Nacre is a lightweight, strong, stiff, and tough material, which makes it a mimicking object for material design. Many attempts to mimic nacre by various methods resulted in the synthesis of artificial nacre with exce...Nacre is a lightweight, strong, stiff, and tough material, which makes it a mimicking object for material design. Many attempts to mimic nacre by various methods resulted in the synthesis of artificial nacre with excellent properties. However, the fabrication procedure was very laborious and time-consuming due to the sequential steps, and only limited-sized materials could be obtained. Hence, a novel design enabling scalable production of high-performance artificial nacre with uniform layered structures is urgently needed. We developed a novel wet-spinning assembly technique to rapidly manufacture continuous nacre- mimic graphene oxide （GO, brick）-sodium alginate （SA, mortar） films and fibers with excellent mechanical properties. At high concentrations, the GO-SA mixtures spontaneously produced liquid crystals （LCs） due to the template effect of GO, and continuous, 6 m long nacre-like GO-SA films were wet-spun from the obtained GO-SA liquid crystalline （LC） dope with a speed of up to 1.5 m/min. The assembled macroscopic GO-SA composites inherited the alignment of the GO sheets from the LC phase, and their mechanical properties were investigated by a joint experimental-computational study. The tensile tests revealed that the maximum strength （0） and Young＇s modulus （E） of the obtained films reached 239.6 MPa and 22.4 GPa, while the maximum values of o and E for the fibers were 784.9 MPa and 58 GPa, respectively. The described wet-spinning assembly method is applicable for a large-scale and fast production of high-performance continuous artificial nacre.展开更多
Research on lake eutrophication in China began in the early 1970s,and many lakes in China are now known to be in meso-eutrophic status.Lake eutrophication has been showing a rapidly increasing trend since 2000.Investi...Research on lake eutrophication in China began in the early 1970s,and many lakes in China are now known to be in meso-eutrophic status.Lake eutrophication has been showing a rapidly increasing trend since 2000.Investigations show that the main reasons for lake eutrophication include a fragile lake background environment,excessive nutrient loading into lakes,excessive human activities,ecological degeneration,weak environmental protection awareness,and lax lake management.Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance,major changes in water chemistry(pH,oxygen,and carbon),lake ecosystem imbalance,and algal prevalence in lakes.Some concepts for controlling eutrophication should be persistently proposed,including lake catchment control,combination of pollutant source control with ecological restoration,protection of three important aspects(terrestrial ecology,lake coast zone,and submerged plant),and combination of lake management with regulation.Measures to control lake eutrophication should include pollution source control(i.e.,optimize industrial structural adjustments in the lake catchment,reduce nitrogen and phosphorus emission amounts,and control endogenous pollution)and lake ecological restoration(i.e.establish a zone-lake buffer region and lakeside zone,protect regional vegetation,utilize hydrophytes in renovation technology);countermeasures for lake management should include implementing water quality management,identifying environmental and lake water goals,legislating and formulating laws and regulations to protect lakes,strengthening publicity and the education of people,increasing public awareness through participation in systems and mechanic innovations,establishing lake region management institutions,and ensuring implementation of governance and management measures.展开更多
基金This research was financially supported by The National Natural Science Foundation of China （Nos. 21325417, 51173162 and 51533008） and State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University （No. LK1403）.
文摘Nacre is a lightweight, strong, stiff, and tough material, which makes it a mimicking object for material design. Many attempts to mimic nacre by various methods resulted in the synthesis of artificial nacre with excellent properties. However, the fabrication procedure was very laborious and time-consuming due to the sequential steps, and only limited-sized materials could be obtained. Hence, a novel design enabling scalable production of high-performance artificial nacre with uniform layered structures is urgently needed. We developed a novel wet-spinning assembly technique to rapidly manufacture continuous nacre- mimic graphene oxide （GO, brick）-sodium alginate （SA, mortar） films and fibers with excellent mechanical properties. At high concentrations, the GO-SA mixtures spontaneously produced liquid crystals （LCs） due to the template effect of GO, and continuous, 6 m long nacre-like GO-SA films were wet-spun from the obtained GO-SA liquid crystalline （LC） dope with a speed of up to 1.5 m/min. The assembled macroscopic GO-SA composites inherited the alignment of the GO sheets from the LC phase, and their mechanical properties were investigated by a joint experimental-computational study. The tensile tests revealed that the maximum strength （0） and Young＇s modulus （E） of the obtained films reached 239.6 MPa and 22.4 GPa, while the maximum values of o and E for the fibers were 784.9 MPa and 58 GPa, respectively. The described wet-spinning assembly method is applicable for a large-scale and fast production of high-performance continuous artificial nacre.
基金This research was supported by the National Basic Research Program of China(973 Program)(Grant No.2002CB412300)the National High Technology Research Development Program of China(863 Program)(Grant No.2005AA60101005).
文摘Research on lake eutrophication in China began in the early 1970s,and many lakes in China are now known to be in meso-eutrophic status.Lake eutrophication has been showing a rapidly increasing trend since 2000.Investigations show that the main reasons for lake eutrophication include a fragile lake background environment,excessive nutrient loading into lakes,excessive human activities,ecological degeneration,weak environmental protection awareness,and lax lake management.Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance,major changes in water chemistry(pH,oxygen,and carbon),lake ecosystem imbalance,and algal prevalence in lakes.Some concepts for controlling eutrophication should be persistently proposed,including lake catchment control,combination of pollutant source control with ecological restoration,protection of three important aspects(terrestrial ecology,lake coast zone,and submerged plant),and combination of lake management with regulation.Measures to control lake eutrophication should include pollution source control(i.e.,optimize industrial structural adjustments in the lake catchment,reduce nitrogen and phosphorus emission amounts,and control endogenous pollution)and lake ecological restoration(i.e.establish a zone-lake buffer region and lakeside zone,protect regional vegetation,utilize hydrophytes in renovation technology);countermeasures for lake management should include implementing water quality management,identifying environmental and lake water goals,legislating and formulating laws and regulations to protect lakes,strengthening publicity and the education of people,increasing public awareness through participation in systems and mechanic innovations,establishing lake region management institutions,and ensuring implementation of governance and management measures.
