Nanostructured ceramics effect

The chapters in this volume present detailed insights into the synthesis-structure-properties relationships of nanostructured materials. In particular, the catalytic and photocatalytic properties of nanoclusters and nanostructured materials with ultrahigh surface-to-volume ratio are demonstrated. The gas absorption characteristics and surface reactivity of nanoporous and nanocrystalline materials are shown for various separation and reaction processes. In addition, the structural manipulation, quantum confinement effects, transport properties, and modeling of nanocrystals and nanowires are described. The biological functionality and bioactivity of nanostructured ceramic implants are also discussed. 

Another area in which preceramic polymers can be utilized effectively is as binders for ceramic powders in near net shaping fabrication processes, such as compression or injection molding with subsequent sintering. Alternatively, an active filler and a polymer [67,68], as reported by Greil and Seibold, can be used in such fabrication. Other potential applications of preceramic polymers is in the general area of coatings, especially for carbon-carbon composites [69], and in the synthesis of nanostructured ceramic particles and composites [70-73]. 

The use of proven catalyst recipes would greatly curtail development times, and the absence of extraneous material avoids unwanted catalytic effects and enhances thermal stability. The fixation of catalyst on ceramic substrates such as washcoats is a well-known, reliable, and relatively straightforward procedure. The fabrication of complex small-scale ceramic structures is, however, more awkward than for metals or plastics, and they exhibit relatively poor mechanical strength. Furthermore, the porous ceramic nanostructure must be sealed to prevent contact between the reaction medium and coolant. 

Typically, electroplating metals and metal alloys is less sophisticated than the corresponding metal oxide or chalcogenide electrodeposition. Further, dense and highly stable deposits are usually obtained. The two-step synthesis approach is more versatile, in a sense that after identifying a synthesis route to a nanostructured metal, various ceramics can be produced by thermal oxidation under an appropriate atmosphere. In fact more porous and sophisticated structures, such as hollow nano-spheres, nanotubes, and nano-peapods, can be synthesized based on the nanoscale Kirkendall effect (NKE) occurring during thermal oxidation [2-5]. 

Kumar K.-N.P., Keizer K., Burgraaf A.J., Okubo T., Nagamoto H., Morooka S. Densification of nanostructured titania assisted by a phase transformation. Nature 1992 358 48-51 Kumar K.-N.P, Kumar J., Keizer K. Effect of peptization on densification and phase-transformation behavior of sol-gel-derived nanostructured titania. J. Am. Ceram. Soc. 1994 77 1396-1400... 

Morita et al. [97] have studied the photoluminescence of CdS Mn and Eu nanoparticles dispersed in zirconia sol-gel films. Luminescence properties of doped semiconductors are characterized by the presence of multi-centers, surface effects, and fast nonradiative decay processes in nanostructured sol-gel ceramic matrix. 

Widgeon, SMera, G., Gao, Y., Sen, S., Navrotsky, A., Riedel, R. (2012b). (Manuscript snbmitted for publication). Effect of precursor on speciation and nanostructure of SiBCN polymer derived ceramics. Journal of the American Ceramic Society. 

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