X-RAY DIFFRACTION BY Fatma Defne Kocaayan Buket Sinem Gökhan Cesur
X-RAY DIFFRACTION
BY
Fatma Defne Kocaayan
Buket Sinem
Gökhan Cesur
HISTORY OF X-RAY DIFFRACTION
1895: Roentgen discovered x-rays
1912: von Laue, Friedrich, and Knipping passed
x-rays through crystal of ZnS and
concluded that:
a) Crystals are composed of periodic arrays
of atoms
b) Crystals cause distinct x-ray diffraction
patterns due to atoms
1914: Bragg and Lawrence showed that
diffraction pattern can be used to determine
relative positions of atoms within a single crystal
(i.e., molecular structure)
1953 : Rosalind Franklin: collected X-ray
diffraction data on Na salt of DNA .Guides
Watson and Crick to determine that DNA is a
double helix.
HISTORY OF X-RAY DIFFRACTION
NOW: Determined atomic structures and in
medical applications
HISTORY OF X-RAY DIFFRACTION
WHAT IS X-RAY DIFFRACTION ?
WHAT IS X-RAY DIFFRACTION ?
Based on constructive interference of
monochoromatic –rays and crystalline sample
BRAGG’S LAW
Crystals composed of parallel atomic planes
incoming waves undergo reflection separetly
from each plane
reflected light creates interference patterns
BRAGG’S LAW
İncoming angle equals to reflection angle
BRAGG’S LAW
Path lenght must equal integer multiples of
wavelength (BRAGG’S differraction rule)
This rule are shown with the Bragg’s equation
nd sin2
BRAGG’S LAW
If the bragg’s equation is Not satisfied NO
REFLECTION can occur,
If the bragg’s equation is satisfied
REFLECTION may occur,
INSTRUMANTATION
The instrumantation consist of four parts and they
are;
Production of x-rays
Collimator
Monochromators
Detector
PRODUCTION OF X-RAYS
X-rays are generated when high velocity electrons impinge on a metal target which are having high melting point,good thermal conductivity and large atomic number.Such as silver, iron,copper,tungsten.
Approximately 1% of the total energy of the beam is converted into x-rays.
The reminder being dissipated as heat.
COLLIMATOR
A series of closely spaced parallel metal plates.
The collimator absorbs all the x-rays except the
narrow beam that passes between gap.
MONOCHROMATORS
Absorb the undesireable radiation and allows
required wavelength to pass.There is two types of
monochromator;
Filter : Using only short wavelength.Zirconium
Crystal : Using variety wavelength.Sodium
Chloride, Lithium Floride
DETECTOR
The x-ray intensities can be measured and
recorded either by photographic or counter
methods.
Both these thypes of methods depends upon
ability of x-rays to ionize matter and differ only
in the subsequent fate of electrons produces by
ionizing process.
TYPES OF DETECTOR
Photographic Method
In order to record position and intensity of x-ray beam a plane cylindrical film is used.
Counter Methods
Geiger-Muller tube counter(the most common)
Propertional counter
Scintillation counter
Solid-state semi conducter detector
Semiconductor detector
HOW DOES IT WORK ?
X-Rays are generated by cathode ray tube,
Filtered to produce monochromatic radiation,
Collimated to concentrate and directed towards
the sample,
The interaction of rays with the sample produces
constructive interference.
HOW DOES IT WORK ?
Diffraction patterns are recorded on a
photographic film.
APPLICATIONS OF X-RAY
DİFFRACTION
Find structure to determine function of proteins
Example : To determine the DNA structure
Differentiation between crystalline and amorphous
materials;
Determination of the structure of crystalline materials
(crystal axes, size and shape of the unit cell, positions
of the atoms in the unit cell)
APPLICATIONS OF X-RAY
DİFFRACTION
Study crystal deformation and stress properties
APPLICATIONS OF X-RAY
DİFFRACTION
Measurement of limits of solid solubility, and
determination of phase diagrams;
Measurement of strain and small grain size;
APPLICATIONS OF X-RAY
DIFFRACTION
Study of rapid biological and chemical processes
In health sector
Example :
Qualitative Analysis Of Mineral
Qualitative Analysis Of Kidney Stone
APPLICATIONS OF X-RAY
DIFFRACTION