Backscattered Scanning Electron Research Articles

ELECTRON MICROSCOPY SIGNS OF NORMAL AND DYSFUNCTIONAL RAT AORTIC ENDOTHELIUM

HighlightsA fundamental distinguishing feature of normal endothelial cell morphotypes from pathological ones is their preserved orientation along the direction of blood flow in the absence of cytoplasmic or membrane defects.The main characteristics of dysfunctional endothelial cells include a spherical shape (indicating a loss of cellular orientation along the direction of blood flow), the presence of large vacuoles within the cell, cytoplasmic vacuolization, impaired plasma membrane integrity, reduced contrast between the nucleus and cytoplasm, and partial detachment of the endothelial cell from the basement membrane.The condition of organelles (mitochondria, Golgi complex, and endoplasmic reticulum) and impaired basement membrane integrity are not sensitive or specific markers of dysfunctional endothelium compared to the aforementioned features Aim. To analyze the electron microscopic features of normal and dysfunctional endothelium using the descending aorta of rats (characterized by laminar blood flow).Methods. The study was conducted on 5 male Wistar rats (age ≈ 6 months, body weight ≈ 500 g). The extracted aortas were chemically fixed in 2.5% glutaraldehyde, post-fixed in 1% osmium tetroxide solution with 1.5% potassium ferrocyanide, incubated with 1% thiocarbohydrazide, stained in 2% aqueous osmium tetroxide solution, contrasted in 1% phosphotungstic acid, stained with 2% gadolinium triacetate, dehydrated in ascending concentrations of ethanol, isopropanol, and acetone, embedded in a mixture of acetone and epoxy resin, and then in pure Araldite 502 epoxy resin, followed by its polymerization. After grinding and polishing, the aorta samples were contrasted with lead citrate, coated with carbon, and visualized using backscattered scanning electron microscopy.Results. Electron microscopic analysis identified three main morphotypes of normal endothelial cells: 1) elongated shape along the direction of blood flow and an elongated nucleus; semicircular shape with an oval, round, kidney-shaped, or polymorphic nucleus with a less pronounced but clearly visible orientation along the direction of blood flow; 3) large nucleus with an even less pronounced but visible orientation along the direction of blood flow. The basement membrane of normal endothelial cells often contained various defects. Dysfunctional endothelium also exhibited several morphotypes, characterized by different combinations of the following features: spherical shape and loss of cell orientation along the direction of blood flow, presence of large vacuoles within the cell, cytoplasmic vacuolization, disruption of plasma membrane integrity, reduced contrast between the nucleus and cytoplasm, and partial detachment of the endothelial cell from the basement membrane. However, pronounced changes in the structure of organelles or the adjacent basement membrane were often not observed in dysfunctional endothelial cells.Conclusion. The preservation of orientation along the direction of blood flow indicates a normal phenotype of endothelial cells in the absence of other signs of dysfunctional endothelium (vacuoles within the cytoplasm, cytoplasmic vacuolization, disruption of plasma membrane integrity, reduced contrast between the nucleus and cytoplasm, and partial detachment of the endothelial cell from the basement membrane).

Experimental assessment of freeze-thaw deterioration in compression-cast fiber-reinforced concrete

An increasing number of critical infrastructures are built in cold and perma-frost regions, resulting in higher susceptibility to damage due to freeze-thaw (F-T) cycles. This paper assesses the mechanical properties and F-T damage evolution of compression-cast fiber-reinforced concrete (CCFRC) through rapid F-T cycling tests. Nine types of fiber-reinforced concrete (FRC) are experimentally investigated through 144 cubic and 39 prismatic specimens. The main parameters considered in the tests include the casting pressure applied during the compression casting procedure (between 0 and 15 MPa), type of the internal added fibers (polypropylene, end-hooked steel, or their combination), fiber content, and number of F-T cycles. The effects of these parameters on the failure modes, strength degradation rates, deterioration evolution, frost resistance durability, microscopic behavior, and F-T resistance of FRC specimens, are examined in detail. The microscopic performance of different specimens is further investigated using the X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and backscattered scanning electron (BSE) tests. Based on the test results, it is shown that: (i) compared with the mass loss rate, the relative dynamic elastic modulus can be a more suitable index to assess the F-T resistance of FRC; (ii) compression casting and addition of fibers can effectively enhance the F-T denudation resistance of CCFRC; (iii) compression casting reduces the compressive and flexural strength degradation rates of CCFRC, but at the expense of more brittle behavior; and (iv) compression casting and use of the mixed polypropylene and end-hooked steel fibers can effectively delay the F-T cycling induced damage, reduce porosity and internal defects, and enhance the micro-structural behavior and F-T resistance of CCFRC. F-T deterioration prediction models are also proposed and shown to provide accurate and effective representation of the behavior of CCFRC materials.

Pore structures and deterioration mechanism of concrete after cryogenic freeze-thaw cycles: Effects of moisture contents and aggregates

With the popularization of all-concrete liquefied natural gas (ACLNG) storage tanks, the performance of concrete after cryogenic exposure (−170 °C) has garnered significant interests from researchers. To investigate the damage mechanism of pore structures and the corresponding influencing factors, this study involved subjecting concrete with two moisture contents, namely air-dried and water-saturated to 10 cryogenic freeze-thaw cycles (CFTCs) to assess the variation laws in strengths. The mercury intrusion porosimetry (MIP), nitrogen adsorption and desorption (NAD), scanning electron microscopy (SEM), backscattered scanning electron (BSE) and low-temperature calorimeter (LTC) methods were employed to evaluate pore characteristics and the phase transition of pore water. Furthermore, pore structures were conducted using fractal dimensions based on the Zhang model and Frenkel-Halsey-Hill model. Findings indicate that there is a more pronounced reduction in strengths after 10 CFTCs in water-saturated state. Following cryogenic exposure, the porosity of paste increases from 4.97 % to 5.58 % and 7.04 %, and the porosity of mortar rises from 6.05 % to 7.20 % and 8.76 %, respectively. Aggregates in mortar contribute to more severe damage to pore structures in cryogenic circumstances, particularly capillary and macropores. The nucleation of pore water and ice contents are greatly influenced by moisture contents, and the frozen fraction is only 84.3 % in air-dried state. The destruction of gel pores is attributed to the continuous multi-order phase transition in water-saturated state. This work conducts a thorough cross-scale analysis of the pore structure in both paste and mortar, and it quantitatively evaluates the phase transition of pore water under cryogenic conditions using the LTC method. Ultimately, the influence of moisture contents and aggregates on the pore structures are evaluated, which provides deeper insights into the deterioration mechanism of concrete following cryogenic exposure.

Exploring the heat capacity and magnetocaloric behaviors of rare-earth based multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17‐xSix alloys

The rare–earth based multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17−xSix (x = 0–0.6) alloys were fabricated by conventional arc melting following the standard annealing and quenching processes. The prepared alloys were characterized by X-ray diffraction (XRD), backscattered scanning electron (BSE) microscope, energy dispersive X-ray (EDX) spectroscopy, magnetization, and heat capacity measurements. Combination of Rietveld refinement of XRD patterns, EDX/BSE analyses confirm the formation of stable rhombohedral Th2Zn17 type crystal structure with R-3 m space group in all studied samples. The investigated samples experience second-order phase transition as confirmed through phenomenological universal scaling analysis. The magnetic entropy change (−ΔSM) and associated relative cooling power (RCP) values for all compositions were found in the range of 1.1–1.4 Jkg−1K−1 and 55–66 Jkg−1 under magnetic field change (ΔH) of 0–1 T. The ΔSM curves as a function of temperature exhibit a wide working temperature range (δTFWHM) over 40 K for all studied compositions. The performance-cost ratio − ΔSM/cost and RCP/cost values are estimated to be 0.1 JK−1$−1 and 5.0 J$−1, respectively. In particular, a large adiabatic temperature change of 7.36 K and 8.09 K was achieved for x = 0.2 and x = 0.4, respectively, at low ΔH= 0–1 T. The better performance-cost ratio and good magnetocaloric properties with near-zero magnetic hysteresis loss may make these alloys promising candidates for magnetic refrigeration.

Influence of supplementary cementitious materials on ITZ characteristics of recycled concrete

The poor performance of recycled aggregate concrete (RAC) limits its application on wide filed. This paper attempted to study the influence of fly ash (FA), slag powder (SP) and silica fume (SF) on the performance of RAC from a microscopic point of view. The compressive strength and chloride resistance were evaluated when FA, SP and SF were used. Then the evolution of ITZ performance with different admixtures was observed by backscattering scanning electron (BSE) microscopy image, Mercury intrusion porosimetry (MIP), microhardness and so forth.Results indicate that, (1) the supplementary cementitious materials (SCMs) can improve the compressive strength and chloride penetration resistance of RAC, with a certain dosage range for different SCMs; (2) the SCMs can refine thepore structure of ITZs for RAC, increase the microhardness and modify the phases around ITZs; (3) the three SCMs both fill the cement paste voids and promote the compactness of ITZ structure by reacting with calciumhydroxide to generate CSH gels, which in turn enhance the macroscopic performance of RAC. The results of this research can provide a meaningful reference for further study of SCMs to improve the ITZs structure of RAC.

Hydration heat and microstructure of SCM-blended cement under semi-adiabatic conditions: Effect of initial temperatures

To reduce the carbon emission of cement industry, supplementary cementitious materials (SCM) are widely used to replace cement. The aim of this study was to illustrate the effect of SCM on the hydration kinetics and microstructure of cement under semi-adiabatic conditions. Two mineral admixtures were used, including granulated blast furnace slag (GBFS) and fly ash (FA). Various properties related to the hydration of the cement were characterised, including peak exothermic hydration, total exothermic hydration, hydration temperature rise and degree of hydration. Results show that the effect of FA or GBFS incorporation on the hydration and microstructure of the cement depends not only on the dosage, but also on the initial temperature (15 °C, 25 °C and 35 °C). X-ray diffraction patterns (XRD), Back-Scattered Scanning Electron (BSEM) and Nuclear Magnetic Resonance (NMR) analysis further confirm that FA and GBFS have a significant effect on the exotherm of hydration, due to the increased initial temperature, the hydration of the cement under semi-adiabatic conditions is accelerated, as well as the fuller chemical activity of the SCM, which leads to a dense and less porous structure and enhanced mechanical properties. Temperature measurements in cement samples were monitored by means of a self-developed semi-adiabatic device and the time-evolution of the degree of hydration was determined.

Application of Thermochemistry and X-ray Semi-Quantitative Phase Analysis in Forsterite Powder Synthesis by Solid State Reaction of Magnesium Oxide and Mg-Chlorite

ABSTRACTIn this paper, high purity forsterite powder with anorthite grain boundary has been synthesized by solid state reaction of industrial grade magnesium oxide and Mg-chlorite at 1100°C. ASTM C547 and X-ray powder diffraction (XRD) were used for chemical and phase analysis of raw materials. For microstructural analysis of prepared specimens, XRD and back scatter scanning electron microscopy (BS-SEM) were used. BS-SEM and elements mapping show the distribution of Mg, Si and O elements in grains, and point analysis of these elements shows the portion of atomic percent as forsterite. The detected elements in grain boundary are Si, Al, Ca and O; and based on XRD pattern of the specimens, the anorthite phase is detected. MAUD software was used for semi-quantitative analysis of phases based on Rietveld method in TC specimen, the amounts of detected phases are 15.6 wt% free periclase and 84.4 wt% forsterite that are very close to calculated amounts for 12.89 wt% free periclase and 87.11 wt% forsterite. The amount of forming phases strongly depends on well mixing, soaking time and temperature, and reactivity of raw materials.

On the geometric relationship between deformation microstructures in zircon and the kinematic framework of the shear zone

We present novel microstructural analyses of zircon from a variety of strained rocks. For the first time, multiple plastically deformed zircon crystals were analyzed in a kinematic context of the respective host shear zones. Our aim was to derive how the orientation of zircon grains in a shear zone affects their deformation, based on careful in situ observations. For sampling, we selected zircon-bearing rocks that were deformed by simple shear. Samples covered a range of P–T conditions and lithologies, including various meta-igneous and meta-sedimentary gneisses.Microstructural analyses of zircon crystals in situ with scanning electron backscatter diffraction mapping show strong geometrical relationships between orientations of: (i) the long axes of plastically deformed zircon crystals, (ii) the crystallographic orientation of misorientation axes in plastically deformed zircon crystals and (iii) the foliation and lineation directions of the respective samples. We assume that zircon crystals did not experience post-deformation rigid body rotation, and thus the true geometric link can be observed. The relationships are the following: (a) plastically deformed zircon crystals usually have long axes parallel to the mylonitic foliation plane; (b) crystals with <c> axes oriented at an angle>15° to the foliation plane are undeformed or fractured.Zircon crystals that have <c> axes aligned parallel or normal to the stretching lineation within the foliation plane develop misorientation and rotation axes parallel to the [001] crystallographic direction. Zircon grains with the <c> axis aligned at 30–60° to the lineation within the foliation plane often develop either two low Miller indices misorientation axes or one high Miller indices misorientation axis. Host phases have a significant influence on deformation mechanisms. In a relatively soft matrix, zircon is more likely to develop low Miller indices misorientation axes than in a relatively strong matrix.These relationships are independent of zircon's grain size and shape, and reflect the strong geometric control of the macroscopic kinematic rotation axis on the crystal-plastic deformation behavior of zircon and on the geometry of its slip systems. We describe previously unknown rheological and crystallographic properties of zircon, which suggest a tool for deriving an orientation of the plastically deformed zircon crystals with respect to the associated foliation and stretching lineation. Additionally, relationships between zircon deformation microstructures and the macroscopic kinematic framework have implications for zircon geochronology. If deformation events result in zircon distortion and, as a consequence, partial or complete resetting of the zircon isotopic system, the age of deformation can be accurately dated.

Heterogeneous Microstructure and Distribution of Trace Elements in Coral &amp;lt;i&amp;gt;Stylophora pistillata&amp;lt;/i&amp;gt; Nursed in the Phosphate Loading Berth Site in the Gulf of Aqaba

Cultured Stylophora pistillata in Phosphate Loading Berth (PLB) sites in the Jordanian Gulf of Aqaba was investigated using Back-Scatter Scanning Electron (BSE) microscopy and Energy-Disperse X-ray (EDX) to determine trace elements and calcium concentrations’ distribution within the micrometer scale. Ca, C, and O in addition to six trace elements (Mg, Sr, S, Cl, Ni, and Na) were mapped within the sample cross section. Samples from the PLB were as expected poorly mineralized as previously reported and showed mineralization heterogeneity in the micrometer length scale in the BSE image. In four selected positions within the cross sections, Ca concentration found to range between 0.44 - 1.80 wt% in low-mineralized regions and between 3.99 - 4.66 wt% in mineralized regions. The average calcium concentrations were in accordance to previous study; about 10% of the Ca existed in the same coral species from other coastal sites in the Gulf of Aqaba. This could be attributed to the role of phosphate in inhibition of calcification and enhancement of photosynthesis. Amounts of trace elements in lower Ca concentration positions within the cross section were relatively very low except for chlorine, whereas positions with higher Ca contained amounts of Na and Sr. This study reports remarkable heterogeneity in mineral distribution within the microstructure of the coral Stylophora pistillata under phosphate pollution stress.

Thermally induced interfacial reactions in Ti/Pd/Si and Ti/Pd/Si(As) ternary systems

In this work, we investigate the effect of temperature on the ternary systems Ti/Pd/Si and Ti/Pd/Si(As) and the phases formed at the interfaces of each system. For this purpose, thin layers of palladium and titanium were evaporated successively on monocrystalline silicon substrates of (111) orientation and also the same system with the silicon substrate being previously implanted with arsenic ions at a flux of 1, 5.1016 at/cm2 and an accelerating energy of 100 keV. These samples were then thermally treated, in a conventional oven under vacuum, in the temperature range between 700 and 950 °C for 30 min for each annealing temperature. The obtained samples were analyzed by several characterization techniques, namely Rutherford backscattering spectroscopy, X-ray diffraction and scanning electron microscopy.

Mineralogy texture and chemistry of the Ellicott meteorite using scanning electron microscope and energy disperse spectroscopy (SEM/EDS)

Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) and Raman spectroscopy have been used to determine the chemistry and mineral components of Ellicott meteorite. Mineral phases and interstitial matrix in the meteorite slab were detected using backscattered electron mode (BSE) and scanning electron microprobe (SEM) and were assessed from atomic proportions of constituent elements, obtained by the EDS analysis. SEM/EDS and Raman shift analyses of mineral phases showed that Ellicott meteorite is characterized by the predominance of Fe-rich (Fe, Ni) alloy kamacite and Ni-Co-rich magnetite. The Iron-nickel phosphide minerals that are called schreibersite and rhabdites along with rare gold have been detected within the kamacite groundmass of meteorite. The presence of Neumann lines, which appear as fine parallel lines running in (up to) four directions, indicates impact with another body. These lines are caused by twinning due to the postconsolidation compression. The chemistry, particularly the lesser content of Ni and texture of unusual abundance ribbons of the iron-phosphide rhabdites and schreibersite where the Widmanstatten texture disappears after the etching by nitric acid, suggests that the Ellicott meteorite is an iron meteorite, hexahedrite type, IIG group.

Reduction mechanism of titanomagnetite concentrate by hydrogen

Titanomagnetite concentrate was reduced by H2–Ar gas mixtures in a laboratory fixed bed reactor at the temperatures from 1123 to 1323K. The effects of reductive conditions on the reduction and metallization degrees were studied, including reduction temperature, reduction time and hydrogen content. And the characteristics of reduced samples were analyzed by X-ray diffraction (XRD), backscattered scanning electron (BSE) and energy dispersive spectrometer (EDS). Results have shown that both the reduction and metallization degrees increased with the increase of temperature and hydrogen content. Due to the low iron oxides content and the high impurities content such as magnesium oxide that baffled the reduction of Fe2+ in TTM concentrate, the reduction degree of TTM concentrate is lower than that of TTM ironsand at the same reduction condition. Above 1123K, the reduction is mainly controlled by interfacial chemical reaction in the whole reduction process and the reduction path is suggested as follows:Fe3−xTixO4→x+y−1FeO+Fe4−2x−yTixO4−y→x+y−1Fe+Fe4−2x−yTixO4−y→3−xFe+xTiO20<y<4−2x,x=0.27±0.02

Isothermal Transformation of Wustite for Low Carbon Micro-Alloyed Steel

The isothermal transformation of wustite (FeO) in the range of 650~350°C was studied using Gleeble 3500 thermal simulated test machine, electron back-scatter diffraction (EBSD) and scanning electron microscopy (SEM). A wustite layer was initially formed by oxidizing low carbon micro-alloyed steel in air at 880°C for 20 seconds. The layer was then isothermally annealed at 650-350°C in argon for up to 10000 seconds. The transformation of FeO was comprised by a proeutectoid reaction and a eutectoid reaction. FeO initially transformed to Fe3O4 by proeutecioid reaction and then the retained FeO transformed to lamellar mixture Fe+Fe3O4 by eutectoid reaction. The proeutectoid and eutectoid reactions both followed a C-curve trend and the nose temperatures were 475°C and 425°C, respectively. An isothermal transformation (IT) diagram was summarized based on our results.

Interface effects on helium retention properties of ZrN/TaN nano-multilayers

In this paper, ZrN/TaN nano-multilayers are fabricated in mixing atmosphere by radio frequency magnetron sputtering. The phase structures, He-related defects, helium content and cross-section morphologies of ZrN/TaN nano-multilayers are characterized by X-ray diffraction, slow positron beam analysis, enhanced proton backscattering spectrome and scanning electron microscope, respectively. The results show that the interface of ZrN/TaN nano-multilayer with 30 nm modulation period is stable and could resist the damage of helium even annealed at 600℃. The He retention rate of ZrN/TaN nano-multilayer with 30 nm modulation period can reach up to 45.6%.

Nano/Ultrafine Structured AA1100 by ARB Process

In this study, the effect of accumulative roll bonding (ARB) process at room temperature and without any annealing among cycles on the microstructure and mechanical properties of a commercially pure aluminum AA1100 was investigated. Microstructural characterizations were done by electron backscattering diffraction (EBSD) and scanning electron microscopy (SEM). It was observed that ARB is a promising process for manufacturing nano/ultrafine grained structures in aluminum sheets. The four cycle accumulative roll bonded (ARBed) sample had an almost RD// ⟨ 111 ⟩ texture, while after the sixth cycle it had a strong {001} ⟨ 111 ⟩ ∼ {112} ⟨ 111 ⟩ copper texture. The tensile strength, elongation, and hardness of the ARBed samples increased with the number of ARB cycles. But their variation was not similar. Observations revealed that the failure mode in the ARBed AA1100 aluminum was a shearing ductile rupture with elongated shallow shear dimples.

The Otto Aufranc Award: Demineralized Bone Matrix Around Porous Implants Promotes Rapid Gap Healing and Bone Ingrowth

Noncemented revision arthroplasty is often complicated by the presence of bone implant gaps that reduce initial stability and biologic fixation. Demineralized bone matrix has osteoinductive properties and therefore the potential to enhance gap healing and porous implant fixation. We determined at what times and to what extent demineralized bone matrix promotes gap healing and bone ingrowth around a porous implant. We inserted porous titanium implants into the proximal metaphyses of canine femora and humeri, with an initial 3-mm gap between host cancellous bone and implants. We left the gaps empty (control; n = 12) or filled them with either demineralized bone matrix (n = 6) or devitalized demineralized bone matrix (negative control; n = 6) and left them in situ for 4 or 12 weeks. We quantified volume healing of the gap with new bone using three-dimensional micro-CT scanning and quantified apposition and ingrowth using backscattered scanning electron microscopy. The density of bone inside gaps filled with demineralized bone matrix reached 64% and 93% of surrounding bone density by 4 and 12 weeks, respectively. Compared with empty controls and negative controls at 4 and 12 weeks, gap healing using demineralized bone matrix was two to three times greater and bone ingrowth and apposition were up to 15 times greater. Demineralized bone matrix promotes rapid bone ingrowth and gap healing around porous implants. Demineralized bone matrix has potential for enhancing implant fixation in revision arthroplasty.

Effect of limestone powder on microstructure of concrete

The effect of limestone powder on microstructure of concrete was studied by using mercury intrusion porosimetry (MIP), backscattering scanning electron(BSE), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The experimental results show that the compressive strength of concrete containing 100 kg/m3 limestone powder can meet the strength requirement. Limestone powder has not pozzolanic activity; it is still unhydrated at the age of 28 days. But its filling effect can make the paste matrix and the interfacial transition zone between matrix and aggregate denser, which will improve the performance of concrete.

Correlating the mechanical properties to the mineral content of carious dentine—a comparative study using an ultra-micro indentation system (UMIS) and SEM-BSE signals

The deterioration of the mechanical properties of carious dentine was assumed to be associated with the decrease in mineral content due to the carious process. This study aimed to compare the mechanical properties of carious dentine studied by an ultra-micro-indentation-system (UMIS) and the mineral content determined using backscattered scanning electron (BSE) imaging. Eight axial sectioned and fine polished primary molar teeth with untreated carious dentine were measured for hardness and elastic modulus using the UMIS. On each specimen two centrally located linear arrays of indentations were made from the pulp to lesion cavity floor, followed by the capture of a BSE image using a solid-state detector. The BSE intensity at the same spot as the indentation array on each specimen was analysed and compared to the UMIS results. The results show that the mechanical properties of dentine are dependent on its mineral content. The decrease in mechanical properties of carious dentine, namely hardness and elastic modulus are directly linked to the reduction in its mineral content ( r 2=0.93 and 0.92, respectively). The relationship between dentine hardness and elastic modulus values ( y ) can be expressed as an exponential function of the mineral content in wt.% ( x ) that is y= ae bx .

Thermal oxidation of InAlP

Producing insulating layers on III–V semiconductors is crucial for a number of important device applications. Al-containing thermal oxides on AlGaAs and InAlAs have been found to possess good insulating characteristics and oxides on InAlP have recently been shown to be even more promising. This paper presents data on the thermal oxidation at 500°C in moist nitrogen (95°C) of MBE-grown InAlP layers (In0.525Al0.475P and In0.494Al0.506P) lattice matched to GaAs. The oxides (20–300 nm thick) have been characterized by Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford back-scattering spectroscopy, transmission and scanning electron microscopy. Oxides are amorphous and appear to be a mixture of indium phosphates and aluminum oxide. The oxidation kinetics are parabolic, and the InAlP layer with the higher Al content oxidizes slightly faster. Electrical measurements performed on metal-insulator-semiconductor (MIS) structures indicate that the oxide has good electrical properties, exhibiting low current densities (up to 14 V), making the oxide films potentially useful for some device applications.

Behaviour of bismuth during simulated processing of model aluminium capacitor foils

The production of high specification, aluminium-based, electrolytic capacitors requires optimization of material composition and heat and surface treatments in order to maximize the area available for formation of the dielectric, anodic film. Commercial foils contain low additions of copper and lead in order to achieve this goal. The present study examines the effects of heat and surface treatments on aluminium foil containing either 50 or 1000 ppm bismuth, as a replacement for lead, by a combination of Rutherford backscattering spectroscopy and scanning electron microscopy. Heat treatment at 823 K results in segregation of bismuth to the surface regions of the foils, with enrichments in the range 4–8 × 1014 Bi atoms cm−2, localized mainly just beneath the thermal oxide, for the selected treatment conditions. The enrichment reduces following alkaline etching, to the range 1–4 × 1014 Bi atoms cm−2. This level of enrichment is maintained during subsequent anodizing, with the enrichment partitioned between the metal and the outermost layers of the anodic films. The enrichment of the metal is about 4 × 1013 Bi atoms cm−2. Electropolishing in perchloric acid solution eliminates the enrichment developed during the heat treatment, probably due to activation during the polishing process. The enrichment remains very low or negligible during subsequent anodizing. The general behaviours of bismuth and lead are similar in aluminium foils subject to the selected heat and surface treatments. However, additional studies are needed of tunnel etching to determine the feasibility of substitution of lead by bismuth in commercial foils.