자료유형  

 학위논문

Control Number  

0017164744

International Standard Book Number  

9798346877622

Dewey Decimal Classification Number  

541

Main Entry-Personal Name  

Riggs, Brian E.

Publication, Distribution, etc. (Imprint  

[S.l.] : University of Colorado at Boulder., 2024

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Physical Description  

136 p.

General Note  

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

General Note  

Advisor: Minton, Timothy K.

Dissertation Note  

Thesis (Ph.D.)--University of Colorado at Boulder, 2024.

Summary, Etc.  

요약Understanding the oxidation mechanisms of carbon and carbon-composite materials is key to the reliable design of heat shields for hypersonic flight through air. To gain a better understanding of the relevant gas-surface interactions, molecular beam-surface scattering experiments have been used to study reactions of O atoms on the surfaces of vitreous (glassy) carbon and a graphitic carbon (Mersen 2340) at high-temperatures. These experiments were performed with pulsed molecular beams of hyperthermal O atoms produced by a laser-detonation source. The efficiencies of the gas-surface interactions, both reactive and non-reactive, were quantified as a function of surface temperature. The angular distributions of the scattered product flux were obtained at specific temperatures, adding further insight into the thermal and non-thermal gas-surface interaction mechanisms. The molecular beam technology used in the beam-surface scattering experiments has served as the basis for a new "table-top shock tunnel (TTST)", which is intended to allow rapid and low-cost measurements of shock-layer chemistry and material response in well-characterized hypersonic flows. Initial characterization of the TTST has been conducted by exposing Kapton H samples to a hyperthermal O/O2 beam at different distances from the throat of the nozzle from which the beam emanates. The observed change in surface roughness as a function of nozzle-to-sample distance is consistent with DSMC simulations of gas compression under the experimental conditions, indicating that the high peak flux of the pulsed hyperthermal beam may lead to transient gas build-up above a test surface, producing a shock layer above the surface that is relevant to hypersonic flow environments. The TTST has been used to investigate the temperature-dependent ablation phenomenology of vitreous carbon and Mersen 2340 graphite. A comparison of the TTST and molecular beam-surface scattering results reveals complications in the TTST environment that make the interpretation of the results difficult. While the molecular beam-surface scattering experiments may be used in the development of air-carbon ablation models, an improved understanding of the ablation phenomena in the TTST will be needed before data from this apparatus may be used routinely as validation of such models that are under development.

Subject Added Entry-Topical Term  

Physical chemistry.

Subject Added Entry-Topical Term  

Chemistry.

Subject Added Entry-Topical Term  

Aerospace engineering.

Index Term-Uncontrolled  

Atomic oxygen

Index Term-Uncontrolled  

Carbon

Index Term-Uncontrolled  

Gas-surface interactions

Index Term-Uncontrolled  

Hypersonic flows

Index Term-Uncontrolled  

Low earth orbit

Added Entry-Corporate Name  

University of Colorado at Boulder Chemistry

Host Item Entry  

Dissertations Abstracts International. 86-06B.

Electronic Location and Access  

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Control Number  

joongbu:654529