Energy Dispersive X-ray Diffraction Method Research Articles

Suppression effects of dental glass-ceramics with polarization-induced highly dense surface charges against bacterial adhesion

This study investigated the surface characteristics and antibacterial ability capacity of surface-improved dental glass-ceramics by an electrical polarization process. Commercially available dental glass-ceramic materials were electrically polarized to induce surface charges in a direct current field by heating. The surface morphology, chemical composition, crystal structure, and surface free energy (SFE) were evaluated using scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and water droplet methods, respectively. The antibacterial capacity was assessed by a bacterial adhesion test using Streptococcus mutans. Although the surface morphology, chemical composition, and crystal structure were not affected by electrical polarization, the polar component and total SFE were enhanced. After 24 h incubation at 37ºC, bacterial adhesion to the polarized samples was inhibited. The electrical polarization method may confer antibacterial properties on prosthetic devices, such as porcelain fused to metal crowns or all ceramic restorations, without any additional bactericidal agents.

The pressure effect on crystal structure of complex ferroelectrics Ba4Sm2Fe2Nb8O30 and Ba4Gd2Fe2Nb8O30

Abstract The crystal structure of complex oxide ferroelectrics Ba4Sm2Fe2Nb8O30 and Ba4Gd2Fe2Nb8O30 have been studied by means of energy-dispersive X-ray diffraction method at high pressure up to 4 GPa at room temperature. At ambient pressure, the crystal structure of both compounds is described by the tetragonal symmetry with space group P4/mbm. At pressure P∼1.8 GPa in Ba4Sm2Fe2Nb8O30 and at P∼2.2 GPa in Ba4Gd2Fe2Nb8O30 the structure phase transition have been observed. The orthorhombic structure model with Pba2 space group for high-pressure phase of those compounds have been proposed. The baric dependences of lattice parameters and unit cell volumes of Ba4Sm2Fe2Nb8O30 and Ba4Gd2Fe2Nb8O30 compounds have been obtained.

Influence of Spark Plasma Sintering (SPS) Modes on Structure of Multilayer Metal - Intermetallic Composites Based on Nickel and Aluminum

Structural features of laminated “nickel - nickel aluminide” composite materials obtained by SPS - sintering of alternately stacked nickel and aluminum foil, thickness 100 and 25 m respectively, have been investigated in this paper. The composition of diffusion layers formed due to the reaction between nickel and aluminum was studied using energy dispersive X-ray microanalysis and X-ray diffraction methods. It was found that phase composition of diffusion layers significantly depends on SPS - sintering temperature.

Electrochemical behavior of uranyl in ionic liquid 1-butyl-3-methylimidazolium chloride mixture with water

Electrochemical behaviors of U(VI) in 1-butyl-3-methylimidazolium chloride (C4MimCl) with various water contents investigated by chronopotentiometry and cyclic voltammetry. The electrochemical reduction of U(VI) was identified to follow two processes: a lower valence intermediate U(V) was initially formed at the potential of ca. −0.2 V(vs. Ag wire). Then, further deposition of UO2 was followed at around −0.8 V. Little amount of water (1–4 wt%) in C4MimCl, however, has an effect on the U(VI) reduction by changing the current density of the redox reaction and the diffusion coefficient of U(VI) in C4MimCl. The deposited product by potentiostatic electrolysis on the surface of stainless steel electrode was characterized by the scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) methods. Although the electrodeposited black film was amorphous, the electrochemical reduced product of U(VI) can be still confirmed to be UO2 by XRD after the crystallization of the amorphous deposits at 1,073 K in nitrogen atmosphere.

The corrosion and wear behavior of TiN and TiAlN coated AISI 316 L stainless steel

In this study, TiN and TiAlN coatings were deposited on AISI 316 L stainless steel substrates by PVD techniques. The composition and crystalline structure of the as-deposited coatings were analyzed by energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) methods, respectively. The corrosion resistance studies of TiN-coated and TiAlN-coated samples were carried out in 0.9 wt % NaCl and SBF solutions using the electrochemical potentiodynamic polarization method and the wear behavior was evaluated with the ball-on-disk wear method at a sliding speed rate of 0.3 m/s under 2.5 N load in a dry medium. It was found that both TiN and TiAlN coatings exhibited relatively good corrosion resistance, however, TiAlN coatings showed a better corrosion resistance than TiN coatings. The TiAlN coating contributes positively against corrosion and wear behavior by increasing the surface hardness and by decreasing the friction coefficient of AISI 316 L stainless steel, respectively.

Microstructure and Properties of 6061 Aluminum Alloy Superficially Modified by Electron Beam Alloying with 1Cr13 Stainless Steel

1Cr13 stainless steel was pre-coated on the surface of 6061 aluminum for electron beam alloying, then the microstructure and properties of the modified layer was discussed and analyzed. Using Scanning electron microscopy (SEM), EDAX energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and other analytical testing methods to analyze the microstructure and phase composition of the modified layer; Using the HX-1000TM automatic turret micro-hardness tester and HSR-2M high-speed reciprocating friction and wear tester to respectively measure its hardness and wear, finally to analyze the modification effect. The results showed that: between the alloyed layer and the substrate obtains a good metallurgical bonding; the modified layer organization composes mainly of martensite and Al-Fe compounds, and has fine grain; the hardness of the strengthening layer is about 4 times that of the substrate, and its wear resistance is a quarter of the matrixs.

Crystallisation Kinetics of Metal Organic Frameworks From in situ Time-Resolved X-ray Diffraction

A time-resolved powder diffraction study of the crystallisation of porous metal organic framework materials with the CPO-27 structure ([M2(dhtp)(H2O)2]·8H2O where, dhtp=2,5-dioxoterephthalate) using the energy dispersive X-ray diffraction method is described. Crystallisation under solvothermal conditions is performed between 70 - 110 °C from clear solutions of metal salts (M=Co2+ or Ni2+) and 2,5-dihydroxyterephthalic acid in a mixture of THF-water in sealed reaction vessels, using both conventional and microwave heating. Integration of Bragg peak areas with time provides accurate crystallisation curves, which are modelled using the method of Gualtieri to determine rate constants for nucleation and for growth and then, by Arrhenius analysis, activation energies. Crystallisation is determined to be one-dimensional, consistent with the elongated morphology of the crystals produced in these reactions. With conventional heating the Co-containing CPO-27 crystallises more rapidly than the isostructural Ni-containing analogue and analysis of the kinetic parameters would suggest a complex multi-step crystallisation process. The effect of microwave heating is upon activation energies: the values for both nucleation and for crystal growth are lowered compared to reactions using conventional heating.

A deconvolution approach for the enhancement of spatial resolution in energy dispersive x-ray diffraction and related imaging methods

A reconstruction approach is presented, allowing the improvement of spatial resolution of images obtained by sequential pixel scanning techniques. Based on a series of measurements taken under different object positions, the signal contributions from individual voxels of significantly reduced size are calculated. Mathematically, the type of reconstruction used can be regarded as a deconvolution or solving an inverse problem. Due to the specific shape of the convolution kernel in the x-ray diffraction example treated here the problem turns out to be ill-posed, and thus its solution using measured (noisy) data requires the application of a suitable regularization method. Detailed studies on this issue led to the development of a novel iterative algorithm, combining several deconvolution runs with preceding and intermediate image processing steps. The Tikhonov method was used for regularization. Depending on the object under investigation, the original Euclidean norm (least-squares fit) was advantageously replaced by the 1-norm (least absolute deviation, LAD problem). The method presented here was developed to overcome resolution limitations in spatially resolved x-ray diffraction measurements on extended objects as used, e.g., for material analysis or the detection of illicit substances in baggage inspection applications. Nevertheless, the technique may easily be utilized for resolution enhancement within other imaging modalities, provided the task can be written as a deconvolution problem and the corresponding convolution kernel is known. According to the features of our experimental setup the developed reconstruction algorithm is explained for energy dispersive x-ray diffraction with pencil beam irradiation as an example application. The spatial resolution enhancement is demonstrated, using simulated and measured data sets corresponding to objects of different material composition.

A method to obtain homogeneously dispersed carbon nanotubes in Al powders for preparing Al/CNTs nanocomposite

Recently carbon nanotubes (CNTs)-reinforced metal matrix composites (MMCs) have attracted increasing attention due to their promising properties. Most research on metallic matrix–CNTs composites (MMCs–CNTs) show that uniform dispersion of CNTs has been by far the most significant challenge in the field of CNTs-reinforced composites. In this research we will present an approach to obtain homogeneously dispersed CNTs in Al powders for preparing Al/CNTs nanocomposite. A novel polyester binder-assisted (PBA) mixing method was used for achieving uniform dispersion of CNTs, and power metallurgy (PM) technique was used for preparing Al/CNTs nanocomposite. The distribution quality of CNTs in Al matrix nanocomposites was also qualified based on image analysis technique. The morphologies, structures and mechanical properties of the Al/CNTs nanocomposite were also investigated in detail by scanning electron microscopy (SEM), energy dispersive x-ray (EDX) spectroscopy, x-ray diffraction (XRD) and mechanical measurement methods. Experimental results show that this method not only achieves good dispersion but it also avoids the damage on structure of CNTs by conventional mixing methods.

<i>In Situ</i> Time-Resolved Energy Dispersive X-Ray Diffraction Studies of Calcium Phosphate Based Bone Cements

In situ monitoring of structural changes, taking place upon calcium phosphate bone cements hardening process was carried out by means of the Energy Dispersive X-Ray Diffraction method. Two different cement systems were studied, one of them based on the octacalcium phosphate and another - on the dicalcium phosphate dehydrate. Both systems contained natural biopolymer chitosan and were soaked in Simulated Body Fluid. The obtained experimental results evidence that during the hardening of the cement containing octacalcium phosphate its partial transformation into hydroxyapatite takes place, whereas no significant changes were detected during the hardening process of cement containing the dicalcium phosphate dehydrate.

Role of biomineralization on the degradation of fine grained AZ31 magnesium alloy processed by groove pressing

Groove pressing (GP) has been successfully adopted to achieve fine grain size up to 7μm in AZ31 magnesium alloy with an initial grain size of 55μm. The effect of microstructural evolution and surface features on wettability, corrosion resistance, bioactivity and cell adhesion were investigated with an emphasis to study the influence of deposited phases when the samples were immersed in simulated body fluid (SBF 5×). The role of microstructure was also evaluated without any surface treatments or coatings on the material. GPed samples exhibit improved hydrophilicity compared to the annealed sample. After immersion in SBF, specimens were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) analysis and X-ray diffraction (XRD) methods. More amount of white precipitates composed of hydroxyapatite and magnesium phosphate along with magnesium hydroxide was observed on the surfaces of groove pressed specimens as compared to the annealed specimens with an increase in immersion time in SBF. Corrosion behavior of the samples estimated using potentiodynamic polarization curves indicate good corrosion resistance for GPed samples before and after immersion in SBF. The MTT assay using rat skeletal muscle (L6) cells revealed that both the processed and unprocessed samples are nontoxic and cell adhesion was promising for GPed sample.

Non-enzymatic acetylcholine sensor based on Ni–Al layered double hydroxides/ordered mesoporous carbon

In this work, a novel non-enzymatic acetylcholine (ACh) sensor was constructed based on electrodepoition of Ni–Al layered double hydroxides (Ni–Al LDHs) on ordered mesoporous carbon (OMC) modified glassy carbon (GC) electrode. The obtained Ni–Al LDHs/OMC nanocomposite was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and electrochemical methods. A novel non-enzymatic acetylcholine (ACh) sensor based on Ni–Al LDHs/OMC was developed. Compared with the pristine OMC and Ni–Al LDHs modified electrodes, Ni–Al LDHs/OMC displayed higher electrocatalytic activity toward ACh and gave a wide concentration interval of 2–4922μM and a low limit of detection (42nM, R=0.999), which is better than some reports in the literatures. The sensor also exhibited long-term stability and remarkable antifouling property. The excellent electrocatalysis for ACh can be attributed to the combination of the unique properties of Ni–Al LDHs nanoparticles and the ordered mesostructure of OMCs matrix.

Pt-Ni Nanoparticles for Oxygen Reduction Prepared by a Sonochemical Method

Sonochemistry was applied to prepare Pt-Ni electrocatalyst materials. To promote uniform alloying, a route based on sonication of precursor metal salts in non-aqueous solution containing a strong reducing agent was used as an alternative to sonication in aqueous solution. Metal nanoparticles consistent with the Pt3Ni stoichiometry were formed by sonication of a reaction mixture that contained a 3:1 mole ratio of Pt4+ and Ni2+ ions in tetrahydrofuran (THF). After isolation, the metal nanoparticles were characterized with the use of transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction and voltammetry methods. The structural and electrochemical studies indicate the sample consisted mainly of particles in the 2 nm–5 nm size range with characteristics of a uniform Pt3Ni alloy. Following activation by potential cycling (20 cycles between 0.05 V and 1.2 V versus a reversible hydrogen electrode at 100 mV/s) to form a Pt-rich surface layer, the sonochemically prepared Pt-Ni nanoparticles showed a three-fold enhancement in O2 reduction kinetics compared with a commercial Pt catalyst.

Simultaneous Removal of SO2 and NO from Flue Gas Using Multicomposite Active Absorbent

A multicomposite active absorbent was prepared using the liquid-phase complex of NaClO2 and NaClO as well as solid-phase slake lime to simultaneous desulfurization and denitrification at a flue gas circulating fluidized bed (CFB). The effects of influencing factors on the removal efficiencies of SO2 and NO were investigated. Removal efficiencies of 96.5% for SO2 and 73.5% for NO were obtained, respectively, under the optimal experimental conditions. The characterization of the spent absorbent was carried out by using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and chemical analysis methods, from which the simultaneous removal mechanism of SO2 and NO based on this absorbent was proposed.

Activated Carbon Fiber Supported PtRu Hollow Nanospheres and PtRu Nanoparticles for Methanol Electrooxidation

Activated carbon Fiber supported PtRu hollow nanospheres have been prepared by a replacement reation in a homogeneous solution with cobalt nanoparticles as sacrificial templates. The morphology, elemental composition, structure and electrocatalytic properties of the PtRu hollow nanospheres have been investigated by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and typical electrochemical methods, respectively. The results indicate that the ACF supported PtRu hollow nanospheres show a high activity and stability for electrocatalytic oxidation of methanol as compared to co-reduced solid PtRu nanoparticles. The reasons of the high electrocatalytic activity due to the high surface area resulted from the hollow nanosphere structure with porous shell.

Corrosion issues related to disposal of 316 SS–zirconium metal waste form under simulated repository conditions

Metal waste form (MWF) alloy of D9 stainless steel with 8·5 wt-% zirconium was cast and evaluated for the corrosion behaviour. The microstructure, phase analysis, corrosion resistance and passive film properties of the alloy were evaluated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and electrochemical methods. The corrosion performance of MWF alloy was carried out in demineralised (DM) water at pH 1, 5 and 8 and also in simulated Kalpakkam and Rajasthan ground water systems. In X-ray diffraction analysis, the identified phases are mostly iron based solid solutions of γ-austenite, Zr–Fe type and Ni–Zr type intermetallics. The typical microstructure of MWF alloy showed the presence of solid solution and the intermetallics. The anodic polarisation results of MWF alloy in Rajasthan ground water and in DM water at pH 5 and 8 showed higher breakdown potential compared with DM water at pH 1 and in Kalpakkam ground water. The electrochemical impedance spectroscopic results of MWF alloy in different media showed the influence of ground water media. The surface morphology after passivation and polarisation revealed the possibility of different types of deposition and dissolution. The corrosion behaviour of MWF alloy in different simulated media and its relation to microstructure and surface morphology are discussed based on the results obtained in relevance with geological repository conditions.

Symmetry breaking and electrical conductivity of La 0.7Sr 0.3Cr 0.4Mn 0.6O 3− δ perovskite as SOFC anode material

This work is focused on nanocrystalline solid oxide fuel cell synthesis and characterization (SOFC) anodes of La 0.7Sr 0.3Cr 0.4Mn 0.6O 3− δ (perovskite-type) with Nickel. Perovskite-type oxide chemical reactivity, nucleation kinetics and phase composition related with La 0.7Sr 0.3Cr 0.4Mn 0.6O 3− δ –NiO to La 0.7Sr 0.3Cr 0.4Mn 0.6O 3− δ –Ni transformation have been analyzed. SOFC anode powders were obtained by sol–gel synthesis, using polyvinyl alcohol as an organic precursor to get a porous cermet electrode after sintering at 1365 °C and oxide reduction by hydrogen at 800 °C/1050 °C for 8 h in a horizontal tubular reactor furnace under 10% H 2/N 2 atmosphere. Composite powders were compressed into 10-mm diameter discs with 25–75 wt% Ni. Electrical and structural characterization by four-point probe method for conductivity, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Rietveld method were carried out. Symmetry-breaking by phase transition from high temperature aristotype R 3 ¯ c to hettotype I4/ mmm has been identified and confirmed by XRD and Rietveld method which can be produced by introducing Ni 2+ cations in the perovskite solid solution. Rietveld analysis suggests that Ni contents are directly proportional to La 0.7Sr 0.3Cr 0.4Mn 0.6NiO 3.95 tetragonal structure cell volume and inversely proportional to Ni cubic structure cell volume after reduction at 1050 °C. Kinetic analysis indicated that the Johnson–Mehl–Avrami equation is able to provide a good fit to phase transformation kinetics. The variation of electrical conductivity reveals the presence of two types of behavior in samples reduced at 1050 °C. First, at low Ni concentration (25%), ρ resistivity decreases when increasing the temperature; then, for Ni concentration higher than 25% ρ resistivity increases.

High-pressure structural transformation ofSiO2glass up to 100 GPa

We have conducted structure measurements of ${\text{SiO}}_{2}$ glass under high pressure up to 100 GPa by an energy-dispersive x-ray diffraction method with synchrotron white x rays. X-ray diffraction data indicate that ${\text{SiO}}_{2}$ glass transforms from a fourfold- to a sixfold-coordinated structure at pressures between 20 and 35 GPa, and then behaves as an amorphous polymorph having a sixfold-coordinated structure at least up to 100 GPa. These results are consistent with those of density measurements by an x-ray absorption method with monochromatic x rays, except for the slight difference in the pressure range where the transformation from a fourfold- to a sixfold-coordinated structure is completed. They are also mostly consistent with those of structure measurements by an x-ray diffraction method with monochromatic x rays but some aspects are quantitatively different. It is presumed that the irradiation of white x rays may have relaxed the structure and deviatoric stresses of ${\text{SiO}}_{2}$ glass in this study.

Synthesis of cobalt nanoparticles to enhance magnetic permeability of metal–polymer composites

Metallic cobalt nanoparticles were synthesized by hydrogen reduction method. Particles were coated in situ with carbon by adding ethene to reaction flow. Particles were characterized by transmission electron microscopy, energy dispersive X-ray emission, X-ray diffraction, X-ray fluorescence and BET method. The observed cobalt particle size distributions in different cobalt batches produced with unvarying reaction parameters was reproducible: The mean diameter of primary cobalt particle varied only 5% from the mean value of 76 nm in different batches. Increased carbon precursor concentration decreased mean diameter of cobalt particles to 17 nm. The produced nanoparticles were used as filler material in 0–3 type metal –polymer composites. Composite samples with varying filler loading were fabricated with mixing extrusion and injection moulding techniques. The magnetic properties of the fabricated composites were measured up to 1 GHz. In order to analyse the particle distribution in composite matrix and its effect on magnetic properties the microstructure was studied.

High-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell by an x-ray diffraction method

We have developed techniques for high-pressure in situ structure measurement of low-Z noncrystalline materials with a diamond-anvil cell (DAC) by an x-ray diffraction method. Since the interaction between low-Z materials and x rays is small and the sample thickness in a DAC is also small, the incoherent scattering from the anvils overwhelms the coherent scattering from the sample at a high-Q range. By using a cubic boron nitride gasket to increase the sample thickness and the energy-dispersive x-ray diffraction method with a slit system to narrow the region from which detected x rays are scattered, we can reduce unfavorable effects of the incoherent scattering from the anvils and correct them accurately. We have successfully measured the structure factor of SiO(2) glass in a DAC over a relatively wide range of Q under high pressure.