Tuesday, 3 July 2012

X-Ray Diffraction - Crystal Structure

It’s useful for studying Crystal structure
This method have the details about
    • Grain size (or) Crystal size
    • Orientation of the crystal
    • Cold worked, Distorted and Internally stressed crystals
    • Re-Crystallization
    • Preferred orientation etc
Methods of Examining and Measuring the condition of Crystal Structure
    1. The Laue back reflection method
    2. The Rotating Crystal method
    3. The DeBye- Scherrer (or) Powder method:
The Laue back Reflection method:
It’s applicable to single crystals (or) poly-Crystalline masses.
When a beam of Mono chromatic (i.e. of Single Wavelength) X-Ray is directed as a narrow pencil at a specimen of a metal diffraction takes place at certain of the crystallographic planes.
 03-laue method- x-rays sheild
01-laue back reflection- method-X-ray-diffraction
    01-electron-waves-travel-x-rays03-LaueBack reflection   
The Rotating Crystal method:
It’s a useful method for determining angles and positions of planes.
Crystallographic planes are brought in to reflecting positions by rotating a crystal (Specimen) about one of it’s axis while simultaneously radially it with a beam of mono chromatic x-Rays.
If crystal orientation planes are known, the angles and directions can be calculated.
05-diffractometer-x ray detector-rotation crystal
The DeBye- Scherrer (or) Powder method:
The narrow pencil of monochromatic X-Rays is diffracted from the powder and recorded by the photographic film as a series of lines of varying armature.
By the Bragg Equation:
nλ=2d Sinθ
λ– Wave length of X-ray
d- Spacing of the atomic planes
θ – Angle of reflection

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