钛酸盐纳米管的水热合成及晶型研究

Hydrothermal Synthesis and Crystal Structure of Titanate Nanotubular

以锐钛矿相为主的氧化钛粉体为原料,在强碱性条件下采用水热合成法制备出外径约10nm的钛酸盐纳米管。用TEM、SEM、XRD和EDS等对不同工艺条件下获得的产物进行了表征,对其热稳定性进行了测试。研究结果表明,纳米管是在NaOH水热处理过程中形成的,而不是在清洗和浸泡过程中形成的。通过控制浸泡液的pH值,可以获得组分为NaxH2-xTi3O7或NaxH2-xTi3O7与TiO2混合物纳米管。纳米管具有较好的热稳定性,在400℃热处理后,其晶型与热处理前无明显变化,500℃热处理后,仍保持纳米管状结构。随着热处理温度的提高,锐钛矿相逐渐向金红石相转变,同时金红石型TiO2和Na2Ti3O7反应生成新的晶相Na2Ti6O13,至800℃时主要以Na2Ti6O13晶体存在,同时有少量金红石型TiO2。

Nanotubular titanates with an external diameter around 10 nm were prepared by hydrothermal processing using commercial anatase-type TiO2 powder as raw material in the NaOH（aq） solution. The products obtained at different conditions were characterized by means of TEM, SEM, XRD, EDS and the thermal stability of the products was tested. The results show that nanotubular titanate formed during hydrothermal treatment rather than in washing or immersing processes. NaxH2-xTi3O7 or mixtures of NaxH2-xTi3O7 and TiO2 nanotubes can be obtained by control the pH values of immersing solutions. The nanotubular titanates are stable with original symmetry crystal structure till 400 ℃ and keeps nanotubular under 500 ℃. At higher heat-treatment temperatures, the anatase structure will change into rutile structure and a new Na2Ti6O13 crystal obtained by the reaction of rutile-type TiO2 with Na2Ti3O7. At 800 ℃, the main crystal Na2Ti6O13 and small quantity of rutile TiO2 is found in the sample.