Rheological properties of organo-inorganic hybrid gels based on functionalized low density polyethylene and clinoptilolite

The results of studying the effect of temperature on the dependence of shear rate on shear stress, effective viscosity on shear rate and effective viscosity on reciprocal temperature in Arrhenius coordinates for nanocomposites based on chemically modified low density polyethylene and clinoptilolite are presented. The object of study was the initial polyethylene functionalized with methacrylic acid filled with clinoptilolite, as well as hybrid gels based on modified polyethylene filled with appreted clinoptilolite. A temperature-invariant characteristic of the viscosity properties of hybrid gels is constructed, which allows predicting the temperature regime of their processing by injection molding and extrusion.

Influence of Data Scattering on Estimation of 100,000 hrs Creep Rupture Strength of Alloy 617 at 700 °C by Larson–Miller Method

The 100,000 hrs creep rupture strength of Alloy 617 at 700 °C is estimated by Larson–Miller method using the rupture data of longer duration than 500 hrs in the temperature range between 593 and 816 °C, corresponding to 700 ± 100 °C. The maximum time to rupture was 40,126.7 hrs. The rupture data exhibit large scattering, especially at 760 °C. After eliminating the shorter time to rupture data at 760 °C, the regression analysis gives us the Larson–Miller constant C = 12.70 and the 100,000 hrs creep rupture strength of 100 MPa at 700 °C, by Swindeman program. The present regression analysis underestimates the constant C and 100,000 hrs creep rupture strength. The linear extrapolation of log tr versus reciprocal temperature 1/T plots to 1/T = 0 gives us an average C value of Cav = 18.5, which is much larger than the constant C of 12.70 obtained by the Swindeman program. It is concluded that the origin of underestimation of the constant C and corresponding 100,000 hrs creep rupture strength is large data scattering. Using an appropriate constant C of 18.45, the 100,000 hrs creep rupture strength at 700 °C is estimated to be 123 MPa. Using the rupture data including the shorter time to rupture data at 760 °C and using C = 18.45, the 100,000 hrs creep rupture strength at 700 °C is estimated to be 116 MPa.

The Influence of Remote Substituents on the Amine-Catalysed Solvolysis Reaction of Some Para-Substituted Oxazolinones in Water–Dmso Mixtures

The kinetics of the morpholine-catalysed solvolysis of some p-substituted (Z)-4-benzylidene-2-phenyloxazolin-5-one in water- dimethylsulfoxide mixtures (20-90% V/V) at different temperatures in the range (40-60°C) have been studied. There is an electronic effect in the predicted direction for para-substitution in the benzylidene moiety in different percentage compositions of binary aqueous solvent mixtures. An electron-withdrawing substituent in the benzylidene ring leads to rate enhancement while an electron-donating substituent retarded the rate. A good linear relationship was obtained from plots of log kobs against the σ-Hammett parameter with a positive slope (ρ) at the various experimental temperatures and solvent compositions. Plots of the reaction rate constant ρ against the dielectric constant and the reciprocal temperature gave straight lines. The thermodynamic parameters Δ H≠, Δ S≠ and Δ G≠ have been determined; Δ G≠ increases gradually as the mole fraction of the cosolvent increase, due to a complex quasi-mirror image compensation of Δ H≠ and Δ S≠. A plot of Δ H≠ versus Δ S≠ for the reaction in water–solvent mixtures gave good straight lines with isokinetic temperatures which are higher than the experimental temperature. The higher negative values of the entropy suggest selective solvation by the more polar water molecules.

THERMOELECTRIC PROPERTIES OF MnSi1.7 FILMS WITH ADDITION OF ALUMINUM AND CARBON

Polycrystalline higher manganese silicide ( MnSi 1.7, HMS) films with addition of aluminum and carbon are prepared on thermally-oxidized silicon substrates by electron beam evaporation and magnetron sputtering, respectively. An aluminum intermediate layer and a carbon cap layer are used as the doping sources. It is found that both the Seebeck coefficient and electrical resistivity are dependent on the amount of aluminum and carbon added to the films. The Seebeck coefficient changes a little in the temperature range 300 to 433 K and decreases considerably above 433 K when aluminum is added to the film. When carbon is added to the film, however, the Seebeck coefficient increases slightly. With addition of aluminum and carbon, the resistivity decreases. As a result, the thermoelectric power factor increases, especially for films with carbon addition. Several activation energies (0.022–0.20 eV) are observed from the curves of logarithm of resistivity versus reciprocal temperature. The larger activation energies of 0.35 and 0.51 eV are consistent with the energy band gaps for higher manganese silicides.

Kinetic Investigation of the Reactions between Triphenylphosphine, Dialkyl Acetylenedicarboxylates and Sh-Acid Such as 2-Thiazoline-2-Thiol or 2-Mercaptobenzoxazole by Uv Spectrophotometry

Kinetic studies were made of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates in the presence of SH-acids, such as 2-thiazoline-2-thiol or 2-mercaptobenzoxazole. To determine the kinetic parameters of the reactions, they were monitored by UV spectrophotometery. The second order fits were drawn by the software associated with a Cary UV spectrophotometer model Bio-300 at appropriate wavelength. The values of the second order rate constant (k2) were calculated using standard equations within the program. Within the temperature range studied, the dependence of the second order rate constant (ln k2) on reciprocal temperature was in agreement with the Arrhenius equation, enabling calculation of the activation energies of all reactions. Furthermore, useful information was obtained from studies of the effect of solvent, structure of reactants (different alkyl groups within the dialkyl acetylenedicarboxylates and SH-acids) and also concentration of reactants on the rate of reactions.

Comparison of Two Methods of Calculation of Activation Energy for some Chosen Industrial Steels after its Oxidation at High-Temperatures in Air

In this work it will be presented the results of calculation of energy activation Q of selected industrial steels (e.g. grade 55 - carbon steel, LH15 – bearing steel, H10S2M, 4H14N14W2M and 50H21G9N4 valve steels) according to Polish Norm by two methods. In the first method the calculations of Q are based on the dependence of value of parabolic growth rate constants kp in function of reciprocal temperature. The second method is based on the calculated parameters, which allow to determine the value of Q for examined steels by using value of Q for pure iron, taken from literature data, and the particular values of mass concentrations of elements in oxidised steels. The growth kinetics of layers were almost according to parabolic law. The values of parabolic rate constant kp were calculated on the basis of measurements of thickness of oxide layers. To the experiment the cylindrical specimens were used. The isothermal process of oxidation was conducted in chamber furnace at 1100, 1060, 1020, 980 and 940°C in the air. Time of oxidation various from 3 till 1303.5 hrs. The comparison of obtained results of activation energy Q for mentioned methods of each individual examined steels gives a good agreement.

Nonlinear Dielectric Relaxation of Mn Doped Polycrystalline (Ba,Sr)TiO3 Thin Films Over the Temperature Range of 4.2 - 473 K

We have investigated the dielectric relaxation currents of Mn doped polycrystalline Ba0.7Sr0.3TiO3 (BSTO) thin films as a function of applied electric field and temperature (4.2 - 473 K). The dielectric relaxation currents followed a power law time dependence, J(t) = Jot-n, over the entire temperature range. Plots of log(Jo) vs. reciprocal temperature were not linear and showed slopes approaching values of 0.35 eV at high temperatures which rapidly decreased to 0.25 meV at lower temperatures. The relaxation currents were found to be nonlinear with applied field. The observed nonlinearity of the field dependence of the relaxation currents can be understood in terms of the nonlinear relaxation component of the total capacitance. An equivalent circuit model for a paraelectric BSTO thin film capacitor is presented and possible polarization mechanisms are briefly discussed.

A defect model for ion-induced crystallization and amorphization

Extensive experimental investigations have been reported on the ion-induced motion of the interface between the crystalline and amorphous phases of silicon. The crystal grows into the amorphous phase at low ion fluxes and high temperatures. The amorphous phase grows into the crystal at high ion fluxes and low temperatures. The experimental observations are shown to fit a model based on a single defect. The concentration of this defect decays by binary recombination, this is, two of the defects annihilate one another. The model accounts for the linear relationship between interface motion and reciprocal temperature, for the Arrhenius temperature dependence of the flux at which no interface motion occurs, and for the temperature independence of the crossover frequency observed in beam pulsing experiments. The defect on which this model is based has a motion energy of 1.2 eV. Assuming that the same defect is also responsible for thermal recrystallization of the amorphous phase gives a formation energy of 1.5 eV for the defect. The defect is believed to be a dangling bond in the amorphous phase.