide groups whereas the ATS-LPS inoculated screws showed predominantly nitroso groups (C-NO). Our data demonstrate that surface analysis can be used to detect organic residuals present on fixation screws. The XPS data confirmed that LPS reacted predominantly with positively charged surface metallic ions (Fe and Cr), whereas proteins reacted with the surface oxide layer of fixation screws, forming C-NO groups. The application of these surface analysis techniques will be helpful in determining if the reprocessing of such items results in an accumulation of organic material that might lead to aseptic loosening, when implanted. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:240-247, 2017.

Comparative analysis of lignin peroxidase and manganese peroxidase activity on coniferous and deciduous wood using ToF-SIMS.

White-rot fungi are distinguished by their ability to efficiently degrade lignin via lignin-modifying type II peroxidases, including manganese peroxidase (MnP) and lignin peroxidase (LiP). In the present study, time-of flight secondary ion mass spectrometry (ToF-SIMS) was used to evaluate lignin modification in three coniferous and three deciduous wood preparations following treatment with commercial preparations of LiP and MnP from two different white-rot fungi. Percent modification of lignin was calculated as a loss of intact methoxylated lignin over nonfunctionalized aromatic rings, which is consistent with oxidative cleavage of methoxy moieties within the lignin structure. Exposure to MnP resulted in greater modification of lignin in coniferous compared to deciduous wood (28 vs. 18% modification of lignin); and greater modification of G-lignin compared to S-lignin within the deciduous wood samples (21 vs. 12%). In contrast, exposure to LiP resulted in similar percent modification of lignin in all wood samples (21 vs 22%), and of G- and S-lignin within the deciduous wood (22 vs. 23%). These findings suggest that the selected MnP and LiP may particularly benefit delignification of coniferous and deciduous wood, respectively. Moreover, the current analysis further demonstrates the utility of ToF-SIMS for characterizing enzymatic modification of lignin in wood fibre along with potential advantages over UV and HPCL-MS detection of solubilized delignification products.

Surface analyses of orthopedic fixation screws submitted different artificial rest soil.

Event Abstract Back to Event Surface analyses of orthopedic fixation screws submitted different artificial rest soil. Rodrigo Franca1, Michelle Alfa2, Nancy Olson2, L’hocine Yahia3 and Edward Sacher4 1 University of Manitoba, Dental Biomaterials Research Lab, Canada 2 University of Manitoba, St-Boniface Hospital Research Center, Canada 3 École Polytechnique de Montréal, Laboratoire d’Innovation et d’Analyse de Bioperformance, Canada 4 École Polytechnique de Montréal, Regroupement Québecois de Matériaux de Pointe, Canada Implantable plates, screws and wires are frequently held in the surgical instrument tray, and are reprocessed every time the instruments are used. There have been questions raised about this practice but there is a lack of data to demonstrate organic residuals on reprocessed implantable plates, screws or wires. The objective of this study was to determine is surface analysis techniques could be used to detect such residual organic material on stainless steel malleolus screws. New malleolus screws were compared to ones that had been coated in purified lipopolysaccharide or Artificial Test Soil (ATS) containing lipopolysaccharide. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and surface time-of flight secondary ion mass spectrometry (TOF-SIMS) were used to assess the fixation screws. Organic material was visualized on the LPS and ATS-LPS inoculated screws but not on the new unsoiled screws. This was further supported by the peaks observed at masses between 40 – 100 D on TOF-SIMS spectra of the LPS inoculated and ATS-LPS inoculated screws. After deconvolution of high resolution XPS analyses, the LPS inoculated screws showed a carbon and oxygen oxidized state whereas the ATS-LPS inoculated screws showed predominantly C-NO (nitroso). In conclusion, our data demonstrated that surface analysis can detect organic residuals present in fixation screws. The XPS data confirmed that LPS reacted predominantly with positively charged surface metallic ions (Fe+ and Cr+) whereas proteins reacted with the surface oxide layer of fixation screws forming C-NO. The application of these surface analysis techniques will be helpful in determining if the reprocessing of such items results in an accumulation of organic material that might lead to aseptic loosening when implanted. Keywords: biomaterial Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Surface and interfacial characterization Citation: Franca R, Alfa M, Olson N, Yahia L and Sacher E (2016). Surface analyses of orthopedic fixation screws submitted different artificial rest soil.. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02947 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Rodrigo Franca Michelle Alfa Nancy Olson L’hocine Yahia Edward Sacher Google Rodrigo Franca Michelle Alfa Nancy Olson L’hocine Yahia Edward Sacher Google Scholar Rodrigo Franca Michelle Alfa Nancy Olson L’hocine Yahia Edward Sacher PubMed Rodrigo Franca Michelle Alfa Nancy Olson L’hocine Yahia Edward Sacher Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Surface Segregation and Inter-Diffusion of Cations and Impurities in Microelectrodes for Solid Oxide Fuel Cells and Electrolyzers

The surface segregation and inter-diffusion of cations and impurities in La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) micro-patterned electrode structures on a single crystal Zr0.84Y0.16O1.92(YSZ) electrolyte was investigated by high-resolution ion beam analysis (Time-of Flight Secondary Ion Mass Spectrometry and Low-Energy Ion Scattering). The outermost and near surface of these microelectrodes showed significant changes in the distribution of the cations and impurities after micro-patterning, annealing and electrochemical testing of the cells. As occurring for bulk LSCF ceramics, strong segregation of Sr towards the electrode surface is observed during annealing of the microelectrode, as well as due to the thermal treatments required for electrochemical measurements. This segregation might have a drastic effect on the surface oxygen exchange reaction as the electrochemically active transition metals (Fe, Co) are not directly exposed to the gas phase. Impurities, such as Si and Ca, are also observed at the annealed electrolyte surface. Furthermore, the microstructured electrode showed that impurities can also migrate between the different components (i.e. Na and Si impurities migrate from the electrolyte to the LSCF electrode, showing a “cleaner” surface after the thermal treatments). This study has provided a further understanding of the migration and segregation of cations and impurities taking place in real devices, building upon previous studies performed on ceramics materials. Figure 1

ToF‐SIMS imaging of lipids and lipid related compounds in Drosophila brain

Drosophila melanogaster (fruit fly) has a relatively simple nervous system but possesses high order brain functions similar to humans. Therefore, it has been used as a common model system in biological studies, particularly drug addiction. Here, the spatial distribution of biomolecules in the brain of the fly was studied using time-of flight secondary ion mass spectrometry (ToF-SIMS). Fly brains were analyzed frozen to prevent molecular redistribution prior to analysis. Different molecules were found to distribute differently in the tissue, particularly the eye pigments, diacylglycerides, and phospholipids, and this is expected to be driven by their biological functions in the brain. Correlations in the localization of these molecules were also observed using principal components analysis of image data, and this was used to identify peaks for further analysis. Furthermore, consecutive analyses following 10 keV Ar2500+ sputtering showed that different biomolecules respond differently to Ar2500+ sputtering. Significant changes in signal intensities between consecutive analyses were observed for high mass molecules including lipids.

Development of mass spectrometry by high energy focused heavy ion beam: MeV SIMS with 8 MeV Cl7+ beam

Particle induced X-ray emission (PIXE) at microprobe of Jožef Stefan Institute is used to measure two-dimensional quantitative elemental maps of biological tissue. To improve chemical and biological understanding of the processes in vivo, supplementary information about chemical bonding and/or molecular distributions could be obtained by heavy-ion induced molecular desorption and a corresponding mass spectroscopy with Time-Of-Flight (TOF) mass spectrometer. As the method combines the use of heavy focused ions in MeV energy range and TOF Secondary Ion Mass Spectrometry, it is denoted as MeV SIMS.At Jožef Stefan Institute, we constructed a linear TOF spectrometer and mount it to our multipurpose nuclear microprobe. A beam of 8MeV 35Cl7+ could be focused to a diameter of better than 3μm×3μm and pulsed by electrostatic deflection at the high-energy side of accelerator. TOF mass spectrometer incorporates an 1m long drift tube and a double stack microchannel plate (MCP) as a stop detector positioned at the end of the drift path. Secondary ions are focused at MCP using electrostatic cylindrical einzel lens.Time of flight spectra are currently acquired with a single-hit time-to-digital converter. Pulsed ion beam produces a shower of secondary ions that are ejected from positively biased target and accelerated towards MCP. We start our time measurement simultaneously with the start of the beam pulse. Signal of the first ion hitting MCP is used to stop the time measurement. Standard pulses proportional to the time of flight are produced with time to analog converter (TAC) and fed into analog-to-digital converter to obtain a time histogram. To enable efficient detection of desorbed fragments with higher molecular masses, which are of particular interest, we recently implemented a state-of art Field Programmable Gate Array (FPGA)-based multi-hit TOF acquisition. To test the system we used focused 8MeV 35Cl7+ ion beam with pulse length of 180ns. Mass resolution of measured SIMS spectra, dominantly determined by the duration of the beam pulse, is in good agreement with resolution estimated from pulse length. With improved high-voltage switching ability that will enable beam pulses with duration of 50ns, a mass resolution of better than 500 is anticipated.

Time-of-flight secondary ion mass spectrometry with transmission of energetic primary cluster ions through foil targets

We developed time-of-flight (TOF) secondary ion (SI) mass spectrometry that provides informative SI ion mass spectra without needing a sophisticated ion beam pulsing system. In the newly developed spectrometry, energetic large cluster ions with energies of the order of sub MeV or greater are used as primary ions. Because their impacts on the target surface produce high yields of SIs, the resulting SI mass spectra are informative. In addition, the start signals necessary for timing information on primary ion incidence are provided by the detection signals of particles emitted from the rear surface of foil targets upon transmission of the primary ions. This configuration allows us to obtain positive and negative TOF SI mass spectra without pulsing system, which requires precise control of the primary ions to give the spectra with good mass resolution. We also successfully applied the TOF SI mass spectrometry with energetic cluster ion impacts to the chemical structure characterization of organic thin film targets.

Gas Phase Initial Oxidation of Incoloy 800 Surfaces

The surface oxidation of Incoloy 800 was studied using dilute O2 gas at temperatures of 300 °C. Samples with two differing grain sizes were studied using time-of flight secondary ion mass spectrometry (ToF–SIMS) and X-ray photoelectron spectroscopy (XPS) as primary analysis tools. A multi-layered oxide film was detected and was composed of an exterior gamma-Fe2O3 with a Cr2O3 layer at the oxide–metal interface also containing significant concentrations of NiCr2O4. Minor concentrations of another spinel oxide, NiFe2O4 were distributed throughout the film. The kinetics of oxidation growth was found to follow a direct logarithmic relationship for both grain sizes, suggesting that the oxide would be a suitably protective. Very small oxide nodules formed at later stages, particularly for the small grained samples. A protocol for assessment of XPS spectral envelopes is advanced. The method measures the percent residual intensities remaining after spectral subtraction of reference spectra and appears to be an effective means for screening of possible components.

Mechanical studies of single glass fibres recycled from hydrolysis process using sub-critical water

The study reports mechanical performance of the recycled glass fibres produced from a water-based solvolysis technology, known as the hydrolysis process. The chemical reaction was carried out using sub-critical water to dissolve polyester resin and recover the glass fibres from composites. The effect of temperatures, times, catalyst and water amount on mechanical properties of the recovered glass fibres were investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and time-of flight secondary ion mass spectroscopy (ToF-SIMS) analyses were also employed to examine the fibre surface associated with the polyester resin eliminated level after the hydrolysis reaction. The results revealed that by carefully adjusting the hydrolysis parameters the tensile strength and failure strain of the recycled fibres decrease by approximately 40–70% in comparison with virgin fibres while Young’s moduli remain similar. The relationship between the hydrolysis conditions, recovered fibres and mechanical performance was discussed in this study.