Abstract
Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, the nucleation of crystals in glass obtained by blending metallurgical slag with silicon dioxide has been studied. The type of crystallization (homogeneous or heterogeneous, volume or surface) is revealed for each of nine compositions of synthesized glass. It is shown that the first crystalline phase in a volume crystallizing glass is perovskite (CaO·TiO2); in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlenite 2CaO·Al2O3·SiO2 in akermanite 2CaO·MgO·2SiO2). The fundamental characteristics of homogeneous (for a catalizing phase, perovskite) and heterogeneous (for a catalyzed phase, melilite) of crystallization are determined: the steady state nucleation rate Ist, time of unsteady state nucleation τ, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of Ist, τ, and U are obtained. The kinetics of the crystallization of glass is studied and the rates of the surface crystal growth are determined in the glass of nine compositions. The influence of grinding the particles of the original glass on the sequence of deposition of the crystalline phases was studied. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.
Highlights
The crystallization ability of oxide glass has been widely studied; the publications on this topic are mainly devoted to studying mass crystallization
In the obtained multicomponent glass, we studied the volume nucleation of crystals according to homogeneous and heterogeneous mechanisms
The first is the process of the formation of the crystallization centers. It consists in the formation of the metastable spinel phase of magnesiochromite, which is the catalyst for the formation of the main catalyzing crystalline phase of diopside
Summary
The crystallization ability of oxide glass has been widely studied; the publications on this topic are mainly devoted to studying mass crystallization. We know of 14 crystalline compounds, for which the temperature dependence of the steady and unsteady crystal nucleation in the bulk nucleation were studied. They are: Li2O·2SiO2, Li2O·SiO2, Na2O·2CaO·3SiO2, 2Na2O·CaO·3SiO2, BaO·2SiO2, CaO·SiO2, Na2O·SiO2, Na2O·2SiO2, MgO·Cr2O3, CaО·MgО·2SiО2, Na2O·Al2O3·6SiO2, 2SnО·P2O5, Na2O·ZnO·P2O5, BaО·B2О3·Р2O5. We synthesized glass based on slag from the Ural Nizhnetagil Blast Furnace Combinate, which in terms of the content of the main oxides can be attributed to the system CaO-MgO-Al2O3-SiO2, which possesses a wide range of glass-forming ability that gives the possibility to choose the composition by an immaterial additional blending [11] [12]. In the obtained multicomponent glass, we studied the volume nucleation of crystals according to homogeneous and heterogeneous mechanisms
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