Amorphous Silicon Oxynitride-Based Powders Produced by Spray Pyrolysis from Liquid Organosilicon Compounds

Silicon oxynitrides (SiOxNy) have many advantageous properties for modern ceramic applications that justify a development of their new and efficient preparation methods. In the paper, we show the possibility of preparing amorphous SiOxNy-based materials from selected liquid organosilicon compounds, methyltrimethoxysilane CH3Si(OCH3)(3) and methyltriethoxysilane CH3Si(OC2H5)(3), by a convenient spray pyrolysis method. The precursor mist is transported with an inert gas or a mixture of reactive gases through a preheated tube reactor to undergo complex decomposition changes, and the resulting powders are collected in the exhaust filter. The powders are produced in the tube at temperatures of 1200, 1400, and 1600 degrees C under various gas atmosphere conditions. In the first option, argon Ar gas is used for mist transportation and ammonia NH3 gas serves as a reactive medium, while in the second option nitrogen N-2 is exclusively applied. Powder X-Ray Diffraction (XRD) results confirm the highly amorphous nature of all products except those made at 1600 degrees C in nitrogen. SEM examination shows the spheroidal particle morphology of powders, which is typical for this method. Fourier Transform Infrared (FT-IR) spectroscopy reveals the presence of Si-N and Si-O bonds in the powders prepared under Ar/NH3, whereas those produced under N-2 additionally contain Si-C bonds. Raman spectroscopy measurements also support some turbostratic free carbon C in the products prepared under nitrogen. The directly determined O- and N-contents provide additional data linking the process conditions with specific powder composition, especially from the point of view of oxygen replacement in the Si-O moieties formed upon initial precursor decomposition reactions by nitrogen (from NH3 or N-2) or carbon (from the carbonization of the organic groups).

Automated summary

The paper explores the preparation of amorphous SiOxNy-based materials from liquid organosilicon compounds through spray pyrolysis method under different gas atmosphere conditions. Various analytical methods confirm the characteristics and composition of the powders produced.