Perchlorate contamination in water due to industrial and space activities remains a serious problem as it seriously affects the function of thyroid glands. Various methods are being explored for the removal of perchlorate from the contaminated water. Among them, adsorption is a simple and cost-effective technique. The development of efficient adsorbent materials is the key to the success of the adsorption method of perchlorate removal. This thesis explores the synthesis of magnetically functionalized novel adsorbent materials from bio-waste such as eggshell and watermelon rind. Synthesis of N-doped activated carbon and Metal-Organic- Framework (MOF) based adsorbents are also explored. The perchlorate adsorption efficiency, adsorption mechanism, adsorption isotherm models, and adsorption kinetics are studied with the developed adsorbents. The regeneration of the spent adsorbents using suitable regents is also demonstrated for their reuse. The high perchlorate adsorption capacity of some of the adsorbents demonstrates their potential for practical applications.

Despite a large number of studies made using both observations and models, due to the inability to disentangle the meterological effects from the aerosol impacts in cloud radiative forcing and poor parameterization in the numerical simulations, the interaction mechanisms between aerosols and clouds remain among the most un certain processes in the prediction of the global climate system

Selective Catalytic Reduction (SCR) is one of the most promising technologies for reducing after-exhaust NOx emissions. Cu zeolites generally provide high SCR conversion rates at temperatures ≤ 350◦C. The limitations associated with powdered catalysts, such as low mass diffusion and high pressure drop, can be minimized to a certain extent by replacing them with structured catalysts. The foam catalysts exhibit superior characteristics, such as a high surface-to-volume ratio, porosity, and tortuosity, which improve the mass diffusion and lower the pressure drop. In this study, α-alumina foam was prepared using a thermo-foaming technique. The procedure followed during this research for the preparation of the Cu-ZSM-5 zeolite coating over alumina foam through in situ hydrothermal and dip-coating methods is also presented in detail. A self-supporting foam catalyst of Cu-ZSM-5 is prepared using a freeze-casting emulsion method. A comprehensive experimental study was conducted to understand the mass transfer and pressure drop characteristics of the foam catalysts. Correlations for the mass transfer coefficient and friction factor were derived for the foam catalyst and validated against the available data in the literature reviewed. A detailed investigation of key SCR reactions, such as the standard SCR, fast SCR, slow SCR, NO oxidation, NH3 oxidation, and NO2 decomposition, was also carried out in this research. The inhibitory effects of the feed reactants were studied by varying the feed concentration. A detailed investigation of the impact of the inhibition effect of NO2 and NH3 on the SCR reaction at low temperatures is also presented.

Scientific missions to Lagrangian points have the potential to enhance the understanding of the universe and to accelerate the exploration of space. A typical mission design to an orbit around the Lagrangian points from the Earth involves two steps. In the first step, an orbit with prescribed geometrical characteristics is designed and in the second step, an optimal transfer trajectory to the orbit from an Earth parking orbit is designed. In the conventional approach to generate the preliminary design, the model of Circular Restricted Three Body Problem (CRTBP) framework is adopted utilizing differential correction (DC) and the transfer trajectory design using manifold theory. In this research, the preliminary design of orbits and transfer to them from the Earth are proposed to be executed under the framework of Elliptic Restricted Three Body Problem (ERTBP) utilizing an evolutionary optimization technique called Differential Evolution (DE). Various periodic orbits and quasi-periodic orbits in the Sun-Earth-spacecraft and Earth-Moon-spacecraft restricted three body systems and transfer trajectories to them from the Earth are generated without leveraging the manifold theory. For the transfer trajectory design in the Earth-Moon system, the proposed two-impulse methodology avoids the bridge segment and generates optimal trajectories with significantly lower flight durations compared to the manifold theory. The preliminary numerical designs are extended to high fidelity ephemeris models. In the ephemeris model, the generated quasi-halo orbits in the Sun-Earth system do not need any theoretical design maneuvers for about five years. For the mission design in the Sun-Earth system, it is substantively concluded that preliminary design using the ERTBP framework does not provide significant advantages over the CRTBP framework due to the near-circular nature of the Earth’s orbit around the Sun. The differential evolution technique is found to be very versatile in solving Lagrangian point mission design problems and avoids many complexities associated with the differential correction based technique. However, the DE based schemes are found to be computationally more intensive. The outcomes of this research can provide valuable methodologies and insights that can significantly enhance the effectiveness of future Lagrangian point missions, thus paving the way for further exploration and scientific discoveries in space.

The work is on Dynamic Compressed Sensing (DCS) system for efficient acquisition and recovery of sparse and compressible time-varying signals. DCS has three key components to be addressed: Estimation of the Sparsity level, indices of those sparse basis functions and their amplitudes. Sparsity Order Estimation (SOE) algorithms based on both Bernoulli/Gaussian sensing matrices and optimal tracking algorithms such as the Kalman filter and Viterbi Algorithm were developed. The developed algorithms resulted in reducing the complexity of CS methods by 25-30 % taking them closer to practical realization.

Electrochemistry deals with the relation between electrical and chemical phenomena and has an ever-increasing impact on everybody's daily life. Out of the myriad applications of electrochemistry, considerable attention has been devoted to the fields of electrochemical (EC) sensing in recent decades because of its inherently fast, accurate, compact, portable, and cost-effective properties. In this scenario, the thesis work aims to address the challenges in the fields of EC sensing by using the rational design of nano-functional materials using graphene quantum dots (GQDs) and metal nanoclusters (MNC). The on-site monitoring of various analyte species in the environment by EC sensors requires enhanced sensitivity, specificity, and accuracy. Herein, we are trying to meet the aforementioned needs by developing various nano-functional materials based on GQDs and MNC. We have developed nitrogen (N-) and sulphur (S-) doped GQDs and gold (Au) and copper (Cu) -based NCs for the EC sensing of toxic heavy metal ions and biologically relevant molecules. The EC sensor materials exhibited excellent sensitivities and lowest detection limits reported hitherto, indicating the potentiality of the developed materials. In conclusion, this thesis presents an understanding of how the logical designing of nano-functional materials can meet the needs and conquer the challenges in the EC sensing of various analytes.

Experiments probing correlations between spin-1/2 nuclei (I) and nuclear spins (S) with large anisotropic interactions (quadrupolar or chemical shift anisotropy ) often offer valuable access routes to molecular structures and dynamics. In such experiments, development of efficient correlation schemes is not trivial and constitutes an ever-evolving theme of research. As these experiments are performed routinely under MAS, interference between the RF filed and the large time- dependent quadrupolar or chemical shift anisotropic interaction leads to complex spin dynamics, often leading to poor and orientation-dependent transfer efficiency.

Mullite ceramics are widely recognized for their superior thermal stability, good creep resistance, low thermal conductivity and resistance to oxidation in high-temperature oxygen-rich environments. This thesis investigates a polymer-derived ceramic approach aimed at overcoming the limitations of traditional oxide composite manufacturing by enabling low-temperature, pressureless sintering while preserving the integrity of reinforcement materials. In this context, aluminosiloxane and zirconoaluminosiloxane precursors were synthesized for mullite and zirconia-mullite ceramics, and thoroughly characterized. Ceramic conversion studies demonstrated that these precursors can form stable ceramic phases at temperatures as low as 900°C, making them suitable for oxide-ceramic matrix composites (OCMCs). Fibrous alumina-reinforced composites derived from these precursors exhibited exceptional thermal and mechanical performance, including the ability to withstand hypersonic heat flux without damage. Additionally, cellular ceramics produced from these precursors formed open-cell structures with low thermal conductivity, critical for thermal protection applications. The influence of ceramic residue on the density, strength, and thermal properties was also explored. The results underscore the potential of these ceramics in advanced aerospace applications, particularly for thermal protection systems in hypersonic vehicles.

Transitional flows with an unsteady inflow play a vital role in a broad range of applications, including biological fluid transport to space applications. In such cases, the thickness of the boundary layer formed over the solid surface varies in both space and time, causing a high level of complexity in the path of vortical structures formed from the shear/boundary layer. Also, time and space-dependent shear stress exerted by the fluid, separation, and associated instability phenomena are to be better understood. In this work, direct numerical simulations (DNS) are performed to study the stability of vortical flow structures associated with an unsteady boundary layer under an adverse pressure gradient condition. A trapezoidal pulse of mean velocity, consisting of the acceleration phase from rest followed by the constant velocity phase and deceleration phase to rest, is imposed at the inlet of the computational domain. The impact of the spatial and temporal components on the evolution patterns of the shear-layer and three-dimensional instabilities are examined in detail. By employing dynamic mode decomposition, some key features of the transitional flow and their time dynamics are extracted.

The realization of a highly developed society with zero-carbon emissions and advanced electrified transportation demands the emergence of batteries delivering superior energy density and charge storage capability. The search of electrochemists to find materials that can outperform Li-ion batteries led to the research on Li-S batteries (LSBs), which are energy-dense, high-capacity energy storage systems. Nonetheless, the widespread development of lithium-sulfur batteries is held back because of some serious concerns. This thesis focuses on developing multifunctional nanostructures as electrode materials to overcome the challenges faced by Li-S batteries (LSBs) and improve the specific capacity. The work introduces a nanostructured graphene-lithium cobalt vanadate-based cathode for LSBs, which delivers excellent capacity with long-term cyclability. Further, studies based on metal sulfide-carbon nanotube-modified separators for LSBs revealed superior electrochemical output with negligible self-discharge. An aqueous processable polymer blend-based cathode binder, which demonstrates better capacity retention and coulombic efficiency over long-term cycling. We envision that this research could provide an effective platform for the emergence of high-performance Li–S batteries.

Protostellar jets are fossil records of the accretion history of protostars. Studying these jets opens up an indirect window of knowledge into the evolutionary stages and activities of the protostar, the direct study of which is difficult due to its highly embedded nature. The research highlights a theoretical and observational study of protostellar jets in radio and near-infrared wavelengths, respectively. The first part of the thesis describes a numerical model for radio jets from protostars, having simplistic geometry, which has been developed for the first time to explain the presence of thermal free-free and non-thermal synchrotron emission in these jets. The model has been successfully employed to estimate relevant physical and micro-physical parameters of protostellar jets for which observational data is available. The second part of the thesis covers a near-infrared investigation aimed at exploring the partially ionized and molecular regions of a massive protostellar jet, HH80-81, by utilizing molecular H2 and [FeII] emission lines as shock tracers. This is the first time detection of these emission lines towards the HH80-81 jet and following this, a qualitative and quantitative analysis of the jet has been carried out, enabling the identification of the nature of shocks and estimation of relevant physical parameters of the protostar and its jet.

This thesis aims to quantitatively analyse the effects of solar wind-magnetosphere-ionosphere (SW-M-I) coupling on the near -Earth space environment and enhance the current understanding of both large and small-scale coupling processes and mechanisms in the SW-M-I system during extreme transient events of supersubstorm and geomagnetic storms.At the first,robust quantitative analyses with regard to the LI-point and network of magnetometer and radars are included in comparative assessments and investigations of different coupling functions and the most significant parameters known to define the SW-M-I coupling. The in situ observations from the MMS, cluster, and THEMIS missions are additionally used to investigate the ion and electron scale coupling during the geomagnetic storm of 31 December 2015.