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Articles 1 - 16 of 16
Full-Text Articles in Engineering
Arc-Discharge In Solution: A Novel Synthesis Method For Carbon Nanotubes And In Situ Decoration Of Carbon Nanotubes With Nanoparticles, Debasis Bera
Electronic Theses and Dissertations
Nanotechnology has reached the status of the 21st century's leading science and technology based on fundamental and applied research during the last two decades. An important feature of nanotechnology is to bridge the crucial dimensional gap between the atomic and molecular fundamental sciences and microstructural scale of engineering. Accordingly, it is very important to have an in-depth understanding of the synthesis of nanomaterials for the use of state-of-the-art high technological devices with enhanced properties. Recently, the 'bottom-up' approach for the fabrication of nanomaterials has received a great deal of attention for its simplicity and cost effectiveness. Tailoring the various parameters …
Transmission Electron Microscopy Studies In Shape Memory Alloys, Madhavi Tiyyagura
Transmission Electron Microscopy Studies In Shape Memory Alloys, Madhavi Tiyyagura
Electronic Theses and Dissertations
In NiTi, a reversible thermoelastic martensitic transformation can be induced by temperature or stress between a cubic (B2) austenite phase and a monoclinic (B19') martensite phase. Ni-rich binary compositions are cubic at room temperature (requiring stress or cooling to transform to the monoclinic phase), while Ti-rich binary compositions are monoclinic at room temperature (requiring heating to transform to the cubic phase). The stress induced transformation results in the superelastic effect, while the thermally induced transformation is associated with strain recovery that results in the shape memory effect. Ternary elemental additions such as Fe can additionally introduce an intermediate rhombohedral (R) …
Interdiffusion Analysis For Nicocraly And Nial Vs. Various Superalloys, Emmanuel Perez
Interdiffusion Analysis For Nicocraly And Nial Vs. Various Superalloys, Emmanuel Perez
Electronic Theses and Dissertations
Hot section components in gas turbines can be NiCoCrAlY-coated to provide the component with an Al reservoir that maintains a protective oxide layer on its surface. Over the service life of the component, the coatings degrade by composition and phase changes due to oxidation/hot-corrosion, and multicomponent interdiffusion from and into the superalloy substrate. In this study, the rate of Al interdiffusion into selected Ni-base superalloys using various diffusion couples of two-phase NiCoCrAlY (beta + gamma) and single beta-phase NiAl with the selected alloys is measured. The diffusion couples were examined with an emphasis on the composition-dependence of Al interdiffusion. Microstructural …
Instrumented Nanoindentation Studies Of Deformation In Shape Memory Alloys, Sudhir Rajagopalan
Instrumented Nanoindentation Studies Of Deformation In Shape Memory Alloys, Sudhir Rajagopalan
Electronic Theses and Dissertations
Near equi-atomic nickel titanium (NiTi) shape memory alloys (SMAs) are a class of materials characterized by their unique deformation behavior. In these alloys, deformation mechanisms such as mechanical twinning and stress induced phase transformation between a high symmetry phase (austenite) and a low symmetry phase (martensite) additionally occur and influence mechanical behavior and thus their functionality. Consequently, applications of SMAs usually call for precise phase transformation temperatures, which depend on the thermomechanical history and the composition of the alloy. Instrumented indentation, inherently a mechanical characterization technique for small sampling volumes, offers a cost effective means of empirically testing SMAs in …
Solar Driven Photoelectrochemical Water Splitting For Hydrogen Generation Using Multiple Bandgap Tandem Of Cigs2 Pv Cells And Thin Film Photocatalyst, Anant Jahagirdar
Solar Driven Photoelectrochemical Water Splitting For Hydrogen Generation Using Multiple Bandgap Tandem Of Cigs2 Pv Cells And Thin Film Photocatalyst, Anant Jahagirdar
Electronic Theses and Dissertations
The main objective of this research was to develop efficient CuIn1-xGaxS2 (CIGS2)/CdS thin film solar cells for photoelectrochemical (PEC) water splitting to produce very pure hydrogen and oxygen. Efficiencies obtained using CIGS2 have been lower than those achieved using CuInSe2 and CuIn1-xGaxSe2. The basic limitation in the efficiencies is attributed to lower open circuit voltages with respect to the bandgap of the material. Presently, the main mechanism used to increase the open circuit voltage of these copper chalcopyrites (CuInSe2 and CuInS2) is the addition of gallium. However, addition of gallium has its own challenges. This research was intended to (i) …
Diffraction Studies Of Deformation In Shape Memory Alloys And Selected Engineering Components, Chandrasen Rathod
Diffraction Studies Of Deformation In Shape Memory Alloys And Selected Engineering Components, Chandrasen Rathod
Electronic Theses and Dissertations
Deformation phenomena in shape memory alloys involve stress-, temperature-induced phase transformations and crystallographic variant conversion or reorientation, equivalent to a twinning operation. In near equiatomic NiTi, Ti rich compositions can exist near room temperature as a monoclinic B19' martensitic phase, which when deformed undergoes twinning resulting in strains as large as 8%. Upon heating, the martensite transforms to a cubic B2 austenitic phase, thereby recovering the strain and exhibiting the shape memory effect. Ni rich compositions on the other hand can exist near room temperature in the austenitic phase and undergo a reversible martensitic transformation on application of stress. Associated …
The Effect Of Colloidal Stability On The Heat Transfer Characteristics Of Nanosilica Dispersed Fluids, Manoj Venkataraman
The Effect Of Colloidal Stability On The Heat Transfer Characteristics Of Nanosilica Dispersed Fluids, Manoj Venkataraman
Electronic Theses and Dissertations
Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes …
Self-Assembled Supramolecular Structures Of Chiral Phospholipids: Structure, Mechanical Properties And Patterning, Nidhi Mahajan
Self-Assembled Supramolecular Structures Of Chiral Phospholipids: Structure, Mechanical Properties And Patterning, Nidhi Mahajan
Electronic Theses and Dissertations
Lipid molecule is well known natural building block to form different supramolecular structures with specific shape, size and functionality. In my thesis work, I have used DC8,9PC 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine), a type of chiral lipid to form the vesicles, tubules and ribbons . By using Atomic Force Microscope, I have studied the morphological features of these particular structures. Also, the mechanical properties of lipid tubules have been studied using AFM. Softlithography has been used to pattern the lipid vesicles and tubules into 2-dimensional and 3-dimensional ordered arrays. The structure of self-assembled hollow spherical vesicles was studied using AFM. The applications of soft …
High Voltage Bias Testing And Degradation Analysis Of Photovoltaic Modules, Vinaykumar Hadagali
High Voltage Bias Testing And Degradation Analysis Of Photovoltaic Modules, Vinaykumar Hadagali
Electronic Theses and Dissertations
This thesis mainly focuses on two important aspects of the photovoltaic modules. The first aspect addressed the high voltage bias testing and data and degradation analysis of high voltage biased thin film photovoltaic modules. The second aspect addressed the issues of reliability and durability of crystalline silicon module. Grid-connected photovoltaic systems must withstand high voltage bias in addition to harsh environmental conditions such as intermittent solar irradiance, high humidity, heat and wind. a-Si:H thin-film photovoltaic modules with earlier generation SnO2:F transparent conducting oxide (TCO) on the front glass installed on the FSEC High Voltage Test Bed were monitored since December …
Cryogenic Shape Memory Alloy Actuators For Spaceport Technologies: Materials Characterization And Prototype Testing, Jennifer Lemanski
Cryogenic Shape Memory Alloy Actuators For Spaceport Technologies: Materials Characterization And Prototype Testing, Jennifer Lemanski
Electronic Theses and Dissertations
Shape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of large forces associated with the strain recovery, smooth and controlled movements, large movement to weight ratio, high reliability, and spark-free operation. The objective of this work is …
Development Of Transparent And Conducting Back Contacts On Cds/Cdte Solar Cells For Photoelectrochemical Application, Upendra Sureshchandra Avachat
Development Of Transparent And Conducting Back Contacts On Cds/Cdte Solar Cells For Photoelectrochemical Application, Upendra Sureshchandra Avachat
Electronic Theses and Dissertations
The development of devices with high efficiencies can only be attained by tandem structures which are important to the advancement of thin-film photoelectrochemical (PEC) and photovoltaic (PV) technologies. FSEC PV Materials Lab has developed a PEC cell using multiple bandgap tandem of thin film PV cells and a photocatalyst for hydrogen production by water splitting. CdS/CdTe solar cell, a promising candidate for low-cost, thin-film PV cell is used as one of the thin film solar cells in a PEC cell. This research work focuses on developing various back contacts with good transparency in the infrared region (~750 - 1150 nm) …
Synthesis And Characterization Of Nanocrystalline Hydroxyapatite Powder; And The Effects Of Oxide-Based Sintering Additives On Tricalcium Phosphate, Himesh A. Bhatt
Synthesis And Characterization Of Nanocrystalline Hydroxyapatite Powder; And The Effects Of Oxide-Based Sintering Additives On Tricalcium Phosphate, Himesh A. Bhatt
Electronic Theses and Dissertations
Calcium phosphate (CP) materials have been used extensively for bone replacement and augmentation due to their similarity to the mineral component of bone. In addition to being non-toxic, they are biocompatible, not recognized as foreign materials in vivo, and most importantly, exhibit osteoconductive behavior, being able to help in bone formation during healing. CPs form an intimate physicochemical bond with the host tissue, termed osseointegration. However the main limitation of calcium phosphates is their inherent brittle nature and poor mechanical performance under complex stress states. As a result, these materials have been used clinically only in non-load-bearing applications, primarily as …
Nondestructive Evaluation Of Thermal Barrier Coatings With Thermal Wave Imaging And Photostimulated Luminescence Spectroscopy, Barbara Franke
Nondestructive Evaluation Of Thermal Barrier Coatings With Thermal Wave Imaging And Photostimulated Luminescence Spectroscopy, Barbara Franke
Electronic Theses and Dissertations
Gas Turbine manufacturers strive for increased operating temperatures of gas turbine engines to improve efficiency and performance. One method of increasing the temperature beyond material limits is by applying thermal barrier coatings (TBCs) to hot section components. TBCs provide a thermal gradient between the hot gases and metallic substrate, and allow an increase in turbine inlet temperatures of 100-150ºC. However, spallation of TBCs can cause catastrophic failure of turbine engines by incipient melting of the substrate. To prevent such an occurrence, non-destructive evaluation (NDE) techniques are critical for quality control, health monitoring, and life assessment of TBCs. Two techniques in …
Structural Evolution In Mechanically Alloyed Fe-Based Powder Systems, Umesh Patil
Structural Evolution In Mechanically Alloyed Fe-Based Powder Systems, Umesh Patil
Electronic Theses and Dissertations
A systematic study of iron-based binary and multi-component alloys was undertaken to study the structural evolution in these powders as a function of milling time during mechanical alloying. Blended elemental powders of Fe100-XBX (where x = 5, 10, 17, 20, 22, 25, 37.5 and 50 at. %) and a bulk metallic glass (BMG) composition (Fe60Co8Zr10Mo5W2B15) were subjected to mechanical alloying in a SPEX 8000 mixer mill. X-ray diffraction technique was employed to study the phase evolution, crystallite size, lattice strain and also to determine the crystal structure(s) of the phases. Depending on the milling time, formation of supersaturated solid solutions, …
Microstructural And Mechanical Characterization Of Al-Al2o3 Nanocomposites Synthesized By High-Energy Milling, Balaji Prabhu
Microstructural And Mechanical Characterization Of Al-Al2o3 Nanocomposites Synthesized By High-Energy Milling, Balaji Prabhu
Electronic Theses and Dissertations
The twin objectives of the investigation were (i) to synthesize Al/Al2O3 metal matrix composites (MMCs) with uniform distribution of the Al2O3 reinforcement in the Al matrix and (ii) to evaluate the effect of volume fraction and size of the reinforcement on the mechanical behavior of MMCs. This was achieved by successful synthesis of Al-Al2O3 MMCs with volume fractions of 5, 10, 20, 30, and 50%, and particle sizes of 50 nm, 150 nm, and 5 µm of Al2O3 synthesized from blended component powders by a high-energy milling technique. A uniform distribution of the Al2O3 reinforcement in the Al matrix was …
Evolution Of Lamellar Structures In Al-Ag Alloys, Sephalika Senapati
Evolution Of Lamellar Structures In Al-Ag Alloys, Sephalika Senapati
Electronic Theses and Dissertations
In the present study, the formation and the evolution of lamellar structures in different Al-Ag alloys were investigated by transmission electron microscopy (TEM). Plates of the hexagonal [gamma] phase form semi-coherently on the {111} planes of the face centered cubic lattice of the alloy after the formation of Guinier-Preston zones. Guinier-Preston zones are metastable coherent preprecipitates which are silver rich in the aluminum-rich Al-Ag alloys. The decomposition of aluminum rich Al-Ag alloys, particularly the sequence of the later stages of precipitate formation was studied. With scanning electron microscopy and high-resolution transmission electron microscopy the development of the [gamma] phase was …