Nanocrystalline functional materials and nanocomposites synthesis through aerosol routes

This paper represents the results of the design of functional nanocrystalline powders and nanocomposites using chemical reactions in aerosols. The process involves ultrasonic aerosol formation (mist generators with the resonant frequencies of 800 kHz, 1.7 and 2.5 MHz) from precursor salt solutions and control over the aerosol decomposition in a high-temperature tubular flow reactor. During decomposition, the aerosol droplets undergo evaporation/drying, precipitation and thermolysis in a single-step process. Consequently, spherical, solid, agglomerate-free submicronic particles are obtained. The particle morphology, revealed as a composite structure consisting of primary crystallites smaller than 20 nm was analysed by several methods (XRD, DSC/DTA, SEM, TEM) and discussed in terms of precursor chemistry and process parameters. Following the initial attempts, a more detailed aspect of nanocrystalline particle synthesis was demonstrated for the case of nanocomposites based on ZnO-MeO (MeO=Bi Cr+), suitable for electronic applications, as well as an yttrium-aluminum base complex system, suitable for phosphorus applications. The results imply that parts of the material structure responsible for different functional behaviour appear through in situ aerosol synthesis by processes of intraparticle agglomeration, reaction and sintering in the last synthesis stage. Rad predstavlja rezultate sinteze nanokristalnih prahova i nanokompozita u kompleksnom sistemu na bazi itrijum-aluminijum oksida, odnosno, ZnO-MeO (MeO = Bi3+, Cr3+), hemijskim reakcijama u aerosolu. Proces ukljucuje ultra-zvucno formiranje aerosola (generator rezonantne frekvence 800 kHz, 1.7 i 2.5 MHz) na bazi prekursorskih rastvora odgovarajucih soli i kontrolu razlaganja aerosola u visokotemperaturnom protocnom cevnom reaktoru. Tokom razlaga-nja sukcesivni procesi isparavanja/susenja, precipitacije i termolize se odigra-vaju na nivou kapi i u jednom koraku. Kao rezultat, dobijaju se sfericne, guste, neaglomerisane, submikronske cestice zahtevanog sastava. Morfologija ovako formiranih cestica, analizirana razlicitim metodama (XRD DSC/DTA, SEM, TEM) ukazuje na njihov kompozitni karakter i postojanje substrukture u vidu agregata tzv. "primarnih cestica" velicine ispod 20 nm.