Investigation of polycarbonate/acrylonitrile butadiene styrene/multiwall carbon nanotube nanocomposites under impact loading

In this study, the effect of polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)‐reinforced multiwall carbon nanotube (MWCNT) nanocomposites under a high‐velocity impact was investigated. PC/ABS (70/30 w/w)/MWCNT nanocomposites containing 1, 2, and 4 wt% were used to manufacture samples for this study. The samples were fabricated in sheet form with 100 × 100 mm dimensions and tested by gas gun for high‐velocity impact tests. The experimental results indicate that the energy absorption, limit velocity, and tensile modulus of the nanocomposite samples increased by approximately 121%, 52%, and 103% for the PC/ABS (70/30 w/w)/2 wt% MWCNT samples respectively. These results were confirmed by a transmission electron microscopy analysis test that was conducted for the state of dispersion of MWCNTs in the nanocomposite samples. The transmission electron microscopy results show that the best morphological structure of carbon nanotube at the interface of PC and ABS is that for the nanocomposite containing 2 wt% MWCNTs, which led to improved interface of the nanocomposites and higher mechanical properties. Copyright © 2016 John Wiley & Sons, Ltd.     

Proposal of a New Hf(IV)/Zr(IV) Separation System by the Solvent Extraction Method

A liquid-liquid extraction study has been conducted to separate hafnium from zirconium, using Cyanex 301 in kerosene. Noticeably, it is the first time that Cyanex 301 is utilized to separate Hf(IV) from Zr(IV). In this series of experiments, several parameters influencing the separation have been investigated, such as the initial pH, the extractant concentration, the metal ion concentration, the temperature, the type of the diluents and the salt addition. Regarding the aging of the Zr(IV) and Hf(IV) solutions, the solutions with a maximum 3 d aging time could be used with no difficulties. It was observed that the initial pH increase caused an increase in the Zr(IV)/Hf(IV) separation factor. Moreover, the distribution decreased with the temperature increase, suggesting that the reaction is exothermic. In agreement with the resulting data, the optimum separation factor illustrates the value of 7 at a pH of 4.00 in the presence of NaCl as an added salt. The attractive characteristics of the presently designed method are the use of low acidic nitrate solutions, the lack of using thiocyanate and a higher extractability of hafnium-Cyanex 301 relative to zirconium-Cyanex 301 complexes.     

Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base

A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0 × 10⁻⁴ and 6.0 × 10⁻⁴ μmol L⁻¹ for Hg(II) and Pb(II) with a 90 s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.     

Microwave-assisted extraction combined with dispersive liquid-liquid microextraction as a new approach to determination of chlorophenols in soil and sediments

A new method was applied for extraction of five chlorophenols from soil and marine sediment samples. Microwave-assisted extraction coupled with dispersive liquid-liquid microextraction followed by semi-automated in-syringe back-extraction technique was used as an extraction technique. Microwave-assisted extraction was performed by using 2.0 mL of alkaline water at pH 10.0. After extraction, the pH of extraction solution was adjusted at 6.0 and dispersive liquid-liquid microextraction procedure was done using 1.0 mL of acetone as a disperser solvent and 37.0 μL of chlorobenzene as extraction solvent. About 20.0 ± 0.5 μL sedimented phase was collected after centrifugation step. Then, chlorophenols were back extracted into 20 μL of alkaline water at pH 12.0 within the microsyringe. Finally, 20.0 μL of aqueous solution was injected into high performance liquid chromatography with ultra violet detection for analysis. The obtained recovery and preconcentration factors for the analytes were in the range of 68.0-82.0% and 25-30, respectively, with relative standard deviations ≤7.6%. The limits of the detection were found in the range of 0.0005-0.002 mg/kg. The method provides a simple and fast procedure for the extraction and determination of chlorophenols in soil and marine sediment samples.     

Observational Constraints on the Modified Gravity Model (MOG) Proposed by Moffat: Using the Magellanic System

A simple model for the dynamics of the Magellanic Stream (MS), in the framework of modified gravity models is investigated. We assume that the galaxy is made up of baryonic matter out of context of dark matter scenario. The model we used here is named Modified Gravity (MOG) proposed by Moffat (J. Cosmol. Astropart. Phys. 003, 2005). In order to examine the compatibility of the overall properties of the MS under the MOG theory, the observational radial velocity profile of the MS is compared with the numerical results using the χ ² fit method. In order to obtain the best model parameters, a maximum likelihood analysis is performed. We also compare the results of this model with the Cold Dark Matter (CDM) halo model and the other alternative gravity model that proposed by Bekenstein (Phys. Rev. D 70:083509, 2004), so called TeVeS. We show that by selecting the appropriate values for the free parameters, the MOG theory seems to be plausible to explain the dynamics of the MS as well as the CDM and the TeVeS models.     

Thermal and mechanical properties of polysulfide/epoxy copolymer system: the effect of anhydride content

Polymerization of a ternary system containing polysulfide (PS), as a liquid elastomer, diglycidylether of bisphenol A resin, and phthalic anhydride was conducted using “design of experiment” technique. The polymerization progress with respect to concentration variations of components were studied by Fourier transform infrared spectroscopy. Fourier transform infrared spectroscopy studies showed that the anhydride plays a decisive role in curing reaction so that, in its absence, the epoxy/PS mixture becomes gel in about 2 hr, whereas, by addition of the anhydride, the pot life of the system can be extended to 48 hr. The cured samples were investigated by thermal gravimetry analysis and differential scanning calorimetry to evaluate thermal properties. Thermal gravimetry analysis and differential scanning calorimetry results indicated that two different soft and hard segments are formed, which have different thermal decompositions. The soft segment consists of loose etheric bonds, which are attributed to PS, and the hard segment is formed during the etherification and esterification reactions of the epoxy resin. Tensile strength test was performed to investigate the mechanical properties of PS/epoxy/anhydride‐cured systems. The results showed that the tensile strength, elongation‐at‐break, and the fracture energy of specimens are essentially dependent on PS/anhydride ratios. Two different segments impart high strength and ductility simultaneously. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of mercury(II) ion by electrochemical cold vapor generation atomic absorption spectrometry.

A technique for determination of mercury is described; it is based on electrolytic reduction of Hg(II) ion on a graphite cathode, the trapping of mercury vapor and its volatilization into a quartz tube aligned in the optical path of an atomic absorption spectrometer. The electrochemical cell consisted of a graphite cathode and an anode operating with constant direct current for the production of mercury atoms. A pre-activated graphite rod was used as the cathode material. The optimum conditions for electrochemical generation of mercury cold vapor (the electrolysis time and current, the flow rate, the type of electrode and electrolyte) were investigated. The characteristic electrochemical data with chemical cold vapor using NaBH4-acid were compared. The presence of cadmium(II), arsenic(III), antimony(III), selenium(IV), bismuth(III), silver(I), lead(II), lithium(I), sodium(I) and potassium(I) showed interference effects which were eliminated by suitable separation techniques. The calibration curve is linear over the range of 5-90 ng ml(-1) mercury(II). The detection limit is 2 ng ml(-1) of Hg(II) and the RSD is 2.5% (n = 10) for 40 ng ml(-1). The accuracy and recovery of the method were investigated by analyzing spiked tap water and river water.     

Crosslinking investigation of polybutadiene thermal degradation by carbon-13 nuclear magnetic resonance

Thermal degradation of polybutadiene (PBD) in anaerobic atmosphere at 250 °C had been studied by carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR) before complete crosslinking. In this investigation four types of low molecular weight PBD with different 1,2-vinyl isomer content had been chosen, then pure and mixed samples of PBD were heated in different time periods. ¹³C NMR spectra showed that two kinds of crosslinking mechanisms occur that both of them produce methyl groups. The first mechanism is a reaction between 1,2-vinyl isomers of two PBD chains, and the second one occurs between 1,2-vinyl isomer of one chain via methylene carbon of cis or trans isomer in another chain. Also ¹³C NMR results showed that the presence of 1,2-vinyl isomer in the PBD structure is necessary and without it none of the mentioned reactions will occur. Furthermore isomers sequence is another important parameter which affects crosslinking. Results show that cis or trans isomer which is not adjacent to 1,2-vinyl isomer does not take part in crosslinking reaction. Moreover such cis or trans isomer can take part in second mechanism of crosslinking that 1,2-vinyl isomer was attached from head to cis or trans isomer, thus in this arrangement of isomers second mechanism of crosslinking will become dominant rather than first mechanism of crosslinking.     

Synthesis of new aromatic polyamides containing α-amino phosphonate with high thermal stability and low heat release rate

The new aromatic polyamides containing α-amino phosphonate were synthesized from phosphorus-based dicarboxylic acid 4 and various aromatic diamines by direct polycondensation reaction. Dicarboxylic acid 4 was successfully synthesized from trimethyl phosphite, 4-aminobenzoic acid and terephthaldehyde via a three-component reaction. The polymerization reaction produced the polyamides 6a–f with high yield and desirable inherent viscosities. The thermal properties of the all samples were investigated by thermo-gravimetric analysis (TGA). The TGA results in N₂ exhibited the 10% mass loss temperatures (T₁₀) in the ranges of 324–345 °C, while the T₁₀ resulted from thermo-oxidative degradation were higher than those. The main data obtained by microscale combustion calorimetry revealed acceptable combustion properties such as very low peak of heat release rate for the synthesized polyamides 6a–f. The all of the results indicated that these polyamides can be potentially utilized as additive for improvement of thermal resistance and combustion behavior of thermoplastic materials.

     

A heuristic method to simulate the pulse propagation in nonlinear fiber bragg gratings

In this paper we simulated the pulse propagation and the switching effects in nonlinear fiber Bragg gratings using a combination of Fourier series analysis technique and Jacobi iterative method. The effects of nonlinearity and dispersion on the pulse propagation have been studied extensively. An all optical self switch was designed by this simulation. This switch is operated based on the input power.