Field Emission-scanning Microscopy Research Articles

H2O2 scavenging and biocompatibility assessment of biosynthesized cellulose/Fe3O4 nanocomposite showed superior antioxidant properties with increasing concentration

Cellulose-based multi-component nanocomposites and biomaterials have some unique properties that give rise to construction in various fields. Recently many studies focused on green technology, which avoids toxic chemicals to make the environment sustainable. The hot-plate combustion method (HPCM) provides a green synthesis that can be used to achieve this goal. Present work deals with the synthesis of cellulose/Fe3O4 nanocomposite (1:1 ratio) via the co-precipitation method and analyzes the biocompatibility and photocatalytic activity. X-ray diffraction (XRD) pattern confirms the formation of cellulose II phase for cellulose and cubic crystalline phase of Fe3O4 particles. Fourier transform infrared (FTIR) analysis showed that the synergy of carbohydrates and proteins is responsible for the fabrication of Fe3O4 nanoparticles and confirms the formation of cellulose/Fe3O4 nanocomposite by the green method. Field emission scanning microscopy (SEM) images revealed two different shapes of cellulose/Fe3O4 nanocomposites including rods and spherical shapes of nanomaterials with particle sizes observed between 20 and 30 nm. The bandgap of cellulose/Fe3O4 nanocomposite was achieved to 2.79 eV, which depicted the best active antibacterial and photocatalyst. The cellulose/Fe3O4 nanocomposite exhibited strong antibacterial as well as antioxidant activity compared with Fe3O4 nanoparticles, towards with maximum of (17.3 ± 0.5 mm) at 2.5 µg/mL against Escherichia coli (MTCC 443) and minimum zone of inhibition of (9.6 ± 1.1 mm) on Staphylococcus aureus (MTTC 3615) at 0.5 µg/mL, respectively. The breakdown of an aqueous medium of methyl orange (MO) dye by the cellulose/Fe3O4 nanocomposite was investigated under visible light irradiation and a higher degradation efficiency of 96.25% was attained at 120 min. The synthesized cellulose/Fe3O4 nanocomposite showed a positive response for photocatalytic and antibacterial activity.

Divalent cation substitution impact on the properties of strontium aluminium hexaferrite (SrAl2Fe10O19)

The strontium aluminium hexaferrite was substituted with the divalent ions (Ba/Ca) with the chemical formula of Sr1-xMxAl2Fe10O19 (M = Ba, Ca; x = 0.1, 0.2), and all the samples were synthesized via sol-gel auto combustion method. The particles are shaped in a hexagonal structure with space group P63/mmc. The field-emission scanning microscopy revealed the platelet-like morphology of the particles. The magnetic studies disclosed the single-domain arrangement of particles and decent energy product value for all the samples (0.36–0.38 MG Oe), implying their potential application in permanent magnets. The declined value of the Dielectric constant at mega-range frequency suggests that the samples could be useful for microwave application.

Studies on the Effect of Substrate Preheating, Interlayer Dwell, and Heat Treatment on Microstructure, Residual Stress, and Mechanical Properties of IN625 Superalloy Built by Direct Metal Deposition

Abstract In this investigation, IN625 alloy samples were processed by the directed energy deposition (DED) approach under various metal deposition strategies such as substrate preheating, interlayer dwell and with combined substrate preheating, interlayer dwell, as well as postheat treatment. The processed sample’s microstructural characteristics, residual stress, microhardness, and tensile properties are assessed in comparison to the manufacturing strategies. Rapid heat dissipation caused finer microstructure near the substrate. There is a growth of columnar grain structure epitaxially in the build direction. The progressive microstructure change seen in the build direction across the cross section was due to the gradual rise of heat accumulation between subsequent layers. The interdendritic zones contained Laves phases. Laves phases have a high Nb, Mo, as well as Si content, according to the energy-dispersive spectroscope (EDS) spectrum. The field emission scanning microscopy (FESEM) microstructural morphology of the deposited samples after their postheat treatment has shown a new microstructure with the combination of equiaxed (recrystallized) and columnar dendritic structure with the reconstruction of columnar dendritic solidification microstructure into equiaxed grains. Heat treatment caused the Laves phases to dissolve in the matrix of IN625 alloy, which led to the precipitation of nanometric γ″ phases. The deposition strategies with substrate preheating significantly decreased the residual stress with moderately improved mechanical properties. The combination of substrate preheating, interlayer dwell, and postheat treatment has shown an outstanding reduction of residual stress along with a remarkable improvement in tensile strength with the retainment of an equivalent ductility compared with other strategies.

Facile route for synthesizing WS2/W2C nano hollow flowers and their application for hydrogen evolution reaction

Recently, catalysts based on tungsten disulfide nanoflowers (WS2 NFs) and tungsten carbide (W2C) materials have been intensively investigated for hydrogen evolution reaction (HER). In this study, a facile and scalable route was utilized to synthesize a nano hollow flowers catalyst based on heterostructure of WS2 and W2C (WS2/W2C NHFs). Besides that, other structures of tungsten compounds including WS2–WO3 flower particles (FPs) and pure WS2 NFs were also prepared by the similar route with slight modification, to compare the differences in their structures and HER activities. Materials properties were comprehensively studied via X-ray diffraction analysis, field emission scanning microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Then, the HER catalytic activities of synthesized materials were also carefully studied. The results indicate that WS2/W2C NHFs exhibits the HER activities much better than that of prepared WS2–WO3 FPs and pure WS2 NFs. The HER performance of WS2/W2C NHFs exhibits a low Tafel slope of about 61 mV.dec−1, an overpotential of − 280 mV at − 10 mA.cm-2, high double-layer capacitance (11.9 mF cm-2) and the superstability in acid media. This improvement is attributed to the synergistic effect of the WS2 and W2C heterostructure as well as the special structure of WS2/W2C NHFs catalyst.

CuxO@Cu mesh electrode with {1 1 1} facet for efficient photo-electro-Fenton reaction and low voltage robustness

In this work, CuxO nanoarrays containing Cu2O and CuO with different morphologies were synthesized on the surface of copper mesh by anodic oxidation method, and the prepared CuxO@Cu mesh electrodes were confirmed by X-ray diffraction (XRD), field emission scanning microscope (SEM), and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and photocurrent were used to characterize the composite electrode. The photo-electro-Fenton (PEF) catalytic system constructed with the prepared CuxO@Cu electrode anode has excellent H2O2 utilization efficiency and pollutant degradation rate. Degradation efficiency of methylene blue (MB) by electro-Fenton (EF), photo-Fenton (PF) and photo-electro-Fenton (PEF) processes were investigated, which was in order: PEF > PF > EF. The effects of applied voltage, current density, pH and H2O2 concentration on MB degradation were investigated. MB could be quickly degraded at CuxO@Cu electrode during heterogeneous photo-electro-Fenton process with a first-order kinetic constant of 3.61 h−1 under 300 W simulated sunlight irradiation at 0.6 V, pH 7.0, 4.9 mmol H2O2. The CuxO@Cu electrode anode was stable and could be reused without catalytic reduction, and also had good degradation efficiency on other organic compounds (p-nitrophenol, tetracycline, norfloxacin), having potential application value in wastewater treatment.

Molecular Interaction of Functionalized Nanoplastics with Human Hemoglobin.

Humans are exposed to excessive nanoplastics (NPs) which have ample affinity for globular proteins. We investigated the interaction of functionalized polystyrene nanoplastics (plain: PS, carboxy: PS-COOH, and amine: PS-NH2) with human hemoglobin (Hb) utilizing multi-spectroscopic and docking approaches to acquire insights into molecular aspects of binding mechanism, which will be helpful in assessing the toxicokinetics or toxicodynamics of nanoplastics NPs. Hypsochromicity and hypochromicity were observed invariably in all the spectra (steady-state fluorescence emission, synchronous and three-dimensional) for all complexes, among which PS-NH2 binds effectively and changes the Hb's conformation by enhancing hydrophobicity around aromatic residues, notably tryptophan. All the NPs bind with the hydrophobic pocket of B-chain in Hb, where PS and PS-NH2 bind via hydrophobic force while PS-COOH binds via hydrogen bonding (predominantly) and van der Waals force, consistent validated with docking results. The minimal shift in absorbance peak also indicates enhanced hydrophobicity by PS-NH2 with larger aggregation as demonstrated in resonance light scattering. The amide band's shift, secondary structural analysis, and presence of characteristic functional group peaks in complexes in Infra-Red spectra confirm the structural changes in the protein. As seen in field emission scanning microscopy images, NPs penetrate the surface of proteins. These findings conclude that polystyrene NPs interact with Hb, causing structural alterations that may affect functional characteristics as well, with the greatest effect being in the order: PS-NH2>PS-COOH>PS.

Analysis of adhesion strength and residual stresses developed by the EDC process

ABSTRACT This paper reports the effect of coating thickness on adhesive properties, and residual stresses by the electric discharge coating (EDC) process on Mg alloy with copper (Cu) nickel (Ni) powder metallurgical (P/M) electrodes. The composite coating layer thickness was measured by optical microscope and it ranges from 10.2 to 102.4 µm. The coating layer was characterized by a Field emission scanning microscope (FESEM) and Energy-dispersive spectroscopy (EDS). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were made to identify the chemical composition and functional group. Residual stresses were evaluated by an ETA diffractometer and it revealed that compressive residual stress increases with a range of −458 ± 118 MPa to −1078 ± 125 MPa and tensile residual stresses decrease from 656 ± 113 MPa to 27 ± 11 MPa. The critical load is measured by scratch test. The result shows the adhesive strength of the coated surface was improved with an increase in layer thickness.

Electrospinning Preparation of PAN/TiO2 Nanofibers and Photocatalytic Regeneration Properties for Methylene Blue dye

The nanofiber membranes prepared by electrospinning method attracted the attention of researchers in the field of pollutant treatment due to their ease of manufacture, efficient performance and ease of removal. Some of these membranes lack the possibility of reuse due to low efficiency and high regeneration cost. In this paper, we were able to prepare nanofiber membranes from polyacrylonitrile (PAN) and PAN/TiO2 by adding different ratios (5,10 and 15) wt% of TiO2 respectively. The resultants nanofibers were characterized using Field Emission Scanning microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR). These prepared membranes enable effective and complete degradation of MB dye in water using ultraviolet (UV) irradiation with the possibility of reuse and high efficiency after washing with distilled water. The efficiency is up to 98% when 15wt% TiO2 was used, while the degradation reaches to 83% when reused the nanofibers composite (PAN/TiO2). The work not only explains the possibility of using and reusing nanofiber films in the treatment of pollutants but also gives a detailed of understanding the behavior of the membrane in dye degradation.

Single-step synthesis of Mn3N2, MnxON and Mn3O4 nanoparticles by thermal plasma arc discharge technique and their comparative study as electrode material for supercapacitor application

In the present study, single-step synthesis of single-phase manganese nitride (Mn3N2), mixed phase manganese oxynitride (MnxON) and manganese oxide (Mn3O4) nanoparticles (NPs) was carried out using the thermal plasma arc discharge (TPAD) method. The experiments were carried out using nitrogen (N2), ammonia (NH3) and oxygen (O2) gas atmospheres at different plasma powers 2, 4 and 6 kW. The phase and elemental compositions of the prepared nanoparticles were examined using X-Ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDX) analysis. All the synthesized powder samples have nearly spherical morphology, which are determined by using Field Emission Scanning Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) analysis. The surface area of the prepared NPs was investigated using Brunauer-Emmett-Teller (BET) analysis, and the obtained results are 40.1, 19.4 and 11.8 m2g−1 for Mn3N2, MnxON and Mn3O4 NPs respectively. The Mn3N2 NPs showed superior storage performance with an outstanding specific capacitance of 508.4 F/g at 1 A/g with pseudocapacitive behavior compared to the mixed and oxide NPs 335.1 and 150 F/g respectively. The Mn3N2 electrode exhibited higher cycling stability with 84.2% capacitance retention after 5000 cycles at a current density of 5 A/g. These results demonstrated that the plasma-prepared single-phase Mn3N2, which is used as a potential electrode material for supercapacitors applications.

Preparation of Chitosan-Carbon Nanotubes Decorated with ZnO@laccase: Application in the Removal of Bisphenol A from Aqueous Solution

Bioremediation with immobilized enzymes has been established as the method for restoring contaminated ecosystems with the help of biological tools on a global scale. The purpose of this work is to immobilize the laccase enzyme for increasing the biocatalyst′s ability in order to remove bisphenol A (BPA). Initially, the nanocatalyst was prepared by immobilizing laccase on chitosan using carbon nanotubes decorated with zinc oxide. Subsequently, Fourier transformed infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and dot mapping were employed to characterize the prepared nanocomposites. Laccase activity, immobilization yield (%), thermal and storage stability, and reusability of laccase immobilized on chitosan-coated carbon nanotubes (CNTs)/ZnO nanocomposites were also measured. The chitosan (CS)-CNTs/[email protected] nanocatalyst performance in different operational conditions (initial concentrations of bisphenol A, amount of nanobiocatalyst, pH, and irradiation time) on the photodegradation process of bisphenol A were also investigated and optimized using the response surface methodology (RSM)-central composite design (CCD) model. The RSM design and experiments demonstrated that 94.51% of BPA was removed under optimal conditions (initial BPA concentration of 100 mg L−1, nanocatalyst amount of 1 g L−1, pH=9, and 40 min of contact exposure). Laccase was a critical factor in this process, and after five recycling cycles, immobilized laccase retained 61% of its original activity, indicating that this nanobiocatalyst can be used in purification processes as a durable and robust catalyst.

Performance of Pandannus amaryllifolius dye on zinc oxide nanoflakes synthesized via electrochemical anodization method

This work presents a study on the effect of Pandanus amaryllifolius dye on the optical properties of zinc oxide nanoflakes synthesized via anodization method. ZnO films were synthesized by anodization method at different applied potentials of 4,8,12 and 16 V under optimum anodization time of 60 min. The synthesized samples were studied and characterized through X-Ray Diffraction, Ultraviolet-Visible spectroscopy and Field Emission Scanning Microscope to evaluate their crystallinity, UV absorption, and surface morphological properties, respectively. The results showed that 12 V sample had the highest (100), (101) and (110) XRD intensity for ZnO and the intensity of the main peak (101) increased by approximately 50% after the adsorption of P. amaryllifolius dye. From the FESEM result, 12 V ZnO exhibited the most closely packed growth of nanoflakes. For optical properties characterized by UV-Vis, there was a significant 10% higher UV absorption sustained between 220–370 nm for the dye treated.

Preparation and characterization of organic red mud and its application in asphalt modification

Red mud, a promising asphalt modifier, can improve comprehensive performance of asphalt. However, the compatibility and performance of organic red mud modified asphalt are also worthy of attention. In this study, organic red mud was prepared with oxalic acid and coupling agent (also called surface modification), and then characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning microscope (FESEM), nitrogen gas adsorption–desorption system (BET) and ultraviolet visible (UV–visible) tests. The application of prepared organic red mud in asphalt modification was explored, including basic performance and aging resistance. The results show that organic red mud prepared by chemical reaction has more uniform particles distribution, smaller specific surface area and stronger ultraviolet reflectivity. After surface modification, the inorganic red mud filler changes from hydrophilic to hydrophobic, and the interaction with asphalt is enhanced, which improves the basic performance of asphalt. More importantly, organic red mud can be homogeneously dispersed in asphalt to inhibit the diffusion of heat and oxygen, and it can reduce the ultraviolet damage to asphalt. Consequently, the thermo-oxidative and ultraviolet aging resistance of asphalt are further enhanced.

SIMPLE EXTRACTION OF THE HYDROXY-APATITE FROM THE EGYPTIAN NILE TILAPIA (OREOCHROMIS NILOTICAS) FISH SCALES

This study aims to recycle the fish scales to extract the hydroxyl-apatite (HApT) compound via a simple and fast chemical treatment of the Egyptian Nile Tilapia (Oreochromis niloticas) fish scales. The method depends on both the NaOH and/or the HCl solutions to dissolve the fish scales then precipitate the HApT 30-32% of the start. The product was characterized by the elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), X-rays Diffraction (XRD), Field Emission Scanning Microscopy (FESEM), Energy Dispersive X-rays spectroscopy (EDX), and Thermo-Gravimetric Analysis (TGA). The results of the FTIR and XRD have revealed the main peaks of an amorphous/crystalline mixed HApT phase that was almost thermally stable after elimination of the entrapped water of preparation and/or the residual organic portion. The particles have exhibited soft homogeneous morphology rather than specifically shaped particles with a 2.25 Ca/P ratio as indicated by the results of the SEM and EDX analysis. The particle size distribution (PSD) analysis has indicated a range of particle size ~250 – 2500 nm with 50% of sample volume < 1 μm. It can be concluded from the results that the studied method is an efficient and economic approach for the HApT extraction as well as the fish scales recycling.

Enhanced The Properties of ZnO Thin Film by Graphene Oxide for Dye Sensitized Solar Cell Applications

In this present work, the effects of coating of graphene oxide (GO) at different concentrations (0, 0.2, 0.3, 0.4, 0.5, and 0.6 mg/ml) onto zinc oxide (ZnO) nanostructured were investigated. ZnO and ZnO coated with GO (ZnO/GO) were prepared using immersion method. The structural, morphology and optical properties of all samples have been studied using x-ray diffraction (XRD), field emission scanning microscopy (FESEM) and UV Vis spectroscopy. The peak obtained from the XRD pattern shows that all samples are in the hexagonal-wurtzite structure. The (002) peak shows the strongest intensity for all samples with the highest (002) peak obtained for the ZnO/GO sample coated at a GO concentration of 0.5 mg/ml. The diameter of ZnO/GO nanostructured samples decreased after coating with GO at concentrations of 0.2 to 0.5 mg/ml and the diameter increased again when ZnO nanostructures were coated with GO at above 0.5 mg/ml. The highest transmission spectrum was obtained for the ZnO/GO sample coated with GO at a concentration of 0.5 mg/ml. In conclusion, the effect of GO coating on ZnO nanostructured can be changed at different concentrations of GO. The optimal properties of ZnO/GO may be suitable as a photoanode in DSSC applications.

Fungal Growth Physicochemical Properties Inhibition by Novel Zinc Oxide/ Glutinous Tapioca Starch Composite

Mango suffers from numerous diseases throughout its life due to fungal growth. Primarily, mango is infected with anthracnose, a disease caused by Collectotrichum gloeosporioides. In the present study, mango fruits were coated with zinc oxide (ZnO) and tapioca starch solution at different concentrations and stored at room temperature for a week. The growth of any black spots on the outer surface of the fruit peel was observed at two-day intervals. The mixed coating material, consisting of ZnO and tapioca starch, inhibited fungal growth. The field-emission scanning microscope (FESEM) results demonstrated that the nanoparticles were uniformly coated on the mango samples. Applying the ZnO coating also effectively maintained the quality attributes and extended the shelf life of the fruits. Consequently, the ZnO and starch coating could be an alternative safe coating technique of protecting mango fruits against anthracnose infection, hence prolonging the freshness and avoiding economic losses during transportation, marketing, and storage.

Green Synthesis of Α-Fe2O3 from Ginger Extract Enhanced the Potential Antioxidant Activity Against DPPH

Synthesis of nano-oxides in an easy and environmentally friendly way using simple and green materials is one of the hot interests of sustainable chemistry for lots of pharmaceutical and medical applications. Herein, we synthesized α-Fe2O3 nanoparticles (α-Fe2O3 NPs) using ginger extract after that calcination at 400 C° for 4 h. The prepared α-Fe2O3 nanoparticles were examined using ultraviolet-visible reflection spectroscopy (UV-VIS), Fourier Transform Infrared Spectroscopy (FTIR), photoluminescence spectroscopy (PL), X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, and zeta potential. After well characterizations, the potency of the prepared α-Fe2O3 nanoparticles to monitor some scavenging activity was explored against DPPH. Results revealed that PL intensity has one peak in the UV region between (480-490) nm of the spectrum depending on the geometric shape and size of the α-Fe2O3 NPS. The UV-visible spectra showed a peak at 296.0 nm, which represented the α-Fe2O3 NPs. The EDX micrograph confirmed pure oxide and the XRD pattern showed that the α-Fe2O3 NPs had an average crystal size (19.3) nm. SEM images of α-Fe2O3 NPs revealed spherical, rod, and irregular shapes and sizes ranging from (15 to 60) nm. Moreover, the antioxidant activity of α-Fe2O3 NPs against DPPH showed 51.8% free radical scavenging ability at 360 μg/mL, which approved good evidence of the antioxidant activity of α-Fe2O3 NPs.

Biosorption of Cr (VI) by acid-modified based-waste fungal biomass from Calocybe indica fruiting bodies production

The world is going through a colossal drinking water scarcity. Unchecked discharge (even at trace levels) of Cr (VI) from industries into water bodies is a serious environmental concern. Here, we report waste fungal biomass (WFB) for the detoxification and removal of chromium ions. Biomass understudy was collected from Calocybe indica fruiting bodies. WFB was used after drying and pretreatment with two distinctive chemical methods, which improved the remediation effectiveness of Cr (VI). Light microscope and Field emission Scanning microscope (FESEM) were employed to elucidate the surface morphology of waste fungal biomass. While Fourier-Transform Infrared-Spectroscopy (FTIR) and Energy Dispersive X-Ray analysis (EDAX) were deployed to explore the mechanism of interaction between Cr (VI) anion and waste fungal biomass. X-ray Photoelectron Spectroscopy (XPS) analyses demonstrated considerable conversion of Cr (VI) into nontoxic Cr (III) species. The most favorable condition for optimum Cr (VI) remediation of 99.66% by treated waste fungal biomass (TWFB) occurred at pH 3, contact time 10 min, adsorbent dosage 3 gL−1, Cr (VI) concentration 4 mgL−1, stirring speed 140 rpm, and temperature 320 K, where for untreated waste fungal biomass (UWFB) the optimum of 85% remediation occurred at a contact time 15 min, and adsorbent dosage 2 gL−1 whereas other experimental conditions remained identical as TWFB biosorbent. Pseudo-second-order kinetics (R 2 > 0.99) model matched the adsorption rate. And, the Freundlich isotherm model (R 2 > 0.99) is shown to be a better match for the experimental data. The optimum amount of Cr (VI) adsorbed by the TWFB and UWFB were 205.8 ± 10.1 and 72.85 ± 2.36 mgg−1, respectively. Thermodynamic parameters revealed that the adsorption was spontaneous (ΔG ˂ 0), endothermic (ΔH > 0), and entropy-driven (ΔS > 0). The generated WFB adsorbent also has significant recycling potential. After five cycles of regeneration and adsorption. It can still keep up good remediation effectiveness of Cr (VI) ions to 85.5%

The Separation Mechanism of Bamboo Bundles at Cellular Level

Bamboo bundles with linear cracks were produced using mechanical treatments that were more environmentally friendly and more efficient than chemical decomposition and steam explosion. This study presented the separation mechanism by analyzing the structure, micro-mechanical properties and chemical constituent of bamboo bundles at the cellular level. The micro X-ray tomography technology (u-CT) morphology of bamboo and bamboo bundles presented that the separation of bamboo bundles was caused by crack propagation, which was related to the structure of the cell types in bamboo. Field emission scanning microscopy (SEM) was performed to observe the appearance of bamboo bundles at the cellular level, which illustrated that the cracks were prone to grow in the middle lamella (ML) in fiber cells and parenchymal cells. The nanoindentation technique and Raman microscopy was used to illustrate that the middle lamella (ML)with low indentation moduli and high lignin content was the weak structure in bamboo. This is interpreted as how the structure and mechanical properties contributed to the separation of the bamboo.

SOFC cathode material of La1.2Sr0.8CoO4±δ with a fibrous morphology: Preparation and electrochemical performance

Using soluble salts as metal-ion sources and polyacrylonitrile (PAN) as a polymer matrix, La1.2Sr0.8CoO4±δ cathode material with a fibrous morphology is prepared by electrostatic spinning, and microstructural characteristic of this material is investigated by field-emission scanning microscopy and X-ray diffraction. Electrochemical performance of the material in solid-oxide fuel cells is then tested. The results demonstrate that phase-pure La1.2Sr0.8CoO4±δ fibrils with tetragonal structure can be prepared from fresh silky precursors using electrospinning after annealing at high temperature. Compared to the conventional cathode material that possesses a plain granular structure, La1.2Sr0.8CoO4±δ fibrils exhibit superior electrochemical performance. At a temperature of 800 °C, the area specific resistance with this fibrous cathode is as low as 0.043 Ω cm2, and maximum power density with the corresponding single-cell is 716 mW cm−2, demonstrating the fast electrode kinetics in the O2 reduction reaction. Comparatively, the area specific resistance with the plain cathode is 0.062 Ω cm2, and the maximum power density with the corresponding single-cell is only 642 mW cm−2. Under a constant voltage load of 0.6 V at a fixed temperature of 750 °C, the power output from a single-cell with the fiber-structured cathode maintains between 615 mW cm−2 and 585 mW cm−2 even after 15 h of running time, showing a slower fading rate and a more stable electrochemical performance than the plain cathode.

LOCALIZED MICROMECHANICAL PROPERTIES OF FINE-PITCH SAC305 DOPED CARBON NANOTUBE SOLDER JOINTS

The addition of carbon nanotube (CNT) to the solder alloy has gained the attention due to its beneficially improve the mechanical properties of the solder alloy. Because of the miniaturization progress of electronic component, micromechanical properties of solder joint need to be focused instead of conventional mechanical properties. In this study, micromechanical properties, and deformation behaviour of SAC305 solder joints with the different CNT doping (weight percentage of 0.01, 0.02, 0.03 and 0.04) were investigated. Localized micromechanical properties included hardness, reduced modulus and stress exponent were determined via nanoindentation approach. Microstructural analysis was performed via optical microscope and field emission scanning microscope (FESEM). Doping of CNT in the SAC305 solder matrix changed the microstructure phase distribution. It was found that, doping of CNT, increase the near eutectic phase and decrease the primary b-Sn phase area. Furthermore, hardness values of SAC305 solder joint increased with increasing of CNT doping weight percentage. Hardness values of SAC305 solder joint increase about ~7 - 40% with the doping of CNT from 0.01 wt. % to 0.04 wt. %. However, localized reduced modulus and stress exponent show random values and no correlated trend with CNT doping were observed. Random values trend of stress exponent revealed that, SAC305 solder joint with the CNT doped involved the combination of deformation mechanism. This is due to the response of phase and CNT in the solder matrix to the localized indentation. In conclusion, a localized approach to hardness properties influenced by the CNT doping weight percentage.