Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate sin...Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.展开更多
Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hi...Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.展开更多
The adsorption of hydrogen molecule on the external surface of pure 0120 nanocapsule and endohedrallyH2 @C120 complex has been examined using the density functional theory calculations. Several different bonding confi...The adsorption of hydrogen molecule on the external surface of pure 0120 nanocapsule and endohedrallyH2 @C120 complex has been examined using the density functional theory calculations. Several different bonding configu- rations are considered for the hydrogen molecule approaching the outer surface of the considered nanocages. It has been found that the adsorbed H2 molecule bound weakly to the outer surface of the pure C1~0 nanocapsules in agreement with the recent experimental and theoretical results while, it prefers to be adsorbed rather strongly on the side wall of the endohedrally /-/2@C120 complex. The adsorption of a single layer and bi-layer of two tt2 molecules on the most stable states of the considered H2@C120 complex appears to be feasible, although the molecules of the second layer are weakly bound. Furthermore, it is found that the formation of 100% coverage is favorable thermodynamically, which corresponds to about 20% by weight storage of 1-12 molecules. Thus, surprisingly, we arrive at the prediction that the C120 nanocapsules can be implemented as a novel material for energy storage.展开更多
利用直流电弧等离子体法在甲烷气氛中制备碳包覆磁性镍纳米胶囊（Carbon-coated Ni nanocapsules,Ni（C）NCs）,将它作为电磁波吸收剂,按照质量比10%、20%、30%和40%与有机石蜡基体复合,在0.1～18GHz范围内测定其复介电常数和复磁导率,...利用直流电弧等离子体法在甲烷气氛中制备碳包覆磁性镍纳米胶囊（Carbon-coated Ni nanocapsules,Ni（C）NCs）,将它作为电磁波吸收剂,按照质量比10%、20%、30%和40%与有机石蜡基体复合,在0.1～18GHz范围内测定其复介电常数和复磁导率,并对其电磁波响应特性及吸收机制进行了研究。研究结果表明,Ni（C）纳米胶囊具有明显的极化损耗特征,其介电常数在低频范围内随频率提高而急剧衰减,而磁导率具有宽化的多重共振峰;随着Ni（C）纳米胶囊添加量的增加,其介电常数逐渐增加,其复磁导率实部和虚部分别在0.1～8GHz、0.1～10GHz出现增加,而在8～18GHz和10～18GHz范围内出现实部减小和虚部平缓变化的特征。根据极化、涡流以及反射损耗的理论分析,发现Ni（C）纳米胶囊以介电损耗为主,并对相关机制进行了探讨。展开更多
基金Supported by Program for the National Natural Science Foundation of China (Nos. 51577021 and U1704253)the Fundamental Research Funds for the Central Universities (DUT17GF107)
文摘Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix(FMCA)was synthesized successfully with a novel confinement strategy.The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz.The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon.The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties.Meanwhile,adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network.The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption.The optimal reflection loss(RL)is up to−45 dB,and the effective bandwidth(RL<−10 dB)is 5.0 GHz with 2.0 mm thickness.The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber,but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51872005,U1508201,52072002)。
文摘Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g^(−1) at 0.05 A g^(−1)), outstanding rate capability (149 mAh g^(−1) at 5 A g^(−1)) and favorable cycle stability (150m Ah g^(−1) at 2 A g^(−1) after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.
文摘The adsorption of hydrogen molecule on the external surface of pure 0120 nanocapsule and endohedrallyH2 @C120 complex has been examined using the density functional theory calculations. Several different bonding configu- rations are considered for the hydrogen molecule approaching the outer surface of the considered nanocages. It has been found that the adsorbed H2 molecule bound weakly to the outer surface of the pure C1~0 nanocapsules in agreement with the recent experimental and theoretical results while, it prefers to be adsorbed rather strongly on the side wall of the endohedrally /-/2@C120 complex. The adsorption of a single layer and bi-layer of two tt2 molecules on the most stable states of the considered H2@C120 complex appears to be feasible, although the molecules of the second layer are weakly bound. Furthermore, it is found that the formation of 100% coverage is favorable thermodynamically, which corresponds to about 20% by weight storage of 1-12 molecules. Thus, surprisingly, we arrive at the prediction that the C120 nanocapsules can be implemented as a novel material for energy storage.
基金National Natural Science Foundation of China(20676070)Natural Science Foundation of Hebei Province(B2015208109)+2 种基金Hebei Training Program for Talent Project(A201500117)Hebei One Hundred Excellent Innovative Talent Program(Ⅲ)(SLRC2017034)Hebei Science and Technology Project(17214304D,16214510D)~~
文摘利用直流电弧等离子体法在甲烷气氛中制备碳包覆磁性镍纳米胶囊（Carbon-coated Ni nanocapsules,Ni（C）NCs）,将它作为电磁波吸收剂,按照质量比10%、20%、30%和40%与有机石蜡基体复合,在0.1～18GHz范围内测定其复介电常数和复磁导率,并对其电磁波响应特性及吸收机制进行了研究。研究结果表明,Ni（C）纳米胶囊具有明显的极化损耗特征,其介电常数在低频范围内随频率提高而急剧衰减,而磁导率具有宽化的多重共振峰;随着Ni（C）纳米胶囊添加量的增加,其介电常数逐渐增加,其复磁导率实部和虚部分别在0.1～8GHz、0.1～10GHz出现增加,而在8～18GHz和10～18GHz范围内出现实部减小和虚部平缓变化的特征。根据极化、涡流以及反射损耗的理论分析,发现Ni（C）纳米胶囊以介电损耗为主,并对相关机制进行了探讨。
