Preparation of size-controlled tungsten oxide nanoparticles and evaluation of their adsorption performance

The present study investigated the effects of particle size on the adsorption performance of tungsten oxide nanoparticles. Nanoparticles 18-73 nm in diameter were prepared by evaporation of bulk tungsten oxide particles using a flame spray process. Annealing plasma-made tungsten oxide nanoparticles produced particles with diameters of 7-19 nm. The mechanism of nanoparticle formation for each synthetic route was examined. The low-cost, solid-fed flame process readily produced highly crystalline tungsten oxide nanoparticles with controllable size and a remarkably high adsorption capability. These nanoparticles are comparable to those prepared using the more expensive plasma process.     

The formation of magnetite nanoparticles on the sidewalls of multi-walled carbon nanotubes

Linear polyethyleneimine (PEI) was used as a non-covalent functionalizing agent to modify multi-walled carbon nanotubes (MWCNTs). Fe₃O₄ nanoparticles were then formed along the sidewalls of the as-modified MWCNTs through a simple solvothermal method. X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, and vibrating sample magnetometry were used to characterize the MWCNT/Fe₃O₄ nanocomposites. Results indicated that Fe₃O₄ nanoparticles with diameters ranging from 50 to 200 nm were attached to the surface of the MWCNTs by electrostatic interaction. PEI was found to improve the electrical conductivity of the MWCNT/Fe₃O₄ nanocomposites. The magnetic saturation value of these magnetic nanocomposites was 61.8 emu g⁻¹. These magnetic MWCNT/Fe₃O₄ nanocomposites are expected to have wide applications in bionanoscience and technology.     

Magnetic removal of dyes from aqueous solution using multi-walled carbon nanotubes filled with Fe2O3 particles

The Fe₂O₃ nanoparticles have been introduced into the multi-walled carbon nanotubes (MWCNTs) via wet chemical method. The resulting products are characterized by TEM, EDX, XRD and VSM. The magnetic MWCNTs have been employed as adsorbent for the magnetic separation of dye contaminants from water. The adsorption test of dyes (Methylene Blue and Neutral Red) demonstrates that it only takes 60 min to attain equilibrium and the adsorption capacities for Methylene Blue and Neutral Red in the concentration range studied are 42.3 and 77.5 mg/g, respectively. The magnetic MWCNTs can be easily manipulated in magnetic field for desired separation, leading to the removal of dyes from polluted water. The integration of MWCNTs with Fe₂O₃ nanoparticles has great potential application to remove organic dyes from polluted water.     

Preparation of ceria nanoparticles supported on carbon nanotubes

By chemical reaction of CeCl₃ and NaOH on carbon nanotube solution and subsequent heat treatment, ceria nanoparticles supported on carbon nanotubes were prepared. The processing parameters affecting the size of ceria particles were discussed. The particles were characterized by XRD and TEM. XRD patterns revealed that the particles exhibited CaF₂-type crystal structure. The TEM micrograph showed that the mean sizes of ceria particles were about 6 nm.     

Manufacturing techniques and property evaluations of conductive composite yarns coated with polypropylene and multi-walled carbon nanotubes

This study uses a melt extrusion method, a method for producing wires, to coat polyester (PET) yarns with polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs). The resulting PP/MWCNTs-coated PET conductive yarns are tested for their tensile properties, processability, morphology, melting and crystallization behaviors, electrical conductivity, and applications. The test results indicate that tensile strength of the conductive yarns increases with an increase in the coiling speed that contributes to a more single-direction-orientated MWCNTs arrangement as well as a greater adhesion between PP/MWCNTs and PET yarns. 8 wt% MWCNTs results in an 18 °C higher crystallization temperature (T_c) of PP and an electrical conductivity of 0.8862 S/cm. The test results of this study have proven that this form of processing technology can prepare PP/MWCNTs-coated PET conductive yarns that have satisfactory tensile properties and electrical conductivity, and can be used in functional woven fabrics and knitted fabrics.     

Effective removal of Zn (II) ions from aqueous solution by the magnetic MnFe2O4 and CoFe2O4 spinel ferrite nanoparticles with focuses on synthesis,characterization, adsorption,and desorption

In this study, the MnFe₂O₄ and CoFe₂O₄ spinel ferrites nanoparticles were synthesized via a practical co-precipitation route to investigate the zinc removal from aqueous solution. The synthesized magnetic adsorbents were characterized by XRD, VSM, FE-SEM, BET, EDS, and DLS analyses. The synthesized adsorbents had a diameter range of 20–80 nm. The specific surface areas of adsorbents were found to be 84.5 and 50.4 m²/g for MnFe₂O₄ and CoFe₂O₄, and the saturation magnetization were 61.39 and 37.54 emu/g, respectively. The effects of initial pH, contact time, metal ion concentration, and temperature on Zn (II) adsorption were precisely investigated. These nanoparticles could remove Zn (II) by following the Langmuir isotherm model at optimum pH = 6, with the high adsorption capacities of 454.5 and 384.6 mg/g for MnFe₂O₄ and CoFe₂O₄, respectively. The results of kinetics studies were well fitted by pseudo-second-order, with the determination coefficients of 0.999 for both adsorbents. The thermodynamics studies showed that the zinc (II) adsorption was an exothermic and spontaneous process. Furthermore, the reusability and the desorption capability of adsorbents were also investigated.     

聚苯乙烯基球形活性炭的制备及其对二苯并噻吩的吸附性能

通过水蒸气活化法制备了聚苯乙烯基球形活性炭,并研究了其对二苯并噻吩(DBT)的吸附性能.采用扫描电镜(SEM)、N2吸附、热重分析(TG)以及液相吸附试验考察了球形活性炭的结构特征.结果表明:以苯乙烯离子交换树脂为原料,通过水蒸气活化法,可以得到比表面积979m2/g～1672m2/g的球形活性炭.其中,BET比表面积和孔容随活化时间和水蒸气流量的增加而增大,而孔径小于0.7 nm的窄微孔却减小.球形活性炭对DBT的吸附量可达109.36mg/g,吸附量与比表面积和总孔容关系不大,而与小于0.7nm的窄微孔成正比.球形活性炭在对DBT的吸附过程中存在不可逆吸附.球形活性炭所含窄微孔的孔容越大,脱附所需要的温度越高,不可逆吸附量越大.     

Si@环化聚丙烯腈/多壁碳纳米管负极复合材料的制备及电化学性能

通过简单高能球磨和高温热解法制备了锂离子电池Si/C电极复合材料,聚丙烯腈（PAN）包覆的纳米颗粒（Si@PAN）与多壁碳纳米管（MWCNTs）混合,制得Si@环化PAN/MWCNTs（Si@c-PAN/MWCNTs）复合材料作为锂离子电池的负极材料。包覆在纳米Si外层的高温热解后的PAN能够有效缓冲Si在充放电过程中巨大的体积变化产生的应力,同时MWCNTs作为Si@c-PAN的基体阻止Si@c-PAN颗粒的团聚,也提高了Si@c-PAN/MWCNTs复合材料电极的导电性能。电化学测试结果表明,Si@c-PAN/MWCNTs复合材料电极在电流密度为0.2 A/g时,其首次放电比容量达到2 098 mA?h/g,库伦效率达到86%;循环50次后Si@c-PAN/MWCNTs复合材料电极的可逆比容量仍能够达到1 278 mA?h/g,在2 A/g放电时其比容量为600 mA?h/g,仍保持良好的循环稳定性。      

Synthesis and enhanced photocatalytic activity of tin oxide nanoparticles coated on multi-walled carbon nanotube

A nanocomposite of SnO₂ nanoparticles coated on multi-walled carbon nanotube (MWNT@SnO₂) was synthesized and characterized by thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, nitrogen physisorption measurements, photoluminescence. The results show that the SnO₂ nanoparticles with a narrow size of 4 nm are uniformly deposited on MWNT. The photocatalytic activity of the nanocomposite was studied using methyl orange as a model organic pollutant. MWNT@SnO₂ exhibits much higher photocatalytic activity than that of commercial TiO₂ (P-25). The promotion is mainly contributed from electron transfer between SnO₂ and MWNT.     

Growth and characterization of carbon nanotubes over CoFe2O4-MgO catalysts at different temperatures

Abstract

A novel approach for synthesizing carbon nanotubes (CNTs) via chemical vapor deposition (CVD) technique has been elucidated. CNTs are catalytically grown on the CoFe₂O₄-MgO nano-catalyst at various growth temperatures (700?°C, 800?°C, 900?°C) to clarify the effect of temperature and to achieve the optimum CNT growth temperature. The structural properties of the catalyst and CNTs were studied with thermal analysis (TGA), X-ray diffraction (XRD), FTIR spectroscopy (IR), Raman spectroscopy, and High Resolution Transmission Electron Microscope (HRTEM). X-ray diffraction is used to study changes in the crystal structure of the CoFe₂O₄+MgO nano-catalyst. The obtained data ratifies the formation of MWCNTs over the nanocatalyst. The intensity of the main peak of CNTs decreases as well as the yield with increasing the growth temperature. The two main Raman modes, G band and the D band, can be identified in the spectra multi-walled carbon nanotubes .The lowest I_D/I_G ratio is obtained at the highest growth temperature. HRTEM images show that the growth temperature has a significant parameter on CNT quality. The average diameters of grown CNTs are 42, 32 and 16?nm for growth temperatures of 700 ?C, 800 ?C and 900 ?C, respectively. The inner and outer diameters of MWCNTs become thinner and the quality of the tubes is enhanced with increasing the growth temperature. Additionally, it can be concluded from the temperature study that the balance between decomposition of acetylene gas and diffusion rate of manufactured carbon atoms in CoFe₂O₄-MgO catalyst nanoparticles occurs at the optimal growth temperature of 900?°C.     

Feasibility of TEOS coated CoFe2O4 nanoparticles to a GMR biosensor agent for single molecular detection

Magnetic properties of 200 nm ferrimagnetic CoFe2O4 nanoparticles before and after coating with TEOS were explored and compared to soft ferrimagnetic MgFe2O4 nanoparticles (200 nm) to evaluate the feasibility as an in-vitro GMR SV (giant magnetoresistance spin-valve) biosensor agent for single molecular detection (SMD). It was found that the magnetic degradation (or variation) of TEOS coated CoFe2O4 and MgFe2O4 nanoparticles are dominantly affected by the chemical dispersion process, which is carried out in the oleic acid (OA), oleylamine (OL), or OA+OL surfactant, before starting major coating process. In addition, the TEOS coating thickness controlled by TEOS concentration and pH level in the buffer solution prominently influenced on the magnetic degradation of TEOS coated nanoparticles. According to the experimental analysis results, the magnetic degradation of TEOS coated nanoparticles is mainly attributed to the variation of particle dipole interaction caused by the degree of particle aggregation depending on TEOS coating process conditions. The TEOS coated CoFe2O4 nanoparticles exhibited a higher magnetic stability for a GMR biosensor agent, e.g., small variation of remnant magnetization, saturation magnetization and magnetic coercivity, than that of MgFe2O4 nanoparticles at the different coating process conditions. The physical and chemical analysis confirmed that this is primarily due to its higher magnetic anisotropy. The experimentally verified high biocompatibility as well as the stably maintained magnetic properties of TEOS coated CoFe2O4 nanoparticles demonstrate that CoFe2O4 nanoparticles can be considered as one of the promising ferrimagnetic nanoparticle sensor agent for an SMD GMR SV biosensor.     

Influence of multi-walled carbon nanotubes on electrochemical performance of transparent graphene electrodes

In this work, carbon-carbon nanocomposites as transparent electrodes were prepared by a chemical reduction of graphite oxide (GO) and multi-walled carbon nanotubes (MWNTs). The electric, optical, and electrochemical properties of graphene-MWNT nanocomposites (G-MCs) were investigated as a function of the MWNT content. It was found that chemically bonded G-MCs were successfully formed with a reduction of the functional groups of the GO and acid-treated MWNTs, resulting in the conjugation of 1D MWNTs onto a 2D graphene surface. The electrical conductivity of the graphene was significantly enhanced by introducing the MWNTs. In addition, the G-MCs showed improved current density and high efficiency compared with graphene alone. This indicated that the improved electrochemical performance of the G-MCs can be attributed to the increase in the activity and electrical conductivity enhanced by π-π interaction between graphene and MWNTs.     

多壁纳米碳管的制备与表面改性处理

以Co-MCM-41作催化剂,采用化学气相沉积(CVD)法催化热解无水乙醇制备纳米碳管(CNTs),然后将纳米碳管在120℃下用浓硝酸回流,进行纯化及表面酸氧化改性处理。通过XRD、FT-IR、TEM、N2吸附-脱附和Raman光谱等分析手段对酸处理前后的纳米碳管进行了表征。结果表明制备出品质较好、管径均匀、管壁较厚、顶端开口的多壁纳米碳管。浓硝酸氧化处理后在纳米碳管的表面存在羧基和羟基等官能团。     

Microstructural investigation of magnetic CoFe2O4 nanowires inside carbon nanotubes by electron tomography

Magnetic nanowires of CoFe 2O4 were casted inside the channel of multiwall carbon nanotubes by mild chemical synthesis. A detailed investigation of these nanowires was performed using mainly the electron tomography technique; this study provides a complete characterization of their microstructure in terms of the spatial organization and the size distribution of individual particles forming the nanowire as well as its residual porosity. In particular, we have shown that the size of the CoFe 2O4 monocrystalline particles is closely dependent on the location of the particle within the nanotube, i.e., small particles close to the tube tip (5 nm) and bigger particles inside the tube channel (15 nm). As the theoretical critical size for superparamagnetic relaxation in CoFe 2O4 is estimated within the range of 4-9 nm, the size distribution obtained by 3D-TEM agrees with the Mossbauer study that suggests the presence of two different magnetic components inside the nanowire. We have shown also that, by using this preparation method and for this internal diameter of nanotube, the CoFe 2O4 nanowire exhibits a continuous structure along the tube, has a residual porosity of 38%, and can fill the tube at only 50%, parameters which influence in a significant manner the magnetic behavior of this system.     

Low-temperature synthesis of Mn(3)O(4) nanoparticles loaded on multi-walled carbon nanotubes and their application in electrochemical capacitors

A low-temperature, efficient and one-step deposition method, in which Mn(CH(3)COO)(2)·4H(2)O serves as precursor and O(2) as oxidant, was employed to deposit Mn(3)O(4) nanoparticles on multi-walled carbon nanotubes (MWCNTs) in ethanol solution at 150 and 200?°C. The resulting Mn(3)O(4)/MWCNT composites were characterized by means of different techniques including x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. It was indicated that the Mn(3)O(4) nanoparticles were attached uniformly on MWCNTs with sizes less than 10?nm, and the loading amount of Mn(3)O(4) could be tuned by changing the initial weight ratio of Mn(CH(3)COO)(2)·4H(2)O/MWCNT. The electrochemical behavior of the Mn(3)O(4)/MWCNT composites was examined by cyclic voltammetry, and the result indicated the specific capacitance of the composite electrode was 330?F?g(-1), nearly 18 times higher than that of the pure MWCNT electrode. The good performance of the as-prepared composites as electrode material may be attributed to the synergistic effects of the Mn(3)O(4) nanoparticles and the MWCNTs.     

Fe3O4包覆碳纳米管软磁性纳米复合微粒的制备及性能

用水解沉淀法在碳纳米管（CNTs）外包覆Fe3O4，制备了CNTs／Fe3O4纳米复合磁性微粒，借助透射电镜、振动探针式磁强计和外加磁场黏度计对其微观形貌、静态磁性能、沉降稳定性和磁流变性能进行了研究。结果表明：Fe3O4在碳纳米管（直径约20nm）表面形成了紧密的包覆层，微粒呈一维纳米管状结构，平均管径约60nm，平均表观密度为1．8g／cm^3，为传统磁流变液中所用铁粉等软磁性颗粒密度的四分之一。复合微粒的磁滞回线与Fe3O4纳米颗粒较为相似，具有较好的软磁性，其饱和磁感应强度（Bs）为0．21T，矫顽力（以）为7．67kA／m，用该软磁性复合微粒配制的磁流变液具有良好的沉降稳定性和磁流变特性。     

Fe3O4纳米粒子修饰碳纳米管的制备及其磁学性能（英文）

通过FeCl2.4H2O和FeCl3.6H2O混合共沉淀,合成平均粒径为6 nm和10 nm的Fe3O4纳米粒子。然后将两种Fe3O4纳米粒子分别与经HNO3氧化处理的多壁碳纳米管(MWCNTs)置于乙醇水溶液(水和乙醇的体积比为1∶1)中,在超声波作用下制备Fe3O4/MWCNT复合材料。用高分辨透射电子显微镜、X-射线光电子能谱、振动样品磁强计、X射线衍射仪、热重分析仪对所制备的Fe3O4/MWCNT复合材料进行表征。结果表明:由6 nm和10 nm Fe3O4纳米粒子所制备的Fe3O4/MWCNT复合材料中,Fe3O4的质量分数分别为26.65%和29.3%,相应的磁饱和强度分别为16.5 emug-1和7.5 emug-1。     

Synthesis and properties of magnetic multi-walled carbon nanotubes loaded with Fe4N nanoparticles

High saturation magnetization (>90 emu/g) multi-walled carbon nanotubes (MWCNTs) and Fe₄N nanoparticles composite were successfully synthesized by gas nitriding at 550 °C. Almost all Fe₄N nanoparticles were evenly distributed inside the carbon nanotubes and formed a special composite microstructure. This composite microstructure shows excellent soft magnetic property, structural stability, and chemical stability at room temperature. The investigations of electromagnetic and microwave absorption performances indicate that microwave absorbing capacity of low frequency band of MWCNTs were greatly improved by addition of Fe₄N nanoparticles.     

Enhanced thermoelectric performance of CuAlS2 by adding multi-walled carbon nanotubes

In this paper, we report the first-ever study on a relatively uniform dispersion of multi-walled carbon nanotubes (MWCNTs) in CuAlS₂ nanoparticles, synthesized by high-energy ball-milling, and study the thermoelectric properties of the bulk materials. A vortex mixer and bath sonicator are used to achieve well dispersion of nanotubes in the matrix, and then the powder is hot-pressed. Carbon nanotubes dispersed in the matrix improve electrical conductivity and Seebeck coefficient. The addition of MWCNT causes an increase in the grain boundary and facilitates phonon scattering, resulting in a reduction in the lattice thermal conductivity and finally total thermal conductivity. The optimum amount of carbon nanotubes is effective for reducing thermal conductivity and increasing electrical conductivity, thereby elevating the figure-of-merit of the nanocomposites. Finally, the figure-of-merit is highly influenced by total thermal conductivity, and the maximum figure-of-merit was obtained for CuAlS₂/0.5 wt% MWCNT composite, which indicated about 20% improvement.     

类鱼骨结构CoFe2O4纳米纤维的制备与性能

采用静电纺丝与高温煅烧相结合的方法, 以聚乙烯吡咯烷酮(PVP)、九水合硝酸铁(Fe(NO₃)₃·9H₂O)和六水合硝酸钴(Co(NO₃)₂·6H₂O)为原料, 制备出了类鱼骨结构的CoFe₂O₄纳米纤维, 并研究了煅烧温度对CoFe₂O₄纳米纤维形貌、磁性能以及微波吸收性能的影响。结果表明: 随着煅烧温度的升高, CoFe₂O₄纤维的结晶度和晶粒尺寸逐渐增大, 纳米纤维的表面形貌由光滑发展为粗糙多孔, 煅烧温度超过800 ℃时, 纳米纤维呈现类鱼骨结构; 随着煅烧温度增加纤维直径逐渐减小, 900 ℃煅烧的纤维平均直径为80.3 nm。所制备的纳米纤维经振动样品磁强计(VSM)测试结果表明, 饱和磁化强度(M_s)随着煅烧温度的升高而增加, 在900 ℃煅烧条件下纤维的M_s达87.13 A·m²/kg。矢量网络分析仪测试结果表明, 不同煅烧温度下纤维的微波吸收性能差异明显, 800 ℃下煅烧的纤维具有最佳的吸波性能。CoFe₂O₄纳米纤维通过磁滞损耗和涡流损耗机制吸收电磁波, 煅烧产生的孔洞和类鱼骨形貌有利于电磁波在孔道表面多次反射从而增加反射损耗。