Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EB...Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor corrosion.The target operating temperature for next-generation tur bine blades is 1400°C.Corrosion is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its reliability.This study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press method.They were then exposed to volcanic ash at 1400°C for 224,and 48 h.After 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing damage.Meanwhile Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the interior.With increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.展开更多
The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theore...The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.展开更多
B and N mixed anions co-doped titania with various crystal phases such as anatase,brookite,and rutile were successfully synthesized by a hydrothermal synthesis followed by heat treatment in an ammonia gas atmosphere a...B and N mixed anions co-doped titania with various crystal phases such as anatase,brookite,and rutile were successfully synthesized by a hydrothermal synthesis followed by heat treatment in an ammonia gas atmosphere at 550-650℃(denoted as BN-Ana_x,BN-Bro_x,and BN-Rut_x,x is the treatment temperature).The colors of as-prepared BN-Ana,BN-Bro,and BN-Rut are red,yellow-green,and cyangreen,respectively.The color changing mechanism of titania was related to their various band gap structure and the existence of B-N bonding.The nitridation temperature exhibits effective color changing compared to that of nitridation time.The different phases of the mixed anion codoped titania possess different photocatalytic deNO_(x) activity.The BN-Ana and BN-Rut show poor photocatalytic deNO_(x) activity,while the BN-Bro shows excellent photocatalytic deNO_(x) activity,better than that of standard titania photocatalyst Degussa P25.The colorful titania with low-photocatalytic activity is heavy metal elements free,indicating their possible applications as nontoxic color pigments or novel cosmetic raw materials.展开更多
The high-capacity vehicle-to-vehicle(V2 V) communication provides a promising solution to support ubiquitous media streaming and content sharing among vehicles.To extend the V2 V links to multiple cells and manage the...The high-capacity vehicle-to-vehicle(V2 V) communication provides a promising solution to support ubiquitous media streaming and content sharing among vehicles.To extend the V2 V links to multiple cells and manage the inter-cell interference,we proposed an UAV-assisted inter-cell V2 V communication model,in which a shared UAV node is placed in the center of V2 V users.By charging the V2 V users underlay spectrum access fee,the cellular network earn profit at the cost of encountering co-channel interference from V2 V links.A Stackelberg game is formulated to model the interactions between the V2 V links and the cellular links,which are the game follower and the leader respectively.Their utility functions are maximized in terms of accessing price as well as transmit power of V2 V users and UAV relays.Simulation evaluations verify that the power-price tradeoff between V2 V network and cellular network has significant potentials to enhance their utility.展开更多
Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications.Particularly,molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunab...Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications.Particularly,molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements.These materials have good durability,are naturally abundant,low cost,and have facile preparation,allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices.Significant advances have been made in recent decades to design and fabricate various molybdenum oxides-and dichalcogenides-based sensing materials,though it is still challenging to achieve high performances.Therefore,many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties.This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants,dangerous gases,or even exhaled breath monitoring.The summary and future challenges to advance their gas sensing performances will also be presented.展开更多
Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation.However,leaking hydrogen in high-temperature production processes can cause an explosion,which endangers ...Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation.However,leaking hydrogen in high-temperature production processes can cause an explosion,which endangers production workers and surrounding areas.To detect leaks early,we used a sensor material based on a wide bandgap aluminum nitride(AlN)that can withstand a high-temperature environment.Three unique AlN morphologies(rod-like,nest-like,and hexagonal plate-like)were synthesized by a direct nitridation method at 1400℃usingγ-AlOOH as a precursor.The gas-sensing performance shows that a hexagonal plate-like morphology exhibited p-type sensing behavior and showed good repeatability as well as the highest response(S=58.7)toward a 750 ppm leak of H2 gas at high temperature(500°C)compared with the rod-like and nest-like morphologies.Furthermore,the hexagonal plate-like morphology showed fast response and recovery times of 40 and 82 s,respectively.The surface facet of the hexagonal morphology of AlN might be energetically favorable for gas adsorption–desorption for enhanced hydrogen detection.展开更多
The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal r...The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal reaction apparatus with a rolling system. The mean particle diameter decreased from 500 to 50 nm with a decrease in the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio from 0.44 to 0.04. The powders were sintered by normal one-step sintering at 1200°C for 5 h and two-step sintering in which temperature was raised to 1200°C at first and then decreased to 1100°C and kept at 1100°C for 5 h. The BaTiO3 particles prepared with the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio of 0.32 and 0.22 showed excellent sinterability and could be sintered to almost full theoretical density by both method. The sintered bodies obtained by both methods showed similarly excellent dielectric and piezoelectric properties.展开更多
Lanthanum and nitrogen co-doped SrTiO3 was synthesized using polymerized complex method with Ti(OC3H7)4, SrCl2·6H2O and La(NO3)3·6H2O as starting materials followed by calcinations in NH3. Ethylene glycol an...Lanthanum and nitrogen co-doped SrTiO3 was synthesized using polymerized complex method with Ti(OC3H7)4, SrCl2·6H2O and La(NO3)3·6H2O as starting materials followed by calcinations in NH3. Ethylene glycol and anhydrous citric acid were used as the precursors of synthesis. The samples were characterized using XRD, TEM, DRS, BET, EDX and XPS. The cubic-perovskite type of La/N co-doped SrTiO3 nanoparticle could be successfully synthesized. The photocatalytic activity of SrTiO3 for DeNOx ability in visible light region (λ > 510 nm) could be improved by co-doping of La3+ and N3_. The high visible light photocatalytic activity of this substance was caused by a narrow band gap energy that enables to absorb visible light.展开更多
To the Editor:Chronic obstructive pulmonary disease(COPD),a clinical syndrome encompassing a spectrum of chronic,progressive,and debilitating respiratory disorders,is increasingly recognized as a multisystemic heterog...To the Editor:Chronic obstructive pulmonary disease(COPD),a clinical syndrome encompassing a spectrum of chronic,progressive,and debilitating respiratory disorders,is increasingly recognized as a multisystemic heterogeneous disease.[1]Because the characteristics of East Asian COPD patients differ from those of Westerners,it would be practical to investigate whether variations in COPD genetic performance exist between East Asian and Western populations.展开更多
基金supported by JSPS KAKENHI(No.23K19087)“Dynamic Alliance for Open Innovation Bridging Human,Environment and Materials”from the Ministry of Education,Culture,Sports,Science and Technology o f Japan(MEXT).
文摘Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor corrosion.The target operating temperature for next-generation tur bine blades is 1400°C.Corrosion is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its reliability.This study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press method.They were then exposed to volcanic ash at 1400°C for 224,and 48 h.After 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing damage.Meanwhile Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the interior.With increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.
基金supported by the BJAST High-level Innovation Team Program (No.BGS202001)the Beijing Postdoctoral Research Foundation (No.2022-ZZ-046)+3 种基金the National Natural and Science Foundation of China (No.51972026)the Japan Society for the Promotion of Science (JSPS)Grant-in-Aid for the Scientific Research (KAKENHI,Nos.16H06439 and 20H00297)the Dynamic Alliance for Open Innovations Bridging Human,Environment and Materials,the Cooperative Research Program of“Network Joint Research Center for Materials and Devices.”the scholarship granted to a visiting Ph.D.student of the Inter-University Exchange Project by the China Scholarship Council (CSC,No.201906460113)。
文摘The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.
基金supported by the KOSéCosmetology Research Foundationthe Japan Society funded the present work for the Promotion of Science (JSPS)Grant-in-Aid for Scientific Research (Nos.16H06439 and 20H00297)。
文摘B and N mixed anions co-doped titania with various crystal phases such as anatase,brookite,and rutile were successfully synthesized by a hydrothermal synthesis followed by heat treatment in an ammonia gas atmosphere at 550-650℃(denoted as BN-Ana_x,BN-Bro_x,and BN-Rut_x,x is the treatment temperature).The colors of as-prepared BN-Ana,BN-Bro,and BN-Rut are red,yellow-green,and cyangreen,respectively.The color changing mechanism of titania was related to their various band gap structure and the existence of B-N bonding.The nitridation temperature exhibits effective color changing compared to that of nitridation time.The different phases of the mixed anion codoped titania possess different photocatalytic deNO_(x) activity.The BN-Ana and BN-Rut show poor photocatalytic deNO_(x) activity,while the BN-Bro shows excellent photocatalytic deNO_(x) activity,better than that of standard titania photocatalyst Degussa P25.The colorful titania with low-photocatalytic activity is heavy metal elements free,indicating their possible applications as nontoxic color pigments or novel cosmetic raw materials.
基金supported in part by the National Key R&D Program of China(2018YFC1314903)the National Natural Science Foundation of China(61801238 and 61427801)+1 种基金the NUPTSF(NY217033)NYIT 2017 Global Faculty Summer Research and Creativity(GFSRC)Grant
文摘The high-capacity vehicle-to-vehicle(V2 V) communication provides a promising solution to support ubiquitous media streaming and content sharing among vehicles.To extend the V2 V links to multiple cells and manage the inter-cell interference,we proposed an UAV-assisted inter-cell V2 V communication model,in which a shared UAV node is placed in the center of V2 V users.By charging the V2 V users underlay spectrum access fee,the cellular network earn profit at the cost of encountering co-channel interference from V2 V links.A Stackelberg game is formulated to model the interactions between the V2 V links and the cellular links,which are the game follower and the leader respectively.Their utility functions are maximized in terms of accessing price as well as transmit power of V2 V users and UAV relays.Simulation evaluations verify that the power-price tradeoff between V2 V network and cellular network has significant potentials to enhance their utility.
基金partly supported by the JSPS Grant-in-Aid for Scientific Research(No.JP16H06439,No.20H00297)by the Dynamic Alliance for Open Innovation Bridging Human,Environment and Materials in Network Joint Research Center for Materialsfinancial grants provided by Indonesia Ministry of Education,Culture,Research,and Technology,under the scheme of Basic Research Program No.2/E1/KP.PTNBH/2021 managed by Institut Teknologi Bandung。
文摘Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications.Particularly,molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements.These materials have good durability,are naturally abundant,low cost,and have facile preparation,allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices.Significant advances have been made in recent decades to design and fabricate various molybdenum oxides-and dichalcogenides-based sensing materials,though it is still challenging to achieve high performances.Therefore,many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties.This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants,dangerous gases,or even exhaled breath monitoring.The summary and future challenges to advance their gas sensing performances will also be presented.
基金This work was financially support by the Japan Society for the Promotion of Science(JSPS)Grant-in-Aid for Scientific Research(KAKENHI)(No.20H00297 and Innovative Areas No.JP16H06439)the Cooperative Research Program of Dynamic Alliance for Open Innovations Bridging Human,Environment and Materials in the“Network Joint Research Center for Materials and Devices”.
文摘Hydrogen is a promising renewable energy source for fossil-free transportation and electrical energy generation.However,leaking hydrogen in high-temperature production processes can cause an explosion,which endangers production workers and surrounding areas.To detect leaks early,we used a sensor material based on a wide bandgap aluminum nitride(AlN)that can withstand a high-temperature environment.Three unique AlN morphologies(rod-like,nest-like,and hexagonal plate-like)were synthesized by a direct nitridation method at 1400℃usingγ-AlOOH as a precursor.The gas-sensing performance shows that a hexagonal plate-like morphology exhibited p-type sensing behavior and showed good repeatability as well as the highest response(S=58.7)toward a 750 ppm leak of H2 gas at high temperature(500°C)compared with the rod-like and nest-like morphologies.Furthermore,the hexagonal plate-like morphology showed fast response and recovery times of 40 and 82 s,respectively.The surface facet of the hexagonal morphology of AlN might be energetically favorable for gas adsorption–desorption for enhanced hydrogen detection.
文摘The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal reaction apparatus with a rolling system. The mean particle diameter decreased from 500 to 50 nm with a decrease in the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio from 0.44 to 0.04. The powders were sintered by normal one-step sintering at 1200°C for 5 h and two-step sintering in which temperature was raised to 1200°C at first and then decreased to 1100°C and kept at 1100°C for 5 h. The BaTiO3 particles prepared with the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio of 0.32 and 0.22 showed excellent sinterability and could be sintered to almost full theoretical density by both method. The sintered bodies obtained by both methods showed similarly excellent dielectric and piezoelectric properties.
文摘Lanthanum and nitrogen co-doped SrTiO3 was synthesized using polymerized complex method with Ti(OC3H7)4, SrCl2·6H2O and La(NO3)3·6H2O as starting materials followed by calcinations in NH3. Ethylene glycol and anhydrous citric acid were used as the precursors of synthesis. The samples were characterized using XRD, TEM, DRS, BET, EDX and XPS. The cubic-perovskite type of La/N co-doped SrTiO3 nanoparticle could be successfully synthesized. The photocatalytic activity of SrTiO3 for DeNOx ability in visible light region (λ > 510 nm) could be improved by co-doping of La3+ and N3_. The high visible light photocatalytic activity of this substance was caused by a narrow band gap energy that enables to absorb visible light.
基金Department of Science and Technology of Sichuan Province(No.2021YJ0156)Active Health and Aging Technologic Solutions Major Project of National Key Research&Development Program(No.2020YFC2006300)
文摘To the Editor:Chronic obstructive pulmonary disease(COPD),a clinical syndrome encompassing a spectrum of chronic,progressive,and debilitating respiratory disorders,is increasingly recognized as a multisystemic heterogeneous disease.[1]Because the characteristics of East Asian COPD patients differ from those of Westerners,it would be practical to investigate whether variations in COPD genetic performance exist between East Asian and Western populations.
