Study on template removal from silicalite-1 giant crystals

Abstract The formation of silicalite-1 giant crystals with a size of up to 3 mm can be achieved by controlling the factors affecting the nucleation and crystallization process using a piece of tube of quartz glass as the silica source under hydrothermal conditions. Once prepared and characterized by scanning electron and optical microscopy, thermogravimetry and single crystal powder X-ray diffraction, a challenge that remains is the removal of the template giving rise to colourless and crack-free crystals. As pointed out by stereoscopical, optical and fluorescence confocal optical microscopies, this was achieved in this study by the calcination protocols developed, involving the use of pure O 2 and 5% of O 2 in Ar and O 2 –O 3 (1.5% of O 3 ), maximum temperatures of 400 °C and heating rates as low as 0.5 °C/min.