氨基功能化CoFe2O4-SiO2 磁性复合材料的制备及其在去除水中重金属离子的吸附性能

钴-铁氧体纳米粒子(CoFe₂O₄ NPs)通过改良的共沉淀法制备,CoFe₂O₄-SiO₂磁性复合材料通过st?ber法合成,为了吸附重金属离子CoFe₂O₄-SiO₂进行了氨基功能化。这种吸附剂的晶体结构、形貌、颗粒尺寸、化学组成和分子结构采用X射线衍射图谱(XRD)、扫描电子显微镜(SEM)以及傅里叶变换红外光谱(FTIR)进行表征。此复合材料具有优良的磁性能,由于其高的饱和磁化强度,磁铁可以将其在30秒内快速分离。同时,CoFe₂O₄ NPs的磁性能可以通过烧结温度进行调节,随烧结温度提高,磁性能增强。溶液的pH及反应时间对重金属离子吸附的影响进行了研究,此外此吸附剂对Cu (II)、Cd (II)、Mn (II) 和Zn (II)具有较高的吸附容量和去除率,这一结果使此复合材料可以潜在应用于废水中重金属离子的吸附上。     

One-pot synthesis of polyaniline/Fe3O4 nanocomposites with magnetic and conductive behaviour. Catalytic effect of Fe3O4 nanoparticles

Polyaniline/Fe₃O₄ nanocomposites were prepared by a one-pot synthesis using N-(4-aminophenyl)aniline as the reagent, molecular oxygen or hydrogen peroxide as the oxidizing agents in the presence of Fe₃O₄ nanoparticles (NPs) in powder and ferrofluid form. Both magnetic NPs in powder and ferrofluid form showed similar catalytic behaviour. The catalytic effect is particularly evident when molecular oxygen was used as the oxidizing agent. However, concerning the morphological aspects, only the composites prepared in the presence of ferrofluid-type Fe₃O₄ NPs showed a preferential morphology of nanorods (between 30 and 110 nm in diameter). All the composites are superparamagnetic at room temperature but at low temperature they are in a blocked state. Inter-particle interactions significantly affect the magnetic properties of the composites. The electrical conductivity of the composites is about 10⁻² S cm⁻¹, in agreement with the values obtained for polyaniline prepared by chemical route. A mechanism of the nanorods formation is proposed.     

La2O3含量对Al2O3/Cu基复合材料组织与性能的影响

以La₂O₃粉、Al粉、CuO粉为反应物原料、纯铜为基体,采用原位合成技术和近熔点铸造法制备颗粒增强Cu基复合材料,研究La₂O₃对Al-CuO体系制备的Cu基复合材料组织及性能的影响。结果表明：添加La₂O₃可获得纳米Al₂O₃颗粒,且弥散分布于Cu基体中,制备的材料组织更加细小、均匀,其材料的电导率及摩擦磨损性能明显提高。当添加0.6%wtLa₂O₃,复合材料的电导率达到90.2%IACS,磨损量达到最小,相比未添加La₂O₃,其导电率提高10.1%,磨损量减小36.6%。     

Synthesis and characterization of polypropiolate sodium (PPNa)-Fe3O4 nanocomposite

Polypropiolate sodium (PPNa)-Fe₃O₄ nanocomposites were successfully synthesized by the precipitation of Fe₃O₄ in the presence of sodium polypropiolate and followed by reflux route. Structural, morphological, electrical and magnetic properties evaluation of the nanocomposite were performed by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), vibrating scanning magnetometry (VSM) and conductivity measurements. Crystalline phase was identified as magnetite with an average crystallite size of 7 ± 3 nm as estimated from X-ray line profile fitting. Particle size estimated from TEM, by log-normal fitting, is ∼9 ± 1 nm. FT-IR analysis shows that the binding of PPNa on the surface of iron oxide is through bidentate linkage of carboxyl group. TGA analysis showed the presence of 20% PPNa around 80% magnetic core (Fe₃O₄)…PPNa-Fe₃O₄ nanocomposite show superparamagnetic characteristics at room temperature. It is found that the a.c. conductivity of the nanocomposites obeys the well-known power law of frequency in which it also depends on temperature. Additionally, its d.c. conductivity showed that two operating regions of the activation energy. Both real and imaginary parts of either permittivity exhibit almost the same attitudes which are the indication of the same ability in the stored energy, and dissipation of energy within the PPNa and PPNa-Fe₃O₄ nanocomposites.     

Magnetic and photoluminescence properties of Fe3O4@SiO2@YP1−xVxO4:Dy nanocomposites

In this paper, we report on the bifunctional Fe₃O₄@SiO₂@YP_0.1V_0.9O₄:Dy³⁺ nanocomposites were prepared by the solvothermal method and sol-gel method. The structure, photoluminescence (PL) and magnetic properties of the nanocomposites were characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, PL excitation and emission spectra and vibration sample magnetometry. It is shown that Fe₃O₄@SiO₂@YP_0.1V_0.9O₄:Dy³⁺ nanocomposites with a core-shell structure present excellent fluorescent and magnetic properties. Additionally, the effects of the magnetic field on the luminescence properties of nanocomposites were discussed.     

Electrical Properties of Atmospheric Plasma-Sprayed La10(SiO4)6O3 Electrolyte Coatings

In this present work, La₁₀(SiO₄)₆O₃ as a promising electrolyte candidate for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been synthesized and its electrical property was investigated as a function of temperature. In order to improve the density and oxide ion conductivity of La₁₀(SiO₄)₆O₃, the feedstock powder was prepared by sintering the oxide mixture powders at proper sintering temperatures and times. The hexagonal apatite-type ceramic coatings with a typical composition of La₁₀(SiO₄)₆O₃ were deposited by atmospheric plasma spraying (APS) with different hydrogen flow rates. With increasing hydrogen flow rate oxide ion conductivity successively decreases. The highest ionic conductivity of the dense composite electrolyte coatings reaches a value of 2.4 mS/cm at 900 °C in air, which is comparable to other apatite-type lanthanum silicate (ATLS) conductors.     

Preparation and characterization of polypyrrole/nano-SrFe12O19 composites by in situ polymerization method

Polypyrrole (PPY)/nano-SrFe₁₂O₁₉ composites were synthesized by in situ polymerization method. The samples were characterized by TEM, SEM, XRD and IR technology. Spherical, conglobulation-like and arborization-like polypyrrole/SrFe₁₂O₁₉ composites were synthesized in an emulsion polymerization system for the first time. It was found that the morphology of PPY/nano-SrFe₁₂O₁₉ composites depended on the SrFe₁₂O₁₉ content of the reaction system. A possible mechanism for the formation of the different morphologic composites had been proposed. It was found that the saturation magnetization (M_S) and remanent magnetization (M_r) for the composites decreased with the decrease of the nano-SrFe₁₂O₁₉ content. The coercivity force (H_c) for the composites increased with the increase of PPY content when the PPY content was at a low value, and then decreased with the increase of PPY content. The possible mechanism for the phenomenon had been proposed. The conductivity was measured, and the variation mechanism of the composites conductivity was analyzed in the paper.     

Preparation of Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites and their adsorption of bovine serum albumin

The magnetic nanocomposites of (1 − x)Ni_0.5Zn_0.5Fe₂O₄/xSiO₂ (x = 0-0.2) were synthesized by the citrate-gel process and their absorption behavior of bovine serum albumin (BSA) was investigated by UV spectroscopy at room temperature. The gel precursor and resultant nanocomposites were characterized by FTIR, XRD, TEM and BET techniques. The results show that the single ferrite phase of Ni_0.5Zn_0.5Fe₂O₄ is formed at 400 °C, with high saturation magnetization and small coercivity. A porous, amorphous silica layer is located at the ferrite nanograin boundaries, with the silica content increasing from 0 to 0.20, the average grain size of Ni_0.5Zn_0.5Fe₂O₄ calcined at 400 °C reduced from about 18-8 nm. Consequently, the specific surface area of the nanocomposites ascends clearly with the increase of silica content, which is largely contributed by the increase in the thickness of the porous silica layer. The Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites demonstrate a better adsorption capability than the bare Ni_0.5Zn_0.5Fe₂O₄ nanoparticles for BSA. With the increase of the silica content from 0 to 0.05 and the specific surface area from about 49-57 m²/g, the BSA adsorption capability of the Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites calcined at 400 °C improve dramatically from 22 to 49 mg/g. However, with a further increase of the silica content from 0.05 to 0.2, the specific surface area increase from about 57-120 m²/g, the BSA adsorption for the nanocomposites remains around 49 mg/g, owing to the pores in the porous silica layer which are too small to let the BSA protein molecules in.     

Synthesis and electrochemical performance of V2O5/NaV6O15 nanocomposites as cathode materials for sodium-ion batteries

V₂O₅/NaV₆O₁₅ nanocomposites were synthesized by a facile hydrothermal method using VO₂(B) nanoarrays as the precursor. X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and galvanostatic charge−discharge test were used to evaluate the structures, morphologies and electrochemical performance of samples, respectively. The results show that the nanocomposites are composed of one-dimensional nanobelts, preserving the morphology of the precursor well, and the hydrothermal reaction time has a significant effect on the phase contents and electrochemical performance of the composites. Compared with pure V₂O₅, V₂O₅/NaV₆O₁₅ nanocomposites exhibit enhanced electrochemical performance as cathode for sodium-ion batteries. It should be ascribed to the synergistic effect between V₂O₅ with high capacity and NaV₆O₁₅ with good cycling performance, and the introduced massive interfacial areas which can provide additional ion storage sites and improve the electronic and ionic conductivities.     

A novel poly(o-anisidine)/CoFe2O4 multifunctional nanocomposite: Preparation,characterization and properties

A novel poly(o-anisidine) (POA)/CoFe₂O₄ nanocomposite was synthesized by a facile in situ polymerization of o-anisidine in the presence of CoFe₂O₄ nanoparticles which were obtained by a simple refluxing process in ethylene glycol. The structures of the resulting nanocomposite were investigated by means of X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra. The optical, thermal and magnetic properties of the POA/CoFe₂O₄ nanocomposite were characterized by UV–visible spectrometer, thermogravimetry analyzer (TGA) and vibrating sample magnetometer (VSM). It was indicated the existence of CoFe₂O₄ in the POA/CoFe₂O₄ nanocomposite. The scanning electron microscopy (SEM) observation illustrated that POA layers were wrapped on the surface of CoFe₂O₄ nanoparticles appearing as small aggregated globules. The POA/CoFe₂O₄ nanocomposite exhibited a ferromagnetic behavior under applied magnetic field at room temperature. The saturation magnetization of POA/CoFe₂O₄ nanocomposite was lower than that of pure CoFe₂O₄ nanoparticles due to the contribution of non-magnetic POA layers.     

Tunable dielectric properties of BaZr0.2Ti0.8O3-Mg2SiO4-MgO composite ceramics

BaZr_0.2Ti_0.8O₃-Mg₂SiO₄-MgO composites were prepared by a solid-state reaction method, and their dielectric and tunable characteristics were investigated for the potential application as microwave tunable materials. It is observed that the addition of Mg₂SiO₄-MgO into BaZr_0.2Ti_0.8O₃ form ferroelectric (BaZr_0.2Ti_0.8O₃)-dielectric (Mg₂SiO₄-MgO) composites. The dielectric constant and loss tangent of BaZr_0.2Ti_0.8O₃-Mg₂SiO₄-MgO composites have been reduced and the overall tunability is maintained at a sufficiently high level. An anomalous relation between dielectric constant and tunability was observed: with the increase of Mg₂SiO₄ content (>30 wt%), the dielectric constant of composite decreases and the tunability increases. The anomalous increased tunability can be attributed to redistribution of the electric field. BaZr_0.2Ti_0.8O₃-Mg₂SiO₄-MgO composites have tunability of 14.2-17.9% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring low dielectric constant.     

Preparation and characteristics of Fe3O4@YVO4:Eu bifunctional magnetic-luminescent nanocomposites

A facile direct precipitation method has been developed for the synthesis of bifunctional magnetic-luminescent nanocomposites with Fe₃O₄ nanoparticles as the core and YVO₄:Eu³⁺ as the shell. Transmission electron microscopy (TEM) images revealed that the obtained bifunctional nanocomposites had a core-shell structure and a spherical morphology. The average size was ∼150 nm, and the thickness of the shell was ∼15 nm. The X-ray diffraction (XRD) patterns showed that a cubic spinel structure of Fe₃O₄ core and a tetragonal phase of YVO₄ shell were obtained. Fourier transform infrared (FT-IR) spectra confirmed that the YVO₄:Eu³⁺ had been successfully deposited on the surface of Fe₃O₄ nanoparticles. Photoluminescence (PL) spectra indicated that the nanocomposites displayed a strong red characteristic emission of Eu³⁺. Magnetic measurements showed that the obtained bifunctional nanocomposites exhibited superparamagnetic behavior at room temperature. Therefore, the bifunctional nanocomposites are expected to develop many potential applications in biomedical fields.     

Synthesis,characterization and low frequency AC conduction of polyaniline/niobium pentoxide composites

New types of conducting polyaniline–niobium pentoxide (PANI/Nb₂O₅) nanocomposites have been synthesized by in situ deposition technique by placing fine grade powder of Nb₂O₅ during in situ polymerization of aniline. The composites formed were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). XRD and TEM indicated the dominant role-played by Nb₂O₅ particles, whereas XPS indicated incomplete protonation of imine moieties. SEM images indicated a systematic morphological variation of particles aggregated in the composite matrix as compared to the pristine PANI. Three step decomposition patterns were observed for PANI and its composites. AC conductivity and dielectric response of the composites were investigated in the frequency range, 10²–10⁶ Hz. AC conductivity obeyed the power law index, which decreased with increasing wt.% of Nb₂O₅. PANI showed high dielectric constant, which could be related to conductivity relaxation phenomenon. Both dielectric constant and dielectric loss decreased with increasing wt.% of Nb₂O₅. Variations in measured AC response parameters with increasing Nb₂O₅ contents of the composite followed systematic trends that are similar to those observed with decreasing temperature and level of doping.     

成分设计优化TiC/Hastelloy复合材料的抗氧化性能

TiC/Hastelloy复合材料是极具应用前景的中温固体氧化物燃料电池连接体材料,而抗氧化性能是影响其应用的关键性能之一。通过无压反应渗透工艺分别制备出含有50vol%和58vol%金属基体的TiC/Hastelloy复合材料。高金属含量使复合材料中的Cr含量增加,促进连续Cr₂O₃氧化层的形成,抑制Ni和Ti原子的外扩散,进而优化复合材料的抗氧化性能。氧化膜中Ti和Ni的氧化物含量降低,复合材料的氧化增重由2.03 mg·cm^-2降低到0.55 mg·cm^-2。同时,为了抑制Cr挥发,在含有58vol%金属基体的TiC/Hastelloy复合材料中引入Co。在氧化过程中,Co和金属基体中的Fe在Cr₂O₃氧化层中具有较快的扩散速率,可以在Cr₂O₃氧化层外侧原位形成CoFe₂O₄层。     

Magnetic annealing effects on multiferroic BiFeO3/CoFe2O4 bilayered films

In situ magnetic annealing effects on c-axis-preferred multiferroic BiFeO₃/CoFe₂O₄ bilayered by chemical solution deposition route are investigated. It is observed that magnetic annealing can enhance the crystallization quality, texture and densification as well as dielectric properties. In addition, the magnetolosses decrease with increasing the magnetic fields. Moreover, both increase of the polarization and decrease of the leakage current due to magnetic annealing are beneficial for potential applications of BiFeO₃ films.     

BN/Al2O3 复合粉末及其聚合物基复合材料的制备与导热性能

采用固-液相共混法制备了多种BN/Al₂O₃复合粉末,通过冻融法和表面修饰法对BN进行了改性处理,改变表面修饰剂类型和摩尔比得到了前驱体和烧结态BN/Al₂O₃复合粉末,并利用机械混合法制备了聚合物基BN/Al₂O₃复合材料,并测试分析了其导热性能。结果表明,经冻融处理的BN分散性和界面相容性明显优于未经冻融处理的BN。多巴胺对BN的改性效果优于聚乙二醇。采用多巴胺作为表面修饰剂且BN与Al(NO₃)₃的摩尔比为1:1时,能够得到纳米Al₂O₃均匀包覆的微米BN粉末,即BN/Al₂O₃微纳复合粉末,其聚合物基复合材料的导热系数可达0.62 W·m^-1·K^-1,是纯聚合物导热系数的3倍,是采用纯微米BN粉末制备的聚合物基复合材料导热系数的1.5倍。在BN表面附着的Al₂O₃可以形成层状热传导通道,能够有效提高聚合物基BN/Al₂O₃复合材料的热导率。     

Dielectric dispersion in Li2O–MoO3–B2O3 glass system doped with V2O5

Li₂O–MoO₃–B₂O₃ glasses containing different amounts of V₂O₅, ranging from 0 to 1.5 mol%, were prepared. The dielectric properties (viz., constant ′, loss tan δ, AC conductivity σ_ac over a wide range of frequency and temperature) have been studied as a function of the concentration of vanadium ions. The variation of AC conductivity with the concentration of V₂O₅ passes through a maximum at 0.8 mol% V₂O₅. In the high-temperature region, the AC conduction seems to be connected with the mixed conduction, viz., electronic and ionic conduction. The dielectric relaxation effects exhibited by these glasses have been analyzed quantitatively by pseudo Cole–Cole plot method and the spreading of relaxation times has been established. Further analysis of these results has been carried out with the aid of the data on ESR, IR and optical absorption spectra.     

Synthesis and microwave absorbing properties of polyaniline/MnFe2O4 nanocomposite

Conductive polyaniline (PANi)-manganese ferrite (MnFe₂O₄) nanocomposites with core-shell structure were synthesized by in situ polymerization in the presence of dodecyl benzene sulfonic acid (DBSA) as the surfactant and dopant and ammonium persulfate (APS) as the oxidant. The structure and magnetic properties of manganese ferrite nanoparticles were measured by using powder X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. Its morphology, microstructure and DC conductivity of the nanocomposite were characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and four-wire-technique, respectively. The microwave absorbing properties of the nanocomposite powders dispersing in resin acrylic coating with the coating thickness of 1_.4 mm were investigated by using vector network analyzers in the frequency range of 8-12 GHz. A minimum reflection loss of −15.3 dB was observed at 10.4 GHz.