Abstract
Scanning electron microscopy and high-resolution transmission electron microscopy have been used to investigate non-classic crystal growth of catalytic nanoparticles, such as zeolites, perovskites, metal and alloy particles. Growth mechanisms of some crystals with novel morphologies, for example, BiOBr flower-like particles and ZnO twin-crystals, have also been studied. A development of sampling method for soot particles inside a candle flame allows us to reveal all four well-known carbon forms, amorphous, graphitic, fullerenic and nanodiamond particles. This article demonstrates that electron microscopy is a powerful tool to study the microstructures of small particles, giving us more freedom to develop new materials.
Highlights
Development of catalysts is an important field in petrochemical research
Its morphology can be predicted by the Bravais–Friedel–Donnay– Harker (BFDH) law: the final polyhedral morphology is formed by slow-growing faces, because all the fast-growing faces would grow out during the process [1,2,3]
When we examined the intermediate specimens at early stages of a crystal-growth process, we found the classic theory of crystal growth was not always followed
Summary
Development of catalysts is an important field in petrochemical research. Every year, a large number of new catalysts with various morphologies are reported. The largest d-spacing in zeolite analcime corresponds to the (211) planes, both the natural and synthetic crystals of analcime have an icositetrahedral shape consisting of 24 {211} facets Another obvious fact in this kinetically controlled mechanism is that the particle at any stage during the growth should be a single crystal. The amorphous cores were removed, leaving very thin zeolite A boxes or hollow cubes This novel morphology can be achieved via the reversed crystal-growth route. The nanocubes underwent oriented self-assembly into spherical particles, enhanced by the surface-adsorbed polymer molecules These polycrystalline spheres had a relatively low density compared to single crystals. It seems to be confirmed that the reversed crystal growth is a common phenomenon in the formation of various materials and more examples will be found in future research
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