X-RAY DIFFRACTION BY Fatma Defne Kocaayan Buket Sinem Gkhan 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
HISTORY OF X-RAY DIFFRACTION 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
WHAT S X-RAY DFFRACTON ? WHAT S X-RAY DFFRACTON ? Based on constructive interference of monochoromatic rays and crystalline sample BRAGGS LAW
Crystals composed of parallel atomic planes incoming waves undergo reflection separetly from each plane
reflected light creates interference patterns BRAGGS LAW ncoming angle equals to reflection angle BRAGGS LAW Path lenght must equal integer multiples of wavelength (BRAGGS differraction rule) This rule are shown with the Braggs
equation 2d sin n BRAGGS LAW If the braggs equation is Not satisfied NO REFLECTION can occur,
If the braggs 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 DFFRACTION Find structure to determine function of proteins Example : To determine the DNA structure
APPLICATIONS OF X-RAY DFFRACTION 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
DFFRACTION Study crystal deformation and stress properties APPLICATIONS OF X-RAY DIFFRACTION 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
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