Hydrate phase equilibrium for the (hydrogen + tert-butylamine + water) system

The three-phase equilibrium conditions of ternary (hydrogen + tert-butylamine + water) system were first measured under high-pressure in a “full view” sapphire cell. The tert-butylamine–hydrogen binary hydrate phase transition points were obtained through determining the points of intersection of three phases (H–L_w–V) to two phases (L_w–V) experimentally. Measurements were made using an isochoric method. Firstly, (tetrahydrofuran + hydrogen) binary hydrate phase equilibrium data were determined with this method and compared with the corresponding experimental data reported in the literatures and the acceptable agreements demonstrated the reliability of the experimental method used in this work. The experimental investigation on (tert-butylamine + hydrogen) binary hydrate phase equilibrium was then carried out within the temperature range of (268.4 to 274.7) K and in the pressure range of (9.54 to 29.95) MPa at (0.0556, 0.0886, 0.0975, and 0.13) mole fraction of tert-butylamine. The three-phase equilibrium curve (H + L_w + V) was found to be dependent on the concentration of tert-butylamine solution. Dissociation experimental results showed that tert-butylamine as a hydrate former shifted hydrate stability region to lower pressure and higher temperature.     

Direct electrodeposition of PbTe thin films on n-type silicon

High quality lead telluride thin films were directly deposited onto n-type silicon (1 0 0) substrates by electrodeposition at room temperature. The deposition mechanism was studied using cyclic voltammetry. The films were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that the deposited PbTe films exhibited a polycrystalline rock salt structure and good optical properties with a direct band gap of 0.31 eV.     

Fe-doped SnO2 transparent semi-conducting thin films deposited by spray pyrolysis technique: Thermoelectric and p-type conductivity properties

In this paper, we report structural, electrical, optical, and especially thermoelectrical characterization of iron (Fe) doped tin oxide films, which have been deposited by spray pyrolysis technique. The doping level has changed from 0 to 10 wt% in solution ([Fe]/[Sn] = 0–40 at% in solution). The thermoelectric response versus temperature difference has exhibited a nonlinear behavior, and the Seebeck coefficient has been calculated from its slope in temperature range of 300–500 K. The Hall effect and thermoelectric measurements have shown p-type conductivity in SnO₂:Fe films with [Fe]/[Sn] ≥ 7.8 at%. In doping levels lower than 7.8 at%, SnO₂:Fe films have been n-type with a negative thermoelectric coefficient. The Seebeck coefficient for SnO₂:Fe films with 7.8 at% doping level has been obtained to be as high as +1850 μV/K. The analysis of as-deposited samples with thicknesses ～350 nm by X-ray diffraction (XRD) and scanning electron microscopy (SEM) has shown polycrystalline structure with clear characteristic peak of SnO₂ cassiterite phase in all films. The optical transparency (T%) of SnO₂:Fe films in visible spectra decreases from 90% to 75% and electrical resistivity (ρ) increases from 1.2 × 10^?2 to 3 × 10³ Ω cm for Fe-doping in the range 0–40 at%.     

Thermodynamic stability of structure-H hydrates of methylcyclopentane and cyclooctane helped by methane

The four-phase equilibria were measured for the methylcyclopentane+methane+H₂O hydrate system (274.28–287.40 K, 1.75–9.34 MPa) and the cyclooctane+methane+H₂O hydrate system (274.08–288.57 K, 1.60–9.33 MPa). Each structure-H hydrate has the lower equilibrium pressure than the pure methane structure-I hydrate in the temperature range of the present work. The isothermal equilibrium pressures of both methylcyclopentane and cyclooctane hydrates are slightly higher than that of methylcyclohexane hydrate.     

Performance of silver nanocubes based on electrochemical surface area for catalyzing oxygen reduction reaction

Ag nanocubes that are 45 nm in size are synthesized and successfully used as catalysts in oxygen electroreduction. Electrochemical surface areas (ESAs) are considered to determine the effect on HO₂⁻ production, which is found to be in the following order: nanocubes < nanoparticles. Comparative data generated using Tafel analyses in 0.1 M NaOH electrolyte without and with methanol show that unchanged slopes on the prepared cubic catalysts can indicate high resistance of Ag nanocubes for methanol oxidation during oxygen reduction reaction. Among these Ag catalysts, nanocubes exhibit 9.29 × 10^− 2 mA cm^− 2 (at − 0.15 V vs. Ag/AgCl), the better activity in the oxygen reduction reaction.     

Phase equilibria in ternary (carbon dioxide + tetrahydrofuran + water) system in hydrate-forming region: Effects of carbon dioxide concentration and the occurrence of pseudo-retrograde hydrate phenomenon

In the present work, the three- and four-phase hydrate equilibria of (carbon dioxide (CO₂) + tetrahydrofuran (THF) + water) system are measured by using Cailletet equipment in the temperature and pressure range of (272 to 292) K and (1.0 to 7.5) MPa, respectively, at different CO₂ concentration. Throughout the study, the concentration of THF is kept constant at 5 mol% in the aqueous solution. In addition, the fluid phase transitions of L_W–L_V–V → L_W–L_V (bubble point) and L_W–L_V–V → L_W–V (dew point) are determined when they are present in the ternary system. For comparison, the three-phase hydrate equilibria of binary (CO₂ + H₂O) are also measured. Experimental measurements show that the addition of THF as a hydrate promoter extends hydrate stability region by elevating the hydrate equilibrium temperature at a specified pressure. The three-phase equilibrium line H–L_W–V is found to be independent of the overall concentration of CO₂. Contradictory, at higher pressure, the phase equilibria of the systems are significantly influenced by the overall concentration of CO₂ in the systems. A liquid–liquid phase split is observed at overall concentration of CO₂ as low as 3 mol% at elevated pressure. The region is bounded by the bubble-points line (L_W–L_V–V → L_W–L_V), dew points line (L_W–L_V–V → L_W + V) and the four-phase equilibrium line (H + L_W + L_V + V). At higher overall concentration of CO₂ in the ternary system, experimental measurements show that pseudo-retrograde behaviour exists at pressure between (2.5 and 5) MPa at temperature of 290.8 K.     

Electrochemical deposition of PbTe onto n-Si(1 0 0) wafers

Electrochemical deposition of PbTe from 50 mM Pb(NO₃)₂ + 1 mM TeO₂ + 0.1 M HNO₃ solution onto n-Si(1 0 0) wafers was studied using cyclic voltammetry (CV), chronoamperometry, ex situ SEM, XRD and EDX. Electrochemical behavior of n-Si(1 0 0) electrode in electrolytes 50 mM Pb(NO₃)₂ + 0.1 M HNO₃ and 1 mM TeO₂ + 0.1 M HNO₃ was also studied. No underpotential deposition (UPD) of Pb and Te onto n-Si was observed in the investigated systems indicating weak Pb–Si and Te–Si interactions. Deposition of Pb and Te on n-Si occurred with overvoltage via 3D island growth. Electrosynthesis of PbTe (NaCl-like structure, a = 0.650 nm) takes place due to codeposition of Pb and Te at potentials E > E_{Pb²⁺/Pb⁰} (lead UPD onto tellurium). Cathodic deposition of PbTe onto n-Si(1 0 0) is irreversible – there is no anodic current in the CV curve. Oxidation of PbTe on n-Si is observed only under illumination, when photoelectrons and photoholes are generated in silicon substrate.     

Preparation of vertically-aligned nickel nanowires with anodic aluminum oxide templates and their application as field emitters

In this study, well-ordered and vertically-aligned nickel nanowires (NiNWs) with a controllable length were grown inside the nanopores of anodic alumina oxide templates (AAOTs) using a simple electrochemical deposition (ECD) method. The electron field emission characteristics of the prepared NiNWs within AAOTs with two pore diameters (100 and 200 nm) and length in the range of 2.7–22 μm were measured and discussed. The turn-on field/the enhancement factor of 8.5 and 7-μm-long NiNWs prepared within 100 and 200 pore diameter AAOTs, respectively, were about 3.46 V/μm/17,621 and 4.8 V/μm/5001, respectively, according to I–V measurements.     

Observation of possible quantum interference effects in SrRuO3 epitaxial thin films grown by high-oxygen pressure dc sputtering

A careful study of the electronic transport and magnetotransport properties of metallic ferromagnetic SrRuO₃ (SRO) thin films is reported. Epitaxial (～150 nm) SRO films were grown on (001)-oriented SrTiO₃ (STO) substrates by dc sputtering technique at high oxygen pressure. Resistivity measurements were performed up to temperatures as low as 2 K in magnetic fields strengths of up to 9 T, applied perpendicular to the film plane. The films featured excellent metallic behavior at room temperature, with a resistivity, ρ(300 K) < 600 μΩ cm. The presence of minima in the ρ–T plots at ～4 K was clearly detected from these measurements. The 9 T magnetic field did not remove the minima signaling its nonmagnetic origin In addition, the ρ(μ₀H = 9 T,T) minima was slightly shifted to higher temperature and the ρ(μ₀H = 9 T,T ≤ 4 K) was larger when it was compared with ρ(μ₀H = 0 T,T ≤ 4 K). Increasing relevance of quantum corrections to the conductivity as the temperature is lowered has been invocated as possible cause of this anomalous electrical behavior. In this case, effects arising from quantum interference of the electronic wavelength are expected. Weak localization and renormalized electron–electron interaction have been considered as possible sources giving rise to quantum correction to the conductivity.     

Electrochemical synthesis of Au/polyaniline–poly(4-styrenesulfonate) hybrid nanoarray for sensitive biosensor design

Au/polyaniline (PANI)–poly(4-styrenesulfonate) (PSS) hybrid nanoarray is fabricated for biomolecular sensing in neutral aqueous solutions. Firstly, an array of one-dimensional Au nanorods (diameter = ca. 200 nm, length = ca. 3 μm) is formed by a template-electrodeposition method using a porous anodic alumina membrane, and then a thin PANI–PSS composite layer is electropolymerized on the surface of the Au nanorods. The resulting Au/PANI–PSS hybrid nanoarray exhibits a quasi-reversible redox electrochemical process at ca. +0.11 V and electrocatalytic oxidation of reduced β-nicotinamide adenine dinucleotide (NADH) is attained with a detection limit of 0.3 μM in a neutral solution.     

Fast formation of thick and transparent titania nanotubular films from sputtered Ti

Ti films sputtered on transparent fluorine-doped tin oxide glass substrates were anodized in fluoride-containing organic electrolyte in the presence of H₂O. In this work, anodic TiO₂ nanotubes (ATNs) as long as 9.2 ± 0.3 μm were obtained with high growth rate of 0.64 ± 0.3 μm min^?1. We demonstrated the optimum anodization conditions for ATN growth on foreign substrates, were within the range of 0.3–0.5% (wt) NH₄F, with 3–5% (vol) H₂O at 60 V. XPS and ICP-MS were utilized to elucidate the increase of thickness and volume expansion obtained from the sputtered Ti film to their ATN forms. The ATN films exhibited excellent uniformity and adhesion to the substrates.     

Thermodynamic modeling for clathrate hydrates of ozone

We report a theoretical study to predict the phase-equilibrium properties of ozone-containing clathrate hydrates based on the statistical thermodynamics model developed by van der Waals and Platteeuw. The Patel–Teja–Valderrama equation of state is employed for an accurate estimation of the properties of gas phase ozone. We determined the three parameters of the Kihara intermolecular potential for ozone as a = 6.815 · 10⁻² nm, σ = 2.9909 · 10⁻¹ nm, and ε · k_B⁻¹ = 184.00 K. An infinite set of ε–σ parameters for ozone were determined, reproducing the experimental phase equilibrium pressure–temperature data of the (O₃ + O₂ + CO₂) clathrate hydrate. A unique parameter pair was chosen based on the experimental ozone storage capacity data for the (O₃ + O₂ + CCl₄) hydrate that we reported previously. The prediction with the developed model showed good agreement with the experimental phase equilibrium data within ±2% of the average deviation of the pressure. The Kihara parameters of ozone showed slightly better suitability for the structure-I hydrate than CO₂, which was used as a help guest. Our model suggests the possibility of increasing the ozone storage capacity of clathrate hydrates (∼7% on a mass basis) from the previously reported experimental capacity (∼1%).     

Effect of negative substrate bias on HWCVD deposited nanocrystalline silicon (nc-Si) films

The influence of the negative substrate bias on the interfacial and microstructural characteristics of nanocrystalline silicon (nc-Si) thin films was deposited by hot wire chemical vapor deposition (HWCVD). Structural characterization of nc-Si films was performed by small angle X-ray diffraction (SAXRD), Raman spectroscopy, X-ray reflectivity (XRR) and field emission scanning electron microscopy (FESEM). Crystalline fraction and crystallite size increases from 61.31 to 74.13% and 13.3 to 21.6 nm, respectively, with an increasing negative bias from 0 to ?200 V. Furthermore, the deposition rate of nc-Si films increases from 25 to 68 nm/min by increase of negative substrate bias from 0 to ?200 V.     

Isothermal phase equilibria for the (HFC-32 + HFC-134a) mixed-gas hydrate system

Isothermal phase equilibria (pressure-composition relations in hydrate, gas, and aqueous phases) in the {difluoromethane (HFC-32) + 1,1,1,2-tetrafluoroethane (HFC-134a)} mixed-gas hydrate system were measured at the temperatures 274.15 K, 279.15 K, and 283.15 K. The heterogeneous azeotropic-like behaviour derived from the structural phase transition of (HFC-32 + HFC-134a) mixed-gas hydrates appears over the whole temperature range of the present study. In addition to the heterogeneous azeotropic-like behaviour, the isothermal phase equilibrium curves of the (HFC-32 + HFC-134a) mixed-gas hydrate system exhibit the negative homogeneous azeotropic-like behaviour at temperatures 279.15 K and 283.15 K. The negative azeotropic-like behaviour, which becomes more remarkable at higher temperatures, results in the lower equilibrium pressure of (HFC-32 + HFC-134a) mixed-gas hydrates than those of both simple HFC-32 and HFC-134a hydrates. Although the HFC-134a molecule forms the simple structure-II hydrate at the temperatures, the present findings reveal that HFC-134a molecules occupy a part of the large cages of the structure-I mixed-gas hydrate.     

Modification of a glassy carbon surface with amine-terminated dendrimers and its application to electrocatalytic hydrazine oxidation

Amine-terminated polyamidoamine (PAMAM) dendrimers were immobilized on glassy carbon electrodes (GCEs) via electrochemical oxidation of the terminal amine groups of dendrimers. The electrochemical immobilization of dendrimers was confirmed by cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). The immobilized dendrimer films were robust and behaved as charge-selective electrochemical gates for oppositely charged redox molecules. The immobilization approach was applied to assemble Au dendrimer-encapsulated nanoparticles (Au DENs, dia. 1.5 ± 0.3 nm) on GCEs, and the resulting Au DEN films showed electrocatalytic activity to hydrazine oxidation.     

Photocatalytic decomposition of 4-chlorophenol over an efficient N-doped TiO2 under sunlight irradiation

Using a new nitrogen precursor of a mixture of ammonia and hydrazine hydrate, N-doped TiO₂ photocatalyst with a high efficiency under visible light was synthesized by a precipitation method. The analysis of X-ray photoelectron spectroscopy (XPS) suggested that the doping concentration of nitrogen was 0.45 at%, while it was 0.21 at% or 0.24 at% using single ammonia or hydrazine hydrate as nitrogen precursor. The patterns of the electron paramagnetic resonance spectroscopy (EPR) indicated that the paramagnetic species of NO₂^2?, NO and Ti³⁺ existed as the proposed active species. The ultraviolet–visible (UV–vis) spectra revealed that the band-gap of the N-doped TiO₂ was 3.12 eV, which was slightly lower than 3.15 eV of pure TiO₂. The N-doped TiO₂ showed higher efficiency under both ultraviolet (UV) and visible light irradiations. Moreover, the degradation grade of 4-chlorophenol (4-CP) using the as-synthesized N-doped TiO₂ under sunlight irradiation for 6 h was 82.0%, which was higher than 66.2% of the pure TiO₂, 60.1% or 65.2% of the N-doped TiO₂ using single ammonia or hydrazine hydrate as precursor. Density functional theory (DFT) calculations were performed to investigate the visible light response of the N-doped TiO₂. Our study demonstrated that the visible activities vary well with the concentrations of NO₂^2? species incorporated by N–TiO₂ series photocatalysts and the higher activity of the as-prepared N-doped TiO₂ was attributed to the enhancement of the concentration of NO₂^2? species.     

A novel all-solid-state thin-film-type lithium-ion battery with in situ prepared positive and negative electrode materials

A novel all-solid-state thin-film-type rechargeable lithium-ion battery employing in situ prepared both positive and negative electrode materials is proposed. A lithium-ion conducting solid electrolyte sheet of Li₂O–Al₂O₃–TiO₂–P₂O₅-based glass–ceramic manufactured by OHARA Inc. (OHARA sheet) was used as the solid electrolyte, which was sandwiched by Cu and Mn metal films. The Cu/OHARA sheet/Mn layer became an all-solid-state lithium-ion battery after applying d.c. 16 V to the layer, and the resultant battery operated at 0.3–0.8 V with reversible capacity of 0.45 μAh cm^?2. High voltage battery was successfully prepared by applying the d.c. high voltage to a five-series of Cu/OHARA sheet/Mn layer, resulting in all-solid-state battery operating at 1.5–4.0 V. The proposed fabrication process will become a new technology to develop advanced all-solid-state rechargeable lithium-ion batteries.     

Synthesis of L10 Fe–Pd films by electrodeposition and thermal annealing

Fe–Pd alloy films have been prepared by electrochemical deposition from an alkaline electrolyte containing Fe sulfate, Pd chloride and 5-sulfosalicylic acid onto polycrystalline titanium substrates. The as-deposited films were nanocrystalline and magnetically soft (coercivity ∼ 25 Oe). L1₀ Fe–Pd films with a (1 1 1) preferred orientation were obtained by post-deposition thermal annealing of films with composition about 37 at% Fe in an (Ar + 5% H₂) gas flow at 500 °C. Such films exhibit hard magnetic properties, with a coercivity up to 1880 Oe, and a slightly anisotropic magnetic response, with a larger in-plane remanence. Preliminary magnetic investigations support magnetization switching through pinning of domain walls.     

The partition coefficients of ethylene between vapor and hydrate phase for methane + ethylene + THF + water systems

The vapor-hydrate equilibria were studied experimentally in detail for CH₄ + C₂H₄ + tetrahydrofuran (THF) + water systems in the temperature range of 273.15–282.15 K, pressure range of 2.0–4.5 MPa, the initial gas–liquid volume ratio range of 45–170 standard volumes of gas per volume of liquid and THF concentration range of 4–12 mol%. The results demonstrated that, because of the presence of THF, ethylene was remarkably enriched in vapor phase instead of being enriched in hydrate phase for CH₄ + C₂H₄ + water system. This conclusion is of industrial significance; it implies that it is feasible to enrich ethylene from gas mixture, e.g., various kinds of refinery gases or cracking gases in ethylene plant, by forming hydrate.     

Isothermal phase equilibria for the (xenon + cyclopropane) mixed-gas hydrate system

Isothermal three-phase equilibria of gas, aqueous, and hydrate phases for the {xenon (Xe) + cyclopropane (c-C₃H₆)} mixed-gas hydrate system were measured at two different temperatures (279.15 and 289.15) K. The structural phase transitions from structure-I to structure-II and back to structure-I, depending on the mole fraction of guest mixtures, occur in the (Xe + c-C₃H₆) mixed-gas hydrate system. The isothermal pressure–composition relations have two local pressure minima. The most important characteristic in the (Xe + c-C₃H₆) mixed-gas hydrate system is that the equilibrium pressure–composition relations exhibit the complex phase behavior involving two structural phase transitions and two homogeneous negative azeotropes. One of two structural phase transitions exhibits the heterogeneous azeotropic-like behavior.