Fe3O4 Nanotubes Research Articles

Root-like MnCO3/Fe2O3/CNTs with high-rate performance as anodes material for lithium-ion batteries

A transition metal compound with high lithium storage is one of the most promising anode materials for lithium-ion batteries (LIBs). The root-like MnCO3/Fe2O3/CNTs composites with the porous structure were synthesized by facile solvothermal methods. The excellent cycling stability and high-rate performance were exhibited, 651.3 mAh/g at 100 mA/g after 250 cycles and 631.5 mAh/g at 500 mA/g after 1000 cycles, which benefit from the porous structure and synergy among MnCO3, Fe2O3, and carbon nanotubes. The porous structure of composites can reduce the charge-transfer resistance, and the extra void can effectively alleviate volume expansion during the charge/discharge process.

Photogenerated cathodic protection properties of Fe2O3 nanotubes prepared by anodic oxidation

Photogenerated cathodic protection as a new type of corrosion protection method has evoked great attention. The n-type semiconductor is normally selected as the photogenerated cathodic protection composite. α-Fe2O3 is a typical n-type semiconductor, which is easy to obtain and environmental-friendly. However, it is normally prepared on the FTO substrate and could hardly protect carbon steel. In this study, α-Fe2O3 nanotubes are fabricated on carbon steel by anodic oxidation method at different oxidation potentials. The corresponding surface morphologies, compositions, and optical absorption properties are characterized with SEM, Raman spectroscopy, and UV-Visible spectrometer. The photoelectrochemical tests show that the prepared α-Fe2O3 can supply cathodic protection to carbon steel. The maximum photogenerated potential drop is obtained for the α-Fe2O3 sample prepared under 50 V at 30 ℃ for 450 s anodic oxidation. It is revealed that the fine structure is benefit to capture light and enhances the photogenerated cathodic protection performance to carbon steel.

Comparison and evaluation of energetic and exergetic performance of an evacuated tube solar collector using various nanofluid

There is a growing interest in renewable energy sources cause the worsening impact of fossil fuel development and abuse on the ecological environment. Solar collectors are major facilities that utilize solar energy, many studies and techniques have been employed to increase the efficiency of the collectors. This paper aims to evaluate the thermal performance of an evacuated tube solar collector(ETSC) in the solar thermal system by using Al2O3, CuO, Fe3O4 and Multi-walled carbon nanotube(MWCNT) nanofluid as working fluids. An evaluation approach for the energy, exergy and entropy of ETSC were proposed. Furthermore, the energy gained and stored by nanofluid in the solar collector was also been studied. The ETSC shown highest energy and exergy efficiency when the 0.01 vol%-MWCNT nanofluid was used which was 33.1% higher than that of water, and it was the same situation of exergy efficiency while the highest was 3.17 under the optimum situation. In addition, the energy gained by 0.01 vol%-MWCNT nanofluid showed the highest potential of energy absorption than other nanofluid, the maximum exergy destruction and entropy generation were achieved when water was used as working fluid of solar collector while the lowest were observed when MWCNT nanofluid with 0.01 vol% was used. Compared to normal working fluid in the ETSC, the use of nanofluid with high thermal conductivity can save more fossil fuels and coals which have a positive effect on protecting the environment.

Dynamic susceptibility of Fe3O4 nanotubes

In this work we performed a detailed numerical analysis to investigate the dynamic susceptibility of 1000 nm long Fe3O4 nanotubes by varying the diameter, the tube wall thickness and the magnitude of the external magnetic field applied along the tube axis. We found two well-defined modes, one of low frequency associated with the caps of the nanotubes, and another of high frequency associated with the central area of the nanotubes, which can be controlled by varying the geometry of the tubes or the external magnetic field to which they are subjected. These results allow us to suggest the use of these nanotubes in applications that require controlling the resonant frequency in the GHz range.

Static and Dynamic Magnetic Properties of Fe3O4 Nanotubes

In this paper, our objective was to investigate the static and dynamic magnetic properties of Fe3O4 nanotubes that are 1000 nm long, by varying the external radius and the thickness of the tube wall. We performed a detailed numerical analysis by simulating hysteresis curves with an external magnetic field applied parallel to the axis of the tubes (along the z-axis). Our findings indicate that nanotubes with an external radius of 30 nm exhibit non-monotonic behavior in their coercivity due to a change in the magnetization reversal mechanism, which was not observed in nanotubes with external radii of 80 nm. Additionally, we explored the dynamic susceptibility of these nanotubes and found that the position and number of resonance peaks can be controlled by manipulating the nanotube geometry. Overall, our study provides valuable insights into the behavior of Fe3O4 nanotubes, which can aid in the design and improvement in pseudo-one-dimensional technological devices.

High-performance, thermal management and long-term preservation Epoxy/TPEDA -Fe3O4@ carboxylic carbon nanotube electromagnetic shielding composites

In this work, a high-performance electromagnetic interference (EMI) latent curing epoxy composites with combination of modified Fe3O4 and carboxylic carbon nanotube (CNTs) were prepared by magnetic orientation. The unique heterogeneous interface among magnetic nanoparticles and conductive nanowires facilitates the loss of interface polarization, the wave absorbance and the dipole polarization, makes EMI SET of the material reach respectively 45.86 dB in X-band at the thickness of 2 mm ± 0.1 mm, significantly exceeding that of other epoxy-based shielding materials. In addition, the composites show excellent thermal capacity reaching 1.59 W/m·K. What's more, the oriented epoxy mixture can be preserved at room temperature for 40 days maintaining a low viscosity state without curing, which has a strong practical application prospect in the field of electronic packaging materials.

Highly enhanced photocatalytic activity of nanotubular Fe2O3/Fe2WO6 nanocomposite film formed by anodizing FeW alloy

This study demonstrates the highly enhanced photocatalytic activity of Fe2O3 nanotubes by making a heterojunction with Fe2WO6 and doping of W6+ ions into the α-Fe2O3 phase for water splitting and decomposition of an organic pollutant. Both nanotubular and compact Fe2O3/Fe2WO6 films are formed by anodizing the magnetron-sputtered Fe-9 at% W alloy in fluoride-containing ethylene glycol electrolyte and subsequent annealing at 450 °C. Their photocatalytic activities are compared with W-free nanoporous Fe2O3 film formed on high-purity Fe. The nanotubular Fe2O3/Fe2WO6 film exhibits a markedly enhanced photoelectrochemical oxygen evolution reaction and photocatalytic degradation of methylene blue compared with the nanoporous W-free Fe2O3 film. Because of the larger surface area, the nanotubular Fe2O3/Fe2WO6 film reveals further increased activity than the compact Fe2O3/Fe2WO6 film. The STEM study discloses the dispersion of Fe2WO6 nanoparticles in the α-Fe2O3 phase after annealing at 450 °C, and XRD analysis shows the possible doping of W species into α-Fe2O3. The formation of the W-doped α-Fe2O3/Fe2WO6 heterojunction likely promotes the separation of photogenerated electron-hole pairs, enhancing photocatalytic activity. Hence, the nanotubular Fe2O3/Fe2WO6 film is a possible candidate for visible-light-driven photocatalysts.

In situ construction of hierarchical Fe2O3 nanotube arrays for real-time detection and degradation of 2-CEES gas

Real-time detection and degradation of chemical warfare agents have great importance in both human healthcare and environmental protection. Herein, hierarchical Fe2O3 nanotube arrays were constructed by a simple in situ solvothermal method for effective monitoring of 2-chloroethyl ethyl sulfur enigma (2-CEES). The resultant Fe2O3 sensor exhibited ultrahigh response (9.6) and short response time (3.7 s) to 10 ppm 2-CEES at 170 ℃. The sensor also behaved low detection limit (30 ppb), good stability, and high moisture resistance. Notably, Fe2O3 nanotube arrays demonstrated high degradation capacity (95.2%) (100 ppm, 10 min). Such excellent performance of the portable Fe2O3 sensor for 2-CEES comes from the synergistic effect of multiple microstructural features, active sites, and surface-adsorbed oxygen species at operating temperature. The 2-CEES sensing mechanism of Fe2O3 nanotube arrays has been discussed in detail. This work offers guidance for designing high-performance sensing materials to realize efficient detection of chemical warfare agents.

Improving a solar collector's efficiency by selecting the composition of the working fluid used

Abstract The study's purpose was to determine the efficiency, as well as the energy and exergy analysis of the vacuum tube solar collector when using a mixture of water with Fe3O4 nanoparticles and multiwall carbon nanotubes in the selected percentage ratio as the working fluid. By varying the concentration of Fe3O4 nanoparticles in the working fluid from 0.05 to 0.15 wt.%, it was found that the maximum efficiency is achieved at a Fe3O4 content equal to 0.1 wt.%. At this concentration, the ratio of Fe3O4 and multiwall carbon nanotubes in the mixture varied from 4:1 to 1:4. It was found that the Fe3O4/multiwall carbon nanotubes ratio (1:4) can increase the efficiency of the solar collector up to 84%. Exergy analysis performed showed that water without the addition of nanoparticles Fe3O4 and multiwall carbon nanotubes was characterized by the maximum values of exergy destruction and entropy generation at any level of solar radiation, and water with the addition of nanoparticles Fe3O4/multiwall carbon nanotubes in a ratio of 1:4 was characterized by the minimum values of exergy destruction and entropy generation.

Creating Highly Active Iron Sites in Electrochemical N2 Reduction by Fabricating Strongly-Coupled Interfaces.

Electrochemical Nc reduction has been regarded as one of the most promising approaches to producing ammonia under mild conditions, but there are remaining pressing challenges in improving the reaction rate and efficiency. Herein, an unconventional galvanic replacement reaction is reported to fabricate a unique hierarchical structure composed of Fe3 O4 -CeO2 bimetallic nanotubes covered by Fe2 O3 ultrathin nanosheets. Control experiments reveal that CeO2 species play the essential role of stabilizer for Fe2+ cations. Compared with bare CeO2 and Fe2 O3 nanotubes, the as-obtained Fe2 O3 /Fe3 O4 -CeO2 possesses a remarkably enhanced NH3 yield rate (30.9µg h-1 mgcat -1 ) and Faradaic efficiency (26.3%). The enhancement can be attributed to the hierarchical feature that makes electrodes more easily to contact with electrolytes. More importantly, as verified by density functional theory calculations, the generation of Fe2 O3 -Fe3 O4 heterogeneous junctions can efficiently optimize the reaction pathways, and the energy barrier of the potential determining step (the *N2 hydrogenates into *N*NH) is significantly decreased.

Efficient degradation of organic pollutants using peroxydisulfate activated by magnetic carbon nanotube.

The magnetic composite of Fe3O4 and carbon nanotube (MCNT) was fabricated in a facile one-pot solvothermal method and employed to activate peroxydisulfate (PDS) for degradation of Rhodamine B (RhB) and other pollutants. The effects of operational factors including MCNT dosage and PDS dosage were studied, and high removal efficiencies of 84.2-99.5% were achieved for these pollutants with 0.3 g/L MCNT and 4 mM PDS. The effects of environmental factors including initial pH, inorganic cations, inorganic anions, humic acid and water matrix were also studied. Reusability test showed that the removal efficiency declined in four consecutive runs, which was attributed to the adsorbed oxidation products on the catalyst surface. Based on quenching experiments, solvent exchange (H2O to D2O), inductively coupled plasma and open circuit potential tests, it was concluded that radicals of ·OH/SO4·- and the non-radical electron-transfer pathway were involved in the MCNT/PDS system, and the contributions of O2·-, 1O2, high-valent iron-oxo species and homogenous activation were insignificant. Moreover, the orbital-weighted Fukui functions of RhB were calculated by density functional theory, and its plausible degradation pathway was proposed based on the calculation results. Finally, toxicity evaluation of the degradation products was performed in the quantitative structure-activity relationship approach.

Effect of surface roughness on the solar evaporation of liquid marbles

Hypothesis: Nanostructured materials are widely used for solar energy harvesting and conversion due to their excellent photothermal properties. It is generally accepted that the better the light absorption ability, the better the photothermal conversion efficiency.Experiment: A series of experiments in solar evaporation of liquid marbles (LMs) by coating the droplets with Fe3O4, Ni nanoparticles (NPs) and carbon nanotubes (CNTs) are conducted.Findings: Conversely, we found that the surface roughness of solar absorber plays a significant role in solar evaporation rather than the light absorption. The results disclose that the Fe3O4 NPs with the lowest absorptivity has the largest roughness on drop surface, while that of CNTs show the opposite properties. The evaporation dynamics of LMs are featured with dome or constant spherical collapse with different roughness. Such dynamic difference arises from the mechanical competition between the capillary force and interparticle interaction. Besides, the strong light-harvesting and near-field radiation enabled by the rough surfaces enhance the solar evaporation. The Fe3O4-LM shows the highest evaporation rate of 6.55 μg/s, which is 1.09 and 1.30 times larger than that of Ni-LM and CNT-LM, respectively. Numerical analysis reveals that the rough surface with stacking arrangement of NPs greatly enhances the light-induced electromagnetic field and heat concentration over the interface, leading to a plasmon-coupling boundary with high temperature for the fast evaporation. Uncovering these properties could be of much help for developments of heatable miniature evaporators or reactors and their counterparts, permitting a broad range of processes with precise temperature and kinetic control.

High-performance acetone sensor based on electrospun Tb-doped α-Fe2O3 nanotubes

Gas sensing requires precise gas detection, hence the need for the development of semiconductors with highly selective and sensitive properties. Herein, different amounts of Tb-doped Fe2O3 nanotubes (NTs) are successfully fabricated for detecting acetone gas using electrospinning followed by calcination at 550 °C. Specifically, the gas sensing investigation indicated that 5% Tb–Fe2O3 NTs to 50 ppm acetone reached 53.2 at 170 °C, which is 13 times higher than that of pure Fe2O3 NTs. In addition, the sensor also displays good selectivity and a low detection limit (200 ppb) for acetone. The significant increase in acetone sensing performance could be ascribed to hollow structures with a high specific surface area and the increase in oxygen vacancies by Tb doping. The proposed Tb-doped Fe2O3 NTs offer an effective strategy for fabricating a highly sensitive acetone sensor, which can work well at a relatively low temperature.

Synthesis of NiSe2 /Fe3 O4 Nanotubes with Heteroepitaxy Configuration as a High-Efficient Oxygen Evolution Electrocatalyst.

The rational design of high-efficient non-noble metal electrocatalysts for oxygen evolution reactions (OER) is of significance in electrochemical energy conversion. However, such low-cost but highly active electrocatalysts remain poorly developed because of the daunting synthetic challenge. Here, the synthesis of NiSe2 /Fe3 O4 nanotubes via a facile self-templating strategy, which manifests unique tetragonal morphology, asymmetric hollow interior, and unusual but adaptable heteroepitaxy structure, is reported. Benefiting from sufficient active sites and their improved activity around the heterointerface, accompanied by the good conductivity, the NiSe2 /Fe3 O4 nanotubes exhibit as a superior OER electrocatalyst, which affords the current density of 10mA cm-2 at a very small overpotential of 199mV, high attainable current density beyond 200mA cm-2 , and mass activity of 984.5 A g-1 , as well as excellent stability for 100 h in the alkaline media. This work provides a unique synthetic pathway to fabricate superior OER electrocatalysts by optimizing their composition and architecture.

Construction of targeted delivery system for curcumin loaded on magnetic α-Fe2O3/Fe3O4 heterogeneous nanotubes and its apoptosis mechanism on MCF-7 cell.

In this work, the magnetic α-Fe2O3/Fe3O4 heterogeneous nanotubes were successfully prepared by solvent hydrothermal-controlled calcination method. The effects of additive concentration, hydrothermal temperature and time on morphology of products were investigated. The α-Fe2O3/Fe3O4 nanotubes with a saturation magnetization of 50emu/g were prepared calcinated at 600°C for 4h using 0.8g of glucose. Their average length, the outer and inner diameters were around 240nm, 178nm and 145nm, respectively. The α-Fe2O3/Fe3O4 heterogeneous nanotubes coated with water-soluble liposome were applied for targeted delivery of curcumin. The release of curcumin inside the hollow structure of the nanocomposites could be triggered and effectively sustained represented a process of slow release. The encapsulation efficiency of curcumin in the α-Fe2O3/Fe3O4-CUR@LIP nanocomposites reached 82.1±0.9%. MTT assays demonstrated that blank carriers had excellent biocompatibility and application of magnetic field significantly elevated the cytotoxicity of α-Fe2O3/Fe3O4-CUR@LIP nanocomposites on MCF-7 cell. Electrochemical experiment and Prussian blue staining indicated that the α-Fe2O3/Fe3O4@LIP nanocomposites could aggregate in cells to promote the internalization of curcumin. Magnetic α-Fe2O3/Fe3O4-CUR@LIP nanocomposites and curcumin enhanced the expression of reactive oxygen species in MCF-7 cells and induced apoptosis by fluorescence detection. Flow cytometry and western blot verified that the α-Fe2O3/Fe3O4@LIP nanocomposites under magnetic field enhanced cells late-apoptosis by adjusting the expression of apoptosis-related proteins.

Vortex tuning magnetization configurations in porous Fe3O4 nanotube with wide microwave absorption frequency

Vortex tuning magnetization configurations in porous Fe3O4 nanotube with wide microwave absorption frequency

Cytotoxicity of Fe3O4 Nanoparticles with Different Morphologies In Vitro

Fe3O4 nanoparticles have been widely used as drug carriers, but their toxicity is rarely reported. Herein, we compared the toxicity of novel Fe3O4 nanorings, nanotubes and conventional Fe3O4 nanospheres. The structure, morphology and magnetic properties of Fe3O4 nanoparticles were characterized via X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. Scanning electron microscope images revealed that the morphologies of Fe3O4 particles were annular, tubular or spherical. The magnetic property measurements demonstrated that saturation magnetization values of nanorings, nanotubes and nanospheres were 85.3, 90.1 and 74.8[Formula: see text]emu/g, respectively. In addition, the cytotoxic effects on the 264.7 mouse macrophages cells of Fe3O4 nanorings, nanotubes and nanospheres were determined by cck-8 test and TUNEL staining assay. Cell viability was slightly decreased on spherical Fe3O4 nanoparticles compared to annular and tubular Fe3O4 nanoparticles.

Steady Squeezing Flow of Magnetohydrodynamics Hybrid Nanofluid Flow Comprising Carbon Nanotube-Ferrous Oxide/Water with Suction/Injection Effect.

The main purpose of the current article is to scrutinize the flow of hybrid nanoliquid (ferrous oxide water and carbon nanotubes) (CNTs + FeO/HO) in two parallel plates under variable magnetic fields with wall suction/injection. The flow is assumed to be laminar and steady. Under a changeable magnetic field, the flow of a hybrid nanofluid containing nanoparticles FeO and carbon nanotubes are investigated for mass and heat transmission enhancements. The governing equations of the proposed hybrid nanoliquid model are formulated through highly nonlinear partial differential equations (PDEs) including momentum equation, energy equation, and the magnetic field equation. The proposed model was further reduced to nonlinear ordinary differential equations (ODEs) through similarity transformation. A rigorous numerical scheme in MATLAB known as the parametric continuation method (PCM) has been used for the solution of the reduced form of the proposed method. The numerical outcomes obtained from the solution of the model such as velocity profile, temperature profile, and variable magnetic field are displayed quantitatively by various graphs and tables. In addition, the impact of various emerging parameters of the hybrid nanofluid flow is analyzed regarding flow properties such as variable magnetic field, velocity profile, temperature profile, and nanomaterials volume fraction. The influence of skin friction and Nusselt number are also observed for the flow properties. These types of hybrid nanofluids (CNTs + FeO/HO) are frequently used in various medical applications. For the validity of the numerical scheme, the proposed model has been solved by another numerical scheme (BVP4C) in MATLAB.

Interfacial engineering of Cu–Fe2O3 nanotube arrays with built-in electric field and oxygen vacancies for boosting the electrocatalytic reduction of nitrates

A Cu–Fe2O3 nanotube array with built-in electric field and OVs provided two grips for the enrichment and anchoring of NO3− near the electrocatalytic electrodes. The NO3− enhancement effect and OV-engineered heterogeneous interface on NO3− electroreduction were verified.

Synthesis and characterization of PEG coated hollow Fe3O4 magnetic nanoparticles as a drug carrier

As a drug carrier, the properties of magnetic nanoparticles for drug loading are significant. In this letter, three different shapes of magnetic nanoparticles for drug carrier systems were compared. We synthesized Fe3O4 magnetic nanospheres, nanorings and nanotubes, and plyethylene glycol was used as a surface modifier for drug loading. The structure characterization of three different shapes of Fe3O4 nanoparticles was elucidated by electron microscopy, and the composition was analyzed by Fourier transform infrared. The drug loading status and drug release of the three types of nanoparticles with different shapes were tested by Ultraviolet Spectrophometometer. The results show that the hollow Fe3O4 magnetic nanorings and nanotubes have better drug loading capacity and are more suitable for drug carriers, compared with nanospheres.