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The programme demonstrates how images and diffraction patterns are formed when an electron microscope is used to examine metallic crystilline specimen and shows the wide range of macrostructural fe...atures which may be revealed by electron microscopy.
Metadata describing this Open University video programme
Module code and title: TS251, An introduction to materials
Item code: TS251; 02; 1974
First transmission date: 26-02-1974
Published: 1974
Rights Statement:
Restrictions on use:
Duration: 00:24:25
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Producer: Jim Stevenson
Contributors: Peter Chapman; Nick Reid
Publisher: BBC Open University
Keyword(s): Diffraction pattern; Microstructure; One million volt electron microscope; Optical analogue; Stainless steel
Footage description: Peter Chapman introduces the programme. He explains, briefly, the advantages of electron microscopy over x-ray diffraction. Film shots of metal specimen being loaded into the AKI EM7 electron microscope at Imperial College, London. Commentary by Chapman explains what is happening and how the instrument works. Peter Chapman with a laser analogue of the electron microscope. He demonstrates that either a diffraction pattern or an image can be obtained from a mask by the use of lenses. Chapman explains the function of each component of the analogue. To demonstrate how the image is focused in the electron microscope, the AEI EM7 is focused and the diffraction pattern is changed to an image. Chapman uses the optical analogue with a more sophisticated mask which models a polycrystaline specimen. He shows that local planes of orientation can be brought into focus by moving the specimen. Film shots then demonstrate this phenomenum on the electron microscope. Both image and diffraction pattern are shown. Chapman uses the light analogue to explain how contrast is achieved in the electron microscope by selection of individual diffracted beams. Film shots of the AEI EM7 electron microscope and its final image screen. The above procedure is carried out. A good image is gradually built up. Chapman uses a ray diagram to explain how crystal defects, such as dislocations, help give a good contrast image in electron micrographs. Film shots of an electron microscope image screen show the effect that tilting a specimen has on the image of a crystal dislocation. Chapman briefly sums up the importance of loading a specimen into the microscope at the correct tilt angle. Nick Reid shows some electron micrographs which illustrate several features of stainless steel specimen. The following are shown: 1. Voids, 2. Foreign particles, 3. Grain boundaries, 4. Dislocations. Short film clip shows dynamic movement of dislocations in a stainless steel specimen.
Master spool number: 6HT/71219
Production number: 00525_5144
Videofinder number: 1553
Available to public: no