Lattice nanostructural materials

As has already been mentioned in the discussion of the stacking model, such equations are particularly useful for the analysis of nanostructured material with weak disorder in order both to assess the perfection of the material and to discriminate among lattice and stacking models (cf. Sect. 8.8.3). 

The next step in the direction of a deeper understanding of nanostructured materials depends on being able to isolate the individual structurally determined cluster units from the crystal lattice and then determine the physical properties of the single clusters in question. This long-term objective has been partially achieved in the gas phase investigation of a structurally determined Gai9R6 cluster [R = C(SiMe3)3] in an FT mass spectrometer (cf. Section 2.3.4.2.5, Ga clusters)... 

Fig. la. Atomic structure ofa two-dimensional nano-structured material. For the sake of clarity, the atoms in the centers of the crystals are indicated in black. The ones in the boundary core regions are represented by open circles. Both types of atoms are assumed to be chemically identical b Atomic arrangement in a two-dimensional glass (hard sphere model), c Atomic structure of a two-dimensional nanostructured material consisting Of elastically distorted crystallites. The distortion results from the incorporation of large solute atoms. In the vicinity of the large solute atoms, the lattice planes are curved as indicated in the crystallite on the lower left side. This is not so if all atoms have the same size as indicated in Fig. la [13]... 

Nickel containing scales exhibit higher conductivity because of the presence of trivalent nickel ions, which introduce vacancies in the lattice of the scale. Therefore, nickel-based coating can lead to superior conductivity and good protection provided that it is alloyed properly with corrosion resistant elements. Cobalt has a lower solubility in molten carbonate and electroless Co has been successfully used for a variety of corrosion-resistant applications. Electroless plating of Ni-Co gives rise to deposition of uniform layers of nanostructured material, which would result in better protection of the substrate. 

Figure 8.47. SRSAXS raw data (open symbols) and model fit (solid line) for a nanostructured material using a finite lattice model. The model components are demonstrated absorption factor A r, density fluctuation background Ipi, smooth phase transition The sohd monotonous line demonstrates the shape of the Porod law in the raw data. At sq the absorption is switching from fully illuminated sample to partial illumination of the sample...

A. Lerf, Intercalation compounds in layered host lattices Supramolecular chemistry in nanodimension, in H.S. Nalwa (Ed.), Handbook of Nanostructured Materials and Nanotechnology, vol. 5, Academic Press, New York, 2000, p. 5. 

Two-dimensional nanostructures have two dimensions outside of the nanometric size range, such as nanoplates, nanosheets, and nanodisks. Graphene is a typical two-dimensional film, which is composed of a one-atom-thick planar sheet of sp -bonded carbon atoms that are densely packed into a honeycomb crystal lattice. This material exhibits a high electrical conductivity, a high surface area of over 2600 m g , an elevated chemical tolerance, and a broad electrochemical window. Therefore, they were used to form two-dimensional nanocomposites with polymers. The graphene not only increases the electrical conductivity of the polymer, but also enhance its mechanical stability. Conducting polymers with various hierarchical structures have been deposited on... 

Graphene is actually the single 2-D layer of graphite with one-atom-thick, sp -bonded honeycomb carbon lattice. This material was first isolated from graphite by exfoliation with adhesive tape in 2004 and fabrication methods of graphene have expanded quickly since then. Graphene and its derivatives are such new carbon nanostructures that their research and applications in orthopedics are still limited. Here, their fabrication methods are briefly overviewed and the readers can refer to literature [40] for more details. 

Mesoscopic materials form the subset of nanostructured materials for which the nanoscopic scale is large compared with the elementary constituents of the material, i. e. atoms, molecules, or the crystal lattice. For the specific property under consideration, these materials can be described in terms of continuous, homogeneous media on scales less than that of the nanostructure. The term mesoscopic is often reserved for electronic transport phenomena in systems structured on scales below the phase-coherence length A0 of the carriers. 

J.L. Marin, R. Riera, R. A. Rosas Confined systems and nanostructured materials. In Nanomaterials, Flandbook of Advanced Electronic and Photonic Materials and Devices, Vol.9, ed. by H.S. Nalwa (Elsevier, Amsterdam 2000) p. 55 J.M. Flartmann, M. Charleux, J. L. Rouviere, H. Ma-riette Growth of CdTe/MnTe tilted and serpentine lattices on vicinal surfaces, Appl. Phys. Lett. 70, 1113-1115 (1997)... 

They were named zeolite ( boiling stone ) in 1756 by Cronstedt, a Swedish mineralogist, who observed their emission of water vapor when heated. At the other size limit, opals constitute another example of a naturally occurring nanostructured material. These gems are made up mainly of spheres of amorphous silica with sizes ranging from 150 nm to 300 nm. In precious opals, these spheres are of approximately equal size and can thus be arranged in a three-dimensional periodic lattice. The optical interferences produced by this periodic index modulation are the origin of the characteristic iridescent colors (opalescence). 

Among several methods, XRD is the most efficient method to determine the crystal size D and the lattice constant d for a bulk and nanostructured materials, as illustrated in Fig. 12.3, based on Bragg diffraction and Scherrer s equation,... 

Superhard materials implies the materials with Vickers hardness larger than 40 GPa. There are two kinds of super-hard materials one is the intrinsic superhard materials, another is nanostructured superhard coatings. Diamond is considered to be the hardest intrinsic material with a hardness of 70-100 GPa. Synthetic c-BN is another intrinsic superhard material with a hardness of about 48 GPa. As introduced in Section 2, ta-C coatings with the sp fraction of larger than 90 % show a superhardness of 60-70 GPa. A typical nanostructured superhard coating is the heterostructures or superlattices as introduced in Section 4. For example, TiN/VN superlattice coating can achieve a super-hardnessof56 GPa as the lattice period is 5.2 nm[101]. 

Ruland and Smarsly [84] study silica/organic nanocomposite films and elucidate their lamellar nanostructure. Figure 8.47 demonstrates the model fit and the components of the model. The parameters hi and az (inside H ) account for deviations from the ideal two-phase system. Asr is the absorption factor for the experiment carried out in SRSAXS geometry. In the raw data an upturn at. s o is clearly visible. This is no structural feature. Instead, the absorption factor is changing from full to partial illumination of the sample. For materials with much stronger lattice distortions one would mainly observe the Porod law, instead - and observe a sharp bend - which are no structural feature, either. 

Carbon nanotubes (CNTs) constitute a nanostructured carbon material that consists of rolled up layers of sp2 hybridized carbon atoms forming a honeycomb lattice. After diamond, graphite and fullerenes, the one-dimensional tubular structure of CNTs is considered the 4th allotrope of carbon (graphene is the 5th). 

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