Curing characteristics and cellular morphology of natural rubber/silica composite foams

Polymer Bulletin - The curing behavior and microstructure of natural rubber/silica foams were studied. Error function-based and autocatalytic models were correlated with the curing characteristics...     

Mixture temperature prediction of waxy oil–water two-phase system flowing near wax appearance temperature

Temperature sensitivity of waxy crude oils makes it difficult to study their flow behaviour in the presence of water especially near their wax appearance temperature(WAT). In this study a method was proposed and implemented to mitigate such difficulties which was applied in predicting mixture temperatures(Tm) of a typical Malaysian waxy crude oil and water flow in a horizontal pipe. To this end, two analytical models were derived firstly from calorimetry equation which based on developed two correlations for defining crude oil heat capacity actualized from the existed specific heat capacities of crude oils. The models were then applied for a set of experiments to reach the defined three predetermined Tm(26 °C, 28 °C and 30 °C). The comparison between the predicted mixture temperatures(Tm,1and Tm,2) from the two models and the experimental results displayed acceptable absolute average errors(0.80%, 0.62%, 0.53% for model 1; 0.74%, 0.54%, 0.52% for model 2). Moreover,the average errors for both models are in the range of standard error limits(±0.75%) according to ASTM E230.Conclusively, the proposed model showed the ease of obtaining mixture temperatures close to WAT as predetermined with accuracy of ± 0.5 °C approximately for over 84% of the examined cases. The method is seen as a practical reference point to further study the flow behaviour of waxy crudes in oil–water two-phase flow system near sensitive temperatures.     

A secure authentication scheme for VANETs with batch verification

Wireless Networks - Vehicular Ad-hoc Networks (VANETs) will start becoming deployed within the next decade. Among other benefits, it is expected that VANETs will support applications and services...     

Flotation study of oxide zinc ore using cationic-anionic mixed collectors

A representative sample of zinc oxide from Dashteh Sefid mine was obtained and then mineral characterization studies were done. The results of mineralogical analysis showed that the main zinc-bearing minerals are smithsonite, hemimorphite and gangue minerals are quartz and dolomite. In the present paper, the effect of important factors including sodium sulfide, collector type (AC and AC/KAX), collector amount, sodium silicate, CMC dosage and frother type (MIBC and pine oil) were investigated. Design of experiment was carried out by the means of Design Expert 7 using Fractional Factorial 2^6–1. The results indicated that collector type, collector amount, CMC and frother dosage were the most effective factors controlling the zinc flotation recovery. For the zinc grade, it was found that all six parameters play a significant role. The maximum recovery and grade of zinc obtained 97.71% and 10.39% under the following optimum conditions: sodium sulfide, 5935.23 g/t; collector type, AC/KAX; collector amount, 654.09; sodium silicate, 300; CMC dosage, 600; frother type, MIBC. The result of two-stage cleaner flotation showed that zinc grade could be increased up to 16.2% with zinc recovery of 61.39%.     

Intersymbol interference cancellation in CDMA 1xEVDO network

This paper presents the BER performance of the physical layer of the code division multiple access 1x Evolution Data Only (EVDO) standard for different data transmission formats, and shows the improvement on the BER performance of the EVDO system over intersymbol interference channel by adapting the low complexity turbo equalization scheme at the receiver. The radio frequency, channel condition, and mobile user data speeds were extracted from a mobile user with a drive experiment on a live wireless EVDO network. Then, the real data were utilized to simulate the actual mobile user's data speeds in our simulations to show the overall BER performance of the EVDO system application. The simulation results are shown over Gaussian and Proakis A channels and the results indicate that significant intersymbol interference cancellation is obtained with an adapted code division multiple access system and the advantages of turbo equalization on the EVDO system are discussed in this research. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of Ti3SiC2 content on the corrosion behavior of Al/Ti3SiC2 composite coatings

The purpose of this study was to investigate the electrochemical corrosion properties of flame-sprayed Al and Al/(5, 10, 15)% Ti₃SiC₂ coatings in a 3.5% NaCl solution. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used for analyzing the microstructural characteristics of the coatings. For examining the corrosion behavior of the coatings, a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used. After the potentiodynamic polarization test, the SEM micrograph of coatings indicated that Ti₃SiC₂ particles played a significant role in pitting corrosion. The results of potentiodynamic polarization tests revealed that Al/Ti₃SiC₂ coating is nobler than that of the pure aluminum coating. On the contrary, the addition of Ti₃SiC₂ particles reduced the process of thickening the passive layer. The results of the EIS tests demonstrated that the presence of Ti₃SiC₂ particles significantly enhances the corrosion resistance of the coatings.     

Effect of borax on the thermal and mechanical properties of ethylene‐propylene‐diene terpolymer rubber‐based heat insulator

The effect of Borax on the mechanical and ablation properties of three different ethylene‐propylene‐diene terpolymer (EPDM) compounds containing 20 phr carbon fiber, 20 phr Kevlar or 10 phr/ 10 phr carbon fiber/ Kevlar was investigated. All formulations contained 30 phr fumed silica powder and 10 phr paraffinic oil. It was found that adding Borax to the composite samples containing carbon fiber or Kevlar fiber or their mixture with an equal ratio can increase the tensile strength, elastic modulus and hardness with a slightly decrease in the elongation at break of the rubber samples. The results of thermogravimetry analysis (TGA) on the various samples showed significant increase in the char yield at 670°C by adding Borax to the rubber compounds. Moreover, ablation resistance of samples was also improved by increasing Borax content. Meanwhile, density and thermal conductivity of the insulator were also reduced up to about 10% when the carbon fiber was replaced with the Borax. The results indicated that composites containing Kevlar have high storage modulus and produce compact and stable char. EPDM rubber composite containing Borax (20 phr), carbon fiber (10 phr), and Kevlar (10 phr) showed thermal and ablative properties comparable with those of the asbestos‐ filled EPDM. The thermal conductivity and ablation rate of the above‐ mentioned sample were 0.287 W/m/K and 0.13 mm/s respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41936.     

Investigation of Plasma Power Effect on the Nicraly/8YSZ Coating Properties

In this study, NiCrAlY coating as a bond coat and 8YSZ coating as a top coat were applied on Inconel 718 super alloy substrates by APS method. The plasma power parameter has changed from 24.75 to 34.8 kW. The results show that with increasing the plasma power, the hardness and bond strength increase from 682 to 818 HV and 12.48 to 22.49 MPa, respectively. Also the image analysis shows that the porosity in coatings, decrease from 22.59 percent to 18 percent by increasing the plasma power.     

An Efficient and Facile Synthesis of CL‐20 from TADNO Using HNO3/N2O5 and Optimization of Reaction Parameters by Taguchi Method

Hexanitrohexaazaisowurtzitane (CL‐20) is an outstanding member of a promising new class of energetic compounds, which is applicable in both propellants and explosives. Herein, CL‐20 was synthesized in an efficient method from tetraacetyldinitrosohexaazaisowurtzitane (TADNO) using N₂O₅/HNO₃. The optimization reaction parameters were performed according to the Taguchi OA method. The yield of reaction at the optimized conditions was 97 % with 98.75 % purity.