Beam Scanning Electron Microscopy Research Articles

The Effect of the Compounding Procedure on the Morphology and Mechanical Properties of PLA/PBAT-Based Nanocomposites

Abstract Poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT)-based nanocomposites filled with 1 vol.% silicon dioxide nanoparticles (nano-SiO2) were prepared using a co-rotating twin-screw extruder and injection molding. The nanocomposites with various blending sequences were investigated using PLA-based and PBAT-based nanocomposite masterbatches. Morphology of the PLA/PBAT/SiO2 nanocomposites was examined using a scanning electron microscope (SEM) and a focused ion beam (FIB) SEM. It is found that the nano-SiO2 locates in the original polymer phase, in which it is firstly incorporated in the masterbatch process, as well as at the interface between the two polymers. However, as the residence time in the extrusion process increases, the nanoparticles migrate from the original phase to the interface, governed by the thermodynamic driving force. The best optimization of mechanical properties is achieved by using the PBAT-based masterbatches with a one-step process or short residence time. The processing history, therefore, has a tremendous impact on the final properties of the resulting materials.

A robust method for particulate detection of a genetic tag for 3D electron microscopy.

Genetic tags allow rapid localization of tagged proteins in cells and tissues. APEX, an ascorbate peroxidase, has proven to be one of the most versatile and robust genetic tags for ultrastructural localization by electron microscopy (EM). Here, we describe a simple method, APEX-Gold, which converts the diffuse oxidized diaminobenzidine reaction product of APEX into a silver/gold particle akin to that used for immunogold labelling. The method increases the signal-to-noise ratio for EM detection, providing unambiguous detection of the tagged protein, and creates a readily quantifiable particulate signal. We demonstrate the wide applicability of this method for detection of membrane proteins, cytoplasmic proteins, and cytoskeletal proteins. The method can be combined with different EM techniques including fast freezing and freeze substitution, focussed ion beam scanning EM, and electron tomography. Quantitation of expressed APEX-fusion proteins is achievable using membrane vesicles generated by a cell-free expression system. These membrane vesicles possess a defined quantum of signal, which can act as an internal standard for determination of the absolute density of expressed APEX-fusion proteins. Detection of fusion proteins expressed at low levels in cells from CRISPR-edited mice demonstrates the high sensitivity of the APEX-Gold method.

Ultrasonic Deposition of Carbon Nanotubes on Polycrystalline Cubic Boron Nitride Composites.

Polycrystalline cubic boron nitride (PcBN) are super-hard materials with high hardness and excellent abrasive resistance, widely used in cutting tools for precision machining of automotive and aerospace parts; however, their brittle properties make them prone to premature failure. Coatings are often applied to PcBN to extend their range of applicability and durability. Conventional coating methods are limited to the thickness range of a few hundred nanometres, poor adhesion to the substrate, and limited stability under ambient conditions. To further the properties of PcBN composites, in this paper, we explore the use of ultrasonic bonding to apply thick coatings (30–80 μm) on PcBN cutting tools. For the first time, a multi-walled carbon nanotube (MWCNT) powder is preplaced on a PcBN substrate to allow an unconventional coating technique to take place. The effects of ultrasonic bonding parameters on the change of mechanical properties of the coated tools are investigated through scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-hardness analyses, and white light interferometry. The structure of the carbon nanotubes is investigated through transmission electron microscopy (pre coating) and cross-section of the bonded MWCNTs is studied via focused ion beam milling and SEM to evaluate the bonding between the multi-walled nanotubes. Optimum processing windows (i.e., bonding speed, energy, and pressure) are discovered for coating MWCNTs on PcBN. Focus ion beam milling analyses revealed a relationship between consolidation parameters and porosity of MW(pCNT) bonds. The proposed method paves the way for the novel design of functional coatings with attunable properties (i.e., thickness and hardness) and therefore improved productivity in the machining of aerospace and automotive parts.

Microscopy Methods for Biofilm Imaging: Focus on SEM and VP-SEM Pros and Cons.

Simple SummaryBacterial biofilms cause infections that are often resistant to antibiotic treatments. Research about the formation and elimination of biofilms cannot be undertaken without detailed imaging techniques. In this review, traditional and cutting-edge microscopy methods to study biofilm structure, ultrastructure, and 3-D architecture, with particular emphasis on conventional scanning electron microscopy and variable pressure scanning electron microscopy, are addressed, with the respective advantages and disadvantages. When ultrastructural characterization of biofilm matrix and its embedded bacterial cells is needed, as in studies on the effects of drug treatments on biofilm, scanning electron microscopy with customized protocols such as the osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA), and ionic liquid (IL) must be preferred over other methods for the following: unparalleled image quality, magnification and resolution, minimal sample loss, and actual sample structure preservation. The first step to make a morphological assessment of the effect of the various pharmacological treatments on clinical biofilms is the production of images that faithfully reflect the structure of the sample. The extraction of quantitative parameters from images, possible using specific software, will allow for the scanning electron microscopy morphological evaluation to no longer be considered as an accessory technique, but a quantitative method to all effects.Several imaging methodologies have been used in biofilm studies, contributing to deepening the knowledge on their structure. This review illustrates the most widely used microscopy techniques in biofilm investigations, focusing on traditional and innovative scanning electron microscopy techniques such as scanning electron microscopy (SEM), variable pressure SEM (VP-SEM), environmental SEM (ESEM), and the more recent ambiental SEM (ASEM), ending with the cutting edge Cryo-SEM and focused ion beam SEM (FIB SEM), highlighting the pros and cons of several methods with particular emphasis on conventional SEM and VP-SEM. As each technique has its own advantages and disadvantages, the choice of the most appropriate method must be done carefully, based on the specific aim of the study. The evaluation of the drug effects on biofilm requires imaging methods that show the most detailed ultrastructural features of the biofilm. In this kind of research, the use of scanning electron microscopy with customized protocols such as osmium tetroxide (OsO4), ruthenium red (RR), tannic acid (TA) staining, and ionic liquid (IL) treatment is unrivalled for its image quality, magnification, resolution, minimal sample loss, and actual sample structure preservation. The combined use of innovative SEM protocols and 3-D image analysis software will allow for quantitative data from SEM images to be extracted; in this way, data from images of samples that have undergone different antibiofilm treatments can be compared.

Correlative Microscopy to Localize and Characterize Iron Deposition in Alzheimer's Disease.

Background:Recent evidence suggests that the accumulation of iron, specifically ferrous Fe2+, may play a role in the development and progression of neurodegeneration in Alzheimer’s disease (AD) through the production of oxidative stress.Objective:To localize and characterize iron deposition and oxidation state in AD, we analyzed human hippocampal autopsy samples from four subjects with advanced AD that have been previously characterized with correlative MRI-histology.Methods:We perform scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS) in the higher resolution transmission electron microscope on the surface and cross-sections of specific iron-rich regions of interest.Results:Specific previously analyzed regions were visualized using SEM and confirmed to be iron-rich deposits using EDS. Subsequent analysis using focused ion beam cross-sectioning and SEM characterized the iron deposition throughout the 3-D volumes, confirming the presence of iron throughout the deposits, and in two out of four specimens demonstrating colocalization with zinc. Analysis of traditional histology slides showed the analyzed deposits overlapped both with amyloid and tau deposition. Following higher resolution analysis of a single iron deposit using scanning transmission electron microscope (STEM), we demonstrated the potential of monochromated STEM-EELS to discern the relative oxidation state of iron within a deposit.Conclusion:These findings suggest that iron is present in the AD hippocampus and can be visualized and characterized using combined MRI and EM techniques. An altered relative oxidation state may suggest a direct link between iron and oxidative stress in AD. These methods thus could potentially measure an altered relative oxidation state that could suggest a direct link between iron and oxidative stress in AD. Furthermore, we have demonstrated the ability to analyze metal deposition alongside commonly used histological markers of AD pathology, paving the way for future insights into the molecular interactions between Aβ, tau, iron, and other putative metals, such as zinc.

Hierarchical porous poly(l-lactic acid)/SiO2 nanoparticles fibrous membranes for oil/water separation

A two-step strategy has been developed to introduce silica nanoparticles into highly porous poly(l-lactic acid) (PLLA) nanofibers. Silica nanoparticles (SiNPs) were firstly synthesized and then modified to be hydrophobic. After PLLA/SiNPs composite fibrous membranes were electrospun and collected, they were re-crystallized by acetone at room temperature for a few minutes. With the re-arrangement of PLLA chains, the nano-/micro-electrospun fibres were transformed from non-porous ones to be porous ones with high surface area. Consequently, SiNPs that were completely covered by PLLA before acetone treatment showed up at the fibre surface. Higher PLLA crystallization also enhanced the Young’s modulus and tensile strength (420 and 8.47 MPa) of the composite membrane. However, incorporation of SiNPs into porous PLLA membranes reduced their modulus and tensile strength (280.66 and 5.92 MPa), but an increase in strain to fracture (80.82%) was observed. Scanning electron microscopy (SEM), focused ion beam SEM, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction were applied to confirm the presence of SiNP in PLLA fibres. The presence of SiNPs inside and outside fibres enhances the hydrophobicity of PLLA/SiNPs nano-fibrous membrane as the water contact angle is greater than 150°. The oil absorption of these porous composite membranes was also tested using four different oils, which can reach the highest absorption capacity when the weight ratio of PLLA and SiNPs is 1:1. The flux of prepared membranes was investigated, and results indicated that SiNPs-loaded membrane effectively enhanced the flux (5200 Lm−2 h−1).

Synaptic Organization of the Human Temporal Lobe Neocortex as Revealed by High-Resolution Transmission, Focused Ion Beam Scanning, and Electron Microscopic Tomography.

Modern electron microscopy (EM) such as fine-scale transmission EM, focused ion beam scanning EM, and EM tomography have enormously improved our knowledge about the synaptic organization of the normal, developmental, and pathologically altered brain. In contrast to various animal species, comparably little is known about these structures in the human brain. Non-epileptic neocortical access tissue from epilepsy surgery was used to generate quantitative 3D models of synapses. Beside the overall geometry, the number, size, and shape of active zones and of the three functionally defined pools of synaptic vesicles representing morphological correlates for synaptic transmission and plasticity were quantified. EM tomography further allowed new insights in the morphological organization and size of the functionally defined readily releasable pool. Beside similarities, human synaptic boutons, although comparably small (approximately 5 µm), differed substantially in several structural parameters, such as the shape and size of active zones, which were on average 2 to 3-fold larger than in experimental animals. The total pool of synaptic vesicles exceeded that in experimental animals by approximately 2 to 3-fold, in particular the readily releasable and recycling pool by approximately 2 to 5-fold, although these pools seemed to be layer-specifically organized. Taken together, synaptic boutons in the human temporal lobe neocortex represent unique entities perfectly adapted to the “job” they have to fulfill in the circuitry in which they are embedded. Furthermore, the quantitative 3D models of synaptic boutons are useful to explain and even predict the functional properties of synaptic connections in the human neocortex.

Three-Dimensional Observation of Internal Defects in a β-Ga2O3 (001) Wafer Using the FIB–SEM Serial Sectioning Method

We reported our observation results on the etch pit shapes on β-Ga2O3 (001) wafers using a scanning electron microscope (SEM) and an atomic force microscope (AFM) in a previous study. However, it was difficult to detect the internal crystal defects that exist under the etch pits. In this study, to gain a detailed understanding of the internal crystal defects under the etch pits in detail, we observed the etch pits on the (001) surface three-dimensionally using a focused ion beam–SEM. The etch pits investigated were “Cicada I” and “Cicada II,” which had the characteristic shapes observed in previous SEM and AFM analysis. Using this method, we revealed the existence of plate-like defects along the (100) plane under the etch pits. The proposed method is useful for understanding internal defects the etch pits which cannot be clarified by observing the surface using SEM and AFM analysis. Furthermore, from the changes in the SEM image contrast, Cicada I and Cicada II were deduced to be internal planar defects, i.e., plate-like voids and stacking faults, respectively.

Refined Calibration Model for Improving the Orientation Precision of Electron Backscatter Diffraction Maps.

For the precise determination of orientations in polycrystalline materials, electron backscatter diffraction (EBSD) requires a consistent calibration of the diffraction geometry in the scanning electron microscope (SEM). In the present paper, the variation of the projection center for the Kikuchi diffraction patterns which are measured by EBSD is calibrated using a projective transformation model for the SEM beam scan positions on the sample. Based on a full pattern matching approach between simulated and experimental Kikuchi patterns, individual projection center estimates are determined on a subgrid of the EBSD map, from which least-square fits to affine and projective transformations can be obtained. Reference measurements on single-crystalline silicon are used to quantify the orientation errors which result from different calibration models for the variation of the projection center.

Morphological characterization and porosity profiles of tantalum glancing-angle-deposited thin films

Abstract. Glancing angle deposition (GLAD) is a physical vapor deposition (PVD) process using a substrate that rotates tilted at an angle to the evaporation source. Depending on the deposition conditions, it provides the controlled formation of regular nanostructures during the PVD process. As a result, a wide variety of shapes, such as spirals or vertical columns, can be easily fabricated in the nanometer range. For this reason, GLAD has already been proven reliable in the production of optical coatings with very low reflectance in a broad spectral range. This paper examines the morphology of tantalum nanostructures deposited on planar silicon substrates by electron beam evaporation. The prepared samples are characterized by scanning electron microscope (SEM) images at a breaking edge with respect to the layer structure and by focused ion beam (FIB) SEM images of the cross-sectional areas with respect to the porosity. The porosity can be used to model the optical properties of the thin film with the effective medium theory (EMT). Our work studies the relationship between the evaporation parameters (growth pitch and deposition angle) and thin film morphology of tantalum so that in future work the optical properties can be linked to the deposition parameters, which in turn can be chosen to achieve highly absorbent infrared radiation layers, e.g., for infrared sensors. It was shown that the porosity across the film thickness of both columnar and screw-like thin films is nearly constant, whereas the porosity profiles of spiral structures show a periodic pattern, the period of which seems to depend on the growth pitch.

Synthesis of Cobalt-Doped TiO2 Based on Metal-Organic Frameworks as an Effective Electron Transport Material in Perovskite Solar Cells.

In this study, Co-doped TiO2 was prepared successfully using a solvothermal method with trimesic acid (H3BTC) as an organic framework to form the Co-doped Ti metal–organic framework (Co-doped Ti-MOF). By thermally decomposing the Co-doped Ti-MOF in air, the framework template was removed, and porous Co-doped TiO2 was obtained. The crystal structure of the material was analyzed using X-ray diffraction. The morphology was examined using scanning electron microscopy (SEM) and focused ion beam SEM. The large specific surface area was determined to be 135.95 m2 g–1 using Brunauer–Emmett–Teller theory. Fourier transform infrared spectroscopy verified the presence of Ti–O–Ti and Co–O vibrations in the as-prepared sample. Furthermore, the results of UV–vis spectroscopy showed that doping with Co remarkably improved the absorption ability of Ti-MOF toward the visible-light region with a band gap energy of 2.38 eV (λ = 502 nm). Steady-state photoluminescence and electrochemical impedance spectroscopy were conducted to illustrate the improvement of electron transfer in the doped material further. The optimum power conversion efficiency of solar cells using 1 wt % Co-doped TiO2 as an electron transport layer was found to be 15.75%, while that of solar cells using commercial dyesol TiO2 is only 14.42%.

Measurement of gap between abutment and fixture in dental conical connection implants. A focused ion beam SEM observation.

Background The aim of the authors was to examine the abutment-fixture interface in Morse-type conical implants in order to verify gaps at this level using a new microscopical approach. Material and Methods In this in vitro study, 20 abutment-fixture complexes were prepared by sectioning (longitudinal and cross-sectional to the long axis) with a microtome and then with a focused ion beam (FIB). This is a micrometric machine tool that uses gallium ions to abrade circumscribed areas to dig deeper into the cuts obtained with the microtome in order to eliminate cut-induced artifacts. This is because the FIB abrasion is practically free from artifacts, which are normally generated by the action of the microtome blades or other techniques. Samples were then observed by scanning electron microscopy (SEM). Results The observation of the abraded parts with the FIB permitted measurement of the real gap between the implant-abutment components. A variable amount of gap was retrieved (from 0 to 3 μm) by the observations, confirming the non-hermetic nature of the connection. It has to be pointed out that in approximately 65% of cases, the gap accounted for less than 1 μm. Conclusions The reported data confirmed that the analyzed connection system allowed for minimal gap. However, from the evidence of the present analysis, it cannot be assumed that the 2 parts of a Morse-type conical implant are fused in 1 piece, which would create a perfectly matched hermetic connection. Key words:Dental abutment, dental implant, focused ion beam SEM, implant-abutment connection, morse taper, microbial leakage.

The architecture of organic matter and its pores in highly mature gas shales of the lower Silurian Longmaxi Formation in the upper Yangtze platform, south China

The nanometer-scale architecture of organic matter (OM) and associated pores in highly mature gas shales from the lower Silurian Longmaxi Formation in the upper Yangtze platform of south China were investigated using field emission scanning electron microscopy (SEM), focused ion beam SEM, and low-pressure gas (N2 and CO2) adsorption bulk pore characterization. The Longmaxi shale comprises fine-grained siliciclastic rocks deposited in a marine shelf environment, which was dominated by quartz and clay minerals. Four porous OM types were found in the Longmaxi shale on the basis of the chemical composition and spatial occurrence of OM, including (1) isolated original OM particles, (2) OM–clay mineral complexes, (3) OM–heavy mineral complexes, and (4) secondary migrated bituminous OM. The pores in the particulate OM are not homogeneously distributed, and the processes leading to different pores depend on the specific OM type. The nature of OM-hosted pores is a result of several factors, such as primary porous kerogen, mechanical compaction, organic–inorganic interactions, gaseous and liquid hydrocarbon generation, retention, and expulsion. Pore volumes and specific surface areas of the Longmaxi shale derived from low-pressure N2 and CO2 adsorption experiments reveal positive linear relationships with total organic carbon contents, which indicates that the pore systems in the highly mature Longmaxi shale are dominated by OM-hosted pores. Additionally, the OM-hosted pores appear connected compared to pores in the mineral matrix. Therefore, the OM-hosted pore systems offer the preferential storage space and primary migration pathways for natural gas in the Longmaxi shale reservoir.

Gas cluster ion beam SEM for imaging of large tissue samples with 10 nm isotropic resolution

We demonstrate gas cluster ion beam scanning electron microscopy (SEM), in which wide-area ion milling is performed on a series of thick tissue sections. This three-dimensional electron microscopy technique acquires datasets with <10 nm isotropic resolution of each section, and these can then be stitched together to span the sectioned volume. Incorporating gas cluster ion beam SEM into existing single-beam and multibeam SEM workflows should be straightforward, increasing reliability while improving z resolution by a factor of three or more.

Revealing the painterly technique beneath the surface of Vermeer\u2019s Girl with a Pearl Earring using macro- and microscale imaging

The initial steps that Johannes Vermeer took to create Girl with a Pearl Earring (c. 1665) are, partially or completely, hidden beneath the painted surface. Vermeer’s painting technique involved applying underlayers that vary in colour and thickness, on top of which he applied the upper paint layer(s). To investigate the painting’s genesis, the Girl was examined using non-invasive scientific imaging as part of the project The Girl in the Spotlight (2018). This was complemented by the re-examination of existing paint cross-sections using microscopic analytical techniques, including focused ion beam-scanning transmission electron microscopy (FIB-STEM). The weave of the canvas, visible in the X-radiograph, was examined using a new computer-assisted thread-level canvas analysis algorithm to measure the thread spacing and thread angles. The canvas was primed with a warm light grey ground, although probably not by Vermeer himself. The tinted ground provided neutral base tone upon which he began to lay in areas of light and shade in his composition, and some outlines around the figure. Multispectral infrared reflectography( MS-IRR) images in four spectral bands spanning the spectral range from 900 to 2500 nm were collected of the painting at high spatial resolution (50 µm/pixel). Visible 3D digital microscopy visualised the underlayers where Vermeer left them visible around the perimeter of the figure as a contour, and where the upper paint layers are thin. These infrared reflectograms and visible micrographs identified three distinct preparatory phases of Girl with a Pearl Earring: the ground, fine black outlines, and underlayers. Some pentimenti were also detected, including a change in the position of her ear. The combination of examination methods showed that the materials beneath the surface played an important role in establishing the three-dimensional space, fall of light, and the eventual colour in different areas of the painting.

(Invited) Latest Advances in 2D and 3D Microstructural Characterization of Fuel Cell Components

Fuel cells are complex systems whose performance and degradation depend on a number of factors spreading over multiple scales. At the lowest spatial scale are nano-sized Pt-group or Pt-group-metal-free (PGM-free) catalysts, various types of catalyst supports, proton-conducting nanometer-thin ionomer film, and gas-transporting nano-pores, all contained within the electrodes of a membrane electrode assembly (MEA). Their properties, composition and spatial distribution largely determine fuel cell performance and affect degradation trends. At the next scale are electrodes, membrane and gas diffusion layer, dictating mass, electrical and thermal transport at the micron-scale. Finally, millimeters-thick flow field plates and larger system components affect the gas transport, water and overall system management. Understanding how all of these factors affect fuel cell performance and degradation is of crucial importance, and it is only possible by applying highly correlated efforts in testing, structural characterization and mathematical modeling. The focus of this talk is to present the latest advancements in the structural characterization approaches for fuel cells at multiple scales. In the recent years, a whole suite of novel 2D and 3D characterization approaches have been developed to provide information ranging from nano-sized catalysts used in the electrodes to macro-level flow field plates. This talk will give an overview of a number of advanced characterization techniques used for fuel cell analysis, starting from some more typically used, such as scanning electron microscopy (SEM), to highly sophisticated techniques such as 3D electron tomography. Techniques such as 2D and 3D high-resolution transmission electron microscopy (HR-TEM), 2D and 3D scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS), 3D focused-ion beam SEM (FIB-SEM), electron energy loss spectroscopy (EELS), scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), and micro- and nano-computed tomography (CT), as well as developed in-situ techniques will be discussed. Challenges in characterization, ranging from sample preparation, ionomer and water imaging, image processing and quantification will be addressed. Finally, the author’s work on advanced characterization of fuel cells will be reported. Multi-scale approach in 3D imaging and property modeling, utilizing electron tomography, FIB-SEM and micro-CT, will be presented with encountered challenges [1]. Advanced 2D STEM characterization with quantification and its application for analysis of fuel cell degradation will be discussed [2]. Lastly, a collaborative work on in-situ water imaging using X-ray synchrotron imaging and revealed effect on membrane changes during operation at high current densities will be shown [3]. The talk will close by discussing the challenges and plan forward for continuing development of fuel cell characterization approaches. Jankovic, S. Zhang, A. Putz, M. S. Saha, D. Susac, Multi-scale imaging and transport modeling for fuel cell electrodes, (invited) Journal of Materials Research, 34 (4) (2019).Kneer, J. Jankovic, D. Susac, A. Putz, N. Wagner, M. Sabharwal, M. Secanell, Correlation of changes in electrochemical and structural parameters due to voltage cycling induced degradation in PEM fuel cells, Journal of The Electrochemical Society, 165 (6) F3241-F3250 (2018).N. Ge, R. Banerjee, D. Muirhead, J. Lee, H. Liu, P. Shrestha, A.K.C. Wong, J. Jankovic, M. Tam, D. Susac, J. Stumper, A. Bazylak, Membrane dehydration with increasing current density at high inlet gas relative humidity in polymer electrolyte membrane fuel cells, Journal of Power Sources, 422 (2019) 163-174.

One-step hydrothermal synthesis of Cu-doped MnO2 coated diatomite for degradation of methylene blue in Fenton-like system

In this work, we have synthesized Cu-doped MnO2@diatomite successfully though a one-step hydrothermal approach. Meanwhile, application for degradation of methylene blue in Fenton-like system was investigated. The compounds were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), Inductively Coupled Plasma analysis (ICP) and UV–vis spectroscopy measurements, beam scanning electron microscope (FIB/SEM), energy dispersive X-ray spectrometer (EDS). The observations revealed that copper was indeed intercalated into layered structure of MnO2 and Density functional theory (DFT) calculations predicted that Cu2+ intercalated MnO2@diatomite brought about the narrowing of band gap and the enhancing of charge mobility during catalysis. Electron Density Difference of CuMnD demonstrated excellent oxidation ability to dissociate H2O2 and generate hydroxyl radical (OH) to degrade the MB. Moreover, the proper copper doping of sample is more easily to form oxygen defect, which generate more surface hydroxyl groups as reaction sites for surface adsorption. In addition, the degradation efficiency of CuMnD was tremendously influenced by the initial pH, H2O2 dosage and copper content of catalyst. Ultimately, 0.02-25-CuMnD along with molar ration of Cu/Mn with 0.4402 showed the best degradation efficiency which was about 96.2% within 4 h with 16.5 mM of H2O2 and pH 2.06.

Factors controlling shale microstructure and porosity: A case study on upper Visean Rudov beds from the Ukrainian Dneiper–Donets Basin

The present contribution aims for a characterization of microstructure and pore-space distribution of upper Visean Rudov beds, considered the main source rock for conventional oil deposits in the Ukrainian Dneiper–Donets Basin and a prospect for unconventional hydrocarbon production in recent years. Broad ion beam–scanning electron microscopy (SEM) mapping revealed a remarkably heterogeneous microstructure controlled by diagenetic precipitates (Fe/Mg carbonates, albite). Formation of these precipitates is likely triggered by organic matter decomposition and represents an important influencing factor for overall porosity and permeability. Furthermore, shale diagenesis also influences mechanical properties, as suggested by nanoindentation tests. The SEM-visible organic matter porosity is restricted to solid bitumen; although pores less than 2–3 nm in vitrinites of overmature samples are indicated by focused ion beam–SEM results, they cannot be resolved clearly by this method. Pore generation in solid bitumen that likely formed in situ in primary amorphous organic matter already starts at the early oil window in samples from the basinal oil-prone organofacies, whereas most porous solid bitumen at peak oil maturity was interpreted as relicts of primary oil migration, representing an earlier oil phase that predominantly accumulated in quartz-rich layers and became nanoporous during secondary cracking. In the terrestrially dominated transitional to marginal organofacies, pore generation in pyrobitumen resulting from gas generation occurs significantly later and is less intense. Formation of authigenic clay and carbonate minerals within pyrobitumen is likely related to organic acids formed during bitumen decomposition and implies the presence of an aqueous phase even in pores that are apparently filled exclusively with solid bitumen.

The Determination and Application of the Point Spread Function in the Scanning Electron Microscope.

A method is presented to determine the spatial distribution of electrons in the focused beam of a scanning electron microscope (SEM). Knowledge of the electron distribution is valuable for characterizing and monitoring SEM performance, as well as for modeling and simulation in computational scanning electron microscopy. Specifically, it can be used to characterize astigmatism as well as study the relationship between beam energy, beam current, working distance, and beam shape and size. In addition, knowledge of the distribution of electrons in the beam can be utilized with deconvolution methods to improve the resolution and quality of backscattered, secondary, and transmitted electron images obtained with thermionic, FEG, or Schottky source instruments. The proposed method represents an improvement over previous methods for determining the spatial distribution of electrons in an SEM beam. Several practical applications are presented.

Backscattered electron imaging of resin-embedded sections.

Scanning electron microscopes have longer focal depths than transmission electron microscopes and enable visualization of the three-dimensional (3D) surface structures of specimens. While scanning electron microscopy (SEM) in biological research was generally used for the analysis of bulk specimens until around the year 2000, more recent instrumental advances have broadened the application of SEM; for example, backscattered electron (BSE) signals under low accelerating voltages allow block-face and section-face images of tissues embedded in resin to be acquired. This technical breakthrough has led to the development of novel 3D imaging techniques including focused ion beam SEM, serial-block face SEM and serial section SEM. Using these new techniques, the 3D shapes of cells and cell organelles have been revealed clearly through reconstruction of serial tomographic images. In this review, we address two modern SEM techniques: section-face imaging of resin-embedded tissue samples based on BSE observations, and serial section SEM for reconstruction of the 3D structures of cells and organelles from BSE-mode SEM images of consecutive ultrathin sections on solid substrates.