γ-AlOOH纳米棒的水热合成与形貌调控

γ-AlOOH作为液相法合成γ-Al₂O₃的前驱体,其形貌与最终产物的性能密切相关。 本文采用水热法合成γ-AlOOH纳米棒,通过改变Al³⁺浓度和沉淀剂的种类调控γ-AlOOH纳米棒的长径比,利用X射线衍射仪(XRD)和透射电子显微镜(TEM)表征产物的晶体结构和形貌。 结果表明,随Al³⁺浓度增大可得到长径比在5.9~8.0的γ-AlOOH纳米棒,而改变沉淀剂的种类可进一步将长径比增大到8.0~10.0。 通过对产物结晶过程的分析,发现增大Al³⁺浓度和增强沉淀剂碱性均可以促进铝离子与羟基的配合。 提高反应体系中Al(OH)₃浓度,有利于γ-AlOOH晶粒的成核,促进了晶核之间的定向接触,从而提高了纳米棒的长径比。 长径比为10.0的γ-AlOOH纳米棒烧结所得纳米γ-Al₂O₃改性变压器油(体积分数为0.1%)的正冲击击穿强度较纯油提高9.9%.

Hydrothermal Synthesis and Morphological Control of γ-AlOOH Nanorods

The morphology of γ-AlOOH, as a precursor to γ-Al₂O₃ in the liquid-phase synthesis system, is closely related with the performance of final product. In this paper, γ-AlOOH nanorods were synthesized by hydrothermal method. The aspect ratio of γ-AlOOH nanorods was modified by changing the concentration of Al³⁺ and the type of base. The crystal structure and morphology of the as-synthesized products were characterized by X-ray diffraction(XRD) and transmission electron microscopy(TEM). The results show that the aspect ratio of γ-AlOOH nanorods can be tuned in the range of 5.9~8.0 with the increase of concentration of Al³⁺, and further adjusted into 8.0~10.0 by changing the type of base. Based on the analysis of the crystallization process, it is believed that the complexation reaction between aluminum ions and hydroxyl groups is accelerated by increasing the concentration of Al³⁺ and the base strength of precipitants. The increase of the content of Al(OH)₃ is beneficial to the formation of γ-AlOOH nuclei and facilitates the oriented attachment of nuclei, leading to a significant increase of aspect ratio of nanorods. The positive impact breakdown strength of transformer oil modified by nano γ-Al₂O₃(volume fraction of 0.1%) obtained by sintering γ-AlOOH nanorods with a length to diameter ratio of 10.0 is 9.9% higher than that of pure oil.