Slag eye formation in single and dual bottom purged industrial steelmaking ladles

ABSTRACT

Argon gas is often injected from the bottom of the ladle during steel refining operations. The injected gas interacts with the liquid (metal and slag) bath and enhances the momentum, heat, and mass transfer rate in the melt. However, during these gas–liquid interactions, an opening of the slag layer called slag eye is formed, which exposes the molten metal surface to the atmosphere, which is generally undesirable. In the current work, a transient, three-dimensional mathematical model is used to study the turbulent gas–liquid interactions in single as well as dual bottom blown industrial steelmaking ladles. A Coupled Level Set Volume of Fluid (CLSVOF) model is used for tracking the steel-argon, steel-slag, and argon-slag interfaces, from which the slag-eye area has been predicted. It is found that the inlet gas purging rate, melt height, slag layer thickness, angular and radial positions of the gas inlets affect the slag opening area. Non-dimensional empirical correlations are proposed to predict the slag opening area in both single as well as dual purged ladles, using non-linear regression analysis.     

Development of docetaxel nanocapsules for improving in vitro cytotoxicity and cellular uptake in MCF-7 cells

The aim of this study was to fabricate docetaxel loaded nanocapsules (DTX-NCs) with a high payload using Layer-by-Layer (LbL) technique by successive coating with alternate layers of oppositely charged polyelectrolytes. Developed nanocapsules (NCs) were characterized in terms of morphology, particle size distribution, zeta potential (ζ-potential), entrapment efficiency and in vitro release. The morphological characteristics of the NCs were assessed using transmission electron microscopy (TEM) that revealed coating of polyelectrolytes around the surface of particles. The developed NCs successfully attained a submicron particle size while the ζ-potential of optimized NCs alternated between (+) 34.64?±?1.5 mV to (?) 33.25?±?2.1 mV with each coating step. The non-hemolytic potential of the NCs indicated the suitability of the developed formulation for intravenous administration. A comparative study indicated that the cytotoxicity of positively charged NCs (F4) was significant higher (p?in vitro on MCF-7 cells. Furthermore, cell uptake studies evidenced a higher uptake of positive NCs (≥1.2 fold) in comparison to negative NCs. In conclusion, formulated NCs are an ideal vehicle for passive targeting of drugs to tumor cells that may result in improved efficacy and reduced toxicity of encapsulated drug moiety.     

Characterization of Oxide Dispersed AlCoCrFe High Entropy Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering

The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV₁ and 1,070 ± 20 HV₁ was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness.     

Numerical Analysis of Heat Transfer from a Moving Surface Due to Impingement of Slot Jets

Heat transfer from a moving surface with uniform wall temperature due to impingement of series of slot jets has been investigated numerically. In the present paper, transition–shear stress transport model has been used for numerical simulations, which can predict the heat transfer in laminar as well as turbulent flows. This model is adopted here to study the transport phenomenon and predict the transition from laminar to turbulent flow seamlessly under different surface velocities. The present model with stationary surface is validated with the correlation given by Martin for series of slot jets. It has also shown good agreement with existing data for both laminar and turbulent slot jets, and is further studied to understand the heat transfer under wide range of flow conditions and the effect of surface velocity on flow regime. The range of Reynolds number is from 100 to 5,000, whereas surface velocity varied up to six times the jet velocity at the nozzle exit. It has been observed that at high surface velocities the heat transfer from the moving wall is more than stationary case. The transition from laminar to turbulent regime is found to be starting at a Reynolds number of 400 and turns completely turbulent at a Reynolds number of 3,000. Q-criterion is used to confirm the transition zone by observing the breaking of vortices at higher Reynolds number.     

Optical Diagnostics Study of Gas Particle Transport Phenomena in Cold Gas Dynamic Spraying and Comparison with Model Predictions

Cold gas dynamic spraying (CGDS), a relatively new thermal spraying technique has drawn a lot of attention due to its inherent capability to deposit a wide range of materials at relatively low-operating temperatures. A De Laval nozzle, used to accelerate the powder particles, is the key component of the coating equipment. Knowledge concerning the nozzle design and effect of process parameters is essential to understand the coating process and to enable selection of appropriate parameters for enhanced coating properties. The present work employs a one-dimensional isentropic gas flow model in conjunction with a particle acceleration model to calculate particle velocities. A laser illumination-based optical diagnostic system is used for validation studies to determine the particle velocity at the nozzle exit for a wide range of process and feedstock parameters such as stagnation temperature, stagnation pressure, powder feed rate, particle size and density. The relative influence of process and feedstock parameters on particle velocity is presented in this work.     

CeO2-filled sol–gel coatings for corrosion protection of AA2024-T3 aluminium alloy

Hybrid organic–inorganic sol–gel-matrices, with up to 20 wt.% incorporated ceria nanoparticles, have been employed as coatings for an AA2024-T3 aluminium alloy. The morphology of the coatings and associated nanoparticles has been examined by conventional and high-resolution transmission electron microscopy, revealing a relatively uniform distribution of 5 nm size nanoparticles across the coating thickness. Electrochemical studies indicate a general beneficial effect of incorporation of ceria nanoparticles, although the performance of the coated alloy depends on the nanoparticle content. Electrochemical polarisation behaviour revealed that the coating decreased the anodic current density by about seven orders of magnitude compared with the uncoated alloy, with high breakdown potentials in chloride-containing solution. Accelerated salt spray testing showed that corrosion in an artificial scratch is blocked most efficiently by high ceria contents, whereas general corrosion is inhibited effectively with comparatively low ceria contents. Electrochemical impedance spectroscopy indicated degradation of the barrier properties of coatings with increased amounts of incorporated nanoparticles. Assessment of the abrasion and scratch resistance, and hydrophobicity also revealed additional beneficial functional properties of the coatings containing nanoparticles.