MS Theses - DO NOT EDIT
http://hdl.handle.net/10106/25210
2024-03-29T07:04:11ZTHE INFLUENCE OF THE INTERACTION OF CARBON BASED MATERIALS WITH IONIC LIQUID ON THE TRIBOLOGICAL PERFORMANCE OF LUBRICATING GREASE AND OIL
http://hdl.handle.net/10106/31644
THE INFLUENCE OF THE INTERACTION OF CARBON BASED MATERIALS WITH IONIC LIQUID ON THE TRIBOLOGICAL PERFORMANCE OF LUBRICATING GREASE AND OIL
Stringent government regulation on environment emissions and demand to develop energy efficient and durable modern mechanical systems has imposed a significant challenge on the lubricant additive manufacturer to develop environment friendly and high performance additives for the lubricating medias like oil and grease. The current industrial additive technology is dominated by phosphorus and sulfur containing the liquid antiwear additive, Zinc dialkyl dithiophosphate and extreme pressure solid additives like Graphite, Molybdenum disulfide. This current additive package possesses harm to the environment and has already met performance limit for applications working under severe operating condition. A proposed solution to combat with this problem is the use of ionic liquid as the next generation green lubricant additive. The unique properties of the ionic liquids such as negligible volatility, nonflammability, and high thermal stability make them potential candidate as an antiwear additive. Also, with the advent of nanotechnology, nanoparticles have recognized considerable attention as solid additives in lubricating oils and greases.
In this research study, the nature of the interaction between ionic liquids and carbonaceous materials like carbon nanotube and soot is considered and is correlated with the tribological performance of the lubricating media, engine oil, and grease. This thesis work is divided into two main section, first section deals with the tribological performance of the combined solid and liquid additive chemistry of multi-walled carbon nanotube (MWCNT) and ionic liquid in lithium lubricating greases, while, the second section is about evaluating the potential of ionic liquid in minimizing the detrimental effect of the increased soot contamination in the engine oil.
As an attempt to study the interaction of MWCNT and ionic liquids, the first approach was to determine the optimal concentration of MWCNT as an antiwear additive in lithium based grease is investigated by analyzing the friction and wear results generated during four ball standard ASTM D2266 test. The results indicate the MWCNTs at optimal concentration of 1wt% decreases the wear by 25% and friction by 39%. Secondly, the antiwear and antifriction performance of the four different ionic liquids in lithium grease was investigated. The excellent antiwear property of the ionic liquid is attributed to the formation of protective phosphate tribofilms on the interacting surfaces. In addition, ionic liquids were blended with the MWCNT to study the synergism between novel solid-liquid combined chemistry. The addition of hydroxyl functionalized MWCNT at 1wt% with the ionic liquid having phosphonium cation and dithiophosphate anion results in the comparable tribological behavior to the grease blends with the MWCNT and ionic liquid alone.
Second Section of the thesis describes the influence of the increased soot contamination on the diesel engine wear. First, the abrasive nature of the soot was examined by using X-ray absorption near edge spectroscopy and high temperature X-ray diffraction. Then the oil formulations were prepared by dispersing the diesel engine soot with three different antiwear additives, namely, ashed Zinc dialkyldithiophosphate, ashless alkyl dithiophospahte and an ionic liquid. The soot concentration at 10wt% exhibits the extremely high wear in the presence of all the three additives. The soot abrades the protective tribofilms formed by antiwear additives and results in sever wear.
Sub-10K Cold-Electron Injection to Silicon at Room Temperature
http://hdl.handle.net/10106/31412
Sub-10K Cold-Electron Injection to Silicon at Room Temperature
The Fermi-Dirac thermal excitation of electrons results in unwanted off-state leakage currents in metal-oxide-semiconductor field-effect transistors (MOSFETs), leading to excessive power consumption in modern electronic devices. The electron thermal excitation results in a theoretical subthreshold slope limit of 60 mV/decade at room temperature, which forces the devices to use a high supply voltage leading to high power consumption. This study investigates a new architecture capable of suppressing electron thermal excitation by using a quantum well (QW) as an energy filter. The QW energy filter is composed of a tunneling barrier 1 (0.5 to 1 nm Al2O3 or 0.3-1 nm Si3N4 or no tunneling barrier) a quantum well (QW) layer (3-5 nm tin oxide, SnO2), and a tunneling barrier 2 (native silicon dioxide, SiO2). The energy filter layers are sandwiched between a chromium electrode and silicon. This energy-filtering structure makes it possible to inject cold electrons into silicon with abrupt current jumps, which correspond to the alignment of the QW levels with the conduction band edge of silicon. Differential conductance (dI/dV) plots show extremely narrow peaks, with their FWHMs (full widths at half maximum) only 0.025mV, corresponding to an effective electron temperature of 0.08 Kelvin at room temperature. This cold electron injection to Si at room temperature has a potential to create transistors that operate with extremely little energy consumption.
2022-12-20T00:00:00ZDispersion study of Metal-Organic Frameworks and Synthesis of MOF-High-density polyethylene fibers
http://hdl.handle.net/10106/31283
Dispersion study of Metal-Organic Frameworks and Synthesis of MOF-High-density polyethylene fibers
Metal-Organic Frameworks (MOFs) are a highly versatile class of materials with a wide range
of potential applications in gas storage, separation, catalysis, drug delivery, and sensing. The
ability to tailor the properties and functionalities of MOFs by varying the organic linkers and
inorganic nodes makes them highly attractive for a wide range of applications. The unique
properties of MOFs also make them promising materials for fundamental studies in materials
science and chemistry. The current investigation focuses on the dispersion study of MOFs and
the synthesis of MOF-Polymer composites. The dispersions of MOFs in various organic solvents
like ethanol, isopropanol, tetrahydrofuran, N-methyl-2-pyrrolidine, triethylene glycol, and
acetone are studied and characterized using UV-Vis Spectroscopy to study the absorbance of
the MOFs in the solvents and to determine the extent of dispersion in the solvents. Both the
visual and spectroscopic studies showed similar results. Later the MOF-polymer composites are
synthesized taking High-Density Polyethylene and are tested for the capture of CO2
2023-05-19T00:00:00ZAssessment of Joule Heating Properties of Various Solder Alloys in BGA Assembly
http://hdl.handle.net/10106/31254
Assessment of Joule Heating Properties of Various Solder Alloys in BGA Assembly
The continuing demands for smaller, yet higher performance devices have resulted in many revolutionary changes in device packaging in recent years, including the change in package form factors, structure, and the type of solder alloys used for the assembly. Because solder joints are exposed to various electrical and thermo-mechanical stresses, not only at use condition but also during their process into the assembly, they are prone to failure. Especially concerned in this respect is the current density that the solder joint is subjected to as it determines the level of Joule Heating (JH), thus the solder temperature, significantly affecting the joint reliability of solder. The JH in solder joints in the existing assembly may be at the manageable level with material redundancy, and more predictable with cumulated knowledge on the electrical and thermal properties of the solder alloys. The structural redundancy is increasingly limited, and even more troublesome is the fact that less familiar solder alloys (as well as joint structure) are employed to the assembly. Better understanding the thermal behavior of new solder alloys/structures in new packaging structures is therefore of utmost importance to enable advanced packaging.
The findings of this research present a greater understanding of different solder alloy’s JH behavior and outside parameters affecting such through the resistivity to temperature calibration method (TCR) with the main objectives: 1) Identify the fundamental mechanism(s) driving the different JH behavior seen if any in the various solder alloys from a microstructural defect view; 2) Determine the impact of variance of PCB structure has on the overall JH level of a package. This thesis presents key evidence in our study regarding a better understanding of metallurgical and structural mechanisms effect on JH behavior. This research explores the benefits and shortcomings of TCR in that it gains information of JH at the interconnect level but determines the average of all interconnects tested. Although, traditional temperature measurements lack the ability or accuracy of determining the temperature change at the interconnect level that TCR offers. Previous work has suggested that resistivity and resistance as the main contributors to JH. Comparison of SAC305 and SnBi-based solder alloys’ JH behavior revealed that microstructural defects such as macrovoids and cavities have been found to have a more significant impact than resistivity on the heat that individual solder joints produce. Although the true mechanism as to why this phenomenon is observed is still being investigated as on a macro-scale this behavior is not observed, our work has pointed to the effects of current crowding around such defects to be the cause of this unanticipated behavior. The presence of these macrovoids was also averse to traditional mechanisms of entrapped gases as the voids present in our research exist at both top and bottom of solder joints instead of only the top. Our research indicates that these macrovoids are caused by differential heating and cooling of adjacent solder joints resulting in internal stresses that displace large amounts of solder. Future work including further study into solder joints with known defects to determine the statistical correlation to this behavior, is also suggested in this thesis.
2023-05-22T00:00:00Z