Effect of maleic anhydride and liquid natural rubber as compatibilizers on the mechanical properties and impact resistance of the NR‐NBR blend

The degree of compatibilization between natural rubber (NR) and acrylonitrile‐butadiene rubber (NBR) was investigated by two different methods. NBR was chemically modified with maleic anhydride in a screw twin mixer with and without reaction initiator, benzoyl peroxide. Also, the effects of molecular weight of liquid natural rubber (LNR) as a compatibilizer were studied. The degree of compatibilization between NBR and NR is determined indirectly through measurements of mechanical properties and impact resistance. The maleic anhydride and benzoyl peroxide concentrations influence the mechanical properties and impact resistance of the blends. Also, the mechanical properties of the blends showed that the molecular weight of LNR played an important role in determing their performance. Copyright © 2004 John Wiley & Sons, Ltd.     

Novel addition in trifluoromethylation of [70]fullerene

Pyrolytic trifluoromethylation of [70]fullerene with CF₃CO₂Ag at 300 °C results in the addition of up to 12 CF₃ groups to the fullerene cage. Forty-six C₇₀(CF₃)_n derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60]fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous (‘linear’) addend arrays, having significantly different coupling constants of the ‘terminal’ quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C₇₀(CF₃)₂ isomers, one has either C_s or C₂ symmetry, the other has C₁ symmetry, whilst the C₇₀(CF₃)₄ derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the NMR); (ii) unsymmetrical compounds that show a ‘linear’ coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF₃ groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C₆₀F₆ as a model.     

Construction of a TiO2–Fe3O4‐decorated molecularly imprinted polymer nanocomposite for tartrazine degradation: Response surface methodology modeling and optimization

We synthesized a novel recoverable and reusable photocatalyst system for tartrazine degradation by one‐step incorporation of Fe₃O₄ and TiO₂ nanoparticles into a molecularly imprinted polymer through a facile precipitation polymerization method. The as‐prepared samples were systematically characterized using X‐ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and vibrating sample magnetometry. Benefiting from the positive synergistic effect, tartrazine was almost completely degraded under UV‐C within 180 min by the multicomponent photocatalyst (Fe₃O₄ + TiO₂ + MIP) in comparison with far fewer activities by the corresponding NIP system and the nonmagnetic and bare structures. On the other hand, the central composite design in response surface methodology was applied to optimize the tartrazine photocatalytic degradation process. Twenty experiments were conducted by adjusting three parameters (nanocomposite dosage, initial pH of the reaction solution, and initial dye concentration) in the multiple variable analysis method. A satisfactory correlation between the experimental and predicted values was obtained (R² = 0.956). Additionally, ANOVA analysis with a p value of 1.15 × 10^–5 indicated that the model terms are highly significant. Under the determined optimum conditions, a verification experiment was conducted and shown the adequately approximate value between the predicted (99%) and the experimental (97%) results, which confirmed the validity of the model.     

Bestimmung von freiem und komplex gebundenem Cyanid, Cyanat und Ammoniak nebeneinander

Zusammenfassung Es wird eine Analysenmethode für Cyanid, komplexe Cyanide, Ammoniak und Cyanat in oxydierende Chlorverbindungen enthaltenden Lösungen beschrieben. Nach unseren Ergebnissen kann auch in solchen Lösungen freies Cyanid enthalten sein. Die Bestimmungen sind nebeneinander nicht durchzuführen, daher werden nach Reduktion mit Arsenitlösung folgende Trennungen durch Wasserdampfdestillation (Wd.) durchgeführt: 1. Wd. bei pH 12; erfaßt wird NH₃ bzw. NH₄ ⁺ und ein kleiner Teil des Cyanates (Hydrolyse zu NH₃). Dieser Teil ist bei kontrollierten Bedingungen proportional der Cyanatkonzentration. 2. Wd. bei pH 7 (Phosphatpuffer). Erfaßt wird freies Cyanid. 3. Wd. bei pH 0 zur Abtrennung des Gesamtcyanids. 4. Verseifung des Cyanats (pH 1, Cyanatkonzentration unter 1,2 g/l) und Wd. bei pH 12. Erfaßt wird die Summe an Ammoniak und Cyanat.

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Determination of free and complex cyanide, cyanate and ammonia in presence of each other

A procedure is described for the analysis of solutions containing cyanide, complex cyanides, ammonia and oxidizing chlorine compounds. Our results show the possible existence of free cyanide ions in such solutions. Simultaneous determination is impossible; therefore, after reduction with arsenite solution, the following separations are made by steam distillation (s. d.): (1) S.d. at pH 12 gives the sample ammonia and some ammonia produced by hydrolysis of cyanate (this is under controlled conditions proportional to the cyanate concentration). (2) S.d. at pH 7 (phosphate buffer) gives the free cyanide. (3) S.d. at pH 0 separates complex and free cyanide. (4) Hydrolysation of cyanate at pH 1 (cyanate conc. below 1.2 g/l) and following s.d. at pH 12 gives the sum of sample ammonia and the ammonia equivalent to the cyanate content.

     

Dispersion studies and electronic transitions in nickel phthalocyanine thin films

Thin films of the organic semiconductor nickel phthalocyanine (NiPc) are structurally investigated using X-ray diffraction and infrared light absorption. The optical absorption and dispersion studies of nickel phthalocyanine were investigated using spectrophotometric measurements of transmittance and reflectance at normal incidence in the wavelength range 190–2100 nm. The absorption spectra recorded in the UV-VIS region show two well-defined absorption bands of the phthacyanine molecules, namely, the Soret and the Q-band. The Davydove splitting of the main absorption peak in the metal phthalocyanines correlates with the relative tendencies of the metal to out-of-plane bonding. The refractive index n as well as the absorption index k were calculated and showed an independent of the film thickness in the film thicknesses range 400–770 nm. The refractive index n showed an anomalous dispersion in the absorption region as well as normal dispersion in the transparent region. Some of the important optical absorption such as the molar extinction coefficient, the oscillator strength, the electric dipole strength have been evaluated. The analysis of the spectral behavior of the absorption coefficient α in the absorption region revealed two indirect allowed transitions with corresponding energies 2.77±0.03 and 1.66±0.02 eV. An energy band diagram has been proposed to account for the optical transitions of NiPc thin film. All previous parameters were as well obtained for films annealed at 523 K for 2 h. Discussion of the obtained results and their comparison with the previously published data are also given.     

Statistical properties for a class of nonlinear squeezed states

Theoretical investigations of dynamical behavior in optical parametric oscillators (OPO) have generally assumed that the cavity detunings of the interacting fields are controllable parameters. However, OPOs are known to experience mode hops, where the system jumps to the mode of lowest cavity detuning. We note that this phenomenon significantly limits the range of accessible detunings and thus may prevent instabilities predicted to occur above a minimum detuning from being evidenced experimentally. As a simple example among a number of instability mechanisms possibly affected by this limitation, we discuss the Hopf bifurcation leading to periodic behavior in the monomode mean-field model of a triply resonant OPO and show that it probably can be observed only in very specific setups.     

Final-state interaction in spin asymmetry and GDH sum rule for incoherent pion production on the deuteron

The contribution of incoherent single-pion photoproduction to the spin response of the deuteron, i.e., the asymmetry of the total photoabsorption cross-section with respect to parallel and antiparallel spins of photon and deuteron, is calculated over the region of the -resonance with inclusion of final-state NN and rescattering. Sizeable effects, mainly from NN rescattering, are found leading to an appreciable reduction of the spin asymmetry. Furthermore, the contribution to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon energy of 550 MeV. Final-state interaction reduces the value of the integral to about half of the value obtained for the pure impulse approximation.Received: 14 February 2003, Revised: 10 April 2003, Published online: 1 July 2003PACS: 11.55.Hx Sum rules - 13.60.Le Meson production - 24.70.+s Polarization phenomena in reactions - 25.20.Lj Photoproduction reactionsE.M. Darwish: Present address: Physics Department, Faculty of Science, South Valley University, Sohag, Egypt.     

Polarisation phenomena occurring at Cu/semiconducting Te layer/electrolyte interfaces studied by rapid pulse techniques

Tellurium films of different thickness are cathodically deposited on copper substrate using sodium tellurite solutions ofpOH 3.95. The kinetics of the primary processes and modes of conduction occurring at the Cu/Te layer/electrolyte interfaces are studied using rapid galvanostatic rectangular pulses. Approximate values for the specific conductance of the surface layer are calculated from the experimental resistance overpotential. Activation over-potentials are explained in view of charge transfer reactions associated with reactions occurring at the electrode/solution interface.

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Polarisationsphänomene an Cu/halbleitende Te-Schicht/Elektrolyt-Phasengrenzen

Zusammenfassung Tellur-Schichten verschiedener Dicke wurden aus Natriumtelluritlösungen vonpOH 3,95 kathodisch auf Kupfer abgeschieden. Es wurden die Kinetik der Primärprozesse und die Art der Leitung an den Cu/Te-Schicht/Elektrolyt-Phasengrenzen mittels schneller galvanostatischer Rechtwinkel-Pulstechnik untersucht. Dabei wurden angenäherte Werte für die spezifische Leitfähigkeit der Oberflächenschicht aus den experimentellen Widerstands-Überpotentialen errechnet. Die Aktivierungsüberpotentiale werden im Hinblick auf Ladungsübertragungsreaktionen in Verbindung mit Reaktionen an der Phasengrenze Elektrode/Lösung erklärt.

     

Investigation of the primary processes occurring at the tin/semiconducting layer/electrolyte interfaces by rapid pulse technique: Part II. Studies of the Sn/Te/electrolyte system

Tellurium layers are cathodically deposited on the surface of tin substrate from a sodium tellurite bath of pH 9.67. The electrode is anodically polarized using rapid galvanostatic rectangular pulses. Apparent specific resistance values calculated from resistance overpotentials demonstrate the semiconducting nature of the tellurium layers. The observed resistance, being too high compared to the reported values for Te crystals suggests the presence of amorphous Te in the electrodeposited phase, as well as the persistence of adsorbed hydrogen cathodically formed. Activation overpotentials are interpreted in view of the primary processes probably operating at the electrode/solution interface. These are associated with the corrosion of tellurium, or occasionally tin in its pores.