Deeper understanding of the basic principles of biomineralization is a major challenge for present and future research. The high complexity of in‐vivo conditions calls for simplified model systems that still involve dynamic processes like reorganization, formation, self‐organization, and development of patterns, respectively. The present contribution deals with hierarchically ordered spherical aggregates of fluorapatite–gelatin composites with fractal architecture that are grown in gelatin matrices. The model system was chosen to mimic formation conditions on a lower level of complexity compared with the natural formation of calcified tissue (bone, teeth). In order to gain insight into structure formation and the motif for this special kind of morphogenesis we investigated the interaction of the organic and inorganic components of aggregates in different growth stages by detailed chemical analyses, thermoanalytical measurements, X‐ray diffraction on solitary particles, and scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) investigations. The close relation of the results and observations to calcified tissue may stimulate advanced interests in the fields of medical and materials development.
Biominerals are impressive composite materials because of their complex organization and perfect adaptation to the demands of living organisms. Structure and development of human teeth are compared to similar composite systems that develop in vitro under biomimetic conditions without the controlling influence of cells.
Form follows the ion: The morphogenesis of fluorapatite–gelatine nanocomposites is studied from both electron microscopy and atomistic simulation revealing ion impregnation effects on the growth mechanisms. Depending on the ionic species used for pre‐treatment of the organic component dramatic changes of the mesoscopic structuring are observed.
Besides temperature at one atmosphere, the applied pressure is another important parameter for influencing and controlling reaction pathways and final reaction products. This is relevant not only for the genesis of natural minerals, but also for synthetic chemical products and technological materials. The present critical review (316 references) highlights recent developments that utilise high pressures and high-temperatures for the synthesis of new materials with unique properties, such as high hardness, or interesting magnetic or optoelectronic features. Novel metal nitrides, oxonitrides as well as the new class of nitride-diazenide compounds, all formed under high-pressure conditions, are highlighted. Pure oxides and carbides are not considered here. Moreover, syntheses under high-pressure conditions require special equipment and preparation techniques, completely different from those used for conventional synthetic approaches at ambient pressure. Therefore, we also summarize the high-pressure techniques used for the synthesis of new materials on a laboratory scale. In particular, our attention is focused on reactive gas pressure devices with pressures between 1.2 and 600 MPa, multi-anvil apparatus at P < 25 GPa and the diamond anvil cell, which allows work at pressures of 100 GPa and higher. For example, some of these techniques have been successfully upgraded to an industrial scale for the synthesis of diamond and cubic boron nitride.
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