Key Engineering Materials Vols. 336-338

Abstract: Au/SiO2 nano-composite multilayer thin films with different thickness were prepared on a quartz substrate by magnetron plasma sputtering. The microstructure, morphology and optical properties of the films were investigated by using TEM and optical absorption spectra. [Au/SiO2]×5 and [Au/SiO2] × 11 multilayer thin films have well-defined interface. The thickness of the multilayer was 60nm and 130 nm for the thin films with 5 and 11 layers, respectively. The optical absorption peaks due to the surface plasma resonance appeared at a wavelength of 560 nm for the both [Au/SiO2]×5 and [Au/SiO2]×11 thin films. The intensity of the absorption peak increased with increasing numbers of deposition layers. The optical absorption spectra of Au/SiO2 multilayer thin films are well agreement with the theoretical optical absorption spectra calculated from rewritten Maxwell–Garnett effective medium theory.

Abstract: A functional gradient (FG) layer based on Ni-ZrO2 (3mol% Y2O3) was obtained by spraying diluted organic suspensions with an airbrush. The different layers were sequentially sprayed onto Y-TZP and Ni substrates, in 25 vol.% compositional steps. Afterwards, two ZrO2 bulk pieces as well as ZrO2 and Ni adherents were successfully joined using this type of FG structure as an interlayer. The microstructure and the possible reactions between the ZrO2 and Ni phases were analyzed. The porosity of each layer was evaluated by micro-hardness measurements.

Abstract: Symmetric three-layer composites prepared by sintering freeze cast compacts of alumina with additions of nanoparticle/whisker SiC, in 1-atm nitrogen at 1700-1800oC have been characterized in terms of microstructure and mechanical properties. Additions of SiC to Al2O3 result in improvement in toughness. In such cases, however, the reduction in strength at small flaw sizes must be overcome. Contact damage resistance is greatly increased in layered composites compared with monolithic composites, possibly due to redirection of indentation flaws along the layer interface.

Abstract: BON film was fabricated as buffer layer by radio frequency plasma enhanced metal-organic chemical vapor deposition with 100 kHz frequency and trimethyl borate precursor. The typical binding energy of each element is 191.5 eV of B1s, 399.4 eV of N1s, and 531.2 eV of O1s in the films detected by XPS. HRTEM showed the film contained amorphous composition and nano-sized crystalline particles. Electrical properties of films were characterized by I–V curve. The order-magnitude of electric conductivity was measured as several tens (
·cm)-1. The hardness of BON film was ~ 10 GPa.

Abstract: Surfactant-zirconium phosphate composites were prepared by surfactant cetyltrimethylammonium bromide intercalating to α-zirconium phosphate. The interlayer spacing of the lamellar structure was greatly expanded to 39.6 Å, as compared to 7.6 Å of α-zirconium phosphate. The molar ratio of surfactant to α-zirconium phosphate in the composites was found to be 1/1.46. The expanded interlayer separation is beneficial for complicated guest molecules intercalating to the galleries of the composites.

Abstract: A multiple impact loading experiment was designed to investigate the cracking behavior in the transitional regions of laser-clad iron base alloy on an electrolytic low titanium aluminium alloys under multiple impact loading in this study. The concept of TCR (transitional crack ratio) was introduced to evaluate the crack resistance of the transitional regions to multiple impact loading (impact resistance). Results showed that the substrate temperature during laser cladding process and the scanning velocity have significant influences on the microstructure of the transitional regions and then the impact resistances of the laser-clad iron alloy coating. The laser-clad iron base alloy coatings obtained at the substrate temperature within 275 ~ 320°C displayed the best impact resistance. Furthermore, the crack mechanism in the transitional regions was analyzed.

Abstract: Functionally structured material is a tailored material to have unique geometric structures and create new functions or high performances. Design and fabrication of 3D ceramic photonic crystals and fractals using CAD/CAM stereolithography are demonstrated as well as their unique functions of reflection and localization of electromagnetic waves as typical examples of functionally structured materials. The outlook of functionally structured materials is briefly discussed.

Abstract: Functionally graded thermoelectric material (TE FGM) is one of main research direction in research field of thermoelectric (TE) materials all over world. A lot of research work on TE FGM has been done to improve the conversion efficiency of TE. Here the development of TE FGM in recent years is discussed in the aspects of the model design, the materials selection, the barrier or joining choice and the device fabrication.

Abstract: Two kinds of thick-walled rings, consisted of WCP/Fe-C gradient composites layers containing about 54 and 70 vol.% of WCP and Fe-C alloy core, were cast by centrifugal casting method. The microstructure, mechanical properties and wear resistance of the gradient composites were investigated. Meanwhile the results were compared with those made of the high speed steel. It was found that WCP in the two kind of gradient composites layers were even well distributed, WCP/Fe-C composites layer of 23-28mm was obtained, the transition layer between the composites layer and matrix alloy core was perfect. The tensile strengths of the two gradient composites layers achieved 345MPa, 460MPa and the impact toughness were 4.6J/cm2, 6.2J/cm2 respectively. Moreover the hardness of the composites layers attained HRA81 and HRA 78. The result of the comparison among the gradient composites layers and that made of the high speed steel showed that the wear resistance of the gradient composites layers containing about 50 and 70 vol.% of WCP was more than 20 times higher than that of the high speed steel under loads of 100N and 200N and sliding velocity of 60 m/s. Finally, the wear-mechanism was discussed.