Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium...Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor nucleation in phase transitions and condensation from atomic collision and coacervation with collision under vacuum conditions were discussed. Magnesium powder and magnesium lump condensates were produced under different conditions and characterized by scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDS）. The right condensation zone temperature approach to the liquid transition primarily improved the magnesium vapor concentration rate. The gas-solid phase transition was primarily inhibited by setting a small condenser temperature gradient. Under the right condensation temperature and temperature gradients, increasing magnesium vapor partial pressure improved crystallization and reduced the oxidation rate.展开更多
Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt...Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt contained in the salt water were investigated by scanning electron microscope （SEM）, transmission electron microscope （TEM）, energy dispersive spectrometer （EDS）, electron probe micro analyzer （EPMA）, X-ray diffraction （XRD）, infrared transmission spectroscope （IR）, and atmospheric corrosion monitor （ACM）. The results showed that, with the deposition, atmospheric corrosion of AA2024 could occur when the relative humidity （RH） was lower than 30%. A main crystalline component of corrosion products, layered double hydroxides （LDH）, [Mg1-xAlx（OH）2]^x＋ Clx-·mH2O （LDH-C1）, was determined, which meant that magnesium ion played an important role in the corrosion process. It not only facilitated the corrosion as a result of deliquescence, but also was involved in the corrosion process as a reactant.展开更多
Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of a...Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of an individual millimeter-sized magnesium particle in water vapor were studied.In order to build an atmosphere of water vapor,an experiment system was established and validated by the experiments of magnesium particle in air.The ignition and combustion of a single magnesium particle were accomplished in a combustor filled with water vapor.The surface changes of the particle during the ignition and a steady-state vapor phase combustion were observed.Based on the data obtained,ignition mechanism was analyzed and ignition temperature was determined.The steady-state combustion of the sample was controlled by diffusion in gas phase,and a one-dimensional,spherically symmetric quasi-steady model was adopted to describe the process.The dependence of burning time on the diameter was investigated,and the conclusion that burning time is proportional to the square of the metal sample diameter was drawn.展开更多
基金Project(51304095)supported by the National Natural Science Foundation of ChinaProject(S2013FZ029)supported by Science and Technology Planning Project of Yunnan Province
文摘Recent findings related to coagulable magnesium vapor nucleation and growth in vacuum were assessed critically, with emphasis on understanding these processes at a fundamental molecular level. The effects of magnesium vapor pressure, condensation temperature, and condensation zone temperature gradient on magnesium vapor nucleation in phase transitions and condensation from atomic collision and coacervation with collision under vacuum conditions were discussed. Magnesium powder and magnesium lump condensates were produced under different conditions and characterized by scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDS）. The right condensation zone temperature approach to the liquid transition primarily improved the magnesium vapor concentration rate. The gas-solid phase transition was primarily inhibited by setting a small condenser temperature gradient. Under the right condensation temperature and temperature gradients, increasing magnesium vapor partial pressure improved crystallization and reduced the oxidation rate.
基金Project(51131007) supported by the National Natural Science Foundation of China
文摘Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt contained in the salt water were investigated by scanning electron microscope （SEM）, transmission electron microscope （TEM）, energy dispersive spectrometer （EDS）, electron probe micro analyzer （EPMA）, X-ray diffraction （XRD）, infrared transmission spectroscope （IR）, and atmospheric corrosion monitor （ACM）. The results showed that, with the deposition, atmospheric corrosion of AA2024 could occur when the relative humidity （RH） was lower than 30%. A main crystalline component of corrosion products, layered double hydroxides （LDH）, [Mg1-xAlx（OH）2]^x＋ Clx-·mH2O （LDH-C1）, was determined, which meant that magnesium ion played an important role in the corrosion process. It not only facilitated the corrosion as a result of deliquescence, but also was involved in the corrosion process as a reactant.
基金supported by the National Natural Science Foundation of China (Grant No. 51006118)
文摘Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction.In this work,the ignition and combustion characteristics of an individual millimeter-sized magnesium particle in water vapor were studied.In order to build an atmosphere of water vapor,an experiment system was established and validated by the experiments of magnesium particle in air.The ignition and combustion of a single magnesium particle were accomplished in a combustor filled with water vapor.The surface changes of the particle during the ignition and a steady-state vapor phase combustion were observed.Based on the data obtained,ignition mechanism was analyzed and ignition temperature was determined.The steady-state combustion of the sample was controlled by diffusion in gas phase,and a one-dimensional,spherically symmetric quasi-steady model was adopted to describe the process.The dependence of burning time on the diameter was investigated,and the conclusion that burning time is proportional to the square of the metal sample diameter was drawn.
