Influence of thermal effects on stability of nanoscale films and filaments on thermally conductive substrates
Influence of thermal effects on stability of nanoscale films and filaments on thermally conductive substrates
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热效应对导热基底上纳米级薄膜和细丝稳定性的影响
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
L. Kondic
中科院分区：
文献类型：
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作者：
I. Seric;S. Afkhami;L. Kondic
我们考虑暴露于外部加热的导热基板上的纳米级厚度的薄膜和细丝。特别关注的是暴露于激光照射的金属膜。由于所涉及的短长度尺度，金属中的热吸收直接耦合到膜的演变，因为吸收长度和膜厚度是可比的。这样的设置需要对流体机械和热效应进行自洽考虑。我们通过基于流体体积的模拟来解决这个问题，其中包括不稳定的液态金属-固体基底相互作用势。这些模拟耦合流体动力学直接与流体和衬底中的温度场的时空演变。我们专注于材料参数的温度变化的影响，特别是表面张力和粘度。关于表面张力随温度的变化，主要发现是，虽然马兰戈尼效应可能不会在所考虑的设置中发挥重要作用，但表面张力的时间变化（修改法向应力平衡）是显着的，并可能导致复杂的演变，包括液体金属-空气界面的振荡演变。薄膜粘度的温度变化也被发现是相关的。因此，在实验中，表面张力和粘度的变化都会影响出射波长。相比之下，灯丝的几何形状被发现是不太敏感的材料参数随温度的变化。
We consider films and filaments of nanoscale thickness on thermally conductive substrates exposed to external heating. Particular focus is on metal films exposed to laser irradiation. Due to short length scales involved, the absorption of heat in the metal is directly coupled to the film evolution, since the absorption length and the film thickness are comparable. Such a setup requires self-consistent consideration of fluid mechanical and thermal effects. We approach the problem via Volume-of-Fluid based simulations that include destabilizing liquid metal-solid substrate interaction potentials. These simulations couple fluid dynamics directly with the spatio-temporal evolution of the temperature field both in the fluid and in the substrate. We focus on the influence of the temperature variation of material parameters, in particular of surface tension and viscosity. Regarding variation of surface tension with temperature, the main finding is that while Marangoni effect may not play a significant role in the considered setting, the temporal variation of surface tension (modifying normal stress balance) is significant and could lead to complex evolution including oscillatory evolution of the liquid metal-air interface. Temperature variation of film viscosity is also found to be relevant. Therefore, the variations of surface tensions and viscosity could both influence the emerging wavelengths in experiments. In contrast, the filament geometry is found to be much less sensitive to a variation of material parameters with temperature.