Joining of ZrO_2 (containing 8% (mol fraction) Y_2O_3,as the composition used in oxygen sensors) to 95Al_2O_3 (widely used at elevated temperature) in green state was described using polymer/layered silicate (PLS) nan...Joining of ZrO_2 (containing 8% (mol fraction) Y_2O_3,as the composition used in oxygen sensors) to 95Al_2O_3 (widely used at elevated temperature) in green state was described using polymer/layered silicate (PLS) nanocomposites contained slurry,without applied pressure. Microstructure of the joined section was investigated. The effects of interlayer and PLS on joining qualities were analysed. The results show that interface cracks are easily produced because of mismatch of both thermal expansion and/or sintering shrinkage between joined samples. With an optimized condition of joining layer composition and solid contents,a fine joint could be obtained without obvious cracks,pores and other defects. This process is suitable for joining of various kinds of advanced ceramics.展开更多
High-yielding low-cost vanadium oxide nanotubes were prepared by hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discover...High-yielding low-cost vanadium oxide nanotubes were prepared by hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discovered to determine the content of V (IV) in vanadium oxide nanotubes by thermogravimetric analysis (TGA). This method can be extended to determine the content of low oxidation state in other transition metal oxide nanomaterials.展开更多
The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared ...The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared laser pumped rare earth doped nonlinear laser crystals by means of self frequency conversion and from infrared laser pumped rare earth doped bulk, fiber and microsphere materials by means of frequency upconversion are introduced in detail. Other kinds of devices and methods are also compared. The typical nonlinear laser crystals such as YAl 3(BO 3) 4, GdAl 3(BO 3) 4, YCa 4O(BO 3) 3 , GdCa 4O(BO 3) 3, and the typical upconversion fluoride fibers are compared and analyzed. The major problems remaining to be solved and the developing trends in the area are also discussed.展开更多
Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and the...Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.展开更多
The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. ...The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. The calculation of the local density of states shows that new states will emerge between the resonant Wannier-Stark states as a result of the intervention of time-dependent impurity potential, and the increase in electric field strength of impurity will result in the growing of the number of new states between the gaps of neighbouring Stark ladders.展开更多
Nano-SrB2O4 powder was prepared by solid-state reaction at room temperature followed by a subsequent calcination process. The highly productive method which can be operated easily confirms to the Green-chemistry princ...Nano-SrB2O4 powder was prepared by solid-state reaction at room temperature followed by a subsequent calcination process. The highly productive method which can be operated easily confirms to the Green-chemistry principles. The XRD patters demonstrate that the component of the as-obtained sample is SrB2O4 after calcination at 600℃. Differential thermal analysis and thermogravimetriy (DTA/TG) curves suggest the process of dehydration and crystal transition from Sr[B(OH)4]2 to SrB2O4·2H2O. SEM image of SrB2O4 shows that the particles are uniform and spherical with average size of 80 nm in diameter. Furthermore, the mechanism of reaction was discussed. The chemical reaction of the process is assumed to be acid-base neutralization reaction. The water generated from the acid-base neutralization reaction and the release of crystal water from Sr(OH)2·8H2O plays an essential role in the reaction system.展开更多
MgB2 with Tc ≈ 40 K, is a record-breaking compound among the s-p metals and alloys. It appears that this material is a rare example of the two band electronic structures, which are weakly connected with each other. E...MgB2 with Tc ≈ 40 K, is a record-breaking compound among the s-p metals and alloys. It appears that this material is a rare example of the two band electronic structures, which are weakly connected with each other. Experimental results clearly reveal that boron sub-lattice conduction band is mainly responsible for superconductivity in this simple compound. Experiments such as tunneling spectroscopy, specific heat measurements, and high resolution spectroscopy show that there are two superconducting gaps. Considering a canonical two band BCS Hamiltonian containing a Fermi Surface of π- and σ-bands and following Green’s function technique and equation of motion method, we have shown that MgB2 possess two superconducting gaps. It is also pointed out that the system admits a precursor phase of Cooper pair droplets that undergoes a phase locking transition at a critical temperature below the mean field solution. Study of specific heat and density of states is also presented. The agreement between theory and experimental results for specific heat is quite convincing. The paper is organized in five sections: Introduction, Model Hamiltonian, Physical properties, Numerical calculations, Discussion and conclusions.展开更多
近年来,美国一直通过“煤炭优先”计划等推动先进燃煤电厂、先进煤化工等技术和装备的发展,并进一步提高效率、降低与碳捕集相关的成本从而支持“煤+碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)”技术的开发与部...近年来,美国一直通过“煤炭优先”计划等推动先进燃煤电厂、先进煤化工等技术和装备的发展,并进一步提高效率、降低与碳捕集相关的成本从而支持“煤+碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)”技术的开发与部署,同时还重点研发从煤及煤基能源等中回收稀土元素的技术。系统梳理了美国煤炭清洁高效利用全过程的研发投入、研发方向和研发机构等情况,结合中国清洁煤技术发展现状,提出在“双碳”目标下发展煤炭清洁高效利用前沿技术的发展建议,可为中国进一步构建绿色低碳、安全高效的现代能源体系提供参考。展开更多
文摘Joining of ZrO_2 (containing 8% (mol fraction) Y_2O_3,as the composition used in oxygen sensors) to 95Al_2O_3 (widely used at elevated temperature) in green state was described using polymer/layered silicate (PLS) nanocomposites contained slurry,without applied pressure. Microstructure of the joined section was investigated. The effects of interlayer and PLS on joining qualities were analysed. The results show that interface cracks are easily produced because of mismatch of both thermal expansion and/or sintering shrinkage between joined samples. With an optimized condition of joining layer composition and solid contents,a fine joint could be obtained without obvious cracks,pores and other defects. This process is suitable for joining of various kinds of advanced ceramics.
基金FundedbytheKeyProjectofMinistryofEducationofChi na (No .9914 3)
文摘High-yielding low-cost vanadium oxide nanotubes were prepared by hydrothermal self-assembling process from vanadium pentoxide and organic molecules as structure-directing templates. Moreover, a new method was discovered to determine the content of V (IV) in vanadium oxide nanotubes by thermogravimetric analysis (TGA). This method can be extended to determine the content of low oxidation state in other transition metal oxide nanomaterials.
文摘The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared laser pumped rare earth doped nonlinear laser crystals by means of self frequency conversion and from infrared laser pumped rare earth doped bulk, fiber and microsphere materials by means of frequency upconversion are introduced in detail. Other kinds of devices and methods are also compared. The typical nonlinear laser crystals such as YAl 3(BO 3) 4, GdAl 3(BO 3) 4, YCa 4O(BO 3) 3 , GdCa 4O(BO 3) 3, and the typical upconversion fluoride fibers are compared and analyzed. The major problems remaining to be solved and the developing trends in the area are also discussed.
基金This work was supported by the China Postdoctoral Science Foundation(China Fund[1998]6)that was entitled“Synthesis of Modified Starch Binder and Its Application in Foundry”.Authors would like to thank academician Jinzong YANG and lecturer Hua ZHANG for the kind analyses and discussions.
文摘Interactions between different components in α-starch based composite binder for green sand mould/core were investigated by using XRD, IR spectra, 1H NMR spectra and SEM. Several adhesive hardening structures and theories of the binder at room temperature were proposed according to the interactions between various compositions. Thus, the reasons for the binder to have excellent combination properties and unique adhesive bonding and self-curing characteristics were explained by these theories successfully. And the theories are of great directive importance to design and development of composite binder for green sand mould/core.
基金Project supported by the Natural Science Foundation of Shanxi Province （Grant No 20031006）.
文摘The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. The calculation of the local density of states shows that new states will emerge between the resonant Wannier-Stark states as a result of the intervention of time-dependent impurity potential, and the increase in electric field strength of impurity will result in the growing of the number of new states between the gaps of neighbouring Stark ladders.
文摘Nano-SrB2O4 powder was prepared by solid-state reaction at room temperature followed by a subsequent calcination process. The highly productive method which can be operated easily confirms to the Green-chemistry principles. The XRD patters demonstrate that the component of the as-obtained sample is SrB2O4 after calcination at 600℃. Differential thermal analysis and thermogravimetriy (DTA/TG) curves suggest the process of dehydration and crystal transition from Sr[B(OH)4]2 to SrB2O4·2H2O. SEM image of SrB2O4 shows that the particles are uniform and spherical with average size of 80 nm in diameter. Furthermore, the mechanism of reaction was discussed. The chemical reaction of the process is assumed to be acid-base neutralization reaction. The water generated from the acid-base neutralization reaction and the release of crystal water from Sr(OH)2·8H2O plays an essential role in the reaction system.
文摘MgB2 with Tc ≈ 40 K, is a record-breaking compound among the s-p metals and alloys. It appears that this material is a rare example of the two band electronic structures, which are weakly connected with each other. Experimental results clearly reveal that boron sub-lattice conduction band is mainly responsible for superconductivity in this simple compound. Experiments such as tunneling spectroscopy, specific heat measurements, and high resolution spectroscopy show that there are two superconducting gaps. Considering a canonical two band BCS Hamiltonian containing a Fermi Surface of π- and σ-bands and following Green’s function technique and equation of motion method, we have shown that MgB2 possess two superconducting gaps. It is also pointed out that the system admits a precursor phase of Cooper pair droplets that undergoes a phase locking transition at a critical temperature below the mean field solution. Study of specific heat and density of states is also presented. The agreement between theory and experimental results for specific heat is quite convincing. The paper is organized in five sections: Introduction, Model Hamiltonian, Physical properties, Numerical calculations, Discussion and conclusions.
文摘近年来,美国一直通过“煤炭优先”计划等推动先进燃煤电厂、先进煤化工等技术和装备的发展,并进一步提高效率、降低与碳捕集相关的成本从而支持“煤+碳捕集、利用与封存(carbon capture,utilization and storage,CCUS)”技术的开发与部署,同时还重点研发从煤及煤基能源等中回收稀土元素的技术。系统梳理了美国煤炭清洁高效利用全过程的研发投入、研发方向和研发机构等情况,结合中国清洁煤技术发展现状,提出在“双碳”目标下发展煤炭清洁高效利用前沿技术的发展建议,可为中国进一步构建绿色低碳、安全高效的现代能源体系提供参考。
