Journal of the American Ceramic Society · 1992 · 23 citations · 8 references
Natural SciencesChemistryMaterials ScienceCeramic MaterialsInorganic ChemistryPhysical ChemistryInorganic MaterialsMetal OxidesMetalsMineral ChemistryPartial MeltingThermal Properties Of CeramicsCrystal Chemistry Of SilicatesMelting BehaviorNickel OxidesSilica-based MaterialsSilicate ChemistrySilicate Melt CrystallizationSilicate Phase EquilibriaThermochemistry Of Oxides
Activity–composition relations of NiO have been determined at 1435°C in melts of the system CaO–NiO–SiO 2 and at 1400°C in melts of the systems CaO–MgO–NiO–SiO 2 , CaO–MgO–NiO–Al 2 O 3 –SiO 2 , and CaO–MgO–NiO–K 2 O–SiO 2 . In the CaO–NiO–SiO 2 and CaO–MgO–NiO–SiO 2 systems the activity coefficient of NiO (γ NiO ) decreases as the polymerization of the melt increases (basicity decrease). γ NiO stays contant up to several weight percent NiO for melts with similar basicity, an indication of Henry's law behavior. Minima in the NiO activity coefficient are observed in melts of the CaO–MgO–NiO–Al 2 O 3 –SiO 2 and CaO–MgO–NiO–K 2 O–SiO 2 systems at NBO/Si ratios between 1.0 and 1.5; i.e., γ NiO decreases with decreasing basicity for NBO/Si ratios >1.5 and increases with decreasing basicity for melts with NBO/Si ratios <1.0 (NBO/Si; nonbridging oxygens per silicon). The addition of Al 2 O 3 and K 2 O to the CaO–MgO–NiO–SiO 2 system results in an increase in the activity coefficient of NiO.
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