Electron Microscopy Emission Research Articles

The study on the properties of the newly extended Gemini surfactants and their application potentials in the petroleum industry

In this study, the newly extended Gemini surfactants (EGSs) were studied as potential candidates in the petroleum industry applications. The performances of EGSs with respect to variant spacer lengths were studied through surface tension, conductivity, dynamic light scattering (DLS), interfacial tension, rheological behavior, field emission electron microscopy (FESEM), core flooding, and corrosion inhibition measurements. The surface pressure (πCMC), surface efficiency (pC20), critical micelle concentration (CMC), maximum surface excess concentration (Γmax), minimum area per molecule of surfactant at the air-water interface (Amin), average the degree of counterion binding to micelle (β), Gibb's free energy of micellization (ΔGmic), and Gibb's free energy of adsorption (ΔGads) of the EGSs were determined from surface tension and conductivity data. The results showed that the EGSs exhibited more surface activity properties, low CMCs, and spontaneously adsorbed at the air-water interface and micellized in the bulk aqueous phase. The surfactants reduced the oil-water interfacial tension (IFT) to ultralow values (10−3 mN/m) at low concentration, and it decreased substantively to very ultralow values (10−4 mN/m) due to the addition of inorganic salts. Also, they exhibited fascinating viscosifying effect and viscoelastic behavior at the experimental temperatures (30 °C–60 °C). The rheological behaviors were influenced by the formation of entangled micelles in aqueous solutions. Furthermore, through core flooding, EGS1 increased oil recovery by 12.30% which is an interesting incremental recovery. Besides, the EGSs surfactants showed high anticorrosion efficacy on A3 carbon steel in 1 M HCl aqueous solution and the inhibitive action mechanism was revealed to be by creating a protective film on the carbon steel surface through physisorption.Overall, the surface activity, interfacial activity, rheological behaviors, and anticorrosion property were dependent on the length of the spacer group. The surfactants, particularly EGS1 demonstrated a more promising interfacial activity and rheological behavior for enhanced oil recovery (EOR) in heterogeneity reservoirs as well as a remarkable anticorrosion property.

In situ fabrication of TiC-NiCr cermets by selective laser melting

In situ synthesis of TiC-NiCr cermets during selective laser melting (SLM) was investigated. Powder mixture consisting Ti, C and Ni80Cr20 solid solution was prepared by milling process to attain the nominal composition of TiC-40 wt% NiCr. Feedstock powder was milled for 7 h by a high energy ball mill. SLM process was applied at three scanning speeds and the effect of input energy density on phase formation, microstructure and hardness of resultant samples was evaluated. Morphology of the powders and microstructure of in situ fabricated cermets were investigated by field emission electron microscopy (FESEM), and structural evolution during SLM was studied by X-ray diffractometery (XRD). The results showed that TiC can be synthesized during SLM process even at relatively low energy densities and the formation mechanism of TiC phase is affected by the input energy density. Relative density of the samples increased from 88.24% to 98.53% with increasing the energy density from 138.7 to 346.7 Jmm−3. The sample fabricated by SLM process using the maximum energy density of 346.7 Jmm−3showed the highest mean microhardness value of 1289 HV.

Homogeneous MnO2@TiO2 core-shell nanostructure for high performance supercapacitor and Li-ion battery applications

In this work, MnO2 layered TiO2 core-shell nanostructure is prepared by a two-step method. The prepared homogeneous MnO2 layered TiO2 core-shell architecture characterized by various physiochemical techniques. The crystalline nature and other structural details of the synthesized core-shell architecture obtained from powder X-ray diffraction (XRD) technique. The formation of core-shell architecture confirmed by field emission electron microscopy (FE-SEM) technique and the elemental analysis carried out using energy-dispersive X-ray spectroscopy (EDS) analysis. The electrochemical behavior of the prepared MnO2 layered TiO2 core-shell architecture studied using cyclic voltammetry (CV), charge-discharge, and electrochemical impedance techniques in 1 M Li2SO4 aqueous electrolyte. The prepared MnO2 layered TiO2 core-shell architecture shows high specific capacitance and energy density value of 564 F g−1 and 38.39 Wh kg−1, respectively, at the applied current density of 2 A g−1. Further, the resistive and capacitive nature of the synthesized electrode material studied from Nyquist and bode diagrams within the frequency range of from 10 mHz to 100 kHz. Finally, a MnO2 layered TiO2 nanorods/activated carbon asymmetric supercapacitor device fabricated and its lithium-ion storage capacity evaluated at different applied current densities. With these outstanding electrochemical performances, prepared MnO2@TiO2 core-shell nanostructure holds good potential to develop high-performance electrochemical energy storage devices.

Ammonia gas sensing performance of nickel ferrite nanoparticles

Single phase nickel ferrite (NiFe2O4) nanoparticles were prepared by the auto-combustion method using metal nitrate as precursor. Phase and purity of the nickel ferrite nanoparticles (NF NPs) were confirmed by using x-ray diffraction (XRD). The crystallite size of nickel ferrite nanoparticles was calculated 17 nm. Using Field Emission Electron Microscopy (FE-SEM) and Higher Resolution Transmission Electron Microscopy (HR-TEM), morphology of the as-synthesized nickel ferrite nanoparticles particles were observed to be spherical shaped. The band gap of the nickel ferrite nanoparticles was calculated to be 1.55 eV by using UV– Vis spectroscopy. In Fourier transform infrared spectroscopy (FTIR) spectra, the presence of band at 412 cm−1 and 612 cm−1 were confirmed the formation of metal-oxygen (M-O) bond. Further, nickel ferrite nanoparticles have been explored for ammonia gas sensing application. The response was observed to be 10% for 100 ppm of ammonia gas at temperature 250 °C. The response time and recovery time of nickel ferrite nanoparticles based sensor were calculated to be 100 s and 119 s respectively for 400 ppm of ammonia gas. The developed gas sensor was exhibit with excellent repeatability and stability behaviour.

Redistribution of carbon caused by butterfly defects in bearing steels

Butterfly defects initiate from inclusions in the subsurface of steel bearing components subject to rolling contact. The white etching matter (WEM) microstructure is a characteristic of butterflies and is related to the dissolution of carbides and thus generally believed to be enriched with carbon, in supersaturated solid solution, relative to the parent microstructure. Here, several butterflies are investigated using wavelength dispersive spectroscopy (WDS), soft x-ray emission spectroscopy (SXES) and electron microscopy (EM). Contrary to established thinking, in all cases investigated the butterfly-neighbouring WEM was found to be depleted in carbon, relative to parent material, by around 27% (measured in counts). Furthermore, the carbon level was shown to be lower than the matrix itself, suggesting that solute carbon is also expelled from the WEM during its formation, possibly due to the low level of solubility of carbon in ferrite. This was observed in both AISI 52100 and 18NiCrMo14-6 bearing steels. In spite of this depletion, nano-indentation found that WEM in both alloys was ~17% harder than the parent material. This may explain the strings of micro-voids observed near the WEM-parent interface, which appear to play a role in the growth of the butterfly cracks. It is suggested that the increased hardness of the WEM is mainly due to microstructural changes, rather than changes in solute carbon concentration.

One-step fabrication of SnO2 porous nanofiber gas sensors for sub-ppm H2S detection

SnO2 porous nanofibers (NFs) were deposited on-chip by using a facile electrospinning method followed by heat treatment at 600 °C and used to detect H2S concentrations at sub-parts per million level. Morphological, compositional, crystal, and atomic structural properties of the as-spun and calcined SnO2 NFs were investigated by field emission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy, respectively. SnO2 porous NFs with an average diameter of 150 nm and consisting of many nanograins were successfully fabricated by on-chip electrospinning. The NFs were crystallized as the tetragonal structure of SnO2 with an average crystallite size and dislocation density of approximately 13.5 nm and 5.615 × 1015 lines/m2, respectively. The sensing characteristics of the SnO2 NF sensors were tested with 0.1–1 ppm H2S from 150 °C to 450 °C. The sensor achieved the optimal performance at 350 °C and exhibited gas response of 15.2 with fast response/recovery times of 15 s/230 s. The H2S gas sensing mechanisms of the SnO2 porous NF sensors were due to the modulation of the resistance along the surface depletion layer and the grain boundaries. The fabricated sensor also indicated a good selectivity to H2S, short-term stability, and the low detection limit of 1.6 ppb. The influence of humidity on the sensor’s performance in a low temperature range is also discussed.

Study on thermal storage properties of microencapsulated organic ester as phase change material for cooling application

ABSTRACT The phase change materials (PCMs) are latent thermal energy storage materials to store and release energy in the form of latent heat with a change in internal energy. The microencapsulation technique overcomes the limitations faced by the PCMs during energy storage and release. In this study, the new ester-based non-paraffin PCM was microencapsulated into an organic shell using in-situ polymerisation technique. The as-prepared MPCMs was characterised using the field emission electron microscope (FESEM), fourier transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The results show that the MPCM characterised using FESEM has exhibited a good morphology. The chemical stability studies carried using FTIR spectroscopy also confirmed the formation of microcapsules was only by physical interaction. The DSC test results also signify that microcapsules have a latent heat of enthalpy of 65.32 kJ/kg, with onset melting temperature of 8.57°C. Thus, this ensures the MPCM to be considered as a potential candidate for the CTES application.

On the structural-optical correlation of ZnO nanospheres synthesized using thermal evaporation technique

Zinc oxide clusters of different sizes and geometrical shapes have been synthesized and characterized experimentally and theoretically. The ZnO cluster models have been built and presented to study the evolution of physico-chemical properties of the metal oxide semiconductor upon reduction of size. However, most of the theoretical models are lack of support from the experimental details. This article aims to correlate the geometry of the theoretical models with their optical properties. The ZnO thin films were synthesized by thermal evaporator at vacuum pressures of 5 × 10−5 Torr. Cluster models of the synthesized ZnO were built based on its crystal structure. The clusters were evaluated as realistic using geometry optimization, and harmonic frequency calculations at the level of B3LYP functional and lanl2dz basis set. We observed that the fabricated ZnO thin film was constructed by small ZnO spherical clusters, which revealed by the Field Emission Electron Microscopy (FESEM) . This observation is in good agreement with our theoretical simulations, which were established based on its crystal structure – characterized by the X-ray diffractometer.

A noticeable effect of Pr doping on key optoelectrical properties of CdS thin films prepared using spray pyrolysis technique for high-performance photodetector applications

High-quality thin film-based photodetectors containing praseodymium doped cadmium sulfide (Pr:CdS) were fabricated through spray pyrolysis and studied for various opto-electrical applications. Field emission electron microscopy (FE-SEM) revealed that the prepared films were highly compacted with an extremely fine nanostructure without any pinhole or crack. X-ray diffraction and FT-Raman spectroscopy studies confirmed the single hexagonal phase of all the films. The crystallite size was found to lie between 19 and 32 nm. Optical spectroscopy revealed that the fabricated films have low absorbance and high transmittance (in range of 70–80%). The energy gap was found to lie in the range of 2.40–2.44 eV. The PL spectra contained an intense green emission band at ~531 ± 5 nm (2.33 eV), and its intensity was enhanced by increasing the Pr doping content in CdS. The dark and photo currents of CdS increased by approximately 950 and 42 times, respectively with the addition of 5.0 wt% Pr. The responsivity (R) and specific detectivity (D*) were remarkably enhanced to 2.71 AW-1 and 6.9 × 1011 Jones, respectively, for the 5.0 wt% Pr:CdS film. The external quantum efficiency (EQE) of 5 wt% Pr:CdS films was 43 times that of pure CdS films, and the on/off ratio was 3.95 × 102 for 5.0 wt% Pr:CdS film. Its high R, D*, and EQE values, and photo-switching behavior make Pr:CdS a good contender for high quality photodetector applications.

Physicochemical assessment of tailor made fibrous polyurethane scaffolds incorporated with turmeric oil for wound healing applications

Nanofibrous scaffold holds a great potential in remodeling of the damaged tissue. This work attempts to fabricate a fibrous wound dressing scaffold based on polyurethane (PU) mats reinforced with turmeric oil via electrospinning technique. The field emission electron microscopy (FESEM) depicted the smaller fiber diameter of nanocomposites compared to polyurethane. Fourier transform infrared spectroscopy (FTIR) and thermal analyses insinuated the existence of turmeric in the PU matrix by the formation of hydrogen bond and reduced weight loss for composite scaffold. Contact angle of the PU scaffold showed a hydrophobic behavior while turmeric oil incorporation resulted in the hydrophilic nature. Atomic force microscopy (AFM) analysis showed a decrease in surface roughness of PU with the addition of turmeric oil. In blood compatibility results, the coagulation times were observed to the higher for PU/turmeric oil than PU. The developed nanocomposites showed a less percentage of lysis of red blood cells suggesting better blood compatibility than PU. Further, cell viability assay depicted enhanced proliferation of fibroblast cells in the developed composites than PU. Overall, it was concluded that fabricated novel scaffold having better physicochemical and good biocompatibility characteristics for wound dressing.

Synthesis and characterization of butylamine-functionalized Cr(III)–MOF–SO3H: Synergistic effect of the hydrophobic moiety on Cr(III)–MOF–SO3H in esterification reactions

Mesoporous solid acid catalysts with partially hydrophobic moieties, [Cr3O(BDC–SO3H)3−x(BDC–SO3NH3Bu)x]n, were prepared from [Cr3O(BDC–SO3H)3]n (MIL-101(Cr)–SO3H) and BuNH2 for the first time and then characterized by the Brunauer–Emmet–Teller (BET) technique, powder X-ray diffraction, field emission electron microscopy, Fourier transform infrared spectroscopy, and thermal and elemental analyses. The nitrogen adsorption–desorption study showed that the specific surface area and total pore volume of MIL-101(Cr)–SO3H decreased after the reaction with butylamine and formation of [Cr3O(BDC–SO3H)3−x(BDC–SO3NH3Bu)x]n. The prepared materials were used as catalysts to investigate the impact of hydrophobic moieties in esterification yields of phthalic anhydride with several alcohols as a probe reaction. The presence of butylamine as a hydrophobic group on MIL-101(Cr)–SO3H increases the esterification yield significantly for hydrophilic alcohols under solvent-free conditions. Moreover, results showed that [Cr3O(BDC–SO3H)3−x(BDC–SO3NH3Bu)x]n can be recovered and reused for several consecutive reactions without significant loss in catalyst activity.

Experimental investigation on the mechanical behavior of red sandstone under the coupled effects of temperature and acidic etching

The red sandstone that commonly exists in nature is used to study the coupled effects of temperature and acidic etching on its mechanical properties. The dry-wet cycle is adopted to accelerate the corrosion process during the test, and the increase in the number of dry-wet cycle indicates the increase of the degree of corrosion. A series of uniaxial compression tests were carried out, and the influence of dry-wet cycle times on the physical and mechanical properties of red sandstones was analyzed. Besides, the crack propagation, phase composition, and the micromorphology of red sandstone were analyzed by means of acoustic emission (AE), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results show that the physical and mechanical parameters of red sandstone such as the P-wave velocity and the uniaxial compressive strength have been deteriorated in different degrees considering coupled effects of temperature and acidic etching. With the increase of the number of dry-wet cycle times, the elastic deformation section of the axial stress-strain curve of the specimen becomes shorter and the softening characteristic is gradually obvious. The evolution of AE is a good evidence for the changes of internal structure of the specimen due to the coupled effects of temperature and acidic etching. The results of the XRD and the SEM indicate that the species of minerals increase and the microstructures of the specimen were changed with the increase in the number of dry-wet cycles.

Characterization of Nano-SiC Powder Prepared by High-Energy Ball Milling as a Mechanochemical Process with Subsequent Annealing Process

SiC nano-powder compound was prepared by mechanochemical process followed by annealing. Phase evaluation and microstructural changes of the powders during the processes were examined by X-ray diffraction, field emission electron microscopy and transmission electron microscopy analyses. Necessary milling times for initial and perfect formation of SiC nano-powder were 50 and 70 hours, respectively. The mean particles size of specimens annealed via FE-SEM images with 70 hours of milling was found to be less than 100 nm.

Growth of Fe doped ZnO nanoellipsoids for selective NO2 gas sensing application

In this work, Undoped ZnO and Fe-doped ZnO nanostructures were successfully synthesized by using the simple hydrothermal method and their structural, morphological by various characterization techniques and studied the gas sensing properties. The Field emission electron microscopy (FE-SEM) observed that the nanorods assembled together to form the flower like in undoped ZnO and after Fe doping it turns into nanoellipsoid like morphology. NO2 gas response analysis revealed that Fe-doped ZnO nanoellipsoids displayed a higher selectivity compared to undoped ZnO. Among the different doping concentration 8 wt% exhibited the highest response of 209.8 when exposed to 100 ppm concentration of NO2.

Simultaneous green synthesis and in-situ impregnation of silver nanoparticles into organic nanofibers by Lythrum salicaria extract: Morphological, thermal, antimicrobial and release properties.

This research has revealed the promising, green and one-pot approach for fabrication of antimicrobial nanohybrids based on organic nanofibers including cellulose (CNF), chitosan (CHNF), and lignocellulose (LCNF) nanofibers impregnated with silver nanoparticles (AgNPs). Lythrum salicaria extract was used as a reducing agent as well as a capping agent. Formation of the spherical AgNPs ranging between 45 and 65 nm was proved by UV-Vis spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). Biomaterials supported AgNPs were characterized and compared for their morphological, thermal, release, and antimicrobial properties. The considerable influence of the phenolic compounds of L.salicaria extract on the synthesis and uniform distribution of AgNPs on nanofibers was confirmed by field emission electron microscopy (FE-SEM). Energy dispersive X-ray spectroscopy (EDX) and ICP-OES analysis of nanohybrids, reflected a high loading capacity for LCNF and also CHNF in contrast to CNF. The release of AgNPs from LCNF substrate was lower than other nanofibers but the order of antimicrobial activity of nanohybrids against E.coli and S.aureus was as this: CHNF ˃ LCNF ˃ CNF. Generally, this research suggested that the efficiency of CHNF and LCNF as immobilizing support of AgNPs is higher than CNF and L.salicaria extract was proposed as a high potential reducing and capping agent.

Influence of growth duration and nitrogen-ambient on the morphological and structural properties of beta-gallium oxide micro- and nanostructures

Micro- and nanostructures of gallium oxide (Ga2O3) were prepared on silicon substrate by the hydrogen-reduction chemical vapor deposition (HR-CVD) technique. We investigated the influence of synthesis duration and growth ambient on the surface morphology, crystal structure and band gap of the grown films by using field emission electron microscope (FESEM), high resolution X-ray diffraction (HR-XRD) and ultraviolet–visible spectrophotometer (UV–vis), while elemental composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Dwell time was found to enhance step coverage of the substrate and also improve the X-ray diffraction peaks. Films fabricated under nitrogen-flowing ambient were observed to have regular shape but with less dense structures, lower Ga/O atomic ratio, weaker XRD peak intensity, and increasing band gap; while samples deposited in N2-deficient environment had characteristics opposite to those of their counterpart. Band gap of films were observed to decrease with increasing film density and Ga/O atomic ratio.

Influence of deposition angle on nano-structure, optical and electrical properties of copper azide (CuN3) thin films

Cu/glass films of 100 (nm) thicknesses were deposited at 0° and 40° and post annealed at three different temperatures with flow of nitrogen. XRD patterns of the films deposited at 40° confirmed formation of CuN3 phase which is due to higher void fraction in these films. Optical properties of the produced samples were obtained using the Bruggeman homogenization method. Results of optical properties of these films showed that the dispersion behavior is sensitive to the annealing temperature, polarization of the incident light and film deposition angle. Clear energy loss peak is obtained for film deposited at 0° and annealed at 350 °C using both s- and p-polarized incident lights with a shift to lower energies for p-polarized incident light. Appearance of these peaks are related to the values of the dielectric functions and the structure of the sample which consists of almost evenly distributed conical shapes with sharp tips leading to the enhancement of plasmon resonances and the corresponding frequency in this sample. The surface morphology of the produced samples was analyzed by means of field emission electron microscope and atomic force microscope. Variation of grain size with annealing temperature is observed which can be due to competition between two processes of diffusion and penetration of nitrogen atoms/molecules in the body of the grains.

Ternary transition metal chalcogenides decorated on rGO as an efficient nanocatalyst towards urea electro-oxidation reaction for biofuel cell application

A ternary transition metal chalcogenide, containing MoS2, NiS, and Co3S4 (MCNS), and MCNS/reduced graphene oxide (MCNS/rGO) composite were prepared as anode catalysts by a simple hydrothermal process for Urea electro-oxidation. It's expected that rGO with high specific surface area provides superior catalytic performance for MCNS/rGO than MCNS. Also, the synergic effect of Mo, Ni, and Co in the composite accelerates the urea oxidation and enhances the performance of the catalyst. The composites were characterized by field emission electron microscopy, transition electron microscopy, and X-ray diffraction spectroscopy. Electrochemical properties of composites were evaluated by cyclic voltammetry. The MCNS/rGO demonstrated superior electrocatalytic performance than the MCNS catalyst. The incorporating of rGO into MCNS creates a high electrochemical surface area for urea electro-oxidation that resulted in a higher current density (18 mA cm−2) than MCNS (3.7 mA cm−2) at the presence of 0.6 M urea and the scan rate of 20 mV s−1. The maximum current density obtained 43 mA cm−2 for MCNS/rGO at the scan rate of 70 mV s−1 in room temperature. Also, single cells based on MCNS and MCNS/rGO supplied a maximum power density of 7.7 mW cm−2 and 21.0 mW cm−2 at room temperature, respectively. Hence, MCNS/rGO can be a favorable electrocatalyst for application in the direct urea fuel cell.

Achieving exceedingly constructional characterization of magnesia-yttria (MgO-Y2O3) nanocomposite obtained via oxalate precursor strategy

Magnesium yttrium oxide (MgO-Y2O3) nanocomposites have been purposefully tailored using an oxalate precursor pathway. Commonly, MgO-Y2O3 nanocomposites possessed a significant technological challenge in electroceramics; particularly remarkable as the anode material for solid oxide fuel cells (SOFC). In this regard, different weight ratios, % of MgO and Y2O3 including (20:80), (50:50) and (80:20) were fabricated based on oxalic acid as a fuel in acidic medium. Indeed, the impact of the annealing temperature on the phase composition, crystallite size, morphology and optical properties was investigated using X-ray diffraction, field emission electron microscope (FESEM), TEM, FTIR and UV–VIS-NIR spectrophotometer. The FESEM results showed the nanocomposite had a cubic like structure with the fine grain sizes of 0–150 nm because of the rapid solidification. The band gap energy was found to be 4.83, 5.10 and 5.08 eV with increasing the ratio of Mg2+ ion from 20 to 50 and 80, respectively. Eventually, our currently studies consider to be an important achievement to investigate and recognize the features of the MgO-Y2O3 system for different applications involving microwave systems, advanced displays (field emission display, plasma display, electroluminescent display), ultra-fast sensors, durable, infrared windows and lasers.

Breakdown characteristics of polyethylene/silicon nitride nanocomposites

Silicon nitride (Si3N4) has been utilized as a nanofiller in polymeric insulation due to its good characteristics in both electrical insulation and thermal conduction properties. In this work, a comparative study was performed between unfilled polyethylene and polyethylene containing different amounts of Si3N4 nanofiller. The study showed that the low density polyethylene (LDPE) added with 15 wt% of Si3N4nanofiller could have higher breakdown strength compared to equivalent LDPE with 10 wt% of Si3N4nanofiller. Morphological characterizations of the nanocomposite samples were performed using field emission electron microscopy (FESEM) and the results showed that the breakdown performance of the investigated materials were affected by the agglomeration of Si3N4 nanoparticles.