Studies on electrical conductivity of gamma irradiated polyaniline

Summary de electrical conductivity at surface of -irradiated polyaniline (PAn) has been studied. EPR spectroscopic results indicate that the variation of spin concentration is consistent with the increase of _de. Electrical conductivity (_de) versus temperature (T) characteristics of unirradiated and irradiated PAn were performed, which demonstrate that the unirradiated curve can fit to ln_deT₁, while the irradiated curve fit to ln_deT_1/4.     

Determination of the cooperativity parameter σ from viscometric data of poly-L-glutamic acid-Na

Summary Viscometry of PLGNa solutions was performed for various degrees of neutralization . The cooperativity parameter in the helix-coil transition was estimated using Ptitsyn's method with some modifications. The increase of thus obtained with decreasing is explained in terms of the a dependence of short-range interactions of PLGNa segments.     

Obtaining corundum-zircon suspensions,their rheological and bonding properties

Conclusions It is shown that the combined grinding of corundum (80%) and zircon (20%) will produce suspensions with high concentrations and binding properties. A study was made of the effect of pH and slip concentration on their rheological properties, density, and the strength of the castings. With a pH of 2.5–3.5 and of 0.50–0.54 we obtained castings with an open porosity of up to 28–30% and _bend of up to 8–9 MPa.Substantial sintering of the material is accomplished even at reduced (1450°C) temperatures. The factors for _bend (on specimens measuring 7×7×70 mm) and _comp (on specimens measuring 10×10×10 mm) with an open porosity of 16–18% are up to 180 and 740 MPa respectively. At 1100 and 1200°C the value of _comp equals 300–340 and 250–300 MPa, respectively.Translated from Ogneupory, No. 6, pp. 22–25, June, 1984.     

The application of Taft-Hancock steric constants to the free-radical initiated copolymerization of N-alkylmaleimides with α-methylstyrene

Summary The rates of free-radical initiated alternating copolymerization of -methylstyrene with N-alkylmaleimides (RMI) decrease in the following order: Me>Et>n-Prn-Bun-Hex>iso-Pr>tert-Bu. A linear relationship was established in the plots of log(k_R/k_Me) against polar substituent constants ^*, true steric factors E_S and corrected steric factors E_S ^C. The best fit was obtained in plots of log (k_R/k_Me) against ^* and E_S ^C while a large scattering of results was observed in the plot of log(k_R/k_Me) against E_S.     

Adsorption of carbon monoxide on Ni/Ti and Ni/TiO2 surfaces preparedin situ in the electron spectrometer: A combined UPS-XPS study

Adsorption of CO on a clean Ti surface is partly associative at 80 K with a 1 -4 separation of 4.2 eV, becoming dissociative at 130 K. On Ni- covered Ti surfaces, however, associative adsorption (4-1, 3.3 eV) occurs at 80 K and partial dissociation, around 200 K. TiO₂ is reduced more effectively on annealing, when it is covered with Ni. On the surfaces of Ni deposited on TiO₂, there is only dissociative adsorption, unlike on Ni/Al₂O₃ and Ni/TiO₂ (non-annealed) surfaces.Contribution No. 565 from the Solid State and Structural Chemistry Unit.     

Solutions of the general equations for the radiation dose dependence of the molecular weights of irradiated polymers with an initial Schulz-Zimm distribution

Summary The general equations for the radiation dose dependence of irradiated polymer molecular weights have been solved exactly. For an initial most probable molecular weight distribution (=1), the solutions are analytical and exact. For the general case (1) the solutions are numerical and exact. The present approach has resulted in the solutions for both =1 and 1 being incorporated into a group of FORTRAN computer programs which will solve experimental data for scission and crosslinking yields by both minimization and exact treatments. Simulated data treated using these FORTRAN programs are give. The FORTRAN programs are available from the authors.     

The impedance of the alkaline zinc-manganese dioxide cell. II. An interpretation of the data

The impedance of small alkaline zinc-manganese dioxide cells has been interpreted in terms of a controlling charge-transfer and diffusion process at the zinc electrode throughout the early stages of discharge. After about 20% of the available charge has been removed, it becomes necessary to include the manganese dioxide electrode circuit components. This network has the circuit elements for charge transfer and a proceeding chemical reaction. The Warburg component for the manganese dioxide electrode need not be considered since the effective area considerably exceeds that of the zinc. The relative areas are confirmed by the magnitudes of the circuit element components. The decomposition of the impedance data has been successfully accomplished as far as 80% discharge; after this point cells show considerable differences from cell to cell, especially in the low-frequency range, which makes a confident interpretation difficult. It is considered that this is due to the loss of the physical definition of the system.Nomenclature C _m,C _z double-layer capacitances of MnO₂ and Zn electrodes, respectively - C _X,R _X parallel branch accounting for current density varying with fractional electrode coverage - R resistance of electrolyte - V open-circuit voltage of cell - Z, Z, Z impedance of cell,resistive component ofZ and reactive component ofZ, respectively - _m, _z transfer resistance of MnO₂ and Zn electrodes, respectively - , _R, _C in Warburg equation:Z _W = ^–1/2(1–i) orZ _W = _R^–1/2– i_Cco^–1/2     

AC Conductivity of Porous Silicon from Monte Carlo Simulations

The AC conductivity of a percolation model with local energetical disorder for porous Silicon in three dimensions, (), is studied by Monte Carlo simulations. The model includes both diffusion and recombination processes and () is obtained by a Fourier transform of the mean-square displacement of the carriers, where hopping diffusion of a single type of carrier (either an electron or an exciton) and two types of carriers (an electron and a hole) are considered. It is found that at low temperatures, the behavior of () depends sensitively on the type of carrier considered.     

Crack resistance of corundum refractories over a wide range of temperatures

Conclusions The ultimate bend strength _bnd and the critical stress intensity factor K_lc of a group of corundum refractories were determined over a wide range of temperatures. It was shown that the temperature dependences of _bnd and K_lc have a similar nature. In the refractories having the usual porous structure, the rate of decrease of K_lc with increasing temperature is less than that of _bnd. Owing to this, the coefficient of crack resistance K_t of the refractories increases at high temperatures.The refractories having a porous-fissured structure, exhibit an almost identical reduction of _bnd and K_lc with increasing temperature and the magnitude of K_t increases very insignificantly.Translated from Ogneupory, No. 3, pp. 8–11, March, 1987.     

Cryochemical Synthesis of Mn-Containing Poly(p-Xylylene)

A Mn-containing polymer was produced by solid-state photopolymerization of a cocondensated mixture of p-xylylene with Mn at 80 K. It was shown that during simultaneous deposition p-xylylene and Mn formed both - and -complexes. Irradiation of the system by UV light resulted in polymerization of p-xylylene with the destruction of the unstable -complexes, while the -bonded compounds were incorporated into the polymer chains. Complexes of Mn with benzyl-type radicals of the polymerized system were also observed. Prolonged storage of the polymerized material at ambient temperature under vacuum led to the gradual decomposition of the organomanganese compounds and complexes.     

Anionic synthesis of ω-1,1-diphenylethylene-terminated polystyrene macromonomers. Rational synthesis of ABC hetero three-armed-star-branched polymers

Summary Polystyrene macromonomers with terminal 1,1-diphenylethylene functionality were prepared by the reaction of one equivalent of poly(styryl)lithium with 1,4-bis (l-phenylethenyl)benzene (PDDPE). The macromonomer functionalities were determined by ¹H NMR [(vinyl CH₂)=5.4 ppm] and UV spectroscopy (_max=260 nm). The stoichiometric linking reaction of poly(styryl)lithium (M_n=15.3x10³ g/mol) with an -1,1-diphenylethylene-terminated polystyrene macromonomer (M_n=5.4x10³ g/mol) followed by addition of styrene monomer has been used to prepare a hetero three-armed, star-branched polymer with M_n=5.8x10⁴ g/mol (5,400-15,300-37,300). The g value ([]b/[]l) was equal to 0.92.     

Numerical simulation of non-Newtonian jets emanating from a converging cone

The effects of the rheological properties on the fluid motion of non-Newtonian jets emanating from a converging cone have been investigated theoretically. Three typical non Newtonian fluid models have been considered; i.e. the power-law fluid, the modified Bingham ngham fluid and the Oldroyd-B fluid. The effects of five parameters on the flow field are analyzed in detail; these parameters are: the contraction ratio of the radius of the cone far upstream to that at the cone exit L; the converging angle of the cone 6; the power-law index n; the Bingham number Bn and the Weissenberg number We. The Galerkin finite-element method incorporated with the upwind scheme was applied to solve the flow problems numerically. Full Newton iteration was used to solve the flow fields and the free-surface positions of power-law and modified Bingham fluids. However, the free-surface position of the Oldroyd-B fluid has to be updated by kinematic iteration to avoid numerical oscillations.Notation a one-half of the cone gap at the cone exit - Bn Bingham number, Eq. (8) - b radius of the cone far upstream - C_o jet swell ratio, Eq. (2) - D rate of the deformation tensor, Eq. (7) - I unit tensor - L contraction ratio, Eq. (2) - m exponent factor of the modified-Bingham fluid, Eq. (8) - n power-law index - n unit normal vector - p, pressure, dimensional and dimensionless - P_atm environmental pressure - U average fluid speed at the cone exit - v, velocity vector, dimensional and dimensionless - We Weisenberg number, Eq. (9) Greek letters viscosity ratio of polymer to solution - one-half of the jet thickness far downstream - _o Newtonian viscosity or consistency of power law fluid - converging angle, Figure 1 - relaxation time of the Oldroyd-B fluid - _D second invariant of tensor D, Eq. (7) - total stress tensor, Eq. (5) - , stress tensor, dimensional and dimensionless - _E elastic stress tensor, Eq. (9) - _V stress tensor, Eqs. (6), (8) and (9) - _o apparent yield stress     

The impedance of the Ledanché cell. I. The treatment of experimental data and the behaviour of a typical undischarged cell

The impedance spectrum of an undischarged commercial Leclanché cell (Ever Ready type SP11) is presented in the forms of the Sluyters plot and the modified Randies plot. The decomposition of the experimental cell impedances into the component parts has been achieved using a computer. The decomposition process and the component processes representing the overall cell behaviour are described.List of symbols R _s in-phase component of (experimental) electrode impedance - R _t charge transfer resistance referred to nominal area of Zn ( cm²) - 1/(C _s) out-of-phase component of (experimental) electrode impedance - angular frequency (= 2f) - R resistance of electrolyte solution - charge transfer resistance - C _L double layer capacitance - C _DL double layer capacitance of electrode referred to nominal area of Zn (F cm^–2) - j –1 - Warburg coefficient - D factor in Equations 1 and 2 - C _s R _s calculated values ofC _s andR _s (first approximation) - C _s R _s calculated values ofC _s andR _s (refined values taking into account the additional network) - C _s R _s calculated values of C_s andR _s (refined values taking into account porosity) - _x resistive part of additional series component (parallel connection) - C _x capacitance part of additional series component (parallel connection) - D factor in Equations 6 and 7     

A new family of “ligated” anionic initiators for the “living” polymerization of (meth)acrylic esters

Summary A new family of ligands (dual - ligand), i.e. chelating lithium alkoxides, Li-O-(CH₂-CH₂O)_nCH₃, is shown to be very effective in promoting the living anionic polymerization of methacrylic and acrylic esters, including a number of primary alkyl acrylates such as n-butyl acrylate and 2-ethylhexylacrylate.     

On the Charge Carrier Concentration in Sodium–Calcium Aluminophosphate Glasses

The dc and ac conductivities of the xNa₂O–(35 – x)CaO–7.5Al₂O₃–57.5P₂O₅glasses (mol %) with x= 0–35 are studied in the frequency range from 20 Hz to 1 MHz at different temperatures. It is found that the dc conductivity strongly depends on xonly for glasses with x 10. For glasses with x 5, the dc conductivity is virtually composition independent. The dependence of the ac conductivity plotted on the log(()/_dc) vs. log(/_dc) coordinates is analyzed. The ac conductivity represented in these coordinates depends on xonly for glasses with x 5, in which the dc conductivity does not depend on x. For glasses with xin the range from 10 to 35, all the isotherms of the ac conductivity closely coincide with each other. This result is discussed in the framework of two hypotheses: (1) the conductivity () is determined by the dynamic polarization (of the Maxwell–Wagner type at low frequencies) of the material due to spatial fluctuations of the density of paths providing the migration of sodium ions and (2) the concentration of charge carriers is independent of x.     

Properties ofSrMO 3-δ(M=Fe,Co) as oxygen electrodes in alkaline solution

Strontium ferrates and cobaltates with compositions SrFeO_3- (0.060.40) and SrCoO_3- (0.040.30) were synthesized. The dependence of the oxygen electrode properties on the value was examined in 1 mol dm^–3 KOH solution. In the SrFeO_3- series, the samples with 0.24<<0.29, showed the highest activity in both oxygen evolution and reduction reactions. In contrast, no strong dependence on the value was observed in SrCoO_3-, which also showed a high catalytic activity for oxygen evolution.     

Behavioral and neurosensory responses of the boll weevil,Anthonomus grandis Boh. (Coleoptera: Curculionidae), to fluorinated analogs of aldehyde components of its pheromone

Competitive field tests with -fluorinated analogs of compounds III and IV (III--F and IV--F, respectively) of the boll weevil,Anthonomus grandis Boh., aggregation pheromone showed these compounds, when combined with the other pheromone components [(±)-I and II], to be as attractive as grandlure [(+)-I, II, and III+IV]. Dose-response curves constructed from electroantennograms of male boll weevils to serial stimulus loads of III, IV, III--F, IV--F, and the corresponding acyl fluorinated analogs (III-acyl-F and IV-acyl-F) showed the -fiuorinated analogs to be as active as the pheromone components (threshold=0.1 g), while the acyl fluorinated analogs had a 10-100 x higher threshold (=1-10 g). Single-neuron recordings showed that IV neurons and II neurons (Dickens, 1990) responded to IV--F and III--F, respectively, while IV-acyl-F and III-acyl-F were inactive. Since a previous study showed compounds I, II, and IV to be essential for behavioral responses in the field, it seems likely that the activity of the -fluorinated analogs observed here is due to the stimulation of IV neurons by IV--F as indicated in single neuron recordings.     

Surface characterization of zirconium titanate (ZrTiO4) powder by measurements of electrical photoconductance and photoassisted oxygen isotope exchange

The photosensitivity of a ZrTiO₄ sample (33 m²/g) prepared by a sol-gel method has been assessed in the presence of O₂ by both photoconductance and oxygen isotope exchange (OIE) measurements at room temperature at wavelengths > 290 nm. For oxygen pressures < ca. 13.3 Pa, the steady-state photoconductance of ZrTiO₄ was unaffected by , which indicated that the direct recombination of the photoproduced charges played the dominant role. At higher pressures, varied as the reciprocal of , which was consistent with the fact that the electronic equilibrium was then governed by O₂ + e^– O ₂ ^– . OIE over ZrTiO₄ occurred predominantly via the overall mechanism which involves the exchange of two surface oxygen atoms for each exchange act. It was very slow as compared with OIE over photocatalytically active anatase samples which, in addition, occurs via another mechanism. These results allow one to predict that this ZrTiO₄ sample is a poorly active photocatalyst for oxidations involving gaseous oxygen, and further illustrate the interest of and OIE measurements to evaluate the photosensitivity of semiconductor oxide samples.     

Role of structure and capacity for energy absorption in increasing the strength and crack resistance of refractory ceramics

Conclusions We identified the influence of the parameters of a heterogeneous structure and also of particles possessing the capacity to absorb energy of deformation on the strength _rup and the crack resistance K_lc of refractory ceramics. The proposed relationships facilitate quantitative evaluation of the influence of these factors and indicate ways of increasing the levels of _rup and K_lc. Comparison of the calculated and experimental values of _rup and K_lc obtained from tests of various types of ceramics indicate the suitability of the equations for assessing the characteristics of strength and crack resistance.Translated from Ogneupory, No. 7, pp. 8–13, July, 1987.     

Prospects for strengthening fibres and films

Conclusions A model of the orientation strengthening of polymers which is based on the concept of the existence of a network of nodes which rearrange during the stretching process has been used to calculate the limiting values of degree of stretch, , and the strength, , of fibres of polyethylene, polycaproamide, polyvinyl alcohol, polypropylene, polyacrylonitrile, and poly-p-phenyleneterephthalamide.According to calculation, increasing the molecular weight of the polymer and decreasing the concentration of the solution being spun should lead to an increase in and ; for Terlon with a molecular weight of about 250,000, =100 and =10 GPa.Translated from Khimicheskie Volokna, No. 5, pp. 33–34, September–October, 1983.