Environmental Engineering Reference
In-Depth Information
Ta b l e 6 . 4
Parameters of evolution of metal-containing molecules in hot argon (
p
D
1atm,
c
M
D
10%,
0
D
1mm).
Compound
MoF
6
IrF
6
WF
6
WCl
6
,g/cm
3
2.6
6.0
3.4
3.5
T
m
, K
290
317
276
548
T
b
, K
310
326
291
620
ε
X
, eV
4.3
2.5
4.9
3.6
ε
M
, eV
6.3
6.5
8.4
8.4
T
1
, K
2200
1200
2500
1700
T
2
, K
4100
4000
5200
5200
T
,10
3
K
δ
12
3.7
13
4.8
T
, K
3600
2900
4600
4200
N
m
,10
16
cm
3
2.0
2.5
1.6
1.8
dM
/
dt
,
μ
g/s
0.66
1.2
0.74
1.1
dl
/
dt
, nm/s
23
20
13
20
τ
chem
,10
3
s
5
0.1
1
0.1
τ
heat
,10
4
s
2.0
2.8
1.3
1.5
10
7
10
7
10
7
10
7
n
1.6
1.9
1.5
1.5
r
, nm
40
42
40
40
N
cl
,10
9
cm
3
1.2
1.3
1.1
1.1
D
0
,cm
2
/s
25
18
36
31
q
2
,
μ
m
88
71
110
100
to the transport process is not strong. Released metal atoms join in clusters, and for
the basic time of residence of this mixture in the tube
0.1 s the cluster growth
pr
ocess proceeds through coagulation. We give in Table 6.4 the average cluster size
n
according to (6.82) at the end of the coagulation process together with its radius
r
,
and the number density of clusters
N
cl
.
Let us evaluate the broadening of the region occupied by metal clusters as a
result of diffusion in the course of the cluster growth process. We have for the
mean square displacement during this process
τ
D
dr
4
Z
Ddt
4
D
0
Z
dt
n
2/3
D
20
D
0
τ
dr
2
D
D
.
(6.94)
n
2/3
We used above the case of cluster diffusion in a rare gas (4.110) and (4.114) for the
diffusion coefficient. As is seen, the relative displacement of clusters in the course
of their growth is small.
