Scanning Electron Microscopy Equipped With Energy Dispersive X-ray Spectroscopy Research Articles

Assessment of Surface Properties of Silica-Bacterial Cell Complex: A Potential Application for Silicate Bioflotation Processes

The objective of the present work was to assess the surface properties of silica-cell complexes formed by Bacillus pumilus strain SKC-2 for bioflotation purposes. This bacterial strain was employed in this study because it is a Gram-positive, mixotrophic bacterium whose metal binding capacity extends to many different metals and circumstances as well as a biosurfactant producer. The strain was found to promote the formation of silica-cell complexes due to the generation of surface-active agents (i.e., extracellular polymeric substrances (EPS)) as represented by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observation. Surface properties of the complexes was assessed by water contact angle and surface tension measurements, demonstrating that bacterial cells reduced the surface tension of the solutions and increased the contact angle of the silica surfaces, representing a larger hydrophobic property. Therefore, the findings of this study provide clear evidence for the potential application of the bacterium Bacillus pumilus strain SKC-2 for silicate bioflotation processes (i.e., as frother and collector).

Possible Role of the Biosurfactant-Producing and Fe-S-Oxidizing Bacterium in Silicate and Sulfide Bioflotation Processes

A biosurfactant-producing-and Fe-S-oxidizing bacterium, namely Pseudoclavibacter sp. strain SKC/XLW-1, was studied in an attempt to seek more benign alternatives for the replacement of relatively toxic chemical reagents in the flotation of silicate and sulfide minerals. Our study showed that Pseudoclavibacter sp. SKC/XLW-1 was capable of yielding biosurfactants as evidenced by a decrease in the surface tension of the solutions and an increase of the contact angle of the pyrite or silica surfaces as a function of time. This bacterial strain was also observed to promote the oxidation of pyrite, thus generating Fe-oxides as well as sulfuric acid as indicated by a decline of the solution pH and FTIR analysis. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) observations of the silica-or pyrite-bacterial cell complexes revealed the presence of bacterial cell aggregation along with silica or pyrite, where silica or pyrite particles become embedded in the biofilm matrix. It is suggested from this study that the bacterium Pseudoclavibacter sp. SKC/XLW-1 could potentially be applicable as the flotation bioreagents (collector, frother or depressant) for both silicate and sulfide flotation processes.

Synthesis, structural and morphological characteristics of NiO nanoparticles Co-doped with boron and nitrogen

To improve the performance of NiO nanoparticles under source light, a nitrogen and boron co-doped nano powder photocatalyst was collected. The UV–Vis diffusive reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy were used to measure photoabsorbance. The morphology of NiO nanophotocatalyst was characterized using Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray diffraction (XRD). The particle size was in correlation with the calcination temperature. It is found that the average crystallite size and specific surface area of the three co-doped NiO catalysts are near 9.57–10.21nm, and 132.7–151.9m2/g, respectively. Degradation of 1-chloro-4-nitrobenzene under UV and visible light illumination was applied to appraise the photocatalytic efficiency. The results indicated that the co-doping of nitrogen and boron performance is a major designation in the band gap decrease, which led to the enhancement of the activity of photocatalytic reaction. The binding energies of O 1s, Ni 2p1/2, Ni 2p3/2, N 1s and B 1s ready a justly complete image of the synthesis sample. The peak of Ni 2p3/2 that emerges at 855.6eV indicated the detection for NiO. The peak of O 1s at 530.9eV is ascribed to the O2− in the NiO. The particles exhibited excellent antimicrobial property.

Influence of calcination temperature on the structural, adsorption and photocatalytic properties of TiO2 nanoparticles supported on natural zeolite

TiO2 nanoparticles supported on natural zeolite (TI-ZE) are prepared via a simple hydrolysis of TiCl4 and then calcined at various temperatures. The as-prepared catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller analysis (BET), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The adsorption and photocatalysis ability was evaluated towards Cr (VI) in dark or under UV light. The XRD analysis showed that the increasing temperature destroyed the original framework structure of zeolite (over 500°C) and the anatase TiO2 formed at 500°C. It was found that the calcination temperature influenced the adsorption behavior and photocatalytic activity. The sample calcined at 300°C presented the optimum adsorption performance because of its highest specific surface area, and the adsorption process followed pseudo-second-order kinetic. The maximum adsorption capacity of different samples has been calculated based on the Langmuir model. The kinetics for the photodegradation of Cr (VI) has been determined in terms of Langmuir–Hinshelwood model. The photocatalysis test indicated that the TI-ZE calcined at 500°C remained the original zeolite structures and possessed the highest removal ratio because of its relatively larger adsorption capacity and better crystallinity of TiO2. Furthermore, the removal efficiency of TI-ZE-5 towards Cr (VI) was still more than 75% after five times cycling, which confirms the durability of TiO2/zeolite catalyst.

Effects of pretreatment and process temperature of a conversion coating produced by an aprotic ammonium-phosphate ionic liquid on magnesium corrosion protection

This paper presents results of treating a magnesium alloy surface using an aprotic ammonium-phosphate ionic liquid (IL) to form a conversion coating for corrosion protection. The IL, tetraoctylammonium di(2-ethylhexyl)phosphate ([N8888][DEHP]), was applied to AZ31B Mg surfaces at room temperature (RT) or 300°C with or without pretreatment. The morphology and composition of the IL-produced conversion coatings were characterized by means of scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion protection performance of the conversion coatings were investigated in a 1wt.% NaCl solution saturated with Mg(OH)2 using the potentiodynamic polarization technique. Results suggested that the IL treatment at 300°C is more effective than RT in corrosion protection. This is attributed to the thermal breakdown of IL molecules and the consequent chemical reactions between the reactive IL decomposition products and the Mg alloy surface, which form a film containing metal phosphates and oxides. It was also found that an appropriate pretreatment process is essential for achieving superior corrosion inhibition.

Designing of CK45 carbon steel and AISI 304 stainless steel dissimilar welds

Gas tungsten arc welding of CK45 and AISI304 stainless steel was performed through preparation of different types of samples using ER308L and ERNi-1 wires. Welded samples were studied by different techniques including optical metallography, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction, hardness measurements and impact test. It was observed that in the buttered specimen, the structure of the weld metal was completely austenitic while the microstructure of unbuttered sample was duplex ferritic-austenitic. M23C6-type carbides were observed within the weld metal of both as-weld specimen types. Effects of different post-weld heat treatments (PWHTs) were investigated. The experimented results concluded that simultaneous grain growth and carbides precipitation were competitive during PWHT. Also, there were not any indication related to sigma-phase in as-welded and PWHTed specimens due to their lower Cr/Ni ratios and insufficient preservation times.

Sol–gel derived hybrid materials doped with rare earth metal ions

Sol–gel derived organic–inorganic hybrid materials doped with rare earth metal ions (Pr 3+) and small amounts of lithium ions (∼0.1–0.2 wt.%) were produced from the tetraethyl orthosilicate (TEOS), AlCl 3·6H 2O (about 10 mol%), ethyl methacrylate, butyl methacrylate and some other organic additions (ca. 35–40 wt.% of organics in the fresh gels) to obtain hybrid organic–inorganic hosts. The gel and hybrid materials obtained were aged at room temperature for three weeks, then heated in an electric drier for 3 h at temperature of 125 °C and investigated for morphology, structure and luminescence properties by X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), 29Si and 27Al MAS nuclear magnetic resonance and fluorescence spectroscopy. An influence of the organic additions and inorganic dopants on microstructure of the materials obtained and their luminescence properties has been examined. Under excitation with UV radiation in a range of ∼210–350 nm, the sharp and relatively intense luminescence emission lines due to 3P 0 → 3H 4 (blue) and 3P 0 → 3F 3 (red) transitions of Pr 3+ ions were observed in the luminescence spectra of gel and hybrid materials of SA-series.