Research on effects of hydrostatic pressure on the dielectric property of Pb(Zn<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3−</Subscript>BaTiO<Subscript>3−</Subscript> PbTiO<Subscript>3</Subscript> relaxor ferroelectric ceramics

The dielectric properties of Pb(Zn1_1/3Nb_2/3)O₃₋ BaTiO₃₋PbTiO₃ relaxor ferroelectric ceramics near the rhombohedral and tetragonal phase boundary were investigated under hydrostatic pressure. It was found that hydrostatic pressure made their phase transition temperature T _c and the peak temperature T _m decreased, and the frequency dispersion and relaxor behavior enhanced. In these disorder systems of composite pervoskite structures, there appeared polar clusters or nanodomains. The unique physical characteristics, which made the relaxor behavior enhanced, is that the correlation length among these nanodomains decreases greatly with the pressure increasing.     

Modification of MgO·Al<Subscript>2</Subscript>O<Subscript>3</Subscript> spinel inclusions in Al-killed steel by Ca-treatment

The modification of MgO·Al₂O₃ spinel inclusions in Al-killed steel by Ca-treatment has been studied by industrial trials and thermodynamic calculations. In the industrial trials, samples were taken systematically during the refining process in which the molten steel was treated by calcium, and the characters of the inclusions were analyzed using scanning electron microscopy (SEM) and energy dispersive spectra (EDS). The effects of Ca-treatment were evaluated by tracking the compositions of the inclusions. The results show that the modification of MgO·Al₂O₃ spinel inclusions by Ca-treatment is effective and the transformation sequence of the inclusions during the refining is Al₂O₃→MgO·Al₂O₃→liquid complex inclusions. The modification of spinel inclusions by Ca-treatment was calculated by FactSage6.0 utilizing its free-energy minimization routines. The results of thermodynamic calculations indicate that spinel inclusions are easier to be modified than Al₂O₃ inclusions and the spinel inclusions in 30CrMo steel would transform to liquid complex inclusions when the content of dissolved Ca in the molten steel exceeds 1×10⁻⁶. Also, the results show that adding more calcium into the molten steel would lower the contents of Al₂O₃ and MgO and increase the CaO content of the inclusions, while the change in SiO₂ content is little.     

Crystal structure and negative thermal expansion of solid solution Lu<Subscript>2</Subscript>W<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript>Mo<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>12</Subscript>

A new series of solid solutions Lu₂W_3−x Mo _x O₁₂ (0.5≤x≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth tungstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients (TEC) of Lu₂W_3−x Mo _x O₁₂ are determined as −20.0×10⁻⁶ K⁻¹ for x=0.5 and −16.1×10⁻⁶ K⁻¹ for x=2.5 but -18.6×10⁻⁶ and −16.9×10⁻⁶ K⁻¹ for unsubstituted Lu₂W₃O₁₂ and Lu₂Mo₃O₁₂ in the identical temperature range of 200 to 800°C. High-temperature X-ray diffraction (XRD) data and bond length analysis suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.     

Synthesis of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript>/Au magnetic composites for immobilization of bovine serum albumin

A method for the two-step synthesis of magnetic composites with a γ-Fe₂O₃ core, silica inner layer and numerous gold nanoparticles supported on the surface of the silica (γ-Fe₂O₃/SiO₂/Au) is described. First, thiol-functionalized γ-Fe₂O₃/SiO₂ composites and gold colloids are prepared by modifying γ-Fe₂O₃/SiO₂ composites with mercaptosilane and reduction of Au³⁺ to Au⁰ with citrate, respectively. Gold nanoparticles are then assembled on the surface of the thiol-functionalized γ-Fe₂O₃/SiO₂ composites to form γFe₂O₃/SiO₂/Au composites. The structure of the composite particles is confirmed by transmission electronic microscopy and powder X-ray diffraction. Immobilization studies with bovine serum albumin (BSA) demonstrate that the γ-Fe₂O₃/SiO₂/Au composites can be used to immobilize BSA, making them useful for biomedical and biological applications.     

Catalytic removal of <Emphasis Type="Italic">tert</Emphasis>-butyldimethylsilyl (TBS) and tetrahydropyranyl (THP) groups from protected alcohols by NO<Superscript>+</Superscript>BF<Subscript>4</Subscript><Superscript>−</Superscript> in methanol

An effective, catalytic method has been developed to remove TBS and THP groups from protected alcohols. TBS and THP ethers were selectively cleaved using a catalytic amount of NO⁺BF₄^– (5 mol%) in methanol at room temperature.     

Preparation and thermal stability of Pd<Subscript>40.5</Subscript>Ni<Subscript>40.5</Subscript>Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>P<Subscript>19−<Emphasis Type="Italic">x</Emphasis></Subscript> bulk metallic glasses

With the addition of Si to replace some P, Pd_40.5Ni_40.5Si _x P_19−x (x=0, 2.5, 5, 9.5, 14, and 19 in atomic number fraction) bulk glassy samples with the diameter of about 5 mm were successfully prepared by use of flux treatment and water quenching technology. With the increase of Si content, the glass forming ability of Pd_40.5Ni_40.5Si _x P_19−x increases first for low Si content and then decreases for high Si content (Si≥9.5at%). The Pd_40.5Ni_40.5Si ₅ P₁₄ glassy alloy possesses the largest supercooled liquid region ΔT of 119 K, the largest reduced glass transition temperature of 0.621, and the largest γ parameter of 0.460, indicating that this glassy alloy possesses very large glass forming ability and very high thermal stability.     

Thermodynamic analysis on the formation mechanism of MgO·Al<Subscript>2</Subscript>O<Subscript>3</Subscript> spinel type inclusions in casing steel

MgO·Al₂O₃ spinel type inclusions in casing steel were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that there are three forms. One is pure MgO·Al₂O₃ spinel, another is the composite oxide of the Mg-Al-Ca-Si-O system, and the third is the complex with oxide as a core covered by sulfide. The formation mechanisms were studied. The influences of slag basicity and vacuum degree on the magnesium content during the vacuum treatment of molten steel and furnace lining in molten steel were calculated with the coexistence theory of slag structure. The results show that the magnesium content increases with the increase in slag basicity and aluminum content in molten steel, and decreases with the increase in CO partial pressure.     

Effect of Mg content on the structural and optical properties of Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>O alloys

Mgx Zn1–x O thin films with x = 0, 0.11, 0.28, 0.44, 0.51, and 0.65 were grown by plasma-assisted molecular beam epitaxy on (0001) sapphire substrates. X-ray diffraction measurement reveals that phase separation of the Mgx Zn1–x O films occurred at x =0.44 and 0.51. Optical absorption spectra show that the absorption edges of the films shift to high-energy side with increasing Mg contents. In resonant Raman spectra, multiple-order Raman peaks originating from ZnO-like longitudinal optical phonons were obser...     

First principles studies on the electronics structures of (Li<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Me<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)FePO<Subscript>4</Subscript> (Me=Na and Be)

Based on density functional theory (DFT) of the first-principle for cathode materials of lithium ion battery, the electronic structures of (Li_1?x Me _x )FePO₄ (Me=Na and Be, x=0–0.40) are calculated by plane wave pseudo-potential method using Cambridge serial total energy package (CASTEP) program. The calculated results show that Li-site doping can improve the electronic conductivity enormously. Doping with Na has a noticeable effect on improving its electrical conductivity. However, serious structural distortion will occur when its doping density is beyond 0.25. In view of this, the best density of doping Na is less than 0.25. Doping with Be has an inconspicuous effect on increasing its electrical conductivity and has good cyclical stability, but it cannot achieve as good results as when it is doped with Na. Therefore we cannot find a middle ground between the two proposals. Considering cost and environmental protection, it is ideal to choose Na. So this method gives a reasonable prediction to the improvement of electronic conductivity through Li-site doping in LiFePO₄ material.     

Second organic aerosol formation by irradiation of α-pinene-NO<Subscript>x</Subscript>-H<Subscript>2</Subscript>O in an indoor smog chamber for atmospheric chemistry and physics

Ozone（O3） and secondary organic aerosol （SOA） are considered to be the most serious secondary air pollutants of concern in most metropolitan areas, as well as for Beijing. In this study, 03 and SOA formation potential of α-pinene, the most abundant biogenic VOCs, is investigated at Tsinghua Indoor Chamber Facility. The experiments were conducted under atmospheric relevant HCs/NOx ratios in both presence and absence of ammonia sulfate seed aerosol. A Scanning Mobility Particle Sizer system （3936, TSI） and a Condensation Particle Counter （3010, TSI） were used to study the SOA formation and a gas chromatograph （GC） equipped with a DB-5 column and a flame ionization detector （FID） was used to measure α-pinene simultaneously. The results show that the presence of ammonia sulfate seed aerosol did not change the formation trend of 03, but significantly contribute to SOA formation. A strong linear relationship （r^2 = 0.90） between SOA yield enhancement （△Y＊） and surface concentration of seed aerosol （PM1, s）has been found, denoting that the PMi, s is the control factor for SOA yield enhancement. And the possible reason for the enhancement is acid-catalyzed heterogeneous reactions.     

Crystal structure, magnetic and photoelectric properties of coordination polymer[ Co2（C3H4N2）4（ C10H2O8） ]n

The coordination polymer is designed and synthe-sized through the choice of organic ligand and coordina-tion geometry of metal ion as well as the control over theinfinite network topology structure, which usually con-tains both the characteristic of the organic molecules andmetal ions. So, it exhibits more singular function and haspotential application in optics, electrics, information, ca-talysis, medicament, metallurgy, novel material and lifesciences fields. And it has been the confluence m…     

Alternative synthetic route for the heterometallic CO-releasing [Sb@Rh12(CO)27]3− icosahedral carbonyl cluster and synthesis of its new unsaturated [Sb@Rh12(CO)24]4− and dimeric [{Sb@Rh12Sb(CO)25}2Rh(CO)2PPh3]7− derivatives

The evolution of the optical absorption spectrum of bimetallic Ag-Au monolayer-protected clusters (MPC) obtained by progressively doping Ag into the experimentally known structure of Au133(SR)52 was predicted via rigorous time-dependent density-functional theory (TDDFT) calculations. In addition to monometallic Au133(SR)52 and Ag133(SR)52 species, 5 different (Ag-Au)133(SR)52 homotops were considered with varying Ag content and site positioning, and their electronic structure and optical response were analyzed in terms of Projected Density Of States (PDOS), the induced or transition electron density, and Transition Component Maps (TCM) at selected excitation energies. It was found that Ag doping led to the effects rather different from those encountered in bare metal clusters. And it was also observed that Ag doping could produce structured spectral features, especially in the 3–4 eV range but also in the optical region if Ag atoms were located in the sub-staple region, as rationalized by the accompanying electronic analysis. Additionally, Au doping into the staples of Ag-rich MPC also gave rise to a more homogeneous induced electron density. These findings show the great sensitivity of the electronic response of MPC nanoalloy systems to the exact location of the alloying sites.