Effects of saccharin and aliphatic alcohols on the electrocrystallization of nickel

The effects of saccharin and three kinds of aliphatic alcohols (n-propyl alcohol, allyl alcohol, propargyl alcohol) on the surface morphology and crystal orientation of electrodeposited nickel from a Watts bath (1 M NiSO₄ + 0.21 M NiCl₂ + 0.51 M H₃ BO₃ have been studied by means of electrochemical methods, scanning electron microscopy, energy-dispersive X-ray analysis and measurements of X-ray diffraction patterns. Saccharin and three kinds of aliphatic alcohols were adsorbed on the electrode and inhibited the reduction of nickel ion. The inhibitory effect on the reduction of nickel ion increased in the order n-propyl alcohol, allyl alcohol and propargyl alcohol. Large granular electrodeposits were obtained from the Watts bath in the absence of organic additives. When saccharin was added, fine-grained crystals were observed and the surface roughness was relatively small. When aliphatic alcohols were added, the size of surface morphological features became smaller in the order n-propyl alcohol, allyl alcohol and propargyl alcohol. Fine-grained, compact and smooth nickel electrodeposits, which had a preferred orientation with a (111) plane parallel to the surface, were obtained from the Watts bath containing both saccharin and propargyl alcohol.     

计算脂肪醇沸点的新方法

直接从脂肪醇的分子结构提取4个结构参数:烷基的极化效应指数PEI、碳原子数目Nc、羟基所连接碳原子上的氢原子个数α-H和羟基与支链相对位置差ΔN,与118种脂肪醇的沸点进行相关分析,得到相关模型方程。运用留一法确证模型方程具有较好的稳定性和预测能力。方程所选用的参数计算简单,物理意义明确,能够被广泛使用。     

Polarographic behaviour of aliphatic azoxy compounds

Both isomeric cis and trans forms of aliphatic azoxy compounds are reduced in the same way in acid and neutral media: they are adsorbed, protonated, then reduced in one 4 electron step to give hydrazo compounds. The intermediate azo isomer is more easily reducible than the depolariser.In basic medium, the azoxy derivatives may be divided into two groups, depending on the ability of the neutral molecule to be reduced or not. When the neutral azoxy compound is reduced, the hydrazo compound is usually the final product of the reduction if the neutral form of the azo compound is also reducible. For cis azoxycyclohexane, trans azo and hydrazo are generated. This result suggests a new reduction path for neutral azoxy compounds. A mechanism is postulated, leading to an intermediate unstable N-hydroxyhydrazine which dehydrates very fast into cis and trans azo compounds.     

Effect of impurities on the electrochemical behaviour of aluminium electrodes anodized in phosphoric acid

The electrochemical behaviour of anodic films formed on pure aluminium (99.999% and 1100) and 6061-Al alloy substrates in phosphoric acid has been investigated in an aluminium saturated phosphate solution of pH 6.23. The polarization resistance data obtained after one day immersion in the electrolyte showed a strong correlation with the pit number, assessed from an outdoor atmospheric exposure test after 4 months. The cathodic polarization measurements of anodized aluminium in the electrolyte were also carried out. Electrochemical behaviour, eg corrosion, hydrogen evolution reaction, was interpreted in terms of “active sites” within the anodic film. It is suggested that the active sites were mainly formed in the presence of impurities or alloy constituents in aluminium substrates.     

Polarographic behaviour of aliphatic azodioxy compounds

The polarographic behaviour of trans azodioxycyclohexane and trans α,α'-azodioxytoluene has been investigated in ethanol-water solutions.In acid medium, a preprotonation of the molecule and the cleavage of an oxygen are first observed, leading to the corresponding azoxy compound (2 electron step). A second reduction step leads to the hydrazo compound through the intermediate azo compound (4 electron step). In neutral medium, a single 6 electron reduction wave is observed.The neutral molecule is reduced in alkaline medium; an unstable intermediate is formed which dehydrates very fast into cis and trans azoxy compounds. In the case of trans α,α'-azodioxytoluene, both cis and trans azoxy compounds are reduced to α,α'-hydrazotoluene which is the final reduction product. In the case of trans azodioxycyclohexane, the corresponding trans azoxy compound is no longer reducible and a mixture of azo, hydrazo and trans azoxy compounds is obtained.     

Preparation of rapeseed oil esters of lower aliphatic alcohols

Rapeseed oil esters with lower aliphatic alcohols (C₁−C₄) were prepared in simple batch mode using an alkali (KOH) or acid (H₂SO₄) catalyst. The transesterification reaction conditions were optimized in order to obtain high yields of esters of the quality defined by standards for biodiesel fuels and for a short reaction time. Under these conditions it was possible to prepare only the methyl and ethyl esters catalyzed by KOH. Propyl and butyl esters were obtained only under acid catalysis conditions. The reaction catalyzed by H₂SO₄ was successfully accelerated using slightly higher catalyst concentrations at the boiling points of the alcohols used. The branched-chain alcohols reacted more slowly than their linear homologs, while t-butanol did not react at all. It was also possible to transesterify rapeseed oil using a mixture of alcohols characteristic of the end products of some fermentation processes (e.g., the acetone-butanol fermentation). A simple calculation was made which showed that, because of the higher price of longer-chain alcohols and because of the more intensive energy input during production the esters of these alcohols, they are economically unfavorable as biodiesel fuels when compared with the methyl ester.     

Degradation of polyester waste by aliphatic and aromatic alcohols

Polyester waste was degraded with ethanol, n-propanol, and benzyl alcohol in an autoclave at 280°C under pressure to give seven unknown compounds. The products of each reaction were isolated by using column chromatography and were identified on the basis of elemental analysis and spectral data.     

Influence of copolymerisation on fracture behaviour of aliphatic polyketones

High strain rate tensile impact properties of aliphatic polyketone terpolymers were investigated and related to the polymer chain structure. Aliphatic polyketones were used as a model system, by changing the termonomer content and type. Aliphatic polyketone is a perfectly alternating copolymer and the structure was changed with the addition of a few mol% of termonomer: propylene, hexylene and dodecene. Studied were the thermal properties with DSC and DMTA, tensile behaviour, notched tensile impact behaviour, notched Izod properties and the temperature development during deformation. The perfectly alternating copolymer had a melting point of 257 °C, a T_g at 15 °C, a high crystallinity (48%), a high yield stress (77 MPa) and yield strain (31%) but a relatively low fracture strain (85%) and an impact strength (notched Izod) of 13 kJ/m². Increasing the propylene content to 6%, lowered the melting temperature to 224 °C, without changing the T_g. The modulus and yield stress were lowered but the impact strength improved. Increasing the length of the termonomer while keeping the T_m at 224 °C lowered the T_g, the modulus, the yield stress but strongly improved the impact resistance. The longer termonomers, with a lower yield stress, reduced the necking behaviour. The temperature increase in front of the notch was about 85 °C. By adding termonomers to aliphatic ketones, the notched impact behaviour improved significantly at the cost of modulus and yield stress.     

Effect of physico-chemical properties of simulated body fluids on the electrochemical behaviour of CoCrMo alloy

The behaviour of the CoCrMo alloy was studied under different experimental conditions of solution pH, chemical composition (phosphate buffer solution with and without addition of bovine serum albumin) and aeration (presence and absence of oxygen in the solution). With this purpose, electrochemical techniques such as open circuit measurements (OCP), potentiodynamic curves, potentiostatic tests and electrochemical impedance spectroscopy (EIS) were employed.The results show that the general corrosion behaviour of CoCrMo alloy depends on the solution pH. Thus, the effect of BSA and the aeration conditions are related to the solution pH. At pH 3 no influence of BSA was observed in deoxygenated solutions which imply that BSA acts over the oxygen reduction reaction in acidic media. On the contrary, a noticeable influence of BSA addition was observed at pH 7.4 (independently on the gas content). Finally, at pH 10, the influence of BSA was only significant in oxygenated solution. It was found that H₂PO₄⁻ favours the formation of passivating compounds which improves the resistance of the CoCrMo alloy to passive dissolution. Therefore, when the concentration of the H₂PO₄⁻ increases (when pH decreases) the polarization resistance of the alloy also increases. On the other hand, the oxygen (aerated conditions) decreases the polarization resistance of the alloy in all the studied conditions.     

Effect of complexing agents on the electrochemical behaviour of orthopaedic stainless steel in physiological solution

This work is aimed at providing a better understanding of the biocompatibility of stainless steel in the human body, where various biomolecules are able to bind metal ions and convey them from the surface of an orthopaedic implant to various parts of the body. The passivation behaviour of orthopaedic stainless steel was studied by potentiodynamic and potentiostatic electrochemical methods in physiological solution as a function of type and concentration of complexing agents added. The latter were used to simulate the complexing effect of biomolecules in vitro. Two complexing agents, EDTA and citrate, were investigated in the concentration range from 0.1 to 100 mM. Their addition induces a pronounced effect on the passivation characteristics of stainless steel. The results were discussed in the context of the formation of soluble complexes of metal ions, which induces an increase in metal dissolution and disturbs the formation of the passive layer. The degree of increased dissolution appears to be related to the stability constants of the complex formed.     

Effect of thermal treatment and applied potential on the electrochemical behaviour of CoCrMo biomedical alloy

CoCrMo alloy are one of the most important biomaterials for orthopaedic applications, widely used in total joint replacements. The thermal treatments applied to CoCrMo alloys modifies the microstructure of the alloy and change the electrochemical and mechanical properties of the biomaterial. Thus, the aim of this research is to characterize the electrochemical behaviour of CoCrMo alloy depending on the thermal treatment at different applied potentials (according to the cathodic, anodic and transpassive electrochemical domains of the alloy).Metallographic study and electrochemical techniques such as potentiodynamic curves, potentiostatic tests at different potentials (selected according to the electrochemical regions of the potentiodynamic curves) and electrochemical impedance spectroscopy (EIS) are employed to characterize the CoCrMo alloy after three different thermal treatments in simulated body fluid (bovine serum solution).The same corrosion mechanisms were observed for the CoCrMo alloy under the three thermal treatments at different applied potentials, however, the rate of the corrosion reactions which take place on the metallic surfaces depends on those thermal treatments and it is related to the amount of carbide inclusions. At passive potentials the study reveals that the properties of the passive layer depend on the microstructure of the alloy. EIS results show that the resistance of the passive layer in bovine serum solution increased with the carbides solubilisation.     

Experimental examination of the room temperature hydrodynamics and electrochemical current-voltage behaviour of the Bi-terminated vibrating wire electrode

An experimental study was made of the room temperature hydrodynamics and current-voltage (I-V) behaviour of a bi-terminated transverse oscillating resonant electrode using an adaptation of the electromagnetically-driven vibrating wire technique recently developed for precise viscosity measurements of cryogenic fluids. For argon, nitrogen, as well as dilute electrolytes, the shapes of the in-phase and quadrature resonance lines agreed with lines obtained by computer simulation. Although such peaks exhibited shorter heights than predicted (probably due to dispersion or some energy loss to the end terminations), observed peak areas agreed with theory. Use of either 50-μm diameter platinum or tungsten wires as working electrodes in three-electrode voltammetry yielded quite well-defined I-V curves for reduction of dilute ferricyanide and iodate as test systems, with Fe(CN)₆^?3 exhibiting near-Nernstian reversibility at the tungsten wire. Well-shaped I-V curves were also obtained for lead (II) reduction on oxide-free platinum. Resonant platinum wires clad with lead films produced by controlled potential deposition yielded, as expected, an advantageous negative shift in potential for H⁺ reduction. Because the mechanical properties of soft or low tensile strength metals deny their direct use as resonant electrodes, clad wires, on the other hand, should enable electrochemical, corrosion, and surface studies of such materials to be accomplished under rather precisely controlled conditions.     

Electrooxidation of aliphatic alcohols on palladium oxide catalyst prepared by pulsed electrodeposition technique

Palladium film can be deposited on gold polycrystalline electrodes, from a deoxygenated alkaline solution containing 50 mM NaOH plus 0.5 mM K₂Pd(CN)₄. A multipulse sequence of potentials of equal amplitude and duration was used for the palladium deposition process. In particular, an optimized waveform of potentials of E₁ = 1.0 V vs. SCE and E₂ = −1.0 V vs. SCE for the relevant pulse duration of t₁ = 0.05 s and t₂ = 0.05 s, for 30 s, was used. Cyclic voltammetry and scanning electron microscopy (SEM) were employed to characterize the gold-palladium modified electrode (Au-Pd) towards the electrooxidation of aliphatic alcohols in alkaline solutions. The voltammetric study suggests that the kinetics involved in the alcohol electrooxidation at the Pd-Au electrode are sensibly higher than those observed on the bare Pd and Au electrodes. In addition, the most interesting aspect of the electrooxidation of aliphatic alcohols at the Au-Pd electrode was that as the number of methylene groups on the homologous series of aliphatic alcohols increased, the molar response also increased. Under pulsed chronoamerometric conditions (PCC), using an optimized triple pulse waveform of potentials the modified electrode exhibits interesting catalytic currents without any apparent poisoning effects during the oxidation of aliphatic alcohols.     

Study on electrochemical behaviour of zinc in dimethylsulphoxide

The kinetics of cathodic deposition and anodic dissolution of zinc in Zn(BF₄)₂ and Zn(ClO₄)₂ solutions in DMSO has been examined using various experimental techniques. It has been found that magnitudes of kinetic parameters of Zn/Zn²⁺---DMSO systems are very close to the values measured in aqueous solutions of these salts. Cathodic efficiency of Zn attains a value of 95%. However, zinc coat contains impurities mainly as incorporated DMSO molecules, which is a conclusion based on X-ray analysis of Zn deposit.     

Effect of temperature on the viscoelastic behaviour of entangled solutions of multisticker associating polyacrylamides

The viscoelactic behaviour of polyacrylamides (PAM) hydrophobically modified with small blocks (≈3 monomer units) of N,N-dihexylacrylamide (2 mol%) has been investigated in the entangled regime as a function of temperature by steady-flow and oscillatory experiments. The effect of temperature on the rheological behaviour of these systems was also investigated in the presence of surfactant. In both cases, the results were compared to those obtained for the unmodified analogue. The experimental data were analysed using a simple Maxwell model and the time-temperature superposition principle. The results indicate that the main effect of a change in temperature and/or addition of surfactant is to modify the lifetime of the physical crosslinks without changing their density, as inferred from a quasi-constant value of the plateau modulus. The comparison between the plateau moduli of the modified and unmodified systems shows unexpected higher values for the former systems.     

温度对电沉积氢氧化镍电化学性能的影响

在0.1mol/L的Ni(NO3)2溶液中,采用电化学沉积法制备出适用于锌镍微电池的氢氧化镍电极,研究了电沉积温度对Ni(OH)2电极的电化学循环伏安性能以及充放电性能的影响。测试结果表明,电沉积方法制备的Ni(OH)2电极适合于微电池的制作。30°C下电沉积制备的Ni(OH)2电极具有优异的电化学性能,其质子扩散系数为7.71×10-12cm2/s,放电比容量为1285μAh/cm2,利用率达91.4%。     

液相色谱─间接光度检测测定脂族醇

在化学键合固定相ＯＤＳ柱（２５０ｍｍ×４．６ｍｍ内径）上,用Ｒｕ（Ｐｈｅｎ）２＋３作甲醇┐水（８９２,Ｖ／Ｖ）流动相添加剂分离并用间接光度法检测某些脂族醇。探讨了流动相中有机溶剂浓度、Ｒｕ（Ｐｈｅｎ）２＋３浓度、ｐＨ值和盐浓度等对醇类的保留时间和检测灵敏度的影响。甲醇、乙醇、正丙醇、异丙醇、正丁醇和叔丁醇具有良好的分离度和检测灵敏度,间接光度法检测可在４５０ｎｍ处,也可在３３０ｎｍ处。同时测定此６种醇的校正曲线线性范围,甲醇、乙醇各为０．５～５０ｍｇ／ｍＬ,其余４种醇各为１～１００ｍｇ／ｍＬ,绝对检测限达微克级。