Elemental Energy Dispersive Spectroscopy Research Articles

Biological Effects of a Three-Dimensionally Printed Ti6Al4V Scaffold Coated with Piezoelectric BaTiO3 Nanoparticles on Bone Formation.

Bone defect repair at load-bearing sites is a challenging clinical problem for orthopedists. Defect reconstruction with implants is the most common treatment; however, it requires the implant to have good mechanical properties and the capacity to promote bone formation. In recent years, the piezoelectric effect, in which electrical activity can be generated due to mechanical deformation, of native bone, which promotes bone formation, has been increasingly valued. Therefore, implants with piezoelectric effects have also attracted great attention from orthopedists. In this study, we developed a bioactive composite scaffold consisting of BaTiO3, a piezoelectric ceramic material, coated on porous Ti6Al4V. This composite scaffold showed not only appropriate mechanical properties, sufficient bone and blood vessel ingrowth space, and a suitable material surface topography but also a reconstructed electromagnetic microenvironment. The osteoconductive and osteoinductive properties of the scaffold were reflected by the proliferation, migration, and osteogenic differentiation of mesenchymal stem cells. The ability of the scaffold to support vascularization was reflected by the proliferation and migration of human umbilical vein endothelial cells and their secretion of VEGF and PDGF-BB. A well-established sheep spinal fusion model was used to evaluate bony fusion in vivo. Sheep underwent implantation with different scaffolds, and X-ray, micro-computed tomography, van Gieson staining, and elemental energy-dispersive spectroscopy were used to analyze bone formation. Isolated cervical angiography and visualization analysis were used to assess angiogenesis at 4 and 8 months after transplantation. The results of cellular and animal studies showed that the piezoelectric effect could significantly reinforce osteogenesis and angiogenesis. Furthermore, we also discuss the molecular mechanism by which the piezoelectric effect promotes osteogenic differentiation and vascularization. In summary, Ti6Al4V scaffold coated with BaTiO3 is a promising composite biomaterial for repairing bone defects, especially at load-bearing sites, that may have great clinical translation potential.

Multi-component (Al,Cr,Nb,Y,Zr)N thin films by reactive magnetron sputter deposition for increased hardness and corrosion resistance

Multi-component nitride thin films in the Al–Cr–Nb–Y–Zr system with non-equimolar composition have been deposited by reactive dc magnetron sputtering. The substrate temperature and substrate bias have been varied, from room temperature to 700 °C and from 0 to −200 V respectively. The relationship between these varied growth conditions on the structure, morphology, mechanical and corrosion properties of the films have been probed.All films consisted of a single solid solution with a NaCl-type structure, as shown by X-ray diffraction. However, elemental energy dispersive spectroscopy maps, obtained in the scanning transmission electron microscope, indicated that there could be partial segregation of Al, Cr and Y atoms within the grains. The microstructure of the films became denser, more fine-grained and smoother as the bias and temperature were increased. Nanoindentation showed that the hardness of the films increased with both bias and temperature, reaching a maximum of 27 ± 2 GPa. The corrosion resistance of the films, studied by performing potentiodynamic polarisation curves in 1 M HCl, was also found to be improved when compared to a commercially available hyper-duplex stainless steel and a ternary reference (Nb,Zr)N thin film as well.

Eighteen years of steel–bentonite interaction in the FEBEX in situ test at the Grimsel Test Site in Switzerland

ABSTRACTCorrosion of steel canisters containing buried high-level radioactive waste is a relevant issue for the long-term integrity of repositories. The purpose of the present study was to evaluate this issue by examining two differently corroded blocks originating from a full-scale in situ test of the FEBEX bentonite site in Switzerland. The FEBEX experiment was designed initially as a feasibility test of an engineered clay barrier system and was recently dismantled after 18 years of activity. Samples were studied by ‘spatially resolved’ and ‘bulk’ experimental methods, including Scanning Electron Microscopy, Elemental Energy Dispersive Spectroscopy (SEM-EDX), μ-Raman spectroscopy, X-ray Fluorescence (XRF), X-ray Diffraction (XRD), and 57Fe Mössbauer spectrometry, with a focus on Fe-bearing phases. In one of the blocks, corrosion of the steel liner led to diffusion of Fe into the bentonite, resulting in the formation of large (width > 140 mm) red, orange, and blue colored halos. Goethite was identified as the main corrosion product in the red and orange zones while no excess Fe2+ (compared to the unaffected bentonite) was observed there. Excess Fe2+ was found to have diffused further into the clay (in the blue zones) but its speciation could not be unambiguously clarified. The results indicate the occurrence of newly formed octahedral Fe2+ either as Fe2+ sorbed on the clay or as structural Fe2+ inside the clay (following electron transfer from sorbed Fe2+). No other indications of clay transformation or newly formed clay phases were found. The overall pattern indicates that diffusion of Fe was initiated when oxidizing conditions were still prevailing inside the bentonite block, resulting in the accumulation of Fe3+ close to the interface (up to three times the original Fe content), and continued when reducing conditions were reached, allowing deeper diffusion of Fe2+ into the clay (inducing an increase of 10–12% of the Fe content).

Weld overlay coating of Inconel 617 M on type 316 L stainless steel by cold metal transfer process

A study of microstructure and volumetric dilution of Cold Metal Transfer (CMT) clad of Nickel based super alloy, Inconel 617M on type 316L stainless steel (SS) substrate was carried out. Overlay coatings were deposited at three different current inputs (80, 90 and 100 A) to synergetic CMT welding set while the wire feed rate and pulse frequency were pre-programmed. The ability of CMT to produce very low dilution and low heat input with the minimal heat affected zone (HAZ), when compared to conventional Tungsten Inert Gas welding (TIG) process was successfully demonstrated. Detailed microstructural evaluation of the cross sections revealed porosity and crack free Inconel 617M overlay with complete fusion, making a metallurgical bonding at the interface. Transverse micro Vickers hardness evaluation from clad to substrate showed the absence of significant HAZ for overlay produced by CMT. Calculation of percentage volumetric dilution, based on elemental Energy Dispersive Spectroscopy (EDS) of Fe-K counts, revealed that the cladding deposited at 100 A current exhibited low dilution value of 6.3% at 100 μm away from the interface while clad produced by TIG show significantly higher dilution value of ~50% at 100 μm from interface. Electron Backscattered Diffraction (EBSD) studies revealed morphology similar to epitaxial growth, with same crystallographic orientation of grains across the interface for CMT overlaid coatings.

The effect of elemental vaporization and redistribution during sub-solvus recrystallization of a single crystal superalloy

The elemental vaporization and redistribution effect during sub-solvus recrystallization (1100°C) of a second-generation single crystal superalloy DD6 containing 2wt% Re has been investigated in this work. For fine polished specimens free from selective chemical erosion effect, accurate elemental energy dispersive spectroscopy (EDS) analysis was taken from the surface to the inner original matrix and across the boundary of the recrystallization reaction front. The results revealed that the vaporization induced elemental depletion of Ni and Al had occurred in the top surface layer. This would lead to the destabilization of the γ phase in the recrystallized aggregates, facilitating the final precipitation of refractory-rich P phase.

Raman microscopy study of synthetic cobalt blue spinels used in the field of art

AbstractThis study aims to provide a better understanding of the Raman spectra of cobalt‐based pigments in works of art. Systematic analyses of 21 industrial blue cobalt‐based pigments were carried out by using elemental energy dispersive spectroscopy and phase analyses by X‐ray diffraction (XRD) and Raman microspectroscopy, which led to the identification of 17 spinel Co‐based pigments. All the minerals contained in each pigment were characterised by all three techniques and subsequently attributed to diluents, extenders, mineralisers or unreacted reagents or to the main mineral phase, whether it was pure or contained doping or lattice modifier elements. In the particular case where doping elements were in low concentration in the host mineral lattice, their distinction by XRD from non‐doped spinel was impossible. On the contrary, Raman microspectroscopy turned out to be a perfect tool for detecting the presence of the doping agents in the spinel lattice. The determination of the elemental and mineralogical composition of the industrial blue cobalt‐based pigments commercially available for artists and studied in this survey represents a significant increase in the amount of analytical data available for this type of pigment as well as a valuable addition in the characterisation by Raman microspectroscopy of these compounds in situ, on works of art. Copyright © 2010 John Wiley & Sons, Ltd.

On the role of carbon in the formation and properties of hot pressed icosahedral Al-Cu-Fe phase

Al-Cu-Fe icosahedral (i) quasicrystal phase exists only within a restricted temperature range between 750 ◦C and 850 ◦C or at a very sharply defined composition around Al62Cu25.5Fe12.5 [1–3]. As a stable i-phase, interests in this system have arised mainly to study its quasiperiodic structure, its bulk and surface properties, and the possibility of growing large single quasicrystals [4–7]. Recently, starting from the Al-Cu-Fe system, work has been performed to study the effects of nonmetallic elemental additions such as oxygen and boron on the structure and stability of the icosahedral phase [8–10]. To the authors’ knowledge, however, no information exists on the effects of metalloid carbon addition on the alloys. In this paper, we present in situ carburization of the i-AlCuFe quasicrystalline phase prepared by the hot-pressing of gas atomized powders at a temperature for which it is thermodynamically stable. The influence of carbon on the formation and mechanical properties of the i-AlCuFe quasicrystalline phase is also studied to contribute to the understanding of the carburization behavior of bulk icosahedral Al-Cu-Fe phase. The starting materials were powders of the composition Al62Cu26Fe12 prepared by gas atomization of the liquid alloy. The majority of the sieved powder particles were less than 38 microns in diameter. The corresponding as-atomized structure consists of primary icosahedral (i) dendrites with small amount of τ phase in the interdendritic region [11]. The bulk quasicrystalline sample, a three-dimensional body 40 × 40 × 8 mm3, was fabricated by hot-pressing the powder particles. The hot-pressing process was performed in two steps. The former was a degassing process at a low temperature of 600 ◦C for 30 min under high-vacuum condition (5 × 10−5 Torr); the latter was a sintering and densification process of the icosahedral phase formed at a high temperature of 800 ◦C for 120 min under a pressure of 35 MPa. In the whole hot-pressing process, a graphite paper of approximately 0.5 mm was used as a separator to protect both graphite mold and graphite punch. In this case, the graphite paper is expected to behave as a carburizer and consequently to induce the contamination of the quasicrystalline forming alloys during hot pressing. The characterization of the hot pressed samples was performed as shown in Fig. 1 on the sample surface and its cross-section, respectively. First, the carbon distribution and microstructure were detected perpendicular to the cross section of sample. Second, a mechanical polishing method was used to remove the surface of the carburized sample layer by layer so as to obtain the depth profiles of the phase constituents and mechanical properties. It should be noted that the measurement of the initial surface started from the freshly abraded surface following the removal of the carbon film. The phase constituents and microstructure were assessed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The chemical analysis was carried out by X-ray energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES) for qualitative purposes, respectively. The Vickers microhardness Hv was determined from at least 15 different indentations, and the fracture toughness KIC was evaluated from the crack length initiated at the corners of the Vickers microindentation by using an empirical equation proposed by Niihara et al. [12]. The SEM image and the elemental EDS X-ray scans of the cross-section of the carburized sample are presented in Fig. 2. A continuous carbon film developed during hot-pressing can be seen on the surface of sample in the upper left-hand side image. The film thickness is about 35 μm. In addition, a spare dispersion of Al element in the carbon film was detected, as evidenced by the X-ray mapping of Al (middle left-hand side). This illustrates that the formation of this film results in the selective consumption of aluminum. Beneath the film a multiphase microstructure in the carburized sample can be observed; the multiphase assemblages were later identified further using XRD technique. Owing