Chemistry Reference
In-Depth Information
10
−
7
m
2
s
−
1
,
c
= 1
.
46 J g
−
1
K
−
1
,
Q
= 1
.
17 kJ g
−
1
), the expression for the
rate constant of the high-temperature decomposition of AP in the mode of linear
pyrolysis is
(
a
= 5
×
10
6
exp
s
−
1
.
30200
R
T
k
= 5
.
9
×
−
(3.2)
Let us now consider the high-temperature linear pyrolysis of AP accompanied by
burning. In the case of the linear pyrolysis of a sample on aluminum and mica hot
surfaces, burning was observed at
T
0
= 530-550
◦
C and
U
10
−
4
ms
−
1
. For a sam-
ple on a stainless steel heater, ignition took place at approximately the same decom-
position rate but at a lower heater temperature (
T
0
≈
≈
500-510
◦
C).
If after the inflammation the sample was left motionless or was retracted from
the heater, a pale yellow luminous deflagration flame was observed on the sample
surface for a few seconds. The burning died out after a 1-2 mm thick layer was burnt
out. After inflammation, the deflagration flame overheated the peripheral parts of the
plate, which resulted in a sharp increase in the linear pyrolysis rate. However, in this
mode, the temperature (
T
0
) dependence of the linear pyrolysis rate is much weaker
than in the case of
T
0
<
500
◦
C (in the mode of linear pyrolysis without burning).
At the transition from
T
0
to
T
S
, the thickness of the gas film,
Z
, along with the
corresponding temperature drop at
U
10
−
4
ms
−
1
should be taken into considera-
tion. However, these characteristics cannot be estimated due to the lack of reliable
data on the gas film composition. The upper limiting value of
T
S
may be determined
from experiments with a sample strongly pressed onto a heater surface (the pressure
W
/
S
≥
1 MPa), which minimizes the gas film thickness. In this case, the experi-
mental points in the plot of
U
against
T
−
0
are quite scattered (a region including
36 points is shown in Fig. 3.5). However the range of
T
0
(540-580
◦
C) corresponds
to the pressure of the gaseous products of the equilibrium dissociative sublima-
≤
U
, mm/s
1.0
1.2
1.4
0.6
0.8
Fig. 3.5
AP linear pyrolysis on a stainless steel plate with high
W
/
S
(for the determination of
T
S
for AP linear pyrolysis in the burning mode) without burning at
W
/
S
=
P
∞
= 0
.
1MPa (
1
), with
burning at
W
/
S
=
P
∞
= 0
.
1MPa (
2
), with burning at
W
/
S
= 1
.
0MPa,
P
∞
= 0
.
1MPa (the
outlined
region
contains 36 points) (
3
), with burning at
W
/
S
= 0
.
1MPa,
P
∞
= 3
.
0MPa (
4
); data from [10]
(
5
), [11] (
6
), [12] (
7
)
