The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were investigated.The coercivity of Nd-Fe-B bulk alloy can be...The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were investigated.The coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co powders.However,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase significantly.On the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,respectively.After the addition of Ce-Co alloy,Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of coercivity.The extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the Nd-Fe-B matrix.In addition,the effect of Ce-Co addition on the magnetic properties of Nd-FeB with different content of rare earth was also studied.The addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd_(2)Fe_(14)B/α-Fe magnets.The addition of Nb to the parent alloy can further improve the coercivity.For Nd_(11)Fe_(81.5)Nb_(1)Ga_(0.5)B_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.展开更多
This study systematically conducted preparation optimization and performance investigations on Co-modified Ce/TiO_(2) catalysts,with a focus on examining how preparation methods and Co loading regulate the catalyst’s...This study systematically conducted preparation optimization and performance investigations on Co-modified Ce/TiO_(2) catalysts,with a focus on examining how preparation methods and Co loading regulate the catalyst’s low-temperature denitrification activity.After identifying optimal preparation parameters via condition screening,multiple characterization techniques-including BET,XRD,XPS,H_(2)-TPR and in situ DRIFTS-were employed to deeply analyze the catalyst’s physicochemical properties and reaction mechanism.Results demonstrated that compared to the impregnation and co-precipitation methods,the Ce-Co_(0.025)/TiO_(2)-SG catalyst(prepared by the sol-gel method with a Co/Ti mass ratio of 0.025)exhibited significantly superior denitrification activity:NO conversion remained stably above 95%in the 225−350℃ temperature range,and it displayed high N_(2) selectivity.Characterization analysis revealed that abundant surface oxygen vacancies,a high proportion of Ce^(3+) species,and prominent acidic sites collectively contributed to enhancing its low-temperature denitrification performance.This work provides reference value for the development of highly efficient low-temperature denitrification catalysts.展开更多
基金Project supported by National Key Research and Development Program of China(2018YFC0115202)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-M201801501)the Program for Creative Research Groups in University of Chongqing(CXQT19031)。
文摘The influence of Ce-Co alloy addition and sintering holding time on permanent magnetic properties and micro structure of nanocrystalline Nd-Fe-B bulk alloy were investigated.The coercivity of Nd-Fe-B bulk alloy can be enhanced greatly by more than 100% after adding Ce-Co powders.However,when the concentration of Ce-Co is up to 30 wt%,the density of the magnet can reach the maximum value of 7.58 g/cm^(3),but the coercivity does not increase significantly.On the other hand,with the increase of holding time to 10 min,the density and coercivity of magnets increase gradually,reaching up to 7.55 g/cm^(3) and 1134.3 kA/m,respectively.After the addition of Ce-Co alloy,Ce-Co may easily diffuse into the Nd-Fe-B matrix during hot-pressing and under the high pressure and temperature,thus increasing the content of grain boundary phase and the pinning effect of grain boundary,which leads to the increase of coercivity.The extension of the hot-pressing holding time may be more conducive to the diffusion of CeCo into the Nd-Fe-B matrix.In addition,the effect of Ce-Co addition on the magnetic properties of Nd-FeB with different content of rare earth was also studied.The addition of Ce-Co can effectively increase the coercivity of nanocomposite Nd_(2)Fe_(14)B/α-Fe magnets.The addition of Nb to the parent alloy can further improve the coercivity.For Nd_(11)Fe_(81.5)Nb_(1)Ga_(0.5)B_(6) alloy with 10 wt% Ce-Co addition,the coercivity can increase from 740.28 to 1098.48 kA/m.
基金Supported by the National Key Research and Development Program of China (2023YFB4102903)。
文摘This study systematically conducted preparation optimization and performance investigations on Co-modified Ce/TiO_(2) catalysts,with a focus on examining how preparation methods and Co loading regulate the catalyst’s low-temperature denitrification activity.After identifying optimal preparation parameters via condition screening,multiple characterization techniques-including BET,XRD,XPS,H_(2)-TPR and in situ DRIFTS-were employed to deeply analyze the catalyst’s physicochemical properties and reaction mechanism.Results demonstrated that compared to the impregnation and co-precipitation methods,the Ce-Co_(0.025)/TiO_(2)-SG catalyst(prepared by the sol-gel method with a Co/Ti mass ratio of 0.025)exhibited significantly superior denitrification activity:NO conversion remained stably above 95%in the 225−350℃ temperature range,and it displayed high N_(2) selectivity.Characterization analysis revealed that abundant surface oxygen vacancies,a high proportion of Ce^(3+) species,and prominent acidic sites collectively contributed to enhancing its low-temperature denitrification performance.This work provides reference value for the development of highly efficient low-temperature denitrification catalysts.
