This paper studied the active-to-passive oxidative mechanism of C/SiC composite under high temperature and oxidative conditions. An analytic model and computational method were established based on the process of gas ...This paper studied the active-to-passive oxidative mechanism of C/SiC composite under high temperature and oxidative conditions. An analytic model and computational method were established based on the process of gas diffusion in boundary layer and the equilibrium relations in surface chemical reactions. Simultaneously, an engineering equation to predict the oxygen partial pressure of active-to-passive transition was derived under the specific temperature zone. The results indicated that the active-to-passive oxidation transition of C/SiC is closely related to the composition of the material. At certain temperature and oxygen partial pressure conditions, the composite with high carbon content is prone to cause active oxidation which is negative to the oxidation resistance of the material.展开更多
We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle （Al2O3-NP） thin film. A thin film of Al2O3 was prepared by embedding Al2O3-...We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle （Al2O3-NP） thin film. A thin film of Al2O3 was prepared by embedding Al2O3-NPs into a polyvinyl alcohol （PVA） as a host polymer, and then inserted between two fiber ferrules to act as a saturable absorber （SA）. By incorporating the Al2O3-PVA SA into the laser cavity, a stable dual-wavelength pulse output centered at 1050 and 1060.7nm is observed at threshold pump power of 80mW. As the pump power is gradually increased from 80 to 300mW, the repetition rate of the generated pulse increases from 16.23 to 59 kHz, while the pulse width decreases from 19 to 6μs. To the best of our knowledge, this is the first demonstration for this type of SA operating in the 1 μm region.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 11172284)the International Science and Technology Cooperative Project from Ministry of Science and Technology (GrantNo. 2013DFA30820)
文摘This paper studied the active-to-passive oxidative mechanism of C/SiC composite under high temperature and oxidative conditions. An analytic model and computational method were established based on the process of gas diffusion in boundary layer and the equilibrium relations in surface chemical reactions. Simultaneously, an engineering equation to predict the oxygen partial pressure of active-to-passive transition was derived under the specific temperature zone. The results indicated that the active-to-passive oxidation transition of C/SiC is closely related to the composition of the material. At certain temperature and oxygen partial pressure conditions, the composite with high carbon content is prone to cause active oxidation which is negative to the oxidation resistance of the material.
基金Supported by the Iraqi Ministry of Higher Education and Scientific Research and University of Baghdad
文摘We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle （Al2O3-NP） thin film. A thin film of Al2O3 was prepared by embedding Al2O3-NPs into a polyvinyl alcohol （PVA） as a host polymer, and then inserted between two fiber ferrules to act as a saturable absorber （SA）. By incorporating the Al2O3-PVA SA into the laser cavity, a stable dual-wavelength pulse output centered at 1050 and 1060.7nm is observed at threshold pump power of 80mW. As the pump power is gradually increased from 80 to 300mW, the repetition rate of the generated pulse increases from 16.23 to 59 kHz, while the pulse width decreases from 19 to 6μs. To the best of our knowledge, this is the first demonstration for this type of SA operating in the 1 μm region.
