Phase relations in the system SrO-Y2O3-CuO-O2 and CaO-Y2O3-CuO-O2 at 1173 K

Phase relations in the systems SrO-Y2O3-CuO-O2 and CaO-Y2O3-CuO-O2 at 1173 K were established by equilibrating different compositions in flowing oxygen gas at a pressure of 1.01 × 105 Pa. The quenched samples were examined by optical microscopy, X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), and electron spin resonance (ESR). In the system SrO-Y2O3-CuO-O2, except for the limited substitution of Y3+ for Sr2+ ions in the ternary oxide Sr14Cu24O41, no new quaternary phase was found to be stable. The compositions corresponding to the solid solution Sr14−xYxCu24O41 and the compound SrCuO2+δ lie above the plane containing SrO, Y2O3, and CuO,displaced towards the oxygen apex. However, in the system CaO-Y203-CuO-O2 at 1173 K, all the condensed phases lie on the plane containing CaO, Y203, and CuO, and a new quaternary oxide YCa2Cu306.s is present. The quaternary phase has a composition that lies at the center of the nonstoichiometric field of the analogous phase YBa2Cu307_~ in the BaO-Y203-CuO-O2 system. The compound YCa2Cu306.s has the tetragonal structure and does not become superconducting at low temperature. Surprisingly, phase relations in the three systems CaO-Y203-CuO-O2, SrO-Y203-CuO-O2, and BaO-Y203-CuO-O2 are found to be quite different.

Gibbs energy of formation of CaCu3Ti4O12 and phase relations in the system CaO-CUO/CU2O-TiO2

he standard Gibbs energy of formation of CaCu3Ti4O12 (CCTO) from CaTiO3, CuO and TiO2 has been determined as a function of temperature from 925 to 1350 K using a solid-state electrochemical cell with yttria-stabilized zirconia as the solid electrolyte. Combining this result with information in the literature on CaTiO3, the standard Gibbs energy of formation of CCTO from its component binary oxides, CaO, CuO and TiO2, has been obtained: View the MathML source (CaCu3Ti4O12)/J mol−1 (±600) = −125231 + 6.57 (T/K). The oxygen chemical potential corresponding to the reduction of CCTO to CaTiO3, TiO2 and Cu2O has been calculated from the electrochemical measurements as a function of temperature and compared on an Ellingham diagram with those for the reduction of CuO to Cu2O and Cu2O to Cu. The oxygen partial pressures corresponding to the reduction reactions at any chosen temperature can be read using the nomograms provided on either side of the diagram. The effect of the oxygen partial pressure on phase relations in the pseudo-ternary system CaO–CuO/Cu2O–TiO2 at 1273 K has been evaluated. The phase diagrams allow identification of secondary phases that may form during the synthesis of the CCTO under equilibrium conditions. The secondary phases may have a significant effect on the extrinsic component of the colossal dielectric response of CCTO.

Completely random nanoporous Cu4O3-CuO-C composite thin films for potential application as multiple channel photonic band gap based filter in the telecommunication wavelengths

In 2003, Babin et al. theoretically predicted (J. Appl. Phys. 94:4244, 2003) that fabrication of organic-inorganic hybrid materials would probably be required to implement structures with multiple photonic band gaps. In tune with their prediction, we report synthesis of such an inorganic-organic nanocomposite, comprising Cu4O3-CuO-C thin films that experimentally exhibit the highest (of any known material) number (as many as eleven) of photonic band gaps in the near infrared. On contrary to the report by Wang et al. (Appl. Phys. Lett. 84:1629, 2004) that photonic crystals with multiple stop gaps require highly correlated structural arrangement such as multilayers of variable thicknesses, we demonstrate experimental realization of multiple stop gaps in completely randomized structures comprising inorganic oxide nanocrystals (Cu4O3 and CuO) randomly embedded in a randomly porous carbonaceous matrix. We report one step synthesis of such nanostructured films through the metalorganic chemical vapor deposition technique using a single source metalorganic precursor, Cu-4(deaH)(dea)(oAc)(5) a <...aEuro parts per thousand(CH3)(2)CO. The films displaying multiple (4/9/11) photonic band gaps with equal transmission losses in the infrared are promising materials to find applications as multiple channel photonic band gap based filter for WDM technology.

Composite cyclodextrin-calcium carbonate porous microparticles and modified multilayer capsules: novel carriers for encapsulation of hydrophobic drugs

Novel composite cyclodextrin (CD)-CaCO3 spherical porous microparticles have been synthesized through Ca2+-CD complex formation, which influences the crystal growth of CaCO3. The CDs are entrapped and distributed uniformly in the matrix of CaCO3 microparticles during crystallization. The hydrophobic fluorescent molecules coumarin and Nile red (NR) are efficiently encapsulated into these composite CD-CaCO3 porous particles through supramolecular inclusion complexation between entrapped CDs and hydrophobic molecules. Thermogravimetric (TGA) and infrared spectroscopy (IR) analysis of composite CD-CaCO3 particles reveals the presence of large CDs and their strong interaction with calcium carbonate nanoparticles. The resulting composite CD-CaCO3 microparticles are utilized as sacrificial templates for preparation of CD-modified layer-by-layer (LbL) capsules. After dissolution of the carbonate core, CDs are retained in the interior of the capsules in a network fashion and assist in the encapsulation of hydrophobic molecules. The efficient encapsulation of the hydrophobic fluorescent dye, coumarin, was successfully demonstrated using CD-modified capsules. In vitro release of the encapsulated coumarin from the CD-CaCO3 and CD-modified capsules has been demonstrated.

Platinum surface additive based nanostructured CuO films for ethanol sensing

In the present work, Platinum (Pt)/Copper (II) oxide (CuO) thin film based ethanol sensors were fabricated by sputtering of Pt in varying concentrations over pre-sputtered nanostructured CuO films. The responses of these sensors as a function of Pt concentrations were studied using operating temperature modulation (200-450 °C) and ethanol concentration modulation (100-2500 ppm). During these modulations, it was found that the sensing response was maximum at operating temperature near 400 °C for all the samples irrespective of the Pt concentration dispersed over them. Moreover, the sensing behavior improves for lower Pt concentration (Pt/CuO-60s) and deteriorates for higher Pt concentration (Pt/CuO-120s). In comparison with bare CuO sample, the sensitivity of Pt/CuO-60s increased up to 22% in the linear range and 33% for maximum ethanol concentration. Hence, the well dispersed optimum Pt additive concentration improves the overall sensing behavior including sensitivity, linear working range and response as well as recovery time.

Sensitivity characteristics of Ag doped BaTiO3-CuO mixed oxide as Carbon-dioxide S ensor

Ag doped BaTiO3-CuO mixed oxide thin films are evaluated for their carbon-dioxide sensing characteristics. The metal oxide films of different thicknesses are deposited on oxidized p type Si < 100 > substrate by RF Sputtering. Sensing characteristics for different CO2 concentration, (300 ppm - 1000 ppm) are obtained for different operating temperatures, (100 degrees C - 400 degrees C). Optimum temperature for maximum sensitivity is found to be 250 degrees C. The effect of annealing on sensing properties is also evaluated. The unannealed films give better sensitivity than that of annealed films. Response time and recovery time are also calculated.

Steady Patterns of Microparticles Formed by Optical Tweezers

In this paper, we propose a method for forming steady patterns of microparticles in a dispersion using optical tweezers. We demonstrate how to control the congregation of particles in a dispersion and to manually fabricate a pattern, The steady pattern (nay be useful for in-depth research, and the method will have applications in biology and nanotechnology.

Kinetics of the chemical looping oxidation of H2 by a co-precipitated mixture of CuO and Al2O3

Chemical-looping combustion (CLC) has the inherent property of separating CO2 from flue gases. Instead of air, it uses an oxygen-carrier, usually in the form of a metal oxide, to provide oxygen for combustion. When used for the combustion of gaseous fuels, such as natural gas, or synthesis gas from the gasification of coal, the technique gives a stream of CO2 which, on an industrial scale, would be sufficiently pure for geological sequestration. An important issue is the form of the metal oxide, since it must retain its reactivity through many cycles of complete reduction and oxidation. Here, we report on the rates of oxidation of one constituent of synthesis gas, H2, by co-precipitated mixtures of CuO+Al2O3 using a laboratory-scale fluidised bed. To minimise the influence of external mass transfer, and also of errors in the measurement of [H2], particles sized to 355-500μm were used at low [H2], with the temperature ranging from 450 to 900°C. Under such conditions, the reaction was slow enough for meaningful measurements of the intrinsic kinetics to be made. The reaction was found to be first order with respect to H2. Above ∼800°C, the reaction of CuO was fast and conformed to the shrinking core mechanism, proceeding via the intermediate, Cu2O, in: 2CuO+H2→Cu2O+H2O, ΔH1073 K0=- 116.8 kJ/mol; Cu2O+H2→2Cu+H2O, ΔH1073 K0-80.9 kJ/mol. After oxidation of the products Cu and Cu2O back to CuO, the kinetics in subsequent cycles of chemical looping oxidation of H2 could be approximated by those in the first. Interestingly, the carrier was found to react at temperatures as low as 300°C. The influence of the number of cycles of reduction and oxidation is explored. Comparisons are drawn with previous work using reduction by CO. Finally, these results indicate that the kinetics of reaction of the oxygen carrier with gasifier synthesis gases is very much faster than rates of gasification of the original fuel. © 2010 The Institution of Chemical Engineers.

La estructura del orden moral : una introducción a la ética de cuño aristotélico-tomista

Resumen: El texto realiza un análisis sobre el orden moral en su objeto material (la conducta humana) y el objeto formal (el bien o la perfección). Se detiene en la experiencia moral planteando los problemas, las dudas y las dificultades tales como la naturaleza humana, el fin natural, la libertad, las pasiones, la necesidad de indigencia y la deóntica, entre otros. Luego estudia el esquema de la estructura del orden moral en el orden moral vivido, disposicional, subjetivo, normativo y de fines. Estas dimensiones se integran a través de la causalidad final.

CuO,CuCl对P2O5-ZnO-Na2O玻璃性质的影响

包边技术是提高大尺寸激光玻璃饱和增益系数的关键。为获得优质包边玻璃,以CuO和CuCl分别作为Cu2+的引入物质,采用传统的玻璃熔制方法,研究了Cu2+掺杂量和不同引入物质对P2O5-ZnO-Na2O体系玻璃形成区、析晶稳定性、物化性能以及吸收系数的影响。研究结果表明,CuO和CuCl都能增大P2O5-ZnO-Na2O体系的玻璃形成区、提高玻璃样品的析晶稳定性。玻璃样品的吸收系数随Cu2+掺杂浓度的增加而明显增大,当Cu2+掺杂摩尔分数达到6%时,样品在1053 nm处的吸收系数为59.46 cm-1,基

Tunable hydrodynamic chromatography of microparticles localized in short microchannels.

This paper describes a new way to perform hydrodynamic chromatography (HDC) for the size separation of particles based on a unique recirculating flow pattern. Pressure-driven (PF) and electro-osmotic flows (EOF) are opposed in narrow glass microchannels that expand at both ends. The resulting bidirectional flow turns into recirculating flow because of nonuniform microchannel dimensions. This hydrodynamic effect, combined with the electrokinetic migration of the particles themselves, results in a trapping phenomenon, which we have termed flow-induced electrokinetic trapping (FIET). In this paper, we exploit recirculating flow and FIET to perform a size-based separation of samples of microparticles trapped in a short separation channel using a HDC approach. Because these particles have the same charge (same zeta potential), they exhibit the same electrophoretic mobility, but they can be separated according to size in the recirculating flow. While trapped, particles have a net drift velocity toward the low-pressure end of the channel. When, because of a change in the externally applied PF or electric field, the sign of the net drift velocity reverses, particles can escape the separation channel in the direction of EOF. Larger particles exhibit a larger net drift velocity opposing EOF, so that the smaller particles escape the separation channel first. In the example presented here, a sample plug containing 2.33 and 2.82 microm polymer particles was introduced from the inlet into a 3-mm-long separation channel and trapped. Through tuning of the electric field with respect to the applied PF, the particles could be separated, with the advantage that larger particles remained trapped. The separation of particles with less than 500 nm differences in diameter was performed with an analytical resolution comparable to that of baseline separation in chromatography. When the sample was not trapped in the separation channel but located further downstream, separations could be carried out continuously rather than in batch. Smaller particles could successfully pass through the separation channel, and particles were separated by size. One of the main advantages of exploiting FIET for HDC is that this method can be applied in quite short (a few millimeters) channel geometries. This is in great contrast to examples published to date for the separation of nanoparticles in much longer micro- and nanochannels.

I：新型稀土永磁材料Nd-Fe-B氧化过程及抗氧化新体系研究II：CuO、Y_2Cu_2O_5、BaCuO_2和RBa_2Cu_3O_(7-δ)超导体磁化率及Cu价态研究

本论文由两大部分组成。第一部分是新型稀土永磁材料Nd-Fe-B氧化过程及抗氧化新体系的研究。Nd-Fe-B永磁体是1983年问世的新型稀土永磁材料。和原有的铁氧体及Sm-Co体系相比，具有磁能积高（50MGOe）。价廉源广，制备简单等三大优点；也有居里温度低（310℃），温度系数大（－0.126%/K），易氧化等三大缺点，我们对Nd-Fe-B合金的氧化过程进行研究，发现该材料热稳定性差，容易发生氧化反应，氧化使材料的结构受到破坏，并给材料的磁性造成不可恢复的损失，整个氧化过程是分阶段的。在室温和干燥的空气中材料基本是稳定的。150℃以下材料磁性受到破坏的主要原因是体系中Nd的氧化。230℃以上材料主体成分Fe也开始氧化，温度升高使反应进程大大加快。到800℃左右反应基本结束，最终产物主要为Fe_2O_3, Nd_2O_3·FeNdO_3和NdBO_3。增加体系中B的相对含量和添加某些新的元素均能提高材料的抗氧化能力，新研制的Nd-Fe-B-Si四元体系和原来的Nd-Fe-B体系相比具有下列显著优点：新体系的抗氧化能力大大提高，经过150℃的长期恒温试验，材料的结构，磁性均未受到破坏，某些体系甚至能在更高的温度下使用，另外，新体系的居里温度Tc也大为提高。比原有Nd-Fe-B磁体高40℃左右。因此该体系是一种大有发展前途的新材料。此外，我们用动态热重法研究了Nd-Fe-B合金的氧化动力学过程，但由于我们新合成的体系构相较为复杂，未能达到预期效果。第二部分是CuO，Y_2Cu_2O_5，BaCuO_2和RBa_2Cu_3O_(7-δ)超导体（R稀土元素）磁化率及铜价态研究，铜的氧化物具有复杂的化学计量关系和磁学性质。在对CuO的磁化率研究中，我们发现在低温区（77K－110K）和一定磁场下，CuO由顺磁突变为抗磁。这种转变与磁场强度有很大关系。这一结果与前人的工作有较大的出入。而与超导体的形为极为相似。所不同的是，转变温度与样品的重量也有关系。实验结果重复。由于铜氧性质在R-Ba-Cu-O超导体中起决定作用，因此有必要对CuO的低温磁性作进一步研究。此外，我们对文献尚未报道的Y_2Cu_2O_5的磁化率在77－300K温度区间进行了测量，发现它是顺磁性物质，室温有效磁矩μ_(eff) = 2.13μB。高于Cu~(2+)的理论有效磁矩（1.73μB）。经过碘量法价态分析，发现Y_2Cu_2O_5中有部分Cu~(3+)，这与磁化率的测定相符合。Tc在90K左右的Y-Ba-Cu-O体系是近期才发现的具有超高温超导材料。该体系有着独特的结构和性质。在对R-Ba-Cu-O及R-Ba-Cu-O-Ag超导体的研究中，我们发现此类超导体属II类超导体，在临界温附近该超导体由顺磁转变为抗磁，此种变化与磁场强度有很大关系，当场强大于一定值后，则观察不到这种转变。在对RBa_2Cu_3O_(7-δ) (R = Y, Sm, Eu, Gd, Dy, Ho, Er, Tm)超导体和具有相同配比但由于合成工艺条件不同而不超导的R'Ba_2Cu_3O_(7-δ) (R' = Y, Sm, Eu, Gd)非超导体的铜价态分析中，我们发现此两类化合物中均含有一定量的Cu~(3+)。且超导体中Cu~(3+)的含量高于非超导体中Cu~(3+)的含量（同样比例）。我们还发现Cu~(3+)对水极为敏感，将RBa_2Cu_3O_(7-δ) (除R = Gd, Dy, Er)超导体在未干燥容器中测出的Cu~(3+)量远远低于干燥容器中所测得的值。我们认为这可能是引起超导体不稳定的重要原因。由于尚缺乏用其它手段检测到超导体中Cu~(3+)存在的例证。故对此问题还有待于今后继续作进一步的研究。