Dust emission by wind erosion in surface is a serious problem in many arid regions around the world,and it is harmful to the ecological environment,human health,and social economy.To monitor the characteristics of sal...Dust emission by wind erosion in surface is a serious problem in many arid regions around the world,and it is harmful to the ecological environment,human health,and social economy.To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion.Therefore,a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert.One sampling system was installed on the flat sand surface at Tazhong,consisting of a meteorological tower with a height of 2 m,a piezoelectric saltation sensor（Sensit）,and a Big Spring Number Eight（BSNE） sampler station.Occurrence of saltation activity was recorded every second using the Sensit.Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface.Sediment was collected from the samplers every 24 h.It is found that saltation activity was detected for only 21.5% of the hours measured,and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions.The threshold wind velocity was variable,its minimum value was 4.9 m s 1,the maximum value was 9.2 m s 1,and the average value was 7.0 m s 1.The threshold wind velocity presented a positive linear increase during the measurement period.The observation site had a sediment discharge of 82.1 kg m 1 over a period of 24 h.Based on hourly saltation counts,hourly sediment discharge was estimated.Overall,there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity.The results show that the changes of sediment discharge do not quite depend on wind velocity.展开更多
Magnesium is a promising metal used as anodes for chemical power sources. This metal could theoretically provide negative discharge potential and exhibit large capacity during the discharge process. However, when the ...Magnesium is a promising metal used as anodes for chemical power sources. This metal could theoretically provide negative discharge potential and exhibit large capacity during the discharge process. However, when the magnesium anode is adopted for practical applications, several issues, such as the discharge products adhered to the electrode surface, the self-discharge occurring on the anode material, and the detachment of metallic particles, adversely affect its inherently good discharge performance. In this work, the types of chemical power sources using magnesium as anodes were elaborated, and the approaches to enhance its anode performance were analyzed.展开更多
b The discharge performance of Mg-Al-Pb-La anode was investigated by electrochemical techniques and compared withthat of Mg-Al-Pb alloy. The results indicate that the Mg-Al-Pb-La anode provides enhanced corrosion resi...b The discharge performance of Mg-Al-Pb-La anode was investigated by electrochemical techniques and compared withthat of Mg-Al-Pb alloy. The results indicate that the Mg-Al-Pb-La anode provides enhanced corrosion resistance at open circlepotential, and exhibits better discharge activity than the Mg-Al-Pb alloy. The utilization efficiency of Mg-Al-Pb-La anode ishigher than that of commercial Mg-Al-Zn （AZ） and Mg-Al-Mn （AM） alloys. A single Mg-air battery with Mg-Al-Pb-La alloy asthe anode and air as the cathode has an average discharge potential of 1.295 V and a discharge capacity of 1370 mA·h/g duringdischarge at 10 mA/cm2, which is higher than that of batteries using Mg-Li anodes. The enhancement in discharge performance ofthe Mg-Al-Pb-La anode is caused by its modified microstructure, which reduces the self-corrosion and accelerates the spalling ofoxidation products during battery discharge. Furthermore, the dissolution mechanism of Mg-Al-Pb-La anode during the dischargeprocess was analyzed.展开更多
The effects of surface treatment, particle size distribution,rare earth composition and B additive on the high rate discharge performance of hydrogen storage alloys were investigated. It is found that the activity, di...The effects of surface treatment, particle size distribution,rare earth composition and B additive on the high rate discharge performance of hydrogen storage alloys were investigated. It is found that the activity, discharge capacity and high rate dischargeability of the alloys are improved after physical and chemical modification as a result of the increase of the surface area and formation of the electrocatalysis layers, which increase both the electrochemical reaction rate on the alloy surface and H diffusion rate in the alloy bulk. It is also found that both the over-coarse and over-fine particle size increase the contact resistance of the electrode, resulting in a decrease of discharge capacity, deterioration of high rate dischargeability and lower discharge plateau. In another word, a suitable particle size distribution can enhance the alloy activity, discharge capacity and high rate dischargeability. In addition, the high rate dischargeability is enhanced by increasing La content and decreasing Ce content of the alloy composition because of enlargement of the unit cell volume and the improvement of the surface activity. Moreover, B additive resultes in the formation of the second phase, and makes the alloys easier pulverization, which greatly improves the activity, discharge capacity and high rate dischargeability.展开更多
Mg-6%Al-5%Pb(mass fraction) anodes with different contents of zinc were prepared by melting and casting.The electrochemical discharge behavior of these anodes in 3.5% NaCl solutions was investigated by galvanostatic t...Mg-6%Al-5%Pb(mass fraction) anodes with different contents of zinc were prepared by melting and casting.The electrochemical discharge behavior of these anodes in 3.5% NaCl solutions was investigated by galvanostatic test and electrochemical impedance spectroscopy(EIS).The microstructures and the corroded surfaces of these anodes were studied by scanning electron microscopy(SEM) and emission spectrum analysis(ESA).The phase structures and the corrosion products of the anodes were analyzed by X-ray diffraction(XRD).The results show that zinc promotes the grain refinement of Mg-6%Al-5%Pb anode and makes the average discharge potential of Mg-6%Al-5%Pb anode more negative during galvanostatic test.Mg-6%Al-5%Pb anode with the addition of 1%(mass fraction) zinc has the best electrochemical performance.The activation mechanism of zinc to Mg-6%Al-5%Pb anode is as follows:The hydrolyzation of dissolved Zn2+ ions reduces the pH value of the solution near the surface of the anode and accelerates the dissolution of Mg(OH)2 film;The precipitated Zn(OH)2 with similar structure as Mg(OH)2 combines with Mg(OH)2 film easily and makes it break down.展开更多
基金Supported by the National Natural Science Foundation of China (41175017 and 41175140)China Meteorological Administration Special Public Welfare Research Fund (GYHY201006012)
文摘Dust emission by wind erosion in surface is a serious problem in many arid regions around the world,and it is harmful to the ecological environment,human health,and social economy.To monitor the characteristics of saltation activity and to calculate the threshold wind velocity and sediment discharge under field conditions have significance on the research of dust emission by wind erosion.Therefore,a field experiment was conducted over the flat sand in the hinterland of the Taklimakan Desert.One sampling system was installed on the flat sand surface at Tazhong,consisting of a meteorological tower with a height of 2 m,a piezoelectric saltation sensor（Sensit）,and a Big Spring Number Eight（BSNE） sampler station.Occurrence of saltation activity was recorded every second using the Sensit.Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0.05 m and the highest sampler at 1.0 m above the soil surface.Sediment was collected from the samplers every 24 h.It is found that saltation activity was detected for only 21.5% of the hours measured,and the longest period of saltation activity occurring continuously was not longer than 5 min under the field conditions.The threshold wind velocity was variable,its minimum value was 4.9 m s 1,the maximum value was 9.2 m s 1,and the average value was 7.0 m s 1.The threshold wind velocity presented a positive linear increase during the measurement period.The observation site had a sediment discharge of 82.1 kg m 1 over a period of 24 h.Based on hourly saltation counts,hourly sediment discharge was estimated.Overall,there was no obvious linear or other functional relationship between the hourly sediment discharge and wind velocity.The results show that the changes of sediment discharge do not quite depend on wind velocity.
基金Project supported by the Postdoctoral Science Foundation of Central South UniversityProject(2014M552151)supported by the China Postdoctoral Science FoundationProject(51101171)supported by the National Natural Science Foundation of China
文摘Magnesium is a promising metal used as anodes for chemical power sources. This metal could theoretically provide negative discharge potential and exhibit large capacity during the discharge process. However, when the magnesium anode is adopted for practical applications, several issues, such as the discharge products adhered to the electrode surface, the self-discharge occurring on the anode material, and the detachment of metallic particles, adversely affect its inherently good discharge performance. In this work, the types of chemical power sources using magnesium as anodes were elaborated, and the approaches to enhance its anode performance were analyzed.
基金Project(2015JC3004)supported by the Science and Technology Plan of Hunan Province,ChinaProject(2016JJ2147)supported by the Natural Science Foundation of Hunan Province,ChinaProject(51401243)supported by the National Natural Science Foundation of China
文摘b The discharge performance of Mg-Al-Pb-La anode was investigated by electrochemical techniques and compared withthat of Mg-Al-Pb alloy. The results indicate that the Mg-Al-Pb-La anode provides enhanced corrosion resistance at open circlepotential, and exhibits better discharge activity than the Mg-Al-Pb alloy. The utilization efficiency of Mg-Al-Pb-La anode ishigher than that of commercial Mg-Al-Zn （AZ） and Mg-Al-Mn （AM） alloys. A single Mg-air battery with Mg-Al-Pb-La alloy asthe anode and air as the cathode has an average discharge potential of 1.295 V and a discharge capacity of 1370 mA·h/g duringdischarge at 10 mA/cm2, which is higher than that of batteries using Mg-Li anodes. The enhancement in discharge performance ofthe Mg-Al-Pb-La anode is caused by its modified microstructure, which reduces the self-corrosion and accelerates the spalling ofoxidation products during battery discharge. Furthermore, the dissolution mechanism of Mg-Al-Pb-La anode during the dischargeprocess was analyzed.
文摘The effects of surface treatment, particle size distribution,rare earth composition and B additive on the high rate discharge performance of hydrogen storage alloys were investigated. It is found that the activity, discharge capacity and high rate dischargeability of the alloys are improved after physical and chemical modification as a result of the increase of the surface area and formation of the electrocatalysis layers, which increase both the electrochemical reaction rate on the alloy surface and H diffusion rate in the alloy bulk. It is also found that both the over-coarse and over-fine particle size increase the contact resistance of the electrode, resulting in a decrease of discharge capacity, deterioration of high rate dischargeability and lower discharge plateau. In another word, a suitable particle size distribution can enhance the alloy activity, discharge capacity and high rate dischargeability. In addition, the high rate dischargeability is enhanced by increasing La content and decreasing Ce content of the alloy composition because of enlargement of the unit cell volume and the improvement of the surface activity. Moreover, B additive resultes in the formation of the second phase, and makes the alloys easier pulverization, which greatly improves the activity, discharge capacity and high rate dischargeability.
基金Project(JPPT-115-168) supported by the National Key Science and Technological Program of China
文摘Mg-6%Al-5%Pb(mass fraction) anodes with different contents of zinc were prepared by melting and casting.The electrochemical discharge behavior of these anodes in 3.5% NaCl solutions was investigated by galvanostatic test and electrochemical impedance spectroscopy(EIS).The microstructures and the corroded surfaces of these anodes were studied by scanning electron microscopy(SEM) and emission spectrum analysis(ESA).The phase structures and the corrosion products of the anodes were analyzed by X-ray diffraction(XRD).The results show that zinc promotes the grain refinement of Mg-6%Al-5%Pb anode and makes the average discharge potential of Mg-6%Al-5%Pb anode more negative during galvanostatic test.Mg-6%Al-5%Pb anode with the addition of 1%(mass fraction) zinc has the best electrochemical performance.The activation mechanism of zinc to Mg-6%Al-5%Pb anode is as follows:The hydrolyzation of dissolved Zn2+ ions reduces the pH value of the solution near the surface of the anode and accelerates the dissolution of Mg(OH)2 film;The precipitated Zn(OH)2 with similar structure as Mg(OH)2 combines with Mg(OH)2 film easily and makes it break down.
