LALGUDI VENKATARAMAN RAMANATHAN

LALGUDI VENKATARAMAN RAMANATHAN

(Fonte: Lattes)

ORCID

ScopusID

Google Scholar

Resumo

Possui graduação em Engenharia Metalúrgica pelo Indian Institute of Technology, Madras, na Índia, M.Sc (1974) e Ph.D. (1977) em Ciência e Engenharia da Corrosão pelo Sir John Cass College of Science and Engineering, R.U. Foi Gerente de Pesquisa e Desenvolvimento no Centro de Ciência e Tecnologia de Materiais (CCTM) do Instituto de Pesquisa Energéticas e Nucleares (IPEN) (2001-2005). Foi Gerente Geral do CCTM no IPEN. (2005-2013) É Pesquisador Sénior no CCTM-IPEN. É Consultor da Agência Internacional de Energia Atômica (AIEA) na área de Corrosão de Materiais em Reatores Nucleares de Pesquisa e ?Chief Scientific Investigator? de diversos Projetos Coordenados da AIEA. Atua na área de Engenharia de materiais e Metalurgica, com ênfase em corrosão e degradação de materiais. Desenvolve pesquisa nos temas: Correlaçao-Microestrutura-Corrosão; Corrosão em Temperaturas Elevadas; Revestimentos; Materiais Compósitos; Terras Raras para Proteção de Materiais Metálicos. Recebeu ?Fellow of the Institute of Materials?, R.U. (1989), ?Fellow of the Institute of Corrosion?, R.U. (1989), ?Distinguished Alumnus Award? do Indian Institute of technology, Madras, India (2014). (Texto extraído do Currículo Lattes em 12 nov. 2021)

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 223

Influência do tratamento superficial sobre o comportamento de oxidação do zircônio e zircaloy-4
1986 - COSTA, ISOLDA; RAMANATHAN, LALGUDI V.
Neste trabalho estuda-se a influencia da concentração de fluoretos na solução de tratamento superficial sobre o comportamento de oxidação do zircônio e zircaloy-4, no intervalo de temperatura de 350 a 7600C, através de analise termogravimétrica. Foram utilizadas duas soluções cujas concentrações de acido fluorídrico eram diferentes, sendo medidas as rugosidades das amostras após os tratamentos artificiais. A influencia da concentração do íon fluoreto sobre o comportamento de oxidação e significativa para temperaturas mais elevadas.
Morfologia de filmes finos nanoestruturados de ZnO produzidos pelo método SILAR
2021 - GALEGO, EGUIBERTO; SERNA, MARILENE M.; RAMANATHAN, LALGUDI V.; FARIA JUNIOR, RUBENS N. de
A utilização do ZnO no campo da nanotecnologia é ampla devido a características físicas únicas tais como, banda proibida (~3,37 eV), energia de ligação de éxciton de 60 MeV, atóxico e de baixo custo. A estrutura cristalina hexagonal permite obter uma ampla diversidade de morfologias e isto permite sua utilização em: lasers de UV, cristais piezoeléctricos, sensores químicos, sensores de gás, diodos emissores de luz, foto detectores e células solares. Uma das possíveis morfologia do filme fino de ZnO é um arranjo unidimensional submicrométrico de bastões, nanobastões e nanofios, o qual tem atraído muito interesse devido a alta área superficial e a alta proporção de aspecto, que são nanopartículas com um comprimento muitas vezes maior do que sua largura. Neste trabalho foi estudada a influência dos parâmetros do método de adsorção de camada iônica e reação sucessivas (SILAR) na obtenção de filmes de ZnO nanoestruturados sobre substrato de vidro recoberto com óxido de estanho dopado com flúor (SnO2:F). Na temperatura de 90°C ocorreu a formação de ZnO e o aumento de nanoestruturas formadas. A quantidade de ciclos e responsável pela densidade superficial, o crescimento acelerase após se atingir a densidade superficial critica. O tempo de permanência no banho de nucleação não tem influência significativa, já no banho de crescimento com o aumento do tempo ocorreu coalescimento das nanoestruturas. O uso do cloreto de zinco como precursor no banho de nucleação apresentou crescimento mais lento para concentrações molares baixas, o aumento da concentração molar resultou em filmes porosos. Os resultados obtidos neste estudo mostraram que alterações simples nas variáveis do processo SILAR para obtenção de ZnO permitiram desde a obtenção de nanoestruturas individuais a filmes compactos ou porosos.
IPEN e a nanotecnologia
2020 - LINARDI, MARCELO; LUGAO, ADEMAR B.; OLIVEIRA NETO, ALMIR; NETTO, ANA P.F.A.; FREITAS, ANDERSON Z. de; CARBONARI, ARTUR W.; RODRIGUES, CLAUDIO; VIEIRA, DANIEL P.; ANDRADE, DELVONEI A. de; ZEZELL, DENISE M.; PARRA, DUCLERC F.; FONSECA, EDVALDO R.P. da; GALEGO, EGUIBERTO; MUCCILLO, ELIANA N. dos S.; SANTIAGO, ELISABETE I.; CARVALHO, ELITA F.U. de; BERNARDES, EMERSON S.; MOURA, ESPERIDIANA A.B. de; SPINACE, ESTEVAM V.; FONSECA, FABIO C.; SILVA, FLAVIA R. de O.; COSENTINO, IVANA C.; MENGATTI, JAIR; PERROTTA, JOSE A.; BRESSIANI, JOSE C.; ROGERO, JOSE R.; RAMANATHAN, LALGUDI V.; ROCHA, MARCELO da S.; PIRES, MARIA A.F.; ROSTELATO, MARIA E.C.M.; RIBEIRO, MARTHA S.; COTRIM, MARYCEL E.B.; IGAMI, MERY P.Z.; WETTER, NIKLAUS U.; VIEIRA JUNIOR, NILSON D.; RODRIGUES JUNIOR, ORLANDO; FARIA JUNIOR, RUBENS N. de; SAKATA, SOLANGE K.; BALDOCHI, SONIA L.; LOPES, THIAGO; ROSSI, WAGNER de; CALVO, WILSON A.P.
Coatings for safe long term wet storage of spent Al-clad research reactor fuels
2015 - RAMANATHAN, L.V.; FERNANDES, S.M.C.; CORREA, O.V.; SOUZA, J.A. de; ANTUNES, R.A.; OLIVEIRA, M.C.L. de
Pitting corrosion of the aluminium cladding of spent research reactor (RR) fuels in wet storage has been observed and the use of conversion coatings to protect the cladding was proposed. A coating prepared by conventional chemical processing as opposed to electrochemical processing is the only option due to constraints related to the shape of the fuel and its high radioactivity. Hence, hydrotalcite (HTC) and boehmite were considered. This paper presents: (a) preparation of hydrotalcite (HTC) coatings from different baths followed by post-coating treatments; (b) corrosion behavior of HTC coated AA 6061 alloy; (c) results of field studies in which uncoated and HTC coated AA 6061 alloy coupons and plates, the latter assembled as a dummy fuel element, were exposed to the IEA-R1 reactor spent fuel basin for extended periods. The laboratory and field tests revealed marked improvements in the corrosion resistance of HTC coated specimens, coupons and plates. The mechanism of corrosion protection is presented.
Morphology of nanostructured thin films of ZnO fabricate from SILAR method
2017 - SERNA, MARILENE M.; GALEGO, EGUIBERTO; RAMANATHAN, LALGUDI V.; FARIA, RUBENS N.
The utilization of the ZnO in the nanotechnology is widely spread due to its superior properties, such as wide direct bang gap (~3.37eV), high exciton binding energy of 60 meV, non-toxicity and low cost [1]. The hexagonal crystalline structure allows obtaining a larger diversity morphologies and this allows its utilization in: UV lasers, piezoelectric crystal, chemical sensor, gas sensor, light emitting diode, photo detectors, and solar cells. One such morphology of ZnO thin film is the one-dimensional (1D) sub-micron rods or nanorods and nanowires, which has attracted interest due to a larger surface area and high aspect ratio. In the solar cell the ZnO has been utilized in the electrode for the dye-sensitized cell in substitution of TiO2. In this study, ZnO nanostructured thin films were prepared by successive ionic layer adsorption and reaction (SILAR) on SnO2-coated glass substrates [2]. In this procedure, the substrate is immersed in successive aqueous baths containing zinc nitrate hydrate and/or hexamethylenetetramine, hydrogen peroxide and triethanolamine. The pH solution was adjusted by addiction of ammonium hydroxide. At a low zinc nitrate concentration of 0.01M the surface is formed by individual nucleus. At a concentration of 0.02 M nanorod arrays were shown and this morphology is of special interest for solar cells application, but the deposition time used in this experiment was insufficient to promote the desired thickness. At a higher concentration of 0.03 M rice like branches morphology was observed but nanorods formation in the flowers was also present. The angular petals suggest that the growth was taken on polar face. For DSSCs applications the thin films prepared in 0.02 M solution was found to be the best choice.
Effect of mixed nanocrystalline rare earth oxide coatings on high temperature oxidation of a ferritic stainless steel AISI 409
2019 - RAMANATHAN, LALGUDI V.; FERNANDES, STELA M.C.; CORREA, OLANDIR V.
Rare earths (RE) have been used to improve the high temperature oxidation resistance of chromium dioxide and alumina forming alloys. The RE can be added to the alloy as elements or as oxide to form dispersions. It can also be applied as a RE oxide coating on the surface of the alloy. In this investigation the sol-gel technique was used to prepare sols of the RE oxides as it produces nanocrystalline oxide particles. In an effort to increase further the oxidation resistance of high temperature alloys, optimization of RE oxide additions to the alloy surface was attempted. This paper presents the effect of nanocrystalline oxide gel coatings of CeO2, Nd2O3, Pr2O3, CeO2 + Nd2O3, CeO2 + Pr2O3 and Pr2O3 + Nd2O3 on the oxidation behavior of a ferritic stainless steel AISI 409 at 1000 °C in air using a thermogravimetric balance. The morphology of the pure oxides was studied and the following formats were observed: CeO2 – rods; Nd2O3 – platelets; Pr2O3 – needles; La2O3 – cuboids. The average oxide particle sizes and the average crystallite sizes were also determined. The oxidation rate of the coated steel specimen was significantly less than that of the uncoated steel specimen, due to formation of a fine layer of chromium dioxide at the steel/oxide interface. The oxidation rates of the different REO coated steel specimens varied with the type of REO. The mixed oxide containing Pr2O3 increased significantly the oxidation resistance of the steel. The CeO2 + Nd2O3 mixture did not increase oxidation resistance of the steel further, compared to those with either one of these two rare earth oxides. The differences in the influence of a specific rare earth oxide or a mixture are attributable to differences in the ionic radii of the RE and the morphology as well as the crystallite sizes of the RE oxides.
Effect of oxygen partial pressure on oxidation behavior of ferritic stainless steel AISI 441 at high temperatures
2019 - SALGADO, MARIA de F.; CARVALHO, IURE S.; SANTOS, RAFAEL S.; PORTO, JOÃO A.S.; CORREA, OLANDIR V.; RAMANATHAN, LALGUDI V.; BRANDIM, AYRTON de S.; LINS, VANESSA F.C.
In this investigation the oxidation behavior of AISI 441 stainless steel (SS) in the range from 850 °C to 950 °C was determined during 50 h in two different atmospheres: (a) synthetic air in a tubular oven; (b) argon with 1 ppm of O2 in a thermal balance. The oxidation kinetics was determined from the measured mass change as a function of oxidation time. Examination of the microstructure of the oxides and determination of their chemical composition were performed by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and glancing angle X-ray diffraction (GAXRD). Chemical analyses showed that films formed on the AISI 441 steel surface consisted mostly of chromium oxide but manganese, iron, titanium and silicon oxides were found in the oxidized layer. In synthetic air, the steel oxidation rate increased gradually as the temperature increased, but in the argon atmosphere with 1 ppm of oxygen, the highest oxidation rate was observed at 900 °C and the lowest at 950 °C.
Electrochemical evaluation of the AISI 316 stainless steel coated by Nb2O5 thin films
2018 - PIERETTI, EURICO F.; CORREA, OLANDIR V.; PILLIS, MARINA F.; RAMANATHAN, LALGUDI V.
Great number of metallic engineering materials form passive films on their surfaces and, therefore, are prone to localized corrosion, usually characterized by the occurrence of pits [1,2]. The improvement of surface properties is a requirement for the metallic components used, for example, in petrochemical industry, in fuel cells, and in nuclear plants. The goal of this work was to investigate the influence of Nb2O5 films deposited by DC magnetron sputtering during 15, 30 and 50 minutes on the electrochemical behavior of the AISI 316 austenitic stainless steel. The corrosion resistance was evaluated by monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization (LP) on an electrolyte composed of 0.1 M H2SO4 in water at 25 °C. Electrochemical tests showed that the coated specimens presented a more capacitive behavior, and were less susceptible to corrosion than specimens without Nb2O5 coatings. The OCP for coated samples at 50 min had the most inferior values. Similar results were obtained by Pillis et al. [3] for Nb2O5 coatings at 15 min and 30 min in NaCl solution. These results suggest that the obtained films have a protective behavior and can be used to avoid the degradation of the AISI 316 austenitic stainless steel in aggressive environments containing sulfur ions.
Oxidação do aço inoxidável ABNT 5601 - grau 409 em altas temperaturas em atmosfera de argônio
2018 - SERRA, EDIOMAR C.; BRANDIM, AYRTON de S.; SANTOS, DIEGO M. dos; CORREA, OLANDIR V.; RAMANATHAN, LAUGUDI V.; SALGADO, MARIA de F.
Aços inoxidáveis são ligas ferrosas resistentes à corrosão, devido seu alto teor de cromo. São utilizadas em ambientes com gases agressivos em altas temperaturas especialmente na indústria e aplicações tecnológicas. O objetivo desta pesquisa é investigar a cinética de crescimento e a composição de filmes do óxido formados sobre o aço ABNT 5601 - grau 409 entre as temperaturas 850 °C e 950 °C, na atmosfera de argônio, contendo 1ppm de O2. As amostras foram oxidadas em uma termobalança, com sensibilidade de ± 1 μg, por 43,4 horas de exposição. A cinética de crescimento dos filmes de óxidos foi estabelecida medindo-se o ganho de massa por unidade de área versus tempo de oxidação seguindo uma lei parabólica. A microestrutura e a composição química dos óxidos foram analisadas por microscopia eletrônica de varredura, espectroscopia dispersiva de energia. Análises químicas descrevem que os filmes formados sobre o aço ABNT 5601 - grau 409 nas diferentes temperaturas em argônio contêm o cromo como elemento majoritário além do Mn, Fe, Ti. Ao se comparar as taxas de oxidação, nas diferentes temperaturas, entre 850 e 950 °C observa-se que o aço apresenta maior taxa de oxidação a 850 °C e menor a 950 ºC.
Is spent nuclear fuel immune from delayed hydride cracking during dry storage? An IAEA coordinated research project
2018 - COLEMAN, CHRISTOPHER E.; MARKELOV, VLADIMIR A.; ROTH, MARIA; MAKAREVICIUS, VIDAS; HE, ZHANG; CHAKRAVARTTY, JAYANTA K.; ALVAREZ-HOLSTON, ANNA-MARIA; ALI, LIAQAT; RAMANATHAN, LALGUDI; INOZEMTSEV, VICTOR
Delayed hydride cracking (DHC) has been responsible for cracking in zirconium alloy pressure tubes and fuel cladding and is a concern for spent fuel storage. For cracking to start, sufficient hydrogen must be present for hydride to form at a flaw tip and the local tensile stress must be sufficiently large to crack the hydride (a crack will not extend if the threshold in the stress intensity factor, KIH, is not exceeded. A high-temperature limit exists when the yield stress of the cladding alloy becomes too low to crack the hydride. In this paper we describe measurements of KIH and the crack growth rate, V, in unirradiated Zircaloy-4 fuel cladding containing approximately 130 ppm hydrogen in the cold-worked stress–relieved condition representing pressurized water reactors (PWRs) and pressurized heavy-water (PHWR) reactors. Four methods are used to evaluate KIH. The test specimen and fixture used in these methods was the pin-loading tension configuration. The test temperature ranged from 227 to 315 C. The mean value of KIH below 280 C had little temperature dependence; it was about 5.5 MPaHm in the PWR cladding and slightly higher at 7 MPaHm in the PHWR material. At higher test temperatures, KIH increased dramatically to more than 12 MPaHm, whereas the crack growth rate declined toward zero. This behavior suggests that unirradiated Zircaloy-4 fuel cladding is immune from DHC above about 320 C; this temperature may be increased to 360 C by irradiation. The implications for spent fuel storage are that during early storage when the temperatures are high, any flaw will not extend by DHC, whereas at low temperatures, after many years of storage, flaws would have to be very large, approaching through wall, before being extended by DHC. To date, spent nuclear fuel is not known to have failed by DHC during storage, confirming the inference.