resumo
Titania-based ceramics with adjustable anatase-rutile fractions were obtained by milling of anatase, quartz and corundum precursors, uniaxial pressing and firing at 1100 degrees C. The influence of silica and alumina, combined with milling time and compaction pressure, was studied by design of experiments. The L9 orthogonal array with a three-level noise factor was employed. Firing of pure titania at 1100 degrees C yielded complete anatase to rutile transformation (ART), whereas stabilized samples show that an optimum amount of 9% silica and 33% alumina reduces phase transformation to only about 5 wt% rutile. An extended correlation matrix combined with analysis of variance (ANOVA) was applied to assess the combined effects of quartz, alumina, milling time and uniaxial compressing pressure on relative density, and anatase to rutile transformation. Results show absence of ART after milling, and controlled partial conversion of anatase to rutile after firing. Very good fitting was obtained by multivariate analysis on considering first and second order terms for dependence on silica contents and interactions between silica and each of the remaining factors, including milling time. This empirical dependence could be interpreted on a sound physicochemical basis, allowing the prediction of suitable compositions and processing conditions to obtain rutile-free samples by conventional ceramic processing, and to design ceramic samples with controlled fractions of anatase and rutile.
palavras-chave
PHOTOCATALYTIC ACTIVITY; PHASE-TRANSFORMATION; THERMAL-STABILITY; POWDER MIXTURES; TIO2; DENSIFICATION; NANOPARTICLES; KINETICS; TEMPERATURE; INCLUSIONS
categoria
Materials Science
autores
Feltrin, J; De Noni, A; Hotza, D; Frade, JR
nossos autores
Jorge Ribeiro Frade
Professor(a) Jubilado(a)agradecimentos
This work was supported by Capes (Coordination of Improvement of Higher Education Personnel) (Brazil) and CNPq (National Council for Scientific and Technological Development) (Brasil) and FCT (Foundation for Science and Technology)(Portugal), under projects PTDC/CTM-ENE/2942/2014 and UID/CTM/50011/2013UID/CTM/50011/2013, financed by COMPETE 2020 Programme and National Funds through the FCT/MECFCT/MEC and co-financed by FEDER (European Regional Development Fund) under the PT2020 Partnership Agreement.