Author ORCID Identifier
0000-0002-3112-7288
Document Type
Dissertation
Date of Award
12-31-2024
Degree Name
Doctor of Philosophy in Chemical Engineering - (Ph.D.)
Department
Chemical and Materials Engineering
First Advisor
Edward L. Dreyzin
Second Advisor
Mirko Schoenitz
Third Advisor
Kerri Lee Chintersingh
Fourth Advisor
Joshua Young
Fifth Advisor
Suhithi M. Peiris
Abstract
This work investigates optimizing gas-generating reactive materials, focusing on particle morphology's effect on ignition and combustion behavior. Metal-based gas-generating energetic materials (EMs) are promising alternatives to replace traditional CHNO compounds. Design of advanced metal-based EMs requires consistent ways of evaluating how their characteristics affect their ignition and combustion. Many relevant evaluation approaches exist; however, the results may be difficult to compare directly across different studies. Commonly, experimentalists ignite metal-based EMs in enclosed chambers and report pressures, P. However, direct comparison of these pressures is hindered by variations in the chamber volume, V, and the EM mass, m. To standardize the data, a parameter (P•V)/m, is proposed. This parameter is both predicted theoretically using a thermodynamic equilibrium code CEA by NASA and recovered from published experimental data. Findings indicate that some aluminum-based nano-thermites have met their theoretical performance levels, while boron-based EMs can be optimized further. Notably, ammonium nitrate demonstrates superior performance as an oxidizer for both aluminum and boron fuels.
Thus, boron-based EMs were further explored experimentally with optimal gas-generating oxidizers; ammonium nitrate (AN), potassium nitrate (PN) and an energetic binder, polytetrafluoroethylene, PTFE. Boron composites with different morphologies and compositions were synthesized via emulsion-assisted milling (EAM). These powders were characterized and tested to understand their ignition and combustion behaviors. In B•PN composites, spherical powders demonstrated more homogeneous mixing, resulting in lower ignition temperatures and shorter ignition delays in closed vessel tests. For the ternary B•AN•PN system, incorporating PN with AN enhanced the oxidizer stability and tuned ignition temperatures and combustion properties. Furthermore, 1-10% PTFE improved flowability, lowered oxidation initiation temperatures, and increased maximum pressures in constant volume explosion experiments.
Further, the performance of aluminum as a fuel was enhanced by either different additives or by modifying its morphology. Micron-sized aluminum powders, with and without 5 wt% gallium, were synthesized as flakes and spherical composites via EAM. Although gallium did not impact the powders' size or oxidation kinetics, it lowered ignition temperatures by altering the transition of amorphous alumina to crystalline y-phase during rapid heating. Additionally, the effect of aluminum powder morphologies (flakes and spheres) prepared using EAM was examined. Spherical aluminum exhibited higher specific surface area, lower ignition temperatures, and greater combustion efficiency, demonstrating the significance of particle morphology for the powder combustion.
Lastly, potential future work is outlined based on the results obtained from different gas-generating EM systems, paving the way for advancements in optimizing performance and expanding the applications of these materials in various energetic fields.
Recommended Citation
Gandhi, Purvam Mehulkumar, "Gas-generating reactive materials: design, evaluation and effect of morphology on their ignition and combustion" (2024). Dissertations. 1805.
https://digitalcommons.njit.edu/dissertations/1805
Included in
Chemical Engineering Commons, Heat Transfer, Combustion Commons, Materials Science and Engineering Commons, Structures and Materials Commons
