Structure and catalytic properties of dealuminated modified zeolites Y

The effect of treatment with a zirconyl nitrate aqueous solution on the structure; the hydroxyl-layer constitution; and the adsorptive, acid, and catalytic properties of dealuminated zeolite Y was studied. The zeolite was prepared by boiling NH₄Y in an ethylenediaminetetraacetic acid disodium salt solution followed by ion exchange with ammonium chloride and calcination in a 100% steam flow at 750°C. X-ray diffraction, IR spectroscopy, and DTA data show the formation of an ultrastable form of zeolite Y. The incorporation of zirconium in zeolite led to an increase in the proportion of strong acid sites, thus raising the yield of cracking products during n-hexane conversion tested on platinum-containing catalyst samples.     

Mechanical equipment of the Tashlyk pumped-storage hydroelectric station and Aleksandrovka hydro development of the Southern Ukraine power complex

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 6–7, November, 1989.     

Low Temperature Elastic Constants of Polycrystalline MgB2

We have used a resonant ultrasound spectroscopy technique to measure the bulk and shear modulus of fully dense, polycrystalline MgB₂ between 4 and 300 K. Both moduli show good agreement with published first principle calculations. The internal friction shows a broad maximum around 40 K.     

Shear localization-martensitic transformation interactions in Fe-Cr-Ni monocrystal

A Fe-15 wt pct Cr-15 wt pct Ni alloy monocrystal was deformed dynamically (strain rate ∼10⁴ s⁻¹) by the collapse of an explosively driven thick-walled cylinder under prescribed initial temperature and strain conditions. The experiments were carried out under the following conditions: (a) alloy in austenitic state, temperature above transformation temperature; (b) alloy in transformed state; and (c) alloy at temperature slightly above M _s , propitiating concurrent shear-band propagation and martensitic transformation. The alloy exhibited profuse shear-band formation, which was a sensitive function of the deformation condition. Stress-assisted and strain-induced martensitic transformation competes with shear localization. The alloy deformed at a temperature slightly above M _s shows a significantly reduced number of shear bands. The anisotropy of plastic deformation determines the evolution of strains and distribution of shear bands. The different conditions showed significant differences that are interpreted in terms of the microstructural anisotropy. Calculated shear-band spacings based on the Grady-Kipp (GK) and Wright-Ockendon (WO) theories are compared with the observed values. The microstructure within the shear bands was characterized by transmission electron microscopy. Regions of sub-micron grain sizes exhibiting evidence of recrystallization were observed, as well as amorphous regions possibly resulting from melting and rapid resolidification. This article is based on a presentation given in the symposium “Dynamic Deformation: Constitutive Modeling, Grain Size, and Other Effects: In Honor of Prof. Ronald W. Armstrong,” March 2–6, 2003, at the 2003 TMS/ASM Annual Meeting, San Diego, California, under the auspices of the TMS/ASM Joint Mechanical Behavior of Materials Committee.     

Composite materials of diamond–(Co–Cu–Sn) system with improved mechanical characteristics. Part 2. The influence of CrB<Subscript>2</Subscript> additive on the structure and properties of diamond–(Co–Cu–Sn) composite

The structural alterations in the diamond–metallic binder transition zone in the diamond(78.4Co–11.76Cu–7.84Sn–2CrB₂) composite upon its sintering in a mold in hydrogen atmosphere at 800°C for 1 h have studied versus the hot re-pressing parameters, and the influence of such alterations on physical-mechanical and tribological properties of the composites has been clarified. Adding 2 wt % CrB₂ to the starting diamond?(80Co–12Cu–8Sn) composite is shown to raise the ultimate compression strength from 816 to 1720 MPa, bending strength from 790 to 1250 MPa, and wear resistance by a factor of 2.4. The improvement of properties of the composite and the increase of its wear resistance are provided due to the formation of Cr₃C₂ nanocarbide in the transition zone and the uniform distribution of Co, CrB₂ phases and CoSn inclusions in the volume of the metallic binder.