Farias Barbara V, Brown Derek, Hearn Allison, Nunn Nicholas, Shenderova Olga, Khan Saad A
Department of Chemical and Biomolecular Engineering, 911 Partners Way, Engineering Building 1, Box 7905, North Carolina State University, Raleigh, NC 27695-7905, United States.
Adámas Nanotechnologies, 8100 Brownleigh Drive, Raleigh, NC 27617, United States.
J Colloid Interface Sci. 2020 Nov 15;580:180-191. doi: 10.1016/j.jcis.2020.07.030. Epub 2020 Jul 9.
We envisage the use of hydroxylated detonation nanodiamonds (ND-OH), a relatively novel carbonaceous filler with high adsorption activity, small size, and large surface area to create Pickering emulsions. The emulsion behavior under shear and the extent to which the microstructure can rebuild after breakdown is dependent on its yield stress.
Using a model system consisting of isopropyl palmitate and water stabilized by ND-OH particles, we investigate the stability of these emulsions, their microstructure and rheological behavior as a function of ND-OH concentration.
Confocal microscopy reveals that increasing ND-OH concentration results in smaller droplet sizes in the emulsions. This behavior is consistent with our rheological results of higher elastic modulus G' and yield stress of the emulsion with increased ND-OH, as the presence of smaller droplets facilitates the formation of a densely packed network. We find the rheological behavior of these emulsions to be a hybrid of colloidal gels and surfactant-stabilized emulsions, with interparticle interactions and droplets deformability dictating their elasticity and yield stress behavior. Structure recovery following large shear reveals the degree of microstructure recovery to depend on the applied stress, with the recovered modulus collapsing into a single master-curve when the applied stress is scaled by the yield stress.
我们设想使用羟基化爆轰纳米金刚石（ND-OH），一种具有高吸附活性、小尺寸和大表面积的相对新颖的碳质填料来制备皮克林乳液。剪切作用下的乳液行为以及微观结构在破坏后能够重建的程度取决于其屈服应力。
使用由棕榈酸异丙酯和由ND-OH颗粒稳定的水组成的模型体系，我们研究了这些乳液的稳定性、微观结构及其流变行为与ND-OH浓度的函数关系。
共聚焦显微镜显示，增加ND-OH浓度会导致乳液中的液滴尺寸更小。这种行为与我们的流变学结果一致，即随着ND-OH含量增加，乳液的弹性模量G'和屈服应力更高，因为较小液滴的存在有利于形成紧密堆积的网络。我们发现这些乳液的流变行为是胶体凝胶和表面活性剂稳定乳液的混合体，颗粒间相互作用和液滴变形性决定了它们的弹性和屈服应力行为。大剪切后的结构恢复表明微观结构恢复程度取决于所施加的应力，当所施加的应力按屈服应力进行缩放时，恢复模量会坍缩成一条单一的主曲线。
