Electrical transport in liquid Sn1-xPbx metallic alloys: a self-consistent approach

The calculations of electrical resistivity of Sn–Pb liquid metallic alloys/solutions are investigated by self-consistent approach. We employ modified empty-core pseudopotential to represent electron–ion interaction, while partial structure factors are calculated using Aschroft–Langreth scheme with hard sphere reference system. The potential parameters for elemental metals were optimised to structural data in our previous paper. Computed results for resistivity as a function of temperature and concentration are discussed with other such results. Overall good agreement confirms the applicability of the present model potential for computing the electrical properties, including thermal conductivity and thermoelectric power for liquid metallic alloys.     

Effect of thermal treatment on phase composition and ethanol oxidation activity of a carbon supported Pt50Sn50 alloy catalyst

A carbon supported Pt–Sn electrocatalyst in the Pt/Sn atomic ratio 50:50 was prepared by the reduction of Pt and Sn precursors with formic acid and thermally treated at 200 °C (i.e., in the presence of solid tin) and 500 °C (in the presence of molten tin) in flowing hydrogen. In the absence of thermal treatment, X-ray diffraction (XRD) analysis showed a solid solution of Sn in the face centered cubic (fcc) Pt and SnO₂. After thermal treatment, the formation of a main phase of hexagonal PtSn (niggliite) and a secondary phase of cubic Pt₃Sn was observed in the Pt50Sn50 catalyst. The relative amount of the PtSn phase increased with increasing thermal treatment temperature. The presence of molten tin gave rise to the formation of some big particles during annealing at 500 °C. The activity for the ethanol oxidation reaction (EOR) of the as-prepared catalyst was higher than that of both thermally treated catalysts and Pt75Sn25/C and Pt50Ru50/C by E-TEK. The higher activity for the EOR of the as-prepared Pt–Sn catalysts was ascribed to the presence of a large amount of SnO₂. Dedicated to Teresa Iwasita’s 65th birthday.     

Effect of delay on phase locking in a pulse coupled neural network

Using a slightly simplified version of the integrate and fire model of a neural network with delay, I study the stability of the phase-locked state dependent on the coupling between the neurons and especially on a delay time. The coupling between neurons may be arbitrary. It is shown that the phase-locked state becomes less stable with increasing delay and that relaxation oscillations occur. Received 28 December 1999 and Received in final form 13 June 2000     

Synthesis and Structural Characterization of new Tri (2-methyl-2- phenylpropyl) tin Carboxylates containing Germanium

Organotincompoundsareextensivelystudiedfortheirbiologicalactivity'.Organogermaniumisanotherkindofelementthathasawiderangeofbiologicalactivity=.Tolinkbiologicalactivepropertiesoforganotinandorganogermaniumcompounds.wehavepreviouslyreportedthebiologicalactivityoftrialkyltingermylpropionates'andanticanceractivityofdibutyltindigermylpropionates'.ItiswellknownthatTorque(his[tri(2-methyl-2-phenylpropyl)tin]oxide)iswidelyusedinagricultureasanacaricide.Inthispaper,asthecontinuationofourpreviouswork"'…     

异丁烷在Pt-Sn-K/Al2O3上的脱氢反应

负载催化剂;异丁烷在Pt-Sn-K/Al2O3上的脱氢反应     

钢铁表面Ni-Sn-P合金镀层组成及其耐蚀性

化学镀;钢铁表面Ni-Sn-P合金镀层组成及其耐蚀性     

New Insights in Asymmetric Tetraorganodistannoxane Ladder Formation. A NMR‐Spectroscopic and Crystallographic study

The syntheses of the asymmetrically substituted tetraorganodistannoxanes [t‐Bu₂(X)SnOSn(Y)(CH₂SiMe₃)₂]₂ ( 1 , X = Y = OH; 2 , X = Cl, Y = OH; 3 , X = Y = Cl) are reported and their structures in solution and in the solid state are characterized by multinuclear NMR spectroscopy and single crystal X‐ray analyses. In toluene, the tetrahydroxy‐substituted derivative 1 is in equilibrium with the organotin oxides cyclo‐[t‐Bu₂Sn{OSn(CH₂SiMe₃)₂}₂O] ( 4 ), cyclo[(Me₃SiCH₂)₂Sn(OSnt‐Bu₂)₂O] ( 5 ), and cyclo‐(t‐Bu₂SnO)₃, and some additional, undefined species containing pentacoordinated tin atoms. In contrast, the dihydroxydichloro‐substituted derivative 2 is inert in solution.     

(tBu2SnAsH)2 und (tBu2SnAsH)3: Zwei neue ring-oligomere Stannylarsine

(^tBu₂SnAsH)₂ and (^tBu₂SnAsH)₃: Two Novel Ring-Oligomeric Stannylarsines ^tBu₂SnCl₂ reacts with NaAsH₂ in liquid ammonia to give the four-membered As–H-functional stannylarsine (^tBu₂SnAsH)₂ ( 1 ). The oligomeric six-membered heterocycle (^tBu₂SnAsH)₃ ( 2 ) is obtained by transamination of ^tBu₂Sn(NH^tBu)₂ with AsH₃. The novel compounds are characterized by NMR (¹H, ¹¹⁹Sn) and mass spectroscopy and their molecule structures determined by X-ray crystallography. In the solid state both compounds contain molecules with planar tin-arsenic rings ( 1 : space group P2₁/n, Z = 2; 2 : space group P6₃/m, Z = 2).     

Crystalline structure and morphological properties of undoped and Sn doped ZnO thin films

Undoped and tin (Sn) doped ZnO thin films have been prepared by spray pyrolysis method. Effect of Sn dopant on the crystalline structure and morphological properties of ZnO thin films has been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) method. XRD patterns confirm that the films have polycrystalline nature. While undoped ZnO film has (101) as the preferred orientation, Sn doped ZnO thin films have (002) as the preferred orientation. Grain sizes, lattice parameters and texture coefficient values of the films were determined. Microstructure was analyzed by SEM and the influence of the doping concentration in the microstructure of the films is investigated.     

First-principles investigations of the Ni3Sn alloy at steam reforming conditions

The structure and surface composition of a Ni₃Sn alloy at conditions relevant for the steam reforming reaction was investigated using density functional theory calculations. Both the flat Ni₃Sn(0 0 0 1) surface and a surface with steps in the closed packed direction [1 0  0]were considered. The adsorption geometries and energies of the species CO, C, OH and H were calculated. Chemical potentials were used to map out which adsorbates are on the surface under varying conditions. It was found that adsorbates preferably bind to Ni as nearest neighbor with Sn as second-nearest neighbor. The binding energy is slightly stronger than on pure Ni. Adsorbate binding to Sn was found to be very unfavorable. Binding free energies indicate that at high temperature the alloy surface will be predominantly covered by CO and C, and at low temperatures one may find H and almost no OH. Even though the nominal composition of the investigated alloy is Ni₃Sn, the surface composition may differ significantly depending on temperature and pressure of the gas phase. This effect was investigated by calculating segregation energies both in the absence and in the presence of adsorbates. For the flat surface, it was found that only the bulk termination is present under relevant conditions. In contrast, it was found that for steps preferential adsorption of CO and C on Ni sites may lead to adsorption-induced segregation at temperatures below 400 °C. When taking segregation into account, the most stable Ni₃Sn surfaces will not bind CO or C at the same condition that Ni does. This is in excellent agreement with the previously proven ability of Ni-Sn alloys to inhibit graphite formation.