Głównym zamierzeniem niniejszego projektu jest opracowanie unikatowego i konkurencyjnego produktu na drodze praktycznego wykorzystania nauki o materiałach. Cel naukowy projektu obejmuje przede wszystkim określenie roli złożonych matryc wiążących z układu MgO-Al2O3-SiO2-H2O, charakteryzujących się ściśle określoną strukturą i właściwościami, w otrzymywaniu nowego typu tworzywa ceramicznego. Innowacyjność proponowanego rozwiązania będzie realizowana przez zastosowanie alternatywnego podejścia technologicznego do wytworzenia materiału bezcementowego zawierającego fazy spinelowe o różnej stechiometrii tworzące się w warunkach „in situ” materiału. Beton ogniotrwały będzie przeznaczony do wykonywania monolitycznych obmurzy ogniotrwałych w różnego rodzaju urządzeniach cieplnych w przemyśle stalowym, metali nieżelaznych i innych.
Projekt finansowany przez NCBiR w ramach programu LIDER VIII - nr umowy LIDER/5/0034/L-8/16/NCBR/2017.
Projekt zostanie zrealizowany przy współpracy z partnerem przemysłowym – Zakładami Magnezytowymi ROPCZYCE S.A. (Członkowie Zespołu ze strony ZMR - mgr inż. Klaudia Wiśniewska, mgr inż. Robert Świerszcz).
https://www.sciencedirect.com/science/article/pii/S0020169318306698
In refractory castables during heat treatment, there is a dynamic change from a hydraulic bond to a ceramic bond. During heating, the emission of water takes place; this changes the conditions inside the material to something similar to the hydrothermal ones. This influences the processes that occur during the heating of the castables, and in consequence, the properties of the final material. The aim of the work was to evaluate the influence of the chelate compounds like citric and tartaric acids, often used in castables as dispersing agents, on the properties of the MgO–Al2O3 phase system during hydrothermal treatment. The performed tests included an XRD analysis, a thermal analysis (TG–DSC–EGA), infrared spectroscopy (FTIR), and an SEM–EDS analysis. Based on the obtained results, it was found that even small amounts of chelate compounds have a strong impact on the processes under hydrothermal conditions which results in changes in the phase composition of the materials.
Hydrotalcite-like compounds (HTlc) are commonly known anionic clay that may potentially be used as hydraulic binder component for refractory materials, ion exchangers, catalyst or carrier of bioactive molecules. According to current state of knowledge LDH (Layered Double Hydroxides) can be synthesized using various methods including mechanochemical synthesis, hydrothermal precipitation, sol–gel syntheses and coprecipitation method. Research on the synthesis of hydrotalcite in the mixture of oxide powders of Al2O3 and MgO cured under specific conditions is particularly important in case of the determination of the relationship between the type (susceptibility to hydration, grain size and specific surface area) of initial powders and reaction kinetics. As a result, the hydration of an equimolar mixture of magnesium and alumina oxides nano- or micro-powders has been proven to be an effective low temperature method of synthesis well crystallized MgAl LDH with highly ordered structures. This investigations clearly show that the kinetics of hydration is influenced only by properties of aluminium oxide as initial powder. The synthesis of Mg6Al2CO3(OH)16∙4H2O as a result of hydration is associated with composite matrix formation which firstly consist of partly reacted initial powders bonded by hydration products. The synthesis of Mg6Al2CO3(OH)16∙4H2O was discussed in terms of molar Gibbs free energy change of reactions within the MgO-Al2O3-CO2-H2O system. The calculated formation Gibbs energy was negative, when Mg(OH)2 was formed as an intermediate product. The standard Gibbs free energies of hydrotalcite formation was estimated based on the simple mechanical mixture model that treats Mg6Al2CO3(OH)16∙4H2O as mixtures of simple oxides. Thermodynamic calculations were performed assuming an equilibrium state between aqueous solutions and corresponding precipitates after synthesis.
The mechanical properties of in-situ spinel (MgAl2O4)-forming alumina-based castables under intermediate temperatures are of critical importance before the refractory lining system reaches normal operating conditions. The objective of this study is to elucidate the role of the hydrotalcite formed within a fine-grained castables matrix, in which no strength loss of the MgO-bonded alumina-based castables without silica fume was observed. Numerous fundamental studies were conducted to examine the factors influencing hydrotalcite formation within the blended pastes composed of MgO and Al2O3 nanopowders; dead burned or fused magnesia and Al2O3 nanopowder; dead burned magnesia and water-dispersed sol of fumed alumina by using: XRD and DSC-TG-EGA(MS). The XRD, FTIR and 27Al MAS NMR analysis of the hydrotalcite calcination products revealed that the spinel begins to form at temperatures as low as 700 °C. Finally, the physical properties, phase composition and microstructure of the refractory castables bonded with the hydrotalcite decomposition-routed nanostructured spinel were evaluated.
This study investigated the effect of the CaO/SiO2 mass ratio of steel slag on the corrosion behavior of spinel-forming alumina-based castables with a content of MgO (3–7 wt.%). Equiweight mixtures of castables and slags were calculated by FactSage, observed by HMTA, fired at 1350 °C, and investigated by XRD. From these results, we conclude that the presence of SiO2-rich phases accelerates the growth of the liquid phase in a narrow temperature range for the tested samples, which accelerates the degradation of castables. The static corrosion test was conducted by means of the coating method at 1450 °C. The corrosion index (IC) in the regions of castables affected by slags was calculated. Phases and phase distributions were evaluated by SEM-EDS. From these results, we conclude that for the slag with the lowest mass ratio of CaO/SiO2 (1.1), the reaction zone occurs only below the slag-refractory interface, which indicates the aggressive character of this slag.