Energy Dispersive Diffraction Research Articles

Comparative performance of anaerobic attached biofilm and granular sludge reactors for the treatment of model mine drainage wastewater containing selenate, sulfate and nickel

Acid mine drainage and mining wastewaters contain, depending on the source, elevated concentrations of metals, e.g. nickel (Ni2+), and oxyanions, e.g. selenate (SeO42−) and sulfate (SO42−). This study compared the performance of two reactor configurations, a biotrickling filter (BTF) and an upflow anaerobic sludge blanket (UASB) reactor, for the treatment of model mining wastewater contaminated with SeO42−, SO42− and Ni2+. The Se removal efficiency of the BTF biofilm was improved by >70% in the presence of SO42−. In contrast, the Se removal performance of the UASB reactor was not affected by the presence of SO42−. The addition of Ni2+ decreased the oxyanion (SO42− and SeO42−) removal efficiency of both the BTF and UASB reactor by >30%. However, the UASB reactor recovered more quickly (∼10 days after Ni2+ addition) from Ni2+ toxicity as compared to the BTF (∼22 days after Ni2+ addition). A Ni2+ removal efficiency of more than 80% was achieved for both the BTF and UASB reactor. Ni2+ was mainly removed via sulfidic (HS−) precipitation by forming nickel sulfide (Ni3S4). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and powder X-ray energy diffraction (P-XRD) revealed entrapped Se and selenium monosulfide (SeS) in the biofilm and granules of both reactor configurations, which could be potentially recovered for further reuse applications. This study demonstrated that the feed wastewater characteristics and the reactor configuration are key factors in achieving an efficient treatment of Se-laden mine drainage wastewater.

Isothermal Section of Er-Ag-Sn System at 873 K

The isothermal section of the Er-Ag-Sn system at 873 K was constructed with the use of scanning electron microscopy, energy-dispersive x-ray microanalysis and x-ray powder diffraction. Two ternary compounds were confirmed at this temperature: ErAgSn (LiGaGe structure type, P63mc, Z = 2, a = 4.6595(2) A, c = 7.2872(3) A) and non-stoichiometric phase ErAg1−xSn2+x (Cu3Au structure type, Pm-3m, Z = 1). For the last one homogeneity range was established (0.08 < x < 0.24) and lattice parameters were determined (a = 4.5007(4), 4.5040(2), 4.5107(1), 4.5412(1) A for the compositions Er25.4Ag23.4Sn51.2, Er25.7Ag23.0Sn51.3, Er25.7Ag21.7Sn52.6, Er25.2Ag18.6Sn56.2 (at.%) respectively). Melting point of the phase Er25.7Ag21.7Sn52.6 (at.%) was determined to be 1199 K by differential thermal analysis.

Corrosion Behavior of W-Mo Co-Penetrated Layer Produced by Glow Discharge Plasma Technique in Acid Solution

Abstract To improve the corrosion resistance of Ti6Al4V alloys in acid solution, a W-Mo co-penetrated top layer was prepared by hollow-cathode glow discharge plasma technique below the β phase transition point. The surface morphology, chemical composition and crystal structure of the coatings were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray power diffraction (XRD), respectively. Results indicate that a dense co-penetrated layer is produced with maximum thickness of approximately 23 μm. The layer is composed of AlMoTi2 and TixW1-x phases. The static corrosion test is conducted in acid (H2SO4 and HCl, separately) at room temperature (RT) by the electrochemical workstation. The results show that the W-Mo co-penetrated layer could achieve relatively stable corrosion potential in reducing acid and the Icorr of co-penetrated layers occupy merely 1/10 and 1/6 of that of Ti6Al4V substrates. In addition, there is barely any corroded product and crack on the corroded surface of co-penetrated layers, indicating no corroded shedding phenomenon occurs. So the corrosion resistance are obviously improved in the premise of keeping the basic properties of the substrate.

Mo segregation and distribution in Ti–Mo alloy investigated using nanoindentation

A titanium alloy with 12 mass% molybdenum was produced using the cold crucible levitation melting technique. By varying the process parameters, microstructures with and without Mo segregation could be obtained. The effects of Mo segregation and ω-phase precipitation on the mechanical properties of the β-type Ti-12 mass% Mo alloy were investigated through nanoindentation measurements. The homogeneous precipitation of an isothermal ω-phase occurred in the samples without Mo segregation, while denser ω-precipitates were detected in the Mo-lean regions of the heterogeneous microstructure. Microstructural examination of ingots was done by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD). The obtained results revealed the presence of bright and dark stripes in the heterogeneous microstructure; these corresponded to the Mo-rich and Mo-lean regions, respectively. A comprehensive analysis of Mo heterogeneity in the Ti-12Mo alloy suggested that Mo segregation had a significant effect on the mechanical properties as well as the distribution of the ω-phase within the grains. The regions with higher Mo contents (and lower amounts of the ω-precipitates) exhibited the lowest hardness and elastic modulus values. Similarly, the indentation marks made within the β-grains oriented almost along the <001> direction were characterised by lower elastic modulus values and in most cases, were followed by the formation of higher pile-ups (as compared to those corresponding to the indents made within grains with an orientation close to the <111> direction).

The effect of ball-milling time and annealing temperature on fracture toughness of Ni-3 wt.% SiC using small punch testing

A set of dispersion strengthened Ni-3 wt.% SiC samples have been prepared via a powder metallurgy route for an application in molten salt reactor (MSR) systems. A mixture of 97 wt.% Ni and 3 wt.% SiC powder was prepared by varying the ball-milling time (8, 24, 36 and 48 h). The ball-milling process was followed by powder consolidation using spark plasma sintering (SPS) and rapid cooling to room temperature. The samples were then annealed at different temperatures (300 °C, 700 °C and 850 °C). The fracture behaviour of the Ni-3 wt.% SiC samples was investigated using the Small Punch Test (SPT). A scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and electron back-scatter diffraction (EBSD), as well as transmission electron microscopy (TEM) were employed to examine the microstructure of the tested Ni-3 wt.% SiC samples. The obtained results show that the SPT fracture energy is strongly dependent on the grain size of Ni matrix, which is affected by ball-milling times and annealing temperature. It has been further found that the segregation of large SiC particles at grain boundaries promotes intergranular fracture and thus significantly reduces the fracture energy. The results indicate that the distribution and size of SiC particles at grain boundary is mainly affected by the ball-milling time. Hence, the ball-milling time governs the fracture toughness of Ni-3 wt.% SiC samples.

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a flash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4 hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the flash heated samples display high saturation magnetization as well as increased coercivity.

Electron beam welding of Nimonic 80A: Integrity and microstructure evaluation

Microstructure, mechanical properties and microhardness of electron beam welded Nimonic 80A sheets and base metal were studied using various tools, i.e. scanning electron microscopy, field emission scanning electron microscope with energy dispersive spectroscopy and electron backscatter diffraction, X-ray diffraction analysis and Vickers microhardness. Very high cycle fatigue behavior of base metal and welded joint under push – pull condition at room temperature was also investigated using ultrasonic fatigue tests. Examination of microstructure shows that weld zone was mainly composed of columnar dendritic, and solidification modes can be changed according to the cooling rate. Moreover, there is little precipitates and MC carbides observed in the weld zone. X-ray diffraction results show that the phase structure of weld zone has not changed after electron beam welding. Additionally, electron backscatter diffraction results show that the weld zone and base metal has a clear difference in grain boundaries characterization and kernel average misorientation. Therefore, microhardness, tensile and very high cycle fatigue behavior of welded joint is lower than base metal.

Thermodynamic analysis and experimental study on the phase equilibria in Fe-Mn-Cr-O system

Oxidation diagram of the Fe-Mn-Cr-O system was determined using Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectrometer and X-ray power diffraction. The 1000 °C isothermal section of the Fe-Mn-Cr-O system was investigated experimentally. The oxide phases, Spinel, Monoxide and Corundum can equilibrate with the Fe-Mn-Cr alloys. Two three-phase equilibrium regions (two oxide phases coexist with alloy phase), Corundum + Spinel + Bcc and Monoxide + Spinel + Fcc, have been detected. The oxide phase boundary of Spinel and Monoxide was obtained. Thermodynamic computations of the Fe-Mn-Cr-O oxidation diagram at 1000 °C and 800 °C were performed. In comparison with the calculated phase diagram, the experimental oxide phase boundary of Spinel and Monoxide turns towards the Fe-Cr side partially. The phase diagram can be used to predict the oxidation of high-strength steel.

Visualizing the morphological and compositional evolution of the interface of InLi-anode|thio-LISION electrolyte in an all-solid-state Li–S cell by in operando synchrotron X-ray tomography and energy dispersive diffraction

The interfacial evolution in ASSLSB is reported.

Spark discharge generation of superparamagnetic Nickel Oxide nanoparticles

The unique properties of superparamagnetic nanoparticles offer many potential applications in various fields, especially in biomedicine. We have synthesized nickel oxide nanoparticles using spark discharge method in the argon gas followed by oxidation at atmospheric conditions. At applied operating conditions, the production rate of the nanoparticles was about 7 mg/h. The produced nanoparticles were characterized in terms of morphology, size, purity, structure, and magnetic property using field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray and electron diffraction, as well as vibrating sample magnetometer analysis. All the characterization techniques suggested the formation of ∼6nm size nickel oxide nanoparticles and some scarce larger size nickel nanoparticles with a high chemical purity and superparamagnetic behaviour. The results indicate that spark discharge in the gas phase is a facile and powerful method for the generation of chemically pure superparamagnetic nanoparticles as candidate for biomedical applications.

Effect of the annealing process on the microstructure and mechanical properties of multilayered Zr/Ti composites

To explore the potential application of Zr-based alloys as structural materials, multilayered Zr/Ti composites were fabricated by a vacuum diffusion annealing bonding process. Scanning electron microscopy (SEM) in tandem with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) was used to characterize the microstructures and chemical elemental distributions of the Zr/Ti laminated metal composites (LMCs). Micro-hardness and in-plane compression tests were conducted to evaluate the mechanical properties of the Zr/Ti LMCs. It is revealed that the microstructure of the Zr/Ti LMCs is composed of alternating Zr layers, Ti layers and Zr-Ti mutual diffusion layers (interface layers). The width of the interface layer increases with increased annealing temperature and time. The micro-hardness test results show that the hardness distribution is uneven among the different layers and that the interface layer has the highest hardness. Compression results indicate that the strength of the Zr/Ti LMCs are higher than that of the constituent materials due to the contribution of the interface layer. The diffusion coefficient and the relation between the microstructure and yield strength are also discussed in this study.

Electron Backscatter Diffraction Studies on the Formation of Superlattice Metal Hydride Alloys

Microstructures of a series of La-Mg-Ni-based superlattice metal hydride alloys produced by a novel method of interaction of a LaNi5 alloy and Mg vapor were studied using a combination of X-ray energy dispersive spectroscopy and electron backscatter diffraction. The conversion rate of LaNi5 increased from 86.8% into 98.2%, and the A2B7 phase abundance increased from 42.5 to 45.8 wt % and reduced to 39.2 wt % with the increase in process time from four to 32 h. During the first stage of reaction, Mg formed discrete grains with the same orientation, which was closely related to the orientation of the host LaNi5 alloy. Mg then diffused through the ab-phase of LaNi5 and formed the AB2, AB3, and A2B7 phases. Diffusion of Mg stalled at the grain boundary of the host LaNi5 alloy. Good alignments in the c-axis between the newly formed superlattice phases and LaNi5 were observed. The density of high-angle grain boundary decreased with the increase in process time and was an indication of lattice cracking.

Emission characteristic and transformation mechanism of hazardous trace elements in a coal-fired power plant

Coal-fired power plant is considered to be main anthropogenic emitter for emission of hazardous trace elements (HTEs), which can cause great damage on environment and human health. Emission characteristic of nine HTEs, namely Hg, Zn, Sb, Pb, Cd, As, Cr, Mn and Ba was carried out on a 320MW coal-fired power plant equipped with SCR, ESP and WFGD. US EPA method 29 was used for flue gas HTEs sampling at inlet or outlet of each APCD simultaneously. Solid or liquid samples like feed coal, ESP ash, bottom ash, fresh slurry, waste water, gypsum were collected at the same time. Scanning electron microscope, energy dispersive spectrometer and X-ray power diffraction spectrometry were adopted to characterize the physical and chemical structure characteristic of some solid samples. Results show that mass balance rate of the HTEs for each device and the system is in acceptable range. Mass amount of HTEs distributed in bottom ash and ESP ash accounts for large proportion, while little of them escapes into atmosphere (<0.05%). The mass amount of Mn and Ba in bottom ash is higher than that of other HTEs. Particulate HTEs are the main form in flue gas before ESP. ESP+WFGD has high removal efficiency for the HTEs in flue gas (99.96–99.99%), in which ESP makes a great contribution. During coal combustion, Mn and Ba enrich in bottom and fly ash equally while As, Cd, Sb, Zn, Pb and Cr will be prone to enrich in fly ash. Concentration of the HTEs in flue gas emitted to atmosphere is relatively low (3.5×10−3–4.30μg/m3) with emission factor of 0.001–1.473g/1012J. Finally, transformation mechanism of the studied HTEs during coal combustion is discussed.

Microstructures and Mechanical Properties of Dissimilar Al/Steel Butt Joints Produced by Autogenous Laser Keyhole Welding

Dissimilar Al/steel butt joints of 6.0 mm thick plates have been achieved using fiber laser keyhole welding autogenously. The cross sections, interface microstructures, hardness and tensile properties of Al/steel butt joints obtained under different travel speeds and laser beam offsets were investigated. The phase morphology and thickness of the intermetallic compound (IMC) layers at the interface were analyzed by scanning electronic microscopes (SEM) using the energy-dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD) techniques. The results show that travel speeds and laser beam offsets are of considerable importance for the weld shape, morphology and thickness of IMC layers, and ultimate tensile strength (UTS) of Al/steel butt joints. This proves that the IMC layers consist of Fe2Al5 phases and Fe4Al13 phases by EBSD phase mapping. Increasing laser beam offsets from 0.3 mm to 0.7 mm significantly decreases the quantity of Fe4Al13 phases and the thickness of Fe2Al5 layers at the interface. During tensile processing, the Fe2Al5 layer with the weakest bonding strength is the most brittle region at the interface. However, an intergranular fracture that occurred at Fe2Al5 layers leads to a relatively high UTS of Al/steel butt joints.

Mitigation of tin whisker growth by inserting Ni nanocones

An innovative controllable way has been proposed to mitigate tin whisker growth by inserting Ni nanocones prepared by electrodeposition. The results reveal that, after inserting Ni nanocones, tin whisker formation is mitigated effectively for 1.6μm Sn coating but there is no inhibition effect for 4.5μm Sn coating. The coatings are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer and electron backscatter diffraction (EBSD). The EBSD results show that Sn grain size without Ni nanocones increases significantly after indentation test compared with Sn grains with Ni nanocones. The inhibition effect of Ni nanocones on whisker growth can be ascribed to its specific structure which prevents dynamic recrystallization and produces horizontal grain boundaries of Sn grains. The structural inhibition method and mechanism proposed are of great importance to the research of tin whisker.

In situ preparation and stabilization of silver nanoparticles-water glass composite

Water glass – silver nanoparticles composite was prepared by simple reduction method of in situ prepared silver hydroxide by ascorbic acid in presence of sodium silicate. Various shapes and forms were produced by treatment of formed dispersion by carbon dioxide. Prepared material was characterised by Vis spectroscopy, scanning electron microscopy - energy dispersive X-ray spectroscopy and X-ray powder diffraction. Average diameter of silver nanoparticles was 22nm. Chemicals used have no or low toxicity and are affordable and environmentally friendly. The method is to use in various applications where long-term stable silver nanoparticles in easily shapeable solid matrix are desired.

Mechanical and electrical properties of ternary Ag-Bi-Ga system at 250 °C

This paper presents a comparative review of the experimental and thermodynamic assessment of a ternary Ag-Bi-Ga system. An isothermal section at 250 °C was calculated using optimized thermodynamic data for the constitutive binaries. Microstructures and phase compositions of studied alloys were analyzed by scanning electron microscopy in combination with energy dispersive spectrometry and X-ray powder diffraction technique. The obtained experimental results were found to support the predicted phase equilibria rather well. The hardness of alloys from three vertical sections (Bi-AgGa, Ag-BiGa, and Ga-AgBi) was determined using Brinell hardness test while the hardness of the individual identified phases was determined using Vickers microhardness test. Additional electrical conductivity measurements were carried out on the same alloy samples. Based on the experimentally obtained results iso-lines of Brinell hardness and electrical conductivity for the entire compositional range were calculated.

Residual stress analysis of energy-dispersive diffraction data using a two-detector setup: Part I — Theoretical concept

A new goniometer setup for energy-dispersive X-ray diffraction is introduced which is based on simultaneous data acquisition with two detectors D1 and D2, both of them freely movable in a horizontal as well as in a vertical plane. From the multitude of measurement configurations that can be realised with this setup, we figured out three efficient concepts which aim at the fast analysis of residual stress depth profiles by combining the diffraction data gathered with the two detectors. The characteristic feature of the first two configurations consists in the vertical (horizontal) positioning of the first (second) detector, which results in a diffraction geometry where the two scattering vectors span a plane that coincides with the X-circle used for sample tilt. Because each detector does see the sample under another viewing angle, both the positive and the negative ψ-branch are covered by just one χ-tilt between 0°and 90°(configuration 1) and 0°and 60°(configuration 2), thus allowing for the simultaneous analysis of the in- and out-of-plane residual stress depth gradients σiiτ and σi3τ (i=1,2), respectively, from data sets dD1hklχ and dD2hklχ. The third configuration introduced in this paper is based on a ϕ-rotation of the sample under a constant tilt angle χ and enables a fast and reliable tracing of shear stress fields σi3τ (i=1, 2).

Residual stress analysis of energy-dispersive diffraction data using a two-detector setup: Part II — Experimental implementation

Based on the theoretical concept of a two-detector setup for the energy-dispersive diffraction method (Apel et al., 2017), the experimental implementation of the proposed measurement concepts is demonstrated. The measurement configurations as well as the formalism for data evaluation introduced in the first part of this series are applied to the analysis of in- and out-of-plane near surface residual stress gradients in mechanically surface treated steel. Diffraction experiments carried out with the Bremsstrahlung of a conventional X-ray tube are shown to yield results with a quality comparable to measurements conducted at a synchrotron beamline. Furthermore, it is demonstrated that the simultaneous measurement of the positive and the negative ψ-branch can partly compensate for the much higher counting times due to the lower photon flux of the X-ray tube. The results are compared and assessed with those obtained by means of synchrotron radiation (beamline EDDI@BESSY II) and the layer removal method (LRM).

Effect of heat treatment on the crystal structure of deformed samples of chromium–manganese steel

Results of studying microstructures and the crystal structure of samples of 35KhGF steel (0.31–0.38 wt % С, 0.17–0.37 wt % Si, 0.95–1.25 wt % Mn, 1.0–1.3 wt % Cr, 0.06–0.12 wt % V, and the remainder was Fe) have been presented. The samples have been selected from hot-rolled pipes subjected to different heat treatments. A study has been carried out in order to explain the choice of the heat-treatment regime based on determining the structure–properties relationship that provides an increase in the corrosion resistance of pipes to the effect of hydrocarbons. Methods of the energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) have been used. In the microstructure of samples, oxide inclusions and discontinuities with sizes of 1–50 μm that presumably consist of the scale were detected. The ferrite grain size and the orientations of crystals were determined; the data on the local mechanical stresses in the Taylor orientation- factor maps were obtained. The grain refinement; the increase in the fraction of the low-angle boundaries; and the decrease in the local mechanical stresses and, therefore, the highest corrosion resistance to the effect of hydrocarbons is achieved by normalizing at 910°С.