A SMALL-ANGLE X-RAY-SCATTERING STUDY OF MICROSTRUCTURE EVOLUTION DURING SINTERING OF SOL-GEL-DERIVED POROUS NANOPHASE TITANIA

被引:18
作者
HACKLEY, VA
ANDERSON, MA
SPOONER, S
机构
[1] UNIV WISCONSIN,WATER CHEM PROGRAM,MADISON,WI 53706
[2] OAK RIDGE NATL LAB,DIV SOLID STATE,OAK RIDGE,TN 37831
关键词
D O I
10.1557/JMR.1992.2555
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The evolution of microstructure as a function of firing temperature in sol-gel derived porous titania xerogels was investigated by small-angle x-ray scattering (SAXS). SAXS curves for xerogels fired below 550-degrees-C exhibit a well-defined structure peak. This peak indicates the presence of a high degree of order in the electron density correlations associated with the interparticle structure factor. Results from electron microscopy and SAXS give a primary particle mean diameter of 50 angstrom, while scaling analysis of the scattered intensity at large momentum transfer values yields the Porod exponent 4, indicating a sharp transition zone between the solid and void phases. The pore volume fraction of the unfired xerogel is consistent with random close-packing of spheres. The internal surface area decreases almost linearly with increasing firing temperature. Rapid grain growth and pore coarsening begin near 90% of theoretical density, and lead to a breakdown in pore interconnectedness and the development of isolated pores. Observed enhanced sintering properties may be attributed primarily to the large surface-to-mass ratio of the sol-gel particles. The SAXS curves were adequately fit using a bicontinuous phase model developed for late-stage spinodal decomposition structures. Alternatively, the microstructure can be described by a hierarchical close-packing of spheres model. SAXS results are compared with data from gas adsorption and electron microscopy.
引用
收藏
页码:2555 / 2571
页数:17
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