Chromium containing Fe3O4/polyacrylonitrile–ethylenediamine as a magnetically recoverable catalyst for alcohol oxidation

A new chromium containing Fe₃O₄/polyacrylonitrile–ethylenediamine has been prepared through in situ polymerization of acrylonitrile onto the surface of magnetic nanoparticles. The polymer magnetic nanocomposite was utilized for the oxidation of a number of aromatic alcohols as a reusable catalyst. The corresponding aldehydes were obtained in high yields within short reaction time under mild conditions.     

Structural properties of 0.8CaZrO3–0.2CaFe2O4 composite

A composite with the 0.8CaZrO₃–0.2CaFe₂O₄ general formula was prepared by means of a double sintering process. Temperature of 1400 °C was found suitable to obtain the composite based on scanning electron microscopy and X-ray diffraction analysis. Phase composition, crystal structure, Mössbauer effect, microstructure and dielectric properties were studied. The influence of Fe ions on the CaZrO₃ structure has been reported. It was found that Fe substituted Zr in CaZrO₃ and vice versa in CaFe₂O₄ in the amount about 1.5 at% in both cases. The approximated formula of the obtained composite was 0.8Ca(Zr_0.9Fe_0.1)O₃–0.2Ca(Fe_0.8Zr_0.2)₂O₄. The SEM observations revealed that liquid CaFe₂O₄ occurred as a filling phase between CaZrO₃ grains which significantly enhanced densification of the material and influence on its properties. The dielectric constant reached the value of 170 at 1 MHz and the accompanying dissipation factor was very low – 0.005.     

N2H4/H2O2/CuSO4常压催化氢化SB

首次以水合肼和双氧水的氧化还原反应对两嵌段共聚物SB进行选择性加氢，并着重考察了各种氢化条件对加氢反应的影响，加氢度达到95％。本方法既具有学术上的理论意义，又对光纤材料国产化有重要意义。     

Nonlinear optical properties of (1−x) CaFe2O4–xBaTiO3 composites

In this paper, we report nonlinear optical properties of a composite nanostructure with the general formula (1−x) CaFe₂O₄–(x) BaTiO₃ (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) prepared by sol–gel and conventional solid-state reaction methods. Structural properties and chemical compositions of the samples were characterized using XRD and HRTEM. Basic optical constants, band gap energy and linear absorption coefficient were calculated through optical absorbance measurements. The nonlinear optical properties were investigated using the single-beam open aperture Z-scan technique. The obtained nonlinearity fits to Two-photon absorption process and all samples display high nonlinear absorption effect. The incorporation of BaTiO₃ into CaFe₂O₄ systems show a significant improvement in the nonlinear optical properties. These composite that exhibit efficient optical limiting can have potential applications in photonic devices.     

A novel noble metal-free ZnS–WS2/CdS composite photocatalyst for H2 evolution under visible light irradiation

A novel ZnS–WS₂/CdS composite photocatalyst for H₂ evolution under visible light irradiation has been successfully synthesized. The loading amounts of WS₂ and ZnS on the CdS surface were optimized. A H₂ evolution rate up to 1224 μmol·h^− 1 has been achieved for the 9.6 mol% ZnS–1 mol% WS₂/CdS photocatalyst. The enhancement of the photocatalytic activity is attributed to the synergistic effect of WS₂ as co-catalyst and ZnS as passivation layer.     

Performance of magnetically recoverable core–shell Fe3O4@Ag3PO4/AgCl for photocatalytic removal of methylene blue under simulated solar light

A novel magnetically recoverable core–shell Fe₃O₄@Ag₃PO₄/AgCl photocatalyst exhibiting rapid magnetic separation, stability and high photocatalytic activity under simulated solar light has been developed. Briefly, Ag₃PO₄ is immobilized on Fe₃O₄ nanoparticles and then an AgCl shell is formed by in situ ion exchange. The complete degradation of the methylene blue (MB) over the Fe₃O₄@Ag₃PO₄/AgCl photocatalyst only took about 60 min, much faster than WO₃–Pd photocatalyst. Fe₃O₄@Ag₃PO₄/AgCl nanocomposites can be easily recovered by a magnet, and reused at least five times without any appreciable reduction in photocatalytic efficiency.     

Microstructural evolution and enhanced mechanical properties of 95Al2O3–Yb/Mg/Si ceramics by optimizing sintering temperature

Designed component of 0.95Al₂O₃–0.015Yb₂O₃–0.01MgO–0.025SiO₂ (95Al₂O₃–Yb/Mg/Si) ceramics were prepared by the traditional mixed-oxide method in the sintering temperature range of 1450–1700 °C. The influence of sintering temperature on the crystal structure, densification, microstructure, mechanical, friction and wear properties of 95Al₂O₃-YbMgSi ceramics were systematically investigated. XRD and SEM analysis results revealed that the increase in sintering temperature was very beneficial to eliminate the pores, increase the density and grain size, which obeys the common grain growth law. Both the flexural strength and hardness of obtained samples were increased almost linearly when the sintering temperature increased from 1450 °C to 1700 °C. The ceramics sintered at 1650 °C showed the optimum properties: H_v = 1812.3, σ = 151.3 MPa, μ = 0.41, ρ = 3.72 g/cm³ and K_c = 8.06e^?5 mm³/N·m, respectively. Furthermore, the results of friction and wear experiments suggested that the 95Al₂O₃–Yb/Mg/Si ceramic prepared at the optimizing sintering process exhibited more stable friction state and lower wear degree under non-lubricated conditions. The enhanced mechanical properties could be attributed to their structure densification, pore elimination and gain growth with the increase of sintering temperature.     

Green synthesis of bi-component Mn3O4–MnO2 nanorods and enhanced catalytic properties

Bi-component Mn₃O₄–MnO₂ nanorods with lengths of up to 30 μm are synthesized using a simple hydrothermal method in the absence of templates. Samples were characterized by FE-SEM, HR-TEM, XRD, XPS, and N₂ adsorption–desorption. The results indicate that the Mn₃O₄–MnO₂ and Mn₅O₈ samples with various morphologies can be easily obtained via modulating Cl⁻ ions and glucose contents. Compared with that of the Mn₅O₈ samples, the bi-component Mn₃O₄–MnO₂ nanorods exhibited higher catalytic properties for oxidative decomposition of MB owing to its adjustable valence state and oxygen content.     

Microstructure evolution and mechanical properties of porous Si3N4 and dense Si3N4 joints bonded using CaO–Li2O-Al2O3–SiO2 glass-ceramic

A novel CaO-Li₂O-Al₂O₃-SiO₂ (CLAS) glass was developed for the joining of porous Si₃N₄ and dense Si₃N₄. A multiphase interlayer consisting of CaAl₂Si₂O₈, LiAlSi₂O₆ and CaSiO₃ phases was formed in joint, which possessed matched CTE with the Si₃N₄ substrates. In addition, the infiltrated layer with bilayer structure in the porous Si₃N₄ substrate was observed. The effects of joining temperature and cooling rate on microstructure, phase evolution and shear strength of joints were studied carefully. The results showed that the kinds of precipitated phases remained invariable with the joining temperature increased, but the crystallinity in the interlayer was improved remarkably as the cooling rate reduced. The maximum shear strength of 45 MPa was obtained when the joining temperature and cooling rate were 1100 °C and 5 °C/min, respectively. Moreover, fracture during the shear test occurred mainly within porous Si₃N₄ side, indicating superior joining of dense Si₃N₄/glass-ceramic/porous Si₃N₄.     

Phase evolution and microwave dielectric properties of SrTiO3 added ZnAl2O4–Zn2SiO4–SiO2 ceramics

Phase evolution and microwave dielectric properties of SrTiO₃ added ZnAl₂O₄–3Zn₂SiO₄–2SiO₂ ceramics system were investigated. With the addition of SrTiO₃, the sintering temperature for dense ceramic is reduced from 1320 °C to 1180–1200 °C. According to the nominal composition ZnAl₂O₄–3Zn₂SiO₄–2SiO₂-ySrTiO₃, phase evolution is revealed by XRD patterns and Back Scattering Electron images: Zn₂SiO₄, ZnAl₂O₄ and SiO₂ phases coexist at y = 0; SrTiO₃ reacts with ZnAl₂O₄ and SiO₂ to form SrAl₂Si₂O₈, TiO₂ and Zn₂SiO₄ at y = 0.2 to 0.8, and SiO₂ phase disappears at y = 0.8; new phase of Zn₂TiO₄ is obtained at y = 1. The existence of TiO₂ has important effect on the dielectric properties. The optimized microwave dielectric properties are obtained at y = 0.6 and the ceramics show low dielectric constant (7.16), high-quality factor (57, 837 GHz), and low temperature coefficient of resonant frequency (−30 ppm °C⁻¹).     

Constructing ZnCo2O4@LDH Core–Shell hierarchical structure for high performance supercapacitor electrodes

In this article, ZnCo₂O₄ nanowires deposited with two kinds of typical layered double hydroxides (Ni–Al,Co–Al LDH) are developed via scalable method. Two materials all display core–shell hierarchical structure. High specific capacitance of 2041 F g⁻¹ and 1586 F g⁻¹ are obtained for ZnCo₂O₄@Co–Al LDH and ZnCo₂O₄@Ni–Al LDH,respectively. Combining with active surface and synergistic effect, the role of hierarchical structure in enhancing performance is revealed. Moreover, two all solid state supercapacitors based on fabricated materials as positive electrodes, activated carbon as negative electrodes and PVA–KOH as polymer electrolyte are assembled. The maximum power and energy densities of ZnCo₂O₄@Co–Al LDH//AC are 6200 W kg⁻¹ and 50.1 Wh kg⁻¹, respectively. While the power and energy densities of ZnCo₂O₄@Ni–Al LDH//AC are 3400 W kg⁻¹ and 27.8 Wh kg⁻¹. At last, an energy storage–conversion system, based on solar cell as input device and assembled asymmetric supercapacitor ZnCo₂O₄@Co–Al LDH//AC as output device, is integrated as a self–sustaining power device, indicating its potential in practical applications.     

Rh–Sr/Al2O3 Catalyst for N2O Decomposition in the Presence of O2

The improving effect of Sr in the catalytic activity of Rh for N₂O decomposition has been studied under 1,000 ppm N₂O/He and 1,000 ppm N₂O/5% O₂/He (GHSV = 10,000 h^?1). Different techniques have been used for catalysts characterization: TEM, SEM-EDX, XRD, N₂ adsorption at ?196 °C and in situ XPS. Sr favours the Rh dispersion and reduction under reaction conditions, and allows the low temperature removal of N₂O in the presence of O₂ (100% decomposition at 350 °C).     

Mechanical properties of Si3N4–Al2O3 FGM joints with 15 layers for high-temperature applications

“Crack-free” alumina-silicon nitride joints, comprised of 15 layers of gradually differing compositions of Al₂O₃/Si₃N₄, have been fabricated using sialon polytypoids as functionally graded materials (FGM) bonding layers for high-temperature applications. Using flexural strength tests conducted both at room and at elevated temperatures, the average fracture strength at room temperature was found to be 437 MPa; significantly, this value was unchanged at temperatures up to 1000 °C. Scanning electron microscopy (SEM) observations of fracture surfaces indicated the absence of any glassy phase at the triple points. This result was quite contrary to the previously reported 20-layer Al₂O₃/Si₃N₄ FGM samples where three-point bend testing revealed a severe strength degradation at high temperatures. Consequently, we believe that the joining of alumina to silicon nitride using polytypoidally functional gradients can markedly improve the suitability of these joints for high-temperature applications.     

Construction of Amorphous CoS/CdS Nanoparticles Heterojunctions for Visible–Light–Driven Photocatalytic H2 Evolution

Catalysis Letters - Due to the poor photocatalytic hydrogen evolution ability of pure CdS, we need to develop a photocatalytic hydrogen evolution catalyst with high activity and no precious metal...