| الوصف: |
A study has been made of the system BaO - A1203 - H20 under varying conditions (temperature, pressure and time) using different starting materials. Of the nine previously reported barium a luminate hydrates, eight (B 1.1AH,* α-BAH2, α-BAH 4' β-BAH4, B1.1AH6, BAH7 , B2AH5 and B3AH7) have been confirmed, and one (Thilo's β-BAH2) was not confirmed. In addition, eight new binary or ternary compounds have been obtained, viz: Y-BAH 2, BAHO.5, B2AH2, B2AH, B3AH6, β-B3A, BxAγHz and BxA. The formula of the last two compounds are uncertain. Besides these, the existence of B2A, which has been questioned by many investigators, has been confirmed. Lattice constants and other crystallographic data have been determined for most of the above compounds, mainly by single crystal X-ray methods or in two cases by selected area electron diffraction. The compounds have also been studied in the following ways: (1) X-ray powder diffraction, (2) infrared spectroscopy, (3) differential thermal analysis, (4) thermogravimetric analysis, (5) static thermal analysis, (6) optical microscopy, (7) chemical analysis and (8) determination of density. The results of these studies are reported. The detailed structure analyses of B3AH6, B2AH5 and α-BAH2 have been performed by X-ray methods. The results show that B3AH6 has the hydrogarnet structure, B2AH5 contains isolated polynuclear anions of formula A12(OH)4-10 formed by sharing edges of centrosymmetrically related Al(OH)6 octahedra, and α-BAH2 is built from isolated helical chains formed from A104 tetrahedra. (*Cement chemical abbreviations: B = BaO, A = Al203, H = H20). |
