| 1. |
- Jayamani, Jayaraj, et al.
(author)
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Corrosion behavior and surface film characterization of TaNbHfZrTi high entropy alloy in aggressive nitric acid medium
- 2017
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In: Intermetallics (Barking). - : Elsevier BV. - 0966-9795 .- 1879-0216. ; 89, s. 123-132
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Journal article (peer-reviewed)abstract
- Corrosion behavior of TaNbHfZrTi high-entropy alloy (HEA) was investigated in nitric and fluorinated nitric acid at ambient (27 °C) and boiling (120 °C) conditions. The alloy passivated spontaneously during potentiodynamic polarization in 11.5 M HNO3 at ambient condition. The corrosion rate was negligible in boiling 11.5 M HNO3, exposed for 240 h. Scanning electron microscopic (SEM) studies did not show any significant corrosion attack. The high corrosion resistance of TaNbHfZrTi HEA was attributed to its single phase bcc structure. X-ray photoelectron spectroscopic (XPS) analysis revealed that the protective passive film formed in boiling nitric acid was predominantly composed of Ta2O5, in contrast to the presence of ZrO2 and HfO2 in air-formed native film. Potentiodynamic polarization studies indicated a pseudo-passivation behavior of the HEA in 11.5 M HNO3 + 0.05 M NaF at ambient condition. In boiling fluorinated nitric acid, SEM images of TaNbHfZrTi HEA displayed a severely corroded morphology indicating the instability of the metal-oxides of the alloying elements. XPS investigations confirmed the presence of ZrF4, ZrOF2 and HfF4 along with un-protective oxides of Ta, Nb and Ti on the film, resulting in decreased corrosion resistance of TaNbHfZrTi HEA in fluorinated nitric acid.
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| 2. |
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| 3. |
- Jayamani, Jayaraj, et al.
(author)
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Corrosion investigations on zircaloy-4 and titanium dissolver materials for MOX fuel dissolution in concentrated nitric acid containing fluoride ions
- 2016
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 473, s. 157-166
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Journal article (peer-reviewed)abstract
- Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a dissolution catalyst in boiling nitric acid for an effective dissolution of the spent fuel. High corrosion rates were obtained for the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. From the obtained corrosion rates it is concluded that CP-Ti is a better dissolver material than Zr-4 for extended service life in boiling 11.5 M HNO3+0.05 M NaF, when complexed with 0.15 M ZrO(NO3)2. XPS analysis confirmed the presence of TiO2 and absence of fluoride on the surface of CP-Ti samples, indicating that effective complexation had occurred in solution leading to passivation of the metal and imparting high corrosion resistance.
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| 4. |
- Jayamani, Jayaraj, et al.
(author)
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Electrochemical Studies and XPS Analysis of the Surface of Zirconium-702 in Concentrated Nitric Acid With and Without Fluoride Ions
- 2018
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In: Transactions of the Indian Institute of Metals. - : Springer Science and Business Media LLC. - 0972-2815 .- 0975-1645. ; 71:3, s. 521-531
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Journal article (peer-reviewed)abstract
- Zirconium exhibited pseudo-passive behavior in fluorinated nitric acid (11.5 M HNO3 + 0.05 M NaF) as the current density measured from the electrochemical studies was several orders higher than the value in fluoride free nitric acid. Impedance studies on zirconium sample exposed in 11.5 M HNO3 for 240 h confirmed the formation of the passive film with high polarization resistance value and the calculated thickness of the film based on the capacitance value was about ~4.5 nm. On the other hand, in fluorinated nitric acid, the charge transfer resistance value associated with the zirconium dissolution process was dominant when compared to that of the film formation. Results of X-ray photoelectron spectroscopic investigations upheld the presence of ZrOF2 and ZrF4 and indicated that the protective oxide layer growth was restricted by the presence of fluoride ions.
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| 5. |
- Jayamani, Jayaraj, et al.
(author)
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Microstructure and Corrosion Behavior of Hf-40 Wt Pct Ti Alloy in Nitric Acid Medium for Reprocessing Applications
- 2016
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In: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 47:9, s. 4393-4403
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Journal article (peer-reviewed)abstract
- The Hf-40 wt pct Ti (Hf-Ti) alloy was developed for neutron poison application in the spent nuclear fuel reprocessing plant. The furnace-cooled Hf-Ti sample exhibited the microstructure comprising equiaxed-α, lamellar-α, and feathery-α. The water-quenched Hf-Ti sample confirmed the presence of lath and internally twinned martensite. In comparison to the furnace-cooled sample, low corrosion current density and passivation current density values obtained for the water-quenched Hf-Ti in 6 M HNO3 at 298 K (25 °C) indicated better passivation ability. The martensitic structure exhibited high hardness (660 HV) and negligible corrosion rate in 6 M nitric acid at 298 K (25 °C). X-ray photoelectron spectroscopic (XPS) analysis confirmed that passivation behavior of this alloy was due to the protective passive film composed of TiO2 and HfO2.
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| 6. |
- Jayamani, Jayaraj, et al.
(author)
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Passive film properties and corrosion behavior of Ni–Nb and Ni–Nb–Ta amorphous ribbons in nitric acid and fluorinated nitric acid environments
- 2015
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In: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 151, s. 318-329
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Journal article (peer-reviewed)abstract
- Potentiodynamic polarization and electrochemical impedance studies revealed the passivation ability and corrosion resistance of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF media at room temperature. Mott–Schottky analysis indicated the formation of n-type semiconducting passive film on these amorphous ribbon samples. Electrochemical parameters such as corrosion current density, passivation current density and donor density confirmed the passive film property of Ni60Nb30Ta10 amorphous ribbon to be superior to that of Ni60Nb40 amorphous ribbon. Weight loss was insignificant in Ni60Nb30Ta10 ribbon exposed to boiling 11.5 M HNO3 for 240 h. XPS analysis revealed that the origin of passivity of Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons in boiling 11.5 M HNO3 was due to the formation of a relatively thick passive film of ≈3 nm enriched with Nb2O5 and a thin passive film of ≈1.5 nm enriched with both Nb2O5 and Ta2O5 on the respective ribbon's surface. In boiling fluorinated nitric acid, Ni60Nb40 ribbon underwent severe dissolution owing to the instability of Nb-oxide passive film and the oxide/metal interface.
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| 7. |
- Poddar, Chiranjit, et al.
(author)
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Oxidation behaviour of Ni60Nb30Ta10 metallic glass below its glass transition temperature
- 2017
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In: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 728, s. 1146-1152
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Journal article (peer-reviewed)abstract
- The oxidation behaviour of Ni60Nb30Ta10 metallic glass in air was investigated below its glass transition temperature (665 °C). The oxidation kinetics followed two-stage parabolic rate law at 450 and 550 °C. The parabolic rate constant increased with increase in the oxidation temperature. At 450 °C, a thin amorphous oxide film consisting predominantly Nb2O5 and Ta2O5, with traces of NiO and Ni2O3 was observed on the surface. At 550 °C, oxidation induced outward diffusion of Ni2+ and Ni3+ ions resulted in a thick oxide layer, containing extensive cubic NiO and monoclinic Ni2O3 with traces of metallic Ni on the surface. Interestingly, at 550 °C the Nb2O5 and Ta2O5 oxides were completely absent on the surface of the oxidised layer.
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| 8. |
- Sardeshpande, Mallika, et al.
(author)
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How People Foraging in Urban Greenspace Can Mobilize Social-Ecological Resilience During Covid-19 and Beyond
- 2021
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In: Frontiers in Sustainable Cities. - : Frontiers Media SA. - 2624-9634. ; 3
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Journal article (peer-reviewed)abstract
- Informal foraging for food and other natural materials in urban greenspaces is an activity undertaken by many across the world. For some, foraging is a necessary means of survival and livelihood, while for others, it provides cultural and recreational opportunities. In the socioeconomic crises induced by Covid-19, foraging can help communities, especially (but not exclusively) vulnerable people, cope with the impacts of lockdowns, and associated economic decline. In the long run, foraging can help improve social–ecological resilience in urban systems, particularly in response to climate, economic, and disease disruptions. First, we elaborate the ways in which urban foraging can provide immediate relief from the shocks to natural, human, social, physical, and financial capital. We then describe how over time, the livelihood, food, and income diversification brought about by foraging can contribute to preparedness for future uncertainties and gradual change. Cities are increasingly becoming home to the majority of humanity, and urban foraging can be one of the pathways that makes cities more liveable, for humans as well as other species we coexist with. Through the capitals framework, we explore the role foraging could play in addressing issues of biodiversity conservation, culture, and education, good governance and social justice, multifunctional greenspace, and sustainable nature-based livelihoods in urban areas.
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| 9. |
- Vetrivendan, E., et al.
(author)
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Argon Shrouded Plasma Spraying of Tantalum over Titanium for Corrosion Protection in Fluorinated Nitric Acid Media
- 2018
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In: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 27:3, s. 512-523
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Journal article (peer-reviewed)abstract
- Argon shrouded plasma spraying (ASPS) was used to deposit a Ta coating on commercially pure Ti (CP-Ti) under inert argon, for dissolver vessel application in the aqueous spent fuels reprocessing plant with high plutonium content. Oxidation during plasma spraying was minimized by shrouding argon system. Porosity and oxide content were controlled by optimizing the spraying parameters, to obtain a uniform and dense Ta coating. The Ta particle temperature and velocity were optimized by judiciously controlling the spray parameters, using a spray diagnostic charge-coupled device camera. The corrosion resistance of the Ta coatings developed by ASPS was investigated by electrochemical studies in 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF. Similarly, the durability of the ASPS Ta coating/substrate was evaluated as per ASTM A262 Practice-C test in boiling nitric acid and fluorinated nitric acid for 240 h. The ASPS Ta coating exhibited higher corrosion resistance than the CP-Ti substrate, as evident from electrochemical studies, and low corrosion rate with excellent coating stability in boiling nitric, and fluorinated nitric acid. The results of the present study revealed that tantalum coating by ASPS is a promising strategy for improving the corrosion resistance in the highly corrosive reprocessing environment.
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| 10. |
- Wilkes, Mark C., et al.
(author)
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Metformin-induced suppression of Nemo-like kinase improves erythropoiesis in preclinical models of Diamond–Blackfan anemia through induction of miR-26a
- 2020
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In: Experimental Hematology. - : Elsevier BV. - 0301-472X. ; 91, s. 65-77
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Journal article (peer-reviewed)abstract
- Diamond–Blackfan anemia (DBA) results from haploinsufficiency of ribosomal protein subunits in hematopoietic progenitors in the earliest stages of committed erythropoiesis. Nemo-like kinase (NLK) is chronically hyperactivated in committed erythroid progenitors and precursors in multiple human and murine models of DBA. Inhibition of NLK activity and suppression of NLK expression both improve erythroid expansion in these models. Metformin is a well-tolerated drug for type 2 diabetes with multiple cellular targets. Here we demonstrate that metformin improves erythropoiesis in human and zebrafish models of DBA. Our data indicate that the effects of metformin on erythroid proliferation and differentiation are mediated by suppression of NLK expression through induction of miR-26a, which recognizes a binding site within the NLK 3′ untranslated region (3′UTR) to facilitate transcript degradation. We propose that induction of miR-26a is a potentially novel approach to treatment of DBA and could improve anemia in DBA patients without the potentially adverse side effects of metformin in a DBA patient population.
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