The effects of defects in purple AuAl2 thin films

Sputter deposited thin films consisting of the intermetallic phase AuAl₂ are known to display a different color than their bulk counterparts, gray or faint pink, instead of the intense purple the phase is famous for. Only after heat treatment is the typical color apparent. The reason for this behavior is assumed to be point defects in the film, a consequence of the deposition method. Heat treatment at 350 °C of 500 nm thin films results in a steady reduction in defects and the color becomes more intense. Ion irradiation by 3.5 MeV Au⁺ ions with fluences between 10¹² and 5 × 10¹⁵ ions cm^–2 reintroduces point defects in the material and thus gradually removes the color again. Interestingly, the color can be brought back to a very similar shade with subsequent thermal treatments, demonstrating reversibility in the process. The samples were investigated by means of X-ray diffraction, reflectometry, electron backscattered diffraction, scanning electron microscopy, light microscopy, transmission electron microscopy and resistivity measurements to obtain information about the correlation between color and the number of defects within the samples. The measured resistivity values were compared with values calculated using the combined Fuchs–Sondheimer/Mayadas–Shatzkes model. Vacancy concentrations were determined from the difference between the model and the measurements.     

Phonon scattering enhancement in silicon nanolayers

Dimensional confinement in silicon nanowires (NWs) is well-known for enhancing phonon scattering, thus leading to a pronounced reduction of thermal conductivity κ with respect to bulk material. The effect of confinement on phonon scattering in nanolayers (NLs), however, has not been fully understood. In this work, thermal conductivity on polycrystalline silicon NLs with roughened surfaces and thicknesses ranging from 30 to 100 nm has been experimentally investigated. For measurement purposes, the nanostructures were fabricated with a dedicated surface nano-machining process, thus producing vertical silicon nanostructures suspended on Al/Si electrodes on a silicon substrate, using SiO₂ as a sacrificial layer. By designing such structures in a four-terminal configuration, their κ could be determined by the current-voltage method. Boron doped silicon NLs were examined, at resistivity ranging between 2 and 10 m $\Upomega$ cm. We found an increase of phonon scattering from the confinement, since κ decreased steadily with the thickness from values typical of thick films (around 30 W m^?1 K^?1) down to <15 W m^?1 K^?1. Compared to NWs, NLs had displayed figures of merit smaller by one order of magnitude. However, due to the larger filling factor, they were able of generating more than five times the electric power per area unit that could be obtained with high-density stacks of top-efficiency NWs.     

Fast Sintering of Nanocrystalline Copper

The behavior of nanocrystalline (nc) copper specimens obtained by high energy ball milling (HEBM) and electromagnetic field-assisted sintering under stress and mechanical compression is explored. High yield stress values combined with plastic behavior are observed. The basic densification mechanisms involved in the production process and the peculiar action on the dislocation network are discussed.     

New strategies for reducing the pork back-fat content in typical Italian salami

In this work the possibility to substitute pork backfat with extra virgin olive oil (EVOO), adsorbed on whey protein-based crumb or white bread crumb, in typical Italian salami is addressed. Five types of salami were manufactured, under the usual commercial conditions, by replacing 0 (Control), 60% and 100% of pork backfat with whey protein-based crumb (WP60-WP100) and white pan bread (PB60-PB100), respectively, soaked in EVOO. Results highlighted that pH, weight loss, colour parameters and microbial counts did not show statistically significant differences between the Control and the modified salami. On the other hand, malonaldehyde was slightly lower in PB100, PB60, WP100 and WP60, compared to the Control. Chemical composition was significantly affected by formulations. Modified salami presented a better fatty acid profile showing lower saturated and higher monounsaturated fatty acids than control. Furthermore in all modified salami atherogenic and thrombogenic indices displayed the lowest values. The Control showed the highest values for Warner-Bratzler Shear, hardness, cohesiveness, gumminess and chewiness. Sensory evaluation of WP60 did not show significant differences compared to the Control, whereas PB100 and WP100 were unacceptable for taste.     

Stress–Strain Characteristics of Tin-Based Solder Alloys for Drop-Impact Modeling

The stress–strain properties of eutectic Sn-Pb and lead-free solders at strain rates between 0.1 s⁻¹ and 300 s⁻¹ are required to support finite-element modeling of the solder joints during board-level mechanical shock and product-level drop-impact testing. However, there is very limited data in this range because this is beyond the limit of conventional mechanical testing and below the limit of the split Hopkinson pressure bar test method. In this paper, a specialized drop-weight test was developed and, together with a conventional mechanical tester, the true stress–strain properties of four solder alloys (63Sn-37Pb, Sn-1.0Ag-0.1Cu, Sn-3.5Ag, and Sn-3.0Ag-0.5Cu) were generated for strain rates in the range from 0.005 s⁻¹ to 300 s⁻¹. The sensitivity of the solders was found to be independent of strain level but to increase with increased strain rate. The Sn-3.5Ag and the Sn-3.0Ag-0.5Cu solders exhibited not only higher flow stress at relatively low strain rate but, compared to Sn-37Pb, both also exhibited higher rate sensitivity that contributes to the weakness of these two lead-free solder joints when subjected to drop impact loading.     

Fabrication and laser operation of Yb:Lu2O3 transparent ceramics from co-precipitated nano-powders

In this article, 5 at.% Yb:Lu₂O₃ transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) posttreatment using co-precipitated nano-powders. The influence of precipitant molar ratio, ammonium hydrogen carbonate, to metal ions (AHC/M³⁺, R value) on the properties of Yb:Lu₂O₃ precursors and calcined powders was investigated systematically. It was found that the powders with different R value calcined at 1100°C for 4 hours were pure cubic Lu₂O₃ but the morphologies of precursors and powders behaved differently. The opaque samples pre-sintered at 1500°C for 2 hours grew into transparent ceramics after HIP posttreatment at 1750°C for 1 hour. The final ceramic with R = 4.8 showed the best optical quality with the in-line transmittance of 79.7% at 1100 nm. The quasi-CW laser operation was performed at 1034 nm and 1080 nm with a maximum output power up to 8.15 W as well as a corresponding slope efficiency of 58.4%.     

Solidification microstructure of centrifugally cast Inconel 625

Centrifugal casting is a foundry process allowing the production of near net-shaped axially symmetrical components.The present study focuses on the microstructural characterization of centrifugally cast alloys featuring different chemical compositions for the construction of spheres applied in valves made of alloy IN625 for operation at high pressure.Control of the solidification microstructure is needed to assure the reliability of the castings.Actually,a Ni-base superalloy such as this one should have an outstanding combination of mechanical properties,high temperature stability and corrosion resistance.Alloys such as IN625 are characterised by a large amount of alloying elements and a wide solidification range,so they can be affected by micro-porosity defects,related to the shrinkage difference between the matrix and the secondary reinforcing phases (Nb-rich carbides and Laves phase).In this study,the microstructure characterization was performed as a function of the applied heat treatments and it was coupled with a calorimetric analysis in order to understand the mechanism ruling the formation of micro-porosities that can assure alloy soundness.The obtained results show that the presence of micro-porosities is governed by morphology and by the size of the secondary phases,and the presence of the observed secondary phases is detrimental to corrosion resistance.     

Electromagnetic imaging within the contrast-source formulation by means of the multiscaling inexact Newton method

We introduce a new imaging technique that integrates the inexact Newton method into a multifocusing scheme within the contrast-source formulation of the inverse scattering problem. Representative results from an extensive validation concerned with both synthetic and experimental scattering data are reported to assess, also through comparisons, advantages and limitations of the proposed approach in terms of accuracy, robustness, and computational efficiency.     

Transfer-free electrical insulation of epitaxial graphene from its metal substrate

High-quality, large-area epitaxial graphene can be grown on metal surfaces, but its transport properties cannot be exploited because the electrical conduction is dominated by the substrate. Here we insulate epitaxial graphene on Ru(0001) by a stepwise intercalation of silicon and oxygen, and the eventual formation of a SiO(2) layer between the graphene and the metal. We follow the reaction steps by X-ray photoemission spectroscopy and demonstrate the electrical insulation using a nanoscale multipoint probe technique.