Sudagar Jothi
VIT University, Physics, Faculty Member
- Dr. J. Sudagar is a Senior Assistant Professor in the Department of Physics at VIT-AP University, Amaravati, Andhra P... moreDr. J. Sudagar is a Senior Assistant Professor in the Department of Physics at VIT-AP University, Amaravati, Andhra Pradesh, India. He had post-doctoral research experience from Indian Institute of Technology Madras, India, and had an India-China Cultural Exchange Ph.D. Scholarship Student with research interests in Corrosion Science, Surface Coatings, Polymer-derived Ceramics, Lightweight-metal alloys and has published 24 SCI papers in these fields based on demonstrated research excellence and accomplishment.edit
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ABSTRACT A vanadium-based conversion coating is proposed as an effective pretreatment for electroless Ni–P deposition on AZ91D magnesium alloy. The magnesium alloy substrate was immersed in a NaVO3 solution with various parameters such as... more
ABSTRACT A vanadium-based conversion coating is proposed as an effective pretreatment for electroless Ni–P deposition on AZ91D magnesium alloy. The magnesium alloy substrate was immersed in a NaVO3 solution with various parameters such as the vanadium concentration, immersion time and bath temperature being varied. The results reveal the quality and corrosion protection performance of the coating increases with increasing treatment time up to a limit. However, excess treatment time induces the formation of cracks in the coating layer, leading to reduced corrosion resistance of the conversion coating. Increasing bath temperature decreases the crack density and increases the thickness of the conversion layer. Electrochemical polarisation results showed that the vanadium treatment in a bath containing NaVO3 of concentration 30 g L21 at 80uC for 15–20 min gives good corrosion resistance. This optimum vanadium treatment was used as a pretreatment for the subsequent electroless Ni–P deposit and it had good passive parameters, showing better corrosion protection on AZ91D substrate than a chromium based treatment.
Research Interests: Materials Engineering, Materials Science, Surface Science, Thin Films and Coatings, Corrosion Science, and 9 moreMagnesium Corrosion, Magnesium, Conversion coating and electroplating technologies, Magnesium Alloys, Vanadium oxide, Design and development of high performance magnesium alloys, Electroless Nickel, Vanadium, and Electroless Metallic Coatings
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ABSTRACT In this paper, the effects of two different types of surfactants on the properties of Ni–P–TiO 2 coating on low carbon steel substrate were investigated. Sodium dodecyl sulphate (SDS) — anionic surfactant and dodecyl trimethyl... more
ABSTRACT In this paper, the effects of two different types of surfactants on the properties of Ni–P–TiO 2 coating on low carbon steel substrate were investigated. Sodium dodecyl sulphate (SDS) — anionic surfactant and dodecyl trimethyl ammonium bromide (DTAB) — cationic surfactant were used for the deposition. Deposits were characterized by a high resolution scanning electron microscope (HR-SEM), an energy dispersive X-ray spectrometer (EDS), and X-ray diffraction (XRD) to study the surface morphology, composition and crystal structure of the coatings respectively. In addition, the influence of surfactants on the corrosion behaviour of Ni–P–TiO 2 coatings was also examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% sodium chloride solution. The results showed that at an optimum concentration of cationic surfactant DTAB, uniform distribution of TiO 2 particles with no defects was observed. The corrosion properties were improved by the incorporation of TiO 2 particles in the Ni–P matrix. The increase in corrosion resistance of the Ni–P-TiO 2 coatings significantly depends on the surfactant and its concentration.
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ABSTRACT Powder particles of polymer derived SiHfCN(O) ceramics were pulsed electric current sintered at 1300 and 1500 ˚C to produce amorphous and partially crystalline ceramic pellets for corrosion studies in salt (NaCl or Na2SO4) and... more
ABSTRACT Powder particles of polymer derived SiHfCN(O) ceramics were pulsed electric current sintered at 1300 and 1500 ˚C to produce amorphous and partially crystalline ceramic pellets for corrosion studies in salt (NaCl or Na2SO4) and acid (HF) environments. While, sodium dramatically accelerated phase transformation and catalysed the crystallization process, the open porosity acted as the main cause for sodium penetration in these materials. The samples, however, were completely disintegrated during fluoride acid tests. The cristobalite and HfO2 crystalline phases were severely corroded and it was found that the SiC grains were relatively stable in comparison with other phases in the system.
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ABSTRACT Surface-dependent mechanical and corrosion resistance has been enhanced by electroless nickel (EN) deposition on laser surface treated (LST) AZ91D substrate (AZ91D/LST/EN). This proposed method enhanced the surface properties in... more
ABSTRACT Surface-dependent mechanical and corrosion resistance has been enhanced by electroless nickel (EN) deposition on laser surface treated (LST) AZ91D substrate (AZ91D/LST/EN). This proposed method enhanced the surface properties in a better way than conventional LST on EN deposited AZ91D substrate (AZ91D/EN/LST). Microhardness, drysliding wear and electrochemical polarization tests were used to study the hardness, wear and corrosion resistance of these modified surfaces and followed by microstructure, phase composition analysis. The conventional, AZ91D/EN/LST samples produced a relatively smooth, crack-free and hard layer consisting of Ni-Mg intermetallic particles; thereby offered a significant increase in hardness and wear resistance and shortcoming of this method is its significant decrease in corrosion resistance, due to the diffusion of Mg into re-melted layer and the formation of Ni-Mg intermetallic phases. On the other hand, this proposed method AZ91D/LST/EN samples produced an increase in surface hardness and wear resistance and maintains a similar and high corrosion resistance.
Research Interests: Wearable Computing, Corrosion Science, Use Wear Analysis, Corrosion Engineering, Corrosion, and 8 moreMagnesium, Magnesium Alloys, Abrasive wear, Design and development of high performance magnesium alloys, Electroless Metallic Coatings, Laser Surface Treatment, Electroless Nikel, and Optics and Lasers In Engineering
ABSTRACTThe electrochemical decomposition of water is an attractive method, however, the performance of the electrodes and efficiencies are of great concern in its large scale production. In this context, we wish to report here the... more
ABSTRACTThe electrochemical decomposition of water is an attractive method, however, the performance of the electrodes and efficiencies are of great concern in its large scale production. In this context, we wish to report here the superior performance of Ni-multiwalled carbon nanotube composite as cathode in the decomposition of water. The current voltage curves recorded with this electrode in different media showed a significant electrocatalysis in the reduction of hydrogen ion; the background electrolysis is shifted in the anodic direction. The nanocomposite composition has been found to be crucial in the efficient production of hydrogen. A coulombic efficiency of about 68% has been obtained at this electrode with a hydrogen production rate of 130L/m2 d. This electrode is more efficient than the 316L stainless steel (composition in percentage: C 0.019, Cr 17.3, Mo 2.04, Ni 11.3, Mn 1.04, N 0.041, Fe bulk) cathode that produces 10 ml/h at an area of 20 cm2 (5L/m2.h) (2). The results obtained with different electrolytes, performance variation with electrode composition, and current densities will be presented. The trials carried out using solar panel instead of DC power source showed similar hydrogen production rates and efficiencies.
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Corrosion behavior of polymer-derived ceramics (PDCs) was investigated in aqueous hydrofluoric acid (HF) and sodium salts (NaCl or Na2SO4). Two oxides (SiCO and SiCNO-(Hf)) and two non-oxide PDCs (SiCN and SiCN-(B)) were examined in this... more
Corrosion behavior of polymer-derived ceramics (PDCs) was investigated in aqueous hydrofluoric acid (HF) and sodium salts (NaCl or Na2SO4). Two oxides (SiCO and SiCNO-(Hf)) and two non-oxide PDCs (SiCN and SiCN-(B)) were examined in this study. The HF acid corroded the oxide PDCs, whereas non-oxide PDCs resisted acid corrosion. Nevertheless, the degradation is slow in some cases to extend the engineering ceramic materials lifespans. The PDCs composites were hot corroded by NaCl or Na2SO4. The Na-salt attacked the PDCs, producing corrosion layers. The cross-sectional X-ray elemental analysis and microstructure surveillance exhibited that the corroded layers comprised of distinct regions. The corrosion mechanism is discussed in line with the experimental discoveries.
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Influence of surfactants on the corrosion properties of chromium-free electroless nickel deposit were investigated on AZ91D magnesium alloy. The corrosion tests were carried out by immersion test (1 M HCl) and electrochemical polarization... more
Influence of surfactants on the corrosion properties of chromium-free electroless nickel deposit were investigated on AZ91D magnesium alloy. The corrosion tests were carried out by immersion test (1 M HCl) and electrochemical polarization test (3.5 wt% NaCl ). The surfactants in the electroless nickel bath increases the corrosion resistance properties of the deposit on the magnesium alloy. In addition, smoothness and amorphous plus nano-crystalline phase were increased and accounted for the significant corrosion resistance. As a consequence, the corrosion potential moved towards the positive direction and the corrosion current density decreased. The immersion tests also provided the same trend as that of electrochemical polarization test. On the whole, the study concluded that corrosion resistance was enhanced by including a surfactant in the electroless deposits on magnesium alloy.
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ABSTRACT Magnesium and its alloys corrode rapidly in the electrolyte bath. Surfactants while used extensively as surface active agents in the electrolyte bath, have been little studied on magnesium surfaces. The influence of surfactants... more
ABSTRACT Magnesium and its alloys corrode rapidly in the electrolyte bath. Surfactants while used extensively as surface active agents in the electrolyte bath, have been little studied on magnesium surfaces. The influence of surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium lauryl sulfate (SLS) on the surface properties such as roughness, morphology and topography of electroless Ni–P deposits on magnesium alloy was researched. The research reveals that the surfactant solutions has significant influence on the composition of coating, surface roughness and surface morphology. In addition, it has marginal effect on the microhardness. Electroless coatings with addition of surfactants produce a smooth surface and average roughness value of 1.412 �m for CTAB and 1.789 �m for SLS, which are less than the value (2.98 �m) without surfactant addition. There was a significant improvement in the rate of deposition. However, the surfactants influence reached maximum at critical micelle concentration and above this value it gets stabilized. The initial structure appears to be dependent upon the percent occluded surfactants. The surface microstructures are discussed in line with the experimental observations.
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Research Interests: Condensed Matter Physics, Electrochemistry, Corrosion Science, Corrosion Engineering, Literature Review, and 15 moreAluminum, Corrosion and different Protection Methods of Surfaces, Corrosion Protection, Conversion coating and electroplating technologies, Aluminum Alloys, Electroless Nickel, Electroless Metallic Coatings, Electroplating, Electroless Deposition, Corrosion and Cathodic Protection, Electroless Tin, Light Weight Structures, Coating Technology for Metals, Composite Coating, and Electroless Nikel
ABSTRACT The present research uses the safer hydrogen halide to prepare the MgO–MgI2/MgBr2 layers onto AZ91 magnesium alloy in alkaline solution. The water–soluble metal salts (MgI2/MgBr2) were not responsible for the corrosion... more
ABSTRACT The present research uses the safer hydrogen halide to prepare the MgO–MgI2/MgBr2 layers onto AZ91 magnesium alloy in alkaline solution. The water–soluble metal salts (MgI2/MgBr2) were not responsible for the corrosion protection; whereas Mg(OH)2 formed first and then converted to MgO by heat–treatments and this MgO was responsible for the corrosion protection. The electrochemical results showed that the development of MgO mitigated the corrosion process and improved the corrosion resistance. This new treatment was then used as a pre–treatment for further electroless nickel (EN) deposition and it showed the good corrosion current density and better corrosion potential on the magnesium substrate. This new treatment and EN depositions were characterised by XPS and SEM. The electrochemical polarisation and EIS test of these EN depositions were evaluated in 3.5 wt.% NaCl. In addition, pitting behaviour of these EN depositions were evaluated by linear sweep voltammetry test.