Properties and structural investigation of one-dimensional SAM-ATP/PANI nanofibers and nanotubes

Core–shell one-dimensional (1D) conducting nanofibers were prepared by the encapsulation of attapulgite (ATP) template with polyaniline (PANI) after the surface modification with APTES to form a SAM on the surface of ATP needle-shaped particle (SAM-ATP), and the 1D PANI nanotubes were obtained by etching the SAM-ATP template with HCl/HF solution after the PANI layers were coated onto the SAM-ATP template. The room temperature conductivity and average specific capacitance of 1D 18.7 wt% SAM-ATP/PANI nanofibers (2.21 S/cm and 418 F/g) were increased compared with pure PANI (0.47 S/cm and 342 F/g) and PANI nanotubes (0.01 S/cm and 282 F/g). The conductivity stability and thermal stability of 1D 18.7 wt% SAM-ATP/PANI nanofibers were clearly improved. These trends were accompanied by significant structural changes as evidenced by TEM, FTIR, and XRD studies.     

Preparation and characterization of polyindole nanofibers by electrospinning method

Polyindole nanofibers with diameter ranging from 770 nm to 250 nm were firstly fabricated by an electrospinning method. Chemically synthesized polyindole was dissolved in acetonitrile to make polymer solution under ultrasonification. Electrospinning of polyindole was then carried out under electrical field strength of 1.0 kV/cm. The electrospun polyindole nanofibers exhibited smooth surface and the diameter of the fibers was ranged from 768 nm to 255 nm. The specific surface areas of polyindole nanofibers were ranged from 32 to 65 m²/g, which is significantly higher than that of the powder with same volume. The electrical conductivity of the polyindole nanofibers can reach 0.24 S/cm, which is much higher than that of the polyindole film. The polyindole nanofibers showed high thermal stability with glass transition temperature (T_g) around 132 °C and melting point (T_m) around 239 °C. The crystallinity of polyindole nanofibers was higher than that of polyindole film due to the formation of ordered molecule chains during the electrospinning. Cyclic voltammetry test results revealed that the doping and de-doping processes of BF₄⁻ ions were reversible and polyindole nanofibers had high electronically activity in the electrolytic solution containing LiBF₄.     

Facile synthesis of polyaniline nanofibers using pseudo-high dilution technique

A new approach for the synthesis of polyaniline nanofibers under pseudo-high dilute conditions in aqueous system has been developed. High yield nanoscale polyaniline fibers with 18–110 nm in diameter are readily prepared by a high aniline concentration 0.4 M oxidation polymerization using ammonium persulfate (APS) as an oxidant in the presence of hydrochloric acid (HCl), perchloric acid (HClO₄), (1S)-(+)-10-camphorsulfonic acid (CSA), acidic phosphate PAEG120 (PA120) and sulfuric acid (H₂SO₄) as the dopants. The novel pathway always produces polyaniline nanofibers of tunable diameters, high conductivity (from 10⁰ to 10¹ S/cm) and crystallinity.     

Preparation and characterization of graphene nanosheets/poly(3-hexylthiophene) thermoelectric composite materials

Graphene nanosheets/poly(3-hexylthiophene) (GNs/P3HT) composites were prepared by oxidative polymerization of 3-hexylthiophene in a GNs dispersed chloroform solution. The phase composition of the composite materials was analyzed by X-ray diffraction and Fourier transform infrared spectra. The thermoelectric properties of the cold pressed composite pellets with different GNs loadings were measured at room temperature. As the GNs loading increased from 0 to 30 wt.%, the electrical conductivity of the composites dramatically increased from ∼10⁻⁶ to ∼1.2 S/cm while the Seebeck coefficient slightly increased from 33.15 to 35.46 μV/K. The highest power factor (∼0.16 μW m⁻¹ K⁻²) was obtained in the 30 wt.% GNs/P3HT composite material.     

Polyaniline nanofibers synthesized by rapid mixing polymerization

Polyaniline (PANI) nanofibers were chemically synthesized by a rapid mixing polymerization with aniline concentration of 0.5 M. The time needed for the formation of PANI in the reaction medium decreased with increase of the molar ratio of ammonium peroxydisulphate (APS)/aniline and temperature. Morphological study showed at the end of polymerization, only the ones prepared with low molar ratio of APS/aniline (e.g. 0.25 and 0.50) and temperature (e.g. 0 and 20 °C) are nanofibers with diameters of ∼50 nm, though the initially formed products are all nanofibers, while with increasing of molar ratio of APS/aniline to 1 and temperature to 20 °C or higher, agglomerates of PANI nanofibers with diameters of ∼100 nm and larger sized irregular particles were formed. The yield of PANI nanofibers was in the range of 13.4–42.3%, which is favorable for mass production of PANI nanofibers. Conductivity measurement, UV–vis and FTIR spectra were performed to characterize the products. The conductivity of the PANI nanofibers increased with molar ratio of APS/aniline at low temperature, while decreased at higher temperature, which might be resulted from the degradation of PANI molecules in the presence of more APS molecules at higher temperature.     

Electrically conducting nylon 6,6–polyaniline short composite fibres synthesised by the solvent coagulation method

Polyaniline (PANI) was blended with nylon 6,6 in concentrated H₂SO₄ and HCl solutions. The solvent coagulation method was utilised to extract short composite fibres of a centimetre in length. A solution of n-butyl acetate, acetone, toluene, 1 μM HCl and chloroform were used as coagulating bath to extract the fibres. The diameters of the fibres ranged from 200 to 300 nm, while the length measured approximately 1 cm, as determined from Scanning Electron Microscopy (SEM). The electrical conductivity varied from 10⁻⁴ to 10⁻² S/cm for different mass fractions of PANI (x_PANI) in the composite fibres. The percolation threshold was reached at x_PANI values between 0.15 and 0.2, and further addition of PANI resulted in saturation of the conductivity of the composite fibre. To observe the effect of MWCNTs on the electrical conductivity of the nylon–PANI fibres, 0.04 g, 0.08 g, 0.4 g and 0.5 g of MWCNTs (1, 2, 10, 12.5 weight percentage, respectively) were added into the nylon–PANI solution and were extracted as fibres in the aforementioned solvents. The electrical conductivity of the short fibres increased by an order of magnitude (0.372 S/cm at 12.5 wt.%) when they were extracted in the presence of the MWCNTs. PANI doped in concentrated HCl exhibited an electrical conductivity of 4.46 S/cm.     

Assessing the efficiency of galvanic cathodic protection inside domestic boilers by means of local probes

The efficiency of cathodic protection implemented through magnesium anodes has been investigated inside a 100 L domestic boiler, as a function of temperature (18-60 °C) and of water conductivity (50-500 μS/cm). Continuous monitoring of potentials and partial currents, corresponding to all metallic parts of the boiler and to six local probes, installed on the critical points of the tank, has been carried out. Cathodic protection is more efficient increasing water conductivity (500 μS/cm) and further low conductivities (50 μS/cm) tend to increase the probability of tank failure in a relatively short time, even in presence of magnesium anodes protection.     

Synthesis and characterization of cobalt-free Ba0.5Sr0.5Fe0.8Cu0.2O3−δ perovskite oxide cathode nanofibers

The cobalt-free perovskite-oxide, Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (BSFC) is a very important cathode material for intermediate-temperature proton-conducting solid oxide fuel cells. Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ nanofibers were synthesized for the first time by a sol-gel electrospinning. Process wherein a combination of polyvinylpyrrolidone and acetic acid was used as the spinning aid and barium, strontium, iron and copper nitrates were used as precursors for the synthesis of BSFC nanofibers. X-ray diffraction studies on products prepared at different calcination temperatures revealed a cubic perovskite structure at 900 °C. The temperature of calcination has a direct effect on the crystallization and surface morphology of the nanofibers. High porosity, and surface area, in addition to an electrical conductivity of 69.54 S cm⁻¹ at 600 °C demonstrate the capability of BSFC nanofibers to serve as effective cathode materials for intermediate-temperature solid oxide fuel cells.     

Bridge effect of silver nanoparticles on electrochemical performance of graphite nanofiber/polyaniline for supercapacitor

In this work, silver (Ag) nanoparticles were deposited onto graphite nanofibers (GNFs) by chemical reduction while polyaniline-coated Ag-GNFs (Ag-GNFs/PANI) were prepared by in situ polymerization. The effect of the Ag nanoparticles intercalated in composite interface on the electrochemical performances, such as CV curve, charge–discharge behaviors, and specific capacitance of the GNFs/PANI was investigated. It was found that nano-sized Ag particles could be uniformly deposited onto the GNFs and that Ag-GNFs were successfully coated by PANI via in situ polymerization. According to the charge–discharge curves, the highest specific capacitance (212 F/g) of the Ag-GNFs/PANI was obtained at a scan rate of 0.1 A/g, as compared to 153 F/g for GNFs/PANI and 80 F/g for PANI. This indicated that the Ag nanoparticles that were deposited onto the GNFs led to a bridge effect between GNFs and PANI to improve the charge transfer, which resulted in the enhanced electrochemical performances of the composites due to a synergistic effect.     

High-rate deposition of amorphous and nanocomposite Ti-Si-C multifunctional coatings

Amorphous (a) and nanocomposite Ti-Si-C coatings were deposited at rates up to 16 μm/h by direct current magnetron sputtering from a Ti₃SiC₂ compound target, using an industrial pilot-plant system, onto high-speed steel, Si, and SiO₂ substrates as well as Ni-plated Cu cylinders, kept at a temperature of 200 or 270 °C. Electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses showed that TiC/a-C/a-SiC nanocomposites were formed consisting of textured TiC nanocrystallites (nc) embedded in a matrix of a-C and a-SiC. Elastic recoil detection analysis showed that coatings deposited at a target-to-substrate distance of 2 cm and an Ar pressure of 10 mTorr have a composition close to that of the Ti₃SiC₂ compound target, as explained by ballistic transport of the species. Increased target-to-substrate distance from 2 cm to 8 cm resulted in a higher carbon-to-titanium ratio in the coatings than for the Ti₃SiC₂ compound target, due to different gas-phase scattering properties between the sputtered species. The coating microstructure could be modified from nanocrystalline to predominantly amorphous by changing the pressure and target-to-substrate conditions to 4 mTorr and 2 cm, respectively. A decreased pressure from 10 mTorr to 4 or 2 mTorr at a target-to-substrate distance of 2 cm decreased the deposition rate up to a factor of ~ 7 as explained by resputtering and an increase in the plasma sheath thickness. The coatings exhibited electrical resistivity in the range 160-800 μΩ cm, contact resistance down to 0.8 mΩ at a contact force of 40 N, and nanoindentation hardness in the range of 6-38 GPa.     

Synthesis of highly conductive poly(3,4-ethylenedioxythiophene) fiber by simple chemical polymerization

Poly(3,4-ethylenedioxythiophene) (PEDOT) fiber was chemically synthesized by the polymerization of 2,5-dihalo-3,4-ethylenedioxythiophene in the presence of BF₃ without a template. The resulting conductive PEDOT fiber exhibited conductivity in the range of 150–250 S/cm (pressed powder pellet). The thermal stability of PEDOT was also improved and UV-spectroscopy analysis of a film exhibited a strong absorption band at 460 nm. The well-defined needle-shaped fibers of PEDOT were examined by SEM, and the average length and diameter of the fibers were 10 and 0.4 μm, respectively.     

Fluorescence studies of electrospun MEH-PPV/PEO nanofibers

We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2′-ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630 nm blue-shifts ∼45 nm, whereas the main emission peak around 590 nm blue-shifts ∼15 nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix.     

Conductive and transparent Bi-doped ZnO thin films prepared by rf magnetron sputtering

Bi-doped ZnO thin films were grown on glass substrates by ratio frequency (rf) magnetron sputtering technique and followed by annealing at 400 °C for 4 h in vacuum (~ 10^− 1 Pa). The effect of argon pressure on the structural, optical, and electrical properties of the Bi-doped films were investigated. The XRD patterns show that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. Some excellent properties, such as high transmittance (about 85%) in visible region, low resistivity value of 1.89 × 10^− 3 W cm and high carrier density of 3.45 × 10²⁰ cm^− 3 were obtained for the film deposited at the argon pressure of 2.0 Pa. The optical band gap of the films was found to increase from 3.08 to 3.29 eV as deposition pressure increased from 1 to 3 Pa. The effects of post-annealing treatments had been considered. In spite of its low conductivity comparing with other TCOs, Bi-doping didn't appreciably affect the optical transparency in the visible range of ZnO thin films.     

Pitting corrosion of titanium by a freshwater strain of sulphate reducing bacteria (Desulfovibrio vulgaris)

Pitting corrosion of titanium (ASTM Grade 2) was investigated by exposing coupons (2.0 × 1.5 cm) to a semi-continuous culture of sulphate reducing bacteria (SRB) strain Desulfovibrio vulgaris. The coupons were exposed to the SRB culture for 90 days along with a control set in uninoculated medium. During the course of the experiment sulphide was estimated at intervals of 4 days and the concentrations ranged from 0.2 to 0.4 mM in the bulk medium. Epifluorescence microscopy revealed extensive colonization by the SRB and the cell count ranged from 10⁴ to 10⁵ cells cm⁻². Optical microscopy revealed the presence of two types of pits; large hemispherical pits of ∼2 mm diameter and many micropits. Pitting was not observed in control coupons exposed to SRB free medium. SEM and CSLM pictures showed the corroded titanium surface with several micropits, along with typical rod shaped SRB cells in the pitted regions. EDAX analysis revealed peaks for Ti, O, N, C, Fe and P in the pitted region. XPS data showed clear peaks for titanium sulphur (three states) and phosphorous. The study reveals that at room temperature and in the presence of 0.2-0.4 mM of sulphide, as well as the putative phosphine, SRB can promote pitting corrosion of titanium by formation of titanium sulphide.     

Temperature and dew point dependent segregation of phosphorus and sulfur in Fe-Mn-P-S model alloy

The dependence of surface segregation of P and S, on temperature and dew point of the annealing atmosphere was studied for an Fe-1Mn-0.02P-0.008S (all in wt.%) model alloy. The specimens were annealed for 1 min within a temperature window of 400 to 800 °C, in N₂-5%H₂ gas atmospheres with a wide range of dew points − 80 to 0 °C. Surface analyses were carried out by using XPS and FE-SEM. At the dew points − 80 and − 40 °C segregation of P was observed at 400 and 600 °C but S segregation occurred only at 800 °C. Phosphorus accumulation increases significantly with increase of dew point and, moreover, at the higher dew point, P replaces S at 800 °C.     

Formation and characterization of aluminide coatings on alloy 800 substrate

Fe-Ni-Cr based Alloy 800 substrates were pack aluminized at 1273 K for 8 hours in argon atmosphere. The cross-section of aluminized substrates indicated formation of multilayer of aluminides as revealed by microscopy, electron probe microanalysis and X-ray diffraction. The outermost layer (~ 150 μm) was found to consist of FeAl + Fe₂Al₅ type phases, while the adjoining layer (~ 250 μm) was composed of an FeAl type phase. The innermost layer (~ 60 μm), which was a solid solution zone, was found to consist of ~ 43 at.% Fe, 38 at.% Cr, 11 at.% Ni containing about 6 at.% Al. In microhardness test, a hardness variation of 213 to 1098 Knoop hardness number along the cross-section was obtained. Scratch test along the cross-section at load levels ranging from 0.9 to 10 N with a loading rate of 30 N/min showed a maximum penetration depth of 12 μm indicating a good adherence of aluminide coatings.     

Line-width of ion beam-modified polystyrene by negative carbon ions for fine adhesion pattern of mesenchymal stem cells

The fine adhesion pattern of mesenchymal stem cells (MSCs) on polytyrene (PS) was investigated by carbon negative-ion implantation with decreasing the implanted line-width. The carbon negative ions with certain ion fluence of 3 × 10¹⁴ ions/cm² and ion energy of 10 keV were implanted through the ridge-pattern mask having slit aperture from 0 to 40 μm. After 2 days of culture of rat MSCs on the modified PS, the MSCs elongated and adhered along the implanted region due to the lowering of contact angle after the ion implantation. The cells stained with fluorescent dye of DAPI were used to observe the position of cell adhesion on the modified line-width. By decreasing the line-width from 40 to 3 μm, we found the adhesion arrangements from the gathering cells to the individual cells. The most probable adhesions of the gathering cells in a lateral direction of the line were found at a wider width than 20 μm, while that of the individual cells were found at a width of about 10 μm. The adhesion arrangement of individual cells helped to increase the distances of cell-to-cell due to the elongated adhesion of cells along the narrowed implanted line-width. The number of adhered cells decreased with a decrease in the implanted line-width, and almost all of them had the same direction of their nucleus at the narrower line-width than 12 μm. Therefore, the controls of the individual cell-adhesion arrangement in a line and the nuclei direction could be achieved by decreasing the implanted line-width to about 10 μm.     

Hydrogen permeation behavior in pure nickel implanted with phosphorus, sulphur and their mixture

The entry and transport of hydrogen in phosphorus (P)-, sulphur (S)- and their mixture (P + S)-implanted nickel specimens with a fluence range of 1 × 10¹⁵ to 1 × 10¹⁷/cm² have been investigated using an electrochemical permeation technique and etching treatment (0.2% HF solution). From the hydrogen permeation transients obtained, the effective hydrogen concentration (C_H), apparent hydrogen diffusion coefficient (D_lag) and breakthrough time (t_lag) were estimated by using the time lag method in addition to the steady state permeation current density (P_∞). It was found that at a fluence of less than 1 × 10¹⁶/cm² almost all hydrogen permeation transients of the implanted nickel specimens were affected by the defects (vacancy, compressive stress and so on) generated during ion implantation process. At a high fluence of 1 × 10¹⁷/cm² the hydrogen permeation transient had a specific behavior because of the formation of amorphous phase for P, the structure change from fcc-structure to bcc-structure for S and both of them for the mixture (P and S). However, a synergistic effect of P and S was not observed on the hydrogen permeation transient. The behavior of these parameters depending on fluence and implanting element was discussed in terms of an amount of hydrogen entry site, the degree of defects, the properties of amorphous phase and structure and so on.     

Effects of sputtering pressure and post-metallization annealing on the physical properties of rf-sputtered Y2O3 films

Y₂O₃ thin films were prepared by rf-sputtering under various sputtering pressures at room temperature. Spectroscopic ellipsometer, X-ray diffraction and semiconductor parameter analyzer were used to characterize the studied films. The results show the crystallinity and leakage current density of the films improved with decreasing sputtering pressure. The effects of post-metallization annealing (PMA) on optical, structural and electrical properties of the films were also evaluated. It is found that PMA can significantly enhance the electrical performance of Y₂O₃ film, and the lowest leakage current is found to be 1.54 × 10⁻⁸ A/cm² at 1 MV/cm for the samples treated at 350 °C for 30 min. The leakage current mechanisms were discussed as well, which reveals that space charge limited current dominates the as-deposited films while Schottky mechanism describes the PMA treated ones well.     

Synthesis and characterization of sol-gel derived gallium-doped zinc oxide thin films

Gallium-doped ZnO (GZO) semiconductor thin films were prepared by a sol-gel spin coating process. The effects of Ga dopant concentrations on the microstructure, electrical resistivity, optical properties, and photoluminescence (PL) were studied. XRD results showed that all the as-prepared GZO films had a wurtzite phase and a preferred orientation along the [0 0 2] direction. ZnO thin films doped with Ga had lower electrical resistivity, lower RMS roughness, and improved optical transmittance in the visible region. The lowest average electrical resistivity value, 2.8 × 10² Ω cm, was achieved in the ZnO thin films doped with 2% Ga, which exhibited an average transmittance of 91.5%. This study also found that the optical band gap of Ga-doped films was 3.25 eV, slightly higher than that of undoped samples (3.23 eV), and the PL spectra of GZO films showed strong violet-light emission centers at about 2.86 eV (the corresponding wavelength of which is about 434 nm).