TEM studies of a platelet form of zeolite L reveal two common types of grain boundary. The first involves an arbitrary translation, without rotation, between adjacent grains. The second involves a 30° relative rotation about the 6-fold c-axis, parallel to the platelet normal. The resulting 30° tilt boundaries have no periodic structure since the adjoining lattices are incommensurate. Occasionally, 30° twist boundaries are observed. These occur only in the vicinity of 30° tilt boundaries, and appear to be outgrowths anchored by one of the grains. In plan view, the 30° twist boundaries exhibit aperiodic moiré patterns generated by the incommensurate overlying hexagonal nets. Such overlayers can block about 90% of the intersected channels of the one-dimensional pore system of zeolite L.
ASJC Scopus subject areas
- Materials Science(all)