MOHAMED R. BERBER Department of Chemistry, Faculty of Science, Tanta University, Tanta 31527, Egypt.

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1 Advanced Materials Development and Performance (AMDP211) International Journal of Modern Physics: Conference Series Vol. 6 (212) World Scientific Publishing Company DOI: /S CONTROL OF NANOPARTICLE SIZE, CRYSTAL STRUCTURE AND GROWTH OF LAYERED DOUBLE HYDROXIDE BY HYDROTHERMAL TREATMENT Int. J. Mod. Phys. Conf. Ser : Downloaded from by on 4/6/18. For personal use only. MOHAMED R. BERBER Department of Chemistry, Faculty of Science, Tanta University, Tanta 31527, Egypt. mrberber@science.tanta.edu.eg INAS H. HAFEZ, KEIJI MINAGAWA, MASAHIRO KATOH Institute of Technology and Science, The University of Tokushima, Tokushima , Japan. minagawa@chem.tokushima-u.ac.jp MASAMI TANAKA Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima , Japan. tanaka@ph.bunri-u.ac.jp TAKESHI MORI Department of Applied Chemistry, Kyushu University, Fukuoka , Japan. mori.takeshi.88@m.kyushu-u.ac.jp Here, we showed the effect of hydrothermal treatment and aging process of urea hydrolysis on crystal structure, particle size and particle size distribution of Mg-Al layered double hydroxide () materials. The obtained materials were characterized by X-ray crystallography and scanning electron microscopy. The studied synthetic parameters showed a great influence on the physicochemical properties of the selected materials. At insufficient conditions of hydrothermal treatments, the formed particles were amorphous and the non- phases dominated the X-ray diffraction chart. The crystal growth increased with increasing hydrothermal temperature. Aging process improved the crystal morphology up to18 hours, while further aging destroyed the particles. The increase of hydrothermal aging led to a wide particle size distribution. Keywords: Urea hydrolysis; particles size;. Coresponding Author: Berber MR, Tanta University, Tanta 31527, Egypt. mrberber@science.tanta.edu.eg 133

2 134 M. R. Berber et al. 1. Introduction Int. J. Mod. Phys. Conf. Ser : Downloaded from by on 4/6/18. For personal use only. Over the past few years, an increasing interest was devoted to the use of clays as host materials in order to create potential products with desirable physical and chemical properties. Layered double hydroxides (s) represent one of the most technologically promising clays because of their broad uses as anion exchangers, adsorbents, catalyst precursors and carriers of bioactive compounds 1-6. s are a family of natural and synthetic compounds having the general formula [M (II) 1-x M (III) x (OH) 2 ](Y n- ) x/n yh 2 O, where M (II) and M (III) represent divalent and trivalent metal ions, respectively, and Y n- is the anion between the layers. They consist structurally of brucite-like [Mg(OH) 2 ] layers, with a net positive charge due to partial substitution of M (II) by M (III). This positive charge is balanced by interlayer anions 7, 8. Since the nature of application is influenced by synthetic conditions, understanding the chemistry of and the factors affecting their physical and chemical properties is an important point of research to develop more advanced materials with high potential applications. Herein, we show the effects of hydrothermal temperature and aging process of urea hydrolysis synthetic technique on the crystal growth and particle size as well as particle size distribution of MgAl- materials. 2. Experimental Work 2.1. Materials Urea (extra pure grade, >99.%; Wako Pure Chemical Industries, Ltd.), MgCl 2.6H 2 O, AlCl 3.6H 2 O, Na 2 CO 3 and KOH (Kanto Chemical Co., Inc.) were used without further purification. All solutions were prepared using deionized water (18.2 MΩ/cm, produced from Milli-Q Grandient ZMQGkt) Urea hydrothermal synthesis A solution of 3.387g MgCl 2.6H 2 O and 2.1g AlCl 3.6H 2 O with metals molar ratio Mg 2+ /Al 3+ of 2. in 5 ml deionized water was prepared by magnetic stirring at room temperature. Then, 5.25 g of urea was added (urea/metals molar ratio was 3.5). The resulting homogeneous solution was transferred into a Teflon-lined autoclave TAF-SR Type (Taiatsu Glass Ind. Co,) and heated in oil bath at 4, 6, 8, 1, 12, 14 and 16 C for 12 h(s). After cooling to room temperature, the precipitate was collected by filtration (using a.45 μm JG Millipore filter paper), washed several times with deionized water untill a negative test was obtained for chloride ion in the washing medium, and finally freeze-dried (EYELA freeze drier FD-1, Tokyo Rikakikai Co., Ltd, Japan). Furthermore, the effect of aging was investigated by repeating the same process at 18, 24 h(s).

3 Hydrothermal Control of Physicochemical Properties Characterization X-ray powder diffraction patterns were recorded on a Rigaku X-ray diffractometer using CuKα radiation at λ=1.545 Å. The measurement was performed in the 2θ range 1.5-7º. The scanning electron micrographs (SEM) were captured by a Hitachi FE-SEM S-47 microscope. The average particle size diameter and particle size distribution ratio were calculated from SEM images by using more than 1 particles. 3. Results and Discussion Int. J. Mod. Phys. Conf. Ser : Downloaded from by on 4/6/18. For personal use only. The determined Mg/Al molar ratio in the precipitated samples at insufficient conditions of hydrothermal treatment was small compared to the starting ones (1.85 at 8 C) and are presumably due to non- phases. The verification of the non- phases was confirmed by the X-ray measurement (see Fig. 1a and b). The Mg/Al molar ratio of the samples prepared from 1-14 C was almost the same as the starting one (1.98 to 2.1). Figure 1 shows the X-ray patterns of the prepared samples at different hydrothermal treatments. At hydrothermal temperature of 4 C there was no precipitate. The formed precipitate at 6 C composed only of non- phases (pattern a). The characteristic peaks of Mg-Al started to appear at 8 C, but the non- phases are still dominates the diffraction chart. Starting from hydrothermal temperature of 1 C, the symmetric reflections of Mg-Al material is formed, but the crystallinity was small. The continuous increase of hydrothermal temperature up to 14 C improved the crystallinity of the prepared. Patterns c, d, and e indicated the formation of single phase Mg-Al with sharp and symmetric diffractions. At hydrothermal temperature of 16 C, we noticed a decrease in the intensity of Mg-Al diffractions, in addition to the appearance of impurity peaks at 2θ of 14.4 and The decrease of crystallinity was an indicator of a turbostratic disorder of layers and the deformation of the crystallographic structure a Pseudoboehmite (PB) Non-hydrotalcite phases Magnesium hydroxide 6º-12h b Magnesium hydroxide 8º-12h C Pure º d 12º Theta º Fig. 1. Effect of hydrothermal temperature on the crystal structure of MgAl. e Theta f º Theta

4 136 M. R. Berber et al. By investigating the effect of aging process at hydrothermal temperature of 14 C (Figure 2), a decrease in crystallinity of above 18 h was found, probably due to turbostratic disorder. Accordingly, it seems that Mg-Al particles reached a wellordered and stable structure up to 18 h of hydrothermal treatment at 14 C. Int. J. Mod. Phys. Conf. Ser : Downloaded from by on 4/6/18. For personal use only º-12h º-18h Fig. 2. Effect of hydrothermal aging on the crystal structure of MgAl. Figure 3 displays the SEM images of the obtained materials. At insufficient conditions of hydrothermal treatment (8 C for 12h; Image a), only amorphous particles of was observed. The amorphous morphology of the particles confirmed the X-ray result of this sample. Images (b and c) revealed large and regular hexagonal platelets of, however image (c) showed some deformed particles. The morphology of the platelets reflected a good crystallinity. Images (d, e and f) showed the effect of hydrothermal aging on the morphology of particles. The increase of aging increased the particle size diameter. Above 18 h(s) of hydrothermal treatment, some deformed particles were observed. 8º-12 a 1º-12h b 16º-12h c º-24h º-12h d 14º-18h e 14º-24h f Fig. 3. SEM images of samples prepared under the effect of hydrothermal temperature and aging.

5 Hydrothermal Control of Physicochemical Properties 137 Table 1 gathers the results of particle size diameter and particle size distribution ratio. The particle size of correlated to the changes of hydrothermal temperature and aging. The increase of hydrothermal temperature increased the particle size. In addition, the increase of hydrothermal aging led to a wide particle size distribution. The highest uniformity of particle size was recorded at 12 h of aging. Consequently, the uniformity of Mg-Al prepared by urea method depended on the rate of hydrolysis of urea as well as hydrothermal aging. Int. J. Mod. Phys. Conf. Ser : Downloaded from by on 4/6/18. For personal use only. Table 1. Effects of hydrothermal temperature and aging on particle size and particle size distribution Sample Average particle diameter ( μm) Average distribution (%) 6º-12 * * 8º-12 * * 1º º º º º º º * Not analysized References 1 K. Motokura, D. Nishimura, K. Mori, T. Mizugaki, K. Ebitani and K. Kaneda, J. Am. Chem. Soc. 126, 5662 (24). 2 Z. P. Xu, S. K. Saha, P. S. Braterman and N. D'Souza, Polym. Degrad. Stabil. 91, 3237 (26). 3 M. R. Berber, K. Minagawa, M. Katoh, T. Mori and M. Tanaka, Eur. J. Pharm. Sci. 35, 354 (28) 4 M. Behrens, I. Kasatkin, S. Kuhl and G. Weinberg, Chem. Mater. 22, 386 (21). 5 I. H. Hafez, M. R. Berber, K. Minagawa, T. Mori and M. Tanaka. J. Agric. Food Chem. 58, 1118 (21). 6 M. R. Berber, I. H. Hafez, K. Minagawa, T. Mori and M. Tanaka, Pharm. Res. 27, 2394 (21). 7 J. W. Boclair, P. S. Braterman, B. D. Brister and F. Yarberry, Chem. Mater. 11, 2199 (1999). 8 V. Rives, Mater. Chem. Phys. 75, 19 (22). 9 A. Violante, P. M. Huang, Clays Clay Miner. 41, 59 (1993).