Equation of state of liquid Fe–17 wt%Si to 12 GPa

Equation of state (EOS) of liquid Fe–17 wt%Si has been investigated at a temperature of 1773 K and pressures up to 12 GPa by the sink/float technique using composite spheres. The EOS of liquid Fe–17 wt%Si, in the form of the second order Birch–Murnaghan equation, produces K _0T=68±2 GPa when K′_0T=4.0. Considering the effect of temperature and pressure on K _0T, extrapolation of this EOS to Earth's outer core conditions reveals that the addition of Si to liquid Fe decreases its density ρ and increases its compressional wave velocity V _P , indicating that Si is a possible light element candidate in the outer core. The possible existence of Si in the cores of other planetary bodies is also discussed.     

Thermodynamics and surface properties of liquid Al–Ga and Al–Ge alloys

The surface properties of Al–Ga and Al–Ge liquid alloys have been theoretically investigated at a temperature of 1100 K and 1220 K respectively. For the Al–Ga system, the quasi chemical model for regular alloy and a model for phase segregating alloy systems were applied, while for the Al–Ge system the quasi chemical model for regular and compound forming binary alloys were applied. In the case of Al–Ga, the models for the regular alloys and that for the phase segregating alloys produced the same value of order energy and same values of thermodynamic and surface properties, while for the Al–Ge system, the model for the regular alloy reproduced better the thermodynamic properties of the alloy. The model for the compound forming systems showed a qualitative trend with the measured values of the thermodynamic properties of the Al–Ge alloy and suggests the presence of a weak complex of the form Al₂Ge₃. The surface concentrations for the alloys show that Ga manifests some level of surface segregation in Al–Ga liquid alloy while the surface concentration of Ge in Al–Ge liquid alloy showed a near Roultian behavior below 0.8 atomic fraction of Ge.     

Vapor–liquid and liquid–liquid equilibrium for binary systems ester + a new protic ionic liquid

This study reports the synthesis of a new protic ionic liquid, bis(2-hydroxyethyl)ammonium butyrate (2-HE₂AB), performed by a Brønsted acid–base reaction between butanoic acid and bis(2-hydroxyethyl)ammonia. The new ionic liquid was characterized by 1D hydrogen NMR spectrum. The ionic liquid shows complete solubility in water, methanol, and ethanol, and is partially soluble in methyl acetate, ethyl acetate, and propyl acetate, while it is not soluble in some alkanes. Density, refractive index, and vapor–liquid equilibrium were measured for the binary system 2-HE₂AB + methyl acetate at atmospheric pressure. Furthermore, density, refractive index, and liquid–liquid equilibrium were measured for the binary systems 2-HE₂AB + ester (methyl acetate, ethyl acetate, or propyl acetate) at 293.2 K. The Peng-Robinson equation of state, coupled with the Wong-Sandler mixing rule, was used in the thermodynamic modeling of density, vapor–liquid, and liquid–liquid equilibrium data. The COSMO-SAC activity coefficient model was used to calculate the activity coefficient within the Wong-Sandler mixing rule. The calculations show deviations for density, for the vapor–liquid equilibrium, and for the non-polar and polar phases of the liquid–liquid equilibrium within 13.0, 0.1, 132.5, and 23.8 %, respectively.     

Spatial heterogeneity in liquid–liquid phase transition

Molecular dynamics simulations are performed to investigate the liquid–liquid phase transition(LLPT) and the spatial heterogeneity in Al–Pb monotectic alloys. The results reveal that homogeneous liquid Al–Pb alloy undergoes an LLPT,separating into Al-rich and Pb-rich domains, which is quite different from the isocompositional liquid water with a transition between low-density liquid(LDL) and high-density liquid(HDL). With spatial heterogeneity becoming large, LLPT takes place correspondingly. The relationship between the cooling rate, relaxation temperature and percentage of Al and the spatial heterogeneity is also reported. This study may throw light on the relationship between the structure heterogeneity and LLPT, which provides novel strategies to control the microstructures in the fabrication of the material with high performance.     

Structural and dielectric behaviors of Bi4Ti3O12 – lyotropic liquid crystalline nanocolloids

We investigated the structural and dielectric dynamics of nanocolloids comprising lyotropic liquid crystals and bismuth titanate (Bi₄Ti₃O₁₂) spherical nanoparticles (≈16–18 nm) of varying concentration 0.05 and 0.1 wt%. The lyotropic liquid crystalline mixture was prepared by a binary mixture of cetylpyridinuium chloride and ethylene glycol mixed in 5:95 wt% ratio. Binary lyotropic mixture exhibited hexagonal lyotropic phase. Structural and textural characterizations of nanocolloids infer that the nanoparticles were homogeneously dispersed in the liquid crystalline matrix and did not perturb the hexagonal ordering of the lyotropic phase. The dielectric constant and dielectric strength were found to be increased with the rise in the Bi₄Ti₃O₁₂ nanoparticles concertation in the lyotropic matrix. A significant increase of one order was observed in the ac conductivity of colloidal systems as compared to the non-doped lyotropic liquid crystal. Relaxation parameters of the non-doped lyotropic liquid crystal and colloidal systems were computed and correlated with other parameters.     

Carbon–ionic liquid double-layer capacitors

A series of electrochemical capacitors, based on activated carbon powders (ACP, specific surface area 870 and 2600 m²/g) and ionic liquids as electrolytes, were prepared and tested. The ionic liquids consisted of 1-ethyl-3-methyl imidazolium (EMIm⁺), 1-butyl-3-methyl imidazolium (BMIm⁺) and 1-methyl-1-propyl pyrrolidinium (BMPy⁺) cations, as well as of tetrafluoroborate, hexafluorophosphate and bis((trifluoromethyl)sulfonyl) imide anions. A typical capacitor consisted of two electrodes each with a mass of ca. 15–30 mg, and showed a capacity of ca. 0.35–1.5 F; this leads to a specific capacity of the carbon electrode material within the range of 45 (ACP 870 m²/g)–180 F/g (ACP 2600 m²/g). The specific capacity expressed versus total surface of carbon material was within the range of 5.2–6.9 μF/cm². The electrochemical stability window of ionic liquids determined at the glassy carbon electrode is within the range of ca. 3.0–4.2 V. The energy stored in a capacitor based on activated carbons and ionic liquids may be high, due to a broad practical electrochemical stability window of ca. 3 V. Ionic liquids are characterised by negligible vapour pressure; such a capacitor emits no volatile organic compounds and may be regarded as environmentally friendly.     

Vapor–liquid–solid growth and narrow-band ultraviolet photoluminescence of well-aligned GeO2 nanowire arrays with controllable aspect ratios

GeO₂ nanowire arrays have been fabricated by thermal evaporation of Ge powder in air via a vapor–liquid–solid mechanism with Au as a catalyst. The GeO₂ nanowires are single crystalline with a hexagonal structure and have a controllable aspect ratio in the range of 23–167. The controllable synthesis of GeO₂ nanowire arrays with different aspect ratios was achieved by adjusting the heating temperature and time. Photoluminescence spectra of the GeO₂ nanowire arrays were measured at room temperature, and two ultraviolet emission peaks at 347 and 364 nm are observed for the first time, which indicates that the GeO₂ nanowire arrays may have potential applications in nanoscale photonic and electronic devices. Moreover, this vapor–liquid–solid growth process may be employed for synthesis of the highly oriented nanowire arrays of other oxides, and provides opportunities for both fundamental research and technological applications.     

Response properties at the dynamic water/dichloroethane liquid–liquid interface

ABSTRACT

We present a novel approach for calculating the static dielectric permittivity profile of a liquid–liquid interface (LLI) from molecular dynamics simulations. To obtain well-defined features, comparable to those observed at solid–liquid interfaces, we find it essential to reference to the instantaneous liquid–liquid interface rather than the more commonly used average Gibbs interface. We provide a coarse-grained approach for the practical definition of the instantaneous interface and present numerical results for the prototypical water/1,2-dichloroethane system. These results show that the parallel components of the dielectric permittivity tensor can be accurately extracted. In contrast, the perpendicular component does not converge to the correct bulk value at large distances from the LLI, highlighting a flaw in the regularly applied coarse-graining procedure.     

Electron–hole liquid in low-dimensional silicon–germanium heterostructures

A brief review is given of the studies in which quasi-two-dimensional spatially-direct and dipolar electron–hole liquids in Si/SiGe/Si type-II heterostructures with a low Ge content in the SiGe layer were discovered and investigated.     

Disorder in liquid Cu–Pd alloys

The disorder in thermodynamic and microscopic structure of liquid Cu–Pd alloy at 1350?K has been studied using regular associated solution model. For this, we have calculated free energy of mixing (G_M ), activity (a), concentration fluctuation in long wavelength limit [S_CC (0)] and chemical short-range order parameter (α ₁) of liquid Cu–Pd alloy at 1350?K. The energetic and structural asymmetry of liquid Cu–Pd alloys has been successfully explained on the basis of regular associated solution model.     

Laser-induced film ejection at interfaces: Comparison of the dynamics of liquid and solid films

The ejection dynamics of nanometer-thin fluid isopropanol and solid CO₂ films are investigated. The films are deposited on a silicon substrate, which is rapidly heated by a nanosecond laser pulse (Nd:YAG, 532 nm). A small fraction of material at the interface evaporates and the film on top is ejected as an intact layer. The kinetic energies of the two different films with thicknesses between 100 nm and 1 μm give an insight into the dynamics of a flying lamella.     

Nonextensive nuclear liquid–gas phase transition

We study an effective relativistic mean-field model of nuclear matter with arbitrary proton fraction at finite temperature in the framework of nonextensive statistical mechanics, characterized by power-law quantum distributions. We investigate the presence of thermodynamic instability in a warm and asymmetric nuclear medium and study the consequent nuclear liquid–gas phase transition by requiring the Gibbs conditions on the global conservation of baryon number and electric charge fraction. We show that nonextensive statistical effects play a crucial role in the equation of state and in the formation of mixed phase also for small deviations from the standard Boltzmann–Gibbs statistics.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions II: beryllium nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons and charged pions, in the interactions with a 5% λ _abs thick stationary beryllium target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20° <θ<125°.     

Ionic liquids screening for desulfurization of natural gasoline by liquid–liquid extraction

Seventy five ionic liquids (ILs) were tested as a sequestering agent of sulfured compounds in natural gasoline (NG). Desulphurization of NG was performed by means of liquid–liquid extraction method at room temperature and atmospheric pressure. Experimental ILs containing imidazolium, pyridinium, and ammonium cations along with organic and inorganic anions were synthesized conventionally and under microwave and sonochemical conditions. The effect of the molecular structure of ILs on the desulfurization efficiency of NG with high sulfur content was evaluated. Analysis indicated that the anion type played a more important role than the cation on the desulphurization process. ILs based on halogen–ferrates and halogen–aluminates exhibited the highest efficiency in sulfur removal, and their efficiency is further improved when there is an excess of metallic salt in a ratio of at least 1:1.3 during the synthesis of the corresponding IL. An explanation for the ability of metallic ILs to remove sulfur-containing compounds from natural gasoline based on the ratio of the ionic charge to the atomic radius is proposed. Furthermore, a method to recover and reuse water-sensitive to halogenated precursors is described.     

Nucleon electromagnetic form factors in a quark–gluon core model

We study the nucleon electromagnetic form factors in a quark–gluon core model framework, which can be viewed as an extension of the Isgur–Karl model of baryons. Using this picture we derive nucleon electromagnetic dipole form factors at low Q ² and the deviation from the dipole form at high Q ², that are consistent with the existing experimental data.     

Corrections to Hawking-like radiation for a Friedmann–Robertson–Walker universe

Recently, a Hamilton–Jacobi method beyond the semiclassical approximation in black hole physics was developed by Banerjee and Majhi. We generalize their analysis of black holes to the case of a Friedmann–Robertson–Walker (FRW) universe. It is shown that all the higher order quantum corrections in the single particle action are proportional to the usual semiclassical contribution. The corrections to the Hawking-like temperature and entropy of the apparent horizon for the FRW universe are also obtained. In the corrected entropy, the area law involves a logarithmic area correction together with the standard term with the inverse power of the area.     

Suppression of forward dilepton production from an anisotropic quark–gluon plasma

We calculate the rapidity dependence of leading-order medium dilepton yields resulting from a quark–gluon plasma which has a local time-dependent anisotropy in momentum space. We present a phenomenological model which includes the temporal evolution of the plasma anisotropy parameter, ξ, and the hard momentum scale, p _hard. Our model interpolates between a 1+1 dimensional collisionally broadened expansion at early times and a 1+1 dimensional ideal hydrodynamic expansion at late times. Using our model, we find that at LHC energies, forward high-energy medium dilepton production would be suppressed by a factor of up to 3 if one assumes an isotropization/thermalization time of 2 fm/c. Therefore, it may be possible to use forward dilepton yields to experimentally determine the time of the onset of locally isotropic hydrodynamic expansion of the quark–gluon plasma as produced in ultrarelativistic heavy-ion collisions.     

Modeling erbium–thulium-co-doped fiber amplifier for 1400–1650 nm band

We present numerical models of tri-valence erbium ion and thulium ion-co-doped fiber amplifiers pumped by 800-nm and 980-nm lasers. The rate and power propagation equations of the models are numerically solved to analyze the gain as a function of co-doping concentrations, fiber length and signal wavelength. The results reveal that with 800-nm or 980-nm pump, gain competition exists between 1470- and 1530-nm bands, which may arise from the pump absorption competition and complicated energy transfer between the two types of active ions, and the results further show that the gain spectra may cover 305 nm (1375–1680 nm) for 800-nm pump and 160 nm (1400–1560 nm) for 980-nm pump. The doping concentrations and fiber length may be tuned to reduce the ripple of the gain spectra.     

Limits on a nucleon–nucleon monopole–dipole coupling from spin relaxation of polarized ultra-cold neutrons in traps

A new limit is presented on the axion-like monopole–dipole P, T-non-invariant interaction in a range (10⁻⁴–1) cm. The spin-dependent nucleon–nucleon potential between neutrons and nucleons of the walls of the cavity containing ultra-cold neutrons should affect the neutron depolarization probability at their reflection from the walls. The limit is obtained from existing data on the ultra-cold neutron depolarization probability per one collision with the walls.