Structural Studies of Jennite and 1.4 nm Tobermorite: Disordered Layering along the [100] of Jennite

Abstract

Transmission electron microscopy of synthetic jennite reveals strong streaking in the electron diffraction patterns along the [100], along which dark‐field imaging and lattice fringing confirm the presence of a layering with a striation‐like morphology. The average periodicity between the layers is ∼35 Å; however, there is significant variation around this value in the range of 20‐40 Å, which is in agreement with the range of periodicities that are associated with the streaking in the diffraction patterns. These results clearly demonstrate the presence of a layering along the [100] with a periodicity that varies spatially throughout the specimen, which results in the presence of a disordered modulated structure. We believe that the disorder is induced by frozen‐in fluctuations in the local calcium:silicon ratio, which correspondingly results in fluctuations in the local structural order and periodicity of the modulated structure. Similar studies of 1.4‐nm tobermorite have revealed streaking along the [100]; however, it was weak and diffuse.