In order to develop the applications of ore tailings, the glass ceramics were prepared by using a conventional melting-quenching-sintering process. The phase component, microstructures, magnetic properties and thermal...In order to develop the applications of ore tailings, the glass ceramics were prepared by using a conventional melting-quenching-sintering process. The phase component, microstructures, magnetic properties and thermal conductivities of the prepared glass ceramics were investigated by using X-ray diffractometer, scanning electron microscopy, vibrating sample magnetometer and thermophysical properties tester, respectively. The results show that orthorhombic olivine-type phase and triclinic sunstone-type phase formed when the glass was annealed at 700 oC, the concentration of olivine-type and sunstone-type phases decreased, the spinel-type cubic phase occurred and the amount increased when the annealing temperatures increased. The magnetic properties from the cubic spinel ferrites were detected in the glass ceramics, and the related saturation magnetization increased with the annealing temperature increasing. The porous glass ceramics with magnetic property showed much lower thermal conductivity, compared with the non-magnetic porous glass-ceramic and the dense glass-ceramics.展开更多
We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of...We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties （for example heat conductivity） within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter ~ is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter 13 are independent oft, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties.展开更多
Molecular dynamics simulation (MDS) is used to study the thermodynamic properties and transport coefficients of an argon system with Lennend-Jones potential. The results on the velocity distribution,mean free path, me...Molecular dynamics simulation (MDS) is used to study the thermodynamic properties and transport coefficients of an argon system with Lennend-Jones potential. The results on the velocity distribution,mean free path, mean collision time, specific heat and self-diffusion coefficient agree well with the existing theoretical/ experimental data. It shows that molecular dynamics method is another bridge to connect microworld and macroworld.展开更多
Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Som...Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Some resonant transmission peaks and stop-frequency gaps can be observed,and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs.With increasing the temperature,the thermal conductance undergoes a transition from the decrease to increase,and can be efficiently tuned by modulating the radius,length of DQDs as well as the interval between DQDs.In addition,at low temperatures,the enhancement of the thermal conductance can be also observed in this case.Some similarities and differences between the cylindrical and rectangular structures are identified.展开更多
High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical propertie...High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical properties and low thermal conductivity,the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K.This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.展开更多
Flow-induced preordering or precursor(FIP) has been studied in a series of lightly cross-linked high-density polyethylene with a combination of extensional rheology and in situ synchrotron radiation small-angle X-ray ...Flow-induced preordering or precursor(FIP) has been studied in a series of lightly cross-linked high-density polyethylene with a combination of extensional rheology and in situ synchrotron radiation small-angle X-ray scattering(SAXS) and wide-angle X-ray diffraction(WAXD) measurements. Based on the incipient strains of SAXS and WAXD signals during extension in a large temperature range, strain-temperature diagrams for flow-induced preordering and nucleation were constructed and revealed that flow-induced crystallization(FIC) undergoes two stages: melt-precursor transition(MPT) and precursor-nuclei transition(PNT). At different temperatures, FIP with different inner structures and morphologies can be induced by strain; these embryos have shape and structure that are related to those of the corresponding critical nuclei. With the strain-temperature diagrams, the thermodynamic properties of FIP are deduced, which shows that compared with the relative nuclei the FIP always has a lower bulk free energy(?H) and a much lower surface free energy(?e). In extreme cases(high temperature), the ?e of FIP can be negligible. The quantitative estimation of the thermodynamic parameters suggests the existence of variant FIPs, which plays a vital role for the subsequent progress of PNT and the whole process of FIC.展开更多
基金Project(51172287)supported by the National Natural Science Foundation of ChinaProject(2012-2013)supported by the Laboratory Research Fund of the State Key Laboratory of Powder Metallurgy,China
文摘In order to develop the applications of ore tailings, the glass ceramics were prepared by using a conventional melting-quenching-sintering process. The phase component, microstructures, magnetic properties and thermal conductivities of the prepared glass ceramics were investigated by using X-ray diffractometer, scanning electron microscopy, vibrating sample magnetometer and thermophysical properties tester, respectively. The results show that orthorhombic olivine-type phase and triclinic sunstone-type phase formed when the glass was annealed at 700 oC, the concentration of olivine-type and sunstone-type phases decreased, the spinel-type cubic phase occurred and the amount increased when the annealing temperatures increased. The magnetic properties from the cubic spinel ferrites were detected in the glass ceramics, and the related saturation magnetization increased with the annealing temperature increasing. The porous glass ceramics with magnetic property showed much lower thermal conductivity, compared with the non-magnetic porous glass-ceramic and the dense glass-ceramics.
文摘We present a rigorous homogenization approach for elcient computation of a class of physical problems in a one-dimensional periodic heterogeneous material. This material is represented by a spatially periodic array of unit cells with a length of More specifically, the method is applied to the diffusion, heat conduction, and wave propagation problems. Heterogeneous materials can have arbitrary position-dependent continuous or discontinuous materials properties （for example heat conductivity） within the unit cell. The final effective model includes both effective properties at the leading order and high-order contributions due to the microscopic heterogeneity. A dimensionless heterogeneity parameter ~ is defined to represent high-order contributions, shown to be in the range of [-1/12, 0], and has a universal expression for all three problems. Both effective properties and heterogeneity parameter 13 are independent oft, the microscopic scale of heterogeneity. The homogenized solution describing macroscopic variations can be obtained from the effective model. Solution with sub-unit-cell accuracy can be constructed based on the homogenized solution and its spatial derivatives. The paper represents a general approach to obtain the effective model for arbitrary periodic heterogeneous materials with position-dependent properties.
文摘Molecular dynamics simulation (MDS) is used to study the thermodynamic properties and transport coefficients of an argon system with Lennend-Jones potential. The results on the velocity distribution,mean free path, mean collision time, specific heat and self-diffusion coefficient agree well with the existing theoretical/ experimental data. It shows that molecular dynamics method is another bridge to connect microworld and macroworld.
基金supported by the National Natural Science Foundation of China (Grant No.11204074)
文摘Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Some resonant transmission peaks and stop-frequency gaps can be observed,and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs.With increasing the temperature,the thermal conductance undergoes a transition from the decrease to increase,and can be efficiently tuned by modulating the radius,length of DQDs as well as the interval between DQDs.In addition,at low temperatures,the enhancement of the thermal conductance can be also observed in this case.Some similarities and differences between the cylindrical and rectangular structures are identified.
基金supported by the Natural Science Foundation for Distinguished Young Scholars of Hebei Province(Grant No.A2013201249)the National Natural Science Foundation of China(Grant No.51372064)
文摘High temperature electrical and thermal transport properties,that is,electrical conductivity,Seebeck coefficient and thermal conductivity,of CdO ceramics have been investigated.Because of the good electrical properties and low thermal conductivity,the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K.This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.
基金supported by the National Natural Science Foundation of China(51325301,51033004,51120135002,51227801)the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics(U1330202)+1 种基金Project 2013BB05 supported by the Key Laboratory of Neutron Physics,China Academy of Engineering Physicsin part supported by"Ludo Frevel Crystallography Scholarships"from the International Centre for Diffraction Data
文摘Flow-induced preordering or precursor(FIP) has been studied in a series of lightly cross-linked high-density polyethylene with a combination of extensional rheology and in situ synchrotron radiation small-angle X-ray scattering(SAXS) and wide-angle X-ray diffraction(WAXD) measurements. Based on the incipient strains of SAXS and WAXD signals during extension in a large temperature range, strain-temperature diagrams for flow-induced preordering and nucleation were constructed and revealed that flow-induced crystallization(FIC) undergoes two stages: melt-precursor transition(MPT) and precursor-nuclei transition(PNT). At different temperatures, FIP with different inner structures and morphologies can be induced by strain; these embryos have shape and structure that are related to those of the corresponding critical nuclei. With the strain-temperature diagrams, the thermodynamic properties of FIP are deduced, which shows that compared with the relative nuclei the FIP always has a lower bulk free energy(?H) and a much lower surface free energy(?e). In extreme cases(high temperature), the ?e of FIP can be negligible. The quantitative estimation of the thermodynamic parameters suggests the existence of variant FIPs, which plays a vital role for the subsequent progress of PNT and the whole process of FIC.
