Rivas-Barbosa Rodrigo, Escobedo-Sánchez Manuel A, Tassieri Manlio, Laurati Marco
División de Ciencias e Ingenierías, Universidad de Guanajuato, Lomas del Bosque 103, 37150 León, Mexico.
Phys Chem Chem Phys. 2020 Feb 21;22(7):3839-3848. doi: 10.1039/c9cp06191f. Epub 2020 Feb 5.
We report on the application of a Fourier transform-based method, 'i-Rheo', to evaluate the linear viscoelastic moduli of hard-sphere colloidal dispersions, both in the fluid and glass states, from a direct analysis of raw step-stress (creep) experimental data. We corroborate the efficacy of i-Rheo by comparing the outputs of creep tests performed on homogenous complex fluids to conventional dynamic frequency sweeps. A similar approach is adopted for a number of colloidal suspensions over a broad range of volume fractions. For these systems, we test the limits of the method by varying the applied stress across the materials' linear and non-linear viscoelastic regimes, and we show that the best results are achieved for stress values close to the upper limit of the materials' linear viscoelastic regime, where the signal-to-noise ratio is at its highest and the non-linear phenomena have not appeared yet. We record that, the range of accessible frequencies is controlled at the higher end by the relative weight between the inertia of the instrument and the elasticity of the complex material under investigation; whereas, the lowest accessible frequency is dictated by the extent of the materials' linear viscoelastic regime. Nonetheless, despite these constrains, we confirm the effectiveness of i-Rheo for gaining valuable information on the materials' linear viscoelastic properties even from 'creep ringing' data, confirming its potency and general validity as an accurate method for determining the material's rheological behaviour for a variety of complex systems.
我们报告了一种基于傅里叶变换的方法“i-Rheo”的应用，该方法通过直接分析原始阶跃应力（蠕变）实验数据来评估硬球胶体分散体在流体和玻璃态下的线性粘弹性模量。我们通过将对均匀复杂流体进行的蠕变测试输出与传统动态频率扫描进行比较，证实了i-Rheo的有效性。对于许多不同体积分数的胶体悬浮液，我们采用了类似的方法。对于这些系统，我们通过在材料的线性和非线性粘弹性区域改变施加的应力来测试该方法的极限，并且我们表明，对于接近材料线性粘弹性区域上限的应力值，能获得最佳结果，此时信噪比最高且尚未出现非线性现象。我们记录到，可达到的频率范围在高端由仪器的惯性与所研究的复杂材料的弹性之间的相对权重控制；而最低可达到的频率则由材料线性粘弹性区域的范围决定。尽管存在这些限制，但我们证实了i-Rheo即使从“蠕变振铃”数据中获取有关材料线性粘弹性特性的有价值信息的有效性，证实了其作为确定各种复杂系统材料流变行为的准确方法的效力和普遍有效性。
