R. Ithnin

Formation of translationally hot ethene by dissociative electron capture of adsorbed 1,2-dichloroethane

Abstract Irradiation of sub-monolayer and 4 layers of adsorbed 1,2-dichloroethane (DCE) on Cu(111) at 110 K with a pulsed 2 keV electron beam causes hot ethene desorption with translational temperatures of 2350 ± 100 K (sub-monolayer), and 2540 ± 200 K and 320 ± 50 K (4 layers). DCE undergoes electron attachment from hot secondary electrons, dissociating to form a short-lived ClCH 2 CH 2 radical which decomposes, generating the high temperature (2350 and 2540 K) ethene. The translational motion is thought to come from part of the heat liberated in the formation of the CuCl bond. The 320 K peak is assumed to arise from radical decomposition at the surface of DCE crystallites.

Structural study of Rb and Cl coadsorption on Cu(111) : a case of overlayer compound formation

A structural study of the adsorption of Rb on a - Cl surface has been conducted using normal-incidence x-ray standing-wavefield absorption at both the Cl and Rb surface atoms. The results indicate reaction of the coadsorbates to form an overlayer of approximately 1.2 ML of RbCl(100) which is essentially incommensurate with the substrate. The RbCl - Cu outermost layer spacing is similar to that seen for pure Rb adsorption on Cu(111). This RbCl layer is spread over the surface and not agglomerated into thicker islands. The results are consistent with prior characterization of the system by Auger electron spectroscopy and temperature-programmed desorption, and with STM studies of NaCl deposition on Al(111).

Protonic Transport Analysis of Starch-Chitosan Blend Based Electrolytes and Application in Electrochemical Device

Two polymer electrolyte systems (unplasticized and plasticized) based on starch-chitosan blend doped with ammonium bromide (NH4Br) were prepared. The conductivity was found to be influenced by the number density (n) and mobility (μ) of the ions. The highest conducting plasticized electrolyte had n and μ values of 8.75 × 1018 cm−3 and 1.03 × 10−3 cm2 V−1 s−1, respectively. Ionic transference number for the highest conducting plasticized electrolyte was found to be 0.92. An electrochemical double layer capacitor (EDLC) using the highest conducting plasticized electrolyte was cycled for 500 times at 0.048 mA cm−2.

Electrical Properties of Starch Based Silver Ion Conducting Solid Biopolymer Electrolyte

In the present study, the electrical and dielectric properties of a solid biopolymer electrolyte system based on starch doped with different amounts of silver nitrate (AgNO3) were analyzed. The electrolyte system was prepared via solution cast technique. Electrical impedance spectroscopy (EIS) measurement for the system was conducted over a frequency range of 50 Hz - 1 MHz at room temperature. It was found that the sample containing 6 wt.% AgNO3 obtained the highest conductivity value of 1.03 × 10-9 S cm-1. The effect of salt concentration on the dielectric properties of the electrolytes was also studied in relation to the conductivity properties. The dielectric studies indicated that the electrolytes in the present study obeyed non-Debye behavior.

Transport Properties of Chitosan/Peo Blend Based Proton Conducting Polymer Electrolyte

The polymer electrolytes were prepared using the solution cast technique. The polymer host consisted of chitosan and poly(ethylene oxide) (PEO). Ammonium nitrate (NH4NO3) was added to the blend solution to provide the charge carriers for ionic conduction. The sample containing 40 wt.% NH4NO3 exhibited a conductivity value of 5.83 × 10-4 S cm-1 at 373 K. Conductivity-temperature relationship for all samples obeyed Arrhenius rule and the activation energy of each samples were obtained. The sample containing 40 wt.% NH4NO3 showed the lowest activation energy at 0.29 eV. The conductivity variation for the prepared electrolyte system was explained using the Rice and Roth model. Sample with 40 wt. % NH4NO3 exhibited the highest number density and mobility of charge carriers with values of 1.39 × 1020 cm-3 and 4.60 × 10-6 cm2 V-1 s-1 respectively. The increase in conductivity was attributed to the increase in the number density and mobility of charge carriers.

Dielectric Studies of Proton Conducting Polymer Electrolyte Based on Chitosan/PEO Blend Doped with NH4NO3

Polymer blend of chitosan and poly(ethylene oxide) (PEO) electrolytes were prepared by employing solution cast method. Ammonium nitrate (NH4NO3) was added to the blend to supply the charge carriers for ionic conduction. The impedance of the electrolytes was measured by electrical impedance spectroscopy (EIS) over the frequency range of 50 Hz to 1 MHz. The permittivity ɛr and electric modulus Mr of the complex were analyzed. Dispersion at low frequencies caused by space charge effect from the electrodes was observed. The modulus plots indicated that the dispersion deviated from the Debye behaviour. The relaxation time, τ decreased to 1.64 × 10-7 s as the NH4NO3 content was increased up to 40 wt.%.

Conduction Mechanism and Dielectric Properties of Solid Biopolymer Electrolyte Incorporated with Silver Nitrate

onic conductivity and dielectric properties of starch based polymer electrolytes doped with silver nitrate (AgNO3) at elevated temperatures were studied. The solid polymer electrolytes were prepared using the solution cast method. X-ray diffraction (XRD) analysis implied that the incorporation of 6 wt.% AgNO3 increased the amorphous phase of the electrolyte. Temperature dependence conductivity plots showed that electrolyte containing 6 wt.% AgNO3 obeyed Arrhenius rule with activation energy, Ea of 0.71 eV. The effect of temperature on the dielectric properties of the electrolyte was also studied in relation to the conductivity properties. The variation of dielectric loss with frequency was obtained from the power law exponent. Temperature dependence of the power law exponent concluded that the conduction mechanism of the 94 wt.% starch-6 wt.% AgNO3 electrolyte followed the correlated barrier hopping (CBH) model.

Hot ethene desorption from Cu(111)

Abstract Irradiation of submonolayer and 4 layers of adsorbed 1,2-dichloroethane (DCE) on Cu(111) at 110K with a pulsed 2 keV electron beam causes ethene desorption with translational temperatures of 2350 ± 100 K (from a submonolayer), and 2540 ± 200 K and 320 ± 50 K (from a 4 layer surface). DCE physisorbed on the Cu(111) surface undergoes electron attachment from the hot secondary electrons generated by the incident beam to form a negative molecular ion. This then dissociates to form a short lived ClCh 2 CH 2 · radical and chemisorbed chlorine. The radical then decomposes generating the high temperature (2350 and 2540 K) ethene and a second chemisorbed chlorine. The translational motion of the ethene is thought to come from part of the heat liberated in the formation of the second CuCl bond as the radical decomposes. The 320 K peak is thought to arise from radical decomposition at the surface of DCE crystallites.

Disorder in YBa2Cu3O7 by entropy measurements and by rf dissipation

New experiments, that characterize thr disorder present in Type II superconducting ceramics, are reported: Electrochemical measurements at 298> T>150 K > Tc ≈ 92 K, in the cell: Cu¦CuBr2 .05 M in CH3OH¦1:2:3¦Pt and /orCu, obtain important thermochemical information, ΔHcell = 30kJ/mole e- and ΔScell = 212J/K/mole e-± 15%, which suggests that the 1:2:3 phase is disordered. The rf dissipation measurements of superconducting lamellae dispersed in a matrix give information on the effects of the static and rf fields on the mixed state.

Sulfur intercalated into barium-copper-rare earth sulfides

We have prepared the sulfide analogues of the new warm (≈ 90 K) superconducting oxides (M1M′2Cu3X8-δ, M = Y, Eu, Gd, M′=Ba, X=S and δ= 0 to 1.5). These are referred to in the literature by the stiochiometry e.g., (1, 2, 3, 7.1) is one of the superconducting phases reported in the literature. The purpose of this work is to find out if the sulfide analogues of the above oxides can be prepared by high temperature reactions in a sulphur atmosphere, the composition of the metallic (superconducting?) phases if present and the structure of the unit cell.