Hydrothermal synthesis of Zn3(OH)2V2O7·nH2O nanosheets and its application in lithium ion battery

Well crystallized zinc vanadium oxide hydroxide hydrate (Zn₃(OH)₂V₂O₇·nH₂O) nanosheets have been successfully synthesized by a simple hydrothermal method. The products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and Raman spectrum. The composition of Zn₃(OH)₂V₂O₇·nH₂O has been studied by thermal analysis (TG, DTA). The results indicate that there are two water molecules in Zn₃(OH)₂V₂O₇·nH₂O molecular formula. Electrochemical properties of Zn₃(OH)₂V₂O₇·nH₂O nanosheets as negative electrode of lithium ion battery were studied by conventional charge/discharge test, which shows steady platform near 1.4 V, suggesting it as an ideal candidate of negative material for lithium ion battery.     

Hydrothermal synthesis of Cu3V2O7(OH)2·2H2O hierarchical microspheres and their electrochemical properties

Uniform Cu₃(OH)₂V₂O₇·2H₂O microspheres assembled by nanorods have been fabricated through a simple hydrothermal method for the first time employing copper hydroxide carbonate (Cu₂(OH)₂CO₃) as copper source without the assistance of any template or surfactant. The formation mechanism was proposed based on the evolution of this morphology as a function of hydrothermal time. The Electrochemical measurements revealed that the Cu₃(OH)₂V₂O₇·2H₂O microspheres displayed a high discharge capacity, which indicates that the Cu₃(OH)₂V₂O₇·2H₂O microspheres are promising cathode candidates for primary lithium batteries used in long term implantable cardioverter defibrillators (ICD).     

Synthesis of Cu2O bi-pyramids by reduction of Cu(OH)2 in solution

In this paper we describe the synthesis of Cu₂O bi-pyramids by reduction of Cu(OH)₂ using hydrazine as reducing agent. Copper chloride is used as a precursor to produce copper hydroxide in aqueous solution and the precipitation of the product is controlled by a slow addition of the reducing agent. All the reactions have been carried out at room temperature and atmospheric pressure with high repeatability. The purification process does not require expensive methods since a solid product is obtained from a reaction in liquid phase. Scanning and Transmission electron microscopy characterization showed interesting bi-pyramidal structures of several microns of edge and different sizes.     

Synthesis and formation mechanism of Cu3V2O7(OH)2·2H2O nanowires

Cu₃V₂O₇(OH)₂·2H₂O nanowires have been synthesized in high yield through a simple and facile low-temperature hydrothermal approach without any template or surfactants. XRD, TG, FE-SEM, TEM and HRTEM were used to characterize the product. The results indicated that the product consisted of wirelike crystals about 80 nm in diameter and length up to several micrometers. The formation of wirelike structure of Cu₃V₂O₇(OH)₂·2H₂O depended crucially on the reaction time and pH value of the precursor suspensions. The optical absorption spectrum indicates that the Cu₃V₂O₇(OH)₂·2H₂O nanowires have a direct band gap of 1.94 eV.     

Ultrasound assisted template-free synthesis of Cu(OH)2 and hierarchical CuO nanowires from Cu7Cl4(OH)10·H2O

Cu(OH)₂ nanowires have been synthesized by an ultrasound assisted solution route in absence of a template, using Cu₇Cl₄(OH)₁₀·H₂O as a precursor. Hierarchical CuO nanowires were obtained by a simple solid-state thermal transformation of these Cu(OH)₂ nanowires. The products were characterized by XRD, SEM, TEM and HRTEM. The ranges of diameters and lengths of the polycrystalline CuO nanowires are ca. 20-30 nm and several micrometers, respectively. Ultrasonic time is found an important factor to morphology of the CuO products. This could be a potential efficient way for large scale fabrication of CuO nanowires with hierarchical structures. Surface photovoltage spectra of the CuO nanowires in air, NH₃ and CH₂Cl₂ atmospheres were investigated, which demonstrates it a good photoelectric gas sensing material.     

Synthesis and characterization of the new layered perovskite, Na0.10(VO)0.45LaTiO4·nH2O

Na_0.10(VO)_0.45LaTiO₄·nH₂O (n ≅ 0.6) has been synthesized by an ion exchange reaction between the single-layered perovskite, NaLaTiO₄, and aqueous VOSO₄. This low temperature phase retains the structure of the parent with a slight contraction of its tetragonal unit cell. Rietveld refinement of X-ray powder diffraction data indicate that the vanadyl units are disordered within the perovskite layers. Infrared spectroscopy, electron spin resonance and magnetic susceptibility are consistent with the presence of isolated vanadyl units. Susceptibility data show Curie-Weiss behavior above 140 K.     

Soft chemistry synthesis and crystal structure of MgxCu3−xV2O6(OH)4·2H2O

Mg_xCu_3−xV₂O₆(OH)₄·2H₂O (x ∼ 1), with similar crystal structure as volborthite Cu₃V₂O₇(OH)₂·2H₂O, was successfully prepared by a soft chemistry technique. The method consists of mixing magnesium nitrate and copper nitrate with a boiling solution of vanadium oxide (obtained by reacting V₂O₅ with few mL of 30 vol.% H₂O₂ followed by addition of distilled water). When ammonium hydroxide NH₄OH 10% was added (pH 7.8), a green yellowish precipitate was obtained. Using X-ray powder diffraction data, its crystal structure has been determined by Rietveld refinement. Compared to volborthite, the vanadium coordination changes from tetrahedral VO₄ to trigonal bipyramidal VO₅, and magnesium replaces copper, preferably, in the less distorted octahedron. At 300 °C, the phase formed is similar to the high pressure (HP) monoclinic Cu₃V₂O₈ phase. However at higher temperature, 600 °C, the phase obtained is different from known Cu₃V₂O₈ phases.     

Structural, thermal, magnetic and electrical studies of the iron oxophosphate Rb7Fe7(PO4)8O2·2H2O

A new iron oxophosphate of composition Rb₇Fe₇(PO₄)₈O₂·2H₂O has been synthesized and studied by X-ray diffraction, TG and DTA analysis, magnetic susceptibility, neutron diffraction, Mössbauer spectroscopy and ionic conductivity. This compound crystallizes in the monoclinic system with the P2₁/c space group and the unit cell parameters a = 8.224(8) Å, b = 22.162(6) Å, c = 9.962(6) Å and β = 109.41(8)°. Its structure is built up from Fe₇O₃₂ clusters of edge- and corner-sharing FeO₅ and FeO₆ polyhedra. Neighboring clusters are connected by the phosphate tetrahedra to form a three-dimensional framework. The Rb⁺ cations and the water molecules are occupying intersecting tunnels parallel to a and c. The presence of water molecules was confirmed by TG and DTA analysis. The magnetic susceptibility measurements have shown the existence of antiferromagnetic ordering below 22 K with a weak ferromagnetic component. Additionally, these measurements show evidence for a strong magnetic frustration characterized by |θ/T_N| ≈ 12. Powder neutron diffraction study confirms the presence of a long range antiferromagnetic order coupled to a weak ferromagnetic component along the b-axis. The strongly reduced magnetic moments extracted from the refinement support the existence of a magnetically frustrated ground state. The Mössbauer spectroscopy results confirmed the presence of only Fe³⁺ ions in both five and six coordination. The ionic conductivity measurements led to activation energy of 0.81 eV, a value that agrees with the obtained for other rubidium phosphates.     

Controllable synthesis and magnetic property of BiMn2O5 crystals

Uniform submicron BiMn₂O₅ particles were prepared via a facile one-step hydrothermal route at low temperature. Bi(NO₃)₃, MnCl₂·4H₂O and KMnO₄ were used as starting materials; KOH as a pH adjustor and also as a mineralizer. Single-crystalline orthorhombic BiMn₂O₅ sample with controllable morphology was obtained. The microstructure strongly depends on the molar ratio of the starting materials, KOH concentration and reaction temperature. X-ray photoelectron spectroscopy shows the existence of Mn⁴⁺ state. Magnetic measurement indicates Néel temperature T_N at 44 K. The susceptibility above T_N obeys the Curie-Weiss law, χ = C/(T − θ), with θ = −350 K. The effective paramagnetic moment μ_eff = 4.66 μ_B/Mn, demonstrating the coexistence of mixed Mn³⁺ and Mn⁴⁺ valences.     

Facile one-pot synthesis and luminescence of hexagonal TbPO4·nH2O hollow spheres

Monodisperse hexagonal TbPO₄·nH₂O hollow spheres were successfully obtained by utilizing Tb(OH)CO₃ colloidal spheres as the precursor and NH₄H₂PO₄ as the phosphorus source through the hydrothermal process. The obtained hollow spheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. They have the average diameter of 200 nm. There are a number of tiny nanorods with the length of about 60 nm on the surface of the spheres. The obtained TbPO₄ hollow spheres exhibit green color emission from ⁵D₄ − ⁷F_J (J = 6, 5, 4, 3) transitions of the Tb³⁺ ions, which are expected to be applied in display applications and biological applications.     

Synthesis, characterization and magnetic properties of hexagonal (VO)0.09V0.18Mo0.82O3 · 0.54H2O microrods

(VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O microrods have been synthesized for the first time via a hydrothermal treatment of aqueous peroxomolybdic acid and vanadyl sulfate. The compound crystallizes in hexagonal rods with space group P6₃, and lattice constants a = 10.586 Å, and c = 3.698 Å. The single crystalline rods exhibit diameters of 1-2 μm and lengths up to 45 μm. A variety of techniques, including X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscope, Fourier-transform infrared spectroscopy, differential scanning calorimetry and static magnetometry were used to characterize the product.     

Microemulsion-assisted solvothermal synthesis of Nd2(CO3)3·8H2O microstructures

Microstructures of Nd₂(CO₃)₃·8H₂O with various morphological structures and sizes were successfully synthesized using the microemulsion-assisted solvothermal method. The obtained products were characterized by X-ray diffraction (XRD), differential scanning calorimetry and thermal gravimetric analysis (DSC-TGA), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron diffraction (ED). The results showed that pyramid-like and spherical Nd₂(CO₃)₃·8H₂O microstructures were synthesized depending on the reaction time and reaction temperature. Moreover, the reaction time and temperature also played important roles in controlling the morphologies and sizes of the resulting Nd₂(CO₃)₃·8H₂O microstructures.     

Controllable synthesis of beta-Mn2V2O7 microtubes and hollow microspheres

β-Mn₂V₂O₇ microtubes with the range of 15-25 μm in length, 2.5-3.5 μm in external diameter, and ca 0.4 μm of the wall in thickness, as well as β-Mn₂V₂O₇ hollow microspheres with an average outer diameter of 2 μm were successfully synthesized in a suitable molar ratio of NH₄VO₃ and MnCO₃ powders via a hydrothermal process. XRD and FESEM were used to characterize the products, and the magnetic susceptibility curve was also measured. In the whole process, the concentration of Mn²⁺ cations derived from MnCO₃ dissolution plays a crucial role in the formation of β-Mn₂V₂O₇ microtubes and hollow microspheres.     

CuS nanotubes prepared using Cu(OH)2 nanowires as self-sacrificial template

Copper sulfide (CuS) nanotubes assembled with nanoparticles have been successfully synthesized by microwave-assisted solvothermal method at 80 °C using Cu(OH)₂ nanowires in the solvent of ethylene glycol. Cu(OH)₂ nanowires act as both the precursor and template for the preparation of CuS nanotubes assembled with nanoparticles. Cu(OH)₂ nanowires are prepared by adding an aqueous solution containing CuCl₂ into an alkaline solution at room temperature and by ultrasonication for 30 min. This method has the advantages of the simplicity and low cost. The samples are characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The method reported herein may be extended to the synthesis of nanotubes of other copper-containing compounds.     

Mg(OH)2-Al(OH)3-微胶囊红磷/高抗冲聚苯乙烯无卤阻燃复合材料

以氢氧化镁(MH)、氢氧化铝(ATH) 和微胶囊红磷(MRP) 为无卤阻燃剂, 高抗冲聚苯乙烯(HIPS) 树脂为聚合物基体, 通过熔融共混法制备了一系列不同组成的MH-ATH-MRP/HIPS复合材料。采用水平燃烧、垂直燃烧、氧指数、锥形量热分析、高温热分解实验等方法研究了复合材料的阻燃性能。结果表明, 阻燃剂用量相同时, 在HIPS基体中同时引入MH和ATH得到的复合材料比单独加入MH或ATH得到的复合材料具有更好的阻燃性能。当MH-ATH/HIPS的质量比为70:30:100时, 复合材料的水平燃烧级别达到FH-1级, 氧指数为25.2%, 但垂直燃烧无级别。在上述体系中加入极少量的MRP(占复合材料的质量分数为2.9%)就可使复合材料的火灾性能指数(FPI) 提高85%, 燃烧过程中热量释放和质量损失更慢、成炭能力明显增强, 垂直燃烧级别达到FV-0级。当MH-ATH-MRP/HIPS的质量比为21:9:12:100时, 复合材料的各项阻燃性能达到最佳, 可以大幅度减少阻燃剂的用量。MH、ATH和MRP对HIPS具有非常显著的协同阻燃作用。同时加入MH和ATH时不仅可以在更宽的温度范围内抑制HIPS的升温和分解, 而且能够在更宽的温度范围内相继释放出水蒸气稀释氧气和可燃气体的浓度, 从而起到协同阻燃作用。加入MRP后复合材料的成炭能力大大增强, 进一步改善了凝聚相阻燃的效果, 因此阻燃性能显著提高。     

Crystal Structure of (H3O)2[(UO2)2(SeO4)3(H2O)2](H2O)3.5

Crystals of (H₃O)₂[(UO₂)₂(SeO₄)₃(H₂O)₂](H₂O)_3.5 were prepared from aqueous solutions by evaporation. The crystal structure [monoclinic system, space group P2₁/m, a = 11.9402(11), b = 13.6452(14), c = 13.7271(12) Å, β = 109.436(7)°, V = 2109.1(3) ų] was solved by the direct method and refined to R ₁ = 0. 048 (wR ₂ = 0. 082) for 3677 reflections with |F _hkl |F _hkl |. The structure consists of [(UO₂)₂(SeO₄)₃(H₂O)₂]₂₋ layers arranged parallel to the (010) plane. The layers are formed by uranium and selenium coordination polyhedra sharing common vertices and are linked with each other by hydrogen bonds through the H₂O and H₃O⁺ groups arranged between the layers. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 412–414. Original Russian Text Copyright ? 2005 by Krivovichev, Kahlenberg.     

A new borophosphate chain anion in an organo-templated iron(III) borophosphate: Synthesis, crystal structure and magnetic properties of (C4H12N2)3Fe6(H2O)4[B6P12O50(OH)2]·2H2O

The organo-templated iron(III) borophosphate (C₄H₁₂N₂)₃Fe^III₆(H₂O)₄[B₆P₁₂O₅₀(OH)₂]·2H₂O was prepared under mild hydrothermal conditions (443 K). The crystal structure was determined from single-crystal X-ray data at 295 K (orthorhombic, Pbca (No. 61), Z=4, a=17.8023(7) Å, b=16.1037(5) Å, c=19.1232(6) Å, V=5482.3(3) Å³, R1=0.055, wR2=0.104, 6576 observed reflections with I>2σ(I)) and contains a new type of borophosphate anion: a mixed open- and loop-branched zehner single chain, , built from heptamers [B₂P₅O₂₁] interconnected by BO₃(OH) tetrahedra sharing their third oxygen corners with additional (terminal) PO₄ tetrahedra to form open branchings. The mixed open- and loop-branched single chains running along [0 0 1] are interconnected by three crystallographically independent iron coordination octahedra to form a 3D framework structure containing eight-membered ring channels running along [0 1 0] and cages, which are occupied by two crystallographically independent piperazine cations and H₂O molecules. The displacement parameters of C and N atoms in the piperazine cations are dramatically influenced by the strength of the hydrogen bond reflecting the shape of the cavities. The magnetic investigations indicate the existence of antiferromagnetic interactions as the major components. A narrow hysteresis at low temperatures indicates a weak ferromagnetic component, due to a non-cancellation of spins.     

Dynamic deformation and fracture of mullite (3Al2O3·2SiO2) ceramics under hypervelocity impact

Shock-recovery experiments have been performed on mullite ceramics to clarify the effect of a phase transition on the microstructural change and deformation mechanism under shock loading. The recovered samples have been examined using the X-ray diffraction method and transmission electron microscope observation. In the samples shocked above the phase-transition pressure, an amorphization of mullite occurs. Mullite nano-crystals with grain sizes less than 10 nm are dispersed in the amorphous phase, indicating that the relatively large starting mullite crystals become nano-crystals accompanied with the amorphization. Mullite bumper-shield experiments have also been performed to examine the influence of shock-induced microstructural changes to ultimate fracture under hypervelocity impact. The results suggest that the phase transition of mullite has an effect on protection against high-velocity impact.     

Ultra-fast synthesis and enhanced photocatalytic properties of alpha-Fe2O3/ZnO core-shell structure

Spindle-like α-Fe₂O₃/ZnO core-shell structures were synthesized by a simple two-step method of microwave hydrothermal synthesis. The as-prepared products were characterized by X-ray diffraction, transmission electron microscopy, high-resolution TEM and selected area electron diffraction. Furthermore, photocatalytic activity was measured through the degradation of methyl orange solution. And the results of degradation reveal that the spindle-like α-Fe₂O₃/ZnO nanocomposites exhibit better photocatalytic activities (3.5 times improvement) than those of the pure spindle-like α-Fe₂O₃ under ultraviolet irradiation. A mechanism was proposed based on which the electrons excited in the photocatalytic process.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.