Recovery of copper from a surface altered chalcopyrite contained ball mill spillage through bio-hydrometallurgical route

Bioleaching studies for chalcopyrite contained ball mill spillages are very scarce in the literature. We developed a process flow sheet for the recovery of copper metal from surface activated (600 °C, 15 min) ball mill spillage through bio-hydrometallurgical processing route. Bioleaching of the activated sample using a mixed meso-acidophilic bacterial consortium predominantly A. ferrooxidans strains was found to be effective at a lixiviant flow rate of 1.5 L/h, enabling a maximum 72.36% copper recovery in 20 days. Mineralogical as well as morphological changes over the sample surface were seen to trigger the bioleaching efficiency of meso-acidophiles, thereby contributing towards an enhanced copper recovery from the ball mill spillage. The bio-leach liquor containing 1.84 g/L Cu was purified through solvent extraction using LIX 84I in kerosene prior to the recovery of copper metal by electrowinning. Purity of the copper produced through this process was 99.99%.     

Effect of MgO in the microstructure formation of zirconia mullite composites from sillimanite and zircon

The effect of MgO additive on the structural, microstructural and hardness properties of zirconia mullite (MUZ) has been discussed. The MgO additive in MUZ not only stabilizes the cubic zirconia phase but also acts as a sintering aid for the formation of cross-linked mullite grains. The electron micrographs of plasma fused MgO–MUZ shows a uniform arrangement of platelet structure of mullite and dendrite structure of zirconia on mullite surface. The micrograph of plasma sintered composites shows a ladder like structure and a complete cross-linked mullite grains whereas the surface morphology of conventionally sintered composites clearly indicates the presence of small and big grains close packed to each other. Appreciable hardness and higher optical band gap have been observed for plasma fused MgO–MUZ composites. A complete dissociation of sillimanite and zircon has been occurred in plasma fused composites for the complete conversion of MUZ whereas the complete dissociation of sillimanite and zircon has not observed in plasma sintered and conventionally sintered composites. These observations have been realized from the X-ray diffraction and Fourier transform infrared studies.     

Taguchi analysis of surface modification technique using W-Cu powder metallurgy sintered tools in EDM and characterization of the deposited layer

The present study describes an experimental research on surface modification during electrical discharge machining (EDM) by depositing a hard layer over the work surface of C-40 grade plain carbon steel using specially prepared powder metallurgy compact tools. The investigated process parameters were composition, compaction pressure, sintering temperature, pulse on-time, peak?Ccurrent setting, and duty factor. Measurements of deposited layer thickness, mass transfer rate, tool wear rate, surface roughness and microhardness were undertaken on the EDM-ed specimens. Different studies like X-ray diffraction, optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were carried out to ascertain the characteristics of the deposited layer on the work surface. These analyses confirmed the presence of the tool materials in the work surface layer. At first, an L-16 orthogonal array was applied as Taguchi DOE technique and the ANOVA was done to study the effects of pertinent process parameters. An optimum condition was achieved using overall evaluation criteria. Later on, a detailed study was carried out to get a smooth and regular deposition of material. The characterization of the deposited layer is presented. The deposited layer with a wide range of average layer thickness of 3?C785???m, enriched with tool materials (W and Cu) and with the formation of tungsten carbide, and having microhardness of 9.81?C12.75?GPa at the hardest zone was successfully deposited over the work surface.     

Compton profile and charge transfer study in intermetallic Ti–Al system

The electronic structure of three intermetallic alloys namely Ti₃Al, TiAl and TiAl₃ in terms of Compton profiles is reported in this work. Directional Compton profiles are calculated for all the three alloys employing CRYSTAL code within the framework of density functional theory. The spherically averaged theoretical values are compared with the measurements made using 59.54 keV gamma-rays from Am²⁴¹ source. The calculations are in overall agreement with measurements in all cases. The measurements are also compared with the superposition of LCAO profiles of elemental solids. For Ti₃Al and TiAl₃ the LCAO values show better agreement whereas for TiAl the synthesized LCAO values are closer to the experiment. Effect of titanium 3d electrons is clearly visible in intermediate range of momentum in the Ti rich alloy. Charge transfer in the three alloys has also been estimated following the superposition of experimental profiles of Ti and Al metals. Comparison of Compton spectra of Ti₃Al, TiAl and TiAl₃ with the superposition of the Compton spectra of elemental constituents suggests a charge transfer of 2.8, 0.9 and 0.6 electron per Al atom, respectively. Such large values seem unreasonable and, therefore, this approach cannot be used for any reliable determination of the charge transfer in this system.     

Aesthetical design of a car profile: a Kano model-based hybrid approach

An amicable aesthetical design of a product is prudent for its wide acceptability and viability. Selection of shape parameters with customer satisfaction is critical in aesthetical design and a challenging task for designers. In the present work, the authors proposed a sequential approach to design a car profile with aesthetical aspects. The methodology is based on Kano model that provides a framework for incorporation of customer satisfaction with the design requirements. Further, Taguchi's robust design approach has been used to find the optimum level of the parameter to achieve initial design estimates and thereafter, response surface method (RSM) is applied to refine the optimum values, precisely. The methodology has been illustrated with a case study.     

Analysis of a Localized Fire in a 3-D Tunnel Using a Hybrid Solver: Lattice Boltzmann Method,Finite-Volume Method,and Fully Explicit Upwind Scheme

A localized fire in a 3-D tunnel is analyzed by solving a combined-mode natural-convection and radiation problem. Nonlocal thermal equilibrium between air and smoke is considered. Separate energy equations are used for the two species. The density and temperature fields required for the solution of the energy equation are computed using the lattice Boltzmann method. The finite-volume method is used to compute radiative information. The energy equations are solved using the fully explicit upwind scheme. The Boussinesq approximation is used to account for the buoyancy effect. Effects of the scattering albedo, the convection-radiation parameter, and the wall emissivities on temperature profiles in the tunnel have been studied.     

TRANSIENT CONDUCTION AND RADIATION HEAT TRANSFER WITH HEAT GENERATION IN A PARTICIPATING MEDIUM USING THE COLLAPSED DIMENSION METHOD

In order to study the mechanisms of heat and mass transfer at the gas–liquid interface, flows inside and around a rising inert bubble are considered and calculated using the numerical algorithm developed in a companion article. Studies of heat and mass transfer are carried out while special attention is paid to the effects of wake vortices. Recoveries of the Sherwood and Nusselt numbers are observed in the wake zone behind bubbles, and a physical explanation is proposed.     

A new strain hardening model for rate-dependent crystal plasticity

This paper presents a crystal plasticity based finite element analysis employing the new microstructure-based strain hardening model recently presented by Saimoto and Van Houtte (2011) [7] to simulate formability and texture evolution in the commercial aluminum alloy 5754. Simulations are performed to compare the predictive capability of the new hardening model against the common work hardening models using a rate-dependent plasticity formulation. The parameters in the numerical models are calibrated using the X-ray data published by Iadicola et al. (2008) [9] for the aluminum sheet alloy 5754. The predictions of the model for balanced biaxial tension and in-plane plane-strain tests are compared against experimental observations presented in Iadicola et al. (2008) [9]. It is concluded that the new model provides the best predictions of the large strain behavior of Aluminum sheet alloy 5754 subjected to various strain paths.