Kinetics and mechanism of formation of gehlenite, Al–Si spinel and anorthite from the mixture of kaolinite and calcite

Ptáček, Petr; Opravil, Tomáš; Šoukal, František; Havlica, Jaromír; Holešinský, Radek

doi:10.1016/j.solidstatesciences.2013.09.014

Cited by 80 publications

(38 citation statements)

References 42 publications

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“…Also hematite was formed due to the high content of iron in the raw material. Anorthite, a Plagioclase, is also formed in high quantities, as confirmed by the XRD diffractogams, by the reaction of calcium carbonate, quartz and the phyllosilicates (saponite clay is a smectite, which belongs to the phyllosilicates group), in accordance with reaction [24,33]:…”

Section: Xrd Studiesmentioning

confidence: 80%

Spectroscopy of 16th century Portuguese tin-glazed earthenware produced in the region of Lisbon

Ferreira

González

Pereira

et al. 2015

Ceramics International

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Section: Xrd Studiesmentioning

confidence: 80%

Spectroscopy of 16th century Portuguese tin-glazed earthenware produced in the region of Lisbon

Ferreira

González

Pereira

et al. 2015

Ceramics International

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“…At temperatures higher than ~1020°C (S‐Exp) the gehlenite grains within the imaged area seem to be fully replaced by wollastonite, although gehlenite could still be detected by Raman spectroscopy and XRD in the finally quenched ceramic. Tschegg et al found that the stability field of gehlenite is affected by the concentration of SiO 2 that is available in the system. It is thus conceivable that wollastonite crystallized from a reaction of gehlenite with free SiO 2 provided by the slow decomposition of metakaolinite:

\begin{matrix} C {normala}_{2} A {normall}_{2} Si {normalO}_{7} \\ Gehlenite \end{matrix} + \begin{matrix} Si O_{2} \\ Silica \end{matrix} \overset{Δ (T) > 800^{\circ} C}{false\to} \begin{matrix} 2 CaSi {normalO}_{3} \\ Wollastonite \end{matrix} + \begin{matrix} A {normall}_{2} O_{3} \\ Corundum \end{matrix} .

…”

Section: Discussionmentioning

confidence: 99%

Insights into the evolution of carbonate‐bearing kaolin during sintering revealed by in situ hyperspectral Raman imaging

2017

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Sintering reactions of clay bodies have previously been studied by numerous experiments that involve quenching of the sintered ceramic bodies to room temperature and analyzing the reaction product by different analytical techniques. In this study, green bodies containing quartz, alkali feldspar, kaolinite, and calcite, were progressively fired in air at various temperatures from room temperature to about 1060°C. For the first time, mineral reactions and textural relationships were studied in situ as a function of temperature and time with a spatial resolution of a few micrometers by confocal hyperspectral Raman imaging. Gehlenite, wollastonite, and pseudowollastonite could unambiguously be identified as newly formed phases during sintering, and their textural evolution could be followed with temperature and time. From 800°C onwards wollastonite formed at the direct contact to gehlenite, whereby at temperatures higher than 990°C wollastonite seems to be gradually replacing gehlenite. The crystallization of pseudowollastonite was observed already ~290°C below the accepted critical temperature (~1125°C) for the wollastonite‐to‐pseudowollastonite transformation, suggesting that pseudowollastonite can form metastably. The results of this study demonstrate that hyperspectral Raman imaging is a powerful method to study in situ phase transitions and recrystallization processes at grain boundaries during high‐temperature sintering of ceramic materials.

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“…With an increasing temperature and reaction time, α' L -Ca 2 SiO 4 could be identified in the expense of wollastonite [15]. On the other hand, the hyperspectral Raman images of experiment AQC-1.2 reveal that wollastonite could also be a breakdown product of dicalcium silicate and free SiO 2 [15,17,29]:…”

Section: The Formation Of Calcium Silicatesmentioning

confidence: 98%

In Situ Hyperspectral Raman Imaging of Ternesite Formation and Decomposition at High Temperatures

et al. 2020

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Knowledge of the high-temperature properties of ternesite (Ca5(SiO4)2SO4) is becoming increasingly interesting for industry in different ways. On the one hand, the high-temperature product has recently been observed to have cementitious properties. Therefore, its formation and hydration characteristics have become an important field of research in the cement industry. On the other hand, it forms as sinter deposits in industrial kilns, where it can create serious problems during kiln operation. Here, we present two highlights of in situ Raman spectroscopic experiments that were designed to study the high-temperature stability of ternesite. First, the spectra of a natural ternesite crystal were recorded from 25 to 1230 °C, which revealed a phase transformation of ternesite to the high-temperature polymorph of dicalcium silicate (α’L-Ca2SiO4), while the sulfur is degassed. With a heating rate of 10 °C/h, the transformation started at about 730 °C and was completed at 1120 °C. Using in situ hyperspectral Raman imaging with a micrometer-scale spatial resolution, we were able to monitor the solid-state reactions and, in particular, the formation properties of ternesite in the model system CaO-SiO2-CaSO4. In these multi-phase experiments, ternesite was found to be stable between 930 to 1020–1100 °C. Both ternesite and α’L-Ca2SiO4 were found to co-exist at high temperatures. Furthermore, the results of the experiments indicate that whether or not ternesite or dicalcium silicate crystallizes during quenching to room temperature depends on the reaction progress and possibly on the gas fugacity and composition in the furnace.

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Kinetics and mechanism of formation of gehlenite, Al–Si spinel and anorthite from the mixture of kaolinite and calcite

Cited by 80 publications

References 42 publications

Spectroscopy of 16th century Portuguese tin-glazed earthenware produced in the region of Lisbon

Spectroscopy of 16th century Portuguese tin-glazed earthenware produced in the region of Lisbon

Insights into the evolution of carbonate‐bearing kaolin during sintering revealed by in situ hyperspectral Raman imaging

In Situ Hyperspectral Raman Imaging of Ternesite Formation and Decomposition at High Temperatures

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