A Sans Study of Capillary Condensation in Porous Media

1989 ◽  
Vol 166 ◽  
Author(s):  
M.Y. Lin ◽  
S.K. Sinha ◽  
J.S. Huang ◽  
B. Abeles ◽  
J.W. Johnson ◽  
...  
Keyword(s):  
Porous Media ◽  
Porous Structure ◽  
Small Angle ◽  
Structure Factor ◽  
Small Angle Neutron Scattering ◽  
Capillary Condensation ◽  
Distribution Model ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Good Agreement

ABSTRACTWe use small angle neutron scattering (SANS) to study the microstructure of porous Vycor glass and the capillary condensation of fluids in the medium. Using a chord distribution model, we can predict the structure factor measured by SANS. Excellent agreement with the data is obtained. The fitted parameters characterize quantitatively the porous structure before and during the process of condensation, and are in good agreement with isotherm measurements. However, at the latest stages of the process, when all the pores are nearly filled, the model can no longer describe the system.

A Chord Distribution Description of Porous Glass

1990 ◽  
Vol 195 ◽  
Author(s):  
M. Y. Lin ◽  
S. K. Sinha
Keyword(s):  
Porous Medium ◽  
Neutron Scattering ◽  
Porous Glass ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Capillary Condensation ◽  
Scattering Data ◽  
Distribution Model ◽  
Microporous Structure ◽  
Good Agreement

ABSTRACTSmall angle neutron scattering data of Vycor is analyzed using a chord distribution model describing the microporous structure. In addition, the same model is applied in interpreting the data taken when capillary condensation takes place in the porous medium. In both cases, the results are in good agreement with other measurements, and shows a promising potential in describing such a bicontinuous system.

Comparison of Small-Angle Neutron Scattering of δ' Precipitation in an Al–Li Alloy at a High-Flux Reactor and at a Pulsed-Neutron Source

1997 ◽  
Vol 30 (5) ◽  
pp. 602-606 ◽  
Author(s):  
G. Albertini ◽  
F. Carsughi ◽  
R. Coppola ◽  
R. K. Heenan ◽  
M. Stefanon
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Size Distribution Function ◽  
Data Sets ◽  
Flux Reactor ◽  
Average Size ◽  
Pulsed Neutron ◽  
Pulsed Neutron Source ◽  
Good Agreement

Two different small-angle neutron scattering (SANS) facilities, the D11 camera at the Institut Laue–Langevin (ILL, Grenoble, France) and the LOQ time-of-flight diffractometer at the Rutherford Appleton Laboratory (RAL, Didcot, Oxon, England), were used in the investigations of δ′-Al3Li precipitation at 463 K in Al–Li 3% alloy. The results obtained from the steady-state reactor and from the pulsed source by using two different data-acquisition techniques and two different procedures for data analysis are compared. The SANS curves for the same set of samples investigated using the two different instruments are in good agreement within the experimental uncertainties. A check was also made on the metallurgically relevant quantities, namely the average size and the size-distribution function of the δ′ precipitates at the various stages of the ageing process, obtained from the two sets of SANS curves by applying the same numerical method. Good agreement was found between the results from the two data sets.

Small Angle Neutron Scatitering Study of Sol-Gel Glasses

1989 ◽  
Vol 166 ◽  
Author(s):  
P. Wiltzius ◽  
S. B. Dierker
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Structure Factor ◽  
Small Angle Neutron Scattering ◽  
Sol Gel ◽  
Scattering Data ◽  
Length Scales ◽  
Internal Interface ◽  
Porous Glasses ◽  
Gel Glasses

ABSTRACTWe present small angle neutron scattering data of porous glasses. Analysis of the structure factor shows that the morphology on length scales between 30 A and 800 A depends on fabrication procedures. Fast gelation leads to a clumpy glass, whereas slow gelation produces a random smooth internal interface.

PHASE TRANSITIONS OF WATER AND XENON ADSORBED IN POROUS VYCOR GLASS

1963 ◽  
Vol 41 (12) ◽  
pp. 3095-3107 ◽  
Author(s):  
G. Litvan ◽  
R. McIntosh
Keyword(s):  
Phase Transition ◽  
Capillary Condensation ◽  
Adsorbed Water ◽  
Surface Concentration ◽  
Adsorptive Capacity ◽  
Temperature Cycle ◽  
Length Variation ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Lower Temperature

Measurements of the expansion of porous Vycor glass containing fixed quantities of adsorbed water indicate that in every instance a phase transition starts below −50 °C, with the main change occurring below −160 °C. Two other anomalies of the length variation were observed near −22 °C and −7 °C when the amount of adsorbed water exceeded the value equivalent to two monolayers. The length of the adsorbent after completion of a temperature cycle was different from the initial length. This is thought to be due to damage suffered by the glass and to the fact that the length of the adsorbent is different for adsorption and desorption although the quantity adsorbed may be the same.The phase transition of adsorbed xenon takes place below the normal triple point and is a function of surface concentration as shown by length variations and equilibrium pressures for fixed quantities adsorbed. All transitions are gradual and hysteresis is exhibited by the isosteres. The adsorption isotherms for xenon – Vycor glass show a decreasing adsorptive capacity and a contraction of the hysteresis loop with lower temperature. The inadequacy of the capillary condensation theory of adsorption in relation to these results is discussed.

THE FREEZING OF WATER AND BENZENE IN POROUS VYCOR GLASS

1960 ◽  
Vol 38 (6) ◽  
pp. 958-971 ◽  
Author(s):  
C. Hodgson ◽  
R. McIntosh
Keyword(s):  
Capillary Condensation ◽  
Solid Phase ◽  
Adsorbed Water ◽  
Freezing Process ◽  
Pressure Measurements ◽  
Equilibrium Pressure ◽  
Vycor Glass ◽  
Dimensional Changes ◽  
Porous Vycor Glass

Freezing has been detected in the adsorbed water and benzene of porous Vycor glass at temperatures below that at which the bulk phases freeze. The evidence presented by equilibrium pressure measurements and dimensional changes of the systems is considered in terms of theories of capillary condensation and freezing in cements and soil. Although not all the results can be explained, it is concluded that the freezing process is a gradual one for both adsorbate–adsorbent systems. The evidence further suggests that hysteresis is absent in isotherms if the solid phase has formed.

Insight into neutron focusing: the out-of-focus condition

2013 ◽  
Vol 46 (5) ◽  
pp. 1361-1371 ◽  
Author(s):  
B. Hammouda ◽  
D. F. R. Mildner ◽  
A. Brûlet ◽  
S. Desert
Keyword(s):  
Standard Deviation ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Neutron Wavelength ◽  
Focus Condition ◽  
The Mean ◽  
The Individual ◽  
Multiple Holes ◽  
Good Agreement

Neutron focusing leads to significant gains in flux-on-sample in small-angle neutron scattering and very small angle neutron scattering instruments. Understanding the out-of-focus condition is necessary for less than optimal conditions such as for short instruments and low neutron wavelengths. Neutron focusing is investigated using a three-pronged approach. The three methods are analytical calculations, resolution measurements and computer simulations. A source aperture containing a single small-size hole and a sample aperture containing multiple holes are used to produce multiple spots on the high-resolution neutron detector. Lens focusing elongates off-axis spots in the radial direction. The standard deviation for the size of each spot is estimated using these three approaches. Varying parameters include the neutron wavelength, the number of focusing lenses and the location of holes on the sample aperture. Enough agreement for the standard deviation of the individual neutron beams was found between the calculations and the measurements to give confidence in this approach. Good agreement was found between the standard deviations obtained from calculations and simulations as well. Excellent agreement was found for the mean location of these individual spots.

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