Tuesday, June 7, 2011

General overview of what we learnt

1.scanning electron microscope

Electron Microscopes were developed due to the limitations of light Microscopes, which are limited by the physics of light to a maximum of 500x or 1000x magnification and a resolution of 0.2 micrometers. This prevented scientists from observing smaller structures that are unable to be seen by a regular light microscope. Therefore, in order to satisfy mankind’s urge to see what goes beyond what we see using a regular electron microscope, the electron microscope was created. A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons. The electrons interact with the atoms that make up the sample producing signals that contain information about the sample's surface topography, composition, and other proper

ties such as electrical conductivity. However, samples must first be placed in a vacuum environment lest the molecules that make up air absorbs the electrons and preventing the specimen from being seen. Samples must also be coated with conductive material, like gold, titanium and palladium

Our questions on this topic

1) What do you think may be caused if there is too much moisture on the specimen?

Water and moisture will readily absorb the electron beam and obscure the specimen from view, therefore producing low quality images and might affect the results of the point analysis feature available in the electron microscope

2) What is the working distance and accelerate voltage if the specimen is titanium?

  • Acceleration voltage: 20kv
  • Spot size: 10nm
  • working distance: 10mm

3) Why can’t we heat the filament too fast?

It will cause the filament to explode violently and damage the electron microscope, preventing the use of the microscope for weeks to come as it is being repaired.

2.composite materials

Composite materials are either man made or naturally occurring materials made

from two or more materials with significantly different physical and chemical properties. This results in a brand new material that may retain the unique traits of the materials that were used to manufacture it. Composites are made up of individual materials referred to as constituent materials. There are two categories of constituent materials: matrix and reinforcement. At least one portion of each type is required. The matrix material surrounds and supports the reinforcement materials by maintaining their relative positions. The reinforcements impart their special mechanical and physical properties to enhance the properties of the matrix. However, these materials are also cheap to produce, and can be used as an alternative to other more expensive materials. However, composite materials tend to be very brittle, and break/shatter easily when great force is applied to it, making it unsuitable for building structures that must be bent to a certain degree

3.Tensile material testing

In this experiment, we were provided sticks made with iron, rubbers or polymers. These sticks were then placed in machines, which stretched the sticks to their breaking point, and recorded the amount of force required for the sticks to break. At the end of our experiment, we can conclude that iron sticks required the largest amount of force to break, and the stick made of rubber required the least amount of force to break

Images captured during the learning process

Snapshot of the “Titania” that we observed in the virtual SEM machine

Data graph of the composition of “Titania” that we acquired in the virtual SEM tour

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