Magnetic expanded graphite(EG)hybrids were synthesized by co-intercalation polymerization of aniline together with transition metal ions.Experimental results show that metal ions(Fe,Co,Ni,Cu)and even their mixtures ca...Magnetic expanded graphite(EG)hybrids were synthesized by co-intercalation polymerization of aniline together with transition metal ions.Experimental results show that metal ions(Fe,Co,Ni,Cu)and even their mixtures can co-intercalate into graphite interlayers with flexibly controllable ratios and contents.Among these co-intercalation compounds,Fe/Ni-intercalated graphite with a predesigned mole ratio of 1:3 transforms into NiFe_(2)O_(4)/FeNi_(3)@EG during the annealing process.The synthesized magnetic EG hybrids present multiband microwave absorption in C and X bands due to improved impedance match as well as significantly enhanced interfacial polarization relaxation induced by multi-componential metals.The reflection values of−39.1 dB at 6.95 GHz and−25.7 dB at 9.4 GHz are achieved with an ultra-low loading of 5 wt.%.This work provides a flexible approach for tuning the components and structures of magnetic EG hybrids,which may contribute to the development of microwave absorption materials with superior performances.展开更多
The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction. The combined effects of cooling patterns after hot rolling...The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction. The combined effects of cooling patterns after hot rolling （HR） and cold rolling （CR） reductions show： （1） as the cooling pattern varied from furnace cooling （FC） to oil quenching （OQ）, the intercritically annealed microstructure was dramatically refined and the fraction of recrystallized ferrite dropped, regardless of CR reductions. This resulted in both high yield/ultimate tensile strengths （YS/UTS） but low total elongation to fracture （El）; （2） as the CR reduction increased from 50% to 75%, the OQ-samples after annealing exhibited a more refined microstructure with relatively higher fractions of retained austenite and sub-structure, leading to higher YS and UTS but lower El; whereas the FC samples appeared to exhibit little difference in overall tensile properties in both cases. The differences in microstructural evolution with cooling patterns and CR reductions were explained by the calculated accumulated effective strain （eAES）, which was considered to be related to degrees of recovery and recrystallization of the deformed martensite （α＇）. The optimal tensile properties of -1 GPa YS and -40 GPa.% UTSxEI were achieved in the OQ-50%CR annealed samples at 650 ℃ for 1 h. This was quite beneficial to large-scale production of ultra-high strength steels, owing to its serious springback during heaw cold working.展开更多
基金the financial support of the National Natural Science Foundation of China(No.51573149)the Key R&D Projects in Sichuan Province(Nos.2020ZDZX0005 and 2020ZDZX0008).
文摘Magnetic expanded graphite(EG)hybrids were synthesized by co-intercalation polymerization of aniline together with transition metal ions.Experimental results show that metal ions(Fe,Co,Ni,Cu)and even their mixtures can co-intercalate into graphite interlayers with flexibly controllable ratios and contents.Among these co-intercalation compounds,Fe/Ni-intercalated graphite with a predesigned mole ratio of 1:3 transforms into NiFe_(2)O_(4)/FeNi_(3)@EG during the annealing process.The synthesized magnetic EG hybrids present multiband microwave absorption in C and X bands due to improved impedance match as well as significantly enhanced interfacial polarization relaxation induced by multi-componential metals.The reflection values of−39.1 dB at 6.95 GHz and−25.7 dB at 9.4 GHz are achieved with an ultra-low loading of 5 wt.%.This work provides a flexible approach for tuning the components and structures of magnetic EG hybrids,which may contribute to the development of microwave absorption materials with superior performances.
基金financially supported by the National Natural Science Foundation of China (Grant.No.51401050)the Fundamental Research Funding for the Central Universities (Grant.No.N160204001),China (A/Prof.Cai)supported by grants through the Australian Research Council (ARC) Laureate Fellowship (Prof.Hodgson)
文摘The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction. The combined effects of cooling patterns after hot rolling （HR） and cold rolling （CR） reductions show： （1） as the cooling pattern varied from furnace cooling （FC） to oil quenching （OQ）, the intercritically annealed microstructure was dramatically refined and the fraction of recrystallized ferrite dropped, regardless of CR reductions. This resulted in both high yield/ultimate tensile strengths （YS/UTS） but low total elongation to fracture （El）; （2） as the CR reduction increased from 50% to 75%, the OQ-samples after annealing exhibited a more refined microstructure with relatively higher fractions of retained austenite and sub-structure, leading to higher YS and UTS but lower El; whereas the FC samples appeared to exhibit little difference in overall tensile properties in both cases. The differences in microstructural evolution with cooling patterns and CR reductions were explained by the calculated accumulated effective strain （eAES）, which was considered to be related to degrees of recovery and recrystallization of the deformed martensite （α＇）. The optimal tensile properties of -1 GPa YS and -40 GPa.% UTSxEI were achieved in the OQ-50%CR annealed samples at 650 ℃ for 1 h. This was quite beneficial to large-scale production of ultra-high strength steels, owing to its serious springback during heaw cold working.
