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Dehydration of Ca3Al2(SiO4)(y)(OH)4(3-y) (0
Hydrogarnet (Ca12Al2(OH)12) and katoite of composition Ca3Al2(SiO4)(0,176)(OH)(11,3) were obtained by hydration of tricalcium aluminium oxide, and for katoite synthesis, by addition of amorphous silica. The thermal dehydration was monitored in situ, by neutron thermodiffractometry, from room temperature to 700 deg C at atmospheric pressure and at a heating rate of 2 deg C/min. On heating, powder neutron diffraction patterns were collected every 300 s. Cell parameters were fitted by the Pawley method. Hydrogamet decomposed to yield (Ca12Al14O32(OH))(mH2O) and Ca(OH)2 that eventually transformed to CaO. For katoite, phases of formula Ca12Al(14-y)Si(y)O32(O,OH)(1+0.5y) related to mayenite were formed. Complementary annealing experiments, for 10 h, at higher temperatures and subsequent quenching lead to the formation of mayenite and traces of Ca3SiO5. Thermogravimetric curves were in agreement with the thermodiffractometry experiments. Also, neutron diffraction data allowed to measure thermal expansion coefficients, at atmospheric pressure, between 25 and 250 deg C for hydrogarnet and katoite: 1.89 x 10-5 +- 0.09 and 1.63 x 10-5 +- 0.07 deg C-1, respectively.
Dehydration of Ca3Al2(SiO4)(y)(OH)4(3-y) (0
Hydrogarnet (Ca12Al2(OH)12) and katoite of composition Ca3Al2(SiO4)(0,176)(OH)(11,3) were obtained by hydration of tricalcium aluminium oxide, and for katoite synthesis, by addition of amorphous silica. The thermal dehydration was monitored in situ, by neutron thermodiffractometry, from room temperature to 700 deg C at atmospheric pressure and at a heating rate of 2 deg C/min. On heating, powder neutron diffraction patterns were collected every 300 s. Cell parameters were fitted by the Pawley method. Hydrogamet decomposed to yield (Ca12Al14O32(OH))(mH2O) and Ca(OH)2 that eventually transformed to CaO. For katoite, phases of formula Ca12Al(14-y)Si(y)O32(O,OH)(1+0.5y) related to mayenite were formed. Complementary annealing experiments, for 10 h, at higher temperatures and subsequent quenching lead to the formation of mayenite and traces of Ca3SiO5. Thermogravimetric curves were in agreement with the thermodiffractometry experiments. Also, neutron diffraction data allowed to measure thermal expansion coefficients, at atmospheric pressure, between 25 and 250 deg C for hydrogarnet and katoite: 1.89 x 10-5 +- 0.09 and 1.63 x 10-5 +- 0.07 deg C-1, respectively.
Dehydration of Ca3Al2(SiO4)(y)(OH)4(3-y) (0
Dehydratation von Ca3Al2(SiO4)(y)(OH)4(3-y) (0 < y < 0.176), untersucht mit Neutronenthermobeugungsanalyse
Rivas-Mercury, J.M. (author) / Pena, P. (author) / Aza, A.H. de (author) / Turrillas, X. (author)
Journal of the European Ceramic Society ; 28 ; 1737-1748
2008
12 Seiten, 23 Bilder, 3 Tabellen, 23 Quellen
Article (Journal)
English
Aluminiumoxid , Calciumverbindung , Hydratisieren , Calciumaluminat , Feuerfestwerkstoff , Dehydratation , Wärmebehandlung (Materialbearbeitung) , Neutronenbeugung , Siliciumoxid , Zersetzungsreaktion , Phasenzusammensetzung , Abschrecken (Abkühlen) , Thermogravimetrie , thermischer Ausdehnungskoeffizient , Röntgenbeugung , Dilatometrie , Kristallstruktur , Gitterparameter , Reaktionsmechanismus
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