2022年5月23日 · In this work, the structural stability of γ-alumina (γ-Al2O3) was investigated by a combination of XRD and high-resoln. solid-state 27Al MAS NMR at an ultrahigh magnetic field of 21.1 T. XRD measurements show that γ-Al2O3 undergoes a phase transition to θ-Al2O3 during calcination at 1000 °C for 10 h.

2020年7月17日 · We report a strategy for the observation and determination of oxygen structure of γ-Al2O3 by using two-dimensional (2D) solid-state NMR spectroscopy at high field. 2D 17O double-quantum single...

2008年5月30日 · In this work, the structural stability of γ-alumina (γ-Al 2 O 3) was investigated by a combination of XRD and high-resolution solid-state 27 Al MAS NMR at an ultrahigh magnetic field of 21.1 T. XRD measurements show that γ-Al 2 O 3 undergoes a phase transition to θ-Al 2 O 3 during calcination at 1000 °C for 10 h.

2022年3月31日 · This work combines the development of well-defined, needle-shaped γ-Al 2 O 3 nanocrystals having a high relative fraction of edge sites with the use of state-of-the-art solid-state NMR to significantly deepen our understanding of this specific signal.

Using our detailed NMR approach, we undertook a combined qualitative and quantitative analysis of the hydroxyl networks in Al 2 O 3-300, Al 2 O 3-500 and Al 2 O 3-700, based principally on comparison of their 1 H-1 H DQSQ MAS NMR spectra, as well as best-fit simulations of their 1 H MAS NMR spectra.

2022年6月8日 · 本工作中，作者首先通过高场27Al NMR定量研究了γ-Al2O3和Al2O3-NS的铝物种分布，阐明了铝物种在脱水前以及不同温度脱水前后的动态转变过程：即五配位铝可以由六配位铝脱水或四配位铝水合形成。 尽管γ-Al2O3中五配位铝 (35 ppm)含量的变化并不明显，但脱水前后谱峰线型的变化说明在不同脱水状态下的五配位Al是不同的。 图2. 超高场 (35.2T) 27Al-27Al DQ NMR揭示Al-O-Al连接方式. 超高场27Al NMR可显著提高27Al核的检测灵敏度和分辨率。

2014年9月1日 · Two highly porous γ-aluminas, a commercial catalyst obtained from the calcination of boehmite and a highly mesoporous product obtained from amorphous aluminum (oxy)hydroxide via a sol–gel-based process were investigated by 27 Al nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), and atomic pair distribution function ...

2018年6月1日 · In this work, the complex (sub-)surface oxygen species on surface-selectively labelled γ-Al 2 O 3 were probed by 17 O dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS). Direct 17 O MAS and indirect 1 H– 17 O cross-polarization (CP)/MAS DNP experiments enable observation of the (sub-)surface bare oxygen species and ...

γ-Al2O3是工业催化反应催化剂中最广泛应用的基底材料，对γ-Al2O3结构的理解对调控物理化学性质仍然有较大难度，中国科学院武汉物理与数学研究所徐君等报道了一种通过在高磁场中进行二维NMR测试，并通过35.2 T高磁场中进行二维17O双量子-单量子同核相关NMR实验，对体相和界面上的不同氧原子进行表征。 此外，通过1H-17O异核二维NMR实验对界面羟基、亚界面上的氧物种进行区分，实现了γ-Al2O3中氧物种的分布情况进行分析。 本文要点. （1） 通过对1H-17O相 …

2019年6月13日 · In contrast to 27 Al NMR spectroscopy, 17 O NMR spectroscopy showed that the Al 3+ vacancies are located at octahedral positions, in accordance with DFT predictions. This structure is by far the most stable structure of the iron analogue γ-Fe 2 O 3 and also seems to be the structure of δ-Al 2 O 3 .