Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study

The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative β values). The values of micellar mole fraction of constituent 1 (X ₁) in surfactant mixtures are more than in the ideal state (X ₁ ^ideal ), which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state.     

Optimization of Cu(II)-ion imprinted nanoparticles for trace monitoring of copper in water and fish samples using a Box–Behnken design

We describe a nanoparticles ion-imprinted polymer (IIP) for the selective preconcentration of copper (II) ions. It was obtained by precipitation polymerization from 2-vinylpyridine (the functional monomer), ethylene glycol dimethacrylate (the cross-linker), 2,2′-azobisisobutyronitrile (the initiator), 2,9-dimethyl-1,10-phenanthroline (the copper-binding ligand) and nickel nitrate (the template ion) in acetonitrile solution. The IIP particles were characterized by Fourier Transformed Infra Red Spectroscopy (FTIR), thermogravimetric and differential thermal analysis, and by scanning electron microscopy. The optimization process was carried out using the Box–Behnken design (BBD). Effects of several factors such as solution pH for adsorption, amount of polymer, type, concentration and volume of eluent for extraction, as well as adsorption and desorption times were investigated. Under the optimum conditions (type and concentration of eluent, HCl 1.6 mol L^?1; volume of eluent, 6 mL; adsorption solution pH, 6.0; amount of polymer, 30 mg; adsorption time, 25 min; desorption time, 25 min), preconcentration factor of the proposed method was approximately 100. Under the optimized conditions, the detection limit was found to be 0.1 μg L^?1, while the relative standard deviation (RSD) for six replicate measurements was calculated to be <4%.     

Amphiphilic antidepressant drug amitriptyline hydrochloride under the influence of ionic and nonionic hydrotropes; micellization and phase separation

Herein we report the micellization and cloud point of an amitriptyline hydrochloride (AMT) under the influence of cationic, anionic and nonionic hydrotropes. Anionic hydrotropes were employed to know the micellar and surface behaviors, besides studying the clouding behavior of AMT drug with cationic, anionic and nonionic hydrotropes. Tensiometric study has been performed and the properties studied include the critical micelle concentration (cmc), maximum surface excess at the air/water interface (Γ_max), the minimum area per of amphiphilic molecule at air/water interface (A_min), and the different thermodynamic parameters, besides clouding phenomenon. Interaction parameters of micelles (β^m) and monolayer (β^σ) indicate that drug-hydrotrope systems show better interaction at the interface than in micelles.     

Thinning analysis for hot forming of single-piece hemispherical dish end using finite element simulation and its empirical modeling

Hot forming is an important forming method for production of small and medium sized single-piece pressure vessel dish ends. Thinning of the blank material with increased degree of forming is quite obvious. Present work shows finite element (FE) analysis of hot forming of single-piece hemispherical dish end (SPHDE) for predicting maximum thinning of blank during forming. Thinning analysis is performed for SPHDE of two different ferrous material grades SA-387 Gr22 and SA-516 as per ASME, Section II, Part A (2004). Percentage thinning results of FE analysis are verified with the practical material thinning data. Based on the thinning analysis, empirical relation for calculation of percentage thinning as a function of different dish ends′ geometry parameters is proposed. Empirically predicted percentage thinning is observed to be in good agreement with practical and FE simulation results. Thinning results obtained based on proposed FE simulation and empirical model can be helpful to design engineer in selecting thickness of developed blank considering thinning allowance for hot forming of SPHDE. Thinning analysis data can be used for optimizing the dish end geometrical parameters for minimum thinning during forming.     

Graphene supported bimetallic G–Co–Pt nanohybrid catalyst for enhanced and cost effective hydrogen generation

A highly active and stable bimetallic nano-hybrid catalyst Graphene–Cobalt–Platinum (G–Co–Pt) is proposed for the enhanced and cost effective generation of hydrogen from Sodium Borohydride. Three different nano-hybrid catalysts namely Graphene–Cobalt (G–Co), Graphene–Platinum (G–Pt) and Graphene–Cobalt–Platinum (G–Co–Pt) are synthesized, characterized using XRD, FTIR, SEM, HRTEM, EDAX and Cyclic voltammetry (CV) analysis and tested for hydrogen generation. The activity and stability of the catalysts are analyzed by estimating the turnover frequency (TOF), the electrochemically active surface area (ECSA), the percentage decay of current density over ten cycles of CV and the decay in the rate of hydrogen generation with the age of catalyst. Among the three catalysts G–Co–Pt exhibits the highest catalytic activity (TOF = 107 min⁻¹, ECSA = 75.32 m²/gm) and stability. The evaluated value of activation energy of the catalytic hydrolysis using G–Co–Pt is 16 ± 2 kJ mol⁻¹.     

Effect of Alloying and Coiling Temperature on the Microstructure and Bending Performance of Ultra-High-Strength Strip Steel

Metallurgical and Materials Transactions A - Two different high-strength B-containing microalloyed steel strips produced in industrial processing conditions, one treated with Ti and the other...     

Preparation of new and novel wave like poly(2-anisidine) zirconium tungstate nanocomposite: Thermal,electrical and ion-selective studies

It is necessary to synthesize new material for the advancements of the technology. In this study, new and novel poly(2-anisidine)@zirconium tungstate(P2A/ZrW_2O_8) was synthesized by simple so-gel method. Physicochemical characterization of P2A/ZrW_2O_8 was done by thermogravimetric analysis(TGA), scanning electron microscopy(SEM), X-ray powder diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), ion exchange and simultaneous four probe dc conductivity studies. The conductivity study revealed its highly semiconducting nature, in the range of 10~(-1)–10~(-2) S·cm~(-1). Ion-exchange capabilities of the composite make it applicable for cation-exchange studies. The result of distribution studies(Kd) revealed its selectivity towards Cd~(2+) compared to other metal ions. This property of the composite was utilized for designing Cd~(2+) selective membrane electrode. Several important physical parameters of the ion-selective electrode were determined, such as Nernstian slope(32.32 mV·decade~(-1)), working pH range was 2.0–4.0 and response time was found ～ 17 s.The analytical utility of this wave like composite membrane electrode was as, indicator electrode in various potentiometric titrations.     

Investigation of sintered properties on infiltrated tungsten–copper composite along the infiltration direction

Tungsten–copper composites exhibit excellent resistance to erosion and good electrical as well as thermal conductivity. W–Cu composites are mainly used for heat sinks, electrical contacts and transpiration cooling applications. In this investigation the microstructure, mechanical and electrical properties of infiltrated tungsten–copper composite along the infiltration direction have been studied. The microstructures of the top, middle and bottom regions of the composite were evaluated using both optical and scanning electron microscope. Bulk hardness, electrical conductivity, instrumented hardness and contiguity were measured along the depth of W–Cu composite. It was found that the copper phase fraction decreases along the infiltration direction of the specimen. The effect of distribution of copper in the W–Cu system has a significant influence on the mechanical and the electrical properties. The effect of copper content on indentation depth, instrumented hardness, Young’s modulus, and stiffness of the composite has been evaluated using an instrumented hardness tester.     

Sol–Gel Synthesis and Formation Mechanism of Ultrahigh Temperature Ceramic: HfB2

Hafnium diboride (HfB₂) powder has been synthesized via a sol–gel‐based route using phenolic resin, hafnium chloride, and boric acid as the source of carbon, hafnium, and boron, respectively, though a small number of comparative experiments involved amorphous boron as boron source. The effects of heat‐treatment dwell time and hafnium:carbon (Hf:C) and hafnium:boron (Hf:B) molar ratio on the purity and morphology of the final powder have been studied and the mechanism of HfB₂ formation investigated using several techniques. The results showed that while temperatures as low as 1300°C could be used to produce HfB₂ particles, the heat treatment needed to last for about 25 h. This in turn resulted in anisotropic particle growth along the c‐axis of the HfB₂ crystals yielding tube‐like structures of about 10 μm long. Equiaxed particles 1–2 μm in size were obtained when the precursor was heat treated at 1600°C for 2 h. The reaction mechanism involved boro/carbothermal reduction and the indications were that the formation of HfB₂ at 1300°C is through the intermediate formation of an amorphous B or boron suboxides, although at higher temperatures more than one reaction mechanism may be active.