Development of a new radioanalytical technique for the determination of manganese(II) using potassium periodate

A radiometric method based on redox substoichiometry was applied to accurate and precise determination of manganese. The proposed technique is based on the substoichiometric oxidation of bivalent manganese to permanganate ions with potassium periodate, followed by isolation of the oxidized species by the extraction with tri-n-octylamine in chloroform. The method was successfully applied to the estimation of manganese content of various certified ores and alloys.     

Solvent-free microwave-assisted synthesis of tenorite nanoparticle-decorated multi-walled carbon nanotubes

Copper-decorated carbon nanotubes (CNTs) have important applications as precursors for ultra-conductive copper wires. Tenorite-decorated CNTs (CuO-CNTs) are ideal candidates and are currently developed using laborious processes. For this reason, we have developed a facile and scalable method for the synthesis of CuO-CNTs from copper acetate. It was found that the optimal loading of copper acetate onto the CNTs was 23.1 wt% and that three 1-minute microwave treatments were sufficient for the decomposition of copper acetate to copper oxide. The loading of copper oxide onto the nanotubes was confirmed using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. The materials were characterised using X-ray diffraction and scanning electron microscopy.     

First principles calculations of the stability of the T2 and D88 phases in the V–Si–B system

The crystal and electronic structures of D8_l-V₅SiB₂ and D8₈-V₅Si₃B ternary compounds have been investigated by means of first principle calculations. The calculated structural parameters are in very good agreement with the experimental data. The calculated values of the enthalpies of formation at T = 0 K of the D8_l-V₅SiB₂ and D8₈-V₅Si₃B ternary compounds are −67.1 and −62.1 kJ/mol of atoms respectively. The total and partial electronic densities of states show a strong hybridization between the B p states and V d states. The defect enthalpies of formation as well as the mixing enthalpies have been computed. These data are essential for the modeling of the D8_l and D8₈ phases in the V–Si–B ternary system. A partial V–VSi₂–VB isothermal section at 298 K is proposed.     

Thermo-optical characterization of CdZnS nanoparticle colloids

Thermo-optical properties of cadmium zinc sulfide (CdZnS) nanoparticle colloids are investigated by interferometry technique. The nanoparticle colloids are synthesized by an improved co-precipitation method. Transmission electron microscopy, UV–vis spectrometry and X-ray diffraction analysis are used to characterize the CdZnS nanocrystals. The thermo-optic coefficient of the colloids has been determined using a Fizeau interferometer. For this purpose, the interference patterns are deformed by a photothermal phase shift which is locally induced in the sample by the focused pump laser beam. The change in the refractive index at this region imposes a shift on the phase of the fringe patterns. Fourier analysis performed on the interference patterns allows us to estimate the values of the thermo-optic coefficient and nonlinear refractive index of the sample. It is shown that the CdZnS nanoparticle colloids enhance the absorption of the laser light and induce high rise in the temperature of the sample, which leads to the nonlinear phase shift.     

Spectroscopic evaluation of a novel multi-element sensitive fluorescent probe derived from 2-(2′-phenylbenzamide)benzimidazole: Selective discrimination of Al3 + and Cd2 + from their congeners

A novel fluorescent chemosensor 2 exhibiting excited-state intramolecular proton transfer (ESIPT) process has been synthesized by condensation approach, among which 2 could be used as a multielement sensitive fluorescent probe for both Al^3 + and Cd^2 +. The emission wavelength of 2 underwent blue shift of 78 nm upon binding with these ions. The cation-induced inhibition of ESIPT phenomenon was responsible for these fluorescence changes. Moreover, the absorption spectra of 2 showed changes with F⁻ and AcO⁻ ions also. TD-DFT studies well displayed the blue shift in the emission wavelength of 2 upon binding with Al^3 + ions.     

Quickest single-step one pot mechanosynthesis and characterization of ZnTe quantum dots

ZnTe quantum dots (QDs) are synthesized at room temperature in a single step by mechanical alloying the stoichiometric equimolar mixture (1:1 mol) of Zn and Te powders under Ar within 1 h of milling. Both XRD and HRTEM characterizations reveal that these QDs having size ∼5 nm contain stacking faults of different kinds. A distinct blue-shift in absorption spectra with decreasing particle size of QDs confirms the quantum size confinement effect (QSCE). It is observed for first time that the QDs with considerable amount of faults can also show the QSCE. Optical band gaps of these QDs increase with increasing milling time and their band gaps can be fine-tuned easily by varying milling time of QDs.     

Sulphated polysaccharides from Indian samples of Enteromorpha compressa (Ulvales,Chlorophyta): Isolation and structural features

Heteroglycan and xyloglucan rich fractions were extracted from Indian samples of Enteromorpha compressa in 25% yield by sequential extractions with water and alkali. This heteroglycan is sulfated and has an apparent molecular mass of 55 kDa. Chemical structural analysis of this polysaccharide revealed a branched structure having 1,4- and 1,2,4-linked rhamnose 3-sulphate, 1,4-linked glucose, 1,3- and 1,6- linked galactose, 1,4- and terminally linked glucuronic acid and 1,4-linked xylose partially sulfated on O-2. Chemical and spectroscopic analysis showed that the 4-M KOH extracted hemicellulosic fraction contained an unusual β-(1,4)-linked linear xyloglucan. Enzyme hydrolysis and analysis of the resulting fragments by matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) showed that this linear polymer contained partially sulfated Glc₃Xyl₂ or Glc₄Xyl₂ as oligomeric building subunits.     

Experimental and simulated instrumented ball in a tumbling mill—A comparison

Tumbling mills play an essential role in modern mineral processing. Because of the nature of the mill, the internal forces make instrumentation of the mill interior difficult. One solution to this problem is the use of an instrumented ball. An instrumented ball, equipped with an accelerometer, rotation rate sensors and a temperature sensor has been built. The instrumented ball and a camera system are used to measure the state of the charge within a laboratory mill. In parallel, a discrete element model (DEM) of the laboratory mill is developed. Using the distributions and moments of the energy terms of the charge, the simulation and experimental results are analyzed and compared. The moments are used to tune the DEM, such that the simulation results are in agreement with the experimental results. The comparison also identifies which aspects require further improvement.     

Sensitivity analysis of a Vision 21 coal based zero emission power plant

The goal of the U.S. Department of Energy's (DOE's) FutureGen project initiative is to develop and demonstrate technology for ultra clean 21st century energy plants that effectively remove environmental concerns associated with the use of fossil fuels for producing electricity, and simultaneously develop highly efficient and cost-effective power plants. The design optimization of an advanced FutureGen plant consisting of an advanced transport reactor (ATR) for coal gasification to generate syngas to fuel an integrated solid oxide fuel cell (SOFC) combined cycle is presented. The overall plant analysis of a baseline system design is performed by identifying the major factors effecting plant performance; these major factors being identified by a strategy consisting of the application of design of experiments (DOEx). A steady state simulation tool is used to perform sensitivity analysis to verify the factors identified through DOEx, and then to perform parametric analysis to identify optimum values for maximum system efficiency. Modifications to baseline system design are made to attain higher system efficiency and to lower the negative impact of reducing the SOFC operating pressure on system efficiency.     

Prediction of anode performances of direct methanol fuel cells with different flow-field design using computational simulation

Three-dimensional computational simulation was employed to illustrate the performance characteristics according to the flow-field design by solving the physics in the flow field and the diffusion layer and by calculating the electrochemical reaction at the catalyst layer. The pressure loss and the concentration distribution in the anode were analyzed for four types of flow field, parallel, serpentine, parallel serpentine and zigzag type. Also the anode current density distribution was predicted at the various overpotentials. The cell performance was proportional to the pressure drop for all the flow-field types. Zigzag type showed the best performance which has a good resistance against the fuel concentration polarization and the next was serpentine.