Chemistry Reference
In-Depth Information
Thus gas evolution in the Microdroplet device was recorded as a step-like curve
with steps of the equal height and varying width.
A high device sensitivity is ensured by applying perfluorinated liquids character-
ized by a low surface tension and forming very small droplets of a constant volume
(
V
10
−
3
cm
3
). It is easy to show that at a displacement rate of one droplet per
hour and a decomposing liquid volume of 1000 cm
3
(the amount of gas evolved per
volume unit for h/c H
2
O
2
is almost identical to that of hydrazine), decomposition
occurring with the rate constant of
k
≤
10
−
13
s
−
1
is recorded. Such a rate con-
stant is approximately 50 times lower than that of the homogeneous decomposition
of the most stable h/c H
2
O
2
samples under real conditions at a temperature of 20
◦
C.
Express methods for monitoring h/c H
2
O
2
and hydrazine stability under conditions
of long-term storage were developed based on the described approach.
The kinetics of the thermal decomposition and explosion of hydrazine were also
studied by a manometric method mentioned above and by a thermograph-based
setup similar to that described in Sect. 10.5.1 with an electrically heated thermostat
and sealed glass ampoules containing hydrazine.
Before discussing the main results of the study of the thermal decomposition of
h/c H
2
O
2
and hydrazine, some comments about the reaction mechanisms should
be made. Data on the decomposition mechanism of highly concentrated liquid hy-
drazine are rare in the literature, although the kinetics of the vapor were thoroughly
investigated by Eberstein and Glassman [5] and Manelis and coworkers [6, 7]. The
h/c H
2
O
2
decomposition mechanism was studied more actively, but most works
have been devoted to the low-temperature process [8, 9, 10, 11]. The most impor-
tant contribution to studying the mechanism of h/c H
2
O
2
low-temperature decompo-
sition was made by Purmal and coworkers [12, 13]. Some of our experimental and
theoretical research was also devoted to gaining a better understanding of the chain
mechanism of h/c H
2
O
2
decomposition; in particular, to the qualitative analysis of
the role of iron ions in the process [14]. However, since this topic is mostly devoted
to macrokinetic aspects of decomposition and explosion processes, material on the
mechanisms of h/c H
2
O
2
and hydrazine decomposition is not presented here.
Thus the topics considered in this chapter are as follows: determination of the for-
mal kinetic parameters of the liquid-phase decompositions of the monopropellants
over the widest possible temperature range; analysis of the effects of practically
important construction materials on the process kinetics; an experimental study of
the thermal explosion initiation mechanism and comparison of the experimental and
theoretical data.
≈
5
×
11.3 Thermal Decomposition of h/c H
2
O
2
11.3.1 Kinetics of the Homogeneous Decomposition of h/c H
2
O
2
The kinetics of the homogeneous decomposition of h/c H
2
O
2
(samples of com-
mercial monopropellant, concentration 94-97%) were studied over the temperature
