SEM Backscattered Electron Images Research Articles

Comparison of large-volume 3D reconstruction using plasma FIB-SEM and X-ray CT.

We demonstrated large-volume three-dimensional (3D) reconstruction using plasma focused ion beam - scanning electron microscopy (PFIB-SEM). We successfully reconstructed a 750 μm (W) × 143 μm (H) × 310 μm (D) volume at a resolution of 200 nm/pix from 1,550 SEM backscattered electron images of a Li-ion battery cathode sheet. The PFIB-SEM system was found to be capable of acquiring and reconstructing larger volume 3D datasets than X-ray computed tomography, and with higher resolution and contrast.

Low-cost (ZrCu)50-xTax high temperature shape memory alloys showing excellent shape memory effect

ZrCu-based alloys, as one of the most potential high-temperature shape memory alloys, show quite high martensitic transformation temperature, relatively low price for the raw materials, and good casting fluidity. In this work, the martensitic transformation (MT) and shape memory effect of (ZrCu)50-xTax high-temperature shape memory alloys were systematically investigated. Both X ray diffraction and SEM backscattered electron image demonstrated the coexistence of the main phase monoclinic martensite phase and the second phase Ta2Cu. SEM results also revealed that increasing Ta content resulted in a larger volume fraction of Ta2Cu phase. Differential scanning calorimetry results showed that the MT temperatures remarkably increased with Ta addition. The ductility of the (ZrCu)50-xTax alloys was reduced to some degree with increasing Ta content. The shape memory effect was improved significantly, in which (ZrCu)98Ta2 alloy showed the 6.19% maximum recovery strain during 8% pre-strain under compression at 25 ​°C.

Precipitation Kinetics of M23C6 Carbides in the Super304H Austenitic Heat-Resistant Steel

The precipitation kinetics of M23C6 carbides in Super304H and TP304H steels were investigated using the selective-etching method, SEM backscattered electron images and Image-Pro-Plus 6.0 software. Precipitation–temperature–time (PTT) diagrams of M23C6 carbides in the as-received Super304H (fine grains), coarsened Super304H (coarse grains) and TP304H (coarse grains) steels all show the typical C-shaped character with nose temperature range from 800 to 850 °C. Compared with the TP304H steel, the same trend is found of the PTT curve of M23C6 carbides for both kinds of Super304H steels, but their start lines move to the right and finish lines to the left. The preferential formation of Nb(C,N) phase at grain boundaries in the Super304H steels inhibited the nucleation of M23C6 carbides in the early stage of precipitation, causing the right shift of the start line of PTT curve. The main reason for the left shift of the finish line of the two Super304H steels was the quicker growing and coarsening rate of M23C6 in the later precipitation stage due to their higher C content than in TP304H. For the difference in PPT curves between the two grain sizes of the Super304H steel, the lower diffusion rate of atoms in the coarse-grained Super304H steel may explain its righter finish line than the fine-grained counterpart, while the reason for its lefter start line is due to the higher solute segregation along coarse-grained boundaries.

Diagenetic F-rich ferroan calcite and zircon in the offshore Scotian Basin, eastern Canada: Significance for understanding thermal evolution of the basin

In the Scotian Basin, offshore eastern Canada, an unusual combination of high heat flow in the Cretaceous and the abundance of halite has resulted in unusual diagenetic minerals such as sphalerite. The Newburn H-23 well is the most distal well in the basin with good core samples and has two previously unknown diagenetic mineral occurrences: fluorine-rich ferroan calcite and diagenetic zircon. This study uses SEM backscattered electron images and EDS analyses, EMP WDS mineral analyses and Raman spectroscopy to determine mineral chemistry and textures to investigate the diagenetic and thermal significance of these minerals. Late diagenetic Fe-calcite contains 1–2.5 wt% fluorine, mostly from adsorption, but rarely as small fluorite crystals. Fluoride is also adsorbed on the surfaces of some framework minerals and chlorite. Fluoride was transported in highly saline formation brines derived from the Argo salt Formation. Zircon grains, 20–40 μm in size, have crystal outlines that are straight adjacent to pores, partially lobate filling porosity, and cross cutting other grains: these may be diagenetic. Some zoned detrital zircon grains show 1–3 μm wide diagenetic outgrowths. Neoformation of diagenetic zircon requires temperatures of >250 °C. Transport of zirconium is favored by ligands in low-pH solution, principally fluoride and phosphate anions, with zirconium mobilized during the alteration of metamict detrital zircon under low-grade metamorphic conditions. The presence of diagenetic sphalerite and the documented mid-Cretaceous thermal event in the Scotian Basin indicate conditions that could have been suitable for the formation of diagenetic zircon in this well. Suitable geological conditions for such diagenetic formation of zircon will be found in a subsiding rift basin with early evaporites that are affected by a subsequent phase of volcanism due to new rifting or subduction.

Precise Pb baddeleyite geochronology by the thermal extraction-thermal ionization mass spectrometry method

The ability to easily obtain precise (~0.1%) age determinations on mafic rocks can facilitate identification of contemporaneous magmatic events across continents and hence open new avenues of research investigations related to large scale mantle processes. We present high precision Pb age determinations on baddeleyite (ZrO2), a common accessory mineral in mafic rocks using the recently developed thermal extraction-thermal ionization mass spectrometer (TE-TIMS) procedure for dating of zircon. In order to constrain the conditions for thermal extraction of Pb from baddeleyite, a sequence of SEM back-scattered electron images were acquired along with energy-dispersive X-ray spectroscopy spot analysis of baddeleyite grains embedded in silica beads at progressively increasing temperature between 1200 and 1590°C. Replicate analyses of twelve preheated (at 1250°C) and silica embedded baddeleyite grains from the Paleoproterozoic Phalaborwa carbonatite using this procedure have yielded a 207Pb–206Pb weighted mean age of 2060.3±0.4Ma, consistent with previously reported 207Pb–206Pb ages for this carbonatite occurrence determined by the conventional U–Pb isotope dilution-thermal ionization mass spectrometry (ID-TIMS) technique. Fourteen baddeleyite fractions from a large Paleoproterozoic N–S striking mafic dyke swarm in the Dharwar craton yielded a 207Pb–206Pb weighted mean age of 2215.9±0.3Ma, also consistent with previously determined conventional ages. All data were corrected for mass fractionation of 0.18%/amu as determined previously on zircon. Both data sets scatter outside measurement errors, implying an external 2 sigma error of 0.055% in the case of the carbonatite and 0.043% for the mafic dyke, which we suggest represents the reproducibility of the fractionation correction. Our results demonstrate that thermal extraction 207Pb–206Pb ages are comparable with the conventional U–Pb ages in both accuracy and precision. This procedure does not need ultra-clean laboratory conditions (<1pg procedure blanks), a prerequisite for conventional high precision U–Pb geochronology, and hence can be easily practised in most TIMS isotope geochemistry laboratories.

SEM-backscattered electron imaging and image processing for evaluation of unhydrated cement volume fraction in slag blended Portland cement pastes

Proper parameters for image taking and minimum field number for image processing were investigated to evaluate volume fraction of unhydrated cement(UHC) in both neat cement paste and slag blended cement paste. Our research suggested that magnification 250× was sufficient for the two pastes, and accelerating voltage should be set as 15 kV and 20 kV for BSE image taking of neat cement paste and slag blended cement paste respectively; the minimum field number increased while the total imaging area stayed the same as the magnification increased within certain statistical bias.

Cover

Cover: SEM backscattered electron image showing an aggregate of meteoritic ablation spheres from the Transantarctic Mountains. For details see the article by van Ginneken et al. on p. 1738. (Image courtesy of Matthias van Ginneken)

Experimental Study for Cement Microscopic Property by Backscatter Scanning Technique

As the technology develops, digital image processing technology has become a necessarily new method for studying particle property and particle analysis. This method helps researchers to gain deeper understanding of microstructure and powder particle property. In the paper work, the characteristics of different ingredients of cement microscopic property are analyzed with the technology of SEM backscattered electron image. Based on experimental analysis, microstructure and all kinds of cement characteristic parameters are analyzed quantificationally. It is seen that this method in the paper effectively and comprehensively computers the microscopic characteristics parameter of powder.

Quantitative Analysis and Research of Cement Powder Mixing Based on Image Processing

As technology develops, digital image processing technology has become a new method for studying particle property and a necessary means for particle analysis. This method helps researchers to gain deeper understanding of microstructure and property of powder particles. In the paper, samples are composed with two kinds of cement powders: cement clinker and slag powder, which have different characteristics and shapes. The paper analyzed the characteristics of different ingredient and mixing evenness degree of cement sample by using the technology of SEM backscattered electron image and the theoretical calculation model. On the basis of experimental analysis, a new method was proposed to quantitatively analyze evenness degree for the cement mixture basing on image processing, which adopts the advanced microscopic analysis technology. This new method is tested by experiments, and results prove that this method is effective and is superior to other methods.

Cover Picture: Thermal Conductivity Imaging of Thermal Barrier Coatings (Adv. Eng. Mater. 7/2005)

The cover shows a SEM backscattered electron image of a cross-sectional thermal barrier coating (TBC) system on the bottom and its correspondent thermal conductivity image on the top. The thermal conductivity image was collected using a novel time-domain thermoreflectance technique with a femtosecond laser and it reveals the conductivity variation in the TBC system, especially in the bond coat. The thermal conductivity value of each point/pixel has an accuracy of 8 % and a spatial resolution of ∼ 3 mm. More on thermal condcutivity imaging can be found in the article by J.-C. Zhao et al. on page 622.

A study on kinetics of Cr xC-coated high-chromium steel by thermo-reactive diffusion technique

There are a lot of technologically interesting characteristics of chromium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation- and corrosion-resistant coating layer on the steel substrates. In the present study, kinetic study of chromium carbide coating of AISI D2 steel coated by pack method at the temperature of 1223, 1273 and 1323 K for 1–4 h was realized. The presence of phases Cr 7C 3 and Cr 3C 2 formed on the surface of steel substrates were confirmed by X-ray diffraction analysis. Cross-sectional observation of optical and SEM back-scattered electron images (SEM-BEI) showed that chromium carbide layer formed on the steel substrates were smooth and compact. The hardness of chromium carbide layer is 1850±35 HV 0.025. The kinetics of chromium carbide coating by pack method showed that a parabolic relationship between carbide layer thickness and treatment time, and activation energy for the process is 278 kJ/mol. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of chromium carbide layer variation and to establish some empirical relationships between process parameters and chromium carbide layer thickness.

Grain-scale variations in trace element composition of fluid-altered zircon, Acasta Gneiss Complex, northwestern Canada

SEM back-scattered electron images of zircon separates from a 2.9 Ga granitic dyke from the Acasta Gneiss Complex, Slave Province, reveal primary igneous oscillatory zoning which is transgressively overprinted by irregular alteration domains. Electron microprobe analyses show that altered zircon domains are depleted in Zr and Si relative to unaltered zircon while retaining a constant Zr/Si ratio. SIMS trace element analyses indicate that LREE are preferentially enriched in the altered domains. Altered zircon contains elevated concentrations of Ba (up to 580 ppm), Ca (up to 2% weight of the element) and common Pb (>50 ppb). The presence of LREE, Ca, Ba and common Pb in the zircons is interpreted to be the result of secondary alteration by an aqueous fluid, and not by primary incorporation during crystallization. We propose that the alteration-related elements are located in amorphous zircon domains.

Computer Simulations of Heterogeneous Reactions Controlled by Diffusion in Modified Aluminide Coatings on a Nickel-Based Superalloy

Materials used in high temperature applications must possess both strength and corrosion resistance. The increase in operating temperatures of industrial energy systems and gas turbines, often coupled with the decrease in fuel quality being employed, has led to the extensive use of coatings capable of providing improved service life. The application of diffusion aluminide coatings on nickel based superalloys has beneficial influence on the high temperature performance of gas turbines operating at elevated temperatures. Platinum addition to basic aluminide coatings significantly improves the oxidation resistance of these coatings [1]. Evidence has now emerged from the oxidation and hot corrosion studies [2] that the high temperature corrosion (HTHC) performance of nickel based superalloys can be improved by the combined addition of platinum and rhodium to nickel aluminide coatings. In the Figure 1, a comparison of the SEM backscattered electron image of the corrosion products of the uncoated MAR M002, Pt-Aluminide, PtRh-Aluminide coatings after 100 h hot corrosion tests at 1173 K is presented. The protective capability of the aluminide coatings is conferred by the ability of the $-NiAl layer to provide aluminum to maintain an Al2O3 based scale at the surface. It is believed that the incorporation of Rh with Pt increases the stability of $-NiAl [3]. This type of coating is very resistant to oxidation owing to its ability to form a slow-growing and adherent oxide, Al2O3 [4,5]. However prolonged oxidation eventually process leads to the depletion of aluminium in the vicinity of the coating/scale interface decreasing the ability $-NiAl to reform the protective -Al2O3. In this work we will show the possibility of adopting a theoretical approach for describing the complex processes occurring in alloy/coating systems induced by reactions at coating/gas interface, e.g., oxidation, sulphidation or other complex processes like hot corrosion. The mathematical model for interdiffusion in multi-component open systems which allows for the description of a wide range of processes (e.g., processes stimulated by reactions at interfaces) is presented. The inverse problem of interdiffusion and the method which permits calculation of the intrinsic diffusivities, for an arbitrary number of components in a system, is also presented. This approach has been used to calculate the effective intrinsic diffusivities of the elements in Pt modified $-NiAl on MAR M002 superalloy. Subsequently, the evolution of the components’ concentration in oxidized Pt modified $-NiAl/MAR M002 system is presented and compared with the experimental results. Figure 1. Comparison of the SEM backscattered electron image of the corrosion products of the uncoated MAR M002, Pt-Aluminide and Pt-Rh-Aluminide coatings after 100 h hot corrosion test at 1173 K. Generalized Model of Interdiffusion This model follows Darken’s postulate [6] that the total mass flow is a sum of the diffusional and drift flows only. The equations of mass conservation (continuity equations), the appropriate expressions describing the fluxes, the postulate of constant molar volume of the system allow for a complete quantitative description of the diffusional transport process. Some aspects of this model for the closed system has been already published [7]. The formulation of the interdiffusion problem for the multicomponent open system and constant intrinsic diffusivities are presented bellow. Data: 1) molecular masses of the elements: M1, . . . , Mr (g mol ), where r denotes the number of components; 2) constant intrinsic diffusivities: D1, . . . , Dr (cm 2 s), which in general, may depend on composition, 3) initial position of the right end of the system (its right border): 7, 4) time of the process duration: t, 5) initial distribution of the elements:

Techniques to quantitatively study the microfabric of soils

Several image processing and analysis techniques, which are described individually elsewhere, are combined to provide powerful new methods for studying the mineralogy and microfabric of soils. The analysis begins with a multi-spectral classification of SEM back-scattered electron images and X-ray maps, followed by particle size routines on the segregated mineral grains. Masking these large grains then permits intensity gradient techniques to be used to study orientation patterns within the matrix. Finally, segmentation of the orientation image into domains of similar alignment shows how the orientation of the matrix relates to that of the skeleton mineral grains. Apart from a little operator assistance in the initial classification, the separate techniques may be run automatically in batch mode with no subsequent operator intervention. Thus, the problems of subjectivity, met within many other techniques, are minimized. Two contrasting soil samples are used to illustrate the technique and the results illustrate the advantage of the objective measurements over qualitative interpretation. In one sample, there is strong alignment of the matrix orthogonal to the direction of alignment of most of the mineral grains. Examples of several applications are given and other possibilities are discussed.

Grain boundary microcracking of granitic rocks from the northeastern region of the Atotsugawa fault, central Japan: SEM backscattered electron images : Engng Geol V30, N2, April 1991, P221–235

Abstract Backscattered electron (BSE) images from granitic rocks gathered in and around the northeastern region of the Atotsugawa fault in central Japan were examined by scanning electron microscopy. BSE images reveal that grain boundary microcracking strongly depends upon the mineralogy of the two adjacent grains. At grain boundaries, there are six possible different mineral pairings of the three main constituent minerals (quartz, plagioclase and K-feldspar) found in granitic rocks. Each grain boundary can be separated into one of two types; a partially to entirely open grain boundary or a closed grain boundary. Grain boundaries can be classified by their decreasing sense of openness: (1) quartz/feldspars (plagioclase and K-feldspars); (2) quartz/quartz; (3) piagioclase/plagioclase; (4) K-feldspar/plagioclase; and (5) K-feldspar/K-feldspar boundaries. Microcracks in grain boundaries are commonly found in a wide zone offset of the shattered zone of the fault. The number and types of partially to entirely open grain boundaries increase with proximity to the fault, following the above sequence. The number and types can be used to detail the special zoning of rock masses around a fault.

Grain boundary microcracking of granitic rocks from the northeastern region of the Atotsugawa fault, central Japan: SEM backscattered electron images

Backscattered electron (BSE) images from granitic rocks gathered in and around the northeastern region of the Atotsugawa fault in central Japan were examined by scanning electron microscopy. BSE images reveal that grain boundary microcracking strongly depends upon the mineralogy of the two adjacent grains. At grain boundaries, there are six possible different mineral pairings of the three main constituent minerals (quartz, plagioclase and K-feldspar) found in granitic rocks. Each grain boundary can be separated into one of two types; a partially to entirely open grain boundary or a closed grain boundary. Grain boundaries can be classified by their decreasing sense of openness: (1) quartz/feldspars (plagioclase and K-feldspars); (2) quartz/quartz; (3) piagioclase/plagioclase; (4) K-feldspar/plagioclase; and (5) K-feldspar/K-feldspar boundaries. Microcracks in grain boundaries are commonly found in a wide zone offset of the shattered zone of the fault. The number and types of partially to entirely open grain boundaries increase with proximity to the fault, following the above sequence. The number and types can be used to detail the special zoning of rock masses around a fault.

Dynamic observation of ferromagnetic domains by using line-sampling strobo SEM.

Recently the observation technique using SEM backscattered electron images becomes important in analyzing core-loss mechanisms of silicon steels. Particularly the high voltage SEM is expected as auseful mean for observing glass-coated products. We have developed a new technique called “line-sampling stroboscopy” which enables the dynamic SEM observation for the periodic phenomena driven at line frequencies. Combining these techniques, the dynamic magnetization process in silicon steel products can be observed in practical drive conditions.