D. Vainchtein

Fundamental and applied aspects of laser surface engineering

Abstract The contribution to this jubilee issue of IJMR concentrates on the analysis of laser surface treatments. In particular laser cladding processes using coaxial and side set-ups are evaluated to determine the optimal processing window that prioritizes the clad quality and the efficiency of the coating method. The microstructural features in these so-called processing maps are illustrated with Inverse Pole Figure (IPF) mapping, texture pole figures and Electron Backscatter Pattern (EBSP) techniques. The distribution of stresses inside Co-based laser coating is measured with the so-called three-dimensional X-ray Diffraction microscopy (3DXRD) and it is found very dispersive, i. e. stresses may change from one grain to another considerably. The mean value of observed hydrostatic stress in all grains at specific laser track depth is gradually changed from tensile state in the upper part of the coating to the compressive state in its lower part close to the substrate. On the other hand the average value of shear stress component does not show any substantial change with depth.

Growth of fractal structures in flames with silicon admixture

Transmission electron microscopy (TEM) measurements and theoretical analysis are combined to construct the physical picture of formation of SiO2 fractal aggregates in a methane/hexamethyldisiloxane/air atmospheric pressure flame. The formation of SiO2 fractal aggregates is described as a multistage process. The first stage is combustion of fuel in a narrow flame front region with formation of main combustion products including SiO2 molecules. Further downstream SiO2 molecules join in liquid nanoclusters. After cooling combustion products due to heat losses to surroundings, the nanoclusters become solid in a cold flame region and join in fractal aggregates there. Along with growth of fractal aggregates, the restructuring process proceeds in a cold flame region that leads to the decrease of the fractal dimension of fractal aggregates. The measured parameters of fractal aggregates are in accord with those followed from theoretical models.

On the formation of copper nanoparticles in nanocluster aggregation source

The influence of pressure and type of inert gas (Ar and Kr) on the morphology and size distribution of nanoparticles produced in a nanocluster source is studied experimentally. The experimental data are used to validate the model of cluster formation from a supersaturated atomic vapor in an inert buffer gas, which has been developed in our previous paper. The model predictions are in accordance with the experimental findings.

Nonlinearities in composition dependence of structure parameters and magnetic properties of nanocrystalline fcc/bcc-mixed Co-Ni-Fe thin films

In this report, the nonlinearities are analyzed in fcc-to-bcc (fcc/bcc) population ratio, lattice parameters (aexpfcc∕aidealfcc and aexpbcc∕aidealbcc) and saturation magnetization (ISobs∕ISa) of the electrodeposited thin Co–Fe–Ni films as a function of average number of electrons in the alloy (ne), which proved to be a convenient way to follow the variation of chemical composition. The enhancement of the saturation magnetization correlated with the nonlinear deformation and connected with a complicated rearrangement of the outer shell electron configurations due to change in composition in a disordered alloy.