SMALL-ANGLE NEUTRON-SCATTERING INVESTIGATION OF SHORT-RANGE CORRELATIONS IN FRACTAL AEROGELS - SIMULATIONS AND EXPERIMENTS
SMALL-ANGLE NEUTRON-SCATTERING INVESTIGATION OF SHORT-RANGE CORRELATIONS IN FRACTAL AEROGELS - SIMULATIONS AND EXPERIMENTS
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DOI：
10.1103/physrevb.48.9345
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发表时间：
1993-10-01
影响因子：
3.7
通讯作者：
JULLIEN, R
中科院分区：
文献类型：
--
作者：
HASMY, A;FORET, M;JULLIEN, R
利用几种三维离格簇-簇算法，计算了由相同球形粒子组成的模拟分形聚集体的中心到中心粒子间距离分布函数f(r)及其傅里叶变换散射函数S(q)。正如预期的那样，f(r)在粒子直径处出现一个δ峰，随后在两倍于此距离处出现不连续，这是球形粒子的非重叠特性的结果。因此，曲线log10S(q)与log10q经历了一个广泛的最小值，随后是大q值的阻尼振荡。将模拟结果与实验结果进行了比较。实验散射函数S(q)由散射强度I(q)与由稀释胶体溶液测量得到的形状因子P(q)之比导出。模拟结果与实验结果的一致性较好，并且很好地考虑了气凝胶密度的影响。实验曲线与理论S(q)曲线的偏离，在较大的颗粒尺寸下更强，归因于对简单散射理论的短波修正。
The center-to-center interparticle-distance distribution function f(r) and its Fourier transform, the scattering function S(q), are computed for simulated fractal aggregates made of identical spherical particles using several three-dimensional off-lattice cluster-cluster algorithms. As expected f(r) exhibits a delta peak at the particle diameter followed by a discontinuity at twice this distance as a consequence of the nonoverlapping character of the spherical particles. As a result the curve log10S(q) versus log10q goes through a broad minimum followed by damped oscillations at large-q values. These simulations are compared with experimental small-angle neutron-scattering results on colloidal silica aerogels. The experimental scattering function S(q) is derived from the ratio between the scattered intensity I(q) and the form factor P(q) determined from measurements on the diluted colloidal solution. The agreement between simulations and experiments is qualitatively good and the influence of aerogel density is well accounted for. The departure of the experimental curves from the theoretical S(q) curve, which is stronger for larger particle sizes, is attributed to short-wavelength corrections to the simple scattering theory.