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LESSON 11(X-ray Diffraction) - Coggle Diagram
LESSON 11(X-ray Diffraction)
Diffraction
In phase
constructive interference
Completely out of phase
Destructive interference
working principle
X-ray are produced by X-ray tube.
How it is produce
Heated filament emits electrons by thermionic emission
Electrons are accelerated by high voltage
Copper rod for heat dissipation
X-rays produced when high speed electrons hit the metal target
Sample Preparation
There are sharp intensity maxima at certain wavelengths superimposed on a continous X-ray spectrum
Intensity maxima - Characteristic of X-ray
X-ray diffraction technique require single wavelength X-ray radiation
X-ray diffraction based on the constructive interference of monochromatic X-rays and sample
Bragg's Law
it relates to the
wavelength of electromagnetic radiation
to the
diffraction angle
and the
lattice spacing
in the crystalline sample
CRYSTALLINE STRUCTURE
In Phase
: X-ray scattered in the same direction and result in constructive interference
Out of Phase
: X-ray will scatter everywhere and cause destructive interference and result in low intensity diffracted beam
nλ = 2d sin (theta)
Arrangement of the atoms
Orderly with grain boundaries
: several peaks shown as ths ordered structure have different lattice point
Randomly packed
: will show a diffuse pattern as the atoms are not packed in an orderly manner
Data Analysis and Interpretation: Peaks
peaks cannot be seen
peaks can be seen
Diffraction angle = 2 x theta
lattice parameter, a. Find distance between the two plane --> find theta --> diffraction angle
