Insights into high-temperature mineral reactions of calcium silicate materials revealed in operando by in situ Raman spectroscopy
Insights into high-temperature mineral reactions of calcium silicate materials revealed in operando by in situ Raman spectroscopy
Dokument öffnen (14.4MB)Art der Hochschulschrift
DissertationPrüfungsdatum
29.06.2022Datum der Veröffentlichung
30.11.2022Erstgutachter
Geisler-Wierwille, ThorstenZweitgutachter
Raith, MichaelMetadaten
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Inhalt
Knowledge of high-temperature calcium silicate materials is becoming increasingly interesting for industry in different ways. On the one hand, their application in the construction, cement, refractory, and ceramics industry is well established due to, in particular, their high melting point, thermal stability, fluxing characteristics, acicular shape, and bioactivity. However, these minerals also form as sinter deposits in industrial kilns and may cause serious and expensive problems during kiln operation. It follows that a detailed understanding of solid-state or solid-melt mineral reactions that form calcium silicate materials as well as the knowledge about their thermal stability are essential to optimize industrial processes, i.e., to fully exploit their technical advantages and to ensure synthesis under optimal conditions.
In this project, the high-temperature mineral reactions and transformations of calcium silicate materials in the CaO-SiO2(-SO3/Al2 O3/P2O5) system and subsystems were studied in both single- and multi-phase experiments by in situ Raman spectroscopy. The green bodies of multi-phase experiments mainly consisted of calcium oxide (lime) and quartz, and sulfate/aluminate/phosphate components were systematically added or replaced. During firing the samples to temperatures between about 660 and 1100 °C, the decomposition and formation processes of mineral phases were monitored and visualized at the micrometer-scale and in operando, i.e., while the reactions were running. For instance, the formation of mono- and dicalcium silicates was found to occur at different in situ temperatures via different reaction pathways. In addition, the polymorphs pseudowollastonite and α’L-Ca2SiO4 were identified. The latter transformed to β-Ca2SiO4 (larnite) during cooling and remained metastable at room temperature.
The formation and temperature stability of ternesite and silicocarnotite, i.e., the sulfate- and phosphate-containing end member of a solid solution series, were studied. Both mineral phases are formed by reactions involving dicalcium silicate. In particular, the grain boundary migration of ternesite by replacing a large quartz grain was observed. With increasing temperature (and time), α’L-Ca2SiO4 formed new reaction rims around ternesite, producing a layered texture with quartz in the center, ternesite in the middle, and α’L-Ca2SiO4 in the outer layer. The heating study with a natural ternesite crystal revealed a phase transformation to α’L-Ca2SiO4 between 730 and 1120 ± 1 °C and confirms that both the ternesite and dicalcium silicate domains can co-exist in this temperature range. It generally depends on the course of the reaction whether ternesite or larnite is detected after quenching to room temperature. Furthermore, two reaction pathways were found to form silicocarnotite between about 1050 and 1150 °C, i.e., at significantly lower in situ temperatures than previously proposed. In addition, a heating study with a natural silicocarnotite crystal was performed for the first time. This experiment revealed, for instance, that the position of the v1(PO4) band shifted from 951 ± 1 cm 1 to ~930 cm-1 at 1200 ± 1 °C. Moreover, the transformation of hydroxylapatite to tricalcium phosphate was investigated and gave new insights into the complex process of the loss of surface hydroxyl groups bound to HAp nanocrystals.
The advantages of in situ hyperspectral Raman imaging compared to conventional experimental and analytical methods, where the sample has to be quenched to room temperature before being analyzed, are clearly demonstrated. This new analytical method is a powerful tool for studying sinter reactions with a high temperature, time, and spatial resolution and offers a wide range of possibilities to study ceramic systems for industrial applications. Das Wissen über Hochtemperatur-Calciumsilikat-Materialien wird für die Industrie in verschiedener Hinsicht zunehmend von Bedeutung. Einerseits ist ihre Anwendung in der Bau-, Zement-, Feuerfest- und Keramikindustrie aufgrund ihres hohen Schmelzpunkts, ihrer thermischen Stabilität, ihrer Flussmitteleigenschaften, ihrer nadelförmigen Gestalt und ihrer Bioaktivität weit verbreitet. Allerdings bilden diese Minerale auch Sinterablagerungen in Industrieöfen und können beim Ofenbetrieb ernsthafte und teure Probleme verursachen. Daraus folgt, dass ein detailliertes Verständnis möglicher Festkörper- bzw. Schmelzmineralreaktionen sowie die Kenntnis der thermischen Stabilitätsbereiche von Kalziumsilikaten unerlässlich sind, um industrielle Prozesse zu optimieren, d. h. um ihre technischen Vorteile voll auszuschöpfen und die Synthese unter optimalen Bedingungen zu gewährleisten.
In diesem Projekt wurden die Hochtemperatur-Mineralreaktionen und -Umwandlungen von Kalziumsilikat-Materialien im CaO-SiO2(-SO3/Al2 O3/P2O5)-System sowohl in Einphasen- als auch in Mehrphasenexperimenten mittels in situ Raman-Spektroskopie untersucht. Die Grünkörper der Mehrphasenexperimente bestanden hauptsächlich aus Calciumoxid (Branntkalk) und Quarz, und Sulfat/Aluminium/Phosphat-Komponenten wurden systematisch hinzugefügt oder ersetzt. Während des Aufheizens der Proben bei Temperaturen zwischen etwa 660 und 1100 °C wurden die Zersetzungs- und Bildungsprozesse der Mineralphasen in operando, d. h. während der laufenden Reaktionen, im Mikrometerbereich überwacht und visualisiert. So wurde beispielsweise festgestellt, dass die Bildung von Mono- und Dicalciumsilikaten bei unterschiedlichen Temperaturen in situ über verschiedene Reaktionswege erfolgen kann. Darüber hinaus wurden die Polymorphe Pseudowollastonit und α’L-Ca2SiO4 identifiziert. Letzteres wandelte sich beim Abkühlen in β-Ca2SiO4 (Larnit) um und blieb bei Raumtemperatur metastabil.
Die Bildung und Temperaturstabilität von Ternesit und Silicocarnotit, d. h. dem sulfat- und phosphathaltigen Endglied einer Mischkristallreihe, wurden untersucht. Beide Mineralphasen werden durch Reaktionen mit Dicalciumsilikat gebildet. Insbesondere wurde die Korngrenzenwanderung von Ternesit durch das Ersetzen eines großen Quarzkorns beobachtet. Mit zunehmender Temperatur (und Zeit) bildete α’L-Ca2SiO4 neue Reaktionsränder um Ternesit, wodurch eine Schichtstruktur mit Quarz im Zentrum, Ternesit in der mittleren und α’L-Ca2SiO4 in der äußeren Schicht entstand. Die Erhitzungsstudie mit einem natürlichen Ternesit-Kristall ergab eine Phasenumwandlung zu α’L-Ca2SiO4 zwischen 730 und 1120 ± 1 °C und bestätigte, dass sowohl die Ternesit- als auch die Dicalciumsilikat-Domäne in diesem Temperaturbereich koexistieren können. Im Allgemeinen hängt es vom Fortschritt der Reaktion ab, ob nach dem Abschrecken auf Raumtemperatur Ternesit oder Larnit nachgewiesen wird. Des Weiteren wurden zwei Reaktionswege zur Bildung von Silicocarnotit zwischen 1050 und 1150 °C gefunden, d. h. bei deutlich niedrigeren in situ Temperaturen als bisher angenommen. Außerdem wurde zum ersten Mal eine Erhitzungsstudie mit einem natürlichen Silicocarnotit-Kristall durchgeführt. Dabei zeigte sich zum Beispiel, dass sich die Position der v1(PO4) Bande bei 1200 ± 1 °C von 951 ± 1 cm 1 auf ~930 cm-1 verschoben hat. Darüber hinaus wurde die Umwandlung von Hydroxylapatit in Tricalciumphosphat untersucht, was neue Einblicke in den komplexen Prozess des Verlusts der an HAp-Nanokristallen gebundenen Hydroxylgruppen an der Oberfläche ermöglichte.
Die Vorteile der in situ hyperspektralen Raman-Bildgebung im Vergleich zu herkömmlichen experimentellen und analytischen Methoden, bei denen die Probe vor der Analyse auf Raumtemperatur abgekühlt werden muss, werden deutlich aufgezeigt. Diese neue Analysemethode ist ein leistungsfähiges Instrument zur Untersuchung von Sinterreaktionen mit hoher Temperatur-, Zeit- und Ortsauflösung und bietet eine breite Reihe von Möglichkeiten zur Untersuchung keramischer Systeme für industrielle Anwendungen.
In this project, the high-temperature mineral reactions and transformations of calcium silicate materials in the CaO-SiO2(-SO3/Al
The formation and temperature stability of ternesite and silicocarnotite, i.e., the sulfate- and phosphate-containing end member of a solid solution series, were studied. Both mineral phases are formed by reactions involving dicalcium silicate. In particular, the grain boundary migration of ternesite by replacing a large quartz grain was observed. With increasing temperature (and time), α’L-Ca2SiO4 formed new reaction rims around ternesite, producing a layered texture with quartz in the center, ternesite in the middle, and α’L-Ca2SiO4 in the outer layer. The heating study with a natural ternesite crystal revealed a phase transformation to α’L-Ca2SiO4 between 730 and 1120 ± 1 °C and confirms that both the ternesite and dicalcium silicate domains can co-exist in this temperature range. It generally depends on the course of the reaction whether ternesite or larnite is detected after quenching to room temperature. Furthermore, two reaction pathways were found to form silicocarnotite between about 1050 and 1150 °C, i.e., at significantly lower in situ temperatures than previously proposed. In addition, a heating study with a natural silicocarnotite crystal was performed for the first time. This experiment revealed, for instance, that the position of the v1(PO4) band shifted from 951 ± 1 cm 1 to ~930 cm-1 at 1200 ± 1 °C. Moreover, the transformation of hydroxylapatite to tricalcium phosphate was investigated and gave new insights into the complex process of the loss of surface hydroxyl groups bound to HAp nanocrystals.
The advantages of in situ hyperspectral Raman imaging compared to conventional experimental and analytical methods, where the sample has to be quenched to room temperature before being analyzed, are clearly demonstrated. This new analytical method is a powerful tool for studying sinter reactions with a high temperature, time, and spatial resolution and offers a wide range of possibilities to study ceramic systems for industrial applications.
In diesem Projekt wurden die Hochtemperatur-Mineralreaktionen und -Umwandlungen von Kalziumsilikat-Materialien im CaO-SiO2(-SO3/Al
Die Bildung und Temperaturstabilität von Ternesit und Silicocarnotit, d. h. dem sulfat- und phosphathaltigen Endglied einer Mischkristallreihe, wurden untersucht. Beide Mineralphasen werden durch Reaktionen mit Dicalciumsilikat gebildet. Insbesondere wurde die Korngrenzenwanderung von Ternesit durch das Ersetzen eines großen Quarzkorns beobachtet. Mit zunehmender Temperatur (und Zeit) bildete α’L-Ca2SiO4 neue Reaktionsränder um Ternesit, wodurch eine Schichtstruktur mit Quarz im Zentrum, Ternesit in der mittleren und α’L-Ca2SiO4 in der äußeren Schicht entstand. Die Erhitzungsstudie mit einem natürlichen Ternesit-Kristall ergab eine Phasenumwandlung zu α’L-Ca2SiO4 zwischen 730 und 1120 ± 1 °C und bestätigte, dass sowohl die Ternesit- als auch die Dicalciumsilikat-Domäne in diesem Temperaturbereich koexistieren können. Im Allgemeinen hängt es vom Fortschritt der Reaktion ab, ob nach dem Abschrecken auf Raumtemperatur Ternesit oder Larnit nachgewiesen wird. Des Weiteren wurden zwei Reaktionswege zur Bildung von Silicocarnotit zwischen 1050 und 1150 °C gefunden, d. h. bei deutlich niedrigeren in situ Temperaturen als bisher angenommen. Außerdem wurde zum ersten Mal eine Erhitzungsstudie mit einem natürlichen Silicocarnotit-Kristall durchgeführt. Dabei zeigte sich zum Beispiel, dass sich die Position der v1(PO4) Bande bei 1200 ± 1 °C von 951 ± 1 cm 1 auf ~930 cm-1 verschoben hat. Darüber hinaus wurde die Umwandlung von Hydroxylapatit in Tricalciumphosphat untersucht, was neue Einblicke in den komplexen Prozess des Verlusts der an HAp-Nanokristallen gebundenen Hydroxylgruppen an der Oberfläche ermöglichte.
Die Vorteile der in situ hyperspektralen Raman-Bildgebung im Vergleich zu herkömmlichen experimentellen und analytischen Methoden, bei denen die Probe vor der Analyse auf Raumtemperatur abgekühlt werden muss, werden deutlich aufgezeigt. Diese neue Analysemethode ist ein leistungsfähiges Instrument zur Untersuchung von Sinterreaktionen mit hoher Temperatur-, Zeit- und Ortsauflösung und bietet eine breite Reihe von Möglichkeiten zur Untersuchung keramischer Systeme für industrielle Anwendungen.
Schlagwörter
in situ, Raman-Spektroskopie, Hochtemperatur, Sinterreaktionen, Raman imaging, calcium silicate, calcium phosphate, high-temperature, solid-state reactions, ternesite, silicocarnotite, hydroxylapatite
Klassifikation (DDC)
550 GeowissenschaftenBöhme, Nadine Susanne: Insights into high-temperature mineral reactions of calcium silicate materials revealed in operando by in situ Raman spectroscopy. - Bonn, 2022. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-68721
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-68721
@phdthesis{handle:20.500.11811/10487,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-68721,
author = {{Nadine Susanne Böhme}},
title = {Insights into high-temperature mineral reactions of calcium silicate materials revealed in operando by in situ Raman spectroscopy},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = nov,
note = {Knowledge of high-temperature calcium silicate materials is becoming increasingly interesting for industry in different ways. On the one hand, their application in the construction, cement, refractory, and ceramics industry is well established due to, in particular, their high melting point, thermal stability, fluxing characteristics, acicular shape, and bioactivity. However, these minerals also form as sinter deposits in industrial kilns and may cause serious and expensive problems during kiln operation. It follows that a detailed understanding of solid-state or solid-melt mineral reactions that form calcium silicate materials as well as the knowledge about their thermal stability are essential to optimize industrial processes, i.e., to fully exploit their technical advantages and to ensure synthesis under optimal conditions.
In this project, the high-temperature mineral reactions and transformations of calcium silicate materials in the CaO-SiO2(-SO3/Al2 O3/P2O5) system and subsystems were studied in both single- and multi-phase experiments by in situ Raman spectroscopy. The green bodies of multi-phase experiments mainly consisted of calcium oxide (lime) and quartz, and sulfate/aluminate/phosphate components were systematically added or replaced. During firing the samples to temperatures between about 660 and 1100 °C, the decomposition and formation processes of mineral phases were monitored and visualized at the micrometer-scale and in operando, i.e., while the reactions were running. For instance, the formation of mono- and dicalcium silicates was found to occur at different in situ temperatures via different reaction pathways. In addition, the polymorphs pseudowollastonite and α’L-Ca2SiO4 were identified. The latter transformed to β-Ca2SiO4 (larnite) during cooling and remained metastable at room temperature.
The formation and temperature stability of ternesite and silicocarnotite, i.e., the sulfate- and phosphate-containing end member of a solid solution series, were studied. Both mineral phases are formed by reactions involving dicalcium silicate. In particular, the grain boundary migration of ternesite by replacing a large quartz grain was observed. With increasing temperature (and time), α’L-Ca2SiO4 formed new reaction rims around ternesite, producing a layered texture with quartz in the center, ternesite in the middle, and α’L-Ca2SiO4 in the outer layer. The heating study with a natural ternesite crystal revealed a phase transformation to α’L-Ca2SiO4 between 730 and 1120 ± 1 °C and confirms that both the ternesite and dicalcium silicate domains can co-exist in this temperature range. It generally depends on the course of the reaction whether ternesite or larnite is detected after quenching to room temperature. Furthermore, two reaction pathways were found to form silicocarnotite between about 1050 and 1150 °C, i.e., at significantly lower in situ temperatures than previously proposed. In addition, a heating study with a natural silicocarnotite crystal was performed for the first time. This experiment revealed, for instance, that the position of the v1(PO4) band shifted from 951 ± 1 cm 1 to ~930 cm-1 at 1200 ± 1 °C. Moreover, the transformation of hydroxylapatite to tricalcium phosphate was investigated and gave new insights into the complex process of the loss of surface hydroxyl groups bound to HAp nanocrystals.
The advantages of in situ hyperspectral Raman imaging compared to conventional experimental and analytical methods, where the sample has to be quenched to room temperature before being analyzed, are clearly demonstrated. This new analytical method is a powerful tool for studying sinter reactions with a high temperature, time, and spatial resolution and offers a wide range of possibilities to study ceramic systems for industrial applications.},
url = {https://hdl.handle.net/20.500.11811/10487}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-68721,
author = {{Nadine Susanne Böhme}},
title = {Insights into high-temperature mineral reactions of calcium silicate materials revealed in operando by in situ Raman spectroscopy},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2022,
month = nov,
note = {Knowledge of high-temperature calcium silicate materials is becoming increasingly interesting for industry in different ways. On the one hand, their application in the construction, cement, refractory, and ceramics industry is well established due to, in particular, their high melting point, thermal stability, fluxing characteristics, acicular shape, and bioactivity. However, these minerals also form as sinter deposits in industrial kilns and may cause serious and expensive problems during kiln operation. It follows that a detailed understanding of solid-state or solid-melt mineral reactions that form calcium silicate materials as well as the knowledge about their thermal stability are essential to optimize industrial processes, i.e., to fully exploit their technical advantages and to ensure synthesis under optimal conditions.
In this project, the high-temperature mineral reactions and transformations of calcium silicate materials in the CaO-SiO2(-SO3/Al
The formation and temperature stability of ternesite and silicocarnotite, i.e., the sulfate- and phosphate-containing end member of a solid solution series, were studied. Both mineral phases are formed by reactions involving dicalcium silicate. In particular, the grain boundary migration of ternesite by replacing a large quartz grain was observed. With increasing temperature (and time), α’L-Ca2SiO4 formed new reaction rims around ternesite, producing a layered texture with quartz in the center, ternesite in the middle, and α’L-Ca2SiO4 in the outer layer. The heating study with a natural ternesite crystal revealed a phase transformation to α’L-Ca2SiO4 between 730 and 1120 ± 1 °C and confirms that both the ternesite and dicalcium silicate domains can co-exist in this temperature range. It generally depends on the course of the reaction whether ternesite or larnite is detected after quenching to room temperature. Furthermore, two reaction pathways were found to form silicocarnotite between about 1050 and 1150 °C, i.e., at significantly lower in situ temperatures than previously proposed. In addition, a heating study with a natural silicocarnotite crystal was performed for the first time. This experiment revealed, for instance, that the position of the v1(PO4) band shifted from 951 ± 1 cm 1 to ~930 cm-1 at 1200 ± 1 °C. Moreover, the transformation of hydroxylapatite to tricalcium phosphate was investigated and gave new insights into the complex process of the loss of surface hydroxyl groups bound to HAp nanocrystals.
The advantages of in situ hyperspectral Raman imaging compared to conventional experimental and analytical methods, where the sample has to be quenched to room temperature before being analyzed, are clearly demonstrated. This new analytical method is a powerful tool for studying sinter reactions with a high temperature, time, and spatial resolution and offers a wide range of possibilities to study ceramic systems for industrial applications.},
url = {https://hdl.handle.net/20.500.11811/10487}
}
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