Papers by Keyword: Celsian

Abstract: Phase equilibria of the BaO-SiO₂-Al₂O₃ ternary system was experimentally investigated using a quenching technique and analyzed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Analysis (EDS) and X-ray Powder Diffraction (XRD). A ternary compound was confirmed in the present work. The liquidus composition in equilibrium with the ternary compound at 1500 °C were quantified. The isothermal sections of the BaO-SiO₂-Al₂O₃ ternary system at 1400 °C, 1500 °C, 1600 °C, and 1700 °C were calculated. Based on the data acquired, the isothermal section at 1500 °C was constructed.

Abstract: A novel celsian/yttrium silicate coating was deposited on carbon fiber reinforced silicon carbide matrix (C/SiC) composite, using BaO-Al₂O₃-SiO₂ (BAS) glass andY₂O₃ powder as starting materials. The effects of sintering temperatures on microstructure and performance of coatings were studied. The results show that the final phases of sintered coatings are composed of celsian, yttrium silicate and remnant glass. The coating are dense, crack-free and pore-free in macroscopic scales when sintered at temperatures above 1400°C. The crystal grains in the coating grow too large, and the coating is loose in microstructure when sintered at temperatures higher than 1450°C. The coated samples sintered at 1450°C for 30min, which have the densest morphology and microstructure, have the lowest weight loss of 0.13 % after oxidation at 1500°C for 90 min.

Abstract: Four samples of Ba-exchanged zeolite A, bearing 0.27, 0.43, 0.58 and 0.74 meq/g Na residual amounts, were thermally treated in the temperature range 200-1500 °C for times up to 28 hours. The same samples were pressed at 30 and 60 MPa to manufacture cylindrical pellets, which were thermally treated at 1300 °C for 5 hours. Thermally treated materials were characterized by room temperature XRD. The sequence of thermal transformations that Ba-exchanged zeolite A undergoes (zeolite ® amorphous phase ® hexacelsian ® monoclinic celsian) and the strong mineralizing action developed by Na are confirmed. Pressing the Ba-exchanged zeolite A powder-like samples to obtain cylindrical pellets is found to expedite the sluggish final phase transition hexacelsian ® monoclinic celsian. The optimum residual Na content of Ba-exchanged zeolite A to be transformed into monoclinic celsian is assessed to range between 0.27 and 0.43 meq/g.