Deng Bing, Advincula Paul A, Luong Duy Xuan, Zhou Jingan, Zhang Boyu, Wang Zhe, McHugh Emily A, Chen Jinhang, Carter Robert A, Kittrell Carter, Lou Jun, Zhao Yuji, Yakobson Boris I, Zhao Yufeng, Tour James M
Department of Chemistry, Rice University, Houston, TX, 77005, USA.
Department of Electrical and Computer Engineering, Rice University, Houston, TX, 77005, USA.
Nat Commun. 2022 Aug 26;13(1):5027. doi: 10.1038/s41467-022-32622-4.
High-surface-area α-AlO nanoparticles are used in high-strength ceramics and stable catalyst supports. The production of α-AlO by phase transformation from γ-AlO is hampered by a high activation energy barrier, which usually requires extended high-temperature annealing (1500 K, > 10 h) and suffers from aggregation. Here, we report the synthesis of dehydrated α-AlO nanoparticles (phase purity ~100%, particle size ~23 nm, surface area ~65 m g) by a pulsed direct current Joule heating of γ-AlO. The phase transformation is completed at a reduced bulk temperature and duration (573 K, < 1 s) via an intermediate δ'-AlO phase. Numerical simulations reveal the resistive hotspot-induced local heating in the pulsed current process enables the rapid transformation. Theoretical calculations show the topotactic transition (from γ- to δ'- to α-AlO) is driven by their surface energy differences. The α-AlO nanoparticles are sintered to nanograined ceramics with hardness superior to commercial alumina and approaching that of sapphire.
高比表面积的α-AlO纳米颗粒用于高强度陶瓷和稳定的催化剂载体。由γ-AlO通过相变制备α-AlO受到高活化能垒的阻碍，这通常需要长时间的高温退火（1500 K，>10 h），并且会发生团聚。在此，我们报道了通过对γ-AlO进行脉冲直流焦耳加热来合成脱水α-AlO纳米颗粒（相纯度100%，粒径23 nm，表面积65 m²/g）。相变通过中间的δ'-AlO相在降低的本体温度和持续时间（~573 K，<1 s）下完成。数值模拟表明，脉冲电流过程中电阻热点引起的局部加热使得能够快速转变。理论计算表明，拓扑转变（从γ-到δ'-到α-AlO）是由它们的表面能差异驱动的。α-AlO纳米颗粒被烧结成纳米晶陶瓷，其硬度优于商用氧化铝，接近蓝宝石的硬度。
