Scalable pressureless sintering of nanocrystalline alumina (Al₂O₃) ceramics is a challenging problem with great scientific and technological interest. This challenge was addressed in our recent works utilizing ultrafine α-Al₂O₃ nanopowders with exceptional sinterability combined with two-step sintering technique. Here the sintering mechanism and kinetic parameters (grain boundary diffusivity and its activation energy) were analyzed from constant heating-rate sintering experiments by three different sintering models and compared with existing sintering data in the literature. We found that the low-temperature sintering of 4.7 nm α-Al₂O₃ nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion, with reasonable activation energy of 4–5 eV that is smaller than that of coarse Al₂O₃ powders and enhanced diffusivity. However, unphysically small activation energy could be obtained if an inappropriate model was used. Lastly, successful two-step sintering was demonstrated under different heating rates. Our work illustrates that the exceptional sinterability of ultrafine α-Al₂O₃ nanopowders are most likely contributed by small size (short diffusion distance), large surface area (large sintering driving force) and good dispersity rather than new sintering mechanism, and highlights the importance of fast firing and the non-equilibrium nature for the low-temperature sintering of such nanopowders.

纳米晶氧化铝（Al ₂ O ₃）陶瓷的可缩放无压烧结是一个具有重大科学和技术兴趣的挑战性问题。在我们最近的工作中，利用具有卓越的可烧结性的超细α- Al ₂ O ₃纳米粉末与两步烧结技术相结合，解决了这一挑战。这里，通过三种不同的烧结模型，从恒定加热速率烧结实验中分析了烧结机理和动力学参数（晶界扩散率及其活化能），并与文献中现有的烧结数据进行了比较。我们发现，在低温度的4.7纳米的烧结α -Al ₂ ö ₃可以通过常规的烧结方法通过晶界扩散很好地解释纳米粉体，其合理的活化能为4-5 eV，小于粗Al ₂ O ₃粉末的活化能，并具有增强的扩散性。但是，如果使用了不合适的模型，则可以获得不自然的小活化能。最后，证明了在不同加热速率下成功的两步烧结。我们的工作表明，超细α- Al ₂ O ₃具有出色的烧结性 纳米粉末最有可能是由于其体积小（扩散距离短），表面积大（烧结驱动力大）和良好的分散性而不是新的烧结机理而引起的，并突出了快速焙烧和低温非平衡性质的重要性。纳米粉末的烧结。