Effects of CaO and Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the reduction of high silicon iron ores

The effects of CaO and Na₂CO₃ on the reduction of high silicon iron ores at 1 250 °C were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na₂CO₃, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na₂CO₃ were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na₂CO₃ was more noticeable than that of CaO, and higher Na₂CO₃ doses resulted in stronger inhibition of the increased metallization rate. However, when Na₂CO₃ was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na₂CO₃ were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na₂CO₃ dosage.     

Electrochemical preparation of V<Subscript>2</Subscript>O<Subscript>3</Subscript> from NaVO<Subscript>3</Subscript> and its reduction mechanism

Vanadium trioxide (V₂O₃) was directly prepared by NaVO₃ electrolysis in NaCl molten salts. Electrolysis products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The existing state and electrochemical behavior of NaVO₃ were also studied. The results indicated that V₂O₃ can be obtained from NaVO₃. VC and C were also formed at high cell voltage, high temperature, and long electrolysis time. During electrolysis, NaVO₃ was dissociated to Na⁺ and VO₃ ^? in NaCl molten salt. NaVO₃ was initially electro- reduced to V₂O₃ on cathode and Na₂O was released simultaneously. Na₂CO₃ was formed due to the reaction between Na₂O and CO₂. The production of C was ascribed to the electro-reduction of CO₃ ^2?. VC was produced due to the reaction between C and V₂O₃.     

Synthesis and characterization of a new Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> pillared triple-layered perovskite KSr<Subscript>2</Subscript>Nb<Subscript>3</Subscript>O<Subscript>10</Subscript>

A n-Hexyl NH₃Sr₂Nb₃O₁₀ is obtained by the stepwise ion-exchange reaction, then is dispersed in aqueous solution of trinuclear acetato-hydroxo iron (III) nitrate, [Fe₃(OCOCH₃)₇OH·2H₂O]NO₃, and the interlayer potassium cations of the perovskite niobate are exchanged with the partially hydrolyzed trinuclear acetato complex ions. On heating, the exchanged complex ions are converted into iron oxide pillars which keep the perovskite sheets apart. The product is characterized by XRD, SEM, EDAX and surface area measurement respectively. Zhang Hui: Born in 1970 Funded by the National Natural Science Foundation of China (No. 50002007), Major Program of Ministry of Education (No. 0201) and Open Foundation of State Key Lab of Advanced Tech. for Materials Synthesis and Processing.     

Effect of Grain Size of CaCO3 and SiO2 on the Formation of C3S Under Different Conditions

The effect of grain size of CaCO3 and SiO2 on the formation of C3S under various conditions, such as rapid heating rate（800 ℃/min）, normal heating rate（30 ℃/min） and in the presence or absence of ZnO, was studied. The results show that the decomposition temperature of CaCO3, the temperature of appearance of liquid phase and the f-CaO content descend when the grain size of CaCO3 and SiO2 becomes smaller, which attributes to the reactive activity enhancement of powders due to the decrease of the particle size. When the grain size of CaCO3 and SiO2 is below 1 μm, the rate of the formation of C3S is greatly raised. A rapid sintering rate and the presence of ZnO have an important effect on the formation of C3S and can lower the temperature of the formation of C3S by about 50 ℃.     

Adsorption of BSA on carbon-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride

Carbon-coated Fe₃O₄ (Fe₃O₄/C) microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) were prepared, characterized and applied to adsorb bovine serum albumin (BSA). The prepared magnetic microspheres had spherical core-shell structure with a uniform and continuous carbon coating coupled with activation by EDC, and possessed superparamagnetic characteristics. The experimental results showed that the adsorption amount of BSA on the EDC-activated Fe₃O₄/C (Fe₃O₄/C-EDC) microspheres was higher than that on the Fe₃O₄/C microspheres. The maximum adsorption of BSA on Fe₃O₄/C-EDC microspheres occurred at pH 4.7, which was the isoelectric point of BSA. At low concentrations (below 1.0 M), salt had no noticeable effect on BSA adsorption. The BSA adsorption of Fe₃O₄/C-EDC microspheres had a better fit to the Langmuir model than the Freundlich isotherm and Temkin isotherm model, and the kinetic data were well described by the pseudo-second-order model. The adsorption equilibrium could be reached within 20 min. High desorption efficiency (97.6%) of BSA from Fe₃O₄/C-EDC microspheres was obtained with 0.5 M Na₂HPO₄ (pH 9.4) as the desorbent.     

Optical and magnetic properties of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> nano-composite films

Fe₂O₃/SiO₂ nano-composite films were prepared by sol-gel technique combining heat treatment in the range of 100–900 °C. The particle size was observed by FE-SEM. Optical properties of the films were investigated by UV-visible spectra. Structural and magnetic characteristics were investigated through FT-IR and VSM. The transparency of the Fe₂O₃/SiO₂ nano-composite films decreased with the content of the Fe₂O₃. Water and organic solvent in the films were evaporated with heat treatment, so the transparency of the films was enhanced under high temperature. It is also found that the saturation magnetization (M _s) of the films increases with the temperature. As the content of the Fe₂O₃ increases, when the content of the Fe₂O₃ is around 30wt%, the M _s of the films has a maximum value.     

Electrochemical Sensing of Heavy Metal Ions based on Monodisperse Single-crystal Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Microspheres

Single-crystal Fe₃O₄ with monodisperse microspheres structure has been used for individual electrochemical detection of heavy metal ions. Morphology and structure of the as-prepared Fe₃O₄ microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Meanwhile the electrochemical properties of the Fe₃O₄ microspheres modified glass carbon electrodes (GCE) were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the enhanced electrochemical response in stripping voltammetry for individual detection of Pb(II), Hg(II), Cu(II), and Cd(II) was evaluated using square wave anodic stripping voltammetry (SWASV). With high specific surface area and excellent catalytic activity toward heavy metal ions, the as-prepared monodisperse and single-crystal Fe₃O₄ microspheres show a preferable sensing sensitivity (22.2 μA/μM) and limit of detection (0.0699 μM) toward Pb(II). Furthermore, the electrochemical sensor of Fe₃O₄ microspheres exhibits excellent stability and it also offers potential practical applicability for the determination of heavy metal ions in real water samples. This study provides a potential simple and low cost iron oxide for the construction of sensitive electrochemical sensors applied to monitor and control the pollution of toxic metal ions.     

Generation of electricity from CO<Subscript>2</Subscript> mineralization: Principle and realization

Current CO₂ reduction and utilization technologies suffer from high energy consuming. Thus, an energy favourable route is in urgent demanding. CO₂ mineralization is theoretically an energy releasing process for CO₂ reduction and utilization, but an approach to recovery this energy has so far remained elusive. For the first time, here we proposed the principle of harvesting electrical energy directly from CO₂ mineralization, and realized an energy output strategy for CO₂ utilization and reduction via a CO₂-mineralization fuel cell (CMFC) system. In this system CO₂ and industrial alkaline wastes were used as feedstock, and industrial valuable NaHCO₃ was produced concomitantly during the electricity generation. The highest power density of this system reached 5.5 W/m², higher than many microbial fuel cells. The maximum open circuit voltage reached 0.452 V. Moreover, this system was demonstrated viable to low concentration CO₂ (10%) and other carbonation process. Thus, the existing of an energy-generating and environmentally friendly strategy to utilize CO₂ as a supplement to the current scenario of CO₂ emission control has been demonstrated.     

Synthesis and characterization of biomimetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/coke magnetic nanoparticles composite material

A composite material (Fe₃O₄/Coke) using coke supported Fe₃O₄ magnetic nanoparticles was successfully prepared via an in-situ chemical oxidation precipitation method and characterized by SEM, XRD, Raman, and FTIR. The results showed that the Fe₃O₄ nanoparticles existed steadily on the surface of coke, with better dispersing and smaller particle size. The catalytic ability of Fe₃O₄/Coke were investigatied by degrading p-nitrophenol (P-NP). The results showed that the apparent rate constant for the P-NP at 1.0 g·L^?1 catalyst, 30 mmol·L^?1 H₂O₂, pH=3.0, 30 °C and the best ratio of Coke/Fe₃O₄ 0.6, was evaluated to be 0.027 min^–1, the removal rate of COD_Cr was 75.47%, and the dissolubility of Fe was 2.42 mg·L^–1. Compared with pure Fe₃O₄, the catalytic ability of Fe₃O₄/Coke in the presence of H₂O₂ was greatly enhanced. And Fe₃O₄/Coke was a green and environmental catalyst with high catalytic activity, showing a good chemical stability and reusability.     

Fabrication and microstructure of C<Subscript>a</Subscript>TiO<Subscript>3</Subscript> coating by laser cladding

In order to explore the way to improve the adhesion of the calcium phosphate bioceramic coating to Ti substrate, the CaTiO3 coating was fabricated on Ti substrate by laser cladding (LC) using powders of CaCO3 and CaHPO4, and then the composition and microstructure of the coatings were investigated. During LC, CaCO3 can hardly react with Ti, and the coating fabricated using CaCO3 powder is mainly composed of the process of CaO, the decomposition product of CaCO3. Moreover, the coating has a loosened structure and part of it has peeled off from the substrate. CaHPO4 reacts vigorously with Ti, and the coating fabricated using CaHPO4 mainly consists of CaTiO3 which is one of the reaction products between Ti and CaHPO4. Chemical bonding is formed at the interface between coating and substrate, which may enhance the adhesion of the CaTiO3 coating to Ti substrate. Furthermore, CaTiO3 dendrite and eutectic of CaTiO3 and Ca2P2O7 are found on the surface of the coating, implying that a transition can be formed between CaTiO3 and some calcium phosphate bioceramic. So CaTiO3 coating fabricated using CaHPO4 can be a potential candidate to improve the adhesion between calcium phosphate coating and Ti substrate. However, there are also pores and cracks existing in the coating, which may degrade the mechanical properties of the coating.     

Fluorescence detection for H<Subscript>2</Subscript>PO<Subscript>4</Subscript><Superscript>-</Superscript> based on carbon dots/Fe<Superscript>3+</Superscript> composite

A novel fluorescent probe for H₂PO₄ ^- was designed and fabricated based on the carbon dots/Fe³⁺ composite. The carbon dots were synthesized by an established one-pot hydrothermal method and characterized by transmission electron microscope, X-ray diffractometer, UV-Vis absorption spectrometer and fluorescence spectrophotometer. The carbon dots/Fe³⁺ composite was obtained by aqueous mixing of carbon dots and FeCl₃, and its fluorescence property was characterized by fluorescence spectrophotometer. The fluorescence of carbon dots was quenched by aqueous Fe³⁺ cations, resulting in the low fluorescence intensity of the carbon dots/Fe³⁺ composite. On the other hand, H₂PO₄ ^- reduced the concentration of Fe³⁺ by chemical reaction and enhanced the fluorescence of the carbon dots/Fe³⁺ composite. The Stern-Volmer equation was introduced to describe the relation between the relative fluorescence intensity of the carbon dots/Fe³⁺ composite and the concentration of H₂PO₄ ^-, and a fine linearity (R ²=0.997) was found in the range of H₂PO₄ ^- concentration of 0.4-12 mM.     

Preparation and characterization of superparamagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/CNTs nanocomposites dual-drug carrier

Fe₃O₄/carbon nanotubes (Fe₃O₄/CNTs) nanocomposites were prepared by polylol high-temperature decomposition of the precursor ferric chloride and CNTs in liquid triethylene glycol. After surface modification with hexanediamine, folate was covalently linked to the amine group of magnetic Fe₃O₄/CNTs nanocomposites. The products were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. Then Fe₃O₄/CNTs were used as a dual-drug carrier to co-delivery of the hydrophilic drug epirubicin hydrochloride and hydrophobic drug paclitaxel. The results indicated that the Fe₃O₄/CNTs had a favorable release property for epirubicin and paclitaxel, and thus had potential application in tumor-targeted combination chemotherapy.     

Preparation and optical properties of Er<Superscript>3+</Superscript>: Na<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> transparent glass-ceramics

Na₂O-Al₂O₃-SiO₂ glass-ceramics doped with Er³⁺ ions were synthesized by the conventional melt quenching technique at a low melting temperature. The samples were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis-NIR scanning spectrophotometry, and fluorescence spectrometry. The results show that the main crystalline phase of glass-ceramics is nepheline.The best heat-treatment process is at 520 °C for 2 h. Because the up-conversion luminescence and near infrared luminescence properties of glass doped with Eu³⁺ are studied in detail.     

Surface organic modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic nanoparticles

The surface organic modification of Fe3O4 nanoparticles with silane coupling reagent KH570 was studied. The modified and unmodified nanoparticles were characterized by FT-IR, XPS and TEM. The spectra of FT-IR and XPS revealed that KH570 was coated onto the surface of Fe3O4 nanoparticles to get Fe-O- Si bond and an organic coating layer also was formed. Fe3O4 nanoparticles were spheres partly with mean size of 18,8 nm studied by TEM, which was consistent with the result 17.9 nm calculated by Scherrer＇s equation. KH570 was adsorbed on surface and formed chemistry bond to be steric hindrance repulsion which prevented nanoparticles from reuniting. Then glycol-based Fe3O4 magnetic liquids dispersed stably was gained.     

Magnetically Recoverable PEI/Titanate@Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Photocatalysts: Fabrication and Photocatalytic Properties

The magnetically separable ternary polyetherimide/titanate@Fe₃O₄ (PTF) photocatalysts of special heterostructure between magnetite (Fe₃O₄) microspheres and titanates nanosheets modified by polyetherimide (PEI) were successfully fabricated via a simple facile hydrothermal deposition method. The as-prepared photocatalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Transmission electron microscopy and UV-vis diffuse reflectance spectroscopy etc. The results showed that the as-fabricated material had a structure of Fe₃O₄ microspheres coated with titanates nanosheets modified by PEI. The special interfacial contact between 3D microsphere and 2D nanosheets in the nanoarchitectures was formed via electrostatic attraction. Furthermore, the resulted photocatalysts were tested by degradation reaction of methylene blue under visible light irradiation and demonstrated an enhanced performance than the pure Fe₃O₄ microspheres, and the photocatalytic activity enhanced with the molar ratio of Fe₃O₄ microspheres and modified titanate gradually, which was attributed to the expansion of the surface area and the different electrostatic contact between the Fe₃O₄ microspheres and titanate nanosheets. Moreover, the obtained results revealed the high yield magnetic separation and efficient reusability of PTF-5 (96.7%) over 3 times reuse.     

Synthesis of polyaniline-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposites and their conductivity and magnetic properties

By using inorganic Fe₃O₄ nanoparticles of different content as nucleation sites, PAn-Fe₃O₄ nanorods were successfully synthesized through a simple, conventional, and inexpensive one-step in-situ polymerization method. The TEM images revealed the size and morphology of the resultant nanocomposite. The EDS pattern confirmed the existence of Fe₃O₄ in the composite. The FT-IR spectral analysis confirmed the formation of PAn encapsulated Fe₃O₄ nanocomposite. With the content of Fe₃O₄ increasing, the conductivity of the nanocomposites gradually decreases, meanwhile, the saturation magnetization increases and reveals a super paramagnetic behavior. With controllable electrical, magnetic, and electromagnetic properties, the well-prepared nanocomposites may have the potential applications in chemical sensors, catalysis, microwave absorbing, and electro-magneto-rheological fluids, etc.     

Modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic nanoparticles by L-dopa or dopamine as an enzyme support

Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.     

Microstructure and mechanical properties of TiB<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB2-30%Al2O3 can be attained due to the plate-like TiB2 particle and its random orientation and excessive Al2O3 grain growth. When sintering temperature is higher than 1 700 ℃, TiB2 grain growth can be found, which obvious improves flexural strength of TiB2 matrix but decreases toughness. It seems that mechanical properties of TiB2-Al2O3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB2 matrix strength together. Anyway, Al2O3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m1/2 can be achieved inTiB2-30vol% Al2O3.     

Synthesis and electrochemical properties of Cr-doped Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> cathode materials for lithium-ion batteries

Cr-doped Li₃V₂(PO₄)₃ cathode materials Li₃V_2−x Cr _x (PO₄)₃ were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li₃V₂(PO₄)₃ were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li₃V₂(PO₄)₃ has the same monoclinic structure as the undoped Li₃V₂(PO₄)₃, and the particle size of Cr-doped Li₃V₂(PO₄)₃ is smaller than that of the undoped Li₃V₂(PO₄)₃ and the smallest particle size is only about 1 μm. The Cr-doped Li₃V₂(PO₄)₃ samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li₃V_2−x Cr _x (PO₄)₃ samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li₃V₂(PO₄)₃ cathode materials are attributed to the addition of Cr³⁺ ion by stabilizing the monoclinic structure. Funded by the Guangxi Natural Science Foundation(No. 0832259) and the National Basic Research Program of China (No. 2007CB613607)     

Fabrication and Characterization of Nano- CaCO3/Polypropylene Foam Sheets

By applying the reinforcing and toughening effect of calcium carbonate （CaCO3） nanoparticles on polypropylene, foam sheets of good performance were successfully fabricated by extrusion. The equipment and conditions of the extrusion were explored. The mechanical properties of the produced foam sheets were tested. The effect of CaCO3 nano-particles on the mechanical properties and the cellular structure of the sheets was comprehensively studied. The experimental results show that the optimum content of CaCO3 nano-particles in the composite material was -4wt%. At this content, the nano-particles were well dispersed in the substrate, and the composite material had maximum tensile strength and impact strength. Surface treatment of the nano-particles only affected the impact strength of the composite material. CaCO3 micro-particles, on the other hand, showed little effect on the properties of the composite material when the micro-particles content was less than 5 wt%. At a content higher than 5wt%, the properties of the composite material significantly worsened.