Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatu...Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatures were investigated using X-ray diffraction（XRD）, scanning electron microscopy（SEM）. It was observed that the crystalline grain size of LMA was not only dependent on the preparation temperature but also on its powder morphology. In the temperature range of 1300 e1550℃, LMA showed platelet grain and the average crystalline grain size increases with the increase in temperature. At1600℃, if the powder was sintered for two times, the equiaxed grain could be found with the decrease in grain space, resulting in the reduction of the crystalline grain size. Styles of specimens（powder or disk） might have no obvious influence on morphologies and sizes of LMA crystalline grains which were synthesized with the well-dispersed raw material mixtures. The synthesis temperature played a key role in influencing the free space for the formation and growth of crystalline grains.展开更多
Coal has long been used as a major fuel for human activities in China.Significant amounts of SO_(2)and NO_(x)released into the atmosphere undergo chemical reactions to form secondary inorganic aerosols(SIAs),inducing ...Coal has long been used as a major fuel for human activities in China.Significant amounts of SO_(2)and NO_(x)released into the atmosphere undergo chemical reactions to form secondary inorganic aerosols(SIAs),inducing haze formation[1].展开更多
Black carbon(BC)is one of the major aerosol components with relatively high implications on climatic patterns through its radiative forcing(RF).South Asia has recently experienced an increased concentration of polluti...Black carbon(BC)is one of the major aerosol components with relatively high implications on climatic patterns through its radiative forcing(RF).South Asia has recently experienced an increased concentration of pollution;however,relatively fewer studies have been carried out on long-term assessment of BC and its implications.The present study analyzed the long-term concentration of BC in selected urban locations over South Asia using the Modern-Era Retrospective analysis for Research and Applications,version 2(MERRA-2).The study employed statistical analysis,including linear regression techniques,to assess the long-term concentration of BC.The results show that a rapid increase of BC is observed over most urban locations of South Asia with the predominance in winter and hence requires strict regional control measures to reduce the excess concentration of BC in the atmosphere.High concentration of BC in winter is attributed to anthropogenic activities and changes in meteorological conditions that enhance the accumulation of pollutants in the atmosphere.The relationship of BC with cloud top temperature and cloud effective radius demonstrates the direct and indirect effect of BC on cloud properties in this region.The RF results reveal that aerosol optical depth has positive aerosol RF in the atmosphere and negative RF at the top of the atmosphere(TOA)as well as at the bottom of the atmosphere(BOA).Negative RF at the TOA indicates less forcing efficiency due to fewer BC aerosols.On the other hand,averaging aerosol RF within the atmosphere reveals positive forcing,which suggests the efficiency force exerted by BC aerosols after absorbing solar radiation.展开更多
基金Project supported by the National Natural Science Foundation of China(51501137)National University of Defense Technology,and Wuhan University of Technology
文摘Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatures were investigated using X-ray diffraction（XRD）, scanning electron microscopy（SEM）. It was observed that the crystalline grain size of LMA was not only dependent on the preparation temperature but also on its powder morphology. In the temperature range of 1300 e1550℃, LMA showed platelet grain and the average crystalline grain size increases with the increase in temperature. At1600℃, if the powder was sintered for two times, the equiaxed grain could be found with the decrease in grain space, resulting in the reduction of the crystalline grain size. Styles of specimens（powder or disk） might have no obvious influence on morphologies and sizes of LMA crystalline grains which were synthesized with the well-dispersed raw material mixtures. The synthesis temperature played a key role in influencing the free space for the formation and growth of crystalline grains.
基金financially supported by the National Natural Science Foundation of China(42325304 and 42107123).
文摘Coal has long been used as a major fuel for human activities in China.Significant amounts of SO_(2)and NO_(x)released into the atmosphere undergo chemical reactions to form secondary inorganic aerosols(SIAs),inducing haze formation[1].
基金Supported by the National Natural Science Foundation of China (42050410321)Key Laboratory of Meteorological Disaster,Ministry of Education (KLME) and Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD),Nanjing University of Information Science&Technology (KLME202210)
文摘Black carbon(BC)is one of the major aerosol components with relatively high implications on climatic patterns through its radiative forcing(RF).South Asia has recently experienced an increased concentration of pollution;however,relatively fewer studies have been carried out on long-term assessment of BC and its implications.The present study analyzed the long-term concentration of BC in selected urban locations over South Asia using the Modern-Era Retrospective analysis for Research and Applications,version 2(MERRA-2).The study employed statistical analysis,including linear regression techniques,to assess the long-term concentration of BC.The results show that a rapid increase of BC is observed over most urban locations of South Asia with the predominance in winter and hence requires strict regional control measures to reduce the excess concentration of BC in the atmosphere.High concentration of BC in winter is attributed to anthropogenic activities and changes in meteorological conditions that enhance the accumulation of pollutants in the atmosphere.The relationship of BC with cloud top temperature and cloud effective radius demonstrates the direct and indirect effect of BC on cloud properties in this region.The RF results reveal that aerosol optical depth has positive aerosol RF in the atmosphere and negative RF at the top of the atmosphere(TOA)as well as at the bottom of the atmosphere(BOA).Negative RF at the TOA indicates less forcing efficiency due to fewer BC aerosols.On the other hand,averaging aerosol RF within the atmosphere reveals positive forcing,which suggests the efficiency force exerted by BC aerosols after absorbing solar radiation.
