Unveiling exceptional sinterability of ultrafine a-Al2O_(3) nanopowders  

作　　者：Hongbing Yang Lu Li Yuanyuan Li Bing Shen Yueming Kang Libin Zhao Jiajie Li Yanhao Dong Jiangong Li 

机构地区：[1]Institute of Materials Science and Engineering and MOE Key Laboratory for Special Functional Materials and Structure Design,Lanzhou University,Lanzhou,730000,China [2]Department of Nuclear Science and Engineering,Massachusetts Institute of Technology,Cambridge,MA,02139,USA

出　　处：《Journal of Materiomics》2021年第4期837-844,共8页无机材料学学报（英文）

基　　金：the support by the National Natural Science Foundation of China(No.51551201 and 51772137);the Fundamental Research Funds for the Central Universities(No.lzujbky-2019-sp03).

摘　　要：Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafine a-Al2O_(3) 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 lowtemperature sintering of 4.7 nm a-Al2O_(3) nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion,with reasonable activation energy of 4e5 eV that is smaller than that of coarse Al2O_(3) 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 a-Al2O_(3) 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.

关 键 词：Nanocrystalline materials SINTERING Alumina(a-Al2O_(3)) Diffusion Activation energy 

分 类 号：TB383[一般工业技术—材料科学与工程]