Ultrahigh-resolution Scanning Electron Research Articles

Elucidation of the Interplay between the Features of the Precursor and the Physicochemical Properties of “Core-Shell” Hierarchical Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a major bottleneck in the operation of proton-exchange membrane fuel cells (PEMFCs) since it introduces large overpotentials (no less than 250-300 mV), which degrade significantly the energy conversion efficiency of the device. In addition, the electrocatalysts (ECs) yielding the lowest ORR overpotentials in the acidic environment found at the PEMFC cathode are based on Pt, a very scarce critical raw material (CRM). Pt raises concerns as it might trigger serious supply bottlenecks in the event of a practical widespread implementation of PEMFCs in the framework of today’s energy transition. Hence, the development of high-performing and durable ECs for the ORR is a major stepping stone towards the large-scale rollout of PEMFCs.In our research group a new breakthrough approach has been devised for the synthesis of ORR ECs, that is completely different form the preparation routes that are commonly adopted in the state of the art [1, 2]. Briefly, the approach consists in the pyrolysis and subsequent treatment of a precursor obtained by coupling suitable carbon species/sacrificial supports with a zeolitic inorganic-organic polymer electrolyte (Z-IOPE). The latter comprises anionic complexes including the Pt “catalyst” and other “co-catalysts”, which are bridged by organic binders [1,2].On one hand, the proposed approach has already shown its potential to yield ECs exhibiting a performance and durability improved with respect to Pt/C benchmark ECs. On the other hand, the proposed approach is extremely flexible, especially with respect to the synthesis of the initial EC precursor. In principle, it is possible to modulate a number of crucial features of such EC precursor, with a particular reference to: (i) the chemical composition (e.g., in terms of Pt, other “co-catalysts” and N; the latter plays a crucial role to stabilize the active sites into “coordination nests” on the EC surface, raising durability); and (ii) the morphology, that can be “templated” on suitable species (e.g., carbon species, sacrificial supports). The very flexibility of the proposed synthetic process needs to be leveraged appropriately to maximize the performance of the final ORR ECs, at the same time minimizing the efforts wasted on approaches with a low development potential.Herein it is elucidated how the modulation in the parameters involved in the synthesis of the EC precursor (e.g., the binder and the approaches to couple the Z-IOPE with the support) impact the physicochemical and electrochemical properties of the final ECs, with a particular reference to the chemical composition, morphology and distribution of the ORR active sites. An extensive characterization of the final ECs is carried out. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are adopted to determine the bulk chemical composition. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to elucidate the surface chemical composition and the chemical states of the surface elements. Ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM) allow for the elucidation of EC morphology. The porosimetric features are probed by automatic gas adsorption instrumentations. Wide-angle X-ray diffraction (WAXD) is crucial to resolve the crystal structure. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) is used to clarify the “ex-situ” electrochemical performance and ORR reaction mechanism. Finally, the most promising ECs are used in the fabrication of single PEMFCs, that are tested as a function of the operating conditions.It is revealed that, in comparison with the Pt/C benchamark, some ECs are characterized by a much higher intrinsic kinetic performance due to the electronic and bifunctional effects bestowed by the carbon nitride support and the «co-catalysts». Finally, the binder has a marked effect on the stoichiometry, size, and distribution of the PtMx aggregates bearing the active sites.

(Keynote) Interplay between Physicochemical Properties of Precursors and “Core-Shell” Hierarchical Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a major bottleneck in the operation of proton-exchange membrane fuel cells (PEMFCs) since it introduces large overpotentials (no less than 250-300 mV), which degrade significantly the energy conversion efficiency of the device. In addition, the electrocatalysts (ECs) yielding the lowest ORR overpotentials in the acidic environment found at the PEMFC cathode are based on Pt, a very scarce critical raw material (CRM). Pt raises concerns as it might trigger serious supply bottlenecks in the event of a practical widespread implementation of PEMFCs in the framework of today’s energy transition. Hence, the development of high-performing and durable ECs for the ORR is a major stepping stone towards the large-scale rollout of PEMFCs.In our research group a new breakthrough approach has been devised for the synthesis of ORR ECs, that is completely different form the preparation routes that are commonly adopted in the state of the art [1, 2]. Briefly, the approach consists in the pyrolysis and subsequent treatment of a precursor obtained by coupling suitable carbon species/sacrificial supports with a zeolitic inorganic-organic polymer electrolyte (Z-IOPE). The latter comprises anionic complexes including the Pt “catalyst” and other “co-catalysts”, which are bridged by organic binders [1,2].On one hand, the proposed approach has already shown its potential to yield ECs exhibiting a performance and durability improved with respect to Pt/C benchmark ECs. On the other hand, the proposed approach is extremely flexible, especially with respect to the synthesis of the initial EC precursor. In principle, it is possible to modulate a number of crucial features of such EC precursor, with a particular reference to: (i) the chemical composition (e.g., in terms of Pt, other “co-catalysts” and N; the latter plays a crucial role to stabilize the active sites into “coordination nests” on the EC surface, raising durability); and (ii) the morphology, that can be “templated” on suitable species (e.g., carbon species, sacrificial supports). The very flexibility of the proposed synthetic process needs to be leveraged appropriately to maximize the performance of the final ORR ECs, at the same time minimizing the efforts wasted on approaches with a low development potential.Herein it is elucidated how the modulation in the parameters involved in the synthesis of the EC precursor (e.g., the binder and the approaches to couple the Z-IOPE with the support) impact the physicochemical and electrochemical properties of the final ECs, with a particular reference to the chemical composition, morphology and distribution of the ORR active sites. An extensive characterization of the final ECs is carried out. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are adopted to determine the bulk chemical composition. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to elucidate the surface chemical composition and the chemical states of the surface elements. Ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM) allow for the elucidation of EC morphology. The porosimetric features are probed by automatic gas adsorption instrumentations. Wide-angle X-ray diffraction (WAXD) is crucial to resolve the crystal structure. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) is used to clarify the “ex-situ” electrochemical performance and ORR reaction mechanism. Finally, the most promising ECs are used in the fabrication of single PEMFCs, that are tested as a function of the operating conditions.It is revealed that, in comparison with the Pt/C benchamark, some ECs are characterized by a much higher intrinsic kinetic performance due to the electronic and bifunctional effects bestowed by the carbon nitride support and the «co-catalysts». Finally, the binder has a marked effect on the stoichiometry, size, and distribution of the PtMx aggregates bearing the active sites.

Pyrolysis kinetic study of the thermal degradation of pre-treated empty fruit bunches

Empty fruit bunch (EFB) wastes are a significant source of biomass waste in Malaysia and have the potential to be a high-quality source of energy. This study aims to evaluate the kinetic of EFB biochar degradation and its characteristics under three conditions of washing pre-treatments. Prior to biochar production via slow pyrolysis process, stirring and soaking techniques were utilised as part of the pre-treatment for the washing process, with varying solid-to-liquid (S:L) ratios of 1:50, and 1:50 to 1:70, respectively. The study analysed the higher heating value (HHV), pyrolysis yield and kinetic activation energy of the biochar. The morphology and elemental composition of the biochar samples were determined using ultra-high resolution scanning electron microscopy (UHR-SEM) and energy dispersive X-Ray detector (EDX). The Coats-Redfern model was used to estimate the activation energies of the EFB biochar from thermogravimetric (TGA) data in a temperature range of 30 °C to 800 °C and a constant heating rate of 10 °C/min under a nitrogen atmosphere. The results showed that washing pre-treatment significantly changed the morphology and elemental compositions of the EFB biochar samples. The higher S:L ratio of 1:70 has a more significant impact on the breakdown of the lignocellulosic structure of EFB. The soaked samples had slightly lower biochar and bio-oil yields (22.73 mf wt. % to 24.86 mf wt. % and 27.97 mf wt. % to 39.39 mf wt. %, respectively) than the stirred samples (25.22 mf wt. % and 49.59 mf wt. %). The pre-treatment process improved the carbon content while reducing potassium by 60.7 to 81.39%. The HHVs of EFB-4 (28.24 MJ/kg) and EFB-3 (26.57 MJ/kg) were higher than those of EFB-2 (26.2 MJ/kg) and EFB-1 (23.14 MJ/kg), indicating an improvement in their fuel properties. The higher kinetic activation energies of EFB-4 (43.27 to 48.30 MJ/mol) indicate better thermal stability than the others. Therefore, concerning improved fuel properties, the recommended pre-treatment of EFB for the pyrolysis process is soaking at 90 °C with an S:L ratio of 1:70. The kinetic analysis revealed that the pyrolysis of pre-treated EFBs follows a multi-step reaction mechanism, with different activation energies for each stage. The obtained kinetic parameters can be used to optimize the pyrolysis process and design efficient pyrolysis reactors for the valorization of EFBs. Overall, this study provides valuable insights into the thermal behavior of pre-treated EFBs and their potential for bioenergy production.

Identification of circular dorsal ruffles as signal platforms for the AKT pathway in glomerular podocytes.

Circular dorsal ruffles (CDRs) are rounded membrane ruffles induced by growth factors to function as precursors of the large-scale endocytosis called macropinocytosis. In addition to their role in cellular uptake, recent research using cell line systems has shown that CDRs/macropinocytosis regulate the canonical AKT-mTORC1 growth factor signaling pathway. However, as CDRs have not been observed in tissues, their physiological relevance has remained unclear. Here, utilizing ultrahigh-resolution scanning electron microscopy, we first report that CDRs are expressed in glomerular podocytes ex vivo and in vivo, and we visually captured the transformation process to macropinocytosis. Moreover, through biochemical and imaging analyses, we show that AKT phosphorylation localized to CDRs upstream of mTORC1 activation in podocyte cell lines and isolated glomeruli. These results demonstrate the physiological role of CDRs as signal platforms for the AKT-mTORC1 pathway in glomerular podocytes at the tissue level. As mTORC1 plays critical roles in podocyte metabolism, and aberrant activation of mTORC1 triggers podocytopathies, our results strongly suggest that targeting CDR formation could represent a potential therapeutic approach for these diseases.

Bio-graphene production from oil palm shell waste valorised through sequential thermal and catalytic means

Cellulose, hemicellulose and lignin made up a large majority of biomass in the world. These three organic polymers can produce bio-gas such as methane (CH4) and carbon dioxide (CO2) which are necessary for bio-graphene fabrication. Carbon layer deposition depends on CH4 while the uniformity and porosity of the carbon layer depend on CO2 and activation agent interaction. By altering the Oil Palm Shell (OPS) biomass precursor through pyrolysis, the remaining content of biomass precursors will enhance bio-graphene development through Chemical Vapor Deposition (CVD) process. The alteration of these biomass precursors is made through thermal manipulation at temperatures of 200 ∘C, 400 ∘C and 600 ∘C. The best thermal means will produce bio-graphene encompassing observable crystallinity, appropriate exfoliation, low defect, high carbon and low oxygen value which possess characteristics that are similar to bio-graphene fabricated from the past years. The different pre-treated biomass through pyrolysis are characterized using proximate analysis, Fourier-transform infrared spectroscopy (FTIR), Field-Emission Scanning Electron Microscope (FESEM), Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Micro-Raman. Additionally, the different bio-graphene samples fabricated from pre-treated biomass precursors were identified and characterized using Atomic Force Microscopy (AFM), Ultra-high Resolution Scanning Electron Microscope (U-SEM), Energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Micro-Raman spectrometer.

(Invited) Correlation between the Porosimetric Features, Morphology, “Ex-Situ” and “in-Situ” electrochemical Performance of Hierarchical “Core-Shell” Carbon Nitride Pt-Alloy ORR Electrocatalysts

The widespread commercialization of proton-exchange membrane fuel cells (PEMFCs) is still bottlenecked by the high loading of platinum-group elements (PGMs), typically platinum, in the cathodic electrocatalytic layer. One strategy to overcome the sluggish kinetics of the oxygen reduction reaction (ORR) taking place at the PEMFC cathode is to increase the mass activity of Pt by implementing Pt-alloy electrocatalysts (ECs) [1]. This strategy allows to decrease the overall Pt loading in the membrane electrode assembly (MEA), the crucial functional component at the heart of the PEMFC.This contribution discusses “core-shell” hierarchical ECs (H-ECs) consisting of: (i) a hierarchical “core” comprising a blend of nanostructured carbons, that are covered by (ii) a carbon nitride (CN) “shell” wherein Pt-alloy active sites are stabilized by C- and N- ligands in “coordination nests” [2]. The active sites are based on Pt together with Ni and Cu as “co-catalysts” to enhance the ORR kinetics [3]. The bulk of the support of the H-ECs is minimized to promote mass transport phenomena.The morphology of the H-ECs is probed by ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM), and is discussed in relation to the synthetic parameters and chemical composition. In a second step, nitrogen physisorption techniques are used to evaluate the porosimetric features of the H-ECs, including the specific surface area and the size distribution of the pores. The porosimetric and morphological features are correlated with the electrochemical performance of the H-ECs as measured: (i) “ex-situ”, via cyclic voltammetry with the thin-film rotating ring-disk electrode method (CV-TF-RRDE); and (ii) in single PEMFC under operating conditions as a function of the partial pressure of oxygen in the cathodic feed. A new framework is finally proposed to rationalize and quantify the porosity-morphology-performance correlation for the H-ECs.

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample.

Thermophysiological comfort of zinc oxide nanoparticles coated woven fabrics

This study investigates physicochemical impact of ultrasonic irradiations on surface topography of woven fabrics. In a simultaneous in-situ sonochemical method, the synthesis and coating of zinc oxide nanoparticles (ZnO NPs) on woven textiles were successfully achieved. Different instruments i.e. Alambeta, moisture management tester, air permeability tester and permetester were utilised during experimentation for thermal evaluation, moisture transportation and air permeation. The results regarding thermophysiological comfort of ZnO coated fabrics were evaluated on the basis of thickness and ZnO NPs coated amount on fabrics. In addition, the achieved results depict the impact of sonication (pressure gradient) on surface roughness of cotton and polyester. The coating of ZnO NPs on fabrics, crystal phase identification, surface topography and fluctuations in surface roughness were estimated by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray Diffractometry (XRD), ultrahigh-resolution scanning electron microscopy (UHR-SEM) and energy dispersive X-ray (EDX). Moreover, thermophysiological properties i.e. thermal conductivity, absolute evaporative resistance, thermal absorptivity, air permeability, overall moisture management capacity and relative water vapour permeability of untreated and ZnO treated samples were evaluated by standard test methods.

Effect of Strain on Strain‐Induced Precipitation Behavior of MnS in 3% Si Steel

Hot compression tests of 3% Si steel with a true strain range of 0.02–0.92 at a strain rate of 1 s−1 and a temperature of 1173 K, based on the Gleeble‐1500 thermo–mechanical simulator, are conducted. The effect of strain on the strain‐induced precipitation behavior of MnS is investigated via cold field‐emission ultrahigh resolution scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The experimental results obtained indicate that the volume density of MnS precipitates increases, whereas the mean diameter of MnS precipitates decreases with the increase in strain during the transient deformation stage. However, during the steady deformation stage, these parameters remain nearly constant. The precipitation behavior of MnS during the transient deformation stage is attributed to the increase in dislocation density with the increase in strain. More dislocations create a larger number of nucleation sites, which, in turn, increase the nucleation rate. At the same time, a model about static recovery affecting the dislocation density in the matrix after deformation is also proposed to elucidate the mechanism of the evolution of MnS in the aging process.

PB-02 Observation of influenza virus particles by ultra-high resolution scanning electron microscope

PB-02 Observation of influenza virus particles by ultra-high resolution scanning electron microscope

Effect of varying the vanadium thickness layer of V2O5/V/V2O5 film on its microstructural and thermochromic properties

In this study, V2O5/V/V2O5 sandwich-structured films were deposited on glass substrates by electron beam evaporation. The thickness of the first (bottom) V2O5 layer was 40 nm and the last (top) layer was 20 nm, while that of the sandwiched vanadium layer varied up to 12 nm for different samples. The effects of varying the thickness of the sandwiched vanadium layer on microstructural and thermochromic properties of the as-deposited and thermal annealed films were investigated. Ultrahigh-resolution scanning electron microscopy revealed the presence of nanostructures with various irregular shapes on the surfaces of all films. Also, the atomic force microscopy revealed an average roughness of ∼10–38 nm for increasing thickness of the sandwiched vanadium layer. X-ray powder diffraction measurements showed the presence of the monoclinic VO2 (M) crystal structure of the films with (011) preferred orientation at 27.94° for both 7 and 12 nm thicknesses of the sandwiched vanadium layers. The varying thickness of the sandwiched vanadium layers enhanced phase transition temperature values to ∼33.92 and ∼29.11 °C for both 7 and 12 nm thicknesses of the sandwiched layers, respectively. These enhanced transition temperature values, as a result of thickness variation of the sandwiched vanadium layers, pointed toward utilization of this method in the successful synthesis of VO2 films for thermochromic windows application and optoelectronics.

The “oro di metà” Gilding in the Fifteenth-Century: A Multi-Analytical Investigation

Few and fragmentary is the information regarding the “oro di metà” (halfway gold) gilding due to the low probability of finding it in paintings as well as its short durability because of tarnishing. However, the very rare, excellent state of conservation of the gilding found in the fifteenth-century wood panel painting of the Master of St. Ivo studied in this work along with a multi-analytical approach allowed shedding light on the structure, the composition and the conservation state of this type of gilding. An Ultra-High Resolution Scanning Electron Microscope (UHR-SEM) along with Energy Dispersive X-Ray (EDX) analysis and polarised light Optical Microscopy (OM) were employed in order to image and analyse a cross-section of a sample taken from the wood panel painting. Results highlighted a divided structure of the gilding which is constituted by two separated layers of gold and silver with different thickness. This is the first time that scientific evidence on this issue is provided. Moreover, considerations on the tarnishing process of the gilding were made. Finally, complementary vibrational spectroscopic techniques such as micro-Raman and micro-ATR-FTIR were employed in order to identify the molecular composition of the “bole” (gilding preparation layer) and the ground layers.

Structure, thermal stability and chromaticity investigation of TiB2 based high temperature solar selective absorbing coatings

Transition metal titanium diboride (TiB2) is a promising material for the solar selective absorbing coatings due to its favorable spectral selectivity and thermal stability. In this research, spectrally selective TiB2/Al2O3 tandem absorber is deposited on stainless steel (SS), which exhibits a high solar absorptance (αs = 0.93) and a low thermal emissivity (ε = 0.11). In this tandem absorber, the TiB2 acts as the main absorber layer and the Al2O3 acts as an antireflection layer. The tandem absorber coating is systematically characterized by ultra-high resolution scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Micro-Raman techniques. The thermal stability in vacuum of the SS/TiB2/Al2O3 tandem absorber coatings is investigated in the temperature range of 400–800 °C for 2 h and 100 h, respectively. SEM and Raman spectra indicate that the change of surface morphology and chemical composition for the coating result in the degradation of optical performance. With the different annealed temperature, the SS/TiB2/Al2O3 tandem absorber coatings exhibit different color, which is further investigated using chromaticity diagram.

Structure, thermal stability and optical simulation of ZrB2 based spectrally selective solar absorber coatings

In the present work, a solar selective coating of ZrB2/Al2O3 was deposited onto stainless steel (SS) substrates using a magnetron sputtering system. The coating exhibited an good selective absorbing properties with an absorptance of 0.92 and an emittance of 0.11. To investigate the thermal stability of the coating, the samples were annealed at 500 °C and 600 °C for 100 h, respectively. Experimental results indicated that the coating was thermally stable at 500 °C. The structure and optical properties of the coating is also characterized using ultra-high resolution scanning electron microscope, UV–vis–NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The reflectance spectra of the SS/ZrB2/Al2O3 coating was successfully simulated by CODE software.

Исследование нанопорошков металлов методом электронной микроскопии

This article presents the results of experiments on the study of metal nanopowders by the method of ultrahigh resolution scanning electron microscopy and transmission microscopy. Electron microscopy is one of the main methods of studying nanomaterials that allows you to directly see the objects under study. In a scanning electron microscope, secondary, reflected and absorbed electrons are used to obtain the image of the sample surface. The remaining emissions are used as additional sources of information. The results of scanning electron microscopy showed that nickel and iron nanoclusters are close to a spherical shape with an average diameter of 50 and 65 nm, respectively. The results of studies by transmission electron microscopy of NP of nickel and iron are consistent with the results obtained using ultrahigh resolution scanning electron microscopy. In contrast to NP of nickel and iron, the histogram of the size distribution of copper NP has a bimodal distribution. The average particle diameter of the first and second fraction is 23.6 and 81 nm, respectively. The results of scanning and transmission electron microscopy showed that copper nanoclusters have distinct crystallographic faces and edges.

Shock-tube study of the formation of iron, carbon, and iron–carbon binary nanoparticles: experiment and detailed kinetic simulations

ABSTRACTAn experimental and computational study of the formation of pure iron nanoparticles, carbon nanoparticles (soot), and binary carbon-coated iron nanoparticles during the pyrolysis of iron pentacarbonyl–argon, ethylene–argon, and iron pentacarbonyl–ethylene–argon mixtures, respectively, behind reflected shock waves is carried out. The shape and size distribution of these nanoparticles are examined on a Zeiss Ultra plus ultrahigh-resolution field-emission scanning electron microscope. The binary iron–carbon particles were also investigated by high-resolution transmission electron microscopy and high-angle annular dark-field imaging (HAADF STEM) on a FEI Osiris transmission electron microscope equipped with a Bruker SuperX detector. Detailed kinetic simulations of the formation of these three types of particles are performed, which predict the concentration, average size, and size distribution of particles.

Hydroxyapatite deposition on the laser modified Ti13Nb13Zr alloy

Abstract The Ti13Nb13Zr alloy was subjected to laser modification with the Nd:YAG laser provided that such treatment would increase the surface roughness followed improved adhesion of hydroxyapatite (HAp) coatings The hydroxyapatite was deposited by electrophoretic method in suspension of 0.5 g HA powder and 100 ml ethyl alcohol. The deposition was carried out for 10 min at 10 V voltage followed by drying at room temperature for 24 h and heating at 800°C for 1 h in vacuum. The thickness of the HAp coatings was found as of about 4.06 μm to 9.05 μm. The examinations of surfaces were carried out at each stage of the experiment with the ultra-high resolution scanning electron microscope. The measurements of surface roughness after laser treatment and after HAp deposition were performed with the Hommel Etamic Waveline profilograph.

Elucidating the Importance of Pore Structure in Determining the Double-Layer Capacitance of Nanoporous Carbon Materials

Porous carbon is a common electrode material used in electrochemical double-layer capacitors, in which energy is stored by physical adsorption of electrolyte ions on the carbon’s surface, forming an electrical double layer (EDL). However, due to the complex nanoporous network of carbon materials, it is difficult to characterize the EDL structure. This work demonstrates that the understanding of the EDL structure in nanoporous carbon materials can be improved by defining the pore shapes using ultrahigh resolution scanning electron microscopy (SEM). The SEM images reveal a continuous network of curved pores. This characterization, along with the experimentally determined surface areas and pore sizes, enabled the investigation of the applicability of various models describing the EDL configuration. This study found that, by using the microscopic information to characterize the 3-D nanostructure and select the appropriate models for the pore shape, it is possible to predict a porous carbon material’s experime...

Multi-scale multi-dimensional microstructure imaging of oil shale pyrolysis using X-ray micro-tomography, automated ultra-high resolution SEM, MAPS Mineralogy and FIB-SEM

The complexity of unconventional rock systems is expressed both in the compositional variance of the microstructure and the extensive heterogeneity of the pore space. Visualizing and quantifying the microstructure of oil shale before and after pyrolysis permits a more accurate determination of petrophysical properties which are important in modeling hydrocarbon production potential. We characterize the microstructural heterogeneity of oil shale using X-ray micro-tomography (µCT), automated ultra-high resolution scanning electron microscopy (SEM), MAPS Mineralogy (Modular Automated Processing System) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM). The organic-rich Eocene Green River (Mahogany zone) oil shale is characterized using a multi-scale multi-dimensional workflow both before and after pyrolysis. Observations in 2-D and 3-D and across nm-µm-mm length scales demonstrate both heterogeneity and anisotropy at every scale. Image acquisition and analysis using µCT and SEM reveal a microstructure of alternating kerogen-rich laminations interbedded with layers of fine-grained inorganic minerals. MAPS Mineralogy combined with ultrafast measurements reveal mineralogic textures dominated by dolomite, calcite, K-feldspar, quartz, pyrite and illitic clays along with their spatial distribution, augmenting conventional mineral analysis. From high resolution Backscattered electron (BSE) images, intra-organic, inter-organic-mineral, intra- and inter-mineral pores are observed with varying sizes and geometries. By using FIB milling and SEM imaging sequentially and repetitively, 3-D data sets were reconstructed. By setting 3-D gradient and marker-based watershed transforms, the organic matter, minerals and pore phases (including pore-back artifacts) were segmented and visualized and the pore-size distribution was computed. Following pyrolysis, fractures from the mm-to-µm scales were observed with preferential propagation along the kerogen-rich laminations and coalescence leading to an interconnected fracture network. The application of these techniques to worldwide oil shale deposits will allow significant insights into estimating mechanical and chemical proprieties of oil shale formations for modeling and designing oil shale pyrolysis processes.

Biomineralization Abilities of Cupriavidus Strain and Bacillus subtilis Strains In Vitro Isolated from Speleothems, Rani Cave, Chhattisgarh, India

ABSTRACTIn vitro culture experiments using three bacterial strains CSJC1, CSJC2, and CSJC3 isolated from speleothems, Rani cave, Chhattisgarh, India, were studied to examine their biomineralization potential. These speleothems showed high microbial cell enumerations on nutrient agar and iron agar (9 × 104 CFU/g) followed by thiosulfate agar (7 × 104 CFU/g), and 60 diverse strains were isolated. The BLASTn sequence search of 16S rRNA sequences with the NCBI database to establish the identity of CSJC1, CSJC2, and CSJC3 strains yielded similarity scores of ≥99% with the respective organisms, and the strains were identified as CSJC1 – Bacillus sp., CSJC2 – Cupriavidus sp., CSJC3 – Bacillus sp. The phylogenetic analysis of CSJC2 strain suggests that it formed a separate major cluster with Cupriavidus sp. and Cupriavidus necator. The phylogenetic analysis of CSJC1 and CSJC3 strains revealed that it formed a major cluster with several strains of Bacillus sp. and Bacillus subtilis. The biominerals induced by Cupriavidus sp. CSJC2 strain imaged with an ultra high-resolution field emission scanning electron microscope (FE-SEM) were seen as calcified coccoid shells that transformed into calcified dumbbells. FE-SEM imaging of biominerals induced by B. subtilis CSJC1 and CSJC3 tested both on B4 media and sheep blood agar individually showed that the precipitates formed calcified dumbbells that were almost similar but not identical phenotypically, indicating that strain-specific morphologies and crystal formation is easier when Ca is present in the media. This is the first comprehensive report on the possible evidences about the role of Cupriavidus sp. in calcite precipitation isolated from speleothems in the Indian caves. These results allow us to postulate that the identified strains may have a role in the biogenic influences in mineral formations at Rani cave.