Concentration Profiles Of Elements Research Articles

Assessing screening criteria for the radiocarbon dating of bone mineral

Radiocarbon dating of bone mineral (carbonate in the apatite lattice) has been the target of sporadic research for the last 40years. Results obtained by different decontamination protocols have, however, failed to provide a consistent agreement with reference ages. In particular, quality criteria to assess bone mineral radiocarbon dating reliability are still lacking.Systematic research was undertaken to identify optimal preservation criteria for bone mineral in archeological bones. Six human long bones, originating from a single site, were radiocarbon-dated both for collagen and apatite, with the level of agreement between the dates providing an indication of exogenous carbon contamination. Several techniques (Histology, FTIR, TEM, LA-ICP-MS) were employed to determine the preservation status of each sample.Research results highlight the importance of a micro-scale approach in establishing bone preservation, in particular the use of trace element concentration profiles demonstrated its potential use as a viable sample selection criterion for bone carbonate radiocarbon dating.

X-ray electron probe microanalysis of the reaction zone of thermally stimulated heterovalent anion substitution in the Ga 2 III Se 3 VI -GaAs solid-phase system

X-ray electron probe microanalysis (EPMA) was used to study the concentration profiles of the main reaction components in the Ga2Se3-GaAs heterojunction obtained as a result of thermally stimulated heterovalent anion substitution. It has been found that the quasi-equilibrium and quasi-steady diffusion modes for delivery of chalcogen to the reaction zone are different with respect to the kinetics of the A2IIIC3VI layer growth. Independent of this, the concentration profiles of the reaction elements are self-organized with time, which allows heterostuctures with a sharp interphase boundary to be reproduced.

A multi-ion beam microanalysis approach for the characterization of plasma polymerized allylamine films

A full characterization of plasma polymerized biofunctional films requires the use of multi-analytical approaches to determine the chemical composition, topography and potential interaction mechanisms of such films with biomolecules and cells. In this work we aim at underlining the versatility of ion-based techniques to contribute to the chemical characterization of plasma polymerized surfaces. The simultaneous use of energy recoil detection (ERD) and Rutherford backscattering (RBS) spectroscopies with incident He ions is an example of this versatility. Performing sequential measurements and the use of correlating computing tools for ERD-RBS interpretation allows providing in-depth concentration profiles of light elements, including namely hydrogen. More accurate analysis of light elements in polymer films can be increased by looking for particular ions with resonant backscattering responses (i.e., non-Rutherford Scattering). In particular, proton beams of 1.765 MeV are used to increase the detection of C and N, and particular incidence and detector angles to diminish the Si substrate contribution. These analytical tools have been applied to allylamine films and multi-layers crosslinked in a capacitive plasma onto both Si and porous Si substrates.

COMPUTER SIMULATIONS AND VERIFICATION OF GRADIENT ZONE FORMATION IN CEMENTED CARBIDES

The thermodynamic and kinetic databases for multi-component W-C-Co-Ti-Ta- Nb-N cemented carbides were established. The Thermo-Calc software was used to describe the phase composition of alloys during gradient sintering. Based on the established thermodynamic and kinetic databases, the volume fractions of different phases and elemental concentration profiles in the WC- Ti(C, N)-Co, WC-Ti(C, N)-TaC-Co and WC-Ti(C, N)-NbC-Co alloys were simulated by means of DICTRA software. The simulated results are in good agreement with the experimental data. In order to verify the reliability of the thermodynamic and kinetic databases, a gradiently sintered WC-Ti(C, N)-TaC-NbC-Co cemented carbide has been prepared. SEM and EDS were employed to examinate the microstructure and composition in the gradient zone. The gradient zone formation of the WC- Ti(C, N)-TaC-NbC-Co cemented carbides was then simulated by DICTRA, and the simulation results show a good agreement with the experimental results.

AN ASSESSMENT OF COMPOSITIONAL AND MORPHOLOGICAL CHANGES IN MODEL ARCHAEOLOGICAL GLASSES IN AN ACID BURIAL MATRIX

The degradation mechanisms of glass in a buried context result in surfaces that have been depleted in various elements. The stability of the glass is primarily affected by the burial environment and the glass composition. However, in all archaeological glasses, the corroded layer that is formed on the surface tends to be low in alkalis, high in silica and lacking in cohesion. The extent to which the material has degraded, along with the physical nature of the corrosion, has a profound effect upon a wide range of factors affecting the stability of artefacts, as well as the choice of conservation techniques to be employed. This study has a number of objectives: determination of the morphology of the surface of the leached layer in glasses of two different compositions with different surface finishes; examination of the transition between the corroded material and the unaffected substrate; and investigation of concentration profile of different elements within the surface layers, as a function of depth. The study uses two glasses, fabricated under laboratory conditions, to replicate two common glass types found in the historical environment; a soda–lime–silica glass typical of those found in the Roman period throughout the Mediterranean and northwestern Europe, and high‐lime–potash glasses typical of those of Western Europe in the late medieval period. Three different surfaces have been prepared to mimic alternative manufacturing techniques such as blown, cast and ground surfaces for each composition. The glasses have been corroded under controlled laboratory conditions to replicate the buried environment. Imaging and chemical information is obtained using SEM–EDX and morphological information using IFM to produce 3‐D mapping from topographical surfaces.

Modeling of Nucleation and Growth of M 23C 6 Carbide in Multi-component Fe-based Alloy

Three-dimensional atom probe (3DAP) technique has been used to study the nucleation and growth of M23C6 carbide in a supersaturated multi-component Fe-based alloy aged at 800°C. 3D images indicate that the radius of M23C6 carbide after ageing for 10 min is about 9 nm. Concentration profiles of alloy elements in the carbide are also obtained. Combined with PANDAT and Thermo-Calc software, attempts to model the early stages of precipitation are present. The calculated particle size and composition of M23C6 carbide is in good agreement with 3DAP data.

Reactive Diffusion upon Planar Dissolving Copper in Solder Melts

Problems of reactive diffusion at a solid phase - melt contact were studied theoretically. The main intention was to calculate the time course of the solid phase dissolving in the case of planar dissolving. In our work we give heed especially to the dominating process, which is the solid metal A dissolving in solder melt B. During the dissolving, melt B saturates with metal A, and the process is influenced by convections which are characteristic for a given experimental configuration. A theoretical description of the kinetics of solid phase dissolving in the melt will be presented for the case of planar dissolving. The aim is to derive a relation for the interphase boundary movement (t) depending on time and a time course of growth of the element A concentration in the melt B. There are difficulties in accurate determination of the interphase boundary movement after heating of specimens for certain time intervals. It should be performed experimentally, since intermetallic phases are formed in original metal A both via diffusion and upon cooling and some phases segregate upon cooling of the solidifying melt. The main intention was to study experimentally the copper dissolving in melts of various solder alloys and the related reactive diffusion. We used pure Sn and Sn-Cu, Sn-Ag-Cu, Sn-Sb, Sn-Zn alloys as solder materials. Experiments aimed at the study of a Cu plate dissolving in the solder melt were carried out at various selected temperatures and times. The problems of reactive diffusion were studied both theoretically and experimentally and the problems that have to be solved preferably were emphasized. Concentration profiles of elements and thickness of layers of phases can be determined with SEM and X-ray microanalyses (WDX, EDX) of specimens after their diffusion heating.

Modificação da superfície e das propriedades tribológicas do titânio por carbonitretação a plasma

Superfícies de TiCxNy foram produzidas por tratamento termoquímico auxiliado por mistura de plasma N2 - Ar - CH4. A influência da concentração do metano, bem como a inserção de átomos C e N na rede cristalina do Ti foram investigadas através da caracterização das propriedades tribomecânicas desse material. Para tanto, amostras de titânio comercialmente puro (grau II) foram carbonitretadas em plasma com mistura de x N2 - y Ar - z CH4 (onde x e y = 4 sccm e z variando de 2,3 e 4 sccm) a 500°C, durante 1 h. Os perfis de concentração de C e N após o tratamento foram analisados por reação nuclear (NRA). As fases na superfície foram identificadas por difração de raios-X com incidência rasante (GIXRD). Foi utilizado ensaio de pino sobre disco para determinação do coeficiente de atrito, cujas áreas desgastadas foram avaliadas por perfilometria e microscopia eletrônica de varredura (MEV). Foi observado que tanto o coeficiente de atrito quanto o mecanismo de desgaste do titânio foram fortemente dependentes da concentração de C e N na superfície. Porém, o perfil de concentração desses elementos intersticiais não foi diretamente proporcional ao fluxo de metano.

Development of matrix-matching hydroxyapatite calibration standards for quantitative multi-element LA-ICP-MS analysis: application to the dorsal spine of fish

A series of hydroxyapatite pellets were produced to use as matrix-matched standards for LA-ICP-MS analysis of trace metals in the first dorsal spine of tuna fish species (albacore tuna, Thunnus alalunga, and Atlantic bluefin tuna, Thunnus thynnus). These structures are interesting because they present growth rings and therefore could potentially be used as indicators of environmental pollution. The produced standards containing twelve analytes (Mg, Al, V, Mn, Zn, As, Sr, Rb, Cd, Ba, Hg and Pb) were prepared by co-precipitation of hydroxyapatite from calcium nitrate tetrahydrate and ammonium dihydrogen phosphate. Once synthesized, the concentration of the analytes in the standards was carefully determined in the laboratory and recoveries for the analytes were calculated. The hydroxyapatite enriched standards were found to be homogeneous and provided a linear calibration (correlation coefficients were better than 0.991 for most of the analytes). The methodology was applied to the determination of trace element concentration profiles in cross-sections of tuna fish dorsal spines. Limits of detection were estimated between 1.4 ng g−1 for cadmium and 751 ng g−1 for aluminium. The measured values for Mg, Zn, Sr and Pb in pelletized SRM 1486 Bone Meal were in good agreement with certified reference values.

Experimental and Theoretical Investigations of Hot Isostatically Pressed–Produced Stainless Steel/High Alloy Tool Steel Compound Materials

Consolidation of tool steel powders and simultaneous joining to a stainless 316L steel are performed by hot isostatic pressing (HIP). Two tool steel grades are considered: a high vanadium alloyed carbon tool steel, and a high vanadium and chromium alloyed nitrogen tool steel. The boundary layer arising during diffusion bonding is in focus and, in particular, the diffusion of carbon and nitrogen over the joint. Measurements of the elemental concentration profiles and corrosion tests by the double loop–electrochemical potentiokinetic reactivation (DL-EPR) method are performed. Comparative calculations with the DICTRA software are performed and are found to be in agreement with the experimental results. It is found that the carbon tool steel grade has a more critical influence on the corrosion resistance of the stainless 316L steel in comparison to the nitrogen tool steel grade.

Kinetic modeling of high temperature oxidation of Ni-base alloys

The rates of isothermal and cyclic oxidation and the elemental concentration profiles as a function of time of oxidation for a few Ni-base superalloys were determined through a modified Wagner’s oxidation model and the solution of coupled elemental diffusion equations. Thermodynamically calculated interfacial elemental concentrations and oxygen partial pressures for the multi-component Ni-base alloys were used as boundary conditions for the solution of Wagner’s equation and the elemental coupled diffusion equations (for Cr, Al and O). The multiple elemental diffusion and mass conservation equations were solved using a numerical procedure. The dependence of self/tracer-diffusivities of Cr, Al and O in the corundum phase on the oxygen partial pressures was deduced using a genetic algorithm based optimization procedure incorporating the experimental parabolic rate constants for several Ni-base alloys. Rates of cyclic oxidation were then deduced from the deterministic interfacial cyclic oxidation spalling model (DICOSM) developed by Smialek [1]. The calculated oxidation rates were in reasonable agreement with the experimental values for a range of multi-component Ni-base alloys.

Ion beam analysis of high pressure deposition of epitaxial PZT thin films

Abstract Epitaxial thin films of Pb(Zr 0.53 Ti 0.47 ) (PZT) ferroelectric ceramic were successfully grown on Sr(Nb)TiO 3 (SNTO) single crystal substrates by an high-pressure RF sputtering technique. Pure O 2 was used as working gas at a pressure above 1 Torr. The crystalline films properties were evaluated by θ –2 θ DRX scans. From these measurements we concluded that the PZT layers were single crystalline and c -axis oriented with a (001)PZT||(001)SNTO crystallographic relationship. Film composition and film–substrate interface characteristics were studied by bombardment of the samples with a 2560 keV 3 He + beam. Rutherford Backscattering (RBS) technique was applied to fit the experimental spectra in order to deduce the elemental depth concentration profile of the films. The high-pressured technique represents a useful and capable method to obtaining in situ epitaxial ferroelectric thin film with high quality structural, compositional and dielectric properties, without post deposit treatment.

Graded materials of (TiB2)pNi with nickel substrate prepared by field-activated pressure-assisted synthesis process

The preparation of functionally graded materials (FGMs) of (TiB2)pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process (FAPAS) was investigated. Ni3Al was chosen as a layer of FGM for the first time due to its great deal of heat released during its synthesis from nickel and aluminium powder. The microstructure, phase composition of layers, micro-hardness and elemental concentration profiles across interfaces were characterized. The significant inter-diffusion of elements between layers showed the formation of good bonds. The measured micro-hardness values of the sample increased monotonically to more than 3 500 HK over a distance of 2 mm from the nickel substrate to the surface layer (TiB2)pNi. The results of this investigation demonstrate the feasibility of the FAPAS process for rapid formation of FGMs with good diffusion bonds.

Characteristics of Diffusion Annealing Between Martensitic Stainless Steel and Nickel in the Form of Coating and Foil

Characteristics of interaction between martensitic stainless steel type AISI 410 with nickel in the form of coating layer and foil were investigated. Nickel was coated on AISI 410 substrate by electroplating in various thicknesses (6-16 μm). The 300-μm-nickel with purity of 99.9% was employed as a foil layer. All specimens were annealed in the temperature range of 700-900 °C for 5, 10, 15, and 60 min. Optical microscopy, SEM and EPMA analyzer were carried out in order to characterize the interdiffusion behavior differences between nickel and AISI 410 while using nickel layer in different form. It was observed that the thickness of nickel coating had a minor effect during annealing on the interaction between Ni and substrate at faying surface. However, the results show that the interaction of nickel coating layer with base material is much faster than foil layer during annealing process. This study suggests that the coating layer diffused faster to the substrate than foil layer; moreover, in the former case, heavy outer load was omitted. The concentration profiles were plotted for two cases. Although in case of using layer in the form of coating the annealing time was relatively short (5-15 min), it was observed that the concentration profiles for main elements had shapes close to the theoretical curve. For various thicknesses (6-16 μm) of Ni coating, the experimental results show that the interaction at faying surface caused the thickness of nickel coating growth. The diffusion zone width was plotted against the annealing temperature and time for both cases and the growth of the diffusion zones was compared.

WDX Studies on Ceramic Diffusion Barrier Layers of Metal Supported SOECs

AbstractSolid oxide electrolyser cells (SOECs) have great potential for efficient and economical production of hydrogen fuel. Element diffusion between the Ni‐cermet electrode and the metal substrate of metal supported cells (MSC) is a known problem in fuel cell and electrolysis technology. In order to hinder this unintentional mass transport, different ceramic diffusion barrier layers (DBLs) are included in recent cell design concepts. This paper is based on wavelength dispersive X‐ray fluorescence investigations of different SOEC and focuses on Fe, Cr and Ni diffusion between the metal grains of the cathode and the metal substrate. Due to the low detection limits and therefore high analytical sensitivity, wavelength dispersive electron probe microanalysis (EPMA) provides a precise method to determine element distribution, absolute element concentration and changes between the reference material and aged cells on a microstructural level by element mappings and concentration profiles. The results of this work show considerable concentration gradients in the metal grains caused by mass exchange during cell operation. Diffusion can be inhibited significantly by integrating different ceramic DBLs of doped LaCrO3‐type or doped LaMnO3‐type perovskite, either by vacuum plasma spraying (VPS) or physical vapour deposition technique (PVD).

Interfaced SEM/EDX and micro-Raman Spectrometry for characterisation of heterogeneous environmental particles — Fundamental and practical challenges

The molecular character of atmospheric particulate matter is of prime importance when interpreting air pollution trends and its subsequent influence on environmental monitoring and preventative conservation. The known methods of estimating the molecular composition normally involve elemental analysis of particles (both as bulk and computer controlled analyses of single particles) with subsequent multivariate analyses to clusterise the elements in groups of elements that are closely related to each other. With this approach one can at best suggest associations. Evidently the application of molecular spectroscopy in addition to elemental concentration profiles would provide intimate information regarding the nature of the particles and consequently their fate. This paper gives an overview of research performed in our laboratory and describes the optimisation of experimental parameters to use scanning electron microscopy with energy-dispersive X-ray detection (SEM/EDX) or electron probe X-ray microanalysis (EPXMA) in parallel with micro-Raman Spectrometry (MRS) to investigate single environmental particles. The challenges associated with the two stand-alone techniques are revealed and consequently those posed with an interfaced approach are discussed. Preliminary results, of an initial investigation of the SEM/EDX interfaced with MRS to ultra-fine heterogeneous environmental particles, are given.

Description of TiO 2 thin films treated in NH 3 atmosphere by optical dispersion models

The influence of a reductive ammonia atmosphere on TiO 2 sol-gel film structural and optical characteristics was investigated. X-ray Diffraction technique, X-ray photoelectron spectroscopy and Rutherford Back Scattering analysis were applied to study the crystallinity, oxidation state and element concentration profile of the modified films. Their optical properties were investigated by UV–Vis spectroscopy. The refractive index and extinction coefficient were obtained by fitting theoretical transmittance curves to experimental ones using Forouhi–Bloomer (FB) and Tauc–Lorentz (TL) physical models. Both models revealed slight decrease (up to 2.6–2.7 eV) of the FB and TL band gaps with increase of the treatment temperature. These results were discussed in terms of the additional energy levels creation due to the defect TiO 2 structure formation during thermal treatment in reductive atmosphere.

Titanium diboride–nickel graded materials prepared by field-activated, pressure-assisted synthesis process

The formation of four-layered functionally graded material (FGM) samples of TiB2–Ni/TiB2–Ni3A + Ni/Ni3Al/Ni by field-activated, pressure-assisted synthesis process (FAPAS) was investigated. The microstructure, phase composition of the interfaces, and mechanical properties of the graded material were characterized. Elemental concentration profiles across interfaces between layers showed significant interdiffusion, indicative of formation of good bonds. The measured microhardness values of the sample increased monotonically from the nickel substrate to the surface layer (TiB2–Ni). The values ranged from about 360 to over 3500 HK over a distance of 2 mm. The results of this investigation demonstrate the feasibility of the FAPAS process for rapid formation of FGMs with good diffusion bonds.

Processing for optically active erbium in silicon by film co-deposition and ion-beam mixing

Techniques of film deposition by co-evaporation, ion-beam assisted mixing, oxygen ion implantation, and thermal annealing were been combined in a novel way to study processing of erbium-in-silicon thin-film materials for optoelectronics applications. Structures with erbium concentrations above atomic solubility in silicon and below that of silicide compounds were prepared by vacuum co-evaporation from two elemental sources to deposit 200–270 nm films on crystalline silicon substrates. Ar + ions were implanted at 300 keV. Oxygen was incorporated by O +-ion implantation at 130 keV. Samples were annealed at 600 °C in vacuum. Concentration profiles of the constituent elements were obtained by Rutherford backscattering spectrometry. Results show that diffusion induced by ion-beam mixing and activated by thermal annealing depends on the deposited Si–Er profile and reaction with implanted oxygen. Room temperature photoluminescence spectra show Er 3+ transitions in a 1480–1550 nm band and integrated intensities that increase with the oxygen-to-erbium ratio.

Synthesis and characterization of TiB 2–Ni–Ni 3Al–CrNi alloy graded material by field-activated combustion

The formation of TiB 2–Ni/Ni 3Al/CrNi alloy functionally graded materials (FGMs) by field-activated combustion synthesis was investigated. Four-layered FGM samples of 50TiB 2–50Ni(wt%)/30TiB 2–70Ni/Ni 3Al/CrNi alloy were produced in which the intermetallic Ni 3Al was reactively formed during the process. Concentration profiles of elements across interfaces between layers showed significant inter-diffusion with indication of formation of diffusion bonding. Measured micro-hardness values increased smoothly from the steel substrate to the outer composite layer of 50TiB 2–50Ni. The values ranged from about 370 to over 3100 HK, over a distance of less than 2 mm. The results demonstrate the feasibility of the field-activated and pressure-assisted combustion synthesis to rapidly form FGMs with good diffusion bonding between the layers. Thermal shock and wear resistance of the FGM were investigated, the wear resistance of the FGM was shown to be higher than the base steel.