title: Microemulsion-based synthesis of CeO(2) powders with high surface area and high-temperature stabilities.
abstract: Pure ceria powders, CeO(2), were synthesized in heptane-microemulsified aqueous solutions of CeCl(3) or Ce(NO(3))(3) stabilized by AOT (sodium bis(2-ethylhexyl) sulfosuccinate), DDAB (di-n-didodecyldimethylammonium bromide), or DDAB + Brij 35 surfactant mixtures. Micellar DTAB (n-dodecyltrimethylammonium bromide) and vesicular DDAB systems were also used as media for generating CeO(2). Characterization of the powders by X-ray powder diffractometry, laser-Raman spectroscopy, and Fourier transform infrared spectroscopy revealed that in the presence of surfactants almost-agglomerate-free nanosized crystallites (6-13 nm) of anionic vacancy-free cubic CeO(2) were produced. In the absence of surfactants 21-nm-sized crystallites were formed, comparing with the 85-nm-sized crystallites when cubic CeO(2) was created via thermal decomposition of cerium oxalate. Surface characterization, by X-ray photoelectron spectroscopy, N(2) sorptiometry, and high-resolution electron microscopy showed AOT- or (DDAB + Brij 35)-stabilized microemulsions to assist in formation of crystallites exposing surfaces of large specific areas (up to ca. 250 m(2)/g) but of low stability to high-temperature calcination (28-13 m(2)/g at 800 degrees C). In contrast, the double-chained DDAB was found to generate cubic CeO(2) crystallites of lower initial surface areas (144 (microemulsion) to 125 (vesicles) m(2)/g)) but of higher thermal stability (55-45 m(2)/g at 800 degrees C). Hence, the latter cerias could be considered as appropriate components for total oxidation (combustion) catalysts.
authors.affiliation: Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat, 13060 Kuwait.
authors.forename: Ali
authors.initials: A
authors.lastname: Bumajdad
authors.forename: Mohamed I
authors.initials: MI
authors.lastname: Zaki
authors.forename: Julian
authors.initials: J
authors.lastname: Eastoe
authors.forename: Lata
authors.initials: L
authors.lastname: Pasupulety
mesh_terms: D002563:Cerium / Q000737:chemistry*; D004655:Emulsions; D015394:Molecular Structure; D010316:Particle Size; D011208:Powders; D013499:Surface Properties; D013696:Temperature
chemical_list: D004655:Emulsions; D011208:Powders; D002563:Cerium; C030583:ceric oxide