Field Emission Gun Scanning Electron Microscopy Research Articles

Self-Powered Photodetector Based on a Ag Nanoparticle-Decorated Gd2O3 Nanorod

A self-powered photodetector based on a silver nanoparticle (Ag NP)-decorated gadolinium oxide nanorod (Gd2O3 NR) has been deposited using the glancing angle deposition (GLAD) technique. Field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM) analyses confirm the successful growth of a Ag NP-decorated Gd2O3 NR with polycrystalline nature. UV–vis spectroscopy reveals the presence of the Ag NP and Gd2O3 NR with photon absorption in visible and UV regions. The electrical analysis was studied for the voltage range of −5 to 5 V. The device demonstrated self-powered characteristics with a significantly low dark current of 0.73 nA. In addition, the device also displayed a stable switching response with a rise/fall time of 0.18/0.17 s at 0 V. Moreover, the device obtained good responsivity (11.8 mA/W) with a high detectivity of 7.63 × 1011 Jones and a low noise equivalent power of 3.67 × 10–12 W at 0 V.

Ag/TiNPS nanocatalyst: biosynthesis, characterization and photocatalytic activity

Wastewater pollution by synthetic dyes has emerged as a serious environmental problem, causing a series of deleterious effects, since they have low biodegradability and considerable chemical stability, requiring advanced treatment technologies, such as Advanced Oxidative Processes (AOPs), such as heterogeneous photocatalysis. In this context, the present work aims to synthesize, characterize, and evaluate the photocatalytic activity of silver/titanium nanoparticles (Ag/TiNPs) using the biosynthesis method from Aloe vera extract for application in the removal of Rhodamine B dye (RhB) to propose an alternative to the problem of wastewater with dyes. Ag/TiNPs were characterized by N2 porosimetry (BET/BJ method), zeta potential (ZP), Field Emission Gun – Scanning Electron Microscope (FEG-SEM) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR). Ag/TiNPs showed SBET = 343 m2 g-1, Dp = 4.9 nm, Vp = 0.26 cm3 g-1, ZP = -15.1 mV and V-type isotherm with H1 hysteresis. ATR-FTIR showed the presence of characteristic functional groups of -OH, -C=O, -CH2, and -CH3. FEG-SEM micrographs presented a heterogeneous and porous surface with nanoparticle size around 12 nm. Regarding the heterogeneous photocatalysis, Ag/TiNPs showed 100% degradation of RhB (k = 0.0219 min-1) under visible irradiation after 120 minutes, with the possibility of reuse in 5 cycles and only 5% reduction in photocatalytic activity. Therefore, Ag/TiNPs showed promising characteristics for application as a nanocatalyst in the treatment of wastewater with dyes.

A bimetallic nanocatalyst from carbonaceous waste for crystal violet degradation

The contamination of wastewater by cationic dyes has caused considerable environmental problems, such as an imbalance in the aquatic ecosystem and a decrease in photosynthetic activity. In this context, this study aims to synthesize and characterize a bimetallic nanocatalyst (MMT@TiO2-NPs/ZnO-NPs), as well as to evaluate its photocatalytic activity in crystal violet (CV) dye degradation. The samples were characterized by X-ray diffraction (XRD), Field Emission Gun – Scanning Electron Microscope (FEG-SEM), N2 physisorption (BET/BJH methods), UV–Vis Diffuse Reflectance Spectroscopy (DRS), zeta potential (ZP), and zero charge point (pHZCP). Central composite rotational design (CCRD 2³) was used for the experimental design to obtain the ideal condition. The diffractograms showed characteristic peaks of MMT (analcime and neighborite), ZnO-NPs (zincite) and TiO2-NPs (anatase) with an average crystallite size determined in the range of 10–50 nm. The MMT@TiO2-NPs/ZnO-NPs showed a high surface area (98.8 ± 0.6 m2 g−1) with IV-type isotherm characteristic of porous materials. Moreover, a heterogeneous morphology with an average particle size of around 16 nm. ZP showed a negative charge (−3.84 ± 0.07 mV) and pHZCP ≈ 5.80, favoring interactions with the CV dye. Ideal condition was [CV] = 32.5 g L−1, [MMT@TiO2-NPs/ZnO-NPs] = 1.75 g L−1 and pH = 12, with a CV removal of 99.97% (k = 0.0789 min−1) under visible radiation. Regarding reuse, MMT@TiO2-NPs/ZnO-NPs showed great photocatalytic stability after six cycles with 90.62% for the CV degradation. Therefore, MMT@TiO2-NPs/ZnO-NPs showed great potential for use in the treatment of industrial textile effluents, helping in the waste management strategy from mid-to long-term perspectives.

Green synthesis of copper oxide nanoparticles using Ficus elastica extract for the electrochemical simultaneous detection of Cd2+, Pb2+, and Hg2.

In this paper, for the first time, we report the use of a new carbon paste electrode based on a low-cost pencil graphite powder modified with polyaniline (PANI) and green synthesized copper oxide nanoparticles using Ficus elastica extract as a sensor for Cd2+, Pb2+, and Hg2+. The elaborated electrode was characterized by FT-IR spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and simultaneous thermal analysis (TGA/DSC). The electrochemical behavior of the sensor was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy techniques. According to CV, as well as square wave voltammetry (SWV) results, it was found that the CuONPs/PANI-CPE sensor was able to determine very low concentrations of Cd2+, Pb2+, and Hg2+ in HCl (0.01 M) either in single metal or in multi-metal solutions with a high sensitivity. Furthermore, Cd2+, Pb2+, and Hg2+ simultaneous detection on CuONPs/PANI-CPE achieved very low limits of detection (0.11, 0.16, and 0.07 μg L-1, respectively). Besides, the designed sensor displayed a good selectivity, reproducibility, and stability. Moreover, CuONPs/PANI-CPE enabled us to determine with high accuracy Cd2+, Pb2+, and Hg2+ traces in environmental matrices.

EXTRACTION AND CHARACTERIZATION OF BIODIESEL DERIVED FROM THE COFFEE HUSK AND ITS EFFECT ON DIESEL ENGINE PERFORMANCE AND EMISSION CHARACTERISTICS

This study investigates the suitability of coffee husk (CH) and spent coffee ground (SCG) as the biomass energy source to produce biodiesel. The chemical composition was determined using the field emission gun scanning electron microscope (FEG-SEM). The carbon and oxygen concentration in CH was 49.84% and 48.06%, respectively, by weight. The SCG had 67.72% of carbon and 26.18% of oxygen by weight. The oil extracted from CH was converted into biodiesel using the transesterification process. The properties of the biodiesel, such as flashpoint, fire point, viscosity, calorific value, and density, were measured. The engine's performance and emission characteristics were investigated by blending the produced biodiesel with regular diesel. It was found that by using CHOME biodiesel-diesel blends, exhaust gas emissions such as HC, CO, and smoke opacity were considerably reduced, while CO<sub>2</sub> and NO<sub>x</sub> emissions increased. The brake thermal efficiency (BTE) of the engine was slightly reduced, and brake specific energy consumption (BSFC) was increased.

Properties of One-Part Alkali Activated Ground Granulated Blast Furnace Slag Using Slaked Lime as Alkali Activator – A Comparative Study with Different Silicate Sources

The paper reports the results of investigating the prospect of using slaked lime as a solid activator to activate the ground granulated blast furnace slag (GGBFS) with micro-silica as an additive. The results of the above-mentioned one-part mix are compared to that of GGBFS activated with solid sodium silicate in combination with slaked lime and quick lime, discretely. The compressive strength is found to be comparable to that of slaked lime and sodium silicate activated GGBFS; the silica fume substitution is recommended at 10% with 5% slaked lime. The main hydration products are C-S-H and C-A-S-H. Although the setting is delayed, strength development is acceptable with curing at ambient temperature. The microstructural analyses conducted through Field emission gun scanning electron microscopy (FEGSEM) and X-ray diffraction (XRD) are in good correlation with the results obtained for strength development.

Zinc oxide nanoparticles: Biosynthesis, characterization, biological activity and photocatalytic degradation for tartrazine yellow dye

The present study aims to synthesize/characterize zinc oxide nanoparticles (ZnO-NPs) to evaluate the application of tartrazine yellow (TY) dye removal. ZnO-NPs were synthesized by the biosynthesis method from Eucalyptus grandis extract. X-ray diffraction (XRD), zeta potential (ZP), N2 porosimetry, Field Emission Gun Scanning Electron Microscope (FEG-SEM), zero charge point (pHZCP) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to the ZnO-NPs characterization. The antimicrobial activity was performed by the MIC (Minimum Inhibitory Concentration) method against gram-positive (S. aureus) and gram-negative (E. coli, K. pneumoniae and P. aeruginosa) strains. For cellular activity assays, MTT (3-(4,5-Dimethylthiazol-2-yl) and DCFH-DA (2′7′ dichlorofluorescein diacetate) tests were performed with cell lines of the 293T, A549 and U87MG. FEG-SEM micrography indicated a heterogeneous and porous morphology with rod-shaped zinc oxide nanoparticles (particle size ranged from 40 to 50 nm). ZnO-NPs showed a negative charge surface (−11.6 ± 0.2 mV), pHZCP ≈ 7.16 with type III and H1 hysteresis (SBET = 3.9 m2/g, and Dp = 16.2 nm) indicating a mesoporous material with pores open at both ends. The optimal condition was [ZnO-NPs] = 0.6 g/L, [TY] = 20 mg/L and pH ≈ 6.0 with 76.1 % (k = 0.0077 min−1) for the TY photodegradation under visible radiation, and after VI cycles of ZnO-NPs recycling, there was a decrease of only 6 %. ZnO-NPs showed antimicrobial activity of 0.625 mg mL−1, as well as a decrease in cell viability in the three tested lines in 100 and 300 µg mL−1. Therefore, ZnO-NPs showed potential application for TY photodegradation to be used in wastewater treatment and nanomedicine.

Adherence of Escherichia coli and blood elements in titanium discs submitted to anodic oxidation. In vitro study

Modifications of implants by means of surface treatments are performed to optimize the biochemical interactions of the bone deposition process. However, if on the one hand they favor the adhesion of blood elements, on the other hand they can also enable the formation of biofilm. This study evaluated the adherence of blood cells and Escherichia coli in titanium discs submitted to surface treatments by anodic oxidation (OA), sandblasting followed by acid etching (JAT) compared with untreated discs (Li). To evaluate the adherence of microorganisms were performed: atomic force microscopy; Field Emission Gun Scanning Electron Microscopy (FEG-SEM); biofilm formation was evaluated by spectrophotometer turbidity analysis and colony forming unit (CFU/mL) before and after simulated brushing. For blood cell adherence, the blood collected from a patient was deposited and fixed on the discs and analyzed in the FEG-SEM being classified according to the "Blood Element Adherence Index". The results showed a slight increase in the adhesion of microorganisms in samples treated by anodic oxidation. However, the microorganisms were distributed singly and not in conglomerates, with no biofilm formation unlike the Li group. Regarding the adherence of blood elements, the Li group showed higher adherence and lower amount was found in the JAT group, but there was no statistically significant difference between the groups. The results of this study suggest that anodic oxidation treatment may favor the adherence of blood cells and fibrin mesh, contributing to the early stages of bone deposition.

Transformation of Waste Toner Powder into Valuable Fe2O3 Nanoparticles for the Preparation of Recyclable Co(II)-NH2-SiO2@Fe2O3 and Its Applications in the Synthesis of Polyhydroquinoline and Quinazoline Derivatives.

Ecological recycling of waste materials by converting them into valuable nanomaterials can be considered a great opportunity for management and fortification of the environment. This article deals with the environment-friendly synthesis of Fe2O3 nanoparticles (composed of α-Fe2O3 and γ-Fe2O3) using waste toner powder (WTP) via calcination. Fe2O3 nanoparticles were then coated with silica using TEOS, functionalized with silane (APTMS), and immobilized with Co(II) to get the desired biocompatible and cost-effective catalyst, i.e., Co(II)-NH2-SiO2@Fe2O3. The structural features in terms of evaluation of morphology, particle size, presence of functional groups, polycrystallinity, and metal content over the surface were determined by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (P-XRD), field emission gun-scanning electron microscopy (FEG-SEM), energy-dispersive X-ray analysis (EDX), high resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET) analysis, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) studies. XPS confirmed the (II) oxidation state of Co, and ICP-AES and EDX supported the loading of Co(II) over the surface of the support. P-XRD proved the polycrystalline nature of the Fe2O3 core and even after functionalization. In comparison to previously reported methods, Co(II)-NH2-SiO2@Fe2O3 provides an eco-friendly procedure for the synthesis of polyhydroquinoline and quinazoline derivatives with several advantages such as a short reaction time and high yield. Polyhydroquinoline and quinazoline derivatives are important scaffolds in pharmacologically active compounds. Moreover, the developed nanocatalyst was recyclable, and HR-TEM and P-XRD confirmed the agglomeration in the recycled catalyst resulted in a decrease in yield after the fifth run. The present protocol provides a new strategy of recycling e-waste into a heterogeneous nanocatalyst for the synthesis of heterocycles via multicomponent reactions. This made the synthesized catalyst convincingly more superior to other previously reported catalysts for organic transformations.

Morphology and microstructure of waste material-based geopolymer with flyash, eggshell powder, and soft soil

The morphological and microstructural evolution of flyash (FA), eggshell powder (ESP), and soft soil (S) geopolymer was studied. The variable parameters for synthesis was precursor concentration (10 %, 20 %, 30 %, 40 %, and 50 %) in soft soil, whereas ESP:FA ratio as 50:50, Na2SiO3:NaOH ratio as 70:30, and curing condition as 50 °C for 7 days were the fixed parameters. The effect of these parameters on the geopolymerization was explained using field emission gun-scanning electron microscopy including an energy dispersive X-ray spectrometer and mapping. The calcium aluminate silicate hydrate gel co-existed along with the highest cementitious product. The geopolymeric gel structure filled the voids between soft soil particles and reinforced the whole matrix.

Effect of Different Surface Modifications of Brazilian Attapulgite (ATP) on the Mechanical and Thermal Properties of LLDPE/ATP Nanocomposites

AbstractIn this work, Brazilian attapulgite (ATP) with different surface modifications is used as a mineral filler in the development of linear low‐density polyethylene (LLDPE) nanocomposites. As a raw mineral, Brazilian ATP has many impurities in its structural channels (ATPr). Thus, sodium polyacrylate, hydrogen peroxide, and sulfuric acid are used to remove impurities from ATPr in a process called acid activation (ATPa). Also, inorganic materials do not have good interfacial interaction with organic polymers. Therefore, as an alternative to this challenge, two surface modifications are made to the ATPa: silanization (ATPs) and organophilization (ATPo). ATPr, ATPa, ATPs, and ATPo are characterized by FT‐IR (Fourier transform infrared spectroscopy), XRD (X‐ray diffraction), TGA (thermogravimetric analysis), and FEG‐SEM (field emission gun scanning electron microscopy). The effectiveness of surface modifications is evaluated for LLDPE/ATP nanocomposites with the addition of 3 wt% ATP (ATPr, ATPa, ATPs, and ATPo) prepared by extrusion. The nanocomposites are analyzed by XRD, thermal characterization (differential scanning calorimetry—DSC), mechanical characterization (Shore D hardness, tensile test, and Izod impact strength), and morphological characteristics (SEM micrographs). It can be noted that the addition of treated ATP increases the mechanical properties. The silanization is more effective when compared to the organophilization treatment.

A Novel Synthesis of a Magnetic Porous Imprinted Polymer by Polyol Method Coupled with Electrochemical Biomimetic Sensor for the Detection of Folate in Food Samples

The present study reports the development and application of a novel, sensitive, and selective voltammetric sensor for the quantitation of folate or vitamin B9 in foodstuffs. The sensor was made from magnetic molecularly imprinted polymers (MMIPs), which were synthesized by the core–shell method using magnetite nanoparticles obtained by the polyol method. The MMIP-based sensor was used for the selective and specific detection of folate in different food samples. The MMIP material was constructed using magnetic water-dispersible nanomaterial, which was prepared by immersing iron (III) acetylacetonate in tri-ethylene-glycol (TEG) solvent. The magnetic water-dispersible nanomaterial was then subjected to polymerization using allyl alcohol as a functional monomer, ethylene-glycol-dimethacrylate (EGDMA) as a cross-linking agent, and 2,2-Azobisisobutyronitrile (AIBN) as a radical initiator. The proposed magnetic materials were characterized by Brunauer–Emmett–Teller (BET), field emission gun scanning electron microscopy (FEG-SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM) analysis. The quantification of folate was performed by square wave voltammetry under optimized conditions using 15 mg of MMIPs and 85 mg of carbon paste. The modified electrode presented a linear dynamic range (LDR) of 2.0–12 µmol L−1 and a limit of detection (LOD) of 1.0 × 10−7 mol L−1 in 0.1 mol L−1 acetate buffer solution (pH 4.0). The proposed sensor was successfully applied for folate detection in different food samples, where recovery percentages ranging from 93 to 103% were obtained. Finally, the results obtained from the analysis of selectivity showed that the modified biomimetic sensor is highly efficient for folate determination in real food samples. Adsorption tests were used to evaluate and compare the efficiency of the MMIPs and magnetic non-molecularly imprinted polymer (MNIPs)—used as control material, through the application of HPLC as a standard method.

Using the synergistic effect of co-doping to engineer magnesium and chlorine co-doping to improve the electrochemical performance of Li2FeSiO4/C cathodes

To compensate for the insufficiency of single doping and to exert the synergistic effect between the elements, further improving the electrochemical performance, a series of Mg and Cl co-doped Li2Fe1−xMgxSiO4–2xCl2x/C (x = 0, 0.01, 0.02, 0.03) nanocomposites (LFS, LFS-1, LFS-2, and LFS-3) have been synthesized by solvothermal method. Experimentally, Mg and Cl co-doping in Li2Fe1−xMgxSiO4–2xCl2x/C were confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscope, and field-emission gun scanning electron microscopy elemental mapping, while electrochemical cycling performance showed improved performance. According to the results, LFS-2 outperforms other nanocomposites in terms of electrochemical performance, rate capability, and initial discharge capacity, with a capacity of 238.3 mAh·g−1 after 100 cycles of charging and discharging at 0.05 C. This is because it has a stable monoclinic structure free of impurities, a lower charge transfer resistance, and a higher Li-ion diffusion coefficient. Our findings suggest that Mg and Cl co-doping might be a feasible low-cost technique to enhance the electrochemical performance of silicate-based cathode materials, taking into account potential and electronic conductivity advantages.

Characterization of chemical elements of calcium silicate-based cements

The aim of this study was to characterize the chemical elements and surface of the cements: Biodentine®, Bio-C Sealer®, Endosequence® BC Sealer, MTA Angelus® and Portland Cement (PC). Material and methods: The cements were manipulated according to manufacturer’s recommendations, inserted in polyethylene tubes and kept in a 95% humidity incubator for 72 hours. The analysis of the chemical elements was performed by energy dispersive X-ray spectroscopy (EDS) coupled to a low vacuum Scanning Electron Microscope (SEM). The surface analysis was performed according to the distribution pattern, shape and particle size in images obtained using Field Emission Gun SEM (SEM-FEG). Data were analyzed descriptively for EDS chemical composition spectra and qualitatively for SEM-FEG images. Results: EDS analysis showed that all evaluated cements contained calcium and silicon rich particles. MTA Angelus® presented bismuth-rich particles, while Biodentine®, Bio-C Sealer® and Endosequence® presented zirconium-rich particles, the latter having tantalum in its composition. All materials showed a uniform distribution pattern of particles on the surface. Biodentine® and Endosequence® showed similarly shaped particles. Conclusion: The cements present particles with uniform distribution pattern and similar chemical composition, differentiating the presence of bismuth or zirconium.

Membrane damage mechanism of protocatechualdehyde against Micrococcus luteus and its effect on pork quality characteristics

This study investigated the mechanism of membrane damage by protocatechualdehyde (PCA) against Micrococcus luteus and assessed effects of PCA on the sensory and physicochemical properties of pork. The mechanism of PCA inhibition on M. luteus was studied by determining the minimum inhibitory concentration (MIC) based on membrane potential, intracellular ATP concentration, intracellular pH, confocal laser scanning microscopy (CLSM), and field emission gun scanning electron microscopy (FEG-SEM). The results showed that the MIC of PCA against M. luteus was 1.25 mg/mL. Hyperpolarization of the bacterial cell membrane, a decrease in the intracellular ATP concentration, and intracellular pH indicated that PCA damaged the cell membrane of M. luteus. FEG-SEM observation revealed that PCA could cause surface collapse, cell membrane rupture, and content outflow of M. luteus. Additionally, PCA was found to inhibit increases in the total number of colonies, the thiobarbituric acid reactive substances (TBARS) value growth rate, and moisture mobility in raw pork. Additionally, it improved the color and texture of raw pork, all of which effectively prolonged its shelf life. This study will encourage the application of PCA as a natural antibacterial agent in the food industry.

Influence of sodium and calcium contaminant in the growth of carbon nanotube on rayon-based carbon fibers

This study investigated the role of contaminants commonly found on rayon-based carbon fibers (CF) for the carbon nanotubes (CNT) synthesis. The most common contaminant found on CF is sodium. From the experimental results, sodium contaminant indeed performed as a catalyst, but with low efficiency. However, some CF samples also contained calcium as a contaminant, and Ca presence made higher density and better-quality CNT growth. Probably Ca acts as the reducing agent, keeping Na in metallic form along the entire growth process. XPS data suggests a new view of sodium oxide/hydroxide to sodium carbonate transition after CNT synthesis. On CF samples with calcium, sodium keeps activity and carbonate does not form, differently of the sample containing just Na. CF free of contaminants (PAN-based CF) helps set apart the effects and Raman Spectroscopy picked up sodium and calcium effects on the CNT crystalline quality. The sodium presence in rayon-based CF worsens CNT quality when growing from the foreign iron-cobalt catalyst. By another hand, calcium presence helps keeping iron-cobalt nanoparticles surface reduced. Images of Field Emission Gun Scanning Electron Microscopy (FEG-SEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) also supported the analysis.

Monitoring the Simultaneous Implantation of Ti and Tb Cations to a Sacrificial Template and the Sol-Gel Synthesis of Tb-Doped TiO2 (Anatase) Hollow Spheres and Their Transition to Rutile Phase

Tb-doped TiO2 (anatase) micro-hollow spheres (HSs) with nano-shells, in the range 0.00-3.00 at.% Tb, were successfully synthesized by a simultaneous chemical implantation route of both Ti and Tb cations from chlorides to a poly-styrene (PST)-co-poly-divinyl benzene (PDVB) sacrificial template, followed by controlled hydrolysis and polycondensation reactions. After water addition to the mixture of the precursors with the template, a decrease in the intensity and a shift to lower wavenumbers of the C=O absorption band in the IR spectra can indicate not only the anchoring of Ti and Tb ions to the carbonyl group of the template but also the hydrolysis of the implanted precursors. This latter process can involve a proton attack on the Ti-Cl, Tb-Cl and C=O bonds, the occupation of a vacant site by a water molecule, and then the dissociation of the dangling Ti-Cl, Tb-Cl ligands and C=O bonds. It gives rise to Ti1-xTbx[(OH)4-uClv]@PST-PDVB and Ti1-xTbx[(OH)4-y]@PST-PDVB complexes (x = 0.00, 0.0012, 0.0170 and 0.030). Finally, polycondensation of these species leads to Ti1-xTbxO2-w'@PST-PDVB compounds. After subsequent thermal removal at 550 °C of the template, the IR bands of the core (template) totally vanished and new bands were observed in the 400-900 cm-1 region which can be attributed to the metalloxane bondings (M-O, M'-O, M-O-M, M-O-M' and/or M'-O-M', being M and M' = Ti and Tb, respectively, i.e., mainly vibration modes of anatase). Then, micron-sized HSs of TiO2 and Tb-doped-TiO2 (anatase) were obtained with nano-shells according to field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM) observations. Furthermore, X-ray photoelectron spectroscopy (XPS) measurements confirmed the presence of Tb4+ (38.5 and 41.2% for 1.70 and 3.00 at.% Tb, respectively) in addition to Tb3+ in the resulting HSs, with increasing Tb4+ content with both Tb doping and higher calcination temperatures. Then, these HSs can be considered as rare earth (RE) co-doped systems, at least for 1.70 and 3.00 at.% Tb contents being the transition to rutile phase favored by Tb doping for those compositions. Finally, diffusion of Tb from the inner parts to the surface of the HSs with the calcination treatments was also observed by XPS.

Fire gilding investigation on early medieval copper-based jewellery by focused ion beam (FIB) on FEG-SEM

The study of ancient gilding is often problematic, as the gilding layers are soft and prone to deformation during sample preparation. In this respect, focused ion beam (FIB) milling on a field emission gun scanning electron microscope (FEG-SEM) provides poorly invasive in situ sampling. The operating process is here detailed and applied on gilded medieval copper-based elite jewellery (10th century) from Prague Castle. Obtained cross-sections and slices of gilded samples were investigated up to nanometer scale without gilding layer deformation. By coupling structural observation with elemental X-ray analysis (EDS) and electron beam diffraction (EBSD), FIB FEG-SEM provided new data on the physical–chemical characteristics of the gilded layer. The gilding has a two-layer metallurgical structure containing a quaternary Au (Hg, Cu, Ag) alloy corresponding to the gold solid solution fcc phase, and a submicrometric inner sublayer formed by a Au-Cu phase, relative to the interdiffusion of copper from the substrate during the fire gilding process. The applied temperature for gilding can be estimated at c. 400 °C. Sintering of the mercury-gold amalgam globules during the fire heating is highlighted. The precise characterisation of the gilding layers provided useful comparative parameters for identifying fire gilding skill levels and assessing the overall quality of the archaeological pieces.

Lanthanum Strontium Cobalt Ferrite (LSCF) perovskites by Sol-Gel Method for Potential Application in Solid Oxide Fuel Cells (SOFC)

Fuel cells are one of the most efficient and effective solutions to environmental problems and high energy demand. They are devices which change chemical energy into electrochemical energy, allowing much higher efficiency than conventional thermomechanical conversion methods. Lanthanum Strontium Cobalt Ferrite (LSCF) perovskites have been widely studied for application as cathodes in solid oxide fuel cells (SOFC) due to their high electrical conductivity, high thermal and chemical stability, low difference in thermal expansion coefficient, and physico-chemical compatibility with the other cells components. The aim of this work was to synthesize perovskitas type La0.7Sr0.3Co0.5Fe0.5O3 by sol-gel method and evaluate the potential for application as a cathode for fuel cell. The results obtained by X-ray powder diffraction (XRD) indicate that the sol-gel method calcined at 900ºC obtained an amount of the perovskite phase above 95%. The Field Emission Gun-Scanning Electron Microscope (FEG-SEM) images of LSCF film produced with 4 layers showed a better quality. Thus, the results obtained by XRD and FEG-SEM, indicate that the sol-gel method calcined at 900ºC has a potential application as cathode in solid oxide fuel cells.

Role of adding carbon nanotubes in the electric and electromagnetic shielding behaviors of three different types of graphene in hybrid nanocomposites

Graphene-related materials (GRM) are promising materials to improve mechanical, electrical, and optical polymer properties. Adding multi-wall carbon nanotubes (MWCNT) on GRM nanocomposites promotes synergistic effects on its electrical properties and electromagnetic interference shielding effectiveness (EMI SE). This study focused on evaluating the addition of MWCNT on three different polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)/GRM nanocomposites. These hybrid nanocomposites were prepared by melt mixing using extrusion and injection-mold processes. The morphologies of the nanocomposites were evaluated by field emission gun scanning electron microscopy (FEG-SEM), and their proprieties were characterized by X-ray diffraction (XRD), oscillatory rheological, dielectric spectroscopy, and EMI SE analyses. The electrical behavior of all hybrid nanocomposites was anisotropic due to the injection-molded preparation process. The lateral size, thickness, and production method of the GRM were indicated to be critical factors for the electrical and EMI SE behaviors of these composites. The nanocomposites with GRM2, which had the smallest lateral size and thickness (graphene nanoplatelets), promoted total attenuation levels around 20 dB with 1.5 wt% of MWCNT, matching the EMI SE required for some commercial applications.