Iron Nanorods Research Articles

Fe@Fe2P Core‐Shell Nanorods Encapsulated in Nitrogen Doped Carbon Nanotubes as Robust and Stable Electrocatalyst Toward Hydrogen Evolution

AbstractHere, we report an efficient hydrogen evolution reaction (HER) electrocatalyst (Fe@Fe2P/NCNT) fabricated from the phosphorization of partially oxidized iron nanorod encapsulated in nitrogen doped carbon nanotubes (Fe@Fe2O3/NCNT) synthesized from iron trichloride and melamine, which only requires ∼0 mV and 78.2 mV overpotentials to achieve cathodic current densities of 1 mA cm−2 and 10 mA cm−2 with Tafel slope of 52.2 mV dec−1 in acidic media, which exhibits higher HER electrocatalytic activity compared to Fe/NCNT requiring a overpotential of 118.5 mV to attain 10 mA cm−2 with Tafel slope of 92.3 mV dec−1. Due to the phosphorization process, additional active sites coming from Fe2P boost the electrocatalytic activity of Fe@Fe2P/NCNT resulting in decrement in overpotentials by 40.3 mV and 186 mV for 10 mA cm−2 and 50 mA cm−2 compared to Fe/NCNT electrocatalyst, respectively. Meanwhile, Fe@Fe2P/NCNT exhibits ignorable degradation in HER activity after 6000 potential cycles suggesting that the Fe@Fe2P/NCNT with superior HER activity and stability could potentially replace the benchmark Pt/C (overpotential@10 mA cm−2: 31 mV) as efficient HER electrocatalyst for water splitting.

Mechanical and Tribological Properties of Graphene Reinforced Natural Rubber Composites: A Molecular Dynamics Study

ABSTRACTGraphene reinforced natural rubber composites are developed to study the improvement in mechanical and tribological properties of natural rubber by the introduction of graphene as reinforcement. Constant strain minimization method has been applied to calculate Young’s and shear modulus of developed structures. A three-layer model containing Fe (Iron) atoms at the top and bottom and polymer matrices in the middle has been constructed to calculate the tribological properties. A shear loading is applied to the top iron nanorod by sliding it to the surface of the polymer matrices for 600 ps with a velocity of 0.01 nm/ps. The results show the increase of 185% in Young’s modulus, 32% in shear modulus and 48% in hardness by reinforcing natural rubber with single-layer graphene oxide sheet, respectively. Also, reduction of 28% and 36% in the friction coefficient and abrasion rate obtained by the introduction of graphene oxide sheet in natural rubber matrix. Also, interaction energy between graphene and natural rubber, the angle, bond and kinetic energy of the polymer and composites has been calculated and discussed.

Electronic excitation induced modifications in elongated iron nanoparticle encapsulated multiwalled carbon nanotubes under ion irradiation

Multi-wall carbon nanotubes (MWCNT) filled with Fe nanorods were shown to have contracted and deformed under heavy ion irradiation. In this study, 120 MeV Ag and 80 MeV Ni ion irradiation was performed to study the deformation and defects induced in iron filled MWCNT under heavy ion irradiation. The structural modifications induced due to electronic excitation by ion irradiation were investigated employing high-resolution transmission electron microscopy, micro-Raman scattering experiments, and synchrotron-based X-ray absorption and emission spectroscopy. We understand that the ion irradiation causes modifications in the Fe nanorods which result in compressions and expansions of the nanotubes, and in turn leads to the buckling of MWCNT. The G band of the Raman spectra shifts slightly towards higher wavenumber and the shoulder G′ band enhances with the increase of ion irradiation fluence, where the buckling wavelength depends on the radius ‘r’ of the nanotubes as exp[(r)0.5]. The intensity ratio of the D to G Raman modes initially decreases at the lowest fluence, and then it increases with the increase in ion fluence. The electron diffraction pattern and the high resolution images clearly show the presence of ion induced defects on the walls of the tube and encapsulated iron nanorods.

Magnetorheology of dimorphic magnetorheological fluids based on iron nanorods

The aim of this paper is to document suitability of partial substitution of magnetic carbonyl iron (CI) microspheres with iron nanorods to obtain dimorphic magnetorheological (MR) suspensions with comparable MR performance to conventional MR suspensions exclusively based on (CI) microspheres while the sedimentation stability is considerably improved. The morphology of CI and iron nanorods was analyzed via scanning electron microscopy and transmission electron microscopy, respectively, and magnetic properties via vibrating sample magnetometry. The steady shear flow and small-amplitude dynamic oscillatory shear measurements were carried out to confirm effective MR performance. The sedimentation test showed positive role of dimorphic composition of dispersed phase on the sedimentation stability.

A molecular dynamics simulation study on enhancement of mechanical and tribological properties of polymer composites by introduction of graphene

Molecular models for graphene reinforced polymer composites are developed to study the enhanced mechanical and tribological properties of the composites by introduction of graphene as reinforcements. Strain constant method is applied to evaluate the Young's modulus and shear modulus of the polymer composites. A layer model containing iron atoms as the top nanorod and the graphene reinforced polymer composites as the core are constructed to study the tribological properties of polymer composites, i.e. friction coefficient and abrasion rate, by sliding the top iron nanorod on the surface of the polymer matrix. The molecular dynamics simulation results show that increases of about 150% in Young's modulus, 27.6% in shear modulus and 35% in hardness of the polymer composites are obtained respectively by incorporation of graphene reinforcements. In addition, decreases of around 35% and 48% in the average friction coefficient and abrasion rate of the polymer composites are achieved. The research findings are discussed and interpreted by monitoring the interaction energy between graphene and the polymer matrix, the angle, bond and kinetic energy of the polymer chains of the polymer composites.

SERS active Ag encapsulated Fe@SiO2 nanorods in electromagnetic wave absorption and crystal violet detection

The present work is focused on the preparation of Fe nanorods by the chemical reduction of FeCl3 (aq) using NaBH4 in the presence of glycerol as template followed by annealing of the product at 500°C in the presence of H2 gas flow. Subsequently, its surface has been modified by silica followed by silver nanoparticles to form silica coated Fe (Fe@SiO2) and Ag encapsulated Fe@SiO2 nanostructure employing the Stöber method and silver mirror reaction respectively. XRD pattern of the products confirmed the formation of bcc phase of iron and fcc phase of silver, though silica remained amorphous. FESEM images established the growth of iron nanorods from the annealed product and also formation of silica and silver coating on its surface. The appearance of the characteristics bands in FTIR confirmed the presence of SiO2 on the Fe surface. Magnetic measurements at room temperature indicated the ferromagnetic behavior of as prepared iron nanorods, Fe@SiO2 and silver encapsulated Fe@SiO2 nanostructures. All the samples exhibited strong microwave absorption property in the high frequency range (10GHz), though it is superior for Ag encapsulated Fe@SiO2 (−14.7dB) compared with Fe@SiO2 (−9.7dB) nanostructures of the same thickness. The synthesized Ag encapsulated Fe@SiO2 nanostructure also exhibited the SERS phenomena, which is useful in the detection of the carcinogenic dye crystal violet (CV) upto the concentration of 10−10M. All these findings clearly demonstrate that the Ag encapsulated Fe@SiO2 nanostructure could efficiently be used in the environmental remediation.

Direction-Specific Interactions Control Crystal Growth by Oriented Attachment

The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.

Real-Time Imaging of Pt 3 Fe Nanorod Growth in Solution

The growth of colloidal nanocrystal architectures by nanoparticle attachment is frequently reported as an alternative to the conventional growth by monomer attachment. However, the mechanism whereby nanoparticle attachment proceeds microscopically remains unclear. We report real-time transmission electron microscopy (TEM) imaging of the solution growth of Pt(3)Fe nanorods from nanoparticle building blocks. Observations revealed growth of winding polycrystalline nanoparticle chains by shape-directed nanoparticle attachment followed by straightening and orientation and shape corrections to yield single-crystal nanorods. Tracking nanoparticle growth trajectories allowed us to distinguish the force fields exerted by single nanoparticles and nanoparticle chains. Such quantification of nanoparticle interaction and understanding the growth pathways are important for the design of hierarchical nanomaterials and controlling nanocrystal self-assembly for functional devices.

CHARACTERIZATION AND ELECTRICAL PROPERTIES OF ALIGNED CARBON NANOTUBES WITH HIGH ASPECT RATIO

High-quality multiwall carbon nanotubes (MWNTs) were produced by a simple one-step technique. The production of MWNTs was based on thermal decomposition of the mixture of a liquid phase organic compound and ferrocene. High degree of alignment was noticed by scanning electron microscopy. The aspect ratio of as-synthesized MWNTs was quite high (more than 4500). Transmission electron microscopy analysis showed the presence of the catalytic iron nanorods at various lengths of MWNTs. Raman spectroscopy was used to know the quality of MWNTs. The ratio of intensity of the G-peak to the D-peak was very high which revealed high quality of MWNTs. Magnetotransport studies were carried out at low temperature and a negative MR was noticed.

Formation mechanism of carbon-encapsulated iron nanorods in a co-carbonization process

Carbon-encapsulated iron nanostructures were prepared by co-carbonization of a mixture of aromatic heavy oil and ferrocene. The morphologies and structural features of the iron/carbon composites were investigated using transmission electron microscopy, high-resolusion transmission electron microscopy and X-ray diffraction measurements. It was found that, by increasing the reaction temperature from 420 to 450 °C the product was changed from nanoparticle to nanorod. The morphologies of the products prepared at 440 °C proved the relationship between nanoparticle and nanorod. Therefore, a model was established to explain the formation mechanism of carbon-encapsulated iron nanorods from the aggregation and self-assembly of partially fused carbon-encapsulated iron nanoparticles.

Phase states and magnetic properties of iron nanoparticles in carbon nanotube channels

The structure, phase composition, and magnetic properties of carbon nanotubes filled with iron nanoparticles and obtained by thermolysis of a mixture of ferrocene and C60 fullerene or ferrocene and orthoxylene at a temperature of 800°C are investigated. Electron microscopy, X-ray diffraction, and Mossbauer spectroscopy data lead to the conclusion that carbon nanotubes are multilayer systems partially filled with iron nanoparticles and/or nanorods. Metallic inclusions in nanotube channels form α-Fe, γ-Fe, and Fe3C phases. The concentration of each phase in the samples is determined. It is shown that 10–20-nm iron clusters in nanotubes exhibit magnetic properties typical of bulk phases of iron. High elasticity of carbon nanotube walls facilitates stabilization of the high-temperature γ-Fe phase; the relative concentration of this phase in a sample can be increased by lowering the concentration of ferrocene in the initial reaction mixture.

Preparation and characterization of aligned iron nanorod using aqueous chemical method

Thin film of metallic iron (α-Fe) nanorod directly from nanorods of akaganéite (β-FeOOH) under hydrogen reduction atmosphere through an aqueous chemical method has been investigated in the present work. The β-FeOOH and reduced α-Fe nanorod are one-dimensional, rod-like shape with diameters of approximately 100–150 and 150–200 nm, respectively. Fe K-edge XANES/EXAFS spectra have been indicated that β-FeOOH and α-Fe nanorods mainly consist of Fe(III) and Fe(0) species. As shown in RIXS spectra, the iron nanorods are quite active and easily oxidized or corroded in the synthetic processes or analytical processes.

Morphology evolution, magnetic and microwave absorption properties of nano/submicrometre iron particles obtained at different reduced temperatures

Nano/submicrometre iron particles were prepared by a hydrogen reduction method in a fluidized bed furnace using α-FeOOH nanorods as precursors. The effect of the reducing temperature (T) on the microstructure, static magnetic properties, microwave electromagnetic parameters and microwave absorption properties of the resultant iron particles was investigated. When T increases from 450 to 650 °C, the as-obtained iron particles show an obvious morphology evolution from anisotropic nanorods to isotropic submicrometre polyhedra. As a result, the saturation magnetization, the complex permittivity and the real permeability all increase, while the coercivity and the imaginary permeability decrease due to the reducing surface effect and shape anisotropy. Nanocomposites containing 30 wt% iron nanorods obtained at 450 °C show a minimal reflection loss (RL) as low as −36.8 dB at 14.1 GHz and an absorption band with RL under −10 dB from 11.6 to 17.0 GHz when the thickness is 1.5 mm, suggesting that they are promising as a strong absorption, thin and lightweight microwave absorber.

From Carbon-Encapsulated Iron Nanorods to Carbon Nanotubes

Carbon-encapsulated iron carbide/iron nanorods (CENRs) with length of 150−350 nm and diameter of 30−60 nm have been synthesized by co-carbonization of an aromatic heavy oil and ferrocene at 450 °C ...

Microwave-Assisted Shape-Controlled Bulk Synthesis of Ag and Fe Nanorods in Poly(ethylene glycol) Solutions

Bulk syntheses of silver (Ag) and iron (Fe) nanorods using poly(ethylene glycol) (PEG) under microwave irradiation conditions are reported. Favorable conditions to make Ag nanorods were established and can be extended to make Fe nanorods with uniform size and shape. The nanorods formation depended upon the concentration of PEG used in the reaction with Ag salt. The obtained Ag and Fe nanorods were characterized using scanning electron microscopy, transmission electron microscopy, and UV–visible spectroscopy. Ag and Fe nanorods crystallized in face centered cubic symmetry. The method uses no surfactant or reducing agent and is greener in nature which could open a myriad of applications.

Diameter controlled growth of iron‐filled carbon nanotubes

AbstractWe report the chemical vapor deposition of Fe‐filled carbon nanotubes (CNTs) from metallorganic precursors (ferrocene, cyclopentadienyliron dicarbonyl dimer) on oxidized silicon substrates precoated with single‐layered or multi‐layered catalyst films (Fe, Au/Fe or Au/Al/Fe). The performed experiments result in thin multi‐walled carbon nanotubes (<40 nm) with a narrow diameter distribution and containing up to several micrometer long single crystalline iron nanorods. Electron scanning microscopy shows that the CNTs grow vertically aligned to the substrate surface. Furthermore transmission electron microscopy (TEM) indicates nearly impurity free CNTs. These investigations are also complemented by X‐ray analysis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth studies, TEM and XRD investigations of iron‐filled carbon nanotubes

AbstractThe formation mechanism of iron filled carbon nanotubes on oxidized silicon substrates precoated with thin metal layers (Fe, Co) has been studied. These filled structures were aligned perpendicular to the substrate surface. The nanotubes were produced by the thermal decomposition of ferrocene in an argon flow. We have studied the nanotube morphology and geometry (diameter, length) in detail. Transmission electron microscopy (TEM), X‐ray diffraction (XRD) and selected area electron diffraction (SAED) were used to analyze the iron nanorods inside the nanotubes. These investigations have revealed a majority fraction of α‐Fe and small amounts of γ‐Fe and Fe3C. Moreover only single crystalline iron was found. In summary we conclude that iron filled carbon nanotubes with this CVD route are formed via an open‐ended, base growth mechanism. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Characterization of Fe nanorods grown directly from submicron-sized iron grains by thermal evaporation

Materials with size down to the nanometer scale exhibit melting points lower than that of their bulk form. This may lead to new catalyst-free approaches for fabricating metal/metal oxides nanostructures. In this Brief Report, we report the observation of Fe nanorods grown directly from submicron-sized Fe grains on Si substrates at $\ensuremath{\sim}650\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, by thermal evaporation. The iron nanorods are single crystalline, several tens of nanometers in diameter, and several hundred nanometers long, and are coated with a thin (several nanometers thick), single-crystalline ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ layer. The growth of Fe nanorods by this approach is due to the partial melting and iron droplet formation on submicron-sized grains at temperatures much lower than its melting point. This study opens a new way to fabricate metal/metal oxides nanostructures without catalysts, at relatively low substrate temperatures.

Formation of Ni-catalyzed multiwalled carbon nanotubes and nanofibers on a substrate using an ethylene inverse diffusion flame

The synthesis of Ni-catalyzed multiwalled carbon nanotubes and nanofibers on a catalytic metal substrate, using an ethylene-fueled inverse diffusion flame as a heat source, was investigated. When the approximate gas temperature was varied from 1400 to 900 K, carbon nanotubes with diameters of 20–60 nm were formed on the substrate. In the regions where the approximate gas temperature was higher than 1400 K or lower than 900 K, iron nanorods or carbon nanofibers were synthesized, respectively. Based on the quantitative analyses of many scanning electron microscope (SEM) and transmission electron microscope (TEM) images, the nanotubes formed closer to the flame had a tendency to have larger diameters. High-resolution TEM images and Raman spectra revealed that the synthesized carbon nanotubes had multiwalled structures, with some defective graphite layers at the wall. Based on the graphite mode of the Raman spectra, it was believed that the optimal synthesis could be obtained if the substrate was positioned at between 5.5 and 5.0 mm from the flame center. However, in the case of higher gas temperatures with respect to the formation of nanotubes rather than nanofibers, the graphite layers on the catalyst metal might be under relatively strong stress due to the large amount of precipitated carbon atoms on the edge. As a result of this strong compressive stress the carbon nanotubes are formed with empty or periodic compartments which are hollow on the inside.

에틸렌 역확산화염을 열원으로 사용하여 촉매금속 기판 상에 합성한 탄소나노튜브와 탄소나노섬유

The synthesis of Ni-catalyzed multi-walled carbon nanotubes and nanofibers on a catalytic metal substrate, using an ethylene fueled Inverse diffusion flame as a heat source, was investigated When the gas temperature was vaned from 1,400K to 900K, approximately, carbon nanotubes with diameters of 20 - 60nm were fanned on the substrate In the regions where the gas temperature was higher than 1,400K or lower than 900K, Iron nanorods or carbon nanofibers were synthesized, respectively. Based on the quantitative analyses of large amount of SEM and TEM Images, the nanotubes farmed closer to the flame had a tendency of having larger diameters. HR- TEM Images and Raman spectra revealed that carbon nanotubes synthesized had multi-walled structures with some defective graphite layers at the wall Based on the graphite mode of the Raman spectra, It was believed that the optimal synthesis could be obtained as the substrate was positioned at between 55mm and 5.0mm, from the flame axis<br/>