Assisted Sintering Via Sol–Gel Deposition in Low-Fired Ceramic Preforms
Sol-assisted sintering technology has already been explored for different materials. The idea consisted of increasing the resistance to fracture initiation through dispersion of nanometer-size particles in a secondary phase. A new method for sol-assisted sintering is proposed in this work. The main advantage is that this method does not interfere with the conformation processes, because it is applied afterwards. Low-fired ceramic preforms are first immersed in a fluid containing a precursor of a selected gel. Then, gelation of sols is induced inside the pores, and the ceramic piece is finally sintered. The presence of deposited nanoparticles increases the available surface area, easing the sintering process. In this paper, we demonstrate that this method produces improved density and enhanced mechanical properties in cast alumina pieces. These alumina bars are low fired at 600°, 700°, 800°, and 1200°C and infiltrated with a sol containing an alumina precursor. Gelation is then induced via pH changes, and the bars are finally heated at 1600°C for 2 h. Non-infiltrated control samples are also sintered under the same conditions for comparison. Surface area, density, and porosity measurements coherently agree with our conclusions. The effect of infiltration is also analyzed with SEM micrographs. It has also been demonstrated that the porosity of preforms to be infiltrated has a remarkable effect on the properties of the final sintered pieces, and that the standard deviation of the modulus of rupture is reduced for treated samples. This process is feasibly applicable to a range of different materials. One drawback, however, is the requirement that low-fired preforms have sufficient chemical and mechanical stability for infiltration.
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Document Type: Research Article
Affiliations: Instituto de Cerámica de Galicia, Universidad de Santiago de Compostela. S-15782 Spain
Publication date: 2005-08-01