Preferred crystal orientation

The orientation of crystals in an electric field during the crystallization process in the Si02-Ti02-Ba0 system is described by Keding and Russel (1997) and Russel (1997). The controlled crystallization of fresnoite. 

Ba2TiSi20g, has been achieved in a glass with the following composition 2.75Si02 lTi02 2Ba0. 

In a study on the effects of oxidation on crystallization, Keding and Russel (1997) found that reduction produced the ion, which acted as a nucleating agent. Russel (1997) managed to control the orientation of the main crystal phases in a specific axial direction in various glass-ceramic systems. The fresnoite system as well as apatite glass-ceramics and lithium disilicate glass-ceramics were particularly suitable. 

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In contrast to nanowires synthesized by the pressure injection method, nanowires derived electrochemically are typically polycrystalline with no preferred crystal orientation. However, some exceptions occur. For example, polycrystalline CdS nanowires fabricated by ac electrodeposition in anodic alumina were shown to have a preferred wire growth orientation along the c axis (Routkevitch et al., 1996). Recently, Xu et al. (2000a, 2000b) prepared... 

Figure 38 shows the XRD pattern (a) and hysteresis loop (b) of FePt C double-layered nanocomposite thin-film medium. The soft underlayer FeCoNi (111) peak and the Zl0 FePt (001) and (002) peaks are shown only in the XRD pattern. This means that the preferred crystal orientation of Tl0 FePt C nanocomposite film is successfully obtained on this SUL by nonepitaxial growth. The polar-Kerr measurement shows a square loop that is only sensitive to the top layer the Kerr effect data shown in this loop give the coercivity Hc = 8.5 kOe, nucleation field Hn = 5.65 kOe, remanence ratio S = 1, and loop slope ( at Hc) a = 3.3, respectively. 

Figure 7(A) shows the superlattice assembly from the cube-like particles, while Fig. 7(B) is the assembly from the polyhedron-shaped particles. The fast Fourier transformation (FFT) of these two images reveals that both assemblies have a cubic packing. But the different shapes possessed by each group of particles affect the crystal orientation of individual particles within the superlattices. XRD of the self-assembled cubelike particles on Si (100) substrate shows the intensified (400) peak, Fig. 7(C), and that of polyhedron-shaped particles reveals the strong reflections of (220), Fig. 7(D). These are markedly different from that of a 3D randomly oriented spinel structured MnFe204 nanoparticle assembly, which shows a strong (311) peak. These indicate that each of the cube-like particles in the cubic assembly has preferred crystal orientation with 100 planes parallel to the Si substrate while for the polyhedron-shaped particle assembly, the 110 planes are parallel to the substrate.

A detailed study of the growth process and the structural evolution of silicalite-1 (MFI) films was undertaken with the aid of grazing incidence synchrotron X-ray diffraction. [65] The diffraction data of the adsorbed and grown zeolite films at different incident and exit angles reflect the distribution of the crystal orientation along the film thickness. The films were prepared via assisted adsorption of nanoscale MFI seed crystals, followed by calcination and subsequent hydrothermal synthesis on the seed layers. The adsorbed (multi-) layer of seed crystals consists of randomly oriented crystals. With progressing hydrothermal growth, the film surface becomes smoother and a preferred crystal orientation with the b-axis close to vertical to the substrate develops. 

An important part of modern experimental surface science and electrochemistry has been performed on single-crystal electrodes. In contrast, the metal deposited on the surface of the quartz resonator always has a rough surface and at best a preferred crystal orientation. Studies with a QCM having a true single crystal surface have not yet been reported. Making a thin (about 1 xm) stable single-crystal metal layer on the surface of quartz seems to be an insurmountable problem. 

Pole figure. This uses a Eulerian goniometer cradle attached to the diffractometer to determine preferred crystal orientations. 

Isotropic carbon, on the other hand, has no preferred crystal orientation and hence possesses isotropic material properties. There ate three types of isotropic carbon pyrolytic, vitreous, and vapor-deposited carbon. Pyrolytic carbons are formed by the deposition of carbon from a fluidized bed onto a substrate. The fluidized bed is formed from pyrolysis of hydrocarbon gas at between 1000 and 2500°C (Hench and Ethridge, 1982). Low-temperature isotropic (LTI) carbons are formed at temperatures below 1500°C. LTI pyrolytic carbon possesses good frictional and wear properties, and incorporation of silicon can further increase hardness and wear resistance (Bokros, 1978). 

Apart from the nucleation density, the preferential orientation of the nuclei is important in surface metal film formation. As the deposit becomes free of the influence of the substrate structure on thickening, instead of the formation of a randomly oriented grain structure, a preferred crystal orientation can develop, which gives a definite texture to the cross section of the deposit [72]. Texture can be expressed in terms of degree of orientation of the grains constituting the deposit. 

Preferred orientation (crystallography) When non-random growth gives the film microstructure a preferred crystal orientation (texture) in some plane. 

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