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Hawking-Page phase transitions of charged AdS black holes surrounded by quintessence 认领
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作者 闫大伟 黄泽榕 李楠 《中国物理C:英文版》 SCIE CAS 2021年第1期355-365,共11页
Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and charged black holes sur・rounded by quintessence are studied in the extended phase space.The quintessence field,with the state parameter-1<... Hawking-Page phase transitions between the thermal anti-de Sitter vacuum and charged black holes sur・rounded by quintessence are studied in the extended phase space.The quintessence field,with the state parameter-1<w<-1/3,modifies the temperature and the Gibbs free energy of a black hole.The phase transition temperature Thp and the Gibbs free energy G are first analytically investigated for the special case of w=-2/3,and then,the results of numerical simulations are shown for general w.The phase transition temperature Thp increases with pressure and decreases with electric potential.In addition,Thp significantly decreases owing to the quintessence field,which generates negative pressure around the black hole. 展开更多
关键词 Hawking-Page phase transition QUINTESSENCE extended phase space
冷凝室喷淋布置对脱硫湿烟气冷凝过程影响的数值模拟 认领
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作者 李璐璐 姚宣 +3 位作者 肖凡 张缦 金燕 杨海瑞 《中南大学学报:自然科学版》 EI CAS 北大核心 2021年第1期116-123,共8页
为获取冷凝室的优化设计参数,基于Fluent软件,采用欧拉-拉格朗日方法,构建三维稳态模型,将优化设计后的冷凝室作为计算对象,充分考虑气液两相之间的动量、质量、能量交换,系统分析冷凝室中喷嘴密度、喷淋层间布置、冷凝室高度对传热传... 为获取冷凝室的优化设计参数,基于Fluent软件,采用欧拉-拉格朗日方法,构建三维稳态模型,将优化设计后的冷凝室作为计算对象,充分考虑气液两相之间的动量、质量、能量交换,系统分析冷凝室中喷嘴密度、喷淋层间布置、冷凝室高度对传热传质的影响规律。研究结果表明:在直径为1 m的冷凝室内喷嘴的布置存在最佳密度,每层喷嘴最佳密度为19个/m^2;在其他运行参数及结构参数不变的条件下,两喷淋层错层布置,更有利于热质交换,可使出口烟温再降低0.32 K;综合考虑出口烟温与容积冷凝负荷,冷凝室最佳高度为3.2 m。 展开更多
关键词 气液两相流 凝结 相变 脱硫湿烟气 传质
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文章速递Anti-parity-time symmetric phase transition in diffusive systems 认领
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作者 曹培超 祝雪丰 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第3期9-16,共8页
Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept... Parity-time (PT) symmetry/anti-parity-time (APT) symmetry in non-Hermitian systems reveal profound physics andspawn intriguing effects. Recently, it has been introduced into diffusive systems together with the concept of exceptionalpoints (EPs) from quantum mechanics and the wave systems. With the aid of convection, we can generate complex thermalconductivity and imitate various wavelike dynamics in heat transfer, where heat flow can be “stopped” or moving against thebackground motion. Non-Hermitian diffusive systems offer us a new platform to investigate the heat wave manipulation.In this review, we first introduce the construction of APT symmetry in a simple double-channel toy model. Then we showthe phase transition around the EP. Finally, we extend the double-channel model to the four-channel one for showing thehigh-order EP and the associated phase transition. In a general conclusion, the phase difference of adjacent channels isalways static in the APT symmetric phase, while it dynamically evolves or oscillates when the APT symmetry is broken. 展开更多
关键词 anti-parity-time symmetry phase transition exceptional point heat transfer
文章速递Detailed structural,mechanical,and electronic study of five structures for CaF2 under high pressure 认领
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作者 郭颖 方钰萌 李俊 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第3期194-204,共11页
Detailed density functional theory(DFT)calculations of the structural,mechanical,thermodynamic,and electronicproperties of crystalline CaF2 with five different structures in the pressure range of 0 GPa–150 GPa are pe... Detailed density functional theory(DFT)calculations of the structural,mechanical,thermodynamic,and electronicproperties of crystalline CaF2 with five different structures in the pressure range of 0 GPa–150 GPa are performed byboth GGA(generalized gradient approximation)-PBE(Perdew–Burke–Ernzerhof)and LDA(local density approximation)-CAPZ(Cambridge Serial Total Energy Package).It is found that the enthalpy differences imply that the fluorite phase→PbCl2-type phase→Ni2In-type phase transition in CaF2 occurs at PGGA1=8.0 GPa,PGGA2=111.4 GPa by usingthe XC of GGA,and PLDA1=4.5 GPa,PLDA2=101.7 GPa by LDA,respectively,which is consistent with previousexperiments and theoretical conclusions.Moreover,the enthalpy differences between PbCl2-type and Ni2In-type phases inone molecular formula become very small at the pressure of about 100 GPa,indicating the possibility of coexistence of twophase at high pressures.This may be the reason why the transition pressure of the second phase transition in other reportsis so huge(68 GPa–278 GPa).The volume changed in the second phase transition are also consistent with the enthalpydifference result.Besides,the pressure dependence of mechanical and thermodynamic properties of CaF2 is studied.Itis found that the high-pressure phase of Ni2In-type structure has better stiffness in CaF2 crystal,and the hardness of thematerial has hardly changed in the second phase transition.Finally,the electronic structure of CaF2 is also analyzed withthe change of pressure.By analyzing the band gap and density of states,the large band gap indicates the CaF2 crystal isalways an insulator at 0 GPa–150 GPa. 展开更多
关键词 density functional theory(DFT) high-pressure phase transition coexistence
文章速递Low thermal expansion and broad band photoluminescence of Zr0.1Al1.9Mo2.9V0.1O12 认领
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作者 王俊平 陈庆东 +3 位作者 陈立刚 纪延俊 刘友文 梁二军 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第3期423-429,共7页
A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are e... A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices. 展开更多
关键词 low thermal expansion phase transition x-ray diffraction(XRD) Raman spectrum luminescence
文章速递Ab initio study on crystal structure and phase stability of ZrC_(2) under high pressure 认领
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作者 郭永亮 韦俊红 +2 位作者 刘潇 柯学志 焦照勇 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第1期350-358,共9页
The structural stabilities and crystal evolution behaviors of the hyper stoichiometric compound ZrC_(2)(carbon rich;C/Zr> 1.0) are studied under ambient and high pressure conditions using first-principles calculati... The structural stabilities and crystal evolution behaviors of the hyper stoichiometric compound ZrC_(2)(carbon rich;C/Zr> 1.0) are studied under ambient and high pressure conditions using first-principles calculations in combination with the particle-swarm optimization algorithm.Six viable structures of ZrC_(2) in P21/c,Cmmm,Cmc2_(1),P4_(2)/nmc,Immm and P6/mmm symmetries are identified.These structures are dynamically stable as their phonon spectra have no imaginary modes at zero pressure or at the selected high-pressure points.Among them,the P21/c phase represents the ground state structure,whereas P21/c,P4_(2)/nmc,Immm and P6/mmm phases are part of the phase transition series.The phase order and critical pressures of the phase transition are determined to be approximately 300 GPa according to the equation of states and enthalpy.Furthermore,the mechanical and electronic properties are investigated.The P21/c and Cmc2_(1) phases display a semi-metal nature,whereas the P4_(2)/nmc,Immm,P6/mmm and Cmmm phases exhibit a metallic nature.Moreover,the present study reveals considerable information regarding the structural,mechanical and electronic properties of ZrC_(2),thereby providing key insights into its material properties and evaluating its behavior in practical applications. 展开更多
关键词 crystal structure phase transition mechanical property electronic band first-principles calculation
文章速递Temperature-induced phase transition of two-dimensional semiconductor GaTe 认领
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作者 王啸宇 王雪 +3 位作者 邹洪帅 付钰豪 贺欣 张立军 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第1期428-433,共6页
GaTe is a two-dimensional Ⅲ-Ⅵ semiconductor with suitable direct bandgap of~1.65 eV and high photoresponsivity,which makes it a promising candidate for optoelectronic applications.GaTe exists in two crystalline phas... GaTe is a two-dimensional Ⅲ-Ⅵ semiconductor with suitable direct bandgap of~1.65 eV and high photoresponsivity,which makes it a promising candidate for optoelectronic applications.GaTe exists in two crystalline phases:monoclinic(m-GaTe,with space group C2/m) and hexagonal(h-GaTe,with space group P63/mmc).The phase transition between the two phases was reported under temperature-varying conditions,such as annealing,laser irradiation,etc.The explicit phase transition temperature and energy barrier during the temperature-induced phase transition have not been explored.In this work,we present a comprehensive study of the phase transition process by using first-principles energetic and phonon calculations within the quasi-harmonic approximation framework.We predicted that the phase transition from h-GaTe to m-GaTe occurs at the temperature decreasing to 261 K.This is in qualitative agreement with the experimental observations.It is a two-step transition process with energy barriers 199 meV and 288 meV,respectively.The relatively high energy barriers demonstrate the irreversible nature of the phase transition.The electronic and phonon properties of the two phases were further investigated by comparison with available experimental and theoretical results.Our results provide insightful understanding on the process of temperature-induced phase transition of GaTe. 展开更多
关键词 two-dimensional semiconductor GaTe temperature-induced phase transition first-principles calculation quasi-harmonic approximation
文章速递Novel structures and mechanical properties of Zr_(2)N:Ab initio description under high pressures 认领
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作者 文敏儒 谢兴 +4 位作者 谢植勋 董华锋 张欣 吴福根 王崇愚 《中国物理B:英文版》 SCIE EI CAS CSCD 2021年第1期434-442,共9页
With the formation of structural vacancies,zirconium nitrides(key materials for cutting coatings,super wearresistance,and thermal barrier coatings) display a variety of compositions and phases featuring both cation an... With the formation of structural vacancies,zirconium nitrides(key materials for cutting coatings,super wearresistance,and thermal barrier coatings) display a variety of compositions and phases featuring both cation and nitrogen enrichment.This study presents a systematic exploration of the stable crystal structures of zirconium heminitride combining the evolutionary algorithm method and ab initio density functional theory calculations at pressures of 0 GPa,30 GPa,60 GPa,90 GPa,120 GPa,150 GPa,and 200 GPa.In addition to the previously proposed phases P42/mnm-,Pnnn-,and Cmcm-Zr2 N,five new high-pressure Zr_(2)N phases of PA/nmm,IA/mcm,P2_(1)/m,P3 m1,and C2/m are discovered.An enthalpy study of these candidate configurations reveals various structural phase transformations of Zr2 N under pressure.By calculating the elastic constants and phonon dispersion,the mechanical and dynamical stabilities of all predicted structures are examined at ambient and high pressures.To understand the structure-property relationships,the mechanical properties of all Zr_(2)N compounds are investigated,including the elastic moduli,Vickers hardness,and directional dependence of Young’s modulus.The Cmncm-Zr2 N phase is found to belong to the brittle materials and has the highest Vickers hardness(12.9 GPa) among all candidate phases,while the I4/mcm-Zr2 N phase is the most ductile and has the lowest Vickers hardness(2.1 GPa).Furthermore,the electronic mechanism underlying the diverse mechanical behaviors of Zr2 N structures is discussed by analyzing the partial density of states. 展开更多
关键词 phase transition phonon dispersion Zr_(2)N first-principles calculations
文章速递High-temperature dielectric switch and second harmonic generation integrated in a stimulus responsive material 认领
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作者 Yingsong Xue Zhixu Zhang +3 位作者 Pingping Shi Wanying Zhang Qiong Ye Dawei Fu 《中国化学快报:英文版》 SCIE CAS CSCD 2021年第1期539-542,共4页
Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a lar... Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_3)_3 N(CH_2)_2 Cl]_2[Mn(SCN)_4(H_2 O)_2] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_4(H_2 O)_2]~(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials. 展开更多
关键词 Dielectric switch Second harmonic generation High-temperature Phase transition Stimulus responsive material
三元层状正极材料失效机理及改性研究进展 认领
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作者 马爱军 曹征领 +4 位作者 陈永炜 季世超 钟允晖 吴浩 程琦 《浙江电力》 2021年第1期106-115,共10页
三元正极材料Li[Ni1xMx]O2因其高容量和高性价比,已然成为锂离子电池最重要的正极材料之一。虽然三元正极材料具有高比容量优势,但是在高电压循环下比容量衰减、容量保持率变差进而易导致安全性降低。由于材料本身结构稳定性及热稳定性... 三元正极材料Li[Ni1xMx]O2因其高容量和高性价比,已然成为锂离子电池最重要的正极材料之一。虽然三元正极材料具有高比容量优势,但是在高电压循环下比容量衰减、容量保持率变差进而易导致安全性降低。由于材料本身结构稳定性及热稳定性较差(阳离子混排、不可逆相变、界面反应、微裂纹等失效途径)而引起的容量衰减阻碍了其应用进程。综述了近年来三元层状正极材料容量衰减导致失效的机理研究进展,总结了目前可以提高三元层状正极材料应用前景的改性方法,以期为三元正极材料在动力电池领域的更大规模应用提供解决方案。 展开更多
关键词 三元正极 失效 混排 相变 微裂纹
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Fragment emission and critical behavior in light and heavy charged systems 认领
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作者 Samiksha Sood Rohit Kumar +2 位作者 Arun Sharma Sakshi Gautam Rajeev K.Puri 《中国物理C:英文版》 SCIE CAS 2021年第1期215-225,共11页
We study the emission of fragments in central collisions of light and heavily charged systems of^4+Ar+^45 Sc and^s4Kr+^197 Au,respectively,using the Quantum Molecular Dynamics(QMD)model as the primary model.The fragme... We study the emission of fragments in central collisions of light and heavily charged systems of^4+Ar+^45 Sc and^s4Kr+^197 Au,respectively,using the Quantum Molecular Dynamics(QMD)model as the primary model.The fragments are identified using an energy based clusterization algorithm,i.e.,the Simulated Annealing Clusterization Algorithm(SACA).The charge distributions of intermediate mass fragments[3≤Zf≤12]are fitted with power-law(∝Zf^-τ)and exp on ential(∝e^-λZf)fits in order to extract the parametersτandλ,whose minimum values are also sometimes linked with the onset of fragmentation or the critical point for a liquid-gas phase transition.Other parameters such as the normalized second moment<S2>,<γ2>,average size of the second largest cluster<Zmax2>,phase separation parameter(Sp),bimodal parameter(P),information entropy(H),and Zipfs law are also analyzed to find the exact energy of the onset of fragmentation.Our detailed analysis predicts that an energy point exists between 20-23.1 MeV/nucleon,which is very close to the experimentally observed value of 23.9 MeV/nucleon for the^40Ar+^45Sc reaction.We also find that the critical energy deduced using Zipfs law is higher than those predicted from other critical exponents.Moreover,no minimum is found for t values of the highly charged system of^84Kr+^197Au,in agreement with experimental findings and various theoretical calculations.We observe that the QMD+SACA model calculations are in agreement with the experimental observations.This agreement supports our results regarding the energy point of the liquid-gas phase transition and the onset of fragmentation. 展开更多
关键词 heavy-ion collisions transport model clusterization algorithm Monte-Carlo technique li・quid-gas phase transition
Al掺杂浓度对Hf0.5Zr0.5O2薄膜铁电性能的影响 认领
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作者 邱宇 朱俊 +2 位作者 周云霞 李康 张钰 《材料导报》 EI CAS 北大核心 2021年第2期2001-2005,共5页
采用脉冲激光沉积法(Pulsed laser deposition,PLD)在Pt/Ti/SiO 2/Si衬底上制备TiN/Al掺杂Hf0.5Zr0.5O2/TiN的MIM(金属-绝缘体-金属)结构薄膜电容器。对Al掺杂浓度为0%~4%(摩尔分数)的Al∶Hf0.5Zr0.5O2薄膜的微观结构以及电学性能进行... 采用脉冲激光沉积法(Pulsed laser deposition,PLD)在Pt/Ti/SiO 2/Si衬底上制备TiN/Al掺杂Hf0.5Zr0.5O2/TiN的MIM(金属-绝缘体-金属)结构薄膜电容器。对Al掺杂浓度为0%~4%(摩尔分数)的Al∶Hf0.5Zr0.5O2薄膜的微观结构以及电学性能进行了研究,在此基础上,还研究了退火温度对Al∶Hf0.5Zr0.5O2薄膜的影响。测试结果表明,随着Al掺杂浓度的增大和退火温度的降低,四方相更加稳定,电滞回线更加细窄,剩余极化强度减小。退火温度为500℃时,掺杂浓度为1.03%(摩尔分数)的Al∶Hf0.5Zr0.5O2薄膜中将诱导出类似反铁电薄膜具有的双电滞回线特性,储能密度更高。分析结果表明,这些变化均是由于Al∶Hf0.5Zr0.5O2薄膜内四方相与正交相之间发生的场致可逆相变以及氧空位的再分布。 展开更多
关键词 脉冲激光沉积(PLD) Al掺杂铪锆氧薄膜 铁电 反铁电 相变
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Cluster mean-field study of spinor Bose-Hubbard ladder:Ground-state phase diagram and many-body population dynamics 认领
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作者 张莉 柳文洁 +1 位作者 黄嘉豪 李朝红 《中国物理B:英文版》 SCIE EI CAS 2021年第2期95-102,共8页
We present a cluster mean-field study for ground-state phase diagram and many-body dynamics of spin-1 bosons confined in a two-chain Bose-Hubbard ladder(BHL).For unbiased BHL,we find superfluid(SF)phase and integer fi... We present a cluster mean-field study for ground-state phase diagram and many-body dynamics of spin-1 bosons confined in a two-chain Bose-Hubbard ladder(BHL).For unbiased BHL,we find superfluid(SF)phase and integer filling Mott insulator(Int MI)phase.For biased BHL,in addition to the SF and Int MI phases,there appears half-integer filling Mott insulator(HInt MI)phase.The phase transition between the SF and Int MI phases can be first order at a part of phase boundaries,while the phase transition between the SF and HInt MI phases is always second order.By tuning the bias energy,we report on the change of the nature of SF-MI phase transitions.Furthermore,we study the effect of the spin-dependent interaction on the many-body population dynamics.The spin-dependent interaction can lead to rich dynamical behaviors,but does not influence the particle transfer efficiency.Our results indicate a way to tune the nature of the SF-MI phase transition and open a new avenue to study the many-body dynamics of spinor bosons in optical lattices. 展开更多
关键词 spinor Bose gases superfluid-Mott insulator phase transition Landau-Zener dynamics
共聚单元与拉伸外场对丁烯共聚物相转变的影响 认领
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作者 郑力荣 李薇 +1 位作者 马哲 盛京 《高分子材料科学与工程》 EI CAS 北大核心 2021年第1期32-36,共5页
利用广角X射线衍射方法原位研究了丁烯/4,4-二甲基-1-戊烯无规共聚物的静态和拉伸诱导相转变行为,发现4,4-二甲基-1-戊烯共聚单元可显著减慢聚丁烯form II向form I的静态转变速度,摩尔分数3.43%及以上插入率则可抑制拉伸诱导晶型转变。... 利用广角X射线衍射方法原位研究了丁烯/4,4-二甲基-1-戊烯无规共聚物的静态和拉伸诱导相转变行为,发现4,4-二甲基-1-戊烯共聚单元可显著减慢聚丁烯form II向form I的静态转变速度,摩尔分数3.43%及以上插入率则可抑制拉伸诱导晶型转变。恒速率拉伸实验结果表明,拉伸应力主导转变动力学。在恒应力作用下,低插入率共聚物中form I含量在经历平台期后快速增加,而循环拉伸结果则进一步说明,应力松弛及重新加载过程中相转变依然遵循应力控制机理。 展开更多
关键词 丁烯/4 4-二甲基-1-戊烯共聚物 相转变 拉伸场 广角X射线衍射
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LiMn_(2)O_(4)的高压结构相变和状态方程研究 认领
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作者 熊伦 张新欣 禹国梁 《首都师范大学学报:自然科学版》 2021年第1期14-19,共6页
在金刚石对顶砧中,利用原位高压同步辐射X射线衍射和密度泛函理论,研究了高锰酸锂(LiMn_(2)O_(4))在高压室温下的结构相变和状态方程.研究结果显示:由立方结构到四方结构的结构相变发生在10.7 GPa,并且四方结构保持到实验的最高压力27.4... 在金刚石对顶砧中,利用原位高压同步辐射X射线衍射和密度泛函理论,研究了高锰酸锂(LiMn_(2)O_(4))在高压室温下的结构相变和状态方程.研究结果显示:由立方结构到四方结构的结构相变发生在10.7 GPa,并且四方结构保持到实验的最高压力27.4 GPa.实验数据得出立方结构的体弹模量及其一阶导数分别为102.2(3.6)GPa和13.7(4.7).利用第一性原理计算研究了LiMn2O4在高压下的压缩行为,由此得到的立方结构体弹模量为110.0(2.0)GPa,二者结果基本一致,因此,本文的结论是准确且自洽的. 展开更多
关键词 LiMn_(2)O_(4) 相变 状态方程 高压 原位高压X射线衍射
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氧化钨/石墨烯的晶相调控及电催化析氢性能研究 认领
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作者 陈雪莹 杨军 +3 位作者 曹一凡 刘鑫悦 许占位 黄剑锋 《陕西科技大学学报》 CAS 2021年第1期126-131,共6页
电解水制氢作为可以实现零污染的可靠制氢方式而受到广泛的关注,但贵金属催化剂高昂的成本限制了其商业化的进程,因此寻求可替代的非贵金属催化剂是非常必要的.氧化钨作为一种过渡金属氧化物,在酸性溶液中具有优良的稳定性但其催化活性... 电解水制氢作为可以实现零污染的可靠制氢方式而受到广泛的关注,但贵金属催化剂高昂的成本限制了其商业化的进程,因此寻求可替代的非贵金属催化剂是非常必要的.氧化钨作为一种过渡金属氧化物,在酸性溶液中具有优良的稳定性但其催化活性较低.通过改变氧化钨/石墨烯复合催化剂的烧结温度,实现氧化钨从WO 3到W 18 O 49的晶相调控,采用X射线衍射分析(XRD),扫描电子显微镜(SEM),拉曼光谱(Raman),X射线光电子能谱(XPS)等手段对该复合结构进行了结构表征和转变过程分析,并且在三电极体系下,酸性电解液中测得了相应的电化学性能,其中富含氧缺陷的W 18 O 49/rGO复合催化剂展现出优异的电催化析氢性能.在50 mA/cm 2的电流密度下的过电位仅为240 mV,Tafel斜率为83 mV/dec,并且能够维持7200 s的高效率产氢. 展开更多
关键词 三氧化钨 氧化石墨烯 相转变 水分解 催化剂
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Layer-dependent charge density wave phase transition stiffness in 1T-TaS_(2)nanoflakes evidenced by ultrafast carrier dynamics 认领
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作者 Rui Wang Junbo Zhou +3 位作者 Xinsheng Wang Liming Xie Jimin Zhao Xiaohui Qiu 《纳米研究:英文版》 SCIE EI CAS 2021年第4期1162-1166,共5页
Novel physical properties emerge when the thickness of charge density wave(CDW)materials is reduced to the atomic level,owing to the significant modification of the electronic band structure and correlation effects.He... Novel physical properties emerge when the thickness of charge density wave(CDW)materials is reduced to the atomic level,owing to the significant modification of the electronic band structure and correlation effects.Here,we investigate the layer-dependent CDW phase transition and evolution of the nonequilibrium state of 1T-TaS_(2)nanoflakes using pump-probe spectroscopy.Both the low-energy single-particle and collective excitation relaxations exhibit sharp changes at〜210 K,indicating a phase transition from commensurate CDW to nearly commensurate CDW state.The single particle process reveals that the phase transition stiffness(PTS)is thickness-dependent.Moreover,a small PTS is observed in thin nanoflakes,which is attributed to the reduced thickness that increases the fluctuation and inhibits the nucleation and growth of discommensurations.In addition,the phase mode vanishes when the discommensuration network appears.Our results suggest that the carrier dynamics could be an efficient operational approach to measuring the quantum phase transition in correlated materials. 展开更多
关键词 charge density wave 1T-TaS_(2) layer-dependent phase transition stiffness ultrafast carrier dynamics
Phase transitions of two spin-1/2 Baxter–Wu layers coupled with Ising-type interactions 认领
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作者 Wei Liu Zhengxin Yan Yixian Wang 《理论物理通讯:英文版》 SCIE CAS 2021年第1期99-105,共7页
Using a Monte Carlo simulation and the single histogram reweighting technique,we study the critical behaviors and phase transitions of the Baxter-Wu(BW)model on a two-layer triangular lattice with Ising-type interlaye... Using a Monte Carlo simulation and the single histogram reweighting technique,we study the critical behaviors and phase transitions of the Baxter-Wu(BW)model on a two-layer triangular lattice with Ising-type interlayer couplings.Via the finite-size analysis,we obtain the transition temperatures and critical exponents at repulsive and attractive interlayer couplings.The data for the repulsive interlayer coupling suggest continuous transitions,and the critical behaviors are the same as those of the 2D BW model,belonging to the four-state Potts universality class.The reduced energy cumulants and the histograms reveal that attractive coupling leads to weak firstorder phase transitions.The pseudocritical exponents with the existence of the interlayer couplings indicate that the first-order transition is very close to the critical point of the 2D standard BW model. 展开更多
关键词 Baxter-Wu model Monte Carlo simulation critical behavior weak first order phase transition
新时代高质量人才需求重构浅析 认领
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作者 高丽娜 吕艳霞 《市场周刊》 2021年第2期169-170,176,共3页
我国发展阶段转换、技术变革与国际背景的时代叠加,推动高质量人才需求特征的转换,对人才培养体系的完善提出了新的挑战。我国社会主要矛盾的转化,凸显人才的战略资源地位;比较优势转换,需要拓展“新人口红利”内涵;只有推动创新培养模... 我国发展阶段转换、技术变革与国际背景的时代叠加,推动高质量人才需求特征的转换,对人才培养体系的完善提出了新的挑战。我国社会主要矛盾的转化,凸显人才的战略资源地位;比较优势转换,需要拓展“新人口红利”内涵;只有推动创新培养模式的转换,才能使人才适应“科技4.0”发展需要。 展开更多
关键词 新时代 人才需求 阶段转换 高质量
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NaYF_(4):Yb,Er@SiO_(2)的高温相变及上转换发光性能研究 认领
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作者 甘明龙 李亚萌 傅俊祥 《有色金属科学与工程》 CAS 2021年第1期75-80,共6页
通过固-液热分解法合成平均尺寸为27 nm的六方相NaYF_(4):Yb,Er上转换纳米晶。制备了NaYF_(4):Yb,Er@SiO_(2)核壳纳米粒子,壳层厚度约为8 nm。将NaYF_(4):Yb,Er@SiO_(2)分别在不同高温下焙烧3 h,发现600℃下产物物相未发生变化,但向非... 通过固-液热分解法合成平均尺寸为27 nm的六方相NaYF_(4):Yb,Er上转换纳米晶。制备了NaYF_(4):Yb,Er@SiO_(2)核壳纳米粒子,壳层厚度约为8 nm。将NaYF_(4):Yb,Er@SiO_(2)分别在不同高温下焙烧3 h,发现600℃下产物物相未发生变化,但向非晶态过渡;700、800℃下NaYF4内核与SiO_(2)壳层发生化学反应,产物物相均转变为NaYSiO_(4)。样品均用980 nm红外激光进行激发,显示出强烈的可见光上转换发射。以初始NaYF_(4):Yb,Er@SiO_(2)的上转换发光强度为对比样,随着焙烧温度的升高,样品的发光强度依次提高。这与理论上低声子能量的氟化物发光强度更高不符,可能原因是高温处理后样品去除了部分晶格缺陷和有机杂质。 展开更多
关键词 NaYF_(4) 上转换 NaYSiO_(4) 纳米晶 相变
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