1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
Browse
43 results
Search Results
Item Fabrication and characterization of polyphenylsulfone-based membranes with nanocomposite additives for water purification application(National Institute of Technology Karnataka, Surathkal, 2019) Nayak, M Chandra Shekhar; Isloor, Arun M.Nowadays, membrane separation processes are became as prestigious over other methods towards water purification, due to the low energy consumption and easy to accessible operational conditions. Polyphenylsulfone (PPSU) based membranes are most widely using water purification membrane processes due to its chemical stability, thermal stability, and better mechanical properties. But, one of the major drawback of this polymer is hydrophobicity. In current research, focused to enhance the hydrophilicity as well as the separation efficacy of PPSU membranes with the incorporation of various inorganic hydrophilic nanoparticles. In present work, PPSU based flat-sheet and hollow fiber membranes fabricated with the incorporation of various nanoparticles such as, BiOCl-AC, MWCNTs, ZSM-5, SnO2 and Al2O3-AAC via phase inversion process. The fabricated membranes morphological changes were studied with scanning electron microscopy and atomic force microscopy techniques. The permeability and separation efficacy of membranes was assessed with water, proteins, dyes, heavy metal solutions and different oil/water samples using dead-end and cross-flow filter units. The PPSU membrane with 2 wt. % BiOCl-AC additive exhibited superior performance towards oil/water separation, above 80 % for diesel fuel and above 90 % for crude oil. The PZ-3 type hollow fiber membrane (0.4 wt. % ZSM-5) showed dye rejection performance of 90.81 % for Reactive Black-5 and 82.84 % for Reactive Orange-16. The PCNT-3 membrane (0.3 wt. % MWCNTs) revealed maximum heavy metal ions removal efficacy of 98.13 % for Pb2+, 76.12 % for Hg2+ and 72.92 % for Cd2+ ions, respectively. SnO2 NPs (0.4 wt. %) incorporated hollow fiber membranes (PS-3) were successful in rejection of Reactive Black-5 (RB-5) and Reactive Orange-16 (RO-16) dyes up to 94.44 % and 73.09 % from aqueous solutions. PPSU with alumina doped acid treated activated charcoal incorporated membrane (PA-3) (1 wt. %) displayed above 90 % rejection with BSA and egg albumin (EA) proteins, above 80 % and 70 % rejection with Pb2+ and Cd2+ heavy metals, and in oil-water separation exhibited above 94 % and 87 % rejection with bio-diesel and kerosene oils, respectively.Item Synthesis and characterization of new heterocycle-based discotic mesogens for optoelectronic applications(National Institute of Technology Karnataka, Surathkal, 2019) D. R, Vinayakumara; Adhikari, A. VasudevaOrganic π-conjugated molecules are gaining significant attention because of their substantial capability of producing low-cost, eco-friendly, flexible and large-area plastic electronics. Certainly, discotic liquid crystals (DLCs) are renowned soft selfassembled one-dimensional (1-D) organic nanostructures as they possess robust cofacial π-π stacking in the longer columnar axis, which provides a significant channel for effective anisotropic charge mobility. These LC materials are recognized to possess superior potential to be utilized as active semiconducting layers in organic electronic devices in comparison to the organic single crystals or amorphous polymers in terms of several aspects. At present, a significant number of researchers are keenly working on this class of materials for their applications in future optoelectronic devices. In this context, it was planned to design, synthesize optically dynamic unconventional discotic molecules based on various heterocyclic moieties (HT1-35) and to study the structureproperty relationships. Also, it was contemplated to employ the selected LC materials in optoelectronic devices and to evaluate their performance. Based on the thorough literature survey, six series of molecules, i.e. Series-1 to 6 carrying important heterocycles appended with variety of substituted aryl motifs were designed by following different designing strategies. They were successfully synthesized using appropriate synthetic protocols and their chemical structures were confirmed by means of routine spectral techniques. Further, their liquid crystalline properties were investigated by set of standard methods. Most of the newly prepared materials were found to be rich in mesomorphism, dominated with columnar (Col) selfassembly. Furthermore, they were subjected to detailed photophysical as well as electrochemical characterizations and the obtained optoelectronic results were corroborated with theoretical simulations (DFT). Majority of them were shown to be superior light absorption and emitting materials. Finally, the columnar LC materials owning essential properties were employed as emissive layer in the fabrication of multilayer OLED devices; the attained results were promising. Conclusively, by improving the molecular design, prospective DLCs with plausible applications in molecular electronics, can be achieved.Item Development of Corrosion Resistant Coatings for Aerospace Aluminium Alloy AA2024- T3(National Institute of Technology Karnataka, Surathkal, 2019) B. G, Prakashaiah; Shetty, A Nityananda.; Rani, B. E. AmithaFive organic molecules, namely, (E)-2-(2-hydroxybenzylidene) hydrazinecarbothioamide (2-MHC), (E)-2-(2,4-dihydroxybenzylidene) hydrazinecarbothioamide (2,4-DHC), (E)-2-(3,4-dihydroxybenzylidene) hydrazinecarbothioamide (3,4-DHC), (E)-2-(2,3,4-trihydroxybenzylidene) hydrazinecarbothioamide (2,3,4-THC) and Bis[[3,4-Dihydroxyphenylmethylene]- carbonothioic dihydrazide] (3,4-DCT) were synthesized and their corrosion inhibition actions on 2024-T3 aluminium alloy were studied in 3.5% NaCl solution. The synthesized inhibitors were found to provide corrosion protection on AA2024-T3 by forming adsorbed layers on the alloy surface. To explore the possibility of using the synthesised inhibitors for corrosion detection applications, the initial studies were carried out on all the five inhibitors. It was found that only 3,4-DHC qualified in the tests, by imparting the colour change at the corrosion sites. From the five inhibitors studied for their inhibition action, the three most effective inhibitors were employed for coatings applications. An oxide layer was created on the aluminium alloy by anodizing the surface in 10 wt % sulphuric acid and was sealed with the three inhibitors, namely, 2,3,4-THC, 3,4-DHC and 3,4-DCT to evaluate their role in the enhancement of corrosion resistance. The order of the corrosion protection efficiencies of the anodised layer is: Ox < Ox-2,3,4-THC < Ox-3,4-DHC < Ox-3,4- DCT. The effect of corrosion inhibitor addition on the anticorrosion properties of primer coatings on aluminium alloy 2024-T3 was investigated. 3,4-DCT, 3,4-DHC and 2,3,4-THC were supplemented to epoxy primer. The addition of 2,4-DCT and 3,4-DHC to primer coating, offered good barrier properties. The addition of 2,3,4-THC provided active corrosion protection along with good barrier properties. The synthesised inhibitors 3,4-DHC and 2,3,4-THC were added to the hybrid sol to study their effect on the corrosion protection efficiency of the sol-gel coating. Addition of corrosion inhibitors to the coating enhanced the corrosion protection abilities of sol-gel coatings. The order of the corrosion protection efficiencies is: Uncoated < sol-gel coated < sol-gel + 2,3,4-THC coated < sol-gel + 3,4-DHC coated.Item Corrosion and Corrosion Inhibition Studies on Mg-Al-Zn Alloy in Aqueous Ethylene Glycol (30% V/V) Medium(National Institute of Technology Karnataka, Surathkal, 2019) H, Medhashree; Shetty, A Nityananda.Magnesium alloys find applications from automobile industries to medical implant materials because of its enhanced properties in comparison with other light weight alloys. Mg-Al-Zn alloy is one such magnesium alloy, which finds variety of applications in automobile industries. The occurrence of corrosion is beneficial in the medical field of application as it avoids one more surgery for the removal of implants, but is a limitation in automobile industry applications. Therefore, the study of corrosion and its controlling measures have vital role in practical applications. In this thesis, corrosion of Mg-Al-Zn alloy and its mitigation were studied using electrochemical techniques - potentiodynamic polarization and AC impedance spectroscopy. The surface morphology and surface composition of the corroded alloy surface were examined by SEM and EDX analyses. The aqueous ethylene glycol (30% v/v) solutions, containing chloride and sulfate ions, were chosen as the corrosive media. The corrosion studies were performed at different chloride ion and sulfate ion concentrations, pH and temperature of the medium. The obtained results concluded the trend of higher corrosion rate at higher concentration of chloride and sulfate ions, lower pH and higher temperature. The synergistic mixtures of sodium dodecyl benzene sulphonate (SDBS) with trisodium phosphate (TSP) and sodium benzoate (SB) were employed as corrosion inhibitors. Similarly morpholine and its two derivatives N-methyl morpholine and dimethyl morpholine were also studied as corrosion inhibitors in the corrosive media. The synergistic mixtures acted as anodic type inhibitors by suppressing anodic reaction. The morpholine and its derivaties acted as mixed type inhibitors. All the inhibitors were more effective at lower temperature and in higher concentration of the corrosive media. The activation and thermodynamic parameters have been calculated and documented. The synergistic mixtures adsorbed on the alloy surface predominantly through physisorption and obeyed Langmuir adsorption isotherm. While the adsorption of morpholine and dimethyl morpholine obeyed Langmuir adsorption isotherm, that of N-methyl morpholine obeyed Temkin adsorption isotherm. The synergistic mixtures of organic-inorganic inhibitors showed higher inhibition efficiency than mixtures of organic-organic inhibitors. The efficiencies of morpholine and its derivatives decrease in the following order: dimethyl morpholine > morpholine > N-methyl morpholine. The possible mechanism of inhibition has been proposed for all the inhibitors.Item Synthesis and Characterization of Copper and Cuprous Oxide Nanofluids(National Institute of Technology Karnataka, Surathkal, 2013) U, Sandhya Shenoy; A, Nityananda ShettyThis Research work entitled, ‘Synthesis and Characterization of Copper and Cuprous Oxide Nanofluids’ deals with the single step chemical synthesis of nanofluids, involving simultaneous in situ synthesis of nanoparticles and their dispersion in the base fluid. Nanofluids have been synthesized by a reliable, versatile and well controlled solution phase approach using mixture of water and ethylene glycol as base fluids. Copper nitrate, copper sulfate and copper acetate have been used as precursors for the synthesis. Copper salts have been reduced using ascorbic acid and glucose. Sodium lauryl sulfate, cetyl trimethyl ammonium bromide and poly vinyl pyrrolidone have been used for the stabilization of the nanofluids. By varying the synthetic conditions precise control on the size of the particles has been established. The as prepared nanofluids have been characterized by X ray diffraction and selected area electron diffraction technique for the phase structure; electron diffraction X ray analysis for chemical composition, transmission electron microscopy and field emission scanning electron microscopy for the morphology; fourier transform infrared spectroscopy and ultra violet - visible spectroscopy for analysis of ingredients of the solution. Thermal conductivity, sedimentation and rheological measurements have also been carried out. Interesting copper and cuprous oxide structures with octahedral, cuboctahedral, truncated cube, whorled leaf like, flower like, hexagonal disc like and star like shapes have been prepared. It has been found that the reaction parameters have considerable influence on the size of the particle formed and rate of the reaction. The as synthesized nanofluids have been found to exhibit Newtonian behavior. The sedimentation measurements showed that the nanofluids have very high stability. Uniform dispersion of the nanoparticles in the base fluid led to promising increase in its thermal conductivity. The reported methods have been found to be facile, expeditious and cost effective for preparing heat transfer fluids with higher stability and enhanced thermal conductivityItem Preparation and Characterization of Chitosan Based Polymer Membranes for Water Purification Application(National Institute of Technology Karnataka, Surathkal, 2013) A, Rajesha Kumar; Isloor, Arun M.; Trivedi, Darshak RFor membranes to be competitive with conventional technology, a membrane process needs to operate with a high rate of flux, high degree of selectivity and high resistance to fouling. Chitosan is an excellent membrane material due to its good film forming nature, hydrophilicity, chemical stability and easy chemical modification. The membranes prepared from pure chitosan cannot offer sufficient mechanical stability for application in flow processes. To overcome this problem, techniques of polymer coating and blending have been employed by researchers. Blended chitosan membranes not only display superior mechanical properties but also they are benefited from the intrinsic advantages of each polymer involved in the blend. Chitosan was blended with polysulfone to prepare PSf/CS ultrafiltration membranes. The chemical modification of chitosan has been carried out in the thesis, N-succinyl chitosan (NSCS) and N-propylphosphonyl chitosan (NPPCS) are the two derivatives prepared, among the two, NPPCS is the novel derivative synthesized. Further, these two derivatives were blended with polysulfone to prepare PSf/NSCS and PSf/NPPCS UF membranes. UF membranes were subjected to permeation, antifouling and heavy metal rejection study. Titanium dioxide nanotubes (TiO2NT) were synthesized and incorporated into PSf/CS blend to prepare PSf/CS/TiO2NT UF and NF membranes. PSf/Poly (isobutylene-alt-maleic anhydride) (PIAM) blend nanofiltration membranes were modified by changing coagulation bath with cross-linked chitosan solution. The nanofiltration membranes were subjected to salt rejection study. The PSf/CS, PSf/NSCS and PSf/NPPCS UF membranes showed enhanced permeation and antifouling property compared to pristine PSf UF membrane. Even the UF process was efficient in the rejection of heavy metal ions effectively. Membranes showed a maximum of >90% rejection for Cu, Cd and Ni at very low pressure via polymer enhanced ultrafiltration (PEUF) process. All the nanofiltration membranes showed improved flux and antifouling properties. A maximum of 46 % NaCl rejection was observed in case of PSf/CS/TiO2 membrane with 8 % of nanotube content. Changing the coagulation bath with cross-linked chitosan solution emerged as a best technique to improve salt rejection property of PSf/PIAM membrane.Item Studies on Corrosion Inhibition of 18% Ni M 250 Grade Maraging Steel under Weld Aged Condition in Acidic Media(National Institute of Technology Karnataka, Surathkal, 2013) B. S., Sanatkumar; Shetty, A. Nityananda; Nayak, JagannathaThe corrosion behaviour of 18 % Ni M250 grade maraging steel under weld aged conditions in two different acid media, namely, hydrochloric acid and sulphuric acid in various concentrations and temperatures have been studied by Tafel polarization and electrochemical impedance spectroscopy techniques. The corrosion rate in the sulphuric acid medium was higher than in the hydrochloric acid medium. Five organic inhibitors were synthesized and characterized using spectral and elemental analysis. The five inhibitors were 1(2E)-1-(4-aminophenyl)-3-(2-thienyl) prop-2-en-1-one (ATPI), 2-(4-chlorophenyl)-2-oxoethyl benzoate (CPOB), 2-(4- bromophenyl)-2-oxoethyl- 4-chlorobenzoate (CPOM), (E)-1-(2,4-dinitrophenyl)-2-[1- (2-nitrophenyl) ethylidene] hydrazine (DNPH) and 5-diethylamino-2-{[2-(2,4- dinitrophenyl) hydrazin-1-ylidene]methyl} - phenol (DDPM). The results pertaining to the corrosion inhibition studies of five inhibitors in two different acid media at different temperatures in the presence of varying concentrations of inhibitors are reported in the thesis. Activation parameters for the corrosion of the alloy and thermodynamic parameters for the adsorption of the inhibitors have been calculated and the results have been analysed. The adsorption of first four inhibitors on the alloy was through both physisorption and chemisorption, with predominant physisorption in both the media. The mode of adsorption for the DDPM predominantly chemisorption in both the media. The adsorption of all the five inhibitors on alloy surfaces follows Langmuir adsorption isotherm. The inhibition efficiencies of first four inhibitors decrease with the increase in temperature, the inhibition efficiency of DDPM increases with the increase in temperature.Item Synthesis, Characterization and Biological Studies of Some New N-Bridged Heterocycles(National Institute of Technology Karnataka, Surathkal, 2013) Malladi, Shridhar Ashok; Isloor, Arun M.Antibiotics, first introduced in the 1940s, dramatically reduced illnesses and deaths caused by bacterial infections. Before the introduction of antibiotics, infectious diseases claimed countless victims. But a hallmark of antibiotics is that they lose their effectiveness over time as bacteria naturally evolve and mutate and so become resistant to the medicine's effects. The rate of growth of antimicrobial resistance has accelerated due to the widespread global use of antibiotics. It is important to find out newer, safer and more effective antibiotics with broad-spectrum of activity. Heterocyclic compounds by virtue of their specific activity could be employed in the treatment of infectious diseases. A systematic investigation of this class of heterocyclic lead revealed that pyrazole containing pharmacoactive agents play important role in medicinal chemistry. The prevalence of pyrazole cores in biologically active molecules has stimulated the need for elegant and efficient ways to make these heterocyclic lead. Owing to the pharmacological importance of pyrazole and its derivatives, in the present work, it has been contemplated to couple various biologically active heterocyclic moieties with pyrazole through active functional systems to form a new molecular framework. Accordingly, different series, viz. triazolothiadiazole (P1-10), oxadiazole (P11-24), thiazole (P25-38), Schiff base (P39-48), Cyanopyridone (P49-63) and pyrazoline derivatives (P64-74) carrying pyrazole ring as core structure have been designed and synthesized. Structures of the newly synthesized compounds were confirmed by FT-IR, 1H NMR, 13C NMR, mass spectral studies followed by elemental analyses. The newly synthesized compounds were tested for their antimicrobial activity. Selected compounds were also screened for anti-inflammatory and antioxidant activity. Some of the synthesized compounds were found to exhibit potent activity. The acute oral toxicity study for few of the biologically active compounds was also performed. Molecular docking studies of selected compounds were carried out for better understanding of the drug-receptor interaction.Item Design and Synthesis of New Donor-Acceptor Type Conjugated Polymers for Photonic Applications(National Institute of Technology Karnataka, Surathkal, 2013) K. A., Vishnumurthy; Adhikari, A. VasudevaIn recent years, a great deal of interest has been focused on the synthesis of novel D-A type conjugated polymers because of their excellent photonic properties. Recently, lots of attentions have been dedicated towards the development of new D-A type polymers with desired properties through proper structural modifications. In this context, the proposed research work has been aimed at design and synthesis of new D-A type conjugated polymers with improved photonic properties. Based on the literature review, five new series of D-A type conjugated polymers (P1-P20) carrying various electron donors and acceptor moieties have been designed. Seven series of bi-functional monomers required for the synthesis of new polymers have been prepared using appropriate synthetic procedures. Structures of new intermediates and monomers have been evidenced using spectral and elemental analyses. Starting from these monomers, five new series of target polymers, viz. (i) poly(3,4-ditetradecyloxythiophene)s carrying thiophene, naphthalene, isopthalyl, vinyl and pyrazole moieties as π-conjugated spacers (Series 1, P1-P5), (ii) poly(cyanopyridines) containing phenyl, carbazole, alkoxythiophene phenothiazine and dipenyl amine based electron donating bridges (Series 2, P6-P10), (iii) poly(3,4- ditetradecyloxythiophene)s involving vinylene π-conjugated spacers (Series 3, P11- P14), (iv) poly(3,4-ditetradecyloxythiophene)s carrying aromatic conjugated cyclic imides (Series 4, P15 and P16), and (v) poly(3,4-ditetradecyloxythiophene)s with imine functionalized electron donors as π-conjugated bridges (Series 5, P17-P20), have been successfully synthesized and their synthetic protocols have been established. Their structures have been confirmed by different spectroscopic and elemental analyses. Their molecular weights have been determined by GPC technique and thermal properties have been evaluated by TGA studies. Electrochemical properties have been studied using CV experiments. The linear optical characteristics have been estimated by UV-visible absorption and fluorescence emission spectroscopy. Their fluorescent quantum yields and solvatochromic behavior have been determined. Finally, their third-order NLO properties have been investigated using open aperture Z-scan technique to investigate their optical limiting behavior. Most of the polymers have exhibited promising results.Item Synthesis and Characterization of Thiophene Based Conjugated Polymers for Optoelectronic Applications(National Institute of Technology Karnataka, Surathkal, 2013) M.G., Murali; D., Udaya KumarIn the last three decades, a great deal of attention has been focused on the synthesis of conjugated polymers, because of their significant applications in the field of optoelectronic devices. In this context, the present research work is concentrated on design and synthesis of five new series of thiophene based donor-acceptor (D−A) conjugated polymers (P1−P12) for optoelectronic applications. The chemical structures of the polymers are designed by the selection of proper electron donor and electron acceptor units and they are synthesized using multistep synthetic routes. The newly synthesized intermediate compounds, monomers and polymers are characterized by 1H NMR and FTIR spectroscopic methods as well as using elemental analyses. All the polymers are thermally stable up to 300 oC under nitrogen atmosphere. The linear optical properties of the polymers are studied by using UVVisible absorption and fluorescence emission spectroscopic techniques. The optical band gap of the polymers is in the range of 1.70 − 2.63 eV. The electrochemical redox behavior of the polymers is investigated by cyclic voltammetry. The electrochemical studies reveal that polymers posses low-lying HOMO and low-lying LUMO energy levels. The preliminary studies on the electroluminescent properties show that polymers P5, P9, P10 and P12 emit red, green, green and white light respectively with lower threshold voltages. The photovoltaic properties of the low band gap polymers P6 and P7 are evaluated by fabricating bulk heterojunction solar cells using polymer as both electron donor and acceptor material. The devices exhibit satisfactorily good power conversion efficiency with high open circuit voltage. The nonlinear optical properties of the polymers are studied using z-scan technique. They show strong optical limiting/saturable absorption behavior. Polymers P1 and P5 are used to prepare polymer/TiO2 nanocomposite films and their nonlinear optical properties are studied. The incorporation of TiO2 nanoparticles into the polymer matrix marginally enhances the nonlinear absorption of the polymer.