Fabrication of hierarchical PANI@W-type barium hexaferrite composites for highly efficient microwave absorption

Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo₂Fe₁₆O₂₇ is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications.     

Targeted design of polyaniline-graphene oxide,barium-strontium titanate,hard-soft ferrite,and polyester multi-phase nanocomposite for highly efficient microwave absorption

The current paper focuses on synthesizing a high-efficiency microwave absorber via incorporating the nanofillers of graphene oxide-polyaniline (GO-PANI), barium-strontium titanate (BST), and soft-hard ferrite within the polyester matrix. The nanocomposite magnets of (Ba_0.5Sr_0.5Fe₁₂O₁₉)_1-x hard/(CoFe₂O₄)_x soft (x = 0.2, 0.5, and 0.8) were prepared using sol-gel auto-combustion method. The GO-PANI and BST were successfully synthesized by in situ polymerization and improved polymerization, respectively. The phase structure, chemical structure, morphology, and microwave absorption properties of the synthesized nanocomposites were characterized by X-ray diffractometer (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM), vector network analyzer (VNA) techniques, respectively. The results showed that the synergistic effects of the combination of dielectric (BST), conductive (GO-PANI), and magnetic materials (hard-soft ferrites) provided the reflection loss values of less than ?20 dB (>99% absorption) in the X-band region. The minimum reflection loss of ?35 dB (>99.99% absorption) was obtained by the optimal formulation including (Ba_0.5Sr_0.5Fe₁₂O₁₉)_0.2 (CoFe₂O₄)_0.8, and the weight ratio of 1: 2 for both BST/soft-hard ferrite and hard-soft ferrite + BST/GO-PANI with the thickness of 1 mm. According to the results, the thickness factor plays a key role in improving the impedance matching. Consequently, the proposed nanocomposite can be employed as a novel kind of microwave absorbers with good impendence matching and high absorption.     

Effect of modified ITO substrate on electrochromic properties of polyaniline films

In this work, we report the morphological and electrochromic properties of electrochemically synthesized polyaniline (PANI) thin films on bare and modified indium–tin oxide (ITO) glass substrates. In the last case, the surface of ITO glass was covered by a self-assembled monolayer of N-phenyl-γ-aminopropyl-trimethoxysilane (PAPTS). Atomic force microscopy images and perfilometry show that smoother and thinner PANI films were grown on PAPTS-modified ITO substrates. PANI-based electrochromic devices (ECDs) were assembled by using a viscous polymeric electrolyte (PE) of LiClO₄ and polymethyl methacrylate (PMMA) co-dissolved in a mixture of propylene and ethylene carbonate. The architectural design of the devices was glass/ITO/PANI/PE/ITO/glass. A dual ECD was also prepared by collocating a poly(3-methylthiophene) (P3MT) thin film as a complementary electrochromic element. The effect of the PAPTS-modified ITO substrate is reflected in a higher optical transmittance at bleach state and a little less color change at 550 nm of PANI-based ECDs.     

Immobilization of Trametes hirsuta laccase into poly(3,4-ethylenedioxythiophene) and polyaniline polymer-matrices

The immobilization of Trametes hirsuta laccase (ThL) in the poly(3,4-ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) matrices was carried out in order to study the catalytic effect of ThL in different biocathode structures in a biofuel cell application. By using 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) as a mediator compound, the immobilized ThL in both polymer matrices, exhibited catalytic activity for the reduction of oxygen into water. The amount of ThL was adjustable in the PEDOT matrix by controlling the working parameters, such as the charge density used in the electropolymerization of EDOT monomer and the ThL concentration used in the electropolymerization electrolyte. In the PEDOT biocathode structure, the utilization of porous material as the PEDOT supporting template was studied in order to improve the current density generated per unit area/volume. Reticulated vitreous carbon foam (RVC foam) was chosen as the PEDOT supporting template material and the biocathodes were manufactured by in situ entrapment of ThL into PEDOT films polymerized on the RVC foam. These biocathodes possessed a high cathodic open circuit potential and produced a large current density, reaching 1 mA cm⁻³ at 0.45 V when 19.5 μg ml⁻¹ of ThL was used in the electrolyte. The performance of these biocathodes was extremely sensitive to variations in pH and the optimal working pH was around 4.2. The biocathode reserved 80%, 50%, and 30% of the catalytic activity after storage in a +4 °C buffer solution for 1 day, 1 week, and 1 month, respectively. The PANI matrix was prepared in a form of printable ink where ThL was in situ entrapped in the PANI matrix during the laccase activated polymerization of aniline using a chemical batch reactor method. Different amounts of the ThL-containing printable PANI ink were then applied on carbon paper and the performance of the ink was subsequently electrochemically characterized. In this way, not only two different polymer matrices, but also two different matrix manufacturing procedures could be compared.     

Synthesis and electrochemical performance of multi-walled carbon nanotube/polyaniline/MnO2 ternary coaxial nanostructures for supercapacitors

Multi-walled carbon nanotube (MWCNT)/polyaniline (PANI)/MnO₂ (MPM) ternary coaxial structures are fabricated as supercapacitor electrodes via a simple wet chemical method. The electrostatic interaction between negative poly(4-styrenesulfonic acid) (PSS) molecules and positive Mn²⁺ ions causes the generation of MnO₂ nanostructures on MWCNT surfaces while the introduction of PANI layers with appropriate thickness on MWCNT surfaces facilitates the formation of MWCNT/PANI/MnO₂ ternary coaxial structures. The thickness of PANI coatings is controlled by tuning the aniline/MWCNT ratio. The effect of PANI thickness on the subsequent MnO₂ nanoflakes attachment onto MWCNTs, and the MPM structures is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FESEM). The results suggest that appropriate thickness of PANI layers is important for building MPM ternary coaxial structures without the agglomeration of MnO₂ nanoflakes. The MPM ternary coaxial structures provide large interaction area between the MnO₂ nanoflakes and electrolyte, and improve the electrochemical utilization of the hydrous MnO₂, and decrease the contact resistance between MnO₂ and PANI layer coated MWCNTs, leading to intriguing electrochemical properties for the applications in supercapacitors such as a specific capacitance of 330 Fg⁻¹ and good cycle stability.     

Stable Langmuir-Blodgett film deposition of polyaniline and arachidic acid

An experimental study was carried out to examine the stable Langmuir-Blodgett (LB) film deposition of mixtures of polyaniline (PA) and arachidic acid (AA) at different concentration ratios, with the aim of developing a systematic methodology for the production of quality PA/AA film at the highest deposition speed. The quality of LB film was examined before, during and after the film deposition process. Images of the PA/AA composite materials at air-liquid interface, based on the Brewster angle microscopy, revealed that a 50/50 concentration ratio of PA/AA composite layer produced the best LB film structure. The feasibility of LB film deposition was determined from dynamic contact angles which were measured by a flow visualization technique. The quality of the deposited film was judged by the transfer ratio and the atomic force microscopy images. The effect of pH was also examined, and it was found that the LB film deposition for the PA/AA system could only be carried out in a narrow range of pH. It was found that the deposited LB film of the PA/AA system had a high transfer ratio and improved surface roughness at the deposition speed 30 mm/min. This deposition speed is much higher than those previously reported.     

聚苯胺—锌二次电池的充放电特性

把聚苯胺作为正极活性物质,构成聚苯胺-锌二次电池,并就其在不同电流下的充放电特性进行了初步探讨。     

碘掺杂聚苯胺催化合成乙酸叔丁酯

以碘掺杂聚苯胺为催化剂,对叔丁醇与乙酸酐之间的酰化反应进行了研究,考察了反应温度、反应时间、催化剂质量分数以及酐醇摩尔比对乙酸叔丁酯收率的影响。实验结果表明,碘掺杂聚苯胺有着较好的催化活性,当反应条件为:反应温度为55℃,反应时间为6 h,酐醇摩尔比为1∶1,催化剂质量分数为7.0%时乙酸叔丁酯的分离收率可达到87.6%,且所得产品无色透明。产品经红外光谱进行了表征。     

分子筛孔道内聚苯胺的微波合成

用微波方法在H型Y、ZSM -5和丝光沸石分子筛孔道内合成了纳米聚苯胺。NaY、ZSM-5和丝光沸石分子筛在NH4 Cl溶液中回流 ,然后经过滤、洗涤、烘干研碎 ,再于 4 50℃下培烧可得到H型Y、ZSM -5和丝光沸石。苯胺分子在正己烷溶液中扩散进入分子筛孔道 ,然后过滤、洗涤、干燥。样品经微波短时间辐射后 ,用氢氟酸除去分子筛骨架 ,再进行过滤、洗涤、干燥 ,然后进行红外光谱测试分析。结果表明 ,微波条件下苯胺可以在合适的分子筛孔道内发生聚合 ,且不同分子筛内合成的聚苯胺的结构有所差别。在分子筛孔道内 ,微波作用合成的聚苯胺与化学氧化法合成的聚苯胺具有相似的结构 ,即本征态的聚苯胺 ,且微波条件下苯胺的聚合机理为自由基聚合机理。