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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 250–300 nm. 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.

The electron channeling contrast imaging technique was used to investigate the microstructure of copper coatings fabricated by cold gas dynamic spray. The high velocity impact characteristics for cold spray led to the formation of many substructures, such as high density dislocation walls, dislocation cells, deformation twins, and ultrafine equiaxed subgrains/grains. A schematic model is proposed to explain structure refinement of Cu during cold spray, where an emphasis is placed on the role of dislocation configurations and twinning.

This paper presents routines to compute the Mott cross section used in the CASINO program (Monte CArlo SImulation of electroN trajectory in sOlid). The routines used tabulated values of the Mott cross section computed in the work of Czyzewski et al. (1990). The cross section is available over the range 0.02 to 30 keV and for the first 94 elements of the Periodic Table. The routines are written in C language and use a binary file to interpolate the cross section. The first routine computes the total Mott cross sections; the second calculates the polar angle of collision. Backscattered coefficients computed using different cross section are compared for C, Al, Ag, and Au. The Rutherford (1911) cross section and the available empirical equations (Browning et al. 1994, Gauvin and Drouin 1993) are compared to tabulated values of Mott. Also, the energy distribution of backscattered electrons is shown for Al and Au at 10 keV. Finally, the relative computation times for the different Mott cross sections are compared. It was found that tabulated Mott cross sections are more accurate and faster than any empirical Mott cross sections. The tabulated Mott cross sections are even faster than simple Rutherford cross sections.

This paper is a description of the stopping power routine utilized in the CASINO program that is based on the experimental measurement of the energy loss function (ELF). In addition, we present an ANSI C standard program that can be used to generate the data needed for the stopping power routine. Both optical and energy loss spectrum (ELS) measurements of the ELF can be used as input to compute the stopping power. For ELS, only the single scattering spectrum is needed. Hence, measurement of the stopping power for a given element or compound of interest can easily be performed and used in the CASINO program. The resulting effect of using these stopping powers in Monte Carlo simulations is generally to increase the backscattering coefficient. Except for carbon, the change of stopping power for pure elements so far compiled is relatively small. In some compounds (i.e., Al2O3 and ZnSe), the discrepancy with the Joy and Luo (1989) expression is significant.

Vickers microindentation and Berkovich nanoindentation tests were carried out on a polycrystalline nickel (Ni) bulk specimen. Electron channeling contrast imaging (ECCI) in conjunction with electron backscattered diffraction was used to image and characterize plastic deformation inside and around the indents using a field emission scanning electron microscope. The ECCI was performed with a 5 keV beam energy and 0° tilt specimen position. The strain field distribution, slip lines, and Taylor lattices were imaged on an indented surface. Orientation mapping was used to investigate the local crystallographic misorientation and identify specific ⟨110⟩ slip systems. An ion milling surface preparation technique was used to remove materials from the surface which permitted the study of deformed microstructure below the indent. A dislocation density of 1011cm−2was calculated based on the curvature of bend contours observed in the ECCI micrographs obtained from the Vickers indents. A yield strength of 500 MPa was calculated based on the size of the strain field measured from the ECCI micrographs of the nanoindents. The combination of ion milling, ECCI, and electron backscattered diffraction was shown to be beneficial to investigate the indentation-induced plastic deformation in a polycrystalline Ni bulk specimen.

A new approach for preparing geological materials is proposed to reduce charging during their characterization in a scanning electron microscope. This technique was applied to a sample of the Nechalacho rare earth deposit, which contains a significant amount of the minerals fergusonite and zircon. Instead of covering the specimen surface with a conductive coating, the sample was immersed in a dilute solution of ionic liquid and then air dried prior to SEM analysis. Imaging at a wide range of accelerating voltages was then possible without evidence of charging when using the in-chamber secondary and backscattered electrons detectors, even at 1 kV. High resolution x-ray and electron backscatter diffraction mapping were successfully obtained at 20 and 5 kV with negligible image drifting and permitted the characterization of the microstructure of the zircon/fergusonite-Y aggregates encased in the matrix minerals. Because of the absence of a conductive layer at the surface of the specimen, the Kikuchi band contrast was improved and the backscatter electron signal increased at both 5 and 20 kV as confirmed by Monte Carlo modeling. These major developments led to an improvement of the spatial resolution and efficiency of the above characterization techniques applied to the rare earth ore and it is expected that they can be applied to other types of ores and minerals.

A forescatter electron detector (FSED) was used to acquire dark-field micrographs (DF-FSED) on thin specimens with a scanning electron microscope. The collection angles were adjusted with the detector distance from the beam axis, which is similar to the camera length of the scanning transmission electron microscope annular DF detectors. The DF-FSED imaging resolution was calculated with SMART-J on an aluminum alloy and carbon nanotubes (CNTs) decorated with platinum nanoparticles. The resolution was three to six times worse than with bright-field imaging. Measurements of nanometer-size objects showed a similar feature size in DF-FSED imaging despite a signal-to-noise ratio 12 times smaller. Monte Carlo simulations were used to predict the variation of the contrast of a CNT/Fe/Pt system as a function of the collection angles. It was constant for very high collection angles (>450 mrad) and confirmed experimentally. The reverse contrast between carbon black particles and the smallest titanium dioxide (TiO2) nanoparticles was predicted by Monte Carlo simulations and observed in the DF-FSED micrograph of a battery electrode coating. However, segmentation of the micrograph was not able to isolate the TiO2 nanoparticle phase because of the close contrast of small TiO2 nanoparticles compared to the C black particles.

The valence states of Mg-Al alloys are compared to those of reference materials (pure Mg and Al metals, and intermetallics). Two methods based on X-ray emission spectroscopy are proposed to determine the phases and their proportion: first, by analyzing the Al valence spectra of the Mg-rich alloys and the Mg valence spectra of the Al-rich alloys; second, by fitting with a linear combination of the reference spectra the Al spectra of the Al-rich alloys and the Mg spectra of the Mg-rich alloys. This enables us to determine that Al and Al3Mg2 are present in the 0-43.9 wt% Al composition range and Mg and Al12Mg17 are present in the 62.5-100 wt% Al composition range. In the 43.9-62.5% Al range, the alloy is single phase and an underestimation of the Al content of the alloy can be estimated from the comparison of the bandwidth of the alloy spectrum to the bandwidths of the reference spectra., Comment: 10 pages. can also be found at: http://journals.cambridge.org/action/displayAbstract?fromPage=online\&aid=3416872

Zero-strain and long-term stability of nanoscale lithium titanate (LTO) anode materials make possible the fabrication of exceptionally stable lithium ion batteries. But one issue must be considered that of nanostructure-induced relaxation in 2D LTO nanosheets which profoundly modifies their Li storage properties and structural stability. Excessively intercalated Li ions at both 8a and 16c sites trigger nucleation of the relaxed LTO structure in the near-surface region, which impedes Li-ion diffusion and causes the increasing polarization of LTO nanosheet electrodes. Nuclei of relaxed LTO then undergo isotropic growth along the 3D Li-ion pathways in LTO to completely convert near-surface regions into relaxed LTO. With increasing population of trapped Li ions, the enhanced conductivity due to Ti4+/Ti3+ reduction gradually eliminates the raised polarization. In the meantime, spontaneous electrolyte/LTO reduction to form the solid electrolyte interphase starts playing a major role in capacity loss once the transformation of near-surface region into relaxed LTO becomes saturated. Elucidation of these fundamental intercalation-induced surface structure transformations contribute greatly into the design of highly performing 2D nanoscaled LTO and other electrode materials.

This paper will present the results for the determination of concentration of Li in silicates cathode materials using x-ray microanalysis with windowless SDD EDS technology and with Electron Energy Loss Spectroscopy (EELS) with state of the art field emission scanning electron microscopes at high spatial resolution. Advantages and disadvantages of both techniques will be covered. The aim of this work is to characterize Li concentration variation at the nm scale in batteries materials. The issue of electron beam damage will be covered and the advantage to work at electron beam energies below 30 keV will be demonstrated.

Lithium transition metal silicates Li2 M SiO4 ( M = Fe, Mn, Co, etc.) have been under intense research due to their double theoretical capacity of 330 mAh/g compared to LiFePO4 (170 mAh/g)1,2,3 . Their development as cathode materials however has been hampered due in part of their rich polymorphism and phase transitions occurring during cycling not allowing full capacity storage and reversible retention. In this work we focus on the electrochemistry of lithium iron silicate (LFS) 5-8. Almost all previous studies have focused solely on the electrochemistry of the high temperature monoclinic phase (m-LFS). According to these studies4,5,8, the monoclinic phase undergoes electrochemically-induced phase transition during cycling to thermodynamically stable low-temperature orthorhombic phase (o-LFS). This prompted us to take a deep look into the structural and electrochemical behavior of the latter phase as it might hold the key in designing high performance lithium iron orthosilicate cathodes. During this investigation we discovered that upon galvanostatic cycling, the specific capacity of an o-LFS/C nanocomposite cathode exhibited gradual increase from 40 to 165 mAh/g and a shift in Li-storage mechanism from solid solution to biphasic type. This intriguing behavior is currently the subject of further characterizations to elucidate the underlying phenomena that can have significant implications to the development of high energy density LIB cathode materials. References Islam, M.S., et al., Silicate cathodes for lithium batteries: alternatives to phosphates? Journal of Materials Chemistry, 2011. 21(27): p. 9811-9818. Zaghib, K., et al., Review and analysis of nanostructured olivine-based lithium recheargeable batteries: Status and trends. Journal of Power Sources, 2013. 232: p. 357-369. Ferrari, S., et al., Electrochemistry of orthosilicate-based lithium battery cathodes: a perspective. Physical Chemistry Chemical Physics, 2014. 16(22): p. 10353-10366. Masese, T., et al., Relationship between Phase Transition Involving Cationic Exchange and Charge–Discharge Rate in Li2FeSiO4. Chemistry of Materials, 2014. 26(3): p. 1380-1384. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals. Sci Rep-UK 2015, 5, 8599. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte Chem Commun 2016, 52, 190-193. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G. Density functional theory insight into the structure stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes. J Power Sources 2016, In revision. Lu, X.; Chiu, H.-C.; Arthur, Z.; Zhou, J. G.; Wang, J.; Chen, N.; Jiang, D.-T.; Zaghib, K.; Demopoulos, G. P. Quasi-equilibrium Li storage in metastable Li2FeSiO4 cathode. 2016, Under review.

The lithium ion battery is an attractive and environmental friendly energy source because of its large versatile applications ranging from portable electronics systems to support renewable energy sources. In addition, lithium ion batteries have the highest energy density among others known chemical batteries and are the most promising technology for portable applications. However, to satisfy such applications is essential to improve some components of lithium ion battery. One of the main challenges is to increase their electrochemical performance by improving the storage of lithium ions in the anode electrode. Graphite has been the most successful materials for the anode electrode, which has reached a specific capacity of 372 mAh g-1. However, those materials have reached its storage capacity limit. Thus, alternative supports which can provide higher capacity than graphite are needed. Carbon nanotubes (CNT) can be a promissory alternative material, especially those that are doped with heteroatoms. The physical and chemical properties of CNT are modified by the dopant atoms intrusion in the carbon lattice that improve the electrical conductivity, morphology and the structure of carbon. The present study shows the synthesis and characterization of silicon doped carbon nanotubes (Si-CNT). Si-CNTs were synthesized by a modified chemical vapor deposition using toluene as carbon source and ferrocene as metal catalyst for the nanotubes growth. Triphenylsilane were used as silicon doping. The effects of various parameters including furnace temperature and silicon concentration were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X ray diffraction (XRD) and Raman spectroscopy. The results showed that the morphological and physical properties of Si-CNT, such as lengths, diameter, defects, and wall thickness, changed in comparison to those of undoped CNT. According to the Raman results the doped nanotubes showed major defect in the structure; this phenomenon can be explained by the integration of the silicon atoms in the structure of the nanotubes, which increase the order of the graphitic network. On the other hand, the elemental atomic composition analysis using SEM by energy-dispersive x-ray spectroscopy (SEM-EDS) showed that silicon is presented with Si content of 0.25±0.09 at. %. The Si-CNT properties and its evaluation as anode materials in lithium ion batteries are discussed.

Preliminary results illustrate the possibility of charge contrast imaging (CCI) of polymeric materials. Possible CCI images of low-density polyethylene and polyvinyl chloride reveal details that may aid in the characterization of the microstructure of polymeric materials. These pictures were obtained with a Hitachi S-3000N variable pressure scanning electron microscope with the environmental secondary electron detector (ESED).

Aluminum-lithium alloys are widespread in the aerospace industry. The new 2099 and 2199 alloys provide improved properties, but their microstructure and texture are not well known. This article describes how state-of-the-art field-emission scanning electron microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy and metallic alloys in general. Investigations were carried out on bulk and thinned samples. Backscattered electron imaging at 3 kV and scanning transmission electron microscope imaging at 30 kV along with highly efficient microanalysis permitted correlation of experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al, and Cu in the T1 precipitates. Zinc and magnesium are also present in “rice grain”–shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted as it provides information in the macro- and microscales with relevant details. Its ability to probe the distribution of precipitates from nano- to microsizes throughout the matrix makes FE-SEM an essential technique for the characterization of metallic alloys.

This article reviews different methods used to perform quantitative X-ray microanalysis in the electron microscope and also demonstrates the urgency of measuring the fundamental parameters of X-ray generation for the development of accurate standardless quantitative methods. Using ratios of characteristic lines acquired on the same X-ray spectrum, it is shown that the Cliff and LorimerKA-Bfactor can be used in a general correction method that is appropriate for all types of specimens and electron microscopes, providing that appropriate corrections are made for X-ray absorption, fluorescence, and indirect generation. Since the fundamental parameters appear in theKA-Bfactor, only the ratio of the ionization cross sections needs to be known, not their absolute values. In this regard, the measurement of ratios of theKA-Bfactor (or intensities at different beam energies of the same material with no change of beam spreading in the material) permits the validation for the best models to compute the ratio of ionization cross sections. It is shown, using this method, that the nonrelativistic Bethe equation, to compute ionization cross section, is very close to the equation of E. Casnati et al. (J Phys B15, 155–167, 1982) and also to the equations proposed by D. Bote and F. Salvat (Phys Rev A77, 042701, 2008) for the computation of the ratio of ionization cross sections. The method is extended to show that it could be used to determine the values of the Coster-Kronig transitions factors, an important fundamental parameter for the generation of L and M lines that is mostly known with poor accuracy. The detector efficiency can be measured with specimens where their intensities were measured with an energy dispersive spectrometer detector, the efficiency of which has been measured in an X-ray synchrotron (M. Alvisi et al.,Microsc Microanal12, 406–415, 2006). The spatial resolution should always be computed when performing quantitative X-ray microanalysis and the equations of R. Gauvin (Microsc Microanal13(5), 354–357, 2007) for bulk materials and the one presented in this article for thin films should be used. The effects of X-rays generated by fast secondary electrons and by Auger electrons are reviewed, and their effect can be detrimental for the spatial resolution of materials involving low-energy X-ray lines, in certain specific conditions. Finally, quantitative X-ray microanalysis of heterogeneous materials is briefly reviewed.

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.

This paper describes how state-of-the-art Field-Emission Scanning Electron Microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy, and metallic alloys in general. Investigations were carried out on bulk and thinned samples. BSE imaging at 3kV and STEM imaging at 30kV along with highly efficient microanalysis permitted to correlate experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al and Cu in the T1 precipitates. Zinc and magnesium are also present in “rice grain” shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted in that it can provide information at the macro and micro scales with relevant details. Its ability to probe the distribution of precipitates from nano-to micro-sizes throughout the matrix makes Field-Emission Scanning Electron Microscopy a suitable technique for the characterization of metallic alloys.

Electrospark deposition (ESD) is a rapid solidification processing technique capable of depositing a metal onto a conductive substrate. The short pulse duration and high pulse frequency, combined with the small amount of material transferred during each pulse, results in high cooling rates being realized, on the order of 105–106 C/sec. This study investigates the ability to induce solute trapping behavior, for a new generation aluminum-lithium alloy, AA2199, using ESD.

The evolution of the microstructure during friction stir welding of a third generation AA2199 Al-Li alloy has been described and related to the mechanical properties of welds. The coupling of electron microscopy and micro-hardness have helped generate an understanding of the relationship between grain structure, precipitate density and morphology behind the observed changes in mechanical properties during post weld artificial ageing. The ability of welds to recover hardness and strength during post weld heat treatment was linked to the limited formation of large scale precipitates which act as sinks for alloying elements. Welds obtained with high tool rotation speed (within parameters studied) showed ultimate tensile strength levels of about 93% of the base metal, an elongation of 6% at fracture, and hardness values ranging between 120–140 HV in the stir zone, thermo-mechanically affected zone, and heat affected zone upon post weld heat treatment.

The fundamental understanding of electron scattering is of critical importance concerning Scanning Electron Microscopy and for electron beam lithography. In these process of great technological importance, it is important to know the volume of diffusion of electrons to define the resolution. Also, it is important to know the rate of energy loss, the number of backscattered and secondary electrons created, their angular distribution, …. All these quantities depend on the shape of the trajectories of the electrons in the solid when they diffuse into it. The use of fractal geometry to describe such trajectories have been previously studied by Gauvin and Drouin1,2 from trajectories computed by Monte Carlo simulations. In these studies, the multifractal behavior of the shape of electron trajectories in solids have also been reported but no explanations have been given to describe the shape of the corresponding f(α) curves. In this paper, we present such explanation for the f(α) curves computed from the electron trajectories simulated in C and in Au with an initial energy of 30 keV (see Gauvin and Drouin2).

The mechanical properties of a 6061 aluminium alloy and of a composite material 6061/ Al 2 O 3/10-20% p have been mesured after heat treatments using a tensile test. Fracture surfaces profiles were used to mesure fractal dimension using the step divider method. The fractal dimension of the fractured surfaces of the composite material 6061/ Al 2 O 3/10-20% p depend on the aging and on the particle volume fraction but is independent of aging time for the unreinforced alloy.

An open source software package dedicated to processing stored electron backscatter patterns is presented. The package gives users full control over the type and order of operations that are performed on electron backscatter diffraction (EBSD) patterns as well as the results obtained. The current version of EBSD-Image (www.ebsd-image.org) offers a flexible and structured interface to calculate various quality metrics over large datasets. It includes unique features such as practical file formats for storing diffraction patterns and analysis results, stitching of mappings with automatic reorganization of their diffraction patterns, and routines for processing data on a distributed computer grid. Implementations of the algorithms used in the software are described and benchmarked using simulated diffraction patterns. Using those simulated EBSD patterns, the detection of Kikuchi bands in EBSD-Image was found to be comparable to commercially available EBSD systems. In addition, 24 quality metrics were evaluated based on the ability to assess the level of deformation in two samples (copper and iron) deformed using 220 grit SiC grinding paper. Fourteen metrics were able to properly measure the deformation gradient of the samples.

Quantitative X-ray microanalysis models, such as ZAF or φ(ρz) methods, are normally based on solid, flat-polished specimens. This limits their use in various domains where porous materials are studied, such as powder metallurgy, catalysts, foams, etc. Previous experimental studies have shown that an increase in porosity leads to a deficit in X-ray emission for various materials, such as graphite, Cr(2) O(3) , CuO, ZnS (Ichinokawa et al., '69), Al(2) O(3) , and Ag (Lakis et al., '92). However, the mechanisms responsible for this decrease are unclear. The porosity by itself does not explain the loss in intensity, other mechanisms have therefore been proposed, such as extra energy loss by the diffusion of electrons by surface plasmons generated at the pores-solid interfaces, surface roughness, extra charging at the pores-solid interface, or carbon diffusion in the pores. However, the exact mechanism is still unclear. In order to better understand the effects of porosity on quantitative microanalysis, a new approach using Monte Carlo simulations was developed by Gauvin (2005) using a constant pore size. In this new study, the X-ray emissions model was modified to include a random log normal distribution of pores size in the simulated materials. This article presents, after a literature review of the previous works performed about X-ray microanalysis of porous materials, some of the results obtained with Gauvin's modified model. They are then compared with experimental results.

A formula to compute total elastic Mott cross-sections as well as a tabulation of the constants to compute total Mott cross-sections for 94 elements are presented herein. This formula and the constants have been obtained from the values of total elastic Mott cross-sections computed by Czyzewski et al. (1990) using Thomas-Fermi-Dirac atomic potentials for atomic numbers greater than 54 and Hartree-fock potentials for atomic numbers less than 55. Also, a Monte Carlo program simulating the trajectories of electrons in bulk specimens using our formula of total elastic Mott cross-sections and the single scattering approach is discussed. Values of backscattering coefficients in energy functions for C, Al, Cu, Ag, and Au computed by this program and by other Monte Carlo programs are compared with values measured experimentally by several researchers.

In industrial metal-forming processes, quantitative and physical models are required to control and optimize the microstructure of the finished products. A detailed understanding of the behavior of polycrystalline materials during deformation processes is essential to develop such models. A number of instruments and analytical tools are available for deformation studies within the microscopy and microanalysis community. In a scanning electron microscope (SEM), the visualization and characterization of deformed microstructures are carried out with electron channeling contrast imaging (ECCI) and electron backscattered diffraction (EBSD). These SEM studies provide a nanoscale spatial resolution, a large field of view and statistically reliable information on a bulk specimen [1]. In this study, complex variations of backscattering intensity (IBSE) were observed in ECCI micrographs of magnesium (Mg) grains after the uniaxial hot compression test. The variations of IBSE across the ECCI micrographs were attributed to plastic deformation of the Mg grains [2]. Recovery, recrystallization and phase transformation processes occurred simultaneously during deformation at high temperature. The interactions between the three processes lead to a complex deformed microstructure consisting of dynamically recrystallized grains and precipitates. The deformed microstructure varied with different deformation variables such as temperature, strain rate and strain [3,4].

Charging effects are inevitable when an electron beam interacts with a partially conductive target material. The conduction and valence bands being overlapped in metals, the evacuation of excess negative charges is complete whereas a gap between these two bands exists in semi-conductors and insulators, preventing an efficient electrical conductivity. Thus, the excess negative charges brought by the electron beam stay trapped at the shallow surface of the specimen and generates a negative electric field at the surface while a positive field is created deep inside the interaction volume [1]. To help reducing these effects, coating with a conductive material [2], determining the neutral accelerating voltage [3] or using positively charged ions in the vicinity of the impact point of the electron beam [4] may generally be used. However, the coating technique, which is the most used, results in a loss of topographic and diffraction contrast in the images.

In the last 10 years, the transmission electron tomography technique was extensively used in biology applications to obtain 3D configurations of small organic structures [1]. Such bright field electron tomography is not generally used in material science applications as the diffraction effects result in strong artefacts during the reconstruction. Bragg’s diffractions are indeed present at certain angles during the acquisition of a bright field tilt series. High angle annular dark field (HAADF) imaging with a scanning transmission electron microscope (STEM) is not significantly affected by dynamic effects. Since the contrast of HAADF depends on material thickness and composition [2], this technique is a good candidate for tomographic acquisitions of materials science samples. However, the reconstruction algorithms have to be adapted and optimum experimental parameters are needed for high resolution three-dimensional (3D) dataset at the nanoscale. The CASINO Monte Carlo software [3] was developed to simulate the effect of parameters such as angular tilt range, angular coverage, beam energy and beam dosage on HAADF-STEM micrograph [4]. In this work, we use a Monte Carlo-based simulation method to accurately model the whole tomographic data acquisition process and test the reconstruction algorithm with these different parameters.

Graphite, the current commercial anode material in batteries suffers from the formation of a surface/electrolyte interface (SEI) layer that adversely affects performance. However, titania (TiO2) does not form an SEI layer and is both abundant and inexpensive, making it a prime anode material replacement [1]. While much work has been done to determine the effects of morphology and phase of TiO2 on lithium intercalation, the effect of the method fabrication of the electrode on its electrochemical performance is still unknown. Currently, electrodes are fabricated using active material, conductive additives, and a non-electroactive polymer binder mixed mechanically with a solvent. In this work, we introduced a chemo-mechanical fabrication method that produces binder-free electrodes. Without binder, more loading of active material is possible. Further, agglomeration of both TiO2 and conductive additives that occurs with the binder-based method is limited by using dispersants. Finally, the electrode is sintered, forming a 3-dimensional mesoporous structure that provided a 25% increase in capacity over the binder-based method, as well as better capacity retention over multiple cycles.

To produce the magnetic core of the electric motors, non-oriented electrical steels (NOES) are used. Recently much attention has been focused on optimizing the efficiency of electric motors and, as such, various materials aspects of NOES are being re-examined. Typically, NOES are used in the form of laminations (~200-1000 μm thick) with an electrically insulating coating applied to the surface. Residual stress is induced during the coating process, which will alter magnetic domain structures of the steel substrate. Variations of the resultant magnetic domains due to coating have been characterized mainly in grain oriented electrical steels [1-3], and only limited numbers of studies are available on non-oriented electrical steels [4]. In this study, the effect of the coating is examined, specifically, its role in creating a residual stress near the coating/steel interface. The stress was investigated by nanoindentation technique. With this method, a tensile stress of ~200 MPa was calculated based on hardness values in the steel substrate, which was linked to the variations in near surface hardness profile, and corresponding magnetic domain structure. The magnetic domain structures were imaged using a field emission scanning electron microscope (FE-SEM).

The scanning electron microscope (SEM) was primary developed for imaging applications. With the introduction of the Si(Li) energy dispersive spectrometer (EDS), simultaneous imaging and x-ray microanalysis became possible. However, long working distance and high current were needed because the position and small solid angle of the EDS detector. SEM was initially and is still optimized for imaging applications, where the high spatial resolution is generally obtained at short working distance. This problem is still relevant today and unfortunately x-ray microanalysis is never performed in the best imaging conditions, i.e., not with the smallest probe size. With the introduction of an annular silicon drift detector (SDD) system, scanning electron microscopy is facing a revolution. This detector is inserted below the objective lens which gives a higher solid angle (up to 1.2 sr). Also, a lower working distance and probe current can be used. An improved spatial resolution becomes possible during x-ray microanalysis. At this point, the time required for x-ray imaging will be of the same order as for the atomic number contrast images achieved through backscattered electrons (BSE) imaging [1].

While the improvement in mechanical properties of nanocomposites makes them attractive materials for structural applications, their processing still present significant challenges. In this paper, cold spray was used to consolidate Al₂O₃/Al nanocomposite powders obtained from mechanical milling. The microstructure and nanohardness of the feedstock powders as well as of the resulting coatings were analysed. The results show that the large increase in hardness of the Al powder after mechanical milling is preserved after cold spraying. Good quality coating with low porosity is obtained from milled Al. However, the addition of Al₂O₃ to the Al powder during milling decreases the powder nanohardness. This lower hardness is attributed to non-optimised milling parameters for proper Al₂O₃ embedding and dispersion in Al and results in a lower coating hardness compared with the milled Al coating. The coating produced from the milled Al₂O₃/Al mixture also shows lower particle cohesion and higher amount of porosity. The overall results are promising and it is believed that an optimization of Al milling with Al₂O₃ will allow production of sound coatings with improved hardness., International Thermal Spray Conference 2010: Singapore, May 3-5, 2010

In this work, anatase nanocrystallites are synthesized from an aqueous titanium(IV) chloride solution by hydrolysis and are used to fabricate mesoporous TiO 2 film photoanodes. The aqueous-synthesized titania nanocrystallites possess high specific surface area (250-350 m 2 /g), 4-5 nm crystallite size, enlarged bandgap, and enhanced surface hydroxylation. Current-voltage measurements of dye-sensitized solar cells (DSSCs) based on the aqueous-synthesized titania showed higher photocurrent (13.0 mA/cm 2 ) and conversion efficiency (5.0%) when compared to cells built from commercial Dyesol (10.7 mA/cm 2 , 4.8%) or P25 (8.5 mA/cm 2 , 4.1%) benchmark nanotitania materials. The enhanced performance is discussed in terms of improved dye loading and associated electron injection and transport facilitated by the nanocrystallite surface characteristics.

SUMMARY Fast secondary electrons (FSE), which result from inelastic scattering of incident electrons, are known to generate a significant number of X-rays for light elements, and also to degrade the spatial resolution of X-ray microanalysis in thin foils. A Monte Carlo program simulating the generation and diffusion of FSE in binary systems has been developed to study the effect of composition on κAB factors and spatial resolution. The effect of accelerating voltage and thickness is also presented.

The current schemes of quantification of x-ray microanalysis in the SEM [ZAF and σ(ρZ) methods] are valid for specimens of homogeneous composition. The determination of the chemical composition of small inclusions using these techniques is impossible because the volume of x-ray emission is not of homogeneous composition. A scheme of quantification to determine the composition of small inclusions embedded in a matrix has been developed using Monte Carlo simulations. This scheme is similar to that developed by Kyser and Murata (1974) for the quantification of thin foils deposited on a substrate using x-ray microanalysis in the SEM.

The fractal behaviour of electron scattering in solids is studied with electron trajectories simulated by Monte Carlo simulations. More precisely, the box-counting dimension of electron trajectories in C, Cu, Ag, and Au is determined. Then, the fractal dimension curve of the position of an electron in function of time simulated in a gold target shows that the first part of the electron trajectory is described by a persistent process and that the last part is described by random walk process. Finally, the multifractal behaviour of an electron trajectory simulated in gold is presented.

The variable pressure scanning electron microscope (VP-SEM) allows imaging of insulators without the need for a conductive coating, due to charge neutralization at the surface from recombination of positive ions and surface electrons. Varying certain parameters such as pressure, bias, and working distance creates incomplete neutralization, and localized charging develops called charge contrast. Although the exact mechanism creating charge contrast imaging (CCI) is unknown, it is agreed that it is related to an optimum charge compensation. The behavior of the CCI is still vague, which presents a problem for determining the mechanisms. This article provides user-friendly methods of finding the optimum levels of charge contrast in the VP-SEM. We show that the CCI is obtained at optimum operating conditions where the specimen current is between 2.5 nA and 3.5 nA. The specimen current is a function of secondary electrons (SE) emission and ionization potential, producing an ion flux. Therefore an optimum specimen current represents the balanced conditions of SE emission and ion flux. Controlling the pressure, working distance, bias, scan rate, and beam current allows the microscopist to set the specimen current at this optimum level for charge contrast imaging. All the work was performed on gibbsite using the S3000N VP-SEM from Hitachi.

The microanalysis of nonconductive specimen in a scanning electron microscope is limited by charging effects. Using a charge density model for the electric field buildup in a nonconductive specimen irradiated by electrons, a Monte Carlo simulation method has been applied to alumina (Al2O3). The results show a change in the depth distribution for characteristic and bremsstrahlung X-ray, φ(ρz) curves, and ψ(ρz) curves (with absorption) for both elements' Kα lines. The influence of the electric field on the measured X-ray intensity is shown. The dependency of this influence by the three parameters, electron energy, X-ray energy, and charge density, is clarified.

In this study the production of rutile (TiO2) nanostructured powders by forced hydrolysis of aqueous Ti(IV) chloride solutions was investigated in terms of precipitation kinetics and nucleation and growth mechanism over the temperature range 70–90 °C and Ti(IV) concentration 0.5–1.5 M. The precipitation kinetics was found to follow the Avrami model exhibiting a slow induction–nucleation stage and accelerating growth stage. The type and speed of agitation was found to have a pronounced effect on the nucleation kinetics that required the adoption of a mechanically agitated (1000 rpm) reactor for the obtainment of reproducible results. An increase in Ti(IV) chloride concentration was found to have a negative effect on kinetics pointing to differences in a precursor complex formation and polymerization behaviour. The obtained nanostructured rutile powder had a spheroidal particle morphology with the interior of the particles characterized by a nucleation core and self-assembled elongated fibres. The nucleation core consisted of primary aggregates of elementary nanocrystallites of ∼10–20 nm size. The nanofibres were found to form via preferential growth of the (1 1 0) atomic planes. The nanostructured rutile powder exhibited high specific surface area in the order of 80 m2/g.

In recent years, carbon nanotubes have raised scientific interest due to their unmatched properties and their numerous potential applications. Their exceptional mechanical properties especially make them candidates for superstrong and lightweight nanocomposites. The present study aims to test the possibility of fabricating nanocomposites, with aluminum as the matrix and carbon nanotubes as the reinforcing phase, using liquid vacuum infiltration. Before infiltrating nanotubes by molten aluminum, it is necessary to enhance their wettability. For this purpose, an electroless plating of copper was carried out to ensure a good quality of the matrix / nanotubes interface. Three steps were needed to make this plating. Firstly, the carbon nanotubes were oxidized in a mixture of strong acids in order to improve their chemical reactivity. Secondly, their surface was activated by the deposition of some catalytic nuclei of palladium. Finally, the electroless copper-plating step was performed. Field Emission Scanning Electron Microscopy, Field Emission Transmission Electron Microscopy, Transmission Electron Microscopy, X-ray microanalysis, and Fourier-Transform Infra Red spectroscopy were used for chemical and microstructural characterization during the different steps of the process with emphasis on studying the interface.