Ni Catalyzed Double-Base Propellants

Metallic nickel is known to catalyze the reduchon of NO in its reachons with aldehydes or hydrocarbon gases, and the primary reachon in the dark zone of a double-base propellant is the reduction of NO to N2. Small amounts of fine Ni particles or organic nickel compounds are incorporated into double-base propellants to increase the reaction rate in the dark zone. 

Fig. 6.29 shows the effect, or lack thereof, of the addihon of Ni particles on the burning rate of a double-base propellant. The double-base propellant is composed of Nc(0-44), ng(0.43), i3gp(0.11), and Iec(0-02) as a reference propellant. This propellant is catalyzed with 1.0% Ni particles (2 pm in diameter). No burning rate change is seen upon the addition of Ni particles.F However, the flame structure is altered significantly by the addition of Ni. The flame stand-off distance between the burning surface and the luminous flame front is shortened, as shown in Fig. 6.30. Though the flame stand-off distance of the reference propellant is about 8 mm at 1.5 MPa and decreases rapidly with increasing pressure (1 mm at 4.0 MPa), the flame stand-off distance of the Ni-catalyzed propellant remains unchanged (0.3 mm) when the pressure is increased.

Figure 6-31 shows the effect of the addition of Ni particles on the burning rate of a double-base propellant. The double-base propellant is composed of 44.0% NC, 43.0% NG, 11.0% DEP, and 2.0% EC as a reference propellant. This propellant is catalyzed with 1.0% Ni particles (2 pm in diameter). No burning rate change is seen on addition of Ni particles1221. However, the flame structure is altered significantly... 

As described in Section 6.4, lead catalysts act on the condensed phase and fizz zone reactions, not on the dark zone reaction, and increase the burning rate. On the contrary, Ni catalysts act on the dark zone reaction, but not on the condensed phase or fizz zone reactions, and do not increase the burning rate. No luminous flame is produced when double-base propellants burn, for example, at 0.5 MPa. However, when catalyzed propellants with metallic Ni or organic Ni compounds burn, a luminous flame is produced just above the burning surface at the same pressure. 

---