| Sol-Emulsion-Gel Synthesis of
Alumina Nanospheroids |
M. Chatterjee, B. Siladitya, M. K. Naskar and D. Ganguli
Pages : 54-57
DOI : 10.1080/0371750X.2000.10799923 |
| Abstract |
| Alumina nanospheroids (1 0-50 nm) were synthesized by the solemulsion-
gel method under simultaneous mechanical agitation
(750-1500 rpm) and sonication (26 kHz). An aqueous alumina sol
("water phase" of high dielectric constant) was emulsified with
an organic solvent ("oil phase" of low dielectric constant) for
obtaining an water-in-oil (w/o) type emulsion. 1,1,1-trichloroethane
(TCE) was used as the "oil phase". The high interfacial
tension between the "water phase" and the "oil phase" was
reduced (i.e., stabilization of the sol droplets) by the addition of
an amphiphilic non-ionic surface active agent (Span 80). Two
vol% of Span 80 was used in all the experiments. The stabilized
sol droplets were subjected to gel formation by increasing the
basicity of the emulsion system with an organic amine (triethylamine,
TEA). The crystallization of phase-pure a-AI20 3 occurred
at a relatively low temperature (800°C, 60 h).
Differential thermal analysis (DT A) indicated the crystallization
of y-AI 20 3at 378°C as the first phase. Transmission electron
microscopy (TEM) revealed that the nanospheroids were generally
in chain-like agglomerates. Particle size analysis as also
BET specific surface area measurements showed the calcined
powders to be composed of large agglomerates with low surface
area, indicative of nanosized primary particles as the building
units. |
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