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Novel materials with neutron shielding property were fabricated by incorporating boron compounds into high-density polyethylene (HDPE)/Ethylene propylene diene monomer rubber (EPDM) blends. A detailed investigation on the morphological, thermal, mechanical, and neutron attenuation properties of suitable proportion of HDPE/EPDM blend with boric acid (BA), boron carbide (BC), and nano boron carbide (NBC) were performed. Morphology of the 20 wt% of EPDM shows better distribution in HDPE matrix. BA filler is localised in the HDPE phase, while NBC shows uniform distribution in HDPE/EPDM blend compared to its micro counterpart. There is a reduction in the tensile strength and modulus with the incorporation of EPDM in HDPE, whereas the ductility of HDPE is enhanced. A significant increase in the tensile toughness of the HDPE/EPDM blend with lower tensile strength and modulus is observed for BA, and BC filled composites. Moreover, HDPE/EPDM composites with NBC show only a marginal increase in the tensile toughness, tensile strength, and modulus. Comparison of the Young's modulus of the HDPE/EPDM blends with theoretical models indicates trends similar to the Coran model. The BA and BC filled composites follow the lower bound series model, whereas NBC composites show behaviour similar to the Halpin Tsai model. Total thermal neutron macroscopic cross-section (0.025 MeV energy neutrons) of 10 cm-1 and mean free path of 0.1 cm was obtained for 20 wt% NBC HDPE/EPDM composites. [ABSTRACT FROM AUTHOR]

A clean and defect-free substrate/coating interface is required to guarantee good adhesion of coatings under service conditions. For this purpose, an etching pre-treatment using High-Power Impulse Magnetron Sputtering (HiPIMS) was performed to modify the surface of 304L stainless steel. The effect of three etching procedures on the substrate properties, such as corrosion resistance and adhesion, was investigated with unprecedented spatial resolution and spectroscopic details. Glancing angle X-ray diffraction showed modification in phase content but no neoformation after steel etching. X-ray photoelectron spectroscopy confirmed the presence of etchant species (6–7 at.%) on the extreme surface of the substrate. Transmission Electron Microscopy and Atomic Probe Tomography showed that the interface was less than a few nanometers wide. Polarization curves in a nitric acid solution at boiling temperature showed, for the first time, that the Ti+ and Zr+ etchings decreased the corrosion current density compared to the untreated original surface. Scratch-test measurements indicated better substrate/coating adhesion using HiPIMS metal ion etching. Electrochemical characterization revealed that Zr etching and thin coating improve the anti-corrosion properties of stainless steel in strong nitric acid conditions. [ABSTRACT FROM AUTHOR]

Abstract In this study, we have performed nanoscale characterization of Si-clusters and Si-nanowires with a laser-assisted tomographic atom probe. Intrinsic and p-type silicon nanowires (SiNWs) are elaborated by chemical vapor deposition method using gold as catalyst, silane as silicon precursor, and diborane as dopant reactant. The concentration and distribution of impurity (gold) and dopant (boron) in SiNW are investigated and discussed. Silicon nanoclusters are produced by thermal annealing of silicon-rich silicon oxide and silica multilayers. In this process, atom probe tomography (APT) provides accurate information on the silicon nanoparticles and the chemistry of the nanolayers.

The investigation of boron delta layers by tomographic atom probe (3DAP) is used to demonstrate that a depth profiling resolution of 0.9 nm (full width at half maximum) can be achieved. Results are compared with measurements provided by secondary ion mass spectrometry. The steepness is found to be below 1 nm/decade. In addition, silicon atomic planes are resolved in the real space demonstrating an in-depth spatial resolution of the 3DAP below 0.2 nm. [ABSTRACT FROM AUTHOR]

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Fabrication of high-quality ultrathin monocrystalline silicon layers and their transfer to low-cost substrates are key steps for flexible electronics and photovoltaics. In this work, we demonstrate a low-temperature and low-cost process for ultrathin silicon solar cells. By using standard plasma-enhanced chemical vapor deposition (PECVD), we grow high-quality epitaxial silicon layers (epi-PECVD) from SiH4/H2 gas mixtures at 175 °C. Using secondary ion mass spectrometry and transmission electron microscopy, we show that the porosity of the epi-PECVD/crystalline silicon interface can be tuned by controlling the hydrogen accumulation there. Moreover, we demonstrate that 13-14% porosity is a threshold above which the interface becomes fragile and can easily be cleaved. Taking advantage of the H-rich interface fragility, we demonstrate the transfer of large areas (∽10 cm2) ultrathin epi-PECVD layers (0.5-5.5 µm) onto glass substrates by anodic bonding and moderate annealing (275-350 °C). The structural properties of transferred layers are assessed, and the first PECVD epitaxial silicon solar cells transferred on glass are characterized. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Silicate glasses are durable solids, and yet they are chemically unstable in contact with aqueous fluids-this has important implications for numerous industrial applications related to the corrosion resistance of glasses, or the biogeochemical weathering of volcanic glasses in seawater. The aqueous dissolution of synthetic and natural glasses results in the formation of a hydrated, cation-depleted near-surface alteration zone and, depending on alteration conditions, secondary crystalline phases on the surface. The long-standing accepted model of glass corrosion is based on diffusion-coupled hydration and selective cation release, producing a surface-altered zone. However, using a combination of advanced atomic-resolution analytical techniques, our data for the first time reveal that the structural and chemical interface between the pristine glass and altered zone is always extremely sharp, with gradients in the nanometre to sub-nanometre range. These findings support a new corrosion mechanism, interfacial dissolution-reprecipitation. Moreover, they also highlight the importance of using analytical methods with very high spatial and mass resolution for deciphering the nanometre-scale processes controlling corrosion. Our findings provide evidence that interfacial dissolution-reprecipitation may be a universal reaction mechanism that controls both silicate glass corrosion and mineral weathering. [ABSTRACT FROM AUTHOR]

A Zn-electroplated steel prone to Zn whiskers has been investigated in order to obtain information about the microstructure of the Zn coating at the root of a whisker. Indeed, the characterization of the Zn coating is essential to understand the Zn whisker growth mechanism. Care was taken to prepare a sample at a whisker root by using a focused-ion beam in a dual-beam scanning electron microscope. The sample was analyzed using energy dispersive X-ray spectrometry and electron backscattered diffraction. Results show three different regions: 1) an inclusion enriched with Ca, Al, and C; 2) the Zn coating with columnar grains; and 3) the root of the whisker. An important point is that recrystallized grains are found at the whisker root. This observation supports recent whisker growth models based on recrystallization. [ABSTRACT FROM PUBLISHER]

This paper presents a review of atomic-scale defects (planar defects and dislocations) analysis using atom probe (AP) and field ion microscopy (FIM). A large part of the discussion is dedicated to the first atomic-scale observation of a Cottrell atmosphere by a three-dimensional atom probe method (3DAP). The nanoscale boron segregation to line dislocations and planar defects in a B2-ordered FeAl (40 at.%A1) is imaged in three dimensions of the real space. The boron-enriched Cottrell atmosphere is imaged in the close vicinity of an edge {001} dislocation as a rod 3 nm in diameter, around to the dislocation line. [ABSTRACT FROM AUTHOR]

In 1949, on the basis of theoretical considerations, Cottrell proposed the concept of 'atmospheres' (called later by his name) to explain some specific behaviour of materials during plastic deformation, such as sharp yield-point formation or the Portevin-LeChatelier effect. In this letter, atomic-scale observations and three-dimensional analyses of a Cottrell atmosphere are reported. They have been performed by three-dimensional atom-probe field-ion microscopy techniques. The ability of this new experimental method to provide atomic-resolution images, both structural and chemical, was confirmed; the basic stacking structure of (001) planes in FeAl could be visualized with success. Moreover the presence of a <001> edge dislocation was also detected in the analysed zone. Further, B enrichment was measured in the vicinity of this defect; the B-rich region appeared as a pipe 5 nm in diameter, parallel to the dislocation line. The concentration of B in the core reached 3 at.%; this local enrichment in boron was accompanied by an Al depletion of more than 10 at.%. Boron in FeAl has a well known tendency to segregate to internal interfaces. In this letter, we show experimental evidence of the solute segregation to dislocation lines. The observed effects of this segregation on mechanical properties of FeAl, both at room temperature and high temperatures, are also discussed. [ABSTRACT FROM AUTHOR]

The introduction of a rubidium fluoride post deposition treatment (RbF-PDT) for Cu(In,Ga)Se2 (CIGS) absorber layers has led to a record efficiency up to 22.6% for thin-film solar cell technology. In the present work, high efficiency CIGS samples with RbF-PDT have been investigated by atom probe tomography (APT) to reveal the atomic distribution of all alkali elements present in CIGS layers and compared with non-treated samples. A Scanning Electron Microscopy Dual beam station (Focused Ion Beam–Gas Injection System) as well as Transmission Kikuchi diffraction is used for atom probe sample preparation and localization of the grain boundaries (GBs) in the area of interest. The analysis of the 3D atomic scale APT reconstructions of CIGS samples with RbF-PDT shows that inside grains, Rb is under the detection limit, but the Na concentration is enhanced as compared to the reference sample without Rb. At the GBs, a high concentration of Rb reaching 1.5 at. % was found, and Na and K (diffusing from the glass substrate) are also segregated at GBs but at lower concentrations as compared to Rb. The intentional introduction of Rb leads to significant changes in the chemical composition of CIGS matrix and at GBs, which might contribute to improve device efficiency. [ABSTRACT FROM AUTHOR]

A position and energy-sensitive detector has been developed for atom probe tomography (APT) instruments in order to deal with some mass peak overlap issues encountered in APT experiments. Through this new type of detector, quantitative and qualitative improvements could be considered for critical materials with mass peak overlaps, such as nitrogen and silicon in TiSiN systems, or titanium and carbon in cemented carbide materials. This new detector is based on a thin carbon foil positioned on the front panel of a conventional MCP-DLD detector. According to several studies, it has been demonstrated that the impact of ions on thin carbon foils has the effect of generating a number of transmitted and reflected secondary electrons. The number generated mainly depends on both the kinetic energy and the mass of incident particles. Despite the fact that this phenomenon is well known and has been widely discussed for decades, no studies have been performed to date for using it as a means to discriminate particles energy. Therefore, this study introduces the first experiments on a potential new generation of APT detectors that would be able to resolve mass peak overlaps through the energy-sensitivity of thin carbon foils.

Nanostructural features of nickel-base superalloys as revealed by atom probe field ion microscopy (APFIM) and atom probe tomography (APT) are reviewed. The more salient information provided by these techniques is discussed through an almost exhaustive analysis of literature over the last 30 years. Atom probe techniques are shown to be able to measure the composition of tiny gamma' precipitates, a few nanometers in size, and to reveal chemical order within these precipitates. Phase separation kinetics in model NiCrAl alloys was investigated with both 3DAP and Monte-Carlo simulation. Results are shown to be in good agreement. Plane by plane analysis of {001} planes of Ni(3)Al-type gamma' phase makes it possible to estimate the degree of order as well as the preferential sites of various addition elements (Ti, Cr, Co, W, Ta, Re, Ru, etc.) included in superalloys. Clustering effects of Re in the gamma solid solution were also exhibited. Due to its ultrahigh depth resolution, the microchemistry of interfaces and grain boundaries can be characterized on an atomic scale. Grain boundaries in Astroloy or N18 superalloys were found to be enriched in B, Mo, and Cr and Al depleted.