Fourier transform infrared study of electrochemically prepared polythienylene films with varying doping levels

Fourier transform infrared (FTIR) spectra of electrochemically prepared polythienylene films doped with various dopant species at varying doping levels have been obtained. These doped polythienylene films exhibit four conspicuous absorption bands at 1330 - 1310, 1200, 1220 - 1080 and 1030 - 1020 cm^?1 made IR active and/or given prominent intensity due to the doping, independent of the difference in dopant species and contents. On the other hand, the bands specific to each dopant species are distinctly observable for the heavily-doped polythienylene films. Some typical band profiles in accordance with varied doping levels will be presented.     

13C NMR spectrum analysis of electrochemically prepared poly(3-methylthienylene) films

The ¹³C NMR spectrum analysis of electrochemically prepared poly(3-methylthienylene) films has been investigated. Both a film doped with ClO₄ ions (P3MT-ClO₄) and an undoped film (P3MT₀) give only two distinct absorption bands through the electrochemical reduction of P3MT-ClO₄. These distinct bands are definitely attributable to the methyl group (upper field) and the thiophene ring (lower field), respectively, and are characteristic of well-defined poly(3-methylthienylene). The correlation between conductivity and ¹³C NMR spectra will be discussed.     

Electrical and optical properties of electrochemically prepared polyselenophene film

The electrical, optical and magnetic properties of flexible shiny films of polyselenophene obtained by the electrochemical method are studied. The electrical conductivity of doped polyselenophene is found to be much lower than that of polythiophene and polypyrrole, which is consistent with its relatively wider ESR linewidth even after doping. The photovoltaic effect is also observed in this polymer and discussed in comparison with optical absorption spectra.     

Temperature dependence of mechanical properties of electrochemically prepared polypyrole film

The mechanical and thermal properties of an electrochemically prepared polypyrrole film are studied. The Young's modulus of this film decreases slightly below 140 °C and steeply above 140 °C, while the tensile strength decreases linearly with increasing temperature. The inflection point of the Young's modulus exists at around 140 °C, which coincides with the temperature at the main peak of the temperature variation of the mechanical loss factor, tan σ. It seems that the main peak of tan σ results from the glass transition of this polymer. The film has a very high thermal diffusivity constant of 0.028 cm²/s at room temperature.     

19F NMR of antimony and arsenic pentafluoride-graphite derivatives

¹⁹F NMR results are reported on first stage SbF₅-GIC and second stage AsF₅-GIC as a function of temperature. Above a “cutting temperature”, we postulate the existence of two fluorine population at least, which we have tried to identify on our spectra according to a pentafluoride oxidation reaction. The results are correlated with a charge transfer coefficient evolving with temperature, and are discussed in comparison with other experimental results.     

Quantitative analysis of iron oxides using Fourier transform infrared spectrophotometry

In this study, a systematic approach based on the application of Fourier transform infrared spectrophotometry (FTIR) was taken, in order to quantitatively analyze the corrosion products formed in the secondary cycle of pressurized water reactors (PWR). Binary mixtures of iron oxides were prepared with known compositions containing pure commercial magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃), and hematite (α-Fe₂O₃) for calibration purposes. Calcium oxide (lime) was added to all samples as a standard reference in obtaining the calibration curves. Using regression analysis, relationships were developed for intensity versus concentration for absorption bands corresponding to each of the phases in their corresponding FTIR spectrum. Correlation coefficients, R², of 0.82, 0.87, and 0.86 were obtained for maghemite-magnetite, hematite-magnetite, and hematite-maghemite systems, respectively. The calibration curves generated were used to quantify phases in multi-component unknown field samples that were obtained from different components (moisture separators, condensers, and high- and low- pressure heaters) of the two units (units 1 and 2) of the secondary cycle of the Comanche Peak PWR.     

Surface plasmon study of electrochemically prepared polymers: Polyazulene

The work reported here shows that by using a modified gold working electrode, the surface plasmon technique can successfully be used to obtain information on the optical constants and the film thickness of electropolymerized films. Polyazulene films deposited at three different surface charge densities are investigated in the oxidized and corresponding reduced forms. Our result shows that the refractive index, and hence the dielectric constant at 632 nm, is complex, the imaginary part being larger for the oxidized form compared to that for the corresponding reduced form. Thickness determination shows that its relationship with the amount of charge is qualitatively similar to that reported for polypyrrole. The film thickness measurement reveals a shrinkage in going from the oxidized to the reduced form as the counter anions are removed. Our study, therefore, shows that the surface plasmon technique can be used to probe ionic processes.     

Morphology and preferred orientation of Y2O3 film prepared by high-speed laser CVD

Yttria (Y₂O₃) films were prepared at high deposition rates of up to 83 nm/s (300 μm/h) by laser chemical vapor deposition (LCVD) using an Y(dpm)₃ precursor. The effects of deposition conditions, mainly total gas pressure and laser power, on morphology, deposition rate and preferred orientation were studied. Plasma was produced around the substrate over a critical laser power resulting in significant increases in deposition temperature and deposition rate. The high deposition rate (300 μm/h) by LCVD was about 100 to 1000 times as high as those by conventional CVD. The morphology of Y₂O₃ films changed from faceted and columnar structures with high (400) orientation to a columnar structure with high (440) orientation, and finally to a cone-like structure with moderate (440) orientation with increasing total gas pressure (P_tot).     

Electronic structure of polyanilines: An XPS study of electrochemically prepared compounds

Polyaniline has been synthesized electrochemically from three different media: acid and basic aqueous solutions and organic solutions. Its electronic structure, determined by X-ray photoelectron spectroscopy, clearly reflects the protonation and chain oxidation processes arising under these conditions. Protonation and deprotonation on the nitrogen sites are shown to extend their influence through the benzene ring. In halogen-substituted derivatives, the polymer protonation level is related with the position of the side group. Considerations on halogen elimination also reveal that any ring position can be involved in the bonding between the monomer units.     

不同溶胶-凝胶镀膜技术制备的电致变色WO3薄膜的影响

研究了不同溶胶-凝胶镀膜技术对电致变色WO3薄膜的影响.采用过氧化聚钨酸法配制溶胶,然后通过脉冲电泳沉积和浸渍提拉两种镀膜技术在ITO导电玻璃基底上分别制备WO3薄膜,对比研究了薄膜的微观形貌、结构、光学和电化学性能.结果表明,两种镀膜技术制备的薄膜均为非晶态且厚度相近,约为252 nm;在可见光范围内,脉冲电泳沉积制备的薄膜的光学调制幅度可达80％,比浸渍提拉制备的薄膜高25％;与浸渍提拉法相比,脉冲电泳沉积制备的薄膜具有更高的电化学活性、更快的响应时间和相对低的循环可逆性.     

Nanoindentation study of amorphous-Co79Zr13Nb8/Cr multilayers

The mechanical properties of Co₇₉Zr₁₃Nb₈/Cr multilayers were investigated using nanoindentation. The hardness is higher than the average value calculated by rule-of-mixture. The hardness and the resistance to plastic deformation characterized by the ratio of H³/E² vary similarly with periodicity (Λ). They all arrive to the maximum at Λ = 8 nm and decrease subsequently when the Λ increases. The hardness dependence on the Λ is fitted by Hall-Petch relation. The fitted index n is much lower than the normal value (~ 0.5) in many crystalline multilayers. The mutual restriction of shear band and dislocation in amorphous/crystalline structure, which is named structure barrier strengthening, should be main mechanism for the hardness enhancement. The SEM study of indents shows that the shear bands are distorted significantly at the smaller Λ (4 nm) and disappear at the larger Λ (> 20 nm). This morphology variation implies a potential improvement of plasticity caused by the restriction effect of the Cr crystalline layers on the shear bands propagation.     

Corrosion mechanism of Mo/Nd16Fe71B13/Mo film in a simulated marine atmosphere

This study describes the corrosion mechanism of Mo/Nd₁₆Fe₇₁B₁₃/Mo film induced by sodium chloride particles in 80% relative humidity (RH) environment. The deliquescence of sodium chloride particles on the Mo/Nd₁₆Fe₇₁B₁₃/Mo film caused the step by step attacks. Initial loosening of the Mo layer allows permeation of electrolyte into Nd–Fe–B layer, resulting in cavitations of electrolyte and subsequent film failure. The second failure step involves corrosion of Nd element in the Nd–Fe–B layer, with Fe element remaining beneath the corrosion product. Corrosion of Fe constitutes the third-step failure, forming a mixture of Nd and Fe corrosion product.     

Porous TiO2 film prepared by micro-arc oxidation and its electrochemical behaviors in Hank's solution

Porous titanium oxide film was prepared by micro-arc oxidation (MAO) method on the surface of titanium alloy in electrolyte containing Ca and P. Surface characterizations of the film were carried out using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) before and after immersion in Hank's solution. Electrochemical behaviors and corrosion resistance were studied by electrochemical techniques. The film was mainly composed of titania, α-tricalcium phosphate (α-TCP) and amorphous Ca-P compounds. α-TCP and amorphous compounds could transformed into hydroxyapatite (HA) when immersed in Hank's solution. MAO film showed higher corrosion potential and lower corrosion current than the titanium alloy and its chemical stability was slightly changed after formation of HA. Fitted electrochemical impedance spectroscopy (EIS) data indicated that after immersion for 2 weeks the MAO film kept good corrosion resistance. Porous TiO₂ film on titanium alloy by MAO method showed good chemical stability in Hank's solution and the transformation of Ca-P compounds into HA indicated that MAO was an effective method for preparing titanium alloys as bioactive artificial bone substitute even when Ca and P in the tissue environment were not abundant.     

Coulomb effects on 13C-NMR and polarons in (CH)x and a bound state of solitons

Using the PPP Hamiltonian model of (CH)_x, we study the effects of the Coulomb interaction on the ¹³C-NMR of doped (CH)_x and the electronic and lattice structures of polarons. The broad asymmetric ¹³C-NMR signal is explained by the Coulomb-induced charge density modulation around charged solitons. Polarons accompany the Coulomb-induced charge and spin density modulations which have a dip at the centre and different spreadings, the former being wider. The lattice dimerization in polarons is not only relaxed but also reversed in a central region. A polaron accompanies four midgap levels. With a suitably screened Coulomb interaction, we can get polaron and soliton levels in good agreement with the data of electrochemical doping voltage spectroscopy.The positively and negatively charged solitons make a breather-like bound state, which may explain the self-pinning of photogenerated solitons.     

Characterization of Delhi iron pillar rust by X-ray diffraction, Fourier transform infrared spectroscopy and Mössbauer spectroscopy

Rust samples obtained from the region just below the decorative bell capital of the Delhi iron pillar (DIP) have been analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy. The identification of iron hydrogen phosphate hydrate in the crystalline form by XRD was unambiguous. Very weak diffraction from the oxyhydroxides/oxides of iron was observed indicating that these phases are most likely to be present in the amorphous form in the rust. The present XRD analysis of rust obtained from an inaccessible area of the DIP has also been compared with earlier analyses of DIP rust obtained from regions accessible to the public. FTIR indicated that the constituents of the scale were γ-, α-, δ-FeOOH, Fe_3−xO₄ and phosphate, and that the scale was hydrated. The unambiguous identification of the iron oxides/oxyhydroxides in the FTIR spectrum implied that they are present in the amorphous state, as XRD did not reveal these phases. The FTIR results have also been compared with earlier FTIR spectroscopic results of atmospheric rust formation. Mössbauer spectroscopy indicated that the rusts contained γ-FeOOH, superparamagnetic α-FeOOH, δ-FeOOH and magnetite, all in the amorphous form. The Mössbauer spectrum also confirmed that iron in the crystalline iron hydrogen phosphate hydrate, whose presence was confirmed by XRD, was in the ferric state indicating that it was a stable end corrosion product.     

固态输送ZrCl4低压化学气相沉积制备ZrC涂层的特征

采用ZrCl4-CH4-H2-Ar反应体系、固态输送ZrCl4粉末低压化学气相沉积(CVD)制备ZrC涂层。研究温度对低压化学气相沉积ZrC涂层物相组成、晶体择优生长、涂层表面形貌、断面结构、涂层生长速度和沉积均匀性等方面的影响。结果表明:不同温度下沉积的涂层主要由ZrC和C相组成;随着温度的升高,ZrC晶粒(200)晶面择优生长增强,颗粒直径增大,表面致密性增加,沉积速率上升;涂层断面结构以柱状晶为主;随着离进料口距离的增加,涂层的沉积速率逐渐减小;1 500℃时,沉积系统的均匀性比1 450℃时的差。     

Magnetoresistivity of DyNi2B2C thin film

We present high-resolution resistivity and magnetoresistivity measurements on a DyNi₂B₂C thin film obtained by laser ablation. The measurements are interpreted in the framework of the theory developed by Yamada and Takada (YT) in the early 1970s (Yamada H., Takada S. Prog Theor Phys 1973;49:1401) for the magnetoresistivity of the antiferromagnetic materials and permit identification of the magnetic field H_c2 that destroys the magnetic ordering. So, we obtain a H–T phase diagram where the antiferromagnetic and paramagnetic states are unambiguously determined and that we compare with data in the literature. Finally, in the paramagnetic state we have found a linear dependence between magnetoresistivity and the square of the magnetization.     

Influence of pH on poly-(N-methylpyrrole) electrochemically synthesized in aqueous solution: an infrared study

Structural changes induced by pH variations or by oxidation state in electrochemically synthesized poly-N-methylpyrrole have been studied by FTIR spectroscopy. With this aim, two different ways have been followed, in the first, polymer synthesis has been carried out in NaNO₃ aqueous solutions at different pH values from acidic to neutral; in a second way a polymer film has been synthesized in a solution at pH=4 and after, introduced in solutions of increasing pH and its infrared spectra analyzed. Evidence of protonation of already synthesized polymer is obtained although no new functional group is formed and only structural changes related with oxidation state are observed.     

Properties of chemically prepared MmNi4.52Mn0.49 alloy

MmNi_4.52Mn_0.49 (Mm is mischmetal) alloy was prepared by a coprecipitation-reduction process. The alloy structure, chemical composition, particle size and surface properties were investigated by using the analysis of X-ray diffraction, inductively coupled plasma emission spectroscopy, particle size analysis and X-ray photoemission spectroscopy. Pressure-composition isotherms of the chemically prepared alloy were measured. The alloy powder was evaluated as the active material of a metal hydride electrode. It is found that the alloy thus obtained has larger specific surface area, different surface states, lower activation energy for hydrogen absorption/desorption and better electrode characteristics than the alloy prepared by conventional arc-melting.