Facile fabrication approach for a novel multifunctional superamphiphobic coating based on chemically grafted montmorillonite/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-polydimethylsiloxane binary nanocomposite

In this paper, a novel multifunctional superamphiphobic coating for anticorrosion was successfully prepared on aluminum substrate via a simple spraying technique. Al₂O₃ nanoparticles were chemically grafted onto montmorillonite (MMT) nanosheets via coupling effect of NH₂-C₃H₆-Si(OC₂H₅)₃ (KH-550) and then modified by low surface energy material polydimethylsiloxane (PDMS). The ethylene tetrafluoroethylene (ETFE) composite coating with 25 wt% MMT/Al₂O₃-PDMS binary nanocomposite exhibited well-designed nano/μ structures and possessed superamphiphobicity with high contact angles towards water (164°), glycerol (158°) and ethylene glycol (155°). This coating demonstrated outstanding self-cleaning ability and strong adhesive ability (Grade 1 according to the GB/T 9286). The superhydrophobicity could be maintained after 8000 times abrasion or annealing treatment for 2 h under 350 °C. The coating still retained high water-repellence after immersion in 1 mol/L HCl (146°), 1 mol/L NaOH (144°) and 3.5 wt% NaCl (151°) solutions for 30 d. It should be noted that this superamphiphobic coating revealed excellent long-term corrosion protection with extremely low corrosion rate (4.3 × 10^?3 μm/year) and high protection performance (99.999%) after 30 d immersion in 3.5 wt% NaCl solutions based on electrochemical corrosion measurements. It is believed that such integrated functional coating could pave new way for self-cleaning and anticorrosion applications under corrosive/abrasive environment.     

A method for determining the charge state of chromium in Cr-doped Bi<Subscript>12</Subscript>SiO<Subscript>20</Subscript> and Bi<Subscript>12</Subscript>TiO<Subscript>20</Subscript> materials

A chemical method for determination of the charge state of chromium in B₂O₃-based materials (Bi₁₂SiO₂₀ and Bi₁₂TiO₂₀ single crystals) in a wide Cr concentration range (1 × 10^–5 – 2 × 10^–2 wt.%)is proposed. The method is based on a color reaction between Cr⁶⁺ and diphenylcarbazide in an acid medium.Translated from Novye Ogneupory, No. 8, pp. 61 – 63, August, 2004.     

The Structure of Fusion-Cast High-Chrome Oxide Refractories in the Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> - MgO - Al<Subscript>2</Subscript>O<Subscript>3</Subscript> System

The phase composition and structure of fusion-cast refractories composed of 57.0 – 84.2% Cr₂O₃, 4.3 – 36.1% MgO, 2.0 – 9.7% Al₂O₃, and 2.4 – 6.9% SiO₂ have been studied by petrographic and x-ray spectral microprobe analysis methods. Refractories high in MgO with modulus M = (Cr₂O₃ +Al₂O₃)/MgO = 1.64 – 3.1 are shown to consist of spinel phase Mg(Cr, Al)₂O₄ and silicate glass. Refractory materials (80.8 – 84.2% Cr₂O₃, 4.3 – 4.7% MgO, 2.0 – 9.7% Al₂O₃, and 2.7 – 6.9% SiO₂ with M = 18.7 – 20.2) are three-phase systems composed of spinel, escolaite, and glass phase. These materials, owing to their high corrosion resistance, have promising potentiality for practical applications.__________Translated from Novye Ogneupory, No. 12, pp. 69 – 74, December, 2004.     

Li<Subscript>2</Subscript>Cu<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> + SiO<Subscript>2</Subscript>/Ti compositions for the catalytic afterburning of diesel soot

Two methods were used to obtain a catalytically active oxide coating on the surface of titanium for the catalytic afterburning of diesel soot: plasma electrochemical formation of an oxide film on the surface of titanium and extraction pyrolytic deposition of the Li₂Cu₂(MoO₄)₃ compound. The Li₂Cu₂(MoO₄)₃/TiO₂ + SiO₂/Ti compositions synthesized by the single-step extraction pyrolytic treatment of the oxidized surface of titanium ensured a high burning rate of soot of ∼300°C. The subsequent deposition of Li₂Cu₂(MoO₄)₃ lowers the activity of the catalyst, due probably to the growth of molybdate phase crystallites and the filling of open oxide film pores. Double lithium-copper molybdate is able to reduce appreciably the concentration of CO in the oxidation products of soot. The advantages of these methods are the possibility of forming high-cohesion durable coatings on surfaces of any complexity, the simplicity of their implementation, and high productivity and low cost. The obtained results can be recommended for use in developing methods for creating composite coatings on catalytic soot filters.     

Preparation and Characterization of LiNi<Subscript>0.8</Subscript>Co<Subscript>0.2</Subscript>O<Subscript>2</Subscript> Synthesized by an Emulsion Drying Method

A layered LiNi_0.8Co_0.2O₂ solid solution, which is a promising cathode material for secondary lithium batteries, was successfully synthesized by an emulsion drying method. Because electrochemical properties significantly depend on the conditions of the synthesis, the calcination temperature was carefully determined on the basis of X-ray diffraction and TG studies. The prepared cathodes were characterized by means of SEM, BET, X-ray diffraction, Rietveld refinement, cyclic voltammetry and a charge-discharge experiment. From the Rietveld analysis, it was found that powder calcined at 800 °C for 12 h exhibits a well ordered and lower cation mixed layered structure than the others. The cyclic voltammetry experiment shows that phase transformation can be suppressed considerably by increasing the calcination temperature to 800 °C. The highest discharge capacity of 188.4 mA h g⁻¹ was obtained from the sample prepared at 800 °C. Furthermore, a high capacity retention ratio of 88.1% was found for the initial value after 50 cycles at a constant current density of 40 mA g⁻¹ between 2.7 V_Li/Li⁺ and 4.3 V_Li/Li⁺. In the rate capability test, the cathode delivered a higher discharge capacity of 153.1 mA h g⁻¹ at a 4 C (800 mA g⁻¹) rate.     

Chemical and electrochemical characterization of TiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> atomic layer depositions on AZ-31 magnesium alloy

In this study, innovative TiO₂/Al₂O₃ mono/multilayers were applied by atomic layer depositions (ALD) on ASTM-AZ-31 magnesium/aluminum alloy to enhance its well-known scarce corrosion resistance. Four different configurations of ALD layers were tested: single TiO₂ layer, single Al₂O₃ layer, Al₂O₃/TiO₂ bilayer and Al₂O₃/TiO₂/Al₂O₃/TiO₂ multilayer deposited using Al[(CH₃)]₃ (trimethylaluminum, TMA), and TiCl₄ and H₂O precursors. All depositions were performed at 120°C to obtain an amorphous-like structure of both oxide layers. The four coatings were then investigated using different techniques, such as scanning electron microscope (SEM), stylus profilometer, glow discharge optical emission spectrometry (GDOES) and polarization curves in 0.05-M NaCl solution. The thickness of all the coatings was around 100 nm. The layers compositions were successfully investigated by the GDOES technique, although obtained data seem to be affected by substrate roughness and differences in sputtering rates between ceramic oxides and metallic magnesium alloy. Corrosion resistance showed to be strongly enhanced by the nanometric coatings, giving lower corrosion current densities in 0.05-M NaCl media with respect to the uncoated substrate (from 10⁻⁴ to 10⁻⁶ A/cm² for the single layers and from 10⁻⁴ to 10⁻⁸ A/cm² for the bi- and multilayers). All polarization curves on coated samples also showed a passive region, wider for the bi-layer (from −0.58 to −0.43 V with respect to Ag/AgCl) and multilayer (from −0.53 to −0.38 V with respect to Ag/AgCl) structures.     

Polyaniline/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> composites as novel media for anticorrosion coatings

In this paper, graphitic carbon nitride (g-C₃N₄) was first proposed for the pioneer application of anticorrosion coatings. Original g-C₃N₄ was facilely treated using HNO₃ and the exfoliated g-C₃N₄ sheets (E-g-C₃N₄) were fabricated, and then, polyaniline/E-g-C₃N₄ composites (PANI/E-g-C₃N₄) as novel anticorrosive media were synthesized by chemical oxidative polymerization and devoted to the corrosion protection of coatings. The E-g-C₃N₄ sheets and PANI/E-g-C₃N₄ composites were characterized by X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, and transmission electron microscopy. The anticorrosion properties of the samples prepared were investigated by electrochemical measurements including Tafel plots, electrochemical impedance spectra, and open-circuit potential. Accelerated corrosion tests of iron panels coated by PANI/E-g-C₃N₄ were performed in 3.5 wt% NaCl solution. Anticorrosive mechanism of PANI/E-g-C₃N₄ was discussed in detail. PANI/E-g-C₃N₄-3 fillers possessed superior corrosion inhibition than individual components on iron coatings, which was due to the synergetic effect of anticorrosion between E-g-C₃N₄ and PANI.     

Synthesis and electrochemical properties of layered LiNi<Subscript>1/2</Subscript>Mn<Subscript>1/2</Subscript>O<Subscript>2</Subscript>prepared by coprecipitation

Spherical LiNi_1/2Mn_1/2O ₂ powders were synthesized from LiOH . H₂O and coprecipitated metal hydroxide, (Ni_1/2Mn_1/2)(OH)₂. The average particle size of the powders was about 10 m and the size distribution was quite narrow due to the homogeneity of the metal hydroxide, (Ni_1/2Mn_1/2)(OH)₂. The tap-density of the LiNi_1/2Mn_1/2O₂ powders was approximately 2.2 g cm_–3, which is comparable to the tap-density of commercial LiCoO₂. The LiNi_1/2Mn_1/2 O₂electrode delivered a discharge capacity of 152, 163, 183, and 189 mA h g^–1 in the voltage ranges of 2.8–4.3, 2.8–4.4, 2.8–4.5, and 2.8–4.6 V, respectively, with good cyclability. Furthermore, Al(OH)₃-coated LiNi_1/2Mn_1/2O₂exhibited excellent cycling behavior and rate capability compared to the pristine electrode.     

Direct electrochemical reduction of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript> in CaCl<Subscript>2</Subscript> melt

The electrochemical reduction of Dy₂O₃ in CaCl₂ melt was studied. The cyclic voltammetry, chronoamperometry, AC impedance and constant voltage electrolysis were employed. A single cathodic current peak in the cyclic voltammogram and one response semicircle in the AC impedance spectrum were observed, supporting a one-step electrochemical reduction mechanism of Dy₂O₃. No intermediates were observed by XRD, which confirmed the following electrochemical reduction sequence: Dy₂O₃ → Dy. The charge transfer resistances and the activation energies involved in the electrochemical reduction step of Dy₂O₃ were obtained by simulating the AC impedance spectra with equivalent circuits. The electrochemical reduction reaction of Dy₂O₃ is controlled by the charge transfer process at a low voltage range and by the diffusion process at a high voltage range.     

Improved performances of mechanical-activated LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/MWNTs cathode for aqueous rechargeable lithium batteries

LiMn₂O₄/multi-walled carbon nanotubes (MWNTs) composite was synthesized by mechanical activation reaction followed by a heat-treatment (500 °C). The LiMn₂O₄ and LiMn₂O₄/MWNTs as cathodes were investigated in 1 M Li₂SO₄ by cyclic voltammetry (CV), galvanostatic charge/discharge (GC), and electrochemical impedance spectroscopy (EIS). The LiMn₂O₄/MWNTs cathode delivered higher discharge capacity (117 mAh g⁻¹) than LiMn₂O₄ (84.6 mAh g⁻¹). Furthermore, the results from EIS showed that LiMn₂O₄/MWNTs had a faster kinetic process for lithium ion intercalation/de-intercalation than LiMn₂O₄. Besides, LiMn₂O₄/MWNTs had better cycling stability and rate capability than LiMn₂O₄, which was confirmed by GC testing. SEM images showed that a three-dimensional network structure was formed during the mechanical activation, giving a decrease of particle size.     

Study of electrochemical properties and the charge/discharge mechanism for Li<Subscript>4</Subscript>Mn<Subscript>5</Subscript>O<Subscript>12</Subscript>/MnO<Subscript>2</Subscript>-AC hybrid supercapacitor

Spinel Li₄Mn₅O₁₂ was prepared by a sol–gel method. The manganese oxide and activated carbon composite (MnO₂-AC) were prepared by a method in which KMnO₄ was reduced by activated carbon (AC). The products were characterized by XRD and FTIR. The hybrid supercapacitor was fabricated with Li₄Mn₅O₁₂ and MnO₂-AC, which were used as materials of the two electrodes. The pseudocapacitance performance of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor was studied in various aqueous electrolytes. Electrochemical properties of the Li₄Mn₅O₁₂/MnO₂-AC hybrid supercapacitor were studied by using cyclic voltammetry, electrochemical impedance measurement, and galvanostatic charge/discharge tests. The results show that the hybrid supercapacitor has electrochemical capacitance performance. The charge/discharge test showed that the specific capacitance of 51.3 F g⁻¹ was obtained within potential range of 0–1.3 V at a charge/discharge current density of 100 mA g⁻¹ in 1 mol L⁻¹ Li₂SO₄ solution. The charge/discharge mechanism of Li₄Mn₅O₁₂ and MnO₂-AC was discussed.     

Investigation on inhibition of CrO4 2− and MoO4 2− ions on carbon steel pitting corrosion by electrochemical noise analysis

The inhibition effect of chromate (CrO₄ ^2–) and molybdate (MoO₄ ^2–) anions on the pitting corrosion of 16Mn carbon steel in 0.1 M NaCl containing bicarbonate solution was studied based on electrochemical noise analysis (ENA) and the potentiodynamic polarization method. The experimental results indicated that, once the pits occur on the surface of the carbon steel after 4–6 h of immersion, increasing the concentration of CrO₄ ^2– and MoO₄ ^2– ions accelerate the repassivation process, and attenuate the duration and the nucleation rate of metastable pits. Further analysis demonstrated that noise resistance R _n might not be suitable for the evaluation of the inhibition efficiency of CrO₄ ^2– and MoO₄ ^2– anions on pitting corrosion in the present system. However, the transient charge q _pit, which is an integral of all current transients during a certain period, can characterize the inhibition performance on pitting corrosion. A new definition of inhibition efficiency based on q _pit is given.     

Effect of aluminium microstructure on corrosion and inhibiting effect of polyacrylic acid in H<Subscript>2</Subscript>SO<Subscript>4</Subscript> solution

The corrosion behaviour of a microcrystalline aluminium (mc-Al) coating fabricated from pure cast aluminium substrate by magnetron sputtering and the pure polycrystalline aluminium (pc-Al) were studied using electrochemical impedance spectroscopy and potentiodynamic polarization techniques in aerated 0.5 M H₂SO₄ at 30 ± 1 °C. The corrosion inhibiting effect of polyacrylic acid (PAA) and synergistic effect of iodide ions was also investigated. Results obtained show that surface microcrystallization increases the corrosion susceptibility of pure cast aluminium leading to decrease in interfacial impedance and an increase in the kinetics of the anodic dissolution. Introduction of PAA into the corrosive medium was observed to retard the corrosion rates of both specimens. The inhibition mechanism was affected by the microstructure of the sample. PAA functions as a mixed inhibitor but under cathodic control for pc-Al and under anodic control for mc-Al. Addition of iodide ions synergistically increased the inhibition efficiency of PAA and this effect was more pronounced with mc-Al.     

The effect of poly(vinyl caprolactone-co-vinyl pyridine) and poly(vinyl imidazol-co-vinyl pyridine) on the corrosion of steel in H<Subscript>3</Subscript>PO<Subscript>4</Subscript> media

The inhibiting effect of two organic copolymers namely poly(vinyl caprolactone-co-vinyl pyridine) (PVCVP) and poly(vinyl imidazol-co-vinyl pyridine) (PVIVP) on the corrosion of steel in phosphoric acid was investigated at various temperatures. The study was carried out by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Inhibition efficiency (E %) increased with polymer concentration to attain 85% at 10⁻⁴ M for PVIVP. Adsorption of polymers on the steel surface in 2 M H₃PO₄ followed the Langmuir isotherm model. EIS measurements show that the dissolution of steel occurs under activation control. Polarisation curves indicate that the tested polymers functioned as cathodic inhibitors. E % values obtained from various methods used are in good agreement with each other. The temperature effect on the corrosion behaviour of steel in 2 M H₃PO₄ in the presence and absence of the inhibitor was studied in the temperature range 298–338 K. The adsorption free energy (ΔG ^o _ads) and the activation parameters (E _a, , ΔS ^o _a) for the steel dissolution reaction in the presence of polymer were determined.     

Combustion of a Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript>-Al-C Powder Mixture in the SHS Regime and the Structure of the Combustion Products

The combustion of pressed specimens of a stoichiometric Fe₂O₃-TiO₂-Al-C powder mixture burning in the SHS regime is studied. It is found that the final product has the same shape and size as the initial specimen. The composition and structure of the final product, which is highly porous high-melting Al₂O₃-TiC-Fe(Ti) composite ceramics, are studied. The mechanism of phase and structure formation in the examined system is proposed.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 4, pp. 60–66, July–August, 2005.     

Synthesis,Characterization and Properties of One-dimensional Complexes of <Emphasis Type="Italic">cis-syn-cis</Emphasis>-Dicyclohexyl-18-crown-6 with K<Subscript>2</Subscript>[M(mnt)<Subscript>2</Subscript>] (M==Ni,Pd, Pt)

Three complexes [K(DC18C6-A)]₂[M(mnt)₂] (DC18C6-A=cis-syn-cis-dicyclohexyl-18-crown-6, isomer A; M=Ni, 1; Pd, 2; Pt, 3; mnt = 1,2-dicyanoethene-1,2-dithiolate, maleonitriledithiolate, [C₂S₂(CN)₂]²⁻) have been synthesized and characterized by elementary analysis, UV–vis, FT-IR spectroscopy and X-ray single crystal diffraction. They are isomorphous and all display infinite one-dimensional chain-like structure formed by [K(DC18C6-A)]⁺ complex cations and [M(mnt)₂]²⁻ (M=Ni, Pd, Pt) complex anions through K–N interactions. Thermal analysis indicates that three complexes are all thermal stable under 260 °C and experience the same decomposition process of dissociation and evaporation of crown ether molecules. Their electrochemical behaviors have been studied by cyclic voltammetry.     

The Oxidative Polycondensation of Benzylidene-4′-hydroxyanilene using Air O<Subscript>2</Subscript>, NaOCl and H<Subscript>2</Subscript>O<Subscript>2</Subscript>: Synthesis and Characterization

In this work, the oxidative polycondensation reaction conditions of benzylidene-4′-hydroxyanilene (B-4′-HA) were studied using oxidants such as air O₂, H₂O₂ and NaOCl in an aqueous alkaline medium between 40 and 95 ^○C. Oligo-benzylidene-4′-hydroxyanilene was characterized by ¹H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. The solubility of oligomer using organic solvents such as DMF, THF, DMSO, methanol, ethanol, CHCl₃, CCl₄, toluene, acetonitrile, ethyl acetate was investigated. According to air O₂ oxidant (flow rate 8.5 L/h), the conversion of B-4′-HA was 82.0% in optimum conditions such as [B-4′-HA]₀=[KOH]₀=0.1015 mol/L at 50 ^○C for 25 h. According to the SEC analysis, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of O-B-4′-HA were found to be 1852 g mol⁻¹, 3101 g mol⁻¹ and 1.675; 2123 g mol⁻¹, 4073 g mol⁻¹ and 1.919; 2155 g mol⁻¹, 4164 g mol⁻¹ and 1.932, using air oxygen, NaOCl and H₂O₂ oxidants, respectively. Also, Thermo gravimetric analysis (TGA) showed oligo-benzylidene-4′-hydroxyanilene to be unstable against thermo-oxidative decomposition. The weight loss of O-B-4′-HA was found to be 95.87% at 1000 ^○C.     

Carbon corrosion characteristics of CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanostructures in acidic media and implications for ORR performance

Accelerated electrochemical corrosion of nitrogen-containing carbon (CN _x ) oxygen reduction catalysts was performed by a chronoamperometric hold at 1.2 V versus NHE in acidic electrolyte using a rotating disk electrode system. Cyclic voltammograms were used to measure the electrochemically active quinone/hydroquinone redox reaction couple indicating the degree of carbon corrosion. Half-cell testing of CN _x oxygen reduction catalyst materials showed superior carbon corrosion resistance compared to Vulcan carbon, the most ubiquitous cathode catalyst support. When oxygen reduction activity was measured before and after carbon corrosion, carbon corrosion resilience trended with the oxygen reduction activity. CN _x catalysts subjected to carbon corrosion testing did not show a change in the onset of oxygen reduction reaction (ORR) activity potentials with only a slight reduction in current density, but showed improved ORR selectivity to the complete reduction of dioxygen to water.     

Role of some thiadiazole derivatives as inhibitors for the corrosion of C-steel in 1 M H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

Inhibition of C-steel corrosion by some thiadiazole derivatives (I–VI) in 1 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques. The presence of these compounds in the solution decreases the double layer capacitance, increases the charge transfer resistance and increase of linear polarization. Polarization studies were carried out at room temperature, and showed that all the compounds studied are mixed type inhibitors with a slight predominance of cathodic character. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were calculated and discussed. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The adsorption of the compounds on C-steel was found to obey Langmuir’s adsorption isotherm. The synergistic effect brought about by combination of the inhibitors and KSCN, KI and KBr was examined and explained. The mechanism of inhibition process was discussed in the light of the chemical structure and quantum-chemical calculations of the investigated inhibitors.     

Structural characterization and electrochemical properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> anode materials synthesized by a hydrothermal method

Cobalt oxide [Co₃O₄] anode materials were synthesized by a simple hydrothermal process, and the reaction conditions were optimized to provide good electrochemical properties. The effect of various synthetic reaction and heat treatment conditions on the structure and electrochemical properties of Co₃O₄ powder was also studied. Physical characterizations of Co₃O₄ are investigated by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller [BET] method. The BET surface area decreased with values at 131.8 m²/g, 76.1 m²/g, and 55.2 m²/g with the increasing calcination temperature at 200°C, 300°C, and 400°C, respectively. The Co₃O₄ particle calcinated at 200°C for 3 h has a higher surface area and uniform particle size distribution which may result in better sites to accommodate Li⁺ and electrical contact and to give a good electrochemical property. The cell composed of Super P as a carbon conductor shows better electrochemical properties than that composed of acetylene black. Among the samples prepared under different reaction conditions, Co₃O₄ prepared at 200°C for 10 h showed a better cycling performance than the other samples. It gave an initial discharge capacity of 1,330 mAh/g, decreased to 779 mAh/g after 10 cycles, and then showed a steady discharge capacity of 606 mAh/g after 60 cycles.