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Item Recent advances in aluminizing of mild steel plates(Elsevier, 2024) Huilgol, P.; Bhat Panemangalore, D.; Bhat, K.U.; Bharadishettar, N.Aluminizing of steels is a surface modification method wherein the steel surface is subjected to thermo-chemical diffusion treatment at temperatures in the range of 700–1000°C. During the treatment, aluminium will diffuse into the surface and subsurface of the steel substrate, producing various aluminide phases. By controlling the process parameters, the type and quantity of aluminide phases can be controlled. The aluminides present beneficial properties, like increased strength and hardness, oxidation resistance, erosion resistance, abrasion resistance, etc. Hence, they are a better candidate material for designing the materials against scratch, erosion, fatigue, wear, oxidation, and corrosion. Many processing routes are available for aluminizing of steels and this entry reviews recent developments in the aluminising of mild steels. © 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Item Hot dip aluminizing of 9Cr-1Mo steels and their heat treatment(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Patel, J.; Huilgol, P.; Jamnapura, N.; Bhat, K.Coupons of 9Cr-1Mo steels of type SA 387 Grade 9 class 2 were hot dip aluminized using Al bath at a temperature of 700 °C for 30 seconds. The samples were further heat treated at 750 °C for durations of 1, 3 and 5 hours, respectively. The samples were characterized using X-ray diffractometry, scanning electron microscopy and energy dispersive spectroscopy. The investigation showed that as coated samples contain an aluminum top coat, a reaction layer and substrate material. Within the reaction layer, two distinct regions corresponding to Fe2Al5 and Fe4Al13 were identified. Chromium up to 2 at% was observed. After heat treatment Al coat was not existing. Two distinct layers, corresponding to a thick Fe2Al5 and a thin FeAl were observed at shorter heat treatment duration. Under longer heat treatment durations, multiple phases, namely, Fe2Al5, FeAl, Fe3Al and solid solution of Al in Fe were observed. © (2015) Trans Tech Publications, Switzerland.Item Hot-dip Aluminizing of Low Carbon Steel in Al & Al-5wt % Cr Baths(Elsevier Ltd, 2018) Huilgol, P.; Bhat, K.U.; Udupa, K.R.Hot dip aluminizing of low carbon steel is carried out in pure aluminium bath and Al-5wt% Cr bath. The coating is characterized by scanning electron microscopy and chemical composition of the coating is analysed by EDS (energy dispersive spectroscopy) attached to SEM. The coating consists of three regions, viz., outer aluminium topcoat, intermediate Fe-Al intermetallics layer and the base alloy. The intermetallics layer consists of FeAl3 and Fe2Al5 phases. Fe2Al5 is the major phase in the intermetallics layer. The growth kinetics of intermetallics layer is parabolic in nature implying that it is diffusion controlled. Addition of chromium forms Al7Cr dispersed intermetallics phases in the aluminium topcoat. Addition of chromium has no influence on the morphology of the intermetallics layer. Scratch resistance of the coating is carried out to evaluate the scratch hardness of the coating. Chromium addition improves scratch resistance of the coating. © 2018 Elsevier Ltd.Item Microstructure and Impression Creep Behavior of Al Based Surface Composite Produced by Friction Stir Processing(Springer India sanjiv.goswami@springer.co.in, 2016) Bhat, K.U.; Udupa, R.K.; Sampath, S.; Huilgol, P.Al–Fe surface composites were prepared through friction stir processing route by using commercial pure aluminium sheet and iron powder. Friction stir processing was done with a tool made up of high speed steel having a 3 mm pin at the tip. Microstructural features of the friction stir nuggets were characterized by using X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. Creep behaviour of the friction stir zone was studied using impression creep techniques. Impression creep experiments were done on substrate aluminium and friction stir region. The results show that the surface of Al substrate is converted into a composite, consisting of Al, Fe powders and iron aluminides. The aluminium grain size is drastically reduced, with a large fraction of crystallites having size in the range of 70 nm. Fe particle size was reduced drastically resulting in interparticle spacing in the range of 500 nm. Dislocation density was drastically increased. Impression creep experiments indicated that friction stirred region shows marginally lower activation energy compared to the base metal. This is attributed to the metastability in the structure in the form of extremely fine grain size and high dislocation density. Because of the combined effect, creep in stir zone takes place with a smaller activation energy compared to creep in base aluminium. © 2016, The Indian Institute of Metals - IIM.Item Preparation of gold nanoparticles by novel bacterial exopolysaccharide for antibiotic delivery(Elsevier Inc. usjcs@elsevier.com, 2016) Pradeepa, n.; Vidya, S.M.; Mutalik, S.; Bhat, K.U.; Huilgol, P.; Avadhani, K.Aim To develop potent drug delivery agents to treat multidrug resistant (MDR) bacterial infections using gold nanoparticles (AuNPs) prepared by bacterial exopolysaccharide (EPS) being a reducing and stabilizing agent. Methods Gold nanoparticles were prepared by EPS, extracted from Lactobacillus plantarum. AuNPs were characterized by UV-visible spectrophotometer, transmission electron microscope (TEM), zeta potential and Fourier transform infrared spectroscopy. Antibiotics used for functionalization of AuNPs were levofloxacin, cefotaxime, ceftriaxone and ciprofloxacin. The resulted functionalized AuNPs were tested against various MDR bacteria by employing different assays such as well diffusion assay, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time killing assay. Key findings The nanostructures exhibited excellent bactericidal activity and reduced MIC and MBC against MDR Gram positive and Gram negative bacteria compared to free drugs. Escherichia coli was the most susceptible MDR bacteria followed by Klebsiella pneumoniae and Staphylococcus aureus. TEM results revealed that the bactericidal activity of nanostructures could be mediated by penetration, loss of cytoplasmic contents and cell lysis. Significance Antibiotic functionalized nanostructures were more potent than free drugs and could be used as potent drug delivery vehicles. © 2016 Elsevier Inc. All rights reserved.Item Effect of current density during electrodeposition on microstructure and hardness of textured Cu coating in the application of antimicrobial Al touch surface(Elsevier Ltd, 2016) Augustin, A.; Huilgol, P.; Udupa, K.R.; Bhat, K.U.Copper is a well proven antimicrobial material which can be used in the form of a coating on the touch surfaces. Those coating can offer a good service as touch surface for very long time if only they possess good mechanical properties like scratch resistance and microhardness. In the present work the above mentioned mechanical properties were determined on the electrodeposited copper thin film; deposited on double zincated aluminium. During deposition, current density was varied from 2 A dm?2 to 10 A dm?2, to produce crystallite size in the range of 33.5 nm to 66 nm. The crystallite size was calculated from the X-ray peak broadening (Scherrer?s formula) which were later confirmed by TEM micrographs. The scratch hardness and microhardness of the coating were measured and correlated with the crystallite size in the copper coating. Both characteristic values were found to increase with the reduction in crystallite size. Reduced crystallite size (Hall–Petch effect) and preferred growth of copper films along (111) plane play a significant role on the increase in the hardness of the coating. Further, TEM analysis reveals the presence of nano-twins in the film deposited at higher current density, which contributed to a large extent to the sharp increase of coating hardness compared to the mechanism of Hall–Petch effect. The antimicrobial ability of the coated sample has been evaluated against Escherichia coli bacteria and which is compared with that of commercially available bulk copper using the colony count method. 94% of E. coli cells were died after six hours of exposure to the copper coated surface. The morphology of the copper treated cells was studied using SEM. © 2016 Elsevier LtdItem Microstructural characterization of low temperature plasma-nitrided 316L stainless steel surface with prior severe shot peening(Elsevier Ltd, 2016) Jayalakshmi, M.; Huilgol, P.; Badekai Ramachandra, B.R.; Bhat, K.U.Surface nanocrystallization by severe deformation has proven beneficial as pre-treatment to plasma nitriding. It aids in achieving thicker nitride layers at lower temperatures thus making the process more economical. In austenitic stainless steels, severe deformation leads to formation of strain induced martensite on the surface while plasma nitriding alone forms expanded austenite. However, structural characteristics of surface layer of pre-deformed steel after plasma nitriding is still a matter of debate. In present study, 316L stainless steel was subjected to severe shot peening: followed by plasma nitriding at 400 °C for 4 h. Characteristics of sample surface before and after treatment were analyzed by scanning electron microscopy, X-ray diffractometry and transmission electron microscopy techniques. Results showed that, this duplex treatment leads to formation of about 45 ?m thick nitride layer; without CrN precipitation. This is significantly high compared to reported data considering the temperature and duration of nitriding treatment employed. Selected area electron diffraction pattern from topmost surface confirmed the co-existence of austenite and martensite while subsurface layer was predominantly consisting of lath martensite. This indicates that major phase in the nitrided layer is martensitic in nature and nitrogen supersaturation leads to transformation of small fraction of martensite to expanded austenite. © 2016 Elsevier LtdItem Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel(University of Science and Technology Beijing, 2018) Huilgol, P.; Rajendra Udupa, K.; Udaya Bhat, K.Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.Item Insights into formation of gradient nanostructured (GNS) layer and deformation induced martensite in AISI 316 stainless steel subjected to severe shot peening(Elsevier B.V., 2018) Jayalakshmi, M.; Huilgol, P.; Badekai Ramachandra, B.R.; Udaya Bhat, K.Severe peening is a well-accepted top-down approach to engender surface nanocrystallization in austenitic stainless steels. In the present study, AISI 316 grade austenitic stainless steel is subjected to severe peening through air blast shot peening technique. Study is aimed at analyzing the microstructural features of the peened layer and deformation induced martensite through transmission electron microscopy technique. Gradient nanostructured (GNS) layer formed as a result of high strain rate, multi-directional deformation during severe peening found to extend to about 500 ?m from the surface. Nucleation of deformation induced martensite is not limited to shear band intersections as affirmed by the published literature related to severe peening. It is observed to nucleate at multiple locations in the austenite matrix. Martensite units thus formed, coalesce with each other to form continuous layer of lath martensite layer at about 15–20 ?m from the surface. Upon further deformation, lath morphology transforms to dislocation cell-type; resulting in fine martensite crystallites at the topmost layer of the peened surface. © 2018 Elsevier B.V.Item T4-like Escherichia coli phages from the environment carry blaCTX-M(John Wiley and Sons Inc, 2018) Mohan Raj, J.R.; Vittal, R.; Huilgol, P.; Bhat, U.; Karunasagar, I.The resistance determinant blaCTX-M has many variants and has been the most commonly reported gene in clinical isolates of extended spectrum beta-lactamase producing Escherichia coli. Phages have been speculated as potential reservoirs of resistance genes and efficient vehicles for horizontal gene transfer. The objective of the study was to determine the prevalence and characterize bacteriophages that harbour the resistance determinant blaCTX-M. Escherichia coli specific bacteriophages were isolated from 15 samples including soil and water across Mangaluru, India using bacterial hosts that were sensitive to ?-lactams. Phenotypic and genotypic characterization based on plaque morphology, host range, restriction fragment length polymorphism (RFLP), presence of blaCTX-M and electron microscopy was performed. Of 36 phages isolated, seven were positive for Group 1 of blaCTX-M. Based on host range and RFLP pattern, the seven phages were classified into four distinct groups, each harbouring a variant of blaCTX-M. Five phages were T4-like Myoviridae by electron microscopy which was further confirmed by polymerase chain reaction (PCR) for T4 specific gp14. Generalized transduction of the CTX-M gene from these phages was also observed. The high prevalence (20%) of this gene blaCTX-M in the phage pool confirms the significant role of Myoviridae members, specifically T4-like phages in the dissemination of this resistance gene. Significance and Impact of the Study: The CTX-M gene that confers resistance to Beta-lactam class of drugs is widespread and diverse. Understanding mechanisms of antimicrobial resistance transfer is a key to devise methods for controlling it. Few studies indicate that bacteriophages are involved in the transfer of this gene but the type of phages involved and the degree of involvement remains to be explored. Our work has been able to identify the class of phages and the magnitude of involvement in the dissemination of this gene. © 2018 The Society for Applied Microbiology