USANS and SANS Study of Porosity in Vycor Glass

USANS AND SANS STUDY OF THE STRUCTURE OF VYCOR
POROUS GLASS
Y. B. Melnichenko, G. D. Wignall,
J. S. Lin, G. W. Lynn (CMSD, ORNL)
D. R. Cole (CSD, ORNL)
M. Agamalian (SNS, ORNL), I. Pozdnyakova (LPI, Russia)
D. Schwahn (DKD, USANS), H. Frielinghaus (KWS-2, CONV. SANS),
A. Radulescu, E. Kentzinger (KWS-3, FOCUSING SANS)
Forschungszentrum Jülich, Germany

WHAT IS VYCOR?
VYCOR GLASS IS MANIFACTIRED FROM A BOROSILICATE MELT (B 2 O 3 +SiO 2 ).
THE MELT IS QUENCHED BELOW T C AND SPINODALLY DECOMPOSES INTO
SiO 2 - and B 2 O 3 -RICH PHASES. THE LATTER CAN BE LEACHED OUT LEAVING A
FULLY PENETRABLE MICROPOROUS GLASS.
IT IS WIDELY USED FOR FILTRATION, SEPARATION, CATALYST SUPPORT, ETC.
VYCOR 7930:
SiO 2 96%
B 2 O 3 3%
SURF. AREA 250 m 2 /g
VOID SPACE 28 %
COMES IN VARIOUS SHAPES:
RODS, TUBES, SHEETS, ETC.

TYPICAL SCATTERING INTENSITY PATTERN FROM VYCOR 7930
(SAXS, ORNL)
COMMON FEATURES:
“VYCOR PEAK” REMINISCENT OF
THE STRUCTURE FACTORS MESURED
ON TWO-COMPONENT SYSTEMS
AFTER SPINODAL DECOMPOSITION
SURFACE ROUGHNESS: POROD LAW
AND DEVIATIONS
AVERAGE PORE SIZE 40 – 45 Å
I, cm -1
1000
100
10
1
VYCOR PEAK
0.00 0.02 0.04 0.06 0.08 0.10
Q, Å -1
Gelb, Gubbins, 1999

FIRST INDICATION OF THE EXISTENCE OF LARGE PORES IN VYCOR:
STRUCTURE OF RODS AND PLATES APPEARS TO BE DIFFERENT
10 8
10 7
10 6
10 5
DRY VYCOR POROUS GLASS
10
-0.0002 -0.0001 0.0000 0.0001 0.0002
4
VYCOR CONTRAST – MATCHED USING
41% H 2O + 59 % D 2O SOLUTION
60
40
20
0
-20
-40
-60
-0.0002 -0.0001 0.0000 0.0001 0.0002

ROCKING CURVES FROM TWO VYCOR PLATES
(DKD INSTRUMENT, IFF JÜLICH)
Intensity [a.u.]
10 5
10 4
10 3
10 2
10 1
-0.5 0.0 0.5
Q [10 -4 Å -1 ]
Vycor
VycorM
Empty

Intensity, [a.u]
COMBINING THE USANS (SLIT GEOMETRY) WITH CONVENTIONAL
PINHOLE SANS REQUIRES:
DESMEARING THE USANS DATA
TRANSFER TO POINT GEOMETRY
10 8
10 7
10 6
10 5
10 4
10 3
10 2
10 1
SLIT GEOMETRY
POINT GEOMETRY
0.1 1
Q, [10 -4 , Å -1 ]
CONVOLUTION [LAKE, 1967]:
I(Q)
slit/th
= W (t)W (u)I{(2pl)
[2T - t)
h
v
u
2
]
0.5
SABINE-BERTRAM [1999]:
}
point/th
W i : COLLIMATION FUNCTIONS
t,u: ANGULAR COORDINATES
2
+
dudt
n 1.
58
1.
58
I(
Q)
~ ( b / n )[ 1 + ( 1/
n )( QR)
b: NUMBER OF SCATTERING EVENTS
R: AVERAGE SIZE OF PARTICLES
I ( Q)
point
= I(
Q)
slit / exp I(
Q)
point/
th / I(
Q)
slit / th
2
]
-2

EXPERIMENTAL EVIDENCE OF THE EXISTENCE OF LARGE
PORES IN VYCOR 7930
I, cm -1
10 10
10 9
10 8
10 7
10 6
10 5
10 4
10 3
10 2
10 1
10 0
10 -1
10 -2
R~12 mm
b=1
Q -4.3
Q -4
1E-5 1E-4 1E-3 0.01 0.1
Q, Å -1

USANS FROM ONE AND TWO VYCOR PLATES STUCK TOGETHER
TWO PLATES
R=10–5 mm
b=1–0.3 (SINGLE PLATE)
b=2.6–0.5 (TWO PLATES)
ONE PLATE

I, cm -1
AVAILABILITY OF mM PORES DEPENDS ON SPECIFICS OF THE
MANUFACTURING PROCESS
10000
8000
6000
4000
2000
VYCOR FROM
CHAND MANUFACTURING Co.
VYCOR 7930 FROM CORNING
0
0.00 0.02 0.04 0.06 0.08 0.10
Q, Å -1
Intensity [a.u.]
1x10 -2 10 1
1x10 -1
1x10 0
SAXS, ORNL USANS, JÜLICH
10 7
10 6
10 5
10 4
10 3
10 2
EMPTY BEAM
VYCOR FROM CHAND
Q [10 -4 Å -1 ]

CONCLUSIONS
DEMONSTRATION OF THE EXISTENCE OF mm PORES IN
VYCOR 7930 (PLATES)
POSSIBLE MECHANISM: PORE COAGULATION DURING LATE
STAGES OF THE SPINODAL DECOMPOSITION

ACKNOWLEDGEMENT
RESEARCH SPONSORED BY THE LDRD PROGRAM OF
ORNL, MANAGED BY UT-BATTELLE, LLC, FOR THE U. S.
DEPARTMENT OF ENERGY UNDER CONTRACT NO. DE-
AC05-00OR22725