3D Oxidized Graphene Frameworks: An Efficient Adsorbent for Methylene Blue

Extraordinary properties of graphene and its derivatives have found application in varied areas such as energy, electronics, optical devices and sensors, to name a few. Large surface area along with specialized functional groups make these materials attractive for removal of dye molecules in solution via adsorption. Industrial effluents contain large amounts of toxic chemicals resulting in pollution of water bodies, which pose environmental hazards in general. Here we report application of 3D oxidized graphene frameworks in the efficient removal of cationic dye molecules such as methylene blue via adsorption. Systematic parametric studies investigating the effect of the initial dye concentration, pH and contact time have been performed. Spectroscopic analysis of the filtrate suggests that tortuous paths in 3D oxidized graphene frameworks result in efficient removal of dye molecules due to enhanced interaction. The hydroxyl groups retained in these 3D oxidized graphene frameworks facilitate adsorption of the dye molecules while passing through the adsorbent. pH studies suggest that maximum removal efficiency for methylene blue was achieved at pH value of 9. The results suggest that these 3D oxidized graphene frameworks can be used for purification of large volumes of contaminated water from cationic dyes in waste water treatment plants.     

Excitation functions of (n,p) reactions for stable isotopes of Cr,Fe and Ni from threshold to 20 MeV

The excitation functions of (n,p) reactions for the stable isotopes of Cr, Fe and Ni were calculated using EMPIRE 3.0 β1 (ARCOLE) from threshold to 20 MeV. The cross-sections are calculated using full featured Hauser–Feshbach statistical model with pre-equilibrium effects by invoking DEGAS option in the code. A good agreement between the calculated and experimental data (EXFOR data base) as well as evaluated data is obtained with option of neutron and proton potentials by Koning (Global) and HFB parity dependent nuclear level density. This is an important step to the validation of nuclear model with superior predictive power. The compound nucleus and pre-equilibrium reaction mechanisms as well as the isotopic effects were also studied.     

Statistical optimization of process parameters for the production of vanillic acid by solid‐state fermentation of groundnut shell waste using response surface methodology

BACKGROUND: Vanillic acid is a flavoring agent and also serves as precursor for vanillin production. Culture medium and fermentation condition for the single step production of vanillic acid from Phanerochaete chrysosporium using lignocellulosic waste as a substrate under solid state fermentation (SSF) were optimized using response surface methodology. RESULTS: The process parameters were chosen by borrowing methodology, and L‐asparagine, pH and moisture content of the solid medium during SSF were identified as the most significant variables. The optimum value of selected variable and their mutual interactions were determined by response surface methodology. The result demonstrated that a yield of 73.58 mg vanillic acid g^?1 substate was predicted under optimum conditions (L‐asparagine 5.98 mmol L^?1 (2.37 mg g^?1 groundnut shell), pH of solid medium 4.51 and moisture content 74.83%). The predicted response was experimentally validated and resulted in a maximum vanillic acid yield of 73.69 mg g^?1 after 8 days of SSF. CONCLUSION: The optimization of fermentation variables resulted in a maximum 10‐fold increase in vanillic acid yield compared with that observed under sub‐optimal conditions (from 7.2 mg g^?1 to 73.69 mg g^?1). Copyright © 2011 Society of Chemical Industry     

Mechanoluminescence glow curves of rare-earth doped strontium aluminate phosphors

The present paper reports the mechanoluminescence (ML) glow curves of rare-earth doped strontium aluminate phosphors. When Sr₃Al₂O₆:Eu, Dy phosphor mixed in epoxy resin is compressed at a fixed pressing rate or fixed strain rate, its elastico ML (EML) intensity increases linearly with deformation time or pressure and attains a maximum value I_m at the time t_m, at which the deformation is stopped. Under the pressed condition, the decay time for fast decrease of EML after t_m, gives the time-constant for stopping the cross-head of the testing machine used to deform the sample, and decay time for slow decrease of EML gives the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. When SrAl₂O₄:Eu phosphor mixed in resin is compressed at a fixed rate, then the EML intensity increases linearly with pressure and when the pressure is decreased at a fixed rate, then the EML intensity decreases exponentially with time, in which the decay time of EML is equal to the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. The EML intensity of SrAl₂O₄:Eu film excited by the impact stress, initially increases with time, attains a peak value and later on it decreases exponentially with time, in which the fast decay of EML intensity gives the decay time of impact stress and the decay time of the slow decrease of the EML intensity gives the lifetime of electrons in the shallow traps lying in the normal piezoelectric region of the crystals. The piezoelectrically-induced detrapping model is found to be suitable for the EML of rare-earth doped strontium aluminate phosphors. Expressions derived on the basis of the piezoelectrically-induced detrapping model are able to explain satisfactorily the characteristics of the EML of the phosphors. It is shown that several parameters of the phosphors can be determined from the ML glow curves.     

Hygrothermoelastic Postbuckling Response of Laminated Composite Plates

The paper deals with the effect of moisture and temperature on the postbuckling response of a laminated composite plate subjected to hygrothermomechanical loadings. Mechanical loading consists of uniaxial, biaxial, shear, and their combinations. The distribution of temperature and moisture on the surface is considered to be uniform. The degradation in material properties due to moisture and temperature is taken into account using a micromechanical model. The mathematical formulation is based on higher order shear deformation theory and von Karman’s nonlinear kinematics. The quadratic extrapolation technique and fast converging finite double Chebyshev series are used for linearization and spatial discretization of the governing nonlinear equations of equilibrium, respectively. The effects of temperature rise, moisture concentration, fiber-volume fraction, and plate parameters on buckling and postbuckling response of the plate are presented.     

Tuning the band gap of ZnO nanoparticles by ultrasonic irradiation

In this present paper, we report the tunability of ZnO nanoparticles by ultrasonic irradiation. Different sized ZnO nanoparticles viz. 2.58–2.97 nm have been synthesized with variation of ultrasonic irradiation time 75–270 min in presence of Histidine as capping agent. UV and visible spectroscopy study revealed that as ultrasonic irradiation time increases, there is increase in amount of formed ZnO nanoparticles and also there is red shift in absorption edge. This confirms the tunability of bandgap of histidine capped ZnO nanoparticles with ultrasonic irradiation. Growth mechanism for controlling the size of ZnO nanoparticles are also discussed.     

Effect of surface wettability and electric field on transition of film boiling to nucleate boiling

Abstract

The phenomena of liquid–solid contact during film boiling due to the effect of surface-wettability have been focused in the present study. The numerical simulations during film boiling exhibit the collapse of vapor layer when the surface-wettability is sufficiently high, that is, for the hydrophilic surface. Vapor film collapse results in contact of liquid with the heated surface, which transforms the boiling mode more toward the nucleate regime. The contact area of liquid increases with time. However, such transition is not observed in the case of hydrophobic surface or the surface with higher contact angles. When a sufficiently strong electric field is applied across the liquid-vapor interface, the vapor film collapses and results in similar transition from film boiling to nucleate boiling. The required intensity of electric field at which the vapor film collapses increases with the increase in surface-superheat.     

Separation of cation–anion mixture using micellar-enhanced ultrafiltration in a mixed micellar system

Aqueous solution containing copper (cation) and potassium permanganate (anion) was treated by ultrafiltration using mixed micellar system comprising of sodium dodecyl sulfate and cetylpyridinium chloride. Simultaneous separation characteristics of both cation and anion, as well as permeate flux were studied for various operating conditions, namely, transmembrane pressure drop and cross-flow rate. The study was carried over a wide concentration range of both solutes. In the mixture, copper concentration was in the range from 0.05 to 4.0 kg/m³ and that of potassium permanganate was 0.05 to 0.25 kg/m³. Retention of copper was in the range of 90–100% and that of potassium permanganate was 96–99%. Permeate flux was found to be less in the mixed micellar system compared to single surfactant system. A four step chemical treatment process was proposed to recover and reuse the surfactants.     

Electrical transport in ethyl cellulose-chloranil system

The charge-transport behaviour in pure and chloranil (Chl) doped ethyl cellulose (EC) system has been studied by measuring the dependence of current on field, temperature, electrode material and dopant concentration. The role of doping molecular concentration in the polymer matrix and modification in the conduction characteristics are studied. Lowering of the activation energy due to doping was observed. The current was found to increase with an increase in the chloranil concentration. An explanation for this has been attempted on the basis of formation of molecular aggregates between chloranil molecules and ethoxy groups of ethyl cellulose. It is suggested that chloranil occupies interstitial positions between the polymer chains and assists in carrier transportation by reducing the hopping barriers. The current-voltage characteristics of different samples are analyzed using space charge limited current theory and quantitative information about the transport parameters is derived. The values of effective drift mobility and trapped charge carrier concentration which result in the build up of space charge have been calculated.