Characterization equipment, calcination

All the solid phases were identified and characterized for crystallinity by X-ray powder diffraction (Philips PW 1730/10 diffractometer, Cu Kq radiation equipped with a PW 1030/70 vertical goniometer and connected to a P.C. computer for quantitative analyses). Crystallinities for Nu-10 and cristobalite were computed by comparing the intensity of the most characteristic diffraction peaks of each sample to that of the corresponding pure 100% crystalline phases used as standards. In some cases calibration curves derived from Nu-10/cristobalite mechanical mixtures were used. Si, Al, and alkali contents were determined either on precursors or calcined samples (900 C, air flow, 4h) by atomic absorption, using a Perkin-Elmer 380 AA instrument after digestion and dissolution of the samples in H,S04/HF solutions and further elimination of HF by gentle heating at 60 C for 12 n. 

Synthesized powders were calcined and characterized by standard techniques of thermogravimetric analysis, BET specific surface area measurements, and particle size determination by sedigraphy, as well as X-ray diffraction, and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) for microchemical analyses. To... 

LSM, SEKZ and LSCF powders were characterized by XRD using a Shimadzu XDR-7000 diffractometer and scanning electron microscopy (SEM-SSX 550, Shimadzu). Infrared spectra were also recorded with FTIR (IR Prestige-21, Shimadzu) in the 400 - 4600 cm"i spectral range. Specific surface area measurements were performed only for the LSM powders. An infrared reflectance spectrum of a LSM pellet prepared from a powder calcined at 900 °C was recorded with a Fourier-transform spectrometer (Bomem DA 8-02) equipped with a fixed-angle specular reflectance accessory (external incidence angle of 11.5°). 

The mixture is stimed under He flow and the temperature is increased to 343 K. Then, water is added in small doses at 30 minutes intervals the water to Ti(OR>4 ratio being of 30. After that, the mixture is kept under reaction for 4 h. The sample is filtered, washed with ethanol and dried at 383 K overnight. The support prepared using this procedure is denoted as Si-Ti and is characterized by therm analysis (TG). An aliquot of this support is calcined at 723 K for 24 h leading to Si-Ti-C support. Fourier Transform Infrared Spectroscopy (FTIR) is carried out on self-supported wafers. The spectra are recorded on a Nicolet 5 ZDX spectrophotometer equipped with an MCT (mercuiy-cadmium-tellnride) detector with a resolution of 4 cm. ... 

---