Effects of ultrasonic irradiation on crystallization and structural properties of EMT-type zeolite nanocrystals Eng-Poh Ng a, * , Hussein Awala b , Jia-Pei Ghoy a , Aur  elie Vicente b , Tau Chuan Ling c , Yun Hau Ng d , Svetlana Mintova b , Farook Adam a, * a School of Chemical Sciences, Universiti Sains Malaysia, USM, 11800 Penang, Malaysia b Laboratoire Catalyse & Spectrochimie, CNRS-ENSICAEN, Universit e de Caen, France c Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia d School of Chemical Engineering, The University of New South Wales, Sydney, Australia highlights graphical abstract  Nanosized EMT zeolites are formed from rice husk ash under ultrasonic irradiation.  The effects of ultrasonic waves in nanosized EMT zeolite synthesis are studied.  Ultrasound induces rapid crystal growth and produces high zeolite yield.  Smaller zeolite nanocrystals with high crystallinity and large defect sites are obtained.  Improved surface hydrophilicity of crystals is beneficial for water sorp- tion applications. article info Article history: Received 20 October 2014 Received in revised form 11 February 2015 Accepted 27 March 2015 Available online 10 April 2015 Keywords: Microporous materials Crystallization Crystal growth Ultrasonic techniques abstract Synthesis of EMT zeolite nanocrystals from rice husk ash biomass (RHA) under continuous ultrasonic irradiation is reported. The aging, nucleation and crystallization stages of EMT zeolite in the system were monitored at ambient temperature, and compared with the conventional hydrothermal method. It was found that ultrasonic wave induced rapid crystal growth of the nanosized EMT zeolite. Complete crys- tallization of EMT nanocrystals was achieved within 24 h which was much faster than conventional hydrothermal synthesis (36 h). Furthermore, XRD and TEM analyses revealed that more nuclei were formed during the nucleation stage, allowing the preparation of smaller zeolite nanocrystals with high crystallinity. The results also showed that sonocrystallization produced EMT zeolite with high yield (ca. 80%). The ultrasound-prepared EMT nanocrystals were also found to have high porosity and high hy- drophilicity, making the material promising for water sorption applications including vapor sensing, heat pump and adsorption technologies. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Zeolites are aluminosilicate microporous solids with well- defined channels and cavities. These materials are commonly * Corresponding authors. E-mail addresses: epng@usm.my (E.-P. Ng), farook@usm.my (F. Adam). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys http://dx.doi.org/10.1016/j.matchemphys.2015.03.047 0254-0584/© 2015 Elsevier B.V. All rights reserved. Materials Chemistry and Physics 159 (2015) 38e45