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Modeling of Neutron Diffraction Patterns from Sheared Silica Gels1

Published online by Cambridge University Press:  22 February 2011

B.D. Butler ,
H.J.M. Hanley ,
C.D. Muzny  and
G.C. Straty
B.D. Butler
Affiliation:
National Institute of Standards and Technology, Boulder, CO 80303
H.J.M. Hanley
Affiliation:
National Institute of Standards and Technology, Boulder, CO 80303
C.D. Muzny
Affiliation:
University of Colorado, Department of Physics, Boulder, CO 80309
G.C. Straty
Affiliation:
National Institute of Standards and Technology, Boulder, CO 80303
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Abstract

Dense silica gels, prepared from suspensions of 24 nm colloidal silica particles, have been studied by small angle neutron scattering. Provided the volume fraction, φ, of the silica is less than about 0.18, the scattered intensity increases at low wavevector, q, as the gelation proceeds and the structure factor, S(q), of the final gel exhibits apparent power law behavior, usually interpreted as a signature of fractal growth. The power law behavior, however, was observed for all measured φ (≤0.30) when the gelation occurred in the presence of an applied shear. Furthermore, the first diffraction maximum, corresponding to the inter-particle contact distance, was more sharply peaked in the high density sheared gels, indicating that the structural arrangement of the silica particles under shear is more densely packed than in gels produced without shear under equivalent conditions. Although it is clear that shear has a marked influence on the gel structure at higher densities, a quantitative interpretation of the diffraction results is difficult because cluster-cluster interference might be present. Such difficulties encountered when trying to interpret the scattering from these dense systems are outlined, and a computer simulation that includes cluster-cluster interference is presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 376: Symposium BB – Neutron Scattering in Materials Science , 1994 , 323
Copyright
Copyright © Materials Research Society 1995

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Footnotes

1

Contribution of the National Institute of Standards and Technology, not subject to copyright in the U.S.

References

REFERENCES

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