Micromeritics ASAP 2460 - Page 342

Appendix C ASAP 2460 Operator’s Manual
C-18 246-42800-01 - Aug 2013
b.) The physical processes occurring for this pressure interval are determined as:
(1.) If Vd
i
is greater than the current increment of volume desorbed (Vl
i
- Vl
i+1
), desorption
from walls only is occurring. Total surface of walls exposed thus far (cm
2
/g) is calcu-
lated as:
for all previously opened pores
where
D
avg,j
= weighted average pore diameter calculated in Step b(2).
A new layer thickness (
 Tw) that will not overcompensate for the actual volume
desorbed in this interval is calculated:
Since no cores are evaporated in this pressure interval, no new pores are revealed.
Thus no ending Kelvin radius and average pore diameter are calculated for this inter-
val. Note that this means the report may have fewer tabulated intervals on the
collected data report than experimental pressure intervals.
(2.) If Vd
i
is less than the volume increment desorbed during this interval ,
the remaining volume is due to new pores with core evaporation taking place in this
interval. K, the number of intervals with new pores exposed, is increased by 1. (For the
interval from the lowest Pr
1
to zero relative pressure, no new pore volume is calculated
and the rest of Step b is skipped.)
The volume desorbed from newly opened pores in this interval is calculated as:
The Kelvin radius for the end of the interval is calculated as:
SA
w
 LP
j
D
avg j,

10
8–
cm
Å
--------------------


j

=
Tw
Vl
i
Vl
i1+
–10
8
Å
cm
-------


SAw
i
--------------------------------------------------------
=
Vl
i
Vl
l1+
–
Vc
i
VI
i
VI
i1+
–Vd
i
–=
Rc
k1+
A–
1 F+P
i1+
ln
----------------------------------------
=