Intensity of diffraction peaks

The main phase of SI is (Nd, Mg)2(Ni,Co)7 phase. According to the intensity of diffraction peak of two alloys, the space group is P63/mmc and crystal plane is (1 1 24), the abundance of the NdNis phase was less than S2... 

The two-dimensional example illustrating the relationships between the direct and reciprocal lattices (or spaces), which are used to represent crystal structures and diffraction patterns, respectively, is shown in Figure 1.40. Pin important property of the reciprocal lattice is that its symmetry is the same as the symmetry of the direct lattice. However, in the direct space atoms can be located anywhere in the unit cell, whereas diffraction peaks are represented only by the points of the reciprocal lattice, and the unit cells themselves are "empty" in the reciprocal space. Furthermore, the contents of every unit cell in the direct space is the same, but the intensity of diffraction peaks, which are conveniently represented using points in the reciprocal space, varies. 

X-Ray powder diffractograms contain in encrypted form information about the structure of the sample material. The positions and intensities of diffraction peaks reveal the information about an ideal crystal structure. The form of the peaks reflects the information about defects in the strncture. Instrumental aberrations affect the apparent peak positions (especially at low and high scattering angles) and intensities of the diffraction peaks as well as the form of the peaks.Hence, properly taking into account the instrumental contributions is essential both for studies aimed at obtaining information about the ideal crystal structure of the material and information about deviations from this ideal structure. 

By collecting the integrated intensities of diffraction peaks and subjecting them to a sequence of analyses, it is possible to determine the positions of the atoms packed in the crystalline unit cell. Such an endeavor constitutes the traditional process of crystal structure analysis, and much of the information that is available today about the shape of polymer molecules and their arrangement in crystals was derived by this method. 

Fig.l shows the XRD patterns of the residues of powder mixtures pyrolyzed at different temperatures. It can be found from these curves that at 1200°C, there is no obvious diffraction peaks except a broad peak for (3-SiC with very low intensity, the diffraction peaks of boron also disappeared. There are some small diffraction peaks of B4C when pyrolysed at 1300°C. Above 1400°C the intensities of diffraction peaks for (3-SiC increased and the peak for h-BN at 26° also appears. When the samples are heat-treated at high temperatures, several reactions may occur. At temperatures below 800°C, PCS will decompose to some hydrocarbons and solid residues. When the temperature increases to temperatures above 1000°C, the solid residues will gradually convert into amorphous SiC plus excessive carbon., then at temperatures above 1200°C, active filler (boron) will react with hydrocarbons and carbon to form B4C. At temperatures above 1300°C, the formed B4C and the unreacted boron will react with protective gas (N2) to form h-BN. When the temperature reaches 1400°C, SiOC phase in the materials begin to decompose into SiO and CO,... 

X-ray diffraction patterns of composites with and without boronfS and S respectively) are compared in Fig.3. As it can be found from these pattern curves, with boron introduced, the intensities of diffraction peaks for p-SiC weakened, meanwhile those for h-BN enhanced, which may be induced by the formation of h-BN as a result of reaction between boron and N2. It is also shown in the XRD patterns that the diffraction peak at 26° for composite S is much sharper than that for S. The diffraction peaks for h-BN and graphite are overlapped as they have the similar... 

Figure 9.22 shows the X-ray diffraction pattern of as-received alumina, epoxy and epoxy-alumina nanocomposites [73]. The as-received micron-size alumina has characteristic peaks at 14.5°, 28.1°, 38.3°, 48.9° and 55.1°. Epoxy is identified by its characteristic peaks at 5° and 17.8°. However, for nanocomposites, peaks are present at 28.1°, 38.3° and 48.9°. The intensity of diffraction peak of alumina decreases and its width increases in the nanocomposite samples, which is attributed to the decrease in size of the alumina particles from micron to nano-size. 

Measure the intensity of diffraction peaks. The crystallinity is indicated by the diffraction peaks sharpness... 

The intensity of diffraction peaks decreased with increasing content of TFPOPH moieties. It can therefore be presumed that the segments containing TFPOPH moieties in the copolymer are not in the crystal unit cell of the copolymer but in the amorphous phase between the crystalline lamellae. 

The semiclassical approach to the problem of atom-crystal inelastic scattering is very attractive due to its relative simplicity, analytical nature and wide applicability. This approach allows one to obtain a simple Gaussian approximation (Brako and Newns 1982 Manson 1991) to the dynamic structural feictor of inelastic phonon scattering and the intensities of diffraction peaks (Billing 1975). The effect of umklapp processes on the dynamic structural factor hcis been considered only in the hard-wall approximation (Berry 1975 Bogdanov 1980) or numerically (Manson 1991). 

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