纳米氧化铝粉体的绿色合成及其物相转变控制研究

以氯化铝、碳酸钠为原料,采用直接沉淀法,并于500～1,200℃煅烧,制备纳米Al2O3粉体。然后用TiO2、BaO对纳米Al2O3粉体掺杂,控制其物相转变过程。通过X射线衍射仪、差式扫描量热仪和透射电子显微镜分析纯净和掺杂后的纳米Al2O3的物相转变过程。结果表明,直接沉淀法所得水合Al2O3,经500℃煅烧后可转变为纳米活性Al2O3,粒径约为10 nm;纯净和掺杂Al2O3样品经1,200℃煅烧2 h后均为纳米粉体,其粒径为40～50 nm;在较高温度下,掺杂氧化钡对Al2O3的物相转变具有强烈抑制作用,粉体直至1,200℃仍未转变为结晶良好的α-Al2O3物相;而氧化钛则对其物相转变有显著促进作用,在1,000℃时粉体的主要物相即为α-Al2O3,1,100℃之后粉体已完全转变为α-Al2O3。

Green Synthesis of Nanocrystalline Alumina and Influence of Barium and Titanium Oxides on Its Phase Transformation

Nanometer Al2O3 powders were prepared in direct precipitation method with sodium carbonate and aluminum chloride as raw materials and subsquent calcination at 500~1,200℃.Then TiO2 and BaO were doped to control the phase transformation of nanometer alumina.X-ray diffractometer,differential scanning calorimeter and transmission electron microscopy were employed to analyze the phase transformation process of pure and doped nanometer alumina.It was indicated that boehmite obtained from the direct precipitation method was transformed to nanometer active alumina(γ-Al2O3) with the diameter of 10 nm.The pure and doped alumina were all still nanoparticles after calcined at 1,200 ℃ for 2 hours.Their grain sizes were 40~50 nm.The doping of BaO hindered the phase transformation of alumina since 800 ℃ and thereafter.As a result,alumina samples doped with BaO didn't transformed completely to α-Al2O3 even calcined at 1,200 ℃ for 2h.In contrast,the doping of TiO2 facilitated significantly the phase transformation of alumina since 900 ℃ and thereafter.Consequently,alumina samples doped with TiO2 were mainly composed of α-Al2O3 at 1,000 ℃ and transformed completely to α-Al2O3 at 1,100 ℃.