Transmission Electron Microscopy Energy-dispersive X-ray Research Articles

Leaching kinetics of ash impurities from aphanitic graphite by combining dual-ultrasound and hydrochloric acid–potassium hydrogen fluoride

The hydrochloric acid-fluoride salt is useful for purifying graphite. Ultrasonic-assisted technique can significantly reduce the leaching time and improve the leaching efficiency. Compared with single-frequency, dual-frequency ultrasound has the advantages of high energy efficiency and wide cavitation area. In this study, the combination of a dual-frequency ultrasound-assisted technique and hydrochloric acid–potassium hydrogen fluoride leaching agent was proposed for the leaching of aphanitic graphite to remove impurity minerals. First, the effects of probe-type ultrasonic power, tank-type ultrasonic power, temperature, HCl concentration, ultrasonication time, and KHF2 concentration on the purification efficiency of impurities from aphanitic graphite with the assistance of dual-frequency ultrasound were investigated. It was found that the combination of dual-frequency ultrasound and hydrochloric acid–potassium hydrogen fluoride can reduce the ash content of aphanitic graphite from 13.02 % to 1.02 % with an ash removal rate of 94.17 %. Second, volumetric reaction models and unreacted shrinkage nucleation models were used to fit the kinetics of impurities from aphanitic graphite with dual-frequency ultrasound-assisted HCl-KHF2 leaching. Kinetic analysis shows that the volumetric reaction model with chemical control was better to fit the leaching process. This is consistent with the calculation results of the activation energy of the reaction (Ea = 58.13 kJ/mol). Finally, laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) were used to analyze the fugacity of impurity minerals during the process of dual-frequency ultrasound-assisted HCl-KHF2 leaching. It was revealed that combining ultrasonic cavitation fragmentation with chloric acid–potassium fluoride generated SiF4 with high solubility, thereby removing silica-bearing impurities more efficiently. The challenges in further reducing ash content from 1.02 % in the leached concentrate of aphanitic graphite could be attributed to the existence of titanium-bearing mineral impurities on the surface of graphite particles and the presence of silica-bearing minerals between graphite carbon layers.

Development and characterization of lipid nanocapsules loaded with iron oxide nanoparticles for magnetic targeting to the blood-brain barrier.

Brain drug delivery is severely hindered by the presence of the blood-brain barrier (BBB). Its functionality relies on the interactions of the brain endothelial cells with additional cellular constituents, including pericytes, astrocytes, neurons, or microglia. To boost brain drug delivery, nanomedicines have been designed to exploit distinct delivery strategies, including magnetically driven nanocarriers as a form of external physical targeting to the BBB. Herein, a lipid-based magnetic nanocarrier prepared by a low-energy method is first described. Magnetic nanocapsules with a hydrodynamic diameter of 256.7 ± 8.5nm (polydispersity index: 0.089 ± 0.034) and a ξ-potential of -30.4 ± 0.3mV were obtained. Transmission electron microscopy-energy dispersive X-ray spectroscopy analysis revealed efficient encapsulation of iron oxide nanoparticles within the oily core of the nanocapsules. Both thermogravimetric analysis and phenanthroline-based colorimetric assay showed that the iron oxide percentage in the final formulation was 12 wt.%, in agreement with vibrating sample magnetometry analysis, as the specific saturation magnetization of the magnetic nanocapsules was 12% that of the bare iron oxide nanoparticles. Magnetic nanocapsules were non-toxic in the range of 50-300μg/mL over 72h against both the human cerebral endothelial hCMEC/D3 and Human Brain Vascular Pericytes cell lines. Interestingly, higher uptake of magnetic nanocapsules in both cell types was evidenced in the presence of an external magnetic field than in the absence of it after 24h. This increase in nanocapsules uptake was also evidenced in pericytes after only 3h. Altogether, these results highlight the potential for magnetic targeting to the BBB of our formulation.

Aminosilane assisted deposition of gold nanoparticles on Zn(OH)2 nanosheets and their application in electrochemical sensor

A facile and efficient method for systematical deposition of gold nanoparticles (AuNPs) on Zn(OH)2 nanosheets (NS) with different Zn and Au ratios was established in the presence of N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TPDT silane), without adding any external reducing agents, at room temperature. Here, TPDT silane behaves as both a stabilizing and reducing agent. UV–vis absorption spectroscopy, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the formation of AuNPs on Zn(OH)2 NS. As the concentration of AuNPs increased, a proportional increase in both the number and size of deposited AuNPs on Zn(OH)2 NS was observed. To understand how the variation in the number and size of AuNPs affects their catalytic activity, the electrocatalytic activity of different composition ratios of Zn(OH)2-Au NS toward nitrite ions was studied using cyclic voltammetry and amperometric technique. The TPDT-stabilized Zn(OH)2-Au NS showed high electrocatalytic activity, attributed to the effective electron transfer from Zn(OH)2 NS to AuNPs, creating a synergistic effect that enhances the overall activity. The optimal Zn(OH)2-Au NS modified electrode showed an amperometric sensitivity of 5.72 nA/µM and a limit of detection of 1.2 µM for nitrite ions in water sample well below the guideline value of WHO. This demonstrates the practical applicability of this method for real-world water analysis.

Atomic-level investigation of structure and formation process of Y3Al5O12 with super-high content of Ce emitting anomalous orange-red emissions

Ce-doped yttrium aluminum garnet (YAG:Ce, Y3Al5O12:Ce) is the most commonly used yellow phosphor in white light-emitting diodes. Recently, we found that (Y1–xCex)3Al5O12:Ce with a super-high content of Ce (x = 0.11–0.21) can be prepared by a polymerized complex method and exhibits anomalous orange–red emission. To understand the nature of this anomalous behavior from the atomic level, we applied high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM-EDS), a state-of-the-art technique that enables analysis of the atomic-level elemental distributions of Al, Y, and Ce. STEM-EDS images on the atomic level were successfully obtained for YAG:Ce. It was found that Ce in Y site has spatially uneven for few nanometers. Ce–K edge extended X-ray absorption fine structure (EXAFS) analysis was also conducted, which revealed a high level of asymmetry around Ce. By combining the STEM-EDS and EXAFS results, a dynamic model for the red emission was proposed. STEM-EDS also revealed that CeO2 nanocrystals were firstly formed with low-temperature annealing and that the reaction of Y with the CeO2 nanocrystals subsequently yielded YAG:Ce, unlike in the conventional one-step high-temperature synthesis.

Evaluation of extremely thin polycrystalline germanium films and their TFT performance fabricated at 400 °C by Cu-induced crystallization on a glass substrate

Germanium (Ge) has high mobility and is more suitable for low-temperature device processes than silicon (Si); thus, it has attracted attention as an upper-layer transistor for monolithic three-dimensional (M3D) integration. We evaluated in detail the crystalline quality of extremely thin polycrystalline-Ge (poly-Ge) thin films thinner than 15 nm fabricated by metal-induced crystallization using copper (Cu-MIC) at 400 °C using micro-Raman scattering, in-plane X-ray diffraction, transmission electron microscopy (TEM), TEM energy dispersive X-ray spectroscopy, and TEM electron diffraction. Additionally, the films were applied to p-ch double-gate (DG) poly-Ge thin-film transistors (TFTs), and their performance was evaluated. As a result, a high I on/I off ratio of 2.8 × 103 was realized by crystallization at 400 °C with a ratio equal to that of crystallization at 500 °C. This study demonstrated the feasibility of Cu-MIC DG poly-Ge TFTs for M3D applications.

Trivalent lanthanum and ytterbium doped meso-silica/ceria abrasive systems toward chemical mechanical polishing (CMP) and ultraviolet irradiation-assisted photochemical mechanical polishing (PCMP)

Ceria (CeO2)-based abrasives are widely utilized in ultra-precision grinding and chemical mechanical polishing (CMP) applications over silica materials due to their unique physicochemical properties. Both mechanical and chemical contributions to polishing processes are highly affected by the size, shape, structure, component, defect of CeO2 abrasives. Herein, the composites involved mesoporous silica (mSiO2) cores and La- or Yb-doped CeO2 shells were synthesized and characterized in terms of X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, scanning transmission electron microscopy–energy dispersive X-ray mapping methods. The polishing effectiveness of the proposed composites toward quartz glass was experimentally evaluated under both CMP and ultraviolet irradiation-assisted photochemical mechanical polishing (PCMP) conditions. The polishing results indicated that the low-modulus mSiO2 cores strongly exerted the cushion effects for the friction and abrasion to substrates. Consequently, the heterostructured mSiO2/La-CeO2 and mSiO2/Yb-CeO2 abrasive systems offered nearly non-damage and ultra-smooth surfaces with angstrom-level roughness compared to conventional rigid abrasives. The enriched Ce3+ and oxygen vacancy defects at La- and Yb- doped CeO2 surfaces were responsible for the improvements of tribochemical and photochemical activities, thus allowing evidently enhanced removal efficiency with the assistance of ultraviolet irradiation. A possible polishing mechanism on the multi-component abrasive systems was also proposed.

Comparative Study of Exsolved and Impregnated Ni Nanoparticles Supported on Nanoporous Perovskites for Low-Temperature CO Oxidation.

This study investigated the redox exsolution of Ni nanoparticles from a nanoporous La0.52Sr0.28Ti0.94Ni0.06O3 perovskite. The characteristics of exsolved Ni nanoparticles including their size, population, and surface concentration were deeply analyzed by environmental scanning electron microscopy (ESEM), transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) mapping, and hydrogen temperature-programmed reduction (H2-TPR). Ni exsolution was triggered in hydrogen as early as 400 °C, with the highest catalytic activity for low-temperature CO oxidation achieved after a reduction step at 500 °C, despite only a 10% fraction of Ni exsolved. The activity and stability of exsolved nanoparticles were compared with their impregnated counterparts on a perovskite material with a similar chemical composition (La0.65Sr0.35TiO3) and a comparable specific surface area and Ni loading. After an aging step at 800 °C, the catalytic activity of exsolved Ni nanoparticles at 300 °C was found to be 10 times higher than that of impregnated ones, emphasizing the thermal stability of Ni nanoparticles prepared by redox exsolution.

A robust Ni/Au process and mechanism for p-type ohmic contact applied to GaN p-FETs

In this study, a new robust ohmic contact preparation process for GaN p-FETs application is developed on p-GaN/AlGaN/GaN, which excluded the commonly used descum step. A specific contact resistivity of approximately 2.0×10–3 Ω·cm2 is obtained based on Ni/Au metal stack. X-ray photoelectron spectroscopy (XPS) analysis revealed that the p-GaN surface underwent oxidation by O2 plasma in the descum step, forming Ga2O3 as a barrier layer between the metal and p-GaN. The resulting Ga2O3 could not be completely removed using a hydrochloric acid solution, resulting in a Schottky contact. Moreover, the Ni/Au ohmic contact mechanism was revealed for the first time by varying the O2 content in the annealing atmosphere. The X-ray transmission electron microscopy–energy-dispersive X-ray spectroscopy and XPS results proved that the Ni (III) oxide or Ni2O3 present at the metal/p-GaN interface and the Ga vacancies formed on the p-GaN surface played a crucial role in facilitating the formation of ohmic contacts.

Atomic-scale investigation of precipitate phases in QE22 Mg alloy

Precipitation-hardenable commercial Mg alloy QE22 (Mg-2.5Ag-2.0Nd-0.7Zr, wt.%) has excellent mechanical properties, but precipitates in this alloy have not been well understood. In this work, precipitate phases γ'', γ, and δ formed during the isothermal ageing process at 150, 200, 250, and 300 °C have been characterized using atomic-resolution high-angle annular dark-field scanning transmission electron microscopy and atomic-scale energy-dispersive X-ray spectroscopy. The morphology, crystal structure, and orientation relationship of these precipitate phases have been determined. Domain boundaries usually exist in a single γ particle, which can be characterized by a separation vector of [11¯01]α. The δ phase forms in situ from its precursor γ phase, consequently leading to the formation of three different variants within a single δ particle. The nucleation of the δ phase is strongly related to the domain boundaries of the γ phase. The formation of the γ phase may be promoted by its precursor γ'' phase. The similarities in atomic structures of the γ'', γ, and δ phases are described and discussed, indicating that transformations between these precipitate phases can be accomplished through the diffusion of added alloying elements.

Selenium-Fortified Kombucha-Pollen Beverage by In Situ Biosynthesized Selenium Nanoparticles with High Biocompatibility and Antioxidant Activity.

Biogenic selenium nanoparticles (SeNPs) have been shown to exhibit increased bioavailability. Fermentation of pollen by a symbiotic culture of bacteria and yeasts (SCOBY/Kombucha) leads to the release of pollen content and enhances the prebiotic and probiotic effects of Kombucha. The aim of this study was to fortify Kombucha beverage with SeNPs formed in situ by Kombucha fermentation with pollen. Response Surface Methodology (RSM) was used to optimize the biosynthesis of SeNPs and the pollen-fermented Kombucha beverage. SeNPs were characterized by Transmission electron microscopy energy-dispersive X-ray spectroscopy (TEM-EDX), Fourier-transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS), and Zeta potential. The pollen-fermented Kombucha beverage enriched with SeNPs was characterized by measuring the total phenolic content, antioxidant activity, soluble silicon, saccharides, lactic acid, and the total content of Se0. The polyphenols were identified by liquid chromatography-mass spectrometry (LC-MS). The pollen and the bacterial (nano)cellulose were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), FTIR, and X-Ray diffraction (XRD). We also assessed the in vitro biocompatibility in terms of gingival fibroblast viability and proliferation, as well as the antioxidant activity of SeNPs and the pollen-fermented Kombucha beverage enriched with SeNPs. The results highlight their increased biological performance in this regard.

Flexoelectric Catalysts Based on Hierarchical Wrinkling Surface of Centrosymmetric High-Entropy Oxide.

A high-entropy oxide nanocomposite with Ag(CuZn)(AlCr)2O4 and CuO phases is fabricated to form an abundantly hierarchical wrinkled surface. Application of a mechanical force to the nanocomposite resulted in a nonhomogeneous strain gradient at the interface between the Ag(CuZn)(AlCr)2O4 and CuO phases, changing the local charge distribution and creating flexoelectric polarization that delayed electron/hole recombination. Transmission electron microscopy energy-dispersive X-ray spectroscopy mapping revealed that the Ag, Cu, Zn, Al, Cr, and O elements were highly distributed throughout the nanocomposite. The nanocomposite produced 2116 μmol·g-1 h-1 of H2 without external light irradiation, which is 980% higher than the H2 produced by the same nanocomposite under the photocatalytic process. A strong electrical field is observed at the interface between the Ag(CuZn)(AlCr)2O4 and CuO phases, demonstrating that a flexoelectric potential (flexopotential) is established at the structural boundaries because the strain gradient is localized at these interfaces. The nanocomposite is a promising approach for environmentally friendly energy production.

Boron Nitride- and Carbon-Supported Iridium–Iron Catalysts for Synthesizing Mono-Alcohols from Biomass-Derived Vicinal Diols

Hydrogenolysis of 1,2-diols to primary and secondary alcohols was investigated over nonoxide-supported Ir–FeOx catalysts using 1,2-butanediol (1,2-BuD) as a model substrate. Boron nitride (BN) has been found as an effective support for 1,2-BuD hydrogenolysis to secondary alcohol (2-butanol (2-BuOH)), similar to rutile TiO2 in our previous report. The addition of Fe species (Fe/Ir = 0.25 (optimal ratio)) to Ir/BN greatly improved the catalytic activity (23 times; 2-BuOH selectivity: ∼70%; highest yield: 64%). Meanwhile, some other supports including carbon supports gave primary alcohol (1-butanol (1-BuOH)) as the main product, which was less affected by the Fe addition or types of carbon supports. Activated carbon (C) provided the highest activity among the screened carbon-type supports. The 74% yield of 1-BuOH was obtained over Ir–FeOx/C. The selectivity pattern given by Ir–FeOx/BN much depends on its calcination temperature: a low calcination temperature (<673 K) led to the change in the selectivity pattern (∼70% of 2-BuOH to >70% of 1-BuOH). Ir–FeOx/BN was reusable for the 2-BuOH synthesis at least 4 times when the suitable calcination treatment (573 K, 1 h) was adopted for catalyst regeneration. In contrast, the addition of acid was necessary for regenerating the Ir–FeOx/C catalyst. Secondary alcohol with high selectivity (>60%) was achieved in related alcohol hydrogenolysis over Ir–FeOx/BN (Ir = 5 wt %, Fe/Ir = 0.25) such as 1,2-propanediol to 2-propanol, glycerol to 1,2-propanediol, and 1,3-butanediol to 2-BuOH. 2,3-Butanediol was formed in 32% yield from erythritol. Over Ir–FeOx/C or Ir/C, good yields of 1-alcohols were formed from 1,2-alkanediols, while reversible cyclization occurred for erythritol. Characterizations with X-ray diffraction, transmission electron microscopy–energy-dispersive X-ray spectroscopy, temperature-programmed reduction with H2, CO adsorption, diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO, X-ray absorption near edge structure, and extended X-ray absorption fine structure suggested that Ir–FeOx/C (Ir = 5 wt %, Fe/Ir = 0.25) consists of Ir particles (about 2 nm), highly distributed and isolated FeOx (valence: ∼2+), and residual acid. In Ir–FeOx/BN (Ir = 5 wt %, Fe/Ir = 0.25), Ir–Fe alloy (Fe0/(Fe0 + Ir0) = 20%) with a two-dimensional nanodendrite structure was formed. The production of primary alcohol over C-supported catalysts is via the route of dehydration + hydrogenation, where the residual acid catalyzes dehydration as the rate-determining step. The high selectivity to secondary alcohol over Ir–FeOx/BN was derived from two aspects: removal of acid (HCl) by calcination and generation of the active Ir–Fe alloy phase in the formation of secondary alcohol.

Evolution of the EUROFER97 microstructure during thermal treatment up to 122,000 h

Detailed knowledge of the microstructural evolution of reduce activation ferritic-martensitic steel EUROFER97 after exposure at high temperatures is essential for determining its applications potential. For this proposal, EUROFER97 was annealed in the temperature range between 450 °C and 650 °C for up to 122,000 h (≈14 years) and subsequently analyzed using transmission electron microscopy (TEM) including high resolution TEM and two-dimensional energy dispersive X-ray (EDX) mapping. The study demonstrates the effects of thermal treatment on the size and composition of the precipitates and allows conclusions about their stability. Application of the extraction replication technique was used to analyze composition and morphology of four particle types present in the untreated EUROFER97: M23C6, VN, TaC and TiN with sufficient statistics. The rapid coarsening of the M23C6 precipitates was observed at 650 °C, while the MX particles were found to be more stable upon thermal treatment. It has been proved that new Laves (WFe2) and modified Z-phases (Cr(V,Ta)N) precipitates are formed in the temperature range from 500 °C to 600 °C. The detailed analysis allows the drawing a time–temperature formation diagram for these two phases, which could be valid for alloys with composition similar to EUROFER97.

A smartphone-based colorimetric assay using Au@Ag core–shell nanoparticles as the nanoprobes for visual tracing of fluvoxamine in biofluids as a common suicide drug

In the present study, bimetallic nanoparticles (NPs) consisting of gold (AuNPs) as the core and silver (AgNPs) as the shell have been synthesized and applied as the nanoprobe for detection of fluvoxamine (FXM) as the anti-depression drug. The physicochemical properties of the prepared citrate-capped Au@Ag core–shell NPs have been characterized by UV–Vis, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. The design of the smartphone-based colorimetric FXM sensor relies on the fast hydrolysis of FXM under alkaline conditions by producing of 2-(Aminooxy)ethanamine without any significant peak at 400–700 nm. The interaction of the resulted molecule with the nanoprobe induced a red shift in the longitudinal localized surface plasmon resonance (LSPR) peak of the nanoprobe, which was accompanied by sharp and vivid color variations in the solution. A linear relationship between the absorption signal increasing by FXM concentration increasing from 1 µM to 10 µM presented a simple, low cost and minimally instrumented format for FXM quantification with a limit of detection (LOD) of 100 nM. The collected visual data with the elegant colorimetric response of the nanoprobe in the presence of FXM from Indian red to light red violet and bluish-purple color offered simple detection of FXM with the naked eye. The satisfactory results of the proposed cost-effective sensor in the rapid assay of FXM in human serum, urine, saliva and pharmaceutical samples guarantee the potential of the nanoprobe for on-site and visual determination of FXM in actual samples. The proposed sensor as the first non-invasive FXM sensor for saliva sample analysis may hold great promise to provide the technical support for the rapid and valid detection of FXM for forensic medicine and clinical organizations.

Espm: A Python library for the simulation of STEM-EDXS datasets

We present two open-source Python packages: “electron spectro-microscopy” (espm) and “electron microscopy tables” (emtables). The espm software enables the simulation of scanning transmission electron microscopy energy-dispersive X-ray spectroscopy datacubes, based on user-defined chemical compositions and spatial abundance maps of constituent phases. The simulation process uses X-ray emission cross-sections generated via state-of-the-art calculations made with emtables. These tables are designed to be easily modifiable, either manually or using espm. The simulation framework is designed to test the application of decomposition algorithms for the analysis of STEM-EDX spectrum images with access to a known ground truth. We validate our approach using the case of a complex geology-related sample, comparing raw simulated and experimental datasets and the outputs of their non-negative matrix factorization. In addition to testing machine learning algorithms, our packages will also help experimental design, for instance, predicting dataset characteristics or establishing minimum counts needed to measure nanoscale features.

Boosting the Catalytic Performance of AuAg Alloyed Nanoparticles Grafted on MoS2 Nanoflowers through NIR-Induced Light-to-Thermal Energy Conversion.

MoS2 nanoflowers (NFs) obtained through a hydrothermal approach were used as the substrate for the deposition of tiny spherical bimetallic AuAg or monometallic Au nanoparticles (NPs), leading to novel photothermal-assisted catalysts with different hybrid nanostructures and showing improved catalytic performance under NIR laser irradiation. The catalytic reduction of pollutant 4-nitrophenol (4-NF) to the valuable product 4-aminophenol (4-AF) was evaluated. The hydrothermal synthesis of MoS2 NFs provides a material with a broad absorption in the Vis-NIR region of the electromagnetic spectrum. The in situ grafting of alloyed AuAg and Au NPs of very small size (2.0-2.5 nm) was possible through the decomposition of organometallic complexes [Au2Ag2(C6F5)4(OEt2)2]n and [Au(C6F5)(tht)] (tht = tetrahydrothiophene) using triisopropilsilane as reducing agent, leading to nanohybrids 1-4. The new nanohybrid materials display photothermal properties arising from NIR light absorption of the MoS2 NFs component. The AuAg-MoS2 nanohybrid 2 showed excellent photothermal-assisted catalytic activity for the reduction of 4-NF, which is better than that of the monometallic Au-MoS2 nanohybrid 4. The obtained nanohybrids were characterised by transmission electron microscopy (TEM), High Angle Annular Dark Field-Scanning Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy (HAADF-STEM-EDS), X-ray photoelectron spectroscopy and UV-Vis-NIR spectroscopy.

Influence of organic fertilization on clay mineral transformation and soil phosphorous retention: Evidence from an 8-year fertilization experiment

Organic fertilizer can improve phosphorus (P) bioavailability, while the mechanism of microbial-driven clay mineral transformation on P retention and utilization with organic fertilization is still unclear. An 8-year organic fertilization experiment was carried out in saline alkaline paddy soil with five treatments: (1) CK, no fertilization; (2) NK, mineral N and K fertilization; (3) NPK, NK with mineral P fertilization; (4) NPKC1, NPK with 450 kg C ha−1 year−1; (5) NPKC2, NPK with 900 kg C ha−1 year−1. The results showed that, compared with NPK treatment, the percentage of illite with more P adsorption sites was increased by 26.8% and 20.7% in NPKC1 and NPKC2 treatments, respectively. Meanwhile, transmission electron microscopy-energy dispersive X-ray spectroscopy analysis further confirmed that there was more P adsorption on silicate clay minerals. Compared with NK treatment, the content of total P and available P was significantly increased with organic fertilization. Besides, the diversity of bacterial community was also increased by organic fertilizer addition, redundancy analysis showed that soil organic carbon was the main factor in the diversity of bacterial community. The relative abundance of Firmicutes and Gemmatimonadetes was promoted, which drove the transformation of clay minerals and improved P availability, respectively. Compared with NPK treatment, P use efficiency in NPKC1 and NPKC2 treatments was increased by 47.2% and 58.2%, respectively, while no significant difference was found between the two treatments. Therefore, appropriate organic fertilization was a better fertilization practice to improve P retention and utilization through bacteria-driven clay mineral transformation in saline-alkaline paddy soil.

Dynamic Tracking of NiFe Smart Catalysts using In Situ X-Ray Absorption Spectroscopy for the Dry Methane Reforming Reaction

The exsolution of nanoparticles from perovskite precursors has been explored as a route to synthesize catalysts with sinter or coke resistance. The characteristics of these exsolved nanoparticles are highly dynamic depending on the redox nature of the environment to which they are subjected. To develop their properties for thermo- and electrocatalytic applications, it is necessary to track the states and behavior of exsolved catalysts with in situ and ex situ characterization. In this study, we conduct in situ X-ray absorption spectroscopy (XAS) along with ex situ scanning transmission electron microscopy high-angle annular dark-field (STEM-HAADF) and energy-dispersive X-ray spectroscopy analysis of the parent perovskite oxide precursor, LaFe0.8Ni0.2O3, as its structure forms bimetallic NiFe nanoparticles and evolves in oxidative, reductive, and dry methane reforming environments. We develop a theory that NiFe exsolution is a function of the reduction potential where LaFe0.8Ni0.2O3 transforms to NiFe alloy supported on LaOx-LaFeOx. The Ni starts to exsolve at 268 °C, while most Fe exsolves at 700 °C. During dry methane reforming conditions, most of the Fe is oxidized by CO2 during the reaction and re-enters the perovskite as LaFeO3, while Ni remains on the surface as nanoparticles in the metallic state. During the oxidative regeneration phase, most of the Fe re-enters the bulk perovskite phase, while Ni is partially regenerated with a small percentage oxidized to large NiO nanoparticles. This study sheds light on the exsolution and regeneration of bimetallic alloy nanoparticles and the influence of the reaction conditions on their catalyst performance.

Effect of reactant ratio and nanofillers type on the microstructural properties, porosity fluctuations and heavy metal removal ability of chitosan-clay hybrid materials

The structure, porosity, and functionality of synthesized chitosan-clay nanocomposites (NCs) are examined throughout this work in relation to the initial stoichiometry and octahedral cavity occupation of the clay fraction. Dioctahedral and trioctahedral smectite are selected as starting materials. X-Ray Diffraction analysis (XRD) confirms the accomplishment of the NCs synthesis process. The stoichiometry fluctuation implies a crystallite exfoliation process provided that the clay fraction contribution must not reach twice the organic ones. From 1:3 stoichiometry ratio, The intercalation process is enhanced by the interlamellar space (IS) closures, and crystallite size increases with crystallinity degree. According to transmission electron microscopy-energy dispersive X-ray (TEM-EDX) investigations, the exfoliation of "clay-particles" wrapping the organic fraction and the intercalation process occurred as the clay fraction abundance increased. Despite the low proportion approved from the synthesis beginning process, Fourier transform infrared spectroscopy (FTIR) reveals the polymer fraction characteristics absorption bands. The Brunauer, Emmett and Teller (BET) analysis of specific surface area and Barrett-Joyner-Halenda (BJH) Analysis of pore size distribution (PSD) supports the findings from TEM/EDX. For slightly saturated soil solution with Pb2+ or Cd2+ cation, Atomic absorption spectroscopy (AAS) evaluate the NCs adsorption capacity. The outcomes are extremely positive for dioctahedral smectite.

In situ annealing studies on the microstructural evolution of a macro defect free electroformed nanocrystalline Ni-Co sheet metal and its relation to tensile properties

The effect of annealing at temperatures between 200 – 400 °C on the microstructural evolution and tensile properties of a recently developed macro defect free electroformed nanocrystalline Ni-32at%Co free-standing sheet metal was investigated. The tensile strength of the materials exhibited an extrinsic Hall-Petch (HP) to inverse Hall-Petch (IHP) transition due to grain growth. In situ transmission electron microscopy (TEM) annealing revealed for the first time that at lower annealing temperatures, in addition to reordering of atoms at grain boundaries, grain rotation and grain recovery were also found to be mechanisms for grain boundary relaxation (GBR). Combined, these mechanisms contribute to the increase in ultimate tensile strength (UTS) observed in the IHP regime of the Ni-32at%Co alloy. TEM energy dispersive X-ray spectroscopy (EDX) and in situ synchrotron X-ray diffraction (XRD) annealing analyses showed that the drop in UTS and ductility in the HP regime after annealing at higher temperatures was associated with the onset of abnormal grain growth and sulfur impurity segregation to random high angle boundaries. Atom probe tomography (APT) further showed that there is no sulfur impurity segregation in the electroformed material before annealing. Increasing in annealing temperature led therefore to a transition from ductile to brittle fracture manifested as a change in dimple to mixed and eventually to faceted brittle fracture surfaces at 400 °C.