Faculty Publications

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    Tribological Response of Magnesium/Glass Microballoon Syntactic Foams
    (Springer Science and Business Media Deutschland GmbH, 2022) Manakari, V.; Parande, G.; Doddamani, M.; Srivatsan, T.S.; Gupta, M.
    Magnesium (Mg)-based materials have great potential to replace the existing aluminum alloys and steels used in applications spanning the industries of defense, aerospace, and automotive due in essence to their excellent specific strength [σ/ρ], damping characteristics, and impact resistance. In this research study, we design an ultralow density magnesium/glass microballoon (GMB) syntactic foam having a density of 1.47 g/cc using the technique of Disintegrated Melt Deposition (DMD). The resultant material offered a healthy combination of extraordinary properties outperforming the existing aluminium and iron syntactic foams in terms of a noticeable improvement in specific strength [σ/ρ]. Further, the wear resistance of magnesium under dry sliding conditions showed a significant enhancement (~2.5 times) following the addition of glass microballoon (GMB). Abrasion and oxidation were identified to be the dominant wear mechanisms post worn-surface analysis. Morphology of the worn specimen provided clean, clear, and convincing evidence for the occurrence of delamination wear, which has traditionally limited the competitive advantage of magnesium and its alloy counterparts for selection and use in safety–critical components in transportation vehicles. This can be effectively overcome by the development of the proposed syntactic foams, which provide a unique cushioning effect against the applied load. © 2022, The Minerals, Metals & Materials Society.
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    Role of Rare Earth Oxide Reinforcements in Enhancing the Mechanical, Damping and Ignition Resistance of Magnesium
    (Springer, 2019) Kujur, M.S.; Manakari, V.; Parande, G.; Doddamani, M.; Mallick, A.; Gupta, M.
    Magnesium based nanocomposites, on account of their excellent dimensional stability coupled with mechanical integrity, have provided the much-needed impetus for utilization in both aerospace-related and automobile-related applications. However, the perceived easy ignition and flammability of magnesium alloys create a detrimental safety feature that hinders the aerospace application opportunities. Incorporation of rare earth metal oxides into magnesium matrix can induce ‘reactive element effect’ (REE), due to their strong rare earth–oxygen interactions. Along with enhancing the protective characteristics of oxides on many metals and alloys, the addition of such rare earth oxides also helps in realizing a refined microstructure and good strength–ductility combination in the composites. This manuscript presents the mechanical properties, damping and ignition resistance characteristics of the new and improved composite materials engineered by reinforcing magnesium with rare earth oxide nanoparticle. Rationale for the observed properties is discussed while concurrently establishing the relationship between microstructure of the engineered composites and resultant mechanical properties. © 2019, The Minerals, Metals & Materials Society.
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    Corrosion of ECAPed magnesium alloys and its background: A Review
    (Chulalognkorn University, 2019) Naik, G.M.; SannaYellappa, N.; Kumar, S.S.S.
    The aim of this review article is to provide a brief mechanistic overview of magnesium alloys, equal channel angular pressing and corrosion behavior of un-ECAPed and ECAPed Mg alloys. The considerate of the corrosion processes of ECAPed Mg alloys builds upon interpretation of the corrosion of fine-grain magnesium alloys. This provides an understanding of the effect of grain size on corrosion of Mg alloys. This deep understanding is essential as a foundation if we are to produce corrosion-resistant magnesium alloys. Considerable has previously been accomplished, but there is enormous scope for development. This present concise review can provide a foundation for further, much desirable research. © 2019 Chulalognkorn University.
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    Recent progress in in vivo studies and clinical applications of magnesium based biodegradable implants – A review
    (National Engg. Reaserch Center for Magnesium Alloys, 2021) Sekar, P.; Narendranath, N.; Desai, V.
    Biodegradable magnesium has regained great attention due to its ability to temporarily offer mechanical strength and degrade completely once the injured pathological tissue is healed. A few clinical applications of Mg-based implants were reported in the last century. However, the knowledge and experience is being gained continuously by studying the host response and degradation behavior of Mg implant in animal models and clinical trials. This led to the development of commercial products emerging from Europe and Asia very recently. The potential of Mg implants in repairing fractures at upper and lower limb of large, small animal models and humans is compared and discussed in detail. In addition the possible future Mg implants that might treat problems concerning to urology and gynecology are reviewed. © 2020
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    Recent progress in equal channel angular pressing of magnesium alloys starting from Segal's idea to advancements till date – A review
    (KeAi Publishing Communications Ltd., 2023) Sekar, S.; Naik, G.M.; Narendranath, S.; Desai, V.
    Lightweight materials with high strength and ductility have immense potential in revolutionizing the automobile, aerospace, bio-medical and defence sector. Magnesium and its alloys are the candidates that are best suited for application in above mentioned sectors. However, achieving combination of properties such as high strength, good ductility and relatively better corrosion resistance in Mg alloys is still challenging. Indeed, equal channel angular pressing (ECAP) is one of the promising techniques that simultaneously enhances the mechanical properties and corrosion behaviour. In this review, an effort has been made to address the influence of ECAP on microstructure, mechanical properties, corrosion and galvanic corrosion of magnesium and its alloys. The reason for deviation of Mg alloys from Hall Petch relation is clarified. The necessity of tailoring the microstructure of Mg alloys in order to achieve desired properties is elucidated. In addition, the recommendations and future directions derived from summary and outlook of review are critiqued. © 2022 The Authors
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    Alkyl carboxylates as efficient and green inhibitors of magnesium alloy ze41 corrosion in aqueous salt solution
    (Elsevier Ltd, 2014) Dinodi, N.; Nityananda Shetty, A.
    Long chain alkyl carboxylates like stearate, palmitate and myristate were investigated for their efficiency in inhibiting the corrosion of magnesium alloy ZE41 in an aqueous salt medium containing 0.2M Na2SO4 and 0.1M NaCl. The techniques like potentiodynamic polarization and EIS, along with SEM and EDX analyses were employed. The inhibition was proposed to be the result of adsorption of alkyl carboxylates, which was found to obey the Langmuir adsorption isotherm. The inhibition was assumed to be the outcome of the formation of a compact modified surface film due to the precipitation of adsorbed alkyl carboxylates of magnesium. © 2014 Elsevier Ltd.
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    Nonlinear transmittance and optical power limiting in magnesium ferrite nanoparticles: effects of laser pulsewidth and particle size
    (Royal Society of Chemistry, 2016) Perumbilavil, S.; Sridharan, K.; Abraham, A.R.; Janardhanan, H.P.; Kalarikkal, N.; Philip, R.
    We report comparative measurements of size dependent nonlinear transmission and optical power limiting in nanocrystalline magnesium ferrite (MgFe2O4) particles excited by short (nanosecond) and ultrashort (femtosecond) laser pulses. A standard sol-gel technique is employed to synthesize particles in the size range of 10-50 nm, using polyvinyl alcohol as the chelating agent. The structure and morphology of the samples are studied using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Growth of the particles in time is tracked through Fourier transform infrared spectroscopy. Nonlinear transmission measurements have been carried out using the open aperture Z-scan technique employing 532 nm, 5 nanosecond pulses and 800 nm, 100 femtosecond pulses, respectively. The measured optical nonlinearity is primarily of a reverse saturable absorption (RSA) nature, arising mostly from excited state absorption for nanosecond excitation, and two-photon absorption for femtosecond excitation. The optical limiting efficiency is found to increase with particle size for both cases. The calculated nonlinear parameters indicate that these materials are potential candidates for optical limiting applications. © The Royal Society of Chemistry.
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    Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy
    (Springer New York LLC barbara.b.bertram@gsk.com, 2016) Gopi, K.R.; Shivananda Nayaka, H.S.; Sahu, S.
    Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing. © 2016, ASM International.
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    Source apportionment of PM2.5 particles: Influence of outdoor particles on indoor environment of schools using chemical mass balance
    (AAGR Aerosol and Air Quality Research hhyang@cyut.edu.tw, 2017) Kalaiarasan, G.; Mohan Balakrishnan, R.M.; Sethunath, N.A.; Manoharan, S.
    Children have higher lung function than adults and they spend most of their day time in schools. Also, children studying at schools located in the vicinity of busy roadways are vulnerable to childhood asthma and respiratory disorders. The present study is focused on estimating the sources of PM2.5 particles present in the indoor air quality in schools which are located adjacent to urban and suburban roadways. The indoor PM2.5 samples from all the four schools were collected using fine dust sampler from 8 a.m. to 4 p.m. The sampling was carried out for one complete week during various seasons including both working and non-working days. The chemical compositions of the PM2.5 samples were analyzed for certain elements like Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti, V and Zn using Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and ions like F-, Cl-, NO3-, PO43-, SO42-, K+, Ca2+, Mg2+, NH4+, Na+ using Ion Chromatography (IC). Source apportionment study using Chemical Mass Balance was carried out using the species concentration of the collected samples. The major sources were found to be Paved Road Dust, Soil Dust, Gasoline Vehicle Emissions, Diesel Vehicle Emissions and Marine Source Emissions. Among these, vehicular emissions contribution was found to be higher for the schools located close to roadways rather than the school located at a considerable distance from highway. The difference in source type contribution at each school clearly depicts the difference in nature of location and type of activities in the vicinity of the sampling sites. © Taiwan Association for Aerosol Research.
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    High Thermoelectric Performance of Co-Doped Tin Telluride Due to Synergistic Effect of Magnesium and Indium
    (American Chemical Society service@acs.org, 2017) Bhat, D.K.; Shenoy, U.S.
    Thermoelectric (TE) materials are considered go-to materials lately in addressing the worldwide energy crisis. We report a study on the effect of co-doping of magnesium and indium in lead-free SnTe both experimentally and theoretically. We show how the resonant levels introduced by indium increase the Seebeck coefficient at lower temperatures and how magnesium enhances the Seebeck at higher temperatures by opening the band gap and decreasing the energy difference between the light and heavy hole valence sub-bands. Synergistically, the effects of band engineering lead to the co-doped sample having high thermoelectric figure of merit (ZT) over a wide range of temperature and record a high power factor of ?42 ?W cm-1 K-2 for SnTe based materials. For the very first time we show the effect of site occupied by the dopant on the electronic structure of the material. The resulting high ZT of 1.5 at 840 K makes SnTe a very suitable material for thermoelectric applications. (Graph Presented). © 2017 American Chemical Society.