Surface tension of substantially undercooled liquid Ti–Al alloy

It is usually difficult to undercool Ti–Al alloys on account of their high reactivity in the liquid state. This results in a serious scarcity of information on their thermophysical properties in the metastable state. Here, we report on the surface tension of a liquid Ti–Al alloy under high undercooling condition. By using the electromagnetic levitation technique, a maximum undercooling of 324 K (0.19 T _L) was achieved for liquid Ti-51 at.% Al alloy. The surface tension of this alloy, which was determined over a broad temperature range 1429–2040 K, increases linearly with the enhancement of undercooling. The experimental value of the surface tension at the liquidus temperature of 1753 K is 1.094 N m^?1 and its temperature coefficient is ?1.422 × 10^?4 N m^?1 K^?1. The viscosity, solute diffusion coefficient and Marangoni number of this liquid Ti–Al alloy are also derived from the measured surface tension.     

Sensing everyday activity: Parent perceptions and feasibility

Mobile and wearable sensors provide a unique opportunity to capture the daily activities and interactions that shape developmental trajectories, with potential to revolutionize the study of development (de Barbaro, 2019). However, developmental research employing sensors is still in its infancy, and parents’ comfort using these devices is uncertain. This exploratory report assesses parent willingness to participate in sensor studies via a nationally representative survey (N = 210) and live recruitment of a low-income, minority population for an ongoing study (N = 359). The survey allowed us to assess how protocol design influences acceptability, including various options for devices and datastream resolution, conditions of data sharing, and feedback. By contrast, our recruitment data provided insight into parents’ true willingness to participate in a sensor study, with a protocol including 72 h of continuous audio, motion, and physiological data. Our results indicate that parents are relatively conservative when considering participation in sensing studies. However, nearly 41 % of surveyed parents reported that they would be at least somewhat willing to participate in studies with audio or video recordings, 26 % were willing or extremely willing, and 14 % reported being extremely willing. These results roughly paralleled our recruitment results, where 58 % of parents indicated interest, 29 % of parents scheduled to participate, and 10 % ultimately participated. Additionally, 70 % of caregivers stated their reason for not participating in the study was due to barriers unrelated to sensing while about 25 % noted barriers due to either privacy concerns or the physical sensors themselves. Parents’ willingness to collect sensitive datastreams increased if data stayed within the household for individual use only, are shared anonymously with researchers, or if parents receive feedback from devices. Overall, our findings suggest that given the correct circumstances, mobile sensors are a feasible and promising tool for characterizing children’s daily interactions and their role in development.     

Thermophysical properties of substantially undercooled liquid Ti-Al-Nb ternary alloy measured by electromagnetic levitation

The thermophysical properties of undercooled liquid alloys at high temperature are usually difficult to measure by experiment. Here, we report the specific heat of liquid Ti₄₅Al₄₅Nb₁₀ ternary alloy in the undercooled state. By using electromagnetic levitation technique, a maximum undercooling of 287?K (0.15 T _L) is achieved for this alloy. Its specific heat is determined to be 32.72?±?2.51?J?mol^?1 K^?1 over a broad temperature range of 1578–2010?K.     

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

The surface tensions of liquid ternary Ni–5%Cu–5%Fe, quaternary Ni–5%Cu–5%Fe–5%Sn and quinary Ni–5%Cu–5%Fe–5%Sn–5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T _L), 349 (0.21T _L) and 363?K (0.22T _L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357?N/m at their liquidus temperatures of 1719, 1644 and 1641?K. Their temperature coefficients are ?4.972?×?10^–4, ?5.057?×?10^?4 and ?5.385?×?10^?4?N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.     

The temperature dependence of the optical dispersion parameters in Si and Ge

Abstract

In Si and Ge, the optical dispersion parameters (single-oscillator energy E_o , dispersion energy E_d and bond energy gap E_g developed by Wemple and DiDomenico, and Phillips) have been analysed in the temperature range 100-300 K using data obtained by Icenogle et al. E_o and E_g exhibit a very small temperature dependence in both materials. The thermal coefficients of the dispersion energy, dE_d/dT, have opposite signs (Si, –41·9 × 10^?4eVK^?1; Ge, +37·7 × 10^?4eVK^?1).     

Pressure dependence of the electrical resistivity of natural cassiterite SnO2 and of undoped and Co-doped nanocrystalline SnO2

The pressure dependence of the electrical resistivity of three different samples of cassiterite, namely natural cassiterite SnO₂, synthetic nanocrystalline SnO₂ (with crystallite size 46?nm) and nanocrystalline Co-doped SnO₂ (with crystallite size 32?nm), has been measured up to 7?GPa at room temperature. The resistivity of natural cassiterite SnO₂ decreases from 2.5?×?10⁴?Ωm at normal pressure and temperature to 1.7?×?10⁴?Ωm at 7.0?GPa. The nanocrystalline SnO₂ has a high resistivity 6.0?×?10⁵?Ωm at normal pressure and temperature and decreases with pressure reaching a value of 2.98?×?10⁵?Ωm at 7?GPa. The activation energy of the electrical conduction of the studied samples were found to be 0.32?eV for the natural SnO₂, 0.40?eV for the nanocrystalline SnO₂ sample and 0.28?eV for the nanocrystalline Co-doped SnO₂. Measurements of the pressure dependence of the electrical resistivity of the Co-doped SnO₂ showed a decrease from 3.60?×?10⁵ to 5.4?×?10⁴?Ωm at 7.0?GPa. We did not observe any pressure-induced phase transition in SnO₂ up to 7?GPa. This study of the high-pressure phase stability of cassiterite corroborates the experimental findings of SnO₂ nanoinclusions in diamonds.     

Dynamic properties of an ultrafine-grained Mg–Zn–Zr alloy

The effect of ultrafine-grained structure formation in Mg–Zn–Zr alloy ZK60 on its mechanical response was investigated at strain rates ranging from quasi-static to dynamic regimes. The study demonstrated that the strength characteristics of the material rise significantly with increasing strain rate, while its ductility is reduced. These effects are particularly pronounced in the dynamic loading regime, at strain rates in the (1?5)?×?10²?s^?1 range. In the ultrafine-grained alloy ZK60, the energy absorption per unit volume, W, is enhanced by grain refinement by a factor as high as eight for the highest strain rate of 5?×?10²?s^?1 investigated. The analysis is focused on the microstructure features that bring about the observed improvement of the tensile characteristics, as well as the deformation and fracture modes prevalent at different strain rates. The results obtained contribute to the exploration and understanding of dynamic behaviour of magnesium alloys.     

On the ultra-high-strain rate shock deformation in copper single crystals: multiscale dislocation dynamics simulations

Multiscale dislocation dynamics plasticity (MDDP) calculations are carried out to simulate the mechanical response of copper single crystals that have undergone shock loading at high strain rates ranging from 1?×?10⁶ to 1?×?10¹⁰?s^?1. Plasticity mechanisms associated with both the activation of pre-existing dislocation sources and homogeneous nucleation of glide loops are considered. Our results show that there is a threshold strain rate of 10⁸?s^?1 at which the deformation mechanism changes from source activation to homogeneous nucleation. It is also illustrated that the pressure dependence on strain rate follows a one-fourth power law up to 10⁸?s^?1 beyond which the relationship assumes a one-half power law. The MDDP computations are in good agreement with recent experimental findings and compare well with the predictions of several dislocation-based continuum models.     

Strain rate response of a Ni–Ti shape memory alloy after hydrogen charging

In this work, we investigate the susceptibility of Ni–Ti superelastic wires to the strain rates during tensile testing after hydrogen charging. Cathodic hydrogen charging is performed at a current density of 10?A/m² during 2–12?h in 0.9% NaCl solution and aged for 24?h at room temperature. Specimens underwent one cycle of loading-unloading reaching a stress value of 700 MPa. During loading, strain rates from 10^?6 to 5?×?10^?2?^?s^?1 have been achieved. After 8?h of hydrogen charging, an embrittlement has been detected in the tensile strain rate range of 10^?6 to 10^?4?s^?1. In contrast, no embrittlement has been detected for strain rates of 10^?3?s^?1 and higher. However, after 12?h of hydrogen charging and 24?h of annealing at room temperature, the embrittlement occurs in the beginning of the austenite-martensite transformation for all the studied strain rate values. These results show that for a range of critical amounts of diffused hydrogen, the embrittlement of the Ni–Ti superelastic alloy strongly depends on the strain rate during the tensile test. Moreover, it has been shown that this embrittlement occurs for low values of strain rates rather than the higher ones. This behaviour is attributed to the interaction between the diffused hydrogen and growth of the martensitic domain.     

Specific heat,enthalpy, and density of undercooled liquid Fe–Si–Sn alloy

The specific heat of liquid Fe₉₀Si_6.95Sn_3.05 alloy has been investigated by electromagnetic levitation drop calorimetery in the temperature range of 1390–2140 K. The enthalpy of this liquid alloy increases linearly with the rise of temperature. Furthermore, the enthalpy obtained from molecular dynamics calculation shows a similar trend to the experimental results in a broader temperature range of 1000–2200 K. The calculated specific heat is 39.7 J mol^?1 K^?1, which agrees well with the experimental result of 39.9 J mol^?1 K^?1. The density of this liquid alloy decreases as a quadratic function of temperature.     

Perspective on “in the wild” movement analysis using machine learning

Recent advances in wearable sensing and machine learning have created ample opportunities for “in the wild” movement analysis in sports, since the combination of both enables real-time feedback to be provided to athletes and coaches, as well as long-term monitoring of movements. The potential for real-time feedback is useful for performance enhancement or technique analysis, and can be achieved by training efficient models and implementing them on dedicated hardware. Long-term monitoring of movement can be used for injury prevention, among others. Such applications are often enabled by training a machine learned model from large datasets that have been collected using wearable sensors. Therefore, in this perspective paper, we provide an overview of approaches for studies that aim to analyze sports movement “in the wild” using wearable sensors and machine learning. First, we discuss how a measurement protocol can be set up by answering six questions. Then, we discuss the benefits and pitfalls and provide recommendations for effective training of machine learning models from movement data, focusing on data pre-processing, feature calculation, and model selection and tuning. Finally, we highlight two application domains where “in the wild” data recording was combined with machine learning for injury prevention and technique analysis, respectively.     

Secondary defects induced by ion and electron irradiation of GaSb

Secondary defects induced by ion and electron irradiation up to 6?dpa (displacements per atom) at liquid-nitrogen temperature in GaSb thin films are compared. For Sn ion (60?keV) irradiation, voids were observed. However, for high-energy electron (2?MeV) irradiation, interstitial-type dislocation loops were produced. The densities of voids and interstitial-type dislocation loops were almost equivalent (8?×?10¹⁴?voids/m² and 3?×?10¹⁴?loops/m²) after irradiations at the same damage level of 6?dpa. It is concluded that the formation of voids by ion irradiation follows the creation of localised vacancy defects in cascade damage.     

Formation of Cu precipitates and vacancy clusters in neutron-irradiated Fe–Cu alloys

Two Fe–Cu binary model alloys, Fe–0.3Cu and Fe–0.6Cu, were irradiated with fission neutrons at doses ranging from 4?×?10^?6 to 0.16 dpa (displacements per atom) at ～573 K to investigate the formation of Cu precipitates and microstructural evolution. The Cu content only affected the formation of Cu precipitates and microvoids at low doses. In Fe–0.3Cu, the formation of microvoids and Cu precipitates initiated at doses of 1.2?×?10^?4 and 4?×?10^?5 dpa, respectively. On the other hand, the formation of microvoids started at a dose of 4?×?10^?4 dpa in Fe–0.6Cu, and Cu precipitates were formed even after irradiation to 4?×?10^?6 dpa. On further irradiation, the difference in the formation of Cu precipitates and microvoids was small. Microvoids grew with increasing irradiation dose up to 3?×?10^?3 dpa in both alloys. Prominent aggregation of Cu atoms occurred upon irradiation from 3?×?10^?3 to 1.6?×?10^?2 dpa and the microvoids shrank. The Cu precipitates no longer grew, and microvoids nucleated and grew in the matrix above a dose of 1.6?×?10^?2 dpa in both alloys. The present studies clearly reveal the relationships between the formation and growth of Cu precipitates and microvoids with irradiation dose.     

First principles determination of the Peierls stress of the shuffle screw dislocation in silicon

The Peierls stress of the a/2?110? screw dislocation belonging to the shuffle set is calculated for silicon using density functional theory. We have checked the effect of boundary conditions by using two models, the supercell method where one considers a periodic array of dislocations, and the cluster method where a single dislocation is embedded in a small cluster. The Peierls stress is underestimated with the supercell and overestimated with the cluster. These contributions have been calculated and the Peierls stress is determined in the range between 2.4?×?10^?2 and 2.8?×?10^?2?eV?Å^?3. When moving, the dislocation follows the {111} plane going through a low energy metastable configuration and never follows the 100 plane, which includes a higher energy metastable core configuration.     

Voids formed from solidifying tin particles in solid aluminium

In this study, voids commonly associated with tin particles in two aluminium alloys containing microalloying additions (0.01 at.%) of tin have been observed by transmission electron microscopy. The voids were generated by quenching the alloys at moderate rates (10²–10³ K s^?1) from a temperature (718 K) in excess of the melting temperature (501 K) of elemental tin in tin–microalloyed aluminium. Estimates of the void volume as a function of the volume of the associated tin particle reveal a linear relationship consistent with the excess volume resulting from the solidification of the tin particle. The formation and stabilisation of shrinkage voids in metallic alloys are suggested to arise from a combination of high vacancy supersaturation, the large volumetric misfit strain of the solidifying tin particle and a reduction in void surface energy associated with segregation of alloying elements.     

Abnormally high residual dislocation density in pure aluminum after Al/Ti/Al laminate annealing for seven days

We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate annealed at 873 K for seven days. The residual dislocation density reaches 7.5 × 10¹⁴ m^?2, higher than that in aluminum after severe plastic deformation processes such as accumulative roll bonding and high-pressure torsion. It is proposed that the high residual dislocation density may result from obstruction of the movement of TiAl₃ nanoparticles by the grain boundary and Ti atoms conglomerating at vacancies distributed in the aluminium matrix at a high temperature for a sufficient time to allow a relatively stable crystal.     

A microcomputer interface for decoding telemetry data and displaying them numerically and graphically in real time

A microcomputer (IBM-PC) interface for decoding ultrasonic telemetry pulse-modulated signals from either unisensor or multisensor (time-multiplexed) transmitters is described. Pulse intervals, recorded by the interface, and corresponding independently measured parameter levels (i.e., swimming directions, speeds, depths, water temperature, and ambient irradiance levels) are entered into a calibration file. The IBM-PC uses this file to convert the signal’s pulse intervals to sensor states and displays these in real time. States of up to eight multiplexed sensors can be displayed concurrently in either numerical or graphical format (as histograms) with low resolution (16 axis divisions) or, for a particular sensor, with high resolution (70 axis divisions). The circuit components mount on the IBM Prototype Card (with foil for interfacing logic) allowing easy installation in the IBM-PC’s expansion slot. The 35K of controlling software is written in Pascal with four subroutines in assembly language.     

Dislocation relaxation in aluminium single crystals at 10 MHz frequency

Abstract

Dislocation relaxation, namely the Bordoni peak, in the three principal planes of a high-purity aluminium single crystal has been studied by measuring the ultrasonic attenuation of longitudinal waves at a frequency of 10 MHz using a conventional ultrasonic single-ended pulse-echo technique. The crystals of <100>, <110>, or <111> orientation were deformed by compression, and the temperature dependence of the ultrasonic attenuation was measured after applying resolved shear stresses ranging up to 60N mm^?2. The results lead to the following conclusions: (i) The temperature of the Bordoni peak is essentially independent of the orientation; (ii) the temperature of the peak decreases up to a resolved shear stress near 28 N mm^?2 and then increases slightly for higher prior stresses; (iii) the peak height increases with increasing deformation; and (iv) a subsidiary peak at the lower temperature side of the Bordoni peak (the Niblett-Wilks peak) appears only at low deformations.     

Does habit strength moderate the intention–behaviour relationship in the Theory of Planned Behaviour? The case of fruit consumption

The present study examined if habit strength moderated the influence of intention on fruit consumption in a Dutch adult sample (N?=?521, 46.3% males, mean age?=?34.50, SD?=?10.87), using the theoretical relations of the Theory of Planned Behaviour (TPB). TPB variables and habit strength were assessed at baseline. Fruit consumption was assessed with a validated questionnaire five weeks later. Three groups were created: low habit strength (n?=?180), medium habit strength (n?=?185) and high habit strength (n?=?156). Confirmatory factor analyses and multi-group path analyses were performed using AMOS 4.0. A good fit was obtained for the overall measurement model and the structural models. Multi-group path analyses showed that intention was a significant predictor of fruit consumption in the low habit (β?=?0.36, p?<?0.001) and medium habit group (β?=?0.30, p?<?0.001), but a non-significant predictor in the high habit group (β?=?0.05, p?=?0.596). Implications for information-based and motivation-based interventions are discussed.     

Frequency-temperature dependent dynamics of dielectrics in ferric oxoborate Fe3BO6 of cocktail structure of nanorods

Oxoborates have both dielectric and magnetic properties useful for magnetodielectric devices, sensors, or biological tools. Such compounds Fe₂BO₄, Fe₃BO₅, or Fe₃BO₆ are known to grow easily as single crystals in a liquid flux. A polycrystalline phase forms only on controlled conditions of a solid state reaction of the basic oxides. In this study, we report highly dielectric Fe₃BO₆ when grown in a specific shape of nanorods (～200?nm diameter and 50–100?µm length) from an iron borate glass, which offers devisable shapes of sheets, discs, and fibers. Frequency (f)-temperature reliant dynamics of dielectric constant ε_r is studied over 25–300°C at 0.1–10^3?kHz frequencies. At low frequency such as 100?Hz, a large ε_r -value 40,000, better than most of high ε_r -value ferroelectrics, incurs at room temperature. At f?≥?50?kHz, although only an order of diminished ε_r -value lasts, it increases steadily with temperature, possibly due to increasing electrical conductivity in a specific resistor–capacitor network. Suppressed dielectric relaxation and spin-flops share a merely weak spin-reorientation transition near 160°C. A stable power loss ≤0.5 lasts at f?>?10?kHz useful for possible applications of magnetodielectric materials.