Effects of CaCO3 content on the densification of aluminum nitride |
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| Affiliation: | 1. Institute for Technological Research of the State of São Paulo, Av. Prof. Almeida Prado, 532, São Paulo, SP 05508-901, Brazil;2. Polytechnic School of the University of São Paulo, Av. Prof. Mello Moraes, 2463, São Paulo, SP 05508-900, Brazil;3. National Institute of Advanced Industrial Science and Technology, Ceramics Research Institute, Moriyama-Ku, Nagoya 463-8560, Japan;1. Department of Inorganic Nonmetallic Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;2. Tianjin College, University of Science and Technology Beijing, Tianjin 301830, China;1. College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China;2. Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 211009, China;3. Nanjing Sanle Electronic Information Industry Group Co. Ltd., Pukou Economic Development Zone, Nanjing 211800, China;4. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;1. Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany;2. Materials Research Institute (IMFAA), Aalen University, Beethoven Str. 1, 73430, Aalen, Germany;3. Department of Materials Science and Engineering, Cornell University, Ithaca, NY, 14853, United States;4. Department of Materials Science and Engineering, Eski?ehir Technical University, 26555, Eskisehir, Turkey;1. College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014, China;2. Research Center of Magnetic and Electronic Materials, Zhejiang University of Technology, Hangzhou 310014, China |
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| Abstract: | The effect of adding up to 13.4 wt.% CaCO3 on the densification behavior of aluminium nitride (AlN) was investigated during pressureless sintering between 1100 and 2000 °C. The presence of second-phases, weight losses, Ca contents, and microstructures of sintered samples were correlated with the densification curves. Two microstructural aspects determined the densification of aluminum nitride with CaCO3: second-phase evolution path and formation of large pores. Additions of small amounts of CaCO3 caused the formation of higher melting point calcium aluminates (mainly CA2) that increased the temperature at which liquid-phase sintering process started, but once activated rapid densification was observed. For larger CaCO3 amounts, liquid-phase started to form at lower temperature, but the initial densification was slow, diminishing the advantage of lower C12A7 related eutectic temperature. Irrespective of the initial CaCO3 content, all second-phase evolution paths converged to CA phase above 1600 °C, suggesting that during sintering of AlN with CaO at high temperatures, a liquid phase with composition of CA phase is more stable than others compositions. The effect of this composition changing on densification is discussed. Large pores were formed in the sites originally occupied by large particles of CaCO3 and retarded the bulk densification in samples with high additive contents. |
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