Aggregation behavior of particles in nonpolar medium is studied with time-resolved light scattering. At low concentrations of surfactant particles are weakly charged and suspensions are not stable. Suspensions get progressively more stable with increasing surfactant concentration as particles get more highly charged. At high concentrations the particles get neutralized and aggregation is again fast. The theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) is able to predict the stability ratios quantitatively by using the experimentally measured surface charge, screening lengths and van der Waals forces.
Photoconductive nonpolar liquids based on azobenzene
Institute of Science and Technology Austria（奥地利科学技术研究所）；College of Chemistry, Chemical Engineering and Materials Science, Soochow University（苏州大学化学化工与材料科学学院）
Surfactant Induced Catastrophic Collapse of Carbon Black Suspension used in Flow Battery Application
炭黑颗粒在用于电化学氧化还原液流电池的浆料电极中充当电子导电添加剂。炭黑颗粒在浆料电极中的稳定性和分散性是其储存和电池有效运行的关键参数。通过添加非离子表面活性剂来改性炭黑浆料制剂可以潜在地赋予所需的性质，例如良好的颗粒分散性、重力稳定性和流动性，从而赋予液流电池更好的性能。与典型的浆料电极配方匹配，我们将炭黑颗粒分散在1M H $_2$ SO $_4$中，其中体积分数$ϕ$ = 0.01至0.06并且c $_{surf.}$ = 0、0.05和0.1M。流变学研究表明，炭黑悬浮液具有胶体凝胶的性质。通过使用定制相机设置在比色皿中随时间跟踪颗粒床的高度来测量该过程的沉降动力学。这里的沉降动力学明显类似于凝胶坍塌。在短时间内，我们观察到快速沉积与结构崩溃的凝胶和在长时间非常缓慢的沉积与压实的沉积物。在$α$（= c $_{surf.}$/c $_{CB}$）$<$ 0.7下，将非离子表面活性剂（Triton X-100）添加到高于CMC的溶剂中改善了颗粒分散并增加了凝胶弹性。然而，对于$α>$，0.7导致形成较弱的凝胶，其在重力下表现出"灾难性坍塌"并且具有较低的粘度。
