Solid State Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India.
J Phys Condens Matter. 2010 May 19;22(19):195107. doi: 10.1088/0953-8984/22/19/195107. Epub 2010 Apr 23.
Mesoscopic structural evolution under thermal annealing of yttrium aluminium garnet fractal aggregates has been investigated by small-angle neutron scattering. Fractal dimension remains invariant with sintering temperature but the extent of the fractal realm is narrowed down significantly. A Monte Carlo simulation, based on Ostwald-ripening type of relaxation of fractal aggregates for a mass conserved system, has been attempted in order to understand the aforementioned novel observation. A local group merge sintering model was adopted for the relaxation of the fractal aggregates. Diffusion driven mass transport over local branches of fractal clusters causes smoothening of branches but keeps the overall shape unaltered at lower resolution. Predictions of the model were found to be consistent, in terms of microstructural evolution, with experimental data. The present simulation was also successful in explaining the evolution of the particle size distribution of the aggregate. To the best of our knowledge this is the first reported experimental and theoretical investigation on the effect of annealing temperature on nano-ceramic fractal aggregates.
采用小角中子散射研究了钇铝石榴石分形聚集体在热退火时的介观结构演化。分形维数在烧结温度下保持不变，但分形范围显著缩小。为了理解上述新的观察结果，尝试了基于质量守恒系统的分形聚集体奥斯特瓦尔德熟化类型弛豫的蒙特卡罗模拟。采用局部团合并烧结模型来弛豫分形聚集体。在分形簇的局部分支上扩散驱动的质量输运导致分支变平滑，但在较低分辨率下保持整体形状不变。模型的预测在微观结构演化方面与实验数据一致。本模拟还成功解释了聚集体粒径分布的演化。据我们所知，这是首次报道关于退火温度对纳米陶瓷分形聚集体影响的实验和理论研究。
