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ABOUT THE COURSE:The objective of the course is to provide a broad overview about different techniques available for structural characterization of various materials systems. It is an amalgamation of the science behind these characterization techniques and their application in material systems. The course is divided into two segments dealing with two major aspects of material structures and characterization; initial part will focus on imaging the microstructure by various microscopy techniques while the later part will deal with understanding the internal structure by diffraction phenomena. For this, the first set of lectures will introduce the fundamental issues of image formation and its inherent attributes and proceed towards details about specific imaging techniques e.g. light/optical microscopy and electron microscopy. Afterwards, the course will cover the basics of diffraction phenomena and related techniques using electron and X-ray sources. At all times, while dealing with these characterization techniques, their importance in materials research and application to real problem solving will be emphasized.INTENDED AUDIENCE : Final year UG and PG students and PhD research scholars from various disciplines like Materials and Metallurgical Engineering, Ceramic Engineering,Nanoscience and Nanotechnology, Physics, Chemistry,Materials Science etc.PRE-REQUISITES : Any introductory courses on Materials Science and EngineeringINDUSTRY SUPPORT :Industries dealing with metal making and processing (e.g. steel or Aluminum industries), semiconductor device making, biomedical applications etc.
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Week 1:
Introduction to microscopy
Basic principles of image formation
General concepts of microscopy: resolution. Magnification, depth of field, depth of focus etc.
Optical microscopy
Image formation, contrast development
Basic components (light sources, specimen stage, lens system, optical train etc.)
Various modes of optical microscopy
Bright field mode (transmission vs. reflection)
Contrast enhancing modes (dark field, polarized light, interference contrast, fluorescent microscopy etc.)
General concepts of electron microscopy
Basic components of electron microscope (electron gun, electro-magnetic lenses etc.)
Aberrations (chromatic, spherical, astigmatism etc.) and their corrections
Electron-materials interaction (elastic vs. inelastic scattering, coherent vs. incoherent scattering, interaction volume)
Transmission electron microscopy (TEM)
Image formation and contrast generation (mass-thickness contrast, atomic number contrast, diffraction contrast etc.)
Modes of TEM (bright field, dark field, HAADF, STEM)
Electron diffraction in TEM
Scattering of electrons in crystalline material (Braggs law, zone axis, order of diffraction etc.)
Electron diffraction in TEM
Concept of reciprocal lattice, Ewald sphere, diffraction from finite crystal
Diffraction pattern (Single crystal vs. polycrystalline diffraction, selected area diffraction etc.),
Indexing of diffraction pattern (camera constant, structure
Application of electron diffraction (DF imaging, dislocation contrast, phase identification etc.)
Scanning electron microscopy (SEM)
Working principle in scanning mode
Signal generation: Inelastic scattering (Secondary vs. backscattered electron, Auger electrons, characteristic X-ray emission etc.)
Basic components of SEM
Detectors: SE (E-T detector), BSE (scintillator vs. solid state), in-lense detector
Optics of SEM (magnification, pixel, resolution, depth of field)
Resolution in SEM (minimum probe size, beam current etc.)
Chemical analysis in SEM
EDS and WDS detectors
Imaging and contrast generation in SEM
Topographic imaging (in SE & BSE mode)
Compositional imaging (BSE mode)
X-ray production
Electromagnetic radiation, continuous spectrum, characteristic spectrum
X-ray absorption (adsorption edge, excitation voltage, Auger effect etc.), X-ray filters
ntensities of diffracted beams
Scattering by single electron (Thomson and Crompton scattering)
Scattering by single atom: atomic scattering factor
Intensities of diffracted beams
Scattering from unit cell: structure factor calculation for various crystal systems
Multiplicity factor and temperature factor
X-ray diffraction profile and analysis
FWHM and line broadening
Crystallite size effect and Scherrer formula
Effect of strain (tensile vs compressive, uniform vs. non-uniform)
Amorphous vs. crystalline materials
