Structural stability of infinite-layer CaCuCO<Subscript>2</Subscript> under high pressure

Since the discovery of high temperature supercon-ductivity by Bednorz et al. in 1986[1], many series of cu- prate superconductors have been synthesized. Critical temperature has been improved continuously. But no verdict has been given upon what mechanism causes su- perconductivity. CaCuO2 conductive layers are the parent structure of the high Tc cuprate superconductors, such as Cu-12 (n-1)n[2], Tl-12(n-1)n[3] and Hg-12(n-1)n[4,5] super- conductor families. In 1988, infinite-layer (Ca0.86S…     

Compression behavior and equation of state of Ni77P23 amorphous alloy

The compression behavior of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using insitu high pressure energy dispersive X-ray diffraction with a syn- chrotron radiation source. The equation of state is determined by fitting the experimental data accord- ing to Birch-Murnaghan equation: -ΔV/V0=0.08606P-3.2×10-4P2 5.7×10-6P3. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa.     

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…     

Stable structure of Zr49Cu44Al7 metallic glass matrix composite with CuZr phase under high pressure up to 40.8 GPa

Ternary Zr₄₉Cu₄₄Al₇ metallic glass matrix composite rods with CuZr nano-phase, exhibiting an elastic strain of 1.6% and a high strength of 1.78 GPa, have been manufactured. The structural evaluation of the ternary metallic glass matrix composite under high pressure has been investigated using angle dispersive X-ray diffraction with a synchrotron radiation source. The investigation shows that the amorphous matrix structure is stable under pressures up to 40.8 GPa at room temperature. No pressure induced CuZr nano-phase disappearing or growing was detected. According to the Bridgeman equation of state, the bulk modulus B ₀ =115.2 GPa has been obtained.     

High pressure effects on the crystal structure and electric conductivity of perovskite like（Ca/Sr）2CuO2Cl2 compounds

The crystal structure stability as well as electric conductance of （Sr/Ca）2CuO2Cl2 compound with K2NiF4 structure was investigated up to 31 GPa using diamond anvil technique. It seems that （Sr/Ca）2CuO2Cl2 is quite stable under pressure but with obvious anisotropic compressibility. The equation of state （EOS） obtained shows relative large bulk modulus.     

Direct observation of the clockwise light-driven rotation of F<Subscript>0</Subscript>F<Subscript>1</Subscript>-ATP synthase complex

The purified thermophilic bacterium PS3 F₁ β _10×His-tag is inserted into the F_oF₁-ATP synthases of chro-matophores isolated from photosynthetic bacteria Rhodo-spirillum rubrum. The studies of biochemical properties of the hybrid chromatophores show that they have both protons-driving capability and photophosphorylation. The fluorescent actin filaments, as a marker of its orientation by video-microscopic experiment, are connected via Maleimido-C₃-NTA to the reconstituted β_10×His-tag of F_oF₁-ATP synthases. The clockwise rotation of F_oF₁-ATP synthases driven by light is observed directly when viewed from the F_o side to F₁. This system should be valuable for further studying the coupling property of F_oF₁-ATP synthase.     

Research on C<Subscript>3</Subscript>N<Subscript>4</Subscript> superhard compound thin film and its application

By combination of DC reactive magnetron sputtering with multiple arcplating, the alternating C₃N₄/TiN compound film is deposited onto HSS. The core level binding energy and the contents of carbon and nitrogen are characterized by X-ray photoelectron spectrum. X-ray diffraction (XRD) shows that compound thin film contains hard crystalline phases of α-C₃N₄ and β-C₃N₄. The Knoop microhardness in the load range of 50, 5–54, 1 GPa is measured. According to acoustic emission scratch test, the critical load values for the coatings on HSS substrates are in the range of 40–80 N. The metal coated with C₃N₄/TiN compound films has a great improvement in the resistance against corrosion. Many tests show that such a coating has a very high wearability. Compared with the uncoated and TiN coated tools, the C₃N₄/TiN coated tools have a much longer cutting life. Foundation item: Supported by the National Natural Science Foundation of China (19875037) Biography: Wu Da-we( (1941-), male, Professor, research direction; thin film and its application.     

Electronic structures and nonlinear optical properties of XAuPH<Subscript>3</Subscript>

The studies on model systems XAuPH3(X-H,F,Cl,Br,I,CN,CH3)have been carried out by using ab intiol HF and DFT B3LYP methods at pseudopotential and double-zeta LANL2DZ level.The results are compared with those of MP2,The properties of the models.i.e.the atomic net charge populations.the frontier molecular orbitals and nonlinear optical(NLO)properties have been investigated under an applied electric field on the basis of optimized structures.The computational results show that for these models characterized as electron acceptor-metal-electron donor(A-M-D)system,the NLO properties are due to intramolecular charge-transfer interaction between the acceptor and the donor.The more charges transfer gives,the better NLO properties.In the selected model systems,IAuPH3 has the biggest βvec and γof 1184.1942 a.u.and 17341.9214 a.u.,whereas IC6H4PH3^ ,A TYPICAL a-π-D organic conjugated system,has βvec and γof 710.7697 and 11664.1405 a.u.respectively.In comparison.IAuPH3 has significant NLO properties.     

Ultrasonic measurements of single-crystal gold under hydrostatic pressures up to 8 GPa in a Kawai-type multi-anvil apparatus

Ultrasonic measurements were conducted on single-crystal gold at ambient condition and hydrostatic pressures up to 8 GPa at room temperature in a Kawai-type multi-anvil apparatus. The P-wave velocities measured at high pressures were in good agreement with Daniels and Smith’s ultrasonic study. The three independent elastic constants of gold at ambient condition were determined to be C11=192.7 GPa, C12=162.9 GPa, and C44=42.4 GPa. On the basis of an analysis of previous elastic data and the present ultrasonic data, the pressure derivatives of three elastic constants were estimated to be C1 ′1= 7.12,C 1′2 = 6.24,and C4′4 = 1.82. The calculated values of isothermal bulk modulus (KT0) and its pressure derivatives ( KT ′0) are KT0 = 166.44 GPa and KT ′0= 6.56. This indicates that Anderson et al.’s model of equation of state of gold might underestimates pressure about 1 GPa at pressure around 23 GPa and ambient temperature. Our results explained the discrepancies among the models of equation of state of gold proposed previously.     

β-Ga2O3的高压原位拉曼光谱

利用金刚石对顶砧（DAC）高压装置产生高压, 在0~23.4 GPa研究β相氧化镓（β-Ga₂O₃）晶体高压原位拉曼光谱. 根据高压拉曼光谱的实验数据, 给出了β-Ga₂O₃晶体拉曼振动频率与压力的关系, 并将外振动谱线144 cm^-1归属于平移模, 169 cm^-1归属于转动模. 在18 GPa附近, 发现两个新的拉曼峰232 cm^-1和483 cm^-1, 由这两个峰的强度随压力的升高逐渐增强可知, β-Ga₂O₃晶体发生了压力导致的结构相变.      

Mineral-phase evolution and sintering behavior of MO-SiO2-Al2O3-B2O3 (M=Ca,Ba) glass-ceramics by low-temperature liquid-phase sintering

In this work, network former SiO₂ and network intermediate Al₂O₃ were introduced into typical low-melting binary compositions CaO·B₂O₃, CaO·2B₂O₃, and BaO·B₂O₃ via an aqueous solid-state suspension milling route. Accordingly, multiple-phase aluminosilicate glass-ceramics were directly obtained via liquid-phase sintering at temperatures below 950℃. On the basis of liquid-phase sintering theory, mineral-phase evolutions and glass-phase formations were systematically investigated in a wide MO-SiO₂-Al₂O₃-B₂O₃ (M=Ca, Ba) composition range. The results indicate that major mineral phases of the aluminosilicate glass-ceramics are Al₂₀B₄O₃₆, CaAl₂Si₂O₈, and BaAl₂Si₂O₈ and that the glass-ceramic materials are characterized by dense microstructures and excellent dielectric properties.     

Catalytic oxidation of phenol in wastewater-A new application of the amorphous Fe78Si9B13 alloy

The amorphous Fe78Si9B13 alloy was used as a heterogeneous Fenton catalyst in the process of phenol degradation.The influences of main operating parameters such as reaction temperature,catalyst amount,hydrogen peroxide dosage and initial pH of solution on phenol degradation rate were investigated.The maximum mineralization of phenol was achieved at 60°C,6 g/L Fe78Si9B13, 0.31 mol/L hydrogen peroxide,with an initial pH of 2.5.More than 99%of phenol was completely removed under the optimum conditions within 10 min for a solution containing 1000 mg/L of phenol.Batch experiments for solutions containing phenol con- centrations ranging from 50 to 2000 mg/L were investigated under the above conditions and the same excellent degradation rate was obtained.The Fe78Si9B13 showed better catalytic activity than iron powder and Fe 2+ .Addition of n-butannol(hydroxyl radical scavenger)decreased the degradation rate of phenol,which demonstrates that hydroxyl radicals were mainly responsible for the removal of phenol.We demonstrated that phenol may be degraded by hydroxyl radicals decomposed by hydrogen peroxide on the surface of Fe78Si9B13 and illustrated the reaction mechanism for this process.This amorphous alloy exhibited high stability in recycling experiments and showed excellent reuse performance even after continuous operations of 8 cycles.     

Phase transition and thermodynamic properties of BaS: An <Emphasis Type="Italic">Ab initio</Emphasis> study

The hydrostatic-pressure-induced transition phase of BaS from the NaCl-type structure (B1) to the CsCl-type structure (B2) is investigated by ab initio plane-wave pseudopotential den-sity functional theory method. It is found that the transition pres-sure from B1 to B2 phases is 8.2 GPa according to the usual con-dition of equal enthalpy. Through the quasi-harmonic Debye model,the dependences of the relative volume V/V0 on the pres-sure P,the thermal expansion parameter ratio on pressure P,and the Debye temperature Θ and heat capacity CV on pressure P and temperature T are estimated.     

Synthesis and modification of well-ordered layered cathode oxide LiNi<Subscript>2/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript>

Oxalic-acid-based co-precipitation method was employed to prepare LiNi_2/3Mn_1/3O₂ sample with a high-ordered structure. Li⁺, Ni²⁺ and Mn²⁺ acetates were used as starting materials. The influence of the amount of lithium source in the starting materials on Li⁺ content, disorder of Li⁺-Ni²⁺ ions, and electrochemical performance has been investigated. Rietveld refinement shows that the sample prepared with 20% excess Li-source in the starting materials exhibits a perfect ordered structure. A specific discharge capacity is as high as 172 mAh/g at C/20 in the voltage range of 4.35–2.7 V. However, the cyclability is not satisfactory: about 25.3% fade in capacity was observed over 50 cycles. Chemically stable SiO2 was coated on the surface of LiNi_2/3Mn_1/3O₂ particles. A significant improvement in cyclability was attained with 3 wt% SiO2 coating, which is ascribable to the protection of LiNi_2/3Mn_1/3O₂ particles from being dissolved into the electrolyte.     

Two-dimensional crystallization and preliminary electron crystallographic result of partially purified F<Subscript>0</Subscript> from porcine mitochondria

After removal of cytoplasmic sector F₁ from submitochondrial particles of F₀F₁-ATP synthase complex with guanidine hydrochloride, the transmembrane sector F₀ was specifically extracted from the stripped membranes in the presence of detergent CHAPS and partially purified. Two-dimensional crystals were produced by the reconstitution of the partially purified F₀ into asolectin and microdialysis. The obtained crystals are able to diffract to 2 nm. The projection map of the negatively stained crystal shows that the crystal has p42₁2 symmetry, lattice constant, a=b=14.4 nm. A unit cell contains four F₀ molecules.     

<Emphasis Type="Italic">Ab initio</Emphasis> study of the effects of Ag/Mn doping on the electronic structure of LiFePO<Subscript>4</Subscript>

Based on density functional theory （DFT） of the first-principle for the cathode materials of lithium ion battery, the electronic structures of Li（Fe1-x）PO4 （Me = Ag/Mn, 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 the Fermi level of mixed atoms Fe1-xAgx moves into its conduction bands （CBs） due to the Ag doping. The Li（Fe1-xAgx）PO4 system displays the periodic direct semiconductor characteristic with the increase of Ag-doped concentration. However, for Fe1-xMnx mixed atoms, the Fermi level is pined at the bottom of conduction bands （CBs）, which is ascribed to the interaction between Mn（3d） electrons and Fe（4s） electrons. The intensity of the partial density of states （PDOS） near the bottom of CBs becomes stronger with the increase of Mn-doped concentration. The Fermi energy of the Li（Fe1-xMnx）PO4 reaches maximum at x = 0.25, which is consistent with the experimental value of x = 0.20. The whole conduction property of Mn-doped LiFePO4 is superior to that of Ag-doped LiFePO4 cathode material, but the structural stability is reverse.     

Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity <Emphasis Type="Italic">V</Emphasis><Subscript><Emphasis Type="Italic">Y</Emphasis></Subscript>

It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B _Z | < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher than that under preceding B _Z ≈ −23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP start to increase, which implies that the magnetosheath field interacting with the Earth’s magnetopause has significantly rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP.     

Preparation and upconversion luminescence of YVO<Subscript>4</Subscript>:Er<Subscript>3+</Subscript>, Yb<Subscript>3+</Subscript>

YVO₄:Er³⁺, Yb³⁺ with varying Yb³⁺ concentrations were prepared by a precipitation method. The results of X-ray diffraction (XRD) show that all the samples have a tetragonal zircon structure; the calculated average crystallite sizes are in the range of 14–22 nm. The lattice constants and cell volume of the samples decrease slightly with the increase in Yb³⁺ concentration. The upconversion luminescence spectra of all the samples were studied under 980 nm laser excitation. The strong green emission is observed, which is attributed to the ²H_11/2 → ⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions of Er³⁺, and the red emission peaks in 650–675 nm can be ignored. The emission intensity for the sample depends on the Yb³⁺ concentration. These results reveal that the upconversion processes of YVO₄:Er³⁺, Yb³⁺ are related to the structure and the doping Yb³⁺ concentration of the sample.     

Microwave sintering of Ca<Subscript>0.6</Subscript>La<Subscript>0.2667</Subscript>TiO<Subscript>3</Subscript> microwave dielectric ceramics

Ca_0.6La_0.2667TiO₃ ceramics were prepared by conventional and microwave sintering techniques and their sinterability, microstructure, and microwave dielectric properties were investigated in detail for comparison. Densified Ca_0.6La_0.2667TiO₃ ceramics were obtained by microwave sintering at 1350°C for 30 min and by conventional sintering at 1450°C for 4 h. An unusual phenomenon was found that some larger grains (grain size range: 8–10 μm) inclined to assemble in one area but some smaller ones (grain size range: 2–4 μm) inclined to gather in another area in the microwave sintered ceramics. The microwave dielectric properties of Ca_0.6La_0.2667TiO₃ ceramics prepared by microwave sintering at 1350°C were as follows: dielectric constant (ɛ _r) = 119.6, quality factor (Qf) = 17858.5 GHz, and temperature coefficient of resonant frequency (τ _f) = 155.5 ppm/°C. In contrast, the microwave dielectric properties of the ceramics prepared by conventional sintering at 1450°C were ɛ _r = 117.4, Qf = 13375 GHz, and τ _f = 217.2 ppm/°C.