An Electrochemical study of the formation of Benzotriazole surface films on Copper, Zinc and a Copper–Zinc alloy

The electrochemical behaviour of Cu, Cu–37Zn and Zn in benzotriazole (BTA) containing chloride solutions was studied and compared using potentiodynamic, cyclic voltammetry and electrochemical impedance spectroscopy. The presence of BTA in the chloride-containing solutions gave rise to higher breakdown potentials, significantly higher polarisation resistances and inhibited the formation of CuCl₂ and zinc-containing corrosion products. These effects were observed for pure Cu, Cu–Zn and to a somewhat lesser extent pure Zn. The electrochemical impedance data were consistent with the formation of a polymeric BTA-containing layer for all three systems.     

The Influence of Copper–Copper Interaction on the Structure and Applications of a Metal–Organic Framework Based on Cyanide and 3-Chloropyridine

The structure of the new metal–organic framework, [(CuCN)₂·(3-Clpy)], 1, was characterized by IR, UV–visible, TGA and X-ray single crystal analysis. The structure of 1 consists of CuCN building blocks, which are connected by CN group to form two different chains; one puckered chain with TP-3 geometry around Cu(1) and a linear Cu(2)(CN)₂ chain. The two kinds of chains are bonded by cuprophilic interactions creating a 3D-network. The network structure of 1 is further close-backed by π–π stacking and hydrogen bonds. The electronic absorption and emission spectra as well as the thermodynamic parameters from TGA of the MOF 1 are discussed. MOF 1 was used as an effective heterogeneous catalyst for the oxidative discoloration of methylene blue dye by dilute solution of hydrogen peroxide as the oxidant. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine the in vitro antitumor activity of MOF 1 on human breast cancer cell line, MCF7.     

Synthesis and Surface Modification of Mesoporous Silicate SBA‐15 for the Adsorption of Metal Ions

Abstract

In this study surface modified SBA‐15, coated with octadecyltrichlorosilane (C18), is considered as an alternative adsorbent for metal ions in water. The SBA‐C18 was loaded with Bis(2,4,4-trimethylpentyl) phosphinic acid (cyanex 272) as the metal ion extractant. The adsorption characteristics of phosphinic acid loaded SBA‐C18 were evaluated for Cu(II) and Zn(II) ions in aqueous solution. Adsorption tests indicated that a contact time of 1 hour was sufficient for adsorption equilibrium to occur. The pH_1/2 values of Zn(II) and Cu(II) onto SBA‐C18, were found to be similar to published data for levextrel ion exchange resins and around 1 pH unit lower than published solvent extraction data for cyanex 272 in xylene.     

Evolution of Acid–Base Properties of the Surface of Zinc Oxide Powders Obtained by the Method of Grinding in an Attritor

The evolution of the acid–base properties of the surface of zinc oxide powders during mechanical grinding in an attritor is studied. The study is performed using the methods of the adsorption of acid–base indicators and X-ray photoelectron spectroscopy. Correlations between the results obtained by these methods are established. It is shown that a monotonic decrease in the particle size of ZnO powders is accompanied by a nonmonotonic change in the surface acid–base properties.     

Kinetic Studies on the Exchange of Bivalent Metal Ions on Amberlite IRC‐718—An Iminodiacetate Resin

Abstract

The rate of uptake of alkaline earth metals, copper, and lead have been investigated by a chelating ion exchange resin containing iminodiacetic acid as ligand attached to the copolymer of styrene and divinyl benzene of macroporous matrix structure. It binds alkaline earth metals, Cu, and Pb by the formation of chelate complexes with the carboxylate group of this resin. The experiments discussed in this work have allowed to establish the paramount importance of the presence of this chelating group in obtaining practically useful rates of metal ion uptake. The kinetic parameters like diffusion coefficient (D _o), activation energies (ΔE _a) and entropy of activation have been evaluated under the conditions favoring a particle diffusion control mechanism and the study followed the three models i.e., Nernst Planck, B _t technique and Ash model. K _d values in demineralised water (DMW) were found in the order Cu²⁺ > Pb²⁺ > Mg²⁺ > Sr²⁺ > Ba²⁺ > Ca²⁺.     

Preparation of Silica-Alumina Hollow Spheres with a Single Surface Hole by Co-axial Microchannel☆

Si/Al composite hollow spheres with a surface hole were prepared with the co-axial microchannel in a one-step method. It is easy to use the technique for size control and continuous operation. At Si/Al...     

Effect of Treatment with NaAlO2 Solution on the Surface Acid Properties of Zeolite β

The influence of treatment with an NaAlO₂ aqueous solution of NaAlO₂ on the surface acid properties of zeolite β was studied as a method to increase the number of both Brønsted and Lewis acid sites. The Hβ samples, prepared by treating with an aqueous solution of NaAlO₂, were characterized by XRD, NH₃-TPD, pyridine-IR, ²⁹Si MAS NMR, and ²⁷Al MAS NMR. The surface properties of the Hβ zeolite changed after treatment with the aqueous NaAlO₂ solution: the number of strong and weak acid sites, the total amount of acid, and the Brønsted and Lewis acid sites increased. The treatment of zeolite β with an aqueous solution of NaAlO₂ may realuminate an Si(0Al)_A site by the isomorphous substitution of Al(OH)₄⁻ anions.     

Inward and Outward Diffusion of Modifying Ions and its Impact on the Properties of Glasses and Glass–Ceramics

In this paper, we review our recent findings about both the cationic inward and outward diffusion processes in glasses and glass–ceramics caused by redox reactions. We provide new insights into these findings by mapping the diffusion depth, the thermal reduction temperature, and time in a three dimensional diagram and by looking into the correlation among the glass composition, structure, topology, and the diffusion process in the polyvalent elements containing glasses. We illustrate the link between glassy dynamics (via the liquid fragility index m) and activation energy of diffusion. Furthermore, the inward diffusion approach is used to study percolation phenomena in glass–ceramics. Finally, we show that the diffusion approaches are potential tools for tailoring the surface performances of bulk glasses and glass fibers.     

Comparative Studies on the Mechanochemistry of Guaiacylglycerol- and Veratrylglycerol- β -Guaiacyl Ether

Treatments of guaiacylglycerol- and veratrylglycerol-β-guaiacyl ether [I] and [II] with CBM, VBM and laboratory refiner furnished α-(2-methoxyphenoxy)-β-hydroxypropioguaiacone 1 as the major product in addition to a few small compounds 2-7 in relatively low yields. In addition, 5,5′-condensation reaction of compound [I] gave compounds 8 9, and 10. Alternatively, Cα-Cβ splitting reaction of veratrylglycerol-β-guaiacyl ether [II] occurrsby the mechanical treatment to give a number of products (6,11-14, and 15). Compounds [II] also formed p-carbonyl phenol 1 and products 2 4, and 7 by an alternate route. For comparison, mechanical treatments of vanillyT alcohol [III],α-methyl vanillyl alcohol [IV], and veratryl alcohol [V] were made with a ceramic ball mill (CBM), vibration ball mill (VBM), respectively. Former two gave vanillin 15 and acetovanillone 16, but no product was found from veratryl alcohol [V].     

Analysis of the Influence of the Loading Scheme on the Stress State of the Surface Layer of Al2O3–TiC-Ceramics with AlN and TiN Coatings

Refractories and Industrial Ceramics - The results of force, thermal, and combined stress analysis of the surface layer of Al2O3–TiC-ceramics with AlN and TiN coatings are analyzed and...     

Synthesis and Surface Properties of Dicephalic Surfactants with a 1,3-Dioxane Ring

A new group of surface active dicephalic derivatives of 1,3-dioxane, i.e., 2-alkyl-5,5-bis{[3-(N,N-dimethylamino)propyl]amido}-1,3-dioxane-di-N-oxides, were synthesized with high yields by the reaction of an appropriate 2-alkyl-5,5-bis-(carboxyethyl)-1,3-dioxane with an excess of N,N-dimethyl-1,3-propanediamine followed by oxidation with an aqueous solution of hydrogen peroxide. Structures and purity of all intermediates and final di-N-oxides were confirmed by means of ¹H-NMR and ESI-MS spectroscopy. Synthesized compounds showed high surface activity with low values of critical micelle concentration and high effectiveness of surface tension reduction (γ _CMC). However, only derivative with the longest 2-alkyl substituent showed good foaming and moderate emulsifying properties.

Simulation of the Process of the Hydrocycloning of Particles of “Light” Fractions on the Filtering Surface of a Drain Pipe

Theoretical Foundations of Chemical Engineering - The process of the separation of inhomogeneous systems is considered for the case in which the density of particles of the dispersed phase is less...     

Electronic Metal–Support Interactions and the Production of Hydrogen Through the Water-Gas Shift Reaction and Ethanol Steam Reforming: Fundamental Studies with Well-Defined Model Catalysts

The electronic properties of Ni and Pt nanoparticles deposited on CeO₂(111) have been examined using core and valence photoemission. The results of valence photoemission point to a new type of metal–support interaction which produces large electronic perturbations for small Ni and Pt particles in contact with ceria. The Ni/CeO₂(111) and Pt/CeO₂(111) systems exhibited a density of metal d states near the Fermi level that was much smaller than that expected for bulk metallic Ni or Pt. The electronic perturbations induced by ceria on Ni made this metal a very poor catalyst for CO methanation, but transformed Ni into an excellent catalyst for the production of hydrogen through the water-gas shift and the steam reforming of ethanol. Furthermore, the large electronic perturbations seen for small Pt particles in contact with ceria significantly enhanced the ability of the admetal to adsorb and dissociate water made it a highly active catalyst for the water-gas shift. The behaviour seen for the Ni/CeO₂(111) and Pt/CeO₂(111) systems illustrates the positive effects derived from electronic metal–support interactions and points to a promising approach for improving or optimizing the performance of metal/oxide catalysts.     

Influence of a Zwitterionic Surfactant on the Surface Properties of Electroless Ni–P Coating on Mild Steel

3-(N,N-Dimethyl myristyl-ammonio) propane sulfonate zwitterionic surfactant (C14-SB) which possessed both positive and negative charges was evaluated in the electroless Ni–P coating process. It was observed that the deposition rate, morphology and microhardness of the deposits were enhanced by the addition of C14-SB surfactant. The excess attractive forces from the negative head of C14-SB were strong enough to draw metallic nickel particles towards the substrate. Ni particles attempting to deposit on the electrolyte container were eliminated by the repulsive force from the positive head of the surfactant monomers. Thus, the deposition rate of the coating process was improved. The surfactant at its critical micelle concentration (CMC) doubles the deposition rate when compared to the substrate without surfactant. In addition, the microhardness of the deposit at the surfactant CMC increased by 62 %. The corrosion rate of the substrate without surfactant was 7.15 mpy, while it was 3.97 mpy for the substrate deposited with C14-SB zwitterionic surfactant at the CMC.     

Preparation of Silica–Alumina Hollow Spheres with a Single Surface Hole by Co-axial Microchannel

Si/Al composite hollow spheres with a surface hole were prepared with the co-axial microchannel in a one-step method. It is easy to use the technique for size control and continuous operation. At Si/Al ratio between 4 and 5, a hole forms on the surface, due to the fast gelation process and high viscosity of the sol. Scanning electron microscopy, nitrogen adsorption–desorption isotherms, and mercury intrusion method are used to characterize the samples. The hole size is 40–150 μm and the particle size is 450–600 μm. The size can be adjusted by the flow rate of the oil phase.     

Surface Science and Catalysis—Studies on the Mechanism of Ammonia Synthesis: The P. H. Emmett Award Address

Abstract

About 5 years ago a Battelle Colloquium on “The Physical Basis of Heterogeneous Catalysis” was held in honor of Professor Emmett where he presented an introductory talk on ″Fifty Years of Progress in the Study of the Catalytic Synthesis of Ammonia″ [1], a field to which he had made significant contributions during this whole period. So why another report on this topic? Justification can perhaps partly be obtained by some of Professor Emmett's concluding remarks which were not completely decisive with respect to the mechanism of this reaction: 'The experimental work of the past 50 years leads to the conclusion that the rate-determining step in ammonia synthesis over iron catalysts is the chemisorption of nitrogen. The question as to whether the nitrogen species involved on the surface is molecular or atomic is still not conclusively resolved. In fact, our own work in this field was mainly induced by this paper, and continuing discussions and correspondence with Professor Emmett were extremely helpful during its progress. I am therefore very much honored to be this year's recipient of the Emmett Award.     

The Interactions between Spheres and between a Sphere and a Half-Space,Based on the Lennard–Jones Potential

This paper investigates the interaction between two rigid spheres and between a rigid sphere and a rigid half-space, based on the Lennard–Jones potential. By using the divergence theorem and integrating the Lennard–Jones potential over the surfaces, the analytical forms of the surface tractions were obtained, and by integrating the Lennard–Jones potential over the volumes, the analytical form of the total force between two rigid spheres was obtained. The results are compared to those with the Derjaguin approximations and with the parabolic approximation for the sphere profile. The accuracy of the Derjaguin approximation and the parabolic approximation were estimated. The analytical surface traction can be used for the adhesive contact between an elastic body and a rigid one.     

Self-Organizing Cyclolinear Organosilicon Polymers in Bulk and on the Surface of Water ?

Cyclolinear organocarbosiloxane polymers with varying content and location of (CH₂)_n groups in the monomer unit were synthesized by reactions of heterofunctional polycondensation and polyaddition of difunctional organocyclosiloxanes and organocyclocarbosiloxanes. Their bulk properties were studied by differential scanning calorimetry and X-ray structural analysis. It was shown that on introduction of CH₂ groups into the methylcyclohexasiloxane unit, the polymer retains the ability to self-organize with formation of a mesomorphic state in a wide temperature range, while on introduction of (CH₂)₂ fragments in a cyclotetrasiloxane unit or in a bridge connecting two methylcyclotetra(hexa)siloxane units it does not. Comparison of the X-ray data of dihydroxy derivatives of decamethylcyclohexasiloxane and decamethyl-5-carbocyclohexasiloxane with packing of cyclolinear organosilicon polymers in bulk shows that the polymer inherits the layered type of crystalline structure typical for monomers. Langmuir films of cyclolinear polymethylcarbosiloxanes with different design of monomer units were studied as well. It was revealed that all polymers form monomolecular films at the air/water interface, excluding those having longer hydrophobic fragment than hydrophilic ones. The ability to form multilayers depends on the surroundings of Si atom in the bridge between the cycles.