Organic-free synthesis of layer-like FAU-type zeolites.

The formation of layer-like FAU-type zeolites was facilitated in the absence of any organic template. Instead, the addition of simple inorganic salts turned out to be an effective and easy to handle alternative to organic additives to induce morphological and even structural changes during zeolite crystallisation.

Minkowski tensor shape analysis of cellular, granular and porous structures.

Predicting physical properties of materials with spatially complex structures is one of the most challenging problems in material science. One key to a better understanding of such materials is the geometric characterization of their spatial structure. Minkowski tensors are tensorial shape indices that allow quantitative characterization of the anisotropy of complex materials and are particularly well suited for developing structure-property relationships for tensor-valued or orientation-dependent physical properties. They are fundamental shape indices, in some sense being the simplest generalization of the concepts of volume, surface and integral curvatures to tensor-valued quantities. Minkowski tensors are based on a solid mathematical foundation provided by integral and stochastic geometry, and are endowed with strong robustness and completeness theorems. The versatile definition of Minkowski tensors applies widely to different types of morphologies, including ordered and disordered structures. Fast linear-time algorithms are available for their computation. This article provides a practical overview of the different uses of Minkowski tensors to extract quantitative physically-relevant spatial structure information from experimental and simulated data, both in 2D and 3D. Applications are presented that quantify (a) alignment of co-polymer films by an electric field imaged by surface force microscopy; (b) local cell anisotropy of spherical bead pack models for granular matter and of closed-cell liquid foam models; (c) surface orientation in open-cell solid foams studied by X-ray tomography; and (d) defect densities and locations in molecular dynamics simulations of crystalline copper.

MFI-type (ZSM-5) zeolite-filled TiO2 nanotubes for enhanced photocatalytic activity.

The present work demonstrates enhanced photocatalytic activity for zeolite-filled TiO2 nanotubes. ZSM-5 zeolite nanocrystals were grown on and into a TiO2 nanotubular skeleton (TiNT/ZSM-5) by multi-step hydrothermal synthesis consisting of in situ seeding and multiple in situ crystallization (MISC). The resulting zeolite nanocrystals were in the range of a few nanometers and they adhere well to the nanotubular inner walls. After crystallization, the photocatalytic activity of this zeolite-filled nanotube catalyst system was compared with neat anatase TiO2 nanotube (TiNT) and with calcined ZSM-5 powder. The results show for TiNT/ZSM-5 a highly enhanced efficiency for the decomposition of acetophenone (used as an aromatic model organic pollutant).

Solid-state NMR characterization of the mineral searlesite and its detection in complex synthesis mixtures.

The mineral searlesite (NaBSi(2)O(5)(OH)(2)) was synthesized and characterized by (1)H, (11)B, (23)Na, and (29)Si magic-angle spinning (MAS) NMR spectroscopy. From these spectra, the (11)B and (23)Na quadrupole coupling parameters and isotropic chemical shifts and the (29)Si chemical shift anisotropies have been precisely determined. These parameters are all consistent with the local environments obtained from the crystal structure for searlesite from X-ray diffraction, and they demonstrate that the synthetic sample has a high degree of both short- and long-range order. Furthermore, these anisotropic parameters are found to provide a unique fingerprinting of searlesite in complex mixtures where the presence of this mineral is not anticipated. This is demonstrated for product mixtures formed in attempts to incorporate boron in the structures of the layer silicates magadiite and kenyaite. These mixtures have been investigated by (11)B, (23)Na, and (29)Si MAS NMR which clearly reveal that the samples are mixtures of searlesite and magadiite/kenyaite and that searlesite production consumes all of the boron in these synthesis mixtures. However, the (29)Si MAS NMR spectra of these mixtures indicate that the presence of boron in the reaction mixtures nevertheless has an important influence on the quality of the magadiite and kenyaite layer silicates produced.

Ultrasonic monitoring of zeolite synthesis in real time

Variations of the phase and amplitude of a transmitted ultrasonic wave package were monitored in real time during the synthesis of zeolite A and zeolite X. For both materials, characteristic changes of the measured attenuation and the sound velocity of ultrasonic waves traveling in the reaction fluid were observed, correlating with the processes of gel formation and zeolite crystallization, respectively. Aging effects of the reaction fluids are demonstrated. The observation of the onset of the zeolite crystallization was verified with ex-situ X-ray diffraction (XRD) measurements.