Highly conductive graphene oxide/polyaniline hybrid polymer nanocomposites with simultaneously improved mechanical properties

Graphene oxide (GO) was added to a polymer composites system consisting of surfactant-wrapped/doped polyaniline (PANI) and divinylbenzene (DVB). The nanocomposites were fabricated by a simple blending, ultrasonic dispersion and curing process. The new composites show higher conductivity (0.02–9.8 S/cm) than the other reported polymer system filled with PANI (10⁻⁹–10⁻¹ S/cm). With only 0.45 wt% loading of GO, at least 29% enhancement in electric conductivity and 29.8% increase in bending modulus of the composites were gained. Besides, thermal stability of the composites was also improved. UV–Vis spectroscopy, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) revealed that addition of GO improves the dispersion of PANI in the polymer composite, which is the key to realize high conductivity.     

Lightweight glass/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-polyaniline composite hollow spheres with conductive and magnetic properties

Lightweight composite hollow spheres with conductive and magnetic properties were prepared by using Hollow Glass Spheres (HGS) as substrate. The morphology, composition, conductive, and magnetic properties of the resultant products were characterized by SEM, EDX, XRD, FTIR spectra, conductivity measurement, and vibrating-sample magnetometry. Polyaniline (PANI) were in situ polymerized on HGS with increasing ratios of PANI to HGS, resulting in the enhanced conductivity of HGS/PANI composites from 1.3 × 10⁻² S/cm to 4.4 × 10⁻² S/cm. Lightweight glass/Fe₃O₄-PANI composite hollow spheres (HGS/Fe₃O₄-PANI) with conductivity of 5.4 × 10⁻³ S/cm and magnetization of 9.25 emu/g were prepared by deposition of Fe₃O₄ nanoparticles onto HGS via electrostatic adsorption first, and then polymerization of aniline onto HGS/Fe₃O₄. The glass/PANI-Fe₃O₄ composite hollow spheres (HGS/PANI-Fe₃O₄) composed of Fe₃O₄ as the outmost layer and PANI as the inner layer were prepared for comparison. The conductivity and magnetization of HGS/PANI-Fe₃O₄ were 1.1 × 10⁻⁴ S/cm and 2.61 emu/g, respectively.     

Polyaniline–sodium montmorillonite clay nanocomposites: effect of clay concentration on thermal, structural, and electrical properties

A simple and facile method was used to synthesize polyaniline (PANI) nanocomposites with sodium montmorillonite clay (Na⁺-MMT) using in situ intercalative oxidative polymerization. Aniline was admixed with Na⁺-MMT at various concentrations, keeping the aniline monomer in the reaction mixture constant. The intercalation of PANI into the clay layers was confirmed by X-ray diffraction studies in conjugation with electron microscope techniques and FTIR spectra, particularly by the narrowing of the Si–O stretching vibration band confirmed the interaction between PANI and the clay. The employed route offers the possibility to improve the thermal properties with simultaneously controlled electrical conductivity. Thermal studies show an improved thermal stability of the nanocomposites relative to the pure PANI. Depending on the loading of the clay, the room temperature conductivity values of these nanocomposites varied between 2.0 × 10⁻⁴ and 7.4 × 10⁻⁴ S cm⁻¹, with the maximum at 44 wt% PANI concentration. The decrease of electrical conductivity at high PANI concentration was ascribed to the decrease of the structural ordering of PANI in the nanocomposite.     

One-step synthesis of conductive graphene/polyaniline nanocomposites using sodium dodecylbenzenesulfonate: preparation and properties

The preparation of conducting graphene/polyaniline–sodium dodecylbenzenesulfonate (PANI–SDBS) nanocomposites using synthesised graphene as the starting material is successfully conducted in the present study. The effect of the anionic surfactant SDBS on the properties of the graphene/PANI–SDBS nanocomposites is studied. The structure and morphology of the synthesised nanocomposites are characterised by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–vis) spectrophotometry, X-ray diffraction and atomic force microscopy (AFM). The electrical conductivity properties of the resulting nanocomposites are determined using a resistance meter measurement system. The FESEM and TEM images reveal that the addition of SDBS surfactant to the PANI transforms the nanofibers of the PANI to a nanosphere morphology of PANI–SDBS. FTIR and UV–vis studies reveal that the conductive graphene/PANI–SDBS nanocomposites are successfully synthesised. AFM characterisation shows that the addition of graphene reduces the root mean square roughness of the surface of the PANI. The electrical conductivity and thermal stability of the PANI are improved after the introduction of SDBS. The nanocomposites containing a 5 wt% graphene loading exhibit the highest electrical conductivity of 2.94?×?10^?2 S/cm, which is much higher than that of PANI (9.09?×?10^?6 S/cm).     

Synthesis of polyaniline/ZrO<Subscript>2</Subscript> nanocomposites and their performance in AC conductivity and electrochemical supercapacitance

Polyaniline/zirconium oxide (PANI/ZrO₂) nanocomposites have been synthesized by incorporating ZrO₂ nanoparticles into the PANI matrix via liquid–liquid interfacial polymerization method. The composite formation and structural changes in PANI/ZrO₂ nanocomposites were investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). PXRD pattern of PANI/ZrO₂ nanocomposites exhibited sharp and well-defined peaks of monoclinic phase of ZrO₂ in PANI matrix. SEM images of the composites showed that ZrO₂ nanoparticles were dispersed in the PANI matrix. The FT-IR analysis revealed that there was strong interaction between PANI and ZrO₂. AC conductivity and dielectric properties of the nanocomposites were studied in the frequency range, 50–10⁶ Hz. AC conductivity of the nanocomposites obeyed the power law indicating the universal behaviour of disordered media. The nanocomposites showed high dielectric constant in the order of 10⁴, which could be related to dielectric relaxation phenomenon. Further, the materials were checked for their supercapacitance performance by using cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). Among the synthesized nanocomposites, PANI/ZrO₂-25 wt.% showed a higher specific capacitance of 341 F g^?1 at 2 m Vs^?1 and good cyclic stability with capacitance retention of about 88% even after 500 charge–discharge cycles.     

Preparation and characterization of polyaniline/exfoliated graphite composite via a combination method of in situ polymerization and thermal expansion

Polyaniline/exfoliated graphite (PANI/EG) composite was prepared via a combination method of in situ polymerization and thermal expansion and characterized, using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). In the in situ polymerization, PANI/graphite intercalation compounds (GIC) composite was synthesized by GIC and aniline. In the thermal expansion, PANI/EG composite was prepared by PANI/GIC composite. The characterization showed that the morphology of PANI/EG composite was analogous to foam and the surface of PANI/EG composite had many micro-apertures. When PANI/GIC composite was synthesized by 0.80 g of GIC and 2.00 g of aniline, PANI/GIC composite would be exfoliated to PANI/EG composite at 200 °C, which had 75.00 mL·g⁻¹ of the expansion volume and 0.01Ω⁻¹ cm⁻¹of the conductivity.     

Raman spectroscopy and AC conductivity of polyaniline montmorillonite (PANI–MMT) nanocomposites

A series of polyaniline/montmorillonite clay (PANI–MMT) nanocomposites were synthesised by in situ polymerisation of aniline in acidic medium in the presence of varying amounts (from 1 to 30 wt%) of MMT and a substoichiometric amount of ammonium persulfate (APS). For a preferred molar ratio of monomer to oxidant of 2:1, the aniline was polymerised and largely incorporated into the MMT. The PANI–MMT nanocomposites were characterised and compared by wide-angle powder X-ray diffraction and UV–Vis spectroscopy. Raman spectroscopy was used to investigate the interaction between clay layers and the intercalated polymer chains. Room temperature AC conductivity was measured in the frequency range 30 Hz to 1 MHz. Pure PANI and all the composites exhibited a low frequency region of frequency independent AC conductivity followed by a high frequency dispersive region where the AC conductivity obeyed a fractional power law of frequency dependence. The fractional exponent n for all the nanocomposites is significantly high as compared to that of pure PANI; n = 0.9 for all the composites whereas for pure PANI n = 0.2. In pristine PANI the onset of the dispersive region ω _c is at a much higher frequency (at 300 kHz) as compared to the nanocomposites in which ω _c is about 10 kHz.     

Dispersion assessment and studies on AC percolative conductivity in polymer-derived Si–C–N/CNT ceramic nanocomposites

Nanocomposites comprise polysilazane-derived SiCN ceramic charged with carbon nanotubes (CNTs) have been prepared by dispersion of multi-walled CNTs with a diameter of 80 nm in a cross-linked polysilazane (HTT 1800, Clariant) using a simple roll-mixer method. Subsequently, the composites were warm pressed and pyrolyzed in argon atmosphere. Scanning electron microscopy (SEM) and 3D Raman imaging techniques were used as major tools to assess the dispersion of CNTs throughout the ceramic matrix. Furthermore, studies on the effect of the volume fraction of CNTs in the nanocomposites on their electrical properties have been performed. The specific bulk conductivities of the materials were analyzed by AC impedance spectroscopy, revealing percolation thresholds (ρ_c) at CNT loadings lower than 1 vol%. Maximum conductivity amounted to 7.6 × 10⁻² S/cm was observed at 5 vol% CNT. The conductivity exponent in the SiCN/CNT composites was found equal to 1.71, indicating transport in three dimensions.     

Synthesis,characterization and low frequency a.c. conduction of polyaniline/fly ash composites

In situ polymerization of aniline was carried out in the presence of fly ash (FA) to synthesize polyaniline/ fly ash (PANI/FA) composites. The PANI/FA composites have been synthesized with various compositions (15, 20, 30 and 40 wt%) of FA in PANI. The composites, thus synthesized have been characterized by infrared spectroscopy and X-ray diffraction. The morphology of these samples was studied by scanning electron microscopy. Further the a.c. conductivity of these composites have been investigated in the frequency range 10²–10⁶ Hz. The presence of polarons and bipolarons are made responsible for frequency dependence of a.c. conductivity in these composites. The Cole-Cole plots indicate clear shift in the distribution of relaxation times as the wt% of FA in PANI changes. These composites show almost symmetric semicircles of Cole-Cole plots indicating the Debye-type relaxation in their polarization response.     

Synthesis of nanocomposites based on MO-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript> (M = Ca,Sr, Ba) glasses

This work examines the effect of KBF₄ additions on the crystallization behavior of glasses based on the multicomponent systems MO-Bi₂O₃-B₂O₃ with M = Ca, Sr, and Ba. The glass-ceramic composites obtained contain a δ-Bi₂O₃-based crystalline phase with a crystallite size of ≃7 nm, evenly distributed over the glass matrix. The 400°C electrical conductivity of the nanocomposites reaches 2 × 10⁻⁴ S/cm, and the activation energy is 1.1 eV, typical of anion conduction. These values are comparable to those reported for δ-Bi₂O₃ ceramics.     

Synthesis and characterization of HDA/NaMMT organoclay

In this study, the rheologic and colloidal characterizations of sodium montmorillonite (NaMMT) were examined. Hexadecylamine (CH₃(CH₂)₁₅NH₂, HDA) was added to the bentonite water dispersion (2%, w/w) in different concentrations in the range 5.6 × 10⁻⁴−9.4 × 10⁻³ mmol/l. The rheological and electrokinetic behaviour of aqueous montmorillonite dispersions was investigated as a function of solid content and HDA concentration. The basal spacings of the HDA/NaMMT composites were studied by X-ray diffraction. The FTIR spectra were obtained from the modified bentonite products, which revealed the characteristic absorbances after treatment with HDA.     

Microstructure,electrical and humidity sensing properties of TiO<Subscript>2</Subscript>/polyaniline nanocomposite films prepared by sol–gel spin coating technique

High sensitive resistive type humidity sensor based titanium oxide/polyaniline (TiO₂/PANI) nanocomposite thin films prepared by a sol–gel spin coating technique on an alumina substrate. The resultant nanocomposites were characterized by using X-ray diffraction (XRD), Field emission electron microscopy, Fourier transform infrared spectroscopy (FTIR), UV–Vis absorbance and energy dispersive spectra analysis. In the XRD patterns of both pure and TiO₂/PANI composite confirms the deposition of PANI on TiO₂ and the average size of the composite particle was found to be 32 nm. Large number of nano grain surface being covered by PANI, which agrees very well with the results obtained by XRD studies. FTIR and UV–Vis spectra reveal that the PANI component undergoes an electronic structure modification as a result of the TiO₂ and PANI interaction. The room temperature resistivity was found to be for TiO₂ and TiO₂/PANI nanocomposite films 1.42?×?10⁶ and 2.56?×?10³ Ω cm respectively. The obtained TiO₂/PANI nanocomposites sensor exhibited higher humidity sensing performance such as high sensitivity, fast response (20 s) and recovery time (15 s) and high stability.     

Elevated temperature sliding wear behavior of WCP-reinforced ferrous matrix composites

WC_P-reinforced ferrous matrix composites were processed by direct addition of WC_P (100–150 μm) and the melt of the matrix alloy to a rotating mold at 1000 rpm. Dry sliding wear behaviors of the composites containing about 80 vol.% of WC_P and high-speed steel counterpart were investigated at room temperature and 400 °C against a rotating die steel ring. And wear experiments were performed under loads of 50, 100, and 150 N and a fixed sliding velocity of 30 m/s. Results show that at room temperature, both materials exhibited a marked increase in wear rate with load applied. Wear rates of the composites and high-speed steel under loads of 50, 100, and 150 N at room temperature achieved 1.61 × 10⁻⁶, 2.14 × 10⁻⁶, 3.56 × 10⁻⁶, and 3.11 × 10⁻⁶, 23.08 × 10⁻⁶, 57.39 × 10⁻⁶ g/m, respectively. At a testing temperature of 400 °C, the composites exhibited a marked increase in wear rates and high-speed steel exhibited mild wear (characterized by extremely low wear rates) over the range of loads considered in these experiments. Wear rates of both the composites and high-speed steel at 400 °C achieved 2.42 × 10⁻⁶, 5.19 × 10⁻⁶, 6.64 × 10⁻⁶, and 4.1 × 10⁻⁶, 8.92 × 10⁻⁶, 26.02 × 10⁻⁶ g/m, respectively, under different loads. Finally, the wear-mechanism was discussed in this article.     

Electrical conductivity and thermal stability of (1 ? x )CsH2PO4/ x SiP y O z ( x = 0.2–0.7) composites

The physicochemical properties of (1 − x)CsH₂PO₄/xSiP _y O _z (x = 0.2–0.7) composites containing fine-particle silicon phosphates as heterogeneous additives have been studied at different humidities. The introduction of silicon phosphates suppresses the superionic phase transition of CsH₂PO₄ and increases the low-temperature conductivity of the materials, which depends significantly on humidity. The CsH₂PO₄-SiP _y O _z materials offer high conductivity (∼3 × 10⁻³ to 10⁻² S/cm at ∼110–230°C) at low water vapor pressures (3 mol % H₂O). Amorphization of the CsH₂PO₄ in the composites markedly changes its thermodynamic properties. The effect of long-term isothermal holding (210°C, 3 mol % H₂O) on the conductivity of the composites has been studied. Original Russian Text ? V.G. Ponomareva, E.S. Shutova, G.V. Lavrova, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 9, pp. 1131–1136.     

A three-dimensional nanostructured PANI/MnOx porous microsphere and its capacitive performance

Three-dimensional nanostructured polyaniline (PANI) and manganese oxide (MnO _x ) composite porous microspheres were prepared by oxidizing aniline with KMnO₄ under interfacial chemical synthesis with 4-amino-thiophenol (4-ATP) as the structure-directing agent on the Au substrate. Surface morphology and chemical composition of PANI/MnO _x microsphere were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermo gravimetric-differential thermal analysis, and Fourier transform infrared spectrum. The result displayed that concentration of KMnO₄ played a key role in forming the 3D nanostructured porous microspheres. To obtain the regular shapes and uniform sizes of the porous microspheres, the optimal concentration of oxidant was 0.15 mol L⁻¹. The electrochemistry performances of PANI/MnO _x microsphere were determined by cyclic voltammograms, electrochemical impedance spectroscopy, and galvanostatic charge–discharge. The specific capacitance of the 3D nanostructured PANI–MnO _x porous microspheres exhibited a maximum value of 828 F g⁻¹ at current density of 2 mA cm⁻² over a potential range of 0.0–0.9 V versus SCE. It has improved 365 and 88 % comparing with that of PANI (178 F g⁻¹) and MnO _x (440 F g⁻¹) obtained at the similar condition. The charge–discharge tests showed the PANI/MnO _x microsphere possessed a good cycling stability. It maintained about 84.2 % of the initial capacitance after 1000 cycles at a current density of 2.0 mA cm⁻².     

MWNTs/PANI composite materials prepared by in-situ chemical oxidative polymerization for supercapacitor electrode

Multi-walled carbon nanotubes (MWNTs)/polyaniline (PANI) composite materials were prepared by in-situ chemical oxidative polymerization of an aniline solution containing well-dispersed MWNTs. The supercapacitive behaviors of these composite materials were investigated with cyclic voltammetry (CV), charge–discharge tests, and ac impedance spectroscopy, respectively. The composites based on the charge-transfer complex between well-dispersed MWNTs and PANI matrixes show much higher specific capacitance, better thermal stability, lower resistance, and were more promising for applications in supercapacitors than a pure PANI electrode. The highest specific capacitance value of 224 Fg⁻¹ was obtained for the MWNTs/PANI composite materials containing MWNTs of 0.8 wt%. The improvement mechanisms of the capacitance of the composite materials were also discussed in detail.     

Electromagnetic interference shielding of carbon nanotube/ethylene vinyl acetate composites

Single-walled carbon nanotube (SWCNT) and ethylene vinyl acetate (EVA) composites were synthesized in an internal mixer by melt mixing. The electrical conductivity as well as electromagnetic interference (EMI) shielding effectiveness (SE) over the X-band (8–12 GHz) and microwave (200–2,000 MHz) frequency ranges of these composites were investigated. It was observed that the electrical conductivity of composites increases with increasing SWCNT loading. A percolation threshold of about 3.5 wt.% was obtained and the electrical conductivity of EVA was increased by ten orders of magnitude, from 10⁻¹⁴ to 10⁻⁴ Ω⁻¹ cm⁻¹. The effect of sample thickness on SE was investigated. The correlation between SE and conductivity of the composites is discussed. The experimental data showed that the SE of the composites containing higher carbon nanotube loadings (above 10 wt.%) could be used as an EMI shielding material and lower SWCNT loadings could be used for the dissipation of electrostatic charge.     

Rubidium ion conducting Rb2 ? 2xAl2 ? xAxO4 (A = Nb, Ta) solid electrolytes

Rb_{2 − 2x} Al_{2 − x} A _x O₄ (A = Nb, Ta) solid solutions have been synthesized, and their conductivity has been measured as a function of temperature and composition. The highest rubidium ion conductivity in the Rb_{2 − 2x} Al_{2 − x} A _x O₄ solid solutions is 3.16 × 10⁻³ S/cm at 300°C and ∼ 2 × 10⁻² S/cm at 700°C. The high rubidium ion conductivity of the synthesized solid electrolytes is mainly due to the formation of rubidium vacancies when Nb⁵⁺ or Ta⁵⁺ substitutes for Al³⁺ and to the specific features of the crystal structure of RbAlO₂.     

Synthesis of expanded graphite filled polyaniline composites and evaluation of their electrical and electrochemical properties

A series of conducting polyaniline/expanded graphite (PA/EG) composite was synthesized by in situ polymerization of aniline in acid medium followed by the addition of expanded graphite in various proportions (1, 2 and 3 wt%). The synthesized samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, ultraviolet–visible absorption, X-ray diffraction and by electrical conductivity measurements. The dc electrical conductivities of the composites were dramatically increased compared with pure polyaniline and found to be 0.50 × 10² S/cm to 6.11 × 10² S/cm. The PA/EG composites showed a reversible electrochemical response up to 150th repeated cycles as revealed by the cyclic voltametry study.