Investigations by the method of NGR-spectroscopy of iron oxides in acid-resistant ceramic materials based on production waste

Author(s):  
A. K. Kairakbaev ◽  
V. Z. Abdrakhimov ◽  
E. S. Abdrakhimova
Author(s):  
M. S. Varfolomeev ◽  
G. I. Shcherbakova

The sintering peculiarities of the ceramic materials which had been prepared by means of semidry pressing are investigated in the article. The fillers were the yttrium oxide Y2O3 and the fused corundum α-Al2O3, the bonding phase was the aluminoxane addition either pure or modified by the yttrium and magnesium compounds. We investigated the processes occurring at the examined ceramics sintering at different temperatures and their influence on the obtained ceramics properties. The phase composition, the thermal and mechanical properties of the test samples at 1500 °C are presented. The produced test ceramic crucibles have advanced thermal resistance and stability against the thermal cycling. The possibility is regarded to use the developed ceramic crucibles for melting and casting of the chemically reactive highly-heat-resistant metals and alloys.


1988 ◽  
Vol 45 (1) ◽  
pp. 34-38
Author(s):  
G. G. Gaprindashvili ◽  
M. K. Kekelidze ◽  
L. K. Tedeishvili

Author(s):  
Alexander A. Il’in

A comparative analysis of various methods for obtaining highly dispersed iron oxides has been carried out. The advantages and disadvantages of traditional and developing methods of synthesis of iron oxides for catalysts, sorbents and ceramic materials are identified. The advantages of the method of mechanochemical synthesis of obtaining highly dispersed iron oxides for catalysts for the medium-temperature conversion of CO in the production of ammonia and the oxidation of methanol to formaldehyde are shown. The methods of X-ray phase, X-ray structural, synchronous thermal analysis and Mössbauer spectroscopy were used to study the process of mechanochemical oxidation of iron and cast iron powders in order to obtain iron oxides. The phase composition and specific surface area of the obtained oxides are investigated. It was found that in the process of mechanical activation of iron-containing powders in the aquatic environment, the system Fe-Fe3O4-FeOOH is formed. Heat treatment at 450 °C for 6 h causes decomposition of FeOOH to α-Fe2O3 and partial oxidation of metallic iron. By the method of differential dissolution, it was established that the cast iron in the presence of water in a roller-ring vibratory mill for 60 min is oxidized to 77.6%, and the iron is oxidized to 88%. Also in the process of dissolving metal powders in oxalic acid solutions using ultrasound FeC2O4 · 2H2O is formed, which under the conditions of thermolysis decomposes to maghemite – γ-Fe2O3 with the release of CO and CO2, and at 400 °C to hematite – α-Fe2O3. The possibility of using the produced iron oxides for obtaining iron-chromium catalysts for the medium-temperature conversion of CO in the production of ammonia and iron-molybdenum catalysts for formaldehyde synthesis is shown. The CO degree conversion is 92.0% at 340 °C, and the productivity by formaldehyde is 13.0 µmol/(g∙s).


Author(s):  
M. S. Kanapinov ◽  
A. V. Maetskii ◽  
A. A. Sitnikov ◽  
N. P. Tubalov ◽  
V. V. Kovalev

The self-propagating high-temperature synthesis (SHS) was used to obtain the heat-resistant porous permeable metal-ceramic material (PPMM) on base of the mixture composed of the alloyed steel's scale powder and the oxides of both metals and complex ore (monazite). The prepared SHS-material can be used as the catalytic agent for the diesel's exhaust gas purifcation. However, instead of the expensive rare-earth elements (REE) cerium and thorium the ground complex ores containing these REE can be used. The influence of the monazite's content up to 18 wt. percents on the physical, mechanical and service properties of the prepared materials were regarded in the article.Ill.8. Ref. 17. Tab. 2.


2018 ◽  
Vol 118 ◽  
pp. 119-131
Author(s):  
M. I. Ryschenko ◽  
O. Yu. Fedorenko ◽  
M. Yu. Lisytkina ◽  
O. V. Shevtsov ◽  
K. V. Bіlohubkina ◽  
...  

Based on the compositions of MgO—Al2O3—TiO2—SiO2 system, the chemically and thermally resistant ceramic was obtained at a firing temperature of 1250 °C by the directed synthesis of tialite and mullite phases. The influence of alternative raw materials of natural and technogenic origin on the operational properties and phase composition of porous and densely-sintered ceramic materials was studied. The using expediency of pyrophyllite containing waste of quartzite mining and ferrotitanium production wastes as the phase forming components of ceramic masses is established. The mechanism of structure- and phase formation of tialite and mullite-tialite ceramics was investigated. It was established that, stabilization of the tialite phase at a temperature of 1200—1250 oC occurs while maintaining the ratio of TiO2/Al2O3 oxides ~ 1.4 and the presence of 1.3 wt. % Fe2O3, as the mineralizing component included in the waste. The possibility of obtaining tialite containing ceramic materials at a lower firing temperature (1200 oC) due to the formation of a tialite solid solution (Mg0.3Al1.4Ti1.5O5) while maintaining the ratio of MgO : TiO2 oxides = 0.18 was proved. Technological principles of the production of chemically and thermally resistant ceramics both with the densely-sintered and with the porous structure, the total porosity of which is respectively 0.41 and 60 %, have been developed. The permeability of porous ceramic materials of mullitе-tialite composition was determined (water permeability coefficient P = 5.39∙10-5 cm2/s), as well as parameters of sorption processes (diffusion rate of Cr2O7-2 and MnO4- ions is 6.38∙10-6 and 1.06∙10-5 cm2/s respectively). This indicates the possibility of using the developed porous ceramics for the manufacture of industrial wastewater filters. Complex studies of the phase composition, structure and properties of the developed ceramic materials confirmed the promise of their use for the manufacture of parts of equipment operating in corrosive environments.


2013 ◽  
Vol 50 (5) ◽  
pp. 68-73 ◽  
Author(s):  
J. Kalnačs ◽  
V. Grehovs ◽  
G. Mežinskis ◽  
L. Bidermanis

Abstract Differential scanning calorimetry was carried out to determine the heat capacity (Cp) of the high temperature resistant ceramic materials to be used as protective coatings for stainless steel tubes of parabolic trough solar collectors in concentrated solar power (CSP) systems. The Ср(Т) measurements and calculations were performed at continuous scanning in the temperature range 20-800 °С. In the work, calibration curves have been derived for conversion of measuring units from mcV into mW. To achieve a better repeatability of measurements, methods for stabilization of the thermal contact between the sample-containing vessel and the probe have been developed. The Ср(Т) dependence was obtained for different ceramic materials.


Author(s):  
Nancy J. Tighe

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.


Author(s):  
J. Y. Koo ◽  
M. P. Anderson

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.


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