Abstract This work presents a study to obtain α-Al 2 O 3 from thermal treatment of the precursor α - Al ( OH ) 3 (bayerite). The precursor was prepared from a cathodic electrosynthesis employing direct current (DC) and alternating current (AC) electrochemical techniques and using an aluminium solution prepared with scrap aluminium cans. Characterization techniques including X-ray diffraction (XDR), scanning electron microscopy (SEM) and thermogravimetric analysis (TG) were used to analyse the thermal behaviour, phase transformation, morphology and particle size of the products obtained. The range of potentials for electrodeposition was between −2.0 and 2.4 V with both DC and AC techniques. The presence of crystalline bayerite in the deposits obtained during all DC and AC experiments was observed, although a species of aluminium oxide (Al 2.427 O 3.64 ) with AC was also identified. The surface morphology of the deposit with DC presented a compact uniform film, whereas with AC a granular form morphology with compact grains in the order of 1–3 µm was evident. In addition, the formation of an amorphous and low crystallinity bayerite precipitate was obtained from the solution, which presented a surface morphology of non-uniform fine grains and agglomerates. The thermal behaviour (TG) indicates three regions of change in the phase, which were verified via the thermal treatment; a transition of bayerite to η-Al 2 O 3 in a temperature range between 290 and 300 °C and subsequently to α-Al 2 O 3 at a temperature of 1100 °C was determined. The α-Al2O3 presents high purity, a surface morphology with fine grains and agglomerates in the order of 1–10 µm and an appreciable porosity.

中文翻译：

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用于从铝废料中获得 α-氧化铝的前体相的电化学制备

摘要 这项工作提出了通过热处理前体 α - Al ( OH ) 3 （三羟铝石）获得 α-Al 2 O 3 的研究。前体是通过阴极电合成制备的，采用直流 (DC) 和交流 (AC) 电化学技术，并使用用废铝罐制备的铝溶液。使用包括 X 射线衍射 (XDR)、扫描电子显微镜 (SEM) 和热重分析 (TG) 在内的表征技术来分析所得产品的热行为、相变、形态和粒度。使用直流和交流技术，电沉积的电位范围在 -2.0 和 2.4 V 之间。在所有 DC 和 AC 实验期间获得的沉积物中都观察到了结晶三羟铝石的存在，尽管有一种氧化铝 (Al 2.427 O 3. 64 ) 与 AC 也被确定。DC 沉积物的表面形态呈现出致密均匀的薄膜，而 AC 沉积物的表面形态是明显的，具有 1-3 µm 数量级的致密晶粒。此外，从溶液中形成了无定形和低结晶度的三羟铝石沉淀物，其表面形态为不均匀的细晶粒和团聚体。热行为 (TG) 表示相中的三个变化区域，这些区域通过热处理得到验证；测定了三羟铝石在 290 到 300 °C 之间的温度范围内转变为 η-Al 2 O 3 以及随后在 1100 °C 的温度下转变为 α-Al 2 O 3 的转变。α-Al2O3 具有高纯度、具有 1-10 µm 数量级的细晶粒和团聚体的表面形态以及可观的孔隙率。