Asymmetric lowered-temperature rolling was applied to the fabrication of fine-grained ZK60 magnesium alloy sheet with weak basal texture along the rolling direction(RD).The results showed that multi-pass lowered-tempe...Asymmetric lowered-temperature rolling was applied to the fabrication of fine-grained ZK60 magnesium alloy sheet with weak basal texture along the rolling direction(RD).The results showed that multi-pass lowered-temperature rolling could significantly improve the microstructure homogeneity and refine the grain size.Meanwhile,a fiber texture along the transverse direction(TD)gradually developed during rolling process.Importantly,the shear deformation along the RD made the c-axis of basal plane rotate to the RD,weakening the basal texture along this direction.Influenced by such microstructure variation,the yield strength along the TD continuously increased due to the successive grain refinement and the increased activation of prismatic slips,whereas the uniform elongation decreased owing to the decline of strain hardening ability.In contrast,the continuous weakening of basal texture along the RD increased the activation of soft basal slips,greatly offsetting the strengthening effect contributed by grain refinement and thereby causing the slight decrease of yield strength.展开更多
Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 templa...Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 template. By changing the sizes of SiO_2 microspheres, a series of HFC microspheres with variable cavity sizes were obtained to study the relationship between cavity size and microwave absorbing(MA) performance for the first time. The morphology and structure of samples were characterized in detail. The results showed that the MA performance of HFC sample depended on its cavity size. In particular, the hollow structure was good for improving MA performance and could make MA move to the high-frequency region. More importantly, as the cavity size increases, the resonance frequency of HFC-i(i=1,2, 3, 4) samples moved to a low frequency, and the optimal matching thickness of HFC-i samples was increasing. Among all HFC-i samples, HFC-3 showed the most excellent MA performance,which could be mainly explained by the quarter-wavelength matching model, intrinsical magnetic and dielectric loss. Furthermore,the MA performance of HFC mixture blended by the equal mass fraction of HFC-2, HFC-3 and HFC-4 was the comprehensive results of three HFC-i samples. All the above suggested that the cavity size in HFC sample had a great influence on the MA performance.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51975146, 51801192, 52205344)the Natural Science Foundation of Shandong Province, China (No. ZR2020QE171)+1 种基金Key Research and Development Plan in Shandong Province, China (No. 2019JZZY010364)the National Defense Basic Scientific Research of China (No. JCK2018603C017)
文摘Asymmetric lowered-temperature rolling was applied to the fabrication of fine-grained ZK60 magnesium alloy sheet with weak basal texture along the rolling direction(RD).The results showed that multi-pass lowered-temperature rolling could significantly improve the microstructure homogeneity and refine the grain size.Meanwhile,a fiber texture along the transverse direction(TD)gradually developed during rolling process.Importantly,the shear deformation along the RD made the c-axis of basal plane rotate to the RD,weakening the basal texture along this direction.Influenced by such microstructure variation,the yield strength along the TD continuously increased due to the successive grain refinement and the increased activation of prismatic slips,whereas the uniform elongation decreased owing to the decline of strain hardening ability.In contrast,the continuous weakening of basal texture along the RD increased the activation of soft basal slips,greatly offsetting the strengthening effect contributed by grain refinement and thereby causing the slight decrease of yield strength.
基金supported by the National Natural Science Foundation of China (20104017)the College Students’ Science and Technology Innovation Activities Plan of Zhejiang (2014R404056)
文摘Uniform core-shell SiO2@Fe_3O_4@C microspheres were prepared by a one-step hydrothermal method with SiO_2 microspheres as the template, and the hollow Fe_3O_4@C(HFC) microspheres were achieved via etching SiO_2 template. By changing the sizes of SiO_2 microspheres, a series of HFC microspheres with variable cavity sizes were obtained to study the relationship between cavity size and microwave absorbing(MA) performance for the first time. The morphology and structure of samples were characterized in detail. The results showed that the MA performance of HFC sample depended on its cavity size. In particular, the hollow structure was good for improving MA performance and could make MA move to the high-frequency region. More importantly, as the cavity size increases, the resonance frequency of HFC-i(i=1,2, 3, 4) samples moved to a low frequency, and the optimal matching thickness of HFC-i samples was increasing. Among all HFC-i samples, HFC-3 showed the most excellent MA performance,which could be mainly explained by the quarter-wavelength matching model, intrinsical magnetic and dielectric loss. Furthermore,the MA performance of HFC mixture blended by the equal mass fraction of HFC-2, HFC-3 and HFC-4 was the comprehensive results of three HFC-i samples. All the above suggested that the cavity size in HFC sample had a great influence on the MA performance.
