Electrochemical Decomposition of HAN-based Ionic Liquid Oxidizers
Open Access
- Author:
- Crisp, Eric
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 25, 2021
- Committee Members:
- Richard A Yetter, Thesis Advisor/Co-Advisor
Stefan Thynell, Committee Member
Daniel Connell Haworth, Program Head/Chair - Keywords:
- HAN
electrolysis
OXSOL 1
hybrid rocket - Abstract:
- Electrochemical decomposition of energetic liquids such as aqueous HAN and OXSOL 1 are studied from a fundamental perspective to obtain the trends and sensitivities related to electrochemical decomposition of energetic ionic liquids in simulated propulsion system conditions. This research can be applied to liquid propellants and oxidizers with high ion concentrations to utilize electrocatalytic decomposition as a conditioning mechanism to enhance reactivity through partial decomposition, or ignition. In the literature, thermal decomposition of aqueous HAN is well studied. The theoretical understanding of electrocatalytic decomposition of energetic liquids studied here is limited due to the complex chemical environment, the presence and influence of electrical work, energetic reactions, and competing, unknown electrochemical mechanisms. A static volume two-electrode electrochemical experiment is utilized to study the effects of ion concentration, electrode surface material, electric field strength, pressure, and temperature. These parameters are quantified through synchronous current and high-speed video data. Graphite electrodes were among the most efficient at inciting significant reaction at both sea level and elevated ambient pressure. It was shown that time to reaction follows a power law dependence on voltage while the separation distance was related linearly to the time to reaction. Through varying the temperature, an apparent activation energy was found to be electrode and species dependent. For copper electrodes, 13M HAN maintains an activation energy of 3.54 kcal/mol whereas OXSOL 1 is 4.56 kcal/mol. For carbon electrodes with 13M HAN, the activation energy drops to 0.567 kcal/mol. This is a significant decrease in the required activation from thermal decomposition relative to electrolytic decomposition. Electrode material was shown to have a significant effect on the electrolysis processes including the degree of reaction, type of reaction(s), and power draw. The oxidation reactions occurring at the anode were shown to be the driving reactions at achieve energetic, autocatalytic decomposition. By increasing the bulk temperature of the ionic liquid, effectively decreased the required electrical energy input to incite the same degree of reaction. As pressure was increased, the efficiency of the electrolysis also increased and enabled the reactive species to ignite rather than generate gas phase species.