摘要 :
We prepared a hardened geopolymer paste by treating a mixture of fly ash and alkali silicate solution at 80 ℃ for eight hours. X-ray diffraction and ~(29)Si-NMR spectra indicated that the hardened geopolymer paste was amorphous w...
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We prepared a hardened geopolymer paste by treating a mixture of fly ash and alkali silicate solution at 80 ℃ for eight hours. X-ray diffraction and ~(29)Si-NMR spectra indicated that the hardened geopolymer paste was amorphous with a zeolite-like structure. Cation exchange examination indicated that its exchange capacity was 150-170, 200-230, and 250-300 meq/100 g against alkali/H_2O ratios of 0.10, 0.15 and 0.20, respectively. The ion selectivity of the hardened geopolymer paste follows the order of Pb > Ba > Sr > K > Na. Except in the case of Cr-adsorption (which causes structural change), the selectivity of divalent ions is greater than that of monovalent ions, and ion selectivity increases in the order of ascending atomic number for the identical valence.
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摘要 :
A-type carbonate apatites with different CO_3 contents were obtained by heating hydroxyapatite powder in dry carbon dioxide atmosphere at 1173 K for 1 to 64 hours. The replacement of Co_3 ions lowered the crystal symmetry to hexag...
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A-type carbonate apatites with different CO_3 contents were obtained by heating hydroxyapatite powder in dry carbon dioxide atmosphere at 1173 K for 1 to 64 hours. The replacement of Co_3 ions lowered the crystal symmetry to hexagonal (P6_3Im) → hexagonal (p-6) → monoclinic (Pb) in that order. The a-axis parameters were linearly increased with the increase of CO_3 ions, while the b- and c-axis parameters were varied little. The lattice parameters of the A-type carbonate apatite completely replaced by CO_3 ions were refined to be a =0.9572(1), b=1.9084(1) and c =0.6877(1). The splitting of IR absorption bands attributed to a PO_4 ion also supported the lowering of crystal Symmetries
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