Optical properties diffraction

V. Other physical determinations w. Thin-layer chromatography X. X-ray diffraction z. Optical properties... 

The hydrated alumina minerals usually occur in ooUtic stmctures (small spherical to eUipsoidal bodies the size of BB shot, about 2 mm in diameter) and also in larger and smaller stmctures. They impart harshness and resist fusion or fuse with difficulty in sodium carbonate, and may be suspected if the raw clay analyzes at more than 40% AI2O2. Optical properties are radically different from those of common clay minerals, and x-ray diffraction patterns and differential thermal analysis curves are distinctive. 

Mica [12001 -26-2]—Cl Pigment White 20, Cl No. 77019. A white powder obtained from the naturally occurring mineral muscovite mica, consisting predominantly of a potassium aluminum siHcate, [1327-44-2] H2KAl2(Si0 2- Mica may be identified and semiquantitatively determined by its characteristic x-ray diffraction pattern and by its optical properties. 

In this study, we report on the GaN nanorod growth by HOMVPE technique with or without using a new precursor, tris(N,N-dimethyldithiocarbamato)gallium(III) (Ga(mDTC)3). The structural and optical properties of GaN nanorods were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). 

Processes such as film extrusion, fiber spinning, injection molding, and drawing tend to impart orientation to products made from semicrystalline polymers. Mechanical, dielectric, and optical properties, to mention only three, are often strongly influenced by orientation. X-ray diffraction offers a direct approach to studying crystallite orientation because the Intensity that is diffracted into a detector placed at an appropriate position is directly proportional to the number of crystal lattice planes that are in the correct orientation for diffraction. The principles of such measurements are well described in textbooks 0,2). 

In the course of his studies of the dyeing process, he became deeply interested in the structure of natural fibers, and most of his efforts were directed toward this new field of research, with the help of able associates, among them R. Brill, M. Dunkel, G. von Susich, and E. Valkd. His investigation of various aspects of the problem utilized physical means (for example, x-ray diffraction, optical properties, and viscosity) and the purely chemical approach. A young scientist, H. Mark, who later became an authority in the field of high polymers, was appointed head of the physical chemistry laboratory. 

SnC>2 nanoparticles have been successfully synthesized by chemical co-precipitation method using ethanol, acetone, tetrahydrofuran (THF) and ether as solvents. X-ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) have been used to study the crystallographic and morphological properties of synthesized SnC>2 nanoparticles, while their optical properties have been studied by UV-Visible absorption spectroscopy. UV-Vis absorption spectra shows a weak quantum confinement in all the synthesized SnCL samples. The photo-catalytic activity of as-synthesized SnC>2 nanoparticles under UV irradiation has been evaluated using Methylene Blue (MB) dye as a test contaminant in water. The results showed that solvents played a key role to control the morphology and photo-catalytic activity of SnCE nanoparticles. 

Colloidal crysfals can be viewed as the mesoscopic counterpart of atomic or molecular crystals. They have been used to explore diverse phenomena such as crystal growth [52-54] and glass transition [55,56], and have many interesting applications for sensors [57], in catalysis [58,59], advanced coatings [60], and for optical/electro-optical devices for information processing and storage [61,62]. In particular, their unusual optical properties, namely the diffraction of visible light and the existence of a photonic stop band, make them ideal candidates for the development of photonic materials [61,63-66]. They may lead to the fabrication... 

Optical examination of etched polished surfaces or small particles can often identify compounds or different minerals hy shape, color, optical properties, and the response to various etching attempts. A semi-quantitative elemental analysis can he used for elements with atomic number greater than four by SEM equipped with X-ray fluorescence and various electron detectors. The electron probe microanalyzer and Auer microprobe also provide elemental analysis of small areas. The secondary ion mass spectroscope, laser microprobe mass analyzer, and Raman microprobe analyzer can identify elements, compounds, and molecules. Electron diffraction patterns can be obtained with the TEM to determine which crystalline compounds are present. Ferrography is used for the identification of wear particles in lubricating oils. 

A note of caution is necessary when deahng with these materials. It is not trivial to distinguish between CuInS(Se)2 and some phases of Cu—S(Se). Diffraction and optical properties may be similar. Elemental analysis is particularly important to verify inclusion of indium in the films and in the correct ratio. A fingerprint of the chalcopyrite XRD is the presence of a weak peak at 26 = 17-18°, corresponding to the (101) chalcopyrite reflection. This is often not seen, although this could be either because the deposit is not chalcopyrite or because weak peaks are usually not seen in nanocrystaUine materials with particularly small crystal size. 

X-ray diffraction, electron diffraction and neutron diffraction all involve using radiations whose wavelengths are of the same order as the distances between the molecules. However, it is possible to obtain valuable information about the state of order of a thin organic film using radiations in the visible and infrared regions. A material which has anisotropic optical properties in the plane normal to the direction of the incident... 

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