Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5306, 69622 Villeurbanne, France.
Nanoscale. 2018 Jan 25;10(4):2154-2161. doi: 10.1039/c7nr07540e.
Studies of the mechanical contact between nanometer-scale particles provide fundamental insights into the mechanical properties of materials and the validity of contact laws at the nanoscale which are still under debate for contact surfaces approaching atomic dimensions. Using in situ Brillouin light scattering under high pressure, we show that effective medium theories successfully predict the macroscopic sound velocities in nanopowders if one takes into account the cementation of the contacts Our measurements suggest the relevance of the continuum approach and effective medium theories to describe the contact between nanoparticles of diameters as small as 4 nm, i.e. with radii of contact of a few angstroms. In particular, we demonstrate that the mechanical properties of nanopowders strongly depend on the surface state of the nanoparticles. The presence of molecular adsorbates modifies significantly the contact laws.
对纳米级颗粒之间的机械接触的研究为材料的力学性能提供了基本的认识，也为接触定律的有效性提供了基本的认识，而这些在接触表面接近原子尺度时仍存在争议。我们使用高压原位布里渊光散射，表明如果考虑到接触的胶结，有效介质理论可以成功地预测纳米粉末的宏观声速。我们的测量结果表明，连续体方法和有效介质理论对于描述直径小至 4nm 的纳米颗粒之间的接触具有重要意义，即接触半径为几个埃。特别是，我们证明了纳米粉末的力学性能强烈依赖于纳米颗粒的表面状态。分子吸附物的存在显著地改变了接触定律。
