The inferior structure/electrochemistry stability due to the volume expansion and the less lithium storage active sites of transition metal oxide (TMO) are critical issue hindering their commercialization.The rational...The inferior structure/electrochemistry stability due to the volume expansion and the less lithium storage active sites of transition metal oxide (TMO) are critical issue hindering their commercialization.The rational design to utilize the combined advantages of both structure and composition is a key strategy to address these challenges.Here,the (FeCoNiMnCrMg)_(2)O_(3)high entropy oxide(HEO) with different morphologic structures are developed through integrating molecule and microstructure engineering.The morphologic structure of high entropy oxide transforms from solid spheres to multishelled core-shell spheres,and then to hollow spheres,which is governed by a thermally induced non-uniform shrinkage process coupled with Kirkendall effect diffusion due to the different calcination temperature.Even with the incorporation of various metallic ions,the high entropy oxide with a homogeneous single-phase solid solution maintained their shape and uniformity in size due to the ability of metal ions to coexist on the same lattice point.Benefiting from the meticulous control of both compositional and geometric factors,the hollow high entropy oxide exhibited a significantly high specific capacity (1722.1 mAh g^(-1)after 200cycles at 1 A g^(-1)) and long-life span for lithium storage(2158.7 mAh g^(-1)over 900 cycles at 4 A g^(-1)).The collaborative lattice and consistent volume demonstrated in this study offer significant potential in directing the development of materials for advanced energy storage solutions.展开更多
The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a sup...The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.展开更多
The role of entropy and enthalpy plays an essential key for the formation of an alloy. This paper illustrates how an alloy is to form and what and why the properties of the alloy are going to have by the entropy and e...The role of entropy and enthalpy plays an essential key for the formation of an alloy. This paper illustrates how an alloy is to form and what and why the properties of the alloy are going to have by the entropy and enthalpy effects via a designed enthalpy-entropy plane (EE-plane) based on the Gibbs free energy equation and the introducing a charactering pseudo-unitary lattice (PUL) for entropy alloys. Based on the PUL scheme, the so-called four effects in high entropy alloys are simply nothing but the entropy effect with the other three accompanying effects: the distortion, slow diffusion and cocktail effects.展开更多
High-entropy catalysts featuring exceptional properties are,in no doubt,playing an increasingly significant role in aprotic lithium-oxygen batteries.Despite extensive effort devoted to tracing the origin of their unpa...High-entropy catalysts featuring exceptional properties are,in no doubt,playing an increasingly significant role in aprotic lithium-oxygen batteries.Despite extensive effort devoted to tracing the origin of their unparalleled performance,the relationships between multiple active sites and reaction intermediates are still obscure.Here,enlightened by theoretical screening,we tailor a high-entropy perovskite fluoride(KCoMnNiMgZnF_(3)-HEC)with various active sites to overcome the limitations of conventional catalysts in redox process.The entropy effect modulates the d-band center and d orbital occupancy of active centers,which optimizes the d–p hybridization between catalytic sites and key intermediates,enabling a moderate adsorption of LiO_(2)and thus reinforcing the reaction kinetics.As a result,the Li–O2 battery with KCoMnNiMgZnF_(3)-HEC catalyst delivers a minimal discharge/charge polarization and long-term cycle stability,preceding majority of traditional catalysts reported.These encouraging results provide inspiring insights into the electron manipulation and d orbital structure optimization for advanced electrocatalyst.展开更多
High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ...High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ceramics by adjusting the proportion of raw materials,and have broad application prospects in many fields.This article provides a review of the high entropy effect,preparation methods,and main applications of high entropy ceramic materials,especially exploring relevant research on high entropy perovskite ceramics.It is expected to provide reference for the promotion of scientific research and the development of further large-scale applications of high-entropy ceramic materials.展开更多
The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x （x=0.01 and 0.03） alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scannin...The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x （x=0.01 and 0.03） alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scanning calorimeter （DSC） and magnetization measurements. The results of energy dispersive X-ray analysis （EDX） and X-ray diffraction analyses showed that the composition and crystal structure of the alloys were desired. DSC measurements were performed to determine the transformation temperatures for each alloy. Both alloys exhibited the first order phase transition around room temperature. The alloys showed an anti-ferromagnetic transition around 60 K. The isothermal magnetic entropy changes of the alloys were determined from the isothermal magnetization measurements by using the Maxwell relation. The maximum values of isothermal magnetic entropy change of the Gd5Ge2.05-xSi1.95-xMn2x alloy with x=0.01 was found to be -12.1 and -19.8 J/（kg·K） using Maxwell equation around 268 K in applied fields of 2 and 5 T, respectively.展开更多
In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12...In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.展开更多
The magnetic properties and magnetocaloric effect（MCE） in EuTi1-xCoxO3（x = 0, 0.025, 0.05, 0.075, 0.1） compounds have been investigated. When the Ti^4＋ ions were substituted by Co2＋ions, the delicate balance was...The magnetic properties and magnetocaloric effect（MCE） in EuTi1-xCoxO3（x = 0, 0.025, 0.05, 0.075, 0.1） compounds have been investigated. When the Ti^4＋ ions were substituted by Co2＋ions, the delicate balance was changed between antiferromagnetic（AFM） and ferromagnetic（FM） phases in the EuTiO3 compound. In EuTi1-xCoxO3 system, a giant reversible MCE and large refrigerant capacity（RC） were observed without hysteresis. The values of -△SM^max were evaluated to be around 10 J·kg^-1·K^-1 for EuTi0.95Co0.05O3 under a magnetic field change of 10 kOe. The giant reversible MCE and large RC suggests that EuTi1-xCoxO3 series could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant.展开更多
The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry ...The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (TC) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|-Smax| = 2.24 J/(kg·K), T_C = 198 K).展开更多
An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38＋xSn12（x = 0, 1.0, 1.5, 2.0, and 2.5） ferromagnetic shape memory alloys is carried out. With the partial replac...An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38＋xSn12（x = 0, 1.0, 1.5, 2.0, and 2.5） ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni_（48）Co2Mn38Sn12 alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x = 1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature,but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases.展开更多
Systematic search of the potential energy surface of tetrapeptide glycine-phenylalanine- glycine-glycine （GFGG） in gas phase is conducted by a combination of PM3, HF and BHandHLYP methods. The conformational search ...Systematic search of the potential energy surface of tetrapeptide glycine-phenylalanine- glycine-glycine （GFGG） in gas phase is conducted by a combination of PM3, HF and BHandHLYP methods. The conformational search method is described in detail. The relative electronic energies, zero point vibrational energies, dipole moments, rotational constants, vertical ionization energies and the temperature dependent conformational distributions for a number of important conformers are obtained. The structural characteristics of these conformers are analyzed and it is found that the entropic effect is a dominating factor in determining the relative stabilities of the conformers. The measurements of dipole moments and some characteristic IR mode are shown to be effective approaches to verify the theoreti- cal prediction. The structures of the low energy GFGG conformers are also analyzed in their connection with the secondary structures of proteins. Similarity between the local structures of low energy GFGG conformers and the α-helix is discussed and many β- and γ-turn local structures in GFGG conformers are found.展开更多
Obstructive sleep apnea-hypopnea syndrome(OSAHS)significantly impairs children's growth and cognition.This study aims to elucidate the pathophysiological mechanisms underlying OSAHS in children,with a particular f...Obstructive sleep apnea-hypopnea syndrome(OSAHS)significantly impairs children's growth and cognition.This study aims to elucidate the pathophysiological mechanisms underlying OSAHS in children,with a particular focus on the alterations in cortical information interaction during respiratory events.We analyzed sleep electroencephalography before,during,and after events,utilizing Symbolic Transfer Entropy(STE)for brain network construction and information flow assessment.The results showed a significant increase in STE after events in specific frequency bands during N2 and rapid eye movement(REM)stages,along with increased STE during N3 stage events.Moreover,a noteworthy rise in the information flow imbalance within and between hemispheres was found after events,displaying unique patterns in central sleep apnea and hypopnea.Importantly,some of these alterations were correlated with symptom severity.These findings highlight significant changes in brain region coordination and communication during respiratory events,offering novel insights into OSAHS pathophysiology in children.展开更多
A part of a long DNA chain was driven into a confined environment by an electric field, while the rest remains in the higher-entropy region. Upon removal of the field, the chain recoils to the higher-entropy region sp...A part of a long DNA chain was driven into a confined environment by an electric field, while the rest remains in the higher-entropy region. Upon removal of the field, the chain recoils to the higher-entropy region spontaneously. This dynamical process was investigated by Monte Carlo simulations. The simulation reproduces the experimentally-observed phenomenon that the recoil of the DNA chain is initially slow and gradually increases in speed due to the presence of the confinement-entropic force. The results show that with increasing the dimension or decreasing the spacing of the nanopillars the recoil velocity of the DNA chain will increase. Further analysis suggests that the characteristic entropy per monomer in the confinement is proportional to the area fraction of the free part in the confinement.展开更多
We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption intera...We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.展开更多
The entropy balance equation that describes the entropy budget of atmospheric systems is derived from the Gibbs relation.The distribution of the entropy flows of a west-Pacific typhoon and a Bengal-Bay cyclone is calc...The entropy balance equation that describes the entropy budget of atmospheric systems is derived from the Gibbs relation.The distribution of the entropy flows of a west-Pacific typhoon and a Bengal-Bay cyclone is calculated and thus the dissipativity of the atmospheric systems is revealed.展开更多
Understanding the effect of curvature and topological frustration on self-assembly yields insight into the mechanistic details of the ordering of identical subunits in curved spaces,such as the assembly of viral capsi...Understanding the effect of curvature and topological frustration on self-assembly yields insight into the mechanistic details of the ordering of identical subunits in curved spaces,such as the assembly of viral capsids,growth of solid domains on vesicles,and the self-assembly of molecular monolayers.However,the self-assembly of nanoparticles with anisotropic surface topology and compartmentalization on curved surfaces remains elusive.By combining large-scale molecular simulations as well as theoretical analysis,we demonstrate here that the interplay among anisotropy,curvature,and chain conformation induces tethered Janus nanoparticles to self-assemble into diverse novel structures on a sphere,including binary nanocluster(C_(B)),trinary nanocluster(C_(T)),nanoribbon(R_(N))and hexagon with centered reverse(HR),which are mapped on a phase diagram related to the length asymmetry of tethered chains and Janus balance of the nanoparticles.The dynamical mechanism for the formation of these structure states is analyzed by examining the detailed kinetic pathways as well as free energy.We also show that the centered-reverse state is more prone to emerging around the topological defects,indicating the defect-enhanced entropy effect on a curved surface.Finally,the analytical model that rationalizes the regimes of these structure states is developed and fits simulations reasonably well,resulting in a mechanistic interpretation based on the order through entropy.Our findings shed light on curvature engineering as a versatile strategy to tailor the superstructures formed by anisotropic building blocks toward unique properties.展开更多
Using the isospin-dependent quantum molecular dynamics model, the entropy of an intermediate-energy heavy ion collision system after the reaction and the number of deuteronlike and protonlike particles produced in the...Using the isospin-dependent quantum molecular dynamics model, the entropy of an intermediate-energy heavy ion collision system after the reaction and the number of deuteronlike and protonlike particles produced in the collision is calculated. In the collision, different parameters are used and the mass number used here is from40 to 93 at incident energy from 150 MeV to 1050 MeV. We build a new model in which the density distribution of the reaction product is used to calculate the size of the entropy. The entropy calculated with this model is in good agreement with experimental values. Our data reveals that with the increase of the neutron-proton ratio and impact parameter, the entropy of the reaction system decreases, and it increases with the increase of system mass and reaction energy.展开更多
基金financially supported by the Central Guidance on Local Science and Technology Development Fund of Sichuan Province(No.2023ZYDF044)LingYan Project(No.2024C01090)
文摘The inferior structure/electrochemistry stability due to the volume expansion and the less lithium storage active sites of transition metal oxide (TMO) are critical issue hindering their commercialization.The rational design to utilize the combined advantages of both structure and composition is a key strategy to address these challenges.Here,the (FeCoNiMnCrMg)_(2)O_(3)high entropy oxide(HEO) with different morphologic structures are developed through integrating molecule and microstructure engineering.The morphologic structure of high entropy oxide transforms from solid spheres to multishelled core-shell spheres,and then to hollow spheres,which is governed by a thermally induced non-uniform shrinkage process coupled with Kirkendall effect diffusion due to the different calcination temperature.Even with the incorporation of various metallic ions,the high entropy oxide with a homogeneous single-phase solid solution maintained their shape and uniformity in size due to the ability of metal ions to coexist on the same lattice point.Benefiting from the meticulous control of both compositional and geometric factors,the hollow high entropy oxide exhibited a significantly high specific capacity (1722.1 mAh g^(-1)after 200cycles at 1 A g^(-1)) and long-life span for lithium storage(2158.7 mAh g^(-1)over 900 cycles at 4 A g^(-1)).The collaborative lattice and consistent volume demonstrated in this study offer significant potential in directing the development of materials for advanced energy storage solutions.
基金Project supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(14JCQNJC4000)the National Natural Science Foundation of China(11604242)
文摘The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.
文摘The role of entropy and enthalpy plays an essential key for the formation of an alloy. This paper illustrates how an alloy is to form and what and why the properties of the alloy are going to have by the entropy and enthalpy effects via a designed enthalpy-entropy plane (EE-plane) based on the Gibbs free energy equation and the introducing a charactering pseudo-unitary lattice (PUL) for entropy alloys. Based on the PUL scheme, the so-called four effects in high entropy alloys are simply nothing but the entropy effect with the other three accompanying effects: the distortion, slow diffusion and cocktail effects.
基金P.G.acknowledges the financial support from the Youth Foundation of Shandong Natural Science Foundation(No.ZR2023OB230)National Natural Science Foundation(No.22309035)Double First-class Discipline Construction Fund Project of Harbin Institute of Technology at Weihai(No.2023SYLHY11).
文摘High-entropy catalysts featuring exceptional properties are,in no doubt,playing an increasingly significant role in aprotic lithium-oxygen batteries.Despite extensive effort devoted to tracing the origin of their unparalleled performance,the relationships between multiple active sites and reaction intermediates are still obscure.Here,enlightened by theoretical screening,we tailor a high-entropy perovskite fluoride(KCoMnNiMgZnF_(3)-HEC)with various active sites to overcome the limitations of conventional catalysts in redox process.The entropy effect modulates the d-band center and d orbital occupancy of active centers,which optimizes the d–p hybridization between catalytic sites and key intermediates,enabling a moderate adsorption of LiO_(2)and thus reinforcing the reaction kinetics.As a result,the Li–O2 battery with KCoMnNiMgZnF_(3)-HEC catalyst delivers a minimal discharge/charge polarization and long-term cycle stability,preceding majority of traditional catalysts reported.These encouraging results provide inspiring insights into the electron manipulation and d orbital structure optimization for advanced electrocatalyst.
文摘High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ceramics by adjusting the proportion of raw materials,and have broad application prospects in many fields.This article provides a review of the high entropy effect,preparation methods,and main applications of high entropy ceramic materials,especially exploring relevant research on high entropy perovskite ceramics.It is expected to provide reference for the promotion of scientific research and the development of further large-scale applications of high-entropy ceramic materials.
文摘The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x （x=0.01 and 0.03） alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scanning calorimeter （DSC） and magnetization measurements. The results of energy dispersive X-ray analysis （EDX） and X-ray diffraction analyses showed that the composition and crystal structure of the alloys were desired. DSC measurements were performed to determine the transformation temperatures for each alloy. Both alloys exhibited the first order phase transition around room temperature. The alloys showed an anti-ferromagnetic transition around 60 K. The isothermal magnetic entropy changes of the alloys were determined from the isothermal magnetization measurements by using the Maxwell relation. The maximum values of isothermal magnetic entropy change of the Gd5Ge2.05-xSi1.95-xMn2x alloy with x=0.01 was found to be -12.1 and -19.8 J/（kg·K） using Maxwell equation around 268 K in applied fields of 2 and 5 T, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274357,51501005,51590880,and 11674008)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-010A1)+1 种基金the China Postdoctoral Science Foundation(Grant No.2016M591071)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504266,51271192,51322605,and 51371075)the Natural Science Foundation of Tianjin,China(Grant No.17JCQNJC02300)
文摘The magnetic properties and magnetocaloric effect（MCE） in EuTi1-xCoxO3（x = 0, 0.025, 0.05, 0.075, 0.1） compounds have been investigated. When the Ti^4＋ ions were substituted by Co2＋ions, the delicate balance was changed between antiferromagnetic（AFM） and ferromagnetic（FM） phases in the EuTiO3 compound. In EuTi1-xCoxO3 system, a giant reversible MCE and large refrigerant capacity（RC） were observed without hysteresis. The values of -△SM^max were evaluated to be around 10 J·kg^-1·K^-1 for EuTi0.95Co0.05O3 under a magnetic field change of 10 kOe. The giant reversible MCE and large RC suggests that EuTi1-xCoxO3 series could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant.
基金Project (50371058) supported by the National Natural Science Foundation of China
文摘The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd1-xTbx)5Si1.72- Ge2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd5Si1.72Ge2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (TC) of the compounds. The magnetic entropy change of (Gd1-xTbx)5Si1.72Ge2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd0.80Tb0.20)5Si1.72Ge2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd0.3Dy0.7)5Si4 compound (|-Smax| = 2.24 J/(kg·K), T_C = 198 K).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51601092,51571121,and 11604148)the Fundamental Research Funds for the Central Universities,China(Grant Nos.30916011344 and 30916011345)+5 种基金Jiangsu Natural Science Foundation for Distinguished Young Scholars,China(Grant No.BK20140035)China Postdoctoral Science Foundation(Grant No.2016M591851)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20160833 and BK20160829)Qing Lan Project of Jiangsu Province,ChinaPriority Academic Program Development of Jiangsu Higher Education Institutions,ChinaNMG–NJUST Joint Scholarship Program for Ishfaq Ahmad Shah(Student ID:914116020118)
文摘An investigation on the magnetostructural transformation and magnetocaloric properties of Ni48-xCo2Mn38＋xSn12（x = 0, 1.0, 1.5, 2.0, and 2.5） ferromagnetic shape memory alloys is carried out. With the partial replacement of Ni by Mn in the Ni_（48）Co2Mn38Sn12 alloy, the electron concentration decreases. As a result, the martensitic transformation temperature is decreased into the temperature window between the Curie-temperatures of austenite and martensite. Thus, the samples with x = 1.5 and 2.0 exhibit the magnetostructural transformation between the weak-magnetization martensite and ferromagnetic austenite at room temperature. The structural transformation can be induced not only by the temperature,but also by the magnetic field. Accompanied by the magnetic-field-induced magnetostructural transformation, a considerable magnetocaloric effect is observed. With the increase of x, the maximum entropy change decreases, but the effective magnetic cooling capacity increases.
文摘Systematic search of the potential energy surface of tetrapeptide glycine-phenylalanine- glycine-glycine （GFGG） in gas phase is conducted by a combination of PM3, HF and BHandHLYP methods. The conformational search method is described in detail. The relative electronic energies, zero point vibrational energies, dipole moments, rotational constants, vertical ionization energies and the temperature dependent conformational distributions for a number of important conformers are obtained. The structural characteristics of these conformers are analyzed and it is found that the entropic effect is a dominating factor in determining the relative stabilities of the conformers. The measurements of dipole moments and some characteristic IR mode are shown to be effective approaches to verify the theoreti- cal prediction. The structures of the low energy GFGG conformers are also analyzed in their connection with the secondary structures of proteins. Similarity between the local structures of low energy GFGG conformers and the α-helix is discussed and many β- and γ-turn local structures in GFGG conformers are found.
基金supported by the National Natural Science Foundation of China (82001919)the Guangdong Basic and Applied Basic Research Foundation (2022A1515010050)+2 种基金the China Postdoctoral Science Foundation (2022M711219)the Key Realm R&D Program of Guangdong Province (2019B03035001)the Foundation of Guangdong Provincial Key Laboratory of Sensor Technology and Biomedical Instruments (2020B1212060077).
文摘Obstructive sleep apnea-hypopnea syndrome(OSAHS)significantly impairs children's growth and cognition.This study aims to elucidate the pathophysiological mechanisms underlying OSAHS in children,with a particular focus on the alterations in cortical information interaction during respiratory events.We analyzed sleep electroencephalography before,during,and after events,utilizing Symbolic Transfer Entropy(STE)for brain network construction and information flow assessment.The results showed a significant increase in STE after events in specific frequency bands during N2 and rapid eye movement(REM)stages,along with increased STE during N3 stage events.Moreover,a noteworthy rise in the information flow imbalance within and between hemispheres was found after events,displaying unique patterns in central sleep apnea and hypopnea.Importantly,some of these alterations were correlated with symptom severity.These findings highlight significant changes in brain region coordination and communication during respiratory events,offering novel insights into OSAHS pathophysiology in children.
文摘A part of a long DNA chain was driven into a confined environment by an electric field, while the rest remains in the higher-entropy region. Upon removal of the field, the chain recoils to the higher-entropy region spontaneously. This dynamical process was investigated by Monte Carlo simulations. The simulation reproduces the experimentally-observed phenomenon that the recoil of the DNA chain is initially slow and gradually increases in speed due to the presence of the confinement-entropic force. The results show that with increasing the dimension or decreasing the spacing of the nanopillars the recoil velocity of the DNA chain will increase. Further analysis suggests that the characteristic entropy per monomer in the confinement is proportional to the area fraction of the free part in the confinement.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.20274040,20574052)the Program for New Century Excellent Talents in Universities(No.NCET-05-0538)+1 种基金the Natural Science Foundation of Zhejiang Province(Nos.R404047,Y405011,Y405553)China Postdoctoral Science Foundation(No.20060401064).
文摘We use the pruned-enriched Rosenbluth method to investigate systematically the segment density profiles of compact polymer chains confined between two parallel plane walls. The non-adsorption case of adsorption interaction energy ε = 0 and the weak adsorption case of ε= -1 are considered for the compact polymer chains with different chain lengths N and different separation distances between two walls D. Several special entropy effects on the confined compact polymer chains, such as a damped oscillation in the segment density profile for the large separation distance D, are observed and discussed for different separation distances D in the non-adsorption case. In the weak adsorption case, investigations on the segment density profiles indicate that the competition between the entropy and adsorption effects results in an obvious depletion layer. Moreover, the scaling laws of the damped oscillation period Td and the depletion layer width Ld are obtained for the confined compact chains. Most of these results are obtained for the first time so far as we know, which are expected to understand the properties of the confined compact polymer chains more completely.
文摘The entropy balance equation that describes the entropy budget of atmospheric systems is derived from the Gibbs relation.The distribution of the entropy flows of a west-Pacific typhoon and a Bengal-Bay cyclone is calculated and thus the dissipativity of the atmospheric systems is revealed.
基金supported by the National Natural Science Foundation of China(Grants No.22025302 and 21873053)L.T.Y.acknowledges financial support from the Ministry of Science and Technology of China(Grant No.2016YFA0202500).
文摘Understanding the effect of curvature and topological frustration on self-assembly yields insight into the mechanistic details of the ordering of identical subunits in curved spaces,such as the assembly of viral capsids,growth of solid domains on vesicles,and the self-assembly of molecular monolayers.However,the self-assembly of nanoparticles with anisotropic surface topology and compartmentalization on curved surfaces remains elusive.By combining large-scale molecular simulations as well as theoretical analysis,we demonstrate here that the interplay among anisotropy,curvature,and chain conformation induces tethered Janus nanoparticles to self-assemble into diverse novel structures on a sphere,including binary nanocluster(C_(B)),trinary nanocluster(C_(T)),nanoribbon(R_(N))and hexagon with centered reverse(HR),which are mapped on a phase diagram related to the length asymmetry of tethered chains and Janus balance of the nanoparticles.The dynamical mechanism for the formation of these structure states is analyzed by examining the detailed kinetic pathways as well as free energy.We also show that the centered-reverse state is more prone to emerging around the topological defects,indicating the defect-enhanced entropy effect on a curved surface.Finally,the analytical model that rationalizes the regimes of these structure states is developed and fits simulations reasonably well,resulting in a mechanistic interpretation based on the order through entropy.Our findings shed light on curvature engineering as a versatile strategy to tailor the superstructures formed by anisotropic building blocks toward unique properties.
文摘Using the isospin-dependent quantum molecular dynamics model, the entropy of an intermediate-energy heavy ion collision system after the reaction and the number of deuteronlike and protonlike particles produced in the collision is calculated. In the collision, different parameters are used and the mass number used here is from40 to 93 at incident energy from 150 MeV to 1050 MeV. We build a new model in which the density distribution of the reaction product is used to calculate the size of the entropy. The entropy calculated with this model is in good agreement with experimental values. Our data reveals that with the increase of the neutron-proton ratio and impact parameter, the entropy of the reaction system decreases, and it increases with the increase of system mass and reaction energy.
