Effect of γ-irradiation on the molecular-topological structure of Viton® fluoroelastomers

The molecular–topological structure of a terpolymer based on vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene has been studied for the first time with the use of thermomechanical spectrometry. A five-block topologically amorphous and crystalline pseudo-network structure with crystallites, which have different initial melting temperatures, as branching points has been detected in the terpolymer at temperatures from–100 to 250°C. When γ-irradiated at a dose of 30 kGy, the crystalline blocks of high-temperature modifications assimilated into one cluster block with the formation of a pseudo-network with a 1.5fold increase in the block-average molecular weight and a decreased initial molecular flow temperature.     

Effect of γ-irradiation on the gauge factor of two-dimensional island platinum films

Four films (A, B, C and D) of two-dimensional island platinum films (2D-I(Pt)Fs) whose mass thicknesses (d_m) are 10, 20, 30 and 40 Å, respectively were deposited onto Corning 7059 glass substrates via the thermal evaporation technique. The increase in the film resistance with time (aging) in air is monitored until stable values are obtained. Each of the prepared films was γ-irradiated by different doses, namely, 100, 200, 300, 500 and 700 Gy; this was done using ¹³⁷Cs (0.662 MeV) radiation source of dose rate 0.5 Gy/min. For each dose the relative change in the film resistance was found at different values of strain either in the tensional or compressional mode. The gauge factor (v) of the Pt films was deduced and we found that; for particular d_m, the gauge factor decreases as the dose increases. Also, for a particular dose, v decreases as d_m increases. Qualitative interpretation for the results was offered on the ground that (i) the transfer of electrons between islands takes place by the thermally activated tunneling mechanism, (ii) the process of γ-irradiation makes the islands spread along the substrate and consequently the inter-island spacing will decrease. The micrographs taken by the Atomic Force Microscope (AFM) confirmed such spreading.     

Effect of γ-irradiation on the properties of poly(ester urethane) elastomer

The influence of irradiation with ⁶⁰Co γ-rays on gelation, change in the mechanical characteristics, and the formation of supermolecular structure in a poly(ester urethane) elastomer synthesized from oligoether adipate and diisocyanate, as well as a diol with or without double carbon-carbon bonds, was studied. It was found that the presence of double carbon-carbon bonds in the structure of the elastomer ensures the predominance of crosslinking over degradation processes. It was shown that γ-irradiation at a dose of 380 kGy is accompanied by the formation of a microglobular structure of ～1 μm size. The specifics of changes in the mechanical characteristics depending on the absorbed dose are discussed.     

Effect of γ-irradiation on the catalytic activity and selectivity of γ-alumina II. Conversion of isopropanol

The catalytic conversion of isopropanol was conducted over a poorly crystalline -alumina irradiated with different doses of -rays (25–150 Mrad). The catalytic reaction was carried out at 180–400°C in a flow technique under atmospheric pressure. The results showed that the dose of 25 Mrad resulted in a decrease of about 50% of the dehydration activity which suffered a further slight decrease upon irradiation at a dose of 50 Mrad. Increasing the dose in the range of 50–150 Mrad effected an increase in the dehydration activity reaching a maximum limit at 100 Mrad, then decreased abruptly by a dose of 150 Mrad. -irradiation led also to creation of some active sites contributing in dehydrogenation of isopropanol to producing acetone. These results were discussed in terms of removal of Brönsted acidity (25–50 Mrad), responsible for the dehydration reaction and to transformation of Lewis to Brönsted acidity (100 Mrad) by the action of liberated water from the dehydration reaction. The drop in dehydration activity due to irradiation at 150 Mrad might result from an efficient removal of the Brönsted acid sites created. The induced dehydrogenation activity of irradiated aluminas was attributed to creation of some electron-donor centers.     

Effect of γ-irradiation on the crystallinity and catalytic activity of NdX and NdY zeolites

Different Nd-zeolites were prepared from the original NaX and NaY zeolites by ion exchange. The hydrated and thermally activated (at 550 °C) samples obtained were irradiated with -rays of 1.5 and 10.0 Mrad. The unirradiated and irradiated samples were characterized mainly by X-ray diffraction and tested for catalytic activity in cumene cracking. The X-ray diffraction patterns indicated a slight decrease of crystallinity after irradiation. However, the irradiated samples exhibited higher catalytic activities than unirradiated ones. -Irradiated hydrated zeolites were found to possess comparable activities, whereas the irradiated dehydrated samples were more active. Higher irradiation doses resulted in more active dehydrated zeolites than those irradiated with a lower dose. The observed higher activity was attributed to the formation of tricoordinate aluminium atoms in the zeolite structure, leading to increase of the number of acidic sites and consequently to a catalytic activity.     

Effect of γ-irradiation on the growth of ZnO nanorod films for photocatalytic disinfection of contaminated water

The growth of ZnO nanorods on a flat substrate containing γ-irradiated seeds and their ability to photocatalytically eliminate bacteria in water were studied. The seed layer was obtained, by the spray pyrolysis technique, from zinc acetate solutions γ-irradiated within the range from 0 to 100 kGy. Subsequently, to grow the rods, the seeds were immersed in a basic solution of zinc nitrate maintained at 90 °C. The rate of crystal growth on the seed layer during the thermal bath treatment was kept constant. The resulting materials were characterized morphologically by scanning electron and atomic force microscopies; X-ray diffraction was used to study their morphology and structure and ultraviolet-visible spectroscopy to determine their absorbance. The obtained seed films were morphologically dependent on the radiation dose and this was correlated with the ZnO nanorod films which presented a texture in the (002) direction perpendicular to the substrate. The rods have a hexagonal mean cross section between 20 and 140 nm. Using these rods, the photocatalytic degradation of Escherichia coli bacteria in water was studied; a positive influence of the crystalline texture on the degradation rate was observed.     

Crystal structure and thermal decomposition mechanism of the supramolecular complex of barium chloride with inositol

The single crystal of [Ba(H2O)2(C6H12O6)2Cl2] was obtained based on the phase equilibrium results. Its structure was determined by X-ray crystallographic analysis. The crystals are monoclinic and in space group C2/c with a=1.901 7(2) nm, b = 0.682 13(8) nm, c = 0.162 60(2) nm,β=96.593(2)°and V= 2.095 3(4) nm3, Z= 4, DC=1.917 g·cm-3. In its solid state, this supramolecular complex is a three-dimensional network with double layers connected by hydrogen bondings. The molecule structure of [Ba(H2O)2(C6H12O6)2Cl2] has a central barium ion that is coordinated to two water molecules, two chlorides, and four hydroxyls from the two inosi-tols. Losing the coordinating water is controlled by random nucleation and growth mechanism (n = 2/3) and 3-dimensional diffusion mechanism (n=2).     

Effect of γ-irradiation on the physicochemical and sensory properties of hazelnuts (Corylus avellana L.)

The present study evaluated the quality of hazelnuts as a function of irradiation dose to determine dose levels causing minimal undesirable changes to hazelnuts. Physicochemical (color, peroxide value (PV), hexanal content, fatty acid composition and volatile compounds) and sensory (color, texture, odor and taste) properties were determined.Results showed a twenty fold increase in peroxide value and twenty-eight fold increase in hexanal content after irradiation at a dose of 7 kGy. An increase was also observed in saturated fatty acids (10%–23%) with a parallel decrease in unsaturated fatty acids (90–77%). Volatile compounds such as ketones, alkanes, alcohols, aldehydes, furans, aromatic hydrocarbons, bicyclic monoterpenes and acids were produced mostly comprising secondary oxidation products of hazelnut lipids after irradiation. Color parameter b* increased (p<0.05) after irradiation at a dose of ⩾5 kGy, while color parameters L* and a* remained unchanged by irradiation. Sensory evaluation showed that texture and color were not affected by irradiation. Taste, the most sensitive sensory attribute showed that hazelnuts retain acceptable sensory quality when irradiated up to a dose of 1.5 kGy.     

Effect of γ-irradiation on optical and electrical properties of Se1−xTex

The effect of γ-irradiation on optical and electrical properties of amorphous and polycrystalline Se_1−xTe_x (0.211<x<0.802) thin films of thickness 180 nm were investigated. The analysis of the absorption coefficient data revealed the existence of indirect transition both before and after irradiating. It was observed that the value of the optical energy gap depends on the value of x, decreasing as x increases. It was found also that the optical energy gap decreases with an increase of γ-doses for all compositions. The obtained results for all Se_1−xTe_x, films have been interpreted in terms of density of states model of Mott and Davis. From the experiment of electrical conductivity σ at various temperatures, it was observed that Se_1−xTe_x. films exhibited ln σ versus T⁻¹ relationships at high temperatures and ln σ(T)^1/2 versus T^−1/4 hopping conductivity behaviour at low temperatures. It was found that the thermal activation energies ΔE decrease with increasing Te content and increases with decreasing γ-doses. X-ray diffraction patterns for the as-deposited Se_1−xTe_x, show that polycrystalline films start to appear for x>0.407.     

Effect of γ-irradiation and thermal annealing on the molecular–topological structure of a copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether)

The molecular–topological structure of a copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether) subjected to γ-irradiation and thermal annealing has been studied for the first time with the use of thermomechanical spectrometry. The pseudonetwork structure of the copolymer contains an amorphous block (interjunction chains) and crystalline segments (branching points). The diblock amorphous and crystalline structure with a crystal structure fraction of 0.21 transformed into an almost completely amorphous structure with a crystallite fraction of 0.06 after the irradiation of the copolymer at a dose of 600 kGy. Thermal annealing at 483 K formed a new structure: a high-temperature amorphous block.     

The particle dimension controlling synthesis of α-MnO2 nanowires with enhanced catalytic activity on the thermal decomposition of ammonium perchlorate

Hydrothermal method synthesis of α-MnO₂ nanowires has been achieved at different temperatures in this work. X-ray diffraction and transmission electron microscopy confirmed the pure phase of the α-MnO₂ nanowires. All of the samples crystallized in a single-phase nanowires shape. The α-MnO₂ nanowires diameter increased from 11 nm to 21 nm with the increase in hydrothermal temperature from 120 °C to 200 °C. The α-MnO₂ catalytic activity on the decomposition of ammonium perchlorate (AP) was characterized through thermogravimetric analysis. The decomposition rate of AP with the addition of α-MnO₂ was size relative. The 11 nm MnO₂ nanowires exhibited the best catalytic activity, which lowered the high-temperature peak of AP by 130 °C.     

Effect of cationic micelles on the decomposition of α-aminophenyl cephalosporins

The intramolecular rates of degradation of α-aminophenyl cephalopsorins were determined with and without hexadecyltrimethylammonium bromide (CTAB). Micellar-derived spectral shifts were used to measure the bind of the ionic forms as well as to determine the effect of CTAB on the apparent dissociation constant of the antibiotics. The rate of the degradation of cephalexin (Cp), cefadroxil (Cf), and cephradine (Cph), increased with surfactant concentration reaching a plateau at high surfactant concentrations. In the plateau region, the rate constant was salt sensitive decreasing with NaBr concentrations. These effects were quantitatively analyzed within the framework of the pseudo-phase model with explicit considerations of ion exchange. All the experimental results were fitted to this model. The intramolecular degradation of Cf, Cp and Cph was catalyzed by 96-, 59-, and 29-fold, respectively. A working hypothesis to rationalize these effects was suggested. The obtained results demonstrate that the quantitative analysis can be used to assess, predict and control the effects of surfactants on the drug stability.     

Ceramide formation on the γ-irradiation of galactocerebroside as a constituent of micelles

The radiation-initiated transformations of galactocerebroside (GalCer) as a constituent of micelles were studied. The radiation-chemical yields of decomposition of the starting substrate and formation of degradation products suggested that the formation of ceramide is the main process in the γ-radiolysis of GalCer. The irradiation of GalCer in the presence of dimethyl sulfoxide, which is an active scavenger of OH radicals, decreased the yield of ceramide. Ceramide was formed as a result of GalCer degradation with O-glycoside bond cleavage in the polar moiety of the lipid.     

Preparation of copper ferrite by sol–gel method and the synergistic catalytic for the thermal decomposition of ammonium perchlorate

Journal of Sol-Gel Science and Technology - In the present work, copper ferrite was prepared by a simple and mild sol–gel method followed by low-temperature calcination, and characterized by...     

Effect of caffeine on DNA conformational changes after in vitro γ-irradiation

The radioprotective action of caffeine upon γ irradiation of DNA solutions is demonstrated by means of low gradient viscometry, flow birefringence, atomic force microscopy and UV spectroscopy. In the presence of caffeine, a decrease in the radiation effect on the DNA coil size in the solution, in the number of doublestranded breaks and damaged nitrogen bases, and in the degree of radiation-induced denaturation is observed.     

Study on the effects of flame retardants on the thermal decomposition of wood by TG–MS

The effect of three flame retardants, K₂CO₃, Na₂SiO₃·9H₂O, and Na₂B₄O₇·10H₂O on the process and composition of volatile products of the thermal degradation of wood has been investigated by the thermogravimetric (TG), differential thermogravimetry (DTG), differential thermal analysis (DTA), and the synchronous thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the ion current intensity and ion peak area of m/z = 18 and 44 MS signals were increased by the flame retardants but the ion peak area of m/z = 28 MS signal was decreased (except K₂CO₃) at the meantime. What’s more, the ion current intensity and ion peak area of m/z = 60 and 68 MS signals were also decreased (except K₂CO₃), which mean that Na₂B₄O₇ can significantly enhances the dehydration and inhibits the depolymerization of wood. Although K₂CO₃ accelerates the dehydration reaction, it cannot inhibit the depolymerization reaction effectively, so the flame retardant efficiency of K₂CO₃ is decreased with the higher concentration. The catalysis of dehydration reaction of Na₂SiO₃ is the worst one.     

Effect of γ-irradiation on conductivity of cadmium-mercury-tellurium single crystals in weak and strong electric fields

The effect of γ-radiation on electrical conductivity of Cd _x Hg_{1 ? x} Te (0.25 ≤ x ≤ 0.95) single crystals in weak and strong electric fields has been investigated. It has been shown that at relatively low fields in which charge carriers are still warm, the dependence (Δσ/σ₀) ～ E ² is observed because of the dominance of scattering on acoustic lattice vibrations with the increasing electric field strength; with a further increase in the field strength, the carriers become hot and the dependence of σ upon E becomes linear. The effect of irradiation by Γ-rays on the dependence of σ upon E in these samples is explained by a significant concentration of the intrinsic impurity centers in the crystals and their redistribution with the increasing radiation dose.     

The effect of γ-irradiation on laser ablation of polyketone

Results of a pioneering study of the effect of laser radiation in vacuum on the surface of a polyketone (alternating terpolymer of ethylene, propylene, and carbon monoxide, POK) plate are presented. It has been found that laser beam irradiation leads to the surface heating of the plate, its melting, and the formation of a characteristic surface microrelief, an ablation crater, from which the gas flow of the ablation plume carries away products that are deposited on surfaces outside the laser beam area to form a coating with a chemical composition close to that of the substrate POK. A rim grows from molten POK around the crater. The melting point of the crystalline modification (377 K), the molecular flow temperature (427 K), and the molecular weight of the coating (25560) are much lower than those of the initial POK (464 K, 477 K, and 159200, respectively), thereby indicating laser-induced chain degradation of POK. The preliminary γ-irradiation of POK to a dose of 100 kGy enhances its laser ablation rate.