Low-temperature Liquid Research Articles

Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Olive and Refined Pomace Olive Oils with Modified Low Temperature and Ultrasound-Assisted Liquid–Liquid Extraction Method Followed by the HPLC/FLD

The cleanup method of modified low temperature was compared with the standardized method of modified ultrasound-assisted liquid–liquid (UALL) extraction for the analysis of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil and refined pomace olive oil. The modified UALL extraction consisted in purification on C18 reversed-phase, Florisil-bonded-phase and NH2 cartridges, and modified low-temperature extraction was followed by alumina-N and NH2 solid-phase extraction (SPE) cartridges. Both methods are followed by reversed-phase high-performance liquid chromatography with fluorescence detection. The chromatograms of the final extracts showed lower interferences in both of the methods. The solvent consumption and cost for the modified UALL method were higher than those of the modified low temperature, and also, it needed more equipment, but its analysis time was less. The limit of detection and limit of quantitation of the modified UALL method were 0.16–0.97 and 0.57–2.93 μg kg−1, respectively, and for the modified low temperature, they were 0.09–1.97 and 0.29–5.99 μg kg−1, respectively. The PAH recoveries for the modified UALL extraction method ranged from 75.0 to 111.0 % (RSD = 3–8 %), and for the modified low temperature, they ranged from 81.5 to 113.8 % (RSD = 3–10 %).

Structural and waveguiding characteristics of Er3+:Yb3Al5−yGayO12 films grown by the liquid phase epitaxy

Erbium (Er3+) doped ytterbium garnet (Er:Yb3Al5−yGayO12; y=0, 0.55 and 1.1) single crystalline thick films have been grown by the low-temperature liquid phase epitaxy method (LPE). The composition of the films was determined using the high resolution XRD, the particle-induced X-ray emission spectroscopy (PIXE) and the particle-induced gamma-ray emission spectroscopy (PIGE). The lattice mismatch between films and substrates was investigated by the high-resolution X-ray diffraction. The surface analysis was carried out by the atomic force microscopy (AFM). Pure infrared emission of Er3+ ions was observed in all films containing gallium. The characteristics such as refractive index, thickness and light propagation were studied by the m-line spectroscopy (MLS) using several wavelengths (633, 964, 1311 and 1552nm). All samples, where y=1.1, were multimode waveguides. For these reasons, the Er:Yb3Al3.9Ga1.1O12 seems to be a promising material for light amplifiers in the IR region.

Reference Correlation of the Viscosity of Toluene from the Triple Point to 675 K and up to 500 MPa

This paper contains new, representative reference equations for the viscosity of toluene. The equations are based in part upon a body of experimental data that have been critically assessed for internal consistency and for agreement with theory whenever possible. The correlations are valid from the triple point (178.0 K) to 675 K, and at pressures up to 500 MPa. The estimated uncertainty at a 95% confidence level varies depending on the region of temperature and pressure from a low of 0.3% for the low-density gas at temperatures from 305 to 640 K at pressures to 0.3 MPa (essentially the uncertainty of the best experimental data) to 0.7% for the saturated liquid at temperatures from 263 to 373 K, to 5% for the low-temperature liquid from 187 to 210 K at pressures to 15 MPa.

Chromatographic behavior of small organic compounds in low-temperature high-performance liquid chromatography using liquid carbon dioxide as the mobile phase.

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns.

Low-temperature liquid phase reduced TiO2 nanotube arrays: synergy of morphology manipulation and oxygen vacancy doping for enhancement of field emission

The partially reduced TiO2 nanotube arrays (TNAs) are prepared via an uncomplicated and low-cost liquid phase reduction strategy using NaBH4 as the reducing agent. By controlling and adjusting the reduction temperatures from 30 to 90 °C, the reduction treatment can not only change their surface morphology but also introduce oxygen vacancies into them, resulting in an optimized morphology, elevated Fermi-level, reduced effective work function and improved conductivity of the TNAs. Meanwhile, the thermal and long-term stability of oxygen vacancy are also investigated, indicating that the oxygen vacancies retain long-term stability from room temperature up to 150 °C. More interesting, partially reduced TNAs show drastically enhanced field emission (FE) performances including substantially decreased turn-on field from 18.86 to 1.53 V μm−1, a high current density of 4.00 mA cm−2 at 4.52 V μm−1, and an excellent FE stability and repeatability. These very promising results are attributed to the combination of the optimized morphology and introduced oxygen vacancies, which can increase FE sites, reduce effective work function and increase conductivity.

Composition and structure of the incombustible residue from thermal decomposition of the ionic liquid N-decylpyridinium tetrachloroferrate(III)

A low-temperature ionic liquid, N-decylpyridinium tetrachloroferrate(III), has been synthesized, and its thermal stability in air has been studied by thermogravimetry. Combustion of the organic part of this ionic liquid leaves a solid residue which has been studied by elemental analysis, X-ray powder diffraction, scanning electron microscopy, IR spectroscopy, and magnetometry. The incombustible residue has been identified as hematite (crystalline α-Fe2O3) which is a weak ferromagnetic at room temperature.

Quantum phase transition and Fermi liquid behavior inPd1−xNixnanoalloys

The ${\mathrm{Pd}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}$ alloy system is an established ideal transition-metal system possessing a composition-induced paramagnetic-to-ferromagnetic quantum phase transition (QPT) at the critical concentration ${x}_{c}\ensuremath{\sim}0.026$ in bulk. A low-temperature non-Fermi liquid (NFL) behavior around ${x}_{c}$ usually indicates the presence of quantum criticality (QC) in this system. In this work, we explore the existence of such a QPT in nanoparticles of this alloy system. We synthesized single-phase, polydispersed and 40--50 nm mean diameter crystalline nanoparticles of ${\mathrm{Pd}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}$ alloys, with $x$ near ${x}_{c}$ and beyond, by a chemical reflux method. In addition to the determination of the size, composition, phase, and crystallinity of the alloys by microscopic and spectroscopic techniques, the existence of a possible QPT was explored by resistivity and dc magnetization measurements. A dip in the value of the exponent $n$ near ${x}_{c}$, and a concomitant peak in the constant $A$ of the $A{T}^{n}$ dependence of the low-temperature ($T$) resistivity indicate the presence of a quantum-like phase transition in the system. The minimum value of $n$, however, remains within the Fermi liquid regime ($n>2$). The dc magnetization results suggest an anticipatory presence of a superparamagnetic-to-ferromagnetic QPT in the mean-sized nanoparticles. The observation of a possible quantum critical NFL behavior ($n<2$) through resistivity is argued to be inhibited by the electron-magnon scatterings present in the smaller nanoparticles.

Phase Diagram of the Kitaev-type Model on a Decorated Honeycomb Lattice in the Isolated Dimer Limit

An effective model in the isolated dimer limit of the Kitaev-type model on a decorated honeycomb lattice is investigated at finite temperature. The ground state of this model is exactly shown to be a chiral spin liquid with spontaneous breaking of time reversal symmetry. We elab- orate the finite-temperature phase diagram by using the mean-field approximation and Monte Carlo simulation. We find that the phase transition between the high-temperature paramagnetic phase and the low-temperature chiral spin liquid phase is always of second order in the Monte Carlo results, although a tricritical point appears in the mean-field phase diagram. The finite-size scaling analysis of the Monte Carlo data suggests that the phase transition belongs to the two-dimensional Ising universality class.

M408 数値解析と実験による低温用管フランジの熱・力学挙動の評価(GS1,3 材料力学(6),修士研究発表セッション)

M408 数値解析と実験による低温用管フランジの熱・力学挙動の評価(GS1,3 材料力学(6),修士研究発表セッション)

Features of the breakage drops low boiling dispersed phase in gradient flow near the heated surface

The mechanisms of the formation of vapor bubbles of a critical size in deformable droplets of the dispersed phase in liquid emulsion been studied. The model is proposed breakup of the droplets in gradient flow of the emulsion near the surface heating under the combined action of viscous shear stresses and thermal overload. Was the dependence of the heat flux density at boiling of dispersed drops of low-temperature liquid phase in a gradient flow of the emulsion near hard surface. Comparison with the data of experimental studies shows the validity of the proposed model concepts that are different from the usual boiling of homogeneous fluids at surface heating.

Towards the Equation of State for Neutral (C2H4), Polar (H2O), and Ionic ([bmim][BF4], [bmim][PF6], [pmmim][Tf2N]) Liquids

Despite considerable effort of experimentalists no reliable vapor-liquid coexistence at very small pressures and liquid-solid coexistence at high pressures have been until now observed in the working range of temperature 290<T/K<350 for ionic liquids. The measurements of high-pressure properties in low-temperature stable liquid are relatively scarce while the strong influence of their consistency on the phase equilibrium prediction is obvious. In this work we discuss the applicability of fluctuational-thermodynamic methodology and respective equation of state to correlate the properties of any (neutral, polar, ionic) liquids since our ultimate goal is the simple reference predictive model to describe vapor-liquid, liquid-liquid, and liquid-solid equilibria of mixtures containing above components. It is shown that the inconsistencies among existing volumetric measurements and the strong dependence of the mechanical and, especially, caloric derived properties on the shape of the functions chosen to fit the experimental data can be resolved in the framework of fluctuational-thermodynamic equation of state. To illustrate its results the comparison with the known experimental data for [bmim][BF4] and [bmim][PF6] as well as with the lattice-fluid equation of state and the methodology of thermodynamic integration is represented. It corroborates the thermodynamic consistency of predictions and excellent correlation of derived properties over the wide range of pressures 0<P/MPa<200.

A dense Bose fluid at zero temperature: condensation and clusters in liquid 4He

We present a full set of wave equations describing a dense Bose fluid, applicable both to non- ideal gases and to liquid 4He. The phonon spectrum in liquid 4He is found and the fraction of condensed particles is calculated at zero temperature for a wide range of densities. The theory also yields the ground-state energy for the quantum liquid 4He in agreement to high accuracy with Monte Carlo simulations and experimental data at low pressure. We also present the derivation of a generalized Hartree-Fock equation describing roton clusters in low temperature liquid 4He, allowing us to confirm that, at low enough temperatures and for a wide range of pressures, the stable clusters consist of 13 bound atoms.

Effect of Treatment Time on the Microstructure of Austenitic Stainless Steel During Low-Temperature Liquid Nitrocarburizing

The effect of treatment time on the microstructure of AISI 304 austenitic stainless steel during liquid nitrocarburizing (LNC) at 703 K (430 °C) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Experimental results revealed that the modified layer was covered with the alloy surface and the modified layer depth increased extensively from 2 to 33.4 μm with increasing treatment time. SEM and XRD showed that when the 304 stainless steel sample was subjected to LNC at 703 K (430 °C) for less than 4 hours, the main phase of the modified layer was expanded austenite. When the treatment time was prolonged to 8 hours, the abundant expanded austenite was formed and it partially transformed into CrN and ferrite subsequently. With the increased treatment time, more and more CrN precipitate transformed in the overwhelming majority zone in the form of a typical dendritic structure in the nearby outer part treated for 40 hours. Still there was a single-phase layer of the expanded austenite between the CrN part and the inner substrate. TEM showed the expanded austenite decomposition into the CrN and ferrite after longtime treatment even at low temperature.

Physicochemical properties of an N-decylpyridinium tetrachloroferrate ionic liquid

A low-temperature ionic liquid N-decylpyridinium tetrachloroferrate was synthesized. The temperature dependences of density and viscosity of the synthesized ionic liquid, as well as its thermal stability and magnetic properties were studied. The response of N-decylpyridinium tetrachloroferrate to magnetic field was visualized, and its structure was calculated at the DFT/B3LYB/6-31G(d,p) level of theory.

Effects of methane annealing ambience on the structure and photoluminescence of BCNO phosphors

Green-emitting BCNO phosphors are synthetized by low temperature liquid method. And then the properties of structure and photoluminescence of BCNO phosphors annealed under methane ambience at 500–700°C for 4h and at 600°C for 3–6h are researched. When the phosphor was annealed for the same time period, the crystallinity was improved first and then became poor as the annealing temperature increased. In addition, the emission peak shifted to high wavelength, and the maximum shift span reached up to 40nm. When the phosphor was annealed at the same temperature, the crystallinity was improved and the emission peak was red-shifted. The multi-peaks fitting results indicated that three luminescence mechanisms which were C-related defect, B–O luminescence center and other defects or vacancies played important roles in BCNO phosphors.

Spectroscopic study of solvation processes and ionic association in lithium salt solutions with ionic and aprotic solvents

The Raman spectra of the mixtures containing the low-temperature ionic liquid ethylmethylimidazolinium bis(trifluoromethanesulfonyl)imide (EMIIm), the salt component lithium bis(trifluoromethylesulfonyl)-imide (LiIm), and the aprotic solvent ethylene carbonate (EC) are studied. It is found that the addition of the lithium salt to the ionic liquid results in the formation of ion pairs or more complex cation-anion aggregates. Dilution of these systems with ethylene carbonate leads to the solvation of lithium ions.

Strength and Reliability of High Temperature Transient Liquid Phase Sintered Joints

Low-temperature transient liquid phase sintering (LT-TLPS) can be used to form high-temperature joints between metallic interfaces at low process temperatures. In this paper, we will describe the processing and shear strength, along with the shock fatigue resistance of sintered joints made by this process. Joints made from different ratios of Ni and Cu high melting temperature constituents paired with Sn-based low melting temperature constituents have been evaluated. For the shear studies, the softening behavior of test samples joined by Ni-Sn3.5Ag and (Ni,Cu)-Sn3.5Ag sinter pastes have been assessed using a fixture designed for high temperature shear testing up to 600°C. The reliability of sinter paste joints in drop-shock environments will be discussed. It is shown that joints formed from these sinter pastes possess improved drop-shock reliability compared to Sn3.5Ag solder joints and melting temperatures considerably higher than those of conventional high temperature solders (e.g. Pb5.0Sn2.5Ag).

Electrocatalysis of formic acid on palladium and platinum surfaces: from fundamental mechanisms to fuel cell applications.

Formic acid as a natural biomass and a CO2 reduction product has attracted considerable interest in renewable energy exploitation, serving as both a promising candidate for chemical hydrogen storage material and a direct fuel for low temperature liquid fed fuel cells. In addition to its chemical dehydrogenation, formic acid oxidation (FAO) is a model reaction in the study of electrocatalysis of C1 molecules and the anode reaction in direct formic acid fuel cells (DFAFCs). Thanks to a deeper mechanistic understanding of FAO on Pt and Pd surfaces brought about by recent advances in the fundamental investigations, the "synthesis-by-design" concept has become a mainstream idea to attain high-performance Pt- and Pd-based nanocatalysts. As a result, a large number of efficient nanocatalysts have been obtained through different synthesis strategies by tailoring geometric and electronic structures of the two primary catalytic metals. In this paper, we provide a brief overview of recent progress in the mechanistic studies of FAO, the synthesis of novel Pd- and Pt-based nanocatalysts as well as their practical applications in DFAFCs with a focus on discussing studies significantly contributing to these areas in the past five years.

Design and Numerical Simulation of a Symbiotic Thermoelectric Power Generation System Fed by a Low-Grade Heat Source

All liquid heating systems, including solar thermal collectors and fossil-fueled heaters, are designed to convert low-temperature liquid to high-temperature liquid. In the presence of low- and high-temperature fluids, temperature differences can be created across thermoelectric devices to produce electricity so that the heat dissipated from the hot side of a thermoelectric device will be absorbed by the cold liquid and this preheated liquid enters the heating cycle and increases the efficiency of the heater. Consequently, because of the avoidance of waste heat on the thermoelectric hot side, the efficiency of heat-to-electricity conversion with this configuration is better than that of conventional thermoelectric power generation systems. This research aims to design and analyze a thermoelectric power generation system based on the concept described above and using a low-grade heat source. This system may be used to generate electricity either in direct conjunction with any renewable energy source which produces hot water (solar thermal collectors) or using waste hot water from industry. The concept of this system is designated “ELEGANT,” an acronym from “Efficient Liquid-based Electricity Generation Apparatus iNside Thermoelectrics.” The first design of ELEGANT comprised three rectangular aluminum channels, used to conduct warm and cold fluids over the surfaces of several commercially available thermoelectric generator (TEG) modules sandwiched between the channels. In this study, an ELEGANT with 24 TEG modules, referred to as ELEGANT-24, has been designed. Twenty-four modules was the best match to the specific geometry of the proposed ELEGANT. The thermoelectric modules in ELEGANT-24 were electrically connected in series, and the maximum output power was modeled. A numerical model has been developed, which provides steady-state forecasts of the electrical output of ELEGANT-24 for different inlet fluid temperatures.

Liquid Phase Stability Under an Extreme Temperature Gradient

Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the "bulk" driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid.