22-11-2012, 11:40 AM
MATERIAL CHARACTERIZATION
optical microscope.pptx (Size: 5.52 MB / Downloads: 34)
Main Objective
Mechanical, electrical and magnetic properties show strong dependence on structural characteristics of a material. Therefore, material characterization is very important part of any structure-property correlation exercise. The objective of this course is to introduce structural characterization of materials at different scales and using different sources to get the required information.
The Microscope
The History
Many people experimented with making microscopes
The first microscope was 6 feet long!!!
The Greeks & Romans used “lenses” to magnify objects over 1000 years ago.
What is Microscope?
This is an optical instrument containing one or more lenses that produce an enlarged image of an object placed in the focal plane of the lens
1. Transmission: beam of light passes through the sample
e.g. Polarizing or Biological microscope
Samples are usually fine powder or thin slices (transparent)
2. Reflection: beam of light reflected off the sample surface
e.g. Metallurgical or reflected light microscope
Surface of materials, especially opaque ones
Types of microscopes
Optical/Light microscopes
Bright field microscope
Dark field microscope
Phase contrast microscope
Fluorescent microscope
Electron microscopes
Transmission electron microscope
Scanning electron microscope
Scanning tunneling microscope
Lenses
Collimated light rays focus at a specific point after passing through a convex lense called the focal point
Distance between center of lens and focal point is the focal length
Strength of lens related to focal length
Short focal length more magnification