THE INTERPRETATION OF THE X-RAY PICTURES OF NANOCRYSTAL MATERIALS IN A NEW WAY
E.N. Moos1, V. N. Selivanov1, E.L. Dzidziguri2, V. V. Levina2
1Agricultural Academy, The
Laboratory of Surface Physics, Ryazan, Russia.
2The Institute of
Stee1 and Alloys (Technological University), The Faculty of the
Theory of Metallurgical Processes, Moscow.
The research of the defective structure and polydispersity of nanocrystal materials (NCM) is the purpose for the explanation of the unusual properties of given objects. One of the basic methods of the NCM research is X-ray structural analysis. The X-ray pictures of NCM essentially differ from the X-ray pictures of coarse-crystalline materials and have no reliable interpretation. We must note that generally accepted Warren-Averbach method for the analyzing crystals substructure according broadening and shape of x-ray diffraction lines (XDL) can be restrictedly applied in case of NCM because of the little size of crystallites, their polydispersity and different distribution of tension fields from dislocations. That is why working out approaches of the effective interpretation of NCM substructure from XDL is an unsolved problem.
In the research there was investigated the influence of the polydispersed system of the isometric crystallites on the type of the x-ray picture of NCM. The defectiveness of crystallites was modeled by dislocations with close-acting and long-distance tension fields. There was shown that polydispersity of crystallites and close-acting fields can considerably change the shape of XDL, moreover, the latest also considerably broaden the XDL of the second order of reflection. There was made a conclusion about the dependence of the character of fields from the extent of correlation of dislocations and sizes of crystallites. It was worked out a simple method of the calculus of monomode distribution of crystallites according to the size and allocation of microdeformations of the crystal lattice along the area of averaging, which rate of diminishing depends upon the distance of the tension field dislocation. There was offered the calculus of average density, correlation extent, semidiameter of correlation and coefficient of dislocations interaction. The advantage of the proposed approach is in the usage of the central part of XDL.
On the basis of the new analysis the
differences in FCC and HDP phases of substructures of cobalt
powder, the anomalous types of X-ray pictures of zirconium and
magnesium oxide powders, there was investigated the substructure
of molibdic films. The results were compared with the other
methods of x-ray structural analysis and TEM. It was offered the
program of calculus of the substructure parameters.