Small-angle neutron scattering characterization of processing/microstructure relationships in the sintering of crystalline and glassy ceramics

Small-angle neutron scattering measurements were used to examine the pore microstructure evolution of glassy silica and polycrystalline alpha-alumina as a function of sintering. It was shown that the two major sintering mechanisms, viscous flow and surface and volume diffusion, lead to very different microstructure evolution signatures in terms of the average pore size as a function of density. However, with respect to topology, the evolution of the porosity per unit surface area as a function of density is remarkably similar in the two systems.

Download Full-text

A Three-phase Model for the Structure of Porous Thin Films Determined by X-ray Reflectivity and Small-Angle Neutron Scattering

MRS Proceedings ◽

10.1557/proc-612-d5.22.1 ◽

2000 ◽

Vol 612 ◽

Cited By ~ 3

Author(s):

Wen-li Wu ◽

Eric K. Lin ◽

Changming Jin ◽

Jeffrey T. Wetzel

Keyword(s):

Thin Films ◽

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Coefficient Of Thermal Expansion ◽

Average Pore Size ◽

Silicon Substrates ◽

Average Pore ◽

X Ray ◽

Wide Range

AbstractA methodology to characterize nanoporous thin films based on a novel combination of high-resolution specular x-ray reflectivity and small-angle neutron scattering has been advanced to accommodate heterogeneities within the material surrounding nanoscale voids. More specifically, the average pore size, pore connectivity, film thickness, wall or matrix density, coefficient of thermal expansion, and moisture uptake of nanoporous thin films with non-homogeneous solid matrices can be measured. The measurements can be performed directly on films up to 1.5 µm thick while supported on silicon substrates. This method has been successfully applied to a wide range of industrially developed materials for use as low-k interlayer dielectrics.

Download Full-text

Evolution of the pore structure during the early stages of the alkali-activation reaction: an in situ small-angle neutron scattering investigation

Journal of Applied Crystallography ◽

10.1107/s1600576716018331 ◽

2017 ◽

Vol 50 (1) ◽

pp. 61-75 ◽

Cited By ~ 10

Author(s):

Claire E. White ◽

Daniel P. Olds ◽

Monika Hartl ◽

Rex P. Hjelm ◽

Katharine Page

Keyword(s):

Neutron Scattering ◽

Pore Structure ◽

Pore Size ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Average Pore Size ◽

Alkali Activation ◽

Average Pore ◽

Free Silica ◽

The Impact

The long-term durability of cement-based materials is influenced by the pore structure and associated permeability at the sub-micrometre length scale. With the emergence of new types of sustainable cements in recent decades, there is a pressing need to be able to predict the durability of these new materials, and therefore nondestructive experimental techniques capable of characterizing the evolution of the pore structure are increasingly crucial for investigating cement durability. Here, small-angle neutron scattering is used to analyze the evolution of the pore structure in alkali-activated materials over the initial 24 h of reaction in order to assess the characteristic pore sizes that emerge during these short time scales. By using a unified fitting approach for data modeling, information on the pore size and surface roughness is obtained for a variety of precursor chemistries and morphologies (metakaolin- and slag-based pastes). Furthermore, the impact of activator chemistry is elucidated via the analysis of pastes synthesized using hydroxide- and silicate-based activators. It is found that the main aspect influencing the size of pores that are accessible using small-angle neutron scattering analysis (approximately 10–500 Å in diameter) is the availability of free silica in the activating solution, which leads to a more refined pore structure with smaller average pore size. Moreover, as the reaction progresses the gel pores visible using this scattering technique are seen to increase in size.

Download Full-text