G. V. Samsonov – författare

The continuous and ever expanding development of high-temperature tech­ nology involves the use of high -temperature refractory materials and one of the most important classes of these is the oxides, i.e., compounds of elements with oxygen. Oxides are the oldest refractory compounds known in technology and this is connected with their high chemical stability and abundance in nature. In addition to the use of oxides as raw materials for metallurgical processes, the refractoriness, chemical stability, and magnetic and other technically important properties of oxides have been put to use since antiquity. At the present time the importance of oxides as bases of many materials for new technology is substantial and is growing rapidly with the development of processes for the direct conversion of various forms of energy into electrical energy, the development of nuclear technOlogy, electronics, semiconductor and dielectric technOlogy, and cosmic technology, where the refractoriness and chemical stability of oxides are used in combination with their specific physical properties. Oxides are the foundation of the so-called oxygen -containing or oxygen refractory materials, which are fundamental to high-temperature tech­ nology. Oxides are no less important as the bases of practically all structural ma­ terials and rocks. A number of oxides are involved in biological processes.

One of the most effective methods of increasing the wear resistance, hardness, surface strength and high-temperature oxidation resistance of metals and alloys is the diffusion satu­ ration of the surfaces by metals and nonmetals. For communicating and discussing the results of the numerous researches carried out in this field in the Department of PJ:tysicotechnical Problems of Materials Science, Academy of Sciences of the UkrSSR, a permanent Scientific Seminar was set up in 1961, which enjoys an ever-increasing popularity among specialists in this field. The present collection contains papers read at the Third Session of this Seminar, held on September 25-28, 1963. The compilers of the collection and the authors of the papers hope that its publication in the U. S. A. will enable American specialists to become acquainted with the main lines along which corresponding work is being conducted in the USSR. This should contribute to an ex­ change of scientific experience in this interesting field which is of such great practical impor­ tance. G. V. Samsonov PREFACE This collection is comprised of papers relating to the diffusion saturation of metals and to coatings of refractory compounds. The papers discuss current problems in the theory and practice of the production of diffusion coatings on metallic materials. A means of classifying the methods of diffusion saturation is proposed, and a new method is described for calculating the diffusion parameters in a heterogeneous medium.

The book we are presenting to American and other English­ speaking readers is a review of the work on the electron struc­ ture of elements, alloys, and compounds, which was started back in the fifties. This work gradually grew into a system of ideas on the electron structure of condensed matter which is now known as the configurational model. This model is based on the assumption of the preferential formation of the most stable configurations of the localized va­ lence electrons in condensed matter. The existence of these stable configurations and the exchange of electrons with the de­ localized (collective-state) subsystem determines those prop­ erties which are related to the electron structure. The conclu­ sions which can be drawn from the applications of the configura­ tional model are only qualitative but they explain quite clearly the nature of various properties of condensed matter, and they are helpful in the search for materials with specified properties. The American edition has been corrected and supplemented in many minor respects. Moreover, the opportunity was taken to revise thoroughly the section on the fundamentals of the configura­ tional model in the light of the latest theoretical developments. other parts of the book have been shortened to eliminate material which is not of fundamental significance or has not yet been de­ veloped sufficiently fully.

The present stage of technological development makes new and ever more complex demands on materials that have to work under conditions of high temperature and pressure, in high vacuum, and in corrosive media. In consequence special importance is now at­ tached to the refractory compounds of transition metals of groups IV to VI with such nonmetals as boron, carbon, silicon, and nitro­ gen. These compounds possess high melting points, great hard­ ness, and high refractory and corrosion-resisting properties. The most widely used and important compounds of this type from a technological point of view are the carbides, which are already fairly widely used in various fields of technology. The present collection of papers contains the results of re­ cent investigations into methods of producing high-purity carbides and also components made of the carbides and their alloys. Great attention has been paid to the study of a wide range of properties of the carbides and of alloys based on them, viz., the electro-and thermophysical, thermodynamic, mechanical, and chemical prop­ erties, and also to the utilization of the carbides as wear-and abrasion-resistant materials. In contrast to many previous publications dealing with carbides, the results presented in this collection relate to the properties of carbides having a definite phase composition, corresponding to a higher degree of purity 0 In some of the contributions the physical and chemical properties of the carbides are interpreted in terms of certain solid-state models and concepts concerning the types of chemical bonding in these compounds.