A novel method for sampling and enriching organic volatile contaminants in the vacuum environment combined with qualitative analysis based on the vacuum simulation test is proposed. A nanofiber is used as absorbent to...A novel method for sampling and enriching organic volatile contaminants in the vacuum environment combined with qualitative analysis based on the vacuum simulation test is proposed. A nanofiber is used as absorbent to collect the organic volatile contaminants in the vacuum environment and then eluted by methanol. The eluent is analyzed by gas chromatography （ GC ） and gas chromatography-mass spectrometry （GC/MS） to identify the composition of the organic contaminants. The nanofiber is composed of polystyrene and it is prepared by electrospinning. Before being used, the nanofiber is processed by ultrasound in ethanol for 15 min to remove some impurities and dried in an oven at 60 ℃, and then 10 mg of the nanofiber is wrapped in a thermoplastic polyester fabric pocket. The vacuum pump oil and di-iso-decyl phthalate （DIDP） are chosen as absorbates to test the absorbent performance of the nanofiber in the vacuum environment. Experiments are performed under the pressure of 10-4 and 103 Pa, respectively. It is shown that the nanofiber-based enrichment device can be used to adsorb the organic contaminants in the vacuum simulation environment.展开更多
As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry,novel sliding electrical contact materials with high self-lubricating performance in multiple environments a...As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry,novel sliding electrical contact materials with high self-lubricating performance in multiple environments are eagerly required.Herein a copper-based composite with WS2 and graphite as solid lubricant are fabricated by powder metallurgy hot-pressed method.The friction and wear behaviors of the composites with and without current are investigated under the condition with sliding velocity of 10 m/s and normal load of 2.5N/cm 2 in both air and vacuum.Morphologies of the worn surfaces are observed by optical microscope and compositions of the lubricating films are analyzed by XPS.Surface profile curves and roughness of the worn surfaces are obtained by 2205 surface profiler.The results of wear tests show that the friction coefficient and wear volume loss of the composites with current are greater than that without current in both air and vacuum due to the adverse effects of electrical current which damaged the lubricating film partially and roughed the worn surfaces.XPS results demonstrate that the lubricating film formed in air is composed of oxides of Cu,WS2,elemental S and graphite,while the lubricating film formed in vacuum is composed of Cu,WS2 and graphite.Because of the synergetic lubricating action of oxides of Cu,WS2 and graphite,the composites show low friction coefficient and wear volume loss in air condition.Owing to the fact that graphite loses its lubricity which makes WS2 become the only lubricant,severe adhesive and abrasive wear occur and result in a high value of wear rate in vacuum condition.The formation of the lubricating film on the contact interface between the brush and ring is one of the factors which can greatly affect the wear performance of the brushes.The low contact voltage drop of the composites in vacuum condition is attributed to the high content of Cu in the surface film.This study fabricated a kind of new sliding electrical contact self-lubricating composite with dual-lubricant which can work well in both air and vacuum environments and provides a comprehensive analysis on the lubrication mechanisms of the composite.展开更多
A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic co...A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.展开更多
Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-C...Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batterieswas conducted. The impacts of temperature, pressure and time were studied respectively. The mechanism of vacuum thermal recovering was also discussed. The results show that: Ni-Cd batteries can be recovered effectively byvacuum-aided recovering system at 573~1173 K. At constant pressure, the increase of temperature can improve theseparating efficiency of cadmium. When the temperature is 1173 K, the cadmium can evaporate completely fromthe residue during 3 h at 10 Pa. The reduction of pressure in the certain range is effective to separate cadmium byvacuum distillation. Distillation time is a very important factor affecting separation of cadmium.展开更多
The lunar surface is a typical vacuum environment,and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission.In addition to the radiator,the sublimator ...The lunar surface is a typical vacuum environment,and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission.In addition to the radiator,the sublimator is recommended as one of the promising options for heat rejection.The sublimator makes use of water to freeze and sublimate in a porous medium,rejecting heat to the vacuum environment.The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface.In this paper,the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of threephase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions.The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle.As the sublimation progresses,the phase-change interface moves downward steadily,the length of the ice-peak increases,but the icicle decreases.The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.展开更多
基金The National Basic Research Program of China(973 Program)(No.2012CB933302)the National Natural Science Foundation of China(No.81172720)+2 种基金the Science and Technology Pillar Program of Jiangsu Province(No.BE2010088)the Municipal Science and Technology Project of Suzhou City(No.SYN201006,SG201028)the Undergraduate Student Scientific Training Program of Southeast University(No.T12261005)
文摘A novel method for sampling and enriching organic volatile contaminants in the vacuum environment combined with qualitative analysis based on the vacuum simulation test is proposed. A nanofiber is used as absorbent to collect the organic volatile contaminants in the vacuum environment and then eluted by methanol. The eluent is analyzed by gas chromatography （ GC ） and gas chromatography-mass spectrometry （GC/MS） to identify the composition of the organic contaminants. The nanofiber is composed of polystyrene and it is prepared by electrospinning. Before being used, the nanofiber is processed by ultrasound in ethanol for 15 min to remove some impurities and dried in an oven at 60 ℃, and then 10 mg of the nanofiber is wrapped in a thermoplastic polyester fabric pocket. The vacuum pump oil and di-iso-decyl phthalate （DIDP） are chosen as absorbates to test the absorbent performance of the nanofiber in the vacuum environment. Experiments are performed under the pressure of 10-4 and 103 Pa, respectively. It is shown that the nanofiber-based enrichment device can be used to adsorb the organic contaminants in the vacuum simulation environment.
基金supported by Major Research Program of National Natural Science Foundation of China(Grant No.91026018)National Natural Science Foundation of China(Grant No.60979017)Doctoral Fund of Ministry of Education of China(Grant No.20110111110015)
文摘As the traditional graphite-based composites cannot meet the requirement of rapid developing modern industry,novel sliding electrical contact materials with high self-lubricating performance in multiple environments are eagerly required.Herein a copper-based composite with WS2 and graphite as solid lubricant are fabricated by powder metallurgy hot-pressed method.The friction and wear behaviors of the composites with and without current are investigated under the condition with sliding velocity of 10 m/s and normal load of 2.5N/cm 2 in both air and vacuum.Morphologies of the worn surfaces are observed by optical microscope and compositions of the lubricating films are analyzed by XPS.Surface profile curves and roughness of the worn surfaces are obtained by 2205 surface profiler.The results of wear tests show that the friction coefficient and wear volume loss of the composites with current are greater than that without current in both air and vacuum due to the adverse effects of electrical current which damaged the lubricating film partially and roughed the worn surfaces.XPS results demonstrate that the lubricating film formed in air is composed of oxides of Cu,WS2,elemental S and graphite,while the lubricating film formed in vacuum is composed of Cu,WS2 and graphite.Because of the synergetic lubricating action of oxides of Cu,WS2 and graphite,the composites show low friction coefficient and wear volume loss in air condition.Owing to the fact that graphite loses its lubricity which makes WS2 become the only lubricant,severe adhesive and abrasive wear occur and result in a high value of wear rate in vacuum condition.The formation of the lubricating film on the contact interface between the brush and ring is one of the factors which can greatly affect the wear performance of the brushes.The low contact voltage drop of the composites in vacuum condition is attributed to the high content of Cu in the surface film.This study fabricated a kind of new sliding electrical contact self-lubricating composite with dual-lubricant which can work well in both air and vacuum environments and provides a comprehensive analysis on the lubrication mechanisms of the composite.
基金supported by the Aeronautical Science Foun-dation of China(No.2012XX51043)‘‘Fanzhou’’Youth Scientific Funds of China(No.20100504)
文摘A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.
文摘Recovery of Ni-Cd batteries was studied by a self-designed vacuum-aided recovering system under laboratory conditions. The fundamental research on a process of disassembling and recovering selected materials from Ni-Cd batterieswas conducted. The impacts of temperature, pressure and time were studied respectively. The mechanism of vacuum thermal recovering was also discussed. The results show that: Ni-Cd batteries can be recovered effectively byvacuum-aided recovering system at 573~1173 K. At constant pressure, the increase of temperature can improve theseparating efficiency of cadmium. When the temperature is 1173 K, the cadmium can evaporate completely fromthe residue during 3 h at 10 Pa. The reduction of pressure in the certain range is effective to separate cadmium byvacuum distillation. Distillation time is a very important factor affecting separation of cadmium.
基金primarily funded by the cooperative project offered by Beijing Key Laboratory of Space Thermal Control Technologyfunded by China Postdoctoral Science Foundation(No.2020 M671618)。
文摘The lunar surface is a typical vacuum environment,and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission.In addition to the radiator,the sublimator is recommended as one of the promising options for heat rejection.The sublimator makes use of water to freeze and sublimate in a porous medium,rejecting heat to the vacuum environment.The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface.In this paper,the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of threephase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions.The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle.As the sublimation progresses,the phase-change interface moves downward steadily,the length of the ice-peak increases,but the icicle decreases.The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.
