Infiltration of liquid metals in a nanoporous carbon

Gallium and mercury are employed as liquid phases in a nanoporous carbon-based energy absorption system. Owing to the large surface tensions, the nanopore surface is non-wettable. Pressure-induced infiltration is observed and defiltration is difficult. The energy absorption efficiency is much higher than that of previously investigated nanoporous silica-based systems. The nominal solid–liquid interfacial tension is dependent on the nanopore size.     

Thermal effects on infiltration of a solubility-sensitive volume-memory liquid

As the ion density at a solid–liquid interface changes, the interfacial tension varies accordingly, which can lead to a large energy density output, particularly when amplified by the high specific surface area of a nanoporous material. This concept is validated by the results of a controlled-temperature infiltration experiment on a hydrophobic zeolite immersed in a saturated aqueous solution of sodium acetate. As the temperature changes, the sodium acetate concentration varies significantly, which in turn causes a variation in infiltration pressure. Since the infiltration and defiltration are reversible, under the working pressure, this system exhibits a volume memory characteristic, with a non-monotonic temperature–volume relationship.     

Melting point depression method for determining the solid–liquid interfacial energy of metal elements: theoretical validation and updated compilation of data

Comparative analyses of the crystal nucleation method and the melting point depression (MPD) method for measuring the solid–liquid interface energy γ_sl are carried out. The MPD method is found more reliable and has several advantages from experiment through data analysis to theoretical generalisation. The MPD data in use, all reported before the 1970s, are updated with the derived γ_sl re-compiled. Finally, by invoking a melting model that we developed recently, an equation for calculating γ_sl is proposed on basis of the melting point depression method.     

Rapid dendritic growth within an undercooled Ni–Cu–Fe–Sn–Ge quinary alloy

A liquid quinary alloy with composition Ni–5%Cu–5%Fe–5%Sn–5%Ge has been prepared from a containerless state by undercooling. Dendritic growth of α-Ni phase took place with a velocity of 28 m s^?1 at the maximum degree of undercooling, which was as high as 405 K (0.24T _L). All of the four solute elements Cu, Fe, Sn and Ge exhibited a significant solute trapping effect during the rapid dendrite growth. Segregation-less solidification is consequently realized when the degree of undercooling is sufficiently large. The lattice constant of α-Ni solid solution phase is found to increase with the amount of multicomponent solute trapping.     

Bulk modulus of semiconductors and its pressure derivatives

Expressions for the bulk modulus and its first and second pressure derivatives for group I–VII, II–VI, III–V and IV–IV semiconductor binary compounds are derived using an ab initio pseudopotential approach to the total crystal energy within the framework of local density functional formalism. The computed results are very close to the available experimental data.     

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.     

Energetics and kinetics of surfaces and interfaces in the Fe-Pb system

The energy and the diffusivity of interfaces in the solid Fe-liquid Pb system have been investigated in the temperature range 650-900°C. Grain-boundary grooves are formed at the solid Fe-liquid Pb interface and these have been studied by atomic force microscopy. From the topography of the grooves the relative interfacial energies and interfacial diffusivities are obtained. It is found that liquid Pb does not wet the grain boundaries in Fe. Possible mechanisms for the growth of the grain-boundary grooves are discussed.     

Mixed-valence impurity in a nanoscale particle

We consider a mixed-valence Anderson impurity with infinite U embedded into a small metallic particle. The nanosize of the system leads to discrete energy levels rather than to a continuum of energy eigenstates for the host. Using the Brillouin-Wigner approximation we show that the magnetic susceptibility, which arises from the van Vleck admixing of the magnetic configuration into the ground state, is only weakly affected by the finite spacing of energy levels, while the specific heat and the entropy display an exponential activation at low temperatures, that is have properties deviating from a Fermi liquid.     

Temperature dependence of nucleation rate in a binary solid solution

The influence of regression (partial dissolution) effects on the temperature dependence of nucleation rate in a binary solid solution has been studied theoretically. The results of the analysis are compared with the predictions of the simplest Volmer–Weber theory. Regression effects are shown to have a strong influence on the shape of the curve of nucleation rate versus temperature. The temperature T_M at which the maximum rate of nucleation occurs is found to be lowered, particularly for low interfacial energy (coherent precipitation) and high-mobility species (e.g. interstitial atoms).     

Solid and liquid thermal expansion and structural observations in the quasicrystalline Cd84Yb16 compound

The structure of single-grain Cd₈₄Yb₁₆ samples aligned along the twofold and fivefold axes has been followed from 300 to 1050?K using high-energy synchrotron X-rays. The quasicrystal phase is stable up to its melting temperature of 914?K and has a large linear thermal expansion of 37.1?ppm?K^?1 over this temperature range. The samples melt congruently over a temperature range of less than 1?K. The liquid is 7% less dense than the solid and, upon cooling from the melt, the quasicrystal phase directly solidifies within a 1?K interval. The amount of undercooling achieved, about 5–25?K, was dependent on the cooling rate. The total scattering function of the liquid is consistent with a dilute liquid Cd structure. These results agree with suggestions that the structure of the liquid must undergo reordering in order to form the solid phases. However, there is no compelling evidence for icosahedral short-range order in the liquid prior to the formation of the quasicrystalline structure.     

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.     

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.     

Neuroimaging of mental imagery: An introduction

Adaptive mechanisms to protect cognitive performance under stressors through compensation in energy investment have previously received much research attention. However, stressors have also often been found to substantially reduce both performance and investment. The mechanisms underlying this dual negative effect are still unclear. This study tested the hypothesis that stressors can immediately hamper performance, which in turn reduces energy investment in later phases. In an experiment (N=103), we compared control and stressor conditions (noise or time pressure), investigating the effects of stressors on performance and information-sampling investment (as behavioural measure of energy investment) in two phases of a judgement task. The results showed an instant negative effect of stressors on performance and a delayed negative effect on information-sampling investment. Furthermore, impaired initial performance predicted the decline in investment over time. Finally, the effects of stressors on investment decline were partially mediated through initial performance level. The present findings contribute to theories aiming to explain the relationship between hampered performance and motivational losses.     

Time as non‐observational knowledge: How to straighten out ΔEΔt≥h

The Energy‐Time Uncertainty (ETU) has always been a problem‐ridden relation, its problems stemming uniquely from the perplexing question of how to understand this mysterious Δt. On the face of it (and, indeed, far deeper than that), we always know what time it is. Few theorists were ignorant of the fact that time in quantum mechanics is exogenously defined, in no ways intrinsically related to the system. Time in quantum theory is an independent parameter, which simply means independently known. In the early 1960s Aharonov (1961–64) and Bohm (1961–64) mounted a spirited attack against the ETU, which sealed its fate to the present date. By emphasising that time is always “well‐defined” in quantum theory, they were led to the conclusion that no ETU should exist, a view shared by many in the 1990s, if Busch (1990) is to be believed. In a similar vein, I emphasize that (a) physical systems occupy a particular energy state at a particular instant of time, if at all; (b) even in absence of all time‐measuring instruments, it is still trivially warranted that one can measure a system's energy as accurately as one pleases, and simply announce “The system's energy is exactly E NOW!”, a possibility which no quantum mechanics of any sort, or any physical theory whatsoever, can afford to tamper with or change, except circularly. One never loses one's own perception of time, when one measures the energy, a fact which no measurement conceivable can interfere with or affect. Both (a) and (b) uniquely entail that energy and time are compatible, if not indeed intimately interconnected, contrary to what the relevant uncertainty seems to affirm. In response to Aharonov's and Bohm's initial problem, I reinterpret ΔEΔt ≥ h, as directly derived from authentic quantum principles, without however having to assume a direct incompatibility between its related concepts, attributing their complementarity to conditions other than ordinarily assumed.     

High-magnetic-field-induced formation of aligned equiaxed grains during directional solidification

The application of a high magnetic field is capable of inducing the formation of aligned equiaxed grains in alloys during directional solidification. The alignment and refinement of the grains is enhanced as the magnetic field intensity increases. The thermoelectric power difference at the liquid/solid interface in four alloys has been measured in situ during directional solidification and it is concluded that the formation of aligned equiaxed grains in a magnetic field should be attributed to the combined action of a thermoelectric magnetic force and a magnetization force.     

On the Moral Value of Physical Activity: Body and Soul in Plato's Account of Virtue

It is arguable that some of the most profound and perennial issues and problems of philosophy concerning the nature of human agency, the role of reason and knowledge in such agency and the moral status and place of responsibility in human action and conduct receive their sharpest definition in Plato's specific discussion in the Republic of the human value of physical activities. From this viewpoint alone, Plato's exploration of this issue might be considered a locus classicus in the philosophy of sport. Indeed, it is in this place that Plato offers a highly distinctive account of the value of physical education in terms of its vital contribution to the development of a part of the soul that he characterises in terms of ‘spirit’, ‘energy’ and/or ‘initiative’. Drawing on more recent work in ethics and philosophy of action, this paper sets out to revisit and evaluate Plato's argument. While concluding that Plato's case ultimately flounders on fundamental uncertainty regarding the logical role of spirit in the explanation of agency, the paper concludes that there is much to be learned – in the philosophy of sport and elsewhere – from the instructive failures of Plato's argument.     

Homeokinetics/Homeodynamics: A Physical Heuristic for Life and Complexity

This essay addresses the puzzlement, the missing piece, sensed when attempts are made to build a bridge from the synchronic, informational genotype to the diachronic, dynamic phenotype—a regular mapping that seems to be extraphysical. There is no formal, dynamic foundation for the bridge. Albert Einstein, Max Delbrück, and Erwin Schrödinger all expressed acute awareness of limitations of contemporary physics when considering biology because physics addresses much simpler sysems. As a proposed remedy, a new physical heuristic, homeokinetics, developed by Arthur Iberall and Harry Soodak (and later recast for biology by me as homeodynamics) is introduced here as a foundation for comprehending energy flows and transformations in complex systems, including those in metabolic networks of living systems. Their individual dynamic stability is flexible and marginal—it must allow for adaptations and changes in physiological and behavioral states to occur in an orderly fashion as external circumstances change. At the population level, stability must allow for evolvability of chemical networks that have energized terrestrial living systems for about 3.9 billion years. Homeokinetics/homeodynamics emphasizes that persistent, marginally stable metabolic networks, as open thermodynamic systems, necessarily organize energy processing as cyclic, physical action modes. Conceptually, that organization is under 2 kinds of biological time pressure—time as a cycle that daily closes the thermodynamic books and time as an arrow orthogonally pressing the cyles into the future, creating joint time as a helix. In most animals, after maturity, the helix is additionally shaped into a tapered ellipsoid by a senesence process that gains influence as dynamic degrees of freedom are frozen out by the constructions of development.     

Preschool language exposure and use: A comparison study of dual-language learners and English monolingual children

This study explored the language experiences of dual language learners (DLL; n = 19) and English monolinguals (EM; n = 13) in preschool classrooms where English is the primary language of instruction and many home languages are present. Using the Language ENvironment Analysis™ system as a primary tool, we quantitatively analysed an average of 34 hours of recordings collected over 5–8 days for each participating child (M_age = 52 months) in six classrooms. Results showed that, during a typical preschool day, DLLs spoke as much as EMs but received less adult talk overall and had more 5-min segments with zero adult–child conversations than their EM peers. Follow-up analyses revealed that teachers generally talked less when children initiated the conversations than when adults initiated the conversations, and this pattern was particularly evident for DLLs. Study implications and future research are discussed.     

Structural stability of W2B5 under high pressure

High-pressure structural stability studies have been carried out on tungsten boride W₂B₅ up to maximum pressure of 36 GPa using a Mao-Bell diamond-anvil cell at beamline BR-12 of the ELETTRA synchrotron facility (λ = 0.68881 Å). The hexagonal phase (S.G:P6₃/mmc) of W₂B₅ is stable up to the maximum pressure studied. The bulk modulus is estimated to be ~347 GPa using the Birch–Murnaghan equation of state. The variation of lattice parameters and bond lengths B–B and W–B have been studied and the c-axis is seen to be marginally more compressible than the a-axis.     

Interfacial structure in SiC/Si3N4 composite whiskers

Abstract

High-resolution TEM techniques have been used to investigate the interfacial structure in SiC/Si₃N₄ composite whiskers grown by a vapour–liquid–solid process. On one side of the whisker a coherent interface with the relationship of (111)β-SiC∥(102) α-Si₃N₄ has been observed, on the other side the interface is (111)β-SiC∥(114)α-Si₃N₄.