Electrodeposition of Zn–Mn alloys at high current densities from chloride electrolyte

The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn²⁺ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transition from dendritic and spongy to smooth, bright, and amorphous structure of Zn–Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hydroxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to decrease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.     

Electrodeposition of Co–W coatings from boron gluconate electrolyte with a soluble tungsten anode

Conditions were determined in which an active anodic dissolution of tungsten is observed in a borongluconate electrolyte used to obtain Co–W coatings (pH ~6.5) and the nature of critical currents of transition to the passivation was found, which makes it possible to use the tungsten anode as a soluble electrode. The anodic dissolution of tungsten occurs under these conditions with a current efficiency of 90–100%, which, in contrast to the case of a graphite anode, does not lead to an additional oxidation of the electrolyte components and polymerization in solution; in combination with the decrease in the concentration of tungstate ions, this reduces the electrolyte performance. It was shown that the use of a soluble tungsten anode in obtaining nanocrystalline cobalt–tungsten coating can improve the electrolyte performance due to the rise in the current efficiency of electrodeposition and to the increase in the microhardness of the coatings in comparison with the case of an insoluble graphite anode.     

Electrodeposition of Ni–Fe alloy from a choline chloride-containing ionic liquid

Journal of Solid State Electrochemistry - The electrochemical deposition of a nickel–iron alloy from a plating solution based on a deep eutectic solvent (a eutectic mixture of ethylene glycol...     

Electrodeposition kinetics of tin—antimony alloy from sulfate electrolyte with organic additives

Kinetics of the Sn-Sb alloy electrodeposition from sulfate electrolytes containing organic additives (syntanol DS-10, Formalin, 1,4-butynediol) is studied by the faradaic impedance method. Bright Sn-Sb alloy coatings are plated in this electrolyte at i_c = 0.5-5 A/dm². With increasing i_c, the Sb content in the alloy decreases from 14 to 6.6 wt %     

Evaluation of stability of silica-supported Fe–Pd and Fe–Pt nanoparticles in aerobic conditions using thermal analysis

The applications of zerovalent iron nanoparticles (nZVI) exploit their high reactivity which decreases due to oxidation in aerobic conditions during manufacture, application, and storage. In this study, we present the new procedure for estimation of the nZVI stability to oxidation in air. The procedure is suitable for characterization of the novel materials based on the supported nZVI. Nanoscale particles were synthesized inside porous silica supports by incipient wetness impregnation with the metal precursor solutions followed by thermal treatment. The TG–DTA studies revealed the decomposition temperature of the supported precursors, as well as the interaction of Fe and precious metal precursors, which resulted in the formation of alloy nanoparticles. Characterization of the samples by XRD confirmed the formation of the nanoparticles of the metallic Pd, Pt, and Fe phases supported on SiO₂ carriers, as well as the formation of solid solutions based on the structure of precious metals. The new procedure for estimation of the nZVI stability included (1) TPR with hydrogen up to 400–425 °C followed by isothermal reduction at these temperatures; (2) in situ reoxidation with oxygen at room temperature. The samples were reduced “as obtained” and after in situ reoxidation. The results of the TPR studies exhibited that introduction of both Pd and Pt protected the Fe nanoparticles from oxidation with oxygen and air at ambient conditions.     

An activated carbon with high capacitance from carbonization of a resorcinol–formaldehyde resin

A polymeric activated carbon (PAC) was synthesized from the carbonization of a resorcinol–formaldehyde resin with KOH served as an activation agent. The nitrogen adsorption–desorption at 77 K, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared PAC. Compared with the commercial activated carbon (Maxsorb: Kansai, Japan), PAC shows superior capacitive performance in terms of specific capacitance, power output and high energy density as electrode materials for supercapacitors. PAC presents a high specific capacitance of 500 F g^?1 in 6 mol l^?1 KOH electrolyte at a current density of 233 mA g^?1 which remained 302 F g^?1 even at a high current density of 4.6 A g^?1. The good electrochemical performance of the PAC was ascribed to well-developed micropores smaller than 1.5 nm, the presence of electrochemically oxygen functional groups and low equivalent series resistance.     

Metalizing carbon nanotubes with Pd–Pt core–shell nanowires enhances electrocatalytic activity and stability in the oxygen reduction reaction

We describe an electrostatically induced self-assembly method to prepare ultrathin Pd nanowires (NWs) surrounding individual multiwalled carbon nanotubes, i.e., Pd_NW/MWNTs, that are noticeable for improving performance in the oxygen reduction reaction (ORR) of their supported Pt_ML electrocatalyst. The carbonaceous by-products in MWNTs, rather than the nanotubes themselves, are modified with the oxygenated terminals to allow the negatively charged and hydrophilic surface while retaining the intrinsic nature of the MWNTs. Encompassing the nanotubes' length are 2-nm-thick Pd NWs that are closely packed and homogeneously dispersed due to the unique processes for preparing Pd_NW/MWNTs and its components. Although the crystal lattice of the Pd NWs expands somewhat, which should cause an unfavorable interaction with supported Pt_ML, this adverse effect is counterweighed by the shape-determined features of Pd NWs, including their high specific surface area, excellent contiguousness, and low-energy atomic configuration. Consequently, these distinct chemical and physical properties substantially expedite the desorption of the intermediates to refresh the active centers during the reduction of oxygen with the Pt_ML electrocatalyst while ensuring a desirable electron transfer rate, so improving the overall ORR kinetics. Indeed, Pt_ML/Pd_NW/MWNTs exhibits the Pt mass and specific activities of 1.45 A/mg_Pt and 0.65 mA/cm² _Pt, respectively, each of which are several times those of the Pt/C and even higher than those of the Pt_ML supported on Pd nanoparticles. These high activities remained over a long-term stability test using the latest US Department of Energy-established protocol.     

Electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes

Specific features of the electrodeposition of iron–molybdenum–tungsten coatings from citrate electrolytes based on iron(III) sulfate in the dc mode and with a unipolar pulsed current were studied. It was shown that varying the relative concentrations of salts of alloy-forming metals and the solution pH makes it possible to obtain lustrous compact coatings with low porosity and various contents of high-melting components. The effect of temperature on the coating composition and current efficiency was examined. The current density ranges providing high electrolysis efficiency were found and it was demonstrated that using a pulsed current favors formation of more compositionally homogeneous surface layers at a smaller amount of adsorbed nonmetallic impurities in the coatings. The iron–molybdenum–tungsten coatings are X-ray-amorphous and have better physicomechanical properties and corrosion resistance as compared with the base, which makes it possible to recommend these coatings for application in techniques for surface reinforcement and restoration of worn-out articles.     

Electrodeposition of Zinc–Nickel Alloys from Ammonium Oxalate Electrolytes

The electrodeposition of zinc–nickel alloys (5–16 at % Ni) from the ammonium oxalate electrolytes is studied. It is shown that the ratio between the alloy components has an effect on the corrosion resistance of the coatings, their structure, chemical and phase composition, and microhardness.     

Electrodeposition of Multilayered Ni–Cr Films from Sulfate–Oxalate Electrolytes

As shown by scanning Auger electron microscopy and Auger electron spectroscopy, multilayered Ni–Cr thin films can be deposited under the action of periodic currents from sulfate–oxalate solutions containing nickel and chromium ions. The chromium-rich layers have an amorphous structure. In the nickel/chromium interphase region, the carbon content is elevated. Nickel layers contain admixtures of a hydroxide nature.     

Synthesis of silica-pillared layered lanthanum titanate with high thermal stability

It is now well established that layered solids other than smectite clays may bepillared to form three-dimensional crosslinked materials, the porosity of which isultimately tunable by the nature of the host substrate and the chemical species     

Thermal stability of high density polyethylene–fumed silica nanocomposites

High-density polyethylene-based nanocomposites were prepared through a melt compounding process by using surface functionalized fumed silica nanoparticles in various amounts, in order to investigate their capability to improve both mechanical properties and resistance to thermal degradation. The fine dispersion of silica aggregates led to noticeable improvements of both the elastic modulus and of the stress at yield proportionally to the filler content, while the tensile properties at break were not impaired even at elevated filler content. Thermogravimetric analysis showed that the selected nanoparticles were extremely effective both in increasing the decomposition temperature and in decreasing the mass loss rate, even at relatively low filler loadings. The formation of a char enriched layer, limiting the diffusion of the oxygen through the nanofilled samples, was responsible of noticeable improvements of the limiting oxygen index, especially at elevated silica loadings. In contrast with commonly reported literature results, cone calorimeter tests also revealed the efficacy of functionalized nanoparticles in delaying the time to ignition and in decreasing the heat release rate values. Therefore, the addition of functionalized fumed silica nanoparticles could represent an effective way to enhance the flammability properties of polyolefin matrices even at low filler concentrations.     

Synthesis and characterization of a series of chiral NHC–Pd complexes derived from l-phenylalanine

The synthesis of a series of chiral Pd(L)PyBr₂ (3a–3e) and Pd(L)PyCl₂ (4d and 4e) complexes from l-phenylalanine is presented (L = (S)-3-allyl-4-benzyl-1-(2,6-diisopropylphenyl)-imidazolin-2-ylidene (a), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-2-ylmethyl)imidazolin-2-ylidene (b), (S)-4-benzyl-3-(biphenyl-4-ylmethyl)-1-(2,6-diisopropylphenyl)imidazolin-2-ylidene (c), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-1-ylmethyl)imidazolin-2-ylidene (d) or (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(2,4,6-trimethylbenzyl)imidazolin-2-ylidene (e). The complexes were characterized by physicochemical and spectroscopic methods, and the X-ray crystal structures of 3a–3c and 4d are reported. In each case, there is a slightly distorted square-planar geometry around palladium, which is surrounded by imidazolylidene, two trans halide ligands and a pyridine ligand. There are π–π stacking interactions in the crystal structures of these complexes. Complex 3a showed good catalytic activity in the Cu-free Sonogashira coupling reaction under aerobic conditions.     

Structure–property relationships of novel fluorinated polycarbonate polyurethane films with high transparency and thermal stability

Research on Chemical Intermediates - Novel polycarbonate diol (PCDL) was synthesized using dimethyl carbonate, 1,5-pentanediol (1,5-PD), 1,6-hexanediol (1,6-HD) and 1,4-cyclohexanedimethanol...     

Determination of the stability and magnetic properties of Fe–Pd nitride using the generalised gradient approximation (GGA)

In this study, an electronic structure calculation of the substituted nitride PdFe₃N was conducted, and a posterior understanding of its structural and magnetic properties was obtained. A first principle method was applied to study the lattice parameter variation in relation to the energy of solid formation. After the equilibrium parameter was found, some properties of the ground state, such as the magnetic moment and the bulk modulus, were calculated. Preliminary observations show that the material properties of γ′-Fe₄N vary significantly with the insertion of the palladium atom in the matrix as well as when the material is subjected to applied pressure. The density of states shows a strong interaction between the s states of nitrogen and, primarily, the s and p states of iron, presenting a weak interaction with the palladium atoms. The analysis of such properties illustrates why these nitrides have a promising future for use in technological applications.     

Effect of Surfactants on Electrodeposition of the Sn–Ni Alloy from Oxalate Solutions

The effects of surfactants on the electrolytic deposition of tin–nickel alloys from oxalate–ammonium electrolytes were determined. The adsorption of the nonionic surfactant at the interface decreases the rate of charge transfer across the interface. As a result, the electrochemical stage of the electroreduction of metals slows down, and the alloy is deposited in the form of shiny finely crystalline coatings. The range of optimum surfactant concentrations in the oxalate–ammonium electrolyte was determined based on the simulation of the interface impedance obtained during the alloy deposition and the electron microscopy studies of the obtained coatings.     

One-pot synthesis of a rose-like Pd–Fe3O4 nanocatalyst for Sonogashira coupling reactions

A one-pot synthesis of rose-like Pd–Fe₃O₄ nanocomposites via the controlled thermal decomposition of Fe(CO)₅ and reduction of Pd(OAc)₂ is reported. This rose-like Pd–Fe₃O₄ composite structure has a high surface area owing to the individual Pd–Fe₃O₄ nanosheets, which imparted a high catalytic activity for Sonogashira coupling reactions. Moreover, the catalyst also demonstrated magnetic recyclability.     

Quasi solid-state quantum dot–sensitized solar cells with polysulfide gel polymer electrolyte for superior stability

Journal of Solid State Electrochemistry - In the case of sensitized solar cells, liquid electrolyte materials are the fundamental components due to its advantage of superior conductivity. However,...     

Preparation of barium ferrite films with high Fe/Ba ratio by sol–gel method

Hexagonal BaFe₁₂O₁₉ ferrite (BaM) thin films were prepared on Si (100) substrate successfully by sol–gel technology and post annealing. The results showed the BaM phase can be formed and crystallized into c-axis textured grains even when the Fe/Ba ratio of the precursor varied from 6.5 to 9.5. However, the behavior of the saturation magnetization (M _s) and intrinsic coercivity (H _c) depended strongly on the Fe/Ba ratio and annealing temperature (T _a) varied from 700 to 900 °C. The M _s and H _c values deceased with an increase of Fe/Ba ratio, for instance, were about 290 emu/cm³ and 4,200 Oe for the Fe/Ba = 6.5 film but only 116 emu/cm³ and 2,300 Oe for the Fe/Ba = 9.5 film. The M _s and H _c values of the Fe/Ba ratio = 6.5 film increased monotonously with increasing T _a, were about 120 emu/cm³ and 2,500 Oe at T _a = 800 °C, and reached to 345 emu/cm³ and 4,600 Oe at T _a = 950 °C.