ETD at Indian Institute of Science
(528 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 - 20 de 28
1.
Structures, Thermodynamics and Phase Relations in Selected Oxide Systems - Lwin, Kay Thi
Understanding of the interrelationship between structure, thermodynamic properties and phase diagrams is very useful for rationalizing the behavior of materials and development of predictive models, which can be used to optimize the composition of materials and their fabrication processes. The properties of materials are governed by its electronic and crystallographic structure. Chemical bonding determines the electronic structure of materials. Furthermore, the electronic structure plays a predominant role in determining the physical, electrical, magnetic, thermal and optical properties of materials. Crystal structure also influences most properties of materials. Since changes in thermodynamic variables such as temperature, pressure, and composition dramatically alter...
2.
Bubble Solid Interaction - Mukherjee, Manas
The interaction of a bubble with solid surfaces, hydrophobic and hydrophilic, was investigated. When a bubble approaches towards a solid surface, a thin liquid film forms between them. The liquid in the film drains until an instability forms and film ruptures resulting in a three phase contact (TPC). Following rupture, the TPC line spreads on the solid surface. In the present study, glycerol-water solutions with varying percentages of water were used to investigate the effect of viscosity. Experiments were carried out with varying bubble size. The rupture and TPC line movement were recorded by high-speed digital video camera. The dependence...
3.
Pulsed Laser Ablation Deposition of Intermetallic Thin Films: A Study of Evolution of Metastable Phases and Ultra-fine Microstructures - Bysakh, Sandip
This thesis is devoted to the deposition of intermetallic thin films by laser ablation deposition (LAD) and their characterization. Pulsed laser ablation and subsequent deposition of the ablated vapours produces films under conditions very far away from equilibrium. Besides the film, which forms directly by quenching the vapour or plasma on substrate, one also obtains under certain conditions micron and sub-micron sized spherical droplets of alloy melt on to the film. The latter travel at very high velocities and impinge on the substrate resulting in a very high rate of heat transfer during solidification from liquid state. Therefore, in this...
4.
Cold Model Study Of Formation And Breaking Of Raceway - Sastry, Ghatty S S R K
The raceway in the ironmaking blast furnace is a void in front of the hot blast tuyeres where coke and supplementary fuel burn to supply heat to the ironmaking process. The air velocity through the tuyeres is high (around 200 m/s) and this causes the coke particles to circulate in a rotating flow field inside the raceway. The size and shape of the raceway determine the gas flow dstribution, the reactions that occur, and the temperature profiles in the lower part of the blast furnace.
It is for these reasons that the raceway has been extensively researched in the past. ....
5.
Processing And Characterization Of B4C Particle Reinforced Al-5%Mg Alloy Matrix Composites - Khan, Kirity Bhusan
Metal matrix composites (MMCs) are emerging as advanced engineering materials for application in aerospace, defence, automotive and consumer industries (sports goods etc.). In MMCs, a metallic base material is reinforced with ceramic fiber, whisker or particulate in order to achieve a combination of properties not attainable by either constituent individually. Aluminium or its alloy is favoured as metallic matrix material because of its low density, easy fabricability and good engineering properties. In general, the benefits of aluminium metal matrix composites (AMCs) over unreinforced aluminium alloy are increased specific stiffness, improved wear resistance and decreased coefficient of thermal expansion. The conventional...
6.
Study Of Friction And Wear Behaviour Of Nano-Embedded Aluminium Alloys - Bhattacharya, Victoria
In general, the bearing alloys have two types of microstructure i.e., either a soft matrix with discrete hard particles or a continuous matrix of the harder metal with small amount of the softer metal finely dispersed in it. The aluminium and copper based bearing alloys which are widely studied fall in the second category. However, the bearing materials which have been studied have micron sized dispersoids. In recent times, it is possible to produce nanoscale dispersoids in a hard matrix by the novel processing route of rapid solidification. This offers an opportunity to study the small length scale effect on...
7.
Studies On Biodegradation Of Organic Flotation Collectors Using Bacillus polymyxa - Chockalingam, Evvie
Numerous organic reagents of diverse structural composition are employed in the froth flotation process for the beneficiation of non-metallic and sulphide ores. Alkyl xanthates are used as collectors for sulphide ores while amines and fatty acids are used for non-metallic ore beneficiation. Although these collector reagents react preferentially with the concerned minerals in the treated ore pulp, excess and unreacted concentration of these organic collectors end up in the mill process effluents. It has been known that even small concentrations of these organic reagents in water streams are toxic to water life, besides their deleterious influence on end stream processes...
8.
Processing, Characterization And Evaluation Of A Functionally Graded Ai - 4.6% Cu Alloy - Sivakumar, V
In some applications the stress across the entire cross-section of a component is not uniform but varies with position. For example, maximum shear stress is highest at the inner surface of a thick-walled cylinder subjected to uniform internal pressure and it decreases continuously towards the outer surface. In such applications it would be more appropriate for the component, too, to have varying strength across the cross-section matching with the stress profile it is subjected to. The present work deals with obtaining such a functionally graded material (FGM), characterizing it and testing its mechanical properties in compression.
Differential aging heat treatment was...
9.
Studies On Bio-Oxidation A Refractory Gold Containing Sulphidic Concentrate With Respect To Optimization And Modeling - Chandraprabha, M N
Although bacterial leaching of sulphidic minerals is a well-known phenomenon, it is only in the last ten years that full-scale bacterial leaching plants have been commissioned for gold
processing. In order for bacterial leaching to compete successfully with other pretreatment processes for refractory ores, particularly with established technologies such as roasting and pressure leaching, it needs to be efficient. This requires the optimization of the parameters affecting the leaching reaction and the growth of bacteria.
The entire biotreatment process is agitation leaching, carried out in stirred reactors or Pachuca type reactors. The bacterial oxidation is a complex reaction involving gaseous, liquid...
10.
Studies On Corrosion Of Some Structural Materials In Deep Sea Environment - Venkatesan, R
Efficient exploitation and conservation of the oceans poses great technological challenges for scientists and engineers who must develop materials, structures and equipment for use in harsh environment of the oceans. For the applications of materials in marine environment, knowledge of the corrosion properties is essential for selection purposes. Presently, effort is being devoted to exploit deep-sea mineral resources. Deterioration of materials in the deep sea is due to the cumulative effect hydrostatic pressure, temperature, pH, dissolved oxygen, salinity and sea current. For the first time, in-situ corrosion measurements on the effect of deep sea environment on some metallic and composite...
11.
Mean Field Study Of Point Defects In B2-NiAl - Gururajan, M P
Point defects control many properties of technological importance in intermetallic compounds such as atomic diffusion, creep, hardness, mechanical properties and sintering. Farther, since intermetallic compounds are characterized by long range atomic order, the point defects in these compounds can be qualitatively different from those in pure metals and disordered alloys. In the present study, we have chosen ?-NiAl for our point defect studies since it is a potential candidate for high temperature applications and a model system for the study of basic phenomena in ordered alloys.
We have used a mean field formulation for studying point defect concentrations. The outline of...
12.
Metastable Phases In Mg-Based Alloys - Subramaniam, Anandh
Mg-based alloys form a variety of interesting structures including stable and metastable crystalline, stable and metastable quasicrystalline, nanocrystalline and amorphous phases. Many of these phases can be made to coexist by suitable processing leading to an interesting combination of properties. Non-equilibrium processing in combination with suitable heat treatments can be used to control the scale and dispersion of these phases. Further thrust to Mg-based alloys is expected through the development of Mg-based bulk metallic glasses. Magnesium matrix composites are also gaining in prominence.
The thesis has been divided into theoretical and experimental parts. The theoretical part focuses on understanding the structure...
13.
Processing And Characterisation Of Bulk Al2 O3 p /AIN-Al Composites By Pressureless Infiltration - Swaminathan, S
Al-Mg alloys were infiltrated into porous alumina preforms at temperatures greater than 950°C where significant amount of nitride forms in the matrix. The present work aims to obtain a process window for growing A1N rich composites over uniform thicknesses so that bulk fabrication of these composites could be carried out. Initial experiments were carried out in a thermo-gravimetric analyser (TGA) to establish suitable conditions for growing useful thicknesses. Al- 2wt% Mg alloy, alumina preforms of particle size 53-63?m and N2 - 2% H2 (5ppm O2) were used for the present study based on previous work carried out in the fabrication...
14.
Processing And High Temperature Deformation Of Pure And Magnesia Doped Alumina - Swaroop, N R Sathya
Creep resistance is an important design criterion at high temperatures especially when continuous attempts are made to increase the efficiencies by increasing the operating temperatures. Alumina is an important high temperature material and in addition to that it is used in wide variety of applications such as substrates for electronic packaging, spark plugs, envelopes for sodium vapour lamps, cutting tools (when reinforced with silicon carbide) and in artificial joint prostheses.
Studies on creep in alumina. have started as early as 1961. There are differing mechanisms proposed to explain the creep behaviour of alumina in the literature, but until now there is...
15.
Symmetry-Breaking Transitions In Equilibrium Shapes Of Coherent Precipitates - Sankarasubramanian, R
We present a general approach for determining the equilibrium shape of isolated, coherent, misfitting particles by minimizing the sum of elastic and interfacial energies using a synthesis of finite element and optimization techniques. The generality derives from the fact that there is no restriction on the initial or final shape, or on the elastic moduli of the particle and matrix, or on the nature of misfit. The particle shape is parameterized using a set of design variables which are the magnitudes of vectors from a reference point inside the particle to points on the particle/matrix interface. We use a sequential...
16.
Modeling Constitutive Behavior And Hot Rolling Of Steels - Phaniraj, M P
Constitutive behavior models for steels are typically semi-empirical, however recently neural network is also being used. Existing neural network models are highly complex with a large network structure i.e. the number of neurons and layers. Furthermore, the network structure is different for different grades of steel. In the present study a simple neural network structure, 3:4:1, is developed which models flow behavior better than other models available in literature. Using this neural network structure constitutive behavior of 8 steels: 4 carbon steels, V and V-Ti microalloyed steels, an austenitic stainless steel and a high speed steel could be modeled with...
17.
Role Of Interfacial Phenomena In Bioprocessing Of Minerals Using Bacillus Polymyxa - Shashikala, A R
In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength....
18.
Studies On The Bioremoval Of Hexavalent And Trivalent Chromium Using Bacillus Polymyxa - Thyagarajan, Hemamalini
The removal of toxic and heavy metal contaminants from aqueous waste streams and industrial effluents is one of the most important environmental issues being faced the world over. In order to combat this problem, the commonly used procedures for removing metal ions from dilute aqueous streams include chemical precipitation, ion exchange, reverse osmosis and solvent extraction. However, these techniques have certain disadvantages such as incomplete metal removal, high reagent and energy requirements, generation of toxic sludge or other waste products that require disposal. The hazardous wastes generated from metal mining and smelting operations also need to be decontaminated before entering...
19.
Microstructure And Texture Evolution And Its Effect On Mechanical Properties In Dilute Magnesium Based AZ21 Alloy - Abdul Azeem, Mohd.
Dilute Mg alloys are exclusively identified for wrought structural applications in automotive industry. Any improvement in mechanical properties of alloys is possible only by grain size refinement and by the development of suitable texture. The grain size, grain size anisotropy and texture in these alloys affect the compatibility stresses in a very complex manner. To launch a full scale study towards understanding the complex deformation mechanisms operating in these alloys, it is necessary to understand the effect of grain size and texture on the mechanical behavior of Mg alloys in a broad or semi-quantitative manner first. Current literature lacks such...
20.
Modeling Of Liquid Flow In A Packed Bed Under Influence Of Gas Flow - Singh, Vikrant
The aim of the current study is to model (non-wetting) liquid flow in a packed bed under the influence of gas flow. It has been observed experimentally that non-wetting liquid flows in a packed bed in form of small droplets and rivulets falling through the void regions. Continuum models have not been successful in predicting liquid flow paths when the liquid is injected through a point source in the packed bed. In the current study, we present a discrete deterministic model for modeling the liquid flow in a packed bed, under the influence of gas flow.
When a high velocity gas...
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