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The microstructures of quenched and tempered steels have been traditionally explored by transmission electron microscopy (TEM) rather than scanning electron microscopy (SEM) since TEM offers the high resolution necessary to image the structural details that control the mechanical properties. However, scanning electron microscopes, apart from providing larger area coverage, are commonly available and cheaper to purchase and operate compared to TEM and have evolved considerably in terms of resolution. This work presents detailed comparison of the microstructure characterization of quenched and tempered high-strength steels with TEM and SEM electron channeling contrast techniques. For both techniques, similar conclusions were made in terms of large-scale distribution of martensite lath and plates and nanoscale observation of nanotwins and dislocation structures. These observations were completed with electron backscatter diffraction to assess the martensite size distribution and the retained austenite area fraction. Precipitation was characterized using secondary imaging in the SEM, and a deep learning method was used for image segmentation. In this way, carbide size, shape, and distribution were quantitatively measured down to a few nanometers and compared well with the TEM-based measurements. These encouraging results are intended to help the material science community develop characterization techniques at lower cost and higher statistical significance.

While a key reaction for oil upgrade, the hydrogenation of arenes substrates remains a challenging one, requiring the use of transition-metal catalysts and harsher reaction conditions than classic ...

In this study, the effect of Scanning Electron Microscopy (SEM) parameters such as magnification ( M ), accelerating voltage ( V ), and working distance (WD) on the 3D digital reconstruction technique, as the first step of the quantitative characterization of fracture surfaces with SEM, was investigated. The 2D images were taken via a 4-Quadrant Backscattered Electron (4Q-BSE) detector. In this study, spherical particles of Ti-6Al-4V (15-45 μm) deposited on the silicon substrate were used. It was observed that the working distance has a significant influence on the 3D digital rebuilding method via SEM images. The results showed that the best range of the working distance for our system is 9 to 10 mm. It was shown that by increasing the magnification to 1000x, the 3D digital reconstruction results improved. However, there was no significant improvement by increasing the magnification beyond 1000x. In addition, results demonstrated that the lower the accelerating voltage, the higher the precision of the 3D reconstruction technique, as long as there are clean backscattered signals. The optimal condition was achieved when magnification, accelerating voltage, and working distance were chosen as 1000x, 3 kV, and 9 mm, respectively.

A novel approach, termed line-rotated remapping (LRR), for high resolution electron backscatter diffraction is proposed to remap patterns with large rotation. In LRR, the displacements during the first-pass cross-correlation is modified to a function of the corresponding Kikuchi lines and the points on the reference pattern. Then, the finite rotation matrix to remap the test pattern to a similar orientation of the reference pattern is determined using the parameters of the Kikuchi lines. We apply LRR to simulated Si patterns with random orientations, and obtain measurement errors below ∼1.0 × 10

Despite high conductivity and large surface area, poor corrosion resistance limits the use of carbon black as a fuel cell catalyst support. Here, the formation of two titanium carbide-based core-shell nanostructures with an ultrathin layer of cobalt oxide were studied as alternative to carbon black. Titanium carbide was selected due to its electrical conductivity and high corrosion resistance. Two different nanostructures on TiC supports were prepared with Pt either on or below a cobalt oxide layer. For the sub-oxide Pt catalyst, the oxide could be removed selectively where it covered the Pt to make it partially exposed and catalytically available, yet sufficient Pt was anchored to the remaining oxide to provide stability. This anchoring prevented Pt nanoparticle detachment and aggregation as determined by ∼100% catalytic activity remained at 0.1 M KOH, and ∼92% catalytic activity remained at 0.1 M HClO4 after 16.7 h, room temperature. A core-shell model has computationally been investigated to confirm the function of the cobalt shell as diffusion barrier to protect carbide from oxidation.

Cu2ZnSnS4 or kesterite and its selenium alloyed counterparts are considered promising for next generation photovoltaic applications due to their excellent optoelectronic properties and earth-abundant, nontoxic composition. In order to alleviate the adverse effects of defects and interfaces on charge separation and transport in current thin film kesterite photovoltaics, new solutions such as the application of an inverted superstrate configuration have been proposed. In this article, sulfurized and selenized kesterite were deposited by solution processing on thin ALD Al2O3 coated TiO2 nanorods to fabricate novel nanostructured devices free of additional buffer layers and hole transfer materials (HTM). The selenized kesterite (CZTSSe) solar cell demonstrated an energy conversion efficiency of 1.85% with high Jsc of ∼20 mA/cm2 while the sulfurized kesterite (CZTS) device showed lower solar cell efficiency but excellent photodetecting properties under reverse bias with adjustable working window from visible-o...

Single crystalline austenitic stainless steel struts with a diameter of 250 μm were successfully fabricated using laser powder bed fusion (LPBF). The struts exhibited a strong 〈110〉 texture parallel to the building direction (BD). Excellent strength-ductility combination was achieved for the struts, which is attributed to the strengthening of the fine cellular sub-grains and the twinning-induce plasticity (TWIP) effect. After deformation, dynamic recrystallization (DRX) was observed and its presence is closely related to the unique microstructure of the single crystalline struts.

We propose a novel “Mn preservation-cold deformation-intercritical annealing” treatment for medium Mn steels. The process produces a large fraction of retained austenite with an enhanced stability, which increases the ductility by ~40% compared to the conventional single-step intercritical annealing in a model 10Mn steel, without sacrificing the ultrahigh strength level.

Lithium transition metal orthosilicates such as Li2FeSiO4 (LFS) have been recognized as promising cathode materials for application in Li-ion batteries because of their high theoretical energy density, safety, and benign/abundant element composition. Their development, however, has been hampered by the challenge of obtaining phase-pure and defect-free Li2FeSiO4 nanoparticles as non-optimized crystal properties have an adverse effect on structural stability and electrochemical performance. Considering the sustainable potential of hydrothermal synthesis in producing electrode materials, here we employ this process to systematically study critical synthesis parameters for optimal control of particle size, morphology, phase purity, and defects of Li2FeSiO4 crystallized in the orthorhombic crystal system with space group Pmn21. It is shown that via a combination of elevated FeSO4 concentration regime and use of EDTA as a complexing agent, phase-pure Pmn21 particle formation can be controlled. Synchrotron-based XRD Rietveld refinement and 57Fe Mossbauer spectroscopy reveal a significant reduction in Li-Fe antisite defects and presence of Fe3+. Additionally, the use of EDTA promotes the formation of unique peanut-shell looking hollow mesocrystals that are advantageous in maximizing electrode/electrolyte contact resulting in higher Li-ion storage capacity than dense LFS particles. On the basis of detailed XRD, SEM, and TEM characterizations, a four-step crystallization mechanism is proposed to explain the formation of the hollow mesocrystals. These findings bring new insight into our pursuit of optimization of Li2FeSiO4 as a cathode material for Li-ion batteries.

This paper will present state of the art characterization of Lithium Ion Batteries usimg low voltage EELS and EDS of Li using the SU-9000 STEM from Hitachi working at 30 keV and 3 keV. Extensive in-situ work in SEM of LIB made with Li anodes will also be presented.

Generating quantitative phase maps is unvaluable to access the phase distribution in a material. X-ray hyperspectral mapping using an energy dispersive spectrometer (EDS) attached to a scanning electron microscope (SEM) is the most practical way to collect these data, mainly due to its relatively ease of operation and availability around the world. In this work, we demonstrate an innovative technique to produce high-quality phase maps based on the correlation between each hyperspectral image pixel spectrum and a set of standards spectra. The standards spectra can be obtained experimentally from bulk specimens of known materials but also via analytical computations. The method is not only robust against electron beam current and spectrometer instabilities but also to statistical noise in the standards as well as in the hyperspectral image spectra. Equally, the method is reliable to produce phase distribution maps at low operating voltage where SEM-EDS quantitative x-ray microscopy is limited by many factors like peak overlapping, continuous background approximations and produces inaccurate phase maps. The results presented in this study will certainly open a new path to produce useful x-ray quantitative data and potentially break the locks of conventional x-ray microanalysis using EDS.

Electron tomography has been widely applied to three-dimensional (3D) morphology characterization and chemical analysis at the nanoscale. A HAADF-EDS bimodal tomographic (HEBT) reconstruction technique has been developed to extract high resolution element-specific information. However, the reconstructed elemental maps cannot be directly converted to quantitative compositional information. In this work, we propose a quantification approach for obtaining elemental weight fraction maps from the HEBT reconstruction technique using the physical parameters extracted from a Monte Carlo code, MC X-ray. A similar quantification approach is proposed for the EDS-STEM tomographic reconstruction. The performance of the two quantitative reconstruction methods, using the simultaneous iterative reconstruction technique, are evaluated and compared for a simulated dataset of a two-dimensional phantom sample. The effects of the reconstruction parameters including the number of iterations and the weight of the HAADF signal are discussed. Finally, the two approaches are applied to an experimental dataset to show the 3D structure and quantitative elemental maps of a particle of flux melted metal-organic framework glass.

A method of calculating the magnitude of the core hole screening of lithium materials is implemented for the simulation of Energy Loss Near Edge Structure (ELNES). ELNES is calculated for a range of lithium materials resulting in improved agreement between calculation and experiment. The technique uses linear response theory to relate the electron density to the core hole shielding contribution from the valence electrons in a crystal. This contribution is then implemented via a non-integer core hole in final state rule calculations.

In the past few decades, nanostructured carbons (NCs) have been investigated for their interesting properties, which are attractive for a wide range of applications in electronic devices, energy systems, sensors, and support materials. One approach to improving the properties of NCs is to dope them with various heteroatoms. This work describes the synthesis and study of sulfur-added carbon nanohorns (S-CNH). Synthesis of S-CNH was carried out by modified chemical vapor deposition (m-CVD) using toluene and thiophene as carbon and sulfur sources, respectively. Some parameters such as the temperature of synthesis and carrier gas flow rates were modified to determine their effect on the properties of S-CNH. High-resolution scanning and transmission electron microscopy analysis showed the presence of hollow horn-type carbon nanostructures with lengths between 1 to 3 µm and, diameters that are in the range of 50 to 200 nm. Two types of carbon layers were observed, with rough outer layers and smooth inner layers. The surface textural properties are attributed to the defects induced by the sulfur intercalated into the lattice or bonded with the carbon. The XRD patterns and X-ray microanalysis studies show that iron serves as the seed for carbon nanohorn growth and iron sulfide is formed during synthesis.

Cu2ZnSnS4 or kesterite was branded as “the dark horse of next-generation solar energy conversion” in a recent viewpoint article due to its advantageous inorganic, earth abundant, non-toxic composition over perovskites. It was also pointed out that an alternative device structure to thin-film configuration could be a key to unlock the full potential of kesterite photovoltaics. In response to this need herein a Cu2ZnSnS4 @TiO2 superstrate solar cell built via ethanol solution processing is described characterized by record efficiency of 5% and excellent stability. More specifically, lithium doping was found to promote kesterite grain growth and minimize interface charge recombination opening new prospects for kesterite photovoltaics.

This paper investigates the effect of depositing thick laser wire Ti-6Al-4V samples on the developed microstructure and subsequent mechanical properties. First, a thermal model is proposed to get a better understanding on the typical thermal cycles that the material has undergone. It is followed by a discussion on the typical structural features that developed in the as-built condition and following three post deposition heat treatments. A stress relief cycle did not substantially affect the morphology of the developed α platelets. Annealing and HIP followed by aging favored the coarsening of the post-deposited microstructure. A strengthening in terms of hardness has been observed only after the stress relief heat treatment. Developed static tensile properties were globally below the wrought levels. Stress-relieved specimens developed the higher strengths, whereas the annealed or HIPed samples followed by aging were associated with a better elongation. Charpy impact properties were higher in the annealed or HIPed condition followed by aging when compared with the stress-relieved ones. No anisotropy in the impact toughness properties was observed. The annealed and aged samples and the HIPed and aged samples produced overall very similar results showing that HIP is not required for enhance materials properties of laser wire deposition applications.

The cold spray technique may be used to fabricate metal matrix composites and to metallize ceramics. Both applications involve the creation of metal/ceramic interfaces, which are well researched for other processes but not nearly as much for cold spray. Here, the effect of ceramic substrate composition and surface roughness on adhesion strength of metallic splats is investigated. Splat adhesion testing was performed on Ti splats deposited on Al2O3 substrates with varying average reduced peak height roughness (Rpk) values. Ti splats sprayed onto Al2O3 with the lowest surface roughness had a higher bond strength (305 ± 87 MPa) than splats deposited on the higher surface roughness Al2O3 (237 ± 47 MPa). Failed interfaces revealed that the bonding mechanism for substrates with higher surface roughness is predominantly mechanical interlocking. Adhesion to the Al2O3 substrate with low surface roughness is predominantly along the periphery of the particle where jetting occurs. Splat adhesion testing was also performed on Ti splats deposited on SiC. Ti splats had a significantly higher bond strength to all Al2O3 substrates than to SiC. Posttest observations of SiC substrates showed little evidence of bonding. Several rebounded or detached splats left traces of Ti along the periphery of the impacted particle.

A number of techniques for the characterization of rare earth minerals (REM) have been developed and are widely applied in the mining industry. However, most of them are limited to a global analysis due to their low spatial resolution. In this work, phase map analyses were performed on REM with an annular silicon drift detector (aSDD) attached to a field emission scanning electron microscope. The optimal conditions for the aSDD were explored, and the high-resolution phase maps generated at a low accelerating voltage identify phases at the micron scale. In comparisons between an annular and a conventional SDD, the aSDD performed at optimized conditions, making the phase map a practical solution for choosing an appropriate grinding size, judging the efficiency of different separation processes, and optimizing a REM beneficiation flowsheet.

The effect of two travel speeds on thin Ti-6Al-4V buildups produced by Laser Wire Deposition (LWD) has been investigated. A travel speed set at 1.4 mm/s promoted recrystallization of columnar prior β grains into horizontal prior β grains. It was associated with lower strength hardly meeting minimum wrought requirements as set by the AMS4911. On the other hand, it was shown that by increasing the travel speed to 7.2 mm/s, sufficiently high cooling rates are occurring creating a fine α + β basket weave structure, while no recrystallization of the prior β grains has been observed. Tensile properties were improved with strength consistently exceeding minimum wrought requirements. An additional stress relief cycle preserved the effect of deposition parameters on material properties. A strong anisotropy in elongation was associated with the slower travel speed where higher values were derived along the Z direction. While the faster travel speed exhibited isotropic properties. Strengthening of the deposits has been observed following a stress relief cycle.

Secondary manufacturing processes used on electrical steels, such as mechanical or laser cutting, have a detrimental effect on the magnetic properties and increase the losses for electric motors. When the process is mechanical, there is both work hardening, and residual stress induced near the cut edge. The knowledge of the type of deterioration near the cut edge and the degree of deterioration is important for designing electrical machines in terms of magnetic field and loss calculations. The present paper evaluates the effect of punching on the microstructure and mechanical properties of non-oriented electrical steel. Scanning Electron Microscopy (SEM) and Electron backscattered diffraction (EBSD) analysis was performed on the cross section of the punched non-oriented electrical steel to study the evolution of microstructure and crystallographic texture near the edge whereas nanoindentation was used to determine the hardness profile. The observed mechanical properties were related to the microstructure near the edge, which was highly heterogeneous. The microstructure of the punched steel consisted of elongated grains and shear bands with ultrafine grains of size smaller than 500 nm. The hardness was maximum in a region where shear bands were observed in the punched microstructure and the value obtained was 4.54 GPa. This hardness increase, with respect to the average hardness of undamaged steel (3.15 GPa), was attributed to various factors such as grain refinement, work hardening and residual stress. Finally, pop-in analysis was done to study the extent of work hardening due to punching and its effect on hardness. The zero pop-in region was extended to a distance of 200 µm from the edge in the fracture section whereas it was 50 µm in roll over section.

The present study systematically investigated the effect of Si additions from 0 to 3 wt.% on the deformation mechanisms of a 0.2C-10Mn-3Al medium Mn steel. Two austenite-ferrite duplex microstructures, characterized by the different austenite characteristics (i.e. fraction and stability), were produced for different Si-alloyed steels by intercritical annealing and subsequently subjected to tensile testing. The influence of Si content on the activation and kinetics of transformation-induced plasticity (TRIP) effect, the formation of deformation twins, as well as the strain partitioning between phase constituents during deformation was studied in detail. For the low austenite fraction (∼30%) duplex structure with a high austenite stability (low Ms temperature), the tensile strength was only slightly changed with Si levels, whereas the uniform elongation was significantly influenced, with first an increase followed by a decreasing trend with higher Si contents. This was attributed to changes in strain partitioning between austenite and ferrite and to different extent of deformation twinning in austenite, which were highly dependent on the solute Si contents and the related microstructural changes. It was found that strain partitioning in this type of microstructure can result in a substantially high strain hardening rate and high uniform elongation. Conversely, for the samples with a high austenite fraction (∼45%) and low stability, the tensile properties were insensitive to the Si content, being mainly controlled by the TRIP effect. In this structure, a higher fraction of martensite was formed at the beginning of the plastic deformation, which decreased the strain partitioning between austenite and ferrite. The TRIP effect after the Luders strain is believed to be the main factor influencing the strain hardening rate of this type of structure.

In this work, it is demonstrated that by applying a nanoscale Al2O3 film via atomic layer deposition (ALD) to the Cu2ZnSnS4–TiO2 p/n junction, the adverse Sn doping effect is prevented and band alignment is optimized. EDS f-ratio mapping and XANES are used to confirm the purity and nanoscale homogeneity of CZTS. Thanks to the engineered interface by ALD Al2O3, high sensitivity photodetectors are designed exhibiting a novel voltage alterable spectral photoresponse. By further integrating a CdS interfacial layer, a TiO2–Al2O3–CZTS/Spiro-OMeTAD/Au solid state nanostructured solar cell is eventually fabricated with an enhanced energy conversion efficiency of 4.2%.

Nitrogen doped carbon nanotubes (N-CNT) were synthesized by a Modified Chemical Vapor Deposition method, using pyridine as carbon and nitrogen source, and ferrocene as catalytic agent for the nanotubes growth. The influence of synthesis parameters as the temperature, carrier gas flow rate, concentration of the reactants and preheating temperature over the morphology and physical properties of the N-CNT, were investigated by high-resolution scanning electron microscopy, transmission electron microscopy and X ray diffraction. The statistical analysis for the length of the N-CNT forest revealed that the synthesis temperature and carrier gas flow rate have significantly influenced on the physical properties of the material. The synthesis temperature not only affected the length of N-CNT forest, but also influenced the mass production, as well as, in diameter and the nitrogen content in the nanotubes. This is an important step towards the high yield production of N-CNT for applications in hydrogen storage, electrocatalysts for fuel cells and other electrochemical devices.

International audience; The effect of non-deformable submicron secondphase particles (d = 200-500 nm) on microstructural refinement during cold spray was examined. Using single particle impact testing, two types of splats were fabricated using two different feedstocks: a Cu-0.21wt.%O powder containing Cu2O second-phase particles and a single-phase Cu. Microstructural evolution analysis using high-resolution electron backscatter diffraction shows grain refinement occurred at a higher rate in the Cu-0.21wt.%O powder. That was due to dynamic recrystallization initiated by particle-stimulated nucleation (PSN). High-strain-rate deformation of cold spray was found to be the key to activate PSN. The present study suggests cold spray is apossible technique to fabricate ultrafine-grained materials by using feedstock containing second-phase particles.

Characterising the impact of lithium additions in the precipitation sequence in Al-Li-Cu alloys is important to control the strengthening of the final material. Since now, transmission electron microscopy (TEM) at high beam voltage has been the technique of choice to monitor the size and spatial distribution of δ' precipitates (Al3 Li). Here we report on the imaging of the δ' phase in such alloys using backscattered electrons (BSE) and low accelerating voltage in a high-resolution field-emission scanning electron microscope. By applying low-energy Ar+ ion milling to the surface after mechanical polishing (MP), the MP-induced corroded layers were efficiently removed and permitted the δ's to be visible with a limited impact on the observed microstructure. The resulting BSE contrast between the δ's and the Al matrix was compared with that obtained using Monte Carlo modelling. The artefacts possibly resulting from the sample preparation procedure were reviewed and discussed and permitted to confirm that these precipitates were effectively the metastable δ's. The method described in this report necessitates less intensive sample preparation than that required for TEM and provides a much larger field of view and an easily interpretable contrast compared to the transmission techniques.

Electron channelling is known to affect the x-ray production when an accelerated electron beam is applied to a crystalline material and is highly dependent on the local crystal orientation. This effect, unless very long counting time are used, is barely noticeable on x-ray energy spectra recorded with conventional silicon drift detectors (SDD) located at a small elevation angle. However, the very high count rates provided by the new commercially available annular SDDs permit now to observe this effect routinely and may, in some circumstances, hide the true elemental x-ray variations due to the local true specimen composition. To circumvent this issue, the recently developed f-ratio method was applied to display qualitatively the true net intensity x-ray variations in a thin specimen of a Ti-6Al-4V alloy in a scanning electron microscope in transmission mode. The diffraction contrast observed in the x-ray images was successfully cancelled through the use of f-ratios and the true composition variations at the grain boundaries could be observed in relation to the dislocation alignment prior to the β-phase nucleation. The qualitative effectiveness in removing channelling effects demonstrated in this work makes the f-ratio, in its quantitative form, a possible alternative to the ZAF method in channelling conditions.

A serious limitation in the use of energy dispersive spectrometers (EDS) for materials characterization arises from the fact that these x-ray detectors provide a poor energy resolution compared to other x-ray techniques. This is mainly due to the broadening function generated by the electronics of the detector. However, new windowless detectors are now capable of resolving low energy peaks like Li Kα with modified electronics and show a system peak full width at half maximum (FWHM) of around 30 eV. In this paper, we investigated how the Richardson-Lucy algorithm can be used to remove, or at least attenuate, the contribution of the broadening function to experimental spectra. This method proved to be efficient in improving the energy resolution at any energy in the EDS spectrum. The resulting system peak FWHM was reduced to as low as 7–8 eV and the separation of low energy x-ray peaks were demonstrated in the low energy range of the spectra. The method was also efficient in reducing the peak broadening at higher energies (Cu Kα) and the broadening function of the detector could be experimentally determined to provide higher accuracy in predicting peak broadening. Although some critical artefacts were noted on the restored spectra, like energy shifts and intensity variations, the method explored in this work is worth to be considered for further quantification tests.

Arsenic water pollution is a serious global environmental issue because of the high toxicity of this chemical element. Hence, the development of versatile materials that can efficiently remove different arsenic species from water is a global challenge. In this study, the bi-functionality of anatase TiO2 nanostructures (nanoparticles (TNP) and nanotubes (TNT)) for the simultaneous photo-oxidation of As(III) to As(V) and adsorption of the generated As(V) was evaluated, and the effect of morphology on the photo-oxidation and adsorption behaviors of the nanomaterials at different pH conditions was determined. In the dark, both the photocatalysts exhibited a remarkably high As(III) adsorption capacity in alkaline conditions because of the high hydroxylation of the nanomaterial surfaces at a basic pH. Upon irradiation, the As(III) ions completely oxidized into As(V) ions in a short time by the TNT and TNP samples at different initial pHs. However, compared with TNP, TNT exhibited a remarkably enhanced photoactivity because of their one-dimensional nanotubular morphology that facilitates the transfer of the photogenerated electron-hole to the surface, improving the hydroxyl radicals photogeneration. Moreover, post-reaction XPS analysis revealed that the As(III) ions adsorbed on TNP under dark conditions completely oxidized into As(V) upon irradiation. As evidenced by the experimental results, TNP exhibited excellent bi-functionality for arsenic removal since the As(V) ions generated by As(III) oxidation both on the material surface and in the aqueous medium were simultaneously adsorbed on the nanoparticle surface. Thus, a better understanding of the morphological effect on the photocatalytic system for oxidizing As(III) and adsorbing As(V) at different pHs was presented and mechanisms are proposed. The study provides guidance for the development of bi-functional nanoparticles through morphological design and surface engineering.

In the last decades, biomaterials have improved the life and its quality for millions around the Globe. Titanium-based biomaterials have rapidly become the gold standard for bone contact applications. Despite their successful performance, their low strength-ductility trade-offs and work-hardening rates limit their use for example for the manufacture of vascular stents. Although a high strength-ductility trade-off and a high work-hardening rate were reported for the TWIP/TRIP Ti–12Mo alloy, strengthening strategies are required to approach its strength to the ones of Co–Cr alloys, main metallic materials used to produce stents. In this study, the investigated strengthening strategy was the increase of oxygen content from 0.04 to 0.18 wt% in the Ti–12Mo alloy. The effect of this increase on its microstructure, mechanical properties and plastic deformation mechanisms was studied. Athermal ω precipitates were observed throughout with the β matrix of both solution-treated alloys. X-Ray diffraction and transmission electron microscopy suggested that the quantity of ω phase was larger in the alloy with a higher oxygen content, contrasting with the common knowledge that O suppresses ω phase precipitation. Independently of oxygen content, {332} twins and stress-induced martensite (SIM) α" occurred in the deformed microstructures. Based on the electron backscatter diffraction analyses, the area fraction of SIM α" decreased by increasing oxygen content. Although elongation decreased with this oxygen content increase, Ti–12Mo-0.18O exhibited a high true uniform elongation of 25% and a true ultimate tensile strength higher than the Ti–12Mo-0.04O alloy. Hardness and yield strength also increased by increasing oxygen content, while elastic modulus did not change.

Characterization of the topmost surface of biomaterials is crucial to understanding their properties and interactions with the local environment. In this study, the oxide layer microstructure of plasma-modified 316L stainless steel (SS316L) samples was analyzed by a combination of electron backscatter diffraction and electron channeling contrast imaging using low-energy incident electrons. Both techniques allowed clear identification of a nano-thick amorphous oxide layer, on top of the polycrystalline substrate, for the plasma-modified samples. A methodology was developed using Monte Carlo simulations combined with the experimental results to estimate thickness of the amorphous layer for different surface conditions. X-ray photoelectron spectroscopy depth profiles were used to validate these estimations.

Cavitation is the main defect encountered during superplastic forming (SPF) of thin sheet aluminum alloys. In the present paper, the influence of preforming operation (cold or hot) on the superplastic forming ability and quality of 1.6-mm-thick sheet of 5083 SPF aluminum alloy is investigated. Specifically, grain size evolution and the characteristics of the cavitation process are discussed as a function of prior deformation and the preforming temperature. Optical and field emission gun scanning electron microscopy (FEG-SEM) were used to study the characteristics of the cavities and microstructure evolution. Image processing was used to measure the surface and volume fractions of the cavities. The results indicate that hot preforming leads to a lower number of cavities per unit surface compared to cold preforming prior to the SPF operation. However, the average cavity sizes and the average grain size are higher in the case of hot preforming compared to cold preforming, which lead to higher susceptibility to crack formation and reduced SPF ability of the alloy.

Current quantitative X-ray microanalysis methods are only available for homogeneous materials. This paper presents a newly developed inverse modeling algorithm to determine both the structure and composition of two-dimensional (2D) heterogeneous materials from a series of X-ray intensity measurements under different beam energies and beam positions. It utilizes an iterative process of forward modeling to determine the optimal specimen to minimize the relative differences between the simulated and experimental characteristic X-ray intensities. The Monte Carlo method is used for the forward modeling to predict the X-ray radiation for a given specimen and experimental setup. Several examples of applications are presented for different types of samples with one-dimensional (1D) and 2D structures, in which the simulated X-ray intensities from phantom samples are used as input. Most of the results obtained from our algorithm agree well with the phantom samples. Some discrepancies are found for the voxels located at deeper depths of the 2D samples. And the discrepancies may be attributed to errors from the Monte Carlo simulations and from the variation of the X-ray range with beam energy. As a proof-of-concept work, this paper confirms the feasibility of our inverse modeling algorithm applied to 2D heterogeneous materials.

A commercial electron energy-loss spectrometer (EELS) attached to a high-resolution cold-field emission scanning electron microscope in transmission mode (STEM) is evaluated and its potential for characterizing materials science thin specimens at low accelerating voltage is reviewed. Despite the increased beam radiation damage at SEM voltages on sensitive compounds, we describe some potential applications which benefit from lowering the primary electrons voltage on less-sensitive specimens. We report bandgap measurements on several dielectrics which were facilitated by the lack of Cherenkov radiation losses at 30 kV. The possibility of volume plasmon imaging to probe local composition changes in complex materials was demonstrated using energy-filtered STEM, either via spectrum imaging or elemental mapping using the “three-windows” method. As plasmonic materials are increasing used for energy, electronics or biomedical applications, the ability of reliably evaluate their properties at low accelerating voltage in a SEM is very appealing and is demonstrated. The energy resolution of the spectrometer, taken as the full width at half maximum of the zero-loss peak, was routinely measured at around 0.55 eV and it is demonstrated that t/λ ratios up to 1.5 allowed practical EEL spectroscopy at 30 kV.

Hollow mesoporous silica capsules HMSC are potential drug transport vehicles due to their biocompatibility, high loading capacity and sufficient stability in biological milieu. Herein, we report the synthesis of ellipsoid shaped HMSC aspect ratio amp; 8764;2 performed using hematite particles as solid templates that were coated with a conformal silica shell through cross condensation reactions. For obtaining hollow silica capsules, the iron oxide core was removed by acidic leaching. Gas sorption studies on HMSC revealed mesoscopic pores main pore width amp; 8764;38 and a high surface area of 308.8 m2 g amp; 8722;1. Cell uptake of dye labeled HMSC was confirmed by incubating them with human cervical cancer HeLa cells and analyzing the internalization through confocal microscopy. The amphiphilic nature of HMSC for drug delivery applications was tested by loading antibiotic ciprofloxacin and anticancer curcumin compounds as model drugs for hydrophilic and hydrophobic therapeutics, respectively. The versatility of HMSC in transporting hydrophilic as well as hydrophobic drugs and a pH dependent drug release over several days under physiological conditions was demonstrated in both cases by UV vis spectroscopy. Ciprofloxacin loaded HMSC were additionally evaluated towards Gram negative E. coli bacteria and demonstrated their efficacy even at low concentrations 10 amp; 956;g ml amp; 8722;1 in inhibiting complete bacterial growth over 18 hours