Energy Dispersive X-ray Results Research Articles

Promoting Effect of MgO in the Photodegradation of Methylene Blue Over MgO/MWCNT/TiO2 Photocatalyst

For the present paper, we prepared MgO/MWCNT/<TEX>$TiO_2$</TEX> photocatalyst by using multi-walled carbon nanotubes (MWCNTs) pre-oxidized by m-chlorperbenzoic acid (MCPBA) with magnesium acetate tetrahydrate <TEX>$(Mg(CH_2COO)_2\cdot4H_2O)$</TEX> and titanium n-butoxide <TEX>$(Ti\{OC(CH_3)_3\}_4)$</TEX> as magnesium and titanium precursors. The prepared photocatalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The decomposition of methylene blue (MB) solution was determined under irradiation of ultraviolet (UV) light. The XRD results show that the MgO/MWCNT/<TEX>$TiO_2$</TEX> photocatalyst have cubic MgO structure and anatase <TEX>$TiO_2$</TEX> structure. The porous structure and the <TEX>$TiO_2$</TEX> agglomerate coated on the MgO/MWCNT composite can be observed in SEM images. The Mg, O, Ti and C elements can be also observed in MgO/MWCNT/<TEX>$TiO_2$</TEX> photocatalyst from EDX results. The results of photodegradation of MB solution under UV light show that the concentration of MB solution decreased with an increase of UV irradiation time for all of the samples. Also, the MgO/MWCNT/<TEX>$TiO_2$</TEX> photocatalyst has the best photocatalytic activity among these samples. It can be considered that the MgO/MWCNT/<TEX>$TiO_2$</TEX> photocatalyst had a combined effect, the effect of MWCNT, which could absorb UV light to create photoinduced electrons <TEX>$(e^-)$</TEX>, and the electron trapping effect of MgO, which resulted in an increase of the photocatalytic activity of <TEX>$TiO_2$</TEX>.

An assessment of Portland cement, cement kiln dust and Class C fly ash for the immobilization of Zn in contaminated soils

Zn-contaminated soils obtained from a steel company in the Republic of Korea were stabilized using Portland cement (PC), cement kiln dust (CKD) and Class C fly ash (FA). The effectiveness of the treatment was evaluated by the United States Environmental Protection Agency toxicity characteristic leaching procedure (TCLP) and the Universal Treatment Standard (UTS) of 4.3 mg/L. X-ray powder diffraction (XRPD) analyses were performed to investigate the crystalline phases associated with Zn immobilization. Scanning electron microscopy (SEM)–energy dispersive X-ray (EDX) analyses were utilized to support the XRPD results. The treatment results showed that the TCLP-Zn concentrations obtained from the 10 wt% PC and 15 wt% CKD treated samples were less than the UTS, after 7 days curing. However, the FA treatment (up to 30 wt%) was not effective in meeting the UTS even after 28 days curing. All PC–CKD treatment combinations were effective in reducing the TCLP-Zn concentrations below the UTS criteria. Moreover, a 20 wt% dose of a PC-FA treatment combination (75/25 PC-FA) was successful in reducing the TCLP-Zn concentrations below 4.3 mg/L after 1 day. The XRPD results showed that ettringite and Zn6Al2(OH)16CO3·4H2O were the possible phases associated with Zn immobilization upon PC and CKD treatment. The SEM–EDX results confirmed the presence of ettringite, while Zn6Al2(OH)16CO3·4H2O was not identified.

Monitoring bacterial-demineralization of human dentine by electrochemical impedance spectroscopy

The purpose of this study was two-fold: (1) to monitor bacterial biofilm formation and bacteria-induced demineralization of dentine in situ by using electrochemical impedance spectrum (EIS); (2) to examine the relationship between EIS findings and changes in the chemical composition and ultrastructure of dentine during bacteria-induced demineralization. In this study, dentine demineralization was induced by Streptococcusmutans (ATCC 25175) in the presence of sucrose in culture medium and was monitored using two EIS measurement systems (Type A with a working electrode and Type B without a working electrode). Scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were employed to examine the morphology, element contents and crystallinity of hydroxyapatite (HAP) on the dentine surface. Transverse microradiography (TMR) was used to characterize the lesion depth and degree of mineral loss during demineralization. The resistance of the bulk dentine (R(d)) and the apparent resistance of dentine (R(a)) measured from the Type A and Type B EIS systems, respectively, decreased gradually with demineralization. The resistance of the biofilm formed on dentine surface was determined by fitting the EIS data with equivalent circuits. The presence of biofilm slightly increased R(a) of dentine before demineralization. However, the electrochemical behavior of biofilm did not affect the decreasing impedance of dentine with demineralization. The SEM, EDX, XRD and TMR results demonstrated that the surface and bulk dentine gradually became more porous due to the loss of minerals during demineralization, which in turn resulted in the decrease in R(d) and R(a) values obtained from EIS systems. This investigation highlighted EIS as a potential technique to monitor biofilm formation and bacterial-induced demineralization in situ.

Phase-Sequenced Deposition of Calcium Titanate/Hydroxyapatite Films with Controllable Crystallographic Texture onto Ti6Al4V by Triethyl Phosphate-Regulated Hydrothermal Crystallization

The aim of this study was to investigate the use of triethyl phosphate (TEP) to regulate the hydrothermal crystallization of hydroxyapatite (HA) films onto Ti6Al4V substrates. The growth mechanism of the HA film and the development of [0001] HA crystallographic texture were studied. Films were crystallized in a 0.232 m Ca(NO3)2−0.232 m EDTA−0.187 m TEP−1.852 m KOH−H2O chemical system with a final isothermal temperature of 200 °C, and then evaluated at synthesis times from 0 to 46 h by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and X-ray pole figures. Thermodynamic phase stability diagrams were calculated to validate experimental findings. XRD, FESEM, TEM, and EDX results demonstrated the crystallization of a CaTiO3 film below 180 °C and a HA film above 180 °C. FESEM and X-ray pole figure analysis revealed a refinement of the orientation of the (0002) HA crystallographic plane and the c-axis o...

InGaN nanopillars grown on silicon substrate using plasma assisted molecular beamepitaxy

Single crystalline and single phaseInxGa1−xN nanopillars were grown spontaneously on (111) silicon substrate by plasma assistedmolecular beam epitaxy. The surface morphology, structural quality, and optoelectronicproperties of InGaN nanopillars were analyzed using scanning electron microscopy (SEM),energy dispersive x-ray (EDXA) analysis, high resolution x-ray diffraction (HR-XRD), andboth room and low temperature photoluminescence spectra. The EDXA results showedthat these nanopillars were composed of InGaN and the amount of indium incorporation inInxGa1−xN NPs could be controlled by changing the growth temperature. The room temperature andlow temperature PL spectra revealed that the emission wavelength could be tuned from ablue to green luminescent region depending on the growth temperature. Thewavelength tuning was attributed to a higher amount of In incorporation at a lowergrowth temperature which was consistent with the EDXA and HR-XRD results.

Electrodeposition of photoactive 1D gallium selenide quantum dots

One-dimensional (1D) quantum dots of gallium selenide have been obtained by cathodic electrodeposition onto the tin doped indium oxide (ITO) glass substrates from aqueous acidic solutions at room temperature. Characterizations of the as-deposited films by energy dispersive X-ray (EDX) spectroscopy confirm a selenium rich chemistry, X-ray diffraction (XRD) shows that mixture of phases like GaSe/Ga 2Se 3, and optical spectroscopy shows a direct optical band gap of 2.85 eV with intermediate transition energy at 1.9 eV. From transmission electron microscopy (TEM), the films show the one-dimensional quantum dots chains in grains. Scanning electron microscopy (SEM) images indicate dimorphous placement of nanoparticles. The elementals surface analysis of the core-shell nanoparticles determined by X-ray photoelectron spectroscopy (XPS) supported the EDX results and confirmed the chemical nature of the material. The photoelectrochemical (PEC) studies of gallium selenide films were carried out and the nanocrystalline gallium selenide films were found to be photoactive in aqueous sodium thiosulphate solution.

Cracks in a powder vibrating sieve disc

A case study of cracks in a powder vibrating sieve disc is presented in this paper. An evaluation of the failed disc was undertaken to assess its integrity that included a visual examination, photo documentation, chemical analysis, micro-hardness measurement, tensile testing, and metallographic examination. The fracture surfaces were examined with the help of a scanning electron microscope equipped with energy-dispersive X-ray (EDX) facility. In addition, the deposits scraped from the inner surface of the bolt holes were subjected to X-ray diffraction. Spectrum analysis and EDX results identified the material of the disc as zinc-coated (galvanized) silicon-killed structural steel. Results indicate that cracks initiated from bolt holes in the disc and propagated in a peripheral direction and a radial direction with different lengths. The cracks are fretting fatigue cracks from high vibration stress. The reason why cracks initiated at holes is that there were fretting wear scars the inner surface of the bolt holes.

Characterization and performance of nanocrystalline materials for thin film electronic and photovoltaic applications

Nanocrystalline materials are quite promising in the fabrication of photovoltaic devices because of their advantages over conventional polycrystalline and amorphous materials. Also, nanocrystalline materials have great potential for technological applications. This paper discusses how nanocrystalline semiconductors were characterized structurally using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Further investigations of the deposited layers included the elemental analysis using Energy-Dispersive X-Ray (EDXR). The results obtained revealed that the nc-Si is polycrystalline in nature with the grain size of ≤100 nm. The elemental analysis reveal that the indium tin oxide consists of Sn 35 wt%, Si 15.54 wt%, In 11.84 wt% and Al 11.74 wt%. The XRD results are found to be consistent with EDXR results. The photovoltaic application of the deposited layer is discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A fluxless fabrication process producing Sn-rich Bi–Sn joints with high melting temperature

Abstract A fluxless bonding process to produce tin-rich bismuth–tin solder joints is presented. The process was designed using Sn–Bi multilayer structure deposited in high vacuum to inhibit oxidation and to achieve the fluxless feature. The composition was chosen to be tin-rich, 95.0 wt.% Sn and 5.0 wt.% Bi, to achieve a solidus temperature significantly higher the 139 °C eutectic temperature of the 57Bi–43Sn eutectuic alloy. The resulting joints were imaged with a scanning acoustic microscope (SAM) and shown to be nearly void-free. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were used to study the microstructure and compositions of the joints. The measured joint thickness was 4.1 μm. SAM and EDX results indicate that the solder joint consists of (β-Sn) matrix embedded with small grains of (Bi) solid solution phase. The melting temperature of the joint was measured to be 210–215 °C, as expected from the designed composition. The fluxless feature of this process gives the packaging community another process to consider for use in devices and packages where the use of flux is prohibited, such as some biomedical, MEMs, fiber optical and photonic devices.

Cerium Chemical Conversion Coating for Aluminum Alloy 2024-T3 and Its Corrosion Resistance

Abstract New golden, yellow-colored cerium chemical conversion coatings on aluminum alloy 2024-T3 (AA2024-T3 [UNS A92024]) surface at room temperature were obtained by immersing the alloy into a cerium solution containing zinc chloride (ZnCl2) and hydrogen peroxide (H2O2). Electrochemical methods and immersion tests were used to study the dynamics of the coatings formation and their corrosion resistance in 3.5% sodium chloride (NaCl) solution. The morphologies of the coatings were recorded by scanning electronic microscopy (SEM). Energy-dispersive x-ray (EDX) analysis and x-ray photoelectron spectroscopy (XPS) were used to analyze the chemical composition and the oxidation state of the elements in the coatings. Polarization experiments and immersion tests in 3.5% NaCl solution showed that the sensitivity to pitting corrosion for the conversion-coated AA2024-T3 was greatly lower than that of the untreated specimens, and the corrosion resistance improved markedly. SEM photographs showed that the coatings consisted of a lot of spherical particles. EDX and XPS experimental results showed that the coatings were made up of oxygen, cerium, and aluminum, and the spherical particles contained higher contents of cerium and oxygen than the other sites. Cerium was mainly in the form of Ce4+. The mechanisms of conversion coatings formation and improvement on corrosion resistance also are discussed.

Initial stages of microbiologically influenced tarnishing on titanium after 20 months of immersion in freshwater.

This paper studies the initial stages of iridescent tarnishes on titanium heat exchanger tubes in contact with running freshwater on the river Tagus in Spain for up to 20 months. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy [(SEM with energy dispersive X-ray (EDX)] and X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering were the techniques used. The EIS data indicated a capacitive behavior, showing a semicircle that was better defined as the experimental time increased, indicating a decreasing tarnishing resistance of titanium. XPS and EDX results indicated that the main elements identified were calcium, phosphorus, nitrogen, and iron. The amount of these elements was higher on the tarnished titanium specimens than on the untarnished specimens. SEM analysis showed the presence of diatoms in the iridescent tarnishes on titanium tubes.

X-ray-based measurement of composition during electron beam melting of AISI 316 stainless steel: Part II. Evaporative processes and simulation

An energy dispersive X-ray (EDX) detector mounted on a laboratory scale electron beam furnace (30 kW) was employed to assess the potential use of X-rays as a means of on-line composition monitoring during electron beam (E B) melting of alloys. The design and construction of the collimation and protection systems used for the EDX are described in Part I. In Part II, a mathematical simulation of the heat, mass, and momentum transfer was performed for comparison to the EDX and vapor deposition results. The predicted flow patterns and evaporation rates are used to explain the differences between the two experimental methods. For the EDX spectra measured, the X-rays generated were from the center of the hearth where fluid flow rising from the bulk of the pool is sufficient to maintain the bulk composition despite the high evaporative flux from the surface. The flow moves radially outward from the center of the pool, with the volatile species being depleted. The vapor deposition technique measures the entire region, giving an average surface composition, and it therefore differs from the EDX results, which gave a near bulk composition. This combined study using in-situ EDX measurements and numerical simulations both provided an insight into the phenomena controlling the evaporation in an EB-heated system and demonstrated the viability of using EDX to measure the bulk composition during EB melting processes.

Fluxless InSn bonding process at 140 °C

Device packages usually need more than one soldering operation to complete. For photonic and fiber optic device packaging, indium solder is often used due to its ductility. Since indium has a relatively low melting temperature of 156.6 °C, the subsequent bonding operation requires a process temperature that is lower than 156 °C . In this paper, we report a new bonding process at 140 °C based on an indium–tin multilayer composite. This is a fluxless bonding technique. In fabrication, a chromiurn–tin–indium–gold multilayer composite is deposited on silicon die in one high vacuum cycle to prevent oxidation. Immediately upon deposition, gold and indium react to form a stable AuIn 2 protective outer layer against oxidation. Silicon substrates are deposited with thin chromium–gold layers. The silicon die and substrate are bonded in a hydrogen environment at 140 °C. Scanning acoustic microscopy (SAM) analysis is used to evaluate the joint quality. This bonding technique consistently achieves uniform and void-free joints. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analyses also are performed on the joint cross sections. The SEM image shows a uniform joint thickness of 5 μm and the joint microstructure. SEM and EDX results indicate the joint consists of In–Sn alloy with embedded AuIn 2 grains. The re-melting temperature of the joint is found to be 125–150 °C, which shows that the joint composition is not exactly eutectic that has a melting temperature of 118 °C, but rather is Sn-rich. The success of this design illustrates the solid-state interdiffusion between Sn and In to form a thin layer of Sn–In eutectic alloy. The fluxless feature of this technology is valuable for bonding and assembling many emerging photonic devices that simply cannot tolerate fluxes.

IDENTIFICATION OF COMPOUNDS PRESENT IN SINGLE SUPERPHOSPHATES PRODUCED FROM BRAZILIAN PHOSPHATE ROCKS USING SEM, EDX, AND X-RAY TECHNIQUES

Scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray techniques were used to obtain data about the mineralogical composition of single superphosphates (SSP) produced from apatite concentrates originating from Araxa, Jacupiranga, Catalao, and Tapira igneous phosphate rock deposits. The SSP samples were investigated both in their original form and after leaching with water to remove water-soluble compounds. Results of chemical analysis and instrumental techniques showed that P compounds were still present in the water-leached material. Anhydrite (CaSO 4 with no hydration water) was the main Ca-S component in the SSP samples. Monocalcium phosphate monohydrate [Ca(H 2 PO 4 ) 2 .H 2 O] was identified in the original but not in the water-leached samples. Results of SEM, EDX, and X-ray confirmed the presence of crystals of triiron (III) potassium octahydrogen hexaphosphate hexahydrate [Fe 3 KH 8 (PO 4 ) 6 .6H 2 O] in the SSP. The results of SEM and EDX analyses suggested that the compounds triiron (III) nonahydrogen hexaphosphate hexahydrate [Fe 3 H 9 (PO 4 ) 6 .6H 2 O], triiron (III) 15-hydrogen octaphosphate tetrahydrate [Fe 3 H 15 (PO 4 ) 8 .4H 2 O], triiron (III) potassium 14-hydrogen octaphosphate tetrahydrate [Fe 3 KH 14 (PO 4 ) 8 .4H 2 O], and barium sulfate (BaSO 4 ) were present in some of the SSP samples. Use of SEM, EDX, and X-ray techniques was shown to be adequate for precise characterization of compounds present in the SSP studied, which will help to understand further the plant availability of the phosphorus contained (especially) in the water-insoluble P fraction of this fertilizer.

What X-Ray Microanalysis Can Tell Us About The Regulation of Intracellular Calcium

Many cell functions, including such critical processes as secretion, neuronal communication, muscle contraction, and even gene expression, are regulated by spatial and temporal changes in the intracellular concentration of Ca2+ ions. The high spatial resolution and analytical sensitivity of energy dispersive x-ray (EDX) microanalysis are ideally suited to characterizing biologically relevant changes in total concentration of cellular Ca. However, EDX results have not yet had a wide impact in the field of Ca regulation, with most laboratories preferring to focus on optically measured changes in free Ca concentrations as the important determinant of biological activity. This paper advocates a more positive perspective for the role of EDX microanalysis in studies of Ca regulation.It is well known that the large majority of cellular Ca is in the bound form, with typical bound/free ratios on the order of l03-104 5. However, the most dramatic changes during Ca2+ -dependent cell activation occur as transients in the free Ca2+ pool.

SEM/EDX studies of the influence of a cobalt adhesion promoter on the interface between rubber skim compounds and tire steel cord

The failed interfaces between natural rubber skim compounds and tire steel cord used as tire cord adhesion test (TCAT) specimens have been studied by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis in order to understand the influence of cobalt boroacylate in the rubber compound as an adhesion promoter. SEM studies indicated a mixture of cohesive failure in the rubber and interfacial failure between the rubber and the brass coating. Cobalt boroacylate leads to more cohesive failure of the rubber (about 88% of the cord area covered by the rubber compared with 73% by the control), due to its degradative effects on rubber. EDX analysis of the failed cord and rubber surfaces at various points gave the concentrations of copper, zinc, cobalt, iron, silicon, sulfur, oxygen, and carbon. Assuming van Ooij's model of interfacial sulfide film formation over the brass (Cu/Zn) layer and analyzing the EDX results, it is clear that the failure occurs at the Cu/Zn and CuxS/ZnS sub-layers.

A study of anomalously coloured regions in ZnSe grown by molecular beam epitaxy

Abstract A low-temperature (4–2 K) photoluminescence (PL) analysis combined with transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) microanalysis study was conducted on samples of ZnSe which were grown at very low growth rates on GaAs (100) substrates by molecular beam epitaxy and exhibited unusual surface colouring effects. PL measurements from bluish-coloured areas showed that the material was optically ‘dead’. However, reddish-coloured areas, which were found to exist in close proximity to the blue areas, exhibited strong dominant free-exciton-related emission centred at 2-8007 eV. This study revealed that the differently coloured regions of ZnSe epilayer surfaces and the drastically different PL which results from these areas were associated with particles formed at the free surface of the epilayer. A correlation between the PL, TEM and EDX results was established. The crystallographic structure of the particles was different from that of the host ZnSe film, and they were enriche...