A novel concept and approach to engineering carbon nanodots(CNDs)were explored to overcome the limited light absorption of CNDs in low-energy spectral regions.In this work,we constructed a novel type of supra-CND by t...A novel concept and approach to engineering carbon nanodots(CNDs)were explored to overcome the limited light absorption of CNDs in low-energy spectral regions.In this work,we constructed a novel type of supra-CND by the assembly of surface charge-confined CNDs through possible electrostatic interactions and hydrogen bonding.The resulting supra-CNDs are the first to feature a strong,well-defined absorption band in the visible to near-infrared(NIR)range and to exhibit effective NIR photothermal conversion performance with high photothermal conversion efficiency in excess of 50%.展开更多
It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without...It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.展开更多
By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any a...By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.展开更多
Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level....Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level.Herein,CNFs anchored with cobalt nanocluster(CNFs-Co)were prepared using chemical vapor deposition and thermal reduction methods.The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91%and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs.Meanwhile,the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g.These excellent electrochemical properties could be attributed to the involved spin state Co,which endows CNFs with large interplanar spacing(0.39 nm)and abundant vacancy defects.Importantly,the spin state Co downshifts the p-band center of carbon and strengthens the Na+adsorption energy from-2.33 eV to-2.64 eV based on density functional theory calculation.This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.展开更多
Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potentia...Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potential.Herein,a porous S-doped carbon nitride(S-C_(3)N_(4−y))foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular selfassembly strategy.The S dopants and N vacancies synergistically adjusted the band structure,facilitating light absorption and enhancing the oxidation ability.Moreover,the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer.Consequently,S-C_(3)N_(4−y) foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution(4960μmol/(h·g))and benzylamine oxidation to N-benzylidenebenzylamine(4885μmol/(h·g))with high selectivity of>99%,which were approximately 17.6 and 72.9 times higher than those of bulk CN,respectively.The photocatalytic coupling pairing reaction promotes the water splitting by consuming H2O2,thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines.This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.展开更多
We investigated the influence mechanism of N-doping for dissolved black carbon(DBC)photodegradation of organic pollutants.The degradation performance of N-doped dissolved black carbon(NDBC)for tetracycline(TC)(71%)is ...We investigated the influence mechanism of N-doping for dissolved black carbon(DBC)photodegradation of organic pollutants.The degradation performance of N-doped dissolved black carbon(NDBC)for tetracycline(TC)(71%)is better than that for methylene blue(MB)(28%)under irradiation.These levels are both better than DBC degradation performances for TC(68%)and MB(18%)under irradiation.Reactive species quenching experiments suggest that h and-O,are the main reactive species for NDBC photodegraded TC,while-OH and h*are the main reactive species for NDBC photodegraded MB.-OH is not observed during DBC photodegradation of MB.This is likely because N-doping increases valence-band(VB)energy from 1.55 eV in DBC to 2.04 eV in NDBC;the latter is strong enough to oxidize water to form-OH.Additionally,N-doping increases the DBC band gap of 2.29 to 2.62 eV in NDBC,resulting in a higher separation efficiency of photo-generated electrons-holes in NDBC than in DBC.AIl these factors give NDBC stronger photodegradation performance for TC and MB than DBC.High-performance liquid chromatography-mass spectrometry(HPLC-MS)characterization and toxicity evaluation with the quantitative structure-activity relationship(QSAR)method suggest that TC photodegradation intermediates produced by NDBC have less aromatic structure and are less toxic than those produced by DBC.We adopted a theoretical approach to clarify the relationship between the surface groups of NDBC and the photoactive species produced.Our results add to the understanding of the photochemical behavior of NDBC.展开更多
本文用热处理方法对奥氏体和珠光体异种钢接头的碳迁移现象及其对接头组织和机械性能的影响进行了研究,认为:焊缝金属有析出物出现;熔合区形成一个增碳层;热影响区形成一个脱碳的铁素体带。随回火参数 P 值增加,焊缝析出物增多,晶界加厚...本文用热处理方法对奥氏体和珠光体异种钢接头的碳迁移现象及其对接头组织和机械性能的影响进行了研究,认为:焊缝金属有析出物出现;熔合区形成一个增碳层;热影响区形成一个脱碳的铁素体带。随回火参数 P 值增加,焊缝析出物增多,晶界加厚;增碳层加宽;脱碳层铁素体晶粒长大;接头拉伸强度,弯曲角和梅氏冲击值均降低,但这种降低在一定温度(如490℃)下逐步达到饱和。展开更多
Dielectric properties of SiC/Ni nanocomposites prepared by a simple and facile electroless plating approach at X band are investigated. Compared to the original SiC nanopartieles （SiCp）, the real part of the permitt...Dielectric properties of SiC/Ni nanocomposites prepared by a simple and facile electroless plating approach at X band are investigated. Compared to the original SiC nanopartieles （SiCp）, the real part of the permittivity, ε＇, and the dielectric loss tangent tang δe of SiC/Ni nanocomposites are clearly enhanced by about 31% and 33%, respectively. The effective equations for complex permittivity of SiC/Ni nanoeomposites are proposed. We also calculate ε＇ and tan δe of SiC/Ni nanoeomposites and the calculated results are well consistent with the measured data.展开更多
We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculatio...We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculations, considering a range of different diameters and chiralities of combined carbon nanotubes. We have investigated three distinct combinations of carbon heterojunctions using density functional theory (DFT) and applying B3LYP/3-21g: armchair-armchair herteojunctions, zigzag-zigzag heterojunctions, and zigzag-armchair heterojunctions. We have shown for first time a detailed study of formation energy of mono-vacancy and B-doped defects of carbon heterojunction nanodevices. Our calculations show that the highest surface reactivity is found for the B-doped zigzag-armchair heterojunctions and it is easier to remove the carbon atom from the network of heterojunction armchair-armchair CNTs than the heterojunction zigzag-armchair and zigzag-zigzag CNTs.展开更多
We studied the co-adsorption of hydrogen molecule and ions （Li, K, Mg, Ca） inside the single-walled carbon nanotubes （SWNTs） by using density-functional theory （DFT）. The band structures （BS）, density of stat...We studied the co-adsorption of hydrogen molecule and ions （Li, K, Mg, Ca） inside the single-walled carbon nanotubes （SWNTs） by using density-functional theory （DFT）. The band structures （BS）, density of states （DOS）, charge transfer and difference charge density are presented. We discussed the interaction between the ions （Li, K, Mg, Ca） and H2 Meanwhile, the binding energy indicates that ionization can increase the adsorption energy of H2 in CNT.展开更多
基金supported by the National Science Foundation of China(No.11204298,61205025,61274126 and 61306081)the Jilin Province Science and Technology Research Project(No.20140101060JC,20150519003JH and 20130522142JH)the Outstanding Young Scientist Program of CAS.
文摘A novel concept and approach to engineering carbon nanodots(CNDs)were explored to overcome the limited light absorption of CNDs in low-energy spectral regions.In this work,we constructed a novel type of supra-CND by the assembly of surface charge-confined CNDs through possible electrostatic interactions and hydrogen bonding.The resulting supra-CNDs are the first to feature a strong,well-defined absorption band in the visible to near-infrared(NIR)range and to exhibit effective NIR photothermal conversion performance with high photothermal conversion efficiency in excess of 50%.
文摘组合搅拌模式是控制特殊钢铸态组织与均质性的重要手段。为深入揭示连铸结晶器电磁搅拌(Moldelectromagnetic stirring,M-EMS)和凝固末端电磁搅拌(Final electromagnetic stirring,F-EMS)的复合作用行为,基于麦克斯韦方程和低雷诺数湍流模型建立断面250mm×280mm的20Cr Mo A齿轮钢大方坯连铸过程电磁-流动-传热与凝固三维耦合数值模型。基于实测M-EMS中心线磁感应强度及F-EMS作用下的铸态组织白亮带宽度验证模型的可靠性。研究结果表明,M-EMS促使结晶器区域钢液产生水平旋流并冲刷凝固前沿,加强钢液和凝固坯壳的换热,可使钢液过热完全耗散及其凝固终点位置不同程度地前移,促进柱状晶向等轴晶的转变(Columnar to equiaxed transition,CET),从而可实现F-EMS作用区域为中心等轴晶区。组合搅拌作用下铸坯末搅区域液相穴宽度减小,糊状区内钢液对凝固前沿的冲刷速度降低,从而不易产生常见的负偏析白亮带缺陷。碳偏析检测结果表明,M-EMS可能造成大方坯出现一定程度的皮下负偏析和CET转变区的正偏析,但其中心偏析和铸态碳极差可获得明显改善。综合表明,合理的组合搅拌模式可有效改善特殊钢大方坯铸态组织的均质性,进而提高其轧材产品的热处理与服役性能。
基金This work was supported by the National Natural Science Foundation of China(Nos.51673040 and 21978048)the Natural Science Foundation of Jiangsu Province(Nos.BK20171357 and BK20180366)+4 种基金Opening Project of Guangxi Key Laboratory of Clean Pulp&Papermaking and Pollution Control(No.GD201802-5)the Fundamental Research Funds for Central Universities(No.2242019k30042)Scientific Innovation Research Foundation of College Graduate in Jiangsu Province(No.KYCX19_0103)Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.1107047002)Fund Project for Transformation of Scientific and Technological Achievements of Jiangsu Province of China(No.BA2018045).
文摘It is essential to manufacture microwave absorbers with strong absorption as well as tunable absorption bands at a low filler content.However,it remains challenging for pure biomass material to reach this goal without loading other components.MoSe_(2),as a transition metal chalcogenide with semiconductor properties,has emerged as a potential microwave absorber filler.Herein,bacterial cellulose(BC)-derived carbon nanofibers/MoSe_(2) nanocomposite was fabricated and phosphoric acid was used to dope phosphorus in BC,in which MoSe_(2) microspheres were dropped on the BC network like a dew-covered spider web.This unique network structure enhances conductive loss and multiple reflections of the incident wave.The collocation of BC and MoSe_(2) is helpful to impedance match and introduces interfacial/dipolar polarization loss;moreover,the P-doping of BC helps to tune the absorption bands.Overall,the optimal reflection loss of undoped one reaches−53.33 dB with only 20 wt.%filler content,whose main absorption peaks focus on X-band.Interestingly,after the P-doping of BC,the main absorption peaks move to Ku-band and the optimal reflection loss gets stronger(−66.84 dB)with the same filler loading.Strong absorption and tunable absorption bands can be realized,and thus wide frequency range is covered.This work is expected to enlighten future exploration of biomass carbon materials on high-performance microwave absorption materials.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50572010 and 10672020, the National Defense Founds under Grant Nos 51420205BQ0154, A2220061080）, and the National Key Basic Research Programme of China under Grant No 5131803.
文摘By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.
基金the National Natural Science Foundation of China(Nos.52271011,52102291).
文摘Carbon nanofibers(CNFs)have received extensive and in-depth studied as anodes for sodium-ion batteries(SIBs),and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level.Herein,CNFs anchored with cobalt nanocluster(CNFs-Co)were prepared using chemical vapor deposition and thermal reduction methods.The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91%and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs.Meanwhile,the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g.These excellent electrochemical properties could be attributed to the involved spin state Co,which endows CNFs with large interplanar spacing(0.39 nm)and abundant vacancy defects.Importantly,the spin state Co downshifts the p-band center of carbon and strengthens the Na+adsorption energy from-2.33 eV to-2.64 eV based on density functional theory calculation.This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.
基金the National Key Research and Development Program of China(No.2022YFA1503003)the National Natural Science Foundation of China(Nos.U20A20250 and 22271081)+1 种基金the Natural Science Foundation of Heilongjiang Province(No.ZD2021B003)the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2020004).
文摘Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potential.Herein,a porous S-doped carbon nitride(S-C_(3)N_(4−y))foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular selfassembly strategy.The S dopants and N vacancies synergistically adjusted the band structure,facilitating light absorption and enhancing the oxidation ability.Moreover,the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer.Consequently,S-C_(3)N_(4−y) foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution(4960μmol/(h·g))and benzylamine oxidation to N-benzylidenebenzylamine(4885μmol/(h·g))with high selectivity of>99%,which were approximately 17.6 and 72.9 times higher than those of bulk CN,respectively.The photocatalytic coupling pairing reaction promotes the water splitting by consuming H2O2,thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines.This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.
基金supported by the Project of the State Key Laboratory of Pollution Control and Resource Reuse Foundation,Nanjing University(No.PCRRF21012)。
文摘We investigated the influence mechanism of N-doping for dissolved black carbon(DBC)photodegradation of organic pollutants.The degradation performance of N-doped dissolved black carbon(NDBC)for tetracycline(TC)(71%)is better than that for methylene blue(MB)(28%)under irradiation.These levels are both better than DBC degradation performances for TC(68%)and MB(18%)under irradiation.Reactive species quenching experiments suggest that h and-O,are the main reactive species for NDBC photodegraded TC,while-OH and h*are the main reactive species for NDBC photodegraded MB.-OH is not observed during DBC photodegradation of MB.This is likely because N-doping increases valence-band(VB)energy from 1.55 eV in DBC to 2.04 eV in NDBC;the latter is strong enough to oxidize water to form-OH.Additionally,N-doping increases the DBC band gap of 2.29 to 2.62 eV in NDBC,resulting in a higher separation efficiency of photo-generated electrons-holes in NDBC than in DBC.AIl these factors give NDBC stronger photodegradation performance for TC and MB than DBC.High-performance liquid chromatography-mass spectrometry(HPLC-MS)characterization and toxicity evaluation with the quantitative structure-activity relationship(QSAR)method suggest that TC photodegradation intermediates produced by NDBC have less aromatic structure and are less toxic than those produced by DBC.We adopted a theoretical approach to clarify the relationship between the surface groups of NDBC and the photoactive species produced.Our results add to the understanding of the photochemical behavior of NDBC.
文摘本文用热处理方法对奥氏体和珠光体异种钢接头的碳迁移现象及其对接头组织和机械性能的影响进行了研究,认为:焊缝金属有析出物出现;熔合区形成一个增碳层;热影响区形成一个脱碳的铁素体带。随回火参数 P 值增加,焊缝析出物增多,晶界加厚;增碳层加宽;脱碳层铁素体晶粒长大;接头拉伸强度,弯曲角和梅氏冲击值均降低,但这种降低在一定温度(如490℃)下逐步达到饱和。
文摘Dielectric properties of SiC/Ni nanocomposites prepared by a simple and facile electroless plating approach at X band are investigated. Compared to the original SiC nanopartieles （SiCp）, the real part of the permittivity, ε＇, and the dielectric loss tangent tang δe of SiC/Ni nanocomposites are clearly enhanced by about 31% and 33%, respectively. The effective equations for complex permittivity of SiC/Ni nanoeomposites are proposed. We also calculate ε＇ and tan δe of SiC/Ni nanoeomposites and the calculated results are well consistent with the measured data.
文摘We present a detailed theoretical study of the behavior of mono-vacancy and B-doped defects in carbon heterojunction nanodevices. We have introduced a complete set of formation energy and surface reactivity calculations, considering a range of different diameters and chiralities of combined carbon nanotubes. We have investigated three distinct combinations of carbon heterojunctions using density functional theory (DFT) and applying B3LYP/3-21g: armchair-armchair herteojunctions, zigzag-zigzag heterojunctions, and zigzag-armchair heterojunctions. We have shown for first time a detailed study of formation energy of mono-vacancy and B-doped defects of carbon heterojunction nanodevices. Our calculations show that the highest surface reactivity is found for the B-doped zigzag-armchair heterojunctions and it is easier to remove the carbon atom from the network of heterojunction armchair-armchair CNTs than the heterojunction zigzag-armchair and zigzag-zigzag CNTs.
基金Supported by the National Natural Science Foundation of China (Nos.11074176 and 10976019)the Research Fund for the Doctoral Program of Higher Education of China (No.20100181110080)
文摘We studied the co-adsorption of hydrogen molecule and ions （Li, K, Mg, Ca） inside the single-walled carbon nanotubes （SWNTs） by using density-functional theory （DFT）. The band structures （BS）, density of states （DOS）, charge transfer and difference charge density are presented. We discussed the interaction between the ions （Li, K, Mg, Ca） and H2 Meanwhile, the binding energy indicates that ionization can increase the adsorption energy of H2 in CNT.
