Synthesis conditions of ordered mesostructured boron nitride prepared from borazinic precursors and CMK-3 carbon templat
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R12.5.1
Synthesis conditions of ordered mesostructured boron nitride prepared from borazinic precursors and CMK-3 carbon template Philippe Dibandjo1, Laurence Bois1, Fernand Chassagneux1 , A. Vuillermoz2, Philippe Miele1. 1 Laboratoire Multimatériaux et Interfaces, UMR 5615, Bât Berthollet, Université Claude Bernard, 43 Bd du 11 nov 1918, Villeurbanne, France. 2 LPMCN, UMR 5586, Bât. L. Brillouin, Université Claude Bernard, 43 Bd du 11 nov 1918, Villeurbanne, France. ABSTRACT The preparation of ordered mesoporous boron nitride by using borazinic precursors as boron nitride source (tri(methylamino)borazine (MAB) and tri(chloro)borazine TCB) and a mesoporous carbon CMK-3 as template is reported. A template elimination performed by hydrogenation allows to obtain an organized porous structure. The X-ray diffraction, TEM and pore size analysis show that the structure of the BN molecular sieves synthesized from CMK-3 consists in a 2D regular array of uniform mesopores of 3.4 nm in diameter. INTRODUCTION Hexagonal boron nitride (BN) has some interesting chemical, thermal and electrical properties [1]. Porous boron nitride could be very useful as holding catalysts, sensors, chromatography or purification materials, since it could be used in air at high temperature [13]. For this purpose, new synthesis ways of porous boron nitride have to be developped, as for instance those involving nanocasting process of mesoporous material [4]. The hard-template route seems to be convenient to prepare mesostructured non-oxide ceramics, since impregnation of a template can be performed using a liquid ceramic precursor, followed by a ceramization step. Mesoporous silica nanocasting has been used to synthesize mesoporous carbon CMKi [5-6]. There is already some promising studies dealing with non-oxide periodic nano-structured ceramics [7-8]. Here, we describe borazinic precursor infiltration in mesoporous carbon using liquid phase infiltration technique [9]. A ceramization step is used to transform the borazinic precursor into boron nitride. The carbon template is then removed by an appropriate thermal treatment under a controlled atmosphere. Two borazinic precursors have been used : tri(methylamino)borazine (HNB(NHCH3))3 (MAB), already used for the preparation of boron nitride fibers [10-11] and trichloroborazine (HNBCl)3, (TCB). The CMK-3 hexagonal mesoporous carbon has been used, which allowed the SBA-15 replication [12-13]. The BN mesoporous materials obtained have been studied by X-ray diffraction, FTIR spectroscopy, TEM, SEM and pore size analysis. Different parameters of the synthesis of porous boron nitride materials are discussed: the nature of borazinic precursor, the ceramization step and the technique used for the carbon template elimination.
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EXPERIMENTAL DETAILS The synthesis of SBA-15 silica is carried out following a procedure described in the literature by Zhao et al.[14] The synthesis of CMK-3 is performed using SBA-15 silica as template and sucrose as carbon source, according the method proposed by Jun et al.[1
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