Recursos de colección

ETD at Indian Institute of Science (3.241 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.

Materials Research Centre (mrc)

Mostrando recursos 1 - 20 de 68

  1. Development of CMOS-Compatible, Microwave-Assisted Solution Processing of Nanostructured Zine Ferrite Films for Gigahertz Circuits

    Sai, Ranajit
    The development of radio frequency integrated circuits (RFICs), especially the dream of integrating analog, digital and radio frequency (RF) components on the same chip that is commonly known as System-on-a-Chip (SoC), is crucial to mobile communications of the future. Such SoC approach offers enhanced performance, greater reliability, and substantially less power consumption of integrated circuits while reducing overall physical size and thus manufacturing cost. However, the progress has been stalled by the lack of miniaturized inductor elements. Rise of unwanted parasitic effects limits down-scaling of the inductor structures and leaves the use of magnetic coating as a viable and attractive...

  2. Investigations into the Structural and Physical Properties of Li2O-M2O-2B2O3 (M=Li, Na & K), BaO-TiO2-B2O3 and 2Bi2O3-B2O3 Glass Systems

    Paramesh, Gadige
    Borate glasses and glass-nano/microcrystal composite fabrication and investigations into their physical properties, have been interesting from their multifunctionalities view point. Certain borate structural units possess high hyperpolarizabilities and give rise to high nonlinear optical effects. High refractive index materials are important for photonic applications. Heavy metal oxide (Bi2O3) containing compounds have high refractive indices. Glasses embedded with wide band-gap semiconducting oxide crystals such as TiO2 received much attention due to their easy processing, stability and promising physical properties. Though TiO2 is used as nucleating agent to fabricate glass-ceramics of various phases, crystallization of TiO2 in glass matrices is difficult and the...

  3. Earth Abundant Alternate Energy Materials for Thin Film Photovoltaics

    Banavoth, Murali
    Inexhaustible solar energy, which provides a clean, economic and green energy, seems to be an alternative solution, for current and future energy demands. Harvesting solar energy presents a challenge in using eco-friendly, earth abundant and inexpensive materials. Although present CdTe and Cu (In, Ga)Se2 (CIGS) technologies, provide light-to-electricity comparable to silicon technology, toxicity of Cd and scarcity of In limits the widespread utilization. Future tera-watt level module capacity would then be feasible by the low-cost technologies. The chalcogenide thin film technology would therefore provide the exceptional utilization in the large-area module monolithic integrations benefitting from the low material consumption owing...

  4. Investigations into the Microstructure Dependent Dielectric, Piezoelectric, Ferroelectric and Non-linear Optical Properties of Sr2Bi4Ti5O18 Ceramics

    Shet, Tukaram
    Ferroelectric materials are very promising for a variety of applications such as high-permittivity capacitors, ferroelectric memories, pyroelctric sensors, piezoelectric and electrostrictive transducers and electro-optic devices, etc. In the area of ferroelectric ceramics, lead-based compounds, which include lead zirconatetitanate (PZT) solid solutions, occupy an important place because of their superior physical properties. However, due to the toxicity of lead, there is an increasing concern over recycling and disposing of the devices made out of these compounds, which has compelled the researchers around the globe to search for lead-free compounds with promising piezo and ferroelectric properties. Ferroelectric materials that belong to Aurivillius...

  5. Studies on Effect of Defect Doping and Additives on Cr2O3 and SnO2 Based Metal Oxide Semiconductor Gas Sensors

    Kamble, Vinayak Bhanudas
    Metal Oxide (MO)semiconductors are one of the most widely used materials in commercial gas sensor devices. The basic principle of chemoresistive gas sensor operation stems on the high sensitivity of electrical resistance to ambient gaseous conditions. Depending on whether the oxide is "p type" or "n type", the resistance increases (or decrease), when placed in atmosphere containing reducing (or oxidizing) gases. The study of conductometric metal oxide semiconductor gas sensors has dual importance in view of their technological device applications and understanding fundamental MO-gas interactions. Metal oxides based sensors offer high thermal, mechanical and chemical stability. A large number of...

  6. Nanostructurization of Transition Metal Silicides for High Temperature Thermoelectric Materials

    Perumal, Suresh
    Transition Metal Silicides (TMS) are well known refractory materials because of their high thermal and structural stability at elevated temperature. In addition TMS materials are known for their moderate thermoelectric applications at high temperature since they exhibit superior semiconducting behavior. But TMS materials have relatively higher thermal conductivity which limits their applications in the field of thermoelectrics. So it is important to reduce their thermal conductivity to enhance conversion efficiency. In this regard, the work is performed to reduce the thermal conductivity of selected silicides such as CrSi2, MnSi2, and β-FeSi2 through alloys scattering and nano-structuring by mechanical alloying. A...

  7. Development of Metal Oxide/Composite Nanostructures via Microwave-Assisted Chemical Route and MOCVD : Study of their Electrochemical, Catalytic and Sensing Applications

    Jena, Anirudha

  8. Interfacing Biomolecules with Nanomaterials for Novel Applications

    Lal, Nidhi
    This thesis deals with the research work carried out for the development of novel applications by integrating biomolecules with various nanostructures. The thesis is organized as follows: Chapter 1 reviews the properties of nanomaterials which are important to consider while developing them for various biological and other applications. It discusses the factors which affect the cytotoxicity of nanocrystals towards living cells, photocatalytic mechanisms of nanocrystals that work behind the inactivation of bacterial cells and gas sensing properties of nanocrystals. It also mentions about the integration of biomolecules with nanomaterials which is useful for the development of biosensors, materials that are presently used...

  9. Novel 1-D and 2-D Carbon Nanostructures Based Absorbers for Photothermal Applications

    Selvakumar, N
    Solar thermal energy is emerging as an important source of renewable energy for meeting the ever-increasing energy requirements of the world. Solar selective coatings are known to enhance the efficiency of the photo thermal energy conversion. An ideal solar selective coating has zero reflectance in the solar spectrum region (i.e., 0.3-2.5 µm) and 100% reflectance in the infrared (IR) region (i.e. 2.5-50 µm). In this thesis, novel carbon nanotubes (CNT) and graphene based absorbers have been developed for photo thermal applications. Carbon nanotubes have good optical properties (i.e., α and ε close to 1), high aspect ratios (> 150), high...

  10. Physicochemical Characterization and Gas Sensing Studies of Cr1-xFexNbO4 and Application of Principal Component Analysis

    Sree Rama Murthy, A
    Monitoring the working environment of laboratories and industries for pollutants is of primary concern to ensure the healthiness of working personnel. Semiconducting metal oxides (SMOs) are sensitive to the gas ambience and can be tuned for sensing purpose. As SMOs are not selective, an array of sensors with differential selectivity may resolve to great extent. The objective of the thesis is to understand the physicochemical properties and gas sensing characteristics of Cr1-xFexNbO4. Applying principal component analysis to the sensor response data either for selection of features or for differentiation of analysts is also of concern. Preparation of Cr1-xFexNbO4, phase characterization,...

  11. Development of Multifunctional Biomaterials and Probing the Electric Field Stimulated Cell Functionality on Conducting Substrates : Experimental and Theoretical Studies

    Ravikumar, K
    Materials with appropriate combinations of multifunctional properties (strength, toughness, electrical conductivity and piezoelectricity) together with desired biocompatibility are promising candidates for biomedical applications. Apart from these material properties, recent studies have shown the efficacy of electric field in altering cell functionality in order to elicit various cell responses, like proliferation, differentiation, apoptosis (programmed cell death) on conducting substrates in vitro. In the above perspective, the current work demonstrates how CaTiO3 (CT) addition to Hydroxyapatite (HA) can be utilised to obtain an attractive combination of long crack fracture toughness (up to 1.7 MPa.m1/2 measured using single edge V-notch beam technique) and...

  12. Mechanisms of Formation and Thermal Stabililty of Functional Nanostructures

    Anumol, E A
    There are many challenges in materializing the applications utilizing inorganic nanoparticles. The primary drawback is the degradation of properties due to aggregation and sintering either due to elevated temperatures or prevailing chemical/electrochemical conditions. In this thesis, various wet chemical synthesis methods are developed to obtain metal nanostructures with enhanced thermal stability. The thesis is organized as below: Chapter 1 presents the problems and challenges in materializing the application of nanomaterials associated with the thermal stability of nanomaterials. A review of the existing techniques to improve the thermal stability and the scope of the thesis are presented. Chapter 2 gives a...

  13. Hydrothermal Synthesis of Carbon Nanoparticles for Various Applications

    Sadhanala, Hari Krishna
    Carbon nanoparticles (CNPs) have drawn great attention in the last few years owing to their unique properties such as excellent water solubility, chemical stability, inertness, low toxicity, good bio-compatibility, and tunable photo physical properties. Recently, researchers have focused on hetero atom (N, S and B) doped CNPs due to their excellent properties. These properties make the CNPs and doped CNPs as potential candidates for a wide range of applications. For example, metal ion detection in aqueous solution, bio-imaging, bio-sensing, photovoltaic devices, cleavage of deoxyribonucleic acid (DNA), and catalysis. Therefore, CNPs are alternative to inorganic semiconductor nanoparticles. However, CNPs with diameter...

  14. Investigation of Structural and Electronic Aspects of Ultrathin Metal Nanowires

    Roy, Ahin
    The constant trend of device miniaturization along with ever-growing list of unusual behaviour of nanoscale materials has fuelled the recent research in fabrication and applications of ultrathin (~2 nm diameter) nanowires. Although semiconductor nanowires of this dimension is well-researched, molecular-scale single-crystalline metal nanowires have not been addressed in details. Such single crystalline Au nanowires are formed by oriented attachment of Au nanoparticles along [111] direction. A very low concentration of extended defects in these wires result in a high electrical conductivity, making them ideal for nanoscale interconnects. Other metal nanowires, e.g. Ag and Cu, have very low absorption co-efficient useful...

  15. Size Dependence of Static and Dynamic Properties of Nanobars and Nanotubes

    Pathak, Sandeep
    This thesis aims at investigating size dependence of properties of nanostructures from the point of view of a general scaling theory that smoothly connects properties of the bulk to that of nanostructures. Two different examples of a ``static'' and a ``dynamic'' property are considered in this study. The first example studied is of size dependence of coefficient of thermal expansion (CTE) which a static property of nanostructures. The CTE of nanobars and nanoslabs is studied using equilibrium molecular dynamics and dynamical matrix formulation in an electrically insulating medium. It is found that the fractional change in CTE from the bulk...

  16. Investigations of Solution Combustion Process and their Utilization for Bioceramic Applications

    Sherikar, Baburao Neelkantappa
    Solution combustion synthesis (SCS) with its origin at IPC department of IISc has been widely practiced for synthesis of oxide materials. It is simple and low cost process, with energy and time savings that can be used to produce homogeneous, high purity, uniformly doped, nano crystalline ceramic powders. The powders characteristics such as crystallite size and surface area are primarily governed by enthalpy, flame temperature of combustion, fuel and fuel to oxidizer ratio ( F/O). In the present work an attempt has been made to investigate the process in order to exercise a control over the phase formation and nature...

  17. "Developing Device Quality Vanadium Dioxide Thin Films for Infrared Applications"

    Bharathi, R
    Vanadium oxides are being used as the thermal sensing layer because of their applications in infrared detectors. They have high temperature coefficient of resistance, favorable electrical resistance and compatibility with the MEMS technology. Of all oxides of vanadium, only vanadium dioxide (VO2)has been highly investigated as it shows first order transition (semiconducting to metal transition-SMT)at 68 oC. First order transition is understood as the sharp change in the electrical resistance. The change in resistivity in this case is of the order of 105 over a temperature change of 0.1 oC at 68 oC in a single crystal. Doping vanadium oxides...

  18. "Developing Device Quality Vanadium Dioxide Thin Films for Infrared Applications"

    Bharathi, R
    Vanadium oxides are being used as the thermal sensing layer because of their applications in infrared detectors. They have high temperature coefficient of resistance, favorable electrical resistance and compatibility with the MEMS technology. Of all oxides of vanadium, only vanadium dioxide (VO2)has been highly investigated as it shows first order transition (semiconducting to metal transition-SMT)at 68 oC. First order transition is understood as the sharp change in the electrical resistance. The change in resistivity in this case is of the order of 105 over a temperature change of 0.1 oC at 68 oC in a single crystal. Doping vanadium oxides...

  19. Thermal Oxidation Strategies for the Synthesis of Binary Oxides and their Applications

    Shinde, Satish Laxman
    Binary oxides constitute an outstanding class of functional materials with potential applications in many fields such as catalysis, gas sensing, field emission, solar cells, photodetection, etc. Due to the difference in their physical/chemical properties, different oxides have been explored for different applications. For examples, SnO2, Cr2O3 and ZnO are being explored for gas sensing due to their high adsorption capacity for volatile gases, ZnO, Cu2O etc. are being explored in solar cells because of high adsorption coefficient in UV/visible region and so on. Various techniques are available for synthesis of binary oxides and tuning their properties. Most of the physical...

  20. Thermal Oxidation Strategies for the Synthesis of Binary Oxides and their Applications

    Shinde, Satish Laxman
    Binary oxides constitute an outstanding class of functional materials with potential applications in many fields such as catalysis, gas sensing, field emission, solar cells, photodetection, etc. Due to the difference in their physical/chemical properties, different oxides have been explored for different applications. For examples, SnO2, Cr2O3 and ZnO are being explored for gas sensing due to their high adsorption capacity for volatile gases, ZnO, Cu2O etc. are being explored in solar cells because of high adsorption coefficient in UV/visible region and so on. Various techniques are available for synthesis of binary oxides and tuning their properties. Most of the physical...

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