Influence of pH, high salinity and particle concentration on stability and rheological properties of aqueous suspensions of fumed silica
Influence of pH, high salinity and particle concentration on stability and rheological properties of aqueous suspensions of fumed silica
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DOI：
10.1016/j.colsurfa.2009.07.050
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发表时间：
2009-10-05
影响因子：
5.2
通讯作者：
Sjoblom, Johan
中科院分区：
文献类型：
--
作者：
Amiri, Asal;Oye, Gisle;Sjoblom, Johan
结合使用多相光散射和瞬态动态流变测定法，以控制 Aerosil 200 水悬浮液的稳定性、流变性和凝胶化，不受 pH、颗粒和电解质浓度的影响。通过获得每个系统中从牛顿流向剪切稀化流转变的颗粒临界浓度，研究了这些参数的影响。这归因于颗粒间力引起的微观结构变化。通过测量样品的表观粘度、屈服应力、时间依赖性瞬态流变和光散射，进一步确认了结果。所有结果均由扩展 DLVO 理论描述。由于短程排斥水合力，即使在高浓度 NaCl 存在下，具有酸性 pH 值或处于等电点的悬浮液也具有高稳定性。另一方面，具有最高盐浓度和碱性pH值的悬浮液表现出时间依赖性流变学、最大屈服值和粘度、流态转变的最小临界颗粒浓度以及高凝胶形成能力。维里。凝胶动力学的阳离子以及关于颗粒和盐浓度的凝胶强度通过三个典型测试来实现：在pH 8.5下动态振荡模式下的时间扫描、应变幅度和频率幅度扫描。发现在较高的盐浓度或较高的颗粒浓度下，胶凝网络的强度更大。发现凝胶的强连接机制控制系统以增加颗粒体积分数或电解质。在 0.6 M NaCl 下测试了系统的结垢理论，发现储能模量的体积分数依赖性的幂律指数为 3.8。此外，应用强凝胶分形模型计算出絮体的分形维数d(f)约为1.85。基于 G' 的指数值为 3.78 和分形絮凝维数为 1.85，提出簇扩散限制簇聚集 (DLCA) 主要控制凝胶形成机制。 (C) 2009 Elsevier B.V. 保留所有权利。
Multiphase light scattering and transient-dynamic rheometry were used in combination in order to control the stability, rheology and gelation of aqueous Aerosil 200 suspensions with regard to the influence of pH, particle and electrolyte concentrations. Effects of these parameters were studied by obtaining the critical concentration of particles for transition from Newtonian to shear thinning flow in each system. This was attributed to microstructural changes due to the interparticle forces. Further confirmation of results was obtained by measuring apparent viscosities, yield stresses, time dependent transient rheometry and light scattering from the samples. All results were described by extended-DLVO theory. Suspensions with acidic pH or at the isoelectric point had high stability even in presence of high concentration of NaCl due to the short-range repulsive hydration forces. On the other hand, suspensions with the highest salt concentration and basic pH showed time dependant rheology, largest yield values and viscosities, smallest critical particle concentration for flow regime transition and high capability of gel formation. Veri. cation of gelation kinetics and the gel strength with regard to particle and salt concentration were implemented by three typical tests: time sweep, strain amplitude and frequency amplitude sweep in the dynamic oscillation mode at pH 8.5. Strength of the gelled networks was found to be greater at either higher salt concentration or higher concentration of particles. Strong-link regime of gel was found to govern the system regarding to increase either in particle volume fraction or in electrolyte. The scaling theory was tested for the system at 0.6 M NaCl and power-law exponent of the volume fraction dependence of storage modulus was found to be 3.8. In addition, applying the fractal model for strong gels calculated fractal dimension of flocs d(f) around 1.85. Based on the exponent value of 3.78 for G' and the fractal flocs dimension of 1.85, it was proposed that cluster-diffusion-limited cluster aggregation (DLCA) was mainly governing the gel formation mechanism. (C) 2009 Elsevier B. V. All rights reserved.