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Professor Charles Newey (O.U.) introduces x-ray diffraction patterns as an analytical tool, and as the subject of the programme. Dr. Peter Chapman (O.U.) demonstrates diffraction of light by narrow... slits, and establishes the dependence of the pattern on the geometry of the mask producing it. Professor Newey takes the argument into three dimensions, nnd explains Braggs' equation in terms of reflection from planes of atoms which he shows on a model. How can these reflections be recorded? The operation of an x-ray camera is described and the expected form of resultant picture is deduced by animation. Professor Newey then shows a real powder camera, and the film produced by it. In the remaining, and more significant part of the programme, actual x-ray diffraction patterns are discussed and conclusions drawn from them as to their meaning and what information they give about the microstructure of a material.
Metadata describing this Open University video programme
Module code and title: TS251, An introduction to materials
Item code: TS251; 01
First transmission date: 27-01-1973
Published: 1973
Rights Statement:
Restrictions on use:
Duration: 00:24:27
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Producer: Colin Robinson
Contributors: Peter Chapman; Charles Newey
Publisher: BBC Open University
Keyword(s): Analytical tool; Animation; Microstructure; Planes of atoms; Reflection; X-ray camera; X-ray diffraction patterns
Footage description: Shot of an X-ray diffraction photograph of sheet aluminium. Charles Newey discusses some of the things which can be learned about materials using X-ray diffraction techniques. Peter Chapman explains how X-ray diffraction photographs are obtained. He uses a laser diffraction apparatus as an analogue for X-ray diffraction. He shows several diffraction patterns for a variety of masks (both single and two dimensional) to explain the general principles of X-ray diffraction. Charles Newey uses a model of a crystal to explain how a crystal diffracts X-rays. He introduces the Bragg equation. Peter Chapman explains why monochromatix X-ray beams are needed for X-ray diffraction. Charles Newey uses a model of a crystal to help explain how the correct orientation of molecules in the crystal is obtained so that X-ray diffraction is made possible. Powder Method for obtaining X-ray diffraction photographs explained. Shot of a diagram which shows the method. Shot of a diffraction pattern with several rings (aluminium). P. Chapman explains that structural analysis of materials is possible with X-ray diffraction photographs. He knows what measurements can be taken and explains how the Bragg equation is solved. Charles Newey with the apparatus for doing X-ray diffraction by the powder method. He explains how it works. Newey with blow-ups of X-ray diffraction patterns for aluminium, copper, nickel and iron. Newey discusses the first three first. He points out the similarity and differences in their diffraction patterns and tells why this is so. Peter Chapman examines reasons for size differences in the above diffraction patterns which are otherwise very similar. He uses a model of a crystal as an aid. Charles Newey examines the X-ray diffraction pattern of a body-centred, cubic crystal (Iron) and compares its pattern with those of ordinary cubic crystals. P. Chapman begins a discussion on the use of X-ray diffraction technique for determining molecular microstructure. Shot of a diffraction pattern - where the rings themselves show detail patterns of polycrystaline materials. Charles Newey shows how a diffraction apparatus is modified to obtain diffraction patterns for polycrystaline materials. Shot of an aluminium diffraction pattern which was obtained by the modified method. Peter Chapman explains how preferred orientation of crystal molecules results in greater intensity for parts of the diffraction pattern. Charles Newey explains how preferred orientation can be induced ink polycrystaline structure. He discusses the techniques for changing materials properties by induced preferred orientation. He goes on to discuss the usefulness of this technique for improving metals and polymers. Newey then examines the X-ray diffraction patterns of 4 polymers, each with different amounts of crystalinity Peter Chapman explains why both amorphous and crystaline patterns can be seen in the same specimen. Charles Newey explains how X-ray diffraction is used in the design of better polymers by changing the proportion of amorphous to crystaline materials.
Master spool number: 6HT/70733
Production number: 00525_5028
Videofinder number: 1551
Available to public: no