In situ SAXS observation on metal-salt-derived alumina sol-gel system accompanied by phase separation

[摘要] The structure formation process of hierarchically porous alumina gels has been investigated by in situ small angle X ray scattering (SAXS) The measurement was performed on the sol-gel solution containing aluminum chloride hexahydrate (AlCl3 6H(2)O) poly(ethylene oxide) (PEO) and propylene oxide (PO) The temporal divergence of scattering intensity in the low q regime was observed in the early stage of reaction indicating that the occurrence of spinodal-decomposition-type phase separation Detailed analysis of the SAXS profiles revealed that phase separation occurs between weakly branched polymenzing aluminum hydroxide (AH) and PEO Further progress of the condensation reaction forms phase-separated two phases that is AH rich phase and PEO rich phase with the micrometer range heterogeneity The growth and aggregation of primary particles occurs in the phase-separated AH-rich domain and there fore the addition of PEO influences on the structure in nanometer regime as well as micrometer regime The moderate stability of oligomeric species allows homogeneous condensation reaction parallel to phase separation and successful formation of hierarchically porous alumina gel (C) 2010 Elsevier Inc All rights reserved

[发布日期] 2010-12-15

[关键词] SAXS;Alumina;Macroporous;Mesoporous;Phase separation;Monolith;Sol-gel