Electrooxidation of acetaldehyde on carbon-supported Pt, PtRu and Pt3Sn and unsupported PtRu0.2 catalysts: A quantitative DEMS study

The oxidation of acetaldehyde on carbon supported Pt/Vulcan, PtRu/Vulcan and Pt₃Sn/Vulcan nanoparticle catalysts and, for comparison, on polycrystalline Pt and on an unsupported PtRu_0.2 catalyst, was investigated under continuous reaction and continuous electrolyte flow conditions, employing electrochemical and quantitative differential electrochemical mass spectroscopy (DEMS) measurements. Product distribution and the effects of reaction potential and reactant concentration were investigated by potentiodynamic and potentiostatic measurements. Reaction transients, following both the Faradaic current as well as the CO₂ related mass spectrometric intensity, revealed a very small current efficiency for CO₂ formation of a few percent for 0.1 m acetaldehyde bulk oxidation under steady-state conditions on all three catalysts, the dominant oxidation product being acetic acid. Pt alloy catalysts showed a higher activity than Pt/Vulcan at lower potential (0.51 V), but do not lead to a better selectivity for complete oxidation to CO₂. C–C bond breaking is rate limiting for complete oxidation at potentials with significant oxidation rates for all three catalysts. The data agree with a parallel pathway reaction mechanism, with formation and subsequent oxidation of CO_ad and CH _{x, ad} species in the one pathway and partial oxidation to acetic acid in the other pathway, with the latter pathway being, by far, dominant under present reaction conditions.     

Development and characterization of silicone/phosphorus modified epoxy materials and their application as anticorrosion and antifouling coatings

Epoxy resin is chosen for our present study owing to its exceptional combination of properties such as easy processing, high safety, excellent solvent and chemical resistance, toughness, low shrinkage on cure, good electrical, mechanical and corrosion resistance with excellent adhesion to many substrates. This versatility in formulation made epoxy resins widely applied for surface coatings, adhesives, laminates, composites, potting, painting materials, encapsulant for semiconductor and insulating material for electric devices. There are numerous paint/coating systems based on epoxy resin available for corrosion and fouling prevention. They however are not completely satisfactory in field applications, where high corrosion, fouling and flame resistance are required. The demand for epoxy resin as corrosion/fouling resistant coatings is restricted mainly due to its inferior characteristics like poor impact strength, high rigidity, and moisture absorbing nature besides inadequate flame retardant properties. It is for this reason that silicones and phosphorus-based compounds are used as modifier in this work by intercrosslinking network mechanism (ICN) to obtain epoxy resin with desired properties ideally suitable for field applications for preventing corrosion and fouling with flame retardantancy. The present work involves the development of solvent free silicone/phosphorus modified epoxy coating systems, since solvent free coating systems are widely used for numerous applications due to their lower cost per unit film thickness, freedom from fire and pollution hazard and ability to provide better performance. For the development of coating systems, epoxy resin (X) serves as base material, hydroxyl terminated polydimethylsiloxane (HTPDMS) as modifier, γ-aminopropyltriethoxysilane (γ-APS) as crosslinking agent and dibutyltindilaurate (DBTDL) as catalyst. Polyamidoamine (A), aromatic amine adducts (B) and phosphorus-containing diamine (C) were used as curing agents. The study also describes the evaluation of corrosion resistant behaviour of unmodified epoxy and siliconized epoxy coatings by potentiodynamic polarization method, electrochemical impedance spectroscopy (EIS), salt-spray and antifouling tests. The results are discussed.     

Mechanical Properties of Porous Materials

Porous materials are commonly found in nature and as industrial materials such as wood, carbon, foams, ceramics and bricks. In order to use them effectively, their mechanical properties must be understood in relation to their micro-structures. This paper studies the mechanical properties of a few common porous materials: carbon rods, ceramics, polymeric foams and bricks. The characterisation of pore structures was performed using a Mercury Porosimeter. Detailed information was obtained on the density, porosity, surface area and pore size distribution. A large number of experiments on either bending or compression were conducted in order to obtain their macro-mechanical properties such as Young's modulus, hardness and strength. Based on the experimental observations, theoretical models were employed to predict the macro-properties from the micromechanics viewpoint. By studying the deformation of pores the global behaviour was calculated. Two simple formulae for the elastic modulus, E, were proposed: for low values of porosity, , E = E⁰(1 – 2) (1 + 4²) where E⁰ is the elastic modulus when the porosity is zero; for high value of porosity such as for foams E = E⁰ (1 – )². The theoretical results agreed well with the experimental ones. The study has provided insights into the mechanical properties of porous materials over a wide range of porosity values.     

Behavioral and physiological responses of cabbage looper,Trichoplusia ni (Hübner), to steam distillates from resistant versus susceptible soybean plants

Soybean plant volatiles, extracted as steam distillates, significantly affected the behavior and biology of the cabbage looper,Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae). Distillates from the susceptible Davis variety attractedT. ni larvae and female adults, whereas those from resistant PI 227687 plants repelled them. When mixed in an artificial diet, steam distillates from PI 227687 plants caused mortality of first-instar larvae. Adults emerging from pupae topically treated with 5 g of such PI 227687 extractable showed developmental abnormalities. Larval feeding was significantly less on Davis leaves treated with PI 227687 volatiles as compared to solvent (acetone) or such Davis extractables. However, Davis volatiles on PI 227687 leaves did not increase larval feeding. HPLC analyses of steam distillates from susceptible Davis versus resistant PI 227687 indicated differences.     

Study of the deactivation and regeneration of copper chromite on γ-alumina and magnesium chromite on γ-alumina catalysts for fuel combustion

The causes of the deactivation of catalysts for fuel combustion MeCr₂O₄/ -Al₂O₃ (Me = Cu or Mg) have been investigated using a variety of complex physical-chemical methods: IRS, ESDR, XPS, TPD and a pulse microcatalytic method. It has been concluded that the observed deactivation of catalysts during fuel combustion is due to the combined effect of high temperatures and reduction media.     

Diamond growth by carbon ion implantation of diamond

Medium energy (5–25 keV) ¹³C⁺ ion implantation into diamond (100) to a fluence ranging from 10¹⁶ cm⁻² to 10¹⁸ cm⁻² was performed for the study of diamond growth via the approach of ion beam implantation. The samples were characterized with Rutherford backscattering/channelling spectroscopy, Raman spectroscopy, X-ray photoemission spectroscopy and Auger electron spectroscopy. Extended defects are formed in the cascade collision volume during bombardment at high temperatures. Carbon incorporation indeed induces a volume growth but the diamond (100) samples receiving a fluence of 4 × 10¹⁷ to 2 × 10¹⁸ at. cm⁻² (with a dose rate of 5 × 10¹⁵ at. cm⁻² s⁻¹ at 5 to 25 keV and 800 °C) showed no He-ion channelling. Common to these samples is that the top surface layer of a few nanometers has a substantial amount of graphite which can be removed by chemical etching. The rest of the grown layer is polycrystalline diamond with a very high density of extended defects.     

Carbon Nanofibers: A New Ultrahigh-Strength Material for Chemical Technology

Carbon nanofibers are described as a new ultrahigh-strength material, which is superior to both ordinary carbon fibers and other high-strength materials. The place occupied by nanofibers in the classification of carbon materials is shown, and an analysis is made of the relationship between the structure of a fiber and its useful properties, in particular, the strength and tensile modulus. Studies on the synthesis of nanofibers are reviewed. It is shown that the practically important problem of producing nanofibers of maximum possible length must be solved by controlling the temperature conditions of the reaction. The prospects for introducing nanofibers into the market of high-strength and heat-resistant materials are analyzed. The most likely prospect seems to be the partial replacement of polyacrylonitrile-based fibers by nanofibers, first and foremost, in the fields where the requirements for high strength are particularly stringent due to safety reasons.     

New developments and capabilities in prosyn—An automated topology and parameter process synthesizer

This paper describes an improved, equation oriented user friendly version of the modular computer package PROSYN—a mixed-integer nonlinear programming (MINLP) process synthesizer. A number of strategies are described and implemented for the outer approximation and equality relaxation algorithm (OA/ER) in order to reduce the undesirable effects of nonstructured nonconvexities in the master problem. These strategies include use of valid outer-approximations for splitters and mixers and various ways of handling the linearizations. An NLP initializer, model generator and a comprehensive library of models for basic process units and interconnection nodes, and a comprehensive library of basic physical properties have been developed and built in the PROSYN package. In this way PROSYN can be used to solve problems at different levels of complexity: from the simple NLP flowsheeting up to the MINLP synthesis through the modeling and decomposition (M/D) strategy and simultaneous heat integration including HEN costs. Applications with PROSYN are demonstrated with several example problems.     

Determination of trace manganese and Ni in neem oil by ETA-AAS with emulsion sample introduction

An emulsion-based method was developed as an alternative for the introduction of oil-based samples into a graphite furnace to produce a more rapid, precise, and accurate method of analysis. The combination of emulsion sampling and electrothermal atomization for atomic absorption spectroscopy was developed and then applied to the determination of Ni and manganese in neem oil from Venezuela. The optimal concentration of neem oil in the emulsion was 30 and 4% for Ni and Mn, respectively, based on the metal concentration of the neem oil. The stability of the emulsion as a function of time was evaluated. The use of aqueous calibration solutions and the accuracy attained using this method make it attractive for the analysis of oil samples. The metal recovery was between 97 and 101%. Based on the emulsion method, the neem oil samples had 1.39 and 0.21 mg of Mn and Ni per kg of oil, respectively. The wet digestion method indicated a Mn and Ni concentration in the neem oil sample of 1.42 and 0.24 mg/kg, respectively.     

Azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component

A number of new azo disperse dyes with polyfluoroalkyl groups attached to the nitrogen atom of the coupling component have been prepared. The influence of polyfluoroalkyl groups on the colour and properties of azo dyes has been studied. The replacement of hydrogen atoms of the methyl group of the coupling component by polyfluoroalkyl radicals causes a hypsochromic shift of absorption maximum in a neutral solution and deepening of the dye colour in an acid solution. All tested dyes showed a high lightfastness on acetate and polyamide fibres.