Polyaniline–DBSA/polymer blends prepared via aqueous dispersions

Stable polyaniline–dodecyl benzene sulfonic acid (PANI–DBSA) aqueous dispersions were obtained by a unique method of aniline polymerization in the presence of DBSA, through an anilinium–DBSA complex appearing as solid needle-like particles, in an aqueous medium. The average size of the PANI primary particles, determined by small angle X-ray scattering (SAXS), is 18.7 nm. These primary particles form aggregates, which further cluster into 50 μm agglomerates. PANI–DBSA/polymer blends were obtained by mixing an aqueous PANI–DBSA dispersion with an aqueous emulsion of the matrix polymer, followed by water evaporation. These blends exhibit electrical conductivity already at a very low PANI–DBSA content (0.5 wt.%). The conductivity level of the various blends depends on the PANI content, on the surfactant present in the polymer matrix emulsion, and it is practically independent of the polymer matrix nature. Thus, a similar structuring mechanism prevails in these blends, irrespective of the polymer matrix (contrary to solution and melt blends). The PANI–DBSA particles strongly segregate within the polymer matrix, already in the combined aqueous dispersion, and upon drying, a very fine conductive network is formed. This strong segregation tendency leads to a conductive network formation already at low PANI–DBSA contents, thus generating the conductive blends.     

Synthesis and properties of polyaniline–cobalt coordination polymer

Polyaniline–cobalt coordination polymer (abbreviated as PANI-Co) was synthesized using peroxydisulphate as an oxidant in the solution containing 0.1 mol dm⁻³ aniline, 0.5 mol dm⁻³ HCl and an adequate content of CoCl₂·6H₂O at room temperature. The conductivity of PANI-Co was 0.5 S cm⁻¹. The cyclic voltammogram results indicated that the PANI-Co film was of electrochemical activity, and the EPR spectrum showed that there were unpaired electrons in the PANI-Co. The relationship between magnetization (M) and the applied magnetic field (H) suggests that PANI-Co was soft ferromagnetic material at room temperature. Thus, the PANI-Co was both conductive and ferromagnetic. Moreover, UV–vis and FTIR spectra showed that there existed a strong interaction between Co²⁺ and PANI chains.     

In situ self-organization of carbon black–polyaniline composites from nanospheres to nanorods: Synthesis, morphology, structure and electrical conductivity

Nanostructured composites of polyaniline (PANI) with carbon black (CB) were synthesized by an in situ self-organization process. The synthesis is based on the polymerization of aniline in a micellar solution of p-toluenesulfonic acid (TSA) with different weight percentages of CB using ammonium peroxydisulfate (APS) as the oxidizing agent. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), UV–vis spectroscopy, and the four-probe meter were used to study the morphological, structural, thermal, and electrical properties of CB–PANI nanocomposites. The results demonstrate that the morphology, thermal stability, and electrical conductivity of the nanocomposites were significantly influenced by the content of CB. SEM results reveal that there was a transition in morphology from composite nanospheres to one-dimensional (1D) composite long nanorods with an increase of CB content. XRD and UV–vis spectra results revealed that there was an increase in the crystallinity and a shift of quinoid transition bands towards lower wavelengths as the amount of CB in the composite increased. The mechanism for the formation of nanostructured composites was explained on the basis of the self-organization of micelles. CB–PANI nanocomposites with a maximum electrical conductivity of 1.38 S/cm were obtained; this is at least three orders of magnitude higher than that of pristine PANI.     

Preparation of polyaniline–titanium dioxide hybrid materials in supercritical CO2

Polyaniline–titanium dioxide (PANI–TiO₂) hybrid materials were synthesized in supercritical CO₂ using two different methods. In the first method, separately synthesized TiO₂ particles were mixed with aniline to perform polymerization in supercritical CO₂. The second method included the preparation of aniline–TiO₂ hybrids through a sol–gel reaction of titanium isopropoxide in the presence of aniline. Further polymerization of aniline–TiO₂ hybrids in supercritical CO₂ produced PANI–TiO₂ hybrid particles. The final products showed the intrusion of PANI into the internal structure of TiO₂. The PANI–TiO₂ hybrid materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), electrical conductivity (EC), Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) measurements. PANI–TiO₂ nano-composites synthesized with the first method showed a relatively low electrical conductivity of 3.78 × 10⁻² S/cm at 20 °C. TGA suggested that the particles contained 40.6% TiO₂ by mass and showed a strong interaction at the interface of TiO₂ and PANI. The electrical conductivity of the hybrid particles produced using the second method increased to 7.75 × 10⁻² S/cm and the TGA results showed 34.4% TiO₂ by mass. Through SEM and TEM analyses it was confirmed that the PANI has been interpenetrated into the three-dimensional network of the TiO₂ when the second method was used.     

In situ synthesis and characterization of polyaniline–CaCu3Ti4O12 nanocrystal composites

High dielectric constant (ca. 2.4 × 10⁶ at 1 kHz) nanocomposite of polyaniline (PANI)/CaCu₃Ti₄O₁₂ (CCTO) was synthesized using a simple procedure involving in situ polymerization of aniline in dil. HCl. The PANI and the composite were subjected to X-ray diffraction, Fourier transform infrared, thermo gravimetric, scanning electron microscopy and transmission electron microscopy analyses. The presence of the nanocrystallites of CCTO embedded in the nanofibers of PANI matrix was established by TEM. Frequency dependent characteristics of the dielectric constant, dielectric loss and AC conductivity were studied for the PANI and the composites. The dielectric constant increased as the CCTO content increased in PANI but decreased with increasing frequency (100 Hz–1 MHz) of measurement. The dielectric loss was two times less than the value obtained for pure PANI around 100 Hz. The AC conductivity increased slightly up to 2 kHz as the CCTO content increased in the PANI which was attributed to the polarization of the charge carriers.     

Pilot plant scale preparation of dodecylbenzene sulfonic acid doped polyaniline in ethanol/water solution: Control of doping, reduction of purification time and of residues

Aiming to produce polyaniline doped with dodecylbenzene sulfonic acid on a pilot plant scale using a 10 L reactor, the synthesis was optimized on a bench scale using a 2³ factorial design, involving the variables: K parameter, DBSA/aniline molar ratio (Q) and final aniline concentration (C). The nominal yield and electrical conductivity were used as control parameters. An ethanol/water (2:5, v/v) solution replaced water as solvent. The samples were characterized by electrical conductivity measurements, infrared spectroscopy, X-ray diffraction, elemental analysis, thermogravimetry and density. The influence of the washing solvent volumes and storage time of oxidizer on the nominal yield and electrical conductivity of PAni/DBSA were also investigated. By using ethanol/water as solvent it was possible to reduce the filtration time, to eliminate the purification step and to control the content of DBSA in the polyaniline bulk, maintaining the principal characteristics, like electrical conductivity and density. The doped polymer was obtained with electrical conductivity in the range of 10⁻¹ to 10⁻³ S cm⁻¹, depending on the dopant concentration. Freshly purchased ammonium peroxydisulfate must be used for higher yields and better reproducibility.     

Adsorption of quinonediimines on aluminum(1 0 0): A computational and FT-IR study

Density functional theory (DFT) calculations were performed on a series of symmetrically substituted quinonediimines, both free and adsorbed on a 42 atom aluminum(1 0 0) lattice. Enthalpies of adsorption for quinonediimines in the emeraldine base oxidation state were calculated to vary from −4.07 to −8.47 kcal mol⁻¹, with the emeraldine salt value at −78.00 kcal mol⁻¹. The enthalpy of absorption for the pernigraniline is calculated to be 30 kcal mol⁻¹. Adsorption onto the aluminum surface caused a change in hybridization of the central imine nitrogen from sp² to sp³, with concomitant formation of a coordinate covalent bond to two electron deficient aluminum atoms of the surface. Experimental IR studies of three quinonediimines show shifts in absorption bands consistent with strong interaction with the aluminum surface, and consistent with frequencies calculations using DFT.     

聚苯胺膜在AZ91镁合金表面的制备

AZ91镁合金在碱性溶液中，用循环伏安法在其表面制备了聚苯胺膜层。用扫描电子显微镜（SEM）研究了聚苯胺膜的表面形貌和截面特征。研究表明在碱性溶液中，AZ91镁合金表面可以制备在空气中稳定的黄黑色聚苯胺膜，而且与基体的结合较好。从而在AZ91镁合金表面制备了既可以导电又可以耐蚀的膜层。     

Synthesis and characterization of doped LaCrO3 perovskite prepared by EDTA–citrate complexing method

The La_0.85Sr_0.15Cr_0.95Ni_0.02Co_0.02O₃ (LSC) interconnect materials for solid oxide fuel cells (SOFCs) were synthesized by EDTA–citrate complexing method. Thermal decomposition behavior of the gel, phase formation and morphology of LSC powders were characterized by thermogravimetry/differential thermal (DSC/TG) analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. It appeared that lower pH value (pH 4.9) of the precursor solution resulted in a transient liquid phase, SrCrO₄, in the calcined LSC powder. The sintering characteristics, electrical conductivity and thermal expansion properties of sintered bars were investigated. La_0.85Sr_0.15Cr_0.95Ni_0.02Co_0.02O₃ prepared in the condition of pH 4.9 showed an electrical conductivity of 15.6 S cm⁻¹ at 800 °C and a thermal expansion coefficient (TEC) of 10.8 × 10⁻⁶ K⁻¹ (20–900 °C), which is suitable for use as interconnect materials for SOFCs.     

Low temperature preparation and transport properties of ternary Pb–Bi–Te alloy

Polycrystalline samples of the ternary compound Pb₂Bi₄Te₅ were prepared by a solvothermal process based on the reaction between BiCl₃, Pb(NO₃)₂, Te, and KBH₄ in N,N-dimethylformamide (DMF), and followed by a post heat-treatment of compacted pellets. The microstructures of samples were characterized using XRD and SEM. The thermoelectric properties were determined by measuring the electric conductivity and the Seebeck coefficient. These samples show a disordered layered structure, with a maximum Seebeck coefficient of 84 μV/K around 520 K.     

Infrared emissivities and microwave absorption properties of perovskite Sm0.5Sr0.5Co1−xFexO3 (0 ≤ x ≤ 0.5)

Sm_0.5Sr_0.5Co_1−xFe_xO₃ (0 ≤ x ≤ 0.5, SSCF) with perovskite-type structure has been successfully prepared by conventional solid-state reaction as a microwave and infrared multi-functional material. The effects of Fe incorporation on the structure, electrical conductivity, infrared emissivity and microwave-absorbing properties were investigated in detail. XRD results have shown that the perovskite structure of SSCF has an orthorhombic symmetry for 0 ≤ x ≤ 0.4 and a cubic symmetry for 0.5, respectively. The incorporation of Fe in SSCF could contribute to the decrease of electrical conductivity, while the infrared emissivities are increased. Moreover, microwave-absorbing properties in the frequency range of 2-18 GHz at room temperature are sensitive to Fe content. The complex permittivity, complex permeability and electromagnetic loss tangent have suddenly a step change at a certain frequency and the step-change frequency position moves slightly to lower frequencies with Fe increased. The optimal reflection loss calculated from the measured permittivity and permeability is 29.33 dB at 7.97 GHz with a thickness of 2.0 mm.     

High-temperature electrical conductivity of Li–Ge ferrites

Electrical conductivity of germanium-substituted lithium ferrites of different compositions have been investigated as a function of composition and temperature. Plots of log(σT) versus 10³/T are almost linear and have shown a transition near the Curie temperature. The activation energy in the ferromagnetic region is in general less than that in the paramagnetic region. An attempt is made to explain the conduction mechanism in Li–Ge ferrites.     

Thermoelectric properties of ternary phases of thallium–tin–tellurium system

In this paper, we present the measurements of conductivity and of thermoelectric power. Measurements were taken for the temperature range of 100–330 K for the three ternary phases of Tl–Sn–Te system. The potential of these compounds as thermoelectric materials was studied.     

Structural and electrical properties of Cd-substituted Li–Ni ferrites

Ferrites with general formula Li_0.5Ni_0.75−x/2Cd_x/2Fe₂O₄ (where x = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by the standard sintering ceramic method. X-ray diffraction analysis confirmed the single-phase spinel structure of the samples. SEM micrographs were taken to study the microstructure. The average grain diameter is found to increase with the cadmium content. The dc resistivity measured as a function of temperature shows that conduction takes place by hopping mechanism. The room temperature dc resistivity decreases with Cd content up to 0.3 and then it increases with further increase in Cd content. The Curie temperature is found to decrease linearly with addition of Cadmium. The variation of Seebeck coefficient with temperature indicates that the samples with x = 0.1, 0.3 and 0.9 show transition from n-type to p-type charge carriers whereas those with x = 0, 0.5 and 0.7 show p-type conduction.     

Microstructure and properties of Ti–Co–Si ternary intermetallic alloys

Ti–Co–Si ternary intermetallic alloys with Ti₅Si₃ as the main reinforcing phase and intermetallic TiCo as the toughening matrix were fabricated by the laser-melting deposition (LMD) process. Microstructure of the intermetallic alloys was characterized by OM, SEM, XRD and EDS. High-temperature oxidation resistance of the alloys was evaluated by isothermal oxidation at 1173 K and metallic dry-sliding wear property was evaluated at room temperature. The effect of reinforcing phase Ti₅Si₃ content on hardness, oxidation and wear resistance of the alloys was investigated. Results indicate that microstructure of the alloys transforms from hypoeutectic to hypereutectic, while hardness and oxidation resistance increases with the increasing Ti₅Si₃ content. The alloys have good oxidation resistance at 1173 K and the oxidation kinetic curves are approximately parabolic. Wear resistance of the alloys is insensitive to the microstructure and is up to 15–19 times higher than the hardened tool steel 1.0%C–1.5%Cr under dry-sliding wear test conditions. The excellent wear resistance of alloys is attributed to the effective reinforcement of Ti₅Si₃ and the excellent toughness of the intermetallic TiCo.     

Electrical conductivity and molecular properties of organodithioheterobimetallics [PhHg]2[M(dithio)2] {M=Ni, Cu or Zn; dithio=isomaleonitriledithiolate (i-MNT) 1,1-dicarboethoxy-2,2-ethylenedithiolate (DED) or trithiocarbonate (CS3)}

Organoheterobimetallic compounds of the type, [PhHg]₂[M(dithio)₂] {M=Ni(II), Cu(II) or Zn(II); dithio=isomaleonitriledithiolate (i-MNT²⁻), 1,1-dicarboethoxy-2,2-ethylenedithiolate (DED²⁻) or trithiocarbonate (CS₃²⁻)} have been synthesized and investigated by molecular spectroscopies and conductivity techniques. Magnetic behaviour, together with electronic spectra, are compatible with square planar coordination geometry around nickel(II) in [PhHg]₂[Ni(dithio)₂]. Magnetic moments, 1.6 BM and 1.25 BM for [PhHg]₂[Cu(i-MNT)₂] and [PhHg]₂[Cu(DED)₂] showed involvement of some sort of Cu–Cu interaction. Their electronic and EPR spectra show distorted square planar geometry with tetragonal/rhombic symmetry around copper(II). Powder X-ray diffraction patterns of the complexes have been compared. All the complexes show σ_rt in 2.29×10⁻¹⁰−4.38×10⁻⁴ S cm⁻¹ range. [PhHg]₂[Ni(DED)₂] and [PhHg]₂[Cu(i-MNT)₂] show semiconducting behaviour as their conductivity increases with increase in temperature with band gaps 0.39 eV; 0.57 eV and 2.38 eV, respectively.     

Elevated temperature wear behaviors of a Co–Mo–Si ternary metal silicide alloy

Wear resistant Co–Mo–Si ternary metal silicide alloy consisting of Co₃Mo₂Si primary dendrite and the interdendritic ductile Co-base solid solution (Co_ss) was designed and fabricated by the laser melting process. The alloy exhibited strong abnormal load- and temperature-dependence of wear under elevated temperature metallic sliding wear test conditions.     

Thermoelectric properties of p-type Pb-doped Bi85Sb15−xPbx alloys at cryogenic temperatures

In this study we have investigated the effect of the Pb on the thermoelectric propertied of Bi-Sb alloy with different Pb-content. The Pb-doped Bi₈₅Sb_15−xPb_x (x = 0, 0.5, 1, 2, 3) alloys were synthesized by mechanical alloying followed by pressureless sintering. The crystal structure was characterized by X-ray diffraction. The Seebeck coefficients, electrical conductivities, and thermal conductivities were measured in the temperature range of 77-300 K. The results show that all the Pb-doped alloys are p-type thermoelectric materials in the whole measurement temperature range. A minimum thermal conductivity of 1.7 W/mK was obtained for Bi₈₅Sb₁₂Pb₃ sample at 150 K. A maximum ZT value of 0.11, which is higher than those previous reported, was obtained for Bi₈₅Sb₁₄Pb₁ at 210 K.