Faculty Publications
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Item Friction Stir Processing: An Emerging Surface Engineering Technique(Springer Science and Business Media B.V., 2020) Bajakke, P.A.; Jambagi, S.C.; Vinayak, V.R.; Deshpande, A.S.Surface modification technologies impart improved surface properties without affecting the bulk properties of the material. The properties could be mechanical, electrical or thermal properties. Until recent past, thermal spray techniques, namely, plasma spraying, high-velocity oxy-fuel coatings and many others widely used for these applications. Friction stir processing (FSP) is a relatively newer technique that uses friction (between two surfaces) as a heat source to form a surface composite on the base alloy. This solid-state process not only refines the given structure but also disperses the reinforcements well within matrix alloy to enhance the surface properties. FSP was earlier employed to low melting point alloys such as aluminum and magnesium-base alloys, but now, with the recent development in tool geometry and tool materials, it can even be effectively used for high melting point alloys like steel and titanium-based alloys. Several process parameters seem to affect temperature and dispersion of reinforcements at the surface. They include rotational speed and traverse speed of the tool, number of passes, cooling medium and the tool geometry. Among these, rotation speed and traversing speed of tool seem to greatly affect the temperature distribution in the plasticized zone formed at the surface. This temperature, in turn, affects the grain refinement and dispersion of reinforcement particles. The present chapter summarizes the effect of these parameters. This chapter also reviews the latest developments in the tool material and its design. Further, their role in augmenting the base alloy properties is also discussed. High hardness, high fracture toughness, chemical inertness and high-temperature strength are few desirable properties of a tool to be used for FSP. In the end, the applicability of FSP as a surface modification technique has been assessed. © 2020, Springer Nature Switzerland AG.Item A review of various materials for additive manufacturing: Recent trends and processing issues(Elsevier Editora Ltda, 2022) Srivastava, M.; Rathee, S.; Patel, V.; Kumar, A.; Koppad, P.G.Tremendous growth has been witnessed in the field of additive manufacturing (AM) technology over the last few decades. It offers a plethora of applications and is already being utilized in almost every sphere of life. Owing to inherent differences between each AM technique, newer fields of research consistently emerge and demand attention. Also, the innovative applications of AM open up newer challenges and thus avenues for focused attention. One such avenue is AM materials. Raw material plays an important role in determining the properties of fabricated part. The type and form of raw material largely depend on the type of AM fabricators. There is a restriction on material compatibility with most of the established AM techniques. This review aims to provide an overview of various aspects of AM materials highlighting the progress made especially over the past two decades. © 2022 The Author(s).Item Amine-grafted zeolites-mesoporous ceramics: Synthesis and adsorption characteristics(2014) Aruldoss, D.; Saigoanker, R.; Jerome, J.D.; Jagannathan, J.Through a facile synthesis method, amine-grafted zeolites-based mesoporous ceramics as effective adsorbents for green-house gases, CO2 in particular, have been synthesized. Analyses on these mesoporous samples, using SAXD and SEM studies, indicate minor modification in the chemical texture of the ceramics. The chemisorbed gaseous species have been analyzed using BET and FTIR spectra. Grafting of the mesoporous solid with less saturated amine species, such as, TETA and DETA, enhances the adsorption of the green-house gas CO 2 by about 40% in comparison to the samples prepared through grafting with more saturated alcohol-based amine group TEA. © 2013 Elsevier Ltd and Techna Group S.r.l.All rights reserved.Item Record-low sintering-temperature (600 °c) of solid-oxide fuel cell electrolyte(Elsevier Ltd, 2016) Prasad Dasari, H.P.; Ahn, K.; Park, S.-Y.; Hong, J.; Kim, H.; Yoon, K.J.; Son, J.-W.; Kim, B.-K.; Lee, H.-W.; Lee, J.-H.One of the major problems arising with Solid-Oxide Fuel Cell (SOFC) electrolyte is conventional sintering which requires a very high temperature (>1300 °C) to fully densify the electrolyte material. In the present study, the sintering temperature of SOFC electrolyte is drastically decreased down to 600 °C. Combinational effects of particle size reduction, liquid-phase sintering mechanism and microwave sintering resulted in achieving full density in such a record-low sintering temperature. Gadolinium doped Ceria (GDC) nano-particles are synthesized by co-precipitation method, Lithium (Li), as an additional dopant, is used as liquid-phase sintering aid. Microwave sintering of this electrolyte material resulted in decreasing the sintering temperature to 600 °C. Micrographs obtained from Scanning/Transmission Electron Microscopy (SEM/TEM) clearly pointed a drastic growth in grain-size of Li-GDC sample (?150 nm) than compared to GDC sample (<30 nm) showing the significance of Li addition. The sintered Li-GDC samples displayed an ionic conductivity of ?1.00 × 10-2 S cm-1 at 600 °C in air and from the conductivity plots the activation energy is found to be 0.53 eV. © 2016 Elsevier B.V. All rights reserved.Item An investigation on high temperature erosion behaviour of plasma sprayed CoCrALY/Al2O3/YSZ on fe and ni based alloys(Universiti Putra Malaysia Press Tower 2, UPM-MDTC Technology Centre Serdang, Selangor 43400, 2017) Nithin, H.S.; Desai, V.; Ramesh, M.R.Parts of aircraft and gas turbines used for power production are subjected to severe erosion damage since aircrafts frequently operate in sandy environment. Low cost fuel such as poor quality coal is used in gas turbines which produce suspended hard particle in the exhaust. In the past, researchers have worked on minimising the erosion by using certain coatings. Development of new coatings is necessary in order to explore further in improving resistance against erosion process under high operating temperature of gas turbine, aero engines and other components. In the present work, the investigation of elevated temperature erosion behaviour of CoCrAlY/Al2O3/YSZ coatings synthesised by plasma spraying on two different base metals, namely, Hastelloy X (Superni 76) and AISI 321 (MDN 321) was carried out. The coated samples were subjected to erosion test at 600ºC with the impact angles of 30º and 90º under steady state condition. Alumina powder was used as erodent material of uneven angular shape of 50 ?m particle size. The morphology and phase formed on eroded surface are characterised using SEM and X-ray diffraction to determine the erosion mechanism. The rate of erosion is determined by weight loss method and the CoCrAlY/Al2O3/YSZ coating showed up to about 25% lower erosion rate than the substrate alloy. It was observed that the erosion resistance of CoCrAlY/Al2O3/YSZ coating on both MDN 321 and Superni 76 gave almost similar erosion resistance which shows that the erosion behaviour of coating is not influenced by substrate unless spray parameter and substrate roughness is changed. © 2017 Universiti Putra Malaysia Press.Item Low-temperature sonochemical synthesis of high dielectric Lanthanum doped Cerium oxide nanopowder(Elsevier Ltd, 2018) Kishor Kumar, M.J.; Kalathi, J.T.Lanthanum (La) doped Cerium Oxide (CeO2) nanopowder was synthesized at a relatively lower temperature (70°C), without calcination in a simple, faster, and efficient way through sonochemical method. X-ray diffraction (XRD) results confirmed the formation of a cubic fluorite structure of nanocrystalline CeO2 and lattice deformation due to La-doping in CeO2. TEM analysis revealed that the size of La-doped CeO2 particles is in the range of 20?50 nm. In addition, selective area electron diffraction (SAED) and high-resolution TEM (HRTEM) analyses portrayed the nano-crystallinity, lattice fringe pattern, and d-spacing details of La-doped CeO2 powder. Lanthanum doping in CeO2 was further confirmed by a shift in Raman band towards the lower frequency (from 464 cm?1 to 457cm?1) along with peak intensity increase. Photoluminescence (PL) emission spectra showed that emission intensity of the La-doped CeO2 at 510 nm is increased due to oxygen vacancy mediated charge transfer. All these results confirm the successful doping of La in CeO2. The La-doped CeO2 powder possesses a high dielectric constant (?r) of 106 and a low dielectric loss (tan ?) of < 0.4 % at 1 kHz. The La-doped CeO2 finds potential applications on developing devices in the field of a thin film capacitor, transistors, and solid oxide fuel cells. © 2018 Elsevier B.V.Item Customizable ceramic nanocomposites using carbon nanotubes(MDPI AG indexing@mdpi.com Postfach Basel CH-4005, 2019) Okolo, C.; Rafique, R.; Sagar, S.S.; Subhani, T.; Saharudin, M.S.; Badekai Ramachandra, B.R.; Inam, F.A novel tweakable nanocomposite was prepared by spark plasma sintering followed by systematic oxidation of carbon nanotube (CNT) molecules to produce alumina/carbon nanotube nanocomposites with surface porosities. The mechanical properties (flexural strength and fracture toughness), surface area, and electrical conductivities were characterized and compared. The nanocomposites were extensively analyzed by field emission scanning electron microscopy (FE-SEM) for 2D qualitative surface morphological analysis. Adding CNTs in ceramic matrices and then systematically oxidizing them, without substantial reduction in densification, induces significant capability to achieve desirable/application oriented balance between mechanical, electrical, and catalytic properties of these ceramic nanocomposites. This novel strategy, upon further development, opens new level of opportunities for real-world/industrial applications of these relatively novel engineering materials. © 2019 by the authorsItem Combustion aided in situ consolidation of high strength porous ceramic structures with a minimum thermal budget(Elsevier B.V., 2020) Pujar, P.; Pal, A.; Mandal, S.The exothermic reaction between a pair of combustible pore formers (urea-ammonium nitrate) is the driving force in realizing low-temperature consolidation of hydroxyapatite (HA) particles. The particles are allowed to sinter in the proximity to the combustible pore formers. The exothermic (?H°rea = -898 kJ/mol) redox reaction between combustible pore formers is successfully utilized in deriving high compressive strength (~24 MPa) of HA at 300 °C. The evolution of gaseous products of combustion results in an interconnected porous network of HA. The estimated compressive strength of sintered HA at 300 °C is comparable with high temperature (1100 °C) conventionally sintered HA, at a fixed open porosity (~40%); which depicts nearly ~82% achievement with a reduction of sintering temperature by ~72%. Also, the pellets sintered at 600 °C have shown ~90% achievement in compressive strength of sintered HA. Further, the saturated pore area of 15% requires a sintering time of 9.58 h at a sintering temperature of 600 °C. Thus, combustion-assisted sintering is an alternative technique proves its potentiality in achieving remarkable compressive strength and paves the way for low-cost porous ceramics. © 2020 Elsevier B.V.