Material characterisations
- 1. MATERIAL CHARACTERISATIONS XRD,SEM AND AFM BY CHANDAN M150478ME MATERIALS SCIENCE AND TECHNOLOGY 1 NITC MED
- 2. X RAY DIFFRACTION • A technique used to determine the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident x-rays to diffract into many specific directions. • The atomic planes of a crystal cause an incident beam of x-rays to interfere with one another as they leave the crystal. the phenomenon is called x-ray diffraction. • A stream of x-rays directed at a crystal diffract and scatter as they encounter atoms. the scattered rays interfere with each other and produce spots of different intensities that can be recorded on film. NITC MED 2
- 4. the path difference between ray 1 and ray 2 = 2d sin “constructive interference of the reflected beams emerging from two different planes will take place if the path lengths of two rays is equal to whole number of wavelengths”. for constructive interference, nλ=2dsin this is called as bragg’s law 4 NITC MED
- 5. SETUP OF INSTRUMENTS 5 NITC MED
- 6. DIFRACTION FROM SINGL CRYSALS 6 NITC MED
- 7. DIFRACTION FROM POWDER CRYSTALS 7 NITC MED
- 8. APPLICATION OF XRD • Structure of crystals • Polymer characterization • Particle size determination • Applications of diffraction methods to complexes I. Determination of cis-trans isomerism II. Determination of linkage isomerism • Miscellaneous applications NITC MED 8
- 9. SCANNING ELECTRON MICROSCOPE • Electron microscopes (SEM) are scientific instruments that use a beam of energetic electrons to examine objects on a very fine scale. • Electron microscopes (SEM) were developed due to the limitations of light microscopes which are limited by the physics of light. • Electron microscopes (SEM) have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than visible light . • Magnifications of up to about 10,000,000x. NITC MED 9
- 10. PRINCIPLE OF WORKING 10 NITC MED
- 11. LIMITATIONS • SEM cannot detect very light elements (H, He, and Li). • Samples must be solid and they must fit into the microscope chamber. maximum size in horizontal dimensions is usually on the order of 10 cm, vertical dimensions should not exceed 40 mm. • Very high vacuum, vibration free, large space. • An electrically conductive coating must be applied to electrically insulating samples . NITC MED 11
- 12. E COLLISION SCATTERING AUGER EFFECT INTERACTION OF ELECTRON WITH SAMPLE 12 NITC MED
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- 14. APPLICATIONS • Topography and morphology • Chemistry • Crystallography • Orientation of grains • In-situ experiments I. Reactions with atmosphere II. Effects of temperature NITC MED 14
- 15. 15 Morphology and Topography Fe Ce Sr NITC MED
- 17. ATOMIC FORCE MOCROSCOPY • AFM works by scanning a probe over the sample surface, building up a map of the height or topography of the surface as it goes along • No need of focusing, illumination, depth of field. • It also have height information that make it simple to quickly measure the height, volume, width of any feature in the sample. • It physically feels the sample’s surface with a sharp probe, building up a map of the height of samples surface. • It provides single atomic level structure so provide high resolution. NITC MED 17
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- 20. LIMITATIONS • AFM can only image a maximum height on the order of 10-20 micrometers and a maximum scanning area of about 150×150 micrometers. • The scanning speed of an AFM is also a limitation. • Highly dependent on AFM probes. NITC MED 20
- 21. COMPARISIONS 21 SR. NO. XRD SEM AFM SAMPLES CONDUCTIVE / INSULATING / SEMI CONDUCTER MUST BE CONDUCTIVE CONDUCTIVE/ INSULATING MAGNIFICATION 2 DIMENSIONAL 2 DIMENSIONAL 3 DIMENSIONAL ENVIORNMENT VACUUM VACUUM VACUUM/ AIR/ LIQUID TIME FOR IMAGE 3- 5 min 0.1 - 1 min 1-5 min HORIZONTAL REVOLUTION 5 nm 5 nm 2 nm VERTICAL REVOLUTION - - 0.05 nm FIELD OF VIEW 1 mm 1mm 0.01 mm DEPTH OF FIELD GOOD GOOD POOR CONTRAST ON FLATE SURFACE POOR POOR GOODNITC MED