Electrodeposited conducting polymer–magnetic metal composite films

Electrically conducting polypyrrole (PPy)–iron group (Ni, Co, Fe and their alloys) composite films have been electrodeposited at cathodic process to give “tailored” soft and hard magnetism. The composites of the PPy doped with dodecylsulfate (DS) (PPy–DS) with NiFe alloy showed soft magnetism with coercivity H_C,∥ <9 Oe, while the PPy–DS with CoMnP alloy showed hard magnetism with H_{C, ∥}>1085 Oe. These results indicate that composites of conducting polymer–magnetic metals can be easily fabricated by electrodeposition.     

Electrochemical synthesis of NbC–Sn composite powder in molten chloride

NbC–Sn composite powder was successfully prepared from SnO₂, Nb₂O₅ and carbon by electrochemical reduction and carbonization in CaCl₂–NaCl molten salt at 900 °C. The reaction pathway was investigated by terminating electrochemical experiments for various durations. The influence of carbon on the final products was considered. NbC particles were obtained by leaching the composite with acid. The results showed that the aggregated NbC–Sn composite powdev contained NbC particles about 50–100 nm and Sn particles about 200 nm. SnO₂ was reduced to Sn in the sintering process. Nb₂O₅ was electrochemically reduced to Nb in molten salt, experiencing some intermediate products of calcium niobates and niobium suboxides. Nb metal obtained was converted to NbC with assistance of carbon. The reduction of Nb oxides may be incomplete and Nb₃Sn would be formed if carbon is insufficient in the cathodic pellet. NbC with good dispersity is produced by leaching NbC–Sn with HCl.     

Ruthenium(II)-mediated synthesis of conducting polyaniline (PAni): A novel route for PAni–RuO2 composite

In this communication we describe the unprecedented ruthenium(II)-mediated synthesis of polyaniline. The synthesis enroutes via formation of a simple ruthenium(II)–tetraaniline complex which on chemical oxidation with hydrogen peroxide in the presence of hydrochloric acid gives conducting polyaniline–RuO₂ composite. The reaction is novel in the way that both the metal center Ru(II) and the coordinated aniline molecules of the intermediate complex 1 take part in the oxidation reaction to yield polyaniline–ruthenium oxide hybrid.     

Electrochemical and photoelectrochemical study of gallium arsenide–polybithiophene composite

Bithiophene (BiTh) was galvanostatically polymerized in the presence of gallium arsenide (GaAs) particles at different concentration. The properties of the composite layers were studied by electrochemical method (cyclic voltammetry), UV–vis spectroscopy and photocurrent measurements. From UV–vis spectroscopy studies, the absorbance of the composites is larger than the polybithiophene absorbance in the UV region. The p-type semiconducting behaviour of the reduced polybithiophene was studied by photocurrent measurements. It was observed that the photocurrents of the composites was higher than that of the PBiTh without GaAs, and increased with GaAs concentration.     

Polypyrrole–metal coil composite actuators as artificial muscle fibres

A polypyrrole (PPy) deposited electrochemically on W micro-coil with the diameter of 0.25 mm from methyl benzoate solution of TBABF₄ showed 11.6% apparent strain induced electrochemically in aqueous NaBF₄ solution. This strain was slightly smaller than that (12.1%) of a free-standing PPy film prepared similarly on W electrode. However, taking the configuration of PPy–W coil (gap:wire diameter = 1:1) into account, the effective strain of PPy at the gap of coil wires should be 23.2%. The enhanced contact area between W coil and PPy reduced voltage drop of the PPy, resulting in exhibiting the large strain. Electrochemically generated displacement and force can be easily tailored by adjusting the length and the number of PPy–coil composite, respectively. The tailor-made actuator should be applicable to a variety of mechanisms, particularly to ‘push’ devices such as a plunger.     

Polyaniline–poly(vinyl alcohol) conducting composite: material with easy processability and novel application potential

The present work reports an easy route for synthesis of polyaniline (PAn) in stable aqueous solution/dispersion form, using poly(vinyl alcohol) (PVA) as an efficient steric stabilizer. Resulting composite successfully combines desirable physical properties like mechanical strength, solution processibility and electrical conductivity of PVA and PAn components. The composite was subjected to versatile characterizations and its different physical properties (especially optical, thermal, mechanical and electrical) were explored. Free standing films can be obtained from the solutions, which exhibit important microwave shielding property over the X-band. This has enhanced the importance of this material to a large extent.     

Electrochemical synthesis of a biomedically important Co–Cr alloy

Co–30 wt.% Cr alloy was prepared by electro-deoxidation in molten calcium chloride at 1123 K. A preliminary study was conducted into the preparation of the mixture of the Co₃O₄ and Cr₂O₃ and the formation of the non-stoichiometric, spinel structured, mixed oxide nominally labeled Co_xCr_yO₄. Constant voltage chronoamperometry was used both to prepare the alloy and to investigate its mechanism of formation. Electro-deoxidation proceeds by the simultaneous rapid reduction of CoO to Co and the slower reduction/substitution of Co_xCr_yO₄ to CaCr₂O₄ and Co metal. The final step of the electro-deoxidation is the reduction of CaCr₂O₄ to Cr metal, which alloys with the Co metal, and release of Ca²⁺ back into the electrolyte.     

Formation and properties of nano- and micro-structured conducting polymer host–guest composites

Process of formation of polyaniline (PANI) at the surface of SiC and CdS nanoparticles or submicron- and micron-sized particles of poly(vinylidene fluoride) (PVDF), polycarbonate and polyamides-11, 12 and properties of the prepared composites are considered. Beginning of the formation of the PANI shell at the particle surface was evaluated. This important result opens the possibility to control properties of the final hybrid composite. In case of CdS nanoparticles PANI was synthesized in the form of nanofibers embedding these nanoparticles. Films of the PANI–polymer composites showed the conductivity of up to ～0.4 S/cm. The planar heterojunction of the compression molded PVDF/PANI–DBSA film with bulk CdS displayed photovoltaic activity.     

Electrophysical properties of ceramic–polymer composite films as function of sintering temperature

The effect of changes in sintering temperature on electrical properties and microstructure of ZnO–polyaniline– polyethylene composite ceramics, prepared in disk form at the pressure of 60 MPa and at five different temperatures, has been investigated. Increasing sintering temperature from 30 to 120 °C noticeably reduces breakdown voltage from 830 to 610 V. Further increase in sintering temperature causes breakdown voltage to increase. Interface voltage barrier height behaves differently when sintering temperature increases, which is in contrast to breakdown voltage behavior. These samples have a very low leakage current, a factor which indicates low degradation. Then again, the higher the sintering temperature gets, the less the nonlinear coefficient becomes. In addition, each sample has hysteresis which decreases through increase of sintering temperature up to 120 °C. Further increase in sintering temperature, however, causes the hysteresis loop to spread. Regarding UV spectra of the samples, it is revealed that there are three impurity levels whose behaviors against sintering temperature are subtractive. Analysis of composite samples by scanning electron microscopy indicates that their microstructure consists of grains and grain boundaries. Resistivity of grain boundaries is the main responsible factor for these changes in varistor characteristic as a function of sintering temperature.     

Reactive spark plasma sintering of TiB2–SiC–TiN novel composite

The effects of adding SiC as a reinforcement and TiN as an additive on TiB₂-based composites fabricated by the spark plasma sintering (SPS) technique were investigated. SPS was implemented at the sintering conditions of 1900 °C temperature, 7 min holding time and 40 MPa pressure. Adding these two secondary phases had noticeable effects on the microstructure of TiB₂-based composites. A relative densities of 99.9% was obtained for TiB₂–SiC–TiN composite. Detection of in-situ formed phases and investigation on them were done using SEM, XRD, EDS and thermodynamic assessment. These evaluations proved the formation of in-situ phases of TiC, BN nano-platelets, TiSi and B₄C in the TiB₂-based composite codoped with SiC and TiN. Formation of these in-situ phases had fascinating effects on the sinterability and ultimate microstructure of titanium diboride.     

Electrical behavior of conducting polymer based ‘polymeric–inorganic’ nanocomposite: Polyaniline and polypyrrole zirconium titanium phosphate

Composites are 21st century material used to meet the demand of improved materials and possess a combination of several desirable properties. Present study focussed on the conducting behavior of ‘polymeric–inorganic’ nanocomposite of conducting polymer polyaniline and polypyrrole. ‘Polymeric–inorganic’ nanocomposite cation-exchangers, i.e., polyaniline zirconium titanium phosphate (PANI-ZTP) and polypyrrole zirconium titanium phosphate (PPy-ZTP), were synthesized via sol–gel mixing of electrical conducting polymers into the matrices of inorganic precipitate of zirconium titanium phosphate (ZTP) having excellent ion exchange properties. The proposed nanocomposite possessed DC electrical conductivity in the semi-conducting range, i.e., 10^?5–10^?3 S cm^?1. The stability in terms of DC electrical conductivity retention was also studied in an oxidative environment by two slightly different techniques viz. isothermal and cyclic techniques. The DC electrical conductivity of composite material was found stable upto 110 °C under ambient conditions.     

A facile and inexpensive method for the preparation of conducting polyaniline–clay composite nanofibers

Hybrid nanofibers constituted by polyaniline doped with phosphoric acid (PAniPh) and two different clays: pristine montmorillonite (MMT-Na⁺) and organoclay functionalized with amino undecanoic acid (MMT-COOH), were successfully prepared by employing a very simple procedure based on previous swelling the clay in anilinium salt solution followed by in situ polymerization under static conditions and low [acid]/[aniline] molar ratio. The nanocomposites were characterized by X-ray diffraction (XRD), field emission-scanning electron micrograph (FEG-SEM), transmission electron microscopy, Fourier transform-infrared (FTIR) spectroscopy, ultraviolet–visible (UV–vis) spectroscopy, electrical conductivity and thermal gravimetric analysis (TGA). Nanocomposites containing around 12% of clay resulted in conducting nano-fibers with ramose structure and higher electrical conductivity than pure PAniPh. The extended conformation was also confirmed from UV–vis spectrum. The best surface conductivity (2.3 S/cm) and highest extended conformation were observed for the PAniPh/MMT-COOH nanocomposite.     

Electrochemical behaviour of high phosphorus electroless Ni–P–Si3N4 composite coatings

Abstract

A high phosphorus electroless nickel bath was used to prepare plain Ni–P and composite coatings containing submicrometre size silicon nitride particles. Deposits were characterised for their composition, morphology and electrochemical behaviour. Codeposition of particles in a Ni–P matrix has not influenced the phosphorus content (10 wt-%). Surface morphology of plain Ni–P deposits was smooth; the composite deposits became slightly rough with small nodules due to particle incorporation. Cross-sectional examination of composite coating revealed that the particles were uniformly distributed throughout the thickness of the coating. Potentiodynamic polarisation and electrochemical impedance studies were carried out in 3·5 wt-% sodium chloride solution in non-deaerated condition. Potentiodynamic polarisation studies showed that the corrosion current density value obtained for composite coatings is lower than that for plain Ni–P coatings. Electrochemical impedance spectroscopy studies showed that the coating resistance of the composite coating is higher than that of plain Ni–P coating. This was further confirmed by SEM analysis of corroded samples.     

In-situ synthesis of WC–Co composite powder and densification by sinter-HIP

In the present study, a complete route which integrates in-situ synthesis of WC–Co composite powder and sinter-HIP is proposed to prepare the ultrafine tungsten carbides. Owing to the in-situ reduction and carbonization reactions of WO_2.9, Co₃O₄ and carbon black powders at 1000 °C, the composite powder with pure phase constitution and ultrafine particle size is synthesized with a rapid procedure. The WC–Co bulk material prepared by the sinter-HIP densification of the composite powder exhibits homogeneous and ultrafine microstructure, as well as the excellent mechanical properties. The proposed method shows potential to be developed as a promising industrial route owing to its advantages of low-cost raw materials and short-term in-situ reactions.     

Electrochemical synthesis of polyaniline on conducting fabrics of polyester covered with polypyrrole/PW12O403−. Chemical and electrochemical characterization

Polyaniline (Pani) has been electrochemically polymerized on conducting fabrics of polyester covered with polypyrrole/PW₁₂O₄₀^3?, obtaining a double conducting polymer layer. Electrochemical synthesis was performed by potentiostatic synthesis at 1 V. The chemical characterization of the material before and after Pani polymerization was performed by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of the coatings was observed employing scanning electron microscopy (SEM). The electrochemical characterization was performed by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). It has been demonstrated that scan rate is an important parameter that influences the response obtained when characterizing conducting fabrics by CV. High scan rates do not allow the observation of redox peaks. However if lower scan rates are employed its apparition has been reported. The electrochemical deposit of polyaniline enhances the electroactivity of the material as it has been demonstrated by CV. SECM measurements showed local response with positive feedback (electroactive material) for the samples in open circuit conditions. XPS analysis also showed a higher doping level (N⁺/N), consistent with higher material electroactivity.     

Densification and oxidation behavior of a novel TiB2–MoSi2–CrB2 composite

Titanium diboride (TiB₂) composite with MoSi₂ and CrB₂ has been prepared and tested to possess excellent oxidation resistance. Dense composite pellets were fabricated by hot pressing of powder mixtures. Microstructural characterization was carried out by XRD and SEM. Hardness and fracture toughness values were measured. Extensive oxidation studies of the composites were also carried out. Density of ≥ 96% ρ_th was obtained by hot pressing at 1800 °C under a pressure of 35 MPa for 1 h. Hardness and fracture toughness were in the range of 18–24 GPa and 3.5–4 MPa·m^1/2 respectively. Crack branching, deflection and bridging mechanisms were observed in the crack propagation paths. Isothermal and continuous oxidation studies of these composites up to 1000 °C showed improved oxidation resistance with the formation of protective glassy layer. TiO₂, Cr₂O₃ and SiO₂ phases were identified on the oxidized surface. Diffusion controlled mechanism of oxidation was observed in the composites.     

Photoconductivity of novel poly（N-vinyl）-3 - [p-nitrophenylazo] carbazole/ CdS-nanoparticle polymer composite

The photoconductive characteristic of the inorganic/organic hybridized polymer system is reported, in which a novel bi-functional photorefractive （PR） poly（N-vinyl）-3-[p-nitrophenylazo]carbazole （PVNPAK） serves as a polymeric charge-transporting and second-order nonliner optical matrix and quantum dots composed of surface passivated cadmium sulfide serve as a charge-generation sensitizer. The hybrid PVNPAK/CdS-nanoparticles polymer composites with different mass ratio of CdS to PVNPAK were prepared. The generation of photocurrent on illumination and photoconductive properties of the PVNPAK/CdS-nanoparticles polymer composites were studied. The results show that the addition of CdS nanoparticle as a photosensitizer can enhance the photoconductivity of the PVNPAK significantly because of the properties of the high quantum efficiency of photosensitization and high charge transport to conducting polymer.     

Environmentally assisted cracking behaviour of Al–Zn–Mg–Cu–Cr alloy bonded with polymer matrix composite stiffener

Studies were conducted to investigate the effect of polymer matrix composite stiffener (patch) on environmentally assisted cracking (EAC) susceptibility of pre-cracked alclad Al–Zn–Mg–Cu–Cr alloy in 3.5 wt.% NaCl environment. The EAC threshold stress intensity of the peak and two-step aged alloy was reduced from 26 to 7 MPa m^1/2 and 31to 8 MPa m^1/2 respectively under the influence of patch. The plateau crack velocity was increased from 2.5 × 10⁻⁹ to 5.1 × 10⁻⁹ m/s for peak aged and 1.2 × 10⁻⁹ to 2.0 × 10⁻⁹ m/s for two-step aged tempers in patched condition. The significant increase in EAC susceptibility was attributed to crevice effect generated by the stiffener.     

Electrochemical corrosion behaviour of Mg–Al alloys with thermal spray Al/SiCp composite coatings

The corrosion protection of Mg–Al alloys by flame thermal spraying of Al/SiC particles (SiCp) composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiCp varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of microchannels, largely in the vicinity of the SiCp, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5–30 vol.% SiCp compared with the unreinforced thermal spray aluminium coatings.     

Preparation of novel core-shell nanoparticles by electrochemical synthesis

Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol （4-ATP） capped Au nanoparticles. The new approach to the fabrication included three steps： preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 run. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.