Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such ma...Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials,particularly when adjustment of the constitution or mixing ratio is limited.In this study,bowl-like and honeycomb titanium dioxide/carbon nanotube(TiO_(2)/CNT)composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration,respectively.Compared to the honeycomb structure,the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization,and augmented multiple reflections.The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics.The bowl-like TiO_(2)/CNT composite exhibited a minimum reflection loss(RL_(min))of-38.6 dB(1.5 mm)with a wide effective absorption band(EAB;<-10 dB)of4.2 GHz,while the honeycomb TiO_(2)/CNT composite showed an RLminof-34.8 dB(2.1 mm)with an EAB of 4.3 GHz.The required mixing ratio in the matrix was only 15 wt%,outperforming that of the most closely related composites.Thus,both the bowl-like and honeycomb TiO_(2)/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.展开更多
Molybdenum disilicide(MoSi_2) based composites with various contents of carbon nanotubes(CNTs) were fabricated by spark plasma sintering(SPS) in vacuum under a pressure of 25 MPa.The composites obtained under a sinter...Molybdenum disilicide(MoSi_2) based composites with various contents of carbon nanotubes(CNTs) were fabricated by spark plasma sintering(SPS) in vacuum under a pressure of 25 MPa.The composites obtained under a sintering temperature of 1500 °C and time of 10 min exhibited optimum mechanical properties at room temperature in terms of fracture toughness and transverse rupture strength.MoSi_2 based composite with 6.0% CNTs(volume fraction) had the highest fracture toughness,transverse rupture strength and hardness,which were improved by about 25.7%,51.5% and 24.4% respectively,as compared with pure MoSi_2.A Mo_(4.8)Si_3C_(0.6) phase was detected in CNTs/MoSi_2 composites by both X-ray diffraction(XRD) method and microstructure analysis with scanning electron microscopy(SEM).It is believed that the fine grains and well dispersed small Mo_(4.8)Si_3C_(0.6) particles had led to a higher hardness and strength of CNTs/MoSi_2 composites because of their particle pullout,crack deflection and micro-bridging effects.展开更多
TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to es...TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.展开更多
An innovative photocatalyst, Carbon nanotube （CNT） supported Ce-TiO2 nanocomposite was successfully synthesized via modi-fied sol gel method and investigated in a batch reactor for abolition of phenol under UV light...An innovative photocatalyst, Carbon nanotube （CNT） supported Ce-TiO2 nanocomposite was successfully synthesized via modi-fied sol gel method and investigated in a batch reactor for abolition of phenol under UV light spectrum. Characterization of catalyst micro-structure and internal properties were done by means of X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, scanning electron micros-copy （SEM）, transmission electron microscopy （TEM） and UV-vis diffuse reflectance spectra （DRS）. Ce doping can inhibit phase transfor-mation from anatase to rutile and eliminate the recombination of electron-hole pairs in the catalyst. The presence of CNT in TiO2 composite can both increase the photoactivity under UV and change surface properties to achieve sensitivity to visible light. The optimum mass ratio of CNT support and cerium （Ce） dopant in TiO2 was the prominent factor to harvest CNT/Ce-TiO2 photocatalyst nanocomposite. The results demonstrated that optimum mass ratio of CNT：TiO2：Ce was 0.02：1.0：0.06, which resulted in the great performance of the photocatalyst to de-grade about 94% of phenol in a 50 mg/L solution in only 3 h. In this paper, dissimilar role of CNT support and Ce dopant in the TiO2 photo-catalysis of phenol was also discussed.展开更多
Sodium-ion batteries(SIBs)have attracted significant attention with respect to renewable energy power generation systems because of the abundant reserves of sodium on earth.However,anode materials are presently limite...Sodium-ion batteries(SIBs)have attracted significant attention with respect to renewable energy power generation systems because of the abundant reserves of sodium on earth.However,anode materials are presently limited by low energy density,poor rate performance and inferior cycling stability.In recent years,tin disulfide(SnS_(2))with a particular layered structure has been considered as a promising anode material for SIBs due to its high theoretical capacity and low cost.Herein,a nervoussystem-like structured SnS_(2)/CNTs composite was successfully synthesized via a hydrothermal method.The SnS_(2)sheets were strung with carbon nanotubes(CNTs)to form a hierarchical porous structure,which is effective for electrolyte diffusion and electronic transmission.The large distance of the(001)plane(0.5899 nm)of SnS_(2)favors Na+insertion-extraction dynamics.Benefitting from these structural characteristics,SnS_(2)/CNTs electrodes exhibit high specific capacity,excellent rate performance and superior cycling stability.A high charge capacity of 642 mAh·g^(-1)was released at 0.2 A·g^(-1),and then,a high reversible capacity of 427 mAh·g^(-1)was retained after 100 cycles.Even charged at 2 A·g^(-1),the SnS_(2)/CNTS electrode maintained a capacity of 282 mAh·g^(-1).The nervous-system-like structure of the SnS_(2)/CNTs composite provides a novel strategy for the development of SIBs with high electrochemical performance.展开更多
Polyaniline （PAn） sensitized nanocrystalline TiO2 composites （TiO2/PAn） were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue （MB）. The results showed that P...Polyaniline （PAn） sensitized nanocrystalline TiO2 composites （TiO2/PAn） were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue （MB）. The results showed that PAn was able to sensitize TiO2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light （λ： 190 ～ 800 nm）, whereas pure TiO2 absorbed ultraviolet light only （λ 〈 380 nm）. Under the irradiation of natural light, MB could be degraded more efficiently on the TiO2/PAn composites than on the TiO2 Furthermore, it could be easily separated from the solution by simple sedimentation.展开更多
We report the construction of a graphene/tourmaline/TiO2(G/T/TiO2)composite system with enhanced charge‐carrier separation,and therefore enhanced photocatalytic properties,based on tailoring the surface‐charged stat...We report the construction of a graphene/tourmaline/TiO2(G/T/TiO2)composite system with enhanced charge‐carrier separation,and therefore enhanced photocatalytic properties,based on tailoring the surface‐charged state of graphene and/or by introducing an external electric field arising from tourmaline.A simple two‐step hydrothermal method was used to synthesize G/T/TiO2composites and poly(diallyldimethylammonium chloride)‐G/T/TiO2composites.In the photocatalytic degradation of2‐propanol(IPA),the catalytic activity of the composite containing negatively charged graphene was higher than of the composite containing positively charged graphene.The highest acetone evolution rate(223?mol/h)was achieved using the ternary composite with the optimum composition,i.e.,G0.5/T5/TiO2(0.5wt%graphene and5wt%tourmaline).The involvement of tourmaline and graphene in the composite is believed to facilitate the separation and transportation of electrons and holes photogenerated in TiO2.This synergetic effect could account for the enhanced photocatalytic activity of the G/T/TiO2composite.A mechanistic study indicated that O2??radicals and holes were the main reactive oxygen species in photocatalytic degradation of IPA.展开更多
Modern communication technologies put forward higher requirements for electromagnetic wave(EMW)absorption materials.Metal-organic framework(MOF)derivatives have been widely concerned with its diverse advantages.To bre...Modern communication technologies put forward higher requirements for electromagnetic wave(EMW)absorption materials.Metal-organic framework(MOF)derivatives have been widely concerned with its diverse advantages.To break the mindset of magneticderivative design,and make up the shortage of monometallic non-magnetic derivatives,we first try non-magnetic bimetallic MOFs derivatives to achieve efficient EMW absorption.The porous carbon-wrapped TiO2/ZrTiO4 composites derived from PCN-415(TiZr-MOFs)are qualified with a minimum reflection loss of−67.8 dB(2.16 mm,13.0 GHz),and a maximum effective absorption bandwidth of 5.9 GHz(2.70 mm).Through in-depth discussions,the synergy of enhanced interfacial polarization and other attenuation mechanisms in the composites is revealed.Therefore,this work confirms the huge potentials of nonmagnetic bimetallic MOFs derivatives in EMW absorption applications.展开更多
A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was emplo...A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51802289)the Science Foundation for the Excellent Youth Scholars of Henan Province(No.212300410089)+2 种基金the Support Program for Scientific and Technological Innovation Talents of Higher Education in Henan Province(No.21HASTIT004)the China Postdoctoral Science Foundation(No.2019M661352)the Natural Science Basic Research Program in Shaanxi Province(No.202032100067)。
文摘Materials that can efficiently absorb electromagnetic waves(EMWs)are required to deal with electromagnetic pollution.Structure design appears to be an efficient way to improve the EMW-absorption performance of such materials,particularly when adjustment of the constitution or mixing ratio is limited.In this study,bowl-like and honeycomb titanium dioxide/carbon nanotube(TiO_(2)/CNT)composites with different CNT contents were fabricated using the methods of hierarchical and mixing vacuum-assisted filtration,respectively.Compared to the honeycomb structure,the bowl-like structure simultaneously facilitated greater interfacial polarization and conduction loss in favor of dielectric polarization,and augmented multiple reflections.The high porosity of the honeycomb structure was conducive to optimizing the impedance matching characteristics.The bowl-like TiO_(2)/CNT composite exhibited a minimum reflection loss(RL_(min))of-38.6 dB(1.5 mm)with a wide effective absorption band(EAB;<-10 dB)of4.2 GHz,while the honeycomb TiO_(2)/CNT composite showed an RLminof-34.8 dB(2.1 mm)with an EAB of 4.3 GHz.The required mixing ratio in the matrix was only 15 wt%,outperforming that of the most closely related composites.Thus,both the bowl-like and honeycomb TiO_(2)/CNT composites are ideal candidates for light-weight and highly efficient EMW-absorbing materials.
基金Project(51371155)supported by the National Natural Science Foundation of ChinaProject(2014H0046)supported by the Key Science and Technology Project of Fujian Province,China+2 种基金Project(3502Z20143036)supported by the Scientific Research Fund of Xiamen,ChinaProject(JB13149)supported by the Education Department Science and Technology Project of Fujian Province,ChinaProject(2012D131)supported by the Natural Science Foundation Guidance Project of Fujian Province,China
文摘Molybdenum disilicide(MoSi_2) based composites with various contents of carbon nanotubes(CNTs) were fabricated by spark plasma sintering(SPS) in vacuum under a pressure of 25 MPa.The composites obtained under a sintering temperature of 1500 °C and time of 10 min exhibited optimum mechanical properties at room temperature in terms of fracture toughness and transverse rupture strength.MoSi_2 based composite with 6.0% CNTs(volume fraction) had the highest fracture toughness,transverse rupture strength and hardness,which were improved by about 25.7%,51.5% and 24.4% respectively,as compared with pure MoSi_2.A Mo_(4.8)Si_3C_(0.6) phase was detected in CNTs/MoSi_2 composites by both X-ray diffraction(XRD) method and microstructure analysis with scanning electron microscopy(SEM).It is believed that the fine grains and well dispersed small Mo_(4.8)Si_3C_(0.6) particles had led to a higher hardness and strength of CNTs/MoSi_2 composites because of their particle pullout,crack deflection and micro-bridging effects.
基金Project(50802034) supported by the National Natural Science Foundation of ChinaProject(11A093) supported by the Key Project Foundation by the Education Department of Hunan Province,China
文摘TiO2-coated activated carbon surface （TAs） composites were prepared by a sol-gel method with supercritical pretreatment. The photocatalytic degradation of acid yellow （AY） was investigated under UV radiation to estimate activity of catalysts and determine the kinetics. And the effects of parameters including the initial concentration of AY, light intensity and TiO2 content in catalysts were examined. The results indicate that TAs has a higher efficiency in decomposition of AY than P25, pure TiO2 particles as well as the mixture of TiO2 powder and active carbon. The photocatalytic degradation rate is found to follow the pseudo-first order kinetics with respect to the AY concentration. The new kinetic model fairly resembles the classic Langmuir-Hinshelwood equation, and the rate constant is proportional to the square root of the light intensity in a wide range. However, its absorption performance depends on the surface areas of catalysts. The model fits quite well with the experimental data and elucidates phenomena about the effects of the TiO2 content in TAs on the degradation rate.
基金Project supported by Research University Grant Scheme (Project A/C No.814004)the Malaysian Technology Development Corporation (MTDC) under the Commercialization of Research and Development Fund (CRDF) (MBF065-USM/05)
文摘An innovative photocatalyst, Carbon nanotube （CNT） supported Ce-TiO2 nanocomposite was successfully synthesized via modi-fied sol gel method and investigated in a batch reactor for abolition of phenol under UV light spectrum. Characterization of catalyst micro-structure and internal properties were done by means of X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, scanning electron micros-copy （SEM）, transmission electron microscopy （TEM） and UV-vis diffuse reflectance spectra （DRS）. Ce doping can inhibit phase transfor-mation from anatase to rutile and eliminate the recombination of electron-hole pairs in the catalyst. The presence of CNT in TiO2 composite can both increase the photoactivity under UV and change surface properties to achieve sensitivity to visible light. The optimum mass ratio of CNT support and cerium （Ce） dopant in TiO2 was the prominent factor to harvest CNT/Ce-TiO2 photocatalyst nanocomposite. The results demonstrated that optimum mass ratio of CNT：TiO2：Ce was 0.02：1.0：0.06, which resulted in the great performance of the photocatalyst to de-grade about 94% of phenol in a 50 mg/L solution in only 3 h. In this paper, dissimilar role of CNT support and Ce dopant in the TiO2 photo-catalysis of phenol was also discussed.
基金financially supported by the National Natural Science Foundation of China(Nos.51704124,51762017 and 11602094)the Key Planned Science and Technology Project of Xiangxi Tujia&Miao Autonomous Prefecture(No.2018GX2001)+2 种基金the Program of Youth Talent Support for Hunan Province(No.2018RS3098)the Key Program of Hunan Provincial Education Department(No.18A285)the Natural Science Foundation of Hunan Province(Nos.2018JJ3415 and 2019JJ50485)。
文摘Sodium-ion batteries(SIBs)have attracted significant attention with respect to renewable energy power generation systems because of the abundant reserves of sodium on earth.However,anode materials are presently limited by low energy density,poor rate performance and inferior cycling stability.In recent years,tin disulfide(SnS_(2))with a particular layered structure has been considered as a promising anode material for SIBs due to its high theoretical capacity and low cost.Herein,a nervoussystem-like structured SnS_(2)/CNTs composite was successfully synthesized via a hydrothermal method.The SnS_(2)sheets were strung with carbon nanotubes(CNTs)to form a hierarchical porous structure,which is effective for electrolyte diffusion and electronic transmission.The large distance of the(001)plane(0.5899 nm)of SnS_(2)favors Na+insertion-extraction dynamics.Benefitting from these structural characteristics,SnS_(2)/CNTs electrodes exhibit high specific capacity,excellent rate performance and superior cycling stability.A high charge capacity of 642 mAh·g^(-1)was released at 0.2 A·g^(-1),and then,a high reversible capacity of 427 mAh·g^(-1)was retained after 100 cycles.Even charged at 2 A·g^(-1),the SnS_(2)/CNTS electrode maintained a capacity of 282 mAh·g^(-1).The nervous-system-like structure of the SnS_(2)/CNTs composite provides a novel strategy for the development of SIBs with high electrochemical performance.
文摘Polyaniline （PAn） sensitized nanocrystalline TiO2 composites （TiO2/PAn） were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue （MB）. The results showed that PAn was able to sensitize TiO2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light （λ： 190 ～ 800 nm）, whereas pure TiO2 absorbed ultraviolet light only （λ 〈 380 nm）. Under the irradiation of natural light, MB could be degraded more efficiently on the TiO2/PAn composites than on the TiO2 Furthermore, it could be easily separated from the solution by simple sedimentation.
基金supported by the National Basic Research Program of China (973 Program,2014CB239300)the National Natural Science Foundation of China (51572191)the Natural Science Foundation of Tianjin (13JCYBJC16600)~~
文摘We report the construction of a graphene/tourmaline/TiO2(G/T/TiO2)composite system with enhanced charge‐carrier separation,and therefore enhanced photocatalytic properties,based on tailoring the surface‐charged state of graphene and/or by introducing an external electric field arising from tourmaline.A simple two‐step hydrothermal method was used to synthesize G/T/TiO2composites and poly(diallyldimethylammonium chloride)‐G/T/TiO2composites.In the photocatalytic degradation of2‐propanol(IPA),the catalytic activity of the composite containing negatively charged graphene was higher than of the composite containing positively charged graphene.The highest acetone evolution rate(223?mol/h)was achieved using the ternary composite with the optimum composition,i.e.,G0.5/T5/TiO2(0.5wt%graphene and5wt%tourmaline).The involvement of tourmaline and graphene in the composite is believed to facilitate the separation and transportation of electrons and holes photogenerated in TiO2.This synergetic effect could account for the enhanced photocatalytic activity of the G/T/TiO2composite.A mechanistic study indicated that O2??radicals and holes were the main reactive oxygen species in photocatalytic degradation of IPA.
基金The authors acknowledge funding from the National Natural Science Foundation of China(Nos.51572157,21902085,and 51702188)Natural Science Foundation of Shandong Province(No.ZR2019QF012)+1 种基金Fundamental Research Funds for the Central Universities(No.2018JC036 and No.2018JC046)Young Scholars Program of Shandong University(No.2018WLJH25).
文摘Modern communication technologies put forward higher requirements for electromagnetic wave(EMW)absorption materials.Metal-organic framework(MOF)derivatives have been widely concerned with its diverse advantages.To break the mindset of magneticderivative design,and make up the shortage of monometallic non-magnetic derivatives,we first try non-magnetic bimetallic MOFs derivatives to achieve efficient EMW absorption.The porous carbon-wrapped TiO2/ZrTiO4 composites derived from PCN-415(TiZr-MOFs)are qualified with a minimum reflection loss of−67.8 dB(2.16 mm,13.0 GHz),and a maximum effective absorption bandwidth of 5.9 GHz(2.70 mm).Through in-depth discussions,the synergy of enhanced interfacial polarization and other attenuation mechanisms in the composites is revealed.Therefore,this work confirms the huge potentials of nonmagnetic bimetallic MOFs derivatives in EMW absorption applications.
文摘A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.
