Enhanced microwave absorption properties in polyaniline and nano-ferrite composite in X-band

Highly conducting polyaniline (PANI) nanocomposite with Mn_0.2Ni_0.4Zn_0.4Fe₂O₄ ferrite was prepared by mechanical blending. The present work reports the EMI shielding characteristics of the ferrite-Pani nanocomposite with different thickness. The saturation magnetization (Ms) for pure MnNiZn ferrite (52 emu/g) and composite (41 emu/g) was measured by VSM at room temperature. The crystalline size of MnNiZn ferrite was found in the range of 25–30 nm as analyzed by TEM and XRD. The complex permittivity, permeability and shielding effectiveness of the composite for different thicknesses were measured in the 8–12 GHz (X-band) frequency range. The composite of 2.5 mm thickness has shown high shielding effectiveness (49.2 dB) due to absorption (SE_A). The high value of SE_A suggests that this composite can be used as a promising absorbing material for X-band frequency range.     

Self-assembled polyaniline nanotubes and nanoribbons/titanium dioxide nanocomposites

Self-assembled polyaniline (PANI) nanotubes, accompanied with nanoribbons, were synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate in an aqueous medium, in the presence of colloidal titanium dioxide (TiO₂) nanoparticles of 4.5 nm size, without added acid. The morphology, structure, and physicochemical properties of the PANI/TiO₂ nanocomposites, prepared at various initial aniline/TiO₂ mole ratios, were studied by scanning (SEM) and transmission (TEM) electron microscopies, FTIR, Raman and inductively coupled plasma optical emission (ICP-OES) spectroscopies, elemental analysis, X-ray powder diffraction (XRPD), conductivity measurements, and thermogravimetric analysis (TGA). The electrical conductivity of PANI/TiO₂ nanocomposites increases in the range 3.8 × 10^?4 to 1.1 × 10^?3 S cm^?1 by increasing aniline/TiO₂ mole ratio from 1 to 10. The morphology of PANI/TiO₂ nanocomposites significantly depends on the initial aniline/TiO₂ mole ratio. In the morphology of the nanocomposite synthesized using aniline/TiO₂ mole ratio 10, nanotubes accompanied with nanosheets prevail. The nanocomposite synthesized at aniline/TiO₂ mole ratio 5 consists of the network of nanotubes (an outer diameter 30–40 nm, an inner diameter 4–7 nm) and nanorods (diameter 50–90 nm), accompanied with nanoribbons (a thickness, width, and length in the range of 50–70 nm, 160–350 nm, and ～1–3 μm, respectively). The PANI/TiO₂ nanocomposite synthesized at aniline/TiO₂ mole ratio 2 contains polyhedral submicrometre particles accompanied with nanotubes, while the nanocomposite prepared at aniline/TiO₂ mole ratio 1 consists of agglomerated nanofibers, submicrometre and nanoparticles. The presence of emeraldine salt form of PANI, linear and branched PANI chains, and phenazine units in PANI/TiO₂ nanocomposites was proved by FTIR and Raman spectroscopies. The improved thermal stability of PANI matrix in all PANI/TiO₂ nanocomposites was observed.     

Electromagnetic properties of polyaniline/maghemite nanocomposites: I. The effect of re-doping time on the electromagnetic properties

This article is to carry out researches on the synthesis of the polyaniline/γ-Fe₂O₃ nanocomposites by a reverse micelle process and the effects of re-doping time on the electromagnetic properties of polyaniline/γ-Fe₂O₃ nanocomposites, investigated by Fourier transform spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray diffraction diffractometer (WAXD), impedance analyzer, micro-ohmeter, and superconductor quantum interference device (SQUID). The nanostructure of the polyaniline/γ-Fe₂O₃ nanocomposites was characterized by micrographs of transmission electron microscopy (TEM). It was found that the dispersed γ-Fe₂O₃ phase is roughly distributed in the polyaniline matrix. Results showed that, in the presence of γ-Fe₂O₃, the growth rate of quinoid ring is markedly retarded. The crystallinity and doping level of polyaniline in the nanocomposites increase with re-doping time, the conductivity and dielectric properties (i.e., permittivity and loss factor) of nanocomposites are hence increased and the ionic polarization relaxation time become shorter from 1.71 × 10⁻⁹ to 7.48 × 10⁻¹⁰ s. The particle size and γ-Fe₂O₃ content in the nanocomposites decrease with re-doping time due to the reduction effect resulting from the doped protonic acid of polyaniline. For the room-temperature SQUID analysis, the superparamagnetic behavior is observed, suggesting the presence of the thermal activation energy contribution to the magnetic moment. The saturated magnetization was decreased with decreasing γ-Fe₂O₃ contents.     

Epitaxial growth of γ-Fe2O3 thin films on MgO substrates by pulsed laser deposition and their properties

Epitaxial γ-Fe₂O₃ films were fabricated by pulsed laser deposition at 350 °C in an oxygen-rich atmosphere onto a (0 0 1) or (1 1 0) MgO substrate utilizing the substrate template effect, while the corundum structure α-Fe₂O₃ was obtained when the same experiment was conducted using sapphire or quartz substrate. X-ray photoelectron spectroscopy analysis and low-temperature SQUID measurements confirmed the formation of γ-Fe₂O₃. After annealing at 500 °C for 1 h under oxygen atmosphere, the γ-Fe₂O₃ phase was still maintained. The saturation magnetization (M_s) of the γ-Fe₂O₃ film was around 400 emu cm^?3 for films 10–50 nm thick, which is in agreement with the bulk value. The ultrathin films showed an enhanced Ms value (489 emu cm^?3). In particular, the M_s of the 5 nm thin film did not diminish even if it was subjected to high-temperature annealing due to the stabilizing effect of the epitaxial growth. The thin films obtained had a flat surface, which is desired for spin filter and other applications.     

Electrical and magnetic properties of the Fe3O4–polyaniline nanocomposite pellets containing DBSA-doped polyaniline and HCl-doped polyaniline with Fe3O4 nanoparticles

DBSA-doped polyaniline (DBSA–PANI) powder and HCl-doped polyaniline with Fe₃O₄ nanoparticles (HCl–PANI–Fe₃O₄) powder were mechanically mixed to obtain the Fe₃O₄–polyaniline nanocomposites. Powders of the nanocomposites were pressed to the pellets. Micromorphology, electrical and magnetic properties of the nanocomposite pellets were studied by using scanning electron microscopy and by measuring the conductivity in 100–300 K and the magnetization curve at room temperature. The DBSA–PANI pellets consist of long fibrils while the HCl–PANI–Fe₃O₄ pellets consist of granular particles. Thus the Fe₃O₄–polyaniline nanocomposites pellets consist of long fibrils and granular particles. The conductivity of the nanocomposite pellets linearly decreases from 0.19 ± 0.06 to 0.05 ± 0.01 S/cm when the HCl–PANI–Fe₃O₄ content increases from 0 to 100 wt.%. The variation of conductivity with temperature reveals that the charge transport mechanism can be considered to be one-dimensional variable-range-hopping (1D-VRH). All the Fe₃O₄–polyaniline nanocomposites show the magnetization curves. The saturation magnetization monotonously increases with increasing HCl–PANI–Fe₃O₄ content while the coercivity is estimated to be about zero independent of the HCl–PANI–Fe₃O₄ content. The saturation magnetization of the HCl–PANI–Fe₃O₄ is 11 emu/g.     

Synthesis,characterization and magnetic properties of polyaniline-magnetite nanocomposites

In this work we report a new and straightforward method to prepare the polyaniline-magnetite nanocomposite PANI-Fe₃O₄. The method utilizes Fe₃O₄ nanoparticles as the oxidizing agent assisted by UV light to synthesize PANI-Fe₃O₄ magnetic nanocomposite. FTIR and XRD analyses confirm that polyaniline has been obtained in the emeraldine salt form and that the mean diameter of the Fe₃O₄ nanoparticles before synthesis was of the order of 25 nm; for the PANI-Fe₃O₄ nanocomposite in HCl after 4 h of reaction, the mean diameters were of the order of 11 nm. Also, feroxyhite was detected as a secondary phase for the nanocomposite. The dc conductivity results for the pure magnetite were about 2.4 × 10^?6 S cm^?1, while the nanocomposites were of the order of 10^?5 S cm^?1, confirming the increase in conductivity with the increasing amount of PANI. The magnetic measurements showed ferromagnetic behavior for the nanoparticles, with high-saturated magnetization (M_S = 74.30 emu g^?1) and a coercive force of 93.40 Oe. In addition, it was observed that the saturated magnetization for the nanocomposite strongly depends on the reaction time under UV irradiation.     

Effects of [SDS]/[H2O] molar ratio on the electromagnetic properties of polyaniline/maghemite nanocomposites

Polyaniline (PANI)/maghemite (γ-Fe₂O₃) nanocomposites were prepared by using the reverse micelle polymerization, where aniline, ferrous and ferric salts and sodium dodecyl sulfate (SDS) act as monomer, precursor of γ-Fe₂O₃ and surfactant, respectively. The effect of the molar ratio of [SDS]/[H₂O] on the electromagnetic properties of PANI/γ-Fe₂O₃ nanocomposites was investigated by Fourier transform spectroscopy (FTIR), UV–visible spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), wide angle X-ray diffraction diffractometer (WAXD), impedance analysis analyzer, micro-ohmetry and superconductor quantum interference device (SQUID). The nanostructure of the PANI/γ-Fe₂O₃ nanocomposites was characterized by micrographs of transmission electron microscopy (TEM). Results showed that both the γ-Fe₂O₃ content and particle size in the nanocomposites decreased with molar ratio of [SDS]/[H₂O]. The γ-Fe₂O₃ phase is non-uniformly distributed in the PANI matrix, and exhibits a broader size distribution at higher [SDS]/[H₂O] molar ratio due to the reduced strength of PANI–γ-Fe₂O₃ interactions. In the presence of γ-Fe₂O₃, the growth rate of quinoid ring is markedly retarded. The retard effect is significantly reduced by increasing the [SDS]/[H₂O] molar ratio, leading to the improvement of crystallinity, conductivity and dielectric properties (i.e., permittivity and loss factor) of nanocomposites. Simultaneously, the ionic polarization relaxation time is shortened from 2.61 × 10^?9 to 1.04 × 10^?9 s. For SQUID analysis at room temperature, the typical superparamagnetic behavior is found with the saturation magnetization decreased with the [SDS]/[H₂O] molar ratio, resulting from the reduced γ-Fe₂O₃ content, smaller γ-Fe₂O₃ particle size, and the wider particle size distribution.     

Conducting and magnetic behaviors of polyaniline coated multi-walled carbon nanotube composites containing monodispersed magnetite nanoparticles

High conductivity and supermagnetism of polyaniline (PANI)-coated multi-walled carbon nanotube (MWCNT) composites containing monodispersed 6 nm iron oxide (Fe₃O₄) nanoparticles has been successfully synthesized by in situ chemical oxidative polymerization using anionic surfactant dodecylbenzenesulfonic acid sodium salt. Hydrophilic 6 nm spherical Fe₃O₄ nanoparticles fabricated by the thermal decomposition process were chemically modified using 11-aminoundecanoic acid tetramethylammonium salt. The modified nanoparticles were further mixed with carboxylic acid containing multi-walled carbon nanotubes (c-MWCNTs) in an aqueous solution to form one-dimensional Fe₃O₄ coated c-MWCNT template and PANI/c-MWCNT nanocomposite were then synthesized via in situ chemical oxidative polymerization in HCl solution. Structural and morphological analysis using FESEM, HRTEM and XRD showed that the fabricated Fe₃O₄ coated c-MWCNT/PANI nanocomposites are one-dimensional core (Fe₃O₄ coated c-MWCNT)–shell (PANI) structures. The electrical conductivity of 1 wt% Fe₃O₄ coated c-MWCNT/PANI nanocomposites at room temperature is 37.7 S/cm, which is decreased to 28.6 S/cm with the loading of 5 wt% Fe₃O₄ nanoparticles. The magnetic properties of Fe₃O₄ coated c-MWCNT/PANI nanocomposites exhibit supermagnetism with saturation magnetization in the range of 0.04–0.15 emu/g, which increases as the amount of Fe₃O₄ nanoparticles increases.     

Optical and electrical characterizations of ZnS nanoparticles embedded in conducting polymer

ZnS nanoparticles of average size (5 nm) have been prepared using thioglycerol. Inorganic–organic hybrid nanocomposites have been synthesized by dispersing nanosized ZnS in the conducting polyaniline matrix. The samples have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM) and UV–vis spectrophotometer. The wavelength of optical absorption peak of ZnS nanoparticle increases from 270 to 330 nm with the decrease of polyaniline concentration. Studies on direct current (DC) electrical conductivity as a function of temperature suggest that three-dimensional Mott’s hopping process occurs in ZnS–polyaniline nanocomposites. The correlated barrier hopping is confirmed from temperature dependent alternating current (AC) conductivity. The incorporation of ZnS nanoparticles enhances the barrier height.     

Antistatic coating and electromagnetic shielding properties of a hybrid material based on polyaniline/organoclay nanocomposite and EPDM rubber

Thermal, mechanical, electrical and microwave radiation absorbing properties of conductive composites based on dodecylbenzenesulfonate doped polyaniline/organoclay nanocomposites and propylene–ethylidene–norbornene rubber have been investigated with special interest on the effect of the nanocomposite concentration. Composites were prepared by melt blending using an internal mixer. Morphology studies by scanning electron microscopy of cryofractured surfaces indicated that the conducting nanocomposites produced heterogeneously distributed aggregates in the continuous elastomeric matrix. The composites exhibit high conductivities, up to 10⁻³ S cm⁻¹ for 40 wt.% of conducting nanocomposite, and good mechanical properties. They also present high microwave attenuation values, in the frequency range of 8–12 GHz. This property depends on the concentration of the conductive nanocomposite and on the film thickness. The composites can be used for antistatic coatings or for electromagnetic shielding.     

Study on synthesis and anticorrosion properties of polymer nanocomposites based on super paramagnetic Fe2O3·NiO nanoparticle and polyaniline

In this study, Fe₂O₃·NiO/PANi nanocomposites were prepared and their anticorrosion properties were investigated. The Fe₂O₃·NiO nanoparticles were synthesized by precipitation–oxidation methods. Fe₂O₃·NiO–PANi nanocomposites were prepared by in situ polymerization of aniline monomer in the presence of Fe₂O₃·NiO nanoparticle. The structure of the polymer nanocomposite was characterized by SEM and X-ray method. The electrical conductivity, magnetic properties and anticorrosion properties of the materials were examined by the conventional four probe method, vibrating magnetometer and by impedance measurement method. The results show that the Fe₂O₃·NiO nanoparticles have the uniform size with the size ranging from 50 to 60 nm. By the formation of polymer nanocomposite, the Fe₂O₃·NiO phase is well dispersed in the PANi polymer matrix. But the Fe₂O₃·NiO nanoparticles are not exfoliated from its agglomerate structure. The polymer nanocomposite showed both magnetic and conductive properties. With increasing Fe₂O₃·NiO content, both the saturated magnetization and the coercive force increase and reach the value of 0.31 emu/g and 162.56 Oe by the Fe₂O₃·NiO content of 5%, respectively. In contrast, the electrical conductivity of the polymer nanocomposite decreases with increasing Fe₂O₃·NiO content from 0.353 S/cm of neat PANi to 0.075 S/cm by the Fe₂O₃·NiO content of 5%. From the anticorrosion investigation, it was revealed that the protective performance of polyurethane paint containing Fe₂O₃·NiO/PANi nanocomposite was significantly improved with increasing Fe₂O₃·NiO/PANi content.     

Characterization of mechanically alloyed nanocomposites in TiO2–B2O3–Mg–C quaternary system

The influence of the simultaneous presence of magnesium and graphite on mechanosynthesis of various nanocomposite powders in TiO₂–B₂O₃–Mg–C quaternary system was investigated. A mixture of boron oxide and titanium dioxide powders along with different amounts of magnesium and graphite was milled using a high-energy planetary ball mill to provide necessary conditions for the occurrence of a mechanically induced self-sustaining reaction (MSR). In the absence of C (100 wt.% Mg), TiB₂ nanopowder was formed as a result of combustion reaction after 34 min of milling. In the presence of both Mg and C, the mechanochemical reaction was completed after different milling times depending on the weight fraction of the reducing agents in the powder mixture. In the presence of x wt.% Mg–y wt.% C (x = 85 and 90; y = 100 − x), the mechanosynthesized composites contained TiB₂ and TiC as major compounds as well as MgO and Mg₃B₂O₆ as unwanted phases. With further increasing the graphite content to 30 wt.%, no mechanical activation was observed after 90 min of milling. The nanocomposite powders showed a bimodal particle size distribution characterized by the presence of several coarse particles (≈ 250 nm) along with finer particles with a mean size of about 75 nm. Formation mechanism of nanocomposites was explained through the analysis of the relevant sub-reactions.     

Optical and electrical transport properties of polyaniline–silver nanocomposite

Polyaniline–silver nanocomposite has been synthesized successfully by the chemical oxidative polymerization of aniline with ammonium peroxydisulphate as an initiator in presence of negatively charged silver nanoparticles. Silver nanoparticles are prepared by standard citrate reduction method. TEM, SEM, XRD, FTIR, TGA, DSC, optical absorption and photoluminescence studies are done for the morphological, structural, thermal and optical characterization of the polyaniline nanocomposite. From the TEM and SEM image, it is observed that nanoparticles are well dispersed in the polyaniline matrix. XRD pattern shows that polyaniline is amorphous, but peaks present in XRD pattern in polymer nanocomposites are for silver nanoparticles. TGA and DSC results show that polyaniline silver nanocomposite is more crystalline and more thermally stable. A surface plasmon absorption band is obtained from the optical absorption at 380 nm, which indicates that silver nanoparticles are present in the polyaniline matrix. The optical band gap of nanocomposite decreases with increasing content of silver nanoparticles. An enhancement in photoluminescence has been observed in polyaniline–silver nanocomposite than that in pure polyaniline. The electrical conductivity of polyaniline–silver nanocomposite increases with increase in silver nanoparticle content than that of pure polyaniline. This is a simple way by which optical and electrical properties of polyaniline may be enhanced by doping with suitable nanoparticles.     

Fabrication,characterization and microwave properties of polyurethane nanocomposites reinforced with iron oxide and barium titanate nanoparticles

Polyurethane (PU) nanocomposites reinforced with magnetic iron oxide nanoparticles and/or dielectric barium titanate nanoparticles fabricated by the surface-initiated-polymerization approach were investigated. The polymer matrix incorporated with different nanoparticles shows different presenting status surrounding the nanoparticles, i.e., chemical bonding, physical entanglement and bulk polymer chain. The nanoparticles have a different effect on the thermal stability of the polymer nanocomposites. By embedding different functional nanoparticles, unique physical properties were observed, such as enlarged coercivity and larger dielectric constant (real permittivity). The synergistic effect of the binary nanoparticle reinforced PU nanocomposite was explored. The addition of the iron oxide nanoparticles does have some effect on the permittivity. However, little difference was observed in the magnetic properties and permeability after the introduction of the dielectric barium titanate nanoparticle into Fe₂O₃/PU nanocomposites. The permeability and permittivity of γ-Fe₂O₃ and BaTiO₃ nanoparticle reinforced PU nanocomposites were investigated with frequencies ranging from 10 MHz to 1 GHz. The predicted microwave properties from Bruggeman’s equation were consistent with the measured data, except for the real permittivity of Fe₂O₃/BaTiO₃/PU. The volume average method (VAM) usually used for fiber-reinforced composites with reinforcements in the thickness direction was applied in this nanocomposite system. The predicted real permittivity by VAM was found to be in better agreement with the measured data than that predicted by Bruggeman’s equation.     

Properties of composite films of titania nanofibers and Safranin O dye

Titania (TiO₂) nanofibers and composite thin films of titania nanofibers and Safranin O dye (SAF) were studied. TiO₂ nanofibers were prepared by electrospinning technique from titanium tetra-isopropoxide precursor solution in ethanol. Surface topology of the nanofibers was observed using scanning electron microscopy (SEM), their crystal structure was studied by X-ray diffraction (XRD) and the chemical composition by X-ray photoelectron spectroscopy (XPS). Properties of the TiO₂ nanofibers were studied in dependence on the values of relative air humidity in the range from 15% to 55%. It was necessary to maintain the relative humidity lower than 30% during electrospinning in order to obtain high quality nanofiber films. The average minimum diameter of the as-prepared TiO₂ nanofibers was found to be around 100 nm. Nanofiber diameter diminishes to about 50 nm after annealing at 420 °C for 1 h. The as-prepared titania nanofiber films were completely amorphous while anatase crystal phase was detected in the films after annealing. In order to prepare the composite films, solution of SAF dye with poly(vinylpyrrolidone) in ethanol/water was dropped off on the prepared titania nanofibers surface. Opto-electrical properties of SAF dye and the resulting nanocomposite films were studied by UV–Vis spectroscopy and current–voltage characteristics. Safranin O is characterized by two strong absorption peaks; one at 274 nm and a wide band with splitting between 420 nm and 600 nm. The optical energy band gap of titania nanofibers was estimated from the UV–Vis measurements to be 3.4 eV. The charge transport in the composite films is influenced by the space charge limited currents due to the very high resistance of the materials.     

Effect of TiO2 on thermal,structural and third-order nonlinear optical properties of Ca–La–B–O glass system

A series of calcium lanthanum metaborate glasses in the composition (wt%) of 23.88CaO–28.33La₂O₃–47.79B₂O₃ modified with TiO₂ up to 20 wt% are prepared by a melt quenching technique to study the influence of TiO₂ on their thermal, structural, linear and nonlinear optical properties. The differential thermal analysis (DTA) studies have demonstrated significant effects due to the presence of TiO₂ on the glass forming ability and crystallization situations. The glass with 15 wt% TiO₂ has achieved a eutectic composition and also exhibited a better glass forming ability among the glasses studied. The FT-IR spectra of these glasses show mainly vibration modes corresponding to stretching of BO₃ trigonal, BO₄ tetrahedral units and of B–O–B bending bonds. At higher concentrations of TiO₂, development of vibration band around 400 cm^?1 has indicated the formation of TiO₆ structural units in the glass network. The red shift of optical absorption edge (UV cutoff) shows a monotonous decrease in direct and indirect optical band gap energies (E_opt) with an increase of TiO₂ content in the glasses based on their absorption spectra. The optical transparency of these glasses is found to be varied from 64 to 87% within the wavelength range 450–1100 nm depending on the TiO₂ content. Besides these studies, linear refractive indices, the nonlinear optical properties of these glasses have also been evaluated.     

Magnetic properties of hydrophilic iron oxide/polyaniline nanocomposites synthesized by in situ chemical oxidative polymerization

This work describes the preparation and characterization of polyaniline (PANI)/hydrophilic iron oxide nanocomposites synthesized from monodispersed 13 nm iron oxide (Fe₃O₄) nanoparticles and aniline monomer in HCl solution by in situ chemical oxidative polymerization. Hydrophilic 13 nm spherical Fe₃O₄ nanoparticles fabricated using the thermal decomposition process were modified using 11-aminoundecanoic acid tetramethylammonium salt. The modified Fe₃O₄ nanoparticles that served as cores were dispersed in an aqueous solution with anionic surfactant dodecylbenzenesulfonic acid sodium salt to form spherical templates and the PANI/Fe₃O₄ nanocomposites were then synthesized via in situ chemical oxidative polymerization on the surface of spherical templates. Structural and morphological analysis using X-ray diffraction and high-resolution transmission electron microscopy showed that the fabricated PANI/Fe₃O₄ nanocomposites are core (Fe₃O₄)-shell (PANI) structures. The magnetic properties of PANI/Fe₃O₄ nanocomposites exhibit supermagnetism with saturation magnetization in the range of 0.23–0.91 emu/g, depending on the amount of 13 nm Fe₃O₄ nanoparticles.     

Effect of Fenton reagent on the synthesis of polyaniline

Polyaniline has been prepared using Fenton reagent. The in situ visible spectra during the polymerization process show that the polymerization of aniline was carried out through an intermediate at 530 nm. The absorption band of the resulting product, polyaniline, appears at 700 nm. The conductivity of polyaniline prepared using Fenton reagent can reach 1.04×10⁻² S cm⁻¹, which is strongly dependent on the concentrations of FeSO₄, H₂SO₄ and polymerization time. The cyclic voltammogram of polyaniline prepared using Fenton reagent is much different from that of polyaniline prepared normally, and has the good electrochemical reversibility and a fast charge transfer characteristic in the solution with pH 4.0. The FTIR spectrum indicates that no absorption band attributed to N–H stretching vibrations is present in polyaniline.     

Fuzzy nanofibrous network of polyaniline electrode for supercapacitor application

Fuzzy nanofibrous network of polyaniline electrode is successfully electrosynthesized for supercapacitor application. The nanofibre network of polyaniline electrode is characterized using Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM) and optical absorption studies. Network of polyaniline is highly porous with interconnected fuzzy nanofibres having diameter typically between 120 and 125 nm. The supercapacitive performance of polyaniline electrode is tested using cyclic voltammetry (C-V) technique in H₂SO₄ electrolyte within potential range of ?100 to 800 mV. The effect of scan rate on the capacitance of polyaniline electrode is studied. The highest specific capacitance of 839 F g^?1 at the voltage scan rate of 10 mV s^?1 is achieved. Additionally stability and charging–discharging of polyaniline electrode are studied.     

Development of in situ NiAl–Al2O3 nanocomposite by reactive milling and spark plasma sintering

NiAl–10 vol.% Al₂O₃ in situ nanocomposite has been synthesized by reactive milling and subsequent spark plasma sintering. The synthesized nanocomposites have ～96% of theoretical density after sintering at 1000 °C for 5 min. Microstructural analysis of consolidated samples using TEM has revealed the presence of α-Al₂O₃ particles of 10–12 nm size in NiAl matrix of submicron grain size. Consolidated NiAl–10 vol.% Al₂O₃ nanocomposite has shown very high hardness of 772 HV_0.3 and compressive strength of 2456 MPa with ～14% plastic strain. The high hardness and compressive yield strength are attributed to the presence of nanocrystalline α-Al₂O₃ particles and the appreciable plastic strain is attributed to the submicron grains of NiAl.