Controlled synthesis of Cu<Subscript>2</Subscript>O micro-crystals with various morphologies by adjusting solution conditions

Micro-crystals of cuprous oxide with different morphologies were prepared by a hydrothermal process with copper sulfate and sodium lactate as precursors. Morphology of cuprous oxide was simply controlled by adjusting solution pH values or addition of different amounts of organic solvent. Structural properties of all the samples were characterized by X-ray diffraction and scanning electron microscopy. The growth mechanism of cuprous oxide micro-crystal under different conditions was discussed. Results show that morphologies of cuprous oxide micro-crystals alter from branched structure to octahedron structure and cube structure with growth conditions.     

Synthesis and crystal structure of Cu<Subscript>2</Subscript>{(UO<Subscript>2</Subscript>)<Subscript>3</Subscript>[(S,Cr)O<Subscript>4</Subscript>]<Subscript>5</Subscript>}(H<Subscript>2</Subscript>O)<Subscript>17</Subscript>

Cu₂{(UO₂)₃[(S,Cr)O₄]₅}(H₂O)₁₇ crystals were prepared by evaporation of aqueous solutions. The crystal structure was solved by the direct method and refined to R ₁ = 0.064 (wR ₂ = 0.177) for 8120 reflections with ¦F _hkl¦ 4 ¦F _hkl¦. Rhombic system, space group Pbca, a = 18.0586(8), b = 19.9898(9), c = 20.5553(8) Å, V = 7420.2(6) ų. The structure is based on {(UO₂)₃[(S,Cr)O₄]₅}^4– anionic layers, formed by combination of UO₇ pentagonal bipyramids and TO₄ tetrahedra through common vertices. The { (UO₂)₃ [(S,Cr)O₄]₅}^4– layers are parallel to the (010) plane. The Cu²⁺ (H₂O)₆ octahedra and additional water molecules are located in the interplanar space and provide binding of the layers in the structure by hydrogen bonds. Based on the occupancy of tetrahedral positions, more accurate chemical formula of the compound should be written as Cu₂{(UO₂)₃[(S_0.804 Cr_0.196)O₄]₅} (H₂O)₁₇.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 408–411.Original Russian Text Copyright © 2004 by Krivovichev, Burns.     

Atomic-scale observation of a two-stage oxidation process in Cu<Subscript>2</Subscript>O

Atomic-scale oxidation dynamics of Cu2O nanocrystallines (NCs) are directly observed by in situ high-resolution transmission electron microscopy.A two-stage oxidation process is observed:(1)The initial oxidation stage is dominated by the dislocation-mediated oxidation behavior of Cu2O NCs via solid-solid transformations,leading to the formation of a new intermediate CuOx phase.The possible crystal structure of the CuOx phase is discussed.(2) Subsequently,CuOx is transformed into CuO by layer-by-layer oxidation.These results will help in understanding the oxidation mechanisms of copper oxides and pave the way for improving their structural diversity and exploiting their potential industrial applications.     

Crystal structure of Gd<Subscript>14</Subscript>Cu<Subscript>48</Subscript>Ga<Subscript>3</Subscript> and Tb<Subscript>14</Subscript>Cu<Subscript>48</Subscript>Ga<Subscript>3</Subscript>

The compounds Gd₁₄Cu₄₈Ga₃ and Tb₁₄Cu₄₈Ga₃ have been synthesized, and their structures have been determined by powder x-ray diffraction (Gd₁₄Ag₅₁ type).     

Microstructure of laser-induced combustion synthesis of Cu<Subscript>59.6</Subscript>Zr<Subscript>36.9</Subscript>Al<Subscript>3.5</Subscript> alloy

Cu_59.6Zr_36.9Al_3.5 alloy are prepared by laser-induced combustion synthesis technology. The microstructure and phases formed of the product is studied by XRD and TEM. The product consists of mixtures of amorphous and crystalline phases, mainly(α-Zr, Zr₂Cu, Zr₁₀Cu₇ and Cu₈Zr₃. The amorphous and nanocrystalline phases content over 50% in volume estimated from the broad peak in the XRD spectrum. TEM and HRTEM results show that the microstructure is characterized by inhomogeneously distributed amorphous, nano Zr₂Cu, relatively gross (∼100 nm) Zr₂Cu, and large grain Cu₁₀Zr₇.     

Simulated Hysteretic Loops for YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7</Subscript>

This paper presents modification for a model to retrace magnetic hysteresis loop and calculate hysteresis energy loss (HEL) in YBa₂Cu₃O₇ (YBCO). In comparison with reported experimental results, it is revealed that the modified model could retrace successfully magnetic hysteresis loop for YBCO. As an application of this model, the calculation formula of HEL has been included in this article. The results show also that HEL in YBCO increases by 14% with the addition of the magnetic NiW substrate. This leads to conclude that the type of substrate has an effect on HEL of YBCO. This modified model can help us to explain experimental results and expect the functioning of superconductor tapes.     

Thermoanalytical study of the polymorphism and melting behavior of Cu<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript>

We have developed a procedure for the synthesis of phase-pure α- and β-Cu₂V₂O₇. Thermal analysis and X-ray diffraction demonstrate that the β-phase (monoclinic structure) exists at low temperatures (stability range 25–610°C), while α-Cu₂V₂O₇ (orthorhombic structure) is stable in the range 610–704°C. The α-phase observed during cooling, in particular at room temperature, is in a metastable state. The melting of the high-temperature phase γ-Cu₂V₂O₇, which forms between 704 and 716°C, has the highest rate in the range 770–785°S and is accompanied by peritectic decomposition and oxygen gas release. Subsequent cooling gives rise to four exothermic peaks, one of which (780.9°C) is attributable to the crystallization of the peritectic melt, one (620.1°C) is due to the γ → α → β phase transformations of Cu₂V₂O₇, and the other two arise from the crystallization of multicomponent low-melting-point eutectics containing α- and β-Cu₂V₂O₇, CuVO₃, and other compounds.     

T-x phase diagram of the Cu<Subscript>2</Subscript>S-Al<Subscript>2</Subscript>S<Subscript>3</Subscript> quasibinary System

The T-x phase diagram of the Cu₂S-Al₂S₃ system was achieved experimentally from 35 different mixtures of the binary compounds. The results of powder X-ray diffraction (XRPD), differential thermal analysis (DTA) and microprobe analysis (EPMA) are presented. The ternary phases CuAlS₂ and CuAl₅S₈ were found and their homogeneity regions were established.     

X-ray diffraction study of the Cu<Subscript>2</Subscript>Se-In<Subscript>2</Subscript>Se<Subscript>3</Subscript>-Cr<Subscript>2</Subscript>Se<Subscript>3</Subscript> system near CuInCr<Subscript>2</Subscript>Se<Subscript>5</Subscript>

The structure of three compounds in the Cu₂Se-In₂Se₃-Cr₂Se₃ system near CuInCr₂Se₅ is determined by single-crystal x-ray diffraction: CuInCr₄Se₈ (I), Cu₂In₂Se₄ (II), and Cu_0.5In_0.5Se (III). I has a cubic (spinel type) structure: a = 10.606(4) Å, Z = 4, sp. gr. F43m. II has a pseudotetragonal (sphalerite type) structure: a = 5.774(2) Å, c = 11.617(6) Å. The structure of II was solved in a reduced unit cell with a = 5.774(2) Å, b = 5.774(2) Å, c = 7.095(6) Å, = 113.95(5)°, = 113.95(5)°, = 90.00(4)°, Z = 1, sp. gr. P1. III has a triclinic cell (disordered structure of II): a = 4.088(1) Å, b = 4.091(2) Å, c = 4.101(1) Å, = 60.05(1)°, = 60.08(1)°, = 89.98(4)°, Z = 1, sp. gr. P1. The Cu and In atoms in I sit in inequivalent tetrahedral sites, and the Cr atoms reside in octahedral interstices of the close packing of Se atoms. The bond lengths are In–Se = 2.538(6), Cr(1)–Se(1) = 2.514(7), Cr(1)–Se(2) = 2.576(8), and Cu–Se = 2.437(5) Å. In II, all of the atoms sit in tetrahedral sites; the mean bond lengths are In–Se = 2.578(6) and Cu–Se = 2.44(1) Å. In III, the Cu and In atoms are fully disordered in the same tetrahedral site; the mean Cu(In)–Se bond length is 2.508(6) Å.Translated from Neorganicheskie Materialy, Vol. 40, No. 12, 2004, pp. 1435–1439.Original Russian Text Copyright © 2004 by Antsyshkina, Sadikov, Koneshova, Sergienko.     

Preparation of nanocrystalline Cu<Subscript>2</Subscript>O thin film by pulsed laser deposition

In this paper, the synthesis of nanocrystalline copper oxides Cu₂O and CuO thin films on glass substrates using a pulsed 532 nm Nd:YAG laser is presented. Deposition of films is achieved at two different substrate temperatures. The influence of substrate temperature on the structural and optical properties of copper oxide films are discussed and analyzed. The X-ray diffraction (XRD) results show that the deposited films are crystalline in nature. Films prepared at 300 °C substrate temperature were Cu₂O and has (111) and (200) diffracted peaks, while films grown at 500 °C were CuO and has (111) and (020) planes. The morphology of deposited films were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). The optical energy gap of Cu₂O and CuO films have been determined and found to be 2.04 and 1.35 eV respectively.     

Phase transitions and transport properties of Cu<Subscript>3</Subscript>Co<Subscript>0.5</Subscript>Se<Subscript>2</Subscript> crystals

We have synthesized a solid solution with the composition Cu₃Co_0.5Se₂ and investigated its structural phase transitions by high-temperature X-ray diffraction on a D8 Advance diffractometer. The results demonstrate that, in the range 100–773 K, the solid solution undergoes two phase transitions: at 560 K, the low-temperature, orthorhombic phase (α) transforms into an intermediate, primitive cubic phase (β); at 765 K, the β-phase transforms into a high-temperature phase (γ, sp. gr. Fm3m). The thermoelectric power, electrical conductivity, and Hall coefficient of the solid solution were measured in the temperature range 80–350 K. The observed temperature variation of its thermoelectric power and conductivity can be accounted for under the assumption that its conduction band has an additional subband due to the cobalt atoms.     

Microwave Synthesis of Cu/Cu<Subscript>2</Subscript>O/SnO<Subscript>2</Subscript> Composite with Improved Photocatalytic Ability Using SnCl<Subscript>4</Subscript> as a Protector

Cu/Cu₂O/SnO₂ composites were successfully prepared with a facile microwave synthesis method. The structure of Cu/Cu₂O/SnO₂ composite was studied by morphology characterizations, such as X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy, which showed that the size of the Cu/Cu₂O/SnO₂ particles is 20–50 nm. The synthesis mechanism revealed that SnCl₄ obstructed between Cu(OH) and ethylene glycol, preventing Cu(OH) being reduced into Cu at high temperature. The photocatalytic property of Cu/Cu₂O/SnO₂ composite was investigated by degrading the mixed dyestuff under the irradiation of visible light at room temperature. Benefiting from the effect of electron transfer, the photocatalytic performance of the microwave-prepared Cu/Cu₂O/SnO₂ composite was much better than that of pure Cu₂O. The possible photocatalytic mechanism of the Cu/Cu₂O/SnO₂ composite catalysts was proposed and elaborated in this study. This synthesis of Cu/Cu₂O/SnO₂ composite may provide a method for other Cu₂O/semiconductor composites microwave preparation.     

The synthesis and characterization of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> thin films from melt reactions using xanthate precursors

Kesterite, Cu₂ZnSnS₄ (CZTS), is a promising absorber layer for use in photovoltaic cells. We report the use of copper, zinc and tin xanthates in melt reactions to produce Cu₂ZnSnS₄ (CZTS) thin films. The phase of the as-produced CZTS is dependent on decomposition temperature. X-ray diffraction patterns and Raman spectra show that films annealed between 375 and 475 °C are tetragonal, while at temperatures <375 °C hexagonal material was obtained. The electrical parameters of the CZTS films have also been determined. The conduction of all films was p-type, while the other parameters differ for the hexagonal and tetragonal materials: resistivity (27.1 vs 1.23 Ω cm), carrier concentration (2.65 × 10⁺¹⁵ vs 4.55 × 10⁺¹⁷ cm^?3) and mobility (87.1 vs 11.1 cm² V^?1 s^?1). The Hall coefficients were 2.36 × 10³ versus 13.7 cm³ C^?1.     

Magnetism induced by nonmagnetic dopant in Li<Subscript>2</Subscript>O,Na<Subscript>2</Subscript>O,K<Subscript>2</Subscript>O and Rb<Subscript>2</Subscript>O: first-principles calculations

First-principles calculations based on the tight-binding linear muffin-tin orbital (TB-LMTO) method are performed to investigate the occurrence of spin polarization in the alkali-metal oxides (M₂O) [M: Li, Na, K, Rb] in antifluorite (anti-CaF₂-type) structure with non-magnetic sp (F, Cl, Br and I) dopants. The calculations reveal that non-magnetic substitutional doping at cation site can induce stable half-metallic ferromagnetic ground state in I₂-VI compounds. Total energy calculations show that the antifluorite ferromagnetic state is energetically more stable than the antifluorite non-magnetic state at equilibrium volume. Ground state properties such as equilibrium lattice constant and bulk modulus were calculated. The calculated magnetic moment is found to be 2.00 μB per dopant atom.     

Thermodynamic properties of Cu<Subscript>5</Subscript>SmSe<Subscript>4</Subscript>

The heat capacity of Cu₅SmSe₄ has been measured from 80 to 300 K. The results have been used to assess the main thermodynamic functions of Cu₅SmSe₄: entropy (S ⁰(T) − S ⁰(0)), enthalpy increment (H ⁰(T) − H ⁰(0)), and reduced Gibbs energy (Φ⁰(T)).     

Facet-dependent Cu<Subscript>2</Subscript>O nanocrystals in manipulating alignment of liquid crystals and photomechanical behaviors

Manipulating the alignment of liquid crystals (LCs) is a hot and fundamental issue for their applications in block copolymers, photonics, actuators, biosensors, and liquid-crystal displays. Here, the surface characteristic of Cu₂O nanocrystals was well controlled to manipulate the orientation of the LCs. The mechanism of the orientation of the LCs induced by Cu₂O nanocrystals was elucidated based on the interaction between the LCs and Cu₂O nanocrystals. To comprehensively prove our assumption, different types of LCs (nematic, cholesteric, and smectic) as well as the same type of LCs with different polarities were selected in our system. Moreover, the photomechanical behaviors of the LC polymer composites demonstrated that the alignment of LCs can be effectively manipulated using Cu₂O nanocrystals.

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Facile synthesis and excellent electromagnetic wave absorption properties of flower-like porous RGO/PANI/Cu<Subscript>2</Subscript>O nanocomposites

Novel porous ternary nanocomposite systems containing reduced graphene oxide (RGO)/polyaniline (PANI)/cuprous oxide (Cu₂O) were prepared via one-step in situ redox method. The RGO/PANI/Cu₂O nanocomposites present a flower-like structure with an average size of 2.0 μm in diameter. The morphologies and properties of the products can be controlled by adjusting the molar ratios of aniline to Cu²⁺. When the molar ratio of aniline to Cu²⁺ is 1:1, the product exhibits excellent microwave absorption property in the frequency range of 2–18 GHz. It can be seen that the maximum reflection loss (RL) of the ternary composite is up to ?52.8 dB at 2.7 GHz with a thickness of only 2 mm, and the absorption bandwidth corresponding to ?10 dB (90% of EM wave absorption) is 13.2 GHz. The microwave absorption property of ternary RGO/PANI/Cu₂O composite is significantly improved due to its special flower-like porous structure, dielectric loss property and well impedance matching characteristics, which is 8.12 times than that of pure RGO and 5.28 times than that of pure PANI. Therefore, our study paves a new way to prepare the promising lightweight and high-performance composite materials combined with the characteristics of three components for electromagnetic absorption.     

Paramagnetism and Superconductivity in Eu<Subscript>0.7</Subscript>Sm<Subscript>0.3</Subscript>Ba<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−δ</Subscript>

Magnetic properties of sintered Eu_0.7Sm_0.3Ba₂Cu₃O_7?δ were investigated both in dc and ac magnetic fields. The dc response reflects the interplay between the rare earth ion paramagnetic and the superconducting charge carrier subsystems, respectively. The harmonic susceptibilities exhibit special features: the second harmonic is anomalously high and the third harmonic in zero dc-field has reversed temperature dependence with respect to the theoretical models. The magnetic relaxation at low fields is monotonous and occurs as a two-stage relaxation, each stage obeying logarithmical time dependence with different rates. At high fields, the relaxation is nonmonotonous with a peak at intermediate time suggesting a temporary re-entrance of irreversibility when the flux-line density increases in the center of the sample because of the redistribution of the vortices toward that region.     

The influence of the cooling rate on bulk metallic glass formation in Mg<Subscript>80</Subscript>Cu<Subscript>15</Subscript>Y<Subscript>5</Subscript> and Mg<Subscript>80</Subscript>Cu<Subscript>10</Subscript>Y<Subscript>10</Subscript>

The Mg–Cu–Y system is known to be one of the best glass formers among the various existing magnesium alloys. The compositions chosen for the current study were Mg₈₀Cu₁₅Y₅ and Mg₈₀Cu₁₀Y₁₀. Different casting processes yielded four different microstructures that were analyzed by means of X-ray diffraction, scanning electron microscopy, high resolution scanning electron microscopy, and energy-dispersive X-ray spectroscopy chemical analysis. The different casting procedures were gravity castings of 3 mm diameter specimens into a copper mold held at different temperatures (cooled to −195 °C with the aid of liquid nitrogen, held at room temperature and heated up to 300 °C) and melt-spinning. Detailed microstructure study was then performed on the melt-spun specimen using transmission electron microscopy and high resolution transmission electron microscopy. The above-mentioned investigation revealed a crystalline rather than amorphous structure. The observed microstructure could not be explained on the basis of current models referring to the frequency of nucleation events.     

Photoconductivity and luminescence anisotropy in ZnIn<Subscript>2</Subscript>S<Subscript>4</Subscript> and ZnIn<Subscript>2</Subscript>S<Subscript>4</Subscript>:Cu<Superscript>2+</Superscript> single crystals

ZnIn₂S₄ and ZnIn₂S₄:Cu²⁺ single crystals are shown to exhibit considerable photoconductivity and luminescence anisotropy. The mechanism of carrier recombination in the crystals is polarization-dependent. Their spectra can be understood in terms of optical transitions involving donor and acceptor levels. The degree and spectral distribution of the anisotropy can be tuned via doping and alternating growth of the three- and one-layer polytypes.