Volume 62, Issue 12

Using symbolic and algebra computation, the extended tanh-function method (ETM) based on the mapping method is further extended. New variable separation solutions of the (2+1)-dimensional generalized Broer-Kaup (GBK) system are derived. From the periodic wave solution and by selecting appropriate functions, the evolutional behaviours of dromions in the background of Jacobian elliptic wave and their interaction behaviours are investigated.

In this paper, J. H. He’s exp-function method is used to obtain a generalized soliton solution with some free parameters of the Konopelchenko-Dubrovsky equation. Suitable choice of parameters in the generalized solution leads to Wazwaz’s solution [Mathematical and Computer Modelling 45, 473 (2007)]. The result shows that He’s method is very effective and convenient.

Based on a new first-order nonlinear ordinary differential equation with a sixth-degree nonlinear term and some of its special solutions, a generalized transformation method is proposed to obtain more general exact solutions of the (2+1)-dimensional Konopelchenko-Dubrovsky equations. As a result, new exact nontravelling wave solutions are obtained including soliton-like solutions and trigonometric function solutions, from which all travelling wave solutions obtained by B.C. Li and Y. F. Zhang [Chaos, Solitons and Fractals (2007), doi:10.1016/j.chaos.2007.01.059] can be recovered as special cases. Compared with Li and Zhang’s method and the method of D. J. Huang, D. S. Li, and H.Q. Zhang [Commun. Theor. Phys. (Beijing, China) 44, 969 (2005)], D. J. Huang and H.Q. Zhang [Rep. Math. Phys. 57, 257 (2006)], D. J. Huang, D. S. Li, and H. Q. Zhang [Chaos, Solitons and Fractals 31, 586 (2007)], the proposed method is more powerful in searching for exact solutions of nonlinear evolution equations in mathematical physics.

Dynamic screening effects on orientation phenomena of 1s→2p ±1 excitations in nonideal plasmas are investigated. A semiclassical method is employed to describe the motion of the projectile electron in order to investigate the variation of the orientation parameter as a function of the impact parameter, projectile energy, thermal energy, and Debye length. The result shows that the preference for the 1s→2p −1 transition significantly decreases with increasing projectile energy. It is found that the dynamic screening effect increases with increasing impact parameter and also with increasing projectile energy. It is also found that the 1s → 2p −1 preference decreases with increasing thermal energy.

In this paper we report the ab-initio theoretical Compton profiles of aluminium nitride (AlN) in the framework of the Hartree-Fock, density functional theory and hybridization of Hartree-Fock to density functional theories using the CRYSTAL03 code. To compare our first ever theoretical data, we have also measured the isotropic Compton profile of AlN, using 59.54 keV γ -rays. The Hartree- Fock scheme-based Compton profile agrees better with the experiment than the other theories. The energy bands, density of states and Mulliken’s population analysis, using the CRYSTAL03 code, are also reported. Our band structure calculations show a large band gap, while Mulliken’s population analysis shows the ionic nature of bonding in AlN.

Density functional theory (DFT) calculations were performed to calculate the electric field gradient (EFG) tensors at the sites of aliminium ( 27 Al) and nitrogen ( 14 N) nuclei in an 1 nm of length (6,0) single-walled aliminium nitride nanotube (AlNNT) in three forms of the tubes, i. e. hydrogencapped, aliminium-terminated and nitrogen-terminated as representatives of zigzag AlNNTs. At first, each form was optimized at the level of the Becke3,Lee-Yang-Parr (B3LYP) method, 6-311G ∗∗ basis set. After, the EFG tensors were calculated at the level of the B3LYP method, 6-311++G ∗∗ and individual gauge for localized orbitals (IGLO-II and IGLO-III) types of basis sets in each of the three optimized forms and were converted to experimentally measurable nuclear quadrupole resonance (NQR) parameters, i. e. quadrupole coupling constant (qcc) and asymmetry parameter (ηQ). The evaluated NQR parameters revealed that the considered model of AlNNT can be divided into four equivalent layers with similar electrostatic properties.With the exception of Al-1, all of the three other Al layers have almost the same properties, however, N layers show significant differences in the magnitudes of the NQR parameters in the length of the nanotube. Furthermore, the evaluated NQR parameters of Al-1 in the Al-terminated form and N-1 in the N-terminated form revealed the different roles of Al (base agent) and of N (acid agent) in AlNNT. All the calculations were carried out using the GAUSSIAN 98 package program.

A modified additivity rule approach has been presented. Total cross-sections (TCSs) for electron scattering of C 3 H 6 isomers (C 3 H 6 and c-C 3 H 6 ) have been calculated at 10 - 300 eV employing the modified additivity rule. The approach for the TCSs of C 3 H 6 isomeric molecules is simple, and it yields better accord with experiments in the present energy range.

The D/H ratio of hydrogen gas in equilibrium with aqueous alkaline earth (Mg, Ca, Sr or Ba) chloride solutions measured at 25 ◦ C using a hydrophobic platinum catalyst, was found to be higher than the D/H ratio equilibrated with the applied pure water. The hydrogen isotope effect between such solutions and pure water changes with the molality of the solutions. The order of the D/H ratios in alkaline earth chlorides is found to be BaCl 2 > SrCl 2 ≥ CaCl 2 ≥ MgCl 2 . The hydrogen isotope effect in the aqueous chloride solutions of Mg, Ca, Sr or Ba ions is significantly larger than that in the aqueous chloride solutions of Li, Na, K or Cs ions. For MgCl 2 and CaCl 2 solutions, the hydrogen isotope effect is opposite to the oxygen isotope effect. The results are compared with the free energy change of transfer from H 2 O to D 2 O, and are discussed for the vapour pressure ratio of H 2 O and D 2 O of CaCl 2 solutions.

A model for the premelting of alkali chlorides is proposed. It is shown that diminishing of the free length of phonons under temperature increase may bring about the instability of the crystal lattice near the melting point. A probable structure of a lattice near this temperature been examined.

Electronic absorption spectra of trivalent praseodymium in various alkali chloride melts were precisely measured. The oscillator strength of the hypersensitive transition, 3 F 2 ← 3 H 4 , showed a clear decrease with increasing temperature. This temperature dependence was the inverse of reported cases for other trivalent lanthanoides. The Judd-Ofelt parameter was analysed, and the calculated oscillator strength showed quite good agreement with the experimentally obtained oscillator strength. However, the Ω2 parameter, which is sensitive to the ligand environment change, showed a clear decrease with increasing temperature and negative values at high temperature. We found that the 3 P 0 ← 3 H 4 transition and its shoulder peak are quite sensitive to the coordination circumstance change of the [PrCl 6 ] 3− complex in molten chlorides. These intensities could be correlated with the octahedral symmetry of [PrCl 6 ] 3− .

Speciation of tungsten in alkali chloride melts (based on NaCl-2CsCl, NaCl-KCl and 3LiCl-2KCl mixtures) was studied between 550 and 750 ◦ C using electronic absorption spectroscopy. OnlyW(IV) and W(V) chloro and oxychloro species can be stabilized under the conditions studied. Tungsten(IV) chloride ions are very sensitive to oxide/hydroxide impurities present in the melt. Anodic dissolution ofWmetal at anodic current densities in the range of 0.005 - 0.1 A/cm 2 produces only [WCl 6 ] 2− ions that can be electrochemically (on a glassy carbon anode) oxidized to [WCl 6 ] − . Small amounts of oxide ions present in the melt result in a gradual conversion of W(IV) chloro species intoW(IV) oxychloro species. In the presence of O 2 in the atmosphere [WCl 6 ] 2− is oxidized into the tungsten(V) species [WOCl 5 ] 2− . Dissolution of tungsten hexachloride, WCl 6 , in an NaCl-2CsCl melt initially yields [WCl 6 ] 2− (due to disproportionation). Reaction of metallic tungsten with Pd(II)-containing melts results in the formation of [WCl 6 ] 2− species. The main spectroscopic parameters of [WCl 6 ] 2− and [WCl 6 ] − complex ions were calculated.

Neptunium behaviour in an LiCl-KCl eutectic melt at 723 K was studied using spectroelectrochemistry. Cathodic reduction of neptunium(IV)-containing melts led to the formation of Np(III) ions and then neptunium metal. Electronic absorption spectra of Np(IV) and Np(III) chloro species in LiCl-KCl melt were recorded and resolved into individual Gaussian bands. The nature of neptunium complex ions in the melt is discussed.

Iron, cobalt and nickel powders are used as binding components for the production of articles of tungsten carbide by the hot pressing method. This fact and the unique properties of binary carbides of tungsten-iron triad metals encouraged the search for new ways of their synthesis. In the present work, the attempt to synthezise binary tungsten-nickel (cobalt, iron) carbides in molten KCl-NaCl-CsCl at 823 K was made. As a result of voltammetry research, it was established that in eutectic KCl-NaCl-CsCl melts the deposition potentials ofWand Ni (Co, Fe) differ by 150 - 350 mV from each other, which makes their co-deposition difficult. It is possible to shift the deposition potentials of tungsten and metals of the iron triad metals towards each other by changing the acid-base properties of the melt. The products of electrolysis in these molten system were identified by X-ray analysis. They are mixtures of tungsten and nickel (cobalt, iron) carbides: Ni 2 W 4 C, W 6 C 2.54 ; Co 3 W 3 C, Co 6 W 6 C, W 2 C, Co 3 C; FeW 3 C.

The electrochemical behaviour of zinc on copper, platinum, and tungsten working electrodes was investigated in a binary ZnCl 2- DMSO 2 room temperature molten salt electrolyte in the temperature range of 60 - 80 ◦ C. Various over-potentials, −0.1, −0.2, −0.3, −0.4, and −0.5 V, were chosen as deposition potentials. The nucleation/growth of zinc changed from progressive to instantaneous if the over-potentials increased from low to high level. The surface morphology and crystal structure of the deposited layer were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Moreover, larger grain size and hexagonal close packing of the zinc layer at −0.5 V were observed by transmission electron microscopy (TEM) with electron diffraction mapping.

We have utilized ZnCl 2- dimethylsulfone (DMSO 2 ) as the electrolyte with added GdCl 3 , FeCl 2 , and CoCl 2 , for electrodepositing a perpendicular GdFeCo magnetic thin film. The reaction at the electrode surface and the electrical conductivity of the ionic substance at different ionic concentrations were studied by cyclic voltammetry and a computerized direct current method. Moreover, the electrodeposition of the GdFeCo thin film was determined by a pulse potential method. Relation between the composition of the deposited thin film and control parameters including applied potentials was determined by EDS analysis. An amorphous structure and the thickness of the thin film were obtained by TEM analysis. Its roughness and uniformity were determined by AFM analysis. Meanwhile, a perpendicular magnetic property and pinning magnetic domain of the thin film were analyzed from results of AGM and MFM.

Molten fluoride salts are very promising carriers for the transport of large amounts of heat for example from a high temperature nuclear reactor to a plant which generates hydrogen by chemical processes or from a nuclear reactor to a heat exchanger being a part of the equipment needed to realize the Brayton cycle with a very high power efficiency. Therefore, in the framework of our project, experimental and theoretical investigations of the interactions of fluoride salts as heat carriers needed as high potential and structural materials for pipelines in order to transport heat at temperatures above 600 ◦ C were started. Experimental investigations of Fe-based and Ni-based materials in molten fluoride salts at high temperatures and with different exposure times were performed. Two components salts (LiF-NaF and NaF-NaBF 4 ) and three components salts (LiF-NaF-ZrF 4 and LiF-NaF-RbF) were chosen in the experiments. The salt analysis was focussed on the content of metallic elements before and after the exposure of the samples to the salt melts. It was done by inductively coupled plasma-optical emission spectrometry (ICP-OES) and by titrimetric techniques. The thickness of the material zone affected by the salt melts, characterized by an enriched / reduced content of elements in comparison to the mean original content, and the material attacked zone, characterized by very tiny channels or chains of pores or pits formed preferably at grain boundaries, were the subject of the analysis performed by electron microscopy / microprobe techniques. Theoretical models for the transport of elements in the material samples exposed to salt melts using experimental data were also developed.