Estudo de fitas nanocerâmicas de zircônia obtidas por tape casting

Abstract

Various processing techniques are based on the suspension of ceramics particles in an aqueous or non-aqueous media. One of these techniques is called tape casting, which need of a stabilized suspension with high concentration of solids and adequate rheological behavior, which can define if a process route is viable or not. Typical tape cast slurries are prepared by dispersion of a powder in an organic or nonorganic solvent, with a dispersant, followed by the addition of binders, plasticizers, and other additives. These slurries are cast through a so-called doctor blade over a flat carrier. In this study were shaped ceramic substrates of nanoparticulate zirconia stabilized with 3 mol% yttria by tape casting process in aqueous medium at thickness range of 100 to 150 micrometers which have great technological interest for applications electro-electronic. Tape casting slurries were prepared with two different compositions: 20% binder – 22% solvent e 25 % binder - 17% solvent (wt.%). A commercial acrylic emulsion served as binder. The stability of the yttria-stabilized zirconia slurries was analyzed by means of rheological characterization through viscosity curves. Both slurries showed a pseudoplastic behavior, which is desired for tape casting. After the tape casting process was made uniaxial pressing at different temperatures (40°C and 60°C) and time (5 and 10 minutes) in ceramic tapes for forming the laminates. Differential Thermal Analysis (DTA) and thermogravimetry (TGA) were performed to define the parameters for the sintering of the laminate. After sintering at 1500°C were performed X Ray Diffraction (XRD), density and porosity, flexural strength, microhardness and Scanning Electron Microscopy (SEM) to evaluate the properties of the obtained laminates. Laminated samples at lower press temperatures showed delamination between the interfaces of the ceramic tapes, however no significant influence on the mechanical behavior of these materials. The composition with higher binder content shows higher values of mechanical resistance due the greater amount of this component provide improvements in the laminate forming process