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Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm[sup 2] . The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC[sub 1-x] , then to αW[sub 2] C and CW[sub 3] , and finally to W crystal. It is suggested that the undulating ‘hill–valley’ morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation. [ABSTRACT FROM AUTHOR]

Abstract. Numerical calculations based on a thermal model were presented, which describe the process of target heating and ablation of cobalt during irradiation by 30-ns laser pulses at 308 nm. The attenuation of laser by vapor has been taken into account in this model. As results of the calculations, the temperature distribution beneath the target surface and the temporal evolution of surface temperature were given. The dependence of ablation rate on laser fluence was also studied based on this model. The surface ablation of cobalt with pulsed excimer laser was investigated experimentally. Our model considering proper vapor attenuation has shown to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Li+ ion-doped BaTiO3 (LBT-x, x = 0, 3%, 5%, 7%) ceramics were prepared by the solid-state reaction method, which were analyzed by XRD and EDS. The Ba2TiO4 phase was formed on the surface of sintered LBT-x ceramics with high Li+ concentration (x = 5%, 7%), and tetragonal phase appeared after the removal of Ba2TiO4 surface layer. According to the results from first-principle calculation of 2 × 2 × 2 and 3 × 3 × 3 supercells, Li+ ions can occupy B site of ABO3 perovskite structure. The LBT-x (x = 3%, 5%, 7%) ceramics showed antiferroelectric-like double hysteresis loops which form [LiTi–Vo]− dipoles and pin the domain walls. The piezoelectric constant d33 also decreases due to pinning effect. [ABSTRACT FROM AUTHOR]