The influence of particle size, blend ratio and some selective bio-additives on the rheological behaviour of an Indian iron ore sample in a slurry concentration range of 60-75% by mass was evaluated. The rheological parameters were measured using a high-precision ThermoFisher Scientific HAAKE TM RheoStress TM 1 Rheometer. The iron ore slurry samples indicated non-Newtonian flow behaviour and fitted quite well with the Bingham plastic model in the studied range of concentrations. The specific multimodal iron ore samples with a broad size distribution indicated a substantial reduction in slurry viscosity, yield stress and improved solids loading compared to monomodal ones. The reduction in apparent viscosity at a given shear rate for the specific iron ore slurry sample was correlated to a distribution modulus () derived from the Farris theory. The application of small dosages (0.8-1% w/w of total solids) of two selective bio-additives extracted from Indian spinach (Basella alba) and Bellyache bush (Jatropha gossypifolia Linn) further reduced the Bingham viscosity and yield stress values through surface modification at higher solids loading. The increase in yield stress values with an increase in solids concentration was attributed to the formation of loosely packed flocs and immobilisation of water within them, thus increasing particle-particle and particle-fluid friction. The bio-additives may be able to improve the fluid mobility among the particles, thus reducing the internal friction constituting the flocs and facilitating the slurry flow with the application of a reasonably lesser shearing force. The study reveals that the blending of fines with coarse iron ore at a controlled particle size distribution supplemented by small dosages of low-cost additives may be employed for preparation and transportation of high-concentration iron ore slurry with improved pipe economics.
Conventional machining of metallic glass is a challenge due to its amorphous nature and inherent brittleness. This work investigates the non-conventional machining of Zr-based metallic glass, Vitreloy-1, using laser processing with a Yb-fiber laser and an electro-jet milling (EJM) process. Grooves were fabricated using these techniques in Vitreloy disks of 1.5 mm thickness to study the machining behavior. The grooves formed with the laser were smooth, although there was observation of dross at the groove edges, which was selectively removed through the EJM process. On the other hand, the EJM process was found to produce dross-free grooves; however, it caused leaching of zirconium from the groove zone, which was understood from the elemental maps obtained using the scanning electron microscope. A comparison of the laser grooving and EJM grooving process was also carried out using Vickers micro-indentation. Indentations made close to the groove edge in laser grooved samples developed shear bands but the same were absent in the EJM grooved samples. Since shear banding tendency is an indicator of the inherent toughness of the metallic glass, the laser grooving technique is found more suitable for nonconventional machining of metallic glass.
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