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Induration of ilmenite pellets by oxidation is an essential step in the pelletization process since it decides the physical and metallurgical properties of the pellets. In this regard, the induration parameters such as temperature and roasting time have been optimized to obtain good quality ilmenite pellets made of concentrates obtained from low-grade ilmenite ores of Odisha, India. The oxidation temperature of 900 °C at a short roasting time of 15 min has been found suitable to achieve recommended requirements of various pellet properties such as cold compressive strength, porosity, metallization, tumble, and abrasion indices. X-ray diffraction and microstructural analysis indicate that the recrystallization of hematite in the oxidation process improves the mechanical strength of the pellets. In contrast, the formation of ferric pseudobrookite phase at 1000 °C and 1100 °C oxidation temperatures impairs the pellet strength.

Cold gas dynamic spraying is a relatively new coating technology in which coatings are produced by spraying metal powders at high velocity. This generates particle–substfrate bonding through severe plastic deformation at temperatures, well below the melting point of the powders. In the present study corrosion resistant nickel coatings were produced on preheated mild steel substrates by cold spraying. The substrate deposition temperature was varied systematically and post fabrication annealing was introduced to reduce the deposition impact stress. Post deposition heat treatment, although improved the interfacial bonding, lead to increased corrosion due to increase in porosity of the samples. Coatings deposited at low temperatures (∼500°C) provide the best corrosion resistance as evidenced through their microstructure.

Although FeTi is a well-known hydrogen storage material, producing FeTi on a commercial scale is quite challenging, and generally, one ends up with a multi-phase system consisting of Fe2Ti and FeTi. As Fe2Ti is inert towards hydrogen, it lowers the hydrogen storage efficacy of FeTi. However, there are some reports, which propose that the presence Fe2Ti in FeTi, primarily on the surface is inevitable and it helps in activation of FeTi. Here, we report results of targeted experiments together with first-principles density functional theory (DFT) based calculations to investigate the hydrogen storage properties of FeTi vis-a-vis origin of inertness of Fe2Ti towards hydrogen storage. The formation enthalpies, calculated using density functional theory, of FeTi–H system were found to be very close to the experimental values (−28.1 and −33.72 kJ/mol H2 for FeTiH and FeTiH2 respectively), and that of Fe2Ti–H systems was positive, indicating the inability to form stable intermetallic-hydrides. This corroborates well with the experimental observations, that the pure phase of Fe2Ti cannot store hydrogen. Further, the Gibbs free energy for FeTiH and FeTiH2 were evaluated at 298 K using first-principles quantum mechanics and statistical thermodynamics theories. The vibrational and electronic entropies were calculated using Debye theory of heat capacities. Gibbs free energy at 298 K for FeTiH and FeTiH2 were found to be −5.01 and −3.52 kJ/mol of H2, respectively. Our present study concludes that proper care must be taken to avoid or minimize the formation of Fe2Ti during the production of FeTi.

Metallic bipolar plates (BPPs) are potential candidates to replace the conventional graphite BPPs in polymer electrolyte membrane fuel cells (PEMFCs) because they are cost-effective and easy to manufacture. In this present work, we report on the development of Ni–Mo–Cr–P electroplated AISI 1020 steel bipolar plates as a BPP material. The microstructure and composition of the Ni–Mo–Cr–P coatings were optimized varying pH of the electrolyte bath and deposition current. Compared to bare AISI 1020 steel, the coating electroplated at pH 5.5 and a pulse-current density of 0.075 A/cm2 showed an improvement in corrosion resistance by three orders of magnitude. The corrosion current densities of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel in the simulated anodic environment is 1.05 × 10−2 and 4.95 × 10−5 A/cm2, respectively, while that in the simulated cathodic environment it is 3.7 × 10−2 and 4.58 × 10−5 A/cm2, respectively. The enhancement of corrosion resistance is due to the formation of a Mo and Cr based passive oxide layer. The interfacial contact resistance (ICR) of bare and Ni–Mo–Cr–P electroplated AISI 1020 steel is 53.2 and 40.06 mΩ, respectively. ICR of Ni–Mo–Cr–P is lower than the bare AISI 1020 because of the semiconducting nature of the two-layered Mo-based passive oxides. Additionally, Ni–Mo–Cr–P coated AISI 1020 steel shows a higher water contact angle than bare AISI 1020 carbon steel. A single-cell PEMFC stack with Ni–Mo–Cr–P coated AISI 1020 steel BPP shows similar polarization behavior as graphite BPP. However, the performance of Ni–Mo–Cr–P coated AISI 1020 steel BPP lacks durability, and further improvement is necessary before it can be commercially implemented.

Electrophoretic deposition was used to deposit graphene oxide on 304 stainless steel to mitigate the aggressive corrosion that occurs in steel bipolar plates of polymer electrolyte membrane (PEM) fuel cells. In this context the deposition parameters i.e., the voltage and time was systematically monitored to obtain the optimum parameters that can give a consistent coating. The deposit thickness and its surface roughness and morphology were evaluated to obtain a smooth coating. Further electrochemical testing of the coating obtained under optimized parameters was done by the dynamic polarization scanning test under PEMFC environment. The corrosion current density improved by almost four times and the polarization resistance increased by 100% indicating that graphene oxide coatings have the potential to be used as anti-corrosive coating on bipolar plates of PEMFC.

Producing large parts by chemical vapour infiltration (CVI) process is quite challenging due to non-uniform nature of temperature and gas precursor distribution. Many a times repeated experiments are required to optimize the process parameters for manufacturing composites with isotropic properties. This is not only cumbersome but also cost intensive. To address this critical issue, we develop a multiscale mathematical model for thermal gradient forced chemical vapour infiltration (TG-FCVI) process considering only heterogeneous decomposition of propylene on carbon preform. The model takes account of the flow field, mass transport, reaction kinetics and the transient nature of porosity to identify the optimum process parameters. As the time taken in deposition is very large, the flow in free channel is much faster than the pores and therefore the flow equations are solved coupling both the domains in steady state (low Mach number flow). The effect of various process parameters on composites homogeneity like temperature, temperature gradient, inlet precursor concentration and inlet gas flow rate were studied. The model was validated with the available experimental data. It has been observed that high temperature gradient and inlet concentration favours homogeneous C-C composite with high final bulk density. However, increasing temperature of reactor and reducing inlet reagent concentration causes surface pore blockage and resulting in inhomogeneity in direction of axial flow

Polymer electrolyte membrane fuel cell (PEMFC) stacks suffer from the high cost and low volumetric energy of non-porous graphite bipolar plates. To resolve this problem, a bilayer coating consisting of Ni and Ni–Cr–P is deposited on AISI 1020 low-carbon steel using pulse electrodeposition. Ni/Ni–Cr–P-coated AISI 1020 is evaluated as a bipolar plate material for PEMFCs. Ni/Ni–Cr–P-coated substrates exhibit better corrosion resistance in both cathodic (air-purging) and anodic (H2-purging) environment than the bare AISI 1020 substrate and lower interfacial contact resistance (ICR) than bare AISI 1020 and stainless steel. Further, it is expected to show better water management as the Ni/Ni–Cr–P coating is more hydrophobic than the bare substrate. Preliminary studies show that Ni/Ni–Cr–P-coated AISI 1020 plate can be a suitable candidate for replacing graphite as the bipolar plate of PEMFCs.