Synthesis and characterization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> magnetic composite nanoparticles by a one-pot process

Fe₃O₄@SiO₂ core–shell composite nanoparticles were successfully prepared by a one-pot process. Tetraethyl-orthosilicate was used as a surfactant to synthesize Fe₃O₄@SiO₂ core–shell structures from prepared Fe₃O₄ nanoparticles. The properties of the Fe₃O₄ and Fe₃O₄@SiO₂ composite nanoparticles were studied by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. The prepared Fe₃O₄ particles were approximately 12 nm in size, and the thickness of the SiO₂ coating was approximately 4 nm. The magnetic properties were studied by vibrating sample magnetometry. The results show that the maximum saturation magnetization of the Fe₃O₄@SiO₂ powder (34.85 A·m2·kg–1) was markedly lower than that of the Fe₃O₄ powder (79.55 A·m2·kg–1), which demonstrates that Fe₃O₄ was successfully wrapped by SiO₂. The Fe₃O₄@SiO₂ composite nanoparticles have broad prospects in biomedical applications; thus, our next study will apply them in magnetic resonance imaging.     

Simultaneously catalytic removal of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> and particulate matter on diesel particulate filter

Diesel engines combine a high fuel economy with high durability and low maintenance costs and are, there-fore, used on a large scale for transportation purposes.However, the environmental pollution by diesel-engine exhausts has become more and more serious in the lastdecade, and currently the regulation of diesel emissions becomes tightened especially with respect to nitrogen ox-ides (NOx) and particulate matters (PM). Since the reduc-tion of both NOx and PM to the admitted level cannot be …     

Microstructures and properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> dispersion-strengthened copper alloys prepared through different methods

Al₂O₃ dispersion copper alloy powder was prepared by internal oxidation, and three consolidation methods—high-velocity compaction (HVC), hot pressing (HP), and hot extrusion (HE)—were used to prepare Al₂O₃ dispersion-strengthened copper (Cu–Al₂O₃) alloys. The microstructures and properties of these alloys were investigated and compared. The results show that the alloys prepared by the HP and HE methods exhibited the coarsest and finest grain sizes, respectively. The alloy prepared by the HVC method exhibited the lowest relative density (98.3% vs. 99.5% for HP and 100% for HE), which resulted in the lowest electrical conductivity (81% IACS vs. 86% IACS for HP and 87% IACS for HE). However, this alloy also exhibited the highest hardness (77 HRB vs. 69 HRB for HP and 70 HRB for HE), the highest compressive strength (443 MPa vs. 386 MPa for HP and 378 MPa for HE), and the best hardness retention among the investigated alloys. The results illustrate that the alloy prepared by the HVC method exhibits high softening temperature and good mechanical properties at high temperatures, which imply long service life when used as spot-welding electrodes.     

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.     

Immobilization of hemoglobin on platinum nanoparticles-modified glassy carbon electrode for H<Subscript>2</Subscript>O<Subscript>2</Subscript> sensing

This work described an amperometric hydrogen peroxide (H2O2) biosensor based on immobilization of hemoglobin (Hb) on a glassy carbon (GC) electrode modified by platinum nanoparticles, which was prepared by an in situ chemical reductive growth method. The electrochemical impedance measurements confirmed that the Hb was immobilized on the platinum nanoparticles-modified glassy carbon surface and has a synergistic effect with platinum nanoparti-cles in improving the catalytic reduction of H2O2. The Hb immobili...     

非均相光催化技术处理废纸制浆废水的比较和优化

研究了不同非均相光催化工艺去除废纸制浆废水总有机碳（TOC）的效果，并对其进行比较和优化．结果表明，将均相和非均相光催化体系复合使用，可显著加快反应速度，提高处理效果在针铁矿、赤铁矿、TiO2分别与FeSO4复合催化的不同体系中，经30min光照后均可去除约57％的TOC．催化剂的晶体结构不同，光催化效果不同，3种催化剂的有效顺序为：针铁矿〉赤铁矿〉TiO2，与FeSO4复合后的顺序不变．针铁矿光催化反应和光解H2O2反应之间存在着很好的协同效应．非均相光催化反应可有效矿化小分子有机物，催化剂用量存在最佳饱和点，适当增加H2O2用量可有效提高处理效果．实验证明，光催化工艺可有效处理废纸制浆废水．     

Growth characteristics of directionally solidified Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/YAG/ZrO<Subscript>2</Subscript> ternary hypereutectic <Emphasis Type="Italic">in situ</Emphasis> composites under ultra-high temperature gradient

Oxide eutectic ceramic in situ composites have attracted significant interest in the application of high-temperature structural materials because of their excellent high-temperature strength, oxidation and creep resistance, as well as outstanding microstructural stability. The directionally solidified ternary Al₂O₃/YAG/ZrO₂ hypereutectic in situ composite was successfully prepared by a laser zone remelting method, aiming to investigate the growth characteristic under ultra-high temperature gradient. The microstructures and phase composition of the as-solidified hypereutectic were characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that the composite presents a typical hypereutectic lamellar microstructure consisting of fine Al₂O₃ and YAG phases, and the enriched ZrO₂ phases with smaller sizes are randomly distributed at the Al₂O₃/YAG interface and in Al₂O₃ phases. Laser power and scanning rate strongly affect the sample quality and microstructure characteristic. Additionally, coarse colony microstructures were also observed, and their formation and the effect of temperature gradient on the microstructure were discussed.     

Effect of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> addition on the oxidation induration mechanism of Hongge vanadium titanomagnetite pellets

As part of a research project to develop a novel clean smelting process for the comprehensive utilization of Hongge vanadium titanomagnetite (HVTM), in this study, the effect of Cr₂O₃ addition on the oxidation induration mechanism of HVTM pellets (HVTMPs) was investigated in detail. The results showed that the compressive strength of the HVTMPs was greatly weakened by the Cr₂O₃ addition, mainly because of a substantial increase in the porosity of the HVTMPs. The Cr₂O₃ addition marginally affected the phase composition but greatly affected the microstructural changes of the HVTMPs. Increased amounts of Cr₂O₃ resulted in a decrease in the uniform distribution of the hematite grains and in an increase in the Fe-Cr solid solutions (Fe_1.2Cr_0.8O₃ and Fe_0.7Cr_1.3O₃) embedded in the hematite grains. Moreover, the compact hematite was destroyed by forming a dispersed structure and the hematite recrystallization was hindered during the oxidation induration, which adversely affected the compressive strength. On the basis of these results, a schematic was formulated to describe the oxidation induration mechanism with different amounts of added Cr₂O₃. This study provides theoretical and technical foundations for the effective production of HVTMPs and a reference for chromium-bearing minerals.     

Preparation and radar-absorbing properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Yb<Subscript>2</Subscript>O<Subscript>3</Subscript> composite powder

Al₂O₃/TiO₂/Fe₂O₃/Yb₂O₃ composite powder was synthesized via the sol-gel method. The structure, morphology, and radar-absorption properties of the composite powder were characterized by transmission electron microscopy, X-ray diffraction analysis and RF impedance analysis. The results show that two types of particles exist in the composite powder. One is irregular flakes (100-200 nm) and the other is spherical Al₂O₃ particles (smaller than 80 nm). Electromagnetic wave attenuation is mostly achieved by dielectric loss. The maximum value of the dissipation factor reaches 0.76 (at 15.68 GHz) in the frequency range of 2-18 GHz. The electromagnetic absorption of waves covers 2-18 GHz with the matching thicknesses of 1.5-4.5 mm. The absorption peak shifts to the lower-frequency area with increasing matching thickness. The effective absorption band covers the frequency range of 2.16-9.76 GHz, and the maximum absorption peak reaches -20.18 dB with a matching thickness of 3.5 mm at a frequency of 3.52 GHz.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the properties of ceramics from steel slag

Ferric oxide is one of the key factors affecting both the microstructure and the properties of CaO-MgO-SiO₂-based ceramics. Research on this effect is significant in the utilization of iron-rich solid wastes in ceramics. Ceramic samples with various Fe₂O₃ contents (0wt%, 5wt%, and 10wt%) were prepared and the corresponding physical properties and microstructure were studied. The results indicated that Fe₂O₃ not only played a fluxing role, but also promoted the formation of crystals. Ceramics with 5wt% of Fe₂O₃ addition attained the best mechanical properties with a flexural strength of 132.9 MPa. Iron ions were dissolved into diopside, consequently causing phase transformation from diopside and protoenstatite to augite, thereby contributing to the enhancement of its properties. An excess amount of Fe₂O₃ addition (10wt% or more) resulted in deteriorated properties due to the generation of an excess volume of liquid and the formation of high-porosity structures within ceramics.     

Preparation and luminescence properties of YeO3：Er^3＋/TiO2 with high specific surface area

The three composites Y2O3 :Er3+ , Y2O3 :Er3+ /Yb 3+ andY2O3 :Er3+ /TiO2 were prepared using coprecipitation and sol-gel techniques. Their morphology, specific surface area, porosity, UV-vis. absorption spectra and fluorescence spectra were measured using SEM, TEM, surface analysis, UV-vis. absorption and photoluminescence spectrophotometry. SEM and TEM showed that samples prepared using coprecipitation were dispersed, while Y2O3 :Er3+ /TiO2 particles possessed a mesoporous surface and average diameter of ab...     

Hydrogen storage properties of MgH<Subscript>2</Subscript> co-catalyzed by LaH<Subscript>3</Subscript> and NbH

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH₂ + 10wt%LaH₃ + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H₂ within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH₃ and NbH upon dehydriding of MgH₂. By contrast, pure MgH₂, an MgH₂ + 20wt%LaH₃ composite, and an MgH₂ + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H₂, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH₂ + 10wt%LaH₃ + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH₂. The introduction of LaH₃ and NbH was beneficial to the hydrogen storage performance of MgH₂.     

Preparation of nanocrystalline Co<Subscript>3</Subscript>O<Subscript>4</Subscript> and its properties as supercapacitors

Electrochemical capacitors store the capacitance through faradic reaction, which is generally named psue-docapacitance or supercapacitance. They are currently extensively studied as novel energy storage devices. Due to their superb characteristics of high power density and long cycle life compared to the conventional batteries, their high pulse-power capability is very excellent. Inter-ests in supercapacitor energy-storage systems have arisen in recent years on account of possible applications…     

Polysaccharide separation mechanism in polysulfone-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic composite membranes

Polysulfone (PSF)-Fe3O4 composite membranes were prepared by the phase-inversion process and their polysaccharide separation mechanism was explored using chondroitin sulfate (CS) and dextran. The mechanism was analyzed from constraints on the magnetic field and geometric deformation. It was found that variations in dextran rejection from 58% to 46% were mainly influenced by the geometric deformation of the composite membrane, while the magnetic field had a significant influence on variations in CS rejection from 82% to 35%. The results indicate that it is possible to continuously separate different types of polysaccharide with a composite membrane by adjusting the external magnetic field.     

Catalysis of organic pollutant photodegradation by metal phthalocyanines immobilized on TiO<Subscript>2</Subscript>@SiO<Subscript>2</Subscript>

A TiO2@SiO2 hybrid support was prepared by the sol-precipitation method using n-octylamine as a template.The photocatalyst manganese phthalocyanine tetrasulfonic acid (MnPcS) was immobilized on the support to form MnPcS-TiO2@SiO2.X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were employed to characterize the catalyst.The photocatalytic degradation of rhodamine B (RhB) and the catalytic oxidation of o-phenylenediamine (OPDA) under visible light irradiation were used as probe reactions.The mineralization efficiency and the degradation mechanism were evaluated using chemical oxygen demand (COD Cr) assays and electron spin resonance (ESR),respectively.RhB was efficiently degraded by immobilized MnPcS-TiO2@SiO2 under visible light irradiation.Complete decolorization of RhB occurred after 240 min of irradiation and 64.02% COD Cr removal occurred after 24 h of irradiation.ESR results indicated that the oxidation process was dominated by the hydroxyl radical (·OH) and superoxide radical (O-·2) generated in the system.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript> addition on the friction and wear properties of (SiC<Subscript>p</Subscript>+Al<Subscript>2</Subscript>O<Subscript>3sf</Subscript>)/Al2024 composites fabricated by pressure infiltration

Aluminum (Al) 2024 matrix composites reinforced with alumina short fibers (Al₂O_3sf) and silicon carbide particles (SiC_p) as wear-resistant materials were prepared by pressure infiltration in this study. Further, the effect of Al₂O_3sf on the friction and wear properties of the as-synthesized composites was systematically investigated, and the relationship between volume fraction and wear mechanism was discussed. The results showed that the addition of Al₂O_3sf, characterized by the ratio of Al₂O_3sf to SiC_p, significantly affected the properties of the composites and resulted in changes in wear mechanisms. When the volume ratio of Al₂O_3sf to SiC_p was increased from 0 to 1, the rate of wear mass loss (K_m) and coefficients of friction (COFs) of the composites decreased, and the wear mechanisms were abrasive wear and furrow wear. When the volume ratio was increased from 1 to 3, the COF decreased continuously; however, the K_m increased rapidly and the wear mechanism became adhesive wear.     

Static synthesis of high-quality MCM-22 zeolite with high SiO2／Al2O3 ratio

We demonstrate a synthesis method to broaden the range of SiO2/Al2O3 ratio (30-100) of high-silica MCM-22 zeolites by prolonging the aging time of the gel before the crystallization. The synthesis conditions such as silica sources, chemical compositions of initial gel and aging time of gel were investigated in detail.High quality MCM-22 products with various morphologies have been synthesized by optimize their synthesis conditions.Our results show that increasing of the aging time can make the gel be homogenization and promote their nucleus formation,which may avoid the formation of impurity phase and thus broaden the range of SiO2/Al2O3 ratio.     

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.     

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.     

Transparent organic light-emitting diodes based on Cs<Subscript>2</Subscript>CO<Subscript>3</Subscript>:Ag/Ag composite cathode

The transparent organic light-emitting diodes (TOLEDs) based on Cs 2 CO 3:Ag/Ag composite cathode are reported in this paper.They show higher efficiency and better stability than the control devices with the Cs 2 CO 3 /Ag cathode.The devices are highly transparent,and show total efficiencies from both sides of the devices comparable with conventional bottom-emitting devices.The electroluminescence (EL) spectrum from the cathode side of the device is closer to the photoluminescence (PL) spectrum of the light...