A magnetic susceptibility study of emeraldine base polyaniline

Paramagnetic spins are found even in carefully synthesized samples of emeraldine base polyaniline. We report here magnetic susceptibility data up to a temperature of 475 K on a number of emeraldine base samples that were synthesized at different oxidant to monomer ratios. All the samples, although electrically insulating, show the presence of Pauli-like susceptibility. A simple albeit physically realistic model involving spin-pairs is shown to lead to such a dependence on temperature. The analysis of the data indicates that polarons in emeraldine base are created in pairs and that the intra-pair interactions encompass a broad distribution of antiferromagnetic exchange couplings.     

Polyaniline-coated iron: studies on the dissolution and electrochemical activity as a function of pH

Polyaniline coatings were electrodeposited from an oxalic acid solution onto iron and their electrochemical activity and corrosion protection properties studied as a function of pH. It was found that the coating (emeraldine salt) had a limited effect on the corrosion protection of iron in acidic solutions. However, in an alkaline borate solution, where the conducting polyaniline was converted to the emeraldine base, the coating had a clear beneficial effect on the local breakdown of iron by chloride anions; much higher pitting potentials were recorded following a 2 h immersion period for the polyaniline-coated substrate relative to the uncoated electrode. Relatively small anions, such as acetates, nitrates and borates, were transported readily across the polymer interface. However, the emeraldine base inhibited the transport of the much larger ethylenediamine tetraacetate (EDTA) species to the iron interface, preventing complexation of the iron by EDTA.     

Effective dehydrogenative oxidation of amines and alcohols via radical mechanism by nano-porous polyaniline catalysis

It has been known that doped polyaniline emeraldine salt (PANI-ES) synthesized by self-stabilized dispersion polymerization (SSDP) method has a nano-porous structure. This nano-porous conjugate polymer with a high surface area is effectively used for the dehydrogenative oxidation reaction of benzylamine and benzylalcohol with or without oxygen. The catalytic activity can be controlled by the various oxidation states of PANI. After oxidation, the resulting structure of PANI-ES is transformed into a pernigraniline base (PB). This result suggests the involvement of radical mechanism by the reversible redox properties of conjugated polyaniline.     

Chromism and molecular weight of polyaniline derivatives

The striking solvatochromic shift observed in polyaniline derivatives correlates with two solvent polarity scales, donor number (DN) and hydrogen bond acceptor scale (Taft's β-scale). The large shift is caused by conformational changes in solution that result in dramatic differences in relative molecular weight values obtained by gel permeation chromatography (MW_GPC) in different solvents. For example, for poly-o-toluidine base in the emeraldine oxidation state, a low transition energy solvent like NMP (excitonic transition, λ_max 608 nm) yields a very high molecular weight value (M_w  15,000 g mol⁻¹) whereas a high transition energy solvent like CHCl₃ (excitonic transition, λ_max 570 nm) yields an absurdly low value (M_w  650 g mol⁻¹). An absolute molecular weight value, M_w  4700 g mol⁻¹, was obtained for the first time using laser light scattering (MW_LS) suggesting that CHCl₃ promotes a highly coiled chain conformation whereas NMP promotes a more expanded, rod-like conformation. A similar trend is observed for poly-o-toluidine base in the fully oxidized pernigraniline oxidation state (Pierels transition). This suggests that even though the Pierels and excitonic transitions have different molecular origins their conformation driven solvatochromic shifts trend in a similar fashion which is different from thermochromic trends reported in previous studies.     

Investigation of interaction among polyaniline,organic acid,and water

In this work, gel permeation chromatography (GPC) and UV–vis spectroscopy are used to investigate interaction between organic acid and polyaniline (PANI) in emeraldine base (EB) form at a molecular level. Dichloroacetic acid (DCAA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) are chosen to study the changes in the GPC chromatograms and the UV–vis spectra of the diluted EB/N-methyl-2-pyrrolidinone (NMP) solutions when the acid was added in the solutions. The studies reveal that the organic acids form H-bonds with EB in an anhydrous solution. DCAA tends to form H-bonds with EB through intra-chain interactions whereas AMPSA tends to form H-bonds with EB through inter-chains. The inter-chain interaction among EB and AMPSA molecules results in the formation of clusters, which occupy a larger hydrodynamic volume and give much higher molecular weights than un-clustered EB molecules. Due to a strong affinity of AMPSA, water molecules are localized inside the clusters when water is present in the solution. Therefore, a small amount of water can rapidly initiate EB protonation (H₂O/AMPSA molar ratio > 5.0) at ambient conditions.     

Electrochemical and physical characterization of lithium ionic salt doped polyaniline as a polymer electrode of lithium secondary battery

Polyaniline films doped with lithium ionic salts such as LiPF₆ and LiBF₄ were prepared by using the electrolyte solution mixture of ethylene carbonate and dimethyl carbonate. The doping level of the polyaniline films was confirmed by X-ray photoelectron spectroscopy and dc conductivity experiments. A doping mechanism of lithium ion through the interaction with a nitrogen at imine site is proposed. Electrochemical cells of Lipolyaniline-LiPF₆ or Lipolyaniline-LiBF₄ were assembled to investigate electrical capacity and its trends over the repeated charge/discharge cycles. The capacity of Lipolyaniline cell was increased and then saturated over 15 cycles. However, it did not reach the half of theoretical capacity of polyaniline material. The mechanism of electrochemical reaction during charge/discharge process of Lipolyaniline cell is presented.     

Features of passivation, oxidation and combustion of tungsten nanopowders by air

The passivation, oxidation and combustion of tungsten nanopowders (NP) (a_s  100 nm), produced by an electrical explosion of wires (WEE) method, has been studied in air medium. The phase transformation for W nanopowders under air-oxidation was investigated. The oxidation process and an analysis of passivated powders were studied by FESEM, EDS, XPS, XRD, TEM, DTA-TGA and size distribution analysis was also observed by a video camera. After the comprehensive testing of passivated, oxidized and burned powders, a chemical process of oxidation of W nanoparticles was suggested.     

贫铀表面激光氮化层的结构和氧化动力学研究

为了研究激光氮化对金属铀表面结构和性质的影响,利用X射线衍射结合原位高温反应器,研究了不同激光氮化工艺后的贫铀表面结构,并对不同温度下UN的氧化过程进行了原位XRD实验分析,获得了相应条件下的氧化动力学曲线。结果显示,激光扫描速率对贫铀表面氮化层的相结构有显著影响,较快的扫描速率能够获得单一的UN结构,较慢的扫描速率将获得UN和U_2N_3的双相混合层。氧化动力学实验表明,表面激光氮化制备的UN层对基材有很好的保护作用,能够显著降低金属铀的氧化腐蚀速率。较低的温度下UN层的氧化非常缓慢,温度升至180℃以上时氧化速率明显加快,其氧化动力学曲线与贫铀有明显差异,文中对此现象和氮化层的氧化机制进行了分析和讨论。     

Preparation by pulsed current electrochemical polymerisation and properties of ordered comb-shaped polyaniline/carbon fibres composites for flexible supercapacitor electrodes

ABSTRACT

Flexible polyaniline/carbon fibres (PANI/CFs) nanocomposites with comb-shaped polyaniline (PANI) nanorods were fabricated by using a one-step pulse current approach. The morphology, chemical structure, crystalline structure and electrochemical performances of well-controlled PANI/CFs composites were characterised and evaluated by FE-SEM, FT-IR, Raman spectra, XRD and electrochemical working station. The electrochemical performance of comb-shaped PANI/CFs nanocomposites as supercapacitor electrodes was obtained by controlling the polymerisation time and types of current. The optimised polyaniline/carbon fibres from preparation with pulse current for 7?min (PANI/CFs-PC-7) composite showed good electrochemical performance with maximum specific capacitance of 323?F?g^?1 of sample mass at a current density loading of 1?A?g^?1, together with better rate capability, bendability and good cycling stability, which are essential in high-performance supercapacitor electrodes. In addition, the highly efficient and convenient approach paves the way to large-scale commercial applications of the flexible ordered nanocomposites.     

热轧板带生产中氧化的基本特点及麻点缺陷的成因与控制

精选了近几十年来日本等国家的学者关于钢铁材料氧化方面的部分研究进展,对相关研究的方法、内容、技术思路进行了整理,编撰成文以飨读者。侧重介绍了热轧过程中板带的氧化与缺陷控制,从板带氧化的基本性质入手,剖析了热轧过程麻点缺陷的成因与控制机理。同时,结合作者自己的研究经验与理解,对缺陷的成因也提出了不同视角的见解,供读者参考。     

An impedance response model for inhibitory effect of antibiotics on bacterial growth in biometallurgy

An impedance response model reflecting the inhibitory effect of antibiotics on bacterial growth in biomet-allurgy was established. Three inhibition parameters, i.e. the maximum amount inhibitory constant of the bacterial growth(K1), the maximum specific growth inhibitory constant(K2) and the lag time inhibitory constant(K3), were included in the model. The influence of these parameters on the response curve was discussed in detail. By fitting experimental data towards the proposed model, three growth parameters (A,μm and λ) in the presence of antibiotics were gained and compared. The results show that the growth ability of bacteria is decreased due to the influence of antibiotics. The experimental and fitted curves have goodness-of-fit in the range of 0. 987-1. 008. Moreover, the kinetic growth parameters obtained from this model are closed to those from the Logistics popular growth model.These results show that the proposed model is validity to reflect the inhibitory effect of antibiotics on bacteria.     

Research and prospect on extraction of vanadium from vanadium slag by liquid oxidation technologies

A series of innovative green metallurgical processes using novel reaction media including the NaOH/KOH sub-molten salt media and the NaOH–NaNO₃ binary molten salt medium, for the extraction of vanadium and chromium from the vanadium slag have been developed. In comparison with the traditional sodium salt roasting technology, which operates at 850 °C, the operation temperatures of these new processes drop to 200–400 °C. Further, the extraction rates of vanadium and chromium utilizing the new approaches could reach 95% and 90%, respectively, significantly higher than those in the traditional roasting process, which are 75% and approximate zero, respectively. Besides, no hazardous gases and toxic tailings are discharged during the extraction process. Compared with the conventional roasting method, these new technologies show obvious advantages in terms of energy, environments, and the mineral resource utilization efficiency, providing an attractive alternative for the green technology upgrade of the vanadium production industries.     

Characterization of roughness and pitting corrosion of surfaces modified by blasting and thermal oxidation

The blasting process generates a renewed surface on the surface of metallic biomaterials with a different topography and a different chemical composition. The impact of particles on the metallic surface increases both the surface roughness and susceptibility pitting corrosion. The aim of this work is to smoothen the sharp edges of blasted Ti6Al4V alloy surfaces by means of oxidation treatment and the evaluation of their susceptibility to pitting corrosion after this thermal oxidation. Oxidation treatments were performed at 500 and 700 °C for 1 h on samples blasted with SiO₂/ZrO₂ and Al₂O₃ particles. Compositional, microstructural and topographical characterization of the blasted surfaces were carried out by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), and atomic force microscopy (AFM). The surface reactivity and corrosion behaviour of the samples were assessed by scanning Kelvin probe (SKP) and by anodic polarization curves. The susceptibility to pitting corrosion of the Ti6Al4V blasted surfaces becomes higher as roughness increases. The oxidation treatment of the Ti6Al4V blasted surfaces causes the presence of nuclei of oxides that cover the area free of particles, especially in the samples treated at 700 °C, giving rise to a higher micro-nano roughness. The presence of the oxide, covering the blasted Ti6Al4V, decreases the surface reactivity leading to a lower passive current and wider pasivation region, decreasing the susceptibility to pitting corrosion.     

Improvement of the oxidation resistance of Tribaloy T-800 alloy by the additions of yttrium and aluminium

The microstructures and oxidation behaviour of the modified Tribaloy T-800 alloys by additions of yttrium and yttrium plus aluminium have been studied. At the presence of yttrium alone, the oxidation rate decreased, and the selective oxidation of chromium was promoted, which was related to the refinement of alloy phase size. The addition of yttrium plus aluminium further reduced the oxidation rate. The selective oxidation of chromium and aluminium were both promoted significantly. The benefits were especially pronounced at 1000 °C, with the formation of protective alumina external layer and no internal oxides, which may be detrimental to the alloy mechanical property.     

Synthesis of polyaniline/camphor sulfonic acid in formic acid medium and their blends with polyamide-6 by in situ polymerization

Blends of polyaniline doped with camphor sulfonic acid (PAni.CSA) and polyamide 6 (PA6) were prepared for the first time by the in situ polymerization of aniline in the presence of a solution of PA6 in formic acid. The conductivity values of the blends prepared by both solution cast and in situ polymerization are in the range useful for electrostatic charge dissipation materials. The conductivity of the blend containing 10% of PAni.CSA was higher, when the in situ polymerization process was used, indicating the formation of conducting pathways in a higher extension. Most of the blends prepared by the in situ polymerization presented only one irreversible peak in the cyclic voltammetry, which is attributed to the presence of defects along the PAni.CSA chains. These defects may be caused by the presence of formic acid as the solvent, as observed by Fourier transformer infrared spectroscopy of the pure polyaniline prepared in the presence of formic acid.     

TiB2涂层熔盐电沉积制备与表征

炭阴极在铝电解槽中受熔盐和铝液腐蚀而影响寿命,而TiB₂涂层是铝电解槽理想的阴极材料。本文以石墨为基体,在KF-KCl-K₂TiF₆-KBF₄熔盐中以0.4-0.7A.cm_-2^{电流密度、}700-800℃温度电沉积TiB₂涂层,通过XRD衍射仪、SEM-EDS、表面粗糙度测量仪及附着力测试仪对不同电流密度和温度下制备的涂层进行表征。结果表明：在石墨基体上可以得到均匀连贯的TiB₂涂层;增大电流密度、降低电解温度可以细化涂层晶粒,提高涂层致密性;在0.6 A.cm_-²、750℃最优电沉积条件下制得的TiB₂涂层的厚度为229 μm,择优取向为<110>,表面粗糙度为14.85 μm,涂层与石墨基体的结合力为6.39 MPa。     

Effect of applied voltage and fluoride ion content on the formation of zirconia nanotube arrays by anodic oxidation of zirconium

Anodised zirconium (Zr) foil at 20 V for 1 h in Na₂SO₄ with 0.5 wt.% NH₄F resulted in 6 μm thick anodic oxide film with nanotubular structure. At 50 V the anodic layer is consisted of an irregular inner layer with the nanotubular structure only at the top of the layer. Nonetheless, the anodic oxides formed are crystalline and photocatalytic ability of the anodic oxide was assessed by photodegradation of methyl orange.     

Resistance to oxidation and ablation of SiC coating on graphite prepared by chemical vapor reaction

A thick SiC coating was prepared on graphite by chemical vapor reaction. The coating reveals a typical crystalline structure with limited porosity and combines well with the substrate. Oxidation tests demonstrate that the coating has a weak self-healing ability at 1100 K and good self-healing ability at temperatures from 1623 to 1823 K. An oxyacetylene torch test verifies that the prepared coating can effectively protect graphite from ablation for 50 s. After the ablation test, the silica microspheres and other interesting silica structures such as microwires, microparticles, microflowers, nanowires and nanoparticles are formed at the ablation center and its surroundings.     

碳热还原结合熔盐法制备碳化钛粉末与表征

以NaCl为熔盐介质,采用锐钛矿型钛白粉和炭黑为原料,探索一种碳热还原结合熔盐法合成高纯碳化钛(TiC)的方法。借助XRD研究了反应温度和原料配比对合成碳化钛的影响,采用SEM、TEM、EDS、粒度分析仪、热力学分析等检测分析手段对合成产物的特性和过程进行分析。结果表明:相比传统的碳热还原合成碳化钛的方法,NaCl熔盐介质的引入可以有效地降低碳化钛的合成温度(从1700℃到1550℃)以及合成高纯碳化钛的时间(从10 h到3 h)。结合研究成果,提出了熔盐介质中溶解-沉淀的合成机理。     

Structure and oxidation behavior of Si-Y co-deposition coatings on an Nb silicide based ultrahigh temperature alloy prepared by pack cementation technique

In order to improve the oxidation resistance of silicide coatings on Nb silicide based alloys, Y-modified silicide coatings were prepared by co-depositing Si and Y at 1050, 1150 and 1250 °C for 5-20 h, respectively. It has been found that the coatings prepared by co-depositing Si and Y at 1050 and 1150 °C for 5-20 h as well as at 1250 °C for 5 h were composed of a thick (Nb,X)Si₂ (X represents Ti, Cr and Hf elements) outer layer and a thin (Nb,X)₅Si₃ inner layer, while the coatings prepared by co-depositing Si and Y at 1250 °C for 10-20 h possessed a thin outer layer composed of (Ti,Nb)₅Si₃ and Ti-based solid solution, a thick (Nb,X)Si₂ intermediate layer and a thin (Nb,X)₅Si₃ inner layer. EDS analyses revealed that the content of Y in the (Nb,X)Si₂ layers of all the coatings was about 0.34-0.58 at.% while that in the outer layers of the coatings prepared by co-depositing Si and Y at 1250 °C for 10-20 h was about 1.39-1.88 at.%. The specimens treated by co-depositing Si and Y at 1250 °C for 10 h were selected for oxidation test. The oxidation behavior of the coating specimens at 1250 °C indicated that the Si-Y co-deposition coating had better oxidation resistance than the simple siliconized coating because the oxidation rate constant of the Si-Y co-deposition coating was lower than that of the simple siliconized coating by about 31%. The scale developing on the Si-Y co-deposition coating consisted of a thicker outer layer composed of SiO₂ and TiO₂ and a thinner SiO₂ inner layer.