Microstructural and thermal properties of plasma sprayed mullite coatings

TitleMicrostructural and thermal properties of plasma sprayed mullite coatings
Publication TypeArticolo su Rivista peer-reviewed
Year of Publication2010
AuthorsDi Girolamo, G., Blasi C., Pilloni L., and Schioppa M.
JournalCeramics International
KeywordsAmorphous phase, Amorphous phasis, Atmospheric plasma spraying, C. Thermal properties, Differential scanning calorimetry, E. Thermal applications, Exothermic peaks, Glassy phase, Heat capacities, heating, Heating up, High temperature, Micro-structural, Mullite, Mullite coatings, Plasma jets, Plasma sprayed, Plasma spraying, Plasmas, Protective coatings, Recrystallization (metallurgy), Recrystallization mechanisms, Recrystallizations, Scanning electron microscopy, SEM, Silicate minerals, Silicon compounds, Sprayed coatings, Temperature of crystallization, Test temperatures, Thermal applications, Thermal expansion, Thermal properties, Thermal spraying, Thermal treatment, X ray diffraction, X ray diffraction analysis

Thick mullite (3Al2O3-2SiO2) coatings were fabricated by atmospheric plasma spraying (APS) in a mixture of crystalline and amorphous phases, as confirmed by X-ray diffraction (XRD) analysis. The coatings were isothermally heat treated in order to study recrystallization mechanism of the glassy phase. The morphology and the microstructure of both mullite feedstock and coatings were investigated by using scansion electron microscopy (SEM). The porosity of as-sprayed coating was in the range between 2 and 3% and substantially remained unchanged after thermal treatment. The thermal expansion of as-sprayed and annealed coatings was measured during heating up to the temperature of crystallization and the corresponding high-temperature extent of shrinkage was calculated. The differential scanning calorimetry (DSC) curves at different heating rates showed a sharp exothermic peak between 1243 and 1253 K, suggesting a rapid recrystallization of the amorphous phase. Finally, the heat capacity of recrystallized mullite coating was measured by DSC experiments. It was approximately 1.02 × 103 J/kg K at 373 K and increased with increasing test temperature. © 2010 Elsevier Ltd and Techna Group S.r.l.


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