Laser remelted surface layers of a Cu-based metallic glass forming alloy have been produced with fully amorphous depths up to 350 μm for single track widths of around 1.3 mm and have been checked by transmission of synchrotron radiation. They have been subjected to indentation hardness and scratch testing, and the development of shear bands in both situations has been addressed. During the cross-sectional hardness indentation tests, Vickers values of over 735 HV2 have been found through the depth of the treated layer, and the scratch testing has revealed extremely low friction coefficient values (<0.02 at 10 N in single-pass and 0.02 at 18 N multi-pass regimes against a diamond stylus). The shear band formation has been related to both scratch test speed (strain rate) and load (contact stress) by methods such as atomic force microscopy measurements and subsequent surface roughness characterization by a height–height correlation function.
In this paper we deal with interfaces involved in TiC/a-C:H nanocomposite coatings, at three different length scales namely coating interface adjacent to the substrate (micron scale), boundary of columnar structures (sub-micron scale) and phase interface between nanocrystallite and amorphous matrix (nanometer scale), and their influences on the properties of the coatings. The coating interface has to be engineered to optimize the adhesion of the coatings, which is a primary requisite for their function. Columnar boundaries (CBs) are harmful as preferential cracking path, resulting in low fracture toughness. Therefore, our efforts are devoted to eliminate CBs by adjusting the deposition parameters. The amorphous carbon matrix is intrinsically brittle as a common characteristic of amorphous materials. Introducing nanocrystalline ceramic particles into an amorphous matrix generates a high density of interphase interfaces that assist in crack path delocalization and termination of crack propagation. Especially, the localization of shear in amorphous matrix is hampered by the particles, leading to a spread of the cracks that enhances the toughness provided the size of TiC particles becomes of the same size as the separation between the crystalline particles. Based on the experimental results, guidelines for the development and optimization of highly adherent and tough nanocomposite coatings are provided.
In this chapter we review the discrete solvent reaction field (DRF) model as implemented in time-dependent density functional theory (TD-DFT). The DRF model is a polarizable quantum mechanics/ molecular mechanics (QM/MM) model for calculating molecular response properties of molecules in the condensed phase. Using this model effective microscopic properties can be calculated which is related to the macroscopic susceptibilities by Lorentz/Onsager local field factors. The macroscopic susceptibilities can then be compared directly with experimental results. We review some of the applications of the DRF model to calculate the microscopic and macroscopic response properties of molecules in the condensed phase. By carefully validating that DFT calculate accurate response properties in the gas phase we have shown that also in the condensed phase results in good agreement with experiments can be obtained. This is particular true for the refractive index and the pure electronic third-harmonic generation (THG) nonlinear susceptibility. On the other hand the model failed to predict the electric field induced second harmonic generation (EFISH) susceptibility due to a poor handling of the rotational contribution. Future directions to resolve this problem are suggested.
