Environmental Engineering Reference
In-Depth Information
Figure 6.19
Parameter
γ
in the size growth equation (6.86) as a function of
a
(6.85) [41, 43].
Let us represent the balance equation for the average cluster size
n
in the coagula-
tion process analogously to (6.70) in the form
dn
dt
D
γ
k
0
N
sat
(
T
)
n
2/3
.
(6.86)
The values of
γ
depending on
a
and defined by (6.85) are given in Figure 6.19 [41,
43].
6.3.4
Cluster Growth in a Hot Gas with Metal-Containing Molecules
In considering the cluster plasma, we will be guided by a plasma consisting of a
buffer gas with metal clusters. A high number density of bound atoms in metal
clusters is realized in the case if a liquid metal-containing compound is inserted
in a flow of a dense plasma. This method of cluster generation in a buffer gas
allows us to obtain an effective source of light [128-131] and is used for prepara-
tion of films of heat-resistant metals as a result of transport of metal clusters and
their deposition onto a surface. So, we consider the scheme of cluster generation if
metal-containing molecules are injected into a hot gas or plasma and are converted
into a gas of metal clusters. The best case for this is if metal-containing molecules
contain halogen atoms, that is, these molecules are
MX
k
,where
M
is a metal atom
and
X
is a halogen atom.
We first find the conditions under which decomposition of metal-containing
molecules in a plasma leads to cluster formation, that is, the process of cluster
generation follows the scheme
MX
k
!
M
C
kX
,
M
C
M
n
1
!
M
n
,
(6.87)
and in a low-temperature region halogen atoms join to form
X
2
molecules. The
equilibrium between components of process (6.87) is described by the scheme
k
2
X
2
M
C
!
MX
k
