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Characterization of Calcined and Reduced Multi‐Component Co−Ni−Mg−Al‐Layered Double Hydroxides
Author(s) -
Tichit Didier,
Ribet Solange,
Coq Bernard
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200102)2001:2<539::aid-ejic539>3.0.co;2-r
Subject(s) - calcination , coprecipitation , brucite , chemistry , spinel , layered double hydroxides , lattice constant , oxide , mixed oxide , crystal structure , phase (matter) , inorganic chemistry , crystallography , mineralogy , magnesium , diffraction , hydroxide , catalysis , metallurgy , materials science , biochemistry , physics , organic chemistry , optics
Several Co−Ni−Mg−Al‐layered double hydroxides (LDH) have been synthesized by coprecipitation at constant pH = 9. All samples present well crystallized, layered structures, no excess phases were detected by X‐ray diffraction, and the lattice a parameter followed the Vegard correlation. The cations thus belong to the same, brucite‐like, lattice. Calcined samples exhibit XRD patterns of the crystallographic phase preferentially adopted by the major cation in the LDH: i.e., a mixed oxide of the rock salt type in the case of Ni or Mg, and a spinel‐like structure for Co. Surface areas reached maximum values in the range of 200−300 m 2 g −1 after calcination at 573 K. They were stabilized with increasing Ni or Mg content, as higher amounts of mixed oxide phase were formed. Programmed temperature reduction showed two domains of H 2 consumption, assigned to reduction of Co 3− x Ni x O 4 species below 720 K, and to NiMg(Al)O and Co 3− x − y Ni x Mg y AlO 6 , of rock salt type and spinel‐like structures respectively, above this temperature. These assignments are in agreement with the XRD patterns and show that Ni and Co are associated in the same crystallographic phases.