Multi-walled Carbon Nanotubes In Matrix Research Articles

Alignment of multiwalled carbon nanotubes‐reinforced epoxy by a novel shear assisted method in the presence of the electric field

AbstractThe application of multiwall carbon nanotubes (MWCNTs) alignment associated with external field techniques is fairly limited in the industry due to the cost implications of scaling such external fields. To address this problem, a new shear‐assisted method is introduced to increase the effectiveness of MWCNTs alignment techniques using electric field. In addition, the effect of curing temperature of polymer in CNT‐reinforced nanocomposites, is studied on the alignment of MWCNTs using our novel shear‐assisted technique. The results show that increasing the temperature during the curing process of the polymer can help with the alignment of MWCNTs using our shear‐assisted technique. This may be attributed to lower gel‐time of polymer matrix at high temperatures that can prevent agglomeration of the MWCNTs in the matrix. Moreover, fractography of reinforced composites has been studied by scanning electron microscopy to investigate the effects of curing temperature on the alignment of MWCNTs in the epoxy matrix.

Shielding effectiveness study of CoZCF-MWCNT nanocomposite materials and its possible application as EM pollution reducer

In this article, Co0.40Zn0.40Cu0.20Fe2O4 (CoZCF) nanoparticles were synthesized using sol-gel method. The Field Emission Scanning Electron Microscopy (FESEM) micrographs delineate the proper encapsulation of the soft magnetic nanoparticles inside the matrix of multi-walled carbon nanotubes (MWCNTs) and ensuring proper fabrication of the CoZCF-MWCNT nanocomposites. The X-ray Diffraction (XRD) analysis and Raman spectroscopy confirms the presence of the multi-phase nature of CoZCF-MWCNT nanocomposites. The static magnetic development of the nanocomposites as a function of temperature and the shielding effectiveness behavior in X-band and Ku-band of microwave radiation have been studied herein. Different static magnetic quantities were extracted. The magnetic observation confirms the presence of ferrimagnetic state with magnetization of 48.4 and 44.8 emu g−1 respectively at room temperature (RT) in CoZCF-MWCNT nanocomposites. The variation of hysteresis loop area with the lowering of temperature depicts the transformation of CoZCF-MWCNT nanocomposites from superparamagnetic to ferromagnetic state. The shielding effectiveness study was conducted in the X- and Ku- bands of electromagnetic radiation and the observation shows a high value of total shielding effectiveness (SET) of ∼ −31.3 dB corresponding to 10.7 GHz. This is due to the high of attenuation of > 99.9% and wide bandwidth. This improved SET of CoZCF-MWCNT nanocomposites gives us completely new insights for the construction of microwave absorber/Radar Absorbing Materials (RAMs) that can contest against harmful electromagnetic pollution.

Realization of diamond nucleation within the multi-walled carbon nanotubes matrix upon electron irradiation

Realization of diamond nucleation within the multi-walled carbon nanotubes matrix upon electron irradiation

Morphological: Optical, and Mechanical Characterizations of Non-Activated and Activated Nanocomposites of SG and MWCNTs

Nanocomposites of silica gel (SG) and multiwalled carbon nanotubes (MWCNTs) of relatively low concentrations (0.25, 0.50, and 0.75 wt%) were characterized before and after annealing. Adsorption is a surface phenomenon, and based on this, the morphology of the composites was investigated by scanning electron microscopy (SEM). The produced images show that the MWCNTs were embedded into the silica gel base material. Fourier transform infrared (FTIR) transmittance spectroscopy showed that MWCNTs were not functionalized within the matrix of silica gel and MWCNT composites. However, after annealing the composites at 400 °C for 4 h in air, evidence of activation was observed in the FTIR spectrum. The effects of the embedding of MWCNTs on porosity, specific surface area, and pore size distribution were studied using Raman spectroscopy. The Raman spectra of the prepared composites were mainly dominated by characteristic sharp scattering peaks of the silica gel at 480, 780, and 990 cm−1 and a broad band centered at 2100 cm−1. The scattering peaks of MWCNTs were not well pronounced, as the homogeneity of the composite is always questionable. Nanosizer analysis showed that at 0.25 wt%, the distribution of MWCNTs within the silica gel was optimal. Vickers hardness measurements showed that the hardness increased with the increasing weight percent of MWCNTs within the composite matrix, while annealing enhanced the mechanical properties of the composites. Further studies are required to investigate the pore structure of silica gel within the matrix of MWCNTs to be deployed for efficient cooling and water purification applications.

Study of the interaction of the bioactive compound saponin from Glycyrrhiza glabra with a carbon nanotube matrix

Saponins are bioactive compounds belonging to the secondary metabolism of plants widely used for their beneficial actions to human health. In this work the association of the saponin from Glycyrrhiza glabra with a matrix of multi-walled carbon nanotubes was promoted to obtain a composite material with improved functional characteristics. For this investigation, chemically modified electrodes (CME) based on carbon paste were developed. Firstly, a carbon paste electrode (CPE) modified with the addition of saponin (SAP) was developed. For the electrochemical optimization of this system, CPE/SAP, studies were carried out using cyclic voltammetry. The determination of parameters such as formal potential (Eo) and potential separation (?E) indicated that the saponin used as a carbon paste modifying agent generated a matrix that favors the transfer of electrons even at low applied potentials. The second step was performed by preparing the modified carbon paste electrode with the carbon nanotube matrix (CPE/CNT). This material, surprisingly, showed a redox pair probably due to the presence of iron atoms from the preparation method, something very beneficial for the purposes of this work. Next the saponin was associated to the carbon nanotube matrix in order to investigate the behavior of the hybrid material formed (CPE/SAP-CNT), which evidenced a significant improvement in the electron transfer process when the saponin interacts with the carbon nanotube matrix, increasing the anodic peak current by more than 3.6 times in relation to the CPE/SAP and 2.1 times when compared to the CPE/CNT. Another important issue concerns the stability of the systems, with the saponin associated with the carbon nanotube matrix presenting significantly improved stability, being able to be used for more than 8 hours or 200 voltammetric cycles with loss of signal of the order of only 2%, while the CPE/SAP showed a 60% loss of signal under the same conditions of use.

A Carbon Nanotube Packed Bed Electrode for Small Molecule Electrosorption: An Electrochemical and Chromatographic Approach for Process Description

Triggering the interaction of nanomaterials with molecules by means of electrical potentials in aqueous media remains challenging, especially if 3D through-flow systems are used as electrodes, as in potential-controlled liquid chromatography (PCC). In this paper, multi-walled carbon nanotubes (MWCNTs) function as a particulate packed bed electrode in order to study the system’s response to various applied potentials and electrolyte compositions. The process principle was analyzed using chronoamperometry and cyclic voltammetry. Applying an electrical potential to the hydrophilic MWCNTs induces the presence of both capacitive and faradaic currents. This leads, over time, to a degradation of the electrode due to structural changes of the MWCNT matrix and an increase in redox reactions on the surface. The role of the electrochemical double layer (EDL) is highlighted as a main player in the process, directly influencing the adsorption capability of the electrode. The EDL rearrangement time and coverage radius depend on the composition of the mobile phase and on the potential applied. The capacity of the electrode for the target (maleic acid) increases at high positive potentials (+800 mV vs. Ag/AgCl), while the presence of electrolytes leads to a capacity decrease. Our research enhances the understanding of capacitive through-flow cells.

Microwave absorption of Mn0.5Zn0.5Fe2O4 nanoparticles integrated in multi-walled carbon nanotubes

Nanoparticles of Mn0.5Zn0.5Fe2O4 are prepared by the simple co-precipitation method. To get smaller nanoparticles having different sizes, as dried powdered sample is annealed for 5 h at 200 and 400 °C. The two annealed samples with low average sizes are encapsulated in multi-walled carbon nanotubes (MWCNTs). Desired crystallographic phase formation is confirmed by recording and analysing X-ray diffraction (XRD) patterns. Other structural and microstructure information is derived using the Rietveld analysis of the observed XRD patterns. The average crystallite sizes of all samples lie in the range of 6–10 nm. Hexagonal phase of MWCNTs is found in both the encapsulated samples. Crystallographic phase formation and integration of the nanoparticles in MWCNTs are further confirmed by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. Elemental analysis confirms the desired atomic percentages of Mn, Zn and Fe in the samples. Microwave (MW) absorption capability of the encapsulated nanoparticles is ensured by recording the reflection loss (RL) profile in the X (8–12 GHz) and Ku (12–18 GHz) bands of frequency. A maximum RL of ~ − 20.3 dB is achieved at a matching frequency of 15.45 GHz for ~ 10 nm nanoparticles in the MWCNT matrix with a layer thickness of 1 mm. This high value of RL with bandwidth corresponding to RL less than − 10 dB of 4.32 GHz suggests that Mn0.5Zn0.5Fe2O4 nanoparticles in the MWCNT matrix could be a significant MW-absorbing material.

Investigation on Properties of Polypropylene/Multi-walled Carbon Nanotubes Nanocomposites Prepared by a Novel Eccentric Rotor Extruder Based on Elongational Rheology

ABSTRACTThe properties of polymer matrix composites are related not only to the chemical composition of the materials but also to the processing equipment used for their preparation which has a direct influence on the microstructure of the composites. In this paper polypropylene (PP)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by melt blending through a self-developed, eccentric rotor extruder (ERE). The structure and elongational deformation mechanism of an ERE were described in detail. The morphological, rheological, thermal and mechanical properties of the resulting PP/MWCNTs nanocomposites were investigated. Scanning electron microscopy (SEM) and rheological analysis showed that the MWCNTs were well dispersed in the PP matrix. The thermal stability was investigated by thermogravimetric analysis (TGA) and indicated that the addition of MWCNTs could effectively improve the thermal stability of pure PP. The percentage of crystallinity and tensile strength of the composites were improved as a result of the heterogeneous nucleation effect of the MWCNTs in the PP matrix. The research results revealed that the enhancement of the properties of PP/MWCNTs composites could be attributed to a better dispersion of the MWCNTs in the matrix as compared to samples prepared by conventional extrusion.

Studies of magnetic, Mössbauer spectroscopy, microwave absorption and hyperthermia behavior of Ni-Zn-Co-ferrite nanoparticles encapsulated in multi-walled carbon nanotubes

To enhance the magnetization as well as to optimize the anisotropy of a mixed spinel nanocrystalline system, Ni2+, Zn2+ and Co2+ are chosen proportionally (0.3, 0.4 and 0.3) in Ni-Zn-Co-ferrite (NZCF). The nanoparticles of such Ni0.3Zn0.4Co0.3Fe2O4 (N3Z4C3) are prepared by co-precipitation method. Prepared nanoparticles are incorporated in the matrix of multi-walled carbon nanotubes (MWCNT) to enhance the microwave absorption. X-ray diffraction (XRD) patterns and their Rietveld analyses confirm the desired phases of N3Z4C3 and N3Z4C3-MWCNT. Distributions of cations in A- and B-sites are determined using Rietveld method. Morphological analyses are carried out by analyzing the observed electron-graphs recorded in high resolution transmission electron microscope (HRTEM). Magnetic and hyperfine behaviors are studied and interestingly, high magnetization (∼84 emu/g) is achieved at room temperature (RT). Microwave absorption capability is investigated by recording reflection losses (RL) in the range of 8–18 GHz. A maximum RL of ∼−22 dB is obtained at 15.24 GHz for 1 mm thick layer of N3Z4C3-MWCNT nanocomposite. Besides, microwave absorption study of Ni0.4Zn0.4Co0.2Fe2O4 (N4Z4C2) encapsulated in MWCNT is included for comparison. AC induction heating capability of NZCF nanoparticles for hyperthermia applications in cancer treatment is carried out and the same for Ni0.3Zn0.4Co0.2Cu0.1Fe2O4 (N3Z4C2C1) is included to make a comparative study. Among all the considered nanoparticles, N4Z4C2 nanoparticles with crystallite size (dcryst) of ∼34.7 nm exhibits maximum specific absorption rate (SAR) of 200 W/gFerrite. Our study suggests that NZCF nanoparticles are important for their applicability as good microwave absorber as well as efficient AC induction heat mediator.

Dawson-type polyoxometalate nanoclusters confined in a carbon nanotube matrix as efficient redox mediators for enzymatic glucose biofuel cell anodes and glucose biosensors

Two new inorganic-organic hybrid materials based on heteropolyoxometalates (POMs): (C4H10N)6[P2Mo18O62]·4H2O (P2Mo18) and (C6H8NO)4[H2P2W18O62]·6H2O (P2W18) are reported as mediators for electron transfer between FAD-dependent glucose dehydrogenase (FAD-GDH) and a multiwalled carbon nanotube (MWCNT) matrix for glucose biofuel cell and biosensor applications. These polyoxometalates were chosen due to their promising redox behavior in a potential range for mediated electron transfer with the glucose oxidizing enzyme, FAD-GDH. P2Mo18 and P2W18 were immobilized on 1-pyrenemethylamine (PMA) functionalized MWCNT deposits. After immobilization of FAD-GDH, the P2W18-modified MWCNT electrode demonstrated mediated electron transfer and provided a catalytic current density of 0.34 mA cm−2 at 0.2 V vs SCE with an open circuit potential (OCP) of −0.08 V vs SCE. A 10-fold increase in catalytic current to 4.7 mA cm−2 at 0.2 V vs SCE and a slightly lower OCP of −0.10 V vs SCE was observed for an equivalent electrode modified with P2Mo18.The apparent superiority of P2Mo18 is related, at least in part, to its improved incorporation in the MWCNT matrix compared to P2W18. Both POM-modified bioanodes showed exceptional stabilities with 45% of their initial performances remaining after 15 days. The mediated electron transfer capacities of the POMs were also evaluated in a glucose sensor setup and showed very satisfying performances for glucose detection, including a sensitivity of 0.198 mA mol L−1 cm−2, a satisfying linear range between 1 mmol L−1 and 20 mmol L−1, and good reproducibility for the P2Mo18 electrode.

Microwave Absorption and the Magnetic Hyperthermia Applications of Li0.3Zn0.3Co0.1Fe2.3O4 Nanoparticles in Multiwalled Carbon Nanotube Matrix.

Nanoparticles of Li0.3Zn0.3Co0.1Fe2.3O4 (LZC) were prepared by the sol-gel method and dried in a furnace at ∼200 °C. The dried sample was annealed at 500, 600, 700, and 800 °C for 5 h each. Rietveld analysis of X-ray diffraction patterns confirms the cubic Fd3̅m phase formation with lattice parameters ranged from 8.376 up to 8.390 Å and allows the crystallite sizes (dcryst) to be estimated. To enhance microwave (MW) absorption as well as the effectiveness for hyperthermia treatment, nanoparticles are taken in the matrix of multiwalled carbon nanotubes (MWCNTs) and the morphology of the so-prepared samples (LZC@MWCNT) was studied by scanning electron microscopy and transmission electron microscopy analyses. Both static and dynamic magnetic properties were investigated on the samples of LZC nanoparticles and compared to those of the samples of LZC@MWCNT. The samples annealed at 500, 600, and 800 °C are excellent candidates in cancer treatment as ac magnetic heating analysis shows that the hyperthermia temperature (42 °C) was successfully achieved for an applied ac magnetic field of 420 Oe and 300 kHz frequency. MW absorption study also reveals that the samples of LZC@MWCNT could be used as a potential MW absorbing material for which a maximum reflection loss (RL) of ∼-21 dB was achieved at a frequency of 15.27 GHz for only 1 mm layer thickness.

Highly sensitive and selective sensor for sunset yellow based on molecularly imprinted polydopamine-coated multi-walled carbon nanotubes

Polydopamine (PDA) can be formed by monomeric self-polymerization in water. This convenient behavior was exploited to prepare a molecularly imprinted polymer (MIP) layer on the surface of multi-walled carbon nanotubes (MWCNTs) with sunset yellow (SY) as a template molecule. The prepared nanocomposites were characterized, and their electrochemical behavior towards SY was investigated. Under the optimized conditions, a glassy carbon electrode modified with the imprinted nanocomposite showed a highly selective and ultrasensitive electrochemical response to SY compared with the performance of control electrodes and previously reported electrochemical sensors for SY. The improved behavior of the developed sensor can be attributed to its superficial highly matched imprinted cavities on the excellent electrocatalytic matrix of MWCNTs and the electronic barrier of the non-imprinted PDA to outside molecules. The fabricated sensor expressed a linear relationship to SY concentrations from 2.2nM to 4.64μM with a detection limit of 1.4nM (S/N = 3). The sensor also exhibited excellent selectivity for SY over its structural analogs, good stability, and adequate reproducibility. The prepared sensor was successfully used to detect SY in real spiked samples. This methodology has potential application value and may be readily adapted to design other PDA-based MIP sensors.

Nanocrystalline LiCo0.8Fe0.2PO4 / Multi-Walled Carbon Nanotubes Positive Electrode for 5-Volts Class Lithium Ion Batteries

1. Introduction Lithium cobalt phosphate (LiCoPO4) with olivine structure has attracted much attention as a new positive electrode material for lithium ion batteries because of its high potential (4.8V vs. Li/Li+), theoretical capacity (167 mAh g-1) and thermal stability due to the P-O covalent bonding. However, the practical use of LiCoPO4 has been limited by the capacity fading during cycling due to the electrolyte oxidation and irreversible structure changes such as amorphization and anti-site defects of the material during charge and discharge1). Besides, it suffers from its poor rate performance related to the inherently low electron conductivity (<10-9 S cm-1)2) and Li+ diffusivity (<10-13 cm2 s-1)2) due to its b-axis oriented diffusion path. To overcome these limitations, we have synthesized Fe-substituted LiCoPO4 (LiCo0.8Fe0.2PO4) nanoparticles which are highly dispersed within a multi-walled carbon nanotube (MWCNT) matrix via an original in-situ material synthesis method called ultracentrifugation (UC) treatment3,4). Here, we also report about the influence of Fe substitution on cycle and rate performances of LiCo0.8Fe0.2PO4. 2. Experimental UC treatment was carried out on the prepared mixture of Co(CH3COO)2・4H2O, Fe(CH3COO)2, CH3COOLi, citric acid, MWCNT and H3PO4 aqueous solution. Obtained composites were electrochemically characterized using a 2032 coin half-cell with Li metal in 1M LiPF6 / EC:PC:DMC (1:1:3, volume ratio). Physicochemical characterizations of the LiCo0.8Fe0.2PO4/ MWCNT composite were conducted by HRTEM, XRD, XPS, XAFS measurements and Mössbauer spectroscopy. 3. Results and Discussion The XRD pattern of LiCo0.8Fe0.2PO4 / MWCNT composite indicates an olivine structure, without impurity phases. The combination of XRD, XPS, XAFS and Mössbauer analysis suggests that substituted Fe3+ into LiCoPO4 crystals was not placed in the Co2+ site, but in the Li+ site. The result of HRTEM observation indicates that LiCo0.8Fe0.2PO4 nanocrystals (ca. 100 nm) were highly dispersed within a MWCNT matrix. In addition, HRTEM images of LiCo0.8Fe0.2PO4 / MWCNT composite showed that a substitution of Fe3+ into LiCoPO4 crystals prevents degradations such as amorphization of LiCoPO4and electrolyte decomposition during charge and discharge processes. Then, LiCo0.8Fe0.2PO4 / MWCNT composite showed a higher discharge capacity of 130 mAh g-1 than LiCoPO4 / MWCNT composite and enabled a 100C (36 seconds) rate discharge with 45 mAh g-1. Furthermore, the obtained composite showed stable cycle performance with 81 % of capacity retention after 100 cycles at 0.2C. These enhancements were achieved by the combination of an entanglement between nanocrystalline LiCo0.8Fe0.2PO4 and MWCNT matrix and Fe3+ substitution in the Li+ site of LiCoPO4. The Fe3+substitution gives a “pillar effect” which effectively prevents an irreversible crystal structure change and electrolyte decomposition during charge and discharge processes, resulting in the stable cycle performance. References 1) A. Boulineau et al., Chem. Mater., 27, 802 (2015). 2) S. Brutti et al., ACS Symposium Series, (2013). 3) K. Naoi et al., Acc. Chem. Res., 46, 1075 (2013). 4) K. Naoi et al., Energy Environ. Sci., 5, 9363 (2012).

Magnetic Multi-Walled Carbon Nanotubes Matrix Solid-Phase Dispersion with Dispersive Liquid–Liquid Microextraction for the Determination of Ultra Trace Bisphenol A in Water Samples

Magnetic nanoparticle-assisted solid-phase dispersion (MMSPD) combined with dispersive liquid–liquid microextraction (DLLME) prior to high performance liquid chromatography with fluorescence detector (HPLC–FLU) is presented for determination of ultra trace Bisphenol A (BPA) in water. Magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized for the adsorption of BPA in water. Ultra trace BPA in water was transferred into the elute solvent by the MMSPD and further concentrated into trace volume extraction solvent by the DLLME. The limit of detection and limit of quantitation were 0.003 and 0.01 µg L−1, respectively. Good linearity of BPA was found, ranging from 0.01 to 10 µg L−1, with good squared regression coefficient (R 2) of 0.9999. Additionally, relative recoveries were 83.1 and 95.9% for two environmental water samples spiked with 0.20 µg L−1 BPA, respectively. All results showed that the MMWCNTs nanoparticle-assisted MMSPD–DLLME–HPLC–FLU method was simple and reliable for the determination of ultra trace BPA in environmental water.

Novel biomimetic composite material for potentiometric screening of acetylcholine, a neurotransmitter in Alzheimer's disease

This work describes a novel approach to produce an antibody-like biomimetic material. It includes preparing composite imprinted material never presented before, with highly conductive support nanostructures and assembling a high conductivity polymeric layer at low temperature. Overall, such highly conductive material may enhance the final features of electrically-based devices. Acetylcholine (ACh) was selected as target analyte, a neurotransmitter of importance in Alzheimer's disease. Potentiometric transduction was preferred, allowing quick responses and future adaptation to point-of-care requirements.The biomimetic material was obtained by bulk polymerization, where ACh was placed in a composite matrix of multiwalled carbon nanotubes (MWCNTs) and aniline (ANI). Subsequent polymerization, initiated by radical species, yielded a polymeric structure of polyaniline (PANI) acting as physical support of the composite. A non-imprinted material (NIM) having only PANI/MWCNT (without ACh) has been prepared for comparison of the biomimetic-imprinted material (BIM). RAMAN and Fourier Transform Infrared spectroscopy (FTIR), Transmission Electron microscopy (TEM), and Scanning Electron microscope (SEM) analysis characterized the structures of the materials.The ability of this biomaterial to rebind ACh was confirmed by including it as electroactive compound in a PVC/plasticizer mixture. The membranes with imprinted material and anionic additive presented the best analytical characteristics, with a sensitivity of 83.86mV decade−1 and limit of detection (LOD) of 3.45×10−5mol/L in HEPES buffer pH4.0.Good selectivity was observed against creatinine, creatine, glucose, cysteine and urea. The electrodes were also applied on synthetic serum samples and seemed a reliable tool for screening ACh in synthetic serum samples. The overall performance showed fast response, reusability, simplicity and low price.

Enhanced microwave absorption and magnetic phase transitions of nanoparticles of multiferroic LaFeO3 incorporated in multiwalled carbon nanotubes (MWCNTs)

Multiferroic nanoparticles of LaFeO3 (LFO) are prepared by a combination of sono-chemical and sol-gel auto combustion method. The as prepared sample is calcined at 500°C for 5h to get the desired crystallographic phase. To enhance the microwave absorption, nanoparticles of LFO are incorporated in the matrix of multi-walled carbon nanotubes (MWCNTs). Crystallographic phases of LFO and LFO-MWCNTs are confirmed by analyzing the X-ray diffractograms (XRD) using Rietveld method. The average size of nanoparticles, crystallographic phase, morphology, and incorporation of LFO nanoparticles in MWCNTs are also obtained by high-resolution transmission electron microscope (HRTEM). Micrographs, nanocrystalline fringe pattern and selected area electron diffraction pattern recorded during HRTEM observations confirmed the formation of the desired nanocomposite phase of LFO-MWCNTs. FTIR and Raman spectroscopy of LFO and LFO-MWCNTs are also recorded at room temperature (RT) which confirm the presence of the individual component in the nanocomposite sample. Hysteresis loops at different temperatures from 300K down to 5K, zero field cooled (ZFC) and field cooled (FC) magnetizations (M) as a function of temperature (T) of LFO-MWCNTs are recorded in SQUID magnetometer. Analysis of the observed magnetic data of LFO-MWCNTs suggests the presence of superparamagnetism above ∼298K and a spin-glass like behavior is found below ∼50K. The electromagnetic wave absorbing properties in X and Ku bands of microwave regions (8–12GHz and 12–18GHz) measured by a vector network analyzer (VNA) confirm the significant enhancement of microwave absorption (RL∼−34.88dB at 10.53GHz for 1mm thickness) of LFO in LFO-MWCNTs, which is quite interesting for such multiferroic system.

Influences of matrix viscosity on alignment of multi-walled carbon nanotubes in one-dimensional confined space

The effects of matrix viscosity on alignment of multi-walled carbon nanotubes (MWCNTs) and physical properties of high density polyethylene (HDPE)/MWCNTs composite nanofibers via nanolayer coextrusion are studied. The alignment states are altered depending upon the matrix viscosity of the composite nanofibers. The morphology and nano-sized diameter of the nanofibers are observed on scanning electron microscope. To characterize the prioritized alignment and dispersion of MWCNTs in the matrix, transmission electron microscopy, polarized Raman spectra, and high resolution optical microscopy are used. It is found that the alignment of MWCNTs in higher viscosity matrix of the nanofibers is better than that in lower viscosity. The aligned MWCNTs composite nanofibers have smaller slope variations of rheological curves with increasing content of MWCNTs. In addition, the higher aligned HDPE/MWCNTs composite nanofibers exhibit higher decomposition temperature and enhanced mechanical properties. However, the poorly aligned nanofibers have higher electrical and thermal conductivities due to the easily formed three-dimensional network.

A novel design of engineered multi-walled carbon nanotubes material and its improved performance in simultaneous detection of Cd(II) and Pb(II) by square wave anodic stripping voltammetry

An engineered multi-walled carbon nanotubes (MWCNTs) material was successfully synthesized via doping nitrogen atoms and grafting thiol groups into activated MWCNTs matrix to improve the electrochemical sensing platform for detecting lead ions and cadmium ions by square wave anodic stripping voltammetry (SWASV). The structure and morphology of the engineered MWCNTs were characterized by Fourier transformed infrared, Raman spectroscopy and Scanning electron microscopy. The results indicated that the engineered MWCNTs exhibited improved dispersibility and selectivity for metal ions detection due to the introduction of nitrogen atoms and thiol groups. In addition, the developed electrode material displayed good repeatability, stability and reproducibility. This study shows the engineered MWCNTs are very promising for potential application in heavy metal ions detection.

Cyclic voltammetry deposition of copper nanostructure on MWCNTs modified pencil graphite electrode: An ultra-sensitive hydrazine sensor

In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS–MWCNTs composite sensor (CuNS–MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50–800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination.

XRD, HRTEM, magnetic, dielectric and enhanced microwave reflection loss of GaFeO3 nanoparticles encapsulated in multi-walled carbon nanotubes

Nanoparticles of GaFeO3 are prepared by a sol–gel method where ultrasonication is used to reduce the distribution of sizes and agglomeration among nanoparticles. To obtain the well crystallographic phase, the as prepared sample is annealed at 800°C for 6h. To explore the applications in the field of microwave devices, multiferroic nanoparticles of GaFeO3 are incorporated in multi-walled carbon nanotubes (MW-CNTs). The formations of the desired crystallographic phases of both the bare and encapsulated samples are confirmed by X-ray diffractograms. Results of high resolution transmission electron microscopy of the coated sample confirm the encapsulation of nanoparticles of GaFeO3 in the matrix of MW-CNTs. Raman spectra are recorded at room temperature and the observed spectra are analyzed to extract different informations like the presence of any impurity, position of different Raman active modes, shift of Raman peak etc. of the sample. The reflection loss of the bare and coated samples in the X and Ku bands of microwave regions (8–12GHz and 12–18GHz) are measured and interestingly, the microwave reflection loss is significantly enhanced due to encapsulation of GaFeO3 by MW-CNTs. This enhancement will improve the quality of applications of GaFeO3 in microwave devices.