Suppression of grain growth in sub-micrometer alumina via two-step sintering method |
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| Authors: | Z. Razavi Hesabi M. Haghighatzadeh Mehdi Mazaheri Dusan Galusek S.K. Sadrnezhaad |
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| Affiliation: | 1. Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran, Iran;2. Vitrum Laugaricio-Joint Glass Centre of IIC SAS, TnU AD and RONA, j.s.c., Trencin, Slovak Republic;3. Center of Excellence for Production of Advanced Materials, Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Tehran, Iran;1. Université de Toulouse, Institut Carnot CIRIMAT, UMR 5085 CNRS – Université Toulouse III Paul-Sabatier – INPT, 118 route de Narbonne, 31062 Toulouse Cedex 9, France;2. CEMES, CNRS UPR 8011 and Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, France;3. CNRS, Institut Carnot CIRIMAT, 118 route de Narbonne, 31602 Toulouse Cedex 9, France;1. Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38050 Trento, Italy;2. INSTM Research Unit, Via G. Giusti 9, 50121 Firenze, Italy;1. Department of Glass and Ceramics, University of Chemistry and Technology, Prague (UCT Prague), Technická 5, 166 28 Prague 6, Czech Republic;2. Department of Organic Technology, University of Chemistry and Technology, Prague (UCT Prague), Technická 5, 166 28 Prague 6, Czech Republic;1. Department of Glass and Ceramics, University of Chemistry and Technology, Prague (UCT Prague), Technická 5, 166 28, Prague 6, Czech Republic;2. Department of Inorganic Technology, University of Chemistry and Technology, Prague (UCT Prague), Technická 5, 166 28, Prague 6, Czech Republic;1. Department of Materials, Loughborough University, Loughborough LE11 3TU, UK;2. Queen Mary, University of London, London E1 4NS, UK;3. School of Metallurgy and Materials, College of Engineering and Physical Sciences, University of Birmingham, Edgbaston, Birmingham B12 2TT, UK;4. Dstl, Porton Down, Salisbury SP4 0JQ, UK;5. ONRG, Middlesex HA4 7HB, UK |
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| Abstract: | Two-step sintering (TSS) was applied to suppress the accelerated grain growth of sub-micron (～150 nm) alumina powder. The application of an optimum TSS regime led to a remarkable decrease of grain size down to ～500 nm; while the grain size of the full-dense structures produced by conventional sintering ranged between 1 and 2 μm. To find how important the temperatures at sintering steps might be, several TSS regimes were conducted. The results showed that the temperatures at both sintering steps play vital roles in densification and grain growth of the alumina compacts. Based on the results, the optimum regime consisted of heating the green bodies up to 1250 °C (first step) and then holding at 1150 °C for more than 60 h (second step). This yielded the finest microstructure with no deterioration of the densification. Heating at 1300 °C (first step) and then at 1200 °C (second step) was not a successful procedure. Lowering the temperature of the second step down to 1100 °C resulted in exhaustion of the densification at 88% -theoretical density. A nearly full-dense structure with an average grain size of 850 nm was obtained when the temperature of the second step was increased to 1150 °C. Empirical results show that not only the first step temperature has to be high enough to reach a structure containing unstable pores, but the second sintering temperature must also be high enough to activate the densification mechanism without grain growth. This means that a considerable densification at the first step does not imply enough second-step densification. |
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