Analytical Scanning Research Articles

Electrochemical, gravimetric and surface studies of Phalaris canariensis oil extract as corrosion inhibitor for 316 L type stainless steel in H2O-LiCl mixtures

The corrosion inhibition action of Phalaris canariensis extract on 316 L stainless steel in the H2O-35 (wt%) LiCl mixture at different temperatures has been evaluated with the aid of weight loss, potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy tests. These studies were complemented by Fourier Transformed Infrared spectroscopy, FTIR, gas/mass chromatography analytical techniques and detailed scanning electronic microscopy studies. Results have indicated that Phalaris canariensis extract is an efficient inhibitor, with an efficiency that increases with its concentration, but it decreases as the temperature increases. Phalaris canariensis extract is physically adsorbed onto stainless steel according to a Temkin type of adsorption isotherm. Phalaris canariensis extract affected both anodic and cathodic electrochemical reactions with a stronger effect on the anodic ones, acting, thus, as a mixed type of inhibitor. Main compounds contained in the Phalaris canariensis extract were palmitic and oleic acids, responsible for its inhibitory properties.

Investigation into the cavitation erosion of rolled Ti6Al4V titanium alloy strengthened by the ultrasonic-assisted laser shock peening process

The novel process known as ultrasonic-assisted laser shock peening (ULSP) is conducted on hot rolled Ti6Al4V titanium alloy with polished surface to improve its cavitation erosion (CE) resistance. The microstructure and phase structure were investigated by transmission electron microscope and X-Ray diffractometer. The microhardness and residual stress were measured by microhardness tester and X-Ray residual stress analyzer. After that, the CE mass loss and morphology were analyzed through high-precision analytical balance and scanning electron microscope to reveal the CE resistance mechanism of ULSP. The results show that ULSP treatment causes plastic deformation at the surface layer, resulting in refined grains and complex dislocation structures. The aforementioned process produces a hardened layer and compressive residual stress (CRS) layer with notable amplitude and deep influence. The surface microhardness of the ULSP-9J specimen is 410 ± 4 HV, which is a 14.8 % increase compared to the LSP-9J specimen. The CRS of the ULSP-9J specimen is −329 ± 6 MPa. As a result, it is vital in preventing the formation and propagation of CE cracks, strengthening the material's resistance to CE damage, reducing mass loss, and enhancing the overall morphology of CE.

Closed form analytical solution and scan pattern shaping theory of three-element Risley prism for LiDAR systems

Three-element Risley prism are emerging technologies in LiDAR. It can convert the FoV into a rectangular shape with high coverage rates in specific conditions, making it suitable for applications in autonomous driving scenarios. The addition of a third prism has been proven effective in eliminating blind spots and singularity problems. One challenge facing the use of three-element scanners in autonomous driving is the accurate positioning control of light beams during high-speed motion, especially in specific scan patterns such as near rectangles. This work introduces a closed-form analytical solution and parameters for the scan patterns of the three-element scanner through a non-paraxial tracing method. The closed-form solution includes two groups of coefficients representing all possible configurations of the three-element scanner. The parameters consist of ten degrees of freedom: angular velocity ratio, M1, M2, deflection angle ratio, k1, k1, initial phases, θ0q(q=1,2,3), distance between the two prisms dair1, dair2, and distance from the screen, P. To our knowledge, this is the first study to discuss these degrees of freedom in the context of the closed-form solution. We obtain its scan patterns by MATLAB 2019a and explore a configuration of three-element Risley prism in near-rectangular scan patterns, achieving a wide FoV and high point cloud density while avoiding blind spots and singularity issues. To validate the simulation results, a three-element Risley prism scanner system based on brushless motor is developed. Our study suggests that the three-element rotating prism scanner holds potential superiority in forward-looking LiDAR solutions.

Geochemistry and microbiology of boreal alluvial soil under salinisation

Soil salinisation in taiga landscapes is in most cases caused by anthropogenic activities. The study was carried out in Perm region (Russia) on the territory of the Verkhnekamskoe Potash Deposit. The inflow of sodium chloride drainage water into ground and surface waters during the production of potash fertilisers contributed to the technogenic salinisation of river valleys in the taiga zone. The purpose of the research was to investigate the microbial composition and chemical properties of alluvial soils in the area affected by NaCl waters in the Lyonva River valley. The chemical properties of soils were determined standard methods such as potentiometric method, titration, and spectrophotometry. The microbial community was determined by 16 s rRNA gene metagenomic analysis. The soil's mineralogical composition was determined using a binocular microscope and diffractometer for XRD. The morphology and microstructure of the samples has been studied using an analytical scanning electron microscope. In Solonchaks, an interdependence of salinity and bacterial species composition was discovered, along with the bacteria's geochemical processes. The topsoil contains a considerable amount of toxic salts, ranging from 5.9 to 17%. The ratio of exchangeable cations in the soil absorption complex changes when exchangeable calcium is replaced by sodium. Salinisation caused the neutralisation of acidic alluvial soils. Bacteria originating from marine and highly mineralised environments predominate in the soil. The soils are dominated by bacteria originating from marine and highly mineralised environments, such as Proteobacteria, Shewanella (75–79%), Thiomicrospira (26%), Desulfuromonas, Marinomonas and Idiomarina (9–10%), Alicyclobacillus (4%). The correlation revealed the connection of some taxa with ions of aqueous extract, as well as with exchangeable sodium, mobile iron and total sulphur. Some bacteria promote azonal geochemical processes within alluvial forest soil, such as the reduction of iron and manganese, the production of sulphides, and the oxidation of sulphur, hydrogen, and iron. Sulphide accumulation resulting in the formation of a hydrotroilite horizon (FeS × nH2O) and iron-bearing formations were found on the soil surface. Studying the properties and degree of soil disturbance makes it possible to identify the contribution of enterprises to environmental pollution, as well as to apply new methods for monitoring, purifying, and storing potassium waste.

Out-of-phase thermomechanical fatigue of a single crystal Ni-base superalloy

The present work studies the out-of-phase thermomechanical fatigue (OP-TMF) behavior of the precisely oriented [001] single crystal Ni-base superalloy ERBO/1 (CMSX-4 type). The OP-TMF tests are performed between minimum and maximum temperatures of 1023 and 1223 K and a cyclic mechanical strain amplitude of ±0.5 %. In accordance with previous findings, the present study confirmed that isothermal low cycle fatigue (LCF) tests at 1023 and 1223 K show significantly longer fatigue lives than the OP-TMF tests, specimens with rougher surfaces fail earlier than polished specimens and deformation bands and cracks form in the specimen surface. Two new results were obtained: First, when comparing OP-TMF cycles with fast cooling (tensile part of cycle) and fast vs. slow heating (compressive part of cycle) one finds that the slower heating/compressive cycle is more damaging. Second, analytical scanning electron microscopy of the flanks of an OP-TMF crack allows to study the diffusion-controlled growth kinetics of the oxide and the underlying zone, which is depleted by the oxide forming elements. These results are discussed in the light of the microstructural, mechanical and chemical results of the present study considering previous work on OP-TMF of superalloy single crystals (SXs).

High‐throughput combinatorial approach expedites the synthesis of a lead‐free relaxor ferroelectric system

AbstractDeveloping novel lead‐free ferroelectric materials is crucial for next‐generation microelectronic technologies that are energy efficient and environment friendly. However, materials discovery and property optimization are typically time‐consuming due to the limited throughput of traditional synthesis methods. In this work, we use a high‐throughput combinatorial synthesis approach to fabricate lead‐free ferroelectric superlattices and solid solutions of (Ba0.7Ca0.3)TiO3 (BCT) and Ba(Zr0.2Ti0.8)O3 (BZT) phases with continuous variation of composition and layer thickness. High‐resolution x‐ray diffraction (XRD) and analytical scanning transmission electron microscopy (STEM) demonstrate high film quality and well‐controlled compositional gradients. Ferroelectric and dielectric property measurements identify the “optimal property point” achieved at the composition of 48BZT–52BCT. Displacement vector maps reveal that ferroelectric domain sizes are tunable by varying {BCT–BZT}N superlattice geometry. This high‐throughput synthesis approach can be applied to many other material systems to expedite new materials discovery and properties optimization, allowing for the exploration of a large area of phase space within a single growth.image

Crystal chemistry and ionic conductivity of garnet-type solid-state electrolyte, Li5-xLa3(NbTa)O12-y

Crystal structures, microtopography, morphologies, elemental compositions, and ionic conductivity have been investigated for Li5-xLa3(Nb,Ta)O12-y using X-ray diffraction (XRD), field-emission analytical scanning and transmission electron microscopies (S/TEM), and electrochemical impedance spectroscopy. Using Rietveld refinements with powder XRD patterns, we determined that the number of Li atoms in the formula is less than 5 and that Li5-xLa3(NbTa)O12-y crystallizes in the cubic garnet structure with a space group Ia-3d. Sintering at varying temperatures (750–1000 °C) for 5 h in an ambient atmosphere produced distinct outcomes. Rietveld refinements disclosed that the sample sintered at 1000 °C (Li3.43(2)La3Nb1.07(2)Ta0.93(2)O12-y, a = 12.8361(7) Å, V = 2114.96(3) Å3) exhibited the highest ionic conductivity, while the 850 °C sample had the lowest conductivity, characterized by lower Li concentration and impurity phases (Li(Nb,Ta)3O88, Li2CO3). Analyses, including XRD and electron microscopy, confirmed the 1000 °C sample as a relatively phase pure with enhanced Li content (Li/La = 1.2), larger grains (15 μm), and uniform crystallinity. The 1000 °C sample introduced additional partially filled Li3 (96h) sites, promoting Li migration, and enhancing ionic conductivity. The resulting XRD pattern at 1000 °C has been submitted to the Powder Diffraction File as a reference.

Ilmenite phase transformations in suevite from the Ries impact structure (Germany) record evolution in pressure, temperature, and oxygen fugacity conditions

Abstract Aggregates of ilmenite with varying amounts of rutile, ferropseudobrookite, and pseudorutile in suevites from the Ries impact structure have been analyzed by light microscopy, analytical scanning electron microscopy, electron microprobe analysis, and Raman spectroscopy to constrain their formation conditions. The tens to hundreds of micrometer aggregates comprise isometric ilmenite grains up to 15 µm in diameter that form a foam structure (i.e., smoothly curved grain boundaries and 120° angles at triple junctions). Grains with foam structure show no internal misorientations, indicating a post-impact formation. In contrast, ilmenite grains with internal misorientation occurring in the core of the aggregates are interpreted as shocked remnant ilmenite originating from the target gneisses. They can contain twin lamellae that share a common {1120} plane with the host, and the c-axis is oriented at an angle of 109° to that of the host. Similarly, the new grains with foam structure display up to three orientation domains, sharing one common {1120} plane for each pair of domains and c-axes at angles of 109° and 99°, respectively. This systematic orientation relationship likely reflects a cubic supersymmetry resulting from the transformation of the initial ilmenite upon shock (>16 GPa) to a transient perovskite-type high-pressure phase (liuite), subsequent retrograde transformation to the polymorph wangdaodeite, and then back-transformation to ilmenite. Whereas, the new grains with foam structure formed from complete transformation, the twin domains in the shocked ilmenite are interpreted to represent only partial transformation. Ferropseudobrookite occurs mostly near the rim of the aggregates. An intergrowth of ferropseudobrookite, ilmenite, and rutile, as well as magnetite or rarely armalcolite occurs at contact with the (devitrified) matrix. The presence of ferropseudobrookite indicates high temperature (>1140 °C) and reducing conditions. The surrounding matrix provided Mg2+ to form the ferropseudobrookite-armalcolite solid solution. Rutile can occur within the aggregates and/or along the ilmenite boundaries; it is interpreted to have formed together with iron during the decomposition of ilmenite at lower temperatures (850–1050 °C). We suggest magnetite in the rims formed by electrochemical gradients driven by the presence of a reducing agent, where Fe2+ within ilmenite diffused toward the rim. Subsequent cooling under oxidizing conditions led to the formation of magnetite from the iron-enriched rim as well as pseudorutile around ilmenite grains. Our study demonstrates that the specific crystallographic relationships of ilmenite grains with foam structure indicate a back-transformation from high (shock) pressures >16 GPa; moreover, the presence of associated Fe-Ti-oxides helps indicate local temperature and oxygen fugacity conditions.

Comprehensive analysis of a thiazole-substituted corrosion inhibitor's impact on N80 carbon steel in acidic conditions: Integrating computational predictions with experimental verifications

The present investigation elucidates the effectiveness of a newly developed organic inhibitor, namely 6,6-diphenyl-2,3-dihydroimidazo[2,1-b]thiazol-5(6H)-one (PHIT) in inhibiting the corrosion of N80 carbon steel (N80-CS) in 15 wt% HCl at 303 K. An integrative approach combining theoretical insights through Density Functional Theory (DFT) and molecular dynamics (MD) simulations with empirical data derived from a suite of analytical techniques (namely, weight loss measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and scanning electron microscopy (SEM)), was employed to assess the corrosion inhibition performance. The research identified the thiazolone fragment as the predominant site of activity within the PHIT molecule. According to EIS results, a significant reduction in the effective double-layer capacitance from 174 (blank) to 36.17 μF/cm2 was registered following the addition of 5 × 10−3 mol/L PHIT to the HCl medium. Moreover, at a low concentration of 10−4 mol/L, the inhibition efficiency reached a maximum of 95 %. The immersion time had a significant effect on the inhibitor's polarization resistance, peaking at 48 h (596 Ω cm2), then experiencing a minor reduction at 72 h (457 Ω cm2), in comparison to the blank measurement at 0.5 h (231 Ω cm2). Besides, the inhibitor demonstrated a high degree of effectiveness across various temperatures with a slight decrement in efficiency from 96.5 % at 303 K to 94 % at 363 K. PDP results confirmed the tested compound as an anodic-type inhibitor. These results affirmed the potential of PHIT as a highly efficacious organic inhibitor for N80-CS in acidic conditions, encouraging further development of its derivatives.

Investigation of effect of post weld heat treatment on microhardness and microstructure of auto TIG welded stabilized SA213 TP347H weldments

Investigation explores the weldability of Niobium stabilized TP347H austenitic stainless steel tubes through the application of optimized welding parameters using Auto TIG welding. This research investigates the influence of post weld heat treatment conditions on microhardness, microstructures, sensitization due to Cr23C6 precipitation, presence of Niobium carbides and formation of twin boundaries in the weldment. Extended post weld heat treatment duration resulted in notable decline in microhardness from 280 to 180 VHN within initial 5-h of soaking. Nevertheless, further prolongation of soaking time (10–15 h) exhibited subsequent rise in microhardness levels to 200 VHN in base, weld and heat affected zone. Increase in hardness is attributed to the emergence of annealing twins in base metal and the precipitation of Niobium carbides within weld and heat affected zone, confirmed by advanced analytical scanning electron microscope. Energy dispersive spectrum line mapping reveals presence of Cr23C6 precipitation following 1-h soak at 720 °C. Subsequent prolongation of soaking time (5-h) demonstrates desensitization in the base metal. Additionally, cooling rate of 300 °C/hr during post weld heat treatment reduces required time for microstructure homogenization, resulting in increased hardness compared to 100 °C/hr rate in the weldment. However, beyond a 5-h soaking time, the cooling rate has a negligible impact on microhardness. Ultimate Tensile Stress of 674.82 and 665.28 N/mm2 for TP347H was achieved against the minimum requirement of 515 N/mm2 as per American Society of Mechanical Engineers Section IX standard.

Grain size impact of ZnO nanoparticles on the structural, and electrical properties in the low-density polyethylene

In this study, low-density polyethylene (LDPE) was employed as a basic polymer. The ZnO particles of the polymer had a 20 nm diameter. The influence of the density of ZnO nanoparticles (NPs) on their structural and electrical properties was measured to examine the average grain size, resistivity, and energy band gap. The ZnO/LDPE nanopolymer was prepared by spin coating, and the microstructure of its material was investigated using analytical scanning electron microscopy techniques (SEM). The microscopic experimental results showed that the ZnO particles were dispersed in the form of white dots in the LDPE polymer. Additionally, a sizeable number of pores was detected, which were influenced by the size and form of the grains. High (ohmic) relationships were shown by the voltage (V) against current (I) curves, the resistivity value (7.4 Ω).

Detection of BiGa hetero-antisites at Ga(As,Bi)/(Al,Ga)As interfaces

In this work, we show how diffraction-based chemically sensitive dark-field transmission electron microscopy (DFTEM) reveals the presence of Bi hetero-antisites (BiGa) at the interface of Ga(As,Bi)/(Al,Ga)As quantum well (QW) structures grown by molecular beam epitaxy on GaAs(001). The presence of BiGa is demonstrated by the striking appearance of “dark-lines” at the interfaces under two-beam DFTEM imaging conditions using the (002) diffraction spot. Additional analytical scanning (S)TEM procedures reveal Ga depletion and Bi accumulation at the exact position of the dark-lines, consistent with BiGa at this location. The precise location of the dark-lines agrees with the position of growth interruptions made to adjust substrate temperature and the As/Ga flux ratio and, most importantly, the realization of a Bi pre-treatment before QW growth. We believe the Bi pre-treatment may have favored formation of BiGa hetero-antisites. We validate the use of g002 DFTEM for further investigations of the intricate bismuth incorporation into the lattice and its dependence on the growth conditions. Finally, g002 DFTEM imaging is positioned as a very powerful technique for the detection of point defects in general in materials with the zinc-blende crystal structure, beyond dilute bismide alloys.

Physio-chemical analysis of pollutants in residential micro-environment through continuous monitoring and settled dust characterization

The concern about indoor air quality in various micro-environments has been on the rise as buildings are vulnerable to an array of contaminants generated from various sources. The study aims to investigate and highlight the pollutant sources and composition in middle-income residential spaces through a case study approach. With large migration from small towns and saturation of megacities, the middle-income population in tier-2 cities in India is on the rise, raising concern about the well-being of the dense urban population. It involves a careful selection of typical MIG housing to identify major pollution sources from outdoor and indoor environments. The focus lies in the findings stemming from continuous air quality monitoring of PM10, PM2.5, SO2, NO2, HCHO, TVOC, CO and C6H6 and an in-depth physio-chemical analysis facilitated by Fourier transform infrared (FTIR), Analytical Scanning Electron Microscope (A-SEM) and energy-dispersive X-ray (EDX) spectroscopy of settled household dust. Analysis unveiled indoor PM2.5 concentrations of 21.93 µg/m3, exceeding WHO standards, whereas, TVOC concentrations were higher indoors than outdoors. Stark disparities between indoor and outdoor dust compositions and sources were also observed. Despite limitations, it provides a portrait of middle-income housing conditions, offering insights for interventions and future research on indoor air quality challenges.

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.

A novel approach to the green synthesis of zinc oxide nanorods using Thymus kotschyanus plant extract: effect of ammonium hydroxide and precursor concentration

This research introduces a pioneering green method for synthesizing zinc oxide nanorods (ZnO NRs) on a glass substrate using Thymus kotschyanus plant extract. The study delves into the intricate effects of ammonium hydroxide and precursor concentrations on the morphology, size, alignment, and crystalline structure of ZnO NRs. Through systematic experimentation, it was found that specific concentrations of these substances play vital roles in the formation and properties of the nanorods. Notably, a low concentration of the precursor coupled with a high concentration of ammonium hydroxide led to well-aligned hexagonal ZnO NRs with a remarkable aspect ratio. Variations in these concentrations were also found to influence the length, diameter, and alignment of the nanorods. The findings were corroborated using a diverse array of analytical techniques, including transmission and scanning electron microscopy, x-ray diffraction, UV–vis spectroscopy, and energy-dispersive x-ray analysis. The UV–vis spectra provided further insights into the optical properties and band gap energy of the ZnO NPs, while EDX analysis confirmed the elemental composition. This work represents a significant advancement in eco-friendly nanomaterial synthesis, providing detailed insights into the controlled fabrication of aligned ZnO NRs. Its innovative approach and extensive investigation into influencing factors make it a valuable contribution to the field of nanoscience.

Comparative in-vitro microscopic evaluation of vertical marginal discrepancy, microhardness, and surface roughness of nickel–chromium in new and recast alloy

Reusing of alloy has become a need of time due to the increasing demand, depletion of resources, and substantial increase in their price. The alloys used require a long-term stay in the oral cavity exposed to a wet environment, so they must have good wear resistance, biocompatibility, and mechanically good strength. In this study, the vertical marginal discrepancy, surface roughness, and microhardness of the new and recast nickel–chromium (base metal) alloys were evaluated. 125 wax patterns were fabricated from a customized stainless steel master die with a heavy chamfer cervical margin divided into 5 groups. Each group had 25 samples. Group A: 25 wax patterns were cast using 100% by weight of new alloy, Group B: the casting was done by using 75% new alloy and 25% alloy by weight, Group C: wax patterns were cast using 50% new alloy and 50% alloy, Group D: 25% new alloy and 75% alloy and Group E: 100% recast alloy. The vertical marginal discrepancy was measured by an analytical scanning microscope, microhardness was tested on a universal testing machine, and surface roughness was on a tester of surface roughness. Castings produced using new alloys were better than those obtained with reused alloys. Alloys can be reused till 50% by weight along with the new alloy and accelerated casting technique can be used to save the lab time to fabricate castings with acceptable vertical marginal discrepancy, microhardness, and surface roughness. This indicated that 50% recasting of (Ni–Cr) can be used as a good alternative for the new alloy from an economical point of view.

Probing individual single atom electrocatalyst sites by advanced analytical scanning transmission electron microscopy

Single atom electrocatalysts (SAEs) are promising next-generation materials for promoting a variety of important reactions, such as the oxygen reduction, nitrogen reduction, and CO2 reduction reactions. While bulk characterization techniques such as X-ray absorption spectroscopy and Mössbauer spectroscopy have significantly enhanced our understanding of these catalysts, direct probing of individual single metal atom sites at the atomic scale is necessary to understand local variations in the properties of these sites and accelerate design and synthesis of improved SAEs. Aberration-corrected scanning transmission electron microscopy (STEM) has become a powerful tool for providing this type of atomic-scale information about SAE metal sites. These sites are typically unstable under the electron beam, however, which, in combination with conventional acquisition methods and detectors, has limited the type and quantity of information obtainable by spectroscopic STEM techniques. Here, we map multiple individual SAE metal sites in a nitrogen-doped carbon containing atomically dispersed Fe and Re (FeReNC) at the atomic scale by direct electron detection electron energy-loss spectroscopy (EELS). Direct electron detection provides an improved signal-to-noise ratio over conventional scintillator-based detectors and enables detection and real space localization of weak signals. In addition, we demonstrate an automated method for identification of metal atom positions, placement of the probe on these sites, and simultaneous EELS and energy dispersive X-ray spectroscopic (EDS) signal acquisition. This simultaneous acquisition of EELS and EDS provides access to the composition and bonding of a wide range of SAE metal sites. Focusing the probe directly on the metal sites also increases the relevant data acquisition rate by more than an order of magnitude over two-dimensional mapping, enabling improved statistical measurements of site properties. The versatility, sensitivity, and speed that these techniques provide enhances our ability to probe the local elemental and chemical environment of a large number of individual SAE metal site structures at the atomic scale, enabling an improved understanding of the variations in the local properties of these electrocatalysts to be gained. As a result, significantly increased information about individual metal sites will be available to future electrochemical studies through these techniques, accelerating the development of advanced SAEs.

Secondary Phase CeO2 Precipitates in Ce,Er-Doped Na0.5La0.5MoO4 Single Crystals Grown by Czochralski Method

Analytical scanning and transmission electron microscopy were used to study the microstructure of Ce,Er-doped Na0.5La0.5MoO4 laser crystals. Crystals were grown by the Czochralski method from the melts with a nominal composition of Na0.5La0.5−xCexEr0.005MoO4, where x = 0.125 and 0.15, then annealed at 700 and 1000 °C in the oxidizing atmosphere. We found the secondary phase precipitation of Ce2O3 oxide in as-grown crystals, while after high-temperature annealing the CeO2 precipitated crystals are always observed. Impurity ions Ce3+ occupy the La sites, and approximately 20% of the nominal Ce content is involved in the formation of Ce oxide secondary phase precipitates. The length of CeO2 precipitated crystals ranged between 100 nm and 550 nm (average length was 200 nm) and their width was 30–70 nm. The mechanism of CeO2 formation is discussed. The orientation relationships of Na0.5La0.5−xCexEr0.005MoO4/CeO2, the degree of coherence of the interface, and the preferential directions of their growth in the matrix were established. CeO2 crystals precipitated in the matrix cause light scattering with a wavelength comparable to the size of the precipitates and lead to deterioration of optical transparency of the material.

Microstructural study of keyhole TIG welded nickel-based superalloy G27

The weld fusion zone (FZ) microstructure obtained after keyhole tungsten inert gas welding and post-weld solution heat treatments (PWSHTs) of a new nickel (Ni)-based superalloy called G27 is studied, and the grain growth behavior in the base material (BM) during PWSHTs is characterized. Microsegregation-induced interdendritic microconstituents in the FZ of as-welded G27 are identified by analytical (scanning) transmission electron microscopy ((S)TEM) as niobium (Nb)-rich MC carbides, Nb-rich Laves eutectic constituents, γ’ and η phases. The Laves eutectics are generally considered brittle and can adversely affect the mechanical properties of the weldment; thus, an hour PWSHTs were performed at 954 °C–1060 °C to eliminate the γ/Laves eutectics. PWSHT up to 1010 °C results in only partial removal of Laves eutectics with an excessive formation of η phase surrounding the Laves phase. Complete dissolution of Laves eutectics with no η phase formation is achieved after a PWSHT is performed at 1060 °C. Relative to INCONEL® alloy 718, the complete elimination of the γ/Laves eutectic constituents in the FZ of G27 through a PWSHT was proven to be achieved without causing excessive grain growth in the BM, which could be due to the pinning effect of the fine molybdenum (Mo)-rich precipitates, that are formed during solution heat treatment and identified as hexagonal close-packed phase particles through extensive (S)TEM analyses.

Influence of β-Mg17Al12 and Al-Mn intermetallic compounds on the corrosion behaviour of cast and solution treated Mg-Al-Zn-Mn alloys

This study aims to investigate the correlation between the microstructure and corrosion behaviour of AZ series alloys, using analytical scanning electron microscopy, X-ray computed tomography, hydrogen evolution test, weight loss method, electrochemical measurement, and observation of corroded morphology. The results indicate that a 3D interconnected eutectic network is effective in preventing localized corrosion in chloride solution. It is also revealed that solution treated Al-Mn intermetallics lead to filiform corrosion, rather than pitting corrosion, as seen τ-AlMn and Al8Mn5 particles. This is due to the potential difference reduction between the complete Al11Mn4 shell and the α-Mg matrix.