Collapse of charge ordering in Bi0.5Sr0.5MnO3 by cation disorder： a magnetic and structural investigation

The structure, transport, and magnetic properties of LaxBi0.5.xSr0.5MnO3 （LBSMO） （x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structural analysis showed that the LBSMO crystallized in an orthorhombic perovskite structure with Pbnm space group for x=-0.1 and Imma space group for x=0.4 and the highly polarizable 6s^2 lone pair of Bi^3＋ was the ttming factor for the structural variations. Magnetic studies revealed that the replacement of Bi ions by La ions resulted in the collapse high temperature charge ordering state of BSMO and it order Ferro Magnetically （FM） with Tc around 355 and 330 K for x=0.1 and 0.4, respectively. Both ESR, temperature and field dependant magnetization suggested that there was a coexistence of FM and the paramagnetic phases well below Tc and the FM and CO-AFM phases below 250 K of LBSMO.     

Magnetic and Transport Properties of La0.5-x Ndx Ba0.5 CoO3 Compounds

Substituting effects of Nd for La in La0.5Ba0.5CoO3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular magnetic moment of the mate-rials decreases monotonically with increasing Nd dopant. When Nd content x ≥0.45, a magnetic phase separation appears in the materials. When x ≤0.45, the Curie temperature decreases monotonically with increasing Nd dopant. This is due to the size effects of the rare earth ions. The electric resistance measurements show that in the studied temperature range, the conduction of the materials belongs to the thermo-diffusion conduction below the Curie temperature, while it belongs to the variable range hopping conduction of polarons over the Curie temperature.     

Magnetic Properties of La1-xSrxCoO3 (0≤x≤0.5)

The measurements of temperature dependence of the magnetic susceptibility of La1-xSrxCoO3 perovskite oxides at different Sr doping (0≤x≤0.5) and annealing temperature were presented. For the sample with x=0.1, a shoulder was observed around 150 K, and a peak which is one feature of spin glass appeared around 50 K in the curve of susceptibility versus temperature. The high-temperature(250～420 K)susceptibility fits well with Curie-Weiss law for all samples. Weiss constant and effective magnetic moment were determined and their variations with Sr doping and oxygen annealing condition were obtained. The Weiss constant increases monotonously with Sr content for x>0.2. The values of effective moments were interpreted with the spin state of cobalt ions. Studies on the susceptibilities of the samples with x=0.2 under different preparation temperatures and annealing temperatures show that the rising of sintering temperature and annealing temperature will increase the para-ferromagnetic transition temperature, and reduce the effective moment to normal value. Our result shows that both Co3 and Co4 ions should be in IS state after annealing and the oxygen annealing causes the transition of Co3 spin state from HS to IS.     

Effect of metal doping into Ce0.5Zr0.5O2 on catalytic activity of MnOx/Ce0.5-xZr0.5-xM0.2xOy/Al2O3 for benzene combustion

The research investigated the effect of doping two metals separately or together into Ce0.5Zr0.5O2 on the catalytic activity of MnOx/Ce0.5–xZr0.5–xM0.2xOy/Al2O3 (M=Y, Mn, Y and Mn) for catalytic combustion of benzene. The prepared catalysts were characterized by X-ray diffraction (XRD), surface area analysis, oxygen storage capacity (OSC), and H2-temperature programmed reduction (H2-TPR). Cata-lytic test was performed on a conventional fixed bed flow reactor. The characterization results revealed that Y and Mn ions entered into the ceria-zirconia mixed oxides framework, which improved the textural properties and greatly promoted the MnOx dispersion on the support surface. The complete conversion temperature of benzene on MnOx/Ce0.4Zr0.4Y0.1Mn0.1Oy /Al2O3 was 563 K, and the selectivity of carbon dioxides was 99%. This catalyst could be applied in a wide range of GHSV and wide concentration condition, showing great potential for application.     

Preparation of Mesoporous Ce0.5Zr0.5O2 Mixed Oxide by Hydrothermal Templating Method

Mesoporous Ce0.5Zr0.5O2 mixed oxide with high specific surface area was synthesized under basic condition in the presence of non-ionic surfactant PEG-4000. The effect of synthesis conditions, such as synthesis temperature and the molar ratio of PEG-4000/（[ Ce] ＋ [ Zr] ）, on specific surface area were investigated. The products were characterized by transmission electron microscopy, powder X-ray diffraction, and nitrogen adsorption-desorption measurements, respectively. The results showed that synthesis temperature and the molar ratio of PEG-4000/（[ Ce] ＋ [ Zr] ） had great influence on specific surface area. Under the optimum synthesis conditions, the prepared Ce0.5Zr0.5O2 mixed oxide presented cubic fluorite-type structure and possessed high surface area of 148.6 m2·g^-1 with wormlike pores.     

Silicide Precipitation in Alloy Ti-6AI-5Zr-0.5Mo-0.25Si

Silicide precipitation in the titanium alloy containing by wt pct 6Al-5Zr-0.5Mo-0.25Si (Alloy 685) has been investigated using electron diffraction. The solutionizing temperature for this alloy is 1323 K. It is observed that no resolvable silicide precipitates are present in the alloy as received, furnace cooled from 1323 K and aged at 823 K, or oil quenched from 1323 K and aged at 823 K. Specimen solutionized at 1323 K for 30 minutes followed by water quenching and aging at 923 K for 24 hours shows fine precipitates at boundaries of α′ platelets. Diffraction analysis shows that the fine precipitates belong to two different types of identifiable hexagonal silicides similar to those observed by Floweret al in the ternary Ti-5Zr-0.5Si alloy to be (TiZr)₅Si₃ and another of unknown stoichiometry. However, aging of the water quenched specimens for 24 hours at higher temperatures, 973 K and 1073 K, results in the precipitation of a silicide similar to the latter one. It is analyzed that this silicide has lattice parameters a = 0.70₂ nm and c = 0.36₈ nm. Since aging at 973 K and 1073 K gives rise to precipitation of the same silicide, it is concluded that this is the stable silicide in Alloy 685 in the temperature range investigated.     

Magnetic properties and magnetocaloric effects of manganite (La_0.8Ho_0.2)_2/3Ca_1/3MnO₃ and (La_0.5Ho_0.5)_2/3Ca_1/3MnO₃

We reported the magnetic properties and magnetocaloric effects(MCE) of(La0.8Ho0.2)2/3Ca1/3MnO3 and(La0.5Ho0.5)2/3Ca1/3MnO3 nanoparticles by sol-gel technique.With this method,we were able to obtain the samples with particle diameters ranging from 50 to 200 nm.In the(La1-xHox)2/3Ca1/3MnO3 compound,an external magnetic field induced a magnetic transition from an paramagnetic phase to a ferromagnetic phase above Ts=105-135 K,leading to magnetocaloric effects.The maximum value of ΔSM was 1.19 J/(kg·K) at 100 K and 2.03 J/(kg·K) at 152 K for a magnetic field change of 5 T.Because both samples had large relative cooling power(RCP) and wide δTFWHM,the study on systems with the(La1-xHox)2/3Ca1/3MnO3-related magnetic transitions may open an important field in searching good magnetic materials.     

Age Hardening of the Al0.5CoCrNiTi0.5 High-Entropy Alloy

Al_0.5CoCrNiTi_0.5 high-entropy alloy was synthesized by vacuum arc melting in a copper mold. This alloy was aged at 773 K to 1473 K (500 °C to 1200 °C) for 24 hours to investigate the microstructure and hardness. The hardness of the as-cast alloy is HV743, and it exhibits a dendritic structure, in which dendrite is composed of body-centered cubic (bcc), face-centered cubic (fcc), and σ phases, and interdendrite is an eutectic structure consisting of bcc and order bcc phases. Apparent age hardening appears at 873 K to 1173 K (600 °C to 900 °C), and no age softening occurs even after 1473 K (1200 °C) aging. The age hardening of this alloy is attributed to the transformation of the bcc phase to σ phase. Detailed variations of hardness and the microstructure of aged alloys are reported in this article.     

稀土锰氧化物Nd_(0.5)Sr_(0.4)Ca_(0.1)MnO_3的磁性研究

通过XRD和SQUID研究了Nd_(0.5)Sr_(0.4)Ca_(0.1)MnO_3多晶样品的结构和磁性.研究结果表明,该样品单相性好,空间群为Pbnm,在高温区呈现顺磁性,随着温度降低出现了顺磁-反铁磁的转变,相变温度点-奈尔温度(T_N=200K),当温度低于200K时,铁磁与反铁磁两相共存,温度低于150K时铁磁逐渐消失,直到完全变为反铁磁.     

Activity coefficient of CuO0.5 in alumina saturated iron silicate slags

Activity coefficient of CuO_0.5 was determined in alumina saturated iron silicate slags by equilibrating with pure copper in alumina crucibles at Fe/SiO₂ = 1.34, temperature of 1473 to 1573 K, and P_o2 = 10^-8 to 10^-10 atm. The activity coefficient of CuO_0.5 in the slag increased with alumina content of the slag and decreased with increasing temperature. A linear regression relationship between CuO_0.5 and temperature at a fixed pet AlO_1.5 was derived. The distribution coefficient of copper(R) increased with decreasing temperature, and a linear regression relation obtained for 0 to 16 pet AlO_1.5 was: InR = 3308/T + 0.99.     

Morphology of the Tin Whiskers on the Surface of a Sn-3Ag-0.5Cu-0.5Nd Alloy

Rapid growth of tin whiskers has been observed on the surface of rosette-shaped NdSn₃ intermetallic phase in a Sn-3Ag-0.5Cu-0.5Nd alloy after air storage. It is shown that various cross sections of NdSn₃ rosettes in the solder matrix reveal different morphologies of tin whiskers, which can be classified as four types: long fibers, short fibers, tiny sprouts, and hillocks. The fibrous whiskers and tiny sprouts are found on the surfaces of specimens exposed to air at room temperature and 423 K (150 °C), while hillocks appear only after storage at 423 K (150 °C). In addition, it is observed that, in most cases, each oxidized NdSn₃ intermetallic phase contains only a single whisker at its center. Through metallographic observations and chemical analyses on the cross sections of the oxidized NdSn₃ intermetallics, a “successive compressive stress model” has been proposed to interpret the tin whisker growth on the surface of a rare earth (RE)–containing solder.     

Temperature dependence of yield stress in fe-1.67 at. pct Cu and fe-0.5 at. pct Au

A supersaturated solid solution of 1.67 at. pct Cu in Fe has a lower temperature dependence of the yield stress (prestrained 0.2 pct at 368°K) than pure iron over the temperature range 77° to 298°K. No change in temperature dependence is observed on aging to form copper clusters (1 hr at 475°C) but after precipitation of ε the temperature dependence is the same as in pure iron. The activation volume at 77°K is unaffected by treatment in the alloy and the amount of deformation. The value is essentially the same as in iron. It was suggested that copper clusters present after aging 1 hr as well as dissolved copper assist formation of double kinks at 77°K reducing the stress required to surmount the Peierls barrier. Addition of 0.5 at. pct Au also reduced the temperature dependence of iron. Formerly Graduate Student, Department of Materials Science and Materials Research Center, The Technological Institute, Northwestern University, Evanston, Ill.     

Intercomparison of Humidity and Temperature Sensors:GTS1, Vaisala RS80, and CFH

GTS1 digital radiosonde, developed by the Shanghai Changwang Meteorological Science and Technology Company in 1998, is now widely used in operational radiosonde stations in China. A preliminary comparison of simultaneous humidity measurements by the GTS1 radiosonde, the Vaisala RS80 radiosonde, and the Cryogenic Frostpoint Hygrometer (CFH), launched at Kunming in August 2009, reveals a large dry bias produced by the GTS1 humidity sensor. The average relative dry bias is in the order of 10% below 500 hPa,increasing rapidly to 30% above 500 hPa, and up to 55% at 310 hPa. A much larger dry bias is observed in the daytime, and this daytime effect increases with altitude. The GTS1 radiosonde fails to respond to humidity changes in the upper troposphere, and sometimes even in the middle troposphere. The failure of GTS1 in the middle and upper troposphere will result in significant artificial humidity shifts in radiosonde climate records at stations in China where a transition from mechanical to digital radiosondes has occurred.A comparison of simultaneous temperature observations by the GTS1 radiosonde and the Vaisala RS80 radiosonde suggests that these two radiosondes provide highly reproducible temperature measurements in the troposphere, but produce opposite biases for daytime and nighttime measurements in the stratosphere.In the stratosphere, the GTS1 shows a warm bias (＜0.5 K) in the daytime and a relatively large cool bias (-0.2 K to -1.6 K) at nighttime.     

Effect of Ca and Y additions on oxidation behavior of magnesium alloys at high temperatures

Oxidation and ignition of magnesium alloys at elevated temperature were successfully retarded by additions of Y and Ca,which could be melted at 1173 K in air without any protection.Thermogravimetric measurements in dry air revealed that the oxidation dynamics curves of Mg-2.5Ca alloy and Mg-3.5Y-0.79Ca alloy at high temperatures followed the parabolic-line law or the cubic-line law.X-ray diffraction(XRD) and scanning electron microscopy(SEM) analysis indicated that the oxide film on the surface of Mg-3.5Y-0.79Ca and Mg-2.5Ca alloys exhibited a duplex structure,which agreed with the results of thermodynamic analysis.By comparison,the ignition-proof effect of the combination addition of Y and Ca was better than that of the single addition of Ca.     

The thermal activation energy for fatigue of Fe- 1 pct Cr- 0.5 pct Mo

The temperature dependence of fatigue crack propagation is considered in an Fe-1 pct Cr-0.5 pct Mo alloy steel. This material was tested at temperatures between 425 and 550 °C, a frequency of 1 Hz, and anR-ratio of 0.1. It is shown that the effect of temperature can be explained in terms of a thermal activation energy for fatigue. The magnitude of this activation energy is a function of ΔK and varies from more than 150 kJ/mole at 15 MPa√m to 30 kJ/mole above 30 MPa√m. The magnitude of these activation energies supports the idea that oxidation, and not creep, is the rate-controlling time-dependent process for the test conditions studied.     

Anomalous Magnetic Behavior in Phase-separated La0.5 Sr0.5 MnO3 +δ Films

(001)La0.5 Sr0.5MnO3 δ films on (001)LaA1O3 substrates were prepared by using a RF magnetron sputtering with powder target.At low temperature, the films exhibit two phase coexistence, which means that ferromagnetic (FM) clusters are embedded in antiferromagnetic (AFM) matrix.Moreover, a shift in hysteresis loop is unexpectedly observed in this inhomogeneous system.We suggest that the anomalous hysteresis loop may result from the unidirectional exchange anisotropy at the interface between AFM and FM clusters.     

JTT-501, a novel oral antidiabetic agent, improves insulin resistance in genetic and non-genetic insulin-resistant models

The effects of histamine on the intracellular Ca2+ concentration ([Ca2+]i), action potential and membrane currents were assessed in single atrial myocytes prepared from guinea-pigs. Histamine caused a concentration-dependent increase in the [Ca2+]i transient in indol/AM loaded myocytes when stimulated electrically at 0.5 Hz. However, the maximum increase in [Ca2+]i transient produced by histamine was less than 50% of that elicited by isoprenaline. The histamine-induced increase in [Ca2+]i transient was significantly inhibited by chlorpheniramine, but not by cimetidine. Pretreatment with nifedipine nearly completely suppressed the histamine-induced increase in [Ca2+]i transient. Cyclopiazonic acid did not affect the histamine response. In the whole-cell current-clamp mode of the patch-clamp method, both histamine and isoprenaline prolonged action potential duration (APD) in atrial myocytes. In the presence of Co2+ or nifedipine, the isoprenaline-induced APD prolongation was abolished and an APD shortening effect was manifested, while histamine still increased APD. The APD prolongation elicited by histamine was reversed by chlorpheniramine. In the voltage-clamp mode, the histamine-sensitive membrane current was inwardly rectifying and reversed close to the calculated value of the K+ equilibrium potential. Histamine had no apparent effect on L-type Ca2+ current, in contrast to the pronounced effect of isoprenaline. These results indicate that in guinea-pig atrial myocytes stimulation of H1-receptors with histamine does not directly activate Ca2+ channels but causes an elevation of [Ca2+]i transient by increasing Ca2+ influx through the channels during the prolonged repolarization of action potentials resulting from inhibition of the outward K+ current.     

Processing and characterization of Ti2AlC, Ti2AlN, and Ti2AlC0.5N0.5

In this article, we report on the fabrication and characterization of Ti₂AlC, Ti₂AlN, and Ti₂AlC_0.5N_0.5. Reactive hot isostatic pressing (hipping) at ≈40 MPa of the appropriate mixtures of Ti, Al₄C₃ graphite, and/or AlN powders for 15 hours at 1300 °C yields predominantly single-phase samples of Ti₂AlC_0.5N_0.5, 30 hours at 1300 °C yields predominantly single-phase samples of Ti₂AlC. Despite our best efforts, samples of Ti₂AlN (hot isostatic pressed (hipped) at 1400 °C for 48 hours) contain anywhere between 10 and 15 vol pct of ancillary phases. At ≈25 μM, the average grain sizes of Ti₂AlC_0.5N_0.5 and Ti₂AlC are comparable and are significantly smaller than those of Ti₂AlN, at ≈100 μm. All samples are fully dense and readily machinable. The room-temperature deformation under compression of the end-members is noncatastrophic or graceful. At room temperature, solid-solution strengthening is observed; Ti₂AlC_0.5N_0.5 is stronger in compression, harder, and more brittle than the end-members. Conversely, at temperatures greater than 1200 °C, a solid-solution softening effect is occurring. The thermal-expansion coefficients (CTEs) of Ti₂AlC, Ti₂AlN, and Ti₂AlC_0.5N_0.5 are, respectively, 8.2 × 10⁻⁶, 8.8 × 10⁻⁶, and 10.5 × 10⁻⁶ °C⁻¹, in the temperature range from 25 °C to 1300 °C. The former two values are in good agreement with the CTEs determined from high-temperature X-ray diffraction (XRD). The electrical conductivity of the solid solution (3.1 × 10⁶ (Θ m)⁻¹) is in between those of Ti₂AlC and Ti₂AlN, which are 2.7 × 10⁶ and 4.0 × 10⁶ Θ ⁻¹ m⁻¹, respectively.     

溶胶-凝胶法制备片式电感用纳米Ni0.5Zn0.5Fe2O4铁氧体材料

研究了溶胶凝胶法制备Ni0.5Zn0.5Fe2O4粉体过程中,原料浓度、PH值和反应温度等因素对最终产物性能的影响,确定出较佳的制备条件;以此条件制备的镍锌铁氧体粉末经X射线衍射分析,证明为尖晶石相,其平均晶粒度小于26nm;对生产浆料的工艺进行了探索,取得一定进展。