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1.
A magnetic composite of nitrogen-doped carbon nanotubes (CN x) decorated with nickel nanoparticles was synthesized by a chemical precipitation and deoxidization method. The decorated CN x were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD pattern showed that CN x, nickel nanoparticles and little nickel oxides coexisted in the composite, TEM observation indicated that nickel nanoparticles were highly dispersed on the outer walls of CN x, Magnetic measurements by VSM demonstrated that the saturated magnetization and remanence of CN x were improved, while the coercivity was lowered after decorating with nickel nanoparticles. 相似文献
2.
Novel composite films consisting of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were fabricated by means of chemical vapor deposition technique and decorated with gold (AuNP) and iridium (IrNP) nanoparticles possessing diameters of 12.5 and 2.7 nm, respectively. The electrochemical responses of fabricated composite films, further denoted as N-MWCNTs/MNPs (M: Au and Ir), toward ferrocyanide/ferricyanide, [Fe(CN)6]3−/4− redox couple was probed by means of cyclic voltammetry and electrochemical impedance spectroscopy techniques. The findings demonstrate that both N-MWCNT/MNP composite films exhibit greater electrochemical response and sensitivity toward [Fe(CN)6]3−/4− compared to unmodified N-MWCNTs. The results verify that the N-MWCNT/MNP composite films are extremely promising for application in electrochemical sensing. 相似文献
3.
By chemical co-precipitation method the nickel spinel ferrite-coated tetrapod-like ZnO composite was prepared. The coating layer was examined by SEM, XRD and EDS, and the VSM measurement was done to study the dependence of magnetic properties of the nickel spinel ferrite-coated tetrapod-like ZnO composite on calcination temperature. Compared with bulk nickel ferrites, the composite presents a higher coercive force with lower saturation magnetization and remanent magnetization. With increase in calcination temperature, its coercive force and remanent magnetization decrease, and the saturation magnetization experiences a monotonous increase followed by a decrease. The nanostructure stability and magnetic behaviors of the nickel spinel ferrite-coated tetrapod-like ZnO composite may be associated with the doping of Zn 2+ ions. 相似文献
4.
The electrochemical activity of an electrode of carbon nanotubes (CNTs) attached with TiO 2 nanoparticles was investigated. A chemical-wet impregnation was used to deposit different TiO 2 particle densities onto the CNT surface, which was chemically oxidized by nitric acid. Transmission electron microscopy showed that each TiO 2 nanoparticle has an average size of 30-50 nm. Nitrogen physisorption measurement indicated that the porosity of CNTs is partially hindered by some titania aggregations at high surface coverage. Cyclic voltammetry measurements in 1 M H 2SO 4 showed that (i) an obvious redox peak can be found after the introduction of TiO 2 and (ii) the specific peak current is proportional to the TiO 2 loading. This enhancement of electrochemical activity was attributed to the fact that TiO 2 particles act as a redox site for the improvement of energy storage. According to our calculation, the electrochemical capacitance of TiO 2 nanocatalysts in acid electrolyte was estimated to be 180 F/g. Charge-discharge cycling demonstrated that the TiO 2-CNT composite electrode maintains stable cycleability of over 200 cycles. 相似文献
5.
Magnetic carbon nanotubes consisting of multi-wall carbon nanotubes (MWNTs) core and Fe 3O 4 shell were successfully prepared by in situ thermal decomposition of Fe(acac) 3 or FeCl 3 or Fe(CO) 5 in 2-pyrrolidone containing acid treated MWNTs at 240 °C with the protection of nitrogen gas. The samples were characterized by TEM, XRD, SEAD, XPS and superconducting quantum interference device. Also, their biocompatibility was compared with naked carbon nanotubes. The results showed that after coated with Fe 3O 4 nanoparticles, the obtained magnetic carbon nanotubes show superparamagnetic characteristic at room temperature, and their blocking temperature is about 80 K. The magnetic properties of the nanotubes are relevant to the content of magnetic particles, increasing content of magnetic nanoparticles leads to higher blocking temperature and saturation magnetization. The results of antimicrobial activities to bacterial cells ( Escherichia coli) showed that the MWNTs have antimicrobial activity, while the magnetic nanotubes are biocompatible even with a higher concentration than that of MWNTs. 相似文献
6.
Multi-walled carbon nanotubes (MWNTs)/Cu-doped ZnO composite powders were prepared by co-precipitation method, and were characterized by X-ray diffraction, electron microscopy, fluorescence spectrum, and ultraviolet spectrum. Experimental results show that the MWNTs can be modified by Cu-doped ZnO nanoparticles with hexagonal wurtzite structure after annealed at 450?°C, and the nanoparticle size is about 15?nm. Two ultraviolet (UV) peaks and a green band centered at about 510?nm are observed in the fluorescence spectrum of MWNTs/Cu-doped ZnO composite powder annealed at 450?°C. Furthermore, MWNTs and Cu doping significantly improve the UV absorption ability of ZnO. 相似文献
7.
Field emission properties of zinc oxide(ZnO) nanoparticles(NPs) decorated carbon nanotubes(CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the Zn O NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory(DFT) combined with the Penn–Plummer method. The ZnO NPs reconstruct the Zn O–CNT structure and pull down the surface barrier of the entire emitter system to 0.49 e V so as to reduce the threshold electric field.The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. 相似文献
8.
Using the solid-phase pyrolysis and chemical vapor deposition of nickel-phthalocyanine, we have fabricated ferromagnetic Ni
nanoparticles in carbon matrices. The composition, structure, morphology, and magnetic properties of samples were investigated
by means of scanning electron microscopy, energy dispersive X-ray microanalysis, X-ray diffraction technique, and ferromagnetic
resonance. It is shown that the sizes of nanoparticles can be varied from ∼10 nm to ∼500 nm depending on the temperature and
time of pyrolysis. The used method allows us to synthesize metal nanoparticles in different carbon matrices: in amorphous
carbon plates, in graphitic capsules, and in carbon nanotubes. 相似文献
9.
Strontium ferrite particles were firstly prepared by sol-gel method and self-propagating synthesis, and then the polyaniline/strontium ferrite/multiwalled carbon nanotubes composites were synthesized through in situ polymerization approach. Structure, morphology and properties of the composite were characterized by various instruments. XRD analysis shows that the output of PANI increases with the increase of the content of MWCNTs, due to the large surface area of MWCNTs. Because of the coating of PANI, the outer diameter of MWCNTs increases from 10 nm to 20-40 nm. The electrical conductivity of the composites increases with the amount increase of MWCNTs and reaches 7.2196 S/cm in the presence of 2 g MWCNTs. The coercive force of the composites prepared with 2 g MWCNTs is 7457.17 Oe, which is much bigger than that of SrFe 12O 19 particles 6145.6 Oe, however, both the saturation magnetization and the remanent magnetization of the composite become much smaller than those of SrFe 12O 19 particles. The electromagnetic properties of the composite are excellent in the frequency range of 2-18 GHz, which mainly depend on the dielectric loss in the range of 2-9 GHz, and mainly on the magnetic loss in the range of 9-18 GHz. 相似文献
10.
The mixed ferrite systems, namely NiFe 2−2xSn xCu xO 4 ( x=0, 0.1, 0.2, and 0.3) nanoparticles have been studied to understand their structural and magnetic parameters. The NiFe 2−2xSn xCu xO 4 nanoparticles were prepared by high energy ball milling (HEBM). The samples were characterized by the X-ray diffraction technique. All samples exhibited spinel structures. The crystalline size and internal strain were evaluated by XRD patterns using Williamson-Hall and Scherrer methods. Magnetic properties of the nanoparticles ferrite were studied by means of alternating gradient force magnetometry (AGFM) and Faraday balance. 相似文献
11.
Aligned functionalized multiwalled carbon nanotubes/polylactic acid (MWNTs-PCL/PLA) composite fibers were successfully prepared by electrospinning processing. The MWNTs bonded with the polycaprolactone chains exhibited excellent uniform dispersion in PLA solution by comparing with the acid-functionalized MWNTs and amino-functionalized MWNTs. Optical microscopy was used to study the aligned degree of the fibers and to investigate the influences of the electrodes distance on the alignment and structure of the fibers, and results showed that the best quality of aligned fibers with dense structure and high aligned degree were obtained at an electrodes distance of 3 cm. Moreover, the MWNTs embedded inside the MWNTs-PCL/PLA fibers displayed well orientation along the axes of the fibers, which was demonstrated by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. 相似文献
12.
Femtosecond laser material processing as micromachining and nanoparticles fabrication require a careful control of the fluences deposited on the samples. In many cases, best results are obtained by using fluences slightly above the Laser Ablation Threshold (LAT), therefore its accurate determination is an important requirement. LAT can be obtained by measuring the intensity of the acoustic signal generated during the ablation process as a function of the laser fluence. In this work femtosecond laser ablation thresholds of commercially polished stainless steel plates, white high impact polystyrene, frosted glass, antique rag papers and silicon oxynitride thin films were determined by using laser ablation induced photoacoustics (LAIP). Results were compared with similar data previously obtained by using a nanosecond Nd:YAG laser. 相似文献
13.
Journal of Nanoparticle Research - Workers are increasingly exposed to nanoparticles, mostly via inhalation. Respiratory protection is recommended as an additional control measure. Particulate... 相似文献
14.
A novel type of gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) composite electrodes is presented. The electrochemical reduction of oxygen on these hybrid electrodes was studied using the rotating disk electrode (RDE) method. The AuNP/MWCNT nanocomposites were prepared by sputter deposition of gold in argon atmosphere on MWCNTs followed by heat-treatment of the catalyst at different temperatures. High-resolution scanning electron microscopy (HR-SEM), glancing incidence angle X-ray powder diffraction (GIXRD) and small-angle X-ray scattering (SAXS) techniques were employed to characterise the surface structure and morphology of catalyst materials. Au nanoparticles with diameter around 20 nm were dispersed at the tips and on the sidewalls of nanotubes. Electrochemical measurements were performed to demonstrate the electrocatalytic properties of the composite catalysts towards O 2 reduction in acid media. The successful preparation of AuNP/MWCNT nanocomposites by magnetron sputtering opens up the possibility of making an efficient dispersion of nanoparticles for electrocatalyst design. 相似文献
15.
FeNi alloy nanoparticles with controllable sizes were attached on the multiwalled carbon nanotubes by adjusting the atomic ratio of metal to carbon in the mixed solution of nitrate with Fe:Ni=1:1 (atomic ratio) via wet chemistry. Transmission electron microscopy (TEM) and high-resolution TEM indicated that quasi-spherical FeNi alloy nanoparticles with sizes in the range 12-25 nm are obtained. FeNi alloy composed of major face center cubic (fcc) and minor body center cubic (bcc) structures, which is proved by the X-ray powder diffraction (XRD). Magnetization measured by vibrating sample magnetometer demonstrated that both the coercive force and saturation magnetizations decrease as the size of the FeNi alloy nanoparticles decreased. The chemical method is promising for fabricating FeNi alloy nanoparticles attached on carbon nanotubes for magnetic storage and ultra high-density magnetic recording applications. 相似文献
17.
The poor efficiency and stability of cost-effective metal compounds are major hurdles to substitute expensive metal-based nanomaterials for the hydrogen evolution reaction (HER). As a result, new concepts and tactics for developing electrocatalysts based on earth-abundant elements must be developed. We present iron-nickel alloy nanoparticles that are supported with carbon (FeNi@C) to improve HER performance in alkaline conditions. FeNi particle was supported on Trimesic acid (TMA) based carbon. In particular, the high conductivity of the carbon and a large number of catalytically active sites in the FeNi demonstrated a synergistic effect, making the hybrid structure a good choice for HER catalyst. Moreover, the physicochemical interaction between the carbon and FeNi metal enhanced the electrocatalytic performance and resulted in achieving 10 mA/cm 2 current density at 190 mV overpotential with 15 h chronopotential cycling, proving the possibility for replacing costly Pt-based catalysts. 相似文献
18.
Catalytic oxidation of multi-walled carbon nanotubes (MWNCTs) with some noble metal nanoparticles was observed by environmental transmission electron microscopy (E-TEM). Amoeba-like movement of the nanoparticles was observed even at a temperature of ∼400 °C, which is much lower than the melting points of any of the metals. In particular, rhodium particles reacted intensely with MWCNTs, and assumed a droplet-like shape. On the other hand, gold particles caused very little erosion of the MWCNTs under the conditions of this study. 相似文献
19.
Nanocomposites based on iron and nickel particles encapsulated into carbon (Fe@C and Ni@C), with an average size of the metal core in the range from 5 to 20 nm and a carbon shell thickness of approximately 2 nm, have been prepared by the gas-phase synthesis method in a mixture of argon and butane. It has been found using X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy that iron nanocomposites prepared in butane, apart from the carbon shell, contain the following phases: iron carbide (cementite), α-Fe, and γ-Fe. The phase composition of the Fe@C nanocomposite correlates with the magnetization of approximately 100 emu/g at room temperature. The replacement of butane by methane as a carbon source leads to another state of nanoparticles: no carbon coating is formed, and upon subsequent contact with air, the Fe 3O 4 oxide shell is formed on the surface of nanoparticles. Nickel-based nanocomposites prepared in butane, apart from pure nickel in the metal core, contain the supersaturated metastable solid solution Ni(C) and carbon coating. The Ni(C) solid solution can decompose both during the synthesis and upon the subsequent annealing. The completeness and degree of decomposition depend on the synthesis regime and the size of nickel nanoparticles: the smaller is the size of nanoparticles, the higher is the degree of decomposition into pure nickel and carbon. The magnetization of the Ni@C nanocomposites is determined by several contributions, for example, the contribution of the magnetic solid solution Ni(C) and the contribution of the nonmagnetic carbon coating; moreover, some contribution to the magnetization can be caused by the superparamagnetic behavior of nanoparticles. 相似文献
20.
Dye-sensitized solar cells (DSSCs) based on a novel composite photoanode of TiO 2 nanoparticles coating on electrodeposited ZnO nanotube arrays are fabricated and characterized. An efficiency of 3.94 % is achieved for the composite cell, increasing 86.7 % than 2.11 % of the ZnO nanotubes cell. The short-circuit current ( J sc) and open-circuit voltage ( V oc) are also enhancing 52.9 % and 25.3 %, respectively. The improvements are because of the high surface area of TiO 2 nanoparticles, as well as fast electron transport and light scattering effect of ZnO nanotubes. 相似文献
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