College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
Phys Chem Chem Phys. 2018 Jun 13;20(23):16184-16192. doi: 10.1039/c8cp02287a.
We systematically investigate the collapse of a set of open-cell nanoporous Cu (np-Cu) materials with the same porosity and shape but different specific surface areas, during thermal annealing, by performing large-scale molecular dynamics simulations. Two mechanisms govern the collapse of np-Cu. One is direct surface premelting, facilitating the collapse of np-Cu, when the specific surface area is less than a critical value (∼2.38 nm-1). The other is recrystallization followed by surface premelting, accelerating the sloughing of ligaments and the annihilation of voids, when the critical specific surface area is exceeded. Surface premelting results from surface reconstruction by prompting localized "disordering" and "chaos" on the surface, and the melting temperature reduces linearly with the increase of the specific surface area. Recrystallization is followed by surface premelting as the melting temperature is below the supercooling point, where a liquid is unstable and instantaneously recrystallizes.
我们通过大规模分子动力学模拟，系统地研究了一组具有相同孔隙率和形状但比表面积不同的开孔纳米多孔铜（np-Cu）材料在热退火过程中的坍塌。有两种机制控制着 np-Cu 的坍塌。一种是直接的表面预熔化，当比表面积小于一个临界值（约 2.38nm-1）时，促进 np-Cu 的坍塌。另一种是再结晶后表面预熔化，当超过临界比表面积时，加速了连接体的剥落和空隙的消失。表面预熔化是由于表面重构导致局部“无序”和“混乱”而产生的，熔化温度随比表面积的增加呈线性下降。再结晶后表面预熔化，因为在过冷点以下，熔化温度低于过冷点，液体不稳定，会瞬间再结晶。
