Thermal Decomposition Mechanism of Ammonium Nitrate on the Main Crystal Surface of Ferric Oxide: Experimental and Theoretical Studies

Abstract

Understanding the decomposition process of ammonium nitrate (AN) on catalyst surfaces is crucial for the development of practical and efficient catalysts in AN-based propellants. In this study, two types of nano-Fe 2 O 3 catalysts were synthesized: spherical particles with high-exposure (104) facets and flaky particles with high-exposure (110) facets. Through thermal analysis and particle size analysis, it was found that the nanosheet-Fe 2 O 3 catalyst achieved more complete AN decomposition despite having a larger average particle size compared to nanosphere-Fe 2 O 3 . Subsequently, the effects of AN pyrolysis on the ( 110) and ( 104) facets were investigated by theoretical simulations. Through studying the interaction between AN and crystal facets, it was determined that the electron transfer efficiency on the (110) facet is stronger compared to that on the (104) facet. Additionally, the freeenergy step diagrams for the reaction of the AN molecule on the two facets were calculated with the DFT + U method. Comparative analysis led us to conclude that the (110) facet of α-Fe 2 O 3 is more favorable for AN pyrolysis compared to the (104) facet. Our study seeks to deepen the understanding of the mechanism underlying AN pyrolysis and present new ideas for the development of effective catalysts in AN pyrolysis.

Combustion Characteristics of Vat-Photopolymerized Fuels with a Spiral Star Port for Hybrid Propulsion

“…At present, two strategies based on chemical and physical modifications are formed to upgrade the combustion characteristics and regression rates of solid fuel. On one hand, utilizing matrix materials with special mass transfer mechanisms, such as paraffin wax , and ethane gel, proves to be an effective method for enhancing the regression rate due to droplet entrainment and a vapor jetting mass transfer mechanism; however, the insufficient mechanical properties of paraffinic fuels at both high and low temperatures limit their widespread use in large engines. , On the other hand, the utilization of energetic materials can also significantly enhance the combustion performance of solid fuel. − Micro/nano metal particles, metal hydrides, and modified composite metal particles with a high energy density, a high gravimetric and volumetric heat, and a high thermal conductivity collectively enhance ballistic performance by increasing the flame temperature and reducing heat blockage. − However, many of the energetic materials are environmentally sensitive, posing safety limitations, while aggregation and agglomeration have been observed at the burning surface.…”