Effect of cerium concentration on corrosion resistance and polymerization of hybrid sol–gel coating on martensitic stainless steel

Stainless steels are increasingly used in the aeronautics field for the manufacture of structural parts. One of them, the X13VD martensitic stainless steel (X12CrNiMoV12-3), known for its good mechanical properties, has a poor corrosion resistance in confined or severe environments. In the past years, Cr(VI) based pre-treatments have been currently used for corrosion protection of different metals, however, they are toxic and due to environmental regulations, they will be definitely banned in a near future. Alternatives to replace Cr(VI) show advantages and drawbacks considering key properties such as: corrosion resistance, adhesion of coatings, fatigue resistance, durability and reliability. However, some of their possible alternatives show high potential.     

Corrosion resistance performance of cerium doped silica sol–gel coatings on 304L stainless steel

The aim of this work is the synthesis and investigation of silane based organic–inorganic hybrid coatings, which can be used to improve the corrosion performance of steel structures subjected to a marine environment. The silane based sol–gel coatings were prepared by dip coating 304L stainless steel in a solution of organically modified silica sol made through hydrolysis and condensation of 3-glycidoxypropyl-trimethoxysilane (GPTMS) as precursor and bisphenol A (BPA) as a cross-linking agent in an acid catalyzed condition. The influence of the addition of cerium and the use of bisphenol A as a cross-linking agent on the microscopic features and morphology as well as on the corrosion resistance of the coatings were examined using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), neutral salt spray tests, potentiodynamic polarization and electrochemical impedance techniques. Results show that cerium modified nano-hybrid coatings exhibit a superior corrosion inhibition performance to that displayed by silica hybrid coatings. Additionally, data showed that the bisphenol A as a cross-linking agent has a significant effect on the morphology and corrosion resistance of the cerium doped silica coating. Omitting the use of bisphenol A causes the creation of defects/cracks in the coating, thereby promoting diffusion of the aggressive electrolyte toward the substrate and decreasing the corrosion resistance of the coating.     

Effect of the dimensions of carbon nanotube channels on copper–cobalt–cerium catalysts for higher alcohols synthesis

A series of carbon nanotube (CNT)-supported copper–cobalt–cerium catalysts were prepared and investigated for higher alcohols synthesis. The superior selectivity for the formation of ethanol and C_2 + alcohols achieved using the CuCoCe/CNT(8) catalyst was 39.0% and 67.9%, respectively. The diameters of CNTs considerably influence the distribution of metal particles and the electronic interaction between the tube surface and the active species. The electronic effect between the encapsulated Co species and the inner surface is greatly improved in the narrowest CNT channel, which is expected to facilitate the reduction of cobaltous oxide and promote the alcohols yield remarkably (291.9 mg/g_cath).     

Preparation and thermophysical properties of fluorite-type samarium–dysprosium–cerium oxides

In the present study, (Sm_1−xDy_x)₂Ce₂O₇ solid solutions were synthesized by solid reaction at 1600 °C for 10 h in air. The phase structure, micro-morphology and thermophysical properties of (Sm_1−xDy_x)₂Ce₂O₇ oxides were examined. XRD results indicated that pure (Sm_1−xDy_x)₂Ce₂O₇ oxides with fluorite structure were prepared. SEM revealed that their microstructures were very dense and there were no other phases among the particles. The thermal conductivity and thermal expansion coefficient of the ceramics remarkably decreased through Dy-doping. Their thermal expansion coefficients were higher than that of YSZ, and their thermal conductivities were much lower than that of 8YSZ. Their excellent thermophysical properties imply that these solid solutions are potential materials for the ceramics layer in thermal barrier coatings.     

Corrosion of the zinc negative electrode of zinc–cerium hybrid redox flow batteries in methanesulfonic acid

Corrosion of zinc in aqueous methanesulfonic acid has been evaluated over a wide range of concentrations of acid (0.5–5 mol dm^?3), dissolved zinc (0.5–2 mol dm^?3), and electrolyte temperature (22–50 °C). The corrosion rate of zinc, in terms of weight loss and the volume of hydrogen evolved, varied with time and it was found to be highly dependent on the surface state and electrolyte conditions. With an initial active layer of zinc present, the corrosion rate rapidly increased following a decline when the proton concentration in the solution decreased to ca. 0.56 mol dm^?3. Organic and inorganic inhibitors were added to the electrolyte to suppress the zinc corrosion in 1 mol dm^?3 methanesulfonic acid. The strong adsorption and blocking effects of cationic organic adsorption inhibitors, such as cetyltrimethyl ammonium bromide and butyltriphenyl phosphonium chloride, led to a significant decrease in zinc corrosion over a 10 h immersion period. With the addition of indium and lead ions inhibitors, the zinc surface showed less activity. Zinc corrosion continued to a smaller extent in the presence of these metallic inhibitors during the first few hours, but the metallic layer of the inhibitors did not cover the surface completely resulting in continued hydrogen evolution and making the inhibitors less effective at longer times.     

Formulation and study of corrosion prevention behavior of epoxy cerium nitrate–montmorillonite nanocomposite coated carbon steel

Nanocomposite coatings which were applied on carbon steel panels based on epoxy cerium nitrate–montmorillonite (MMT) were synthesized and formulated. Nanoparticles were incorporated into epoxy resin by mechanical and sonication processes. The state of dispersion, dissolution, and incorporation were characterized by optical microscopy, sedimentation tests, X-ray diffraction, and transmission electron microscopy. To investigate anticorrosive properties of nanocomposite coatings, electrochemical impedance spectroscopy and salt spray tests were employed. The experimental results showed that epoxy cerium nitrate–MMT nanocomposite coatings were superior to the neat epoxy in corrosion protection effects. In addition, it was observed that the corrosion protection of nanocomposite coatings was improved as the clay loading was increased up to 4–2 wt% cerium nitrate.     

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16?×?2 surfaces

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.     

Sol–gel based layer-by-layer deposits of lanthanum cerium molybdate nanocontainers and their anticorrosive attributes

The present study focuses on the synthesis of novel lanthanum cerium molybdate (LCM) nanoparticles by sol–gel synthesis method and their use in the development of nanocontainers in an anticorrosive coating application. The obtained nanoparticles were used as core material with two different polyelectrolytic shells comprising of polypyrrole (PPY) and polyacrylic acid (PAA) or polyethyleneimine (PEI) and polystyrene sulfonate (PSS) involving the entrapment of benzotriazole (BTA) as the corrosion inhibitor using layer-by-layer (LBL) deposition method. At each step of this nanocontainer synthesis, the thickness of the layers, surface charges and the presence of the functional groups were determined by particle size, zeta potential and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The X-ray diffractograms (XRD) indicated the change in the crystallinity of the nanoparticles and nanocontainers while thermogravimetric analysis (TGA) showed the thermal degradation behavior of the nanocontainers. The morphological studies conducted using scanning electron microscopy (SEM) exhibited the formation of nanocontainers containing nanoparticles in their cores. The release of BTA from the nanocontainers was evaluated at different pH values. The anticorrosive performance of the nanocontainers was examined by incorporation of the nanoparticles and nanocontainers in a commercial epoxy coating system and to be applied on mild steel and magnesium panels by electrochemical corrosion analysis. Tafel plots demonstrated the decrease in the current density with an increase in the loading percentage of nanocontainers in the epoxy system while Bode plots confirmed the significant improvement in the corrosion protection of the mild steel and magnesium by LCM nanoparticles and nanocontainers.

     

Mesoporous copper–cerium–oxygen hybrid nanostructures for low temperature catalytic oxidation of carbon monoxide

Mesoporous copper–cerium–oxygen hybrid nanostructures were prepared by one-pot cetyltrimethylammonium bromide surfactant-assisted method, and were characterized by thermogravimetry, X-ray diffraction, transmission electron microscopy, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy and temperature-programmed reduction techniques. Low temperature carbon monoxide oxidation was used as probe reaction to investigate the application of the prepared mesoporous copper–cerium–oxygen hybrid nanostructures in catalysis. The product calcined at 400 °C, with disordered wormlike mesoporous structure, high specific surface area (SSA) of 117.4 m²/g and small catalyst particle size of 8.3 nm, shows high catalytic activity with the 100 % CO conversion at 110 °C, indicating its potential application in catalysis. Catalytic activity results from the samples calcinied at different temperature suggested that high SSA, small catalyst particle size, finely dispersed CuO species and synergistic effect between CuO and CeO₂ were responsible for the high catalytic activity of the catalysts.     

Corrosion study of hybrid sol–gel coatings containing boehmite nanoparticles loaded with cerium nitrate corrosion inhibitor

To improve the corrosion protection of sol–gel derived hybrid silica/epoxy coatings containing boehmite nanoparticles, inorganic corrosion inhibitor was introduced into the coating via encapsulation in the nanoparticles. The morphology and chemical structure of the deposited films were studied by Scanning Electron Microscopy (SEM) and Fourier Transformed Infra-red Spectroscopy (FT-IR). The anticorrosion and self-healing properties of the coatings were evaluated by Electrochemical Impedance Spectroscopy (EIS). The high corrosion resistance performance of such coatings is due to the presence of encapsulated cerium nitrate corrosion inhibitor that can be released at the defects within the coating, hindering the corrosion reactions at defective sites.     

Effects of Several Factors on Viscosity of Alumina-spinel Slurries

1IntroductionSpinelismorestablethanaluminainoxidation ,al kali,salt,fusedmetal,slagandcarbonatmosphere .Inrecentyears ,moreattentionhasbeengiventoit .Andithasbeenwidelyusedinthefieldofinsulated materials ,high performanceceramicsandrefractories .Concentratedalumina spinelslurrieswithgoodfluid ityarecrucialtopreparealumina spinelcastables .Whethertheconcentratedslurrycanbeobtainedornothastightrelationshiptoitsrheologicalbehavior .Ingener al ,therheologicalbehavioroftheslurryisaffectedbyanumber…     

Influence of CO2 on storage and release of NOx on barium‐containing catalyst

A barium‐containing three‐way automotive emission catalyst was submitted to a NO_x storage step in flowing lean gas mixture containing 340 ppm NO and 8 vol% O₂ in helium. NO_x release was carried out in the 250–550°C temperature range, either in pure helium or in the presence of a 10 vol% CO₂ in helium mixture. It was shown that at 450–550°C all of the stored NO_x on the barium trap can be released fastly in the CO₂‐containing gas mixture or, after a longer time, in pure helium: these data show that NO_x release can occur in the absence of a reducing agent. The NO_x release was not complete at 350°C and did not occur at 250°C. The assisting effect of CO₂ as regards to NO_x release was interpreted in terms of the existence of the CO_2,gas + *NO_2,stored ⇌ *CO_2,stored + NO_2,gas equilibrium, suggesting the competitive storage of CO₂ and NO₂ for a unique type of barium storage sites (*). This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of Water Vapor on the Adsorption of VOCs on Lignin‐Based Activated Carbons

Abstract

Activated carbons with a wide range of burn‐off degrees obtained from Eucalyptus kraft lignin have been used to study the influence of the presence of water vapor on VOCs adsorption. The amount adsorbed and the rate of adsorption of both benzene and water vapor increase with activated carbon burn‐off as a consequence of an increase of micropore volume, broadening of micropore size distribution and increasing development of meso‐ and macroporosity. Similar results were found for MEK and methanol. Benzene is only partially desorbed at the adsorption temperature and an appreciable amount of it remains in the carbon, most likely in the narrow micropores. On the contrary, water vapor is completely desorbed at the adsorption temperature and its adsorption profile clearly exhibits two steps with different adsorption rates, associated to water molecules adsorbed on the active sites given rise to cluster formation and further migration and filling of the micropores. Adsorption with mixtures of VOC and water vapor has been carried out. The total amount adsorbed by the carbon, near the equilibrium point, is higher than in the case of the stream containing only the VOC. The adsorption rates for the mixtures streams are similar to that for the corresponding streams containing only the VOC in the case of carbons with a well developed porous structure. However, the presence of water vapor increases the rate of adsorption on the activated carbons with narrower microporosity. Saturation of the activated carbon with water vapor prior to the adsorption of a mixture containing benzene and water vapor has shown little effect on the amount of benzene adsorbed, suggesting that water and benzene molecules are adsorbed in different sites on the carbon surface.     

Influence of the coke filler on the carcinogenicity of pitch–coke mixtures on carbonization

The emissions of benzo[a]pyrene at different temperatures and its concentration in the exhaust gases are measured in laboratory experiments on the carbonization (at temperatures up to 850°C) of coalpitch and petroleum-pitch binders and their mixtures with roasted petroleum and pitch coke. These pitch–coke mixtures are similar in composition to the anode mass used in aluminum production. The experiments confirm that the total benzo[a]pyrene emissions are much greater in the carbonization of petroleum pitch produced by cracking (T _so = 100°C) than for electrode pitch (T _so = 89°C) and other coal pitch. In most experiments, the benzo[a]pyrene emissions in the carbonization of pitch–coke mixtures is markedly less than for individual binder pitches. It is found that the benzo[a]pyrene emissions in the carbonization of a mixture based on pitch coke are much less than for a mixture based on petroleum coke in the high-temperature region that presents the greatest environmental hazard.     

Research on the Influence of Zircon Additive on the Properties of Sintered High Alumina Refractories

The influence of zircon particle size and adding quan-tity on the properties of high alumian refractories have been researched,The phase composition and microstructure were analysed by SEM and X-ray diffraction,The research il-lustrated that high alumina refractories can be greatly im-proved by adding proper quantity of zircon micro powder to form dense corundum-mullite-zirconia matrix.     

Effects of ultrasound on adsorption and desorption of chromium(Ⅵ) on activated carbon

研究了超声波对活性炭吸附/脱附Cr(Ⅵ)的影响,结果表明：有无超声波作用下,活性炭对Cr(Ⅵ)的吸附率均随pH值的升高而减小,相对于无超声作用体系,超声作用下的相平衡向吸附量减小的方向移动,且pH值越大,其减小的幅度越大;当Cr(Ⅵ)初始浓度由20 mg·L^-1增至110 mg·L^-1时,超声波作用下的Cr(Ⅵ)去除率由99.9%降至79.8%,平衡吸附量则由3.3 mg·g^-1增至15.0 mg·g^-1,与无超声波作用下的效果接近,但无超声波作用时的吸附率持续上升至平衡,而超声波作用下的吸附率先快速增加至近平衡,再出现小幅下降后又缓慢增至平衡。脱附实验发现,无论有无超声作用,活性炭表面Cr(Ⅵ)在蒸馏水中的脱附率均很小;添加NaOH可显著改善脱附效果,脱附率随NaOH用量的增加而增加,且超声场中NaOH对脱附的促进作用显著高于非超声场中的效果。     

Study on Properties of Magnesia-Hercynite Brick

Using magnesia and hercynite as materials, we researched the magnesia-hercynite brick in order to solve the problem of chrome-free brick used in the burning zone of cement rotary kiln. Effect of different firing temperature and different content of hercynite on properties of the brick were studied. The results show that the magnesiahercynite specimen fired at 1600℃ was densified and when the hercynite content is 7%, the cold crushing strength and the adhesive strength of rupture of the specimen have the highest value.     

The Effect of Foreign Ions on Separation of Hafnium from Zirconium on Diphonix® Resin

The weight distribution coefficients (λ_M) of the most often occurring in zirconium salts ions (M(II), M(III) and M(IV)) have been determined in established earlier optimal conditions for separation of zirconium from hafnium by means of Diphonix® resin. Their values range from 21 (λ_Zn(II)) to 1830 (λ_Ti(IV)) and depend on the charge of M ion as well as on its radius. For ions of the highest λ_M (Ti(IV) and Fe(III)) their influence on hafnium – zirconium separation has been studied. Ti(IV) ions at concentration of 1% (in relation to Zr) has been found to noticeably affect separation of hafnium from zirconium by means of Diphonix® resin.     

Effect of Addition of Al and Mg on properties of Periclase-Spinel-Carbon Brick

Periclase-spinel-carbon brick was made from sintered spinel,fused magnesia and flake graphite as principal raw materials,the influence of Mg/Al(w/w) ratio and the addition of Al,Mg in the matrix of periclas-spinel-carbon brikc on the carbonization and thermal expansion coeffi-cient and the weight los of the brick after heating at 1500℃ in a flowing stream of dry N2for 1.5 h have been studied.The results show that to control Mg/Al(w/w) ration and to add both Al and Mg appropriately can obvi-ously improve the properties of the bricks.     

Effect of Ba Addition on Catalytic Activity of Pt and Rh Catalysts Loaded on γ-Alumina

The catalytic activity of Pt catalyst loaded on -alumina was improved by Ba addition in simulated automotive exhaust gases. On the other hand, the result of Rh catalyst was the opposite. From the results of the partial reaction orders in C₃H₆–O₂ reaction and TPR, it was concluded that the Ba addition to Pt catalyst suppressed the hydrocarbon chemisorption on the Pt catalyst and therefore allowed the catalytic reaction to proceed smoothly. On the other hand, Ba addition to Rh catalyst caused such a strong oxygen adsorption on Rh that rejected the hydrocarbon adsorption and suppressed the reaction.