Nanocomposites and nanomaterials

The study of ultrasonic treatment influence on the properties of ZnO-MoO3 system
Sachuk O.V., Diyuk O.A., Zazhigalov V.A.
Department of Heterogeneous Catalytic Oxidation Processes, Institute for Sorption and Problems of Endoecology of the NAS of Ukraine. General Naumov str., 13, Kyiv-03164, Ukraine. 
E-mail: Slena951@ukr.net 

It is known that compositions based on zinc and molybdenum oxides (zinc molybdates) are widely use in electronic, as materials for cryogenic phonon-scintillation/bolometric detectors, UHF-dielectric and photoelectric devices, photocatalysts and heterogeneous catalysts. The traditional methods of zinc molybdates preparation (solid phase synthesis, precipitation, hydrothermal synthesis etc.) have some drawbacks and the creation of new methods preparation of these compounds is very actual. It is found that ultrasonic treatment (UST) allows to acceleration of the chemical reactions, obtaining the highdispersive, homogeneous and chemical pure mixtures of solid particles in solutions at room temperature. 
In this communication the results sonochemical treatment on ZnO-MoO3 properties reported.The ultrasonic treatment of ZnO-MoO3 system (Zn/Mo=1:1) was carried out in water solution during 1 hour.
The XRD data show that the UST of Zn/Mo composite leads to change in the crystalline modification of the initial oxides and chemical reactions between oxides with the formation of suboxide phase molybdenum Mo8O23 and α -ZnMoO4 triclinic modification, respectively. The calculation of crystallite size by Scherer equation shows their decrease after sonomodification from 56 to 33 nm. Investigation of the samples by IR- spectroscopy shows that ultrasonic activation is accompanied by a shift of the absorption bands terminal Мо=O bond from 998 to 950 cm-1, linear bridging Mo–O–Mo bond from 863 to 897 cm-1, Zn-O bond from 490 to 531 cm-1 and formation of angular Mo-O-Mo bridging bond in Mo8O23. According to results, obtained by BET and BJH methods the ultrasonic effect is not accompanied by porous structure change (main pore volume is 88 nm) and leads to an increase of macropores volume only.  The study of catalytic properties of sonotreated Zn/Mo = 1:1 composite showed their better catalytic activity in ethanol selective oxidation compared to initial mixture. It is found that the main product of this reaction is acetic aldehyde with a maximum yield of 98 %, which can be achieved at 190°C.