Doping competition of anions during the electropolymerization of pyrrole in aqueous solutions

The doping competition of anions in the electropolymerization of pyrrole was studied in aqueous solutions containing two kinds of anions with the same concentration of 0.1 mol dm^-3. The composition analysis of the polypyrrole (PPy) films prepared shows that the doping amount of p-toluene sulfonate (TsO^-) prevails over that of perchlorate, chloride and nitrate anions. The conductivity of the PPy film is close to the higher value of the two PPy films doped with a single anion. When polymerization is performed in the solution containing TsO^- and NO₃^-, TsO^-is mainly doped at Structure I, while NO₃^- is mainly at Structure II of the PPy film.     

On the Mechanism of breakdown of passivity of iron for instationary conditions

The formation of Fe²⁺-ions is studied in 0.5 M H₂SO₄ and 1 M HClO₄ during changes of the potential of passivated iron specimen with the rotating-ring-disk technique. An Fe²⁺-pulse is found during the decrease of the electrode potential serving as an indicator for the short exposure of small areas of bare metal to the electrolyte. In the presence of aggressive anions the repassivation of these defects is prevented leading to the formation of pits. The increase of the pit nucleation after potential changes coincides qualitatively with the occurrence of the Fe²⁺ transients. The adsorption mechanism may be excluded for these conditions because it postulates the action of aggressive anions for the very beginning of the breakdown process.     

The behaviour of homogeneous AlCu4 and AlZn3 in weakly acid and in O2-saturated chloride solutions

The electrochemical behaviour of a homogeneous binary Al–4wt.%Cu and of a homogeneous binary Al–3wt.%Zn alloy in weakly acid chloride solutions, in O₂-saturated chloride and citrate buffer solution and in Fe²⁺/Fe³⁺-containing citrate buffer solution has been examined using a rotating disc electrode. In weakly acid and in O₂-containing solutions the behaviour of the AlCu and of the AlZn alloy differs from the behaviour of pure Al. H⁺ -and O₂-reduction at these alloys take place at a much higher rate. Under certain conditions, the reactions are even under transport control. Obviously, this is caused by the preceding selective dissolution of Al. Clusters from residual Cu and Zn, respectively, can pierce the passive layer and act as cathodic sites. In an electrolyte, where the passive layer is not dissolved, the AlZn and the AlCu alloy behave like pure Al. This is shown with the Fe²⁺/Fe³⁺ redox system in a neutral buffer solution.     

The dynamical behavior of the electrochemical polymerization of indole on Fe in acetonitrile–water mixtures

This study reports on the stability of polyindole (PInd) films on Fe. Current oscillations emerge during the potentiostatic polymerization of indole upon its anodic oxidation on an Fe electrode in acetonitrile containing tetrabutyl-ammonium tetrafluoro-borate (N(Bu)₄BF₄). The oscillatory response of the system depends on the concentration of water, indole (Ind) and N(Bu)₄BF₄. For low concentrations of N(Bu)₄BF₄, the polymerization of Ind is possible and is enhanced in the presence of H₂O. The addition of H₂O leads also to an increase of the Fe dissolution. Increasing the concentration of Fe³⁺ ions at the Fe|polymer interface induces a mechanical instability of the polymer film. The origin of the present dynamical behavior is discussed on the basis of a breakdown and reconstruction of the polyindole film due to the accumulation of Fe³⁺ ions at the Fe|polymer interface. The kinetics of the indole polymerization coupled with the Fe electrodissolution includes the catalytic oxidation of indole by Fe³⁺ ions.     

Ultrasonic-assisted in situ synthesis and characterization of superparamagnetic Fe3O4 nanoparticles

Superparamagnetic Fe₃O₄ nanoparticles were synthesized via a modified coprecipitation method, and were characterized with X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Zeta potential and FT-IR, respectively. The influences of different kinds of surfactants (sodium dodecyl benzene sulfonate, polyethyleneglycol, oleic acid and dextran), temperatures and pH values on the grain size and properties were also investigated. In this method, Fe³⁺ was used as the only Fe source and partially reduced to Fe²⁺ by the reducing agent with precise content. The following reaction between Fe³⁺, Fe²⁺ and hydroxide radical brought pure Fe₃O₄ nanoparticles. The tiny fresh nanoparticles were coated in situ with surfactant under the action of sonication. Comparing with uncoated sample, the mean grain size and saturation magnetization of coated Fe₃O₄ nanoparticles decrease from 18.4 nm to 5.9-9.0 nm, and from 63.89 emu g⁻¹ to 52-58 emu g⁻¹ respectively. When oleic was used as the surfactant, the mean grain size of Fe₃O₄ nanoparticles firstly decreases with the increase of reaction temperature, but when the temperature is exceed to 80 °C, the continuous increase of temperature resulted in larger nanoparticles. the grain size decreases gradually with the increasing of pH values, and it remains unchanged when the PH value is up to 11. The saturation magnetization of as-prepared Fe₃O₄ nanoparticles always decreases with the fall of grain size.     

Corrosion of X65 steel in CO2-saturated oilfield formation water in the absence and presence of acetic acid

Electrochemical corrosion behavior of X65 steel in CO₂-saturated formation water in the absence and presence of acetic acid was studied by electrochemical measurements, scanning vibrating micro-electrode (SVME), localized electrochemical impedance spectroscope (LEIS) and surface analysis techniques. It is found that, when steel is immersed in formation water, the dissolution of Fe dominates the anodic process and the steel is in active dissolution state. Adsorption of intermediate product on the electrode surface results in generation of an inductive loop in the low frequency range of EIS plot. As corrosion proceeds, the concentration of Fe²⁺ in the solution increases. When the product of [Fe²⁺] × [] exceeds solubility product of FeCO₃, FeCO₃ will deposit on the electrode surface, and protects the steel substrate from further corrosion. The steel is in a “passive” state. When the electrode surface is completely covered with FeCO₃ film, the inductive loop in the low frequency range disappears. In the presence of acetic acid in formation water, the cathodic reaction will be enhanced due to the direct reduction of undissociated acetic acid. Addition of acetic acid degrades the protectiveness of corrosion scale, and thus, enhances corrosion of steel by decreasing the FeCO₃ supersaturation in solution.     

Das anodische und kathodische Verhalten des Eisens in sulfathaltigen Elektrolyten. Chaire d'Electrochimie,Faculté des Sciences,Strasbourg, France

The anodic and cathodic behaviour of iron in sulphate containing electrolytes The formation of Fe₂(SO₄)₃ on passive iron at p_H = 1 appears probable from a thermodynamical point of view. At high SO₄^2? concentrations the equilibrium system contains but low concentrations of Fe³⁺, and no Fe²⁺ ions, a fact showing the relatively elevated stability of the Fe₂(SO₄)₃ layer on passive iron. In slightly acid solution (p_H = 4) the passivity of the iron is determined by iron oxide layers. The formation of FeSO₄ from metallic iron and sulphate ions is restricted to the transpassive zone (p_H 4 to 7), in alkaline solutions even to the active zone. In the p_H region 2 to 14 the passive layer on iron has about the same composition in the systems Fe|H₂O + SO₄^2? and Fe|H₂O.     

Wolframite Conversion in Treating a Mixed Wolframite–Scheelite Concentrate by Sulfuric Acid

Complete wolframite conversion in sulfuric acid is significant for expanding the applicability of the sulfuric acid method for producing ammonium paratungstate. In this paper, the conversion of wolframite in treating a mixed wolframite–scheelite concentrate by sulfuric acid was studied systematically. The results show that the conversion of wolframite in sulfuric acid is more difficult than that of scheelite, requiring rigorous reaction conditions. A solid H₂WO₄ layer forms on the surfaces of the wolframite particles and becomes denser with increasing H₂SO₄ concentration, thus hindering the conversion. Furthermore, the difficulty in wolframite conversion can be mainly attributed to the accumulation of Fe²⁺ (and/or Mn²⁺) in the H₂SO₄ solution, which can be solved by reducing Fe²⁺ (and/or Mn²⁺) concentration through oxidization and/or a two-stage process. Additionally, the solid converted product of the mixed wolframite–scheelite concentrate has an excellent leachability of tungsten in an aqueous ammonium carbonate solution at ambient temperature, with approximately 99% WO₃ recovery. This work presents a route for manufacturing ammonium paratungstate by treating the mixed concentrate in sulfuric acid followed by leaching in ammonium carbonate solution.     

酸根离子对镨盐化学转化膜的组成及性能的影响

为探究转化液主盐酸根在成膜过程中的重要作用,采用扫描电子显微镜、能谱仪、x射线光电子谱仪结合电化学测试对两种常见酸根对应镨盐在镁合金表面形成转化膜后的形貌、成分、元素化学状态以及耐腐蚀性能进行比较,并基于酸根离子在水溶液中的反应过程分析其对转化膜成分及性能的作用机制.结果表明,以PrCl3作为主盐比以Pr(NO3)3作为主盐形成的化学转化膜更加致密;且前者受基体成分的影响较小,形成膜层的Pr、O含量(质量分数)明显高于后者;前者的耐腐蚀性能优于后者.酸根离子对转化膜成分及性能的影响主要体现在镨盐电离后在转化液中形成的相应稀酸与基体合金的作用机制及其对转化膜形成过程的影响.     

Influence of cations and anions on the formation of β-FeOOH

In the presence of cations such as Cr³⁺, Cu²⁺ and Ni²⁺, and anions such as and , precipitation of β-FeOOH from Fe³⁺-solution containing Cl⁻ by hydrolysis have been investigated by means of X-ray diffraction technique (XRD), Mössbauer spectroscopy (MS) and transmission electron microscopy (TEM). XRD peaks of β-FeOOH were broadened when the cations were added as sulfates, and this tendency for Cr³⁺ was significantly observed. When the cations were added as nitrates, there was no significant change in XRD peaks. Inductively coupled plasma (ICP) analysis showed that only Cr added as sulfate was contained in β-FeOOH. Ni and Cu added as sulfates, and any cations added as nitrates were not contained in it. When β-FeOOH was synthesized with Na₂SO₄, the XRD peaks were broadened. XRD-peak broadening was mainly caused by the coexistence of ion. The incorporation of cations in β-FeOOH is affected by coexistent anions, and the XRD-peak broadening is caused by not only cations but also anions. This behavior has been discussed in association with the stability of Fe³⁺-complexes in the solution.     

Synthesis and characteristics of poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe3O4 nanocomposite

Poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe₃O₄ nanocomposite was successfully synthesized by an in situ polymerization of 1-(2-carboxyethyl) pyrrole in the presence of synthesized Fe₃O₄ nanoparticles. Evaluation of structural, morphological, electrical and magnetic properties of the nanocomposite was performed by XRD, FT-IR, TEM, TGA, magnetization and conductivity measurements, respectively. XRD analysis reveals the inorganic phase as Fe₃O₄ and TGA shows about 90 wt% loading of Fe₃O₄ in the nanocomposite. FT-IR analysis indicates a successful conjugation of Fe₃O₄ particles with polypyrrole acetic acid. Magnetization measurements show that polypyrrole acetic acid coating decreases the saturation magnetization of Fe₃O₄ significantly. This reduction has been explained by the pinning of the surface spins by the possible adsorption of non-magnetic ions during the polymerization process. The conductivity and dielectric permittivity measurements strongly depend on the thermally activated polarization mechanism and thermal transition of PPyAA in the nanocomposite structure. Large value of dielectric permittivity (?′) of the nanocomposite at lower frequency is attributed to the predominance of species like Fe²⁺ ions and grain boundary defects (interfacial polarization).     

铁闪锌矿的Leptospirillum ferrooxidans菌浸出及电化学性能(英文)

采用纯种L.ferrooxidans菌研究矿浆浓度、pH及外加Fe3+离子对铁闪锌矿生物浸出的影响。结果表明,锌的浸出率随着矿浆浓度的降低而增加。在生物浸出过程中调节pH值到1.6对铁闪锌矿的溶解有促进作用。外加Fe3+离子加速了铁闪锌矿的生物浸出,但当外加Fe3+离子浓度超过2.5g/L时,促进作用变弱。这是因为高浓度的Fe3+离子会对细菌生长产生抑制作用且促进黄钾铁矾的生成。在L.ferrooxidans菌存在条件下,利用电化学测试方法进一步了解有、无外加Fe3+离子时铁闪锌矿的溶解过程。实验数据表明,外加Fe3+离子可以增加腐蚀电流密度,有利于锌的提取。交流阻抗谱表明,添加Fe3+离子后没有改变反应过程的控制步骤。     

Crystallization and infrared radiation properties of iron ion doped cordierite glass-ceramics

Heterogeneous ion solution is an important method to improve the wanted property of polycrystalline materials. In this paper, for the purpose of infrared radiation property modification, different contents Fe₂O₃ were doped in MgO-Al₂O₃-SiO₂ system glasses. The effects of Fe₂O₃ doping on nucleation mechanism, crystallization behaviors and especially infrared radiation properties of this cordierite-crystalline based glass-ceramics were systematically investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results show that, the doping of iron ion can promote the phase separation of this magnesium aluminosilicate glass, and therefore change the crystallization mechanism of this glass from surface crystallization to bulk crystallization. The iron ion incorporates into the crystal structure of cordierite by mean of substituting Mg²⁺ in M site. The substitution of Fe³⁺ to Mg²⁺ can form the vacant site of Mg²⁺ cations. For the effects of lattice distortion, impurity and vacancy defects which caused by the incorporation of iron ion, the infrared radiation performance of cordierite based glass-ceramics can be improved effectively.     

Na2S选择性浸出铜转炉烟灰中的砷及Fe2(SO4)3稳定化砷(英文)

研究砷(As₂O₃)的Na₂S碱性浸出,以及用Fe₂(SO₄)₃沉淀砷。采用基于中心组合设计的响应面法对相关因素的影响进行定量和定性分析,提出用于参数优化的统计模型。结果表明,在Na₂S浓度100 g/L,固液比0.163 g/mL和温度80℃的最优预测条件下,89%的砷可从烟灰中去除。研究发现,固液比和Na₂S浓度是影响浸出过程的显著因素。在沉淀过程中,当pH为4.8、Fe³⁺与砷的摩尔比和H₂O₂与砷的摩尔比分别为5:1和4:1时,浸出液中99.93%以上的砷以无定形砷酸铁的形式被除去。Fe³⁺与砷的摩尔比和pH值为最显著因素,而且他们之间的相互作用也是显著的。     

Intermolecular interactions in the structure of new molecular semiconductor [Pd(dddt)2]2CF3SO3

An X-ray structural investigation of a new molecular semiconductor, [Pd(dddt)₂]₂CF₃SO₃ (1), where dddt²⁻ is 5,6-dihydro-1,4-dithiin-2,3-dithiolate, is made. Crystal data of 1:a = 6.521(7) Å, b = 8.354(4) Å, c = 16.113(6) Å, α = 87.12(4)°, β = 85.51(6)°, γ = 67.94(7)°, V = 811(1) ų, triclinic, space group P. Crystal structure 1 is characterized by layers of [Pd(dddt)₂]^1/2+ radical cations, with [CF₃SO₃]⁻ anions located between them. In these layers, [Pd(dddt)²]^1/2+ cations form dimers with strongly shortened intermolecular contacts Pd…Pd 3.031 (2) Å. The [CF₃SO₃]⁻ anion in the structure of 1 is disordered.     

Hydro-chemical conversion of galena in FeCl3-KCl solution

The behaviours of complexation and dissolution of PbCl₂ on the surface of galena were investigated to explore the process of hydro-chemical conversion of galena (PbS) in chloride media. By means of solution chemistry calculation, the production and dissolution of the products PbCl₂ were studied. And the passivation of the galena was studied by Tafel curve. The results show that PbCl₄²⁻ is the main form of PbCl₂ presented in the saturated potassium chloride (KCl) solution. The PbCl₂ crystal is easy to precipitate when the total concentration of chloride ion ([Cl⁻]_T) is equal to 0.92 mol/L, and it is inclined to dissolve when [Cl⁻]_T is more than 0.92 mol/L. The chloride complexing reaction rate strongly depends on the Fe³⁺ion concentration when it is less than 6×10⁻⁴mol/L, while passivation occurs on the surface of the electrode when Fe³⁺ concentration is larger than 6×10⁻⁴mol/L. The reaction rate increases obviously when KCl is added, since the activity of Cl⁻ increases; thus accelerates the dissolution of PbCl₂.     

Effect of exchangeable cations on the physicochemical properties of smectite

The effect of exchange cations (Mⁿ⁺: Li⁺, Na⁺, K⁺, NH ₄ ⁺ , Ca²⁺, Mg²⁺, Fe³⁺, and Al³⁺) and thermal treatment on the physicochemical properties of smectite was investigated. Before thermal treatment, unheated (25°C) Mⁿ⁺-smectite showed increased d ₀₀₁ spacing upon glycol solvation; after heating at 300°C or above (400°C), d ₀₀₁ spacing upon glycol solvation of Al-, Fe-, Mg-, Li-smectite decreased and reached 10 Å. However, an increase in d ₀₀₁ of Ca²⁺-, Na⁺-and NH ₄ ⁺ -smectite upon glycol solvation indicated that d ₀₀₁ varied with the nature of exchangeable cation and the temperature of heating. The results generally suggested the following: d ₀₀₁ of homoionic smectite before and after heating at various temperatures depended upon the nature of exchangeable cation. The cation exchangeable capacities (CECs) and the BET surface areas (S_BETs) were functions of the type of exchangeable cations, since S_BETs drop off in the following order: Na⁺-smect > Ca²⁺-smect > Mg²⁺-smect > NH ₄ ⁺ -smect > Li⁺-smect > K⁺-smect > Fe³⁺-smect > Al³⁺-smect. Finally, we have noted good progress in the exchangeable properties of synthesized clay in comparison with the Na homoionic smectite form, except for K homoionic clay, which have the lowest CECs, S_BETs, and consequently, the lowest exchangeable properties.     

Magnetic properties of ndfeb thin films grown by a pulsed laser deposition

High energy product Nd₂Fe₁₄B films were grown onto Si(100) substrate by a KrF pulsed laser ablation using the targets of Nd_xFe_90.98-xB_9.02 (x=17.51~27.51). The films of the Nd₂Fe₁₄B single phase did not exhibit a preferred orientation. However, [221], [006] and [222] axes were prominent for the films grown at the substrate temperature above 680°C by using the target of Nd_27.51Fe_63.47B_9.02. This condition provided superior magnetic properties along the out-of-plane direction of films resulting in the magnetic properties of 4πM_s≅7 kG, 4πM_r≅4 kG, and iH_c≅1000 Oe. The deposition rate wasn’t influenced much by changing the substrate temperature (T_s), but it increased linearly by increasing the beam energy density. The beam density of 3 J/ cm² created the optimal condition for the highest 4πM_r andiH _c simultaneously. The higher content of Nd induced a higher coercivity and concentration of 4πM_r at the same time due to the finer grain size without a prominent change in 4πM_s. The films of x=27.51 exhibited a grain size of less than 12 nm while that of x= 17.51 produced a size about 15 nm.     

Influence of Cu on nanostructure of Fe3O 4 particles

Cu is effective on the refinement of Fe₃O₄ rust particles but its mechanism is not clarified. In this study, the influence of Cu on the nanostructure of Fe₃O₄ particles was investigated through a detailed analysis of the characteristics of the artificially synthesized Fe₃O₄ particles formed with Cu²⁺ by various means. X‐ray absorption fine structure analysis showed that Cu is substituted for octahedral Fe and exists as Cu_xFe_(3‐x)O₄ in Fe₃O₄. The first‐principle calculation showed that lattice strain resulted around the substituted Cu. These results suggest that this lattice strain around substituted Cu inhibited the lattice growth and contributed to the refinement of Fe₃O₄ particles.