Rao Pratap M, Zheng Xiaolin
Department of Mechanical Engineering, Stanford University, Stanford, California 94305, USA.
Nano Lett. 2009 Aug;9(8):3001-6. doi: 10.1021/nl901426t.
This paper describes a simple and yet rapid flame synthesis method to produce one-dimensional metal oxide nanostructures by directly oxidizing metals in the postflame region of a flat flame. Single and bicrystal alpha-Fe(2)O(3) nanoflakes and CuO nanoneedles were grown in the postflame region by a solid diffusion mechanism and were aligned perpendicularly to the substrate with a surface coverage density of 10 nanostructures per square micrometer. The alpha-Fe(2)O(3) nanoflakes reached lengths exceeding 20 microm after only 20 min of growth. This rapid growth rate is attributed to a large initial heating rate of the metal substrate in the flame and to the presence of water vapor and carbon dioxide in the gas phase that together generate thin and porous oxide layers that greatly enhance the diffusion of the deficient metal to the nanostructure growth site and enable growth at higher temperatures than previously demonstrated.
本文描述了一种简单且快速的火焰合成方法，通过在扁平火焰的火焰后区域直接氧化金属来制备一维金属氧化物纳米结构。通过固体扩散机制在火焰后区域生长出单晶和双晶α-Fe₂O₃纳米片以及CuO纳米针，它们垂直于基板排列，表面覆盖密度为每平方微米10个纳米结构。仅生长20分钟后，α-Fe₂O₃纳米片的长度就超过了20微米。这种快速的生长速率归因于火焰中金属基板的高初始加热速率以及气相中水蒸气和二氧化碳的存在，它们共同形成了薄而多孔的氧化层，极大地增强了贫金属向纳米结构生长位点的扩散，并使得能够在比之前所展示的更高温度下生长。
