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Abstract: Nanocomposite coatings consisting of Ag and TiC x (x <1) crystallites in a matrix of amorphous SiC were deposited by high-rate magnetron sputtering from Ti–Si–C–Ag compound targets. Different target compositions were used to achieve coatings with a Si content of ∼13at.%, while varying the C/Ti ratio and Ag content. Electron microscopy, helium ion microscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed to trace Ag segregation during deposition and possible decomposition of amorphous SiC. Eutectic interaction between Ag and Si is observed, and the Ag forms threading grains which coarsen with increased coating thickness. The coatings can be tailored for conductivity horizontally or vertically by controlling the shape and distribution of the Ag precipitates. Coatings were fabricated with hardness in the range 10–18GPa and resistivity in the range 77–142μΩcm. [ABSTRACT FROM AUTHOR]

Abstract: Background: The concentration of iron in the brain increases with aging. Furthermore, it has also been observed that patients suffering from neurological diseases (e.g. Parkinson, Alzheimer…) accumulate iron in the brain regions affected by the disease. Nevertheless, it is still not clear whether this accumulation is the initial cause or a secondary consequence of the disease. Free iron excess may be an oxidative stress source causing cell damage if it is not correctly stored in ferritin cores as a ferric iron oxide redox-inert form. Scope: Both, the composition of ferritin cores and their location at subcellular level have been studied using analytical transmission electron microscopy in brain tissues from progressive supranuclear palsy (PSP) and Alzheimer disease (AD) patients. Major conclusions: Ferritin has been mainly found in oligodendrocytes and in dystrophic myelinated axons from the neuropili in AD. In relation to the biomineralization of iron inside the ferritin shell, several different crystalline structures have been observed in the study of physiological and pathological ferritin. Two cubic mixed ferric–ferrous iron oxides are the major components of pathological ferritins whereas ferrihydrite, a hexagonal ferric iron oxide, is the major component of physiological ferritin. We hypothesize a dysfunction of ferritin in its ferroxidase activity. General significance: The different mineralization of iron inside ferritin may be related to oxidative stress in olygodendrocites, which could affect myelination processes with the consequent perturbation of information transference. [Copyright &y& Elsevier]

The microstructure of NiAl-type (β′) precipitates in an aged ferritic steel (Fe–12.7Al–9Ni–10.2Cr–1.9Mo, at.%) is characterized by transmission and analytical electron microscopy (AEM) and atom probe tomography (APT). The alloy shows a duplex precipitation of β′ particles: primary with an average diameter of 130nm and secondary with an average diameter of 3nm. Based on APT, the primary and secondary β′ have compositions of Ni41.2Al43.6Fe12.7Cr0.8Mo1.4 and Ni26.3Al41.6Fe26.9Cr3.3Mo1.7, respectively. [Copyright &y& Elsevier]

Abstract: Aluminium/alumina composites based on ceramic preforms prepared via freeze-casting are examined. Domains composed of alternating but also interpenetrating ceramic and metallic lamellae are observed. Single-domain samples were extracted from composites processed under different conditions. In situ scanning electron microscopy analyses were carried out to investigate the damage evolution under compressive load. The composite is strong and brittle when loaded along directions parallel to the freezing direction. When compressed in other directions, the behavior is controlled by the soft metal. The plastic anisotropy is less pronounced than theoretical predictions for laminates, which is explained by the presence of bridges between the ceramic lamellae. Coating the preform with Cu or Cu2O prior to melt infiltration reduces the compressive strengths of the composites. Transmission electron microscopy analysis shows that even in the case of a Cu coating a Cu2O layer is formed during processing, weakening the interface and preventing the dissolution of Cu in the aluminium alloy. [Copyright &y& Elsevier]

The addition of Cr to (Mo0.85Nb0.15)Si2 crystals significantly improves the thermal stability of the lamellar structure composed of C11b–MoSi2 and C40–NbSi2 phases. Analysis using electron microscopy indicates the segregation of Cr atoms at the C40/C11b lamellar interface. This leads to a decrease in the lattice misfit strain at the interface and better thermal stability of the lamellae. [Copyright &y& Elsevier]

Context: Man-made vitreous fibers (MMVFs) are noncrystalline inorganic fibrous material used for thermal and acoustical insulation (e.g., rock wool, glass wool, glass microfibers, and refractory ceramic fibers). Neither epidemiologic studies of human exposure nor animal studies have shown a noticeable hazardous effect of glass wools on health. However, MMVFs have been anecdotally associated with granulomatous lung disease in several case reports. Case presentation: Here, we describe the case of a patient with multiple bilateral nodular opacities who was exposed to glass wool fibers and coating materials for 7 years. Bronchoalveolar lavage fluid revealed an increased total cell count (predominantly macrophages) with numerous cytoplasmic particles. Lung biopsy showed peribronchiolar infiltration of lymphoid cells and many foreign-body- type granulomas. Alveolar macrophages had numerous round and elongated platelike particles inside the cytoplasm. X-ray microanalysis of these particles detected mainly oxygen/aluminum/silicon and oxygen/magnesium/silicon, compatible with kaolinite and talc, respectively. No elemental evidence for glass fibers was found in lung biopsy. Discussion: The contribution of analytical electron microscopy applied in the lung biopsy was imperative to confirm the diagnosis of pneumoconiosis associated with a complex occupational exposure that included both MMVFs and coating materials. Relevance to clinical or professional practice: This case study points out the possible participation of other components (coating materials), beyond MMVFs, in the etiology of pneumoconiosis. [ABSTRACT FROM AUTHOR]

Abstract: Abnormal grain growth is a commonly observed phenomenon in perovskite materials. In order to study this phenomenon, grain growth experiments were conducted over a temperature range from 1425 to 1600°C for the model system SrTiO3 to analyse the nucleation of abnormal grains and to identify the growth mechanism involved for normal and abnormal grains. Grain boundaries of normal and abnormal grains were investigated in quenched samples by high-resolution transmission electron microscopy and by energy-dispersive spectroscopy in a scanning transmission electron microscope. No amorphous film was observed at the grain boundaries for either normal or abnormal grains. Non-stoichiometry at the grain boundaries was identified as a possible reason for the differences in growth speed. The results are compared to the nucleation and growth of abnormal grains in BaTiO3. [Copyright &y& Elsevier]

Abstract: This paper describes a novel multi-scale study of stress corrosion cracking in cold-worked 304 type stainless steels, which are widely used in pressurized water reactors and boiling water reactors. The influence of cold work and Cr concentration on the stress corrosion cracking behaviour of the steel has been examined. A methodology has been developed in order to characterize the same crack tip region with nanoscale secondary ion mass spectroscopy, electron back-scattering diffraction and transmission electron microscopy. This has offered a unique insight into the chemistry and microstructure, showing that the right combination of techniques can provide much of the information needed to understand the processes involved in crack propagation. A model for crack propagation based on brittle fracture and localized oxidation and shearing near the crack tip has been proposed. [Copyright &y& Elsevier]

Abstract: Transmission electron microscopy (TEM) in combination with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy was applied to analyze the microstructure and the local chemical composition of as-sintered and aged Y2O3-doped ZrO2 (YDZ) thick-film substrates with yttria contents of 8.5mol.% (8YDZ) and 10mol.% (10YDZ). Selected-area electron diffraction and dark-field TEM imaging show nanoscale precipitates of the tetragonal YDZ phase, which are coherently embedded in grains consisting of the cubic phase. A distinct coarsening of the tetragonal regions is observed after 2500h annealing of 8YDZ at 950°C in an oxidizing atmosphere. This coarsening is accompanied by decomposition on the cationic sublattice on the nanoscale, leading to the depletion of yttrium in the tetragonal regions. The decomposition is discussed in terms of spinodal decomposition which takes place even at a high doping concentration of 8.5mol.% Y2O3. [Copyright &y& Elsevier]

Abstract: The Tyrolean iceman, a 5300-year-old mummy, presents tattoos on different parts of his body. Skin samples of several line tattoos and a cross tattoo were investigated by optical microscopy and various electron microscopy techniques (TEM, EFETEM, EELS, EDXS, electron diffraction). The epidermis of the investigated skin areas was mostly lacking. The tattooing particles are distributed in the connective tissue and could be identified as soot. In some areas between the soot particles, different silicate crystals are present such as almandine and quartz, along with some not exactly definable crystals. The crystals possibly derived from stones of the fireplace from which the soot was taken for tattooing. Additionally, in the medial part of the right leg, putative ash particles were seen in the tattooed area. Furthermore, in non-tattooed skin areas, a vivianite crystal and small grains of CaPO4 and nearby Fe, P and O could be detected, these having formed most probably after the death of the Tyrolean Iceman during his long period in the mountains. On the surface of two leg specimens, a small layer with brown granules was visible by means of optical microscopy, and these were identified as melanin granules in the stratum basale of the epidermis. [Copyright &y& Elsevier]

Abstract: We have fabricated nanocrystalline Mg–Al powders with nominal Al compositions of 4 and 8 at% by the electrodeposition technique and have compared their hydrogenation characteristics with those for a commercially available pure Mg powder. It is elucidated that interestingly the amount of Al incorporated in MgH2 increases with decreasing the hydrogenation temperature. This observation indicates that the magnesium hydride phase has a limited solubility for aluminum and the supersaturation of hydride with Al is attributed to the slower mobility of aluminum at low temperatures. The rejection of Al during hydride formation is shown to result in a higher fraction of the intermetallic phase, thus reducing the hydrogen capacity. It is suggested that the presence of the intermetallic phase prior to hydrogenation enhances the hydride nucleation rate, which further decreases the hydrogen capacity in comparison to pure Mg. [Copyright &y& Elsevier]

previously developed Monte Carlo code has been extended to the X-ray microanalysis in a (scanning) transmission electron microscope of plan sections, consisting of bilayers and triple layers. To test the validity of this method for quantification purposes, a commercially available NiOx (x ∼1) thin film, deposited on a carbon layer, has been chosen. The composition and thickness of the NiO film and the thickness of the C support layer are obtained by fitting to the three X-ray intensity ratios I (NiK)/I (OK), I (NiK)/I (CK), and I (OK)/I (CK). Moreover, it has been investigated to what extent the resulting film composition is affected by the presence of a contaminating carbon film at the sample surface. To this end, the sample has been analyzed both in the (recommended) "grid downward" geometry and in the upside/down ("grid upward") situation. It is found that a carbon contaminating film of few tens of nanometers must be assumed in both cases, in addition to the C support film. Consequently, assuming the proper C/NiOx /C stack in the simulations, the Monte Carlo method yields the correct oxygen concentration and thickness of the NiOx film. [ABSTRACT FROM AUTHOR]

Abstract: Foil and sheet forms of the nickel-based superalloy 625 have been examined in an ‘as-processed’ condition and following creep-rupture testing in air at 750°C and 100MPa. Both scanning and transmission electron microscopies were employed to correlate microstructures with creep behavior, and indicate the additional processing required to achieve foil form reduces creep life compared to thicker-section wrought product forms. Prior to creep testing, the microstructure consists of γ phase with M6C precipitates. This microstructure changes during creep into one consisting of orthorhombic δ phase extending across the γ grains, and grain boundaries dominated by the presence of rhombohedral μ phase, δ phase, and a Si-rich variant of diamond-cubic M6C (η phase). Thermodynamic modeling was also used to calculate the stable temperature ranges and compositions of equilibrium phases. The phases predicted by modeling and their compositions generally agree with those observed within alloy 625 after creep testing. [Copyright &y& Elsevier]

The icosahedral quasicrystal (QC) has been found to form, along with a minor amount of α-Al, in the rapidly solidified Al18Mg3Mn2 complex metallic alloy. From the compositional analysis, the QC was found to be close to (AlMg)82Mn18. The quasilattice constant (a R =0.4604nm) of the QC phase suggests that it is basically an Al–Mn type of Mackay quasicrystal, which conforms to the composition analysis. The rationale behind the formation of the Al–Mg–Mn ternary quasicrystal from the T-Al18Mg3Mn2 alloy is discussed. [Copyright &y& Elsevier]

Soil mineral phases play a significant role in controlling heavy metal mobility in soils. The effective study of their relation needs the integrated use of several analytical methods. In this study, analytical electron microscopy analyses were combined with sequential chemical extractions on soils spiked with Cu, Zn and Pb. Our aims were to study the metal sorption capacity of soil mineral phases and the effect of presence of iron oxide and carbonate on this property of soil minerals. Copper and Pb were found to be characterized by higher and stronger sorption on the studied samples than Zn. Only the former two metals showed significant differences in their immobilized metal amounts on the studied samples and soil mineral particles. Highest metal amounts were sorbed on the swelling clay mineral particles (smectites and vermiculites), but iron-oxide phases may also have similar lead sorption capacity. Alkaline conditions due to the carbonate content of soils resulted both in increased sorption on the mineral particles for Cu and in enhanced role of precipitation for all the studied metals. On the other hand, the intimate association of phyllosilicates and iron resulted in significant increase in metal sorption capacity of the given particle. The results of sequential extractions could be successfully completed by the analytical electron microscopy analyses for studying the sorption capacity of discrete mineral particles. Their integrated use helps us in better understanding the heavy metal–mineral interactions in soils. [Copyright &y& Elsevier]

Abstract: The microstructure of the transfer layer, and the underlying severely plastically deformed layer (SPDL), formed during the dry sliding of a spinodally hardened Cu–15wt.% Ni–8wt.% Sn bronze against a stainless steel, is characterized at the nanoscale by conventional and analytical transmission electron microscopy, including energy-dispersive spectroscopy and electron energy loss spectroscopy. The SPDL consists of a Cu–Ni–Sn solid solution with elongated nanograins, due to extensive dislocation glide and twinning. In contrast, the transfer layer, 2–3μm thick, is an equiaxed nanocomposite comprised of a Cu-rich metallic phase with a (Fe,Cr)2O3-based oxide precipitates, and forms as a result of the mechanical mixing and compaction of wear debris. The bronze in this layer has undergone dealloying, indicative of the importance of thermal effects. The dispersion of oxide in the transfer layer suggests a different type of forced mixing, possibly turbulent mixing. The transfer layer is observed to improve significantly the wear resistance of the bronze. [Copyright &y& Elsevier]

An analytical electron microscope was used for direct measurement of the concentration profiles of In1-xGaxAsyP1- y quantum wells (QWs) and barriers grown by molecular beam epitaxy on GaAs substrates. The well and barrier layers had compositional differences on the group III (In/Ga) sublattice only, the group V (As/P) sublattice only, and on both sublattices. These were annealed over a range of temperatures (700-950degC), and the resultant changes in the QW widths and compositional profiles were determined along with the changes in the photoluminescence (PL) emission wavelength. The structures were annealed either uncapped or capped with either a 100-nm-thick layer of low temperature (250degC) grown InGaP (LT-InGaP) or with CVD-grown SiO2. The LT-InGaP layer contains excess phosphorus expected to be present as P-antisite defects. This was used to enhance interdiffusion on the group V sublattice during annealing, producing a blue-shift in PL response. The SiO2 capping leads to outdiffusion of Ga from the top GaAs layer producing additional group III defects that enhance interdiffusion of the group III sublattice. The interdiffusion activation energies and diffusivities were obtained from Arrhenius plots for each of groups III and V QWs profile changes. The compositional profiles of the QW after annealing are used to infer the defects involved in the interdiffusion process on each sublattice. [ABSTRACT FROM PUBLISHER]

Abstract: This note describes a new technique for in situ sampling of fine particulate matter (PM) including colloids in natural environments. The technique is based on a microlysimeter which is easy to move between field and laboratory and can be routinely used for in situ monitoring. The design of the device aims at limiting bias and artefacts encountered with current sampling methods based on successive field collection of liquid samples, transport, storage and filtration in the laboratory. Samples are directly collected on transmission electron microscopy (TEM) grids, thus totally eliminating the modifications classically due to handling of samples from collection to analysis. Detailed physical and chemical microscopic studies of individual particles can then be performed in order to fully characterize PM in natural media such as soil solutions, atmospheric fallout, rainfall and any aquatic system. This technique can be applied in a number of research fields, such as the characterization and determination of pollution vectors, the tracing of sources of emissions, or investigations on particle interactions. [Copyright &y& Elsevier]

Abstract: A brief review of the current literature concerning compounds based upon the R5(Si x Ge1− x )4 structure reveals that essentially all examined alloys contain “linear features” similar to those first observed by Szade et al. on the surface of Gd5Si4, Gd5Si2Ge2 and Gd5Ge4 samples. Attempts to characterize these features, using a variety of techniques, have proven to be a difficult task. Rather than becoming clearer and better understood, discrepancies in the reported data have resulted in much confusion. A series of comprehensive experiments involving optical, scanning and transmission electron microscopy, X-ray diffractometry, magnetization, and heat capacity measurements have been performed in an attempt to clarify the situation. These experiments, coupled with a critical examination of published data, allow certain misconceptions and apparent contradictions to be understood and explained. Of major importance is the discovery that the volume fraction of the linear feature present is far lower than what one may estimate on the basis of etched samples. The results of this study support previous data that show the linear features are a second phase of composition R5(Si x Ge1− x )3, and reveal the various difficulties associated with proper identification of this phase due to its small size scale and low volume percentage. [Copyright &y& Elsevier]

The interdiffusion of Pd–Ag thin film diffusion couples is investigated by transmission electron microscopy and X-ray diffractometry at a temperature of 723K. By comparison with calculated diffractograms, it is shown that a diffusion-induced recrystallization takes place, which produces a first generation of new grains with a dominant composition of 24.5at.% Pd inside the diffusion zone. [Copyright &y& Elsevier]

We applied the parametric bootstrap to the X-ray microanalysis of Si-Ge binary alloys, in order to assess the dependence of the Ge concentrations and the local film thickness, obtained by using previously described Monte Carlo methods, on the precision of the measured intensities. We show how it is possible by this method to determine the statistical errors associated with the quantitative analysis performed in sample regions of different composition and thickness, but by conducting only one measurement. We recommend the use of the bootstrap for a broad range of applications for quantitative microanalysis to estimate the precision of the final results and to compare the performances of different methods to each other. Finally, we exploited a test based on bootstrap confidence intervals to ascertain if, for given X-ray intensities, different values of the estimated composition in two points of the sample are indicative of an actual lack of homogeneity. [ABSTRACT FROM AUTHOR]

Abstract: Metallic Bi nanoprecipitates (NPs) were observed at grain boundaries (GBs) in a series of Bi-doped Sr1−x Ba x TiO3 ceramics sintered at low temperature, using analytical electron microscopy. Most GBs fell into two groups, according to their local structure and chemistry, one with the NPs and the other with titania-based amorphous film. The solution of Ba into the lattice was only about one-third of the nominal value, and the remaining Ba dopants were driven into triple pockets or wetted the GBs during the sintering. Lower Ba doping initiated less liquid, resulting in a core–shell structure. Bi dopants were co-soluted with Ba, thereby suppressing the Bi segregation at GBs. The extra Bi could not diffuse out through the dewetted GB as fast as via the titania-based film, compelling them to precipitate locally. These metallic NPs may initiate several modes of polarization that increase the dielectric constants detected at 1kHz. [Copyright &y& Elsevier]

Abstract: The cation chemistry in two sets of strontium barium niobate (SBN) micro-crystals, synthesized at 1100°C via molten NaCl and KCl salts was investigated using analytical electron microscopy. Na+ and K+ ions were found to enter the tungsten bronze (TB) structure to form the filled TB phase Sr4−m Ba m Na2Nb10O30 or the partially filled TB phase (Sr,Ba)4+n K2−2n □ n Nb10O30. Small Na+ ions fill the A2 sites, leaving Sr2+ and Ba2+ ions to fill the A1 sites. The shifts in the actual compositions (m) from the nominal ones imply there may be morphotropic phase boundaries for the given composition range. In contrast, the large K+ ions partially fill two of the A1 sites, creating vacancies and results in the formation of (Sr4−m Ba m )(Ba n K2−2n □ n ) Nb10O30. A correlation between Ba, Sr and K contents reveals that m and n have a linear relation (m ≈3n). This leads to the new formula Sr4−3y/4Ba y K2−2y/4□ y/4 Nb10O30 (0< y <4), which illustrates a balance in the solution energy. [Copyright &y& Elsevier]

Abstract: The formation of carbides in Fe3Al-based alloys containing chromium, zirconium and carbon has been studied. Cr–Fe-carbides are generally observed in Zr-free material after heat treatment above 300°C. Nevertheless, small additions of Zr entirely prevent their formation and fine-scale Zr-rich carbides are formed instead. These particles are found after hot rolling and subsequent cooling. They are stable up to 1000°C. At higher temperatures, they partially dissolve and partially transform into coarse particles. These coarse particles do not dissolve even after annealing at 1350°C for 2h. Fine-scale Zr-carbides are difficult to form after high-temperature annealing and quenching. At temperatures ranging from 800°C up to 1000°C, carbides are formed in a very limited manner first at grain boundaries and, after longer annealing times, rarely also in the grain interiors. [Copyright &y& Elsevier]

Abstract: An optimal integration of modern computational tools and efficient experimentation is presented for the accelerated design of Nb-based superalloys. Integrated within a systems engineering framework, we have used ab initio methods along with alloy theory tools to predict phase stability of solid solutions and intermetallics to accelerate assessment of thermodynamic and kinetic databases enabling comprehensive predictive design of multicomponent multiphase microstructures as dynamic systems. Such an approach is also applicable for the accelerated design and development of other high performance materials. Based on established principles underlying Ni-based superalloys, the central microstructural concept is a precipitation strengthened system in which coherent cubic aluminide phase(s) provide both creep strengthening and a source of Al for Al2O3 passivation enabled by a Nb-based alloy matrix with required ductile-to-brittle transition temperature, atomic transport kinetics and oxygen solubility behaviors. Ultrasoft and PAW pseudopotentials, as implemented in VASP, are used to calculate total energy, density of states and bonding charge densities of aluminides with B2 and L21 structures relevant to this research. Characterization of prototype alloys by transmission and analytical electron microscopy demonstrates the precipitation of B2 or L21 aluminide in a (Nb) matrix. Employing Thermo-Calc and DICTRA software systems, thermodynamic and kinetic databases are developed for substitutional alloying elements and interstitial oxygen to enhance the diffusivity ratio of Al to O for promotion of Al2O3 passivation. However, the oxidation study of a Nb–Hf–Al alloy, with enhanced solubility of Al in (Nb) than in binary Nb–Al alloys, at 1300°C shows the presence of a mixed oxide layer of NbAlO4 and HfO2 exhibiting parabolic growth. [Copyright &y& Elsevier]

Abstract: The detailed evolution of the graphitized microstructure of carbon steel during annealing has been studied by thin-foil transmission electron microscopy, enabled by the refined dispersion of small graphite nodules produced. The graphitization annealing of 0.38wt.% carbon steel in the quenched martensitic state resulted in the formation of graphite nodules, of the order of 2–5μm in diameter, after 2–4h. Two types of graphite nodules were observed to form: one possesses an irregular morphology and exhibits a coring particle (either a nitride or an oxide), whilst the other is more regularly spheroidal and apparently without a nucleating particle at its core. Analytical electron microscopy has been employed to characterize the microstructure of the graphite nodules formed, in order to provide a better understanding of their nucleation and growth, in particular, the mechanism of formation of the spheroidal graphite nodules without an apparent nucleating particle. For these more spherical nodules, the results showed that the outer mantles had a strong graphitic character, whilst the core regions exhibited a more amorphous carbon structure. It is deduced from the available experimental evidence that the nucleation sites most likely to result in this structure are dissolving cementite particles in the martensite. [Copyright &y& Elsevier]

A new mechanism of cleaving-healing of garnet in metamorphic rocks during exhumation is reported. Almandine garnet with submicron multiple-phase inclusions characteristic of the GRAIL reaction, garnet + rutile = kyanite + ilmenite + low-quartz, was found by analytical electron microscopy to have non-epitaxial rutile nanoparticles distributed along internal {110} microcrack trails at the acute corner of submicron multiple-phase inclusions defined by the intersecting (110) and (011) mould surfaces. Such garnet microcracks were formed during lithostatic decompression due to a relatively high compressibility of quartz in the inclusion pockets and stress concentration at the acute corner. Spontaneous healing with accompanied formation of non-epitaxial rutile nanoparticles was activated predominantly via the GRAIL reaction due to high surface tension at the tip of microcracks and, to a lesser extent, decreasing lithostatic pressure or increasing inclusion pressure upon exhumation. This new mechanism of microcracking and healing involves stress build up, fracture propagation, mineral reaction, transport of elements to the reaction site and lowering of reaction boundaries by capillarity effect, all under the influence of thermodynamic and kinetic factors at the submicron-scale. Thus, TiO2 nanoparticle trails in garnet provide additional information on the P–T path and may shed light on exhumation rates/mechanisms and metamorphic reactions/processes. Careful scrutiny of host minerals on the submicron scale is required to tell whether there are other metamorphic-reaction facilitated healing processes being overlooked by inappropriate techniques or being obliterated by the predominant healing processes of fluid infiltration and resorption zoning. [ABSTRACT FROM AUTHOR]

The compositions of sub-15 nm particles in six related vanadium high strength low alloy steels, made by simulated thin slab direct charged casting, have been determined using electron energy loss spectroscopy (EELS). Such particles are considered to be responsible for dispersion hardening. For the first time, particles down to 4 nm in size have had their composition fully determined. In all the steels, the particles were nitrogen and vanadium rich and possibly slightly substoichiometric carbonitrides. Equilibrium thermodynamics predicted much higher carbon to metal atomic ratios than observed in all cases so that kinetics and mechanical deformation clearly control the precipitation process. Thus it is important to formulate the steel with this in mind. [ABSTRACT FROM AUTHOR]

A series of experiments with and without sample retreatment was performed on a starting mixture of dolomite plus quartz at 0.5 GPa and 600 °C in a CO2-H2O fluid with a mole fraction of CO2 of 0.2 for durations up to 582 h. The initial reaction of dolomite and quartz led to rapid formation of talc and calcite instead of tremolite and calcite by the intended reaction: 5 dolomite + 8 quartz + H2O = tremolite + 3 calcite + 7 CO2. With continued treatment, the talc + calcite + quartz assemblage gradually reacts to form increasing amounts of tremolite and diopside with the eventual loss of quartz and nearly complete loss of talc. The detailed structure of the amphibole and the nature of the Mg enrichment were revealed using AEM analysis of individual amphibole crystals. The most abundant defects are triple-chain chain multiplicity faults (CMFs), which appear as isolated lamellae with single periodicity in short-duration experiments and increasingly as groups of lamellae with variable multiplicity and periodicity in longer duration experiments and especially in a long-duration experiment without retreatment. In this latter experiment, a calcian clinojimthompsonite domain extending 15 unit cells along the b axis was observed. The sample after 582 h and five retreatments shows, on average, 3.5% true solid solution with Mg expressed as the Mg-cummingtonite (MC) component after correction for the presence of CMFs. This sample is thought to most closely approach the equilibrium composition for the amphibole. The sample after 250 h with three retreatments has about 10%, whereas that after 582 h without retreatment has 0.6% MC component, the latter having a relatively high density of CMFs. This study affirms the importance that precursor non-amphibole biopyriboles play in the formation of tremolitic amphibole. [ABSTRACT FROM AUTHOR]

Although oriented rutile needles in garnet have been reported from several ultrahigh-pressure (UHP) rocks and considered to be important UHP indicators, their crystallographic features including growth habit and lattice correspondences with garnet host have never been properly characterized. This paper presents a detailed analytical electron microscopic (AEM) study on evenly distributed oriented rutile needles in garnet of two eclogitic rocks from Sulu. Some garnet in one UHP diamondiferous quartzofeldspathic rock from the Saxonian Erzgebirge, and in one high-pressure (HP) felsic granulite from Bohemia also contain a few unevenly distributed oriented rutile needles. They have also been studied for the purpose of comparison. Despite different distribution patterns, AEM revealed that all rutile needles are oriented along the 〈111〉 directions of garnet with their lateral sides surrounded by the {110} planes of garnet, and that the growth directions of most needles are close to the normal of the {101} planes of rutile. No other specific crystallographic orientation relationships between rutile and garnet host were observed, and there is no pyroxene associated with rutile, as necessitated by the precipitation reaction of rutile in garnet as previously proposed. A simple solid-state precipitation scenario for the formation of the rutile needles in garnet in these two eclogitic rocks is not justified. Three alternative mechanisms are considered for the formation of oriented rutile needles: (i) the rutile needles may be inherited from precursor minerals; (ii) the rutile needles may be formed by a dissolution–reprecipitation mechanism; and (iii) the rutile needles may be formed by cleaving and healing of garnet with rutile deposition. None of these mechanisms can fully explain the observations, although the first one is less likely and the third one is preferred. This study presents an example where the presence of oriented/aligned inclusions in minerals does not necessarily imply a precipitation origin. [ABSTRACT FROM AUTHOR]

Inhaled dust particulates are able to relocate to the extrapulmonary compartments, particularly the lymph nodes that drain the lung. There is little information about the concentration and type of asbestos in the lymphatics and lymph nodes. Quantitative analysis of asbestos lymph node burden conducted by light and analytical transmission electron microscopy has shown ferruginous bodies in lymph nodes that drain the lung and appreciable numbers of short asbestos fibers accumulate in lymph nodes in occupationally exposed individuals. The location of lymph nodes in the thoracic cavity was categorized according to the Naruke anatomical map. Tissue from eleven individuals with a history of asbestos exposure were selected for a comparative study of the asbestos content of lung with that found in the thoracic lymph nodes. The study used a digestion technique for tissue preparation and evaluated ferruginous body burden and concentration of asbestos fibers (> 0.5 µm in length). Comparison was made between sites and analysis was made as to the population of fibers detectable by light microscopy and defined as "Stanton fibers." The findings indicated the vast majority of all asbestos fiber types in all sites were shorter than 5 µm and would not have been counted in a light microscopy count scheme that included only those fibers > 5 µm. There were reproducible patterns of asbestos types of found in various lymph nodes, although there were variations in the amount of asbestos found in the sites sampled. In summary, asbestos fibers found in thoracic lymph nodes have predominately short fibers and, in this study group, consisted of a mixture of commercial and noncommercial amphiboles. When a long/thin fiber was found in the lung or lymph tissue, its detection required the use of analytical transmission electron microscopy for identification. [ABSTRACT FROM AUTHOR]

Abstract: Multi-cycle bending deformation of an individual boron nitride (BN) nanotube is performed inside a 300kV high-resolution analytical transmission electron microscope (TEM) using a piezo-driven scanning tunneling microscope (STM)–TEM holder. Phenomenological peculiarities of the deformation are recorded under the detailed control of nanotube morphology, atomic structure, chemistry and electrical transport during all stages of deformation. Interestingly, it is found that the nanotube layers are very flexible in the vicinity of a relatively rigid nanotube fragment filled with BN matter and may withstand 20 or even more reverse bending cycles. At the same time, the filled part is gradually graphitized such that the normal to the BN graphitic layers is perpendicular to both the nanotube axis and the bending axis. [Copyright &y& Elsevier]

Abstract: Analytical scanning electron microscopy of solar cells returned from the Hubble Space Telescope (HST) at the end of HST Service Missions SM-1 (1993) and SM-3B (2002) has revealed abundant remains of micrometeoroids. We have documented the most common residue compositions, and in this paper we suggest how they relate to mineral phases, and show how it is possible to estimate the proportion of the original micrometeoroid preserved. From a total of 273 impacts examined and analysed, we found 61/162 impacts on solar cells from SM-1 were produced by micrometeoroids, as were 45/111 from SM-3B. In each survey approximately 25% of damage features could not be assigned to a particular origin (micrometeoroid or space debris). A cumulative micrometeoroid flux curve for randomly selected cells shows impact features ranging from 3 to nearly 3800μm in size. To assist interpretation of space exposed surfaces, impact residues from known meteoritic and terrestrial analogue mineral phases were produced by light gas gun assisted acceleration of buckshot projectiles into solar cell targets at 5.5–6.3km s−1. Mg- and Fe-rich residues were found in 30/61 impacts from SM-1 and 26/45 from SM-3B, with variable Mg:Fe ratio, usually lacking Ca, and likely to be from olivine or low-Ca pyroxene. Only in a few examples is it possible to determine the divalent cation to silicon ratio, and thereby positively identify olivine or pyroxene. Vesicular Fe-, Mg-, Ni- and S-rich residues, found in eight impacts from SM-1 and 5 from SM-3B, closely resemble residue from light gas gun shots of phyllosilicate-rich meteorite grains, and may be from a layered silicate such as serpentine or smectite interlayered with tochilinite. Fe- and S-rich immiscible melt droplets, low in nickel, are probably of troilite origin. Fe-, Ni- and P-rich residue is almost certainly from the phosphide schreibersite, and iron–nickel metal residues show an elemental ratio characteristic of kamacite. One Mg-, Cr-, Fe- and O-rich residue suggests a spinel precursor. Ca-rich particles found within the spall zone of several craters closely resemble residue from calcium carbonate. Mg sulfates are also present. Very little aluminous silicate residue was found (one residue from each survey). One extraordinarily well-preserved assemblage contains residues from five mineral components and may represent impact by a chondrule fragment. Derivation of incident particle sizes from impact feature dimensions, by use of calibrated damage equations, reveals that the majority of impacting micrometeoroids had diameters of less than 10μm, although the mass flux is concentrated in grains of more than 50μm diameter. In one well-preserved crater, the mass of residue was calculated to be 60ng, approximately 25% of the particle mass as suggested by experimental crater size calibration. The smallest impacts were produced by grains of between 600nm and 1.3μm. The most common residue assemblages suggest that the majority of micron to millimetre scale micrometeoroids have an origin from chondritic material, similar to interplanetary dust particles, micrometeorites, and possibly the hydrous carbonaceous chondrites of the CM, CR or CI group. The relative contribution of cometary as opposed to asteroidal particle sources cannot yet be assessed from this data set. [Copyright &y& Elsevier]

Qualitative and quantitative electron energy-loss spectroscopy analyses have been performed on niobium and stable niobium oxides (NbO, NbO2 and Nb2O5). At integration windows (Δ) greater than 75 eV, k-factor analysis can be used to distinguish between the stoichiometry of the three oxides within 5.7% error. As seen in other metal oxides, with increasing oxidation state the metal ionization edges shift to higher energies relative to the O-K edge. Normalized M2,3 white-line intensities show a strong correlation with 4 d occupancy for each compound. The data are in correspondence with that observed in the literature for 4 d transition metals using normalized L2,3 white lines. Lastly, a distinctive energy-loss near-edge, structure of the O-K edge was observed for each oxide, which could be used as a fingerprint for analysis of unknowns. [ABSTRACT FROM AUTHOR]

Abstract: We show that the solution-precursor plasma spray (SPPS) method can be used to deposit ∼75% dense coatings of metastable ceramics in the ZrO2–10mol% Al2O3 binary system. The microstructure of the resulting SPPS coatings contains a rich variety of features and phases, as determined using X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The SPPS coatings are predominantly nanostructured (grain size <100nm), and made of tetragonal phase of ZrO2 (t-ZrO2) with Al3+ in solid solution. The Al3+ solute appears to stabilize partially the t-ZrO2. These coatings also contain some grains of monoclinic (m-ZrO2) and orthorhombic (o-ZrO2) phases, and Al-rich grain boundary amorphous phase. Crystalline Al2O3 phases are absent in the as-sprayed SPPS coatings. However, after a prolonged heat treatment (1400°C, 30h), α-Al2O3 grains precipitate out in the coating, and the t-ZrO2 grains coarsen and transform to m-ZrO2. [Copyright &y& Elsevier]

Abstract: Microtome sections of proton exchange membrane cells produce a wide range of information ranging from macroscopic distribution of components through specimens in which the detailed distribution of catalyst particles can be observed. Using modern data management practices it is possible to combine information at different scales and correlate processing and performance data. Analytical electron microscopy reveals the compositional variations across used cells at the electrolyte/electrode interface. In particular analytical techniques indicate that sulphur concentrations are likely to diminish at the interface Nafion/anode interface. [Copyright &y& Elsevier]

The evolution of microstructure and composition of the Fe3C iron carbide phase (cementite) during a graphitisation anneal of a quenched, medium carbon steel has been studied by analytical electron microscopy, including energy dispersive X-ray spectroscopy (EDX), electron energy loss spectroscopy (EELS) and energy filtered transmission electron microscopy (EFTEM) imaging. During heat treatment at 680 °C, dissolution of the cementite particles dispersed in the martensitic matrix was completed within a time period of 1.5 h, during which time graphite nodules began to form. However, a non-graphitic carbon-rich amorphous phase was also detected during this heat treatment. It is postulated that these amorphous particles could be an intermediate stage during the overall graphitisation process. [ABSTRACT FROM AUTHOR]

Abstract: A thermodynamic and kinetic assessment was made of secondary austenite (γ2) growth in the welding microstructure of a UNS S32304 duplex stainless steel during reheat cycles, between 900 and 1250°C. Calphad-based numerical simulation and analytical electron microscopy characterization analyses were performed. A non-monotonic relationship between the proportion of γ2 and reheating temperature was observed, a maximum γ2 fraction being attained at ∼1050°C. γ2 formed at higher reheating temperatures (above ∼1100°C) displayed an outer shell rich in chromium and nitrogen and a core region depleted in these alloying elements; in contrast, γ2 formed at lower reheating temperatures (under ∼1000°C) displayed almost homogeneous chemical composition. [Copyright &y& Elsevier]

Abstract: Heat treatment of arc-evaporated cubic Al0.7Cr0.3N hard coatings in Ar up to 1450°C causes precipitation of AlN. The Cr-enriched matrix transforms into Cr via Cr2N under N2 release. These reactions are investigated by simultaneous thermal analysis, mass spectrometry, X-ray diffraction, and analytical transmission electron microscopy. [Copyright &y& Elsevier]

Abstract: It was previously found that CaO additives in Si3N4 containing SiO2 segregate to the ∼1nm thin amorphous grain boundaries in preference to dissolving in the interior of the SiO2 rich glass pockets. Moreover, Ca was detected at some of the β-Si3N4/silica interfaces. Using sensitive imaging and analytical methods available from modern transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM), the Ca distribution was accurately mapped with a resolution approaching 1nm. Liquid–liquid phase separation occurs at the liquid (now glass) triple pockets at higher Ca levels. Electron energy-loss spectrometry provides compositions of the separated phases, one being nearly pure SiO2 and the other containing significant Ca and N, and also insights about their bonding nature. The Ca and N containing liquid tends to reside in the tips of the liquid pockets with re-entrant geometries. The two β-Si3N4/liquid interfaces and the actual triple line regions were also assessed. Evidence emerged that these entities are diffuse spanning well more than a nanometer in width and having high N levels; Ca also often adsorbs to these. The β-Si3N4/liquid interfaces for the two liquids have different compositions, and that of the grain boundary film is intermediate between these values. Thus, this chemical information yields a comprehensive picture of this phase separation and of the various interfaces in this system. [Copyright &y& Elsevier]

Abstract: An inert gas atomization technique was employed to produce spray deposits of an Al–18Si–5Fe–1.5Cu (wt.%) alloy. The spray-deposited alloy was subsequently hot extruded with a reduction ratio of 6:1 and extrusion temperature of 480°C. The microstructural features of the as-spray-deposited and extruded alloys were examined using optical, scanning electron and transmission electron microscopy techniques, and chemical analyses of phases were carried out using energy dispersive X-ray analysis and spectroscopic methods. The microstructure of the spray-deposited alloy revealed the presence of a cellular and plate-like morphology of β-Al5SiFe phase coexisting with δ-Al4Si2Fe phase in contrast to the presence of only δ-Al4Si2Fe phase in atomized powder particles. The formation of the β-Al5SiFe phase is suggested to arise as a result of phase transformation of δ-Al4Si2Fe phase during slow cooling of the spray deposit. The hot extrusion of the alloy resulted in fragmentation of both intermetallic phases and Si into nano-sized particles. The microstructure evolution during spray deposition and hot extrusion of the alloy is discussed. [Copyright &y& Elsevier]

Abstract: Quantitative analytical electron microscopy study of dopant distribution in the microstructure of selected Nd-α-sialon samples revealed the presence of relatively large amounts of glassy phase at quadruple pockets, which exhibited a common composition similar to a melilite solution. Al segregants were depleted from adjacent grain boundaries to satisfy the “stoichiometry” of such glass. Existence of this glass results in significant deviation of the Nd-α-sialon composition from the expected values, which shifts the α-β-sialon phase boundary. Only extra Nd2O3 additives enable a monolithic α-sialon microstructure. The absence of similar glass in Yb-α-sialon materials keeps the phase relations from such deviations. [Copyright &y& Elsevier]

Abstract: Core loss electron energy loss spectroscopy spectrum imaging is used to map vanadium-based precipitates with dimensions as small as 1nm in a matrix of high strength low alloy steel. The transmission electron microscopy specimen was prepared by the focused ion beam liftout technique followed by low energy ion milling. Characterisation of such precipitates is discussed. [Copyright &y& Elsevier]

Abstract: Previous studies of the structure of core nanocrystals of ferritin (Ft) in the brains of patients with Alzheimer’s disease (AD) have shown differences in the mineral compound in comparison with physiological Ft. Both Ft cores have a polyphasic composition but whereas the major phase in physiological Ft is hexagonal ferric iron oxide (ferrihydrite), the major phases in brain AD Ft are two cubic mixed ferric–ferrous iron oxides (magnetite and wüstite). One of these (wüstite) is similar to what is detected in hemosiderin (Hm) cores in primary hemochromatosis (Quintana, C., Cowley, J.M, Marhic, C., 2004. Electron nanodiffraction and high resolution electron microscopy studies of the structure and composition of physiological and pathological ferritin. J. Struct. Biol. 147, 166–178). We have studied, herein, the distribution of iron, Ft, and Hm in sections of AD hippocampus using analytical microscopy. Iron present in Ft cores was directly mapped in a nanoSIMS microscope and the iron distribution has been correlated with the constituent elements N, P, and S. Ft and Hm cores were visualized at an ultrastructural level in an analytical transmission electron microscope. In senile plaques, Ft was observed in the coronal region associated with a non-β-amyloid component and in the periphery of plaques, together with Hm, in sulfur-rich dense bodies of dystrophic neurites. Hm was also found in lysosomes and siderosomes of glial cells. Ft was observed in the cytoplasm and nucleus of oligodendrocytes. Ft was particularly abundant in myelinated axons in association with oligodendrocyte processes. These findings provide new arguments to support the hypothesis of a dysfunction of Ft (with eventual degradation to Hm) in AD resulting in an increase of toxic brain ferrous ions that may contribute to the production of free radicals that induce both cellular oxidative stress and aged-related myelin breakdown associated with cognitive decline and AD (Bartzokis, G., 2004. Age-related myelin breakdown: a developmental model of cognitive decline and Alzheimer’s disease. Neurobiol. Aging 25, 5–18). [Copyright &y& Elsevier]

Abstract: A (Ti,Al)N coating which showed excellent adhesion to a stainless steel substrate is investigated using electron energy loss spectroscopy in an analytical electron microscope. Two interface layers are observed and identified as TiN x and ∼Ti3Al7. The presence of these layers can account for the excellent adhesion. [Copyright &y& Elsevier]

Abstract: Nano-sized precipitates were produced in nitrogen-containing commercial martensitic steels by a new thermomechanical treatment (TMT). A steel with the TMT should have a maximum operating temperature >50°C over the steel given a conventional heat treatment. A >100°C increase should be possible for a steel developed for the TMT. [Copyright &y& Elsevier]

Continuous-fiber-reinforced SiC/SiC-based matrix composite materials, to be used in the first-wall blanket of a fusion reactor, were prepared by the infiltration of SiC cloth with SiC- based suspensions of various chemical compositions. The compositions were tailored with respect to the calculated activation in a fast-neutron flux. Liquid-phase sintering was used for material densification, using different sintering aids, such as A1203, Y2O3, P2O5, AIN, etc. The microstructures of the differently prepared materials were studied with scanning and transmission electron microscopy and microanalysis. [ABSTRACT FROM AUTHOR]