Showing papers by "U. Kamachi Mudali published in 2018"
TL;DR: In this article, the nano-titania and nano-calcium carbonate at 2% by weight of cement were added to fly ash concrete to increase the pozzolanic activity resulting in faster hydration, early-age strength and long-term compressive and split tensile strength.
56 citations
TL;DR: In this paper, the development of hydroxyapatite (HAP) coating on laser textured metallic implants using electrophoretic deposition was discussed, and the surface roughness of the metallic implants was increased by increase in the overlapping rate.
46 citations
TL;DR: In-situ Raman and X-ray photoelectron spectroscopic studies were performed for the identification of native and corroded surface oxide layers of modified 9Cr-1Mo steel as discussed by the authors.
39 citations
TL;DR: In this paper, anodic electrophoretic deposition of graphene oxide (GO) on 316L SS with pH-dependent microstructures was described, and detailed studies on structural characteristics, thermal stability, and elemental composition of the GO flakes were carried out using advanced characterization techniques.
Abstract: This paper describes anodic electrophoretic deposition of graphene oxide (GO) on 316L SS with pH-dependent microstructures. GO flakes were synthesized by modified Hummers’ method. Detailed studies on structural characteristics, thermal stability, and elemental composition of the GO flakes were carried out using advanced characterization techniques. Results showed successful oxidation and exfoliation forming GO flakes that are hydrophilic in nature. Acidic (pH 3.4) and basic (pH 11) aqueous GO suspensions were prepared, and the zeta potential as well as the average particle size distribution of the suspensions was ascertained. The GO suspensions were exhibiting zeta potential values of −32.9 and −36.8 mV and average particle size of 1–2 µm and 800–900 nm at acidic pH of 3.4 and alkaline pH of 11, respectively. Using anodic electrophoretic deposition (EPD) methods, GO was coated on 316L SS substrate from acidic and alkaline suspension and coatings were characterized. The increased value of ID/IG by Raman spectra analysis, partial restoration of C = C skeleton in the de-convoluted C 1s XPS spectra analysis, and the presence of C–C and C–H stretching bands in ATR-FTIR spectra were correlated with partial reduction of GO during the deposition on 316L SS surface. Though there was no difference in the chemical composition of the coatings formed from the acidic and alkaline pH suspension, atomic force microscopy and field emission scanning electron microscopy characterization showed difference in topography and morphology of the coatings. 316L SS substrates coated with GO in acidic pH showed higher RMS and average roughness and dense agglomerated wrinkled microstructure compared to substrates coated with alkaline pH suspension. Again GO coating from acidic pH suspension showed hydrophobicity. The present study showed that the microstructures of the GO coatings on 316L SS can be tuned by varying the pH of the GO suspension during EPD process.
20 citations
TL;DR: In this article, one-dimensional bioactive glass nanorods (BGNR) of 45S5 composition was synthesized by tuning the parameters of sol-gel process and hybridized with two-dimensional reduced graphene oxide sheets (rGO).
17 citations
TL;DR: It is established that p-PBI resin is a potential candidate material for the recovery of U(VI) and Th(IV) from an aqueous stream, e.g. mine water samples.
Abstract: Four types of polybenzimidazole (PBI)-based polymers ( m -PBI, p -PBI, pyridine-based m -PBI and alkylated m -PBI) have been prepared and characterized. Extraction behaviour of heavy metal ions, viz. U(VI), Th(IV) and Pd(II), with these polymers was investigated. Distribution ratios for the extraction of these metal ions were measured as a function of nitric acid concentration. Extraction data reveal that, in general, p -PBI exhibits a higher distribution ratio for U(VI), Th(IV) and Pd(II) compared with the other polymeric resins evaluated in the present study. Column chromatography experiments were carried out with a solution of U(VI), Th(IV) and Pd(II) in dilute nitric acid media using columns packed with m - and p -PBI polymeric material for understanding the sorption and elution behaviour. The p -PBI-based resin has shown higher palladium sorption capacity (1.8 mmol g −1 ). The studies also established that p -PBI resin is a potential candidate material for the recovery of U(VI) and Th(IV) (capacity 0.22 mmol g −1 and 0.13 mmol g −1 ) from an aqueous stream, e.g. mine water samples.
16 citations
TL;DR: In this article, the corrosion behavior of the candidate materials of stainless steel (SS) 410, 2.25Cr-1Mo and 9Cr- 1Mo steels was investigated in molten LiCl-KCl-UCl3 salt by thermogravimetric analysis under inert and reactive atmospheres at 500 and 600
13 citations
TL;DR: 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 as discussed by the authors.
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.
13 citations
TL;DR: The phase stability and durability of YSZ coating in providing corrosion resistance and protection to high-density graphite (HDG) for high-temperature molten salt applications were investigated in this paper.
Abstract: The high temperature corrosion behaviour of yttria stabilized zirconia (YSZ) coated high density graphite (HDG) with and without SiC interlayer was evaluated in LiCl–KCl molten salt at 600 °C. The YSZ coated HDG samples without interlayer were tested for 50, 250, 1000 and 2000 h and the YSZ coated HDG samples with SiC interlayer were studied for 50, 500, 2000 and 3500 h durations. Characterisation of the corrosion tested samples revealed no delamination or failure of the YSZ coating in both the cases, and insignificant weight gain was observed in all the tested samples in the molten salt. The lamellar morphology of the plasma spray coating was intact even after exposure to molten salt for long duration, implying no corrosion attack of the coating and HDG in the molten salt. SEM cross-section examination confirmed neither coating degradation, nor penetration of molten salt into the HDG substrate. X-ray diffraction and Laser Raman spectroscopic analyses ascertained that no phase change occurred in YSZ after the long exposure in molten salt. Present study confirmed the phase stability and durability of YSZ coating in providing corrosion resistance and protection to HDG for high-temperature molten salt applications.
11 citations
TL;DR: In this paper, the authors showed that Zirconium exhibited pseudo-passive behavior in fluorinated nitric acid (11.5 m HNO3 + 0.05 m NaF) for 240h and the calculated thickness of the film based on the capacitance value was about 4.5 nm.
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.
11 citations
TL;DR: In this article, a method for enhancing the biofouling resistance of cupronickel (90-10 Cu-Ni) alloy by surface modification involving sand blasting, pickling and coating with silane was proposed.
Abstract: The paper focuses on a novel method for enhancing the biofouling resistance of cupronickel (90-10 Cu-Ni) alloy by surface modification involving sand blasting, pickling and coating with silane. After optimizing the experimental parameters for polishing, pickling and sandblasting in order to develop a hydrophobic surface, the surface morphology and the wetting properties of the modified surface were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and contact angle meter. The enhancement in resistance to bacterial adhesion was demonstrated by adhesion studies on Pseudomonas sp., the major biofilm former in marine environment. The silane based coating on the sand blasted surface of cupronickel alloy brought about two order reduction of bacterial attachment as compared to the control sample.
TL;DR: In this paper, the polynomial expressions of enthalpy increments obtained for rare earth hafnate in the temperature range 298-1700 K were obtained by using the inverse drop method by using a high-temperature differential calorimeter.
Abstract: Compounds of the general formula RE2O3·2HfO2 with RE = Sm, Eu, Gd, Dy, etc., are considered potential candidate materials for use in the control rods of future nuclear reactors. Sm2O3·2HfO2, Eu2O3·2HfO2, and Dy2O3·2HfO2 were prepared by solid-state route and characterized by XRD technique. Enthalpy increment measurements have been carried out on these compounds in the temperature range 730–1679 K by inverse drop method by using a high-temperature differential calorimeter. From the enthalpy values, other thermodynamic functions, namely heat capacity, entropy, and Gibbs energy functions, were computed. The polynomial expressions of enthalpy increments obtained for rare earth hafnate in the temperature range 298–1700 K is given as:
$$\begin{aligned} & H_{\text{T}}^{0} - H_{298}^{0} /{\text{J mol}}^{ - 1} = 259.890\;T + 21.610 \times 10^{ - 3} \;T^{2} + 32.389 \times 10^{5} \;T^{ - 1} -90{,}271{-\!\!-}\left( {{\text{Sm}}_{2} {\text{O}}_{3} \cdot2{\text{HfO}}_{2} } \right) \\ & H_{\text{T}}^{0} - H_{298}^{0} /{\text{J}}\;{\text{mol}}^{ - 1} = 261.134\;T + \, 22.273 \times 10^{ - 3} \;T^{2} + 25.988 \times 10^{5} \;T^{ - 1} -88{,}553{-\!\!-}\left( {{\text{Eu}}_{2} {\text{O}}_{3} \cdot2{\text{HfO}}_{2} } \right) \\ & H_{\text{T}}^{0} - H_{298}^{0} /{\text{J}}\;{\text{mol}}^{ - 1} = 255.016\;T + 18.030 \times 10^{ - 3} \;T^{2} + 29.332 \times 10^{5} \;T^{ - 1} -87{,}474{-\!\!-}\left( {{\text{Dy}}_{2} {\text{O}}_{3} \cdot2{\text{HfO}}_{2} } \right) \\ \end{aligned}$$
TL;DR: Alumina coating, with high electrical resistivity, has been proposed over Inconel 600 rings for application in fission chamber neutron detectors, operating at 923 K in fast breeder reactor as mentioned in this paper.
Abstract: Alumina coating, with high electrical resistivity, has been proposed over Inconel 600 rings for application in fission chamber neutron detectors, operating at 923 K in fast breeder reactor. For imp...
TL;DR: Diluent degradation products in gamma radiolyzed Plutonium URanium Extraction (PUREX) solvent were characterized, under the conditions similar to those prevailing in the hot cell for reprocessing as mentioned in this paper.
Abstract: Diluent degradation products in gamma radiolyzed Plutonium URanium Extraction (PUREX) solvent were characterized, under the conditions similar to those prevailing in the hot cell for reprocessing. ...
TL;DR: Mesoporous MnCO3 was synthesised by a co-precipitation method using MnSO4 and (NH4)HCO3 as manganese and carbonate source, respectively and exhibited good rate capability, high reversibility and cyclic stability over 1000 cycles.
Abstract: We report a rapid and facile synthesis of MnCO3 with uniform mesopores for supercapacitor applications. Mesoporous MnCO3 was synthesised by a co-precipitation method using MnSO4 and (NH4)HCO3 as manganese and carbonate source, respectively. Powder X-ray diffraction study confirmed the formation of rhodochrosite phase of MnCO3. X-ray photoelectron spectroscopic study ascertained the oxidation state of Mn as 2+ in MnCO3. Scanning and Transmission electron microscopic studies revealed that nanograins of size less than 10 nm agglomerated into submicron sized spherical particles of MnCO3. N2 sorption studies displayed a typical type-IV isotherm with H2 hysteresis, demonstrating mesoporosity of as-prepared MnCO3. Furthermore, the mesoporous MnCO3 particles were evaluated for their capacitance properties by cyclic voltammetry and galvanostatic charge-discharge cycling in aqueous 0.1 M Mg(ClO4)2 electrolyte. The fabricated mesoporous MnCO3 electrodes delivered a specific capacitance of 144 F g-1 at a current density of 0.34 A g-1. It also exhibited good rate capability, high reversibility and cyclic stability over 1000 cycles.
TL;DR: In this article, the effect of surface-modified fly ash concrete through the addition of nano-TiO2 and CaCO3 against sulphate attack and calcium leaching was investigated, where four types of concrete mix were designed and casted as cylindrical concrete blocks.
Abstract: The global warming gas, CO2, is liberated when clay and limestone are crumbled for the production of cement. About 8–10% of the universal CO2 emissions are emitting from the cement factories. With concerns arising over environmental issues associated with cement usage, it is the need of the hour to reduce its consumption. Fly ash, the waste material from thermal power plants, is a widely used supplementary cementitious material that extends the life of the concrete structures. The intervening of nanotechnology into construction industry has provided wider opportunities to better the performance of concrete in rigorous conditions, especially acids and alkali environment. This work endeavours to study the effect of surface-modified fly ash concrete through the addition of nanoparticles against sulphate attack and calcium leaching. Nanophase modification was performed by integrating nano-TiO2 and CaCO3 for enhanced durability and corrosion resistance. Four types of concrete mix, namely fly ash concrete (FA), FA with 2% TiO2 nanoparticles (FAT), FA with 2% CaCO3 nanoparticles and FA with 2% TiO2:CaCO3 (FATC) nanoparticles, were designed and casted as cylindrical concrete blocks. The specimens were immersed in 1% sulphuric acid solution and sea water to study the resistance of concrete against sulphate attack and calcium leaching, respectively. Results showed that nanophase modification of fly ash concrete improved the resistance to sulphuric acid attack and calcium leaching. Among the nanophase-modified specimens, FAT and FATC specimens showed superior performance.
TL;DR: In this article, the degradation behaviour of transition metal nitride films with reactive magnetron sputtering on high-density graphite and niobium (Nb) crucibles with molten uranium was investigated.
Abstract: Transition metal nitride films have a unique combination of properties and finds application as protective coatings. The present paper deals with the degradation behaviour of HfN coating deposited by reactive magnetron sputtering on high-density (HD) graphite and niobium (Nb) crucibles with molten uranium. Uranium melting experiments were carried out with uranium shots placed in HfN-coated crucibles and heated to 1573 K under ultra high purity argon gas for 25 min. The study showed delamination of HfN coating deposited on Nb and HD graphite crucibles. The degradation of HfN-coated niobium was attributed to partial melting and surface oxidation. Uranium melting of HfN-coated HD graphite crucible led to coating spallation that could be attributed to thermal expansion mismatch and also resulted in the formation of uranium–carbon mixture of unusual morphology. The paper highlights the results of the present investigation.
TL;DR: In this paper, the authors evaluated the physical properties such as density, viscosity, and interfacial tension of 1.1 M DHOA/n-dodecane as a function of temperature and duration of heating.
Abstract: Abstract N,N-dihexyloctanamide (DHOA) is being considered as a promising extractant in the aqueous reprocessing of spent nuclear fuels. In view of rise in temperature of the solvent during reprocessing of fast reactor fuel, the present study aimed at evaluating the physical properties such as density, viscosity, and interfacial tension and Pu(IV) extraction behavior in 1.1 M DHOA/n-dodecane as a function of temperature and duration of heating. The influence of nitric acid in altering the physical properties with respect to temperature was evaluated. Physical properties and extraction behavior of the solvent changed to a remarkable extent with temperature. Quantitative amount of Pu(IV) could be back-extracted from loaded, solvent in three contacts at 313 K. FT-IR studies were carried out to evaluate the thermal stability of the solvent. Thus, the performance of the solvent, 1.1 M DHOA/n-dodecane is satisfactory at higher temperatures also.
TL;DR: In this article, the zinc oxide (ZnO) nano structures on titanium have been synthesized by a simple wet chemical method with the formation of nano structures under mild conditions in the absence of any seed, catalysts or surfactants.
Abstract: Titanium is known for excellent corrosion resistance for the sea water-cooled condenser material but susceptible to biofilm formation and bio-fouling, leading to deterioration in the heat transfer properties. Present study involves an attempt to use nanotechnology based surface modification of titanium to improve the antibacterial property and thereby resistance to biofouling. Synthesis of zinc oxide (ZnO) nano structures on Ti by a simple wet chemical method was achieved with the formation of nano structures under mild conditions in the absence of any seed, catalysts or surfactants. These nano structures were characterized using Field emission scanning electron microscopy which showed nano needle like structures. Grazing Incidence X-ray diffraction pattern showed a Wurtzite phase ZnO with strong peak at (002), indicating nano structure growth along the c-axis. Laser Raman Spectroscopy studies also confirmed the presence of Wurtzite crystals of ZnO nano structures. The antibacterial activity of these ZnO coatings with respect to gram negative bacteria, Pseudomonas aeruginosa sp. was investigated qualitatively and quantitatively. Epifluorescence microscopy and total viable count analysis have confirmed that ZnO nanostructures on the titanium substrate provided antibacterial activity against Pseudomonas aeruginosa.
TL;DR: In this paper, the authors proposed a partially stabilised zirconia (PSZ) coatings for the molten salt environment at high temperature as they showed good corrosion resistance.
Abstract: Plasma-sprayed partially stabilised zirconia (PSZ) coatings are being proposed for the molten salt environment at high temperature as they showed good corrosion resistance. In the present study, gr...
TL;DR: In this paper, the corrosion behavior of INCONEL Alloys 600 (UNS N06600), 625, 690, and 690 was investigated under Cl2 bubbling.
Abstract: Pyrochemical reprocessing utilizing molten chloride salt medium has been considered as one of the best options for the reprocessing of spent metallic fuels from future fast breeder reactors. Purification of molten salt is an important step where chlorine gas is purged in molten LiCl-KCl eutectic salt at 873 K. Materials for manufacturing of vessels and components for salt purification system should possess high corrosion resistance under such a highly corrosive environment. The present paper discusses the corrosion behavior of INCONEL Alloys 600 (UNS N06600), 625 (UNS N06625), and 690 (UNS N06690) and their welds in molten LiCl-KCl eutectic salt at 873 K under Cl2 bubbling. Characterization of the exposed surfaces was performed by using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy, and glancing incidence x-ray diffraction. The results of the present study indicated that N06600 and N06690 offered better corrosion resistance compared to N06625. Surface morphology of the exposed b...
TL;DR: In this paper, the effect of oxidizing ions present in simulated high level liquid waste (HLW) on the corrosion behavior of solution annealed, sensitized 304L SS and 304l SS weld was investigated by potentiodynamic anodic polarization technique.
Abstract: The effect of oxidizing ions present in simulated high level liquid waste (HLW) on the corrosion behaviour of solution annealed, sensitized 304L SS and 304L SS weld was investigated by potentiodynamic anodic polarization technique. Potentiodynamic anodic polarization studies showed a higher passivation current density and increased corrosion potential (Ecorr) in simulated HLW when compared to 3 M HNO3 in all the specimen mentioned above. In addition, the effect of microstructure of thermally aged 304L SS weld on the corrosion behavior was investigated in simulated HLW medium. Thermal ageing of 304L SS weld was carried out at 1023 K/100 h. Optical microscopy confirmed step microstructure for solution annealed and ditch microstructure for the sensitized specimens. The weld region was found to possess delta-ferrite distributed in austenite matrix. Thermal ageing resulted in fragmentation/dissolution of delta-ferrite and transformation of delta-ferrite to carbides and sigma phases. The thermally aged 304L SS weld specimen showed only a marginal decrease in corrosion resistance in simulated HLW when compared to the 304L SS weld.
TL;DR: In this paper, a detonation gun (D-gun) spray coating was applied on the spent mixed oxide nuclear fuels with high plutonium content from prototype fast breeder reactor to improve corrosion resistance.
Abstract: Electro-oxidative dissolution of the spent mixed oxide nuclear fuels with high plutonium content from prototype fast breeder reactor need to be carried out in boiling 11.5 M HNO3. Nickel electrode connectors employed in the electrolyser of the dissolver should possess good corrosion resistance as well as good electrical conductivity. Alumina coating deposited on Ni by plasma spraying was evaluated by electrochemical polarization and impedance experiments in 11.5 M HNO3 at room temperature. In order to improve corrosion resistance, alumina coating relatively denser than plasma spray coating was deposited over Ni by detonation gun (D-gun) spray coating. This alumina coating exhibited a high insulation resistance and the weight loss of alumina coated Ni disc was only 3% compared to 29% for bare Ni disc sample when exposed to the vapour of 11.5 M boiling HNO3 for 12 h. However, coating delamination observed at the alumina/bond coat interface was attributed to the penetration of HNO3 vapour through the pores in the coating. Since alumina coating deposited by D-gun technique over Ni was also found to offer only short-term protection against corrosion due to HNO3 vapour, monolithic dense alumina sleeve fabricated through powder metallurgy route was recommended instead of coating, for better corrosion protection in HNO3 vapour compared to thermal spray coating.