No abstract

The direct solid analysis of ceramic powders can be carried out by inductively coupled plasma atomic emission spectrometry (ICP-AES) using slurry sample introduction. However, a highly stable suspension is needed in order to obtain a representative aerosol for introduction into the ICP. In this work, the importance of the effect of the rheology and the stability of the ceramic suspensions on the analytical results provided by slurry nebulization ICP-AES is demonstrated. The basic concepts involved in the stabilization and homogenization of ceramic slurries are discussed. A general overview of the stabilizing mechanisms (electrostatic, steric and electrosteric) and the role of the different stabilizing additives, and the most adequate use of them, is described. Alumina (A1,03) slurries, as a case study, are discussed. The rheological parameters, such as zeta potential, viscosity and sedimentation have been studied by changing the pH of the slurry and by introducing different dispersing additives (Dolapix PC-33, Darvan-7, Darvan-C, sodium hexametaphosphate, glycerol plus Kodak photoflow, Triton X-1 00 and Produkt PKV-5088). Their effect on stability is discussed, as well as the relationship between the stability of the slurry and the intensity and precision of the measurements provided by ICP-AES. It is clearly demonstrated that higher intensities and lower relative standard deviation values are obtained for a well-dispersed, stable slurry.

The microwave-assisted acid dissolution of sintered bodies of ties, high-temperature stability, high-temperature strength, 28 structural and electronic advanced ceramic materials was wear resistance, corrosion/oxidation resistance, chemical systematically evaluated. These materials included zirconiainertness, or electrical, optical and/or magnetic properties.1 based ceramics, such as m-ZrO 2 (a non-stabilized monoclinic These materials are used in structural applications (machine zirconia), Ca-PSZ and Mg-PSZ (two partially stabilized and cutting tools, wear components, heat exchangers, aerozirconias), Y-FSZ (a fully stabilized zirconia) and Ce-TZP, space components, automotive engine components such as Yb-TZP and Y-TZP/Ce (three tetragonal polycrystalline turbocharge rotors and roller cam followers, power generation zirconias); alumina-based ceramics, such as Al 2 O 3 , mullite and components, biomedical implants, processing equipment used spinel; ceria-based ceramics, such as CeO 2 -Gd 2 O 3 (cubic ceria for fabricating a variety of polymer, metal and ceramic parts) gadolinia); titania-based ceramics, such as TiO 2

This work reports on the synthesis of mullite powders by a suspension combustion process. Aluminum nitrate, as a source of Al, and a colloidal silica suspension, as a source of Si, are used as reagents, and urea serves as the fuel. This colloidal suspension allows a complete mixing of the reactants, thus promoting a core-shell reaction to produce the mullite. The powders obtained need to be treated at a high temperature to form the mullite. However, when ammonium nitrate is also added as a combustion aid, the mullite phase is directly obtained without any further treatment. A chemical reaction involving all these compounds is proposed, and the thermodynamic parameters are calculated in order to predict the temperature reached during the combustion process. The addition of ammonium nitrate reduces the temperature of the reaction by ca. 1501C. Once the conditions for the combustion reaction are optimized, the Al/Si ratio is modified in an attempt to obtain monophasic mullite. J ournal

Abstract