FeCl3-doped polyvinylidene fluoride

Infrared (350–4000 cm^–1) and optical (1.15×10⁴–2.95×10⁴cm^–1) spectra, differential thermal analysis (DTA) and d.c. electrical resistivity of FeCl₃- doped polyvinylidene fluoride (PVDF) films, over the doping mass fraction range 0 w 0.40, have been measured. The i.r. spectra provided evidence of: (a) the presence of both and phases in the undoped, and a phase in the doped PVDF films; (b) a head-to-head content of 20%; and (c) a different doping mode beyond a 0.25 doping level. The optical spectra resulted in two induced energy bands, and a probable interband electronic transition, due to doping. Dipole relaxation and premelting endothermic peaks were identified by DTA. Electrical conduction is thought to proceed by interpolaron hopping among the polaron and bipolaron states induced by doping. The hopping distance, R _o, is calculated according to the Kuivalainen model. A numerical equation is adopted to formulate the dependence of R _oon doping level and temperature. It is found that R _o< CC separation length. This implies that, in doped PVDF, charge carrier hopping is not an intrachain process.     

Thermocapillary stability during gravity flow of a liquid film

Thermocapillary rupture of a film under conditions of turbulent undulatory flow is associated with the buildup of wave motion on its surface. Here an approximate solution to the problem and criterial relations are obtained for determining the limits of stable film flow.Notation _min, kg/m·sec minimum irrigation intensity at which no film rupture occurs - ₁, kg/m· sec irrigation intensity at which the first dry spot appears - q, W/m² thermal flux density - _D, °C temperature at the rupture section - x, m space coordinate along the warm surface in the direction of flow - y, m coordinate in the direction normal to the warm surface - _o, m mean thickness of the film between large waves - _c, m thickness of the continuous layer - _cr, m critical film thickness - _o=/_o andl _o=l _o/_o dimensionless initial amplitude and length of a wave - , sec^–1 recurrence frequency of large waves - t_cr, sec time till thermocapillary rupture of a film - t_p, sec time of penetration of a thermal perturbation through the film thickness - u, m/sec velocity of thermocapillary flow of the liquid - , W/m·°C thermal conductivity - c_p, kJ/kg·°C specific heat - , kg/m linear density - , N·sec/m² dynamic viscosity - a, m²/sec thermal diffusivity - , N/m surface tension - , N/m² tangential stress at the film surface - L, m length of the warm pipe segment - L_o, m distance from the inlet to the section where wave motion at the film surface occurs - ¯w, m/sec mean velocity of downward flow of liquid in the film - , m mean thickness of the laminar layer - g, m²/sec free-fall acceleration due to gravity Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 4, pp. 581–591, October, 1980.     

Chitosan-based electrolyte for secondary lithium cells

The system chitosan : ethylene carbonate : LiCF₃SO₃ was prepared by the solution cast technique. To verify that the conductivity of the material is due to the salt, the electrical conductivity at room temperature of the chitosan acetate film and that of the chitosan acetate films containing different amounts of ethylene carbonate added to it were measured. The order of magnitude of the electrical conductivity was 10^–10 S cm^–1. Films containing fixed content of chitosan and plasticizer but different amounts of salt were then prepared in the same manner and the highest electrical conductivity obtained was 1.3 × 10^–5 S cm^–1 at room temperature. These results indicate that the conductivity is due to the salt. Conductivity-temperature studies show that the ln T versus 10³/T graphs obey Arrhenius rule implying that the conductivity occurs by way of some thermally assisted mechanism. Polarization current measurement shows that the lithium ion transference number is 0.09. A LiMn₂O₄/chitosan-LiCF₃SO₃/C cell was fabricated which cycled between 1.5 to 2.5 V with fading capacity. This could be the result of LiF formation due to interaction between the salt and the fluorine in the binding agent.     

Optical properties of high-T c superconductors: Evolution of the superconducting gap with doping

A study of the optical conductivity spectra of high-Tc cuprates with c-axis polarization elucidates the evolution of superconducting gap with doping. The results are consistent with the d-wave gap in the clean limit superconductivity in the CuO₂ plane which couples with the adjacent planes via Josephson effect. It is suggested that the maximum of the d-wave gap is large (2_o 400 cm^–1) and it is independent of doping and material.     

Fluctuations in the resistive transition in aluminum films

The excess conductivity due to the thermodynamic fluctuations in aluminum films is experimentally investigated. The excess conductivity is described by the sum of the Aslamazov-Larkin and the Maki-Thompson terms. An empirical formula is found on the relation between the pair-breaking parameter (0) in the absence of the magnetic field and the normal-state film resistanceR _N ^sq as (0)=6×10^–4 R _N ^sq . This formula might be explained in terms of the localized moments and the proximity effect in films. The result of the magnetic field dependence of the pair-breaking parameter revealed that (0) cannot be described by an effective magnetic field. The temperature dependence of the excess conductivity at higher temperatures systematically deviates from the theoretical values due to the breakdown of the mean-field theory.     

Electrical properties of Li2O-La2O3-SiO2 electrode glasses after Ta2O5 doping and Ta implantation

Electrical conductivities, , of the Li₂O-La₂O₃-SiO₂ glasses were investigated as functions of Ta₂O₅ doping and Ta ion-implantation. A linear relationship between logarithm and the inverse of the sample temperature, T, was found in 2 to 4 mol% Ta₂O5 doped Li₂O-La₂O₃-SiO₂ glasses. The conductivity increases as Ta₂O₅ content increases at sample temperatures above 100°C. Fluences of 50 keV Ta ions per cm² from 5 × 10¹⁶ to 2 × 10¹⁷ were implanted into 0% and 2% Ta₂O₅ containing Li₂O-La₂O₃-SiO₂ glass samples. The activation energy of the conductivity was deduced from the relation between log and 1/T. It was found in implanted samples that the conductivity increased, but the activation energy and T _k–100 decreased, where T _k–100 is the sample temperature when the conductivity reaches 100 × 10^–1 S/cm. However, the Ta₂O₅ containing implanted samples show higher conductivities, lower activation energies and lower T _k–100. X-ray photoelectron spectroscopy (XPS) was used to study the structural modification introduced by implantation. Bridging oxygen (BO) and non-bridging oxygen (NBO), were observed in all samples. The changes in relative concentrations of BO and NBO before and after implantation clearly indicate the structure modification which results in the increase of the conductivity. It was clearly demonstrated in this study that both doping Ta₂O₅ and implanting Ta ions enhance the conductivity of Li₂O-La₂O₃-SiO₂ electrode glasses.     

On the thermohydrodynamic analysis of a Bingham fluid in slider bearings

Summary A theoretical analysis of finite slider bearings with the Bingham rheological model is presented which includes a full consideration for thermal effects. Full thermohydrodynamic (THD) as well as simplified ISOADI solutions are presented for a wide range of operating conditions. Results are authenticated with a number of published one-dimensional isoviscous solutions. An extensive set of parametric studies of the Bingham model together with an illustrative example is presented.Notation a Clearance ratio - B Pad length in the direction of motion (m) - c _o Lubricant specific heat (J/Kg K) - f Friction coefficient - F Frictional force (Pa) - H _b Thickness of the stationary component (m) - h Film thickness (m) - h ₁,h ₂ Maximum and minimum film thickness (m) - h _a,h _b Height of the lower and upper boundary of core (m) - h _L,h _H Height of the lower and upper boundary of fluid film (m) - h _conv Convective heat transfer coefficient (W/m² K) - K _f Bearing characteristic number - k _o Thermal conductivity of the lubricant (W/m K) - L Bearing length in the axial direction (m) - m Slope of the slider bearing - P Pressure (Pa) - P _a Ambient pressure (Pa) - P _L Average unit load (Pa) - P _max Maximum pressure (Pa) - P _s Supply pressure (Pa) - Q _in Inlet flow rate (m³/sec) - Q _leakage Leakage flow rate (m³/sec) - S _h Difference between the maximum and minimum film thickness (m) - T Temperature (^oC) - T _a Ambient temperature (^oC) - T _b Stationary component temperature (^oC) - T _max Maximum temperature (^oC) - T _mean Mean temperature (^oC) - T _s Lubricant temperature supplied (^oC) - T _exit Exit temperature (^oC) - U ₁,U ₂ Velocity of the lower and upper surface along the film (m/sec) - U _L,U _H Velocity of the lower and upper boundary of fluid film along the film (m/sec) - U _c,W _c Velocity of core along the film and in the axial direction (m/sec) - u, v, w Velocity component along, across the film and in the axial direction (m/sec) - W Bearing load-carrying capacity (N) - W _L,W _H Velocity of the lower and upper boundary of fluid film in the axial direction (m/sec) - x, y, z Coordinate system (m) - x _b,y _b Coordinate system used in the stationary component (m) - Temperature-viscosity coefficient (1/K) - Yield stress-temperature coefficient (1/K) - Shear rate (1/sec) - Non-Newtonian viscosity (Pa·sec) - ₁, ₂ Temperature-rise parameters - _s Aspect ratio of the slider bearing - Viscosity (Pa·sec) - _i Inlet viscosity (Pa·sec) - _eff Effective viscosity (Pa·sec) - _o Density of the lubricant (Kg/m³) - Shear stress (Pa) - ₀ Critical shear stress (Pa)     

Electrical properties of In doped CdS thin films

Indium doped polycrystalline cadmium sulphide CdS:In thin films have been prepared by the spray pyrolysis technique on glass substrates in an enclosed dome. The different scattering mechanisms such as lattice, impurity and grain boundary scattering for CdS:In films are observed at low temperature, in the range of 303 to 120 K. The experimentally determined mobilities due to these scatterings are well interpreted with those of theoretically calculated mobilities. The d.c. conductivity for CdS:In films has also been studied in the same temperature region. The Mott variable range hopping conduction process followed below the temperature of 150 K. The Mott parameters such as N(E _F ), R, W and are found to be 1.26 × 10¹⁹ eV^–1cm^–3, 9.8 × 10^–-7cm, 0.02 eV^–1 and 2.38 × 10⁶cm^–1, respectively from the conductivity data.     

Electrochemical doping of alkali metals into C60 thin film

The electrochemical properties of an evaporated C₆₀ film were studied by voltammetry in organic electrolyte solution. Four reversible reduction waves were observed, corresponding to the formation of alkali metal salts of fullerene, A _x C₆₀ (A Li, K, Rb,x=1, 2, 3, 4). The voltammograms observed for each cation species were compared and discussed in relation to the cation radius. The change of optical density spectrum by the redox reactions was measured in the wavelength range of visible light. The resistivity of a C₆₀ film protected by a polyimide film decreased rapidly by four orders of magnitude after the electrochemical doping of potassium ions.     

The electrical conductivity of graphite intercalated with superacid fluorides: experiments with antimony pentafluoride

The electrical conductivity in graphite measured normal to the crystallographic c-axis is observed to increase after intercalation with acid molecules which act as acceptors. This behaviour is regarded as the result of ionization of the acid molecule which, in turn, increases the positive current carriers in the host graphite. Since the carrier density depends on the degree of ionization of the acid, it follows that the stronger the acid the greater the increase in carrier concentration, and assuming no adverse mobility effects, the greater the electrical conductivity. The hydrogen fluoride-antimony pentafluoride system produces some of the strongest acid substances known. The experiments described here represent the initial examination of the electrical conductivity resulting from intercalation of this material into graphite. The experiments consisted of intercalating graphite powder with antimony pentafluoride in a copper tube and swaging the sheathed compound into wire. The measured conductivity of the graphite intercalation compound, when the copper conductivity is subtracted out and allowance is made for departure from ideal density, is about 1×10^{6 –1} cm^–1. This is approximately 40 times the conductivity of pristine graphite and more than one and a half times the conductivity of pure copper.     

Soft chemical synthesis and characterization of lithium nickel oxide electrode materials

Soft chemistry was used to prepare ordered nanophase Li_0.6NiO₂ electrode materials by completing the oxidation of Ni²⁺ to Ni³⁺ and/or Ni⁴⁺ species with H₂O₂ oxidant during solution reactions at 50–60 °C and evaporation at 105–150 °C rather than during sintering. Both elemental analysis and electron spectroscopy for chemical analysis (ESCA) results indicate that oxidation was completed. The deconvoluted ESCA spectra of nickel ions exhibited a semi-quantitative ratio of Ni⁴⁺Ni³⁺=6040 which presented no significant change with increase of sintering time. After sintering for up to 11 h at 700°C, ordered Li_0.61Ni_0.96O_2.0 ceramics were formed (R3m, a ₀=0.2837 nm, c ₀=1.417 nm). Distribution of the crystallite size was in the range of 80–200 nm. As sintering times were increased, the crystallite shapes exhibited a more distinct morphology, and the ordering degree of the cations was enhanced, while the conductivity was sharply enhanced up to 2.0×10^{–1 –1} cm^–1 at 30 °C. Compared to conventional ceramic and solution methods, the ordered nanophase Li_0.61 Ni_0.96O_2.0 ceramics was obtained at 700 °C with shorter sintering times ( 11 h).     

Observations of polyaniline surface morphology modification during doping and de-doping using atomic force microscopy

Chemically synthesized 30 m thick polyaniline films were studied during the doping and dedoping process by imaging the polymer surface using in situ atomic force microscopy (AFM). The polymer, which was initially in the base non-conducting form, was doped using aqueous solutions of both tosylic acid (pH = 0.2) and HCl (pH = 0.2 and 1.0). De-doping was accomplished by exposing the same doped polymer surface to NH₄OH (pH = 12) base solution. AFM images showed that it was necessary to cycle the polymer surface three times between acid and base before a reproducible surface morphology was established. For the case of doping with tosylic acid, AFM images showed that the polyaniline surface was immediately roughened; the changes in mean roughness for the base and acid conditions were ~ 5.4 and ~ 6.7 nm, respectively. In addition there appeared to be an increase in the size of surface channels and cracks. When doping with HCl (pH = 1.0), no change in surface morphology was observed; however, noticeable surface roughening occurred over 10 min for the case of the lower pH = 0.2 solution; mean roughness changes for the base and acid conditions were ~ 17.9 and 39.2 nm. Radio frequency measurements, which determined the polymer complex permittivity, and d.c. conductivity measurements were used to determine the level of doping in the samples studied by AFM which were exposed to acid solutions.     

Torsional Oscillator Study of Thin Helium Films on Hydrogen Substrates

We have made torsional oscillator measurements of thin helium films on a Mylar surface preplated with 2 and 5 layers of H ₂ . The minimum ⁴ He coverage needed for superfluidity, or inert layer, n _o on both surfaces is found to be 6 mole/m ² . This is equivalent to 1/2 of a monolayer at bulk liquid density. The superfluid transition in coverages above n _o is similar to that found on bare Mylar, exhibiting the standard Kosterlitz-Thouless characteristics. We find no anomaly in _s or the dissipation in the film that can be identified with a second transition reported in recent third sound experiments.     

Ammonia sensing by hydrochloric acid doped poly(<Emphasis Type="Italic">m</Emphasis>-aminophenol)–silver nanocomposite

Processable poly(m-aminophenol) (PmAP) was synthesized using ammonium persulfate oxidant in 0.6 M sodium hydroxide solution at room temperature. Then, in situ PmAP–silver nanocomposite film was obtained by casting PmAP film from dimethyl sulfoxide with silver hydroxide ammonia mixture at 140 °C. The nanocomposite film was doped with hydrochloric acid (HCl) by general solution doping technique. The undoped and HCl-doped films were characterized by ultraviolet visible spectroscopy, Fourier transformed Infrared spectroscopy, transmittance electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction analysis. Spectroscopic characterizations confirmed that the PmAP was doped by silver nanoparticles and it was further doped by HCl used. So, the synthesized PmAP–silver nanocomposite showed a conductivity of 1.01 × 10⁻⁶ S/cm, which was increased to 3.27 × 10⁻⁴ S/cm after HCl doping. The well dispersed silver nanoparticles with average size 130–150 nm was observed by SEM and TEM analysis. Unlike conventional ammonia sensor here, the resistivity of the nanocomposite film was decreased on exposure to ammonia gas and the sensing properties of the HCl-doped nanocomposite films were also reproducible. It can be seen that the % response of doped nanocomposite was unchanged while, the response time was decreased with increasing ammonia vapor concentrations in air. The ammonia-sensing characteristics of the HCl-doped nanocomposite film was explained on the basis of a proposed mechanism.     

The effect of CuO on the grain growth of ZnO

The grain growth kinetics in the 1, 2, 3 and 4 wt.% CuO doped ZnO was studied using the simplified phenomenological grain growth kinetics equation Gⁿ – G₀ⁿ = K₀ t exp (– Q/RT) together with microstructure properties of the sintered samples. The grain growth exponent value (n) was found to be 3 for 1, 2 and 3 wt.% CuO doped ZnO and 5.5 for 4 wt.% CuO doped ZnO. The apparent activation energy was decreased with CuO doping up to 3 wt.% from 250 kJ/mol to 150 kJ/mol but it was not changed significantly (155 kJ/mol) by 4 wt.% CuO doping. CuO doping up to 3 wt.% promoted the grain growth of ZnO whereas 4 wt.% CuO doping inhibited the grain growth of ZnO because of formation of Cu-rich secondary phase in the grain boundaries.     

Transport properties in3He-4He mixtures near the superfluid transition

We report measurements of the temperature, density, and concentration gradients in³He-⁴He mixtures, induced by a vertical heat flux. The flat horizontal cell included two superposed capacitors and the density was determined by means of the dielectric constant method. The experiments were carried out on mixtures with mole fractionsX ₃=0.37, 0.15, and 0.05 at saturated vapor pressure, with special emphasis on the region near the superfluid transition. Our measurements under steady-state conditions give the conductivity , the thermal diffusion ratiok _T , and the coefficient of thermal expansion. We describe the singular behavior of these quantities in the neighborhood ofT (X). In the superfluid phase, we test with fair success a relation by Khalatnikov between gradX/ gradT and several static properties. From the relaxation times needed to attain steady-state conditions, and in combination with measured static and transport properties, we obtain in the normal phase the mass diffusionD, which diverges strongly asT is approached. In the superfluid phase, we test successfully a scaled relation that results from the solution of Khalatnikov's hydrodynamic equations. From our data the dispersion relations for scattered light are calculated: _o/q ² in both the normal and the superfluid phases and ₂/q ² in the normal phase.Research supported by NSF grant DMR 8024056.     

Structure of dispersion media by nuclear magnetic resonance

The change of the diamagnetic shielding constant of a benzene molecule interacting with the solid phase surface is calculated.Notation _d diamagnetic shielding constant - e, m_e electron charge and mass, respectively - c speed of light - _b ^o benzene wave function - _m ^o and _m ^o* eigenfunctions of benzene molecule and their conjugates - W_mo matrix elements of the perturbation operator - E _o ^o energy of the ground state of a benzene molecule - e _m ^o energy of the excited states of a benzene molecule - a ₀ Bohr radius Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 476–482, September, 1981.     

A novel route for the synthesis of processable conducting poly(m-aminophenol)

Polymerization of m-aminophenol (mAP) in aqueous NaOH solution was done chemically by using ammonium persulfate (APS) as an oxidative initiator. The product poly(m-aminophenol) (PmAP) was found to be highly soluble in aqueous sodium hydroxide, dimethyl sulfoxide (DMSO) and N,N-dimethyl formamide (DMF). From the intrinsic viscosity measurement, the optimum condition for the polymerization was established with 0.6 M NaOH medium with the ratio of monomer to oxidant as 1:1.5 (mol:mol). The polymer was characterized by FTIR and ¹H NMR spectroscopy, elemental (CHNS) and thermogravimetric (TGA) analyses. From the spectroscopic analysis the structure of the polymer was found to resemble that of hydroxy polyaniline as the polymer contains free –OH groups attached to o/m position in the phenyl ring. The elemental analysis of the polymer also confirmed the same. From TGA study, the polymer was found to be thermally stable. A freestanding film of poly(m-aminophenol) was cast in DMSO solution followed by solvent removal and drying of the film at 100 °C for 7–8 h in an oven. A dc conductivity of 4.8 × 10⁻⁴ S cm⁻¹ was obtained for the synthesized polymer film after doping with H₂SO₄ solution.     

Conductive biodegradable film of N-octyloxyphenyl-N′-(4-methylbenzoyl)thiourea

Thiourea derivatives are versatile family of ligands which provides wide range of electronic properties since they consist of rigid π-systems on their structures. In this work, a new type of thiourea compound with general formula Me-C₆H₄C(O)NHC(S)NHC₆H₄-OC₈H₁₇ of N′-(4-methylbenzoyl)thiourea (MBTU) was successfully synthesised and characterized by using NMR, FTIR and UV–vis analysis. The development of new conductive biodegradable film based on MBTU has been accomplished by incorporating chitosan to the polymer-dopant system via solution-cast technique. The impedance measurement technique was employed to determine conductivity of biodegradable film. It shows that, with the addition of MBTU, the increasing of conductivity is from 10 ^?9 to 10 ^?8 Scm ^?1 . TNM results show that the conductivity of biodegradable film is governed by electronic conducting species. It is proven that MBTU compound exhibits promise and has great potential to be explored and used as doping system in conductive materials application in the future.