Recursos de colección

ETD at Indian Institute of Science (3.494 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.

Metallurgy (metalrg)

Mostrando recursos 1 - 20 de 137

  1. Microstructural Studies on High Cr-Mo Secondary Hardening Ultra-High Strength Steels

    Veerababu, R
    Secondary hardening ultra-high strength (SHUHS) steels possess a unique combination of strength, fracture toughness and stress corrosion cracking resistance, which makes them candidate materials for aircraft landing gear and armour applications. There is a sustained drive to develop stronger and tougher materials for such applications. The objectives of this thesis are two-fold: first, to develop a new SHUHS alloy that is stronger than the existing SHUHS steel developed at Defence Metallurgical Research Laboratory (DMRL), Hyderabad and second, to establish processing-structure-property correlations for the new alloy. Empirical design and development of these complex steels involves enormous effort, cost, time and materials...

  2. Bioremediation of Chromium : Mechanisms and Biosensing Applications

    Prabhakaran, Divyasree C
    Water pollution, especially caused due to the indiscriminate release of heavy metals as a result of anthropogenic activities is a major concern worldwide. Chromium, a heavy metal, regardless of its commercial importance has found to be a potent water pollutant. Chromium generally exist as hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium in the environment. Cr(VI) is ascertained to be more toxic compared to Cr(III) and the former is identified as a carcinogen by the World Health Organisation (WHO). Some of the conventional methods currently available for chromium pollution mitigation are not cost effective and most importantly lead to secondary pollution in...

  3. Design and Fabrication of Conjugated Molecule Based Resistive Sensor for Environmental Monitoring Detecting Targeted Analytes

    Mallya, Ashwini N
    Volatile organic compounds (VOCs) in air and heavy metal ions, anions, microorganism in water are environmental contaminants that require detection at certain low concentrations to avoid detrimental effects. Analytical instruments can accurately determine the concentration and composition of the contaminants at trace levels. However, these methods require skilled personnel to operate. Hence sensors should have fast response, low maintenance and easy to handle. In the present work, environmental monitoring sensor for volatile organic compounds, anion and E. coli was developed. The sensor is resistive sensor architecture with organic nanocomposite as sensing layer. The conjugated organic molecule with receptor moieties that...

  4. Effect of Humidity and Temperature on Wear of TiN and TiAIN Coatings

    Govindarajan, Sumanth
    When loss of material due to sliding of two solids is promoted/prevented, in the presence of chemically reacting liquid or gas, tribochemical wear is said to occur. Tribochemical wear, in which corrosive media promotes material loss, is a serious concern in a variety of applications like machining, bio-implants, gas turbine engines etc. The most pervasive corrosive media encountered in applications are water and air. Air also contains water vapour along with oxygen, both of which adsorb and react with most materials, thus influencing their wear behaviour. The need for higher operating temperatures and compression ratios in gas turbine engines require...

  5. Mechanical and Corrosion Properties of Selective Laser Melted Alloys

    Suryawanshi, Jyoti Balaji
    Selective laser melting (SLM) of metallic powders is an additive manufacturing technique that is widely employed to produce 3D components, and is fast becoming an important method for manufacturing near-net shape and complex metallic parts. In this thesis, a comprehensive investigation on the effect of SLM on the mechanical and corrosion properties of the Al-12Si (AS), 316L stainless steel (SS), and 18(Ni)-300 grade managing steel (MS) is investigated, with particular emphasis on the developing (micro- as well as mesa-)structure -property correlations. Detailed microstructural characterization combined with quasi-static tensile, fracture toughness, fatigue crack growth, and unmatched fatigue tests were conducted. The...

  6. Whisker Growth from Electrodeposited Sn Coatings - Developing Materials Science and Mechanics Based Insights

    Jagtap, Piyush
    Pure Sn and Sn-alloys are widely used in electrical and microelectronic devices as protective layer to prevent oxidation of Cu conductors and also as a component of Pb-free, Sn-based solders. Sn coatings, typically 0.5-10 μm thick, deposited on substrates, e.g., Cu, brass, etc., are prone to spontaneous growth (i.e., without any external stimuli) of Sn whiskers under ambient conditions. The growth of whiskers from Sn plating has caused numerous failures in micro-electronic devices, mainly due to short-circuiting, leading to failure of components or devices. Whisker growth is, thus especially very critical in aviation, space and defines applications, where the electronic...

  7. Study on Development of Aluminium Based Metal Matrix Composites Using Friction Stir Processing

    Dixit, Saurabh
    Composite materials are multifunctional materials having unique mechanical and physical properties that can be tailored to meet the requirements of a particular application. Aluminium based Metal Matrix Composites (MMC) always draw the attention of researchers due to its unique characteristics such as better strength to weight ratio, low wear rate and lower thermal expansion coefficient. There are various methods for manufacturing of MMC that can be grouped into two major categories: (a) Solid sate method such as powder metallurgy, co-extrusion and (b) Liquid state method such as stir casting. All of these methods for production of composites have their own...

  8. Interface Engineering and Evaluation of Device Performance in Organic Photovoltaics

    Rao, Arun Dhumal
    In recent years, organic photovoltaics (OPVs) have attracted considerable attention as a potential source of renewable energy over traditional materials due to their light weight, low production cost, mechanically stability and compatibility with flexible substrates in roll to roll processing for high volume production. In the OPVs interface plays an important role in determining the performance of the device. Interface signifies formation of efficient contact with electrode, film, and transport of free charge carrier, which results in better performance in the device. Interface engineering also helps in improving mechanical robustness of the device. Hence, understanding of interface, modification and its...

  9. Morpological Architecturing of Electroactive Materials in Organic Electronics

    Khanum, Khadija Kanwal
    Morphological architecturing is one of the smart and efficient ways to maximize the number of excitons harvested from the known photoactive materials and existing fabrication technologies. Surfaces and interfaces play a vital role in absorbing light and therefore when patterned regularly, aid in the improvement of light absorption. This thesis deals with the study of light management by morphologically architecturing the organic electroactive materials. Here, morphological architecturing is carried out using electrospinning technique by optimizing various parameters. In the first part, organic photovoltaic system is tailored by morphologically modifying the conjugated polymer active layer and analyzing the enhancement in light...

  10. Correlation Between Structure, Microstructure and Enhanced Piezoresponse Around the Morphotropic Phase Boundary of Bismuth Scandate-Lead Titanate Piezoceramic

    Lalitha, K V
    Piezoelectric materials find use as actuators and sensors in automotive, aerospace and other related industries. Automotive applications such as fuel injection nozzles and engine health monitoring systems require operating temperatures as high as 300-500 oC. The commercially used piezoelectric material PbZr1-xTixO3 (PZT) is limited to operating temperatures as low as 200 oC due to the temperature induced depolarization effects. PZT, in the undoped state exhibits a piezoelectric coefficient (d33) of 223 pC/N and ferroelectric-paraelectric transition temperature (Tc) of 386 oC. The enhanced properties of PZT occur at a region between the tetragonal and rhombohedral phases, called the Morphotropic Phase Boundary...

  11. Investigation of Graphene Oxide Based Multilayered Capsules/Films for Drugs Delivery And Antimicrobial Applications

    Kurapati, Rajendra
    Polyelectrolyte multilayer capsules fabricated by layer-by-layer (LbL) self-assembly technique consistsing of core-shell structure have emerged as potential drug delivery systems along with their applications in micro-reactors, cosmetics, vaccines and antimicrobial coatings. Various ligands and stimuli responsive entities can be incorporated into the core and shell of the capsules for targeted delivery and/or controlled release applications. Though multilayer capsules have been studied extensively as delivery systems, their utility for encapsulation of hydrophobic drugs and multiple drugs have not been explored in detail so far. Application of traditional polyelectrolyte capsules has several limitations, which renders them inapplicable for encapsulation of multiple drugs,...

  12. Microstructural Developments and Mechanical Properties of Electroless Ni-B Coating

    Pal, Soupitak
    Phase transformation behavior, micro structural development, mechanical and tribological properties of electroless Ni-B coating was characterized using different characterization techniques. As deposited electroless Ni-B coating containing 94 wt. % of NI and 6 wt. % of B is amorphous. It crystallizes via two exothermic reactions one at 3000C and another at 430˚C. It has been observed that there is also slow evolution of the heat in between this two exothermic reactions. XRD studies display that as deposited coating undergoes multi-stage crystallization events. At the first exothermic peak NI3B phases crystallizes, in between two a phase mixture of Ni and Ni3B...

  13. Structural, Ferroelectric, Piezoelectric and Phase Transition Studies of Lead Free (Na0.5Bi0.5)TiO3 Based Ceramics

    Garg, Rohini
    Ferroelectric materials, especially the polycrystalline ceramics, are very promising material for a variety of applications such as high permittivity dielectrics, ferroelectric memories, piezoelectric sensors, piezoelectric/electrostrictive transducers, electrooptic devices and PTC thermistors. Among the ferroelectric based piezoelectric ceramics the lead–zirconate-titanate Pb(Zr1-xTix)O3 (PZT) have dominated transducer and actuator market due to its excellent piezoelectric and dielectric properties, high electromechanical coupling, large piezoelectric anisotropy, ease of processing and low cost. However, the toxicity of lead based compounds has raised serious environmental concerns and therefore has compelled the researchers to look for new lead free alternatives with good piezoelectric and ferroelectric properties. (Na0.5Bi0.5)TiO3 (NBT)...

  14. Effect of Heat Treatment and Modification on Flow and Fracture Behaviour of a Newly Developed Al-Si Based Cast Alloy

    Joseph, Sudha
    The compression behavior of a newly developed near eutectic Al-Si based cast alloy with three different microstructures has been investigated in the present work. Microstructures with modified and unmodified Si particles and matrix with different tempers are investigated. The main objective of this work is to understand the effect of heat treatment and modification on the fracture behavior of the alloy under compression. This alloy is subjected to compressive loading at different strain rates and temperatures during the operation of the engines. Hence, the effect of strain rates and temperatures is also considered. The compression tests are carried out at...

  15. Development of Hybrid Organic/Inorganic Composites as a Barrier Material for Organic Electronics

    Gupta, Satyajit
    The ultra high barrier films for packaging find applications in a wide variety of areas where moisture and oxygen barrier is required for improved shelf-life of food/beverage products and for microbial free pharmaceutical containers. These materials also find applications in micro electro mechanical systems such as ICs, and for packaging in industrial and space electronics. Flexible and portable organic electronics like OLEDs (Organic Light Emitting Diodes), OPVDs (Organic Photo Voltaic Devices) and dye sensitized solar cells (DSSCs) have a good potential in next generation solar powered devices. In fact, organic insulators, semiconductors, and metals may be a large part of...

  16. Synthesis and Transformation of AuCu Intermetallic Nanoparticles

    Sinha, Shyam Kanta
    Investigations on size dependent phase stability and transformations in isolated nanoparticles have gained momentum in recent times. Size dependent phase stability generates size specific particle microstructure which consequently yields size specific functionality. One important prerequisite for conducting studies on nanoparticles is their synthesis. A substantial amount of research effort has therefore been focused on devising methodologies for synthesizing nanoparticles with controlled shapes and sizes. The present thesis deals with both these two aspects: (a) synthesis of nanoparticles and (b) phase transformations in nanoparticles. The system chosen in this study is AuCu intermetallic nanoparticles. The choice of AuCu nanoparticle was due...

  17. Micro-scale Fracture Testing of Graded (Pt,Ni)Al Bond Coats

    Nagamani Jaya, B
    PtNiAl bond coats are diffusion aluminide coatings deposited on superalloy based turbine blades for oxidation resistance and improved adhesion between the substrate and the YSZ thermal barrier coating on top. They are deposited by pack aluminisation, which makes their microstructure inherently graded and heterogeneous as well as replete with a variety of precipitates and second phase particles. The microstructure also continuously evolves during thermal cycling, because of interdiffusion with the substrate and the continuous loss of Al to the thermally grown oxide scale on top. During service, the bond coats are exposed to impact, thermal expansion mismatch, thermo-mechanical fatigue and...

  18. Interdiffusion Study in Group IVB, VB and VIB Refractory Metal-Silicon Systems

    Roy, Soumitra
    The knowledge of diffusion parameters provides important understanding of many physical and mechanical properties of materials. In most of the applications silicides are grown by a diffusion controlled process mainly in thin film condition. Because of this reason, most of the studies till date are available in thin film condition. Although more than one phase is present in all these systems, mainly disilicides were found at the interface. In this thesis bulk interdiffusion studies are conducted by coupling pure refractory metals (group IVB, VB and VIB elements) with single crystal Si. Several phase layers grow between binary refractory metal and...

  19. Thiophene Derivative Photovoltaics : Device Fabrication, Optimization and Study of Charge Transport Characteristics

    Swathi, S K
    In the recent years area organic photovoltaics is generating a lot of interests because whole process of synthesis and fabrication is less energy intensive process as well as it is cost effective compared to conventional inorganic Si based photovoltaic technology. This work mainly deals with the fabrication and optimization of device fabrication conditions for organic photovoltaic materials. In first part of the work, the solar cell fabrication conditions were optimized for the commonly used system P3HT – PCBM. The fabricated device was optimized for the solvents used for the active material, concentration of the active material solution, donor- acceptor...

  20. Densification Mechanisms for Spark Plasma Sintering in Alumina and Alumina Based Systems

    Chakravarty, Dibyendu
    The densification mechanisms of polycrystalline α-alumina by spark plasma sintering are highly contradictory, with different research groups suggesting diffusion to dislocation controlled mechanisms to be rate controlling. The specific objective of this work was to investigate densification mechanisms of α-alumina during the intermediate and final stages of sintering by SPS, analyze the microstructural development and establish sintering trajectories. In addition, zirconia and yttria were added in different weight percentages to study the effect of solute concentration on the densification kinetics of spark plasma sintered alumina. The present work adopts a different approach from the classical method adopted previously to analyze...

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