高热导率Si_3N_4陶瓷的高压合成及性能研究
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摘要
在高温高压条件下(HPHT,4～5 GPa,1430～1530℃),采用高压烧结技术,利用Y_2O_3、MgO作为烧结助剂,通过和不同质量配比的氮化硅(a-Si_3N_4,β-Si_3N_4)粉体复合,制备了具有高热导率和高致密性的Si3N4陶瓷。本实验采用X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱EDS、热导率测定仪、维氏硬度计对样品进行了分析和表征,研究了压强、烧结温度、保温时间对热导率和致密性的影响。结果表明:超高压条件有效降低了烧结温度,缩短了烧结时间。当烧结条件在5 GPa,1490℃,1 h时,其硬度为16. 5 GPa,此时β-Si_3N_4复合陶瓷的致密化最优,气孔率(0. 26%)和晶格缺陷显著改善。研究发现适当的延长烧结时间可以促进晶粒正常长大,同时产生较高的热导率,最高可达到64. 6W/(m·K)。
Using Y_2O_3 and MgO as sintering aids,the Si_3N_4 ceramics with high thermal conductivity and high compactness were successfully prepared from a-Si_3N_4 and β-Si_3N_4 powders at different mass ratios in the pressure range of 4. 0-5. 0 GPa and the temperature range of 1430-1530 ℃. The samples were analyzed and characterized by Energy dispersive spectrum( EDS),X-ray diffraction( XRD),Optical microscope and scanning electron microscopy( SEM) measurements. The results show that the sintering temperature and the sintering time are reduced effectively under the condition of ultra-high pressure. When the sintering time is 1 h under 5 GPa and 1490 ℃ condition,the hardness is 16. 5 GPa. The β-Si_3N_4 composite ceramic densification are optimal,the porosity and lattice defects significantly improve at the same time. It has been found that proper extension of sintering time can promote the normal growth of grain and produce a high thermal conductivity,and the highest thermal conductivity value can reach 64. 6 W/( m·K).
Using Y_2O_3 and MgO as sintering aids,the Si_3N_4 ceramics with high thermal conductivity and high compactness were successfully prepared from a-Si_3N_4 and β-Si_3N_4 powders at different mass ratios in the pressure range of 4. 0-5. 0 GPa and the temperature range of 1430-1530 ℃. The samples were analyzed and characterized by Energy dispersive spectrum( EDS),X-ray diffraction( XRD),Optical microscope and scanning electron microscopy( SEM) measurements. The results show that the sintering temperature and the sintering time are reduced effectively under the condition of ultra-high pressure. When the sintering time is 1 h under 5 GPa and 1490 ℃ condition,the hardness is 16. 5 GPa. The β-Si_3N_4 composite ceramic densification are optimal,the porosity and lattice defects significantly improve at the same time. It has been found that proper extension of sintering time can promote the normal growth of grain and produce a high thermal conductivity,and the highest thermal conductivity value can reach 64. 6 W/( m·K).
引文
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