Synthesis of iron(III) oxide from solution under exposure to external electric field

New method for controlling the physicochemical properties and morphology of iron oxide is suggested. The methods of transmission and scanning electron microscopy and X-ray phase and thermal analysis were used to study the structure and properties of highly dispersed iron oxides formed under exposure of the reaction mixture to an external electric field. The effect of synthesis conditions on the formation of structure and morphology of particles of iron oxide, a compound that finds practical application as a pigment or catalyst base, was examined.     

Orientation of liquid crystalline 5CB under an external electric field

The orientation characteristics of pre-aligned liquid crystalline 5CB (4-n-pentyl-4′-cyanobiphenyl) in a germanium cell with unidirectional rubbed polyimide-coated surfaces have been investigated. Orientation of 5CB molecules near the polyimide surface and those representing average properties of the system (i.e., the bulk) are compared. The orientation of the bulk is monitored by transmission Fourier transform infrared (FT-IR) spectroscopy while that of the molecules next to the surface is observed via attenuated total reflection (ATR) FT-IR spectroscopy. There are significant differences in orientation characteristics between the two groups of molecules. For molecules near the polyimide surface, there is an observable difference in orientation of the soft and hard segments of the liquid crystalline. Moreover, they show depth dependent orientation.     

Conformational analysis of diphenylacetylene under the influence of an external electric field

Theoretical investigation of the torsional potentials of a molecular wire, diphenylacetylene, was carried out at the B3LYP/6-311+G** level by considering the influence of the external electric field (EF). It demonstrates that many molecular features are sensitive to the EF applied. In particular, the torsional barrier increases and the LUMO-HOMO gap decreases with the increase of EF. Quantitative correlations between these features and the external EF were revealed. The current-voltage behavior corresponding to different conformers was studied as well by non-equilibrium Green's function method combined with the density functional theory. Further, the evolution of the LUMO-HOMO gap and the spatial distribution of molecular orbital were used to analyze these structure-property relationships.     

Synthesis of dumbbell-shaped manganese oxide nanocrystals

Dumbbell-like homogeneous MnO nanocrystals are obtained for the first time via the pyrolysis of manganese formate in trioctylamine/oleic acid media and the orientation aggregation mechanism is proposed for this 1D growth route.     

基于密度泛函理论的外电场下c-C4F8的结构及其特性

采用密度泛函理论CAM-B3LYP/DGDZVP2对c-C4F8进行优化计算,得到基态分子结构.在该结构基础上施加线性外电场(0~10.284 V·pm^-1),获得了c-C4F8的几何特性、能量、前线轨道能级、键能和红外光谱数据.结果表明:当电场沿x轴变大时,c-C4F8的点群从D2d变为C1,偶极矩和极化率不断增大,结构稳定性降低;分子总能量和能隙不断减小,且C(4)-F(10)键的键能降低速度最快,最有可能率先在外电场作用下断裂,导致c-C4F8结构和对称性被破坏.同时c-C4F8的绝热电子亲和能单调上升,分子吸收自由电子的能力增强;红外光谱中,吸收峰的个数增加,4个主要吸收峰发生了红移.     

The effect of an external electric field on surface morphology of co-deposited Pd/D films

The polarized PdD electrode undergoes significant morphological changes when exposed to an external electric field. These changes range from minor, e.g. re-orientation and/or separation of weakly connected globules, through forms that result from a combined action of the field as well as that connected with the evolution of gaseous deuterium, to shapes that require substantial energy expenditure.     

Effect of external electrical field on phase behavior and morphology development of polymer dispersed liquid crystal

Phase diagrams for mixtures of liquid crystal (LC)/monomer with and without an external electrical field applied have been established using polarized light microscope (PLM).The (isotropic + nematic) coexistent phase region and (isotropic + isotropic) phase boundary of LC/monomer mixtures were observed to shift upward to higher temperatures when the external electrical field exists. It was found that the electrical field applied during the cross-linking polymerization has a significant influence on the phase diagrams for the LC/polymer mixtures by rendering the coexistent phase regions shift upward to higher temperatures. The influence of the external electrical field on the processes of the isotropic-isotropic phase separation and liquid crystal ordering in PDLC formation has also been investigated. The results revealed that both the processes could be highly accelerated by the electrical field.     

Synthesis and electrochemistry of a vanadium-pillared manganese oxide

A new manganese dioxide pillared by vanadium oxide species has been synthesized hydrothermally from permanganate. It has the electrochemically active MnO₂ layer structure, which has been extensively studied as a battery cathode. The vanadium oxide ions, together with the water molecules, reside in between the oxide sheets; dehydration occurs without structural change. The (VO_y)_0.1MnO₂·nH₂O has a rhombohedral structure, with hexagonal parameters a=2.843(6) Å, c=22.08(2) Å. It reacts readily with lithium with a capacity around 150 mAh g⁻¹; the pillar ions do not appear to impede reaction.     

Morphology and physicochemical properties of nanosized particles of electrochemically obtained manganese oxide

The structure and properties of nanodisperse manganese oxides obtained under conditions of an external electric field are studied using transmission and scanning electron microscopy, X-ray diffraction analysis, thermic analysis, and atom-emission spectroscopy. The influence of synthesis conditions on formation of structure and morphology of nanoparticles is studied. It is shown that effect of electric field on reaction media allows us to control the physicochemical properties and morphology of manganese oxide.     

Transient effects in electrolytic cells submitted to an external electric field

We analyse transient effects in an electrolytic cell submitted to an external voltage and determine the relaxation time of the redistribution of the ions and of the potential. We consider the case in which adsorption effects at the interface with the electrodes are present and show that the typical relaxation time, for applied voltage V ₀25 mV, is of the order of tens of seconds for commercial nematic liquid crystals. When V ₀>25 mV the linearized analysis is no longer valid. In this case, the relaxation time depends on the applied voltage. Increasing V ₀, but still remaining in the low amplitude limit, the relaxation time starts increasing. This indicates that the reduction of the actual field in the sample, for moderate values of V ₀, plays an important role. For large values of V ₀, the relaxation time is a decreasing function of V ₀. This result is interpreted in terms of a simple model, according to which the ionic charge is localized in a surface layer whose thickness depends on the amplitude of the applied voltage.     

Numerical simulation of droplet coalescence behavior in gas phase under the coupling of electric field and flow field

The coalescence behavior of droplets in an electric field belongs to the important research contents of electrohydrodynamics. Based on the phase field method of the Cahn–Hilliard equation, the electric field and the flow field are coupled to establish the numerical model of twin droplet coalescence in a coupled field. The effects of flow rate, electric field strength, droplet diameter, and interfacial tension on the coalescence behavior of droplets during the coalescence process were investigated. The results show that the dynamic behavior of the droplets is divided into coalescence, after coalescence rupture, and no coalescence under the coupling of electric field and flow field. The proper increase of the electric field strength will accelerate the coalescence of the droplets, and the high electric field strength causes the droplets to burst after coalescence. Excessive flow rates make droplets less prone to coalescence. Under the coupling field, the larger the droplet interface tension, the smaller the droplet diameter, the smaller the flow rate, and the shorter the droplet coalescence time. The results provide a theoretical basis for the application of electrostatic coalescence in gas–liquid separation technology.     

Synthesis, morphology, and magnetic characterization of iron oxide nanowires and nanotubes

We have explored the synthesis of iron oxide particles, tubes, and fibrils within the pores of nanoporous polycarbonate and alumina membranes. The membranes contain uniformly distributed cylindrical pores with monodispersed diameters (varying between 20 and 200 nm) and thicknesses of 6 and 60 microm, respectively. By hydrolysis and polymerization of iron salts, particles of different sizes and phases were formed in the pores, building iron oxide particle nanowires. Alternatively, by the sol-gel technique, using as reagents metalloorganic compounds, fibrils and tubes of different iron oxide phases were prepared. Structural and morphological investigations performed using scanning electron microscopy and transmission electron microscopy revealed ordered iron oxide particle wires, tubes, and fibrils formed inside the membrane nanopores. Magnetic characterization was accomplished with a vibrating sample magnetometer. Below the blocking temperature (T(B)), the magnetic behavior of the nanowires was governed by dipolar interaction between nearest-neighbor nanoparticles inside the pore, whereas the energy barrier, and therefore the T(B) value, was mainly governed by dipolar interaction between magnetic moments over larger (interpore) distances. As expected, crystalline iron oxide nanotubes exhibited magnetic perpendicular anisotropy due to their magnetocrystalline and shape anisotropy.     

Response properties of AgCl and AgBr under an external static electric field: A density functional study

Density functional theory has been applied to investigate the effect of electric field on the electronic properties of AgCl and AgBr crystals using a static electric field perturbation. A reduction in the band gap value and widening of the band widths are observed with increase in the macroscopic field value indicating a considerable red shift in the absorption spectrum of AgCl and AgBr in the presence of an external electric field. Further, dielectric properties and lattice vibrations at the gamma point are calculated with three different functionals using the CPKS and the Berry phase approach as implemented in CRYSTAL09 code. Finally, the breakdown strength of AgCl and AgBr crystal is evaluated using Callen’s equation. In contrast to the case of alkali halides, it is found that the inclusion of the numerically calculated effective mass ratio into the Callen’s equation considerably improves the agreement between the calculated dielectric strength and the available experimental datum.     

Influence of external electric field on oxygen and carbon monoxide adsorption

The induction of negative charge in a ZnO film causes oxigen adsorption on an oxidized surface apparently in the form of O ₂ ^– . Electroadsorbed oxygen forms CO adsorption centers. On coadsorption from a 2CO+O₂ mixture, equal quantities of CO and O₂ are adsorbed with the formation of CO ₃ ^– complexes decomposing above 400 °C with CO₂ liberation into the gas phase.

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ZnO , -, O ₂ ^– . CO. 2CO+O₂ CO O₂ CO ₃ ^– , 400 °C CO₂ .

     

Synthesis and structure of quasi-one-dimensional zinc oxide doped with manganese

Nanotubes of manganese-doped zinc oxide Zn_{1 − x} Mn _x O (0 ≤ x ≤ 0.2) were synthesized by heating the Zn_{1 − x} Mn _x (HCOO)(OCH₂CH₂O)_1/2 precursor in air at 500°C. The precursor with extended crystals was synthesized by a solvothermal method based on heat treatment of a mixture of Zn_{1 − x} Mn _x (HCOO)₂ · 2H₂O with an ethylene glycol excess at 100–130°C. The tubular morphology of Zn_{1 − x} Mn _x O particles was identified by transmission electron microscopy. Tubular quasi-one-dimensional particles were shown to have a nanodispersed polycrystalline structure, the size of separate crystallites being from 5 to 20 nm. X-ray photoelectron spectroscopy suggested that the manganese distribution on the outer surface layer of Zn_{1 − x} Mn _x O nanotubes is nonuniform.     

Synthesis of allyl complexes of iron,manganese and molybdenum by phase transfer catalysis

Synthetic methods are described for the convenient and efficient preparation of σ- and π-allyl complexes of iron, manganese and molybdenum from metal carbonyl halides and allyl halides in phase transfer catalyzed reactions.     

Thermochemical reclaiming of vulcanized rubbers under exposure to electromagnetic field

A method for reclaiming of vulcanized rubbers, combining the treatment with a chemical degrading agent and exposure to electromagnetic field, was described. This method considerably extends the technological potentialities of reclaiming, allowing utilization of waste based on virtually any kind of rubber, in particular, nonpolar, in the form of coarse crumb.     

Correlation between phase composition and activity of complex oxide catalysts

Correlation between the catalytic activity in oxidation of carbonaceous materials and a change in the phase composition of the La_1?x Cs _x VO_4±y and Ce_1?x Pr _x O_2?d catalysts was studied. The activity values obtained by iso- and polythermal methods are close.     

Polarizability and alignment of dielectric nanoparticles in an external electric field: bowls, dumbbells, and cuboids

We employ the coupled dipole method to calculate the polarizability tensor of various anisotropic dielectric clusters of polarizable atoms, such as cuboid-, bowl-, and dumbbell-shaped nanoparticles. Starting from a Hamiltonian of a many-atom system, we investigate how this tensor depends on the size and shape of the cluster. We use the polarizability tensor to calculate the energy difference associated with turning a nanocluster from its least to its most favorable orientation in a homogeneous static electric field, and we determine the cluster dimension for which this energy difference exceeds the thermal energy such that particle alignment by the field is possible. Finally, we study in detail the (local) polarizability of a cubic-shaped cluster and present results indicating that, when retardation is ignored, a bulk polarizability cannot be reached by scaling up the system.