Introduction
X-ray diffraction is an analytical technique looking at X-ray scattering from crystalline materials. Each material produces a unique X-ray "fingerprint" of X-ray intensity versus scattering angle that is characteristic of its crystalline atomic structure. Qualitative analysis is possible by comparing the XRD pattern of an unknown material to a library of known patterns. The three-dimensional structure of non-amorphous materials is defined by regular, repeating planes of atoms that form a crystal lattice.
Working
When a focused X-ray beam interacts with these planes of atoms, part of the beam is transmitted, part is absorbed by the sample, part is refracted and scattered, and part is diffracted. When an X-ray beam hits a sample and is diffracted, we can measure the distances between the planes of the atoms that constitute the sample by applying Bragg's Law. Bragg's Law is nλ=2d sinθ, where the integer n is the order of the diffracted beam, λ is the wavelength of the incident X-ray beam, d is the distance between adjacent planes of atoms (the d-spacings), and θ is the angle of incidence of the X-ray beam. Since we know λ and we can measure θ we can calculate the d-spacings. The characteristic set of d-spacings and theirs intensity generated in a typical X-ray scan provides a unique "fingerprint" of the phases present in the sample. When properly interpreted, by comparison with standard reference patterns and measurements, this "fingerprint" allows for identification of the material. Presence of an amorphous material in the sample can be determined by occurrence of specific wide halo on diffraction pattern.
Software
Diffrac Plus software for Bruker AXS diffractometer D8 Advance allows carrying ou...
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...pplied to phase quantification only if structures of all phases are known. At the same time still a direct method, an internal standard method and relative intensity ratio (RIR) method are used. It should be noted that each of the available methods has its intrinsic limitation, so that final choice should be made based on specific task and material to be analysed.
APPLICATIONS
• Rocking curves:
Composition, thickness (300-10000 Å), mismatch
• Reciprocal lattice mapping:
Composition, thickness (at least 500 Å), mismatch
Mosacity and defects profile
• Reflectivity measurements:
Composition, thickness and interface roughness, Layer thickness range of 50-1500 Å (thin layer measurement)
• Pole figures:
Finding layer composition, orientation with respect to substrate
• quality samples) and phase analysis
The complete experimental procedure is available in the General Chemistry Laboratory Manual for CSU Bakersfield, CHEM 213, pages 20-22, 24-25. Experimental data are recorded on the attached data pages.
Physical Chemistry Laboratory Manual, Physical Chemistry Laboratory, Department of Chemistry, University of Kentucky, Spring 2006.
The color that was chose to be shined through the sample was purple. The spectrophotometer was set at a wavelength of 400nm to represent the purple color. It was zeroed using the blank meaning the spectrophotometer read zero as absorbance amount. The blank consisted of 5mL of water and 2.5 mL AVM and it was placed in cuvette. A solution with a known concentration of 2.0x10-4 M was used in the spectrometer. For this solution, 5 mL of the solution with 2.5 mL of AMV was placed in the cuvette. The cuvette was placed inside of spectrophotometer and the amount of absorbance was recorded. This procedure that involves a solution with a known concentration was repeated for the concentrations:1.0x10-4 M,5.0x10-5 M,2.0x10-5M, and1.0x10-5M.A unknown solution absorbance was measured by putting 5 mL of unknown solution with 2.5 mL AMV in a cuvette. The cuvette was placed in the spectrophotometer and the amount of absorbance was recorded. The procedure that deals with the unknown solution was repeated 2 more times with the same solution and the same amount of solution and AMV. The average of the three unknown solution was calculated and the concentration of the unknown solution was
Dai, X., Reading, M., & Craig, D.Q.M. (2008). Mapping Amorphous Material on a Partially Crystalline Surface: Nanothermal Analysis for Simultaneous Characterisation and Imaging of Lactose Compacts. Journal of Pharmaceutical Science, 98, 1499–1510.
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In summary, the rate of cooling from the austenite phase is the main determinant of final structure and properties.