NCMN Central Facility for X-Ray Structural Characterization
The NCMN X-Ray Characterization Facility is dedicated to materials identification and characterization through non-destructive, X-Ray Diffraction (XRD) technique. The following equipment is utilized: (1) Bruker-AXS D8 Discover High-Resolution Diffractometer; (2) Rigaku D-Max/B Horizontal Q/2Q X-Ray Diffractometer (with normal and small angle goniometer).
Powder X-Ray Diffraction
High Resolution X-Ray Diffraction
Bruker-AXS D8 Discover High-Resolution Diffractometer
This recently acquired system is a state-of-the-art machine including HI-STAR area detector, centric 1/4-circle Eulerian cradle, domed hot stage, hi-flux in-plane hardware, laser/video sample-alignment system, Göbel mirror, V-groove Ge crystal monochromator, fine tilt stage, and dual-beam path analyzer module. The system can be configured for grazing-incidence in-plane XRD, grazing-incidence XRD, x-ray reflectivity, high-temperature XRD, high-resolution XRD (rocking curves, reciprocal space maps), texture (pole figures), residual stress, and microdiffraction and capillary diffraction.
Rigaku D/Max-B Diffractometer:
X-Rays are produced by a 2 kW, copper target, sealed tubeor diffracted beam then converges (is “focused”) into a diffracted beam monochromator which removes all radiation except the Cu Ka wavelength (about 1.544 Å) which then enters a scintillation counter. The sample and detector are rotated with respect to the incident beam at angles q and 2q, respectively. A typical XRD scan consists of a plot of detector angle (2q) vs. diffracted intensity. These diffractograms can be printed out or saved to disk in application-friendly ASCII format. Analysis can be carried out in the facility on any of 3 PCs equipped with qualitative and quantitative XRD software and access to the latest ICDD powder diffraction file database.
Most powder, thin-film, and bulk samples are acceptable. The sample holders can accommodate samples up to 30 x 30 x 10 cm in size (sometimes larger) with the 30 x 30 cm surface tangent to the diffracting circle. The amount of material needed for a diffraction pattern depends on the diffracting power of the sample and the type of analysis desired. For example, phase identification of a well crystallized powder, with small (< 40 mm) particle size, may only require 1 mg. or less.
Rigaku X-Ray Diffraction Laue Camera System:
This instrument consists of a 2 kW, copper target X-Ray tube, a Polaroid XR-7 camera system, a manual goniometer with three rotational axes, and a movable platform. The camera uses film that is sensitive to x-radiation. The Laue x-ray diffraction method requires a continuous (white) spectrum of X-Ray which is what you get from an unfiltered, unmonochromatized X-Ray tube. The single crystal sample is fixed in position throughout the X-ray exposure with respect to the incident beam and the camera. Using this configuration, we obtain diffraction peaks (show as white spots on film) from many sets of crystal planes simultaneously because, although the geometry and d-spacing are different for each set of diffracting planes, there is a wavelength of radiation present for which the Bragg law is satisfied. The relative location of these spots on the film can be used to determine crystal structure and orientation. The system can be set up to allow transmission (sample between incident radiation and film) or back-reflection (film between sample and incident radiation Laue patterns)
Dr. Shah Valloppilly, Specialist