Features of the synthesis and the study of nanocrystalline cobalt-nickel spinel

A nanocrystalline compound nickel cobaltite (NiCo₂O₄) with the average size of crystals of ～20 nm at 700°C has been synthesized using the method of combined crystallization of solutions of nitrates with the subsequent thermal and ultrasonic treatment. The optimal sintering mode of the NiCo₂O₄ powder (1300°C, 2 h, air) has been selected, and ceramics (60–65 nm) with open porosity of 25–30% have been prepared. The temperature and frequency dependences of the electrical conductivity of nickel cobaltite have been studied. It has been assumed that the high values of the electrical conduction and pseudo-capacity of NiCo₂O₄ are due to the variable valence of Ni and Co in oxides. It is recommended to use cobaltite nickel as an electrode material of a supercapacitor and a catalyst of the oxygen isolation in fuel elements.     

Thermocouple sheaths for measuring metal temperatures continuously during melting

Conclusions For the preparation of sheaths, a body was developed consisting of magnesia, fired at 1400°C, and electrofused magnesia, in the ratios 8020 with an addition of 3% B₂O₃. The boric anhydride plays the roles of mineralizer during the firing, and of plasticizer, increasing the fluidity of the body during hot casting under pressure. The introduction of B₂O₃ halves the required addition of paraffin.Electron microscopic study of the specimens, without additives and with an addition of boric anhydride, revealed important differences between the growth terraces of the periclase crystals.Testing the experimental sheaths showed that they are promising materials for service at temperatures above 1700°C.Translated from Ogneupory, No. 2, pp. 16–19, February, 1971.     

Heavy metals in domestic wastewater with respect to urban population in Ostrava,Czech Republic

During dry weather periods, domestic wastewater is a major component of urban wastewater influent to a wastewater treatment plant (WWTP). For this reason, the quantity and quality of domestic wastewater have a considerable effect on the resultant contamination of urban wastewater and on the subsequent selection of appropriate WWTP technology. The aim of this study was to quantify the amount of hazardous elements in domestic wastewater to determine the average daily production of domestic wastewater and risk elements per inhabitant and quantify the proportion of households in the total load of urban wastewater. Wastewater samples were collected from nine local sewer systems in Ostrava, the Kravare WWTP and the Central Wastewater Treatment Plant of Ostrava (Czech Republic). We found that the average production of wastewater from households is approximately 135 L per person per day. The results also show that the share of households in urban wastewater is approximately 60% in the case of Cd, 35–21% in the case of Zn, Cu, As and less than 15% for Pb, Cr, Fe, Ni and Mn.     

Refractory compounds of basic composition for the monolithin lining of steel-teeming ladles

Conclusions Questions of the method of production of basic ramming compounds at Panteleimonovka Refractory Plant and their use in the monolithic lining of the walls of 160-ton steel-teeming ladles of the No. 2 Converter Shop of Kirvoi Rog Steel Combine are considered.An analysis of the wear of the lining during service showed that it occurs as the result of spalling of the sintered zone and salamandering of the lining. The use of a movable thermally insulated lid made it possible to hold the temperature of the ladle lining within limits of 730–1120°C between heats and to obtain a basic rammed lining life of 21–39 heats as opposed to an average life for the shop of 14.8 heats.A reserve for increasing the ladle basic lining life is optimization of the thermal conditions of its service, including high-temperature heating of the lining before pouring of the metal, the use of thermally insulated lids with the minimum consumption of time for placing of them, an increase in the life of the well refractory to the life of the walls and bottom, and elimination of cooling of the lining between heats.A Discussion: Problems of the Production and Use of Refractories for the Lining of Steel-Teeming Ladles. [For the start of the discussion see No. 8 (1988) and for the continuation Nos. 9–12 (1988) and Nos. 1–3, 5, and 7 (1989).]Deceased.I. I. Glaka, N. F. Drobot, N. V. Kurmaz, B. P. Zinchenko, S. A. Poznyak, I. M. Ryaboshapkin, V. V. Slushko, A. A. Chulkov, Yu. Bormatov, S. I. Vanchyuk, V. I. Dobrovol'skii, B. G. Zhuravel', N. I. Kiyan, L. I. Nekrasov, N. M. Sokolov, P. V. Khomenko, G. A. Nikitenko, S. Dorgobuzov, P. I. Valiev, N. N. Gorbatko, V. I. Kovalenko, and M. I. Lyakhov of Krivoi Rog Steel participated in the preparation and tests of the basic monolithic linings.Translated from Ogneupory, No. 8, pp. 1–4, August, 1989.     

Electrical and tribological properties of composite material with copper matrix reinforced by superelastic hard carbon

Electrical and tribological properties of a copper-based composite material reinforced by superelastic hard carbon particles are studied. Composite material specimens have been produced using the hightemperature pressing of mixtures of copper and fullerene powders. Electrical and tribological reciprocal tests carried out using the plane-on-plane arrangement have shown that the coefficient of friction of the composite material–Ni pair is lower than that of the reference L63 brass–Ni pair at similar values of contact electrical resistance. The abrasive wear resistance of the composite material is 40 times higher than that of brass. The developed copper-based composite materials reinforced by superelastic carbon particles hold promise for use in sliding electrical contacts.     

Synthesis and Study of Composite Materials in the ZrO 2 (Y 2 O 3 )–MgAl 2 O 4 System

Powders–precursors of a tetragonal solid solution based on partially stabilized zirconium dioxide (t-ZrO2) and aluminum-magnesium spinel (MgAl2O4) are synthesized using the method of the cocrystallization of solutions of nitrate salts from which nanocrystalline (<100 nm) composite materials are fabricated at 1400°C in the ZrO2(Y2O3)–MgAl2O4 system with an open porosity of 3%. The structure, physical–mechanical properties, and thermal stability of the nanocomposites are investigated. It is established that the introduction of MgAl2O4 into the matrix of the solid t-ZrO2 solution increases the thermal resistance of the ceramics under the thermal cycling conditions (20–1000°С). The effect of thermal cycling on the phase composition, hardness, and bending strength of the ceramics in the ZrO2(Y2O3)–MgAl2O4 system is investigated.     

Preparation and Characterization of Nanoceramics for Solid Oxide Fuel Cells

Precursor powders in the ZrO₂–HfO₂–Y₂O₃–CeO₂, In₂O₃–ZrO₂, and NiO–Nd₂O₃ systems for components of solid oxide fuel cells have been prepared by liquid-phase synthesis. We have determined formation conditions and the particle size of ZrO_2- and In₂O_3-based solid solutions and neodymium nickelate (Nd₂NiO₄), demonstrated the feasibility of producing nanocrystalline powders (10–30 nm) of tailored chemical composition in the temperature range 500–900°C, and optimized powder consolidation conditions. Nanoceramics with a crystallite size from 60 to 90 nm have been obtained and their microstructure and phase composition have been investigated. We have studied the electrical properties of the ZrO_2- and In₂O_3-based solid solutions and the Nd₂NiO₄ compound and established the range of their electrical conductivity at temperatures from 300 to 1000°C: 2.27 × 10^–3 to 2.51 S/cm for the ZrO₂-based solid solution, 8.91 × 10¹ to 6.59 × 10³ S/cm for the In₂O₃-based solid solution, and 3.98 × 10² to 5.02 × 10² S/cm for Nd₂NiO₄.