Characterization of Physico-Chemical Properties of Oil/Water Systems: Interfacial Behavior Prediction

The tractability of petroleum is intimately related to the type of emulsion that is formed during its production. The characteristics of water/oil and oil/water emulsions depend on some factors such as the density and the composition of the oil. In this work, the properties of oils coming from the Campos Basin, Brazil, were evaluated by means of water-in-oil emulsion physico-chemical, interfacial, and characterization tests. Such properties have been correlated with the tractability of the petroleum in order to establish a behavior prediction method based on the properties of such petroleum. The main tool used in this work was the chemiometry technique. Through this method, it was possible to conclude that density, viscosity, surface tension, and nickel content were the properties that influenced the separation of the oils. Density, pour point, initial temperature of crystal formation (TIAC), characterization factor, and nitrogen content were the properties that influenced the diameter of the emulsion drops.     

Ovarian recovery after total body irradiation and allogeneic bone marrow transplantation: long-term follow up of 79 females

Seventy-nine females undergoing allogeneic BMT following conditioning with total body irradiation (TBI), were prospectively followed between March 1983 and March 1992 with regular gynaecological examinations, including plasma levels of luteinising hormone (LH), follicle stimulating hormone (FSH), 17-beta oestradiol (E2) and pelvic ultrasonography. The end-points of this study were the following: (1) early and late effects of TBI on ovarian function, (2) compliance and results of hormonal replacement therapy (HRT), and (3) predictive events for ovarian recovery. During the first year post-BMT most adult women complained of vasomotor and/or genitourinary tract symptoms. These were associated with decreased E2 and increased LH-FSH plasma levels and a deterioration in their sexual life (94% of sexually active women). Forty-nine adult females were selected to receive systemic hormonal replacement therapy (HRT), consisting of cyclic transdermal oestrogens plus medroxyprogesterone acetate (MPA) or cyclic oral therapy with low doses of conjugated oestrogens and MPA: these patients were selected on the basis of age (< 45 years), absence of medical contraindications or subjective refusal. Compliance and tolerability were overall good: most women (65%) never stopped HRT; this was discontinued in 14 patients for medical reasons and in 3 because of refusal. Forty-three females completed 6 months of HRT: vasomotor symptoms disappeared in 91% of 58 women who previously referred these symptoms. Improvement of genitourinary symptoms was seen both with local and systemic hormonal therapy. However sexual symptoms were reduced in 21 of 26 women (81%) given HRT compared with 8 of 19 (42%) women given local treatment (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Secondary dendrite arm spacing and solute redistribution effects on the corrosion resistance of Al–10 wt% Sn and Al–20 wt% Zn alloys

In general, aluminum alloys provide the most significant part of all shaped casting manufactured. An optimum range of properties can be obtained as a function of different cooling rate processes, such as sand, plaster, investment, permanent molds and die castings. It is well known that the dendritic network affects not only the mechanical properties but also the corrosion resistance. However, the literature is scarce on reports concerning the influences of dendrite arm spacing on corrosion resistance and mechanical behavior. The aim of this study is to investigate the influence of as-cast microstructure features, i.e., dendrite arm spacing and solute redistribution on the corrosion resistance of samples of aluminum alloys. In order to investigate the electrochemical behavior of solute and solvent of different aluminum systems, samples with the same order of magnitude of dendritic spacings were analyzed to permit comparison between Al–10 wt% Sn and Al–20 wt% Zn alloys. A casting water-cooled assembly promoting upward directional solidification was used in order to obtain controlled casting samples of these alloys. In order to characterize the dendritic structure, longitudinal sections from the directionally solidified specimens were analyzed by using optical and electronic microscopy techniques. The corrosion resistance was analyzed by both the electrochemical impedance spectroscopy technique and Tafel extrapolation method conducted in a 3% NaCl solution at room temperature. Although both systems present an Al-rich dendritic matrix, different responses to corrosive action as a function of dendritic spacing have been detected.     

Group transfer polymerization and its use in water based pigment dispersants and emulsion stabilizers

Group transfer polymerization (GTP) can be used to make AB diblock acrylic polymers. It provides excellent control of the structure of these polymers. With a hydrophilic B block, these polymers have been used to prepare water based emulsions, pigment dispersions, and slurries. These systems have property advantages over emulsions and dispersions made with conventional stabilizers. These advantages include increased stability, smaller particle sizes, lower viscosities, and less moisture sensitivity. The structure of the AB diblock polymer affects the properties of both the pigment dispersion and the emulsion particle. The composition, size and ratio of each block affect the overall quality. For aqueous systems, a balance of hydrophobic ‘A’ blocks and very hydrophilic ‘B’ blocks is needed for optimum properties. The hydrophobic ‘A’ blocks, which are homo or copolymers of methacrylate monomers (such as butyl or ethylhexyl methacrylate), are surface active and can associate with either pigment or emulsion polymer surfaces. The hydrophilic ‘B’ blocks, which are neutralized acid or amine containing copolymers, provide both ionic as well as steric stabilization in water-borne systems.     

The influences of macrosegregation, intermetallic particles, and dendritic spacing on the electrochemical behavior of hypoeutectic Al-Cu alloys

The purpose of this research is (1) to investigate the influence of Al(2)Cu intermetallic particles associated with the dendritic arm spacing on the corrosion resistance of different hypoeutectic Al-Cu alloys and (2) to evaluate the electrochemical behavior of a hypoeutectic Al-Cu alloy directionally solidified under unsteady-state heat flow. The as-cast samples were produced using vacuum arc remelting and vertical upward water-cooled solidification. Microscopic examinations were carried out with optical microscopy and scanning electron microscopy + energy dispersiveX-ray analyses. To evaluate the surface corrosion behavior of such alloys, all corrosion tests were performed in a 0.5-M NaCl solution at 25 degrees C using an electrochemical impedance spectroscopy technique and potentiodynamic polarization curve analysis. Based on the tests, corrosion rate and impedance parameters were obtained. The present research has underlined the use of appropriate techniques of characterization for determining Al(2)Cu distribution, morphology, and fraction within the typical microstructures of Al-Cu alloys. The experimental results have established correlations between the Al-rich phase dendritic arm size, the intermetallic particles distribution in the eutectic mixture, the macrosegregation profile, and the resulting corrosion resistance.     

A comparative study on comb electrodes devices made of MWPECVD diamond films grown on p-doped and intrinsic silicon substrate

Diamond is considered as a very promising material for the development of devices for radiation detection. Unlike other conventional photoconductive detectors diamond-based devices should provide high discrimination between UV and visible radiation. In this work we present the electro-optical properties of devices based on randomly oriented diamond films, synthesized in a microwave plasma enhanced chemical vapor deposition reactor. A comparative study on devices with coplanar interdigitated Cr/Au electrodes (with different interelectrode pitches) made of films grown simultaneously on intrinsic and p-doped silicon (100) substrates has been performed. The chemical-structural, morphological, electrical and optical properties of ROD films have been studied. In particular, the optical response has been measured in air using a Xe flash lamp coupled with an optical quartz fiber and a properly tailored front-end electronics based on a charge sensitive amplifier. Experimental results gave indications on how the device performances are dependent on the two types of employed substrates.     

The assessment of a smart anticorrosive coating by the electrochemical noise technique

Zinc phosphate and related compounds are convenient replacements for chromates. However, more eco-compatible pigments are being investigated. The objective of this research was to develop a modified zeolitic rock which is intended to replace phosphate pigments in anticorrosive paints. The modified zeolitic rock was obtained by grinding the rock followed with ionic exchange with molybdenyl ions. This “composite” has an intelligent behavior because molybdenum compounds are leached from the zeolite particle by corrodent species. The anticorrosive properties of this zeolitic rock were studied by electrochemical techniques, employing inhibitor suspensions, and formulating anticorrosive coatings. Coatings performance was evaluated by accelerated tests (humidity chamber and salt spray) and electrochemical noise measurements (ENM). Electrochemical noise data were analyzed in the time domain. The noise resistance (R_n) was compared, as far as possible, with the polarization resistance.     

Grain size effects in the quasi-static fracture resistance of a thermally embrittled RPV steel (annealed microstructures)

The elastic-plastic fracture toughness and crack extension behavior under quasi-static loading regimes of the as-received and several thermally embrittled states of a reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters. Through a simple rule of mixture that is typically applied for composite materials, it was found that the equivalent grain size (EGS) of dual-phase annealed microstructures is the controlling parameter of the fracture properties. It was concluded that a Hall-Petch type relationship correlates the J-fracture mechanics criteria to the EGS.