Matching Items (3)
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- All Subjects: Materials Science
- Genre: Masters Thesis
Description
Hydrogel polymers have been the subject of many studies, due to their fascinating ability to alternate between being hydrophilic and hydrophobic, upon the application of appropriate stimuli. In particular, thermo-responsive hydrogels such as N-Isopropylacrylamide (NIPAM), which possess a unique lower critical solution temperature (LCST) of 32°C, have been leveraged for membrane-based processes such as using NIPAM as a draw agent for forward osmosis (FO) desalination. The low LCST temperature of NIPAM ensures that fresh water can be recovered, at a modest energy cost as compared to other thermally based desalination processes which require water recovery at higher temperatures. This work studies by experimentation, key process parameters involved in desalination by FO using NIPAM and a copolymer of NIPAM and Sodium Acrylate (NIPAM-SA). It encompasses synthesis of the hydrogels, development of experiments to effectively characterize synthesized products, and the measuring of FO performance for the individual hydrogels. FO performance was measured using single layers of NIPAM and NIPAM-SA respectively. The values of permeation flux obtained were compared to relevant published literature and it was found to be within reasonable range. Furthermore, a conceptual design for future large-scale implementation of this technology is proposed. It is proposed that perhaps more effort should focus on physical processes that have the ability to increase the low permeation flux of hydrogel driven FO desalination systems, rather than development of novel classes of hydrogels
ContributorsAbdullahi, Adnan None (Author) / Phelan, Patrick (Thesis advisor) / Wang, Robert (Committee member) / Dai, Lenore (Committee member) / Arizona State University (Publisher)
Created2019
Description
This study analyzes the thermoelectric phenomena of nanoparticle suspensions, which are composed of liquid and solid nanoparticles that show a relatively stable Seebeck coefficient as bulk solids near room temperature. The approach is to explore the thermoelectric character of the nanoparticle suspensions, predict the outcome of the experiment and compare the experimental data with anticipated results. In the experiment, the nanoparticle suspension is contained in a 15cm*2.5cm*2.5cm glass container, the temperature gradient ranges from 20 °C to 60 °C, and room temperature fluctuates from 20 °C to 23°C. The measured nanoparticles include multiwall carbon nanotubes, aluminum dioxide and bismuth telluride. A temperature gradient from 20 °C to 60 °C is imposed along the length of the container, and the resulting voltage (if any) is measured. Both heating and cooling processes are measured. With three different nanoparticle suspensions (carbon nano tubes, Al2O3 nanoparticles and Bi2Te3 nanoparticles), the correlation between temperature gradient and voltage is correspondingly 8%, 38% and 96%. A comparison of results calculated from the bulk Seebeck coefficients with our measured results indicate that the Seebeck coefficient measured for each suspension is much more than anticipated, which indicates that the thermophoresis effect could have enhanced the voltage. Further research with a closed-loop system might be able to affirm the results of this study.
ContributorsZhu, Moxuan (Author) / Phelan, Patrick (Thesis advisor) / Trimble, Steve (Committee member) / Prasher, Ravi (Committee member) / Arizona State University (Publisher)
Created2010
Description
Thermal management is a critical aspect of microelectronics packaging and often centers around preventing central processing units (CPUs) and graphics processing units (GPUs) from overheating. As the need for power going into these processors increases, so too does the need for more effective thermal management strategies. One such strategy is to utilize additive manufacturing to fabricate heat sinks with bio-inspired and cellular structures and is the focus of this thesis. In this study, a process was developed for manufacturing the copper alloy CuNi2SiCr on the 100w Concept Laser Mlab laser powder bed fusion 3D printer to obtain parts that were 94% dense, while dealing with challenges of low absorptivity in copper and its high potential for oxidation. The developed process was then used to manufacture and test heat sinks with traditional pin and fin designs to establish a baseline cooling effect, as determined from tests conducted on a substrate, CPU and heat spreader assembly. Two additional heat sinks were designed, the first of these being bio-inspired and the second incorporating Triply Periodic Minimal Surface (TPMS) cellular structures, with the aim of trying to improve the cooling effect relative to commercial heat sinks. The results showed that the pure copper commercial pin-design heat sink outperformed the additive manufactured (AM) pin-design heat sink under both natural and forced convection conditions due to its approximately tenfold higher thermal conductivity, but that the gap in performance could be bridged using the bio-inspired and Schwarz-P heat sink designs developed in this work and is an encouraging indicator that further improvements could be obtained with improved alloys, heat treatments and even more innovative designs.
ContributorsYaple, Jordan Marie (Author) / Bhate, Dhruv (Thesis advisor) / Azeredo, Bruno (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2021