Rodriguez Philippe, Caussat Brigitte, Ablitzer Carine, Iltis Xavière, Brothier Meryl
CEA, DEN, DEC, SPUA, LCU, Cadarache, F-13108 Saint-Paul-lès-Durance, France.
J Nanosci Nanotechnol. 2011 Sep;11(9):8083-8. doi: 10.1166/jnn.2011.5097.
In order to study the feasibility of coating very dense powders by alumina using Fluidized Bed Metal Organic Chemical Vapour Deposition (FB-MOCVD), experiments were performed on a commercial tungsten powder, 75 microm in median volume diameter and 19,300 kg/m3 in grain density. The first part of the work was dedicated to the experimental study of the tungsten powder fluidization using argon as carrier gas at room temperature and at 400 degrees C. Due to the very high density of the tungsten powder, leading to low initial fixed bed heights and low bed expansions, different weights of powder were tested in order to reach satisfactory temperature profiles along the fluidized bed. Then, using argon as a fluidized bed former and aluminium acetylacetonate Al(C5O2H7)3 as a single source precursor, alumina thin films were deposited on tungsten particles at a low temperature range (e.g., 370-420 degrees C) by FB-MOCVD. The influence of the weight of powder, bed temperature and run duration was studied. Characterizations of the obtained samples were performed by various techniques including scanning electron microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (EDS) analyses, Field Emission Gun SEM (FEG-SEM) and Fourier Transform InfraRed (FT-IR) spectroscopy. The different analyses indicated that tungsten particles were uniformly coated by a continuous alumina thin film. The thickness of the film ranged between 25 and 80 nm, depending on the coating conditions. The alumina thin films were amorphous and contained carbon contamination. This latter may correspond to the adsorption of species resulting from incomplete decomposition of the precursor at so low deposition temperature.
为了研究使用流化床金属有机化学气相沉积法（FB-MOCVD）用氧化铝包覆极细粉末的可行性，对一种商业钨粉进行了实验，该钨粉的中位体积直径为75微米，颗粒密度为19300千克/立方米。工作的第一部分致力于在室温及400摄氏度下以氩气作为载气对钨粉流化进行实验研究。由于钨粉密度极高，导致初始固定床高度较低且床层膨胀较小，因此测试了不同重量的粉末，以在流化床中获得令人满意的温度分布。然后，以氩气作为流化床形成气体，乙酰丙酮铝Al(C5O2H7)3作为单一源前驱体，通过FB-MOCVD在低温范围（例如370 - 420摄氏度）将氧化铝薄膜沉积在钨颗粒上。研究了粉末重量、床层温度和运行持续时间的影响。通过各种技术对所得样品进行了表征，包括结合能量色散X射线光谱（EDS）分析的扫描电子显微镜（SEM）、场发射枪扫描电子显微镜（FEG-SEM）和傅里叶变换红外（FT-IR）光谱。不同分析表明，钨颗粒被连续的氧化铝薄膜均匀包覆。薄膜厚度在25至80纳米之间，具体取决于包覆条件。氧化铝薄膜为非晶态且含有碳污染。后者可能对应于前驱体在如此低的沉积温度下不完全分解产生的物种吸附。
