2. Thesis and Dissertations
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Item Multi Directional Forging Of Zinc Aluminium (Za27) Based Composites Reinforced With Sic and Al2O3 Particles(National Institute of Technology Karnataka, Surathkal, 2021) N, Anjan B.; V, Preetham Kumar G.Selection of materials with the expected characteristics is a very important for any industrial application. In the engineering and automotive industries, the current tendency is to use metal matrix composite for production of various components for high performance application. The aim of this study was to investigate the effect of SiC and Al2O3 (5 and 10 wt %) reinforcement in ZA27 matrix alloy. Further to investigate and develop the application of the MDF techniques, which may lead to an improvement in mechanical and tribological properties of these composite for industrial application. To analyse the influence of parameters such as applied load, sliding distance and sliding speed on dry sliding wear behavior of solutionized and MDF processed material using pin on disc test rig was conducted. In this study, the composite were prepared by stir casting technique followed by squeezing process. Multi directional forging (MDF) is one of the severe plastic deformation (SPD) techniques used to develop ultrafine-grained (UFG) materials. Multi directional forging technique was used to process the ZA27/SiC/Al2O3 /SiC + Al2O3 composites to produce refined microstructure in order to study the relationship between the microstructure and mechanical properties. The effects of the MDF processes have been studied on ZA27 based composite at 100 °C and 200 °C of processing temperature with a total equivalent strain of 0.54 and 1.08 respectively. Before MDF process, base alloy and prepared composites were homogenized at 365°C for 5 hours by using muffle furnace and quenched in water to room temperature. The standard metallographic technique was used to analyse the microstructural features of the ZA27 based composite. MDF processed composite were characterized by analyzing the X-Ray diffraction (XRD) profiles and studying microstructures using optical microscopy, scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). Density was measured using standard density measurement kit and both theoretical and experimental densities were compared. Mechanical properties such as hardness, tensile strength and ductility from tensile test and fracture surface morphologies of the tensile test samples of both MDF processed and unprocessed composites were studied. Wear behavior of composites before and after MDF process were studied with their wear mechanisms. iv Results revealed that, density of ZA27 alloy decreased by incorporation of SiC and Al2O3 particles. Some Clusters and fair dispersion of SiC and Al2O3 particles in ZA27 matrix were observed in microstructure and confirmed by EDX. SiC reinforced composites performs better when compared with Al2O3 reinforced, mixture of SiC+Al2O3 particles reinforced and ZA27 base matrix material. As the percentage of reinforcement increased from 5 wt% to 10 wt% the properties of the material also increased. Porosity level decreased with an increase in the number of MDF passes when compared with unreinforced materials. Composites reinforced with SiC particles in 5 and 10 wt % were MDF processed at different temperature. The average grain size was reduced from 25-30 µm to 0.2-0.35 µm, 0.45-0.5 µm respectively in the case of samples MDF processed at 100 °C up to three passes and for 200 °C up to six passes it shows 0.8-1.0 µm, 0.9-1.2 µm respectively. The initial lamellar Al-rich and Zn-rich phase was gradually refined to a spherical shape and distributed more uniformly with an increasing number of passes. Ultimate tensile strength of the composite material was increased with that addition of SiC particles and also by MDF process. The highest ductility was obtained when the sample forged at 100 °C 3 passes. Initial ascast condition showed a brittle type of fracture. Brittle mode of fracture was transformed into ductility mode by MDF processing. Wear results showed that samples tested with lower load and sliding distance were showing abrasive type of wear mechanism but as the applied load and sliding distance increased, mechanism changed to adhesion type. This is due to the rise in temperature between the interface of pin and disc, material detached from the pin as debris gets adhered to the surface of pin which influences the mode of mechanism to switch from abrasion to adhesion. MDF processed ZA27/SiCp for 3 passes at 100 °C showed better wear resistance with ultra-fine grains and higher hardness. Composites reinforced with Al2O3 particles in 5 and 10 wt % were MDF processed at 100 °C up to three passes reduced the grain size from 20-30 µm to 0.4-0.45 µm, 0.5- 0.6 µm respectively with the dual type of microstructure having both lamellar to the cellular structure. On further MDF processing at 200 °C upto 6 passes showed the grain size of 1.2-1.4, 1.5 µm with equiaxed grain structure. Small cracks were seen at the edges of the Al2O3 particle because of load applied during MDF process upto 3 v passes at 100 °C and with a higher number of passes the Al2O3 particle broken into several pieces and forms a cluster of Al2O3 particle. Addition of Al2O3 particle increased the UTS and hardness values in both 5 and 10 wt % reinforced composites and further improvement in UTS and hardness value is due to MDF process upto three passes at 100 °C and upto six passes at 200 °C. The ductility of Al2O3 particle reinforced composites was low when compared with other composites. Wear rate of Al2O3 reinforced composite was more when compared with SiC reinforced ones. Results of wear test showed that Al2O3 reinforced composites MDF processed for 3 passes at 100 °C gives higher wear resistance, with abrasion type of wear mechanism. For ZA27/SiC +Al2O3 composites with the average grain size reduced from 15-20 µm to 0.2-0.25 µm, 0.3-0.4 µm when processed at 100 °C upto three passes and 0.8-0.9 µm, 0.9-1.1 µm when processed at 200 °C upto Six passes. Hardness, ultimate tensile strength and ductility of the composites were improved by MDF processing. Substantial improvement in ductility of the present composites after several MDF passes can be attributed to the elimination of as-cast morphology as well as grain refinement, reduction in micro porosity (or micro-voids), redistribution of reinforcing particles, and also the change in the composition of the phases. In an overall, the results of wear test shows, SiC reinforced composite performed better as compared with Al2O3 reinforced and Mixture of SiC+Al2O3 reinforced material. Wear study of composites indicated that the specific wear rate was highly influenced by applied load and sliding distance. As an application, a Cylinder Roller Bearing is fabricated by best performing ZA27/SiC/ Al2O3/SiC+Al2O3 composite material.Item Hydrothermally Synthesized Functional Nanomaterials for Dielectric, Triboelectric and Photocatalytic Applications(National Institute of Technology Karnataka, Surathkal, 2021) Sunil; K, Udaya Bhat.Hydrothermally synthesized functional nanomaterials are utilized for various applications. The functional nanomaterials, like TiO2, La2O3, ZnO, GO and rGO/ZnO were synthesized and used for various applications, like parallel plate capacitor, triboelectric nanogenerators and photocatalytic applications. This method not only yielded nanomaterials with uniform dimensions, but also permitted to tailor the dimensions and morphologies. The materials were characterized to examine the structure, morphology and nature. The primary objective was to explore the potential of hydrothermally synthesized TiO2 in parallel plate capacitor applications. The flexibility of the TiO2 was achieved by incorporating TiO2 nanoparticles in Nylon-6 polymer. These materials were characterized to find the dielectric permittivity (ε) using impedance spectroscopy. The results showed that the ε value is 124 at 1 kHz for Nylon-6/TiO2 polymer nanocomposites and 4472 at 1 kHz for hydrothermally grown unique microstructural films exhibiting colossal dielectric permittivity. The La2O3-based and ZnO-based triboelectric nanogenerator (TENG) devices were fabricated by screen-printing the hydrothermally synthesized La2O3 and ZnO nanomaterials on copper foil (conductive substrate), respectively, with Teflon film (back coated on copper foil) as counter material. The TENG was subjected to mechanical motion by means of a in-house built motorized fixture. The maximum power density generated by La2O3-based TENG device was 7.125 W/m2 at an external load resistance of 30 MΩ and ZnO-based TENG was 0.58 W/m2 at 3 MΩ. The operation life-cycle of the TENG device was analyzed by decay in the voltage after prolonged cycle of operations. The decay in the voltage generated by the TENG devices was negligible after 105 cycles of tapping operations. The TENG device generated enough power and was capable to carry out the smooth functioning of the self-powered devices. The hydrothermally synthesized graphene oxide (GO) was used in the preparation of rGO/ZnO nanocomposites for the methyl orange dye degradation. The advantages of the hydrothermal synthesis of GO over Modified Hummers’ method is the use of less harmful chemicals, less instrumentation and eco-friendly nature. The nanocomposite was capable of degrading the methyl orange with almost equal kinetic rate constant (0.0523 min-1) compared to the rGO/ZnO nanocomposite, where GO prepared following the Modified Hummers’ method. Low-constant, low-temperature, eco-friendly and industrial scalability are the main advantages of the hydrothermally synthesized functional nanomaterials, which can be further used in various applications.Item Development and Characterization of Biomedical Porous Ti - Nb - Ag Alloy through Powder Metallurgy Method(National Institute of Technology Karnataka, Surathkal, 2021) J, Shivaram M.; Arya, Shashi Bhushan.; Nayak, Jagannatha.One of the major concerns in biomedical implants is the mismatch in the elastic modulus of the implant material and the bones leading to stress shield effect. The present investigation focuses on the development of low elastic modulus, porous Ti−Nb−Ag alloy through powder metallurgy (PM) space holder method. Elemental powders of Ti, Nb and Ag with varying amounts were mixed with the powders of space holder (NH4HCO3). These powders are blended using ball milling for 1h, 5h, 10 h, 15 h, and 20 h. The powders were compacted by applying a load of 500 MPa. These compacts were initially calcinated at 200ºC for 2 h to remove the space holder and then finally sintered at 1200ºC for 3 h under ultrahigh vacuum sintering furnace. Microstructure of the porous alloys exhibited micropores, macropores and interconnected pore structures. It was found that with increasing ball milling time, the porosity and pore size decreased while the mechanical properties and electrochemical corrosion properties [in simulated body fluid (SBF)] were improved. XRD results indicated formation of small amount martensite phase and intermetallic compound of Ti2Ag along with the α and β phases. Role of Nb was studied with various Nb content (x = 25, 30 and 35 wt%) in Porous Ti−xNb−5Ag alloys. Increase in Nb content led to decrease in porosity, reduction in both the elastic modulus and compression strength but improved corrosion resistance in SBF. Samples with different porosity levels (22% to 68%) with pore size ranging from 98 μm to 130 μm were fabricated by varying the amount of space holder. Increase in porosity further leads to the reduction in the compression strength, elastic modulus and also corrosion resistance in SBF. Tribocorrosion behaviour of porous Ti−20Nb−5Ag alloys were evaluated in SBF solution by applying various loads (0 N, 1N, 5N, 10N). The results indicate that increasing the applied loads lead to a material degradation and corrosion. The porous Ti−20Nb−5Ag samples are alkali-heat treated using 5 M NaOH, to aid the hydroxyapatite formation in SBF. Alkali treated samples were immersed in SBF for 7, 14 and 21 days at 37 ºC to examine the hydroxyapatite formation. The Ca/P ratio confirmed the formation of adequate hydroxyapatite coating. Further, the electrochemical corrosion test was conducted on hydroxyapatite coated porous alloy in SBF. The hydroxyapatite coated porous alloy after 21 days of immersion in SBF shows excellent corrosion resistance. The cytotoxicity test was conducted on the porous Ti−20Nb−5Ag alloy using MG-63 human osteoblast cells by incubating for 1, 4, and 7 days. The results indicated excellent cell growth and proliferation on porous alloy surface. Cytotoxicity test confirms that developed porous sample has non-toxic in nature and highly suitable for implant application.Item Welding of Dissimilar A5754-A5083 and A6061- A6082 Aluminium Alloys for Automotive Applications(National Institute of Technology Karnataka, Surathkal, 2021) Rajeshkumar, R.; Banerjee, Kumkum.; Devakumaran, K.In the present study, dissimilar aluminium alloy combinations A6061 T6-A6082 T6 and A5754 H111-A5083 H111 were welded using the cold metal transfer (CMT), tungsten inert gas (TIG) welding and friction stir welding (FSW) processes. Each dissimilar combination was welded by two different fillers, such as ER4043 and ER5356, in CMT and TIG. Since FSW is a solid-state welding process, no filler materials were used. The miniature tensile samples were extracted from the interface regions of the TIG and CMT welded joints and the stir zone (SZ) of the FSWed joint. The TIG and CMT welded alloys' individual interface microstructure has been correlated with mechanical properties. The SZ of FSWed parts is of prime importance because this zone primarily decides the resulting property of the welded joint. Therefore, the microstructural features and mechanical properties of the SZ in the FSWed joints have been investigated in detail. The tensile properties of the overall weld region samples have been determined using macro-tensile testing samples. The dissimilar A6061-T6 and A6082-T6 joints welded by CMT and TIG welding processes using two different fillers (ER5356 and ER4043) exhibited higher strength in the A6082 interface in comparison to the A6061 interface. When the dissimilar A5754 and A5083 alloys were welded by CMT and TIG welding processes using two different fillers (ER5356 and ER4043) fillers, the interface region of the A5083 side exhibited higher strength than the interface region of the A5754. In the FSWed joints, the refined grain structure in SZ increased the hardness and strength. The overall joint tensile properties of the dissimilar joints are essential for identifying a suitable welding process to join A6061-A6082 and A5754-A5083 dissimilar alloys. Among the A6061-A6082 dissimilar joints, the CMT joint produced by ER5356 filler and the FSW joint exhibited higher tensile properties than the other joints. The tensile properties of the A6061-A6082 dissimilar CMT joint produced by ER5356 filler and the FSW joint are nearly the same. However, the FSW process does not use any shielding gas, filler materials, and the surface preparation is also not critical for the process. These factors can play a vital role to reduce the cost of welding effectively. Also, the FSW process is environment friendly, due to the absence of fumes and shielding gases. In the case of A5754-A5083 dissimilar joints, the FSW joint shows higher tensile properties than the other joints. Therefore, the FSW process can be recommended as the preferable joining method among all the investigated processes.Item Performance and Reliability of Nanoparticles Reinforced Lead-Free Solder Joints – A Study(National Institute of Technology Karnataka, Surathkal, 2021) Tikale, Sanjay Vinayak.; Prabhu, K Narayan.The present study involved the development of Sn-3.6Ag, 99Sn-0.3Ag-0.7Cu (SAC0307), 96.5Sn-3Ag-0.5Cu (SAC305), and 96.5Sn-3Ag-0.5Cu-0.06Ni-0.01Ge (SAC305-NiGe) lead-free solders with the addition of Al2O3 nanoparticles and multi-walled carbon nanotubes (MWCNT). The effects of multiple reflow cycles and the addition of Al2O3 nanoparticles and MWCNT in 0.01, 0.05, 0.1, 0.3, and 0.5 weight percent concentration on microstructure development and mechanical strength of the solder joint were first investigated. The addition of nanoparticles in low weight percent concentration improved the wettability and solder joint shear strength. Based on superior shear strength and improved ductility compared to the original solder, nanocomposites containing 0.01 and 0.05 wt. pct. Al2O3 nanoparticles were selected and tested for the performance and reliability of the joint. The surface mount 2220 capacitor joint and single-lap-shear joint assemblies reflowed on bare copper and electroless Ni-coated Cu substrates were used in this study. The reliability of the solder joint was assessed in terms of the joint shear strength under varying thermal environments like thermal shock, multiple heating cycles, and aging. The nanocomposite with 0.05 wt.% nanoparticles addition yielded the most significant increase in the joint strength compared to the unreinforced solder. The Ni-substrate coating significantly suppressed the IMC growth under different thermal conditions. The joint reliability of nanocomposites improved for samples reflowed on Ni-coated substrate compared to that on bare Cu substrate. The Weibull analysis showed that the performance and reliability of the solder joint can be greatly improved by the addition of Al2O3 nanoparticles in small weight percent concentrations and Ni-coating on the substrate. The ANOVA study suggests that the solder joint performance was majorly influenced by the operating environments, solder composition, and the substrate coating. SAC305-NiGe and SAC0307 based nanocomposites were found to be better than all solder compositions studied in the present study. The low-silver content SAC0307+0.05Al2O3 nanocomposite will be an effective alternate solder composition in place of high silver content Sn-Ag-Cu solders.Item Exploration of Calcium Rich Marine Benthos Bio-Waste to Develop Bio-Genic Hydroxyapatite for Bone Regeneration and UV Protection(National Institute of Technology Karnataka, Surathkal, 2021) Hadagalli, Komalakrushna.; Mandal, Saumen.In this study, a scalable biogenic synthesis of phase-pure hydroxyapatite (Ca10(PO4)6(OH)2, HA) (Ca/P = 1.66) scaffold from the marine-resource-derived HA together with different pore formers were conventionally sintered to produce physiologically relevant scaffolds with porous architecture. A combination of moderate compressive strength (12−15 MPa) with elastic modulus up to 1.6 GPa was achieved with ∼98% interconnected porosity using wheat flour as the pore former. More importantly, the faster nucleation and growth of the biomineralized apatite layer with full coverage within 3 days of incubation in a simulated body fluid, together with a combination of mechanical properties, establish the potential of marine-resource-derived biomimetic HA scaffold as a new generation of cancellous bone analogue. MTT assay and cell morphological analysis established the good cytocompatibility of naturally derived HA porous scaffolds, as evident from the good cellular adhesion, proliferation, and phenotypical features of osteoblast cells. The effect of Fe3+ ionic substitution in HA was studied using structural modification, such as lattice parameter, crystallite size, and particle size resulting into a drastic improvement in UV absorption through a tailored optical band structure. Ca2+ of HA being larger (0.99 Å) compared to Fe3+ (0.64 Å) contributes to the shrinkage of the lattice. Hence, hexagonal lattice parameters, a and c of HA are reduced successively as the concentration of Fe3+ increases, is observed via XRD. UV absorption of Fe-HA in the entire UVA and UVB range with an increase in Fe content because of the remarkable decrease in band gap with undoped and doped HA. Also, present work explores the use of marine resourced prawn exoskeleton/shell as a new class of naturally occurring composite containing UV absorbing proteins. Mycosporine-like amino acids with a central aromatic ring in the exoskeleton/shell of naturally occurring prawns (Fenneropenaeus Indicus) offer excellent UV protection. The presence of tryptophan, phenylalanine, and tyrosine, forming the basic building blocks of mycosporines, is confirmed by structural, compositional, and microscopic studies on prawn shells. The UV spectroscopic signatures at 290 and 320 nm provides strong evidence for the highest UV absorption. UV absorption attributes to the presence of mycosporine-like amino acids.Item Materials and Processes in the Fabrication of Particulate-Free and Particulate-Based Screen-Printed Metal and Metal Oxide Films for Electronic Applications(National Institute of Technology Karnataka, Surathkal, 2021) Manjunath G.; Mandal, Saumen.In the present study, approaches towards the processing of screen-printed metal and metal oxide films for the optoelectronic and gas sensing applications are elaborated. Phase pure, highly reactive, nanocrystalline functional materials namely conducting (Ag and Ag-Cu) and semiconducting (CaVO3, pristine and doped ZnO) particles of nano to sub-micro size, which are decent for the formulation screen printing inks are obtained using polyol and facile solution combustion synthesis route respectively. A novel aqueous based combustible particle-free silver and ZnO screen printing inks possess the desirable thixotropic and shear thinning properties for the screen printing, are formulated by using eco-friendly binder Na-CMC and solvent water. The conventional particle based pristine and Sr-doped ZnO screen printing inks are comprised of 60 wt % of functional materials (ZnO/Sr-doped ZnO) and remaining organic vehicle made of Na-CMC and water. Crystalline silver films are processed by depositing particle free silver screen printing inks followed by annealing at 200 ºC, displays electrical conductivities in the range of 2-8 ×106 Sm-1. High conductive films with minimal thickness (3 μm) and high dimensional accuracy used as electrode for TFTs exhibit a μsat, Ion/Ioff, and Vth of 0.88 cm2 V−1s−1, 102, and ~0.3 V, respectively. High crystalline screen printed ZnO sensor processed at 500 °C from aqueous particle free-ZnO inks showed significantly high gas response (S = 336) and selectivity towards 5 ppm of NH3 under ambient conditions. Porous, well-adhered particle-based screen printed ZnO sensors processed from glycine fuel system exhibited good gas sensitivity towards NH3, C2H5OH, Cl2. Sr-doped ZnO sensor with smaller crystallite size and lesser lattice distortion exhibited highest gas response 70 towards the 50 ppm of NH3 gas at room temperature and also high selectivity to ammonia against various gases such as xylene, acetone and toluene. Upon RuO2 activation, NH3 response of RuO2/Sr-doped ZnO heterostructure sensor was diminished to ~2. La-doped BaSnO3 sensor exhibited superior gas response upon exposure of both the NH3 and HCHO gases than the BaSnO3, ceria and ruthenate sensitized La-doped BaSnO3 sensors.Item A study on Sedimentation Issue in Magnetorheological Fluids(National Institute of Technology Karnataka, Surathkal, 2021) N, Aruna M.; Rahman, Mohammad Rizwanur.The purpose of this dissertation is to investigate the sedimentation problem in magnetorheological fluids (MRFs). MRFs are the class of smart materials since some of the physical properties can be changed with the application of an external magnetic field. In particular, the shear stress and viscosity characteristics which can modify by varying the intensity of the magnetic field can be varied. The main property of MRFs is the capability of changing their rheological behavior within milliseconds and reversibly with off-state and on-state magnetic field conditions. At present, MRFs are very attractive for a large number of applications such as vibration-dampers, clutches, brakes up to the recent biomedical applications and virtual reality devices. MRFs typically consist of 1-10 m micron-sized magnetic particles dispersed in a carrier liquid. Sedimentation stability is the main problem that restricts the application of MRFs, and the main factors affecting the stability are high-density magnetic particles, volume fraction, and type of carrier liquids. Therefore, studying the preparation and performance of the MRFs is crucial to use MRFs extensively for various applications. To minimize the settling of magnetic particles used in MRFs various new types of additives, surface modifiers, different carrier fluid with varying viscosity, ferrite particles, and changing the particle volume fraction are used to address the sedimentation issue in the present work. First, the effects of three different clay additives are added in carbonyl iron particles along with poly-alpha-olefin oil for sedimentation effect in MRFs are investigated. Experimental investigations have been carried for sedimentation testing for MRFs which contain with and without additives to know the damping force of fabricated mono-tube magnetorheological (MR) damper. Further, the effect of different surface area fumed silica additive added in silicone oil to minimize the settling of carbonyl iron particles in MRFs. The carrier fluid with varying viscosity plays a major role in the stability of MRFs, so the MRFs were prepared with three different carrier fluids with varying viscosity. The ferrite particles based MRFs are stable against settling than the CIPs based MRFs due to the density of the particles used is very less. The rheological properties of the MRFs, including field-dependent yield-stress, were measured at off-state and magnetic fields applied using a parallel plate design magnetorheometer. Hence, in this present work minimize the sedimentation of the particles in MRFs with slight variation in the rheology properties have been formulated in lab-scale at cost-effective than the commercial available MRFs.Item Study of Flow Accelerated Corrosion of Carbon Steel Pipeline in Oilfield Environment(National Institute of Technology Karnataka, Surathkal, 2021) S, Ajmal T.; Arya, Shashi Bhushan.Flow accelerated corrosion (FAC) and erosion-corrosion (EC) are the major reasons for steel pipeline failure in the oil and gas industry. The present thesis focuses on the FAC and EC study of API X70 steel in a synthetic solution of oilfield water under a turbulent flow condition. The tests were carried out at a more critical location (90º pipe elbow) in a circulating loop system at a fixed flow velocity of 3 m s-1. Multiple electrodes were located at intrados (inner face) and extrados (outer face) of the 90º pipe elbow. The influence of flow on corrosion (FAC) and passivation was examined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) tests. Corrosion rates of the electrodes located at the intrados are more than that at the extrados. Shear stresses are simulated using the CFD method and it is observed that the corrosion rate is inversely proportional to shear stresses. The effect of oleic acid hydrazide (OAH), a green inhibitor on X70 steel was investigated for the first time under flow condition. The maximum inhibition efficiency is found at 87.7% (extrados electrode E4) for 0.30 g/L OAH concentration. The studied inhibitor is good in the protection of the API X70 steel with higher efficiency in the dynamic corrosive environment. The laser surface melting (LSM) technique is used to examine the corrosion behavior of X70 steel using laser powers of 2, 2.5, and 3 kW. It is found that the resistance against FAC of the X70 steel is significantly improved by surface modification. LSM treated X70 steel exhibited higher corrosion resistance than untreated and inhibitor-used conditions. Slurry erosion-corrosion behavior by electrochemical and weight loss measurements for both untreated and laser melted samples located at the 90⁰ elbow test section was tested and compared. Laser surface melted samples exhibited improved hardness with enhanced EC resistance as compared to that of untreated counterparts due to alteration of surface metallurgy.Item Synthesis and Characterization of Znmn2o4 and Pvdf/Ca-Al LDH Nanofibers for Sustainable Energy Applications(National Institute of Technology Karnataka, Surathkal, 2020) Shamitha, C.; Anandhan, S.ZnMn2O4 (ZMO) and PVDF/Ca-Al LDH (PCAL) nanocomposite nanofibers were synthesized from using electrospinning technique. For the synthesis of ZMO nanofibers styrene-acrylonitrile random copolymer (SAN) was used as the sacrificial polymeric binder and the nanofibers were calcined at three different temperatures (773, 873, and 973 K). Structural, morphological and optical properties of these ceramic nanofibers were characterized. X-ray diffraction and X-ray photoelectron spectroscopy results revealed the presence of hexagonal ZnMnO3 and MnO phases in the ZMO nanofibers produced. Based on the findings, a plausible mechanism of formation of ZMO nanofibers was proposed. The nanofibers calcined at 773 K exhibited a specific surface area of 79.5 m2.g-1, which is higher than that of the zinc manganite nanofibers synthesized hitherto by sol-gel electrospinning. The suitability of ZMO nanofibers was investigated as bifunctional electrocatalysts for water splitting towards Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). The results demonstrate that ZMO nanofibers are promising candidate as bifunctional electrocatalysts for water-splitting applications. A new synthetic route for Ca-Al layered double hydroxide (LDH) nanosheets was adapted and these two-dimensional nanosheets were used as filler for poly(vinylidene fluoride) (PVDF) to produce composite nanofibers by electrospinning. The polymorphism, crystallinity, and the interaction between PVDF and LDH were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry. The synergetic effect of PVDF-LDH interaction and in situ stretching due to electrospinning facilitates the nucleation of electroactive β phase up to 82.79%, which makes it a suitable material for piezoelectric-based nanogenerators. The piezoelectric performance of PCAL nanofibers was demonstrated by hand slapping and frequency-dependent mechanical vibration modes, which delivered a maximum open-circuit output voltage of 4.1 and 5.72 V, respectively. Moreover, the applicability of PCAL nanofibers was explored in lithium-ion batteries (LIBs) as gel polymer electrolyte (GPE). The PCAL based GPE exhibited enhanced electrochemical properties, such as high ionic conductivity, optimal Li-ion transference number, and improved electrolyte uptake due to the presence of a highly interconnected porousstructure. They exhibited improved charge-discharge profile compared to pristine PVDF and commercial Celgard® 2400 separator membrane. Along with high electrochemical performance, the PCAL based GPE showed superior mechanical and low thermal shrinkage properties, indicating its suitability in battery separator application.