The bulk A1-12 Si eutectic composites were fabricated through a conventional liquid metal casting route, especially with the help of ultrafine ceramic powders made by self-propagating high-temperature synthesis （SHS...The bulk A1-12 Si eutectic composites were fabricated through a conventional liquid metal casting route, especially with the help of ultrafine ceramic powders made by self-propagating high-temperature synthesis （SHS） process. The SHS powders were fabricated by the chemical reaction between micro-sized SiC and A1 particles at very high combustion temperatures, producing the coarse A1 particles （several tens of microns） containing ultrafine SiC ceramic particles. Microstructural observation revealed that the addition of ultrafine SiC particles has a crumbling tendency of Si eutectic phase. It is suggested that the casting method combined with SHS process is promising for fabricating the Al-based MMC with ultrafine ceramic particles.展开更多
The transmission spectra of one-dimensional （1D） photonic crystals （PCs） with parallel and twisted nematic liquid crystals （LCs） as defect layers are discussed by 4 X 4 matrix method, respectively. The results s...The transmission spectra of one-dimensional （1D） photonic crystals （PCs） with parallel and twisted nematic liquid crystals （LCs） as defect layers are discussed by 4 X 4 matrix method, respectively. The results show that the photonie band gap （PBG） mainly depends on the periodic arrays of dielectric composites. The orientation of director and the symmetry of the director configuration have important influence on the location and amplitude of defect modes. The location and amplitude of defect modes can be controlled conveniently by changing the orientation of director. The symmetry of the director configuration can help us understand the defect modes spectra.展开更多
基金supported by the Korea Atomic Energy Research Institute (KAERI) R&D Program
文摘The bulk A1-12 Si eutectic composites were fabricated through a conventional liquid metal casting route, especially with the help of ultrafine ceramic powders made by self-propagating high-temperature synthesis （SHS） process. The SHS powders were fabricated by the chemical reaction between micro-sized SiC and A1 particles at very high combustion temperatures, producing the coarse A1 particles （several tens of microns） containing ultrafine SiC ceramic particles. Microstructural observation revealed that the addition of ultrafine SiC particles has a crumbling tendency of Si eutectic phase. It is suggested that the casting method combined with SHS process is promising for fabricating the Al-based MMC with ultrafine ceramic particles.
基金supported by the National Natural Science Foundation of China(No.10805040)the Talent Introduction Program of Henan University of Technology(No.2007BS041)
文摘The transmission spectra of one-dimensional （1D） photonic crystals （PCs） with parallel and twisted nematic liquid crystals （LCs） as defect layers are discussed by 4 X 4 matrix method, respectively. The results show that the photonie band gap （PBG） mainly depends on the periodic arrays of dielectric composites. The orientation of director and the symmetry of the director configuration have important influence on the location and amplitude of defect modes. The location and amplitude of defect modes can be controlled conveniently by changing the orientation of director. The symmetry of the director configuration can help us understand the defect modes spectra.
