Sintering of viscous droplets under surface tension.
Sintering of viscous droplets under surface tension.
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DOI：
10.1098/rspa.2015.0780
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发表时间：
2016-04
期刊：
影响因子：
--
通讯作者：
Dingwell DB
中科院分区：
文献类型：
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作者：
Wadsworth FB;Vasseur J;Llewellin EW;Schauroth J;Dobson KJ;Scheu B;Dingwell DB
我们进行实验，以研究高粘度液滴的烧结。球形玻璃珠的独立圆柱体被加热到其玻璃化转变温度以上，导致它们在表面张力下致密化。我们以高的空间和时间分辨率确定珠包的演变体积。我们使用这些数据来测试一系列现有模型。我们扩展的模型，占时间依赖性的液滴粘度，从非等温条件下产生的，并占非零的最终孔隙度。我们还提出了一种方法来考虑的初始分布的孔隙间隙的液体球，这使得模型可以使用没有拟合参数的半径。我们发现一个很好的协议之间的模型和数据的时间小于毛细管松弛时间尺度。对于更长的时间，我们发现数据和模型之间的差异越来越大，因为达西放气时间尺度接近烧结时间尺度。我们得出结论，烧结系统的渗透性降低抑制后期致密化。最后，我们确定剩余的，被困气体的体积分数在平衡时使用X射线计算机断层扫描，并比较这与理论值的临界气体体积分数的重叠领域的系统。
We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres.