Physico‐mechanical properties of nano‐polystyrene‐decorated graphene oxide–epoxy composites

Nano‐polystyrene (nPS)‐decorated graphene oxide (GO) hybrid nanostructures were successfully synthesized using stepwise microemulsion polymerization, and characterized using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), field‐emission scanning electron microscopy and transmission electron microscopy. XRD and FTIR spectra revealed the existence of a strong interaction between nPS and GO, which implied that the polymer chains were successfully grafted onto the surface of the GO. The nPS‐decorated GO hybrid nanostructures were compounded with epoxy using a hand lay‐up technique, and the effect of the nPS‐decorated GO on the mechanical, thermal and surface morphological properties of the epoxy matrix was investigated using a universal tensile machine, Izod impact tester, thermogravimetric analysis and contact angle measurements with a goniometer. It was observed that in the epoxy matrix, GO improved the compatibility. © 2017 Society of Chemical Industry     

Physicomechanical properties of wollastonite (CaSiO3)/styrene butadiene rubber (SBR) nanocomposites

The purpose of this study was to investigate the effect of bare wollastonite (BW) and modified wollastonite (MW) nano‐rods into the styrene butadiene rubber (SBR). SBR nanocomposites were prepared by the incorporation of different wt % (0.3–4.5) of BW and MW nanorods. All nanocomposites were characterized by thermal gravimetric analyzer (TGA) and differential scanning calorimeter (DSC). The particle size and morphology of BW and MW nanorods were characterized by field‐emission scanning electron microscope (FE‐SEM), transmission electron microscope (TEM), and Fourier transform infrared (FTIR) spectrophotometer, while FE‐SEM and AFM analyses were performed for BW/SBR and MW/SBR nanocomposites. The obtained results revealed the existence of stronger interaction between the SBR and MW nanorods into MW/SBR as compared to BW/SBR nanocomposites. FE‐SEM and AFM images showed a perfect dispersion of the MW nanorods in SBR matrix at 3 wt % loading. Thermal stability of MW/SBR nanocomposites was also increased significantly by the addition of MW nanorods. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42811.     

Exploration of Staphylococcus nepalensis (KY024500) Biosurfactant towards Microbial Enhanced Oil Recovery

Oleochemicals have long been used as biolubricants, biopolymers, and biosurfactants; an effective alternative to petroleum-based products. The present study explores the biosurfactant potential of a novel strain, isolated from rocks of earthquake-prone area. On the basis of morphological, biochemical and 16S rRNA sequencing analysis, the isolate was identified as Staphylococcus nepalensis (KY024500). A biosurfactant yield 2.39, 1.39, and 0.9 g L⁻¹ was obtained using glycerol, waste orange peel, and diesel as a sole carbon source, respectively. Based on oil recovery experimental findings through sand pack column, the obtained biosurfactant from waste orange peels as a sole carbon source was carried forward for further analysis. Thus, obtained biosurfactant from waste orange peels were subjected to solvent extraction and purified by column chromatography. The purified biosurfactant thus obtained was characterized with the help of fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC–MS), and MALDI TOF MS/mass spectroscopy (MS) analysis. FTIR spectroscopic analysis revealed the presence of a carbonyl, amine, hydroxyl, and methyl as functional groups. The GC–MS analysis showed the presence of benzene dicarboxylic acid diethyl ester and pthalic acid as fatty acids while MALDI TOF MS/MS analysis shows lysin-glycin as a hydrophilic dipeptide moiety. This study also demonstrates Microbial Enhanced Oil Recovery (MEOR) potential of the biosurfactant as more efficient than commercial ones. The biosurfactant obtained from waste orange peel as carbon source was able to facilitate a 20% higher recovery of diesel from sand pack recovery column.     

Optimal controller for synchronous power system with prescribed degree of stability

From a practical point of view, it may not be necessary to fix precisely the eigenvalues of the closed-loop system. If it is ensured that the eigenvalues of the closed-loop system lie within a certain region of the complex plane such as the sector of the left half plane Re(s) < 0, our design for an optimal regulator will be satisfactory. This can be achieved by minimising a quadratic performance index and, at the same time, ensuring that the poles of the closed-loop system lie to the left of the imaginary axis beyond a certain predesignated value ?α, where α > 0, which may be chosen by the designer.An attempt has been made to design an optimal regulator which would satisfy the requirement of positioning the dominant pole in such a way that it would lie to the left of Re(s) = ?α for some α > 0. The performance index chosen is

$\text{∫}\text{0}\text{∞}\text{exp}\text{(2∞t)(}\text{x}{}^{\mathrm{t}}\text{QX}\text{+}\text{u}{}^{\mathrm{T}}\text{R}{}_1\text{u)dt}$

This will ensure that the control law we obtain would give an asymptotically stable closed-loop system with a degree of stability of at least α. Results of the analysis for a simple synchronous power system model with excitation control are presented in this paper.     

Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.     

Perovskite-type catalytic materials for environmental applications

Perovskites are mixed-metal oxides that are attracting much scientific and application interest owing to their low price, adaptability, and thermal stability, which often depend on bulk and surface characteristics. These materials have been extensively explored for their catalytic, electrical, magnetic, and optical properties. They are promising candidates for the photocatalytic splitting of water and have also been extensively studied for environmental catalysis applications. Oxygen and cation non-stoichiometry can be tailored in a large number of perovskite compositions to achieve the desired catalytic activity, including multifunctional catalytic properties. Despite the extensive uses, the commercial success for this class of perovskite-based catalytic materials has not been achieved for vehicle exhaust emission control or for many other environmental applications. With recent advances in synthesis techniques, including the preparation of supported perovskites, and increasing understanding of promoted substitute perovskite-type materials, there is a growing interest in applied studies of perovskite-type catalytic materials. We have studied a number of perovskites based on Co, Mn, Ru, and Fe and their substituted compositions for their catalytic activity in terms of diesel soot oxidation, three-way catalysis, N₂O decomposition, low-temperature CO oxidation, oxidation of volatile organic compounds, etc. The enhanced catalytic activity of these materials is attributed mainly to their altered redox properties, the promotional effect of co-ions, and the increased exposure of catalytically active transition metals in certain preparations. The recent lowering of sulfur content in fuel and concerns over the cost and availability of precious metals are responsible for renewed interest in perovskite-type catalysts for environmental applications.     

The resistance of packed beds of moth gram (Vigna aconitifolius) to airflow

The resistance of packed beds of clean moth gram (Vigna aconitifolius) to airflow was studied at moisture contents varying from 5.64 to 19.42% dry basis (d.b.) and at superficial air velocities ranging between 0.0104 and 0.8321 m s^?1 with bed depths of 0.2–0.6 m and bulk densities ranging from 745 to 875 kg m^?3. The airflow resistance of moth gram increased with increase in airflow rate and bulk density and decreased with moisture content. Results indicated that a 13.78% increase in moisture content decreased the pressure drop by 26.58% whereas, a 7.7% increase in bulk density increased the pressure drop by 43%. The modified Shedd's equation and Hukill and Ives equation were evaluated to see if they predicted pressure drop accurately. Airflow resistance was accurately described by the modified Shedd's equation. The statistical model that related airflow rate and bulk density could fit pressure drop data reasonably well. For loose fill beds an increase in grain moisture content increased the minimum fluidization velocity value from 1.1009 to 1.2391 m s^?1 whereas, for grain beds with 12.47% moisture content, the increase in bulk density decreased the minimum fluidization velocity value from 1.1152 to 1.0306 m s^?1.     

Efficient solar photo-electrochemical hydrogen generation using nanocrystalline CeFeO3 synthesized by a modified microwave assisted method

Pure phase of CeFeO₃ perovskite was synthesized by using a modified microwave-assisted method and was systematically studied by photo-electrochemical (PEC) investigations for water splitting reaction. Characterization studies confirm the formation of crystalline orthorhombic single phase perovskite structure with space group Pbnm and having agglomerated sponge-like morphology with nano size grains. DRS shows broad absorption in UV–Visible region, while tauc plot also inferred estimated band gap of 1.9 eV. The photo-activity of their screen printed thin film was analyzed by PEC studies, which includes photocurrent, EIS spectra, MS-plot, J-V plots. On illumination, EIS analysis of CeFeO₃ reveals improved charge transfer at interfaces of semiconductor/electrolyte. The photocurrent density difference of CeFeO₃ was increased to 6.9 mA cm^?2 at an applied bias of 1.5 V vs (Ag/AgCl). PEC H₂ evolution shows significant cumulative hydrogen rate of 12.3 μmol cm^?2 h^?1. All these results reveal that the microwave-synthesized CeFeO₃ is a potential candidate for PEC application under the visible light illumination.     

Fixed-bed column study on removal of Mn(II), Ni(II) and Cu(II) from aqueous solution by surfactant bilayer supported alumina

In the present work, the potential of modified alumina for the removal of heavy metals such as Mn(II), Ni(II) and Cu(II) was evaluated in a fixed-bed column operation. The effects of bed depth, flow rate and initial concentration on the removal of Mn(II), Ni(II) and Cu(II) were investigated at the optimum pH. The modified alumina was found to be very efficient for the removal of such heavy metals from water environment. Bed depth service time (BDST) model was best fitted to adsorption data. The theoretical and experimental breakthrough curves were comparable for all heavy metals.     

Application of response surface methodology to evaluate the removal efficiency of Mn(II), Ni(II), and Cu(II) by surfactant-modified alumina

Surfactant-modified alumina (SMA) was prepared and used for the removal of Mn(II), Ni(II), and Cu(II) from aqueous environment. Batch studies were conducted to find out optimum pH of the medium, adsorbent dose of SMA, and contact time. They were further optimized using response surface methodology (RSM). In the present study, a three-factor, three-level Box–Behnken experimental design was used to derive a second-order polynomial equation and construct three-dimensional (3D) surface plots and two-dimensional (2D) contour plots to examine the response. The level of significance for each independent variable and their interaction effects were examined by means of analysis of variance (ANOVA), F test, and Student’s t test results. In addition, the percentage effects of the different factors and their interactions on the removal efficacy were also investigated by plotting a Pareto chart. The models were validated for accurate prediction of the percentage (%) removal by performing numerical optimization. The optimum values of three tested variables were determined at pH 6.2, 8.2, and 5.3; adsorbent dose = 20, 5, and 4 g/L; and contact time = 30, 60, and 75 min for the adsorption of Mn(II), Ni(II), and Cu(II) ions, and the corresponding removal efficiency was found to be 77.04, 93.83, and 97.23 %, respectively.