Catalytic Effect of Added Fe₂O₃ Amount on Thermal Decomposition Behaviors and Burning Characteristics of Ammonium Nitrate/Ammonium Perchlorate Propellants

ABSTRACT

Ammonium nitrate (AN) and ammonium perchlorate (AP) are investigated as propellants for their thermal decomposition behaviors and burning characteristics. The performance effects of AP particle size, AP content in the oxidizer (ξ), and a catalytic amount of Fe₂O₃ on the propellants are evaluated. A dependency exists between the thermal decomposition behaviors of the propellants and both AP particle size and ξ. Addition of Fe₂O₃ further affected the thermal decomposition behaviors of the propellants; these behaviors are not dependent on the added amount. Furthermore, the burning characteristics are dependent on the AP size, ξ, and the amount of Fe₂O₃ added. The low-pressure ignitability of the propellants containing 2% Fe₂O₃ with ξ = 0.2 and 0.4 is inferior to the propellant with ξ = 0 (no AP) and the propellants containing 4% Fe₂O₃ with ξ = 0.2 and 0.4. An increase in 4% Fe₂O₃ caused a positive catalytic effect, causing an equal or higher burning rate of the propellants than that of 2% Fe₂O₃, except in the case of AN/AP propellants with coarse AP at ξ = 0.4 and 0.6 above 4 MPa.

KEYWORDS:

• Ammonium nitrate
• ammonium perchlorate
• iron oxide
• composite propellant
• burning characteristics

Nomenclature

Chemicals

AN	=	Ammonium nitrate
AP	=	Ammonium perchlorate
HTPB	=	Hydroxyl-terminated polybutadiene

Acronyms

CAP	=	Coarse AP
DTA	=	Differential thermal analysis
FAP	=	Fine AP
PDL	=	Pressure deflagration limit
TG	=	Thermogravimetry

Symbol

R	=	Ratio of the burning rate of propellant with Fe2O3 to that of the corresponding propellant without Fe2O3 (–)
T1	=	Peak temperature of first decomposition (K)
T2	=	Peak temperature of second decomposition (K)
χ	=	Ratio of the burning rates of propellant with 4% Fe2O3 and that of the corresponding propellant with 2% Fe2O3 (–)
ξ	=	Mass ratio of AP to whole oxidizer (–)