Influence of γ-ray Irradiation on the PTC Effect of EPDM/Carbon Black Composite

Introduction The positive temperature coefficient(PTC) effect is characterized by an increase of resistivity with an elevated temperature.The PTC effect of carbon black(CB) filled polymers is useful for self-regulation heaters,over-current protectors,sensors,etc.Much work has been done on the PTC effect of the carbon black filled crystalline polymer composite[1-4],whereas carbon black filled amorphous polymers have not drawn researchers much attention because the PTC effect in these composites is small or cannot be detected[5-7].In this work,the influence of γ-ray irradiation on the PTC effect of CB filled amorphous ethylene-propylene-diene terpolymer(EPDM) composites was studied.     

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, ⁶⁰Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.     

Electrophysical Properties of Composites Based on Polyethylene Modified with Multi-Walled Carbon Nanotubes with High Content of Fe–Co-Catalyst

Russian Journal of Applied Chemistry - The effect of the residual catalyst for the synthesis of multi-walled carbon nanotubes (MWCNTs) on the electrophysical properties of MWCNT–polyethylene...     

Effects of Citric Acid Concentration and Activation Temperature on the Synthesis of Carbon Nanotubes

A series of Ni-La-Mg catalyst samples were prepared by citric acid complex method, and carbonnanotubes were synthesized by catalytic decomposition of CH4 on these catalysts. The effects of the citricacid concentration and the activation temperature on catalytic activity were investigated by CO adsorption,TEM and XRD techniques. The experimental results showed that the particle size of the catalysts preparedthrough gel auto-combustion varied with the concentration of citric acid. Therefore carbon nanotubes with different diameters were obtained correspondingly. The effect of activation temperature on the activity of catalyst was negligible from 500 to 700℃, but it became pronounced at lower or higher temperatures.     

Influences of Temperature and Coal Particle Size on the Flash Pyrolysis of Coal in a Fast-entrained Bed

IntroductionCoal is the major primary energy source in China,which accounts for about three quarters of the total en-ergy consumption.Most of coal in China contains a rel-atively high content of volatile substances.The reserveof lignite accounts for about…     

Effect of Plasma Treatment Conditions on the Structure and Hydrophilic Properties of TiOх and СuxO/TiOх Coatings

Colloid Journal - In this work, formation of nitrogen-containing TiOх and СuxO/TiOх coatings, as well as their structure-related phase composition, elemental composition, and...     

Effect of Oxygen Redistribution on the Normal and Superconducting Properties of Yttrium High‐Temperature Superconductors

An anomaly is found in the vicinity of T_max 560$ K on electric resistance versus temperature curves for yttrium hightemperature superconductors of the 123 phase. Xray phase analysis suggests a structural phase transition in the vicinity of T_max due to oxygen redistribution in the mobile sublattice of this compound. Investigation of samples with Y partially replaced by Ca has shown that the structural phase transition does not depend on carrier concentration in the conduction band.     

Study on the Effect of Nano and Active Particles of Alumina on Natural Rubber–Alumina Composites in the Presence of Epoxidized Natural Rubber as Compatibilizer

Natural rubber composites with alumina of different particle sizes (28 nm nano particles, 200 nm active particles and > 1000 nm raw alumina) were prepared by the usual rubber processing technique. Epoxidized natural rubber (ENR) was used in the composites as compatibilizer. Cure characteristics and mechanical properties of all composites were analyzed. The values of minimum rheometric torque (M_L), maximum rheometric torque (M_H) and torque difference (M_H – M_L) increased. Maximum enhancement was observed for the nano-filled composites. It endorses the view that nano alumina reveals highest interaction with natural rubber in presence of ENR. Scorch time and optimum cure time values for nano-composites were highest among all types of composites. Vulcanization reaction for the sulfur curing system of the composites was found to follow first order rate kinetics. Specific rate constant decreased with decreasing particle size in composites. Crosslink densities of composite-vulcanizates showed increasing trend with decreasing particle size of alumina. Mechanical properties of the composite vulcanizates increased with decreasing particle size of alumina - nano composites exhibiting much higher mechanical strength. Results of oxidative resistance reveal that particle size of alumina in composite vulcanizates has a significant impact on aging behavior.     

Density Functional Theory and MP2 Calculations of the Transition States and Reaction Paths on Coupling Reaction of Methane through Plasma

The two possible reaction paths of producing ethane on coupling reaction of methane through plasma were theoretically investigated by B3LYP and MP2 methods with 6-311G^* respectively and further compared with the previous results calculated from B3LYP/6-31G^*. The new investigated results consistently confirmed the previous conclusion. And the influences of the calculation methods and basis sets on the calculated results were also discussed.     

The Influences of Polymers and Temperature on the Foam Properties of 3‐Dodecylalkoxyl‐2‐hydroxylpropyl Trimethylammonium Chloride

The foam performances of 3‐dodecoxy‐2‐hydroxypropyl trimethylammonium chloride (C₁₂TAC) have been determined in the existence of different relative amount of polymer. The experimental results show that the foaming ability of the mixture systems of the C₁₂TAC/PEG and C₁₂TAC/PVP is stronger than that of the surfactant solutions in the absence of polymer, and with the increase of relative amount of polymer both foaming efficiency and foam stability of the surfactant solutions are evidently enhanced. For the aqueous solution of the surfactant, effect of temperature on foaming properties has also been examined. The results show that both the foaming ability and stability of the foams of the surfactant solutions are highest (or strongest) at 30°C.     

exo- and endo-Complexes of Fe(0) with Carbon Allotropic Modifications on the Example of Fullerene С60: a Density Function Theory Study

Russian Journal of General Chemistry - Structures of exo- and endo-complexes of fullerene C60 with zero-valent Fe0, in which the metal is localized inside and outside fullerene molecule,...     

Methane Reforming with Carbon Dioxide on the Co/α-Al2O3 Catalyst: The Formation, State, and Transformations of Surface Carbon

The interactions of oxidized and reduced Co/-Al₂O₃ (4 wt % CoO) with H₂, CH₄, CO₂, and O₂ and their mixtures are studied in flow and pulse regimes using a setup involving a DSC-111 differential scanning calorimeter and a system for chromatographic analyses. It is shown that treatment with hydrogen at 700°C results in the partial reduction of cobalt oxide to Co. Methane poorly reacts with the oxidized catalyst but readily reacts with the reduced catalyst to form H₂ and surface carbon. The initial surface carbon transforms into other forms, which block the cobalt surface to different extents and differ in the heats of reaction with CO₂. Carbon dioxide may react with the surface carbon to form CO (rapidly) and with metallic Co to form CO and CoO (slowly). Thus, the main route of methane reforming with carbon dioxide on Co/-Al₂O₃ is the dissociative adsorption of CH₄ to form surface carbon and H₂ and the reaction of surface carbon with CO₂ to form CO via the reverse Boudouard reaction.     

Living/controlled free radical copolymerization of chlorotrifluoroethene and butyl vinyl ether under 60Co γ-ray irradiation in the presence of S-benzyl O-ethyl dithiocarbonate

Living/controlled free radical copolymerization of chlorotrifluoroethene and butyl vinyl ether has been successfully achieved at room temperature under (60)Co γ-ray irradiation in the presence of S-benzyl O-ethyl dithiocarbonate. The alternating and block copolymers have been obtained with well-defined molecular weights and narrow molecular weight distributions.     

Effect of Co60 γ-irradiation on the optical properties of thin films from the system GeSe3–Sb2Se3–ZnSe

Optical transmittance in the range from 200 nm to 1100 nm is measured for fresh and γ-irradiated thermally evaporated chalcogenide films of GeSe₃, Sb₂Se₃, ZnSe, (GeSe₃)₈₀(Sb₂Se₃)₂₀ and (GeSe₃)₇₀(Sb₂Se₃)₁₀(ZnSe)₂₀. The effect of ZnSe incorporation with both GeSe₃, Sb₂Se₃ results in amorphous γ-radiation sensitive (GeSe₃)₇₀(Sb₂Se₃)₁₀(ZnSe)₂₀ composition as obtained from the estimated optical parameters. Optical energy gap, E_g, for (GeSe₃)₇₀(Sb₂Se₃)₁₀(ZnSe)₂₀ film shows a noticeable decrease from 1.81 eV at 0 kGy to 1.52 eV at 690 kGy and conversely the corresponding band tail width, E_e, increases from 0.123 eV at 0 kGy to 0.138 eV at 690 kGy. By contrast, the estimated values of E_g and E_e for (GeSe₃)₈₀(Sb₂Se₃)₂₀ compositions, show no change with different γ-irradiation doses in the same range. The obtained results could be explained in terms of the band edge shift into the energy gap due to either the formation of localized states at the edges or weakening in the composition cohesive energy as reformation of new weaker bonds appear.     

Pretreatment of Alumina and Its Influence on the Properties of Co/Alumina Catalysts for Fischer-Tropsch Synthesis

16.6%Co/γ-Al_2O_3 catalysts prepared by incipient wetness impregnation method were used for Fischer-Tropsch synthesis.The support was pre-treated with different concentration of NH_4NO_3 aqueous solution.The effect of support pre-treatment on the properties of support and performance of supported- cobalt-based catalysts was investigated.To treat the support with NH_4NO_3 aqueous solution enlarged the pore ofγ-Al_2O_3,decreased the impurity Na_2O content,and weakened the surface acidity ofγ-Al_2O_3. The change in the properties of the support decreased the interaction between cobalt species and support, enhanced the CO hydrogenation rate and the C_(5 )selectivity.For all catalysts,increasing the reaction temperature increased the CO hydrogenation rate or the CO conversion,slightly decreased the total hydrocarbon selectivity,and favored the formation of methane and light hydrocarbons,while the chain growth probability decreased.For 16.6%Co/γ-Al_2O3 catalysts,prepared with the support treated with 100 g/L NH_4NO3 aqueous solution,the CO conversion,the CH_4 selectivity,and the C_(5 )selectivity were 83.13%,6.86% and 82.75% respectively,and the chain growth probability was 0.83 under the condition of 493 K,1.5 MPa,500 h~(-1)and the molar ratio of H_2 to CO being 2.0 in feed.     

Thermophysical Properties of High Temperature Reacting Mixtures of Carbon and Water in the Range 400–30,000?K and 0.1–10?atm. Part 2: Transport Coefficients

The present contribution is continuation of Part 1: Equilibrium composition and thermodynamic properties. This paper is devoted to the calculation of transport properties of mixtures of water and carbon at high temperature. The transport properties, including electron diffusion coefficient, viscosity, thermal conductivity, and electrical conductivity are obtained by using the Chapman?CEnskog method expanded to the third-order approximation (second-order for viscosity), taking only elastic processes into account. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 400 to 30,000?K for pressures of 0. 10, 1.0, 3.0, 5.0 and 10.0?atm. with the results obtained are compared to those of previously published studies, and the reasons for discrepancies are analyzed. The results provide reliable reference data for simulation of plasmas in mixtures of carbon and water.     

Metal-organic Chemical Vapor Deposition of GaSb/GaAs Quantum Dots： the Dependence of the Morphology on Growth Temperature and Vapour V/Ⅲ Ratio

GaSb quantum dots have been widely applied in optoelectronic devices due to its unique electrical and optical properties.The effects of metal-organic chemical vapor deposition（MOCVD） parameters,such as growth temperature and vapour V/Ⅲ ratio[V/Ⅲ ratio means the molar ratio of trimethylgallium（TMGa） and triethylantimony（TESb）],were systematically investigated to achieve GaSb quantum dots with high quality and high density.The features of surface morphology of uncapped GaSb quantum dots were characterized by atomic force microscope（AFM） images.The results show that the surface morphologies of quantum dots are strongly dependent on growth temperature and vapour V/Ⅲ ratio.GaSb quantum dots with an average height of 4.94 nm and a density of 2.45× 1010 cm-2 were obtained by optimizing growth temperature and V/Ⅲ ratio.     

Studies on the Voltammetric Behavior of Nicardipine Hydrochloride and its Voltammetric Determination at the Co/GC Modified Electrode

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Effect of cobalt weight content on the structure and catalytic properties of Co/CNT catalysts in the fischer–tropsch synthesis

Cobalt-based Fischer–Tropsch synthesis (FTS) catalysts containing 1 to 40 wt % cobalt supported on multi-walled carbon nanotubes (CNTs) have been investigated. The CNTs have been characterized by low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray photoelectron spectroscopy. All catalysts have been prepared by impregnating, with an ethanolic solution of cobalt nitrate, the CNTs preoxidized with concentrated nitric acid and have been tested in the FTS at 220°C and atmospheric pressure. Correlations have been established between the cobalt weight content of the catalyst and the Co particle size determined by transmission electron microscopy and X-ray diffraction. The Co content and particle size have an effect on the activity and selectivity of the catalyst and on the target fraction (C₅₊) yield in the FTS. The highest CO conversion is observed for the catalyst containing 20 wt % Co; the highest selectivity and activity, for the catalyst containing 5 wt % Co; the highest C₅₊ yield, for the catalyst containing 10 wt % Co.