Mechanical nanocrystalline phases

Oh, S.M., Li, J.G. Ishigakia, T. Nanocrystalline Ti02 powders synthesized by in-flight oxidation of TiN in fliermal plasma Mechanisms of phase selection and particle morphology evolution. J. Mater. Res. 20 (2005), pp. 529-537. 

DSSCs convert sunlight to electricity by a different mechanism than conventional p-n junction solar cell. Light is absorbed directly at the solid/liquid interface by a monolayer of adsorbed dye, and initial charge separation occurs without the need of exciton transport.42,43 Following the initial charge separation, electrons and holes are confined in two different chemical phases electrons in the nanocrystalline... 

Nanocrystalline materials form an exciting area of materials research because bulk materials with grain size less than 100 nm have properties not seen in their microcrystalline counterparts. But the brittleness of nanoceramics has limited their potential for use in structural applications, namely, research on nanoceramics shows that they are not inherently tougher than their microcrystalline counterparts. Many strategies have been proposed to improve the mechanical properties of nanoceramics by using reinforcement by a second-phase addition and hybridization to develop nanocrystalline matrix composite materials. 

The key of the mechanical and physico-chemical properties of bone lies in its micro- and nanostructure. The apatite crystals of the mineral phase are nanocrystalline and irregular platelet shaped with dimensions in the range of... 

The goal of materials research is really the reverse process, the bottom-up method. In this approach, it is hoped that perfect well-controlled nanoparticles, nanostrucmres, and nanocrystals can be synthesized, which may be compacted into macroscopic nanocrystalline samples, or assembled into superlattice arrays, which may, in mrn, be used in a variety of applications such as nanoelectronic or magnetic devices. Some scientists have even envisioned a time when so-called molecular assemblers will be able to mechanically position individual atoms or molecules, one at a time, in some predefined way (Drexler, 1986). The feasibility of such machines has been hotly debated but, regardless, such systems engineering goals are not really within the scope of this chapter. At present, methods for synthesizing metal and ceramic clusters and nanoparticles fall in one of two broad categories liquid phase techniques or vapor/aerosol methods. 

The anthors [89, 135] nsed mechanical activation of stoichiometric mixtnre of BiiOi and V2O5 to synthesize nanocrystalline bismuth vanadate powders. Structural evoluton of the desired BiiV05 5 through an intermediate phase (BiV04> was monitored by XRD, DTA and TEM investigations. 

Recently reported meso- and macroscale self-assembly approaches conducted, respectively, in the presence of surfactant mesophases [134-136] and colloidal sphere arrays [137] are highly promising for the molecular engineering of novel catalytic mixed metal oxides. These novel methods offer the possibility to control surface and bulk chemistry (e.g. the V oxidation state and P/V ratios), wall nature (i.e. amorphous or nanocrystalline), morphology, pore structures and surface areas of mixed metal oxides. Furthermore, these novel catalysts represent well-defined model systems that are expected to lead to new insights into the nature of the active and selective surface sites and the mechanism of n-butane oxidation. In this section, we describe several promising synthesis approaches to VPO catalysts, such as the self-assembly of mesostructured VPO phases, the synthesis of macroporous VPO phases, intercalation and pillaring of layered VPO phases and other methods. 

Penn R L and Banfield J F 1999 Formation of rutile nuclei at anatase (112) twin interfaces and the phase transformation mechanism in nanocrystalline titania Am. Miner. 84 871... 

GPa and from 70 to 30 GPa, respectively. The hardness values obtained for the diamond/p-SiC composite fdms at lower and moderate TMS flow rates can be directly related to the high density of the interfaces or grain boundaries present in the fdms owing to the nanocrystallinity of both the phases. Frictional and mechanical properties of the diamond/p-SiC nanocomposite fdms clearly indicate that p-SiC volume fraction can be considered as an important compositional factor to determine any physical properties of the nanocomposite film system. 

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