Synthesis of nanocrystalline solid solutions based on zirconia and hafnia

Nanosized (2–8 nm) amorphous powders of the solid solution based on zirconia and hafnia are synthesized through back coprecipitation upon treatment of gels at temperatures from +20 to −77°C. Heat treatment of these powders at temperatures up to 1000 and above 1100°C leads to the formation of cubic (fluorite type, O _h ⁵ = Fm3m) and tetragonal phases of the Zr₈₂Hf₁₀Y₃Ce₅O _x composition, respectively. It is revealed that a decrease in the synthesis temperature (from +20°C to −6°C) results in a decrease in the size of gel agglomerates from 30 to 1 μm. Recrystallization processes in the gels prepared using cryochemical treatment are developed very slowly in the temperature range 500–1200°C (the crystallite size does not exceed 25 nm). Original Russian Text ? T.I. Panova, V.B. Glushkova, A.E. Lapshin, 2008, published in Fizika i Khimiya Stekla.     

Ceramics and Thick Films Based on Bi2 – x(Pb, Sb)xSr2Ca2Cu3Oy Compounds as High-Tc Superconductors and Electrode Materials

Complex cuprates of the compositions Bi_1.6Pb_0.4Sr_1.8Ca₂Cu₃O _y and Bi_1.7Pb_0.2Sb_0.1Sr₂Ca₂Cu₃O _y are synthesized. The electrical properties of the superconductors prepared are investigated. Thin films based on the bismuth cuprates studied are produced. It is demonstrated that the thin films prepared can be used as electrodes being in contact with a solid electrolyte for designing oxygen partial pressure gauges.     

Geoceramic Matrices for Immobilization of Nonpartitioned Radioactive Wastes

Immobilization of radioactive wastes (RW) containing large amounts of process alkalis in ceramic matrices based on acid and basic rocks is studied. Immobilizing characteristics of samples with an RW content of 15% are obtained. The best geoceramic matrices are characterized by the forward leaching rates with double-distilled water of 1 × 10^{- 4} and 1 × 10^{- 5} g cm^{- 2} day^{- 1} for Sr and Cs, respectively, and the steady-state leaching rate of about 2 × 10^{- 6} g cm^{- 2} day^{- 1}. Possible fixation mechanisms of the radionuclides in the matrices studied are discussed. Comparative analysis of properties of the geoceramic matrices and borosilicate and some other existing matrices for RW immobilization makes it possible to recommend some kinds of the geoceramics as matrices for immobilization of nonfractionated intermediate- and high-level radioactive wastes.     

Formation and stability of fluorite-like solid solutions in the Zr — Mg — Y — Al — O system

The method of x-ray phase analysis is used to study the kinetics of the interaction of ZrO₂ Y₂O₃, MgO, and A1₂O₃ and the succession of the formation of phases in synthesis of a cubic solid solution of fluorite-like Zr_1-x(Y, Mg)x O_z in the range 1100–1500°C. The effect of Y₂O₃ and A1₂O₃ on the composition and stability of the obtained material is investigated. The kinetic parameters of the oxide interaction are determined. The solid solution is shown to behave unusually in the synthesis.     

Mechanochemical Synthesis of ZrO2–CeO2 Solid Solutions

ZrO₂–CeO₂ solid solutions (12 and 13 mol % CeO₂) were prepared by mechanochemical synthesis in different media. The mechanical activation medium was shown to have a significant effect on the phase composition and particle size of the resultant powders. The conditions for sintering the powders were optimized.     

Thermal conductivity of a refractory board in helium,air, and vacuum

Measurements have been made on the thermal conductivity of a refractory board over the range 400–1300°K in air, helium, and vacuum.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 6, pp. 1014–1019, June, 1978.     

Solid Solutions of Rare-Earth Cuprates and Their Electrical Properties

Mixed cuprates based on La–Sm, La–Gd, Pr–Y, Pr–Nd, and Sm–Gd oxides are synthesized, and their physicochemical properties are investigated. The electrical properties of the studied cuprates are interpreted within the model of oxidation–reduction reactions.     

Early Postoperative Immunothrombosis of Bioprosthetic Mitral Valve and Left Atrium: A Case Report

A 72-year-old female patient with mixed rheumatic mitral valve disease and persistent atrial fibrillation underwent mitral valve replacement and suffered from a combined thrombosis of the bioprosthetic valve and the left atrium as soon as 2 days post operation. The patient immediately underwent repeated valve replacement and left atrial thrombectomy. Yet, four days later the patient died due to the recurrent prosthetic valve and left atrial thrombosis which both resulted in an extremely low cardiac output. In this patient’s case, the thrombosis was notable for the resistance to anticoagulant therapy as well as for aggressive neutrophil infiltration and release of neutrophil extracellular traps (NETs) within the clot, as demonstrated by immunostaining. The reasons behind these phenomena remained unclear, as no signs of sepsis or contamination of the BHV were documented, although the patient was diagnosed with inherited thrombophilia that could impede the fibrinolysis. The described case highlights the hazard of immunothrombosis upon valve replacement and elucidates its mechanisms in this surgical setting.