Rietveld Structure Refinement of Hydrothermally Grown Zinc Peroxide Nanoparticles
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Rietveld Structure Refinement of Hydrothermally Grown Zinc Peroxide Nanoparticles A. García-Ruiz1,*, M. Aguilar2, A. Aguilar3, A. Escobedo-Morales3, R. Esparza3 and R. Pérez3 1
UPIICSA-COFAA, Instituto Politécnico Nacional (IPN). Té 950, Col. Granjas-México, Iztacalco, 08400, México, D. F., MEXICO. 2 Instituto de Física, Universidad Nacional Autónoma de México (UNAM). A. P. 20-364, 01000 México, D. F., MEXICO. 3 Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México (UNAM). P.O. Box 48-3, 62251, Cuernavaca, Mor., MEXICO. *E-mail: [email protected]
ABSTRACT Nanocrystals of zinc oxides have demonstrated to be very important materials for several applications in many fields, particularly in catalysis. Nanocrystalline zinc peroxide (ZnO2), which is a precursor of zinc oxide (ZnO), has been prepared by means of a hydrothermal process from zinc acetate dehydrates. On the other hand, it is of great interest to have a detailed structural characterization, in order to correlate it with the catalytic properties of the synthesized material. In this work, some results are presented about the nanostructure of the prepared zinc peroxide. By using X-ray diffraction followed of a pattern refinement by the Rietveld techniques, refined average cell parameters and crystallite size were calculated and, from these refined values, crystallite morphology was simulated in an averaged manner. With the aim to get a more complete characterization, besides these results, some micrographs of the crystalline structure of ZnO2, observed by TEM, were also included in this work.
INTRODUCTION Recently, there has been increasing interest in zinc peroxide (ZnO2) and zinc oxide (ZnO), attracting the attention of many researchers because they have demonstrated to be very useful semiconductor materials with applications in rubber industry [1,2], in the high-tech plastic processing [3], as an oxidant in explosives and pyrotechnic mixtures [4]. Zinc peroxide can also be useful in the cosmetic [5,6] and pharmaceutical and therapeutic applications[6-9]. Stable nanoparticles of zinc peroxide can additionally be used as precursor for preparation of ZnO nanoparticles [10-13]. It is found that ZnO2 nanoparticles decompose into ZnO at about 230 ºC and is stable up to 36 GPa at ambient temperature. With a great potential in applications, ZnO nanocrystals can be used as catalyst and photocatalyst [11, 14-17]. ZnO could be added to zeolites in order to improve their catalytic properties. Nanocrystals, consisting of small crystallites of diameter < 100 nm, often have novel physical and chemical properties differing from those of the corresponding bulk materials [18]. The unique properties of nanocrystalline materials open up the general question of how crystallite size and shape affect the structural stability, and numerous efforts have been focused
on controlling the sizes and shapes of inorganic nanocrystals, since they modify the surface area of the crystallites generally improving, among others, their catalytic properties. As mentioned a
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