Faculty Publications
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Item Basic concepts of ultrasound and its effects on fuel processing(Bentham Science Publishers, 2023) Poddar, M.K.; Dikshit, P.K.; Chakma, S.Ultrasound-assisted technique is well-known for process intensification via chemical and physical changes under the influence of acoustic cavitation. Acoustic cavitation is the phenomenon of nucleation, growth, and collapse of cavitation bubbles into a liquid medium that augments the reaction kinetics and the final process yield. This chapter provides a fundamental and detailed understanding of the acoustic cavitation phenomenon. It includes the history and origin of the acoustic wave and its formation, the concept of cavitation bubbles, bubble nucleation and growth mechanism, cavitation effects, and its types. Numerous process parameters, such as applied frequency, intensity, temperature, dissolved gas content, etc., also directly or indirectly influence the cavitation threshold are also highlighted. Further, the ultrasound's physical and chemical effects involving various chemical and biochemical processes to enhance the process yield are also reviewed. The mode of generation of ultrasound energy and its measurement technique are also briefly discussed. Finally, an overview of modeling and simulation of radial motion of single bubble growth, its oscillation in both ultrasound-assisted and conventional systems, and bubble growth rate under rectified diffusion are also discussed in detail. © 2023 Bentham Science Publishers. All rights reserved.Item Studies on the surface oxidation of molten aluminium - Silicon alloys using laser as a probe(Materials Science and Technology, 2007) Udupa, K.R.; Chatterjee, S.An attempt has been made to study for the first time the surface oxidation of molten aluminium-silicon alloy using laser as a probe. A ray of low powered laser was made to fall on freshly prepared surface of molten aluminium-silicon alloy and intensity of the reflected beam was measured using a light detecting resistor (LDR). The change in intensity of reflected laser beam which was due to surface degradation of the molten liquid on oxidation was recorded. Intensity profile which showed variation of intensity (registered as reciprocal of resistance on LDR) with respect to time was generated for pure aluminium melt and molten aluminium-silicon alloy. The intensity profile revealed three regions indicating different mechanisms of oxidation in each stage. It was found that alloying addition influences the nature of intensity profile. Copyright © 2007 MS&T'07®.Item Characterization of ZnO films produced by thermal evaporation and oxidation(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Prabukumar, C.; Jayalakshmi, M.; Bhat, K.ZnO nanostructures such as nanowires and nanorods are beneficial in solar energy harvesting because they provide a structure with a large surface area. Also, they provide a direct pathway to electron transportation, eliminating the scope for grain boundary scattering. In this investigation, thin ZnO films were prepared by thermal evaporation of the Zn metal, which was followed by oxidation. Evaporation parameters and oxidation temperatures were fixed. The oxidation duration was the variable. The effect of oxidation time, on the morphology and structural properties were studied by using scanning electron microscopy and X-ray diffractometry. The study shows that with increase in oxidation time, the morphology changed to nanorods from initial flake morphology. As a function of oxidation time, the crystallinity and texture became more dominant. By using, I-V characteristic curves, it was found that the morphology changes alter the surface electrical conductivity of the prepared ZnO films. © (2015) Trans Tech Publications, Switzerland.Item Sliding of various ductile materials (Al 6061, Al 6082) using pin on disc setup(Elsevier Ltd, 2019) Srinivasula Reddy, I.; Kaliveeran, V.The present study focuses on understanding the variation of coefficient of friction over a period of time. At various sliding cycles, the coefficient of friction was noted from the well-controlled sliding experiments. Friction tests were conducted using Aluminium alloys (Al 6061 and Al 6082) with 10 N constant normal load and at sliding speed of 1.5 m/s. The detailed friction results have been presented and discussed to understand the influence of coefficient of friction on the contact tractions at the interface. The obtained friction results are compared with the results mentioned in literature, where reciprocating sliding experiments were conducted. From this comparison, it is concluded that the formation of oxide and nitride layers are dominant, when the friction tests are conducted using pin on disc setup. © 2019 Elsevier Ltd. All rights reserved.Item Technical aspects of biodiesel and its oxidation stability(2009) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.Biodiesel is a clean burning alternative renewable fuel made from natural renewable sources. It is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, which conform to ASTM specifications for use in diesel engines. Biodiesel present a very promising alternative fuel to diesel oil and properties of this oil offer the advantage of immediate substitution in existing diesel engines with little or no modifications at all. But one of the major technical problems associated with the biodiesel is its susceptibility to oxidation, which can cause the fuel to become acidic and to form insoluble gums and sediments that can plug fuel filters. This is due to the unsaturated fatty acid chains and the presence of the double bond in the molecule, which produce a high level of reactivity with the oxygen, especially when it placed in contact with air. The oxidation of fatty acid chains is a complex process that proceeds by a variety of mechanisms. The various other factors influence the oxidation process of biodiesel includes light, temperature, extraneous materials, peroxides, size of the surface area between biodiesel and air. One of the methods of improving biodiesel oxidative stability includes the deliberate addition of antioxidants or modification of the fatty ester profile. This article discusses the technical aspects of biodiesel and its oxidation stability.Item Progress in Electrochemical Trifluoromethylation Reactions(Wiley-VCH Verlag, 2020) Bhaskaran, R.P.; Babu, B.P.The importance of fluorinated organic molecules in drugs and pharmaceuticals led to the development of several synthetic methods for introducing fluorine into bioactive molecules and trifluoromethylation is one of the key approaches for the same. Electrochemical organic synthesis has emerged as one of the most sustainable, green synthetic strategies in recent years and new developments in electroorganic synthesis also focus on electrochemical trifluoromethylation of organic compounds. A considerable number of reports have appeared in recent literature and this review surveys all the recent developments in electrochemical trifluoromethylation reactions. This highly sustainable trifluoromethylating protocol will emerge further soon and pave the way for more energy-efficient and green protocols. (Figure presented.). © 2020 Wiley-VCH GmbHItem Molybdenum based mixed oxide containing Mo0.65V 0.25W0.10 was investigated for the partial oxidation of methanol. The structural property and catalytic activity of the mixed oxide catalyst was studied by surface area (BET), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infra-red spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal activation of the catalyst resulted increase in the conversion of methanol and the selectivity to formaldehyde. The thermal activation of the MoVW mixed oxide in nitrogen atmospheres induces partial crystallization of a Mo5O14-type oxide at 813 K. The SEM images of the thermally activated catalyst show needle like particles. These particles were agglomerates of platelet-like crystallites of a few hundreds of nanometers in size. SEM and EDX techniques show that the mixed oxide is characterized by an inhomogeneous elemental distribution on the length scale of a few microns. XRD of the thermally activated catalyst showed a nanocrystalline material identified as a mixture of Mo5O 14, MoO3 and MoO2-type MoVW oxides. The catalytic activity of the MoVW mixed oxide show a good conversion of methanol and selectivity to formaldehyde. © 2005 Springer Science+Business Media, Inc.(Partial oxidation of methanol to formaldehyde on molybdenum based mixed oxide catalyst) Badekai Ramachandra, B.; Choi, J.-S.; Choo, K.-Y.; Sung, J.-S.; Song, S.-D.; Kim, T.-H.2005Item Thermal stability and high-temperature wear of Ti-TiN and TiN-CrN nanomultilayer coatings under self-mated conditions(Elsevier Ltd, 2007) Srinivasan, D.; Kulkarni, Trupti.G.; Anand, K.Ti-TiN and TiN-CrN nanomultilayers were thermally stable retaining uniform and sharp layer interfaces up to 24 h at 773 K, without any oxidation or phase transformation accompanying each individual layer. Decreasing the multilayer spacing resulted in an increase in the hardness in both cases. The coating hardness was found to be independent of the substrate type, when applied on HS718, Ti64 and HCHCr substrates. In scratch testing, the multilayers displayed a better resistance to the onset of failure, as compared to the monolayer TiN. The substrate plasticity played an important role in determining the coating failure mode. Self-mated wear tests revealed the CrN-TiN system to exhibit the best wear behaviour, both at room temperature and at 773 K. The Ti-TiN coatings are more accommodative with all three substrates, as compared to TiN-CrN and TiN. © 2006 Elsevier Ltd. All rights reserved.Item Biological treatment of toxic petroleum spent caustic in fluidized bed bioreactor using immobilized cells of thiobacillus RAI01(2008) Potumarthi, R.; Mugeraya, G.; Jetty, A.In the present studies, newly isolated Thiobacillus sp was used for the treatment of synthetic spent sulfide caustic in a laboratory-scale fluidized bed bioreactor. The sulfide oxidation was tested using Ca-alginate immobilized Thiobacillus sp. Initially, response surface methodology was applied for the optimization of four parameters to check the sulfide oxidation efficiency in batch mode. Further, reactor was operated in continuous mode for 51 days at different sulfide loading rates and retention times to test the sulfide oxidation and sulfate and thiosulfate formation. Sulfide conversions in the range of 90-98% were obtained at almost all sulfide loading rates and hydraulic retention times. However, increased loading rates resulted in lower sulfide oxidation capacity. All the experiments were conducted at constant pH of around 6 and temperature of 30?±?5 °C. © 2008 Humana Press.Item Biological sulfide oxidation using autotrophic Thiobacillus sp.: Evaluation of different immobilization methods and bioreactors(2009) Ravichandra, P.; Gopal, M.; Jetty, A.Aims: Evaluation of various immobilization methods and bioreactors for sulfide oxidation using Thiobacillus sp. was studied. Methods and Results: Ca-alginate, K-carrageenan and agar gel matrices (entrapment) and polyurethane foam and granular activated carbon (adsorption) efficacy was tested for the sulfide oxidation and biomass leakage using immobilized Thiobacillus sp. Maximum sulfide oxidation of 96% was achieved with alginate matrix followed by K-carrageenan (88%). Different parameters viz. alginate concentration (1%, 2%, 3%, 4% and 5%), CaCl2 concentration (1%, 2%, 3%, 4% and 5%), bead diameter (1, 2, 3, 4 and 5 mm), and curing time (1, 3, 6, 12 and 18 h) were studied for optimal immobilization conditions. Repeated batch experiments were carried out to test reusability of Ca-alginate immobilized beads for sulfide oxidation in stirred tank reactor and fluidized bed reactor (FBR) at different sulfide concentrations. Conclusions: The results proved to be promising for sulfide oxidation using Ca-alginate gel matrix immobilized Thiobacillus sp. for better sulfide oxidation with less biomass leakage. Significance and Impact of the Study: Biological sulfide oxidation is gaining more importance because of its simple operation. Present investigations will help in successful design and operation of pilot and industrial level FBR for sulfide oxidation. © 2009 The Society for Applied Microbiology.