Nonlinear optical properties of Eu<Subscript>2</Subscript>O<Subscript>3</Subscript> doped 5ZnO-20Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>-75TeO<Subscript>2</Subscript> glasses

The third-order optical nonlinearities, including third-order nonlinear susceptibility X^(3), nonlinear refractive index (n2) and temporal response, were measured with forward DFWM using Nd:YAG mode-locked pulse laser. The results show that Eu203 doped 5ZnO-20Nb2O5-75TeO2 glasses have large n2 and ultra-fast temporal response. Raman spectra show that Eu2O3 dopant induces the changes in the local structure of glasses. The higher the dopant concentration, the larger the nonlinear refractive n2 and the faster the temporal response. The enhancement on the third-order optical nonlinearities can be attributed to the deformation of the electronic clouds in [TeO4] enhanced by Eu2O3 dopant.     

Adsorption and catalytic combustion of ARB on CuO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

CuO-Fe2O3 composite material with strong magnetism and a large surface area is prepared by the co-precipitate method. Its adsorption properties towards Acid Red B (ARB) and the regeneration by catalytic combastion of organic compounds have been studied. The results show that the prepared CuO-Fe2O3 composite is an excellent adsorbent for ARB adsorption at acid condition. The presence of Cl^- has no effect on ARB adsorption. But the SO4^2- can inhibit ARB adsorption. After being recovered by the magnetic separation method, the adsorbent can be regenerated by catalytic oxidation of absorbate at 300℃ in air atmosphere. The combustion reactions of ARB in the presence or absence of CuO-Fe2O3 are studied by in situ diffuse refieclion FTIR. The results indicate that, in the presence of CuO-Fe2O3, the degradation temperature is significantly lowered by the catalysis of CuO-Fe2O3, and ARB can be oxidized completely without volatile organic compound by-product; in comparison, in the absence of CuO-Fe2O3, the temperature needed for oxidation of ARB is higher and the reaction is incomplete with some N-containing harmful compounds produced. The reusability of CuO-Fe2O3 is also studied in successive seven adsorption-regeneration cycles.     

Effect of the synthesis route on the structural and dielectric properties of SrBi<Subscript>1.8</Subscript>Y<Subscript>0.2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>9</Subscript> ceramics

This work is devoted to the synthesis and characterization of yttrium-doped SrBi₂Nb₂O₉ ceramics prepared by three methods: solid state reaction, co-precipitation, and hydrothermal. Multiple characterizations, specifically scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), were used to validate the structural feature. The crystallite size was estimated by Scherrer’s formula and the Williamson–Hall plot. The effect of the process on the band intensities of the FTIR spectra was investigated. The crystallite size and microstructure of ceramics prepared from different synthesis processes were strongly influenced by the sinterability. SEM images revealed nanograin ceramics for materials prepared by co-precipitation and hydrothermal methods and micrograin ceramics prepared by the solid state method. The synthesized compounds underwent phase transitions at 480–465°C. The dielectric and electrical properties of these Y-doped SrBi₂Nb₂O₉ ceramics appear to be dependent on the grain size.     

Evolution of resistive switching polarity in Au/Ar<Superscript>+</Superscript> bombarded SrTi<Subscript>0.993</Subscript>Nb<Subscript>0.007</Subscript>O<Subscript>3</Subscript>/In sandwiches

We investigated the resistive switching characteristics of Au/Ar+bombarded SrTi 0.993 Nb0.007O3/In sandwiches.The evolution of the resistive switching polarity with sweeping voltage was observed.Our experiments showed that under a macroscopic electrode the homogeneous trapping-detrapping-type conduction and filament-type conduction coexist and compete with each other.For a large sweeping voltage range,the trapping-detrapping-type conduction dominates.However,for a small range the latter dominates. If the bias voltage is too large,the filament conduction could be destroyed.These results will help deepen the understanding of the resistive switching polarity,and will aid in future device design.     

Fabrication and properties of aluminum silicate fibrous materials with <Emphasis Type="Italic">in situ</Emphasis> synthesized K<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript> whiskers

To improve their mechanical and thermal insulation properties, aluminum silicate fibrous materials with in situ synthesized K₂Ti₆O₁₃ whiskers were prepared by firing a mixture of short aluminum silicate fibers and gel powders obtained from a sol-gel process. During the preparation process, the fiber surface was coated with K₂Ti₆O₁₃ whiskers after the fibers were subjected to a heat treatment carried out at various temperatures. The effects of process parameters on the microstructure, compressive strength, and thermal conductivity were analyzed systematically. The results show that higher treatment temperatures and longer treatment durations promoted the development of K₂Ti₆O₁₃ whiskers on the surface of aluminum silicate fibers; in addition, the intersection structure between whiskers modulated the morphology and volume of the multi-aperture structure among fibers, substantially increasing the fibers' compressive strength and reducing their heat conduction and convective heat transfer at high temperatures.     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

Selective formation of tetrahedral Pt nanocrystals from K2PtCl6／PVP

Tetrahedral platinum (Pt) nanocrystals (3-8 nm) are synthesized in high selectivity (ca. 80%) from hydrogen reduction of aqueous K2PtCI6 by using polyvinylpyr-rolidone (PVP: Mw≈360000) as a protector. Morphology (TEM) measurements of the metal colloids and UV-Vis absorption of the colloidal solution are employed to monitor the tetrahedron formation during the syntheses with varying K2PtCl6/PVP ratios. The results clearly show a two-stage process for the selective formation of tetrahedral nanocrystals. Rapid nucleation and crystal formation at the early stage result in round-like crystallites and the external facet evolution in thereafter slow crystal growth leads selectively to the formation of the tetrahedrons.     

Preparation of Al<Subscript>72</Subscript>Ni<Subscript>8</Subscript>Ti<Subscript>8</Subscript>Zr<Subscript>6</Subscript>Nb<Subscript>3</Subscript>Y<Subscript>3</Subscript> amorphous powders and bulk materials

Amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The isothermal crystallization kinetics was analyzed by the Johnson–Mehl–Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ·mol?1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent (n) imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al₇₂Ni₈Ti₈Zr₆Nb₃Y₃ powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.     

Investigation of the cross-reaction mechanism of C<Subscript>6</Subscript>H<Subscript>5</Subscript>F-HNO<Subscript>2</Subscript> aqueous solution irradiated at 355 nm by transient absorbance spectrum technique

The transient absorption spectrum technique was employed to investigate the cross-reaction mechanism of C6H5F-HNO2 aqueous solution irradiated at 355 nm. The characteristic and the kinetic parameters of transient species were also detected. Hydroxyl radical derived from the photolysis of HNO2 was added to monofluorobenzene with a second-order rate constant of （5.83±0.17）×10^9 L·mol^-1·s^-1 to form an adduct, C6H5F…OH, which was able to react with HNO2 as the main reaction pathway with a rate constant of （8.3±0.1）×10^7 L·mol^-1·s^-1. The C6F6…OH adduct can also be decayed by elimination of H2O to yield monofluorophenyl radical C6H4F-. By GC-MS technique, the final products were identified to be monofluorophenol, nitro-monofluorobenzene, nitro-monofluorophenol and para-fluorobiphenyl.     

Photocatalytic degradation kinetics of Rhodamine B catalyzed by nanosized TiO<Subscript>2</Subscript> film

A fixed bed photocatalytic reactor was designed,and dynamic fast scan of UV-Vis adsorption spectrum was adopted to study the photocatalytic degradation dynamic behavior of Rhodamine B,a kind of dye generally recognized as to be degraded difficultly ,on the surface of nanosized TiO2 thin film,The results indicate that the photocatalytic degradation process of Rhodamine B does not comply with the first-order reaction kinetic process ,As a result,a kinetic model of Rhodamine B photocataly tic degradation ,reaction is brough forward ,and the model is proved by the theoretical deduction and experiment.     

Synthesis and magnetic properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/helical carbon nanofiber nanocomposites from the catalytic pyrolysis of ferrocene

High purity Fe3O4 /helical carbon nanofiber composites were obtained on a large scale by the catalytic pyrolysis of ferrocene in the presence of tin powder at 500°C over 12 h. The sizes of Fe 3 O 4 nanoparticles are 35–65 nm in size, and the diameters of the helical carbon nanofibers range from 40–70 nm. The shapes and compositions of the nanocomposites are simply controlled by adjusting the reaction temperatures. On the basis of the obtained experimental results the formation of the helical Fe3O4/carbon nanofiber composites was investigated and discussed. The magnetic hysteresis loop of the products shows ferromagnetic behavior with saturation magnetization (M s ), remanent magnetization (M r ) and coercivity (H c ) values of ca. 29.8 emu/g, 9.6 emu/g and 306.6 Oe, respectively.     

Electrical conductivity optimization of the Na3AlF6-Al2O3-Sm2O3 molten salts system for Al-Sm intermediate binary alloy production

Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ electrolysis medium in the temperature range from 905 to 1055℃. The temperature (t) and the addition of Al₂O₃ (W(Al₂O₃)), Sm₂O₃ (W(Sm₂O₃)), and a combination of Al₂O₃ and Sm₂O₃ into the basic fluoride system were examined with respect to their effects on the conductivity (κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature (t) and decreases with the addition of Al₂O₃ or Sm₂O₃ or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na₃AlF₆-AlF₃-LiF-MgF₂-Al₂O₃-Sm₂O₃ system are W(Al₂O₃) + W(Sm₂O₃)=3wt%, W(Al₂O₃):W(Sm₂O₃)=7:3, and a temperature of 965 to 995℃, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.     

Electro-deoxidation of V<Subscript>2</Subscript>O<Subscript>3</Subscript> in molten CaCl<Subscript>2</Subscript>-NaCl-CaO

The electro-deoxidation of V₂O₃ precursors was studied. Experiments were carried out with a two-terminal electrochemical cell, which was comprised of a molten electrolyte of CaCl₂ and NaCl with additions of CaO, a cathode of compact V₂O₃, and a graphite anode under the potential of 3.0 V at 1173 K. The phase constitution and composition as well as the morphology of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 3 g of V₂O₃ could be converted to vanadium metal powder within the processing time of 8 h. The kinetic pathway was investigated by analyzing the product phase in samples prepared at different reduction stages. CaO added in the reduction path of V₂O₃ formed the intermediate product CaV₂O₄.     

One-pot synthesis of PVP-coated Ni<Subscript>0.6</Subscript>Fe<Subscript>2.4</Subscript>O<Subscript>4</Subscript> nanocrystals

Novel poly(N-vinyl-2-pyrrolidone) (PVP)-coated nickel ferrite nanocrystals were prepared by simultaneously pyrolyzing nickel(II) acetylacetonate (Ni(acac)₂) and iron(III) acetylacetonate (Fe(acac)₃) in N-vinyl-2-pyrrolidone (NVP). The PVP coating was formed in situ through polymerization of NVP. The crystalline structure of the resultant nickel ferrite was analyzed by high-resolution transmission electron microscopy, electron diffraction patterns, and powder X-ray diffraction. In addition, the valence state of Ni and the metal contents of Ni and Fe in different valence states were analyzed by X-ray photoelectron spectroscopy (XPS), atomic absorption and the phenanthroline method. The surface coating layer of PVP and its binding states were characterized by Fourier transform infrared spectroscopy in combination with XPS. Colloidal stability experiments revealed that the nanocrystals could be dispersed well in both phosphate-buffered saline and Dulbecco’s Modified Eagle Medium.     

Synthesis of highly ordered SnO2／Fe2O3 composite nanowire arrays by electrophoretic deposition method

Highly ordered SnO2/Fe2O3 composite nanowire arrays have been synthesized by electrophoretic deposition method. The morphology and chemical composition of SnO2/Fe2O3 composite nanowire arrays are characterized by SEM, TEM, EDX, XPS, and XRD. The results show that the SnO2/Fe2O3 composite nanowires are about 180 nm in width and tens of microns in length, and they are composed of small nanoparticles of tetraganal SnO2 and rhombohedral α-Fe203 with diameters of 10-15nm. The SnO2/Fe2O3 composite nanowires are formed by a series of chemical reactions.     

Fabrication of porous alumina templates with a large-scale tunable interpore distance in a H<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>-C<Subscript>2</Subscript>H<Subscript>5</Subscript>OH-H<Subscript>2</Subscript>O solution

Highly ordered porous alumina templates with a large-scale tunable interpore distance （100-445 nm） have been successfully fabricated under an electric field of 40-180 V by modifying oxalic acid solution with adequate alcohol. The results under our experimental conditions show that the phenomena of burning and breakdown during the high-field anodization process can be avoided by adding a proper amount of alcohol to the oxalic acid solution. An excellent linear relationship between interpore distance and anodization voltage is obtained under 40-170 V, and the maximum anodization voltage that could be used to avoid burning and breakdown is 180 V.     

La<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>7</Subscript> TBCs toughened by Pt particles prepared by cathode plasma electrolytic deposition

La₂Zr₂O₇ thermal barrier coatings (TBCs) with dispersed Pt particles were prepared by cathode plasma electrolytic deposition (CPED) with ceramic balls added to the cathode region. Compared with the conventional CPED, when ceramic balls are used in the cathode region, the plasma discharge ignition current density decreases approximately 62-fold and the stable plasma discharges occur at the whole cathode surface. Such TBCs with a thickness of 100 μm exhibit a crack-free surface and are composed of pyrochlore-structured La₂Zr₂O₇. Cyclic oxidation, scratching, and thermal insulation capability tests show that such TBCs not only exhibit high resistance to oxidation and spallation but also provide good thermal insulation. These beneficial effects are attributed to the excellent properties of TBCs, such as good thermal insulation because of low thermal conductivity, high-temperature oxidation resistance because of low-oxygen diffusion rate, and good mechanical properties because of the toughening effect of Pt particles.     

Mineral-phase evolution and sintering behavior of MO-SiO2-Al2O3-B2O3 (M=Ca,Ba) glass-ceramics by low-temperature liquid-phase sintering

In this work, network former SiO₂ and network intermediate Al₂O₃ were introduced into typical low-melting binary compositions CaO·B₂O₃, CaO·2B₂O₃, and BaO·B₂O₃ via an aqueous solid-state suspension milling route. Accordingly, multiple-phase aluminosilicate glass-ceramics were directly obtained via liquid-phase sintering at temperatures below 950℃. On the basis of liquid-phase sintering theory, mineral-phase evolutions and glass-phase formations were systematically investigated in a wide MO-SiO₂-Al₂O₃-B₂O₃ (M=Ca, Ba) composition range. The results indicate that major mineral phases of the aluminosilicate glass-ceramics are Al₂₀B₄O₃₆, CaAl₂Si₂O₈, and BaAl₂Si₂O₈ and that the glass-ceramic materials are characterized by dense microstructures and excellent dielectric properties.     

Dissolution of Al<Subscript>2</Subscript>TiO<Subscript>5</Subscript> inclusions in CaO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> slags at 1823 K

Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al₂TiO₅ inclusion was immersed in a CaO-SiO₂-Al₂O₃ molten slag for different durations at 1823 K. The Al₂TiO₅ dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO₂ diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/w(SiO₂) value in the reaction region. A liquid product (containing 0.7–1.2 w(CaO)/w(SiO₂), 15wt%–20wt% Al₂O₃, and 5wt%–15wt% TiO₂) forms on the inclusion surface when Al₂TiO₅ is dissolved in the slag. Al₂TiO₅ initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al₂TiO₅ dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.     

Synthesis, Characterization and Calorimetry of Ni（C4H8N2O3）2Cl2

A coordination complex was synthesized from NiCl2 and dipeptide glycylglycine（GG）. It was characterized by element analysis, NMR and TG methods, and then was determined to be Ni（C4HsN2O3）2Cl2. Using an isoperibolic reaction calorimeter, the standard molar enthalpy of formation of Ni（GG）2Cl2（solid） has been determined to be -（1 674.66±2.02） kJ · mol^-1 at 298.15 K.