A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C_(3)N_(4))have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high l...A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C_(3)N_(4))have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high luminescent quantum efficiency.What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level.Hence,it is time to summarize the related research on CN structural evolution and make a prospect on future developments.In this review,we first summarize the research history and multiple structural evolution of CN.Then,the progress of improving the luminescence performance of CN through structural evolution was discussed.Significantly,the relationship between CN structure evolution and energy conversion in the forms of photoluminescence,chemiluminescence,and electrochemiluminescence was reviewed.Finally,key challenges and opportunities such as nanoscale dispersion strategy,luminous efficiency improving methods,standardization evaluation,and macroscopic preparation of CN are highlighted.展开更多
Satisfying the mold-flux performance requirements for high-speed continuous casting necessitates the development of a new non-Newtonian-fluid mold flux with shear-thinning behavior, i.e., a mold flux whose viscosity i...Satisfying the mold-flux performance requirements for high-speed continuous casting necessitates the development of a new non-Newtonian-fluid mold flux with shear-thinning behavior, i.e., a mold flux whose viscosity is relatively high under lower shear rates and relatively low under higher shear rates. In this work, a mold flux that exhibits shear-thinning behavior was developed by adding different amounts of Si_3N_4 to the CaO–SiO_2–CaF_2 mold flux. The shear-thinning behavior was investigated using a rotational viscometer. In addition, the microstructure of the newly prepared slags was studied by high-temperature Raman spectroscopy and X-ray photoelectron spectroscopy. The results showed that the mechanism of shear-thinning was attributable to a temporary viscosity loss caused by the one-way shear stress, whereas the corresponding magnitude of shear-thinning was closely related to the degree of polymerization(DP). Finally, the non-Newtonian fluid mold flux was used for laboratory casting tests, which revealed that the mold flux could reduce slag entrapment and positively affect the continuous casting optimization.展开更多
We put forward a new approach for the synthesis of Ag@AgCl plasmonic photocatalyst via a hydrothermal-deposition-photoreduction method. The cetylmethylammonium chloride （CTAC） was used alone as both a source of reac...We put forward a new approach for the synthesis of Ag@AgCl plasmonic photocatalyst via a hydrothermal-deposition-photoreduction method. The cetylmethylammonium chloride （CTAC） was used alone as both a source of reactants and surfactant. The structure of the prepared photocatalyst was determined by XRD, SEM, EDX and UV-Vis spectroscoscopy. The photocatalytic properties were investigated by degradation of an organic pollutant, Rhodamine B, under visible light irradiation. The results reveal that the experimental conditions have a great effect on the morphology of Ag@AgCl crystals. Ag@AgC1 crystal is cubic and the Ag@AgCl sample which is photoreduced for 40 min exhibits the highest photoactivity, and 80.6 % RhB is degraded after irradiation for 2 hours using this catalyst. The high photocatalytic activity observed is attributed to the surface plasmon resonance effect ofAg nanoparticles.展开更多
The isothermal crystallization kinetics of pure fused quartz of blank specimen N- 0 and specimen N- 3 in troduced with 3 mass% nano-Nd2O3 was researched by means of XRD and Avrami equation. The results show that cryst...The isothermal crystallization kinetics of pure fused quartz of blank specimen N- 0 and specimen N- 3 in troduced with 3 mass% nano-Nd2O3 was researched by means of XRD and Avrami equation. The results show that crystallization mechanisms of fused quartz in two specimens are both heterogeneous nucleation type caused by surface structure defects,and the grain growth mode of two specimens are both two-dimensional growth ac companied by one-dimensional and three-dimensiona growths,specimen N- 3 has the higher degree of grain growth in one-dimensional and three-dimensional than specimen N- 0; introducing nano-Nd2O3 can obviously reduce the ＂active nucleation sites＂of glass structure on the fused quartz particles surface,enhance the stability o glass structure,increase the activation energy of fused quartz crystallization from 874 k J · mol- 1to 1 270 k J·mol- 1,and decrease the crystallization rate of fused quartz obviously.展开更多
Hydrogen production from electrolytic water is an important sustainable technology to realize renewable energy conversion and carbon neutrality.However,it is limited by the high overpotential of oxygen evolution react...Hydrogen production from electrolytic water is an important sustainable technology to realize renewable energy conversion and carbon neutrality.However,it is limited by the high overpotential of oxygen evolution reaction(OER)at the anode.To reduce the operating voltage of electrolyzer,herein thermodynamically favorable glycerol oxidation reaction(GOR)is proposed to replace the OER.Moreover,vertical Ni O flakes and NiMoNH nanopillars are developed to boost the reaction kinetics of anodic GOR and cathodic hydrogen evolution,respectively.Meanwhile,excluding the explosion risk of mixed H_2/O_(2),a cheap organic membrane is used to replace the expensive anion exchange membrane in the electrolyzer.Impressively,the electrolyzer delivers a remarkable reduction of operation voltage by 280 mV,and exhibits good long-term stability.This work provides a new paradigm of hydrogen production with low cost and good feasibility.展开更多
The formation mechanism of intragranular ferrites with acicular morphology was discussed.The ferrites were characterized by scanning electron microscopy.The results showed that the ferrites had an acicular structure w...The formation mechanism of intragranular ferrites with acicular morphology was discussed.The ferrites were characterized by scanning electron microscopy.The results showed that the ferrites had an acicular structure with radial,symmetrical,and acicular laths,and that the inclusions were the nucleation sites of the intragranular acicular ferrites.Transmission electron microscopy（TEM）was used to characterize the inclusions.The results of TEM with energy dispersive spectroscopy and TEM-selected area electron diffraction indicated that the complex inclusions consisted of Ti-Al complex oxides and MnS.The jagged edges of the complex inclusions can be ascribed to the effects of the crystal structure.The stabilization energy U of the coordination polyhedron growth units varies with the type of connection according to the calculation results.A larger Ucorresponds to more stable growth units,which induces the preferentially oriented growth of inclusions,at which point acicular ferrites are formed.展开更多
Single-site metal atoms(SMAs)on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance.However,rational design of configuration-optimized SMA...Single-site metal atoms(SMAs)on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance.However,rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging.Herein,N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4 centers(d-FeN4).This unique d-FeN4 demonstrates much higher intrinsic activity toward oxygen reduction reaction(ORR)in HClO4 than FeN4 without micropore underneath and commercial Pt/C.Both theoretical calculation and electronic structure characterization imply that d-FeN4 endows central Fe with medium spin(t2g 4 eg 1),which provides a spin channel for electron transition compared with FeN4 with low spin.This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR,thus showing faster kinetics than FeN4.This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.展开更多
The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffracto...The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffractometer(XRD)and scanning electron microscopy(SEM)were used to investigate the phase compositions,distribution and morphology of the ceramic samples.SM-11J49 capacitance measurement instrument and CS2674A pressure tester were used to measure the dieletric properties of the samples.The results show that the compactness and the dielectric constant of the ceramics increases first and then decreases when the doped MgO content was changed from 1.5 to 4.5 wt.%.The trend of breakdown strength is characterized by M-shaped pattern with the increase of doped-MgO content.Calculation results demonstrate that when the doped-MgO content is 2.0%,the samples have the highest energy storage density.展开更多
Luminescent materials often suffer from thermal quenching(TQ),limiting the continuation of their applications under high temperatures up to 473 K.The formation of defect levels could suppress TQ,but rational synthesis...Luminescent materials often suffer from thermal quenching(TQ),limiting the continuation of their applications under high temperatures up to 473 K.The formation of defect levels could suppress TQ,but rational synthesis and deep understanding of multiple defects-regulated luminescent materials working in such a wide temperature range still remain challenging.Here,we prepare a negative thermal quenching(NTQ)phosphor LiTaO_(3)∶Tb^(3+)by introducing gradient defects V_(Ta)^(5−),Tb_(Li)^(2+),and(V_(Ta)Tb_(Li))^(3−)as identified by advanced experimental and theoretical studies.Its photoluminescence significantly becomes intense with rising temperatures and then slowly increases at 373 to 473 K.The mechanism studies reveal that gradient defects with varied trapping depths could act as energy buffer layers to effectively capture the carriers.Under thermal disturbance,the stored carriers could successively migrate to the activators in consecutive and wide temperature zones,compensating for TQ to enhance luminescence emission.This study initiates the synthesis of multi-defect NTQ phosphors for temperature-dependent applications.展开更多
A composite coating with inner and outer layers was prepared for the thermal protection of woven silica fiber fabrics.Using a sol mixture of a silica sol and AlF3/SiO2 particles mixed in the stoichiometric molar ratio...A composite coating with inner and outer layers was prepared for the thermal protection of woven silica fiber fabrics.Using a sol mixture of a silica sol and AlF3/SiO2 particles mixed in the stoichiometric molar ratio for mullite,hollow silica spheres and short mullite fibers were added to the inner layer and outer layer,respectively.The phase composition and thermal evolution of the coating,along with the interfacial microstructure between the coating and the matrix,were characterized by means of X-ray diffraction,differential scanning calorimetry/thermogravimetry,scanning electron microscopy,and tensile strength testing.Mullite whiskers grew between 950°C and 1200°C and helped prevent thermal cracking during the drying and densification processes.The hollow silica spheres might play dual roles,weakening the adhesion between the coating and the fibers by reducing their direct contact,but strengthening the joining between the coating and substrate by embedding themselves among the fabrics.展开更多
基金Natural Science Foundation of Hebei ProvinceTangshan Talent Funding Project,Grant/Award Number:E2022209039+1 种基金Key Research Project of North China University of Science and Technology,Grant/Award Number:ZD-YG 202301Tangshan Talent Punding Project,Grant/Award Number:A202202007
文摘A series of carbon nitride(CN)materials represented by graphitic carbon nitride(g-C_(3)N_(4))have been widely used in bioimaging,biosensing,and other fields in recent years due to their nontoxicity,low cost,and high luminescent quantum efficiency.What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level.Hence,it is time to summarize the related research on CN structural evolution and make a prospect on future developments.In this review,we first summarize the research history and multiple structural evolution of CN.Then,the progress of improving the luminescence performance of CN through structural evolution was discussed.Significantly,the relationship between CN structure evolution and energy conversion in the forms of photoluminescence,chemiluminescence,and electrochemiluminescence was reviewed.Finally,key challenges and opportunities such as nanoscale dispersion strategy,luminous efficiency improving methods,standardization evaluation,and macroscopic preparation of CN are highlighted.
基金financially supported by the National Natural Science Foundation of China (Nos.51574109 and 51604119)
文摘Satisfying the mold-flux performance requirements for high-speed continuous casting necessitates the development of a new non-Newtonian-fluid mold flux with shear-thinning behavior, i.e., a mold flux whose viscosity is relatively high under lower shear rates and relatively low under higher shear rates. In this work, a mold flux that exhibits shear-thinning behavior was developed by adding different amounts of Si_3N_4 to the CaO–SiO_2–CaF_2 mold flux. The shear-thinning behavior was investigated using a rotational viscometer. In addition, the microstructure of the newly prepared slags was studied by high-temperature Raman spectroscopy and X-ray photoelectron spectroscopy. The results showed that the mechanism of shear-thinning was attributable to a temporary viscosity loss caused by the one-way shear stress, whereas the corresponding magnitude of shear-thinning was closely related to the degree of polymerization(DP). Finally, the non-Newtonian fluid mold flux was used for laboratory casting tests, which revealed that the mold flux could reduce slag entrapment and positively affect the continuous casting optimization.
基金Funded partly by the National Natural Science Foundation of China(Nos.51172063,51202056,51372068)Hebei Natural Science Funds for Distinguished Young Scholar(No.B2014209304)+1 种基金Hebei Natural Science Funds for the Joint Research of Iron and Steel(No.B2014209314)Hebei Provincial Foundation for Returned Scholars
文摘We put forward a new approach for the synthesis of Ag@AgCl plasmonic photocatalyst via a hydrothermal-deposition-photoreduction method. The cetylmethylammonium chloride （CTAC） was used alone as both a source of reactants and surfactant. The structure of the prepared photocatalyst was determined by XRD, SEM, EDX and UV-Vis spectroscoscopy. The photocatalytic properties were investigated by degradation of an organic pollutant, Rhodamine B, under visible light irradiation. The results reveal that the experimental conditions have a great effect on the morphology of Ag@AgCl crystals. Ag@AgC1 crystal is cubic and the Ag@AgCl sample which is photoreduced for 40 min exhibits the highest photoactivity, and 80.6 % RhB is degraded after irradiation for 2 hours using this catalyst. The high photocatalytic activity observed is attributed to the surface plasmon resonance effect ofAg nanoparticles.
文摘The isothermal crystallization kinetics of pure fused quartz of blank specimen N- 0 and specimen N- 3 in troduced with 3 mass% nano-Nd2O3 was researched by means of XRD and Avrami equation. The results show that crystallization mechanisms of fused quartz in two specimens are both heterogeneous nucleation type caused by surface structure defects,and the grain growth mode of two specimens are both two-dimensional growth ac companied by one-dimensional and three-dimensiona growths,specimen N- 3 has the higher degree of grain growth in one-dimensional and three-dimensional than specimen N- 0; introducing nano-Nd2O3 can obviously reduce the ＂active nucleation sites＂of glass structure on the fused quartz particles surface,enhance the stability o glass structure,increase the activation energy of fused quartz crystallization from 874 k J · mol- 1to 1 270 k J·mol- 1,and decrease the crystallization rate of fused quartz obviously.
基金the financial support from National Natural Science Foundation of China(92163117,52072389,52172058,51972006)。
文摘Hydrogen production from electrolytic water is an important sustainable technology to realize renewable energy conversion and carbon neutrality.However,it is limited by the high overpotential of oxygen evolution reaction(OER)at the anode.To reduce the operating voltage of electrolyzer,herein thermodynamically favorable glycerol oxidation reaction(GOR)is proposed to replace the OER.Moreover,vertical Ni O flakes and NiMoNH nanopillars are developed to boost the reaction kinetics of anodic GOR and cathodic hydrogen evolution,respectively.Meanwhile,excluding the explosion risk of mixed H_2/O_(2),a cheap organic membrane is used to replace the expensive anion exchange membrane in the electrolyzer.Impressively,the electrolyzer delivers a remarkable reduction of operation voltage by 280 mV,and exhibits good long-term stability.This work provides a new paradigm of hydrogen production with low cost and good feasibility.
基金Item Sponsored by National Natural Science Foundation of China(51574106,51474089)Key Funds of Natural Science Foundation of Hebei Province of China(E2016209396)+1 种基金Natural Science Foundation of Hebei Province of China(E2013209207)Research Science Institute on High-level Personnel of Colleges in Hebei Province of China(GCC20142030)
文摘The formation mechanism of intragranular ferrites with acicular morphology was discussed.The ferrites were characterized by scanning electron microscopy.The results showed that the ferrites had an acicular structure with radial,symmetrical,and acicular laths,and that the inclusions were the nucleation sites of the intragranular acicular ferrites.Transmission electron microscopy（TEM）was used to characterize the inclusions.The results of TEM with energy dispersive spectroscopy and TEM-selected area electron diffraction indicated that the complex inclusions consisted of Ti-Al complex oxides and MnS.The jagged edges of the complex inclusions can be ascribed to the effects of the crystal structure.The stabilization energy U of the coordination polyhedron growth units varies with the type of connection according to the calculation results.A larger Ucorresponds to more stable growth units,which induces the preferentially oriented growth of inclusions,at which point acicular ferrites are formed.
基金support from the National Natural Science Foundation of China(grants 92163117,52072389,and 52172058)State Key Laboratory of ASIC&Sys-tem(grant 2020KF002)+2 种基金J.W.thanks the Program of Shanghai Academic Research Leader(grant 20XD1424300)for financial support.LL.acknowledges support from the Discovery Program of the Natural Sciences and Engineering Research Council of Canada(NSERC,grant DG RGPIN-2020-06675)Use of the Advanced Photon Source was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under contract DE-AC02-06CH11357Technical support from APS beamline scientists Dr.George E.Ster-binsky and Dr.Tianpin Wu,and from TLS beamline scientist Dr.Lo-Yueh Chang,is greatly appreciated.
文摘Single-site metal atoms(SMAs)on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance.However,rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging.Herein,N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4 centers(d-FeN4).This unique d-FeN4 demonstrates much higher intrinsic activity toward oxygen reduction reaction(ORR)in HClO4 than FeN4 without micropore underneath and commercial Pt/C.Both theoretical calculation and electronic structure characterization imply that d-FeN4 endows central Fe with medium spin(t2g 4 eg 1),which provides a spin channel for electron transition compared with FeN4 with low spin.This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR,thus showing faster kinetics than FeN4.This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.
文摘The Ba_(0.3)Sr_(0.6)Ca_(0.1)TiO_(3)(BSCT)powder was prepared through the solid-state reaction.And then preparing ceramic samples with quantitative doped-Bi_(2)O_(3)·3TiO_(2) and diferent doped-MgO.X-ray diffractometer(XRD)and scanning electron microscopy(SEM)were used to investigate the phase compositions,distribution and morphology of the ceramic samples.SM-11J49 capacitance measurement instrument and CS2674A pressure tester were used to measure the dieletric properties of the samples.The results show that the compactness and the dielectric constant of the ceramics increases first and then decreases when the doped MgO content was changed from 1.5 to 4.5 wt.%.The trend of breakdown strength is characterized by M-shaped pattern with the increase of doped-MgO content.Calculation results demonstrate that when the doped-MgO content is 2.0%,the samples have the highest energy storage density.
基金the National Key Research and Development Program of China(Grant No.2018YFB0704103)the Natural Science Foundation of Shanghai(Grant Nos.22ZR1472100 and 20ZR1465900)+3 种基金the National Natural Science Foundation of China(Grant Nos.92163117 and 62175210)the State Key Laboratory of ASIC&System(Grant No.2020KF002)the Innovation Project of Shanghai Institute of Ceramics(Grant No.E21ZC1770G)L.L.thanks the Taiwan Light Source for technical support.J.W.thanks the Program of Shanghai Academic Research Leader(Grant No.20XD1424300)for financial support.The authors thank Professor Zhijun Zhang for providing valuable assistance in stress luminescence testing.
文摘Luminescent materials often suffer from thermal quenching(TQ),limiting the continuation of their applications under high temperatures up to 473 K.The formation of defect levels could suppress TQ,but rational synthesis and deep understanding of multiple defects-regulated luminescent materials working in such a wide temperature range still remain challenging.Here,we prepare a negative thermal quenching(NTQ)phosphor LiTaO_(3)∶Tb^(3+)by introducing gradient defects V_(Ta)^(5−),Tb_(Li)^(2+),and(V_(Ta)Tb_(Li))^(3−)as identified by advanced experimental and theoretical studies.Its photoluminescence significantly becomes intense with rising temperatures and then slowly increases at 373 to 473 K.The mechanism studies reveal that gradient defects with varied trapping depths could act as energy buffer layers to effectively capture the carriers.Under thermal disturbance,the stored carriers could successively migrate to the activators in consecutive and wide temperature zones,compensating for TQ to enhance luminescence emission.This study initiates the synthesis of multi-defect NTQ phosphors for temperature-dependent applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.51272171,51372164)
文摘A composite coating with inner and outer layers was prepared for the thermal protection of woven silica fiber fabrics.Using a sol mixture of a silica sol and AlF3/SiO2 particles mixed in the stoichiometric molar ratio for mullite,hollow silica spheres and short mullite fibers were added to the inner layer and outer layer,respectively.The phase composition and thermal evolution of the coating,along with the interfacial microstructure between the coating and the matrix,were characterized by means of X-ray diffraction,differential scanning calorimetry/thermogravimetry,scanning electron microscopy,and tensile strength testing.Mullite whiskers grew between 950°C and 1200°C and helped prevent thermal cracking during the drying and densification processes.The hollow silica spheres might play dual roles,weakening the adhesion between the coating and the fibers by reducing their direct contact,but strengthening the joining between the coating and substrate by embedding themselves among the fabrics.
