Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By i...Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By inserting additional layers and disrupting the regularity, two more defective crystals are also proposed. Photonic band structure of the ideal crystal and its dependence on the structural parameters are explored at the first step. Transmittance of the defective crystals and its changes with the thicknesses of the layers are studied. After extracting the optimum values for the thicknesses of the unit cells of the crystals, the optical response of the proposed structures at different temperatures and incident angles are investigated. Changes of the defect layers’ induced mode(s) are discussed by taking into consideration of the temperature dependence of the In Sb layer permittivity. The results clearly reflect the high potential of the proposed crystals to be used at high temperature terahertz technology as a promising alternative to their electronic counterparts.展开更多
In order to strengthen pure tin and improve its dry sliding resistance, Sn/SiC and Sn/Zn composites were fabricated via a powder metallurgy route. Microstructure,hardness and pin-on-disk wear resistance of pure tin an...In order to strengthen pure tin and improve its dry sliding resistance, Sn/SiC and Sn/Zn composites were fabricated via a powder metallurgy route. Microstructure,hardness and pin-on-disk wear resistance of pure tin and the fabricated composites were compared to those of Sn–7.5 Sb–3.5 Cu Babbitt alloy. The dominant wear mechanism at different applied loads was determined by analyzing worn surfaces and wear debris in each case. The results showed that the hardening effect of Zn was much higher than that of SiC. The hardening role of Zn in the tin matrix was ascribed to the direct load transfer mechanism. Microscopic studies of the worn surfaces revealed that the pure tin was susceptible to surface fatigue wear and plowing damage, depending on the normal load applied during the wear test. In the case of Sn/SiC composite and the Babbitt alloy, delamination wear mechanism resulting from subsurface crack propagation controlled the wear rate. While the highest hardness and the lowest coefficient of friction were obtained for the Babbitt alloy, the Sn/Zn composite exhibited the highest wear resistance at a constant applied load, indicating the importance of asperity contact type in the wear process.展开更多
文摘Optical features of a semiconductor–dielectric photonic crystal are studied theoretically. Alternating layers of micrometer sized SiO2/In Sb slabs are considered as building blocks of the proposed ideal crystal. By inserting additional layers and disrupting the regularity, two more defective crystals are also proposed. Photonic band structure of the ideal crystal and its dependence on the structural parameters are explored at the first step. Transmittance of the defective crystals and its changes with the thicknesses of the layers are studied. After extracting the optimum values for the thicknesses of the unit cells of the crystals, the optical response of the proposed structures at different temperatures and incident angles are investigated. Changes of the defect layers’ induced mode(s) are discussed by taking into consideration of the temperature dependence of the In Sb layer permittivity. The results clearly reflect the high potential of the proposed crystals to be used at high temperature terahertz technology as a promising alternative to their electronic counterparts.
文摘In order to strengthen pure tin and improve its dry sliding resistance, Sn/SiC and Sn/Zn composites were fabricated via a powder metallurgy route. Microstructure,hardness and pin-on-disk wear resistance of pure tin and the fabricated composites were compared to those of Sn–7.5 Sb–3.5 Cu Babbitt alloy. The dominant wear mechanism at different applied loads was determined by analyzing worn surfaces and wear debris in each case. The results showed that the hardening effect of Zn was much higher than that of SiC. The hardening role of Zn in the tin matrix was ascribed to the direct load transfer mechanism. Microscopic studies of the worn surfaces revealed that the pure tin was susceptible to surface fatigue wear and plowing damage, depending on the normal load applied during the wear test. In the case of Sn/SiC composite and the Babbitt alloy, delamination wear mechanism resulting from subsurface crack propagation controlled the wear rate. While the highest hardness and the lowest coefficient of friction were obtained for the Babbitt alloy, the Sn/Zn composite exhibited the highest wear resistance at a constant applied load, indicating the importance of asperity contact type in the wear process.
