The present study considered the problem of halloysite nanoscroll synthesis by energy modeling of the formation of chrysotile and halloysite particles. The main aim of the study was to reveal an energy preference between scrolled and platy morphologies of the particles. Both hydrosilicates possess the ability to scroll spontaneously but relatively facile hydrothermal synthesis of the nanoscrolls is available only to the former, whereas halloysite forms mainly plates under the same conditions. This issue was investigated by a phenomenological energy model, taking into account: (1) strain energy due to the size difference between metal oxide and silica sheets; (2) surface-energy difference on the opposite sides of the layer; and (3) adhesion energy. Calculations showed that the halloysite layer had a significant scrolling potential due to the first energy component, but the surface-energy difference acted in the opposite direction and tried to unbend the layer. In contrast, these two actions were co-directional in chrysotile layers. In both cases, the formation of multi-layered plates became more energy favorable when the specific surface energy of the edges decreased. In the range 0.5–3 J/m2 for the specific surface energy, only halloysite layers showed an energy preference for platy particles over nanoscrolls, especially at small layer sizes. Certain processes, such as hydration, could reduce the corresponding specific surface energy value and, as a result, could stabilize the platy morphology of halloysite at the earliest stages of particle growth under hydrothermal conditions.

中文翻译：

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温石棉和埃洛石层的管状和板状形态之间竞争的能量建模

本研究通过对温石棉和埃洛石颗粒形成的能量建模来考虑埃洛石纳米卷的合成问题。该研究的主要目的是揭示粒子的滚动和板状形态之间的能量偏好。两种水合硅酸盐都具有自发滚动的能力，但纳米卷的相对容易的水热合成仅适用于前者，而埃洛石在相同条件下主要形成板。这个问题是通过现象学能量模型研究的，考虑到：（1）由于金属氧化物和二氧化硅片之间的尺寸差异引起的应变能；(2) 层两侧的表面能差；(3)粘附能。计算表明，由于第一能量分量，埃洛石层具有显着的滚动势，但表面能差作用在相反的方向并试图使层伸直。相比之下，这两种作用在温石棉层中是同向的。在这两种情况下，当边缘的比表面能降低时，多层板的形成变得更有利于能量。在比表面能 0.5-3 J/m2 的范围内，只有埃洛石层显示出比纳米卷更偏爱板状颗粒的能量，尤其是在小层尺寸下。某些过程，例如水合，可以降低相应的比表面能值，因此可以在水热条件下颗粒生长的最早阶段稳定埃洛石的片状形态。