The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sint...The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering(SPS).The as received recycled HDDR powder has coercivity(Hci)=830 kA/m and particles in the range from 30 to 700 μm(average 220 μm).After burr milling,the average particle size is reduced to 120 μm and subsequently the Hci of fine(milled) powder was 595 kA/m.Spark plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain coarsening.The optimal SPS-ing of coarse HDDR powder at 750℃for 1 min produces fully dense magnets with Hci=950±100 kA/m which further increases to 1200 kA/m via thermal treatment at 750℃for 15 min.The burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci=940 kA/m.The fine powder is further sieved down from 630 to less than 50 μm mesh size,to evaluate the possible reduction in Hci in relation to the particle size.The gain in oxygen content doubles for <50 μm sized particles as compared with coarser fractions(>200 μm).The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer(<100 μm)fractions.Similarly,the Hci reduces from 820 kA/m in the coarse particles(>200 μm) to 460 kA/m in the fine sized particles(<100μm).SPS was done on each HDDR powder fraction under the optimal conditions to measure the variation in Hci and density.The Hci of SPS-ed coarse fraction(>200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles(<100 μm).The thermal treatment further improves the Hci to>1000 kA/m only up to 100 μm sized fractions with>90% sintered density.The full densification(>99%) is observed only in the coarse fractions.The loss of coercivity and lack of sinterability in the fine sized particles(<100 μm) are attributed to a very high oxygen content.This implies that during recycling,if good magnetic p展开更多
目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命...目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命终末期的认识及态度。应用Likert5级计分法,非常赞同计1分,完全不赞同计5分。结果在ICU医护人员中发放330份问卷,回复率为95.4%。87.2%的受访者赞同对ICU生命终末期患者实施限制或撤除生命支持治疗,但超过一半的受访者不赞同对生命终末期患者停止机械通气治疗,不愿意主动提出限制或撤除生命支持的建议。结论 ICU医护人员对生命终末期患者实施撤除生命支持治疗持肯定态度,但不愿主动提出限制或撤除生命支持的建议。展开更多
基金Project supported by European Community’s Horizon 2020Program [H2020/2014-2019] under grant Agreement No.674973(MSCA-ETN DEMETER)
文摘The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering(SPS).The as received recycled HDDR powder has coercivity(Hci)=830 kA/m and particles in the range from 30 to 700 μm(average 220 μm).After burr milling,the average particle size is reduced to 120 μm and subsequently the Hci of fine(milled) powder was 595 kA/m.Spark plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain coarsening.The optimal SPS-ing of coarse HDDR powder at 750℃for 1 min produces fully dense magnets with Hci=950±100 kA/m which further increases to 1200 kA/m via thermal treatment at 750℃for 15 min.The burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci=940 kA/m.The fine powder is further sieved down from 630 to less than 50 μm mesh size,to evaluate the possible reduction in Hci in relation to the particle size.The gain in oxygen content doubles for <50 μm sized particles as compared with coarser fractions(>200 μm).The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer(<100 μm)fractions.Similarly,the Hci reduces from 820 kA/m in the coarse particles(>200 μm) to 460 kA/m in the fine sized particles(<100μm).SPS was done on each HDDR powder fraction under the optimal conditions to measure the variation in Hci and density.The Hci of SPS-ed coarse fraction(>200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles(<100 μm).The thermal treatment further improves the Hci to>1000 kA/m only up to 100 μm sized fractions with>90% sintered density.The full densification(>99%) is observed only in the coarse fractions.The loss of coercivity and lack of sinterability in the fine sized particles(<100 μm) are attributed to a very high oxygen content.This implies that during recycling,if good magnetic p
文摘目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命终末期的认识及态度。应用Likert5级计分法,非常赞同计1分,完全不赞同计5分。结果在ICU医护人员中发放330份问卷,回复率为95.4%。87.2%的受访者赞同对ICU生命终末期患者实施限制或撤除生命支持治疗,但超过一半的受访者不赞同对生命终末期患者停止机械通气治疗,不愿意主动提出限制或撤除生命支持的建议。结论 ICU医护人员对生命终末期患者实施撤除生命支持治疗持肯定态度,但不愿主动提出限制或撤除生命支持的建议。
