The Effect of Barium Doping on the Selective Structure of Bi-2223 Phase

The partial substitution of Sr by Ba in the two nominal compositions of Bi_1.8Pb_0.4Sr_2−x Ba _x Ca_2.2Cu₃O _y [x=0.0, 0.1, 0.2, and 0.3 (A group)] and Bi_1.66Pb_0.34Sr_2−x Ba _x Ca₂Cu₃O _y [x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 (B group)] have been investigated by resistivity, ac susceptibility measurements and by XRD and SEM analysis. In general, the nature of the temperature dependence of resistivity and susceptibility measurements indicate the presence of a superconducting transition between grains coupled by weak links. However, the XRD and SEM analyses show that the relative composition of initial elements used in Bi-(2223) is essential to the site that is selected by the Ba ions. In the A group, Ba doping up to x=0.1 will improve the phase formation of Bi-2223, and improve the superconductivity properties of the samples. In the B group, although Ba doping up to x=0.1 will enhance the phase formation of Bi-2223, it will decrease the coupling between the grain and the superconductivity properties of these systems. The presence of lower Tc phases will begin to appear for x>0.1, in both of these systems. The superconductivity properties and the phase formation of Bi-(2223) will decrease as the Ba concentration increases.     

A modified Peng–Robinson equation of state for phase equilibrium calculation of liquefied,synthetic natural gas,and gas condensate mixtures

A modified Peng–Robinson equation of state, MPR2 EOS, is introduced by incorporating a new alpha function and a temperature dependent function for covolume, b. The modified cubic EOS has three input per each substance: critical temperature, critical pressure, and acentric factor. The coefficients of temperature dependence of the alpha and beta functions, relating to the parameters a and b of the new cubic EOS, are obtained by simultaneous fitting of saturated experimental vapour pressure and liquid density data for several pure components. The percent absolute average deviation (AAD%) of 1.38, 4.80 and 2.89 are obtained to correlation of the saturation vapour pressure, liquid density and vapour volume, respectively. Also the ADD% of 2.575 is computed for prediction of saturation enthalpy of vapourisation of the pure compounds. For calculation of phase equilibrium of mixture, the modified PR EOS is used for prediction of liquid density of the LNG mixtures. Also the new EOS is applied for construction of the phase envelop of synthetic natural gas, SNG, mixtures and calculation vapour–liquid equilibria of gas condensates. The results demonstrate that the new MPR2 EOS can be used for calculation of vapour–liquid equilibrium of pure components and mixtures with good accuracy.     

Effect of spherical-agglomerate strength on the distribution of force during uniaxial compression

We employ the carbon paper technique with the aim of investigating the effect of spherical-agglomerate (pellet) strength on force distributions, through confined compression of approximately 1 mm sized pellets formed from microcrystalline cellulose and polyethylene glycol. The carbon paper technique relies on the transference of imprints from compressed pellets onto white photo quality paper, which are digitised and processed via image processing software. The investigated pellets can both deform plastically and develop localised cracks in response to an applied stress, while remaining largely intact during confined compression. Our results indicate that such crack formation - henceforth referred to as fracture - has a decisive influence on force distributions. Previous work on non-fracturing systems has found that the distribution of normalized forces tends to narrow with increasing particle deformation. No narrowing is observed after the point of fracture in this study and the width of the distributions - as quantified by the standard deviation of non-normalized forces - is found to increase with the difference between non-normalized mean force and fracture force. Additional corroborative results show that spatial force-force correlations typically exhibit a marked change once the fracture force is exceeded.     

Dye adsorption and desorption properties of Mentha pulegium in single and binary systems

This article deals with the dye adsorption and desorption properties of Mentha pulegium (MP) from single and binary (mixture of dyes) systems. Direct Red 80 (DR80) and Acid Black 26 (AB26) were used as model dyes. The Fourier transform infrared (FTIR) was used to investigate the biosorbent characteristics. The effects of biosorbent dosage, contact time, dye concentration, salt, and pH on dye removal were studied. The biosorption isotherms, kinetics, and thermodynamic were studied. In addition, dye desorption was carried out to study adsorbent recovery. The results showed that the isotherm data of single and binary systems of dyes followed the Langmuir isotherm. The adsorption kinetic of the dyes was found to conform to a pseudosecond order kinetic model. Desorption tests showed maximum dye releasing of 97% for DR80 and 95% for AB26 in single system and 92% for DR80 and 94% for AB26 in binary system of dyes at pH 12. The thermodynamic data showed that the biosorption process is spontaneous, endothermic, and a physisorption reaction. It can be concluded that MP is an ecofriendly biosorbent to remove dyes from single and binary systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of novel pyridine‐based polyureas with enhanced solubility and high thermal stability

The main aim of this study was the preparation of modified polyureas with improved thermal stability and solubility. Accordingly, a series of aromatic/aliphatic pyridine‐based polyureas was synthesized from the reaction of a novel diamine (DA) with different diisocyanates, including 4,4′‐diphenylmethane diisocyanate, toluene diisocyanate, 1,5‐naphthalene diisocyanate, and isophorone diisocyanate, by a solution polymerization route. The DA monomer was prepared via a two‐step reaction. The nucleophilic substitution reaction of oxydianiline with 6‐chloronicotinoylchloride led to the preparation of a diamide dichloro compound, and the subsequent reaction of this compound with 4‐aminophenol resulted in the preparation of the DA. After polymerization, the structural characterization and physical properties of the polymers were examined. The resulting polymers were soluble in common polar aprotic solvents, and they showed improved thermal stabilities in comparison with common polyureas. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Photocatalytic degradation of triazinic ring-containing azo dye (Reactive Red 198) by using immobilized TiO2 photoreactor: bench scale study

The decolorization and degradation of triazinic ring-containing azo dye by using TiO(2)-immobilized photoreactor is reported. A simple and easy method was used for the immobilization of photocatalyst. Reactive Red 198 (RR 198) was used as model compound. Photocatalytic degradation processes were performed using a 5 L (bench scale) solution containing dye. Batch mode immersion type method was used for the treatment of dye solution. UV-vis, ion chromatography (IC) and chemical oxygen demand (COD) analyses were employed to evaluate the results of the photocatalytic degradation of RR 198. Dye solution was completely decolorized in relatively short time (35 min) after UV irradiation in combination with hydrogen peroxide. The results verified that all of the dye molecules were destructed. Kinetics analysis indicates that the dye photocatalytic decolorization rates followed first order model (R(2) = 0.99). Ion chromatography analysis was used to investigate the formation and destruction of aliphatic carboxylic acids and formation of inorganic anions during the process. Formate and oxalate anions were detected as main aliphatic carboxylic intermediates, which were further oxidized slowly to CO(2). UV/TiO(2)/H(2)O(2) process proved to be capable of successful decolorization and degradation of the RR 198.     

Equilibrium and kinetics studies for the adsorption of direct and acid dyes from aqueous solution by soy meal hull

This paper deals with the application of Soy Meal Hull (SMH), an agricultural by-product, for the removal of direct and acid dyes from aqueous solutions. Four textile dyes, C.I.Direct red 80 (DR80), C.I.Direct red 81 (DR81), C.I.Acid blue 92 (AB92) and C.I.Acid red 14 (AR14) were used as model compounds. Physical characteristics of SMH such as surface area, Fourier transform infra-red (FTIR) and scanning electron microscopy (SEM) were obtained. The surface area of SMH was found to be 0.7623 m(2)/g and the presence of functional groups such as hydroxyl, amine and carbonyl groups were detected. The effect of initial dye concentration, pH, contact time and SMH doses were elucidated at 20+/-1 degrees C. Results show that the pH value of 2 is favorable for the adsorption of all four dyes. The data evaluated for compliance with the Langmuir, Freundlich and BET isotherm models. It was found that data for DR80 and DR81 fitted well with Langmuir isotherm, for AB92, BET isotherm is preferred, while for AR14, the Freundlich isotherm is the most applicable. The adsorption capacities of SMH for DR80, DR81, AB92 and AR14 were, 178.57, 120.48, 114.94 and 109.89 mg/g of adsorbent, respectively. Also, adsorption kinetics of dyes was studied and the rates of sorption were found to conform to pseudo-second order kinetics with good correlation (R(2)> or =0.9977). Maximum desorption of > or =99.8% was achieved for DR80, DR81 and AB92 and 86% for AR14 in aqueous solution at pH 10. Based on the data of present investigation, one could conclude that the SMH being a natural, eco-friendly and low-cost adsorbent with relatively large adsorption capacity might be a suitable local alternative for elimination of dyes from colored aqueous solutions.     

A Low-Power SRAM Using Bit-Line Charge-Recycling

Low-power SRAM design is crucial since it takes a large fraction of total power and die area in high-performance processors. Reducing voltage swing of the bit-line is an effective way to save the power dissipation in write cycles. Voltage swing reduction of bit-lines is, however, limited due to possible write-failures. We propose a new low-power SRAM using bit-line charge recycling (CR-SRAM) for the write operation. In the proposed write scheme, differential voltage swing of a bit-line is obtained by recycled charge from its adjacent bit-line capacitance, instead of the power line. Applying such a charge recycling technique to the bit-line significantly reduces write power. A test chip with 32 Kbits (256 rows x 128 columns) is fabricated and measured in 0.13 mum CMOS to demonstrate operation of the proposed SRAM. Measurement results show 88% reduction in total power during write cycles compared to the conventional SRAM (CON-SRAM) at V_DD = 1.5 V and f = 100 MHz.     

Room-temperature indentation creep of lead-free Sn–Bi solder alloys

Creep behavior of the lead-free Sn–Bi alloys with bismuth contents in the range of 1–5 wt.% was studied by long time Vickers indentation testing at room temperature. The materials were examined in the homogenized cast and wrought conditions. The stress exponents, determined through different indentation methods, were in good agreement. The exponents of 13.4–15.3 and 9.2–10.0, found respectively for the cast and wrought conditions, are close to those determined by room-temperature conventional creep testing of the same material reported in the literature. Due to the solid solution hardening effects of Bi in Sn, creep rate decreased and creep resistance increased with increasing Bi content of the materials. Cast alloys, with a rather coarser grain structure and some Bi particles at the grain boundaries, showed typically higher resistance to indentation creep compared to the wrought materials. These two factors have apparently resulted in a less tendency of the material for grain boundary accommodated deformation, which is considered as a process to decrease the creep resistance of soft materials.     

The comparison of direct borohydride-hydrogen peroxide fuel cell performance with membrane electrode assembly prepared by catalyst coated membrane method and catalyst coated gas diffusion layer method using Ni@Pt/C as anodic catalyst

Carbon supported Ni@Pt nanoparticles are synthesized using sodium dodecyl sulphate (SDS) and sodium borohydride (NaBH₄) as a structure-directing and reducing agents, respectively. The metal loading in synthesized nanocatalyst is 20 wt% and the ratio of Ni:Pt in the nanocatalyst is 1:1. The structural characterizations and morphologies of Ni@Pt/C nanocatalyst are investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The electrocatalytic activity of Ni@Pt/C catalyst toward borohydride $\left({\text{BH}}_4^{?}\right)$ oxidation in alkaline medium is studied by means of cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The results show that Ni@Pt/C catalyst has superior catalytic activity toward borohydride oxidation (8825.38 mA mg Pt^?1). The Membrane Electrode Assembly (MEA) used in fuel cell set-up is fabricated with catalyst-coated membrane (CCM) and catalyst coated gas diffusion medium (CCG) techniques. The effect of two MEA performances on current–voltage (I–V) and current–power density (I–P) curves in the direct borohydride-hydrogen peroxide fuel cell was investigated using Pt/C 0.5 mg cm^?2 as cathode catalyst and Ni@Pt/C 1 mg cm^?2 as anode catalyst. The influence of cell temperature, sodium borohydride and hydrogen peroxide concentration on the I–V and I–P is determined. The results show that the maximum power density in MEA prepared using CCM method (CCM-MEA) is 68.64 mW cm^?2 at 60 °C, 1 M sodium borohydride and 2 M hydrogen peroxide (H₂O₂) that is higher than MEA prepared using CCG method (CCG-MEA). The impedance results show that with increasing temperature and discharging current, the overall anodic and cathodic charge transfer resistances reduce.