Abstract: Despite great efforts in the research area of zeolite nanoparticles and their use in the synthesis of bimodal materials, still little is known about the impact of the synthesis conditions of the zeolite nanoparticles on its own characteristics, and on the properties and the formation mechanism of the final bimodal materials. A zeolite β nanoparticles solution is applied in a mesotemplate-free synthesis method, and the influence of the hydrothermal ageing temperature of the nanoparticles solution on both the zeolitic and porosity characteristics of the final bimodal material has been studied. Transmission electron microscopy in combination with 3-dimensional reconstructions obtained by electron tomography revealed that the zeolite β nanoparticles are connected by neck-like structures, thus creating a wormhole-like mesoporous material. Considering the zeolitic properties, a clear threshold is observed in the synthesis temperature series at 413 K. Below and at this threshold, the biporous materials show no apparent zeolitic characteristics, although these materials exhibit a more condensed and uniform SiOSi network in comparison to Al-MCF. Synthesis temperatures above the threshold lead to bimodal structures with defined zeolitic properties. Moreover, the dimensions of the nanoparticles are studied by TEM, revealing an increasing particle size with increasing temperature under the threshold of 413 K, which is in agreement with a sol-mechanism. This mechanism is disturbed after the threshold due to the start of the crystallisation process.

Abstract: Several TEM techniques are used to characterise the local structure of low dimensional forms of carbon. HREM is particularly useful to describe the defect structure of thin films of diamond or fullerenes and C-60-C-70 nanoclusters. A columnar form of graphite is analysed, mainly by electron diffraction which allowed us to propose a growth mechanism. Diffraction contrast dark field microscopy, in combination with electron diffraction, allows a detailed characterisation of carbon nanotubes; e.g. the chirality distribution of tubes in ropes of single wall tubes is studied by selected area electron diffraction. (C) 1998 Elsevier Science Ltd. All rights reserved.

Abstract: We present results of Monte Carlo simulations of chains of C-60 and chains of C-70 molecules encapsulated in a single-walled carbon nanotube (SWCNT). We observe the changes in the configuration of the fullerene molecules when varying tube radius and temperature. In particular, the evolution of the pair correlation functions reveal a transition from linear harmonic chain behavior to a hard-sphere liquid upon heating, demonstrating the possibility of tuning properties of C-60- and C-70@SWCNT peapods with radius and temperature.

Abstract: We report single-crystal X-ray diffuse scattering measurements on C-60.C8H8 fullerene-cubane showing that the C-60 molecules are orientationally disordered at 300 and 150K and get ordered at low temperatures. Monte Carlo simulations provide further insight in the orientational behavior of both C-60 and C8H8 molecules; low-temperature molecular orientations are predicted.

Abstract: The recently discovered structural phase transition in Polymerized KC60 at about 50K leads to a doubling of the unit cell volume and is accompanied by a metal-insulator transition. Here, we show that the ((a) over right arrow + (c) over right arrow, (b) over right arrow, (a) over right arrow – (c) over right arrow) superstructure results from orientational charge density waves along the polymer chains and correlated displacements of the K+ ions. The presented model can also account for the metal-insulator transition. The effect is specific for the space group Pmnn of KC60 and is absent in both Rb- and CsC60 (space group 12/m), in agreement with the present experimental knowledge of these compounds.