Hollow Silica Granules by Microwave Processing


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Conventional methods of processing hollow silica granules are tedious, expensive and time consuming. The present work aims at the production of hollow silica granules by a rapid, simple & cost-effective process, by employing microwave heat treatment which reduces the time factor drastically. Microwave processing is an emerging field and is fast catching up as an excellent alternative to the electrical heating methods. Spherical hollow silica granules with in-situ fibrous network were obtained by firing the sol-gel derived silica gel in a microwave furnace. Sol was synthesized using TEOS, distilled water, HCl & Ethanol and was allowed to age in a wide tray at ambient temperature & pressure. The ageing time of the gel was varied from 1-80 days and the characteristics of the granules hence obtained were studied. The temperature of heat treatment was also varied and it was observed that spherical granules form in the temperature range of 1250-1400°C. For comparison, the same gel was heat treated in a conventional furnace and the characteristics of the granules hence obtained were also studied. It was observed that conventionally sintered granules were less dense than the microwave derived ones but were not hollow. This paper describes the processing of hollow silica granules and the effect of gel ageing duration and temperature of sintering on the final product obtained.



Edited by:

B.S.S. Daniel and G.P. Chaudhari




S. Nagapriya et al., "Hollow Silica Granules by Microwave Processing", Advanced Materials Research, Vol. 585, pp. 87-91, 2012

Online since:

November 2012





37 FLOAT (Small).


43 SINK (Large).


64 SINK (Small).




[1] A novel, rapid and cost-effective technique for the synthesis of hollow silica granules with internal fibrous network has been established through microwave processing.

[2] Spherical hollow granules are observed to form in the temperature range of 1250-1400ºC.

[3] Granules obtained were amorphous and SEM revealed fibrous network within the granule.

[4] Gel ageing time of 2-4 weeks is preferable for maximum yield of floating spherical granules.

[5] Conventional firing of gels at identical conditions led to formation of porous granules unlike hollow ones obtained through microwave.