Université de Technologie de Compiègne, EA 4297 Transformations Intégrées de la Matière Renouvelable, B.P. 20529, 60205 Compiègne Cedex, France.
Langmuir. 2010 Feb 16;26(4):2333-8. doi: 10.1021/la902759s.
Dry water is a very convenient way of encapsulating a high amount of aqueous solutions in a powder form made of hydrophobic silica nanoparticles. It was demonstrated in previous studies that both solid and liquid interfacial properties influence the quality of the final product resulting occasionally in mousse formation. To explain this behavior, contact angles of silica nanoparticles have been measured for water and water/ethanol solution by means of liquid intrusion experiments. It was found that the quality of the final product correlates with the contact angle, i.e., contact angle close to 105 degrees leads to mousse formation whereas a slightly higher value of approximately 118 degrees allows dry water formation. The proposed explanation was based on the energy of immersion and adhesion defined as the energy needed for a spherical particle to respectively penetrate into the liquid or attach at the liquid/air interface. Significantly lower energy of immersion calculated for lower contact angle might account for particle penetration into the liquid phase during processing, leading to continuous network aggregation, air entrapment, and finally mousse formation.
干水是一种非常方便的方法，可以将高浓度的水溶液封装在由疏水二氧化硅纳米颗粒制成的粉末中。之前的研究表明，固液界面性质会影响最终产品的质量，有时会导致形成泡沫。为了解释这种行为，通过液体侵入实验测量了水和水/乙醇溶液中二氧化硅纳米颗粒的接触角。结果发现，最终产品的质量与接触角相关，即接触角接近 105 度会导致形成泡沫，而略高的值约为 118 度则允许形成干水。提出的解释基于浸润能和粘附能，定义为球形颗粒分别穿透液体或附着在液体/空气界面所需的能量。对于较低的接触角，计算出的浸润能显著降低，这可能是由于颗粒在加工过程中穿透到液相中，导致连续的网络聚集、空气夹带，最终形成泡沫。
