Improved corrosion protection of aluminum alloys by electrodeposited silanes

Organofunctional silanes recently have emerged as outstanding, environmentally friendly corrosion protectors for metal substrates, compared with conventional chromate treatments. A simple immersion technique is typically used to coat the metal surface with silane films. However, the thickness and uniformity of the films are uncontrolled in this process. This paper proposes a new deposition technique for the silane films on the metal surface, i.e., by electrodeposition. Hydrolyzed silanes are water-soluble, ionized molecules, so they can be deposited on metals by electrodeposition. Various combinations of silane mixtures were tested at different voltages, pH values, bath concentrations, and exposure times on panels of alloy aluminum and mirror-polished ferro-plate. The surface structure was characterized by scanning electron microscopy (SEM) and ellipsometry. The resistance of the film to corrosion was investigated by direct current (DC) polarization and electrochemical impedance spectroscopy (EIS) techniques. Electrodeposition results in a more organized and uniform film with fewer pores, compared with immersed or dipped films. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appears on pp. 320–26 of the Proceedings.     

The distribution of grain boundary planes in polycrystals

During the last ten years, techniques have been developed to measure the distribution of grain boundaries in polycrystals as a function of both lattice misorientation and grain boundary plane orientation. This paper presents a brief overview of the techniques used for these measurements and the principle findings of studies implementing these techniques. The most significant findings are that grain boundary plane distributions are anisotropic, that they are scale invariant during normal grain growth, that the most common grain boundary planes are those with low surface energies, that the grain boundary populations are inversely correlated with the grain boundary energy, and that the coincident site lattice number is a poor predictor of the grain boundary energy and population.     

Preparation of Protein-Stabilized β-Carotene Nanodispersions by Emulsification–Evaporation Method

This work was initiated to prepare protein-stabilized β-carotene nanodispersions using emulsification–evaporation. A pre-mix of the aqueous phase composed of a protein and hexane containing β-carotene was subjected to high-pressure homogenization using a microfluidizer. Hexane in the resulting emulsion was evaporated under reduced pressures, causing crystallization and precipitation of β-carotene inside the droplets and formation of β-carotene nanoparticles. Sodium caseinate (SC) was the most effective emulsifier among selected proteins in preparing the nanodispersion, with a monomodal β-carotene particle-size distribution and a 17-nm mean particle size. The results were confirmed by transmission-electron microscopy analysis. SC-stabilized nanodispersion also had considerably high ζ-potential (−27 mV at pH 7), suggesting that the nanodispersion was stable against particle aggregation. Increasing the SC concentration decreased the mean particle size and improved the polydispersity of the nanodispersions. Nanodispersions prepared with higher β-carotene concentrations and higher organic-phase ratios resulted in larger β-carotene particles. Although increased microfluidization pressure did not decrease particle size, it did improve the polydispersity of the nanodispersions. Repeating the microfluidization process at 140 MPa caused the nanodispersions to become polydisperse, indicating the loss of emulsifying capacity of SC due to protein denaturation.     

Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15–20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34–36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10⁻⁵–10⁻⁶ mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to pertrochemical-derived products.     

Informational Entropy: a Failure Tolerance and Reliability Surrogate for Water Distribution Networks

Evolutionary algorithms are used widely in optimization studies on water distribution networks. The optimization algorithms use simulation models that analyse the networks under various operating conditions. The solution process typically involves cost minimization along with reliability constraints that ensure reasonably satisfactory performance under abnormal operating conditions also. Flow entropy has been employed previously as a surrogate reliability measure. While a body of work exists for a single operating condition under steady state conditions, the effectiveness of flow entropy for systems with multiple operating conditions has received very little attention. This paper describes a multi-objective genetic algorithm that maximizes the flow entropy under multiple operating conditions for any given network. The new methodology proposed is consistent with the maximum entropy formalism that requires active consideration of all the relevant information. Furthermore, an alternative but equivalent flow entropy model that emphasizes the relative uniformity of the nodal demands is described. The flow entropy of water distribution networks under multiple operating conditions is discussed with reference to the joint entropy of multiple probability spaces, which provides the theoretical foundation for the optimization methodology proposed. Besides the rationale, results are included that show that the most robust or failure-tolerant solutions are achieved by maximizing the sum of the entropies.     

Use of cascade reduction potential for selective precipitation of Au,Cu, and Pb in hydrochloric acid solution

Optimization of reduction potential for electroseparation was studied for the recovery of gold, copper, and lead from acidic solution. A linear sweep voltammetric method enabled us to determine characteristic reduction potentials for each metal and the kinetics of the metal deposition indicated by current-voltage curves. In order to precipitate the metal species sequentially, reduction potentials were examined for the individual and mixed solutions of Au(III), Cu(II), and Pb(II). The three metals were reasonably well isolated from the mixed solutions such as Cu(II)/ Pb(II) and Au(III)/Cu(II)/Pb(II) in the order of the corresponding reduction potentials, in particular, the mass transfer controlled reduction potentials, obtained from linear sweep voltammetry (LSV) measurement.     

A helical drive in-pipe robot based on compound planetary gearing

The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent years, various in-pipe robots have been developed for inspection and maintenance tasks inside such pipes. In this paper, a novel in-pipe robot is proposed and developed for gas/oil well interventions at thousands of meters downhole. Due to the nature of such intervention, in-pipe robot design must be capable of carrying a very large payload, as large as 2500?N inside a pipe with diameter as small as 54?mm. The proposed design concept is based on a compound planetary gearing system. One of the major novelties of this design is the use of pipe wall as a ring gear for one stage of the compound planetary gear system; the other novelty is the generation of helical angle when the planetary gears are expanded to press on the pipe wall. The proposed concept is compact, efficient, and has never been reported before. In this paper, the helical angle, the velocity, and load capability of the proposed system will be analyzed. The load transportation capability of the proposed robot is also measured based on an experiment. Initial data have shown great potential in carrying large payloads.     

Synthesis and self-assembly of hyperbranched polyester peripherally modified by touluene-4-sulfonyl groups

In this paper, hyperbranched polyesters (HPs) were synthesized in the molten state from 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) and 2-ethyl-2-hydroxymethyl-1,3-propanediol (TMP) using acid catalysis. The modified hyperbranched polyesters were obtained through the chemical modification of the hyperbranched polyester cores by substituting a controlled fraction of the terminal hydroxyl groups with touluene-4-sulfonyl chloride using triethylamine (TEA) as an acceptor of HCl. The resultant polyesters were characterized by ¹H NMR, ¹³C NMR, FT-IR, UV and GPC and their self-assembly behaviors were investigated. The results revealed that self-assembled structures could be formed in selected solvents (trichloromethane/acetone or trichloromethane/n-hexane).     

Hydrodynamic characteristics of a FCC regenerator

The hydrodynamic and gas mixing characteristics have been determined in a FCC regenerator (0.48 m I.D.x3.4 m high) with FCC particles. Solids holdup in the dense bed decreases with increasing gas velocity, but it increases in the freeboard region. The bubble/void fraction increases with an increase along the bed height at a given gas velocity and increases with increasing gas velocity at a constant bed height. Backmixed tracer gas at the wall region is higher than that at the center region of the bed. The gas backmixing coefficient decreases with increasing gas velocity.     

几种表面活性剂在香精产品中的应用

本文阐述了几种表面活性剂在香精中应用的调配研究过程以及期间出现的不同现象,并对其进行了对比、比较.细述了这几种表面活性剂在应用过程中所出现的不同特征.