Abstract The stability of aluminum oxyhydroxide (AlOOH, boehmite) to radiolysis and dehydration to alumina (γ-Al2O3) under vacuum was investigated using TGA followed by detailed, structural analysis with Raman, powder X-Ray Diffraction (pXRD), high energy X-Ray Diffraction (heXRD), 27Al Magic Angle Spinning Nuclear Magnetic Resonance (27Al MAS NMR) spectroscopy, Scanning Electron Microscopy (SEM), and nitrogen adsorption. Slight structural deviations from annealing temperatures prior to phase transformation are evident using these techniques. Radiolytic characterizations by room temperature Electron Paramagnetic Resonance (EPR) spectroscopy showed that while boehmite preheated to 300 °C under vacuum remained crystalline boehmite as determined by bulk structural characterizations, this phase produced the largest amount of EPR-detectable defects. A more dramatic mass loss of 16% was achieved by preheating boehmite to 400 °C under vacuum that resulted in a phase similar to γ-Al2O3, but enriched with residual OH groups. Complete dehydration to γ-Al2O3 was accomplished by preheating to 550 °C, which showed no indication of residual OH groups. These results demonstrate that the residual OH groups contribute to the hydrogen gas evolved in the radiolysis of boehmite.

中文翻译：

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勃姆石中放射性活性热转变相的鉴定

摘要 使用 TGA 研究了羟基氧化铝（AlOOH，勃姆石）在真空下辐射分解和脱水成氧化铝 (γ-Al2O3) 的稳定性，然后使用拉曼、粉末 X 射线衍射 (pXRD)、高能 X-射线衍射 (heXRD)、27Al 魔角自旋核磁共振 (27Al MAS NMR) 光谱、扫描电子显微镜 (SEM) 和氮吸附。使用这些技术可以明显看出相变之前的退火温度的轻微结构偏差。室温电子顺磁共振 (EPR) 光谱的辐射分解特征表明，虽然勃姆石在真空下预热至 300 °C，但仍为晶体勃姆石，如块体结构特征所确定，但该相产生了最大量的 EPR 可检测缺陷。通过在真空下将勃姆石预热至 400 °C，产生了类似于 γ-Al2O3 的相，但富含残留的 OH 基团，从而实现了 16% 的更显着的质量损失。通过预热至 550 °C，完全脱水为 γ-Al2O3，这表明没有残留的 OH 基团。这些结果表明残留的 OH 基团有助于在勃姆石的辐射分解中产生氢气。