자료유형  

 학위논문

Control Number  

0017162331

International Standard Book Number  

9798383220849

Dewey Decimal Classification Number  

620.11

Main Entry-Personal Name  

Cheng, Li.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of California, San Diego., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

158 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-01, Section: B.

General Note  

Advisor: Bandaru, Prabhakar.

Dissertation Note  

Thesis (Ph.D.)--University of California, San Diego, 2024.

Summary, Etc.  

요약The electrokinetic streaming potential (Vs) obtained through electrolyte flow in a microchannel is shown to be related to the underlying surface pattern. Pillar, mesh and groove patterns were studied for comparing the relative magnitudes of the Vs with air-/liquid- filled surfaces. A record value of the related figure of merit, in terms of the developed Vs per unit applied pressure, of ~ 0.127 mV/Pa, was observed in a mesh texture liquid filled surface (LFS) impregnated with electrolyte immiscible oil. Besides, a new plasma processing-based methodology for enhancing the streaming potential (Vs) that may be obtained in electrokinetic flows for a given pressure gradient over a silicon surface based microchannel is indicated. The dependence of the Vs on both the surface zeta potential as well as the electrolyte slip length was carefully determined through a series of experiments involving variation of CF4 and Ar-based plasma parameters, incorporating pressure, exposure time, and power. A record value of ~ 0.1 mV/Pa was obtained through using CF4 plasma at 500 W, 10 mTorr, and 300 s of exposure. Enhanced electrokinetic phenomena, manifested through the observation of a large streaming potential (Vs), were also obtained in microchannels with single layer graphene (SLG) -coated and few layer graphene (FLG) -coated surfaces. In comparison to silicon microchannels, the Vs obtained for a given pressure difference along the channel (ΔP) was higher by 75% for the graphene-based channels, with larger values in the SLG case. Computational modeling was used to correlate the surface charge density, tuned through plasma processing, and related zeta potential to measured Vs.Porous layers emergent from the bulk tungsten (W) interface subsequent to helium (He) plasma exposure, under conditions relevant to thermonuclear experiments, were found to significantly modulate the structural attributes of the W - as deduced through nanoscale indentation measurements. Plastic deformation of nanofibers constituting the fuzzy surface layer, along with an increased yield strength with layer depth, was quantified. A power-law relationship between the indentation modulus (Eind) and the porosity of the fuzzy W was indicated. A decrease in the Eind of the bulk W underneath the fuzzy layer with increasing plasma exposure temperature, in agreement with molecular-dynamics computations, was observed. The incorporation of energetic helium gaseous species into materials such as tungsten (W), imparts intrinsic surface fragility, yielding fuzzy tungsten. To enhance the robustness of the surface layers, aluminum oxide (AlOx) was deposited by atomic layer deposition into the fuzzy W. The conformally deposited ceramic yields a new class of surface composites. Structural characterization of the fuzzy W-AlOx composites through nanoindentation testing indicated enhanced indentation modulus (Eind) and hardness (Hind) and was modeled through various rules of mixtures approaches. The distribution of AlOx in fuzzy W was explored and a systematic study of the extent of incorporation of the AlOx into the fuzzy W was carried out. The synthesized composites may be utilized for improved structural characteristics, e.g., in reducing crack initiation and fracture.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Engineering.

Subject Added Entry-Topical Term  

Nanotechnology.

Index Term-Uncontrolled  

Electrokinetic

Index Term-Uncontrolled  

Fuzzy tungsten

Index Term-Uncontrolled  

Nanoindentation

Index Term-Uncontrolled  

Plasma treatment

Index Term-Uncontrolled  

Streaming potential

Index Term-Uncontrolled  

Zeta potential

Added Entry-Corporate Name  

University of California, San Diego Mechanical and Aerospace Engineering

Host Item Entry  

Dissertations Abstracts International. 86-01B.

Electronic Location and Access  

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Control Number  

joongbu:657603