Sphere Pore Geometry (Cheng/Yang - Micromeritics ASAP 2460 Operator's Manual

Appendix C
P =
Po =
R =
r =
p
T =

Sphere Pore Geometry (Cheng/Yang)

When you use the Cheng/Yang
value of L is determined when the solved-for relative pressure is within 0.1% of the collected absolute
pressure.
*

6N +
P
 
1 12
------ - ----------------------------------------------------------------- -
ln =
 
Po
RTL d
where
32
10 =
*
=
12
*
=
22
d =
0
where:
D
A
D
S
L =
N =
1
N
=
2
P =
Po =
R =
T =
C-28
equilibrium pressure
saturation pressure
gas constant (8.31441 × 10
radius of the cylindrical pore,
analysis bath temperature (K), from an entered or calculated value on the Po
and Temperature Options window
11
method, the following equation is solved for each value of P. The
* 3 32
 
N L 10
d
 
2 22
---- 0
–
 
3
–
L
0
4
the number of cm that are equal to Å
Å
S
------------ -
Å
, where
S
6
4d
S
A
A
-------------- -
Å
, where
A
6
4D
A
D + D
A s
------------------- -
2
= molecular diameter (Å) from the Horvath-Kawazoe Physical Properties
window
= diameter of sample atom (Å) from the Horvath-Kawazoe Physical
Properties window
pore width (nucleus to nucleus) (Å)
2
4 L N , where N = number of sample atoms/cm
S S
2
4 (L - d ) N , where N
0 A
equilibrium pressure
saturation pressure
gas constant (8.31441 × 10
analysis bath temperature (K), from an entered or calculated value on the Po
and Temperature Options window
7
erg/mol K)
L
-- -
2
6 12
T T d T
    
----- - 1 ---- - 2 ---- 0 ----- -
+ +
    
12 8 L 90
4
2
  
6 mc
S A
------------------------------- -
= 
 
S A
----- - ------ -
+
 
S A
2
       
3 mc
A A
------------------------------------------ -
=
2
= number of gas molecules/cm
S
7
erg/mol K)
ASAP 2460 Operator's Manual
T

3 ----- - 4
+

80
2
at monolayer
2
246-42800-01 - Aug 2013