The mechanically induced changes in structure, thermal relaxation of metastable mechanically induced defects and gas-solid interaction of zinc ferrite were investigated by using the XRD, SEM , Mossbauer spectroscopy, measurements of particle size and chemical analysis.
The formation of the spin arrangement in ground zinc ferrite is connected with a redistribution of the cations in the close-packed anionic sublattice. On the basis of the Rietveld analysis the degree of mechanically induced inversion as well as the exact coordinates of atoms and lattice parameters in non-treated and mechanically treated zinc ferrite was determined.
In situ X-ray diffraction analysis revealed that the thermal relaxation of metastable mechanically induced defects occurs in ground zinc ferrite in the temperature range 600-1000 K. The structural metastability at sufficiently high degrees of inversion is manifested by the decrease of the initial temperature of zinc ferrite decomposition to 750 K. Thus, above 750 K two competitive processes take place: the decomposition of zinc ferrite to Zincite and Maghemite and the recovery of the undecomposed metastable phase.
Zinc ferrite plays an important role as an adsorbent in hot gas desulphurization. The influence of mechanical activation on the capacity S of zinc ferrite and on the following oxidation (regeneration) has been studied. The mechanically induced degree of inversion strongly decreasing the decomposition temperature of zinc ferrite as well as the breakage of grain size lead to an increase of reactivity of zinc ferrite in the reaction with H2S. The following oxidation of the sulphurized zinc ferrite is also influenced by the primarily performed mechanical activation.
25 crystallographers from 6 countries gathered in a modern campus of the Military Academy Liptovsky Mikulas near a great lake (Liptovska Mara) in the midst of romantic Slovak mountains Liptov to discuss a number of interesting problems regarding x-ray diffraction analysis of structure of polycrystalline materials: solid state amorphisation induced in the Fe -Ti system by mechanical deformation (S. Enzo), texture development in electrotechnical nonoriented silicon steels (M. Cernik), microdeformations in zinc oxide thin films (P. Sutta, Q. Jackuliak, V. Tvarozek and I. Novotny) etc. A pretty volume of proceedings (multilangual, 86 + II pages, ISBN 80 - 8040 - 013 - x) has been provided to attendees of the conference upon registration. The social program included a conference banquet, an excursion into mountains and a visit to the department of physics (incl. x-ray diffraction laboratory) of the host Academy. These annual conferences are intended to serve as a communication pool for powder diffraction crystallographers in the region of Czech and Slovak Republics with international participation.
Thanks to the endeavour of the local organizers (Dr. Sutta, head of the department of physics of the Academy), beautiful surroundings and deep concern of the participating crystallographers, the conference was a big success.
Jaroslav Fiala
The book deals with techniques that attemt to minimize time and effort of scientists performing experiments by suitable arrangement of the experimental procedure.
The book is divided into five chapters. The first, introductory chapter provides a review of a number of basic statistical methods used in experimental design: t -test, F-test and analysis of variance (ANOVA). Chapter 2 introduces randomization, replication, blocking, and the use of ANOVA to separate the variation due to treatments, blocks and residual error. Both one- and two-way data classification schemes (latin squares, graeco- latin squares and so on) are discussed. The third chapter introduces factorial designs (designs with more than one factor) and puts emphasis on discovering whether main effects and interactions are important. Several methods to calculate and interpret the main effects and interactions of variables (columns of contract coefficients, Yates algorithm, comparison of effects with suitable reference distribution and plotting the effects and residuals on normal probability paper) are described in detail. Chapter 4 covers fractional factorial designs which are useful when a large number of factors has to be included in an initial investigation. It explaines how to generate half - as well as higher- fraction designs and to work out the aliases, how to decide which fractions to run when dealiasing effects and how to understand the concept of design resolution. The last chapter is devoted to the response surface methodology (how to set up, analyse and interpret the results of central composite designs, how to map out a response surface and how to calculate the coordinates of its stationary point).
It is a very good, clearly, carefuly and easy to read text of the ACOL (Analytical Chemistry by Open Learning) series designed for training, continuing education and up dating of technical slaff concerned with analytical chemistry (by Thames Polytechnic, London in conjunction with the Royal Society of Chemistry). The text is equipped with self assessment questions (SAQ) which provide for readers a way of finding out whether they understand what they have just been studying. Author's responses to each SAQ are given at the end of each chapter. The book is completed with a description of ten foremost commercial software packages directed specifically towards experimental design and with a list of most important books (and a couple of papers) dealing with this topic. Although designed primarily for chemists this book on experimental design will be very useful and applicable to physics, geology and materials science, too.
Jaroslav Fiala