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Volume 10 - Materials Characterization Part 10

Tham khảo tài liệu 'volume 10 - materials characterization part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Amorphous materials produce diffuse diffraction patterns characterized by relatively few broad features. This conti with diffraction patterns from polycrystalline materials characterized by many relatively sharp diffraction rings unless crystallite size is very small. The total diffracted intensity from a randomly oriented sample polycrystalline amorphous or liquid consists of th components. Assuming correction of the data for such effects as polarization and absorption the total scattering 01 diffracted intensity consists of the interatomic interference scatted ngpd the smooth featureless terfjisand i representing coherent and incoherent atomic scattering. The distance information of interest is contafngdrei2 shows a total intensity curve for silica glass. The related equations follow t s I s Ic s lị 5 Eql wheres 4 sin 2 is the angle between the incident and diffracted beamíẶsntHie wavelength anil is the background intensity. One purpose of data reduction is to sepárate f Fig. 2 The total x-ray diffraction pattern for silica glass. It is the total diffracted intensity I b is the background intensity and s 4 n sin 0 Ă. The ordinate is multiplied by a factor of 1 3 and 9 in the three sets of curves. It is convenient to define a reduced intense _ lf w - Wl f Eq 2 The sum of the atomic scattering factors squared in the unit of composition that2js Sjổ. Division by this term largely removes the effect of the atomic electron distributions on the scattering and results in an intensity correspoi approximately to vibrating point atoms. The RDF rG r is obtained by taking the Fourier sine transform ộf rG r 4irr2 pr - p0 5i i sin jr ds Eq 3 where 4 2 w represents the probability weighted by the product of the scattering factors of finding atoms separate distance in the sample. The bulk density paramet G.is Equation 3 can be used to illustrate several important considerations for data collection. The integral is to be taken fl 0 to5 oo. Although this is not experimentally .