Sphere Pore Geometry (Cheng/Yang - Micromeritics ASAP 2020 Confirm Operator's Manual

ASAP 2020 Confirm

k

k
r
p

Sphere Pore Geometry (Cheng/Yang)

When you use the Cheng/Yang
The value of L is determined when the solved-for relative pressure is within 0.1% of the col-
lected absolute pressure.

------ -
n

Po
where
R
T
d
0
L
P
Po
N
1
N
2
e*
12
1. Cheng, Linda S. and Yang, Ralph T., Chemical Engineering Science 49(16), 2599-2609 (1994).
C-24
– 4.5 – k
 
------------------- -
=
 
k
– 1.5 – k

------------------- -
=

k
= radius of the cylindrical pore,
1
method, the following equation is solved for each value of P.
* *
  
6 N + N
P

1 12 2
--------------------------------------------------------------------------------------------------- -
=

RT L d
6
d
1
  
0
---- - ----- - T
– +
  
1
L 12
= gas constant (8.31441 x 10
= analysis bath temperature (K), from an entered or calculated
value on the Po and Temperature Options dialog
A  
D + D
A S
--------------------------- -
=
2
where:
D = molecular diameter (Å) from the Horvath-Kawazoe Physical
A
Properties dialog
D = diameter of sample atom (Å) from the Horvath-Kawazoe Physical
S
dialog
= pore width (nucleus to nucleus) (Å)
= equilibrium pressure (mmHg)
= saturation pressure (mmHg)
2
= 4 L N , where N
S
= 4 (L - d )
0
A
S
----------- -
= , where
6
4d
S
2

, = 1.0
k 1 – 0
2


, = 1.0

k 1 – 0
L
-- -
2
3 32 4
L 
10 J A /J cm
22
3
 
–
0
12
d
1 1
   
0
-- - T ---- - ----- - T
+ +
   
2 3
8 L 90
7 ergs/mole K)
= number of sample atoms/cm
S
2
N , where N = number of gas molecules/cm
A s
2
  
6 MC
S
-------------------------------------------- -
A =
S  
S A
----- ----- -
+
 
S A
4
1

----- -
T

4
80
2
at monolayer
2
 
A
202-42811-01 - Mar 2011
Appendix C