Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,a...Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.展开更多
Bi/Bi_(2)Fe_(4)O_(9)nanocomposites consisting of Bi_(2)Fe_(4)O_(9)nanosheets decorated with Bi nanodots were synthesized by a hydrothermal method.The formation of Bi nanodots on the Bi_(2)Fe_(4)O_(9)nanosheet surfaces...Bi/Bi_(2)Fe_(4)O_(9)nanocomposites consisting of Bi_(2)Fe_(4)O_(9)nanosheets decorated with Bi nanodots were synthesized by a hydrothermal method.The formation of Bi nanodots on the Bi_(2)Fe_(4)O_(9)nanosheet surfaces was attributed to the reducibility of 2-methoxyethanol in the precursor solution.Comparative photocatalytic evaluation reveals that the Bi/Bi_(2)Fe_(4)O_(9)nanocomposites significantly enhance the degradation efficiency(99.0%)of bisphenol A compared with Bi_(2)Fe_(4)O_(9)nanosheets(64.2%)under 120 min simulated solar irradiation.This remarkable enhancement can be attributed to the established Bi/Bi_(2)Fe_(4)O_(9)heterojunction structure,which effectively facilitates the separation of photogenerated electron-hole pairs and accelerates interfacial charge transfer between the metallic Bi nanodots and semiconductor Bi_(2)Fe_(4)O_(9)nanosheets.The synergistic effects arising from this unique architecture ultimately lead to superior photocatalytic performance.展开更多
Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-N...Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-Nb mixed-oxide catalyst was synthesized as an NH_(3)-SCR catalyst for NO_(x)emission control.After the intro-duction of Sn,both the NH_(3)-SCR activity and the hydrothermal stability of the catalyst were remarkably promoted.Even after hydrothermal aging at 1000℃,the developed Ce_(1)Sn_(2)Nb_(1)O_(x)catalyst achieved more than 90%NO_(x)conversion at 325-500℃.Various methods,including N2-physisorption,X-ray diffraction,in-situ high-temperature X-ray diffraction,high-resolution transmission electron microscopy,X-ray pho-toelectron spectroscopy,X-ray absorption fine-structure spectroscopy,temperature-programmed reduc-tion of hydrogen,temperature-programmed desorption of ammonia,and density functional theory calculations were used to investigate the promotional effects induced by the Sn species.The characteri-zation results showed that the addition of Sn not only promoted the formation of the Ce-Nb active phase but also improved its thermal stability,contributing to the excellent NH_(3)-SCR performance and hydrothermal stability.This study provides an excellent sintering-resistance catalyst for the application of diesel engine NO_(x)emission control.展开更多
The study of the effects of supercritical CO_(2)(ScCO_(2))under high temperature and high pressure on the mechanical properties and fracturing potential of shale holds significant implications for advancing our unders...The study of the effects of supercritical CO_(2)(ScCO_(2))under high temperature and high pressure on the mechanical properties and fracturing potential of shale holds significant implications for advancing our understanding of enhanced shale gas extraction and reservoir exploration and development.This study examines the influence of three fluids,i.e.ScCO_(2),deionized water(DW),and ScCO_(2)tDW,on the mechanical properties and fracturability of shale at immersion pressures of 15 MPa and 45 MPa,with a constant temperature of 100C.The key findings are as follows:(1)Uniaxial compressive strength(UCS)of shale decreased by 10.72%,11.95%,and 23.67%at 15 MPa,and by 42.40%,46.84%,and 51.65%at 45 MPa after immersion in ScCO_(2),DW,and ScCO_(2)tDW,respectively,with the most pronounced effect observed in ScCO_(2)tDW;(2)Microstructural analysis revealed that while ScCO_(2)and DW do not significantly alter the microstructure,immersion in ScCO_(2)tDW results in a more complex surface morphology;(3)Acoustic emission(AE)analysis indicates a reduction in stress for crack damage,with a decreased fractal dimension of AE signals in different fluids.AE energy is primarily generated during the unstable crack propagation stage;(4)A quantitative method employing a multi-factor approach combined with the brittleness index(BI)effectively characterizes shale fracturability.Evaluation results show that ScCO_(2)tDW has a more significant effect on shale fracturability,with fracturability indices of 0.833%and 1.180%following soaking at 15 MPa and 45 MPa,respectively.Higher immersion pressure correlates positively with increased shale fracturability.展开更多
The emerging n-type Mg_(3)(Sb,Bi)_(2)-based materials have attracted considerable attention for their excellent thermoelectric performance.Whereas,practical thermoelectric device applications require materials that ex...The emerging n-type Mg_(3)(Sb,Bi)_(2)-based materials have attracted considerable attention for their excellent thermoelectric performance.Whereas,practical thermoelectric device applications require materials that exhibit not only superior thermoelectric performance but also robust mechanical properties.This work systematically investigates the mechanical and thermoelectric properties of Mg_(3.2-x)Ce_(x)SbBi_(0.97)Te_(0.03).The x=0.04 sample exhibits a Vickers hardness of up to 1012 MPa.The compressive and bending stress–strain curves show that minor doping can enhance the strength while maintaining high plasticity.展开更多
Isotope effect on superconductive transition temperature(T_c)is an essential indicator to examine whether the mechanism of superconductors is conventional.Unconventional isotope effect of BiS_(2)-based superconductors...Isotope effect on superconductive transition temperature(T_c)is an essential indicator to examine whether the mechanism of superconductors is conventional.Unconventional isotope effect of BiS_(2)-based superconductors has been previously reported in ambient-pressure tetragonal phase.However,to comprehensively ascertain the nature of superconductivity,the investigation of BiS_(2)-based system in high-pressure structure is highly desirable.In this work,we carried out the first-principles calculations of phonon spectra and superconductivity in high-pressure monoclinic phase of LaO_(0.5)F_(0.5)BiS_(2)with ^(32)S and ^(34)S,and observed that the corresponding isotope coefficient is 0.13≤α≤0.20.This value is much greater than that of BiS_(2)-based superconductors in ambient-pressure phase,but slightly smaller than that of conventional MgB_2.Taking into account the calculated T_(c) lower than experimental results,we finally conclude that the moderate phonon-mediated pairing plays a significant role in forming superconductivity of BiS_(2)-based system in high-pressure phase,moreover,the cooperative multiple paring interactions should also be considered.展开更多
Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupli...Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupling,and 1T-VTe_(2)monolayer theoretically predicted to host an intrinsic magnetism as experimentally suggested.In this work,we successfully constructed a vertical heterostructure composed of the two-dimensional Bi(110)monolayer and 1T-VTe_(2)monolayer by using molecular beam epitaxy(MBE).Scanning tunneling microscopy(STM)measurements revealed that the growth of Bi preferably occurs along the step edges of the VTe_(2)monolayer,forming a Bi(110)monolayer on top of the VTe_(2)monolayer next to a peripheral Bi bilayer.The Bi(100)/VTe_(2)heterostructure exhibits a specific lattice registry with a well-defined moiréperiodicity.Scanning tunneling spectroscopy(STS)measurements further unveiled an universal suppression in the local density-of-states at the boundary of the Bi(110)/VTe_(2)bilayer.By examining the atomic structures of Bi(110)boundaries,we found this effect does not originate from the previously proposed atomic reconstruction at the step edge of Bi(110),but is likely related to the magnetic properties of the VTe_(2)monolayer.展开更多
Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-co...Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials展开更多
The escalating atmospheric CO_(2) levels necessitate efficient catalytic technologies for its conversion into value-added chemicals.This review systematically summarizes recent advances in ZrO_(2)-based catalysts for ...The escalating atmospheric CO_(2) levels necessitate efficient catalytic technologies for its conversion into value-added chemicals.This review systematically summarizes recent advances in ZrO_(2)-based catalysts for CO_(2) hydrogenation,emphasizing their multifunctional roles beyond conventional supports.Owing to its tunable crystalline phases,abundant oxygen vacancies,and synergistic metal-support interactions,ZrO_(2) significantly enhances catalytic performance in producing methane,methanol,and other products.Key design strategies,such as phase engineering,morphology control,and the construction of inverse or composite structures,are discussed in relation to their influence on CO_(2) adsorption,intermediate stabilization,and reaction pathway regulation.Mechanistic insights reveal that ZrO_(2) facilitates H_(2) dissociation,promotes hydrogen spillover,and stabilizes active metal species,thereby optimizing product selectivity and catalyst durability.Furthermore,tandem catalytic systems integrating ZrO_(2) with zeolites demonstrate exceptional potential in steering C-C coupling while suppressing over-hydrogenation.This review not only elucidates structure-activity relationships and kinetic behaviors but also outlines future research directions,including in situ characterization and scalable catalyst design,thereby providing critical guidance for the development of high-performance CO_(2) hydrogenation catalysts and advancing carbon-neutral fuel and chemical production.展开更多
A unique discontinuous lamellar microstructure of titanium alloys consisting of lamellar colonies at prior β-Ti grain boundaries and internal interwoven α-laths is prepared by a TiH_(2)-based powder metallurgy metho...A unique discontinuous lamellar microstructure of titanium alloys consisting of lamellar colonies at prior β-Ti grain boundaries and internal interwoven α-laths is prepared by a TiH_(2)-based powder metallurgy method.The α-variants get various crystallographic orientations and become discontinuous during vacuum annealing at 700℃.Remarkably,nanoscale phase δ-TiH compound layers are generated between α-laths and β-strips,so that dislocations are piled up at the α/δ/βinterfaces during tensile deformation.This leads to dislocation slips being confined to individual α-laths,with differentslips and particularly pyramidal<c+a>slips being activated.The efficiency of wavy slip is promoted and the work hardening rate is enhanced.Finally,the combined effect of dispersed micro-shear bands and lath distortions is considered contributive for alleviating the stress concentration at grain boundaries,resulting in a high-promising synergy of enhanced ultimate tensile strength of 1080 MPa and good elongation to fracture of 13.6%.展开更多
Neuromorphic computing devices leveraging HfO_(2) and ZrO_(2) materials have recently garnered significant attention due to their potential for brain-inspired computing systems.In this study,we present a novel trilaye...Neuromorphic computing devices leveraging HfO_(2) and ZrO_(2) materials have recently garnered significant attention due to their potential for brain-inspired computing systems.In this study,we present a novel trilayer Pt/HfO_(2)/ZrO_(2-x)/HfO_(2)/TiN memristor,engineered with a ZrO_(2-x) oxygen vacancy reservoir(OVR)layer fabricated via radio frequency(RF)sputtering under controlled oxygen ambient.The incorporation of the ZrO_(2-x) OVR layer enables enhanced resistive switching characteristics,including a high ON/OFF ratio(∼8000),excellent uniformity,robust data retention(>105 s),and multilevel storage capabilities.Furthermore,the memristor demonstrates superior synaptic plasticity with linear long-term potentiation(LTP)and depression(LTD),achieving low non-linearity values of 1.36(LTP)and 0.66(LTD),and a recognition accuracy of 95.3%in an MNIST dataset simulation.The unique properties of the ZrO_(2-x) layer,particularly its ability to act as a dynamic oxygen vacancy reservoir,significantly enhance synaptic performance by stabilizing oxygen vacancy migration.These findings establish the OVR-trilayer memristor as a promising candidate for future neuromorphic computing and high-performance memory applications.展开更多
Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric...Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric（TE）measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices, respectively. High TE performances with figure-of-merit（ZT） values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi_2Te_3 thin films, respectively. These ZT values are higher than those of p-type Bi_2Te_3 alloys as reported. Relatively high ZT of the GeTe/B_2Te_3 superlattices at 300-380 K were 0.62-0.76. The achieved high ZT value may be attributed to the unique nano-and microstructures of the films,which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi_2Te_3-based thin films can serve as high-performance materials for applications in TE devices.展开更多
Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several chall...Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.展开更多
The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Bas...The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.展开更多
To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.Thi...To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.This produced chemically bonded interacting composite photocatalysts of FA-SiO,and graphitic-phase carbon nitride(g-C_(3)N_(4)).Compared with the spherical silicon dioxide prepared using tetraethyl orthosilicate(TEOS-SiO_(2)),the mesoporous structure of FA-SiO_(2),allowed DCDA to react in a smaller space,which facilitated the transformation of DCDA to melamine by the thermal degradation kinetics of FA-C_(3)N_(4)/DCDA.This ultimately boosted the formation of an N-atom-removed triazine ring structure and a multistage structure combining lumps and rods in the composite photocatalysts of g-C_(3)N_(4),and FA-SiO_(2),which led to a higher visible-light utilization efficiency,a suitable valence-band position,and the photocatalytic activity for methylene blue reaching 3.56 times that of g-C_(3)N_(4).The findings indicate that mesoporous FA-SiO,has the potential to improve the structural and photocatalytic properties of g-C_(3)N_(4),-based materials.展开更多
High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based...High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.展开更多
Electrocatalytic nitrogen reduction reaction is a carbon-free and energy-saving strategy for efficient synthesis of ammonia under ambient conditions.Here,we report the synthesis of nanosized Bi2O3 particles grown on f...Electrocatalytic nitrogen reduction reaction is a carbon-free and energy-saving strategy for efficient synthesis of ammonia under ambient conditions.Here,we report the synthesis of nanosized Bi2O3 particles grown on functionalized exfoliated graphene(Bi2O3/FEG)via a facile electrochemical deposition method.The obtained free-standing Bi2O3/FEG achieves a high Faradaic efficiency of 11.2%and a large NH3 yield of 4.21±0.14μgNH3 h^-1 cm^-2 at-0.5 V versus reversible hydrogen electrode in 0.1 M Na2SO4,better than that in the strong acidic and basic media.Benefiting from its strong interaction of Bi 6p band with the N2p orbitals,binder-free characteristic,and facile electron transfer,Bi2O3/FEG achieves superior catalytic performance and excellent long-term stability as compared with most of the previous reported catalysts.This study is significant to design low-cost,high-efficient Bi-based electrocatalysts for electrochemical ammonia synthesis.展开更多
基金supported by the National Natural Science Foundation of China (No. 52374292)China Baowu Low Carbon Metallurgy Innovation Foundation, China (No. BWLCF202309)the Natural Science Foundation of Changsha City, China (No. KQ2208271)。
文摘Some active metal oxides(Al_(2)O_(3),TiO_(2),and Cr_(2)O_(3))were selected as dopants to the Al_(2)O_(3)-based ceramic shells for investment casting of K417G superalloy.The effects of dopant types and contents(0,2,5,and 8 wt.%)on the wettability and interfacial reaction between the alloy and shell were investigated by a sessile-drop experiment.The results show that increasing the Al_(2)O_(3) doping contents(0−8 wt.%)reduces the porosity(21.74%−10.08%)and roughness(3.22−1.34μm)of the shell surface.The increase in Cr_(2)O_(3) dopant content(2−8 wt.%)further exacerbates the interfacial reaction,leading to an increase in the thickness of the reaction layer(2.6−3.1μm)and a decrease in the wetting angle(93.9°−91.0°).The addition of Al_(2)O_(3) and TiO_(2) dopants leads to the formation of Al_(2)TiO_(5) composite oxides in the reaction products,which effectively inhibits the interfacial reaction.The increase in TiO_(2) dopant contents(0−8 wt.%)further promotes the formation of Al_(2)TiO_(5),which decreases the thickness of the interfacial reaction layer(3.9−1.2μm)and increases the wetting angle(95.0°−103.8°).The introduced dopants enhance the packing density of the shell surface,while simultaneously suppress the diffusion of active metal elements from the alloy matrix to the interface.
基金Funded by the National Natural Science Foundation of China(No.50902108)。
文摘Bi/Bi_(2)Fe_(4)O_(9)nanocomposites consisting of Bi_(2)Fe_(4)O_(9)nanosheets decorated with Bi nanodots were synthesized by a hydrothermal method.The formation of Bi nanodots on the Bi_(2)Fe_(4)O_(9)nanosheet surfaces was attributed to the reducibility of 2-methoxyethanol in the precursor solution.Comparative photocatalytic evaluation reveals that the Bi/Bi_(2)Fe_(4)O_(9)nanocomposites significantly enhance the degradation efficiency(99.0%)of bisphenol A compared with Bi_(2)Fe_(4)O_(9)nanosheets(64.2%)under 120 min simulated solar irradiation.This remarkable enhancement can be attributed to the established Bi/Bi_(2)Fe_(4)O_(9)heterojunction structure,which effectively facilitates the separation of photogenerated electron-hole pairs and accelerates interfacial charge transfer between the metallic Bi nanodots and semiconductor Bi_(2)Fe_(4)O_(9)nanosheets.The synergistic effects arising from this unique architecture ultimately lead to superior photocatalytic performance.
基金supported by the National Natural Science Foundation of China(52225004 and 22276202)the National Key Research and Development Program of China(2022YFC3701804)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2019045).
文摘Catalytic activity and hydrothermal stability are both crucial for the application of the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR)catalyst in diesel vehicles.In this study,a tin(Sn)-modified Ce-Nb mixed-oxide catalyst was synthesized as an NH_(3)-SCR catalyst for NO_(x)emission control.After the intro-duction of Sn,both the NH_(3)-SCR activity and the hydrothermal stability of the catalyst were remarkably promoted.Even after hydrothermal aging at 1000℃,the developed Ce_(1)Sn_(2)Nb_(1)O_(x)catalyst achieved more than 90%NO_(x)conversion at 325-500℃.Various methods,including N2-physisorption,X-ray diffraction,in-situ high-temperature X-ray diffraction,high-resolution transmission electron microscopy,X-ray pho-toelectron spectroscopy,X-ray absorption fine-structure spectroscopy,temperature-programmed reduc-tion of hydrogen,temperature-programmed desorption of ammonia,and density functional theory calculations were used to investigate the promotional effects induced by the Sn species.The characteri-zation results showed that the addition of Sn not only promoted the formation of the Ce-Nb active phase but also improved its thermal stability,contributing to the excellent NH_(3)-SCR performance and hydrothermal stability.This study provides an excellent sintering-resistance catalyst for the application of diesel engine NO_(x)emission control.
基金financial support from the Science and Technology Innovation Program of Hunan Province(Grant No.2023RC1021)the National Natural Science Foundation of China(Grant No.52231012)+1 种基金the Natural Science Foundation of Hainan Province(Grant No.424QN213)the Scientific Research Foundation of Hainan University.
文摘The study of the effects of supercritical CO_(2)(ScCO_(2))under high temperature and high pressure on the mechanical properties and fracturing potential of shale holds significant implications for advancing our understanding of enhanced shale gas extraction and reservoir exploration and development.This study examines the influence of three fluids,i.e.ScCO_(2),deionized water(DW),and ScCO_(2)tDW,on the mechanical properties and fracturability of shale at immersion pressures of 15 MPa and 45 MPa,with a constant temperature of 100C.The key findings are as follows:(1)Uniaxial compressive strength(UCS)of shale decreased by 10.72%,11.95%,and 23.67%at 15 MPa,and by 42.40%,46.84%,and 51.65%at 45 MPa after immersion in ScCO_(2),DW,and ScCO_(2)tDW,respectively,with the most pronounced effect observed in ScCO_(2)tDW;(2)Microstructural analysis revealed that while ScCO_(2)and DW do not significantly alter the microstructure,immersion in ScCO_(2)tDW results in a more complex surface morphology;(3)Acoustic emission(AE)analysis indicates a reduction in stress for crack damage,with a decreased fractal dimension of AE signals in different fluids.AE energy is primarily generated during the unstable crack propagation stage;(4)A quantitative method employing a multi-factor approach combined with the brittleness index(BI)effectively characterizes shale fracturability.Evaluation results show that ScCO_(2)tDW has a more significant effect on shale fracturability,with fracturability indices of 0.833%and 1.180%following soaking at 15 MPa and 45 MPa,respectively.Higher immersion pressure correlates positively with increased shale fracturability.
基金supported by the National Natural Science Foundation of China(Nos.12174297,and 12204342)the Fundamental Research Program of Shanxi Province(Nos.202203021212323,and 202203021212304)+2 种基金the Taiyuan University of Science and Technology Scientific Research Initial Funding(No.20222015,and 20232094)Funding for Outstanding Doctoral Research in Jin(Nos.20222039,and 20222040)the Research Practice and Innovation Program for Graduate Student of Shanxi Province(Nos.2024KY631,and 2024SJ301).
文摘The emerging n-type Mg_(3)(Sb,Bi)_(2)-based materials have attracted considerable attention for their excellent thermoelectric performance.Whereas,practical thermoelectric device applications require materials that exhibit not only superior thermoelectric performance but also robust mechanical properties.This work systematically investigates the mechanical and thermoelectric properties of Mg_(3.2-x)Ce_(x)SbBi_(0.97)Te_(0.03).The x=0.04 sample exhibits a Vickers hardness of up to 1012 MPa.The compressive and bending stress–strain curves show that minor doping can enhance the strength while maintaining high plasticity.
基金Project supported by the National Natural Science Foundation of China(Grant No.12175107)the Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant Nos.NY219087 and NY220038)。
文摘Isotope effect on superconductive transition temperature(T_c)is an essential indicator to examine whether the mechanism of superconductors is conventional.Unconventional isotope effect of BiS_(2)-based superconductors has been previously reported in ambient-pressure tetragonal phase.However,to comprehensively ascertain the nature of superconductivity,the investigation of BiS_(2)-based system in high-pressure structure is highly desirable.In this work,we carried out the first-principles calculations of phonon spectra and superconductivity in high-pressure monoclinic phase of LaO_(0.5)F_(0.5)BiS_(2)with ^(32)S and ^(34)S,and observed that the corresponding isotope coefficient is 0.13≤α≤0.20.This value is much greater than that of BiS_(2)-based superconductors in ambient-pressure phase,but slightly smaller than that of conventional MgB_2.Taking into account the calculated T_(c) lower than experimental results,we finally conclude that the moderate phonon-mediated pairing plays a significant role in forming superconductivity of BiS_(2)-based system in high-pressure phase,moreover,the cooperative multiple paring interactions should also be considered.
基金financially supported by the National Key Research and Development Program of China(Grant No.2021YFA1400403)the National Natural Science Foundation of China(Grant Nos.12374183,92165205)+2 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20233001)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)the Fundamental Research Funds for the Central Universities(Grant No.020414380207).
文摘Interplay between topology and magnetism can give rise to exotic properties in topological materials.Two-dimensional bismuth has been extensively studied owing to its topological states with a strong spin-orbit coupling,and 1T-VTe_(2)monolayer theoretically predicted to host an intrinsic magnetism as experimentally suggested.In this work,we successfully constructed a vertical heterostructure composed of the two-dimensional Bi(110)monolayer and 1T-VTe_(2)monolayer by using molecular beam epitaxy(MBE).Scanning tunneling microscopy(STM)measurements revealed that the growth of Bi preferably occurs along the step edges of the VTe_(2)monolayer,forming a Bi(110)monolayer on top of the VTe_(2)monolayer next to a peripheral Bi bilayer.The Bi(100)/VTe_(2)heterostructure exhibits a specific lattice registry with a well-defined moiréperiodicity.Scanning tunneling spectroscopy(STS)measurements further unveiled an universal suppression in the local density-of-states at the boundary of the Bi(110)/VTe_(2)bilayer.By examining the atomic structures of Bi(110)boundaries,we found this effect does not originate from the previously proposed atomic reconstruction at the step edge of Bi(110),but is likely related to the magnetic properties of the VTe_(2)monolayer.
基金Project supported by the Australian Research CouncilZhi-Gang Chen thanks the USQ start-up grantstrategic research grant
文摘Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials
基金supported by the Natural Science Foundation of Jiangxi Province for Distinguished Young Scholars(20232ACB213001)National Natural Science Foundation of China(22362022,52361040,22568029)+1 种基金the Thousand Talents Plan of Jiangxi Province(jxsq2023101072)the Natural Science Foundation of Jiangxi Province(20252BAC250133,20232ACB203004).
文摘The escalating atmospheric CO_(2) levels necessitate efficient catalytic technologies for its conversion into value-added chemicals.This review systematically summarizes recent advances in ZrO_(2)-based catalysts for CO_(2) hydrogenation,emphasizing their multifunctional roles beyond conventional supports.Owing to its tunable crystalline phases,abundant oxygen vacancies,and synergistic metal-support interactions,ZrO_(2) significantly enhances catalytic performance in producing methane,methanol,and other products.Key design strategies,such as phase engineering,morphology control,and the construction of inverse or composite structures,are discussed in relation to their influence on CO_(2) adsorption,intermediate stabilization,and reaction pathway regulation.Mechanistic insights reveal that ZrO_(2) facilitates H_(2) dissociation,promotes hydrogen spillover,and stabilizes active metal species,thereby optimizing product selectivity and catalyst durability.Furthermore,tandem catalytic systems integrating ZrO_(2) with zeolites demonstrate exceptional potential in steering C-C coupling while suppressing over-hydrogenation.This review not only elucidates structure-activity relationships and kinetic behaviors but also outlines future research directions,including in situ characterization and scalable catalyst design,thereby providing critical guidance for the development of high-performance CO_(2) hydrogenation catalysts and advancing carbon-neutral fuel and chemical production.
基金financially supported by the National Natural Science Foundation of China(Nos.52301145,52275329)the Applied Basic Research Program of Liaoning Province,China(No.2023JH2/101300158)+1 种基金the Fundamental Research Fund for the Central Universities,China(No.N2202010)the Key Research Programs of High Education Institutions in Henan Province,China(No.24A430017).
文摘A unique discontinuous lamellar microstructure of titanium alloys consisting of lamellar colonies at prior β-Ti grain boundaries and internal interwoven α-laths is prepared by a TiH_(2)-based powder metallurgy method.The α-variants get various crystallographic orientations and become discontinuous during vacuum annealing at 700℃.Remarkably,nanoscale phase δ-TiH compound layers are generated between α-laths and β-strips,so that dislocations are piled up at the α/δ/βinterfaces during tensile deformation.This leads to dislocation slips being confined to individual α-laths,with differentslips and particularly pyramidal<c+a>slips being activated.The efficiency of wavy slip is promoted and the work hardening rate is enhanced.Finally,the combined effect of dispersed micro-shear bands and lath distortions is considered contributive for alleviating the stress concentration at grain boundaries,resulting in a high-promising synergy of enhanced ultimate tensile strength of 1080 MPa and good elongation to fracture of 13.6%.
基金financially supported by the National Research Foundation of Korea(no.NRF-2021R1A2C2010781)grant funded by the Korean Government(Ministry of Science and ICT)Korea Institute for Advancement of Technology(KIAT)grant funded by the Korea Government(MOTIE)(no.P0012451,The Competency Development Program for Industry Specialist)Korea Government(MOTIE)(no.P0020966,HRD Program for Industrial Innovation).
文摘Neuromorphic computing devices leveraging HfO_(2) and ZrO_(2) materials have recently garnered significant attention due to their potential for brain-inspired computing systems.In this study,we present a novel trilayer Pt/HfO_(2)/ZrO_(2-x)/HfO_(2)/TiN memristor,engineered with a ZrO_(2-x) oxygen vacancy reservoir(OVR)layer fabricated via radio frequency(RF)sputtering under controlled oxygen ambient.The incorporation of the ZrO_(2-x) OVR layer enables enhanced resistive switching characteristics,including a high ON/OFF ratio(∼8000),excellent uniformity,robust data retention(>105 s),and multilevel storage capabilities.Furthermore,the memristor demonstrates superior synaptic plasticity with linear long-term potentiation(LTP)and depression(LTD),achieving low non-linearity values of 1.36(LTP)and 0.66(LTD),and a recognition accuracy of 95.3%in an MNIST dataset simulation.The unique properties of the ZrO_(2-x) layer,particularly its ability to act as a dynamic oxygen vacancy reservoir,significantly enhance synaptic performance by stabilizing oxygen vacancy migration.These findings establish the OVR-trilayer memristor as a promising candidate for future neuromorphic computing and high-performance memory applications.
文摘Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices of different thicknesses are prepared on the silicon dioxide substrates by magnetron sputtering technique and thermally annealed at 573 K for 30 min. Thermoelectric（TE）measurements indicate that optimal thickness and thickness ratio improve the TE performance of Bi_2Te_3 thin films and GeTe/B_2Te_3 superlattices, respectively. High TE performances with figure-of-merit（ZT） values as high as 1.32 and 1.56 are achieved at 443 K for 30 nm and 50 nm Bi_2Te_3 thin films, respectively. These ZT values are higher than those of p-type Bi_2Te_3 alloys as reported. Relatively high ZT of the GeTe/B_2Te_3 superlattices at 300-380 K were 0.62-0.76. The achieved high ZT value may be attributed to the unique nano-and microstructures of the films,which increase phonon scattering and reduce thermal conductivity. The results indicate that Bi_2Te_3-based thin films can serve as high-performance materials for applications in TE devices.
基金financially supported by the National Natural Science Foundation of China(No.52171046)National Natural Science Foundation of China-key programme(No.52234010)the Fundamental Research Funds for the Central Universities and Shaanxi Provincial Key Science and Technology Innovation Team(No.2023-CX-TD-14).
文摘Al_(2)O_(3)-based eutectic ceramics are considered as promising candidates for ultra-high-temperature structural materials due to their exceptional thermal stability and mechanical properties.Nonetheless,several challenges must be overcome before they can be widely used.This paper reviews in detail the tailoring of microstructure from the aspect of process parameters,the updated knowledge gained in microstructure(crystallographic orientation,high-resolution interfacial structures)and the latest means of optimizing eutectic microstructure(seed-induced method,introducing low-energy grain boundaries and high-entropy phase).Additionally,the paper explores future techniques for the fabrication of bulk ceramic materials and effective toughening approaches.This review highlights the achievements made especially in the last 15 years,current limitations in Al_(2)O_(3)-based eutectic ceramics,and offers comprehensive insights and strategic guidance for further mechanical breakthroughs.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174321,52274339 and 52074186).
文摘The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.
基金supported by the Medical Special Cultivation Project of Anhui University of Science and Technology(Nos.YZ2023H2B013 and YZ2023H2B012),China.
文摘To explore high value-added utilization pathways of fly ash,the mesoporous structure of silicon dioxide extracted from fly ash(FA-SiO_(2))was utilized to restrict the dicyandiamide(DCDA)thermal degradation process.This produced chemically bonded interacting composite photocatalysts of FA-SiO,and graphitic-phase carbon nitride(g-C_(3)N_(4)).Compared with the spherical silicon dioxide prepared using tetraethyl orthosilicate(TEOS-SiO_(2)),the mesoporous structure of FA-SiO_(2),allowed DCDA to react in a smaller space,which facilitated the transformation of DCDA to melamine by the thermal degradation kinetics of FA-C_(3)N_(4)/DCDA.This ultimately boosted the formation of an N-atom-removed triazine ring structure and a multistage structure combining lumps and rods in the composite photocatalysts of g-C_(3)N_(4),and FA-SiO_(2),which led to a higher visible-light utilization efficiency,a suitable valence-band position,and the photocatalytic activity for methylene blue reaching 3.56 times that of g-C_(3)N_(4).The findings indicate that mesoporous FA-SiO,has the potential to improve the structural and photocatalytic properties of g-C_(3)N_(4),-based materials.
基金supported by the Tianjin Natural Science Foundation, China (Grant No. 06YFJMJC01000)
文摘High performance X8R dielectric ceramics were prepared by dopingBi2O3 to BaTiO3-based ceramics.The effect of small amounts（≤1.2 mol%） ofBi2O3 additive on the microstructure and dielectric properties of BaTiO3-based ceramics have been investigated.The Bi2O3 ,acting as a sintering additive,can effectively lower the sintering temperature of BaTiO3-based ceramics from 1300 to 1130 °C.The bulk density of BaTiO3-based ceramics increased and reached the maximum value with increasingBi2O3 content.The dielectric constant increased with increasingBi2O3 until it reached the maximum value with 0.8 mol%Bi2O3 additive,and the dielectric loss decreased with increasingBi2O3 content.Optimal dielectric properties of ε=2470,tanδ=0.011 and △ε/ε 25 ≤±9%（-55-150 °C） were obtained for the BaTiO3-based ceramics doped with 0.8 mol%Bi2O3 sintered at 1130 °C for 6 h.
基金financially supported by Liaoning Revitalization Talents Program—Pan Deng Scholars(XLYC1802005)Liaoning BaiQianWan Talents Program+4 种基金the National Science Fund of Liaoning Province for Excellent Young ScholarsScience and Technology Innovative Talents Support Program of Shenyang(RC180166)Australian Research Council(ARC)through Discovery Early Career Researcher Award(DE150101306)and Linkage Project(LP160100927)Faculty of Science Strategic Investment Funding of University of NewcastleCSIRO Newcastl Energy Centre。
文摘Electrocatalytic nitrogen reduction reaction is a carbon-free and energy-saving strategy for efficient synthesis of ammonia under ambient conditions.Here,we report the synthesis of nanosized Bi2O3 particles grown on functionalized exfoliated graphene(Bi2O3/FEG)via a facile electrochemical deposition method.The obtained free-standing Bi2O3/FEG achieves a high Faradaic efficiency of 11.2%and a large NH3 yield of 4.21±0.14μgNH3 h^-1 cm^-2 at-0.5 V versus reversible hydrogen electrode in 0.1 M Na2SO4,better than that in the strong acidic and basic media.Benefiting from its strong interaction of Bi 6p band with the N2p orbitals,binder-free characteristic,and facile electron transfer,Bi2O3/FEG achieves superior catalytic performance and excellent long-term stability as compared with most of the previous reported catalysts.This study is significant to design low-cost,high-efficient Bi-based electrocatalysts for electrochemical ammonia synthesis.
