ETD at Indian Institute of Science
(529 recursos)
Repository of Theses and Dissertations of Indian Institute of Science, Bangalore, India. The repository has been developed to capture, disseminate and preserve research theses of Indian Institute of Science.
Mostrando recursos 1 - 17 de 17
1.
Diffusion In Porous Solids : Void Disorder, Orientation And Rotation, Reaction And Separation, And Levitation Effect - Anil Kumar, A V
Diffusion in bulk has been well studied and our understanding may be said to be adequate if not complete. Similarly, surface diffusion has been investigated by a number of workers and a fair understanding of it has emerged. When guest particles are confined within the micropores of solids such as zeolites, the resulting phase is neither bulk nor an adsorbed phase but something in between. Properties of such a phase have not been understood sufficiently. Such phase found within these porous solids display rich variety in their property. In part, such a variety arises from the large number of factors...
2.
Synthesis And Investigation Of Transition Metal Oxides Towards Realization Of Novel Materials Properties - Ramesha, K
Transition metal compounds, especially the oxides, containing dn (0 ? n ? 10) electronic configuration, constitute the backbone of solid state/materials chemistry aimed at realization of novel materials properties of technological importance. Some of the significant materials properties of current interest are spin-polarized metallic ferromagnetism, negative thermal expansion, second harmonic nonlinear optical (NLO) susceptibility, fast ionic and mixed electronic/ionic conductivity for application in solid state batteries, and last but not the least, high-temperature superconductivity. Typical examples for each one of these properties could be found among transition metal oxides. Thus, alkaline-earth metal (A) substituted rare-earth (Ln) manganites, Ln?.xAxMn?3, are currently...
3.
Layered Oxides And Phosphates Of Bismuth: New Structural Types And Related Properties - Bharathy, Muktha
The thesis entitled "Layered Oxides and Phosphates of Bismuth: New Structural Types and Related Properties" consists of three parts and six chapters. It begins with an introductory note providing a brief overview of the existing literature on bismuth based layered oxides.
Part A of the thesis describes novel variants of the Aurivillius, Scheelite and Fluorite related phases with special emphasis on photocatalytic behavior of these materials.
Chapter 1 describes two new compounds, LiBi4Nb3O14 and LiBi4Ta3O14 characterized by single crystal X-ray diffraction to depict a unique structure, which have similarities with both an ideal Aurivillius phase and a typical hexagonal tungsten bronze. Photo-degradation...
4.
Slow Dynamics In Soft Condensed Matter : From Supercooled Liquids To Thermotropic Liquid Crystals - Chakrabarti, Dwaipayan
This thesis, which contains fourteen chapters in two parts, presents theoretical and computer simulation studies of dynamics in supercooled liquids and thermotropic liquid crystals. These two apparently diverse physical systems are unified by a startling similarity in their complex slow dynamics. Part I consists of six chapters on supercooled liquids while Part II comprises seven chapters on thermotropic liquid crystals. The fourteenth chapter provides a concluding note.
Part I starts with an introduction to supercooled liquids given in chapter 1. This chapter discusses basic features of supercooled liquids and the glass transition and portrays some of the theoretical frameworks and formalisms...
5.
Molecular Simulations Of Temperature Induced Disorder And Pressure Induced Ordering In Organic Molecular Crystals - Murugan, N Arul
Crystallographically solids with well defined crystal structures are normally assumed to be highly ordered. However, it is not uncommon to find considerable degree of disorder amongst many of these crystalline substances. Disorder among crystalline substances often arise from the rotational motion which leads to the well known class of plastic crystalline substances. Typically, globular molecules such as methane, carbon tetrachloride or adamantane exhibit plastic crystalline phase with significant amount of orientational disorder. In many other substances, disorder arises from torsional motion as in the case of biphenyl, p- or o-terphenyls, stilbene or azobenzenes. In case of molecules with flexible segment,...
6.
Perovskite Related Oxides: Development Of New Synthetic Methods, Materials And Properties - Mandal, Tapas Kumar
Oxides of ABO3 composition (A = alkali, alkaline earth or rare earth metal in general, B = transition metal) constitute a large family of metal oxides of current interest to solid state and materials chemistry. Among the several structure types exhibited by ABO3 oxides (ilmenite, LiNbO3, perovskite, YAIO3/YMnO3, KSbO3, pyrochlore, among others), the perovskite structure is probably the most well known and widely investigated. The ideal perovskite structure consists of a three-dimensional (3D) framework of corner-sharing BO6 octahedra in which the A cation resides in the dodecahedral site surrounded by twelve oxide ions. The ideal cubic structure occurs when the...
7.
Investigation Of A Novel Class Of Conducting Polyaniline And Related Systems - Chaudhuri, Debansu
The interest in conjugated polymers has been two-fold. A rich variety of intriguing physical phenomena, combined with its immense technological implications in the area of molecular electronics, sensors etc. has inspired the researchers all over the globe. The work presented in this thesis is focussed on one of the most widely studied conjugated polymers, namely polyaniline (PANI), which is well known for its high conductivity and remarkable stability in the proton-doped form. The thesis is divided into two chapters and each chapter is further divided into several parts.
In the first chapter, we take a look at some novel systems...
8.
Studies On Electrode Materials For Lithium-Ion Batteries - Palale, Suresh
In the early 1970s, research carried out on rechargeable lithium batteries at the Exxon Laboratories in the US established that lithium ions can be intercalated electrochemically into certain layered transition-metal sulphides, the most promising being titanium disulphide. Stemming from this discovery for titanium disulphide, there has been increased interest on lithium-ion intercalation compounds for application in rechargeable batteries. The first rechargeable lithium cell was commercialized in late 1980s by Moli Energy Corporation in Canada. The cell comprised a spirally wound lithium foil as the anode, a separator and MoS2 as the cathode. The cell had a nominal voltage of 1.8...
9.
Organically-Templated Open-Framework And Hybrid Materials - Behera, Jogendra Nath
Open-framework inorganic and inorganic-organic hybrid materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. Besides aluminosilicate zeolites, the metal phosphates and carboxylates constitute large families of open-framework structures. The possibility of building open architectures with the sulfate and selenate anions as the basic building units has been explored in this thesis. Investigations of a variety of open-framework metal sulfates and selenates, as well as a family of jarosites of different transition metals are
presented. More importantly, studies directed towards the synthesis and understanding of the magnetic properties of...
10.
Investigations Of Open-Framework Metal Carboxylates, Sulfates And Related Materials - Dan, Meenakshi
Open-framework materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. Furthermore, these materials exhibit fascinating architectures with unusual bonding and coordination patterns. Besides aluminosilicate zeolites and metal phosphates, metal carboxylates constitute an important family of open-framework structures. In this thesis, results of investigations of a variety of open-framework metal carboxylates, as well as a new family of rare-earth sulfates are presented. More importantly, studies directed towards an understanding of the mechanism of formation of open-framework phosphates and carboxylates and the importance of synthesis parameters like temperature in...
11.
Growth Kinetics And Electronic Properties Of Semiconducting Nanocrystals In The Quantum Confined Regime - Viswanatha, Ranjani
Properties of nanocrystals are extremely sensitive to their sizes when their sizes are smaller or of the order of the excitonic diameter due to the quantum confinement effect. The interest in this field has been concentrated basically in understanding the size-property relations of nanocrystals, for example, the pronounced variation in the bandgap of the material or the fluorescence emission properties, by tuning the sizes of the nanocrystals. Thus, the optical and electronic properties of semiconductor nanocrystals can be tailor-made to suit the needs of the specific application and hence is of immense importance. One of the major aspects necessary for...
12.
Studies On Direct Methanol And Direct Borohydride Fuel Cells - Kothandaraman, R
A fuel cell is an electrochemical power source with advantages of both the combustion engine and the battery. Like a combustion engine, a fuel cell will run as long as it is provided fuel; and like a battery, fuel cells convert chemical energy directly to electrical energy. As an electrochemical power source, fuel cells are not subjected to the Carnot limitations of combustion (heat) engines. Fuel cells bear similarity to batteries, with which they share the electrochemical nature of the power generation process and to the engines that, unlike batteries, will work continuously consuming a fuel of some sort. A...
13.
Structure, Organization And Phase Transitions In Anchored Alkyl Chain Bilayers In Layered Organic-Inorganic Hybrids - Barman, Sudip
This thesis deals with the conformation and phase-transitions in anchored alkyl chain bilayer assemblies in organic-inorganic hybrids. The alkyl chain bilayers in organic-inorganic hybrids bear a striking resemblances to the lipid bilayers that are an integral part of biomembranes. However, unlike the lipid bilayer where individual lipid molecules can undergo the total absence of translational mobility. The anchored bilayer are, therefore, the simplest model system for understanding the structure, organization and thermal behaviour of alkyl-chain assemblies. The anchored bilayer in the organic-inorganic hybrids also offer the advantage that unlike the lipid bilayers that are essentially fluid like, these are solids...
14.
Theoretical And Computer Simulation Studies Of Vibrational Phase Relaxation In Molecular Liquids - Roychowdhury, Swapan
In this thesis, theoretical and computer simulation studies of vibrational phase relaxation in various molecular liquids are presented. That includes liquid nitrogen, both along the coexistence line and the critical isochore, binary liquid mixture and liquid water. The focus of the thesis is to understand the dependence of the vibrational relaxation on the density, temperature, composition and the role of different interactions among the molecules. The density fluctuation of the solute particles in a solvent is studied systematically, where the computer simulation results are compared with the mode coupling theory (MCT). The classical density functional theory (DFT) is used to...
15.
Investigations Of Open-Framework Metal Phosphates, Phosphites And Phosphite-Oxalate Materials - Mandal, Sukhendu
Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids. Most of them are based upon oxygen containing materials especially phosphates, and they exhibit fascinating architectures with unusual bonding and coordination environment. Besides metal phosphates and phosphites, inorganic-organic hybrids constitute an important family of open-framework structures. In this thesis, results of investigations of a variety of open-framework metal phosphates, metal phosphites,...
16.
Noble Metal And Base Metal Ion Substituted Ceo2 And Tio2 : Efficient Catalysts For Nox Abatement - Roy, Sounak
In recent times, as regulations and legislations for exhaust treatment have become more stringent, a major concern in the arena of environmental catalysis is to find new efficient and economical exhaust treatment catalysts. Chapter 1 is a review of the current status of various NOx abatement techniques and understanding the role of “auto-exhaust catalysts” involved therein. Chapter 2 presents the studies on synthesis of ionically substituted precious metal ions like Pd2+, Pt2+ and Rh3+ in CeO2 matrix and their comparative three-way catalytic performances for NO reduction by CO, as well as CO and hydrocarbon oxidation. Ce0.98Pd0.02O2- showed better catalytic activity...
17.
Investigation Of Electronic And Magnetic Structure Of Transition Metal Oxides With Emphasis On Magnetoresistive Systems - Topwal, Dinesh
Electronic structure of transition metal oxides has been a subject of intense research since decades due to the wide spectrum of properties that they exhibit, like high temperature superconductivity, metal-insulator transitions (MIT), phase separation etc. Among these, colossal magnetoresistance (CMR), i.e. a sharp drop in the electrical resistance by the application of an external magnetic field, is a property of fundamental and technological importance. In the present study we investigate several of these interesting properties ranging from colossal magnetoresistance, metal-insulator transitions and phase separation phenomena on a wide range of magnetoresistive systems. All these properties originate in transition metal oxides...
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