Structure properties for the superconductor MgCNi3 under high pressure with synchrotron radiation

The recent discovery of superconductivity at 39 K in the superconductor MgB2[1] shows that intermetallic compounds with simple structure types are worth serious reconsideration as sources of new superconducting mate-rials. Subsequent to this discovery, He et al. observed a new intermetallic superconductor MgCNi3[2] at about 8 K. The perovskite crystal structure for MgCNi3 is shown in Fig. 1, with the atomic positions: Mg: 1a (0,0,0), C: 1b (0.5,0.5,0.5) and Ni: 3c (0,0.5,0.5). This mater…     

[Zn(bim)2]·(H2O)1.67: A metal-organic open-framework with sodalite topology

Considerable efforts have been focused on the crystal engineering of the supramolecular architectures with desired properties such as zeolitic, magnetic and electric conducting materials[1—3]. But crystal engineering is still a great challenge to the chemists since lack of control over the coordination modes of metal centers and ligands during assembly of extended structures[4]. Some successful synthetic strategies based on topologic control of building blocks have been developed especially i…     

Archaeal acylamino acid releasing enzyme/lipase:Crystallization and preliminary crystallographic analysis in a new crystal form

A primitive orthorhombic crystal form of acylamino acid releasing enzyme‘lipase(APE1547)from hyperthermophilic archaeon Aeropyrum pernix strain K1 has been obtained at 291K.The diffraction pattern of the crystal extends to 0.27nm resolution at 100K using Cu Kαradiation.The crystal belongs to the space group P212121 with unit cell dimensions of b=6.399,b=10.439and c=16.953nm.The presence of two molecules per asymmetric unit gives a crystal volume per protein mass(Vm)of 0.0022nm^3 Da^-1 and a solvent content of 43% by volume.A full set of X-ray diffraction data were collected to 0.3nm from the native crystal.     

Forming mechanism of refined granular crystalline of Cu70Ni30 alloy by undercooled solidification

Moth glass fluxing and cyclic superheating techniques were adopted to effectively uudercool the Cu₇₀Ni₃₀ alloy in vacuum. Within the undercooling range of 21 K to 270 K, the microstructure evolution ol the alloy was investigated. When the inell was undercooled to △T > △T', (210 K) , the grain refinement took place abruptly, liascd on the observation of the solidified microstructure, the rnierocheinieal-analysis and the calculated results with UCT model, it is found that the secondary grain refinement mechanism consists of two stages. The dendrite is, firstly, broken into hag-ments owing to the stress caused by uneven shrinking during rapid solidilication, then the fragments, under the driving force of surface and strain energies, merge through the migration of l>ouinlaries, i. c. recryslallization, thus leading to the formation of secondary granular-crystalline .     

METALLIC PHASE AND INSULATING CHARACTER OF ALKALI-EARTH METAL DOPED C60①

The three dimensional EHMO crystal orbital calculations for crystalline Ba6 C60,Ca3 C60 and Ca5 C60 are reported. The ground state of partially doped Ca3 C60 is found to be insulating with an indirect energy gap of 0. 5eV. In contrast, the. Cas C60 forms a metallic conducting phase with a set of three half - filled bands crossing the Fermi level which is Found to locate close to a peak of the density of state. The character of crystal orbitals near the Fermilevel for both Ca3 C60 and Ca5 C60 is completely carbon - like. In both cases the Ca3 atoms are almost fully ionized and C60 molecules form a stable negative, charge state with six to ten additional electrons. The conductivity of Ba6 C60 is resute.4 from the incomplete charge tranfer. The valance charge of every Ba ion is about 0. 33. The total charge tranfer of six Ba atoms is almost the same as that of five Ca atoms.     

Fabrication of MgB2 superconducting films by different methods

MgB₂ superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL₂O₃ substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density J_c of 10⁷ A/cm² at 15 K in zero field for the thin film and of 10⁵ A/cm² for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100 μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.     

Fabrication of MgB2 superconducting films by different methods

MgB₂ superconducting films have been successfully fabricated on single crystal MgO(111) and c-AL₂O₃ substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K, while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density J_c of 10⁷ A/cm² at 15 K in zero field for the thin film and of 10⁵ A/cm² for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100 μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.     

Non-catalytic nucleation coating for undercooled Cu50Ni50 melt

A non-catalytic nucleation coating (B-F3) was prepared by the high temperature curing process of the sol-gel glass film based on the viscous flow mechanism of the coating. X-ray diffraction technology was adopted to study the crystallization behavior of the coating as a function of treating temperature. It was evident that no crystallization phenomenon happened on the coating which kept stable after the heat treatment of 60 min at 1773 K. The purified melt of Cu₅₀Ni₅₀ was selected to evaluate the effectiveness of undercooling heredity of the coating in the undercooling experiments. The maximum undercooling of the melt solidified in the coated mold could reach 236 K. Based on the solidified microstructural evolution at different undercoolings, a single crystal of the alloy Cu₅₀Ni₅₀ was achieved with no aid of the selection process of the crystal in the mold with the B-F3 coating by means of undercooling technology.     

Thermodynamic analysis and preparation of β-SiC/ZrO2 composites

A predominance area diagram for the Zr-Si-C-O system at 1773 K was plotted according to correlative thermodynamic data. β-SiC/ZrO₂ composites were prepared based on the phase diagram by carbothermal reduction of zircon (ZrSiO₄) in argon atmosphere. Zircon and carbon black were mixed according to the C/ZrSiO₄ mass ratio of 0.2, and with 0, 1wt% and 2wt% extra addition of La₂O₃. Phase evolution of the mixture was investigated at 1723-1803 K by X-ray powder diffraction, and the microstructure of the product prepared at 1803 K for 4 h was examined by scanning electronic microscope. The results show that the decomposition of ZrSiO₄ and the formation of β-SIC can be promoted by increasing the heating temperature and adding La₂O₃. The β-SiC/ZrO₂ composites can be prepared at 1803 K for 4 h in a mixture of zircon, carbon black and La₂O₃, and the contents of β-SIC and m-ZrO₂ in the product sample with 2wt% La₂O₃ reach the highest values of 10.8wt% and 89.2wt%, respectively. The crystal size of the products is about 200 nm.     

Different climatic controls of soil δ 13Corg in three mid-latitude regions of the Northern Hemisphere since the Last Glacial period

Paleoecological records of soil δ^13Corg from three regions in the middle latitudes of the Northern Hemisphere, including the Chinese Loess Plateau （CLP）, the Great Plains and adjacent areas of North America and northwestern Europe, showed different variations since the Last Glacial period. An attempt was made to evaluate the causes for the difference in δ^13Corg on the basis of the modern climatic data collected in these regions and of the modern C3 and C4 plant distributions. The analysis indicates that temperature, especially the growing season temperature, has a dominant control on the growth of C4 plants. When the mean annual or growing season temperatures are below the ＂threshold value＂, the growth of C4 plants is limited. When the temperature is above the ＂threshold value＂, C4 plants can grow under a wide range of precipitation. However, when the precipitation is high enough to favor the growth of trees, the proportions of C4 plants in local biomass will decline. The implicit control factor recovered by sedimentary records is consistent with the control factor on modern C3/C4 distribution. Pure C3 plants have been dominating the local biomass since the Last Glacial period in European loess region, mainly owing to the low local temperature. The increases in C4 plants from the late Pleistocene to the Holocene in the Chinese Loess Plateau, the Great Plains and adjacent areas, mainly reflect the influence of increasing temperature.     

Multiferroic and magnetoelectric properties of La0.1Ba0.9Fe12O19 ceramics

La0.1Ba0.9Fe12O19 powders with similar hexagonal crystal structure to Ba Fe12O19 have been successfully synthesized using polymer precursor method. The powders were suppressed into pellets, which were sintered into ceramics at 1,300 °C for 1 h. The structure and morphology of the ceramics have been determined by X-ray diffraction（XRD） and field emission scanning electron microscopy（FESEM）. Clear electric hysteresis loops upon different amplitude of external fields indicates that La0.1Ba0.9Fe12O19 is a kind of possible ferroelectric compound. The maximum remnant polarization of La0.1Ba0.9Fe12O19 ceramic is estimated to be ＊9.6 l C/cm2. The Fe O6 octahedron in its perovskite-like hexagonal unit cell as well as the shift of Fe3？off the center of octahedron are proposed to be the origin of electric polarization in La0.1Ba0.9Fe12O19. Simultaneous occurrence of large ferroelectricity and strong ferromagnetism has been observed in La0.1Ba0.9Fe12O19 ceramics. More interestingly, this compound demonstrates electronic polarization behavior being actuated by an applied magnetic field, indicating the existence of magnetoelectric（ME） coupling effect in the La0.1Ba0.9Fe12O19 ceramics. Our results may lead to new device applications such as magnetically recorded ferroelectric memory.     

Structural and Chemical Diversity of Tl－Based Cuprate Superconductors

The Tl-based cuprate superconductor family is the largest family in crystal structure and chemical composition among all high Tc cuprate superconductors. The Tl family can be divided into two sub-families, the Tl single layer family and the Tl double layer family, based on their crystal structural characteristics. The Tl single layer family is an ideal material for investigating the evolution of crystalline formation, charge carrier density, chemical composition, transport properties, superconductivity and their relationships. The Tl family contains almost all possible crystal structures discovered in high-Tc cuprate superconductors. Tl cuprate superconductors are of great importance not only in studying high-temperature superconductivity but also in commercial applications.     

具有改善四环素降解活性的(GO/TiO2)N一维光子晶体光催化剂的设计

(GO/TiO₂)_N (GO represents graphene oxide, and N represents the period number of alternate superposition of two dielectrics) one-dimensional photonic crystal with different lattice constants was prepared via the sol–gel technique, and its transmission characteristics for photocatalysis were tested. The results show that the lattice constant, filling ratio, number of periodic layers, and incident angle had effects on the band gap. When the lattice constant, filling ratio, number of periodic layers, and incident angle were set to 125 nm, 0.45, 21, and 0°, respectively, a gap width of 53 nm appeared at the central wavelength (322 nm). The absorption peak of the photocatalyst at 357 nm overlapped the blue edge of the photonic band gap. A slow photon effect region above 96% reflectivity appeared. The degradation rate of tetracycline in (GO/TiO₂)_N photonic crystal was enhanced to 64% within 60 min. Meanwhile, the degradation efficiency of (GO/TiO₂)_N one-dimensional photonic crystal was effectively improved compared with those of the GO/TiO₂ composite film and GO/TiO₂ powder.     

不同结构和形态的天然镁硅酸盐:与K反应制备生物柴油的K2MgSiO4催化剂

In this work, different magnesium silicate mineral samples based on antigorite, lizardite, chrysotile (which have the same general formula Mg₃Si₂O₅(OH)₄), and talc (Mg₃Si₄O₁₀(OH)₂) were reacted with KOH to prepare catalysts for biodiesel production. Simple impregnation with 20wt% K and treatment at 700–900°C led to a solid-state reaction to mainly form the K₂MgSiO₄ phase in all samples. These results indicate that the K ion can diffuse into the different Mg silicate structures and textures, likely through intercalation in the interlayer space of the different mineral samples followed by dehydroxylation and K₂MgSiO₄ formation. All the materials showed catalytic activity for the transesterification of soybean oil (1:6 of oil : methanol molar ratio, 5wt% of catalyst, 60°C). However, the best results were obtained for the antigorite and chrysotile precursors, which are discussed in terms of mineral structure and the more efficient formation of the active phase K₂MgSiO₄.     

Mn0.8Zn0.2Fe2O4 nanoparticulates spinel ferrites:An approach to enhance the antenna field strength for improved magnitude versus offset（MVO）

Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about the presence of hydrocarbon in seabed logging(SBL) environment.In the present work,Mn0.8Zn0.2Fe2O4 nanoferrites were prepared by a sol–gel technique at different sintering temperatures of450 °C,650 °C and 850 °C to increase the strength of electromagnetic(EM) antenna.XRD,FESEM,Raman spectroscopy and HRTEM were used to analyze the phase,surface morphology and size of the nanoferrites.Magnetic properties of the nanoferrites were also measured using an impedance network analyzer.However,nanoferrites sintered at 850 °C with initial permeability of 200 and Q factor of 50 were used as magnetic feeders with the EM antenna.Lab scale experiments were performed to investigate the effect of magnetic field strength in scale tank.SPSS and MATLAB softwares were also used to confirm the oil presence in scale tank.It was observed that the magnitude of the EM waves for the antenna was increased up to 233%.Finally,the correlation values also show 208% increase in the magnetic field strength with the presence of the oil.Therefore,antenna with Mn0.8Zn0.2Fe2O4 nanoferrites based magnetic feeders can be used for deep water and deep target hydrocarbon exploration.     

Effect of cooling rate on the crystallization behavior of perovskite in high titanium-bearing blast furnace slag

The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace (BF) slag was studied using confocal scanning laser microscopy (CSLM). Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O2?, when Ti₂O₃ was involved in the formation of perovskite.     

Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating

A wear resistant Cr₇C₃/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr₇C₃ primary particles uniformly distributed in the γ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr₇C₃/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr₇C₃/γ-Fe ceramal composite coating is attributed to the coating’s high hardness, strong covalent atomic bonding and refined microstructure.     

Microstructure and wear resistance of PTA clad Cr7C3/γ-Fe ceramal composite coating

A wear resistant Cr₇C₃/γ-Fe ceramal composite coating was fabricated on substrate of the hardening and tempering C degree steel by PTA (plasma transferred arc) cladding with (wt%) Fe-25Cr-7C elemental powder blends. Microstructure of the coating was characterized by OM, SEM, XRD and EDS. Wear resistance of the coating was tested under dry sliding wear condition at room temperature. The results indicate that the PTA clad ceramal composite coating has a rapidly solidified fine microstructure consisting of Cr₇C₃ primary particles uniformly distributed in the γ-Fe matrix and is metallurgically bonded to the C degree steel substrate. The PTA clad Cr₇C₃/γ-Fe ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test conditions. The excellent wear resistance of the Cr₇C₃/γ-Fe ceramal composite coating is attributed to the coating’s high hardness, strong covalent atomic bonding and refined microstructure.     

Creep behavior and dislocation mechanism of Ni3Al based single crystal alloy IC6SX at 760℃

The creep behavior and dislocation mechanism of Ni₃Al-based single crystal alloys IC6 SX with crystal orientation[001] which was prepared by seed crystal method under the testing conditions of 760℃/500 MPa,760℃/540 MPa and 760℃/580 MPa were investigated. The experimental results showed that the creep properties,dislocation morphology and mechanism of this alloy were different under different stress conditions. With the stress increasing from 500 MPa to 580 MPa, the creep life decrease...     

The research and progress of micro-fabrication technologies of two-dimensional photonic crystal

The novel material of photonic crystal makes it possible to control a photon, and the photonic integration will have breakthrough progress due to the application of photonic crystal. It is based on the photonic crystal device that the photonic crystal integration could be realized. Therefore, we should first investigate photonic crystal devices based on the active and the passive semiconductor materials, which may have great potential application in photonic integration. The most practical and important method to fabricate two-dimensional photonic crystal is the micro-manufacture method. In this paper, we summarize and evaluate the fabrication methods of two-dimensional photonic crystal in near-infrared region, including electron beam lithography, selection of mask, dry etching, and some works of ours. This will be beneficial to the study of the photonic crystal in China.