Structural and magnetic properties of Sr2Fe1−xGaxMoO6 (0≤x≤0.25)

We have investigated the structure, magnetization and magnetoresistance (MR) of the double perovskite compounds Sr2Fe1−xGaxMoO6 (0≤x≤0.25). Rietveld refinement results show that the anti-site defects (ASDs) concentration increases with x, giving rise to highly disordered samples at the B/B positions, for the highest doping levels. The evolution of bond lengths and ions oxidation states could be understood by the distribution of trivalent Ga ions at the B/B positions, which leads to the formation of more disorder structure. The saturation magnetization and Curie temperature decreased with the Ga content increases in the samples, and their origin was found that the cations disorder for the Ga-doped compounds is annihilating double exchange mechanism due to the presence of significant amounts of Fe and Ga cations on the B site. The low-field magnetoresistance of Sr2FeMoO6 (SFMO) can be greatly enhanced by replacing the Fe by the nonmagnetic Ga ion up to a temperature of 300 K,since Ga ions may act as a barrier for electron transport along the chain in the ferromagnetic segregation and weaken the ferromagnetic exchange.

Biochemical properties of C78SC96S rhFGF-2: A double point-mutated rhFGF-2 increases obviously its activity

Fibroblast growth factor-2 (FGF-2) is a multifunctional polypeptide that affects many cellular functions and phenomena. The wild-type recombinant human fibroblast growth factor rhFGF-2(W) and the mutant C78SC96S rhFGF-2(M) were expressed in Escherichia coli and their products were purified. The results by the means of fluorescence spectroscopy and CD spectrums, suggested that due to its decreased hydrophobicity rhFGF-2 is not deposited as an inclusion body. The mitogenic activity of the expressed rhFGF-2(M) on 3T3 fibroblasts was shown to be 10-fold more than the expressed rhFGF-2(W) of which the biological activity was a little less than that of the standard rhbFGF(W), indicating that the increased biological activity was due to the change of its secondary structure, dimerization and affinity binding to FGF receptor (FGFR).

The thermal cycling behavior of Lanthanum-Cerium Oxide thermal barrier coating prepared by EB-PVD

Bulk material and coatings of Lanthanum-Cerium Oxide (La2Ce2O7) with a fluorite structure were studied as a candidate material for thermal barrier coating (TBC). It has been showed that such material has the properties of low thermal conductivity about four times lower than YSZ, the difference in the thermal expansion coefficient between La2Ce2O7 and bond coat is smaller than that of YSZ in TBC systems, high phase stability between room temperature and 1673 K, about 300 K higher than that of the YSZ. The coating prepared by electron beam physical vapor deposition (EB-PVD) showed that it has good thermal cycling behavior, implying that Such material can be a promising thermal barrier coating material. The deviation of coating composition from ingot can be overcome by the addition of excess La2O3 during ingot preparation and/or by adjusting the process parameters.

Neodymium-cerium oxide as new thermal barrier coating material

Neodymium-cerium oxide (Nd2Ce2O7) was proposed as a new thermal barrier coating material in this work. Monolithic Nd2Ce2O7 powder was prepared by the solid-state reaction at 1400 degrees C. The phase composition, thermal stability and thermophysical properties of Nd2Ce2O7 were investigated. Nd2Ce2O7 with fluorite structure was thermally stable in the temperature range of interest for TBC applications. The results indicated that the thermal expansion coefficient (TEC) of Nd2Ce2O7 was higher than that of YSZ (6-8 Wt-% Y2O3 + ZrO2) and even more interesting was the TEC change as a function of temperature paralleling that of the superalloy bond coat. Moreover, the thermal conductivity of Nd2Ce2O7 is 30% lower than that of YSZ, which was discussed based on the theory of heat conduction. Thermal barrier coating of Nd2Ce2O7 was produced by atmospheric plasma spraying (APS) using the spray-dried powder. The thermal cycling was performed with a gas burner test facility to examine the thermal stability of the as-prepared coating.

Competition between band filling and steric effect in ordered double perovskites Sr2-xLaxMnMoO6

The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2-xLaxMnMoO6(0 <= x <= 1). The compounds have a monoclinic structure (space group P2(1)/n) and the cell volume expands monotonically with La doping. The T-C and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-xLaxMnMoO6 decreases only at low doping levels (x <= 0.2); while at high doping levels (0.8 <= x <= 1), electrical resistivity tends to increase greatly. The results suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.

Preparation, structure and luminescence of BaMAl10O17 : Eu2+ (M = Be, Mg, Ca, Zn, Cd, Mn, Co, Li) system

The BaMA(10)O(17) (M = Be, Mg, Ca, Zn, Cd, Mn, Co, Li) system has been synthesized by solid state method and characterized by XRD. The results show that when M is Mg, Zn, Mn, Co, Li, there exists the structure of beta-Al2O3 for BaMAl10O17 system, and when M indicates Cd, beta-Al2O3 structure is formed accompanying alpha-Al2O3 phase, and when M represents Be and Ca, beta-Al2O3 structure cannot be formed. This demonstrates that the condition forming beta-Al2O3 structure compounds for the system BaMAl10O17 is 0.05nm < R-M < 0.09nm (R-M represents the radius of M). The thought that if a M ion can form a stable spinel structure there exsits a corresponding magnetoplumbite and beta-alumina structure is proposed for BaMAl10O17 system according to the experimental results. When M is Li, Be, Zn, Eu2+ activator produces an emission of nearly 450 nm with half height width about 50 nm, when M is Mn, there are simultaneously the emissions of Eu2+ and Mn2+ and the excitation energy of Eu2+ can transfer to Mn2+ in the host, when M is Cd, Eu2+ displays a double-emission band, which can be explained by the Jahn-Teller's effect. It is possible for the system BaMAl10O17 with M being Li, Be, Zn to become blue-emitting component in three colour lamp through further study.

Synthesis, crystal structure and properties of (Z)-3-triphenylstannyl-1,1-diphenyl propenol

Five new organotin compounds were synthesized and characterized, X-ray crystal structure analysis of (Z)-3-triphenylstannyl-1,1-diphenyl propenol was performed, The crystal belongs to space group P2(1)/n. The cell parameters are: a = 1.235 7(2) nm, b = 0.987 4(2) nm, c = 2.208 1(4) nm, beta = 95.23(3)degrees, V = 2.683 0(9) nm(3), Z = 4, R = 0.027 9, R-w = 0.064 5. The tin atom of the molecule exists in a distorted tetrahedron, Z isomer of double bond is obtained.

The double-melting behavior of poly(ether diphenyl ether ketone)

Poly(ether diphenyl ether ketone) (PEDEK) synthesized by the nucleophilic route has the following chemical structure: [GRAPHICS] At some given temperatures for a given time isothermally crystallized PEDEK sample exhibits two endothermic peaks which are similar to PEEK and PEEKK The melting behavior of PEDEK crystallized from the glassy state is investigated through differential scanning calorimeter (DSC). We consider that the high-melting peak is related to the perfect crystals and the low-melting peak is associated with a few imperfect crystals. (C) 1997 John Wiley & Sons, Inc.

Barrier properties of vinylidene chloride copolymers

The permeability coefficients of a series of copolymers of vinylidene chloride (VDC) with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer) to oxygen and carbon dioxide have been measured at 1.0 MPa and 30 degrees C, while those to water vapor have been measured at 30 degrees C and 100% relative humidity. All the copolymers are semicrystalline. VDC/MA copolymers have lower melting temperature compared with VDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higher than that of VDC/acrylate copolymers with the same VDC content. The barrier property of the copolymers is predominantly controlled by crystallite, free volume fraction, and cohesive energy. The permeability coefficients of VDC/MA copolymers to oxygen, carbon dioxide, and water vapor were successfully correlated with the ratio of free volume to cohesive energy.

Synthesis and characterization of a new double-cubane Mo-Fe-S cluster compound, [NEt(4)](3)[Mo2Fe6S8(mu-OMe)(3)(SPh)(3)Cl-3]

The new double-cubane cluster compound [NEt(4)](3)[Mo2Fe6S8(mu-OMe)(3)(SPh)(3)Cl-3] is synthesized from (NH4)(2)MoS4, FeCl3, Fe powder, S powder, NaSPh and NEt(4)Br in MeOH-DMF, its crystal structure is determined by X-ray crystallography, and results of XPS indicate a valence state of +4 for Mo.

STRUCTURE AND SITE-SYMMETRY INVESTIGATION ON THE HEXAGONAL KCAY(PO4)(2)

A new double phosphate, KCaY(PO4)(2), isostructural with hexagonal LaPO4, is reported. It crystallizes in the hexagonal system with a = 0.6903 nm and c = 0.6331 nm. Its vibrational spectra, IR and Raman spectra showed that the site symmetry of the PO4 anion slightly deviated from D-2 toward C-2.

ALKYLATION OF ISOBUTANE WITH BUTENE OVER LAYERED DOUBLE HYDROXIDE PILLARED HETEROPOLYOXOMETALATE ACID-BASE CATALYSTS

[Si(W2O7)(6)](8-) pillared LDH structure hydroxides were synthesized by the method of restructuring of the thermally decomposed hydrotalcite-like compounds for Zn-Al and Mg-Al oxide systems. [P(W2O7)(6)](8-) pillared Ni-Al LDH structure hydroxide was synt

CRYSTAL-STRUCTURE AND THERMODYNAMIC PARAMETERS OF NYLON-1010

WAXD, SAXS, FTIR, DSC and density techniques have been used to investigate the crystal structure, crystal density rho(c), amorphous density rho(a), equilibrium heat of fusion DELTAH(m)degrees and equilibrium melting temperature T(m)degrees. By extrapolating the straight lines in the FTIR absorbance against density plot to zero intensity, rho(c) and rho(a) were estimated to be 1.098 and 1.003 g/cm3 respectively. The rho(c) obtained was too low in value. From X-ray diffraction patterns of uniaxially oriented fibres, the crystal structure of Nylon-1010 was determined. The Nylon-1010 crystallized in the triclinic system, with lattice dimensions: a = 4.9 angstrom, b = 5.4 angstrom, c = 27.8 angstrom, alpha = 49-degrees, beta = 77-degrees, gamma = 63.5-degrees. The unit cell contained one monomeric unit, the space group was P1BAR, and the correct value of rho(c) was 1.135 g/cm3. The degree of crystallinity of the polymer was determined as about 60% (at RT) using Ruland's method. SAXS has been used to investigate the crystalline lamellar thickness, long period, transition zone, the specific inner surface and the electron density difference between the crystalline and amorphous regions for Nylon-1010. The analysis of data was based upon a one-dimensional electron-density correlation function. DELTAH(m)degrees was estimated to be 244.0 J/g by extrapolation of DELTAH(m)degrees in the plot of heat of fusion against specific volume of semicrystalline specimens to the completely crystalline condition (V(sp)c = 1/rho(c)). Owing to the ease of recrystallization of melt-crystallized Nylon-1010 specimens, the well-known Hoffman's T(m)-T(c) method failed in determining T(m)degrees and a Kamide double extrapolation method was adopted. The T(m)degrees value so obtained was 487 K.

A SIMPLE METHOD FOR PREDICTION OF GAS-PERMEABILITY OF POLYMERS FROM THEIR MOLECULAR-STRUCTURE

A method for the prediction of gas permeabilities (P) through polymers from their chemical structure has been developed on the basis of the ratio of molar free volume to molar cohesive energy, V(f)/E(coh). The permeation of small gas molecules through polymer membranes is dependent on the chain packing density measured by V(f) and segmental motion of polymer chains measured by E(coh). But no simple relationship between P and V(f) or E(coh) alone was found. The permeability data of more than 60 polymers covering 7 orders of magnitude for six gases have been treated with linear regression analysis. All plots of log P vs. V(f)/E(coh) gave good straight lines. It is also found that a linear relationship holds when plotting both the intercepts and slopes of log P vs. V(f)/E(coh) lines against square of the diameters of gas molecules. Therefore, the permeabilities of all the non-swelling gases through a great variety of polymers can be estimated using two correlations above. Moreover, this method is more accurate than others in the literature and may found useful for the selection of gas separation or barrier membrane materials.

急倾斜金属矿体开采岩体移动规律与变形趋势预测研究

Rockmass movement due to mining steep metallic ore body is a considerable question in the surface movement and deformation issue caused by underground mining. Research on coal mining induced rockmass movement and its prediction problem have been performed for a long-term, and have achieved great progress at home and abroad. However, the rockmass movement caused by mining steep metal mine is distinctivly different from coal seam mining.. Existing surface movement laws and deformation prediction methods are not applicable to the rockmass movement caused by mining steep metal mine. So far the home and abroad research to this theory is presently at an early stage, and there isn’t mature theory or practical prediction method, which made a great impact on production. In this paper, the research object—Jinchuan nickel mine, which is typical steep metal mine, characterized by complex geological conditions, developed faults, cracked rockmass, high geostress, and prominent engineering stability problems. In addition, backfill mining method is used in the mine, the features of rockmass movement caused by this mining method are also different from other mining methods. In this paper, the laws of rock mass movement, deformation and destroy mechanism, and its prediction were analyzed based on the collection of data, detailed in-sit engineering geology survey, ground movement monitoring by GPS, theoretical analysis and numerical simulation. According to the GPS monitoring of ground surface movement, ground subsidence basin with apparent asymmetry is developing, the influence scope is larger in the upper faulted block than in the lower faulted block, and the center of ground movement is moving along the upper faulted block direction with increasing depth of mining. During the past half and seven years, the largest settlement has amounted to 1287.5mm, and corresponding horizontal displacement has amounted to 664.6mm. On the ground surface, two fissure belts show a fast-growing trend of closure. To sum up, mining steep metal mine with backfill method also exist the same serious problem of rockmass movement hazards. Fault, as a low intensity zone in rockmass, when it located within the region of mining influence, the change of potential energy mainly consumed in fault deformation associated with rockmass structure surface friction, which is the essence of displacement and stress barrier effects characterized by fault rupture zone. when steep fault located in the tensile deformation region incurred by underground excavation, no matter excavation in hangingwall or in footwall of the fault, there will be additional tensile stress on the vertical fault plane and decrease in the shear strength, and always showing characteristics of normal fault slip, which is the main reason of fault escarpment appeared on the ground surface. The No.14 shaft deformation and failure is triggered by fault activation, which showed with sidewall move, rupture, and break down features as the main form of a concentrated expression of fault effects. The size and orientation of principal stress in surrounding rock changed regularly with mining; therefore, roadway deformation and damage at different stages have different characteristics and distribution models. During the process of mining, low-intensity weak structures surface always showed the most obvious reaction, accompany with surface normal stress decrease and shear strength bring down, to some extent, occurred with relative slide and deformation. Meanwhile, the impact of mining is a relatively long process, making the structure surface effect of roadway deformation and damage more prominent than others under the influence of mining. Roadway surrounding rockmass deformation caused by the change of strain energy density field after excavation mainly belongs to elastic deformation, and the correspondented damage mainly belongs to brittle rupture, in this circumstance, surrounding rockmass will not appear large deformation. The large deformation of surrounding rockmass can only be the deformation associated with structure surface friction or the plastic deformation of itself, which mainly caused by the permanent self-weigh volume force，and long-term effect of mining led to the durability of this deformation Good pitting fill effect and supporting effect of backfill, as well as the friction of rockmass structure surface lead to obvious macro-rockmass movement with long-lag characteristics. In addition, the loss of original intensity and new structure surface arisen increased flexibility in rockmass and fill deformation in structure surface, which made the time required for rockmass potential energy translate into deformation work associated with plastic deformation and structure surface friction consumed much, and to a large extent, eliminated the time needed to do those plastic work during repeated mining, all of which are the fundamental reason of rockmass movement aftereffect more significant than before. Mining steep deposits in high tectonic stress area and in gravity stress area have different movement laws and deformation mechanism. The steep deposit, when the vertical size of the mining areas is smaller than the horizontal size of the orebody, no matter mining in gravity stress area or in high tectonic stress area, they have similar features of ground movement with mining horizontal orebody; contrarily, there will appear double settlement centers on the ground surface under the condition of mining in high tectonic stress area, while there will always be a single center under the other condition. Meanwhile the ground movement lever, scale of mining influence area and macro features of ground movement, deformation and fracture are also different from mining in gravity stress area, and the fundamental reason lies in the impact of orientation of the maximum principal stress on rock movement features in in-site rock stress field. When mining thick and steep deposit, the ground surface movement and deformation characteristic curves are significantly different from excavating the horizontal ore bed and thin steep deposit. According to the features of rockmass movement rate, the development process of mining-induced rockmass movement is divided into three stages: raising stage, steadily stage and gradually decay stage. Considering the actual exploitation situation, GPS monitoring results and macro-characteristics of surface movement, the current subsidence pattern of Jinchuan No.2 mine is in the early stage of development. Based on analysis of surface movement rate, surface subsidence rate increase rapidly when mining in double lever at the same time, and reach its peak until the exploitation model ended. When double lever mining translate into single, production decreased, surface subsidence rate suddenly start to reduce and maintain a relatively low value, and the largest subsidence center will slowly move along with the hangingwall ore body direction with increasing depth of mining, at the same time, the scope and extent of subsidence in footwall ore body will begin magnify, and a sub-settlement center will appear on ground surface, accompanied with the development and closure trend of ground fissure, the surrounding rockmass of shaft and roadway will be confronted to more frequent and severe deformation and failure, and which will have a negative impact on the overall stability of No.2 mine mining. On the premise of continuity of rockmass movement, gray system model can be used in ground rockmass movement prediction for good results. Under the condition of backfill mining step by step, the loose effect of compact status of the hard, broken rockmass led to lower energy release rate, although surrounding rockmass has high elastic energy, loose and damage occurred in the horizontal ore body, which made the mining process safety without any large geological hazards. During the period of mining the horizontal ore body to end, in view of its special “residual support role”, there will be no large scale rockmass movement hazards. Since ground surface movement mainly related to the intensity of mining speed and backfill effect, on the premise of constant mining speed, during the period of mining the horizontal ore body to end, the rate of ground surface rockmass movement and deformation won’t have sudden change.