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Raman spectroscopy is a noninvasive and highly sensitive analytical technique capable of identifying chemical compounds in environments that can mimic SOFC operating conditions. Here we demonstrate the use of Raman spectroscopy to perform local thermal and temporal measurements, both of which are essential if phase formation diagrams are to be mapped out and compared to thermodynamic phase stability predictions. We find that the time resolution of the Raman technique is more than sufficient to capture essential dynamic effects associated with a change of chemical composition.

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This research aimed to synthesize zeolites from perlite obtained from Lopburi Province, Thailand, and from rice husk ash, under hydrothermal condition. The experiments were carried out in an autoclave with SiO 2 /Al 2 O 3 molar ratios of 1 to 40, NaOH concentrations of 1 to 4 N, and starting pressure of 1 atm. The rice husk ash and AlCl 3 •6H 2 O were used to adjust the SiO 2 /Al 2 O 3 molar ratio. The autoclave was heated with the rate of 1.5 °C/min to the set points of 140 and 170 °C at which it was kept isothermally for 2 h. The results showed that the products detected were analcime, Na-P1, and sodalite octahydrate. However, at very low SiO 2 /Al 2 O 3 ratio and NaOH concentration, no zeolite could be formed at 140 °C. The analcime could be formed at almost all conditions, except at low concentration of NaOH and the SiO 2 /Al 2 O 3 ratio below 25. Furthermore, the Na-P1 could be detected in every area except at high concentration of NaOH and high SiO 2 /Al 2 O 3 ratio at which only analcime and sodalite octahydrate were found. The sodalite octahydrate was formed preferably at high concentration of NaOH and high ratio of SiO 2 /Al 2 O 3. At temperature of 170 °C, the formation of analcime was enhanced, while the others seemed to be unaffected. Finally, phase diagrams of detected zeolites were constructed.

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