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[Display omitted] • Adhesive forces of a single anisole on G-OH/Gr surface are got via AFM experiments. • Anisole exhibits two types of adhesive forces on G-OH surface. • Hydroxyl group has significant effect on the adhesive force of G-OH to anisole. • Conformational changes of anisole cause two peaks of its force-height curve to G-OH. Measuring and understanding interaction forces between hydroxylated graphene (G-OH) and aromatic compounds is significant for the applications of composites based on G-OH, such as 3D graphene derivatives preparation and wastewater treatment. In this research, the adsorption/separation mechanical behavior of anisole on graphene and G-OH surfaces was investigated by atomic force microscopy (AFM) experiments and molecular dynamics (MD) simulations. The adsorption and separation curves of anisole on graphene and G-OH surfaces were obtained by experiments, and the adhesive forces of a single anisole were achieved by the Poisson statistics method. It is found that there are two types of adhesive forces between anisole and G-OH. For graphene and anisole, two extreme values are got by the adsorption and separation processes, and the adhesive force obtained by the separation process is approximately equal to one type of adhesive force between anisole and G-OH. Furthermore, MD simulation results reveal that the maximum adhesive force of anisole on the G-OH surface depends on its position relative to the hydroxyl group, and anisole has a greater affinity near the hydroxyl group. The position and planar angle of the anisole conformations cause the difference in adhesive forces. [ABSTRACT FROM AUTHOR]

• Texturing effects on nanotribological properties and subsurface damage are studied. • Nanoscale friction and wear behaviour of GaN can be regulated by texture parameter. • Nano-texture can alleviate dislocation development and reduce subsurface damage. • The m -GaN exhibits lower wear and thicker damage layer compared with the c -GaN. Surface nanotribological properties and subsurface damage of flat and textured gallium nitride (GaN) substrates during both linear and circular nanoscratching processes are investigated using molecular dynamics simulation. Results show that the surface texture can remarkably reduce not only the surface friction and wear but also the scratching-induced subsurface damage regardless of the tip radius and penetration depth. Tangential force and friction coefficient decreased with an increase in groove width or depth primarily due to the reduced contact area. The effect of texturing on stress distribution can affect the development of dislocation to alleviate the nanoscale material deformation and removal and thereby reduce surface wear and subsurface damage. Increasing tip radius can reduce the friction coefficient and surface wear, but it promotes subsurface damage. By contrast, increasing tip penetration depth can increase the friction, wear, and subsurface damage for flat and textured GaN substrates. Compared with the c -plane, the m -plane GaN substrate exhibits higher friction but lower material wear, and it has a considerably thicker subsurface damage layer due to the difference in their dislocation networks. This work can provide useful insights into the design of GaN-based material with antifriction and wear properties through the surface texturing treatments. [ABSTRACT FROM AUTHOR]

• Nano abrasive machining of monocrystalline GaN is studied by molecular dynamics simulations. • Deformation of monocrystalline GaN is associated with both the propagation of dislocation and the contact of workpiece/tool. • Dislocation and phase transition are identified in the deformation layer after nano abrasive machining. • Pile-up and elastic recovery of monocrystalline GaN are affected by the stagnation region and slip system. • Effects of cutting velocity, depth of cut and abrasive shape on deformation are systematically investigated. Molecular dynamics simulations are carried out to investigate the nano abrasive machining of monocrystalline gallium nitride (GaN). Effects of the cutting velocity, depth of cut (DOC) and abrasive shape on the atomic strain, stress, temperature, cutting forces, and deformation layer are systematically investigated, aiming at understanding the deformation behaviour of monocrystalline GaN during nano abrasive machining. The results show that the strain, stress and temperature were increased by using the higher cutting velocity, the larger DOC or cub-octahedral abrasive. Being affected by both the average stress and the elasto-plastic deformation zone right ahead the diamond particle, the cutting forces increase with the increase in DOC but decrease under a larger cutting velocity, or when using a cub-octahedral abrasive. The deformation layer in the subsurface is insensitive to the cutting velocity, while impressively shrinks under a larger DOC or cub-octahedral abrasive used. As the stress and temperature rise, the use of higher cutting velocity, larger DOC or cub-octahedral abrasive would facilitate the nucleation of dislocation, phase transition and the development of pile-up. This work can enrich the understanding on the nanoscale deformation mechanism of monocrystalline GaN material during the ultra-precision machining process. [ABSTRACT FROM AUTHOR]