High-resolution Electron Microscopy Analysis Research Articles

Point-defect-induced electronic polarization to enhance H* generation for removal of bisphenol A

Intrinsic point defects in metal core-shell materials can regulate electron redistribution, thereby reducing catalytic energy barriers and enhancing their ORR activity. However, their specific contributions to electron transfer and mass transport pathways remain unclear. In this study, defect-rich hollow OCo@Co3O4 nanoparticles were successfully synthesized using ZIF-67(Co) as a sacrificial template through controlled annealing and internal electric field substitution reactions. High-resolution electron microscopy analysis and density functional theory (DFT) calculations co-revealed the growth mechanism of Co and O vacancies, as well as antisite defects. The formation of oxygen vacancies significantly lowered the energy barrier for Co vacancy formation, playing a crucial bridging role in the development of antisite defects. The electric field polarization induced by Co-O atomic displacement resulted in asymmetric charge distribution, optimizing the adsorption of active hydrogen (H*) and oxygen atoms and facilitating the generation and release of reactive oxygen species (ROS). Electrocatalytic experiments demonstrated that under the combined action of singlet oxygen (1O2) and H*, bisphenol A (BPA) can be efficiently degraded. This study successfully bridges the knowledge gap between atomic defects and advanced electrocatalysis, providing a new perspective and insight for the in-depth analysis of the structure-performance relationship of electrocatalyst materials in the future.

Investigating the Temperature Dependency of Trimethyl Aluminum Assisted Atomic Surface Reduction of Li and Mn-Rich NCM

Most next-generation electrode materials are prone to interfacial degradation, which eventually spreads to the bulk and impairs electrochemical performance. One promising method for reducing interfacial degradation is to surface engineer the electrode materials to form an artificial cathode electrolyte interphase as a protective layer. Nevertheless, the majority of coating techniques entail wet processes, high temperatures, or exposure to ambient conditions. These experimental conditions are only sometimes conducive and can adversely affect the material structure or composition. Therefore, we investigate the efficacy of a low-temperature, facile atomic surface reduction (ASR) using trimethylaluminum vapors as a surface modification strategy for Li and Mn-rich NCM (LMR-NCM). The results presented herein manifest that the extent of TMA-assisted ASR is temperature-dependent. All tested temperatures demonstrated improved electrochemical performance. However, ASR carried out at temperatures >100 °C was more effective in preserving the structural integrity and improving the electrochemical performance. Electrochemical testing revealed improved rate capabilities, cycling stability, and capacity retention of ASR-treated LMR-NCM. Additionally, post-cycling high-resolution scanning electron microscopy analysis verified that after extended cycling, ASR carried out at T > 100 °C showed no cracks or cleavage, demonstrating the efficiency of this method in preventing surface degradation.

ω-Strengthened Ti-23Nb alloy with twinning-induced plasticity developed via reverse martensitic transformation

The twinning-induced plasticity (TWIP) effect contributes to high strength and ductility synergy in metastable β Ti alloys. Moreover, stress-induced α″ martensites (SIMs) are usually concurrent with TWIP, resulting in low yield strength. As a new pathway, the production of ω-strengthened metastable β Ti alloys from full α″ Ti alloys can be accomplished via reverse martensitic transformation. However, the deformation mechanisms of the metastable β Ti alloys acquired by this pathway have not been adequately reported. Accordingly, in this study, the full α″-type solution-treated (ST) samples of Ti-23Nb at.% alloy were annealed at 573 K followed by slow cooling to acquire the air-cooled (AC) and furnace-cooled (FC) samples with β phase and ω precipitates. Mechanical properties and deformation behaviors of these samples were systematically investigated. The AC and FC samples exhibited higher yield strengths than the ST samples. Although SIMs still existed in the AC samples, they were completely suppressed in the FC samples. The annealed samples demonstrated high ductility due to the TWIP effects stemming from {332}<113>β twins. Furthermore, a distorted α″ phase exhibiting the abnormal orientation relationships (ORs) <11¯0>β//<001>α″, {332}β//{100}α″, and {110}β//{110}α″ with both β matrix and twin was revealed by high-resolution transmission electron microscopy and crystallographic analyses. These ORs were governed by the lattice distortion associated with a unique β matrix → distorted α″ → {332}β twin pathway. This study suggests that metastable β Ti alloys with enhanced mechanical properties can be achieved via the α″ → β reverse martensitic transformation and ω precipitation.

Microwave-assisted Morinda citrifolia L leaves extract mediated synthesis, magnetic and antimicrobial studies of pure and calcium substituted zinc ferrite

In this study, ZnFe2O4 and calcium-substituted Zn1-xCaxFe2O4 (x = 0.2, Ca2-ZF & x = 0.4, Ca4-ZF) are synthesized using Morinda citrifolia L. leaves extract via the microwave method, and calcined at 800 °C for 4 h to enhance the crystallinity. The purity and structural features of the ferrites were analyzed using powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FT-IR) techniques confirming single phase formation and functional groups. Morphology and elemental presence were examined using high-resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray analysis (EDX) that exhibit polyhedral morphology of the particles and confirm elemental composition. The bandgap of Zn1-xCaxFe2O4 determined using the Kubelka method from UV-DRS data, is found to increase as calcium concentration and is in the range 1.73–1.91 eV. Room-temperature VSM studies showed a transition from superparamagnetic behavior to soft ferromagnetic behavior upon Ca substitution. Zn0.6Ca0.4Fe2O4 (Ca4-ZF) composition exhibits maximum saturation magnetization, remnant magnetization and coercivity of 196 x10−3emu/g, 0.411 x10−3emu/g, and 0.091 Oe, respectively, making it suitable for biomedical applications such as cell separation, detection, and gene delivery support. The antibacterial and antifungal studies demonstrate better inhibition for ZF than for Cax-ZF compounds. The pure ZF shows a maximum zone of inhibition against Bacillus subtitles bacteria and Candida albicans fungus of 23.7 mm/250 μg/mL and 28.1 mm/250 μg/mL, respectively.

Thermoelectric, mechanical and electrochemical properties of pure single-phase FeSb

This study primarily focused on forming pure single-phase FeSb and explored its thermoelectric, mechanical, and electrochemical properties since no reports are available. The FeSb binary alloy has been synthesized through the vacuum melting method, and the phase formation has been confirmed through powder X-ray diffraction (PXRD). The PXRD results show that the synthesized FeSb binary alloy belongs to the hexagonal crystal structure with space group P63/mmc, which coincides with ICSD no. 53971. The pure single phase has been formed by creating a deficiency of 10 % in antimony. The High-Resolution Scanning Electron Microscopy (HR-SEM) and Energy Dispersive X-ray (EDX) analysis have been used to identify the pure single-phase and various elemental components of the hot-pressed pellet of FeSb0.9. The atomic wt.% of iron (Fe) and antimony (Sb) have been identified through EDX spectral analysis. The highest Seebeck coefficient value of −5.4 μV/K is achieved at 497 K, and the lowest electrical conductivity value of 24049 S/m is achieved at 447 K. The hardness of the material is found to be 6.076 GPa, which is much more sufficient for thermoelectric material during industrial handling. The magnetic characteristics of the prepared pure phase FeSb compound have also been measured by Vibrating Scanning Magnetometer (VSM) analysis, which has a weak ferromagnetic nature. Furthermore, three electrodes were employed to study the electrochemical properties, and the alloy has attained the appreciable specific capacitance of 169.5 F/g at 2 A/g.

Understanding the Role of the Binder on the Microstructure and Properties of PTFE-Based Solvent-Free Electrodes

Solvent-free processing, also known as dry-processing refers to a group of manufacturing methods which avoid the use of solvents in the production of electrodes for energy storage applications. This concept has been around for more than a decade, although its popularity has increased dramatically over the last couple of years after the purchase of Maxwell technologies by Tesla. Maxwell patented a novel processing route which involves dry mixing the active material powder with a PTFE binder to form an electrode without the use of any solvent. Solvent-free processes have significant advantages in terms of sustainability, safety and cost over conventional slurry casting.A detailed analysis of the slurry casting process showed that around a quarter of the total manufacturing cost of the battery pack originated from solvent associated steps. Avoiding the use of toxic and flammable solvents such as N-methyl Pyrrolidone (NMP) also naturally leads to an improvement in the safety of the manufacturing environment. More importantly, it was reported that the manufacturing steps associated with solvent removal accounted for half of the embodied energy of a typical Li-ion battery. The embodied energy of a Li-ion battery is a crucial figure of merit in terms of sustainability which is too often neglected. To put things into perspective, Volvo has recently published a carbon footprint report for their fully electric Volvo C40 Recharge and compared it to their internal combustion engine (ICE) equivalent, the XC40. They reported that the production of the electric version generated 26 tonnes of CO2-equivalents compared to 16 tonnes for the ICE model, representing a large increase of almost 70% in the embodied energy of the car. Novel and more sustainable manufacturing processes are urgently needed to reduce as much as possible the embodied energy of Li-ion batteries and make them more sustainable to enable a durable green energy transition.Although the concept of solvent-free processing seems attractive, most of its current development is happening behind closed doors in industry. However, an in-depth characterisation of this new type of electrodes and a comparison with conventional slurry cast electrodes would be beneficial to understand the challenges and opportunities brought by these new systems and help accelerate their development on a larger scale. Within the family of solvent-free processes, three main techniques have emerged: dry painting, powder injection molding and PTFE-fibrillation. Studies dedicated to electrodes based on PTFE-fibrillation are rare and often focused on solid-state systems. In order to dispel some of the mystery surrounding the novel microstructures obtained through the PTFE-fibrillation process and their performance, this work focuses on the characterisation of these new electrodes and investigate the role of the PTFE binder on the microstructure and electrochemical performance of solvent-free electrodes. Our results highlight the crucial importance of the PTFE binder on the mechanical properties of the solvent-free electrodes and reveal how the peculiar mechanical behavior of these composite electrodes during the manufacturing process influences the final microstructure of the electrodes and their electrochemical performance. This work presents a deep insight into PTFE-based solvent-free electrodes by investigating their microstructure, mechanical and electrochemical properties using advanced characterization techniques including High Resolution Analytical Scanning Electron Microscopy, X-Ray Computed Tomography, Electrochemical Impedance Spectroscopy and mechanical testing.

Untreated vs. Treated Carbon Felt Anodes: Impacts on Power Generation in Microbial Fuel Cells.

This research sought to enhance the efficiency and biocompatibility of anodes in bioelectrochemical systems (BESs) such as microbial fuel cells (MFCs), with an aim toward large-scale, real-world applications. The study focused on the effects of acid-heat treatment and chemical modification of three-dimensional porous pristine carbon felt (CF) on power generation. Different treatments were applied to the pristine CF, including coating with carbon nanofibers (CNFs) dispersed using dodecylbenzene sulfonate (SDBS) surfactant and biopolymer chitosan (CS). These processes were expected to improve the hydrophilicity, reduce the internal resistance, and increase the electrochemically active surface area of CF anodes. A high-resolution scanning electron microscopy (HR-SEM) analysis confirmed successful CNF coating. An electrochemical analysis showed improved conductivity and charge transfer toward [Fe(CN)6]3-/4- redox probe with treated anodes. When used in an air cathode single-chamber MFC system, the untreated CF facilitated quicker electroactive biofilm growth and reached a maximum power output density of 3.4 W m-2, with an open-circuit potential of 550 mV. Despite a reduction in charge transfer resistance (Rct) with the treated CF anodes, the power densities remained unchanged. These results suggest that untreated CF anodes could be most promising for enhancing power output in BESs, offering a cost-effective solution for large-scale MFC applications.

Light-absorption-driven photocatalysis and antimicrobial potential of PVP-capped zinc oxide nanoparticles

Toxic dyes in water bodies and bacterial pathogens pose serious global challenges to human health and the environment. Zinc oxide nanoparticles (ZnO NPs) demonstrate remarkable photocatalytic and antibacterial potency against reactive dyes and bacterial strains. In this work, PVP-ZnO NPs have been prepared via the co-precipitation method using polyvinylpyrrolidone (PVP) as a surfactant. The NPs’ microstructure and morphology were studied using X-ray diffraction (XRD), having a size of 22.13 nm. High-resolution transmission electron microscope (HR-TEM) and field emission scanning electron microscopy (FESEM) analysis showed spherical-shaped PVP-ZnO NPs with sizer ranging from 20 to 30 nm. Fourier Transform Infrared Spectroscopy (FT-IR) confirmed the hybrid nature of the NPs, and UV–Vis spectroscopy showed an absorption peak at 367 nm. The PVP-ZnO NPs exhibited high photocatalytic activity, achieving 88% and nearly 95% degradation of reactive red-141 azo dye with 10 mg and 20 mg catalyst dosages, respectively. The antibacterial properties of the NPs were demonstrated against Escherichia coli and Bacillus subtilis, with inhibition zones of 24 mm and 20 mm, respectively. These findings suggest that PVP-ZnO NPs can be effectively used for water treatment, targeting both dye and pathogenic contaminants.

Non-destructive evaluation and corrosion study of magnetic pulse welded Al and low C steel joints

Dissimilar material (Al and steel) tubes have been successfully joined together using magnetic pulse welding technique by setting optimized parameters i.e., discharge voltage and standoff distance. The welded interface has revealed an irregular wavy morphology with melt pockets (max. width ∼20 μm) consisting of intermetallic compound embedded in elemental mixture. High resolution electron microscopy and compositional analysis through energy dispersive x-ray spectroscopy (EDXS) have revealed the formation of 2–3 μm long rod-shaped Fe-Al intermetallic compound. Non-destructive ultrasonic C-scans of the sample welded at 15.5 kV discharge voltage and 1.25 mm air gap have indicated sound welds between the two materials depicting 80% joint integrity while considering the backwall reflection threshold at 50%. The corrosion behaviour at the weld interfaces has been investigated in aqueous solution of 3.5 wt. % NaCl using both potentiodynamic and immersion tests revealing the influence of the intermetallic compound layer on corrosion.

Structural, thermal, electrical and magnetic properties of Fe2CrAl FulHeusler alloy prepared by ball milling

The outcomes of experiments on the physical, electrical, magnetic and thermal assets of Fe2CrAl full Heusler alloy are discussed. Different studies scientifically investigated the physical properties of Fe2CrAl Heusler alloys. The ternary full Heusler alloy Fe2CrAl was synthesized by the automatic mechanical alloying method. The influence of annealing at various temperatures was studied. Cu2MnAl - type structure of L21 type phase was confirmed using X-ray diffraction analysis. Williamson-Hall plot (W–H plot) proved the small value of strain-induced expansion. High-resolution electron microscopy analysis suggests that the Fe2CrAl Heusler alloy has a nano flake-like structure with a typical particle size of ⁓ 120 nm. Energy dispersive X-ray spectroscopy study clearly shows that all the elements are present in the Fe2CrAl full Heusler alloy. Thermal stability was tested using thermal analysis techniques. Interpreting the results obtained from the Seeback measurement discloses the metallic to semiconducting like behavior, which is feasible for spintronics. VSM measurements indicate the soft ferromagnetic property of the Fe2CrAl alloy, which is demandable for spintronics device applications.

A comparison of carbon impurities in pre- and post-melt uranium Part 1: Scanning electron microscopy analysis

Although C impurities in U have been studied for decades, fundamental questions regarding their incorporation, migration, and transformations during metal processing still exist. In two written Parts, we compare the chemical speciation, distributions, crystallography, and morphologies (e.g., size and shape) of C-containing impurities in U metal both before and after melting using high-resolution analytical electron microscopy (AEM). This first Part demonstrates the variability of carbide inclusions in U metal with respect to their chemical phases and morphologies as observed by scanning electron microscopy (SEM). A variety of inclusion types, such as the pill-shaped U monocarbide (UC), previously only hypothesized, are summarized. Additionally, delineation between hopper-shaped U carbonitride U(C,N) and dendritic U carbide inclusions is discussed in relationship to historic literature.

A comparison of carbon impurities in pre- and post-melt uranium Part 2: Scanning/Transmission electron microscopy analysis

The speciation and morphology of U carbide inclusions in pre- and post-melt U metal have been explored using high-resolution analytical electron microscopy (AEM). This report presents Part 2 of our study, in which aberration (Cs) corrected transmission and scanning transmission electron microscopies (S/TEM) were used to elementally and crystallographically characterize C-containing impurities and defect features in U samples for comparison with results obtained by scanning electron microscopy (SEM) in Part 1, previously published by this journal. Elemental mapping and unit cell matching of inclusions by S/TEM are consistent with phases observed by SEM, and new dislocations can be observed associating with some inclusion morphologies but not others.

Impact on the microstructure, optical and electrical properties of cubic boron nitride thin films under post thermal annealing

High quality cubic boron nitride (c-BN) films are of importance for practical high power and high temperature device applications; however, the synthesis of c-BN films with high crystalline quality and desirable electrical properties remains challenging due to the poor adhesion and existence of the sp2-bonded interfacial layer. In this work, we demonstrate the impact of post-thermal annealing on the microstructure and electrical properties of interfacial layer in c-BN films. The spectral and high-resolution electron microscopic analysis reveals that in addition to the generally reported stress release, this post annealing causes a phase transition and re-orientation of sp2-BN interfacial layers. The studies on their optical and electrical properties reveal that the c-BN film annealed at 700 °C exhibits a maximal band gap of 5.90 eV and highest mobility of 15 cm2V−1s−1 due to the phase transition and rearrangement of the interfacial layer. The c-BN/Si heterojunction after annealing shows rectifying performance at room temperature due to the presence of interfacial sp2-BN layer, where its defect levels and thickness play important roles on the carrier transport. This work provides additional insight on understanding and modulating the interface for the future applications of c-BN films in the fields of optics, optoelectronics, electrics.

Efficient magnetic and antibacterial properties of CdO/ZnO nanocomposites prepared via facile hydrothermal method

The effect of molar composition on the efficiency of antibacterial and magnetic properties of binary transition metal oxide nanocomposites synthesized using pH optimized hydrothermal method is reported. Its response to X-ray diffraction confirmed the crystallinity of nanocomposites. The average crystallite size is observed to be 27.37 nm, 30.21 nm and 32.3 nm for 1:1, 2:1 and 1:2 molar ratioed CdO/ZnO nanocomposites respectively. FT-IR spectroscopy revealed the presence of moisture and other functional groups, which is further confirmed the Thermogravimetric analysis showing approximately 1.5% of thermal decomposition within 200 °C in all composition. The synthesized composites are characterized for surface morphology using High-resolution scanning electron microscopy and Energy dispersive X-ray analysis showed mixed nanorods, nanotubes and spheroid structures. The optical band gap of proposed nanocomposites is characterized by UV-diffused reflectance spectroscopy showing the variation of optical band gap confirming the change in a molar proportion of CdO/ZnO nanocomposites particles. Investigation on magnetic properties displayed its paramagnetic behavior by illustrating the hysteresis curves of all nanocomposites. The antibacterial activities of proposed nanocomposites investigated for both Gram-positive and Gram-negative bacteria showed its efficiency towards antibacterial application.

Influence of Global Operating Parameters on the Reactivity of Soot Particles from Direct Injection Gasoline Engines

The aim of this study is to investigate the impact of global operating parameters, e.g., engine speed, brake mean effective pressure, and air–fuel ratio, of a turbocharged 4-cylinder GDI engine on the reactivity of soot particles against oxidation. The knowledge of soot reactivity is crucial for optimizing gasoline particulate filter regeneration strategies and is, consequently, a key parameter for reducing fuel consumption and CO2 emissions. In this work, time-resolved in-cylinder soot concentrations and exhaust particle size distributions are measured by using two-color pyrometry, engine exhaust particle sizer and smoke meter, respectively. Reactivity against oxidation by molecular oxygen is determined by temperature programmed oxidation analysis. To derive a physicochemical explanation for varying soot reactivity, the morphological and nanostructural primary particle structure of collected samples is analyzed using high-resolution electron microscopy and image analysis algorithms. The results reveal that engine operating parameters affect soot reactivity differently. While engine speed has only a slight effect, a reduction of air/fuel ratio (λ < 1.0) or an increase of BMEP > 10 bar significantly reduces the soot oxidation reactivity. These findings give evidence, that the quality of the fuel/air mixture is a significant parameter influencing soot reactivity. Measured soot concentrations substantiate the hypothesis that low-sooty homogeneous premixed combustion of a homogeneous fuel/air mixture favors formation of high-reactive soot particle fractions. Reactive soot particle aggregates are composed of multiple soot fractions of different reactivity. Reactive primary particles are composed of short graphene-like layers and vice versa, providing a physicochemical explanation for varying soot reactivity depending on engine operating conditions.

Temperature-Driven Chemical Segregation in Co-Free Li-Rich-Layered Oxides and Its Influence on Electrochemical Performance

Co-free Li-rich layered oxides are gaining interest as feasible positive electrode materials in lithium-ion batteries (LIBs) in terms of energy density, cost reduction, and alleviating safety concerns. Unfortunately, their commercialization is hindered by severe structural degradation that occurs during electrochemical operation. The study at hand demonstrates advanced structural engineering of a Li-rich Co-free oxide with composition Li1.1Ni0.35Mn0.55O2 by spray pyrolysis and subsequent calcination of an aqueous precursor, creating a segregated structure of two distinct layered phases with space groups R3̅m (rhombohedral) and C2/m (monoclinic). This particular structure was investigated with powder neutron diffraction, high-resolution analytical transmission electron microscopy imaging, and electron energy loss spectroscopic characterization. This complex structure contributes to the high electrochemical stability and good rate capability observed for this compound (160 mAh/g at C/3 and 100 mAh/g at 1C). These results provide new insights into the feasibility of developing and commercializing cobalt-free positive electrode materials for LIBs.

Metallic technetium sequestration in nickel core/shell microstructure during Fe(OH)2 transformation with Ni doping

This study investigates the impacts of Ni doping on technetium-99 (Tc) sequestration in aqueous solutions through transformation of Fe(OH)2(s) to iron spinel (magnetite) under alkaline conditions. Extensive solid characterization was performed for the mineral phases produced, as well as the Tc/Ni speciation and distribution within these phases. X-ray diffraction results show that iron spinel was the dominant mineral product without detectable Ni incorporation. The doped Ni ions mainly precipitated as fine Fe/Ni oxide/hydroxide particles, including strongly reduced nanometer˗sized spheroidal Ni-rich and metallic Ni phases. High-resolution analytical scanning transmission electron microscopy using energy dispersive X-ray spectroscopy and electron energy loss spectroscopy on the produced solid samples (focused ion beam-prepared specimens) revealed three Tc distribution domains dominated by nanocrystals and, especially, a Tc-rich metallic phase. Instances of metallic Tc were specifically found in spheroidal, Ni-rich and metallic nanoparticles exhibiting a core/shell microstructure that suggests strong reduction and sequential precipitation of Ni-Tc-Ni. Mass balance analysis showed nearly 100% Tc removal from the 4.8 × 10−4 M Tc solutions. The finding of the metallic Tc encapsulation indicates that Tc sequestration through Ni-doped Fe(OH)2(s)˗to˗iron spinel transformation process likely provides an alternative treatment pathway for Tc removal and could be combined into further waste treatment approaches.

Co-precipitation induces changes to iron and carbon chemistry and spatial distribution at the nanometer scale

Association of organic matter (OM) with mineral phases via co-precipitation is expected to be a widespread process in environments with high OM input and frequent mineral dissolution and re-precipitation. In contrast to surface area-limited adsorption processes, co-precipitation may allow for greater carbon (C) accumulation. However, the potential sub-micrometer scale structural and compositional differences that affect the bioavailability of co-precipitated C are largely unknown. In this study, we used a combination of high-resolution analytical electron microscopy and bulk spectroscopy to probe interactions between a mineral phase (ferrihydrite, nominally Fe2O3•0.5H2O) and organic soil-derived water-extractable OM (WEOM). In co-precipitated WEOM-Fe, nanometer-scale scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) revealed increased Fe(II) and less Fe aggregation relative to adsorbed WEOM-Fe. Spatially distinct lower- and higher-energy C regions were detected in both adsorbed and co-precipitated WEOM-Fe. In co-precipitates, lower-energy aromatic and/or substituted aromatic C was spatially associated with reduced Fe(II), but higher-energy oxidized C was enriched at the oxidized Fe(III) interface. Therefore, we show that co-precipitation does not constitute a non-specific physical encapsulation of C that only affects Fe chemistry and spatial distribution, but may cause a bi-directional set of reactions that lead to spatial separation and transformation of both Fe and C forms. In particular, we propose that abiotic redox reactions between Fe and C via substituted aromatic groups (e.g., hydroquinones) play a role in creating distinct co-precipitate composition, with potential implications for its mineralization.

Textural and genetic relationships between glauconite and celadonite at the nanoscale: two different structural-compositional fields

Abstract. Glauconite and celadonite coexist at the nanometre scale in Early Jurassic submarine volcanic rocks of the Betic Cordillera (southern Spain) as a result of microbial activity. Samples from the limit between the two micas, recognizable in scanning electron microscopy, have been extracted using the focussed ion beam technique and studied by high-resolution analytical electron microscopy. Both micas are present as randomly oriented differentiated small crystals in the boundary area. They define clearly distinct compositional fields with gaps affecting to Fe, Mg and K. At the lattice scale, celadonite shows a high degree of order, with homogeneous orientation of the visible lattice parameters being a difference from glauconite, formed by packets no more than 10-layers thick. Smectite layers were also detected alongside glauconite packets, in accordance with X-ray diffractograms which indicate that glauconite is a mica–smectite interstratification being more than 90 % mica layers. The compositional gap indicates that celadonite is not the endmember of the glauconitic series and the two micas represent two different structural tendencies of mica, with glauconite having more distorted octahedral sheets, indicated by systematically higher b parameters than celadonite.

Magnetic resonance imaging during the templated synthesis of mesoporous TiO2 supporting Pt nanoparticles for MOR

Mesoporous TiO2 was prepared, inside “Taurasi” grape skins. The peel impregnation was followed by magnetic resonance imaging, to monitor the transport process in the natural template and the interaction of the solute with the templating structure.Moreover, the prepared mesoporous structure was used to support ultra-small platinum nanoparticles (USNPs), allowing high dispersion and maximizing active metals utilization. USNPs characterization was performed by means of high-resolution analytical transmission electron microscopy, CO-Diffuse Reflectance Infrared Fourier Transform spectroscopy, and X-ray photoelectron spectroscopy. Low Pt loaded TiO2 was then tested in methanol oxidation reactions, showing an excellent behavior: negligible onset potentials (0.06 V) and very high If/Ib ratio (3.85). The results obtained in this work evidence the outstanding performances of the synthesized nano-electrocatalysts.