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Fast and Almost Complete Nitridation of Mesoporous Silica MCM‐41 with Ammonia in a Plug‐Flow Reactor
Author(s) -
Hayashi Fumitaka,
Ishizu Kenichi,
Iwamoto Masakazu
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03375.x
Subject(s) - analytical chemistry (journal) , nitrogen , transmission electron microscopy , scanning electron microscope , silicon nitride , nitride , mesoporous material , ammonia , silicon oxynitride , plug flow , materials science , chemistry , volumetric flow rate , lattice constant , silicon , diffraction , layer (electronics) , catalysis , nanotechnology , metallurgy , composite material , quantum mechanics , biochemistry , physics , organic chemistry , chromatography , optics , thermodynamics
The title reaction proceeded well to yield silicon (oxy)nitride at 973–1323 K using a plug‐flow reactor. The degree of nitridation was studied as a function of temperature and time of nitridation, the sample weight, and the flow rate of ammonia. It was dependent on the reaction temperature and the amount of ammonia supplied per sample weight. The nitridation at 1273 K for 10–25 h yielded the oxynitride with 36–39 wt% nitrogen, which was very close to 40 wt% of Si 3 N 4 . Characterization with X‐ray diffraction, field‐emission scanning electron microscopy and transmission electron microscopy measurements, and nitrogen adsorption revealed the conversion of MCM‐41 to the corresponding oxynitride without essential loss of the mesoporous structure, the decrements of the lattice constant and the pore diameter by 20–35%, and the increments of the wall thickness by ca. 45%. Solid‐state 29 Si nuclear magnetic resonance spectra during the nitridation clearly showed fast decrease in SiO 4 species and slow in SiO 3 (OH). Various intermediate species, SiO x N y (NH 2 or NH) z , were observed to be formed and finally, ca. 70% SiN 4 species, ca. 20% SiN 3 (NH 2 or NH), and ca. 10% SiON 2 (NH 2 or NH) were produced, being consistent with the results of the above mentioned elemental analysis.