Revista Română de Materiale / Romanian Journal of Materials 2011, 41 (3), 255 - 261 255 INFLUENŢA CONDIŢIILOR DE PREPARARE ASUPRA CARACTERISTICILOR NANOMETRICE ALE PULBERILOR DE ZIRCONĂ ŞI ALUMINĂ INFLUENCE OF PREPARATION CONDITIONS ON NANOMETRIC CHARACTERISTICS OF ZIRCONIA AND ALUMINA POWDERS ŞTEFANIA STOLERIU ∗ , ECATERINA ANDRONESCU, ALEXANDRA LUCIA CARABĂŢ, BOGDAN ŞTEFAN VASILE Universitatea Politehnica Bucureşti, Str. G. Polizu, nr. 1, 011061, sect. 1, Bucureşti, România Scopul lucrării îl reprezintă sinteza şi caracteri- zarea unor pulberi ceramice de zirconă total stabilizată cu Y 2 O 3 (8%) şi de alumină, obţinute prin metoda (co)- precipitării, din cloruri metalice corespunzătoare. Ca solvenţi s-au folosit apa şi etanolul, iar pentru precipitare, pH-ul soluţiei a fost variat, prin folosirea de amoniac. Valorile de pH considerate au fost 7,5, 10,5 şi 12,5. Precipitatele obţinute au fost uscate la 80°C, timp de 24 de ore şi ulterior calcinate la 350°C, timp de 2 ore. Pulberile au fost evaluate prin analize termice diferenţiale, prin difracţie de raze X, prin microscopie electronică de baleaj şi transmisie. În cazul pulberilor de 8YSZ, difractogramele de raze X atestă prezenţa ZrO 2 tetragonal, iar pentru pulberea de alumină, pe lângă γ-Al 2 O 3 alumină se decelează şi δ-Al 2 O 3 . Din imaginile TEM se observă că granulele de ZrO 2 tetragonal prezintă o morfologie aproape sferică, particulele având dimensiuni cuprinse între 5 nm şi 12 nm. De asemenea s-a observat că cea mai bună condiţie de obţinere a nanopulberilor a fost, utilizarea apei ca solvent şi asigurarea unui pH bazic de 12,5. The paper’s aim was to prepare and characterize ceramic powders of fully stabilized zirconia (with 8 mol% yttria), and alumina, obtained through co-precipitation starting from the corresponding chlorides. Co- precipitation was taken using water or ethanol as a solvent and considering the pH influence (7.5, 10.5 and 12.5 obtained by using ammonia solution) upon precipitation was analyzed. The obtained powders were dried at 80 °C for 24 h and afterwards calcinated at 350°C for 2 hours. The powders were evaluated through thermal analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The XRD results show that 8YSZ calcinated powders is a tetragonal ZrO 2 and, concerning alumina powder, besides γ-Al 2 O 3 , δ-Al 2 O 3 was identified. The TEM examination shows that the tetragonal ZrO 2 has a spherical like morphology with a size ranging from 5 nm to 12 nm. Also, it was observed that the best condition for nanopowders obtaining was using as solvent water and a pH value of 12.5. Keywords: zirconia, alumina, nanopowders, (co-)precipitation 1. Introduction In recent years, more and more attention has been attracted by nanotechnology, which produces materials with sizes in the range of 1-100 nm. The new trend is developing nanotechnologies towards achieving cheap experimental procedures, which allow obtaining reproducible results. [1]. Both zirconia and alumina are important for a wide range of applications, starting with ceramic and ending with the catalysts [2,3]. A convenient method for obtaining nanomaterials is the hydrocompounds calcination, which are obtained by hydrolysis of salts in different liquid media. It has been shown that the final properties of zirconia and alumina powders depend on certain chemical parameters like: the precursor salts, precipitation environment, etc. [2]. These parameters act on the tendency of agglomeration of primary particles during the formation of new structural networks [2]. There are many methods for obtaining nanopowders, like: sol-gel, hydrothermal, combustion, precipitation, etc [4]. Among these methods, the cheapest one proves to be the precipitation. This method allows obtaining pure fine particles, for both, unary as well as multicomponent oxide systems. [5]. Moreover, if during the precipitation, pH environment, the temperature or reaction time is controlled, the ceramic particles might have some predefined size [6]. The present study aims to obtain fully stabilized zirconia and alumina nanopowders by means of (co)-precipitation method, varying the pH and the precipitation environment, analyzing in this way the influence of these two parameters on nanopowders characteristics. 2. Experimental procedure Fully stabilized zirconia (with 8 mol% yttria), and alumina powder was obtained through (co-) precipitation method starting from the correspon- ∗ Autor corespondent/Corresponding author, Tel. +40214023997, e-mail: s_stoleriu@yahoo.com