Dispersive X-ray Analysis Research Articles

Effect of metallurgical evolution during post-weld aging treatment on localised corrosion of resistance spot welding joints of A286 superalloy

ABSTRACTThe combined effect of resistance spot welding and precipitation hardening on the localised corrosion of A286 superalloy is studied. The specimens tested by double loop electrochemical potentiokinetic reactivation were welded in the solution treated condition, and then subjected to different precipitation hardening treatments. For both base metal and weld nugget, the maximum localised corrosion is reached when η phase is clearly observable. The fact that the localised corrosion resistance of weld nugget is different from that shown by base metal may be explained by the segregation of Ni and Ti towards the interdendritic region of weld nugget (studied by using scanning electron microscope/energy dispersive X-ray analysis).

Nanoparticle concentrations and composition in a dental office and dental laboratory: A pilot study on the influence of working procedures

ABSTRACTDuring material treatment in dentistry particles of different size are released in the air. To examine the degree of particle exposure, air scanning to dental employees was performed by the Scanning Mobility Particle Sizer. The size, shape and chemical composition of particles collected with a low-pressure impactor were determined by scanning electronic microscopy and X-ray dispersive analysis. The average concentrations of nanoparticles during working periods in a clean dental laboratory (45,000–56,000 particles/cm3), in an unclean dental laboratory (28,000–74,000 particles/cm3), and in a dental office (21,000–50,000 particles/cm3), were significantly higher compared to average concentrations during nonworking periods in the clean dental laboratory (11,000–24,000 particles/cm3), unclean laboratory (14,000–40,000 particles/cm3), and dental office (13,000–26,000 particles/cm3). Peak concentration of nanoparticles in work-intensive periods were found significantly higher (up to 773,000 particles/cm3), compared to the non-working periods (147,000 particles/cm3) and work-less intensive periods (365,000 particles/cm3). The highest mass concentration value ranged from 0.055–0.166 mg/m3. X-ray dispersive analysis confirmed the presence of carbon, potassium, oxygen, iron, aluminum, zinc, silicon, and phosphorus as integral elements of dental restorative materials in form of nanoparticle clusters, all smaller than 100 nm. We concluded that dental employees are exposed to nanoparticles in their working environment and are therefore potentially at risk for certain respiratory and systematic diseases.

Negative photoconductivity in metal-organic potassium oxalate oxalic acid dihydrate single crystal

The single crystals of potassium oxalate oxalic acid dihydrate (KH3(C2O4)2.2H2O) were synthesized using the slow solvent evaporation technique at room temperature. The unit cell parameters of the crystal were determined using single crystal X-ray diffraction technique. The crystal belongs to triclinic crystal system, –P1 space group. The structural analysis of synthesized crystal was carried out using powder X-ray diffraction technique. The surface morphology of the crystal was studied using Field Emission Scanning Electron Microscope (FESEM). The elemental composition was determined and mapped using Energy Dispersive X-ray (EDAX) analysis. The crystal was studied using UV-visible transmission spectrum. The photoluminescence properties of the crystal were studied by recording the emission spectrum. The thermal stability of the crystal was analyzed using Differential Scanning Calorimetry (DSC). Furthermore, light induced I-V studies reveal the probability of the synthesized crystal in photo-resistance applications.

Efficiency of magnetite as nanocrystalline bulk catalyst for the reduction of 4-nitrophenol

Magnetite nanocristals were prepared via the co-precipitation technique. X-ray Diffraction, surface area measurements, Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis and Temperature Programmed Reduction technique were used for the characterization of the prepared solids. Their catalytic performance was investigated in the 4-nitrophenol reduction. It has been found that the thermal preparation conditions strongly influenced the properties of the prepared samples. Hot co-precipitation leads to a decrease in catalytic performance regardless of the catalyst amount. The reaction duration decreases when increasing the catalyst amount. The catalytic behavior was directly related to the redox properties and the rate constant values were found to be significant in comparison with the literature data.

Effect of temperature on wear and tribofilm formation in highly loaded DLC-steel line contacts

Abstract In the present study the tribological properties of DLC coatings are analysed by performing Stribeck experiments with a block on ring (BoR) configuration, developed for a rotational tribometer, under different temperatures operated with a conventional 5W30 engine oil. Both, block and ring are made of steel and surface hardened, whereby a-C:H coating with CrN adhesion and CrC gradient layer is deposited on the latter. Results reveal, that the amount of formed Zinc dialkyldithiophosphate (ZDDP) tribofilms can be linked directly to changes of wear volume and boundary friction coefficient (COF). Furthermore, wear and tribofilms can trigger topological surface adaptations, leading to a different frictional behaviour in the fluid lubrication regime as well. Optical, energy dispersive X-ray (EDX) and thermoelastohydrodynamic (TEHD) numerical analysis were carried out in order to gain a holistic understanding of phenomena taking place in DLC/steel tribosystems. Findings indicate, that anticipated positive effects of DLC coatings are partly suppressed due to the onset of these films under conditions relevant in automotive engines.

English

Aqueous extract of Kigelia africana fruits have been utilized in the syntheses of silver nanoparticles (AgNPs) and copper-silver bimetallic nanoparticles (Ag-CuNPs). The synthesized nanoparticles have been characterized using UV-vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX), x-ray diffration (XRD) and transmission electron microscopy (TEM). The antimicrobial activities have been evaluated against both Grams-negative and Grams-positive strains of bacteria and fungus. The UV-vis and FTIR techniques revealed the formation of nanoparticles and the active components were adsorbed on the surface of the particles thereby stabilizing the nanoparticles. The SEM reveals uniform microspheres of AgNPs and anisotropic particles for AgCuNPs. TEM shows a particle size of 10 nm. The nanoparticles inhibit the growth of both Grams-negative and Grams-positive bacteria. The present nanoparticles synthesized from aqueous extract of K. africana fruits inhibits Klebsiella pneumoniae more than any of the antibiotics tested in this study. It competes very well with augmentin against Pseudomonas aeruginosa and with meropenem against Candida albicans with inhibition zones of 23 and 25 mm, respectively. The bimetallic nanoparticles have demonstrated effectiveness against Staphylococcus aureus, with maximum inhibition zone of 27 mm. Key words: Green synthesis, bioreduction, nanoparticles, bimetallic particles, Kigelia africana, antimicrobial activities.

Effect of Alumina Nanofiller and Diphenyl Phthalate Plasticizer on a Silver Ion Conducting Polyethylene Oxide Based Nanocomposite Solid Polymer Electrolyte

A novel silver ion conducting thin film nanocomposite solid polymer electrolyte (NSPE) has been prepared by blending poly(ethylene oxide) (PEO) as a polymer host with silver trifluoromethane sulfonate (AgCF3SO3) as a dopant ionic salt, aluminum oxide (Al2O3) as an inorganic nanofiller, and diphenyl phthalate (DPP) as a plasticizer using classical solvent casting technique and characterized by means of X-ray diffraction (XRD), electrical conductivity studies, field emission scanning electron microscopic (FESEM) and energy dispersive X-ray (EDX) analyses. Electrochemical cells have been fabricated and their discharge characteristics under dead load and at a constant load of 1 MΩ have been studied at ambient temperature (298 K).

Alginate-polymethacrylate hybrid hydrogels for potential osteochondral tissue regeneration

Porous scaffolds based on alginate-polymethacrylate hybrid hydrogels intended for bone and cartilage regeneration were prepared through controlled calcium ions diffusion from an agar mould. The double interconnected network of such materials combines into a single porous structure maintained by both noncovalent crosslinks (calcium ions for alginate) and covalent crosslinks (polymethacrylate crosslinked by the addition of mixtures of mono and bifunctional monomers). The alginate component ensures the appropriate micro-environment to mimic the extra-cellular matrix, whereas the polymethacrylate improves the mechanical performances of the hybrid hydrogels, helping to overcome the mechanical limitations of the alginate component. Morphological characterization and porosity analysis of the hybrid scaffolds were assessed by scanning electron microscopy and micro-computed tomography. Relative concentration and distribution of calcium ions were evaluated by atomic absorption and dispersive X-ray analysis, respectively. Uniaxial compressive mechanical tests were conducted to evaluate the compressive elastic modulus of the hybrid hydrogels that was correlated with their swelling ratio and crosslinking degree. As was envisaged a much higher modulus (about seven times) was obtained for the hybrid Alg/HE hydrogel than with alginate alone.

Preparation and Characterization of Nanoporous Sodium Carboxymethyl Cellulose Hydrogel Beads

A series of nanoporous sodium carboxymethyl cellulose (NaCMC) hydrogel beads were prepared using FeCl3 ionic crosslinker by changing polymer and crosslinker percentages (%). Characteristics of the hydrogels were investigated by gel content, swelling test, degradation test, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), Scanning Electron Microscope/Energy Dispersive X-ray Analysis (SEM/EDX), and Atomic Force Microscopy (AFM). Swelling experiments were studied by changing time, temperature, and pH. The swelling percentage (S%) regularly decreased with increasing the amounts of polymer and crosslinker, in contrast with gel content results. NaCMC hydrogels were found to be sensitive to pH variations. The degradation test showed that hydrogels had good stability and their degradation period varied from 30 to 36 days. According to SEM analysis, NaCMC hydrogels had mostly nanoporous structure. The average granule and pore sizes of the least swollen NaCMC-12 hydrogel were found to be 13.1±0.3 nm and 82.1±3.2 nm. The elemental compositions of hydrogels were determined with EDX. The minimum average surface roughness (Ra) and root mean square roughness (Rms) parameters were found to be 15.7±1.9 nm and 20.3±2.2 nm for NaCMC-12 hydrogels by AFM. Due to their good morphologies, stabilities, and swelling behaviors, NaCMC hydrogels can be suitable for biomaterial applications.

Synthesis and Characterization of Aluminium Oxide (Al<sub>2</sub>O<sub>3</sub>) Nanoparticles and its Application in Azodye Decolourisation

The adsorption behaviour of an azodye Methylene Blue (MB) over aluminum oxide nano particles (AONP) generated by sol-gel method has been studied to investigate the physicochemical process involved andexplore the potential use of AONP in wastewater treatment. The variables incorporated in the present study are concentration of dye, dosage of adsorbentand contact time. The characterizations of AONPs were carried out using X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive Analysis of X-rays (EDAX) and Raman spectroscopy. SEM image showed the distribution pattern of nanoparticles. FTIR spectra revealed thatfunctional groups (O-Al-O) are present. Raman spectra showed the crystalline nature of nanoparticles. Averagesize of Al2O3 nanoparticle from XRD peak was found to be 25 nm having rhombohedral structure. Chemical composition of AONPs was confirmed from EDAXspectroscopy measurement. The smaller dosage of AONP was tested for the photocatalytic degradation.

New Magnetic Polymer Nanocomposites on the Basis of Isotactic Polypropylene and Magnetite Nanoparticles for Adsorption of Ultrahigh Frequency Electromagnetic Waves

ABSTRACTIn this study, we report about the preparation of magnetic polymer nanocomposites on the basis of isotactic polypropylene and magnetite Fe3O4 nanoparticles. The structure and composition of polymer nanocomposite materials have been studied by scanning electron microscopy, atomic force microscopy, and X-ray dispersive analysis. The magnetic properties of polymer nanocomposites based on PP+Fe3O4have been investigated. It is found that not significant adhesion and agglomeration of nanoparticles occur, by increasing the nanoparticle content in polymer matrix up to 40%, and therefore they act as single-domain nanoparticles. The samples of nanocomposites based on PP+Fe3O4, with up to 40% content of Fe3O4, exhibit superparamagnetic properties. It was also found out that the magnetic polymer nanocomposite material based on PP+Fe3O4 is able to absorb ultrahigh frequency electromagnetic waves in the frequencies range from 0.1 to 30 GHz. The increase in Fe3O4 concentration from 5 to 40% at the 400 µm thicknesses of the films leads to an increase in absorption of electromagnetic waves of high frequency from 15 to 22.7%.

ANTI-BACTERIAL ACTIVITY STUDIES ON TEXTILE MODIFIED WITH SILVER METAL, COPPER, ZINC AND MAGNESIUM OXIDES NANOPARTICLES

The anti-bacterial characteristics of different nano-structured metal and metal oxides modified cotton fabrics were investigated. In this study, silver metal, copper, zinc and magnesium oxides have been supported on bleached cotton fabrics. Reduction, wet method, sol gel and precipitation methods were used in the preparation of the antibacterial nanoparticles (NPs). The preparation of the antibacterial-loaded cotton was carried out in-situ and ex-situ by pad dry methods. Formation of the supported nanoparticles was confirmed using x-ray diffraction (XRD), scanning electron microscopy studies (SEM) and energy dispersive x-ray (EDX) analyses. Antibacterial studies on the supported nanoparticles were done on gram positive (Bacillus and S. aureus) and gram negative (E-coli) bacteria by agar diffusion method. The loaded antibacterial nanoparticles are effective against the bacteria under investigation. Under the given experimental conditions, the maximum inactivation performances of each loaded inorganic agent were investigated. The loaded fabrics show the following antibacterial performance order against Bacillus: Ag=CuO>ZnO>MgO. However, the activity order is CuO>Ag>ZnO=MgO against S.aureus and E.coli. The inactivation performances depend on the type, purity and the amount of antibacterial nanoparticles on the textile surfaces.

Synthesis of Polyurethane/Silica Modified Epoxy Polymer Based on 1,3-Propanediol for Coating Application

Studies on the synthesis of polyurethane/silica modified epoxy polymer using 1,3-propanediol has been conducted. Synthesis of polymers made by reaction of tolonate and 1,3-propanediol (ratio NCO/OH=2.5) as the building blocks of polyurethane with diglycidyl ether bisphenol A (DGEBA) epoxy and catalyst dibutyltin dilaurate (DBTL).The total weight of the polyurethane used was 20% (w/w) of the total epoxy. Based on Fourier Transform Infrared (FTIR) and 1H-Nuclear Magnetic Resonance (1H-NMR) spectra indicated the existence of a new bond that is formed from the reaction of isocyanate group and hydroxyl group, where the hydroxyl groups derived from epoxy and 1,3-propanediol. The addition of silica (5, 10, and 15% w/w to epoxy) into the epoxy-modified polyurethane has been carried out through sol-gel reaction of tetraethyl orthosilicate (TEOS). The isocyanate conversion rate for the addition of silica 5, 10, and 15% are 95.69; 100, and 100%, respectively. The morphology and element identification by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX), showed that Si element has been successfully added in the polymer. From the tensile strength and elongation analysis, also thermal stability analysis using Thermal Gravimetric Analyzer (TGA), the increase of silica amount into the polyurethane modified epoxy did not significantly affect to thermal properties, but decrease the tensile strength of the polymer.

Experimental Analysis of Resistance to Electrocorosion of a High Chromium Cast Iron with Applications in the Vehicle Industry

We obtained a new Fe-C material, a cast iron with high chromium content. The experimental material was analyzed by microstructural (SEM electronic) and chemical (EDAX characteristic X-ray dispersive energy analysis) point of view. The addition of chromium is aimed to increase the corrosion resistance and durability of FC250 castings used on industrial scale in the manufacture of automotive brake discs. The material was obtained using an industrial scale furnace. The experimental results showed a substantial increase in corrosion resistance by the addition of chromium.

Synthesis and characterization of (100-x) Ba0.82Sr0.03Ca0.15Zr0.10Ti0.90O3 + (x) Mg0.25Cu0.25Zn0.5Mn0.05Fe1.95O4 composites with improved magnetoelectric voltage coefficient

Multiferroic composites having the nominal composition (100-x) [Ba0.82Sr0.03Ca0.15Zr0.10Ti0.90O3] (BSCZTO) + (x) [Mg0.25Cu0.25Zn0.5Mn0.05Fe1.95O4] (MCZMFO) (where x = 5, 10, 20, 40, 60, 80 and 100 wt %) were synthesized by solid state sintering method. The structural, morphological and magnetic properties of the composites were elucidated through X-ray diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electronic Microscopy (SEM), Energy Dispersive Analysis of X-ray (EDAX) and vibrating sample magnetometer (VSM). XRD and FTIR analyses revealed that MCZMFO and BSCZTO phases coexist with cubic spinel and tetragonal perovskite structure without interacting with each other. The lattice constant of MCZMFO and BSCZTO phases in the composites increases with increase of MCZMFO phase due to increased inner stress. SEM and EDAX analyses reveal a homogeneous microstructure with uniform dispersion of MCZMFO grains and presence of Mg, Cu, Zn, Mn, Fe, O, Ba, Sr, Ca, Zr and Ti elements respectively. At low frequencies, the dielectric dispersion for x = 80 and 100 wt % composites is due to interfacial polarization emanating from the interface of the two phases. At higher frequencies, the electron hopping does not follow the fast variation of the alternating applied electric field as a consequence the dielectric constant remains constant. The electrical conductivity exhibits that the conduction mechanism is in conformity with electron hopping model. The real part of the initial permeability increases except for x = 20 wt % composites and the peak of Q-factor spreads with the MCZMFO content in the composites. Two semicircular arcs have been observed for x = 80 and 100 wt % (MCZMFO) composites which corresponds to both grain and grain boundary contribution to electrical properties. Electric modulus study reveals the satisfactory polaron hopping and the presence of negligibly small electrode effect contribution. The magnetic properties increases with increase of MCZMFO phase in the composites. The maximum magnetoelectric coupling coefficient is found to be 1.74 V cm−1Oe−1 for x = 20 wt % composites and this value is significantly larger than those reported particulate composite in literature and as well as the close proximity to the theoretical value (2.4 V cm−1Oe−1). This significant large value of magnetoelectric coupling coefficient makes BSCZTO/MCZMFO composites potential candidates for multifunctional devices applications.

At the nano-level modified cotton knitwear prototype development

This article reviews efficiency of the fluorine, silica and zinc compounds containing textile coating conformity with the day-to-day wearing conditions of cotton knitwear used as the first level clothing to the wearer skin. Silica sol modified with the zinc acetate dehydrate was used for the weft knitted cotton single-jersey and double-jersey fabrics chemical modification. The experimental part of the presented research includes the evaluation of the fabrics structure characteristics, air and vapour permeability and water-repellent abilities. The wettability of cotton textiles were evaluated by the water contact angle before and after modification as well after hydrothermal treatment. Images of the obtained modified fibres surfaces analysed by scanning electron microscopy, and fibres surface chemical composition has been determined with dispersive X-ray analysis. Conformity of modified textiles properties important to the wearing comfort and the inserted additional functions determined by testing textiles “in vitro” verified “in vivo” in experimental wearing process where 100 volunteers of different professions had participated.

Control of imipenem resistant-Klebsiella pneumoniae pulmonary infection by oral treatment using a combination of mycosynthesized Ag-nanoparticles and imipenem

Klebsiella pneumoniae (Kp) a common cause of pneumonia leads to intense lung injury and mortality that are correlated with infective exacerbations. A significant increase in the prevalence of imipenem resistant K. pneumoniae (IRKP) has been observed in common human pathogens. The rapid emergence of IRKP has limited the availability of anti-bacterial treatment options. Silver nano-particles (AgNPs) are one of the well-known antibacterial substances showing such multimode antibacterial action. Therefore, AgNPs are suitable candidates for use in combinations with imipenem in order to improve its antibacterial action. Fifteen fungal species were screened for mycosynthesis of silver nanoparticles (AgNPs), only eight fungal species were found to reduce the silver salt into silver nanoparticles which was characterized by UV–visible spectrophotometric analysis, Energy Dispersive Analysis of X-ray (EDX) and transmission electron microscopy. Consistent with characterized silver nanoparticles, mycosynthesized AgNPs by Verticillium albo-atrum (RCMB 039001) was found the higher in concentration (as detected by UV–visible spectrophotometric analysis) and the least in size (as detected by TEM analysis) so, it was chosen for further studies such as in vitro antibacterial activity against Imipenem resistant K. pneumonia (IRKP), MIC, FIC measurements and in vivo study. In this work a strong synergistic antibacterial effect between AgNPs and imipenem was detected in vitro (with FIC Index 0.07) and in vivo against IRKP strain. These results suggested that sliver nanoparticles have an effective antibacterial action on bacterial count, histopathology as well as protective immune response in an IRKP rat model.

Synthesis and Characterization of CeO<sub>2</sub> Doped ZrO<sub>2</sub> Ceramics by a Simple Sol-Gel Route

It is well known that sol-gel technique is a simple method to produce nano sized ceramic powders. In this study, cerium oxide doped zirconia samples, with 10 mol%-12mol% and14mol% CeO2, were synthesized by sol-gel technique and characterized. The surface morphology, elemental composition, microstructure, and phase analysis, of the sintered CeO2 doped ZrO2 ceramics were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDS) analysis, and X-ray diffraction (XRD) respectively. X-ray diffraction for samples sintered at 1550 °C for 4h revealed that the zirconia ceramics have a tetragonal phase structure. The addition of CeO2 can raise the content of the tetragonal phase, but the minor monoclinic phase exists even at the CeO2 content of 10 mol%. The effect of dopant concentration on the lattice parameter, average primary crystallite size and micro-strain was studied. Relative densities for CeO2 doped ZrO2 bulk ceramics varied between 95% and 99 %, depending on the CeO2 addition.

Microscopic Characterization and Analysis of Electrospun TiO<sub>2</sub>-PVP and TiO<sub>2</sub>-PVDF Fibers

Titanium dioxide (TiO2) is a suitable material to be used in the field of photocatalytic water treatment. In this research, TiO2 membrane fibers were synthesized using a combination of non-aqueous sol gel method and electrospinning technique. Titanium isopropoxide (TTIP) was used as the precursor for the TiO2 filler of the fibers. Both polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were used as the polymer base to obtain the respective membrane fibers. The effects of weight concentration of TTIP as well as the type and molecular weight of the polymer on the morphology of the fibers were studied. Microscopic characterization using field-emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray (EDX) analysis was performed to obtain the morphology and elemental composition of the fibers. Sub-micron range fibers with a continuous network were generally obtained. Fibers that are subjected to post-electrospinning calcination have a lower fiber diameter. Polymer decomposition is shown to occur during calcination which yielded higher purity TiO2 fibers. The use of higher molecular weight polymers can produce a stronger fibre network for membranes.

Pd/Ag alloy as an application for hydrogen sensing

A highly sensitive H2 gas sensor was fabricated using a Micro Electromechanical Systems (MEMS) procedure having an embedded micro-heater. The palladium-silver (Pd/Ag having stoichiometric ratios 77:23) thin film was deposited by the RF/DC magnetron sputtering and used as the hydrogen sensing layer designed as a zig-zag pattern. Morphological and structural properties of the Pd/Ag thin film was studied by Field emission scanning electron microscope (FESEM), Atomic force microscopy (AFM) and Energy Dispersive Analysis of X-rays respectively. The working temperature of the micro heater showed a linear relation with variations of the heater voltage. The electro thermal properties of the H2 sensor were studied by finite element method (FEM). The sensing properties of the fabricated H2 sensor as the change of electrical resistance were studied with respect to hydrogen concentration and temperature. Experimental results showed high sensor response and response time after application of the heater voltage. The sensing properties of the alloyed Pd/Ag thin film were more improved than those of pure palladium. The maximum sensor response (Rs) of the fabricated H2 sensor was 14.26% for 1000 ppm H2. The sensor response of the fabricated H2 sensor showed linear behavior with the heater voltage (operating temperature) and positively corresponded with the hydrogen concentration.