Journal of Colloid and Interface Science, Vol.299, No.2, 747-753, 2006
Evidences of segregated SnO2 type nanoparticles coating lavered double hydroxide at moderate temperature
A series of layered double hydroxide (LDH) materials prepared by classical coprecipitation in the presence of divalent Co2+, trivalent Al3+, and tetravalent Sn4+ cations have been investigated as a function of the temperature. As illustrated for the cation composition (Co: Al: Sn) of (0.75: 0.175: 0.075). the segregation of SnO2-type nanodomains in an interphasing LDH sand-rose region is directly evidenced by transmission electron microscopy and selected area electron diffraction (TEM/SAED). At moderate temperature (<= 400 degrees C) the local environment around the cobalt cations is strongly modified. whereas the local structure is found to be Unchanged in the vicinity of the tin cations. It is explained on the basis of the breakdown of the lamellar assembly and of the partial oxidation of Co2+ cations and that tin dioxide domains are still segregated front LDH particles. Even if the tin dioxide component does not participate front a structural point of view in the LDH composition. its beneficial effect on the textural properties is significant, increasing the Specific Surface area and narrowing the pore size distribution. (c) 2006 Elsevier Inc. All rights reserved.
Keywords:layered double hydroxide;local structure X-ray absorption spectroscopy;nitrogen gas adsorption