Atomic force microscopy has been used to image the various facets of two morphologically distinct samples of silicalite. The smaller (20 microm) sample A crystals show 1 nm high radial growth terraces. The larger (240 microm) sample B crystals show growth terraces 1 to 2 orders of magnitude higher than the terraces on sample A with growth edges parallel to the crystallographic axes. Moreover, the terraces on the (010) face are significantly higher than the terraces on the (100) face - inconsistent with the previously proposed 90 degrees intergrowth structure. Sample A highlights that under certain synthetic conditions, silicalite grows in a manner akin to zeolites Y and A, via the deposition of layers comprising, in the case of silicalite, pentasil chains. It is probable that the rate of terrace advance is identical on the (010) and (100) faces, and it is the rate of terrace nucleation that dictates the overall growth rate of each facet and hence the relative size expressed in the final crystal morphology. Analysis of the growth terraces of sample B and detailed consideration of the structures of both MFI, and a closely related material MEL, lead to the proposal of a generalized growth mechanism for silicalite including the incorporation of defects within the structure. These defects are thought to be responsible for both the relative and the absolute terrace heights observed and may also explain the hourglass phenomenon observed by optical microscopy. The implications of this growth mechanism, supported by results of infrared microscopy, generate a new dimension to the continuing debate on the existence of intergrowths within one of the most important structures relevant to zeolite catalysis.

An array of analytical techniques comprising powder X-ray diffraction, solid-state NMR spectroscopy, high-resolution transmission electron microscopy, nitrogen adsorption, and UV/vis diffuse reflectance spectroscopy has been applied to study the incorporation of indium phosphide semiconductor inside MCM-41 materials by metal organic chemical vapor deposition. Line broadening in the X-ray diffraction patterns suggests the existence of both large surface deposited indium phosphide particles and nanosized indium phosphide particles deposited within the pores. High-resolution transmission electron microscopy corroborates this result:  surface deposits have been imaged, and analysis of electron diffraction patterns provides evidence of the existence of nanoparticles. Nitrogen adsorption provides information on pore filling. Quantum-confinement effects, brought about by the nanoparticle size regime, are evidenced by upfield shifting of the indium phosphide resonance in the 31P magic-angle-spinning NMR spectra and by blue shifting of the band gap dependent transition in the UV/vis absorption spectra.

Crystal growth in zeolite A has been studied by atomic force microscopy (AFM), which is a very powerful technique for imaging nanoscale surface features. However, imaging microcrystallites is far from trivial due to the difficulty in controlling their orientationsurfaces inclined to the horizontal yield distorted images in an AFM. In this study the origin and correction of image distortion is discussed and a general method for sample preparation that can be easily adapted to any microcrystalline powder is detailed. Crystal growth in zeolite A, chosen for its industrial importance, is discussed in detail and is shown to occur via a process akin to a terrace−ledge−kink (TLK) layer mechanism.

The growth of crystals of the structurally related zeolites FAU and EMT may be characterized by layer upon layer propagation. This previously proposed mechanism has been confirmed by results of an investigation into the crystal growth features in zeolite Y by atomic force microscopy. The intergrowing surfaces of the crystal (see schematic representation on the right) are constructed by the deposition of sodalite‐like building units, leading to the formation of terraces.

Second-order quadrupolar broadening has rendered the study of cation sites in microporous materials almost impossible until the recent advent of the 2D multiple-quantum NMR experiment. In conjunction with computer lattice-energy-minimisation calculations we employ this powerful new technique to study the complex microporous titanosilicate ETS-10 and titanium aluminosilicate ETAS-10 systems. Evidence is presented for Ðve unique cation sites di †ering greatly in their behaviour towards dehydration. Strong evidence is also given for preferential potassium cation siting.