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A correlation between band alignment at an electron transport layer/perovskite interface and the locus of hysteresis in perovskite solar cells is proposed.

Hot-pressing leads to low temperature densification of garnet type Li5La3Bi2O12 solid electrolyte and density functional theory calculations allow to explore its metastable properties under the formation of impurities.

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.

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

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 ...

Dendrite formation, which could cause a battery short circuit, occurs in batteries that contain lithium metal anodes. In order to suppress dendrite growth, the use of electrolytes with a high shear modulus is suggested as an ionic conductive separator in batteries. One promising candidate for this application is Li7La3Zr2O12 (LLZO) because it has excellent mechanical properties and chemical stability. In this work, in situ scanning electron microscopy (SEM) technique was employed to monitor the interface behavior between lithium metal and LLZO electrolyte during cycling with pressure. Using the obtained SEM images, videos were created that show the inhomogeneous dissolution and deposition of lithium, which induce dendrite growth. The energy dispersive spectroscopy analyses of dendrites indicate the presence of Li, C, and O elements. Moreover, the cross-section mapping comparison of the LLZO shows the inhomogeneous distribution of La, Zr, and C after cycling that was caused by lithium loss near the Li electrode and possible side reactions. This work demonstrates the morphological and chemical evolution that occurs during cycling in a symmetrical Li–Li cell that contains LLZO. Although the superior mechanical properties of LLZO make it an excellent electrolyte candidate for batteries, the further improvement of the electrochemical stabilization of the garnet–lithium metal interface is suggested.

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.

Monte Carlo simulations are commonly used in elemental quantification using energy-dispersive spectroscopy (EDS). Here, the Monte Carlo program MC X-ray was incorporated into the image processing software Dragonfly by Object Research Systems (ORS) as a simulation library. The simulation program has been transformed into a complete microscope simulator where the tools of Dragonfly allow complex voxel-based geometries to be constructed, and the electron beam and detectors can be freely placed inside the 3D space. Computation times of simulations have been improved drastically through new data structures and parallelization. Simulations of backscattered electron imaging and EDS mapping are presented here to demonstrate the capabilities of this new library.

Accurate elemental quantification of materials by X-ray detection techniques in electron microscopes or microprobes can only be carried out if the appropriate mass absorption coefficients (MACs) are known. With continuous advancements in experimental techniques, databases of MACs must be expanded in order to account for new detection limits. Soft X-ray emission spectroscopy (SXES) is a characterization technique that can detect emitted X-rays whose energies are in the range of 10 eV to 2 keV by using a varied-line-spaced grating. Transitions producing soft X-rays can be detected and accurate MACs are required for use in quantification. This work uses Monte Carlo modeling coupled with multivoltage SXES measurements in an electron probe micro-analyzer (EPMA) to compute MACs for the L2,3-M and Li Kα transitions in a variety of aluminum alloys. Electron depth distribution curves obtained by the software MC X-ray are used in a parametrized fitting equation. The MACs are calculated using a least-squares regression analysis. It is shown that X-ray distribution cross-sections at such low energies need to take into account additional contributions, such as Coster–Kronig transitions, Auger yields, and wave function effects in order to be accurate.

Achieving aggregation-free nanocomposites is a challenge for the conventional casting process in Li-ion battery electrode fabrication, which leads to inhomogeneous dispersion of active and conductive components – a property which further accelerates, or triggers, battery degradation. This becomes even more challenging when using 2D nanomaterials. In this paper, electrophoretic deposition (EPD) is used to fabricate nanolayered composite anodes composed of spinel lithium titanate (LTO) and reduced graphene oxide (rGO). First, the electrode material precursors, 2D-lithium titanate hydrate (LTH) and graphene oxide nanosheets, are formulated into a stable colloidal suspension and electrophoretically co-deposited (EPD) onto copper substrate. Subsequently, the binder-free deposits are annealed at 600 ​°C in a 5% hydrogen environment for 6 ​h to induce in-situ topotactic transformation of the precursors into LTO/rGO nanolayered composites. Comparing to their PVDF-built electrodes, the EPD nanolayered composites exhibit robust electrochemical performance in terms of power capability, cyclability and impedance control. This performance enhancement is due to a well-established graphene oxide-based percolation network for both electronic and ionic conduction engineered with the help of EPD. Therefore, the local deep discharge to lower state-of-charges is avoided, hence avoiding the serious capacity fade from which nano-LTO suffers. Through this research, EPD casting technology presents itself as superior mesoscale construction strategy for nanostructured LIB electrodes.

Direct photo-to-chemical energy conversion realized through photocatalysis could provide the ultimate solution to the intermittency problem of solar energy. Among different designs of photocatalytic solar energy storage systems, the two-electrode system offers the simplest configuration for enabling highly integrated solar energy conversion and storage in one electrode and on-demand electrocatalytic discharge in the other. In this study, a novel type of visible light chargeable two-electrode Na-ion energy storage system has been developed, to the best of our knowledge, for the first time. It consists of a WO3–(TiO2)–CdS photo absorbing, energy storing bi-functional electrode, a Pt foil counter electrode, and a sacrificial hole scavenging electrolyte. This device delivered a discharge capacity of 12.3 μA h cm−2 (or 18.1 mA h g−1) after 10 min light charging without exhibiting signs of photo/chemical corrosion on the chalcogenide sensitizer. Further by controlling the working voltage window, structure distortion due to overcharging was avoided, thereby leading to an improvement of cyclability (discharge capacity retention after 5 working cycles) from 36% to 64%, and this was eventually elevated to ∼90% upon optimizing the discharging rate. A stable overall solar-to-electrical energy efficiency of ∼0.3% has been achieved for the system. Moreover, a modified photo-rechargeable two-electrode system was developed by replacing the sacrificial hole scavenger and Pt with polysulfide aqueous electrolyte and Cu2S electrocatalytic electrode, respectively. In this way the issue of non-regenerable hole scavenger consumption and instability of Pt in sulfide electrolyte was resolved, establishing a new design, highly promising towards the development of an all-sustainable photo-rechargeable system.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate (TiNb2O7, TNO)/rGO anodes upon reductive annealing. Control tests revealed that EPD is superior to conventional PVDF-based casting in maximizing the performance benefits from using reduced GO in Li-ion electrode fabrication as is the case of TNO that is plagued with conductivity and capacity fading problems. In this particular study, we show that there is a synergy developed between GO and EPD with the former (1) stabilizing the EPD suspension, (2) acting as a flexible binder net that affords mechanical integrity during the volume expansion of TNO, (3) serving as a conductive filler, and (4) contributing to Li-ion storage via pseudocapacitance. As a consequence, a superior percolation network is developed. Thus while both EPD- and PVDF- built TNO/rGO composite anodes exhibited high initial capacities (∼350 and 318 mA h g−1) at 0.5 C cycling, respectively, their cycling behaviour was quite different with the latter experiencing high internal polarization and extended degradation. Post-mortem PEEM-XANES analysis clearly demonstrated a highly homogeneous mesostructure in the case of the EPD-built TNO/rGO anode vs. a highly segregated and dis-jointed rGO and TNO component clustering in the PVDF-built electrode.

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...

Pt and Pt–Sn nanoparticles were synthesized and supported onto carbon nanotubes (CNT), the electrocatalytic activity towards the ethanol oxidation reaction was analyzed. The effect of the solvent employed for the synthesis was evaluated. Metal nanoparticles synthesis was made using water (Pt–Sn/CNT-W) or ethanol (Pt–Sn/CNT-E) as a solvent. Pt–Sn/CNT-W material presented only Pt–Sn alloy nanoparticles homogeneously distributed on the carbon nanotubes support. Pt–Sn/CNT-E sample showed non well-dispersed nanoparticles forming agglomerates along the CNTs surface with predominantly Sn4+ superficial species (SnO2) as show the XPS, FTIR and electrochemical results. These surface arrangements had important effects on the electrocatalytic properties. Pt–Sn/CNT-W shows higher ethanol electrooxidation activity than the Pt–Sn/CNT-E, which is attributed to: a) the double catalytic effect and the intrinsic electronic mechanism favored by the presence of Sn; b) the good particle dispersion of the bimetallic active phase on the CNT and; c) the absence of SnO2 species.

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.

© 2019 The cold spray process and laser-induced projectile impact test (LIPIT) are used to deposit Ti powder particles on sintered polycrystalline Al 2 O 3 . Whereas LIPIT allows real-time observations of single particle impact and measurement of particle impact velocity, cold spray rapidly and simultaneously deposits particles with a wide range of deposition velocities and sizes. By use of these two techniques, the effect of particle velocity and substrate morphology on adhesion strength of single splats is investigated. The critical velocity for deposition is identified to be approximately 580 m/s for the Ti/Al 2 O 3 system when using LIPIT and particles of 10 μm. Above the critical velocity, flattening ratio (FR) is also evaluated and observed to be linearly dependent on the particle impact velocity. Splat adhesion testing is performed on LIPIT-deposited as well as on cold spray-deposited powder particles to measure adhesion strength. This analysis shows that adhesion strength is highly affected by local substrate surface morphology, where particles bond more weakly to relatively smooth portions of the substrate. Therefore, mechanical bonding plays a significant role in adhesion. Also, adhesion strength decreases with an increase in FR and therefore velocity. This decrease can be associated with fracture of the ceramic substrate and rebound forces.

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.

Li-ion storage electrodes are manufactured through the conventional cast process involving the use of a toxic solvent (n-methyl-2- pyrrolidone, NMP) and the binder polyvinylidene fluoride (PVDF). This process can be problematic for nanosized materials as they form viscous suspensions that prevent the formation of uniformly dense coatings. Additionally, the NMP solvent is very hazardous. Herein lies the viability of using electrophoretic deposition (EPD) as an alternative manufacturing process that would both eliminate the need for a toxic solvent and improve electrode properties is presented. In particular, it is shown that styrene- butadiene rubber (SBR) enables the assembly of carbon-coated LTO and carbon nanoparticles into bridged hetero-aggregates that render themselves to fast growth of adherent highly performing LIB electrodes. The electrodes are built by suspending C-coated LTO, carbon, and SBR at 80/10/10 wt% ratio in a medium consisting of 90/10 vol% acetonitrile and water, performing 3–5 stages of 15-s constant current deposition cycles followed by pressing at 4 MPa and drying in a vacuum oven. Raman spectroscopy, thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS) with SEM were performed to examine carbon/LTO composite film homogeneity and compared to conventional PVDF-based electrodes. More importantly, photoemission electron microscopy (PEEM) and X-ray absorption near edge structure (XANES) were used to probe the presence/distribution of the SBR binder in the coating. The EPD-based electrode exhibits superior rate capability when compared to the PVDF-based electrodes. The conductivity, as shown by EIS, of the pressed EPD electrodes was 15 times higher than that of the pressed PVDF electrodes demonstrating the superiority of EPD in fabricating highly conductive electrodes for high-power LIB application.

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.

Climate change, population growth, and rising fossil fuel prices have encouraged governments and scientists for alternate energy resources. This energy transition requires a high-performance energy storage device to satisfy the high energy and power demand and lithium-ion battery (LIB) is one of the promising one. The performance of these batteries ultimately relies on the properties of their components. In this regard, to meet the high-power demand in high-power applications (such as electric vehicles (EVs) and hybrid EVs), materials with rapid lithium transport are required. Lithium Nickel Manganese Cobalt Oxide (NMC) has attracted scientists’ attentions due to its outstanding performance as a cathode material. Therefore, understanding the effect of various factors on lithium diffusivity in NMC is critical to develop high-performance LIBs for high-power applications. Electrochemical methods such as potentiostatic and galvanostatic intermittent titration techniques (PITT and GITT) have been frequently utilized to experimentally quantify lithium diffusivity in NMC. These techniques need the knowledge of electrode particle shape and dimension, and uncertainty about these parameters leads to substantial errors in predicting the diffusion coefficient. In addition, because these techniques consider the response of the whole electrochemical cell, it is hard to distinguish the effect of different structural factors on Li diffusivity in a single NMC active material. Therefore, an appropriate method still needs to be developed to capture the structural effects on lithium diffusivity in NMC. For this purpose, a multi-level modelling from Density Functional Theory (DFT) to kinetic Monte Carlo (KMC) should be implemented. In this study, we will use DFT to find the ground state energy of NMC at different lithium concentrations and configurations. Also, the minimum energy path of lithium migration and the related activation barrier will be found by Climbing Image-Nudge Elastic Band (CI-NEB) method. Then by implementing the configurational dependent activation barrier into the KMC simulation, the lithium diffusivity will be studied. This atomistic simulation gives insight about the structural effects on lithium diffusivity in NMC to further develop this cathode material for high performance LIBs.

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.

Monte Carlo simulations were performed to investigate the behavior of the peak to background ratio (P/B) of particles on a substrate as a function of different variables such as take-off angle, tilt angle, particle size, and beam energy. The results showed that the P/B highly depends on the beam energy, the size of particles, and the composition of the substrates. Results showed that the rate of intensity reduction of the peak is less than the background for a high tilt angle (60 degrees), and thereby, the P/B increases at a high tilt angle. It was shown that by increasing the take-off angle, the P/B initially reduces and then reaches a plateau. Results showed that the P/B highly depends on the size of particles. Analyses showed that by moving the electron beam from the center to the side of the particle, the P/B increases. Finally, the spherical particles have higher sensitivity of the P/B to the beam position than the cubical particles.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate (TiNb2O7, TNO)/rGO anodes upon reductive annealing. Control tests revealed that EPD is superior to conventional PVDF-based casting in maximizing the performance benefits from using reduced GO in Li-ion electrode fabrication as is the case of TNO that is plagued with conductivity and capacity fading problems. In this particular study, we show that there is a synergy developed between GO and EPD with the former (1) stabilizing the EPD suspension, (2) acting as a flexible binder net that affords mechanical integrity during the volume expansion of TNO, (3) serving as a conductive filler, and (4) contributing to Li-ion storage via pseudocapacitance. As a consequence, a superior percolation network is developed. Thus while both EPD- and PVDF- built TNO/rGO composite anodes exhibited high initial capacities (∼350 and 318 mA h g-1) at 0.5 C cycling, respectively, their cycling behaviour was quite different with the latter experiencing high internal polarization and extended degradation. Post-mortem PEEM-XANES analysis clearly demonstrated a highly homogeneous mesostructure in the case of the EPD-built TNO/rGO anode vs. a highly segregated and dis-jointed rGO and TNO component clustering in the PVDF-built electrode.

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 electron probe microanalysis or scanning electron microscopy, the Monte Carlo method is widely used for modeling electron transport within specimens and calculating X-ray spectra. For an accurate simulation, the calculation of secondary fluorescence (SF) is necessary, especially for samples with complex geometries. In this study, we developed a program, using a hybrid model that combines the Monte Carlo simulation with an analytical model, to perform SF correction for three-dimensional (3D) heterogeneous materials. The Monte Carlo simulation is performed using MC X-ray, a Monte Carlo program, to obtain the 3D primary X-ray distribution, which becomes the input of the analytical model. The voxel-based calculation of MC X-ray enables the model to be applicable to arbitrary samples. We demonstrate the derivation of the analytical model in detail and present the 3D X-ray distributions for both primary and secondary fluorescence to illustrate the capability of our program. Examples for non-diffusion couples and spherical inclusions inside matrices are shown. The results of our program are compared with experimental data from references and with results from other Monte Carlo codes. They are found to be in good agreement.

In this work, a relatively inactive cathode material, βII orthorhombic Li2FeSiO4 with the Pmn21 space group, is shown to undergo crystal structural changes when subjected to nanosizing by high-energy milling that have a pronounced activation impact on Li-ion intercalation electrochemistry. In particular, we present evidence of mechanically induced structural annealing including lattice expansion, reduction of anti-site defects and preferred crystal orientation, opposite of what expected typically from nanosizing. As a result of this type of unreported structural activation for orthosilicates, a threefold increase of the accessible discharge (=intercalation) capacity of the high-energy milled Pmn21 material is attained, much higher than what would be expected solely from surface area increase due to nanosizing and surface area increase. Such mechanochemically induced structural annealing activates Li-ion diffusion (one order of magnitude enhancement in DLi) into less accessible sites via the combined effects of anti-site defect removal and modulation of the Fe–O coordination adjustment. Structural activation of intercalation materials via controlled mechanochemistry opens new possibilities in nanoengineering high energy density Li-ion storage electrodes.