Electron Probe X-ray Microanalysis Research Articles

Influence of cast part size on macro- and microsegregation patterns in a high carbon high silicon steel

In this work, the macro and microsegregation of Cr, Si and Mn have been investigated in a high-carbon high-silicon cast steel using X-ray fluorescence (XRF) and electron probe microanalysis (EPMA), respectively. Two different keel block sizes with leg thicknesses of 12.5 and 75 mm have been compared. In each of the keel blocks, three different locations along the leg thickness have been analyzed: A) zone near surface (≈1 mm); C) the central zone of the leg thickness and B) an equidistant zone from A and C. After comparing the analysis performed by XRF in these three zones no macrosegregation of the Cr, Mn and Si has been observed in any of the two keel blocks. However, clear microsegregation patterns have been obtained by EPMA for these three elements; interdendritic zones are enriched while dendrites are impoverished in these elements implying that their partition coefficient is lower that the unity (k < 1). This coefficient has been estimated using the EPMA measurements and Thermo-Calc calculations, finding good agreement between both approaches for Si and Mn but not for Cr. Finally, for both keel block leg thicknesses, similar microsegregation intensity, measured in terms of alloying element concentration has been observed. This result suggests that the cast part size (or dimension) do not have a strong influence on the microsegregation profiles. This it attributed to the back diffusion phenomena involving redistribution of solute during the solidification process.

Structure and calorimetric study of complex oxides based on lanthanum, tungsten, and alkaline earth elements MeLa2WO7 (Me = Mg, Ca, Sr, Ba)

As a result of citrate synthesis by the “sol–gel” method, we obtained samples of the compounds of ternary oxides with lanthanum, tungsten, and alkaline earth elements with the general formula MeLa2WO7 (Me = Mg, Ca, Sr, Ba). The structure of the samples obtained was studied by the X-ray diffraction, electron probe, and X-ray spectral microanalysis; the infrared and Raman spectra of the compounds were obtained. The results of indexing for SrLa2WO7 and BaLa2WO7 are in good agreement with the previously published crystallographic data. The heat capacity of the samples was measured by using of adiabatic calorimetry and their thermodynamic functions were calculated.

Interfacial reactions between ZrSnNb and FeCrAl alloy during diffusion bonding, hot-rolling and annealing

The clad plate between ZrSnNb and FeCrAl alloy was fabricated through diffusion bonding at 850 °C for 5 h under mechanical pressure in an argon atmosphere, and subsequent hot rolling at 800 °C with 20, 37 and 50% rolling reduction. The annealing treatment on hot-rolled plate was carried out in vacuum at 800 °C for 480 h. Interface observation and phase analysis were performed by Electron Probe X-ray Micro-Analyzer (EPMA). The interface of clad plate was tightly bonded, and there were no cracks and pores. After 5 h solid-state diffusion bonding, the Zr3Fe phase formed at the diffusion layer with about ∼3 μm thickness. The αZrCr2, ZrFe2 and Zr3Al intermediate phases formed at the interface in the 20% and 50% hot-rolled samples. While αZrCr2, Zr3Fe and Zr3Al phases formed at the interface in the 37% hot-rolled sample. There is no reasonable evidence temporarily to explain the formation of Zr3Fe phase at diffusion layer of 37% hot-rolled sample, and further study is necessary in near future. After annealing at 800 °C for 480 h, intermetllics formed and identified as αZrCr2, ZrFe2 and Zr3Al and Zr2Fe. The average thickness of diffusion layer in FeCrAl/ZrSnNb clad plates with 20%, 37% and 50% rolling reduction was 6 μm, 9 μm and 11 μm, respectively. The results in this study could provide possible valuable guidance for fabricating multilayer fuel cladding materials for the application in nuclear reactor.

The Geochronology and Geochemistry of Zircon as Evidence for the Reconcentration of REE in the Triassic Period in the Chungju Area, South Korea

The Chungju rare-earth element (REE) deposit is located in the central part of the Okcheon Metamorphic Belt (OMB) in the Southern Korean Peninsula and research on REE mineralization in the Gyemyeongsan Formation has been continuous since the first report in 1989. The genesis of the REE mineralization that occurred in the Gyemyeongsan Formation has been reported by previous researchers; theories include the fractional crystallization of alkali magma, magmatic hydrothermal alteration, and recurrent mineralization during metamorphism. In the Gyemyeongsan Formation, we discovered an allanite-rich vein that displays the paragenetic relationship of quartz, allanite, and zircon, and we investigated the chemistry and chronology of zircon obtained from this vein. We analyzed the zircon’s chemistry with an electron probe X-ray micro analyzer (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The grain size of the zircon is as large as 50 µm and has an inherited core (up to 15 µm) and micrometer-sized sector zoning (up to several micrometers in size). In a previous study, the zircon ages were not obtained because the grain size was too small to analyze. In this study, we analyzed the zircon with laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for dating purposes. The REE patterns and occurrence of zircon in the quartz–allanite vein match well with previous reported recrystallized zircon, while the behavior of the trace elements shows differences with magmatic and hydrothermal zircon. The 206Pb/238U ages obtained from the zircon in the quartz–allanite vein are from 240.1 ± 2.9 to 257.1 ± 3.5 Ma and this age is included in the tectonic evolution period of the study area. Therefore, we suggest that the quartz–allanite veins in the Gyemyeongsan Formation were formed during the late Permian to early Triassic metamorphic period and the zircon was recrystallized at that time. The Triassic age is the first reported age with zircon dating in the Gyemyeongsan Formation and will be an important data-point for the study of the tectonic evolution of the OMB.

Mixed n-type electronic, oxide ion, and protonic conduction in In-doped SrTi1-xRuxO3-δ

As part of a study of mixed n-type electronic and ionic conductors, the conductivities of indium doped strontium ruthenium titanates were determined. The SrTi1-x-yRuxInyO3-δ (x ​= ​0.1–0.4, y ​= ​0–0.2) compositions were prepared by conventional solid-state synthesis. Samples were determined to be of a single phase by X-ray powder diffraction and electron probe microanalysis. The temperature and pO2 dependences of the electrical conductivities were investigated by using DC and AC four-probe methods. STRIO820 and STRIO640 have conductivity of 6.4 and 5.4 Scm−1, respectively, at 900 ​°C and pO2 ​= ​1 ​atm. The conductivities of the In-doped samples under the same conditions were lower than that of SrTi1-xRuxO3-δ by around two orders of magnitude. For STRIO622, when pO2 was increased from 10−4 to 1 ​atm, the DC conductivities decreased, indicating n-type conduction. The pO2 dependence of conductivity was analyzed using the relation σT ​= ​ApO21/x ​+ ​σi. STRIO622 shows significant ionic conductivity, with σi ~0.21 Scm−1 at 1000 ​°C. The DC conductivities of STRIO622 in reducing environments (5% H2/N2 saturated with water) show protonic conduction at low temperatures. The thermal expansion coefficients (TECs) were ~8.9–11.2 ​× ​10−6 ​K−1 ​at 200 ​≤ ​T ​≤ ​990 ​°C.

Trace element distributions between matte and slag in direct nickel matte smelting

ABSTRACTBehaviour of trace elements in the nickel matte smelting was studied at 1673 K (1400°C) by equilibration-quenching techniques followed by direct phase analyses using electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. The matte-slag samples at silica saturation were equilibrated with SO2-CO-CO2-Ar mixtures of fixed pSO2, pS2 and pO2 in order to obtain a pre-determined oxidation degree for the sulphide matte, and thus to generate a targeted iron concentration of the nickel-copper–iron sulphide matte (Ni:Cu = 5, w/w), depending on the slag chemistry. The slag composition was varied from 0 to 2 wt-% K2O and 0–10 wt-% MgO in silica saturation. The studied trace elements were Co, Ge, Pb, Se and Sn, but also the matte-to-slag distributions of the slag forming fluxing components Mg (MgO) and Si (SiO2) were determined experimentally. Selenium was the only trace element studied which strongly enriched in the low-iron nickel mattes, and the deportment became larger when the sulphide matte depleted with iron. All the other trace elements behaved in the opposite way.

Investigation of the electromechanical behaviors in Cu-stabilized GdBCO coated conductor tapes using high-cycle fatigue tests at 77 K and related fractographic observations

In applications employing high-temperature superconducting conductors, various cyclic loading (fatigue) conditions produced by mechanical, thermal, or periodic electromagnetic forces are inevitable. Applying coated conductor (CC) tapes under fatigue loading conditions is expected to critically affect the long-term reliability of its superconducting performance. Most studies evaluating the mechanical and electromechanical characteristics use quasi-static uniaxial tensile tests. Few have focused on the characterization of CC tapes under fatigue loading. In this study, the electromechanical property characterization of Cu-stabilized GdBa2Cu3Oy (GdBCO) CC tapes including fatigue behaviors were investigated at 77 K. High-cycle uniaxial fatigue tests were carried out on GdBCO CC tapes 4 and 12 mm in width, and the two were compared in terms of mechanical and electromechanical aspects at a stress ratio of 0.1. The mechanical and electrical fatigue limits of the CC tapes were determined at 77 K. The 4 mm wide CC tapes showed less fatigue limits when compared to the 12 mm wide ones. However, regardless of the CC tape width, the sequence in the obtained characteristic strengths at 77 K was the same: yield strength > irreversible stress limit > mechanical fatigue limit > electrical fatigue limit. Fracture surface morphologies were observed using scanning electron microscopy-energy dispersive x-ray spectroscopy and electron probe micro-analysis to clarify the fatigue fracture mechanism and to examine the influence of the architecture of the CC tapes on fatigue behaviors. Damage along the edges, caused by slitting during fabrication of the 4 mm wide CC tapes, generated a stress concentration, eventually resulting in earlier crack initiation not only on the substrate, reducing mechanical fatigue strength, but also on the superconducting layer, degrading the measured critical current.

Osteointegration technology in long bone defect reconstruction: experimental study

The purpose of this experimental study was to evaluate the osteointegration of a bioactive 3D-cylindrical titanium-alloy implant (bone-graft substitute) for tibial shaft defect reconstruction. An experimental study was done in 7 mongrel dogs. Tibial shaft defect was repaired using an original titanium-alloy (Ti6Al4V) cellular cylindrical implant. with a bioactive layer of hydroxyapatite by anode microarc oxidation. Histological study (hematoxylin-eosin stain and immunohistological reaction using ostepontin polyclonal antibodies) and scanning electron microscopy (electron probe X-ray microanalysis for calcium and phosphorus saturation in the tissue matrix) were applied to assess bone tissue regeneration. Experimental study revealed osteoconduction starting from the endosteum of bone fragments adjacent to the bone defect and developed to the central part of the implant. In 4 weeks, graft osteointegration was achieved in all animals. Implant cells were filled with spongy bone tissue and the graft external surface was covered with a connective tissue structures similar to the periosteum ones. Cellular titanium bone-graft substitute with bioactive coatings placed into bone defect stimulates reparative osteogenesis and graft osteointegration.

Dentinal element incorporation, interfacial adaptation, and pH change induced by bioceramic sealer, mineral trioxide aggregate-based sealer, and epoxy resin-based sealer – An in vitro, scanning electron microscopy electron probe X-ray microanalysis study

Aim: Comparative evaluation of Dentinal Element Incorporation, Interfacial Adaptation, and pH change induced by Bio-ceramic Sealer, mineral trioxide aggregate (MTA)-based sealer, and Epoxy Resin-based sealer. Materials and Methods: Freshly extracted eighty mandibular premolar teeth were divided into four groups (n = 20) based on the sealer used for obturation, i.e., AH Plus (Group I), Endoseal MTA (Group II), EndoSequence BC Sealer (Group III), or Unfilled, unimmersed (Group IV), which served as the control. Specimens of Group I, II, and III were immersed in calcium and magnesium-free phosphate-buffered saline for 7 days. Specimens were sectioned longitudinally, and the ultrastructure of the dentine material interface and the elemental incorporation in the interfacial layer was analyzed using a wavelength dispersive scanning electron microscope-X-ray spectroscopy electron probe microanalyzer (SEM). The interfacial adaptation was measured using SEM. pH was calculated using pH meter. Statistical Analysis: Data were statistically analyzed using one-way ANOVA and Duncan's multiple range tests. Results: At the interface, both bio-ceramic materials formed a tag-like structure rich in calcium and silicon deposits, which were significantly higher in EndoSequence and Endoseal MTA, respectively. Endosequence BC sealer showed fewer interfacial gaps and the highest pH change as compared to the other groups. Conclusions: Bio-ceramic sealers showed better interfacial adaptation, element incorporation in the interfacial layer, and increased alkalinity of pH, leading to a superior marginal seal as compared to AH Plus and the control group.

Experimental Study and Thermodynamic Calculations of the Distribution of Ag, Au, Bi, and Zn Between Pb Metal and Pb–Fe–O–Si slag

The present article continues the series reviewing the thermochemistry of complex multicomponent pyrometallurgical systems. The recovery of multiple metals through the Pb-based primary and recycling processes is an economic driving force for the circular economy of the future. In this study, equilibrium distributions of Ag, Au, Bi, and Zn between PbO–FeO–Fe2O3–SiO2 silica saturated slag and Pb metal phases were investigated experimentally, using high-temperature equilibration followed by rapid quenching. The measurement of phase compositions was done using microanalytical methods. Electron Probe X-ray Microanalysis (EPMA) was applied for those elements which present at relatively high concentrations. The Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was used to measure very low concentrations of Ag and Au in slag. The starting mixtures of materials were planned using FactSage software and preliminary thermodynamic database to target specific proportions of phases and concentrations of Pb in slag after the achievement of equilibrium. Measured slag/metal distribution coefficients follow the sequence Zn ≫ Ag > Bi ≫ Au. Newly obtained results were critically assessed and used to improve the thermodynamic database. Integration between experiments and thermodynamic database development permits cross-analysis of distribution coefficients obtained in the present study with the parallel measurements of distribution in copper-based systems. The liquid slag phase was described using a two-sublattice Modified Quasichemical Model (MQM). Single sublattice MQM was applied for the liquid metal phase.

Application of phase equilibrium studies of CaO–SiO2–Al2O3–MgO system for oxide inclusions in Si-deoxidized steels

In the steelmaking process, the compositions of the oxide inclusions could be modified by refining slags to a large extent. The chemistries of the oxide inclusions and refining slags can be described by the system CaO–SiO2–Al2O3–MgO. Phase equilibria and liquidus temperatures in this system have been experimentally investigated in the composition and temperature ranges related to the oxide inclusions and refining slags by means of high-temperature equilibration, quenching and electron probe X-ray microanalysis. Isotherms in the interval of 20 °C between 1260 and 1560 °C were determined in the primary phase fields of wollastonite, anorthite, spinel, and melilite. Effects of the mass ratio of (Al2O3+SiO2)/((Al2O3+SiO2)+(CaO + SiO2)) and MgO content on the liquidus temperatures have been discussed to assist inclusion control. To obtain the lowest liquidus temperature of Al2O3–SiO2–CaO–MgO system inclusions, refining time ought to be properly controlled.

Growth behavior of aluminum borate whiskers on zirconia toughened alumina (ZTA) particle surface

In this work, B4C-covered zirconia-toughened alumina (ZTA) particles are prepared and oxidised at 1050 °C for different times (0, 2, 4, and 8 h) in air. The X-ray diffraction and electron probe micro-analysis results show that the covering layer is mainly composed of oxide B2O3 intermetallics, residual B4C particles, and Al18B4O33 whiskers. The scanning electron microscopy results show that the growth of Al18B4O33 whiskers on the ZTA particles enhances with increasing heat preservation time; the optimum holding time is determined to be 8 h Al2O3 in the ZTA particles diffuse into the covering layer and combine with B2O3 to form Al18B4O33 whiskers; the Al18B4O33 whiskers grow via the liquid-solid mechanism.

Chondroplasty Efficacy of Bone Matrix

Aim To study the chondroplasty efficacy of the bone matrix obtained using an original technology in restoring cartilage defect of the knee joint. Material and Methods Marginal defects were modeled on the surface of the distal end of the femur in 40 adult male Wistar rats. The bone matrix obtained using an original technology was implanted in the damaged area in animals of the experimental group. Material was investigated by means of light microscopy, transmission and scanning electron microscopy, and electron probe X-ray microanalysis. Results It was found that the bone matrix implanted did not cause an immune rejection reaction, activated reparative chondrogenesis for a prolonged period. In the area of articular cartilage lesion, the regenerate acquiring cellular and histochemical characteristics of the hyaline cartilage tissue was formed. The chondroinductive properties for the bone matrix were ensured by localized growth factors and morphogenetic proteins released during osteoclastic resorption. Conclusion The application of the bone matrix as a stimulator of chondrogenesis is theoretically reasonable and has a good perspective in treatment of damages and diseases of the articular cartilage.

Effects of preform aperture/hole wall ratio on the microstructure and properties of ZTAp/HCCI matrix honeycomb structure composites

Zirconia toughened alumina particles (ZTAp)/high chromium cast iron (HCCI) matrix honeycomb structure composites were successfully prepared by the non-pressure infiltration casting process. The transformations of ZTA ceramic particles and high chromium cast iron during the compound process were analyzed by using x-ray diffraction (XRD) and Electron probe microanalysis (EPMA). The maximum stress and average value of the maximum stress simulated by COMSOL Multiphysics software shows a trend of decreasing first and then increasing with decreasing preform aperture/hole wall ratios. The maximum stress and average value of the maximum stress are minimal among the six comparison groups and the stress range is 0.8 ∼ 1.8 GPa with preform aperture/wall ratio of 1.25. Owing to the change in the main impregnation resistances influenced by the hole wall value, the dispersion uniformity of ZTA ceramic particles in the composites becomes better with preform aperture/wall ratio of 1.43, 1.25 or 1.11. When the preform aperture/hole ratio is 1.25, the compressive strength of the samples reaches a maximum value of 1240 MPa. And the trend of the compressive mechanical properties is consistent with the results of the stress simulation. The wear volume loss of the composites reaches the smallest with preform aperture/hole wall ratio of 1.25, because the protective effect of ZTA ceramic particles and the supporting effect of high chromium cast iron achieve the best synergistic cooperation at this ratio.

Corrosion resistance by HVOF coating on gas turbine materials of cobalt based superalloy

Abstract In the parts of gas turbines, external degradations such as corrosion occur at places like turbine blades, when the temperature is high. The turbines become less operative and flare with sound because of the degradation due to corrosion. The thermocyclic hot corrosion performance of the 25%(Cr3C2-NiCr) + 75%NiCrAlY coatings as well as the cobalt based super alloy (Superco-605) substrate alloy was studied in a molten salt environment of Na2SO4 −50%V2O5 at 750 °C for 50 cycles. Each cycle consists of an hour heating followed by 20 min of cooling, in room temperature environments. The response and kinetics were studied by means of thermogravimetry. The samples subjected to corrosion will be investigated using techniques of Optical microscopy, X-ray diffraction (XRD), Scanning electron microscopy/Energy dispersive X-ray analysis (SEM/EDX) and Electron probe microanalysis. The major phases observed on coated material shows the formation of oxides of Chromium Oxide (Cr2O3), Nickel Oxide (NiO), and Aluminium oxide (Al2O3) which gives high protection against corrosion and prevents the penetration of corrosive species into the coating.

Experimental Liquidus Studies of the CaO-ZnO-Fe2O3 System in Air

Phase equilibria in the CaO-ZnO-Fe2O3 system have been investigated at 1483-1673 K (1210-1400 °C) for oxide liquid in equilibrium with air and solid oxide phases: (a) zincite (Zn,Fe,Ca)O1+x; (b) spinel (Zn,Fe,Ca)Fe2O4; (c) lime (Ca,Zn)O; (d) calcium ferrites dissolving zinc oxide: brownmillerite Ca2(Fe,Zn)2O5−x, and calcium diferrite (Ca,Zn)Fe4O7. High-temperature equilibration on inert metal (platinum) substrates, followed by quenching and direct measurement of the Ca, Zn and Fe concentrations in the phases with the electron probe x-ray microanalysis (EPMA) has been used to accurately characterize the system in equilibrium with air. All results are projected onto the CaO-ZnO-“FeO1.5” plane for presentation purposes. The present paper presents systematic characterization of liquidus over a wide range of compositions in this system in equilibrium with air.

Impact of MgO and K2O on Slag-Nickel Matte Equilibria

Slag chemistry of the direct nickel matte smelting was studied in typical industrial high-grade nickel matte smelting conditions at 1400 °C and 0.1 atm pSO2. The experimental technique used involved equilibration, quenching and direct elemental phase composition analysis by Electron Probe X-ray Microanalysis. Magnesia and potassia, a typical gangue constituent of sulfidic nickel concentrates and a common impurity of industrial grade silica flux (sand), respectively, were adopted as slag modifiers in concentrations typical to industrial operations. Their effects on oxidation degree of the nickel-copper-iron matte and equilibrium concentrations of Ni and Cu in the slag were studied as a function of oxygen partial pressure. Solubility of silica in the slag increased significantly with additions of MgO and K2O in the constrained case studied, at silica saturation. Equilibrium concentrations of Ni and Cu in the slag containing MgO and K2O were about a quarter lower compared to the pure iron silicate slag, in the entire oxygen partial pressure range studied.

PbI2 Single Crystal Growth and Its Optical Property Study

In this work, we used the chemical vapor transport (CVT) method to grow PbI2 crystals using iodine as a self-transporting agent. The crystals’ structure, composition, and uniformity were confirmed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA) measurements. We investigated the band gap energy using absorption spectroscopy measurements. Furthermore, we explored the temperature dependence of the band gap energy, which shifts from 2.346 eV at 300 K to 2.487 eV at 20 K, and extracted the temperature coefficients. A prototype photodetector with a lateral metal–semiconductor–metal (MSM) configuration was fabricated to evaluate its photoelectric properties using a photoconductivity spectrum (PC) and persistent photoconductivity (PPC) experiments. The resonance-like PC peak indicates the excitonic transition in absorption. The photoresponse ILight/IDark-1 is up to 200%.

Evolution of the Structure and Mechanism of the Formation of Welded Joints of Medium-Carbon Steels upon Rotary Friction Welding

The structure of the contact lines and of the thermomechanically affected zone of welded joints of medium-carbon steels obtained by rotary friction welding have been studied using metallography and scanning electron microscopy supplemented with X-ray electron microprobe analysis. The results of the microhardness distribution over the cross section of the welded joint are presented. The phase transformations realized at each stage of the technological process of welding in the regions subjected to the thermodeformation influence have been analyzed. The results of the uniaxial tensile and impact bending tests supplemented by the fractography of the fracture surface are presented.

Thermodynamic description and simulation of solidification microstructure in the Co-Ti system

The Co-Ti binary system has been investigated by means of experimental measurements and thermodynamic calculations. In order to provide new phase relationship in the Co-Ti system, 9 key alloys were prepared by arc melting under vacuum. All alloys were examined for phase and composition analysis by means of X-ray diffraction and electron probe microanalysis after annealing at 900 °C for 60 days and 1000 °C for 30 days, respectively. The invariant equilibrium among liquid, L12 and C36 Laves phases was experimentally determined to be an eutectic with the reaction temperature at 1154 °C. A revised Co-Ti phase diagram is presented according to the present experimental results and reliable literature data. A consistent set of thermodynamic parameters for the Co-Ti system was then obtained by means of CALPHAD (CALculation of PHAse Diagram) approach. The present thermodynamic parameters can describe the experimental results satisfactorily. Scheil solidification simulation was employed to analyse the experimental microstructure of as-cast alloys. The calculated mole fractions of the constitution phases in a few key as-cast alloys are in good agreement with the experimental data obtained by the image J software. The present work indicated that the comprehensive application of the thermodynamic calculation and decisive experiment is an efficient strategy to obtain the desired solidification microstructure.