Electron Probe Microanalysis Results Research Articles

Comparison of Mineral Trioxide Aggregate's Composition with Portland Cements and a New Endodontic Cement

The aim of this study was to compare the compositions of mineral trioxide aggregates (MTAs), Portland cements (PCs), and a new endodontic cement (NEC). Our study also investigated the surface characteristics of MTA and NEC root-end fillings when immersed in normal saline. For part I, we prepared samples of 9 brands of MTAs, PCs, and NEC. The materials were imaged and analyzed by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDXA). In part II, 3-mm-deep root-end preparations were filled with MTA or NEC and stored in normal saline for 1 week. Samples were imaged and analyzed by SEM and electron probe microanalysis (EPMA). EDXA investigations revealed differences in the dominant compounds of NEC, PCs, and MTAs. The major components of MTA and PC are the same except for bismuth. The most significant difference was the presence of higher concentrations of Fe (minor element) in gray MTA and PC when compared with white ones. EPMA results revealed remarkably different elements in MTA compared with surrounding dentin, whereas in the NEC group the distribution patterns of calcium, phosphorous, and oxygen were comparable. NEC differs chemically from MTAs and PCs and demonstrates comparable surface composition with adjacent dentin as a root-end filling material.

Microstructure and elemental distribution of americium-containing uranium plutonium mixed oxide fuel under a short-term irradiation test in a fast reactor

In order to investigate the effect of americium addition in MOX fuel on the irradiation behavior, the ‘Am-1’ program is being conducted in the experimental fast reactor Joyo. The Am-1 program consists of two short-term irradiation tests of 10min and 24h irradiations and a steady-state irradiation test. The short-term irradiation tests were successfully completed and the post irradiation examinations (PIEs) are in progress. This paper reports on the results of PIEs for Am-containing MOX fuel irradiated for 10min. MOX fuel pellets containing 3% or 5% Am were fabricated in a shielded air-tight hot cell using a remote handling technique. The oxygen to metal ratio (O/M) of these fuel pellets was 1.98. They were irradiated at peak linear heating rate of about 43kWm−1. Focus was being placed on migration behavior of Am during the irradiation. The ceramography results showed that structural changes such as lenticular pores and a central void occurred early, within the brief 10min of irradiation. The results of electron probe microanalysis revealed that the concentration of Am increased in the vicinity of the central void.

Effects of SrTiO 3 additives on the structure and microwave dielectric properties of Ba 4.2Sm 9.2Ti 18O 54 ceramics

The effects of SrTiO 3 additives on the microstructure and the dielectric properties of Ba 4.2Sm 9.2Ti 18O 54 (BST) materials have been investigated. The microstructure of BST doped with SrTiO 3 was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The XRD, SEM and EPMA results showed that small amounts of SrTiO 3 (less than 4 wt.%) could be accommodated in BST while a secondary metatitanate phase appeared in the samples with 8 wt.% SrTiO 3 added, the addition of SrTiO 3 increased the lower solubility limit ( x values) of Ba 6−3 x Sm 8+2 x Ti 18O 54. The relative permittivities and the TC f values showed an approximately linear increase with increasing additions of SrTiO 3. It was observed that near zero TC f values could be achieved with the addition of SrTiO 3 to BST ceramics. With 4 wt.% SrTiO 3 addition and sintered at 1360 °C for 2 h, BST ceramics exhibited excellent dielectric properties: ɛ r = 81.2, Q f = 8470 GHz and TC f = −1.5 ppm/°C.

On the Accelerating Degradation of DMFC at Highly Anodic Potential

A convenient method of investigating the degradation of a direct methanol fuel cell (DMFC) was carried out at highly anodic potential (i.e., ). Accelerating degradation of a DMFC was investigated by electrochemical methods, X-ray diffraction (XRD), transmission electron microscopy (TEM), electron probe microanalysis (EPMA), and X-ray photoelectron spectroscopy (XPS). The degradation was preliminarily diagnosed and predicted with electrochemical impedance spectroscopy and verified with microscopic examination. The EPMA and XPS results showed that the sulfonic acid vanished in the broken anodic layer compared to the original one, which results in an increase of internal resistance (Rs). The increase of interfacial and electrochemical reaction resistance in the degraded cell might be a result from catalytic degradation. Ru dissolves from the anodic catalyst to decrease the catalytic activity then reduced near the cathode. The evidence for Ru dissolution was determined by stripping combined with EPMA and XPS analyses. Its reduction near the cathode was observed through TEM and EPMA. The catalysts in both the anode and cathode aggregated to decrease the catalytic activity in the degradation process by XRD and TEM. On the basis of the electrochemical study and related analysis, we proposed a mechanism for this accelerating degradation of DMFC.

The effect of ion exchange on glass surface morphology and composition

Abstract The surface morphology and K+, Na+ concentration distributions of plate glass were investigated by atomic force microscope (AFM) and electron probe microanalyzer (EPMA) before and after ion exchange. The AFM images indicate that the surface microcrack of chemical strengthened glass can be closed to a certain extent and the surface smoothness can be improved. The EPMA results indicate that the relationship between the weight gain and time, temperature follows Fick’s law, which are same as that of the thickness of ion exchanged layer, the total exchanged amount. Consequently, a simple and accurate weighing method was first proposed to estimate the ion exchange state.

Trace element associations with Fe- and Mn-oxides in soil nodules: Comparison of selective dissolution with electron probe microanalysis

Selective dissolution methods have been largely used to get insight on trace element association with solid phases. Modern instrumental techniques offer many tools to test the validity of selective dissolution methods and should be systematically used to this end. The association of trace elements with Fe- and Mn-oxides in soil nodules has been studied here by electron probe microanalysis. The results were compared with findings from an earlier study on selective dissolution of the same nodules by hydroxylamine hydrochloride, acidified hydrogen peroxide, and Na-citrate-bicarbonate-dithionite. Electron probe microanalysis results were consistent with previous findings using selective dissolution and showed that P, As and Cr were mainly present in Fe-oxides, while Co was mainly associated with Mn-oxide phases. These results support the applicability of the studied selective dissolution methods for fractionation of trace elements in soils and sediments containing appreciable amounts of Fe and Mn-oxide phases.

Ba3YRu0.73(2)Al1.27(2)O8 and Ba5Y2Ru1.52(2)Al1.47(2)O13.5: New Perovskite Ruthenates with Partial Octahedra Replacement

Dark red single crystals of the new phases Ba3YRu0.73(2)Al1.27(2)O8 and Ba5Y2Ru1.52(2)Al1.47(2)O13.5 have been grown from powder mixtures of BaCO3, Y2O3, Al2O3, and RuO2 . The compositions given in the formulas result from the refinements of the crystal structures based on single crystal X-ray diffraction data (hexagonal P63/mmc (No. 194), Z = 2, Ba3 YRu0.73(2)Al1.27(2)O8: a = 5.871(1), c = 14.633(3) Å , R1 = 0.035, wR2 = 0.069 and Ba5Y2Ru1.52(2)Al1.47(2)O13.5: a = 5.907(1), c = 24.556(5) Å, R1 = 0.057, wR2 = 0.114). Ba3YRu0.73(2)Al1.27(2)O8 crystallizes in a 6H perovskite structure, Ba5Y2Ru1.52(2)Al1.47(2)O13.5 has been characterized as a 10H Perovskite. Due to similar spatial extensions of (Ru2O9) facesharing pairs of octahedra and (Al2O7) vertex-sharing pairs of tetrahedra, both structures show partial mutual substitution of these units. Consequently, the title compounds may be written as Ba3Y(Ru2O9)1−x(Al2O7)x, x = 0.64(1) and Ba5Y2RuO6(Ru2O9)1−x(Al2O7)x, x = 0.74(1). This interpretation is supported by the results of electron probe microanalysis using wavelength-dispersive X-ray spectroscopy. An oxidation state of Ru close to +5 for the (Ru2O9) units, as can be derived from the distances d(Ru-Ru), additionally leads to similar charges of both the (Ru2O9) and the (Al2O7) units.

Structural effects of nanocomposite films of amorphous carbon and metal deposited by pulsed-DC reactive magnetron sputtering

The relationship between metal-induced (W, Mo, Nb and Ti) structures and the surface properties of Me–DLC thin films is discussed. Nanocomposite films were deposited on c–Si wafers by pulsed-DC reactive magnetron sputtering controlling the gas ratio CH 4/Ar. The sputtering process of metals such as Ti, Nb and Mo (unlike the tungsten) in the presence of methane shows a low reactivity at low methane concentration. The deposition rate and the spatial distribution of sputtered material depend of Z-ratio of each metal. The surface contamination of metal targets by carbon, owing to methane dilution, limits the incorporation of metals into DLC films according to an exponential decay. Results of electron probe microanalysis and X-ray photoelectron spectroscopy indicate a C rich Me/C composition ratio for low relative methane flows. According to the depth profile by secondary ion mass spectrometry, the films are systematically homogeneous in depth, whereas at high carbon contents they exhibit a metal-rich interfacial layer on the substrate. Moreover, high resolution transmission electron microscopy has evidenced important structural modifications with respect to DLC standard films, with marked differences for each Me/C combination, providing nanodendritic, nanocrystallized or multilayered structures. These particular nanostructures favour the stress decrease and induce significant changes in the tribological characteristics of the films. This study shows the possibilities of controlling the amorphous carbon films structure and surface properties by introducing metal in the DLC matrix.

Eta Phase and Boride Formation in Directionally Solidified Ni-Base Superalloy IN792 + Hf

A series of directional solidification experiments have been conducted to elucidate the formation mechanism of eta and Cr-rich phases in the Ni-base superalloy IN792 + Hf. Both eta and Cr-rich phases were found to be the final solidification products developed from the remaining liquid after γ/γ′ eutectic reaction. The (Ti + Ta + Hf)/Al ratio in the residual liquid played a significant role in the nucleation of eta phase. During the solidification of γ/γ′ eutectic, the continual increase of (Ti + Ta + Hf)/Al ratio in the residual liquid eventually led to the completion of γ/γ′ eutectic reaction and caused the nucleation of eta phase. The results of electron probe microanalysis and transmission electron microscopy revealed that the Cr-rich phase was Cr, Mo, and W containing M5B3 and M3B2 type borides. The formation of these boride phases was found to be strongly influenced by the formation of γ/γ′ eutectic. Because of the limited solubility of Cr, Mo, and W in γ′ phase, these elements were enriched in the residual liquid during the solidification of γ/γ′ eutectic. In addition, boron would preferentially segregate into liquid due to its very limited solubility in both γ and γ′ phases so that the possibility of boride formation in the residual liquid ahead of the γ/γ′ eutectic was increased. A modified Scheil model was adopted to explain the influence of solidification rate on the formation of eta phase and borides, and the results were discussed.

The influence of magnetron sputtered silver and titanium coatings on the compaction and properties of surface modified PM Ti-48Al powders

Thin layers of silver and titanium were deposited onto commercial Ti–48Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment. Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained for the silver and titanium contents in the coated particles. The surface modified Ti–48Al particles exhibited improved sintering ability than the unmodified ones. The consolidated samples have duplex microstructures formed by γ-TiAl and γ-TiAl + α2-Ti3Al grains. Ag-rich nanoprecipitates were detected in the microstructure of the compacted Ti-48Al + Ag sample. The coatings are no longer visible at the grains boundaries after a subsequent homogenization heat treatment at 1200°C. The highest values of hardness and Young’s modulus were obtained for the Ti–48Al + Ag sample, associated with a higher density and a lower percentage of pores.

Experimental observations elucidating the mechanisms of structural bcc-hcp transformations inβ−Tialloys

The formation mechanisms of two hcp ? phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary ? forms predominantly on prior bcc ? grain boundaries, whereas at lower temperatures so-called bainitic ? plates nucleate both at grain boundaries and intragranularly. This morphological transition with decreasing temperature is associated with a change in transformation mechanism. The combined results of EPMA, OM and dilatometry show that the growth of these bainitic ? plates is partitionless, and not accompanied by a volume change. Subsequently, a posttransformation redistribution of Fe takes place, which causes a dilatation that can be modelled based on the diffusion of Fe and the interface-area density. This mechanism as well as the formed microstructure are similar to bainite in steel, and therefore we chose to denote this transformation product as bainitic ?. In addition, the AFM observations on bainitic ? plates show an invariant plane strain surface relief with tilt angles that are consistent with the Burgers’ transformation model based on shear. In contrast, the AFM results show that the formation of primary ? is accompanied by an irregular dip on a free surface, which is in agreement with the volume decrease measured using dilatometry. Furthermore, the EPMA results show that primary ? is formed by a partitioning transformation. The change in transformation mechanism with decreasing temperature is supported by the observed trend in both the dilatation and the volume fraction ? as a function of temperature.

Fabrication of Cu 2 ZnSnS 4 thin films by co‐evaporation

Cu2ZnSnS4 (CZTS) thin films were fabricated by co-evaporation of elemental sources on quartz glass substrates. The deposition was performed at the substrate temperature between 400 oC and 600 oC. From the results of electron probe microanalysis, it was confirmed that the nearly stoichiometric CZTS thin films were obtained in all substrate temperature. The X-ray diffraction patterns revealed that CZTS thin films have a kesterite structure with a strong preferred orientation. From the scanning electron microscope observation, the grain size becomes larger with increasing the substrate temperature. The CZTS thin films showed p -type conductivity. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of nanostructure on biodegradation behaviors of self‐setting apatite/collagen composite cements containing vitamin K2 in rats

Apatite cement and collagen were combined by a mechanochemical method to create a new self-setting apatite/collagen composite cement, and menatetrenone (VK2) was loaded into a drug-delivery system to test biocompatibility in rats. Powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and electron probe microanalyzer (EPMA) were performed to characterize the physicochemical properties of apatite/collagen composite cements. The XRD results suggested that ground apatite/collagen cement was completely transformed into bone-like hydroxyapatite, but that without grinding was incomplete. The SEM and EPMA results suggested that ground apatite/collagen cement was homogeneously dispersed of nanoapatite crystals in collagen matrices, similar to that in natural bone. In contrast, the cement without grinding was heterogeneously distributed. To evaluate in-vivo cement density (CMM), microradiograms were measured for 72 days after implanting apatite/collagen composite cements in intramuscular tissue on the backs of rats, and cross sections of the cements and surrounding soft tissues were observed by microscope. The CMM results of the apatite/collagen composite cements suggested that the biodegradation rate was dependent on the cement quality and nanogeometrical structure. The CMM result of VK2-loaded apatite/collagen cements suggested that the biodegradation rates of the cements were significantly dependent on their formulation. The CMM of ground apatite/collagen cement increased until 7 days and then decreased, and bone-like cells penetrated deeply in the center. The microphotograph and CMM results of apatite/collagen without grinding indicated that a lot of bone-like cells penetrated into the cement and the cement shape was totally deformed.

SEM evaluation of neodentinal bridging after direct pulp protection with mineral trioxide aggregate

The purpose of this study was to observe the basic morphology and determine the chemical composition of neodentinal bridges adjacent white mineral trioxide aggregate (WMTA) when used as a direct pulp capping material. The experimental procedures were performed on six intact dogs' teeth. The pulps were exposed and cavities were filled with WMTA. After 2 weeks, neodentinal bridge formation was evaluated by scanning electron microscope (SEM) of cross-sections of the specimens and electron probe microanalysis (EPMA) of the pulpal surfaces. Results of SEM observation showed that the most characteristic reaction of pulp cells was the intimate connection of cell processes and secreted extracellular fibres with the crystals of the pulp capping material. Results of EPMA indicated that the mineralisation of neodentinal bridge formation occurred progressively from the periphery to the central area. Based on these results, it appears that WMTA has the potential to be used as a direct pulp capping material during vital pulp therapy.

Electrochemical properties of lead dioxides formed on various lead alloy substrates

Electrochemical properties of lead dioxides, formed on various lead alloy substrates (Pb–In, Pb–Sn, Pb–Sb, Pb–Tl and Pb–Bi), were investigated using electrochemical techniques with X-ray diffraction (XRD) and electron probe micro analyzer (EPMA). Additive elements, selected by applying Hume-Rothery rules, have similar atomic radius and electronegativity to lead. The reduction capacity of lead dioxides that were formed on Pb–Sb and Pb–Sn alloy substrates decreased, whereas the reduction capacity of lead dioxides formed on Pb–In, Pb–Tl and Pb–Bi alloy substrate increased, compared with those formed on the pure lead substrate. The change of the lattice constant of β-lead dioxides and the existence of additive elements in the lead dioxide layer were confirmed from the analysis results of XRD and EPMA. We concluded that the substitution of additive elements for lead in the β-lead dioxide caused the change of its lattice constant to affect the reduction capacity.

Corrosion behavior of low alloy steels containing Cr, Co and W in synthetic potable water

The corrosion behavior of new alloy steels was investigated using potentiodynamic (PD) tests, electrochemical impedance spectroscopy (EIS) and galvanostatic test in synthetic potable water. PD test results showed that all specimens exhibited active corrosion behavior, and corrosion rate tended to decrease as a result of adding alloying elements. The EIS measurements were taken to determine the polarization resistance (RP) of the rust layer. The RP values of the new alloy steel were much larger than that of carbon steel. Furthermore, more alloying elements led to a remarkable increase in the RP values. The chemical state of alloying elements (Cr, Co and W) in the rust layer of new alloy steels was analyzed by electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). EPMA and XPS results showed that alloying elements existed in protective compounds in the rust layer. Corrosion of the new alloy steels was suppressed by insoluble compound formed near the surface.

Corrosion behavior of low alloy steels containing Cr, Co and W in synthetic potable water

The corrosion behavior of new alloy steels was investigated using potentiodynamic (PD) tests, electrochemical impedance spectroscopy (EIS) and galvanostatic test in synthetic potable water. PD test results showed that all specimens exhibited active corrosion behavior, and corrosion rate tended to decrease as a result of adding alloying elements. The EIS measurements were taken to determine the polarization resistance ( R P ) of the rust layer. The R P values of the new alloy steel were much larger than that of carbon steel. Furthermore, more alloying elements led to a remarkable increase in the R P values. The chemical state of alloying elements (Cr, Co and W) in the rust layer of new alloy steels was analyzed by electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). EPMA and XPS results showed that alloying elements existed in protective compounds in the rust layer. Corrosion of the new alloy steels was suppressed by insoluble compound formed near the surface.

Effect of Co and W on the corrosion behaviour of 1% Cr steel in flowing synthetic seawater

AbstractThe aqueous corrosion characteristics of 1% Cr‐steel alloyed with small amounts of Co and W in synthetic seawater was studied by using immersion weight‐loss tests, electrochemical corrosion tests (potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co‐ and W‐bearing steels present higher Rp values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co‐and W‐bearing steels is attributed to the protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO4 compound. These compounds act as a factor for corrosion resistance in aqueous solutions.

Plasma-induced damage in PZT thin films etched by inductively coupled plasma

We investigated the etching damage induced by Ar/(Cl 2+CF 4) plasma and improvement in etching damage by O 2 annealing. PZT thin films were etched for 1 min in an ICP using a gas mixture of Cl 2 80%/CF 4 20% with 20% Ar addition. The etching conditions were fixed at a substrate temperature of 30 °C, RF power of 700 W, DC bias voltage of −200 V and a chamber pressure of 15 mTorr. To improve the ferroelectric properties of PZT thin films after etching, the samples were annealed for 10 min at 600 °C in O 2 atmosphere. After O 2 annealing, the remanent polarization-on-fatigue property was recovered to the characteristics of the as-deposited film. According to X-ray diffraction (XRD) analysis, an increase in (100) and (200) phases showed the improvement in structure of the PZT thin films after the O 2 annealing process. In addition, transmission electron microscope (TEM) images showed that the etched PZT surface is damaged by the bombardment of energetic particles, but that the damaged surface can be recovered by O 2 annealing. The results of electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) showed that O 2 annealing supports the substitution of oxygen vacancies on the PZT surface by O atoms. This decrease in oxygen vacancies improves the fatigue characteristics of PZT thin films.

Sputtering of carbon–tungsten mixed materials by low energy deuterium

In the divertor of next step fusion experimental devices such as ITER, simultaneous presence of carbon and tungsten material will lead to their mixing during the redeposition process. In the present paper, sputtering experiments on C–W mixed material by low energy hydrogen beam had been performed. The C–W mixed material was simulated by the deposits during the D 2 arc discharge between carbon and tungsten electrode. Five types of C–W mixed materials having different W concentrations which ranged from 0 to 75 wt% were used as the specimens for the sputtering experiment. It was found that the sputtering yield strongly depends on the W concentration in the C–W mixed materials. From the results of electron probe micro-analysis, it was indicated that carbon material is preferentially sputtered by chemical sputtering. The formation of W–C bonding is considered to be the reason for the low sputtering yields of C–W mixed material layers.