Scanning Electron Microscopy With Energy Dispersive Spectroscopy Research Articles

Reduction of an Ilmenite Concentrate by Using a Novel CO2/CH4 Thermal Plasma Torch

Plasma technology has emerged as a very helpful tool in a variety of sectors, notably metallurgy. Innovators and scientists are focused on the problem of finding a more ecologically friendly way of extracting titanium and iron metal from natural ilmenite concentrate for industrial applications. A direct current (DC) plasma torch operating at atmospheric pressure is used in this study to describe a decarbonization process for reducing an ilmenite concentrate. The plasma gases employed in this torch are CO2 and CH4. The molar ratio of the gases may be crucial for achieving a satisfactory reduction of the ilmenite concentrate. As a result, two molar ratios for CO2/CH4 have been chosen: 1:1 and 2:1. During torch operation, a thin layer of graphite is formed on the cathode to establish a protective barrier, prolonging the cathode’s life. The material was analyzed using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The output gases were analyzed using mass spectrometry (MS). In addition, a thermodynamic analysis was performed to predict the development of thermodynamically stable phases. An economic assessment (including capital expenditures (CAPEX) and operating expenditures (OPEX)) and a carbon balance were developed with the feasibility of the piloting in mind.

Updating mechanism of siderite roasting through insights into reactions between inherent oxides of iron and carbon

The roasting of siderite (FeCO3) was investigated to clarify the reaction mechanism in inert atmosphere using micro fluidized bed reaction analyzer coupled with on-line particle sampling (MFBRA-P). Thermodynamic results indicated that the reactions of 6FeO + CO2 → C + 2Fe3O4 and 3FeO + CO → C + Fe3O4 are both possible to occur in the transformation process of siderite to Fe3O4. The presence of C was identified in the final solid product through analysis scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and calcination experiment of product sample in the atmosphere containing O2. Combining thermodynamic and experimental results, an updated reaction mechanism of siderite roasting in inert atmosphere was proposed. The siderite is first decomposed to form FeO and CO2, and in turn FeO rapidly reacts with CO2 to form Fe3O4 and CO. Meantime, the released CO2 or CO during decomposition reacts with FeO to form C and Fe3O4.

Determination of binding energies in high purity 2H graphite using XPS

This study focuses on the detailed characterization of graphite, employing techniques such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Graphite, a crucial material for engineering applications and advanced technologies, was analyzed in its pure state as provided by the manufacturer, without any pretreatment. XPS analysis revealed a spectrum dominated by carbon, with binding energies confirming the expected electronic structure and the presence of surface functional groups, including oxygen, silicon, and phosphorus. Although these impurities were identified, they do not appear to have affected the binding energies of the primary carbon, suggesting that their influence is confined to the surface properties and does not extend to the internal electronic structure of the graphite. XRD corroborated the high structural purity and detected a secondary SiP2O7 phase in minimal quantities. These findings validate the high quality of the graphite and provide critical information for the scientific community, establishing a benchmark for comparisons in future studies and developments of materials. This work underscores the value of combining XPS, XRD, and SEM-EDS for the thorough characterization of carbon-based materials.

Microanalytical investigation of brazilian coat of arms paintings on paper

Heraldry in Latin American art of the twentieth century can be considered rare. In this context, the material composition of coat of arms paintings on paper attributed to the Brazilian painter José Wasth Rodrigues is investigated for the first time using a microanalytical approach. Microsamples from 5 municipal coats of arms dated 1932 were analysed using Raman microscopy, Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR), and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). SEM-EDS results revealed the artist's choice of using metallic aluminium and brass in the representation of silver and gold colours, respectively. Raman microscopy analyses showed the use of traditional inorganic pigments, such as ultramarine blue, indigo, Prussian blue, yellow chromates and vermillion. In contrast, the results showed that the painting with an unusual signature attributed to the artist (W. instead of J.W.R, commonly found) contains synthetic organic dyes Orange 5, Red 53, and Yellow 1 (introduced in the 1900s). This discovery raised hypothesis of questioning authorship for this particular painting. ATR-FTIR analysis of a paint fragment from one painting confirmed the use of gum arabic as a binder. ATR-FTIR analyses of efflorescences collected from a blue paint layer of a particular coat of arms suggest protein and lipid content, raising suspicion of either the use of the tempera technique in this particular paint or remains of a past microorganism activity. Robust information was obtained on the chemical characterization of the coat of arms, enhancing comprehension of the painting techniques employed by the artist and providing insight into the production of heraldic art in Brazil at the beginning of the 20th-century.

Mechanical Performance Optimization and Microstructural Mechanism Study of Alkali-Activated Steel Slag–Slag Cementitious Materials

The optimal proportion of alkali-activated steel slag–slag cementitious materials is investigated by considering the combined effects of steel slag content, alkali content, water glass modulus, and water–binder ratio using the Box–Behnken design in response surface methodology. Qualitative and semi-quantitative analyses of X-ray diffraction (XRD) patterns and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) images are conducted. The microstructural mechanism is elucidated based on the chemical composition, surface morphology, and microscale pore (crack) structures of the samples. A microreaction model for the alkali-activated steel slag and slag is proposed. The optimal composition for alkali-activated steel slag–slag cementitious materials is as follows: steel slag content, 38.60%; alkali content, 6.35%; water glass modulus, 1.23; and water–binder ratio, 0.48. The strength values predicted by the response surface model are p1d = 32.66 MPa, p7d = 50.46 MPa, and p28d = 56.87 MPa. XRD analysis confirms that the compressive strength of the sample is not only influenced by the amount of gel formed, but also, to a certain extent, by the CaCO3 crystals present in the steel slag, which act as nucleation sites. The SEM-EDS results confirm that the gel phase within the system comprises a hydrated calcium silicate gel formed through the reaction of volcanic ash and geopolymer gel formed through geo-polymerization. Analysis of the pore (crack) structure reveals that the compressive strength of the specimens is primarily influenced by porosity, with a secondary influence of the pore fractal dimension.

Effect of ion penetration on the aging of EPDM components used in caustic liquid transfer lines by microscopic analysis

The waste transfer lines at the United States Department of Energy's Hanford Site Tank Farm in Benton County, Washington, USA have flexible sections that are fabricated from ethylene propylene diene monomer (EPDM) hoses. The hoses are of a hose-in-hose design with an inner hose that carries the waste and an outer hose that acts as containment in the event of an inner hose failure. During waste transport, the inner hoses are exposed to several stressors including caustic solutions at high temperatures and high pressures. These hose-in-hose transfer lines (HIHTL) are exposed to several stressors including caustic solutions at high temperatures and high pressures during the waste transport. The aging behavior of the HIHTL inner hose were evaluated by exposure to solutions at 77 °C containing 6.25, 12.50, and 25.00% (v/v) sodium hydroxide (NaOH) for 12-months. After the exposure, the burst pressure of the HIHTL specimens were measured and compared to the unaged samples.The burst pressure of the HIHTL specimens exposed to the 6.25% NaOH solution exhibited the most significant deterioration and those exposed to 25.00% NaOH solution had the least deterioration. Examination of the inside surface of the HIHTL specimens with scanning electron microscopy showed that the surface deterioration for the specimens exposed to 6.25% NaOH solution were the most severe and the samples exposed to 25.00% NaOH solution had the least deterioration. Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS) analysis of the specimens showed that the specimen aged with the 6.25% NaOH solution had that greatest sodium ion penetration into the material with the sodium concentration being significantly higher than those seen with the other specimens. In addition, when the specimens aged with both the 12.50% and the 25.00% NaOH solutions were examined, a white crystalline coating was observed on the inside surfaces of the specimens which appears to have acted as a barrier that protected the EPDM material from attack by the NaOH solutions.

Cellulose acetate scaffold containing hydroxyapatite/graphene oxide nanocomposite by electrospinning for advanced regenerative therapies

The aim of this study was to synthesize and characterize Cellulose Acetate (CA) porous scaffolds using the electrospinning technique associated with Hydroxyapatite (HA) and different concentrations of graphene oxide (GO), for advanced regenerative therapies application. The scaffolds were categorized into four distinct groups based on their composition: (1) Pure CA scaffolds; (2) CAHA scaffolds; (3) CAHAGO 1.0% scaffolds; (4) CAHAGO 1.5% scaffolds. Transmission Electron Microscopy (TEM) was used for the characterization of the nanocomposite. The scaffolds were analyzed by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS), and in vitro cell viability assays (WST). For the biological test analysis of Variance (two-way) was used, followed by Tukey’s post-test (α = 0.05). The TEM analysis allowed for the visualization of the deposition of HA on the graphene sheets, confirming the synthesis of the nanocomposite. XRD revealed the predominant presence of CaP phases in the CAHA, CAHAGO 1.0%, and CAHAGO 1.5% groups, underscoring the inherent mineral composition of the scaffolds. FTIR demonstrated cellulose characteristics and PO4 bands in the groups containing HA, confirming the effective incorporation of this material. Raman spectroscopy revealed distinct peaks in the GO groups, conclusively verifying the successful integration of graphene into the scaffold matrix. The micrographs showcased irregular pores filling the entire surface, arising from the intricate overlapping of fibers during scaffold formation. Importantly, all scaffolds exhibited excellent cell viability in the conducted assays. A proliferation process was observed in CAHA and CAHAGO 1.5% groups after 48 h ( p < 0.05). In conclusion, the scaffolds synthesized hold significant promise in the realm of tissue engineering and provide a fresh perspective on the possibilities for regenerative therapies.

Study on corrosion characteristics of reinforcing bars in concrete under industrial SO2 environment

Sulfur dioxide (SO2) is the primary pollutant in industrial atmospheres, leading to significant damage to industrial buildings. The corrosion caused by SO2 in concrete, including neutralization and solid phase volume expansion, poses particular concerns. However, there is a lack of research on the electrochemical behaviour and corrosion mechanisms of reinforcing bars embedded in concrete. This study conducted indoor simulations of reinforced concrete specimens exposed to industrial SO2 corrosion utilizing an SO2 testing chamber. The corrosion behavior of the reinforcing bars was monitored through half-cell potential, weak polarization, and electrochemical impedance spectroscopy (EIS). Additionally, the corrosion mechanisms of the reinforcing bars under SO2 exposure were investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and Raman spectra. The results demonstrated a consistent correlation between variations in corrosion potential (Ecorr) and corrosion current density (icorr) of steel rebars in different types of concrete. The corrosion rates of the reinforcing steel in C1 (w/b=0.57), C2 (w/b=0.47), and C3 (w/b=0.37) concrete exceeds 0.1 μA/cm2 after 42, 72, and 90 days of SO2 corrosion, respectively. At this time, the ratio of the depth of neutralization to the thickness of the protective layer is 0.51–0.65. The rust exhibits a layered structure with a presence of S elements adsorbed and deposited on the surface of the rust layer. Moreover, the research has identified the accumulation of S elements within corrosion pits, which can be attributed to localized acidification reactions. The rust products identified include iron hydroxide (FeOOH), and iron oxide (Fe2O3), rozenite (FeSO4·4 H2O). The formation of FeSO4·4 H2O in corrosion pits suggests that significant localized corrosion on the surface of reinforcing bars in concrete under the impact of SO2.

Removal of Fe3+ Ions from Aqueous Solutions by Adsorption on Natural Eco-Friendly Brazilian Palygorskites

This work focuses on the characterization of five palygorskite clays from the Brazilian state of Piaui and their feasibility as eco-friendly adsorbents for the removal of Fe3+ ions from aqueous solutions. For characterization, we applied the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), size distribution measurements, density measurement by He pycnometry, superconducting quantum interference device (SQUID) magnetometry, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTA), zeta potential measurement, hydrophobicity determination by contact angle, Brunauer–Emmett–Teller surface area analysis (BET technique) and atomic force microscopy (AFM). Batch experiments were performed in function of process parameters such as contact time and initial concentration of Fe3+. The natural palygorskites (Palys) had excellent performance for the removal of Fe3+ from aqueous solutions by adsorption (around 60 mg/g), and the Langmuir is supposedly the best model fitted the experimental data.

Insights on the Mortars of Ancient Roman Aqueducts: Aqua Virgo and Aqueduct Y, Rome (Italy)

Despite the archaeological importance of Aqua Virgo, a Roman aqueduct built in 19 BC and still functioning nowadays, there is a lack of information about the mortars coming from the inner duct. This work aims to investigate the mortars from Aqua Virgo and Aqueduct Y, an unidentified aqueduct running under the first one in the La Rinascente area (between Via del Nazareno and Via dei Due Macelli, Rome, IT) through Optical Microscopy (OM), X-ray Powder Diffraction (XRPD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The aim is to understand which materials guarantee such longevity and differentiate between different intervention phases. Local natural materials with pozzolanic behaviour—in particular, Pozzolane Rosse—and ceramic fragments are widely employed, mixed or not, for the realisation of the hydraulic mortars under investigation, independently of the intervention phase. Of particular interest is the discovery of an amorphous binder composed of Si, Al, Ca, K and Mg in some samples characterised by the absence of calcite.

Hematite colour revisited: Particle size and electronic transitions

Hematite has been used as a pigment since ancient times, due to its natural abundance and colour that ranges from vivid red to purple. Caput mortuum is a purple α-Fe2O3 whose colour has been ascribed as originating from particle size. In this work, submicrometric synthetic, natural and commercial hematites were investigated by diffuse reflectance spectroscopy (DRS), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and Raman microscopy aiming to clarify the origin of the purple colour. From the results it was concluded that the purple colour is associated with crystallinity, that promotes a significant decrease in absorption below 500 nm and, simultaneously, an increase in the 6A1(6S) → 4T1(4G) d-d transition at ca. 880 nm. The behaviour of the ca. 880 nm band can be explained by the more extensive magnetic interaction between adjacent Fe3+ ions in crystalline samples but cannot explain the spectral behaviour in the green–blue region considering only the d-d transitions. A plausible explanation is that in the distorted FeO6 octahedra, both the Fe-O distances and the Fe-O-Fe angles area are affected, thus interfering in the low energy oxygen-to-iron charge transfer transition, whose tail span the 400 nm – 500 nm region and is more intense than the d-d transitions in hematite nanoparticles, nanofilms and defective (red) Fe2O3 samples. The decrease in the intensity of the charge transfer band as a consequence of the FeO6 octahedral distortion is yet to be confirmed by further experiments, but the experimental results clearly show that the purple colour of hematite is due to a decrease in optical absorption below 500 nm.

AI assisted steel cleanness evaluation: Predicting the morphology of La-traced non-metallic inclusions using backscattered-electron images

This study shows how computer vision, a field of artificial intelligence (AI), can be used to gain access to morphological information for a better process understanding and furthermore, how it can be implemented in the evaluation of active tracing experiments. Non-metallic inclusions (NMIs) play a crucial role in determining the chemical and physical properties of the final steel product. The active tracing technique allows for tracking the formation and modification mechanisms of detrimental NMIs throughout the steelmaking process by adding rare earth elements (REEs) to the melt. The interaction of REEs with NMIs results in the formation of traced multiphase particles and, therefore, lead to challenges for accurate evaluation by automated scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). However, obtaining information about the REE distribution in traced NMIs without extensive, time-consuming human effort is not feasible using the existing method. A two-step classification process with AI was established, which included training and testing of two random forest classifiers (RFC). The first RFC achieved for the binary NMI/non-NMI classification an accuracy of 94.8 %. Four different morphology-based classes were considered in the second classification, whereas traced homogeneous NMIs and NMIs with a high La content got classified with a precision exceeding 90 %. However, caution is required in interpreting results for traced heterogeneous NMIs, as they have a higher prediction error of 37.2 %.

Microstructure and electrical property of composite Co-W/CuO multilayered oxide coating for solid oxide fuel cell interconnector

To overcome the challenges related to the electrical resistance owing to the growth of the Cr-containing oxide layer in the SOFC system at high temperature, a composite coating of Co-W/CuO was fabricated on ferritic stainless steel for interconnectors by composite electroplating and pre-oxidation treatment. Compared to the Co-W alloy coating, the addition of CuO led to the formation of Cu-Co spinels and Cu-W composites, which affected the surface microstructure of the coating. Scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM) investigations shows that CuWO4 nano-particles formed in the Cr-rich layer beneath the CoWO4 layer, of which the lattice deviation leads to the formation of oxygen vacancies. The CuWO4 acted as conductive pathways, reducing the electrical resistance. Long-term oxidation exposure further demonstrated that the Co-W/CuO coated SUS 430 exhibited a stable electrical conductivity of 10.23 mΩ cm2.

Aircraft ice-nucleating particle and aerosol composition measurements in the western North American Arctic

Abstract. Knowledge of the temperature-dependent concentration of ice-nucleating particles (INPs) is crucial to understanding the properties of mixed-phase clouds. However, the sources, transport and removal of INPs around the globe, and particularly in the Arctic region, are poorly understood. In the Arctic winter and spring, when many local sources are covered by ice and snow, it is not clear which INP types are important. In this study, we present a new dataset of aircraft-based immersion mode INP measurements and aerosol size-resolved composition in the western North American Arctic from 11 to 21 March 2018. Aerosol samples were collected between ∼ 70 and 600 m above the surface on filters that were analysed using both a freezing droplet-based assay and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The measured INP concentrations were at or close to the limit of detection, with concentrations at −20 ∘C of 1 L−1 or below. The size-resolved composition measurements indicates that the aerosol concentrations were low, dominated mostly by sea spray aerosol and mineral dust. Further analysis shows that mineral dust is important for the ice-nucleating properties of our samples, dominating over the sea spray aerosol particles in the four cases we analysed, suggesting that mineral dust is a relevant type of INP in the Alaskan springtime Arctic. Furthermore, the INP concentrations are more consistent with fertile soil dusts that have an ice-active biological component than what would be expected for the ice-active mineral K-feldspar alone. While we cannot rule out local high-latitude sources of dust, the relatively small size of the mineral dust implies that the dust was from distant sources.

Analysis of pigments and mortars from the wall paintings of the Roman archaeological site of Las Dunas (San Pedro de Alcántara, Malaga S Spain)

This study aims to describe the composition, texture, and arrangement of mortars and pictorial layers from a newly excavated Roman archaeological site in the province of Baetica, southern Spain. Representative fragments with well-preserved pictorial layers were analyzed using optical imaging, spectrophotometry, Scanning Electron Microscopy with Energy-Dispersive Spectroscopy (SEM-EDS) mapping, and X-ray diffraction. The results reveal similarities to other well-studied Roman archaeological sites, particularly in the use of mixtures of natural (hematite, goethite, aragonite, phyllosilicates, and quartz) and synthetic minerals (cuprorivaite) used in classical Roman pigments. However, the mortar from the investigated site shows a distinctive use of ferromagnesian silicates (olivine and pyroxenes from local ultramafic rocks) as aggregate material, making this site unique among all Roman provinces. Additionally, the common occurrence of Mg in the binder of the mortars under the form of brucite, hydromagnesite and magnesium silicate hydrates, indicates the use of a magnesian (dolomitic) lime that, according to the chemical analyses, was obtained by adding up to 15 wt% of powdered dolomitic marbles from nearby Roman quarries to the limestone. We speculate that this addition might be intended to improve the workability and mechanical resistances of the mortar in combination with the abundant ferromagnesian silicates used as aggregates, some of them showing chemically reactive rims in contact with the binder. In conclusion, this study provides further evidence of the advanced knowledge and skills achieved by Roman craftsmen who were able to adapt traditional recipes to suit local resources, obtaining materials of excellent quality and durability.

Soil conditioners promote the formation of Fe-bound organic carbon and its stability

The close association of soil organic carbon (SOC) with Fe oxides is an important stabilization mechanism for soil organic matter (SOM) against biodegradation. Soil conditioners are of great importance in improving soil quality and soil health. Yet it remains unclear how different conditioners would affect the fractionation of SOC, particularly the Fe-bound organic carbon (Fe-OC). Field-based experiments were conducted in farmland to explore the fractionation of organic carbon (OC) and Fe oxides under the effects of three different soil conditioners (mineral, organic, and microbial conditioners). The results showed that all soil conditioners increased the total OC and Fe-OC contents, with the contribution of Fe-OC to total OC increasing from 1.57% to 2.99%. The low OC/Fe molar ratio indicated that surface adsorption played a crucial role in soil Fe-OC accumulation. Nuclear magnetic resonance (NMR) results suggested that soil conditioner altered the composition of SOM, accelerating O-alkyl C degradation and increasing recalcitrant alkyl C and aromatic C sequestration. Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) analysis indicated that all conditioners promoted the association of OC and Fe oxides. Furthermore, comprehensive analysis of 13C isotope and synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy showed that the mineral conditioner enhanced the association of microbial-derived OC and Fe oxides, whereas the organic conditioner increased the association of plant-derived OC with Fe oxides. These findings provide important insights into the potential mechanisms through which soil conditioners regulate the stability of OC and guide agricultural management.

Ion Fluence-Dependent Structural and Electrical Characteristics of Electrochemically Synthesized PANI/ZnO Nano

The electrochemical synthesis and ion irradiation effects of polyaniline/zinc oxide (PANI/ZnO) nanocomposite films on stainless steel substrates were investigated in this study. The structural, morphological and electrical properties of the films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and current-voltage (I-V) measurements. The results show that the films have a nanofiber network structure with an average diameter of 50-60 nm. The vibrational modes and structural properties of the films are influenced by ion fluence. The electrical conductivity and mobility of the films increase significantly at low fluence (1.0 × 1011 ions/cm2), reaching values of 1.14 × 10-2 S/cm and 3.56 × 10-5 cm2/V-s, respectively. However, at high fluence, electrical properties degrade due to the damage caused by the ion irradiation. This study demonstrates the potential of PANI/ZnO nanocomposite films for applications in the optoelectronic devices and energy storage devices.

The ability of drinking water treatment sludge to degrade methylene blue in water through combined adsorption/photo Fenton-like process

In the present study, drinking water treatment sludge (DWTS) was reused as a catalyst in advanced oxidation processes for the removal of methylene blue (MB) from aqueous solutions. After determining their chemical and mineralogical compositions by X-ray Powder Diffraction (XRD), BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), Inductively Coupled Plasma (ICP), and FT-IR spectra. DWTS has been used as a heterogeneous photo Fenton-Like catalyst for the oxidation of MB under different parameters, including pH (3-6), H2O2 concentration (9.79-29.37 mM), and dose (1-2.5 g/L). The results showed that within 180 min and under UV light irradiation, more than 86% of MB having a concentration of 50 mg/L were removed using a catalyst loading of 1.5 g/L, a H2O2 dosage of 23.17 mM and a solution pH of 5. The DWTS has a satisfactory stability as the catalyst is stable and have very less iron leaching property.

Coconut waste to green nanomaterial: Large scale synthesis of N-doped graphene nano sheets

In this paper, a breakthrough was achieved in large-scale production of N-doped Graphene Nano Sheets (N-GNS) using coconut fruits. The main objectives were to produce N-GNS on a large scale and assess its electrical conductivity. The process involved two key steps: first, producing GNS from coconut fruits through pyrolysis, and then generating N-GNS by doping with nitrogen using ammonia solution at room temperature. Various analytical techniques were used to characterize the produced N-GNS, including X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and electrochemical cyclic voltammetry and electrochemical impedance spectroscopy. The XRD data indicated that the C (002) peak of N-GNS shifted to a higher 2θ value (2θ = 24.72°) compared to GNS (2θ = 23.86°), suggesting an incorporation of nitrogen into carbon structure in N-GNS. This was further supported by XPS data, which identified N-pyridine (BE = 402.0 eV) and C-N (BE = 286.8 eV) in N-GNS. TEM images showed that N-GNS had a flat surface, and the distance between graphene layers slightly expanded (0.36 nm) compared to graphene layers (0.34 nm). SEM images and EDX data validated the morphology, resembling honeycomb lattices, with a significant content of N atoms. Raman data successfully identified the D-band and G-band in N-GNS, further validating its production. Most importantly, N-GNS exhibited electrical conductivity, making it a promising candidate for conductive and supporting materials in various applications. The significance of this research extends beyond N-GNS production, opening up new avenues for the sustainable synthesis of valuable nanomaterials from coconut fruit waste, contributing to both graphene technology and environmental conservation.

Hydrogen diffusion in cerium oxide thin films fabricated by pulsed laser deposition

Cerium oxide (CeO2) is well known to be reducible by hydrogen (H2), yet the diffusion and solution properties of hydrogen in ceria at elevated temperatures have remained challenging to evaluate. We therefore fabricated nanometer-thin (∼100 nm) cerium oxide films on Si(111) substrates by pulsed laser deposition (PLD) and quantitatively investigated the H depth distributions therein by means of resonant 1H(15N,αγ)12C nuclear reaction analysis (NRA) before and after annealing in H2 gas at 773–973 K. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) reveal that the as-deposited films exhibit single phase CeO2 structure and partially reduced stoichiometry (CeO1.69). H2 annealing does not largely change the H content of the as-deposited films; in all conditions several atomic percent of hydroxyl (OH) are found to exist in a thin (∼4 nm) surface layer, whereas stably bound hydrogen in the bulk of the films is almost uniformly distributed and of much smaller quantity (∼0.2 at.%) than the oxygen vacancy concentration in the partially reduced ceria. Its low concentration and high thermal stability identify this bulk H species as likely being strongly bound to defects in the polycrystalline films rather than as a hydride species that interacts weakly with O-vacancies. The H diffusion coefficient and activation energy in the ceria films are determined as > 10−18 m2 s−1 at 773–973 K and <1.69 eV, respectively. The observed diffusion activation energy is somewhat larger than theoretical predictions for thermal diffusion of H in stoichiometric bulk CeO2, suggesting that defects and oxygen vacancies in the PLD-fabricated ceria thin films possibly have an impact on the H mobility.