Synthesis and Properties of Ceramics from Ferric Oxide Nanopowder

Possibilities of receiving ceramics from the nanodisperse ferric oxide (II, III) powder are investigated. In a hot pressing facility (by Spark Plasma Sintering method) the ceramics with fine-grained (about 1 micron and less) structure made. Structure of the received ceramics is investigated by the method of scanning electronic microscopy. Radiographic examination of initial nanopowder and the received ceramics is also carried out. If in the phase relation the initial powder and the ceramics sintered at 800 о С are magnetite Fe3O4 (75-1610), the ceramics sintered at 900 о С – Fe3O4 (75-33), and at 1200о С the diffraction picture of a mixture of two phases – a iron protoxide FeO (46-1312) phase and a metal Fe (6-696) phase – took place. Microhardness of the ceramics was 8 GPa, ultimate compression strength – 0,8 GPa. Thereby availability of use of the SPS method is shown

Investigation of Subcontact Layers in SiC after Diffusion Welding

In our early analytic reports [1,2] has been made the supposition that during the diffusion welding (DW) in subcontact area of SiC is formed the intermediate amorphous layer. In the present work are given the first results of transmission electron microscopy (TEM) and electron diffraction investigations of subcontact layers in n0-n- 4H-SiC. TEM examinations show that the boundary between aluminium and silicon carbide looks like stripy interface layer of ~ 25 nm thickness. This is the evidence that during diffusion welding in subcontact surface layer of SiC the shear micro deformations have been taking place and due to this process the plane inclusions of small-grained phase have been appeared. The image of contact area obtained in diffracted SiC rays (dark field) apparently confirms that stripy zone belongs to silicon carbide because the aluminium (black zone) fell out of contrast. Diffraction picture obtained from bulk zone of silicon carbide looks like monocrystallin, but the micro diffraction pattern obtained from the subcontact (stripy zone) gives a lot of concentric rings, that makes evidential the fact of existence of small-grained inclusions. Deciphering of this electron-diffraction pattern reveals the presence of such elements as residue SiC, Al, Si, as well as inclusions of graphite.

MOMENTUM-TRANSFER STRUCTURE OF POMERON AT ACCELERATOR ENERGIES

A representation of Pomeron amplitude derived asymptotically in the framework of the geometrical diffraction picture is shown to be consistent with the gross feature of the experimental data of the differential cross-section of pp and [Formula: see text] scattering in the low energy region [Formula: see text] over a wide range of momentum transfer. It is found that the most peripheral part of the diffraction interaction is characterized by a mass parameter of 0.4–0.5 GeV indicating the dominance of the two-pion states.

RHEED Observation of Tin Atomic Chains Formation on Vicinal Gallium Arsenide Plane

In the present work by means of measurements of RHEED intensity the research of the arrangement of tin atoms on vicinal surfaces of GaAs crystals was carried out. The orientation of crystals was close to (001). The intensity of diffracted electrons was measured in different points of the diffraction picture to reveal the arrangement of tin atoms on terraces or on edges of terraces. It was shown that tin atoms may decorate edges of terraces and thus form chains. Concentrations of tin atoms located on terraces and their edges were established. It was revealed, that tin atoms decorate edges of terraces only at rather high temperatures of a substrate.

Quasiperiodic Crystals: A Revolution in Crystallography

At the beginning of my career, I encountered a book that Professor Von Hippel edited. In the Preface to that book he wrote the following: “Many foresee that science and industry are building a Tower of Babel and thai this undertaking will be halted as in Biblical times: the laborers, more and more specialized, will finally cease to understand each other. The editor, for one, does not share this is gloomy conviction. On the contrary, as our knowledge grows, old boundaries vanish and the view expands to broader horizons. However, people accustomed to boundaries in certain places tend still to respect them after their actual disappearance. To make them feel at home with their new neighbors is a driving motive of this book and its companion volume.”The Materials Research Society, being dedicated to interdisciplinariness, has shared Prof. Von Hippel's optimism, and I hope that in this lecture I can give you a small inkling of how interdisciplinary our current research is and how many different fields it touches.The work that I am going to discuss resulted from the rapid solidification study of aluminum transition metal alloys. One day more than three years ago. Prof. Shechtman, who is the hero of this investigation, came into my office with an electron diffraction picture with ten spots arrayed about the central spots (Figure 1).