No abstract

Magnesia (MgO) is widely used in the production of refractory materials due to its high melting point, high thermal shock, and excellent slag resistance. The properties of refractory materials depend upon magnesia sources and processing parameters. In this work, three different magnesium sources, namely, magnesium hydroxide concentrate, magnesium carbonate concentrate, and intermediate flotation concentrate, were obtained from the Zinelbulak talc-magnesite, Uzbekistan, by causticization-hydration and flotation processes, respectively. A series of refractory materials were prepared on the basis of these magnesium sources, and their effects on physico-mechanical properties and microstructures were investigated as a function of sintering temperature, molding pressure, and the particle size of magnesium sources. The experimental results showed that a refractory material obtained from the magnesium hydroxide concentrate at 1600°C for 4 h demonstrated favorable parameters due mainly to a higher degree of contact among fine particles. The results obtained from X-ray diffraction and optical microscopy confirmed the presence of periclase and forsterite as the predominant phases in refractory specimens. The prepared refractory materials meet the requirements of the State Standards (Nos.4689-94 and 14832-96) for magnesia and forsterite refractories, respectively. It is, therefore, suggested herein that the use of different magnesium sources derived from the Zinelbulak talc-magnesite will offer the potential to provide economic benefits in the refractory industry.

No abstract

No abstract

Studies are performed on the material composition of micaceous minerals of the vermiculite series in the Tebinbulak deposit. It is established that the micaceous materials studied consist of Mg-biotite, Mg-, Na-and Ca-hydrobiotite, and the chemical formula for the minerals is worked out. Results of the studies are of considerable practical value for developing the technology for preparing expanded vermiculite and preparing various materials based upon it.Vermiculite, formed from magnesium-iron micas, i.e. biotite and phlogopite, has practical applications. Under natural conditions vermiculitization of these micas occurs very slowly and therefore in minerals not only the final products of the process, i.e. vermiculite, are encountered, but also hydrated mica to a different degree of hydration [1].There are many deposits of vermiculite. The composition of micaceous minerals of any deposit has marked differences. Known deposits of vermiculite ore in the USA (Libby, Montana and Epury, South Carolina) whose overall reserve is estimated as 250 -500 thousand tons and the content of vermiculite in the rocks is on average 50%, for example represented mainly by weathered vermiculite and hydrophlogopite with a different degree of hydration [2,3].One of the largest deposits of vermiculite rock, located in the Republic of South Africa (Lulekon deposit), is represented by micaceous minerals of vermiculite in the form of two varieties: vermiculite of high quality of golden-brown color, and hydrobiotite a little worse in quality. A feature of this deposit is the fact that the natural value of the pH of the water suspension of micaceous minerals of vermiculite is 6.5, which provides the possibility of using them in hydroponics. Vermiculite of the deposit is exported i large amounts to Japan [4].In South West Africa in the territory of Rhodesia there is a deposit of copper-containing vermiculite. In Uganda and Sudan deposits of vermiculite in an ore-bearing zone have been discovered laid down with alkali and carbonate rocks. The ore consists of phlogopite and vermiculite, within whose crystal composition there are Ca 2+ ions, so-called calcium hydrophlogopite. In Sierra Leone in Hangha chromite deposit vermiculite is mined containing cations of chromium of different valency [5].A large deposit of vermiculite in Russia is the Kordovsk deposit in the Murmansk region represented by micaceous minerals Mg-hydrophlogopite, Mg-vermiculite, weathered vermiculite and sungulite. The Barchinsk deposit consists of Ca-hydrophlogopite and Ca-and Na-vermiculite.The technological properties of micaceous minerals of vermiculite depend on raw material chemical composition; the degree of mica hydration, i.e. the amount of water molecules within the crystal structure of the original material; the form of interlayer cations; grain a size and firing regime (maximum temperature, rate and duration of heating) [6].The aim of this work is to study the material composition of micaceous minerals of vermiculite of the Tebinbulak deposit that until recently ha...