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• Dedicated scanning transmission electron microscope with low beam voltage (10 keV). • Electron energy loss spectroscopy (EELS) acquisition at 10, 20 and 30 keV. • Accurate elemental quantification by electron energy loss spectroscopy at 20 keV. Electron beam damage in electron microscopes is becoming more and more problematic in material research with the increasing demand of characterization of new beam sensitive material such as Li based compounds used in lithium-ion batteries. To avoid radiolysis damage, it has become common practice to use Cryo-EM, however, knock-on damage can still occur in conventional TEM/STEM with a high-accelerating voltage (200–300 keV). In this work, electron energy loss spectroscopy with an accelerating voltage of 30,20 and 10 keV was explored with h-BN, TiB 2 and TiN compounds. All Ti L 2,3, N K and B K edges were successfully observed with an accelerating voltage as low as 10 keV. An accurate elemental quantification for all three samples was obtained using a multi-linear least square (MLLS) procedure which gives at most a 5 % of standard deviation which is well within the error of the computation of the inelastic partial-cross section used for the quantification. These results show the great potential of using low-voltage EELS which is another step towards a knock-on damage free analysis. [ABSTRACT FROM AUTHOR]

An in situ monoclinic variants selection and rearrangement study on Y2O3–ZrO2 coatings was conducted using electron backscattered diffraction. The sequence growth of variants with the correspondence of (100)m ∼// (010)t, [010]m ∼// [001]t, and [001]m ∼// [100]t (CAB‐OR2) was found initially and converted to the 90°‐rotated sequence growth with (100)m ∼// (100)t, [001]m ∼// [001]t, and [010]m ∼// [010]t (ABC‐OR2) after heat treatment. In another coating, most of the variants first exhibited interleaving growth and changed to typically fourfold growth. This in situ evolution of both variants orientation relationship and arrangement revealed the effects of stress and stress relief on the martensitic transformation. Moreover, the variants selection might be diversified during the cyclic transformation, and the classical phenomenological theory could mainly be proved by the transformation triggered by temperature, instead of external stress. Furthermore, the variants orientation relationship was exactly confirmed by the tetragonal grain reconstructions. In particular, the orientation variation of reconstructed tetragonal grains was also found and could mainly be explained by the behavior of stress relief and dynamic recrystallization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Combining climbing-image nudge elastic band (CI-NEB) method with the sudden approximation approach enhances the accuracy of determining the threshold displacement energies. • Monte Carlo simulation and theoretical calculations can be used to study the knock-on damage in materials. • At moderate beam energies, the knock-on damage is maximized in Li-containing materials (Lithium battery materials). Thus, very low or very high beam energies offer lower knock-on damage. • While threshold displacement energy (TDE) is the principal parameter for assessing the Li sensitivity to knock-on damage across similar structures, other parameters, including cross-section, density, weight fraction, atomic weight, and atomic number, can impact the knock-on damage. To fulfill power and energy demands, lithium-ion battery (LIB) is being considered as a promising energy storage device. For the development of LIBs, high-resolution electron microscopy characterization of battery materials is crucial. During this characterization, the interaction of beam-electrons with Li-containing materials causes damage through several processes, especially knock-on damage. In this study, we investigated this damage by determining the probability of knock-on damage and performing Monte Carlo simulation. For this objective, the threshold displacement energies (TDEs) were computed using sudden approximation technique for three sets of materials, including pure elements, LiX (X = F , Cl, Br), and Li 2 MSiO 4 (M = Fe, Co, Mn). By including the Climbing-Image Nudge Elastic Band (CI-NEB) method into the sudden approximation approach, it was found that the accuracy of the predicted TDEs could be improved. Results also indicated that at moderate electron energies, the knock-on damage for Li in both its elemental and compound forms maximized. In addition, it was shown that the TDE should be the principal parameter for assessing the Li sensitivity to knock-on damage across similar structures. Nonetheless, other parameters, including cross-section, density, weight fraction, atomic weight, and atomic number, were found to impact the knock-on damage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highlights • An electron energy-loss spectrometer was installed on a cold-field emission scanning electron microscope (SEM). • The use of low accelerating voltage in a SEM in transmission mode allows reducing delocalization and beam damage as well as preventing Cherenkov radiation losses. • The energy resolution of the spectrometer was about 0.5 eV and was sufficient to record high quality core-loss and low-loss data in the SEM in transmission mode. • Bandgap measurement was facilitated at low beam voltage as Cherenkov radiations do not occur for materials of refractive index lower than 3 at E 0 = 30 kV. • Low-loss spectrum imaging and elemental mapping with the "three-windows" technique provided substantial information regarding alloy composition and plasmonic properties. Abstract 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (Al3Li). 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. [ABSTRACT FROM AUTHOR]

The effect of non-deformable submicron second-phase 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 CuO 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 a possible technique to fabricate ultrafine-grained materials by using feedstock containing second-phase particles. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• A new line-rotated remapping (LRR) for HR-EBSD is proposed to effectively measure elastic strain with large lattice rotation. • The maximum lattice rotation that can be remapped by LRR was as large as ∼26°, the deviation is smaller than ∼1.0 × 10–3, using the simulated Si patterns. • The tolerance angle is influenced by the number of matched Kikuchi bands, and decreases with the increase of detection distance. • The LRR method is applied to experimentally evaluate the deformation mechanism of Ni. 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 × 10−3 for lattice rotations up to ∼26°. The maximum angle that may be remapped by LRR decreases with the distance between the specimen and the screen, which in turn reduces the number of matched Kikuchi lines. We also employ LRR in experiments to quantitatively characterize rotations and elastic strains of a Ni single crystal subject to nanoindentation and tension measurements. Although more experimental data on pattern center and image contrast are required to properly assess the performance of LRR, our method is a promising technique to improve strain measurements in the presence of large rotations. [ABSTRACT FROM AUTHOR]

• The correlation technique indicates how good an experimental EDS spectrum matches a specific phase in a standard spectrum library. • The correlation technique is robust to statistical acquisition noise. • The method is suitable for accurate phase recognition at low beam voltage. • Computed standards spectra using analytical models can be used to generate a standard library and provide phase differentiation. 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. [ABSTRACT FROM AUTHOR]

Dark-field (DF) images were acquired in the scanning electron microscope with an offline procedure based on electron backscatter diffraction (EBSD) patterns (EBSPs). These EBSD-DF images were generated by selecting a particular reflection on the electron backscatter diffraction pattern and by reporting the intensity of one or several pixels around this point at each pixel of the EBSD-DF image. Unlike previous studies, the diffraction information of the sample is the basis of the final image contrast with a pixel scale resolution at the EBSP providing DF imaging in the scanning electron microscope. The offline facility of this technique permits the selection of any diffraction condition available in the diffraction pattern and displaying the corresponding image. The high number of diffraction-based images available allows a better monitoring of deformation structures compared to electron channeling contrast imaging (ECCI) which is generally limited to a few images of the same area. This technique was applied to steel and iron specimens and showed its high capability in describing more rigorously the deformation structures around micro-hardness indents. Due to the offline relation between the reference EBSP and the EBSD-DF images, this new technique will undoubtedly greatly improve our knowledge of deformation mechanism and help to improve our understanding of the ECCI contrast mechanisms. [ABSTRACT FROM AUTHOR]

Based on results recorded on real materials with new generation field-emission scanning electron microscopes (FE-SEMs), the actual potential of the technique is evaluated. Nanoscale characterization of bulk and nanomaterials using Z-contrast imaging, X-rays and Kikuchi diffraction is presented. The advantage of using the full range of accelerating voltages of the FE-SEM is demonstrated on an energy storage material, and the benefit of using diffraction contrast imaging in bulk crystalline materials to characterize stacking faults, dislocation structures and nanotwins is illustrated. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties of non-oriented electrical steels (NOES) are an important factor in determining the efficiency of electric vehicle drivetrains. Due to the highly variable texture of NOES, the relationships between crystal orientation, the magnetic domain structure, and the final magnetic properties are complicated and not fully understood. In this study, a NOES sample was characterized with a method capable of imaging surface magnetic domains using scanning electron microscopy (SEM) with an electron backscatter diffraction (EBSD) system equipped with a forescatter detector. This method used type II magnetic contrast without a specialized SEM setup, and imaged with a resolution limit of approximately 250–300nm. The domain structure of the NOES sample was successfully related to β, which was defined as the angle between the closest magnetic easy axis and the surface of the sample (the RD–TD plane). However, it was shown that if the easy axes were aligned between neighbouring grains with respect to the grain boundary normal, the domain structure could align with an easy axis that was not the closest to the surface, and complex domain structures could be become wider. This structure and width change of complex domain structures has not been previously observed from single crystal or large-grained material studies. The successful application of this method to reveal the influence of surrounding grains can be used to better understand the magnetic properties of NOES. [Copyright &y& Elsevier]

Grain boundary diffusion of Al in polycrystalline Mg was measured from diffusion couple experiments between 603 and 693K by high-resolution scanning electron microscopy microanalysis. Grain boundary diffusion of Al is found to increase with increasing misorientation between adjacent Mg grains, and the grain boundary diffusion coefficients of Al can be two orders of magnitude faster than the volume diffusion of Al in Mg. The difference between grain boundary and volume diffusion of Al becomes larger at lower temperatures. [ABSTRACT FROM AUTHOR]

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from −20° to −40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. SCANNING 35:375-386, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

While conventional mechanical and chemical polishing results in stress, deformation and polishing particles embedded on the surface, flat milling with Ar+ ions erodes the material with no mechanical artefacts. This flat milling process is presented as an alternative method to prepare a Pb–Ag alloy cross-section for scanning electron microscopy. The resulting surface is free of scratches with very little to no stress induced, so that electron diffraction and channelling contrast are possible. The results have shown that energy dispersive spectrometer (EDS) mapping, electron channelling contrast imaging and electron backscatter diffraction can be conducted with only one sample preparation step. Electron diffraction patterns acquired at 5 keV possessed very good pattern quality, highlighting an excellent surface condition. An orientation map was acquired at 20 keV with an indexing rate of 90.1%. An EDS map was performed at 5 keV, and Pb–Ag precipitates of sizes lower than 100 nm were observed. However, the drawback of the method is the generation of a noticeable surface topography resulting from the interaction of the ion beam with a polycrystalline and biphasic sample. [ABSTRACT FROM PUBLISHER]

• The Richardson-Lucy (RL) algorithm was successfully applied to energy dispersive spectrometer (EDS) spectra for spectrum deconvolution by using the system (noise) peak of the spectrometer as the point spread function (PSF). • The spectrometer system peak full width half maximum (FWHM) of a windowless silicon drift detector was reduced to 7–8 eV after restoration. • RL deconvolution could be applied to any energy levels of the spectrum by computing a synthetic PSF based on the broadening function of the spectrometer which depends on the process time used. • An experimental relation between the X-ray peak energies and the FWHM values could be obtained experimentally on microanalysis standards and the parameters for calculating the theoretical broadening could be determined by least-square fitting. • Peak energy shift and intensity ratio variations were measured after restoration and must be accounted for quantification purposes. 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. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The application of Ti-48Al-2Cr-2Nb (TiAl-4822) produced by laser powder bed fusion (LPBF) is hindered by its severe cold cracking susceptibility caused by the intrinsic brittleness of α 2 and γ phase. Although the high cooling rate of LPBF is normally deemed detrimental for brittle materials, the present study proposed a counterintuitive strategy to mitigate cold cracking, by taking advantage of the high cooling rate rather than suppressing it. By reducing laser input energy, the cooling rate of LPBF increased, which led to the formation of a massive ductile β phase. The unique β and α 2 phase distribution and the transition of β → α 2 were also revealed, further proving the presence of the massive β phase. Compared with the sample without β phase, the β-containing sample successfully mitigated cold cracking. This study shows a novel method to alleviate the cracking problem of LPBF-processed TiAl-4822, providing new insights into the future LPBF process design of TiAl-4822 and other TiAl-based alloys. • A novel strategy to mitigate cracking in the intrinsically brittle Ti-48Al-2Cr-2Nb (TiAl-4822) processed by additive manufacturing • Taking advantage of the high cooling rate in laser powder bed fusion, which is normally considered detrimental. • Massive β phase was achieved in TiAl-4822 for the first time • Acicular microstructure in TiAl-4822 was first observed • A modified continuous cooling transformation (CCT) diagram for TiAl-4822 [ABSTRACT FROM AUTHOR]

The majority of studies performed on the formation of surface features by femtosecond laser radiation focuses on single scan procedures, i.e. manipulating the laser beam once over the target area to fabricate different surface topographies. In this work, the effect of scanning stainless steel 304 multiple times with femtosecond laser pulses is thoroughly investigated over a wide range of fluences. The resultant laser-induced surface topographies can be categorized into two different regimes. In the low fluence regime ( F Σline,max < 130 J/cm 2 ), ellipsoidal cones (randomly distributed surface protrusions covered by several layers of nanoparticles) are formed. Based on chemical, crystallographic, and topographical analyses, we conclude that these ellipsoidal cones are composed of unablated steel whose conical geometry offers a significant degree of fluence reduction (35–52%). Therefore, the rest of the irradiated area is preferentially ablated at a higher rate than the ellipsoidal cones. The second, or high fluence regime ( F Σline,max > 130 J/cm 2 ) consists of laser-induced surface patterns such as columnar and chaotic structures. Here, the surface topography showed little to no change even when the target was scanned repeatedly. This is in contrast to the ellipsoidal cones, which evolve and grow continuously as more laser passes are applied. [ABSTRACT FROM AUTHOR]

The microstructure of a deformed Mg-Al-Ca alloy was imaged using an electron-beam energy of 20 keV in a cold field-emission scanning electron microscope. The backscattered electron (BSE) micrographs showed a non-uniform contrast, the simplest being in the form of parallel contours inside a number of grains. This contrast is described as rotation contour contrast (RCC) and is attributed to local rotation of the crystal during the deformation of the grain. A model is presented to relate the rotation of crystal planes about one rotation axis to the channeling contrast in the channeling pattern and, consequently, to RCC in the BSE micrograph. This model was validated with the electron backscatter diffraction technique such that the RCCs in the BSE micrograph were reconstructed using the electron backscatter diffraction pattern intensities. The appearance of the RCCs was attributed to the change in the electron-beam position across a Kikuchi band due to local crystal rotation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The Zr–2.5Nb pressure tube alloy used in Canada Deuterium Uranium (CANDU) nuclear reactors consists of a dual-phase microstructure produced by a multi-step manufacturing process. The metallurgical characteristics of the pressure tubes influence their in-reactor behavior, especially with respect to reactor life-limiting properties such as diametral creep. In order to predict the in-reactor behavior of pressure tubes, a greater understanding of the influence of tube-to-tube variations in metallurgical factors such as texture, grain size, and β-phase percentage would be greatly beneficial. In this paper, a testing method combining high temperature nanoindentation with subsequent electron channeling contrast imaging (ECCI) in the scanning electron microscope (SEM) is presented to compare two back end pressure tube off-cuts. Nanoindentation was used to measure local mechanical properties such as hardness, modulus, and strain rate sensitivity. Post-examination of residual indents with ECCI allowed for the correlation of microstructural characteristics to nanomechanical properties. A difference in hardness was observed between the two tubes in the axial normal plane, which was correlated to differences in β-phase area percentage and/or morphology. [Copyright &y& Elsevier]

Abstract: This paper reports an analytical method for the comprehensive two-dimensional gas chromatography (GC×GC) separation and identification of nitrogen compounds (N-compounds) in middle distillates according to their types (basicity). For the evaluation of the best chromatographic conditions, a non-polar×polar approach was chosen. The impact of the second dimension (stationary phase and column length) on the separation of basic and neutral N-compounds was evaluated by mean of two-dimensional resolution. This study revealed that the implementation of polar secondary column having free electron pairs improves drastically the separation of N-compounds. Indeed, the presence of permanent dipole-permanent dipole interactions between neutral N-compounds and the stationary phase was enlightened. The comparison of two different nitrogen chemiluminescence detectors (NCD) was also evaluated for GC×GC selective monitoring of N-compounds. Owing to higher resolution power and enhanced sensitivity achieved using developed chromatographic and detection conditions, it was possible to identify univocally and to quantitate N-compounds (i) by class of compounds and (ii), within a class, by carbon number. Finally, quantitative comparison of GC×GC-NCD with conventional gas chromatography illustrates the benefits of GC×GC leading to an excellent correlation with results obtained by American Society for Testing Materials (ASTM) methods for the determination of basic/neutral nitrogen ratio in diesel samples. [Copyright &y& Elsevier]

• A novel quantitative inverse modeling algorithm for WDS/EDS data is proposed. • The algorithm extracts the structural and compositional information simultaneously. • The feasibility of the algorithm applied to 2D heterogeneous materials is shown. 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. [ABSTRACT FROM AUTHOR]

• DFT (LAPW+Lo) is a well-established technique for calculating EELS near-edge fine structure of materials • A partial core hole is often used to simulate the final state of an ionisation event, due to electron shielding • A novel strategy is proposed to asses the electronic shielding and therefore the required value of the core hole • Good fit with experimental data is achieved • Quantitative EELS at 30 keV 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. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel Li 2 FeSiO 4 mesocrystals exhibit improved Li-ion storage properties. • EDTA-regulated formation of impurity-free and defect-free hollow Pmn2 1 crystals. • Li 2 FeSiO 4 mesocrystals form via a 4-step hydrothermal crystallization mechanism. Abstract Lithium transition metal orthosilicates such as Li 2 FeSiO 4 (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 Li 2 FeSiO 4 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 Li 2 FeSiO 4 crystallized in the orthorhombic crystal system with space group Pmn 2 1. It is shown that via a combination of elevated FeSO 4 concentration regime and use of EDTA as a complexing agent, phase-pure Pmn 2 1 particle formation can be controlled. Synchrotron-based XRD Rietveld refinement and 57Fe Mössbauer 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 Li 2 FeSiO 4 as a cathode material for Li-ion batteries. [ABSTRACT FROM AUTHOR]

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 Lüders strain is believed to be the main factor influencing the strain hardening rate of this type of structure. [ABSTRACT FROM AUTHOR]

Titanium-based biomaterials are the gold standard for orthopedic implants; however, they are not generally suitable for the manufacture of intravascular stents. Their low strength-ductility trade-off and low work hardening rate are their main limitations. However, Ni-free alloys are desirable for such application in order to avoid allergic reactions caused by the high Ni-content materials currently applied. Therefore, in this study, three alloys of the Ti-Mo-Fe system (Ti-8Mo-2Fe, Ti-9Mo-1Fe and Ti-10.5Mo-1Fe) were designed to present high strength-ductility compromise and high work hardening rate. Their microstructures, mechanical properties and plastic deformation mechanism were investigated. Athermal ω precipitates were observed in the β matrix of all solution-treated alloys. In the solution-treated β matrix of the Ti-9Mo-1Fe alloy, additional nanometer-sized α" particles were detected by transmission electron microscopy (TEM). Although the combined TWIP/TRIP effects were expected by the design method on the Ti-8Mo-2Fe and Ti-9Mo-1Fe alloys, no TRIP effect was actually observed. In fact, stress-induced martensitic (SIM) transformation occurred mainly at the {332}<113> twins/matrix interfaces for all the strained microstructures and acted as a localized stress-relaxation mechanism, delaying the fracture. Based on the electron backscatter diffraction (EBSD) analyses, in the Ti-8Mo-2Fe and Ti-10.5Mo-1Fe alloys, the formation of a dense network of {332}<113> twins was responsible for their high and steady work hardening rates (1370 and 1120 MPa) and large uniform elongations (22% and 34%). The absence of SIM α" as the primary mechanism of plastic deformation and solid solution hardening of Fe resulted in their high strengths (yield strength of 772 and 523 MPa). In Ti-9Mo-1Fe, the formation of mechanical twinning was hindered, resulting in limited strain-hardening capability and low uniform elongation (6%). The nanometer-sized α" particles in its β matrix along with the athermal ω precipitates are thought to impair the mechanical twinning and the ductility of this alloy. • Coexistence of α" and athermal ω particles was found in the β matrix of Ti-9Mo-1Fe. • Nanometer α" particles in Ti-9Mo-1Fe are thought to hinder mechanical twinning. • Bo-Md method failed in predicting TRIP effect in Ti-8Mo-2Fe and Ti-9Mo-1Fe alloys. • Stress-induced martensite was mainly formed at twin/matrix interfaces. • Stress-induced martensite acted as a stress-relaxation mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Uniaxial compression tests were carried out at room temperature and at strain rates of 0.001, 0.01, 0.1 and 1s−1 on samples of high-purity titanium. The initial texture was favorably oriented for contraction twinning. The double-differentiation method was employed to detect the initiation of twinning as well as of dynamic recrystallization. Critical strains of about −0.24 and −0.65 were determined, respectively, for these two mechanisms. The relevant mechanisms were identified by means of electron backscatter diffraction (EBSD) techniques. At a true strain of ε =−0.3, two main kinds of primary twins, contraction and extension, were observed and second-generation twins were also identified by means of the EBSD analysis. The presence of low Schmid factor (SF) (<0.2) twins was established as well as the absence of potential high SF (>0.4) twins. The appearance of the low SF twins is explained in terms of the low accommodation work required in the neighboring grains; this involves prismatic glide in the present case. The absence of the potential high SF twins, on the other hand, is justified as requiring the operation of a combination of several difficult deformation modes: basal glide, pyramidal glide, and twinning. [Copyright &y& Elsevier]

[Display omitted] • Arsenic photo-oxidation/adsorption bi-function by TiO 2 nanostructures was studied. • Correlation between generated ROS and photocatalytic activity was established. • One-dimensional morphology of TiO 2 nanotubes promotes higher As(III) photooxidation. • Bi-functional behavior took place exclusively on TiO 2 nanoparticles. • Higher density of –OH groups favors As(V) adsorption by the complexes formation. 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 TiO 2 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. [ABSTRACT FROM AUTHOR]

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}<113> 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. [ABSTRACT FROM AUTHOR]

• A novel quantification approach is proposed for STEM tomography. • 3D high-resolution quantitative element maps are reconstructed. • HAADF-EDS bimodal tomography shows advantages compared with EDS-STEM tomography. 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. [ABSTRACT FROM AUTHOR]