X-RAY DIFFRACTION. Fatma Defne Kocaayan Buket Sinem Gökhan Cesur

Transcription

1 X-RAY DIFFRACTION BY Fatma Defne Kocaayan Buket Sinem Gökhan Cesur

2 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

3 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.

4 HISTORY OF X-RAY DIFFRACTION NOW: Determined atomic structures and in medical applications

5 WHAT IS X-RAY DIFFRACTION?

6 WHAT IS X-RAY DIFFRACTION? Based on constructive interference of monochoromatic rays and crystalline sample

7 BRAGG S LAW Crystals composed of parallel atomic planes incoming waves undergo reflection separetly from each plane reflected light creates interference patterns

8 BRAGG S LAW İncoming angle equals to reflection angle

9 BRAGG S LAW Path lenght must equal integer multiples of wavelength (BRAGG S differraction rule) This rule are shown with the Bragg s equation 2d sin n

10 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,

11 INSTRUMANTATION The instrumantation consist of four parts and they are; Production of x-rays Collimator Monochromators Detector

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13 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.

14 COLLIMATOR A series of closely spaced parallel metal plates. The collimator absorbs all the x-rays except the narrow beam that passes between gap.

15 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

16 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.

17 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

18 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.

19 HOW DOES IT WORK? Diffraction patterns are recorded on a photographic film.

20 APPLICATIONS OF X-RAY DİFFRACTION Find structure to determine function of proteins Example : To determine the DNA structure

21 APPLICATIONS OF X-RAY DİFFRACTION 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)

22 APPLICATIONS OF X-RAY DİFFRACTION Study crystal deformation and stress properties

23 APPLICATIONS OF X-RAY DIFFRACTION Measurement of limits of solid solubility, and determination of phase diagrams; Measurement of strain and small grain size;

24 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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