Preparation of fine ceria powders by hydrolysis of cerium(IV) carboxylate solutions
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The authors are indebted to Yoshizawa Lime Industry Co. Ltd. for supplying the CaO crucibles.
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Fig. 1—X-ray powder diffraction analysis of precipitate from cerium(IV) carboxylate solution in the presence of water and atmospheric oxygen: (a) observed XRD pattern; and (b ) International Center for Diffraction 340394. Precipitation conditions: 220 7C, 2.5 MPa, 0.17 kmol/m3 cerium(IV) carboxylate, 1.3 kmol/m3 free carboxylic acid, and 120 min.
Preparation of Fine Ceria Powders by Hydrolysis of Cerium(IV) Carboxylate Solutions YASUHIRO KONISHI, SATORU ASAI, TETUYA MURAI, and HIROFUMI TAKEMORI Many of the technological uses of rare earths often require oxide powders with specific particle size, morphology, and purity. Various preparation routes have been reported for rare earth oxides, using aqueous solutions or alkoxides in alcohols. The hydrometallurgical process called hydrolytic stripping is also a promising route for producing oxide materials, which involves precipitation of oxides by direct hydrolysis of metal-loaded carboxylic acid extractant dissolved in an organic solvent using water at elevated temperatures.[1,2] The hydrolysis of metal carboxylate in the organic phase enables the elimination of anion contamination of the oxide product, because the organic solvent having a low dielectric constant is free from ionic species. Using the hydrolytic stripping technique, powders of a-Fe2O3, Fe3O4, CuO 1 Cu2O, Mg(OH)2, g-Mn2O3 ZrO2, and several ferrites MFe2O4 (M: Ni, Co, Zn, or Mn) have been prepared at 130 7C to 245 7C.[3–8] However, no information is available concerning the preparation of rare-earth oxide powders directly from metal carboxylate in the organic phase. The purpose of this study is to establish
YASUHIRO KONISHI, Associate Professor, SATORU ASAI, Professor, TETUYA MURAI, Graduate Student, and HIROFUMI TAKEMORI, Undergraduate Student, are with the Department of Chemical Engineering, Osaka Prefecture University, Osaka 593, Japan. Manuscript submitted January 15, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS B
Fig. 2—Extent of ceria precipitation as a function of time at different temperatures and pressures: (n) 220 7C and 2.5 MPa; (l) 160 7C and 0.61 MPa; and (●) 140 7C and 0.36 MPa. Precipitation conditions: 0.050 kmol/m3 cerium(IV) carboxylate and 0.34 k
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