Nanocrystalline domains

Thermolysis of this powder at 400 C yielded a brown powder with a Ga In P ratio of 2.69 1.00 4.16, and significant C, H, and Cl contamination. An XRD pattern of this sample (Figure IB) showed it to be nanocrystalline (domain size ca. 1 nm), with (111), (220) and (311) reflections located between those expected for GaP (25) and InP (30) (Table I), indicative of the presence of a ternary GalnP mixed-metal semiconductor in the powder sample. 

Overall, cellulose I is mainly responsible for the mechanical properties of reinforced polymer composites due to its high elastic modulus and crystallinity. The elastic modulus of perfect cellulose crystals has been calculated and estimated between 130 GPa to 250 GPa, whereas the tensile strength is approximately between 0.8 GPa to 10 GPa [28]. In previous studies cellulose has already been processed into films, gels, fibers, microfibers, nanofibers and nanocrystals for different applications [29-32]. Actually, cellulose fiber is the bundle of microfibrils comprising nanocrystalline domains linking through amorphous domains [33]. 

At this point, the low-frequency (boson) peak is often termed a crystalline size peak characteristic of acoustic vibrations of the nanocrystalline domains. Its position can be used to calculate the nanocrystallite size using the following equation [48-50] ... 

Brezesinski, K Wang, J., Haetge, J., Reitz, C Steinmueller, S.O., Tolbert, S.H., Smarsly, B.M., Dimn, B and Brezesinski, T. (2010) Pseudocapacitive contributions to charge storage in highly ordered mesoporous group V transition metal oxides with iso-oriented layered nanocrystalline domains. / Am. Chem. Soc, 132 (20), 6982-6990. 

The reflexes appear broad and point to apparent nanocrystalline domains. Using the Scherrer method (STOE, WinXPow) the averaged elongation of the Ce02 lattice planes was calculated wiA 111 = 13 nm, 200 = 19 nm, 220 = 13 nmand 311 = 12 nm. 

Figure C2.17.9. Size-dependent changes in PXRD linewidtlis. PXRD can be used to evaluate tire average size of a sample. In tliese cases, different samples of nanocrystalline titania were analysed for tlieir grain size using tire Debye-Scherr fonnula. As tire domain size increases, tire widtlis of tire diffraction peaks decrease.

Specifically, this volume focuses on the synthesis, processing, and structural tailoring of nanocrystalline and nanoporous materials. Nanocrystalline materials possess unique hybrid properties characteristic of neither the molecular nor the bulk solid-state limits and may be confined in nanometersized domains in one, two, or three dimensions for unusual size-dependent behavior. Nanoporous materials, characterized by well-defined pores or cavities in the nanometer size regime and controlled pore diameter and structure, give rise to unique molecular sieving capabilities and ultrahigh internal surface areas. Nanoporous structures also act as hosts and templates for the fabrication of quantum dots and quantum wires. 

The Raman spots are caused by nanocrystalline carbon adsorbed on isolated silver particles [41]. An example for such a Raman spectrum is shown in Eig. 8.10. The broad structure between 2,500 and 5,000 cm is caused by fluorescence. The Raman bands in the region at 1,350 cm (D-band) and 1,590 cm (G-band) as well as the secondary Raman bands between 2,500 and 3,000 cm were observed in the experiments. The carbon lines mainly agree with results reported in the literature [42]. Only the splitting of the D-band is different and may be indicative for probing a small number of carbon nanocrystallits. The domain size of the carbon can be estimated from the intensity ratio of the D- and G-bands according to Tuinstra and Koenig [42]. Similar experiments of... 

Moyer et al. [41] demonstrated that the two dimensionally domain size of nanocrystalline carbon was found to be in the order of 10 nm. Additional spectroscopic Raman measurements on nanocrystalline carbon adsorbed at separate isolated silver nanoparticles revealed temporal fluctuations in the peak intensities of the characteristic carbon bands and intermittent on/off behavior [41]. The SERS literature (e.g., [5, 10, 11]) frequently reports this phenomenon, called blinking. Most authors interpreted the blinking that only few nanocrystallites were involved. 

---