With the development of the miniaturization of electronic equipment and lightweight weapon equipment,there are new requirements for electromagnetic wave absorption material(EMWAM).EMWAM has outstanding electromagnetic...With the development of the miniaturization of electronic equipment and lightweight weapon equipment,there are new requirements for electromagnetic wave absorption material(EMWAM).EMWAM has outstanding electromagnetic wave absorption properties and lightweight characteristics become an important direction of research.In this study,graphene/g-C_(3)N_(4)(GGCN)EMWAM was first synthesized in situ by simple heat treatment,in which the g-C_(3)N_(4) had a porous structure and dispersed on the surface of graphene.The impedance matching of the GGCN was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C_(3)N_(4) semiconductor property and the graphite-like structure.The EMW loss mechanism of GGCN was also analyzed by simulating GGCN’s electric field mode distribution and resistance loss power density.The analysis result shows that the distribution of g-C_(3)N_(4) among GGCN sheets can produce more polarization effects and relaxation effects by increasing the lamellar spacing.Furthermore,the polarization loss of GGCN could be increased successfully by porous g-C_(3)N_(4).Ultimately,the EMW absorption property of GGCN is optimized significantly,and GGCN exhibits excellent EMW absorption performance.When the thickness is 2 mm,the effective absorption bandwidth(EAB)can reach 4.6 GHz,and when the thickness is 4.5 mm,the minimum reflection loss(RLmin)at 4.56 GHz can reach-34.69 dB.Moreover,the practical application of EMWAM was studied by radar cross-section(RCS)simulation,showing that GGCN has a good application prospect.展开更多
In order to improve the multi-ion cooperative transition, we proposed and exploited a novel nanoscale effect, namely the nanoshell effect in bulk materials. Based on the effect, an optimal material structure was desig...In order to improve the multi-ion cooperative transition, we proposed and exploited a novel nanoscale effect, namely the nanoshell effect in bulk materials. Based on the effect, an optimal material structure was designed by coating the surfaces of Ca F_(2):Yb^(3+)micron size particles with ZrO_(2). An about 2 times higher intensity of cooperative luminescence is observed upon laser excitation at 980 nm. Dynamical analysis exhibits that the novel effect plays a key role in improving the performance of cooperative transitions. Our results also suggest that the nanoshell effect in bulk materials is likely to be significant in some special cases, which have not been reported yet in the literature.展开更多
The growth regularities of nanomaterials are often concealed by the contingency of preparation. Therefore, it is always very difficult to figure out growth regularities of nanomaterials due to the accompanying undulat...The growth regularities of nanomaterials are often concealed by the contingency of preparation. Therefore, it is always very difficult to figure out growth regularities of nanomaterials due to the accompanying undulation of products. A series of precise synthesis was performed by using an automatic nanomaterial synthesizer (ANS) in order to explore the growth regularity of complex NaREF4 (RE: rare earth) upconversion nanocrystals (UCNCs). The use of ANS significantly enhances the experimental controllability, repeatability, and success rate. Mass experimental research exhibited that the NaLu_(0.795−x)Y_(x)F_(4):Yb^(3+)/Tm^(3+) (x = 0−0.795) UCNCs can vary their sizes continuously in a wide range to accurately meet the experimenter’s design merely by controlling the concentration of Y^(3+). A notable growth regularity was obtained and intuitively shown in growth phase diagrams. Furthermore, in the case of having excellent monodispersity, pure hexagonal phase, and uniform morphology, the prepared UCNCs still retained superior upconversion luminescent (UCL) properties. The regular changes in UCL properties further confirmed the growth regularity of the UCNCs. After analyzing the experimental data, we found that NaLu_(0.795−x)Y_(x)F_(4) combined the advantages of NaYF_(4) and NaLuF_(4) hosts with desired sizes. These results provide a guidance for the exploration of growth regularities of other similar nanomaterials and also for the structure design of the required nanomaterials.展开更多
基金supported by the National Natural Science Foundation of China(No.51872058)the Supporting Program for Innovation Team of Outstanding Youth in Colleges and Universities of Shandong Province(No.2020KJA005)the Natural Science Foundation of Shandong Province(No.ZR2022QB156).
文摘With the development of the miniaturization of electronic equipment and lightweight weapon equipment,there are new requirements for electromagnetic wave absorption material(EMWAM).EMWAM has outstanding electromagnetic wave absorption properties and lightweight characteristics become an important direction of research.In this study,graphene/g-C_(3)N_(4)(GGCN)EMWAM was first synthesized in situ by simple heat treatment,in which the g-C_(3)N_(4) had a porous structure and dispersed on the surface of graphene.The impedance matching of the GGCN was well adjusted by decreasing the dielectric constant and attenuation constant due to the g-C_(3)N_(4) semiconductor property and the graphite-like structure.The EMW loss mechanism of GGCN was also analyzed by simulating GGCN’s electric field mode distribution and resistance loss power density.The analysis result shows that the distribution of g-C_(3)N_(4) among GGCN sheets can produce more polarization effects and relaxation effects by increasing the lamellar spacing.Furthermore,the polarization loss of GGCN could be increased successfully by porous g-C_(3)N_(4).Ultimately,the EMW absorption property of GGCN is optimized significantly,and GGCN exhibits excellent EMW absorption performance.When the thickness is 2 mm,the effective absorption bandwidth(EAB)can reach 4.6 GHz,and when the thickness is 4.5 mm,the minimum reflection loss(RLmin)at 4.56 GHz can reach-34.69 dB.Moreover,the practical application of EMWAM was studied by radar cross-section(RCS)simulation,showing that GGCN has a good application prospect.
基金Project supported by the National Natural Science Foundation of China(12174150)the Open Fund of the State Key Laboratory on Integrated Optoelectronics。
文摘In order to improve the multi-ion cooperative transition, we proposed and exploited a novel nanoscale effect, namely the nanoshell effect in bulk materials. Based on the effect, an optimal material structure was designed by coating the surfaces of Ca F_(2):Yb^(3+)micron size particles with ZrO_(2). An about 2 times higher intensity of cooperative luminescence is observed upon laser excitation at 980 nm. Dynamical analysis exhibits that the novel effect plays a key role in improving the performance of cooperative transitions. Our results also suggest that the nanoshell effect in bulk materials is likely to be significant in some special cases, which have not been reported yet in the literature.
基金supported by the National Natural Science Foundation of China(12174150)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics+1 种基金Tsinghua National Laboratory for Information Science and Technology(TNList)Cross-Discipline Foundationthe Major Science and Technology Tendering Project of Jilin Province(20170203012GX).
基金This work was supported by the National Natural Science Foundation of China(NSFC)(No.11774132)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,and Tsinghua National Laboratory for Information Science and Technology(TNList)Cross-discipline Foundationthe Major Science and Technology Tendering Project of Jilin Province(No.20170203012GX).
文摘The growth regularities of nanomaterials are often concealed by the contingency of preparation. Therefore, it is always very difficult to figure out growth regularities of nanomaterials due to the accompanying undulation of products. A series of precise synthesis was performed by using an automatic nanomaterial synthesizer (ANS) in order to explore the growth regularity of complex NaREF4 (RE: rare earth) upconversion nanocrystals (UCNCs). The use of ANS significantly enhances the experimental controllability, repeatability, and success rate. Mass experimental research exhibited that the NaLu_(0.795−x)Y_(x)F_(4):Yb^(3+)/Tm^(3+) (x = 0−0.795) UCNCs can vary their sizes continuously in a wide range to accurately meet the experimenter’s design merely by controlling the concentration of Y^(3+). A notable growth regularity was obtained and intuitively shown in growth phase diagrams. Furthermore, in the case of having excellent monodispersity, pure hexagonal phase, and uniform morphology, the prepared UCNCs still retained superior upconversion luminescent (UCL) properties. The regular changes in UCL properties further confirmed the growth regularity of the UCNCs. After analyzing the experimental data, we found that NaLu_(0.795−x)Y_(x)F_(4) combined the advantages of NaYF_(4) and NaLuF_(4) hosts with desired sizes. These results provide a guidance for the exploration of growth regularities of other similar nanomaterials and also for the structure design of the required nanomaterials.
