Enhanced thermal conductivity in Si3N4 ceramic by addition of a small amount of carbon |
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| Affiliation: | 1. Engineering Ceramics Research Group, Korea Institute of Materials Science, Changwon, Gyeongnam, 51508, Republic of Korea;2. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai, 200050, China;1. Key Laboratory for Liquid-solid Structural Evolution & Processing of Materials of Ministry of Education School, Shandong University, Jinan, 250061, PR China;2. Key Laboratory of Special Functional Aggregated Materials, Ministry of Education, Shandong University, Jinan, 250061, PR China;3. Key Laboratory of Colloid and Interface Chemistry, School of Chemistry and Chemical Engineering, Ministry of Education, Shandong University, Jinan, 250100, PR China |
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| Abstract: | In order to fabricate Si3N4 ceramic with enhanced thermal conductivity, 93 mol%α-Si3N4-2 mol%Yb2O3-5 mol%MgO powder mixture was doped with 5 mol% carbon, and sintered firstly at 1500 °C for 8 h and subsequently at 1900 °C for 12 h under 1 MPa nitrogen pressure. During the first-step sintering, the carbothermal reduction process significantly reduced the oxygen content and increased the N/O ratio of intergranular secondary phase, resulting in the precipitation of Yb2Si4O7N2 crystalline phase, higher β-Si3N4 content and larger rod-like β-Si3N4 grains in the semi-finished Si3N4 sample. After the second-step sintering, the final dense Si3N4 product acquired coarser elongated grains, lower lattice oxygen content, tighter Si3N4-Si3N4 interfaces and more devitrified intergranular phase due to the further carbothermal reduction of oxynitride secondary phase. Consequently, the addition of carbon enabled Si3N4 ceramic to gain a significant increase of ∼25.5% in thermal conductivity from 102 to 128 W∙m−1 K−1. |
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| Keywords: | Silicon nitride Carbon Microstructure Thermal conductivity |
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