Effect of piperidones on hydrogen permeation and corrosion inhibition of mild steel in acidic solutions

The influence of 3-methyl-2,6-diphenyl piperidin-4-one (MDPO) and 2-phenyl decahydroquinoline-4-one (PDQO) synthesised in the laboratory on hydrogen permeation and corrosion inhibition of mild steel in 1N H₂SO₄ has been studied using weight loss and various electrochemical AC and DC corrosion-monitoring techniques. Both the compounds inhibit the corrosion of mild steel in H₂SO₄. Potentiodynamic polarisation studies clearly reveal that they behave predominantly as cathodic inhibitors. The extent of decrease in hydrogen permeation current through steel surfaces has been studied by the hydrogen electropermeation technique. Double layer capacitance (C _dl ) and charge transfer resistance (R _t ) values are derived from Nyquist plots obtained from AC impedance studies. The adsorption of these compounds on mild steel surfaces from H₂SO₄ obeys Temkin’s adsorption isotherm.     

Interfacial adsorption characteristics of ionic polymeric amphiphiles with comb‐like structures: Effect of dodecyl and poly(ethylene oxide) side chains

Two sets of terpolymers, polymer A and polymer B consisting of almost same level of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) component at 0.635 ± 0.005 m and varying dodecyl methacrylate (DoDMAc) and monomethoxy poly(ethylene glycol) acrylate (PEGAc) components have been designed. Polymer A, consisting of less C₁₂ component, has been shown to promote intermolecular aggregated structures wherein C₁₂ domains exhibit compact packing characteristics. It is demonstrated that in polymer B, AMPS segments are predominantly present as ionic clusters contributing to a high pKa at about 9.50 for a low α of 0.20. From the results of interfacial adsorption estimations at air/solution and water/hexane interface, it is shown that open coil structures provided under high pH (>9.0) conditions promote efficiency of adsorption. This is shown from higher surface excess concentration (Γ) and lower interfacial area (a) estimated using Gibbs adsorption isotherm equation. For example, at water/hexane interface, polymer A exhibits Γ of 1.20 × 10^?3 moles/1000 m² at pH 3.2 and 1.97 × 10^?3 moles/1000 m² at pH 10.0. Significantly, in case of polymer B consisting of ionic clusters of AMPS, adsorption at the liquid/liquid interface is more efficient in comparison to polymer A at all pH. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 3257–3271, 2008     

Hydrocarbon group type analysis of petroleum heavy fractions using the TLC-FID technique

Hydrocarbon group type analysis is important in all conversion processes and in preparation of feed for these conversion processes so as to learn the selectivity of the different type of catalysts for product yield and quality. The use of the Mark 5 Iatroscan detector and the method reported here allowed for a rapid and quantitative hydrocarbon group type analysis of petroleum residues without prior separation of asphaltenes. SARA type analyses of petroleum residues have been performed by a three stage development using n-hexane, toluene and DCM (95%):MeOH (5%). The standard deviation and coefficient of variation in repeated measurements by this method were as low as 0.65 wt% or less and 3.5 wt% or less, respectively. The time required for analysis of 10 samples could be as short as 90 min. Received: 20 May 1997 / Revised: 12 August 1997 / Accepted: 16 August 1997     

Shape and size transformation of gold nanorods (GNRs) via oxidation process: A reverse growth mechanism

The anisotropic shape transformation of gold nanorods (GNRs) with H₂O₂ was observed in the presence of “cethyl trimethylammonium bromide” (CTAB). The adequate oxidative dissolution of GNR is provided by the following autocatalytic scheme with H₂O₂: Au⁰ → Au⁺, Au⁰ + Auⁿ⁺ → 2Au³⁺, n = 1 and 3. The shape transformation of the GNRs was investigated by UV-vis spectroscopy and transmission electron microscopy (TEM). As-synthesised GNRs exhibit transverse plasmon band (TPB) at 523 nm and longitudinal plasmon band (LPB) at 731 nm. Upon H₂O₂ oxidation, the LPB showed a systematic hypsochromic (blue) shift, while TPB stays at ca. 523 nm. In addition, a new emerging peak observed at ca. 390 nm due to Au(III)-CTAB complex formation during the oxidation. TEM analysis of as-synthesised GNRs with H₂O₂ confirmed the shape transformation to spherical particles with 10 nm size in 2 h, whereas centrifuged nanorod solution showed no changes in the aspect ratio under the same condition. Au³⁺ ions produced from oxidation, complex with excess free CTAB and approach the nanorods preferentially at the end, leading to spatially directed oxidation. This work provides some information to the crystal stability and the growth mechanism of GNRs, as both growth and shortening reactions occur preferentially at the edge of single-crystalline GNRs, all directed by Br⁻ ions.     

Experiments to Explore the Mechanisms of Heat Transfer in Nanocrystalline Alumina/Water Nanofluid under Laminar and Turbulent Flow Conditions

Abstract

Heat transfer characteristics of water-based nanocrystalline alumina (Al₂O₃) nanofluids flowing through a uniformly heated tube under a fully developed laminar and turbulent flow regime is investigated experimentally in the present work to explore the heat transfer mechanism in nanofluids. In a laminar flow, the increase in Nusselt number was attributed to the thermophysical properties of the nanofluid. The movement of nanoparticles, along with the turbulent eddies in the turbulent core region and diffusion mechanism, such as thermophoresis, in the laminar sublayer are believed to be the reasons for enhanced heat transfer in turbulent region. The compatibility of Al₂O₃/water nanofluids was also examined by monitoring its color.     

Gamma radiation dosimetry in mega rad range using sugar solution

The formation of Malonaldehyde under gamma irradiation of solid sucrose and aqueous sucrose, fructose and arabinose solutions has been studied in the Mega rad range. Malonaldehyde (MA) concentration was estimated spectrophotometrically after complexing with 2-Thio-barbituric acid. The effect of free radical scavengers (KI and N₂O) on the yield of Ma was investigated. Of the systems studied a 5% aqueous sucrose solution gave a proportional response of MA formation with dose in 0.2 to 5 Mega rad range. A 5% aqueous solution of sucrose prepared from sucrose irradiated in solid state also gave a smooth response of MA yield with dose from 8 to 30 Mega rad. The aqueous and solid sucrose systems together can be conveniently used for dosimetry in the range of 0.2 to 30 Mega rad.     

Determination of crude fat in meat by supercritical fluid extraction: direct method: PVM 3:2000

Meat samples are prepared by passing meat through a food chopper, bowl cutter, or food processor, subsampling the meat, and mixing the meat with granular diatomaceous earth. No drying step is necessary. Supercritical CO2 is then used to extract crude fat (which is defined as the components of meat that are extractable with petroleum ether, without digestion of the sample). Extracted material is deposited on glass wool contained in collection vials. After removal of any residual moisture from the extracts, percent crude fat is determined by weight gain of the collection vial. This method has been peer-verified by 3 laboratories, for a wide variety of raw and processed meat products containing 6-28% crude fat. Samples were prepared at the submitting laboratory. Ground samples were split into 4 portions, packed in Whirlpack bags, and immediately frozen. Frozen samples were sent by overnight room temperature, and percent fat was determined (in triplicate), without further processing of the samples. Analysis of the samples was completed within 1 week of sample prepara. tion. On the basis of this study, it can be estimated that all repeatability and reproducibility values are <3.0. Mean accuracy of the direct gravimetric supercritical fluid extraction method for meat samples ranged from +0.22 to -1.41 when the method was compared with AOAC Method 960.39. Interferences are unlikely but would include any nonfat substance that is added to (processed) meat, is soluble in nonpolar solvents, and is present in a quantity that would alter results. This method is expected to perform equally well for all meats with fat content within the stated range of applicability.