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Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Riverside Electronic Theses and Dissertations (2023)

Flash pyrolysis microreactor coupled with molecular beam extraction and photoionization time-of-flight mass spectrometry along with theoretical calculations are employed to study the pyrolysis of gas phase molecules with relevance to chemical vapor deposition (CVD) and fuel combustion. This dissertation presents a comprehensive exploration of the flash pyrolysis mechanisms of various organosilanes and hydrocarbons, including allyltrichlorosilane, allyltrimethylsilane, 1,1,2,2-tetraethylsilane, trimethylchlorosilane, tetraethylsilane, cyclohexane, and cycloheptane. Chapters 3 to 6 of this dissertation focus on investigating the decomposition pathways and identifying key reaction products of various CVD precursors through a combination of experimental observations and theoretical analyses. The study specifically examines allyltrichlorosilane, allyltrimethylsilane, 1,1,2,2-tetramethylsilane, trimethylchlorosilane, and tetraethylsilane. The findings reveal that allyltrichlorosilane decomposes primarily through Si-C bond homolysis, while the thermal decomposition of allyltrimethylsilane proceeds primarily via molecular eliminations. The pyrolysis of 1,1,2,2-tetramethylsilane involves molecular elimination reactions, Si-Si bond fission, H2 elimination, and decomposition to trimethylsilane and methylsilylene. Trimethylchlorosilane predominantly undergoes HCl molecular elimination, while tetraethylsilane follows Si-C bond homolysis. These studies have conducted a thorough examination of the pyrolysis mechanism of organosilane precursors, providing a comprehensive overview, and investigating their potential applications in SiC thin film production. Additionally, Chapters 7 and 8 explore the thermal decomposition mechanisms of cyclohexane and cycloheptane, elucidating the diradical mechanism in the primary initiation reactions. These comprehensive studies provide valuable insights into the intricate pyrolysis mechanisms of organosilanes and aviation fuel prototypes, facilitating the development of accurate models and efficient utilization strategies for these compounds.

    Cover page: Thermal Decomposition Mechanisms of Molecules Relevant to Chemical Vapor Deposition and Fuel Combustion by Flash Pyrolysis Photoionization Time-of-Flight Mass Spectrometry
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2022)
    To develop chemical kinetics models for the combustion of ionic liquid-based monopropellants, identification of the elementary steps in the thermal and catalytic decomposition of components such as 2-hydroxyethylhydrazinium nitrate (HEHN) is needed but is currently not well understood. The first decomposition step in protic ionic liquids such as HEHN is typically the proton transfer from the cation to the anion, resulting in the formation of 2-hydroxyethylhydrazine (HEH) and HNO3. In the first part of this investigation, the high-temperature thermal decomposition of HEH is probed with flash pyrolysis (<1400 K) and vacuum ultraviolet (10.45 eV) photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS). Next, the investigation into the thermal and catalytic decomposition of HEHN includes two mass spectrometric techniques: (1) tunable VUV-PI-TOFMS (7.4-15 eV) and (2) ambient ionization mass spectrometry utilizing both plasma and laser ionization techniques whereby HEHN is introduced onto a heated inert or iridium catalytic surface and the products are probed. The products can be identified by their masses, their ionization energies, and their collision-induced fragmentation patterns. Formation of product species indicates that catalytic surface recombination is an important reaction process in the decomposition mechanism of HEHN. The products and their possible elementary reaction mechanisms are discussed.
      Cover page: Thermal and Catalytic Decomposition of 2‑Hydroxyethylhydrazine and 2‑Hydroxyethylhydrazinium Nitrate Ionic Liquid
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